Chapter 02: The Curing Molecule

10/09/2022 eben van tonder Bacon & the Art of Living Bacon Curing, Bacon History, bacon processing, nitrate, nitrite curing, sodium nitrite

Introduction to Bacon & the Art of Living

The story of bacon is set in the late 1800s and early 1900s when most of the important developments in bacon took place. The plotline takes place in the 2000s with each character referring to a real person and actual events. The theme is a kind of “steampunk” where modern mannerisms, speech, clothes and practices are superimposed on a historical setting. Modern people interact with old historical figures with all the historical and cultural bias that goes with this.

The Curing Molecule

Before we get into storytelling, it will be of great value to have a technical discussion about meat curing. The story will be more enjoyable if you understand how curing works. This chapter is designed to give you enough background to understand the fundamentals of curing and some of its complexities. This is not intended to be a science textbook and so I take the liberty to present matters in a somewhat simplified manner. I don’t for example always indicate when I am talking about an ionic compound when I write a simple notation for nitrite as NOO. I also added, “Want to know more?” sections for those who have a chemical background or those who want to gain a deeper understanding. Get through Chapter 2 and a story awaits which will blow your mind!

What is Meat Curing?

The most important question in a work on the history of meat curing is to understand what meat curing is! Meat curing is the process whereby meat is changed into a form that lasts outside a refrigerator. We can say that it imparts longevity to meat. In the curing process, there are two changes that we can identify with our senses. A delicious taste develops and the colour change to a characteristic pinkish/ reddish colour. A slightly less obvious characteristic is cured meat is safe from microorganisms which make us sick. These characteristics are observed through observation but what happens as far as chemical reactions are concerned?

The large molecule which is the building block for muscle or meat is called a protein. An important class of proteins in our body is called hemeproteins (also spelt haem protein or hemoprotein). These are proteins which have something attached to them that biochemists refer to as a heme prosthetic group. A prosthesis helps a person who lost a limb to still accomplish a certain task like a handshake. The prosthesis in the case of proteins is non-protein additions to the protein which accomplish specific tasks. The heme prosthetic group allows proteins to carry oxygen, facilitate electron transfer and participate in oxygen reduction among other processes. Curing is the reaction between protein and the small gaseous molecule called nitric oxide (NO).

In curing nitric oxide is bound onto this heme component. It is this binding of nitric oxide to the protein which we observe as a pinkish/ reddish colour. Nitric oxide is responsible for key characteristics of cured meat. The colour, the longevity and the fact that the product is free from microorganisms, likely to make us sick. Another characteristic of cured meat we observed with our senses is the cured taste. Exactly how the taste is altered through curing is something which we have not completely worked out yet.

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Nitric oxide is the most important molecule related to the cured colour of meat. This does not say that other chemical species also derived from nitrogen do not play a role in changing the colour. This is true related to colour formation as well as anti-microbial ability. An example is nitrogen dioxide (NO₂). The researcher Cornforth (1998) showed that pink rings that form in beef roasts cooked in gas ovens and turkey rolls are produced by nitrogen dioxide (NO₂). Similarly, we know that both nitrite and nitric oxide plays a very important role in the antimicrobial working of the curing process. The researcher, Scairer (2012), reported on the antimicrobial value of nitric oxide.

How is Nitric Oxide formed?

Let’s begin by looking at how nitric oxide is formed. For our discussion, what is essential to know is that it is formed both inside the body or by the body itself and outside the body. Almost every cell in our bodies can produce it. There are also two basic types of reactions that produce it.

i. Meat proteins contain an amino acid called L-Arginine. The body has the ability to access its nitrogen and combines it with an oxygen atom to create nitric oxide. Beginning in the 1990s scientists started to understand that certain bacteria also have the ability to convert L-arginine into L-citrulline and nitric oxide which cures meat. The exact mechanism is still under investigation but this remarkable discovery accomplishes what has become like the search for the holy grail namely the curing of meat without the use of nitrate or nitrite.

ii. The second major way that nitric oxide is created is the conversion of nitrate to nitrite and the nitrite to nitric oxide. The source of nitrate can be salts such as sodium or potassium nitrate or it occurs in large volumes in certain plants which we regularly consume. Bacteria break the nitrate down to nitrite and nitrite is changed into nitric oxide through mainly chemical reactions. In conventional curing operations, either nitrate or nitrite salts are used to create nitric oxide which cures meat.

This means that bacteria are involved in the reactions involving nitrate and L-Arginine. Interestingly enough, this seems to be the reason why this remarkable discovery remained unidentified for so many years. The conversion of L-Arginine only takes place when no nitrate is present. If nitrate is present the bacteria use the nitrogen found in nitrate and not L-arginine. That L-Arginine plays a role in salt-only, long-term curing processes has been suspected for many years and in the 1990s it was identified that the reaction was mediated through bacteria. What seemed to have happened was that the scientific community continued to relegate this to the realm of long-term cured hams and bacon. It is only in recent years that commercial quick-curing factories using bacterial fermentation became a reality in large high throughput commercial curing plants using bacterial fermentation and no nitrates or nitrites. In fact, so successful have these developments in meat fermentation been that meat curing is achieved in approximately the same time as is done with sodium nitrite.

That sets the first part of the stage for our discussion about meat curing. My own life is a good example of how only knowing the facts as I presented above about meat curing does not mean that you can use the techniques. The reality is that these methods can only be effectively applied within the framework of a complete curing system and developing such a system is far more complex than one imagines. I have, for example, known that bacteria are able to use L-Arginine to create nitric oxide for a full five years before I started to unravel the context and requirements of what it will take to use this to cure meat in a commercial curing operation. Colour stability and a safe microenvironment must be created. The formation of biofilm must be managed. The speed of the reaction must be increased. So I can go on and on and the point is simply this, it is a wonderfully complex endeavour.

Let’s return to the consideration of the two curing paths that we just looked at. In the course of this chapter, I will make repeated references to these two reactions. The story of bacon is, in a nutshell, the story of ways to produce nitric oxide in the fastest possible time to cure meat.

It has been an obsession of many curers and scientists to find another way to cure meat. In other words, not to use the nitrate-nitrite-nitric oxide path to curing due to questions that emerged about the safety of nitrate and nitrite. The use of bacteria to cure the meat achieves this! However, right at the outset, I want to caution that nitrate, nitrite and nitric oxide are like the Father, the Son and the Holy Spirit in that where you find one, you find them all due to the high reactivity of these nitrogen species (Reactive Nitrogen Species) as we refer to them. Creating nitric oxide with bacteria from L-Arginine may seem like solving the problematic use of nitrate and nitrites in meat curing but if the two cousins of nitric oxide (nitrate and nitrite) will in any event both appear in meat cured with bacteria only, is it really addressing the problem?

A far more fundamental question exists namely if the hysteria against nitrate and nitrite is warranted! Is the use of nitrite or nitrate really problematic? Are these really entities of concern when we consider human health? In recent years evidence started to emerge that the exact opposite is true namely that if we do not ingest sufficient nitrate and nitrite, this has far more detrimental health effects on humans than having them in our food.

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A closer look at the nitrate-nitrite-nitric oxide sequence in our bodies:

The researcher, Weitzberg (2010) reportes that “several lines of research . . . indicate that the nitrate-nitrite-nitric oxide pathway is involved in regulation of blood flow, cell metabolism, and signaling, as well as in tissue protection during hypoxia (meaning, a lower-than-normal concentration of oxygen in arterial blood).” This is the exact curing reaction when we begin with slatpetre (NO₃^–) or with nitrite NO₂^– as is the predominant current system of curing in high throughput curing operations. When we use sodium nitrite to cure the meat, the process still results in the formation of nitric oxide (NO). The curing reaction is therefore a “natural reaction” which takes place in our bodies and is essential to life.

Can we remove nitrogen (nitrate or nitrite) from our diets?

We are all aware of the importance of oxygen to our everyday lives. Without it, life as we know it is not possible. A second element as important to life as oxygen is nitrogen. Where does nitrogen come from and why is it important to life? Let’s take a step back and consider nitrogen for a moment before we return to nitrate and nitrite in food and the chemistry of curing.

The Importance of Nitrogen

I have written extensively about how reactive nitrogen species are formed from atmospheric nitrogen and I will leave the subject to be discussed later.

Sufficient to point out that nitrogen is one of the most essential plant foods and is taken up in the structure of plants. From the plants, they provide sustenance to animals when they eat the grass. The ability of animals to absorb nitrogen is a key element in what makes food nutritious. From very early it has been shown by various scientists that animals fed with food containing no nitrogen get sick and even die whereas animals fed with food high in nitrogen thrive. This is important since, in evaluating the use of nitrogen in meat curing (through nitric oxide), the first thing we must realise is that without nitrogen, there is no nutrition. We need nitrogen like we need water or oxygen to live.

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The role of nitrogen in plants:

Nitrogen is part of the green pigment of plants, responsible for photosynthesis, called chlorophyll. It further is responsible for a plant’s rapid growth, increasing seed and fruit production, and improving the quality of leaf and forage crops. (Plant Nutrients and Lilies) This is important as we will later see how nitrate, nitrite and nitric oxide not only cures meat and ensures the overall health of our bodies, but how the same reaction is key to the nutrition of plants. The curing reaction is by no ways something foreign. It is vitally important to all aspects of animal and plant life and humans form part of this group of animals.

Nitrogen as plant food:

Potassium (K) and nitrogen (N) together with phosphorous (P) are considered the primary nutrients of plants. These are normally lacking in the soil because plants use them for growth and thus deplete it. As we will see, nature replenishes nitrogen, but modern farming created the demand to add extra nitrogen to the soil. Potassium (K), nitrogen (N) and phosphorous (P) are all part of the macronutrients. The secondary nutrients are calcium (Ca), magnesium (MG), and sulphur (S). These nutrients are normally abundant in the soil. When lime is applied to acidic soil, large amounts of calcium and magnesium are added. Decomposing organic matter normally yields enough sulphur. Potassium (K) is absorbed in bigger volumes than any other mineral element except nitrogen and in some cases, calcium. It assists in the building of proteins, photosynthesis, and fruit quality and it reduces diseases. (Plant Nutrients and Lilies) The abundance of potassium in plants can be seen from where we first identified it namely from potash or plant ashes soaked in water in a pot. Potassium is derived from this practice predating the industrial revolution.

All proteins, the building blocks of muscles contain nitrogen. Our bodies use nitric oxide to stay healthy in many different ways. To such an extent that without nitric oxide in our bodies, life will not be possible. The question is now if the body produces enough nitric oxide on its own and the answer is no. We need to supplement what the body can produce through our diet. Some of the foods where we get nitrate or nitrite in our diets are:

-> Vegetables

By far the biggest source of nitrates is leafy green vegetables. The way that the nitrates end up as nitric oxide in our bodies is the nitrate-nitrite-nitric oxide sequence. These vegetables also contain nitrites and these turn into nitric oxide through the steps of nitrite-> various-chemical-reactions ->nitric oxide.

-> Water

Borehole water often has nitrate and nitrite from animal and human waste and fertilisers in surrounding areas. The sequence of reactions that change the nitrates in water into nitric oxide is the same as above namely nitrate-> nitrite-> nitric oxide.

-> Cured Meat

Nitrate salts are found naturally around the world. Potassium nitrate for example we know as saltpetre. Nitrite salts are manufactured salts containing sodium and nitrite. Saltpetre (potassium or sodium nitrate) is used in meat curing to this day. If we consume cured meat we ingest nitrates or nitrites and it ends up changing into nitric oxide in our bodies either through the reaction nitrate-nitrite-nitric oxide or nitrite-nitric oxide. Cured meat is, however by far the smallest and most insignificant source of nitrates and nitrites.

What is important to focus on here is the path from nitrate to nitric oxide. Let me illustrate it in greater detail using saltpetre as an example. Saltpetre can be represented as one nitrogen atom and three oxygen atoms and to make it easy, I will write it as NOOO to focus on the number of oxygen atoms. The astute observer will see that I leave the metal part of saltpetre out and I represent only the nitrate part. Nitrate joins forces with metals like sodium, calcium, or potassium to form sodium nitrate, potassium nitrate (which is known as saltpetre) or calcium nitrate. In terms of curing meat, only sodium plays a further role and we will look at that later, but for now, it’s helpful to ignore the first part of the pair and focus only on the nitrate part.

When nitrate connects to one of the metals it forms a very stable salt which does not easily lose an oxygen atom. We said we represent nitrate in this chapter as NOOO, but you remember that the actual representation is NO₃^–. The stable molecule now loses an oxygen atom through bacteria that use the extra oxygen atom in its metabolism. So, NOOO loses an oxygen atom through the action of bacteria and nitrite is formed which we represent as NOO (actually, NO₂^–). In contrast to nitrate, nitrite is an unstable molecule and is easily changed to one of the other Reactive Nitrogen Species (RNS) such as nitric oxide. If NOO loses an oxygen atom, NO or nitric oxide is formed. This reaction happens chemically and not through bacteria and it involves nitrate first changing into other forms before it ends up as nitric oxide.

Ancient curing methods start with nitrate, which is changed to nitrite and eventually to nitric oxide. This is the way that it was done before sodium nitrite became available around the world after World War I and many artisan curers still prefer to start with nitrate when they cure meat. The reason for this is that the bacteria also contribute to the development of flavours in the meat which one loses if one starts directly with nitrite in the form of sodium nitrite which does not require bacteria to change into nitric oxide to cure the meat. It became the norm following World War II to skip the step of changing nitrate to nitrite which is time-consuming and may result in inconsistent curing by beginning the reaction sequence by using sodium nitrite and not nitrate.

Whether you talk about the reaction nitrate-nitrite-nitric oxide or nitrite-nitric oxide, these scenario has at their heart the loss of one oxygen atom in every step. The opposite is also possible mainly that oxygen atoms can be added. At times, nitric oxide can gain an atom to form NOO or nitrite and NOO to form NOOO or nitrate. Remember that we said that where you find one, you are likely to find the others. So, where you have either nitrate, nitrite or nitric oxide, you are likely to find the others also.

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Ionic compounds:

It is easy to see that the 3 following the O which represents oxygen indicates that one nitrogen atom binds to three oxygen atoms in the nitrate molecule, but what does the minus sign indicate? The nitrogen and three oxygen atoms form a unit or a package. The nett charge of this package is, however, negative, which is what the minus sign indicates. We call this not a molecule, but a very special molecule called an ion (where there is only one atom) or an ionic compound as in the case of nitrate with nitrogen and oxygen atoms in the molecule. A compound is supply two or more elements grouped together. An ion is what we call a unit like this (which can be an atom or a molecule) but it has a net electrical charge which is either + (positive) or – (negative). Ionic compounds are held together by these ionic bonds or electrostatic forces, as we refer to them. The ion by itself has a charge as either + or – but when it connects with another ion of opposite charge, the molecule is neutral overall. It has a component which is positively charged (called an anion – a positively charged ion) and a negatively charged component (called a cation – a negatively charged ion). An example of an ionic compound from everyday life is table salt with one positively charged sodium ion (Na+) and one negatively charged chloride ion (Cl⁻) called sodium chloride or table salt. We call it a salt because one component is alkali and the other is acidic.

The combination of nitrogen and oxygen yields several salts of importance for example saltpetre. Like table salt is the colloquial term for sodium chloride, so the colloquial term for potassium nitrate is saltpetre. The nitrate component or ion, NO₃^– reacts with metal ions such as sodium, magnesium, potassium, or calcium. The metal components occur in solution (mixed into water) as a strong acid in the form of (HNO₃) with a strong base (KOH) which reacts to form a crystal [P⁺].[NO₃^–] or PNO_3. Traditionally, saltpetre refers to potassium nitrate.

Another metal it often combines with is sodium to form sodium nitrate. Sodium or natrum (German) is represented by the letters “Na” for sodium and again, the nitrate component which is NO₃^– combines to give sodium nitrate written as [Na⁺].[NO₃^–] to form NaNO₃.

The final example is the metal calcium, abbreviated Ca which represents calcium, but calcium combines with two sets of nitrates (NO₃^–) x 2 written as (NO₃)₂ and the complete name is therefore Ca(NO₃)_2.In our discussions here we ignore the metal part of the molecule being in our examples above potassium (K), sodium (Na) and Calcium (Ca). For easy of reference, when we talk about nitrate, we only refer to the NO₃^–component but often, there would be either K or Na or Ca attached to the nitrate but because it plays no role in the rest of the chemical reaction, we will conveniently ignore these metal components.

Summarise different metals that combine with nitrate:

NOOO (nitrate) + K (potassium) = KNO₃ (Potassium Nitrate)

NOOO (nitrate) +Na (sodium) = NaNO₃ (Sodium Nitrate)

NOOO (nitrate) + Ca (Calcium) = Ca(NO₃)₂ (Calcium Nitrate)

You not only learned three different metals that can attach to nitrate. The same three can also lose an oxygen atom to form a nitrite salt.

NOO (nitrite) + K (potassium) = KNO₂ (Potassium Nitrite)

NOO (nitrite) +Na (sodium) = NaNO₂ (Sodium Nitrite)

NOO (nitrite) + Ca (Calcium) = Ca(NO₂)₂ (Calcium Nitrite)

This is another equally likely reaction which involved the gaining of oxygen atoms and not losing it (reduction). An example of an oxidation reaction is the reaction with L-Arginine which we looked at briefly and the oxidation of ammonia (NO₃)/ ammonium (NH₄⁺), both of which creates nitric oxide and are mediated through bacteria. We will tell the story of the formation of nitric oxide from ammonia in a subsequent chapter.

We summarise the two reactions as follows:

-> Reduction (losing oxygen atoms)

One way to create nitric oxide is by removing oxygen atoms. We remove one of the three oxygen atoms from nitrate (NOOO), and we get nitrite (NOO). In the name, the “a” is replaced with an “i” and, nitrite has one less oxygen atom than nitrate. If we remove one more oxygen atom from nitrite (NOO) we get nitric oxide (NO) which is the primary curing molecule.

So, let’s review the simple but important chemistry. Don’t worry about trying to remember these. We will refer to them so many times that you will easily remember them when we are done.

NOOO or (NO₃^–) = Nitrate or Saltpetre

NOO or (NO₂^–) = Nitrite

NO = Nitric Oxide

When nitrate loses one oxygen atom, it changes to nitrite and nitrite that loses one oxygen atom changes to nitric oxide.

NOOO (nitrate) – O = NOO (nitrite)

NOO (Nitrite) – O = NO (nitric oxide)

We have seen that to form nitric oxide from nitrate salts, you lose two oxygen atoms. Chemists say that the number of oxygen atoms is reduced. The word “reduced” will be important as we will say that the nitrate or nitrite is reduced, we mean that it lost an oxygen atom.

The same salts that nitrate forms with metal are formed by the more reactive nitrite.

NOO (nitrite) + K (potassium) = KNO₂ (potassium nitrite)

NOO (nitrite) +Na (sodium) = NaNO₂ (Sodium Nitrite)

NOO (nitrite) + Ca (Calcium) = Ca(NO₂)₂ (Calcium Nitrite)

-> Oxidation (Gaining Oxygen Atoms)

Earlier, we have seen that nitric oxide is created by our bodies through certain processes in our cells. Instead of taking an oxygen atom away, it created nitric oxide by starting with a nitrogen atom and then it adds an oxygen atom to the nitrogen atom, and it forms nitric oxide. This process is called oxidation (adding an oxygen atom).

Ammonia is oxidized through bacteria which adds an oxygen atom to nitrogen and creates nitric oxide. More about this later when we drill down into sal ammoniac. Another way this happens is when ammonia is burned in the presence of oxygen. In this case, it is also oxidized to either nitrogen gas (N2) or nitric oxide (NO). It must be noted that the oxidation of ammonium salts usually produces nitrogen gas.

The Ever-Presence of Nitrogen

Let’s return to considering how gas, nitrogen, enters our world and becomes part of the nutrition of plants and animals. Otto et al (2010) estimate that with 1.4 billion lightning flashes each year, an estimated 8.6 billion tonnes of chemicals of one form or other are generated from the general formulation of NOx. Don’t get scared with the introduction of the x. It tells us we have a variable from which the exact number differs. You are already familiar with three of the forms this can take. Look at Nitric Oxide (NO), nitrite (NO2-), and nitrate (NO₃^–) and see if you can spot the function of the x which in this case is either an implied 1, an overtly stated 2 or 3. Can you tell me why the 1 is implied and for what form of nitrogen and oxide?

This estimate by Otto et al (2010) is staggering. It dwarfs what the curing industry can produce. It comprehensively obliterates the notion that nitrogen or nitric oxide or even nitrite for that matter are evil chemical species, which is produced by humans, and added to meat which will, so it is reported, do harm to the human body.

Otto, et al (010) and many others show conclusively that the presence of nitrate and nitric oxide is pervasive on planet earth. Nitrite is far less prevalent than nitrate. Nitrite is highly reactive and does not stay in this state very long (similar to nitric oxide). It forms a salt such as sodium nitrate which is more stable and is naturally found in some vegetables and meat, but still, nitrites often occur in vegetables. Most current sodium nitrites in dietary sources are made by humans. Nitric Oxide is also “fleeting” being a gas which quickly reacts to become another species.

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“Nitrogen is an essential element for all forms of life and is the structural component of amino acids from which animal and human tissues, enzymes, and many hormones are made. For plant growth, available (fixed) nitrogen is usually the limiting nutrient in natural systems. Nitrogen chemistry and overall cycling in the global environment are quite complex due to the number of oxidation states. Nitrogen itself has five valence electrons and can be found at oxidation states between −3 and +5. Thus, numerous species can form from chemical, biochemical, geochemical, and biogeochemical processes.” (Hanrahan, 2005) Below I list the oxidation state of different nitrogen species (and important chemical data).

Global nitrogen species and selected chemical data by: Hanrahan, 2005.

If you’re interested to learn more, google oxidation states. For those with a lively interest in this, I give the oxidation state of key nitrogen species.

The special Oxidation States of Nitrogen

Ox. state	Species
+5	NO₃	Nitrate ion, oxidizing agent in acidic solution.
+4	NO₂	Nitrogen dioxide is a brown gas usually produced by the reaction of concentrated nitric acid with many metals. It dimerizes to form N₂O₄.
+3	NO₂	An oxidizing agent usually produces NO(g) or a reducing agent to form the nitrate ion.
+2	NO	Nitrogen oxide is also called nitric oxide. A colourless gas is produced by the reaction of metals with dilute nitric acid which then reacts with O₂ in the air to form the brown NO₂ gas.
+1	N₂O	Dinitrogen oxide is also called nitrous oxide or laughing gas.
0	N₂	Commonly found in air and very unreactive because of the very strong triple bond.
-1	NH₂OH	NH2OH Hydroxylamine, a weak base, can act as either an oxidizing agent or a reducing agent.
-2	N₂H₄	Hydrazine, a colourless liquid, is a weak base. Used as rocket fuel. It is disproportionate to N₂ and NH₃.
-3	NH₃	In basic solutions and as NH₄ agent in aqueous solutions. When ammonia is burned in the presence of oxygen it is oxidized to either N₂ or NO. The oxidation of ammonium produces nitrogen gas. salts usually.

Demonstrating Oxidation and Reduction

Let’s illustrate this with a helpful diagram which illustrates both oxidation and reduction of nitrate found in beetroot.

Nitrate–nitrite–nitric oxide pathway. Adapted from Niayakiru et al., 2020 by Milton-Laskibar (2021).

In the illustration above, beetroot contains nitrate (NOOO). Nitrate loses an oxygen atom and nitrite (NOO) is created. This is done through bacteria. It loses another oxygen atom and nitric oxide (NO) is created. These are examples of reduction reactions or losing-an-oxygen-atom reactions. In our current survey, nitric oxide (NO) can now react with a heam protein to cure the meat.

Nitric oxide (NO) can gain an oxygen atom to create nitrite (NOO) and nitrite can gain an oxygen atom to create nitrate (NOOO). There is another mechanism whereby nitric oxide (NO) gains two oxygen atoms at once and nitrate (NOOO) is created directly, skipping the formation of nitrite (NOO) completely. These are all examples of oxidation reactions or gaining-an-oxygen-atom reactions.

I add another graph to explain the various ways that oxidation and reduction take place of nitrate, nitrite and nitric oxide.

Changing Perceptions

Meat curing is no longer the only industry to recognise the importance of nitric oxide. It turns out the molecule vilified for hundreds of years as purportedly being bad for us, possesses some remarkable qualities which recently became the intense subject of scientific investigation. Without it, life is not possible and the reason why few people know about it is that it has only been discovered as late as the 1980s and 1990s.

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Nitric oxide turns out to be an extremely important molecule.

The Biologically Essential Molecule, Nitric Oxide; Reactive Oxygen Species (ROS) and Reactive Nitrogen Species (RNS)

Years ago, before the importance of nitric oxide was appreciated, consumers looked upon the fact that nitrite (which is very reactive and much more poisonous than nitrate) is used in food with great scepticism. They failed to understand that in nature N (nitrogen) easily and often becomes NO (nitric oxide), NOO (nitrite) or NOOO (nitrate or saltpetre). Also, NOOO (nitrate or saltpetre) often and easily becomes NOO (nitrite) and NO (nitric oxide). Where you find NO, chances are that you will also find NOO and NOOO. Likewise, where you find NOO, you will find NO and NOOO. This is a normal part of the functioning of the human body.

The fact that nitrite is poisonous must be qualified by the statement that nitrite is poisonous under certain conditions. What exactly those conditions are will become a major focus of our study, but simply to say that because something is poisonous under specific conditions, that it is dangerous to include it in food is itself a false assertion.

During this work, I will introduce a very important comparison namely between Oxygen and Nitrogen. Oxygen is like nitrogen in that under certain conditions it is toxic and can lead to death. In fact, it can be stated that ANY cell with a nucleus, as a normal process of the metabolism of the cell, generates both reactive species of oxygen and nitrogen. (Griendling, 2016)

We understand that even oxygen has unintended negative consequences such as ageing us and causing the ultimate demise of the body despite the fact that we recognise it as foundational to life on earth. The same two-edged sword experience is what we encounter in the discipline of curing and it is extremely important to understand it and responsibly ensure that no negative environment exists that may cause the nitrogen species to be harmful to humans in any shape or form.

The facts so far are crystal clear. Nitric Oxide (NO), the curing molecule, as its cousins of nitrate or saltpetre (NOOO) and nitrite (NOO) are essential to human and animal life and the functioning of our bodies. Nitrogen is probably no more or less dangerous than oxygen.

It’s Present in our Bodies!

Green et al, (1982) gave us these interesting results of nitrate and nitrite found in our urine, saliva, plasma, gastric juices and milk which points to the fact that these compounds are ever-present in the body. It is part and parcel of human physiology!

When discussing nitric oxide which we have seen as an essential part of our biology, or whether we are talking about nitrate or even nitrite, the first thing to grasp is that these molecules are naturally part of the human body and, as you can see from the table above, they are found in our saliva and our gastric juices. There are other places they are also found on the human body, but we will get to that later. A blanket statement such as that nitrite is bad for us we can unequivocally call an incorrect statement!

Conclusion

The curing molecule is Nitric Oxide. There are different ways to produce nitric oxide. One is to start with the more stable nitrogen salt, saltpetre or nitrate (NOOO). Bacteria use nitrate or saltpetre in respiration in the absence of air and nitrite is created (NOO). Nitrite comes into contact with chemical elements which facilitates the loss of another oxygen atom which brings nitric oxide about which reacts with the protein. It is this reaction that presents itself to us as creating a pinkish/ reddish colour. Nitric Oxide, an extremely important and versatile molecule is created in the human body through a chemical reaction with the amino acid, L-Arginine. This same reaction is also mediated through bacteria added directly to the meat and fermentation becomes a very productive method to cure meat without the use of sodium nitrate or nitrate. So, nitric oxide comes to us through that which our bodies produce naturally or through our diet when we ingest either nitric oxide, nitrates or nitrites.

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Part 6: More Health Benefits of Nitrite

09/04/202212/27/2022 eben van tonder The Truth About Meat Curing: What the popular media do NOT want you to know! health, nitrate, sodium nitrite

By Eben van Tonder
4 September 2022

Part 6 in our series, The Truth About Meat Curing: What the popular media do NOT want you to know!

Introduction

The importance of nitrite in our diet can hardly be overstated. These dietary sources include cured meats even though it is by no means the largest source. The challenge is to understand the factors which prevent cured meats from being seen as a superfood and address these. The presence of nitrites does not seem to be one of these!

In Part 5. Nitrite – the Misunderstood Compound we looked at the protective effects of dietary Nitrate/Nitrite on lifestyle-related diseases mainly from the work of Kobayashi (2015). We also looked at work done which shows the adverse effect of the lack of nitrites on the body. Here I list more health benefits, this time mainly from the work of Rassaf (2014).

Nitrite

By way of overview, let’s briefly list again the sources of nitrite for the human body.

– Three Sources of Nitrite

1. NO -> produced endogenously from L-arginine by NO-synthases (NOSs)

In the body, nitric oxide (NO) is oxidised to nitrite. (Rassaf, 2014)

NO rapidly reacts with oxyhaemoglobin to form methemoglobin and nitrate. (Rassaf, 2014)

On the other hand, several pathways exist in the body that provides the reduction of nitrite to NO, with haemoglobin, myoglobin, neuroglobin, cytoglobin, xanthine oxidoreductase, eNOS and mitochondrial enzymes being involved (for reviews see: van Faassen et al. 2009; Lundberg et al., 2009). The extent of contribution of the different pathways depends on the tissue, the pH, oxygen tension and redox status (Feelisch et al., 2008).

2. Nitrite reduced from nitrate

Sources for nitric oxide (NO) formation in mammals. NO is formed by the endothelial NOS (eNOS) using L-arginine as a substrate in an oxygen-dependent manner. Dietary nitrate is reduced to nitrite via commensal bacteria in the oral cavity. Nitrite can be reduced to NO in eNOS independently via deoxygenated myoglobin (Mb), haemoglobin (Hb), neuroglobin (Ng), xynthin oxidoreductase, protons, aldehyde oxidase and enzymes of the respiratory chain to bioactive NO. (figure and description by Rassaf, 2014)

3. Dietary sources

Cured meat, baked goods, beets, corn, spinach etc. are major sources of nitrite. (Rassaf, 2014)

Reference list below for nitrite dietary contributions.

Sindelar (2012), as quoted by (Kobayashi, 2015)

Hord (2009) as quoted by (Kobayashi, 2015)

Benefits of Nitrite

As I said, I now list more health benefits of nitrite.

In Part 5. Nitrite – the Misunderstood Compound from the work of Rassaf (2014)

-> Contribute to protection against UV-induced cell damage.

The presence of nitrite, but not nitrate, reduced the extent of apoptosis, or the death of cells which occurs as a normal and controlled part of an organism’s growth or development, in cultured endothelial cells during UVA-irradiation in a concentration-dependent manner by inhibiting lipid peroxidation. (Rassaf, 2014) Endothelial cells form the inner lining of a blood vessel and provide an anticoagulant barrier between the vessel wall and blood.

The protective effect described above was abolished by simultaneous administration of a NO scavenger (Suschek et al., 2003) suggesting that nitrite-derived NO may contribute to protection against UV-induced cell damage (Suschek et al., 2006). (Rassaf, 2014)

-> Protection of gastric mucosa from hazardous stress.

We look at this when we considered the work of Kobayashi (2015) but due to the importance, I mention the point again. Nitrite, generated from nitrate by oral bacteria ‘the so called enterosalivary cycle’, and then converted to NO (Benjamin et al., 1994; Lundberg et al., 1994; 2009; 2006; 2008; Kapil et al., 2010a) in the stomach was also suggested to play an important role in the protection of gastric mucosa from hazardous stress (Miyoshi et al., 2003). (Rassaf, 2014)

-> Cardiovascular Benefits

Since the rate of NO generation from nitrite depends on the reduction in oxygen and pH, nitrite could be reduced to NO in ischaemic tissue or tissue lacking oxygen and exert protective effects (for review, see van Faassen et al., 2009). Nitrite-mediated protection was independent of endothelial nitric oxide synthase (Webb et al., 2004; Duranski et al., 2005).

-> The Brain

Depending on the timing of application nitrite might not only reduce irreversible brain injury following ischaemia/reperfusion but also vasospasm following cerebral haemorrhage. (Rassaf, 2014) Ischaemia/ reperfusion refers to the paradoxical exacerbation of cellular dysfunction and death, following restoration of blood flow to previously ischaemic tissues which refers to the demand of tissue for energy, for example from oxygen, and this demand is not matched by supply moslty due to to a lack of blood flow.

-> Protection of the Liver

Nitrite exerted profound dose-dependent protective effects on cellular necrosis which refers to the loss of cell membrane integrity as a result of exposure to a noxious stimulus and apoptosis which refers to a form of programmed cell death that occurs in multicellular organisms. Nitrite has a highly significant protective effect observed at near-physiological nitrite concentrations. (Rassaf, 2014)

-> Protection of the Lungs

In a mouse model of pulmonary arterial hypertension, inhaled nebulized nitrite has been demonstrated to be a potent pulmonary vasodilator that can effectively prevent or reverse pulmonary arterial hypertension. (Rassaf, 2014)

-> Protection of the kidneys

In rats subjected to 60 min of bilateral renal ischaemia and 6 h of reperfusion sodium nitrite administered topically 1 min before reperfusion significantly attenuated renal dysfunction and injury. (Rassaf, 2014)

Renal ischemia associated with renal artery stenosis (RAS) which is the narrowing of one or more arteries that carry blood to your kidneys is the most frequent condition occurring with renin-dependent hypertension. Renovascular hypertension (RVH) results from occlusion (the blockage or closing of a blood vessel or hollow organ) of blood flow to either kidney, which stimulates renin release. Increased renin leads to a series of actions that rapidly leads to increased systemic blood pressure or hypertension or abnormally high blood pressure. (Rassaf, 2014)

Similarly, in mice subjected to bilateral renal ischaemia for 30 min and 24 h reperfusion, renal dysfunction, damage and inflammation were increased; these effects were all reduced following nitrite treatment 1 min prior to reperfusion. (Rassaf, 2014)

-> Crush syndrome and shock

Limb muscle compression and subsequent reperfusion are the causative factors in developing a crush syndrome. In rats subjected to bilateral hind limb compression for 5 h followed by reperfusion for 0 to 6 h, nitrite administration reduced the extent of rhabdomyolysis markers such as potassium, lactate dehydrogenase and creatine phosphokinase. Nitrite treatment also reduced the inflammatory activities in muscle and lung tissues, finally resulting in a dose-dependent improvement of survival rate. (Rassaf, 2014)

Similarly, in a mouse shock model induced by a lethal tumour necrosis factor challenge, nitrite treatment significantly attenuated hypothermia, mitochondrial damage, oxidative stress and dysfunction, tissue infarction and mortality. (Rassaf, 2014)

Nitrite could also provide protection against toxicity induced by Gram-negative lipopolysaccharide. (Rassaf, 2014)

Conclusion

Rassaf (2014) concluded that “taken together, the nitrate-nitrite-NO pathway appears to play a crucial role in protecting the heart, vessel, brain, kidney and lung against ischaemia/reperfusion injury. Nitrite treatment may be advantageous in well-known NO deficient states such as, for example, hyperlipidaemia. Timing and dose of nitrite application as well as the potential to convert nitrite to NO in the tissue are important to obtain a reduction in injury.

That nitrite is not a compound to be avoided at all costs is clear. It is essential to our health and dealing with the stress and strain of living life and mediating the effects of the many injuries we incur. The mass hysteria against the use of nitrites in cured meat is unfounded. The discussion about adapting our formulations to include the latest science related to diet and nutrition needs to take place as it is true for every food group in existence but lumping the meat industry into the same group as producers of cigarettes, for example, is unjustified and dangerous. A far more balanced and responsible discussion is called for and I hope that this series contributes to the discussion.

The full list of contributions to this series is available at The Truth About Meat Curing: What the popular media do NOT want you to know!

References

Hord, N.G.; Tang, Y.; Bryan, N.S. Food sources of nitrates and nitrites: The physiologic context for potential health benefits. Am. J. Clin. Nutr. 2009, 90, 1–10.

Kobayashi, J. (2015) NO-Rich Diet for Lifestyle-Related Diseases, Article in Nutrients, June 2015, DOI: 10.3390/nu7064911

Rassaf T, Ferdinandy P, Schulz R. Nitrite in organ protection. Br J Pharmacol. 2014 Jan;171(1):1-11. doi: 10.1111/bph.12291. PMID: 23826831; PMCID: PMC3874691.

Therapeutic Uses of Inorganic Nitrite and Nitrate – From the Past to the Future

08/23/202208/24/2022 eben van tonder The Truth About Meat Curing: What the popular media do NOT want you to know! nitrate, nitrate curing, nitrite, nitrite curing, sodium nitrite

EarthwormExpress Introduction

I present a complete paper by Anthony R. Butler and Martin Feelisch where they trace the benefits and therapeutic uses of nitrate and nitrates. It forms part of a segment in EarthwormExpress, The Truth About Meat Curing: What the popular media do NOT want you to know! Having studied the matter of the potential detrimental addition of nitrites to curing brines from a human health perspective and having examined thousands of scientific articles on the subject I came to the conclusion that most of the negative press in the popular media on the subject is irrational and based on a partial evaluation of the salient points related to the issue.

Circulation

Volume 117, Issue 16, 22 April 2008; Pages 2151-2159

https://doi.org/10.1161/CIRCULATIONAHA.107.753814

Online published: Therapeutic Uses of Inorganic Nitrite and Nitrate

Abstract

Potential carcinogenic effects, blue baby syndrome, and occasional intoxications caused by nitrite, as well as the suspected health risks related to fertilizer overuse, contributed to the negative image that inorganic nitrite and nitrate have had for decades. Recent experimental studies related to the molecular interaction between nitrite and heme proteins in blood and tissues, the potential role of nitrite in hypoxic vasodilatation, and an unexpected protective action of nitrite against ischemia/reperfusion injury, however, paint a different picture and have led to a renewed interest in the physiological and pharmacological properties of nitrite and nitrate. The range of effects reported suggests that these simple oxyanions of nitrogen have a much richer profile of biological actions than hitherto assumed, and several efforts are currently underway to investigate possible beneficial effects in the clinical arena. We provide here a brief historical account of the medical uses of nitrite and nitrate over the centuries that may serve as a basis for a careful reassessment of the health implications of their exposure and intake and may inform investigations into their therapeutic potential in the future.

The presence of nitrite (NO₂⁻) and nitrate (NO₃⁻) in bodily fluids has been known for some time. Dietary studies carried out by Mitchell et al¹ at the beginning of the 20th century established that the amounts of nitrate excreted in the urine are higher than those ingested with the food, suggesting that the excess nitrate must be a product of endogenous biosynthesis. Later metabolic balance studies by Green et al^2,3 showed that this assumption was correct and provided unequivocal evidence for mammalian nitrate biosynthesis. Griess,⁴ using his eponymous chemical test, showed that human saliva contains small quantities of nitrite, and the detection of very high levels of nitrite in the urine of a volunteer, who happened to have contracted a fever, was the first indication that endogenous production of nitric oxide (NO) is part of the immune response. Nitrite is not normally present in urine, and it was Cruickshank and Moyes⁵ who realized that it originated from bacterial reduction of urinary nitrate, an observation that forms the basis of today’s dipstick tests for urinary tract infection. Shortly after the discovery by Palmer et al⁶ that vascular endothelial cells produce NO from l-arginine, Marletta et al⁷ reported that the same pathway accounts for the production of nitrite and nitrate by activated macrophages, and countless investigators have since used nitrite and nitrate to assess NO production in basic and translational research studies. More recently, the ease with which nitrate is reduced to nitrite and nitrite is converted into NO has occasioned interest in the role of plasma nitrite in vascular smooth muscle relaxation,⁸ the control of blood pressure and flow,⁸ and possible therapeutic uses of nitrite.^9,10 Subsequent animal experimental studies revealed that a number of organs are protected against ischemia/reperfusion-related tissue injury after systemic application of small amounts of nitrite,¹¹ suggesting further therapeutic uses. Strangely, this renewed interest in nitrite/nitrate, together with emerging data suggesting possible new roles for these anions in physiology, coincides with the conclusion by the International Agency for Research on Cancer that “ingested nitrate or nitrite under conditions that result in endogenous nitrosation is probably carcinogenic for humans.”¹² The purpose of this review is neither to consider the physiological role of naturally occurring nitrite and nitrate in organs and bodily fluids or their usefulness as biomarkers of NO activity nor to discuss their possible role as carcinogens; rather, it is to explore the uses of inorganic nitrite and nitrate in medicine, not only modern medicine but also medicine of the past. It transpires that medical interest in these oxyanions of nitrogen is not new.

Discovery and Chemical Properties

Nitrates, particularly potassium nitrate (known also as niter or nitre and saltpeter), have been known since prehistoric times, and in the Middle Ages, natural deposits were commercially exploited. The Chinese invented gunpowder around 800 CE, and with its appearance in Europe during the 13th century, potassium nitrate became strategically important. Demand increased further with the Agricultural Revolution of the 19th century and the use of nitrates as fertilizers. Natural sources were eventually supplemented by synthetically produced nitrate at the beginning of the last century.¹³

Nitrite is present at trace levels in soil, natural waters, and plant and animal tissues. In pure form, nitrite was first made by the prolific Swedish chemist Scheele¹⁴ working in the laboratory of his pharmacy in the market town of Köping. He heated potassium nitrate at red heat for half an hour and obtained what he recognized as a new “salt.” The 2 compounds (potassium nitrate and nitrite) were characterized by Péligot¹⁵ and the reaction established as 2KNO₃→2KNO₂+O₂.

The release of oxygen from a substance known to alchemists as “aerial niter” since the times of Paracelsus explains the role of nitrates in gunpowder, rocket propellants, and other explosives.¹⁶ Sodium nitrite rapidly gained importance in the development of organic chemistry during the 19th century, when it was discovered that nitrous acid (HNO₂) reacts with aromatic amines (ArNH₂) to produce diazonium ions,¹⁷ a highly important synthon for the dyestuffs industry and for synthetic organic chemistry generally: ArNH₂+HNO₂+H⁺→ArN=N⁺+2H₂0.

The mechanism of such diazotization reactions has been subject to extensive study.¹⁸ Diazotization may be responsible, in part, for the carcinogenic role of nitrite under certain conditions, particularly in the context of drug-nitrite interactions.¹⁹

Nitric acid (HNO₃) is a strong acid that is completely ionized at all biologically interesting pHs. Although nitrous acid (HNO₂) is a weak acid, with a pK_a of 3.15 (pK_a is the pH at which the acid is 50% dissociated), it is also, at physiological pHs, completely dissociated, except in the stomach, on the surface of airways, within select cellular compartments (eg, the mitochondrial intermembrane space, endosomes, secretory vesicles, lysosomes, and other acidic organelles), and on the skin.

Nitrite as a Vasodilator

The scope of this review is limited to inorganic nitrite and nitrate, but interest in a medical role for inorganic nitrite was first aroused because of the spectacular success of organic nitrites and related compounds in the treatment of angina pectoris. Butter,²⁰ writing about the treatment of angina in 1791, gave no drug treatment and had little more to offer than the recommendation of a tranquil lifestyle. However, while working at the Edinburgh Royal Infirmary in the 1860s, Brunton²¹ noted that the pain of angina could be lessened by venesection and wrongly concluded that the pain must be due to elevated blood pressure. As a treatment for angina, the reduction of circulating blood by venesection was inconvenient. Therefore, he decided to try the effect on a patient of inhaling amyl nitrite, a recently synthesized compound and one that his colleague had shown lowered blood pressure in animals (A. Gamgee, unpublished observation). The result was dramatic.²¹ Pain associated with an anginal attack disappeared rapidly, and the effect lasted for several minutes, generally long enough for the patient to recover by resting. For a time, amyl nitrite was the favored treatment for angina, but its volatility made it troublesome to administer, and it was soon replaced by chemically related compounds that had the same effect but were less volatile. The most popular replacement was glyceryl trinitrate (GTN), an organic nitrate better known as nitroglycerin.²² The fact that this compound is highly explosive and a component of dynamite appears not to have been a problem. In his 1894 textbook, Phillips²³ lists a number of chemically related compounds that can be used in the treatment of angina. The list includes not only amyl nitrite but also propyl, ethyl, and isobutyl nitrites, as well as GTN. A similar list is provided by White²⁴ in his 1899 textbook. GTN, a drug introduced into allopathic medicine thanks to extensive homoeopathic studies by Hahnemann,25 occasioned greatest favour among practising physicians, and by 1956, in a symposium on hypotensive drugs,26 it was the only drug of this type that was listed. GTN was first synthesized by Sobrero at the University of Torino in 1812, and considering the way in which he handled it, he was fortunate not to cause a fatal accident.27 He thought it too explosively violent to have any practical use. Nobel, the highly successful Swedish entrepreneur, was able to moderate its action by incorporating it into kieselguhr to form dynamite. It is largely from this invention that the Nobel family fortune is derived. Tragically, Nobel’s younger brother Emil was killed while working with GTN, a dark episode in Nobel’s life. Sobrero bitterly resented Nobel’s commercial success with what he saw as his invention, although Nobel always acknowledged his debt to Sobrero.28 It is a curious coincidence that by 1895 Nobel had developed angina and was prescribed GTN as treatment, but it is a happier coincidence that the 1998 Nobel Prize for Physiology or Medicine was awarded for the discovery of the role of NO as a signalling molecule in the cardiovascular system. Now that NO is known to be an important vasorelaxant, it is easy to see why drugs of this type act the way they do. Each is a substrate for ≥1 enzyme systems, possibly located in the vascular wall, that convert it into nitrite and subsequently to NO. One such enzyme, a mitochondrial aldehyde dehydrogenase, has been purified and partially characterized.²⁹ However, the contribution of this or other enzyme systems to the overall vasodilation by these drugs is difficult to assess because multiple metabolic pathways appear to act in concert.³⁰

In view of the range of organic nitrites and related compounds that act as vasodilators, it is not surprising that potassium and sodium nitrites were tested in this regard. In 1880, Reichert and Mitchell³¹ published a very full account of the biological action of potassium nitrite on humans and animals. At that time, the value of amyl nitrite in the treatment of angina was severely compromised by the short duration of its effect, so the search for an improved drug had begun. The effect of potassium nitrite on the nervous system, brain, spinal cord, pulse, arterial blood pressure, and respiration of healthy human volunteers was noted, as was the variability between individuals. The most significant observation was that even a small dose of <0.5 grains (≈30 mg) given by mouth caused, at first, an increase in arterial blood pressure, followed by a moderate decrease. With larger doses, pronounced hypotension ensued. They also noted that potassium nitrite, however administered, had a profound effect on the appearance and oxygen-carrying capacity of the blood. They compared the biological action of potassium nitrite with that of amyl and ethyl nitrites and concluded, rather interestingly, that the similarity of action depends on the conversion of organic nitrites to nitrous acid. Observations similar to those of Reichert and Mitchell were made by Atkinson³² and Densham.³³ Practicing physicians, including Hay³⁴ and Leech,³⁵ examined the therapeutic value of inorganic nitrites as hypotensive drugs and noted that, although of slower onset, their therapeutic effect lasts much longer, and they might be seen as superior drugs. They soon appeared in the Materia Medica of the time. In 1906, the drug supplier Squibb sold a 1-lb bottle of sodium nitrite (sodii nitris) for $1,³⁶ and by the mid-1920s, an injectable solution of sodium nitrite became available (Nitroskleran, E. Tosse & Co, Hamburg, Germany) for the treatment of hypertension and vasospasm.³⁷ Instructions for using sodium nitrite to treat angina are given in Martindale’s Additional Pharmacopoeia and in the US National Standard Dispensatory of 1905.³⁸ A textbook on Materia Medica for medical students in 1921 gives details of the appropriate dose,³⁹ but by the middle of the 20th century, its medicinal use had essentially ceased, largely because of adverse side effects. Blumgarten⁴⁰ noted that sodium and potassium nitrites often caused nausea, belching, stomachache, and diarrhoea. Although these side effects may have caused physicians to hesitate in prescribing sodium nitrite for angina, another event precipitated the fall of inorganic nitrite from favour (see below).

Interest in the vasodilator properties of nitrite enjoyed a renaissance with the notion that nitrite may be involved in the regulation of local blood flow after conversion to NO by nonenzymatic mechanisms^41,42 and an oxygen-sensitive nitrite-reductase⁴³ and S-nitrosothiol–synthase⁴⁴ function of haemoglobin. Like NO, inhaled nebulized nitrite has been shown to be an effective pulmonary vasodilator⁴⁵ and, along with organic nitrites,⁴⁶ suggested for potential use in neonatal pulmonary hypertension. Although there is no doubt that appropriate pharmacological doses of nitrite can normalize elevated blood pressure,⁴⁷ the question of whether physiological concentrations of nitrite are vasodilator active is still a matter of debate.^48,49

Conversion of Nitrite Into NO and NO-Related Products

In view of the close chemical connection between nitrite and NO, it is tempting to assume that nitrite acts as a source of NO when functioning as a vasodilator. However, such conversion requires either strongly acidic conditions or enzymatic catalysis. At low pH, nitrous acid can give rise to the spontaneous generation of NO: 2HNO₂→H₂O+N₂O₃ and N₂O₃→NO+NO₂.

Solutions of acidified nitrite have been used successfully to generate NO and to induce vasorelaxation in isolated blood vessel studies,⁵⁰ and the same reaction mechanism has been proposed to explain the biological action of nitrite.^51,52 However, pHs at which this occurs are generally not found within living systems,⁵³ with the exceptions mentioned above. On the other hand, the enzyme xanthine oxidoreductase converts nitrite into NO when oxygen levels are low, and this is a more likely course of action⁵⁴ in the vascular system, at least under ischemic conditions. In fact, recent data suggest that hypoxic NO formation from nitrite is carried out by multiple enzyme systems¹⁰ and occurs in virtually all tissues and organs (Feelisch et al, unpublished data, 2006). Independently of its reduction to NO, nitrite is converted into NO-related products, including S-nitrosothiols and NO-heme species, at normal physiological pH and oxygen levels.⁵⁵ Although it cannot be excluded that some of the biological effects of nitrite may be mediated by nitrite itself, it is fair to assume that most of the physiological and therapeutic actions of nitrite that require conversion into NO and NO-related products involve enzymatic catalysis.

Nitrite as an Antidote for Cyanide and Hydrogen Sulfide Poisoning

In popular literature, cyanide (CN⁻) is considered the acme of human poisons. In fact, it is by no means the most poisonous substance generally available, but it acts very rapidly, and it is on this rapid action that its reputation rests. Large doses cause instant death; even with low doses, the characteristic symptoms of cyanide poisoning (loss of consciousness, motionless eyes, dilated pupils, cold skin, and sluggish pulse and respiration) appear within seconds. Despite the catastrophic consequences of an overdose, potassium cyanide was used in medicine for many years as a treatment for chest complaints,⁵⁶ particularly a dry cough.⁵⁷ It was not removed from the British Pharmacopoeia until 1945.

By the end of the 19th century, it was established that the toxicity of cyanide was due to interference with the process of cellular respiration.⁵⁸ Keilin⁵⁹ showed that cyanide reacts with the ferric heme of the enzyme cytochrome c oxidase, a vital link between the tricarboxylic acid cycle and formation of metabolic water causing inhibition of mitochondrial respiration. Because cyanide also reacts with methemoglobin,⁶⁰ it should be possible to prevent the reaction of cyanide with cytochrome c oxidase by massively increasing the concentration of methemoglobin in the blood. Nitrite oxidizes the central iron atom of haemoglobin from the ferrous (Fe2+) to the ferric (Fe3+) state, producing methemoglobin, and is, therefore, a potential antidote for cyanide poisoning. The clinical use of nitrite in this setting was first proposed by Hug⁶¹ and is now universally used. Sodium thiosulfate also is included in the antidote to provide a source of sulfur to aid the conversion of cyanide into thiocyanate by rhodanese. The first cases of acute cyanide poisoning in humans to be treated with nitrite and thiosulfate were reported in 1934. One patient had ingested 5 g potassium cyanide but recovered after being given 1.5 g sodium nitrite and 18 g sodium thiosulfate.⁶² In many countries, nitrite is part of the cyanide antidote kit. Nowadays, patients are given an ampoule of amyl nitrite by inhalation or an intravenous injection of 3% sodium nitrite, followed by a slow injection of 50% sodium thiosulfate.⁶³

Although formation of methemoglobin is generally accepted as the explanation of the efficacy of nitrite as an antidote, evidence suggests that this is not the complete explanation.^64,65 There may be alternative or additional routes whereby nitrite detoxifies, but no details are available.⁶⁶ Compounds that promote NO release in vivo (like bradykinin) modify cyanide toxicity. Whether this is an alternative mode of action of nitrite in detoxification or just another source of nitrite from endogenous NO is, at this time, difficult to assess.

Nitrite also is an efficacious antidote to poisoning by hydrogen sulfide (H₂S), an occupational hazard with high lethality and long-term neurological sequelae in survivors. Like NO and CO, low concentrations of H₂S are produced endogenously and have vasodilator properties, but the physiological significance of its formation is currently unknown.⁶⁷ Supraphysiological concentrations of sulfide, as experienced after H₂S inhalation, lead to rapid inhibition of mitochondrial respiration by reversible binding to the central iron atom of cytochrome c oxidase in place of oxygen, explaining why H₂S poisoning shares many similarities with cyanide intoxication.⁶⁸ Nitrite administration, which is superior to that of oxygen alone⁶⁹ and often is combined with hyperbaric oxygen therapy, is most effective when given immediately after H₂S exposure.⁷⁰ It is thought to act via induction of methemoglobinemia and subsequent binding of hydrosulfide anions (HS⁻) to the oxidized blood pigment, leading to inhibition of cytochrome c oxidase and reinstitution of aerobic respiration in the tissues. Although this mode of action appears reasonable, the rather slow rate of methemoglobin formation by nitrite is inconsistent with the rapid recovery typically observed in the clinical setting, suggesting, as with the treatment of cyanide poisoning, the involvement of additional mechanisms. Although nitrite has been known for many years to have protective and antidotal effects against experimental sulfide poisoning in rodents,⁷¹ nitrite administration for H₂S intoxication was introduced into human therapy only in the mid-1970s.⁷² The recommended dosage regimen for nitrite in sulfide intoxication is identical to that established for the treatment of cyanide poisoning, ie, initiation with inhalations of amyl nitrite followed by intravenous injection of 10 mL of a 3% solution of sodium nitrite.⁷³

Other Medical Uses of Inorganic Nitrite

In view of the success of nitrite with angina, it was tried for the treatment of other medical conditions. Law⁷⁴ recommended the administration of very large doses (20 grains or 1.3 g) of sodium nitrite to treat epilepsy. Other physicians tried this dose and found that the side effects were far too serious to continue the treatment, with considerable consequences for the therapeutic use of inorganic nitrite. The toxic nature of such high doses was confirmed by Ringer and Murrell,⁷⁵ who concluded that Law had been using an impure sample of sodium nitrite that was largely sodium nitrate. They attempted to establish a safe dose, but the reputation of sodium nitrite had suffered, and because of the success of GTN, nitrite disappeared from widespread use. The final blow came when Magee and Barnes¹⁹ reported that certain nitrosamines, which could be formed in the stomach by reaction between nitrite and naturally occurring secondary amines in food, are strongly carcinogenic in rodents. Although these findings were quickly confirmed by others and have been extended to other animal species, a causal relationship between nitrite and nitrate exposure and human cancer has not been unequivocally demonstrated.⁷⁶ Nevertheless, further medical use of nitrite ceased for decades, except as an antidote in emergencies, and maximal contaminant levels of nitrite and nitrate levels in drinking water and foods soon became strictly regulated in most countries worldwide. In light of the negative image, nitrite has acquired over the years, it is somewhat surprising that the use of nitrite as an antibacterial agent in canned food has continued. More recently, the antimicrobial properties of nitrite that form the basis for its use in food preservation have been explored for potential benefit in lung and skin diseases.

Acidified Nitrite

Acidification is a prerequisite for nitrite to act as an antimicrobial agent, suggesting (albeit not proving) that the active principle is NO. It has been known for some time that the nitrite found in human saliva originates from nitrate that is actively secreted into the oral cavity and gets partially reduced there by the local commensal bacterial flora.⁷⁷ After swallowing, nitrite ends up in the acidic environment of the stomach, and the NO thus produced is thought to contribute to the antibacterial effects of gastric juice. Similarly, the nitrite produced from nitrate in sweat is believed to exert antimicrobial effects on the surface of the skin.⁷⁸ Thus, acidified nitrite may be a component of innate immunity at several locations on and within the body. Some attempts to capitalize on this insight point in potentially promising therapeutic directions, although few of these findings have made their way into the clinic.

The effectiveness of acidified nitrite in killing antibiotic-resistant Pseudomonas bacteria might offer a possibility to eradicate a major cause for chronic lung infections in cystic fibrosis patients,⁷⁹ provided a safe mode of administration can be found. The antimicrobial properties of NO can be exploited by dermal application of creams containing nitrite and an acidifying agent, eg, ascorbic acid, to treat a number of skin diseases.⁸⁰ The same concept has been demonstrated to increase microcirculatory blood flow in Raynaud patients^81,82 and to accelerate wound healing.⁸³ Although the effects of acidified nitrite are typically ascribed to the generation of NO, the possibility that part of the nitrite applied is absorbed and converted into NO-related products in the tissue cannot be excluded.

Use of Inorganic Nitrate in Medicine

Although modern manuals of Materia Medica and pharmacopeias state that potassium nitrate has no drug action other than as a diuretic (see below), historical records show that it has been used extensively in medicine over the years to treat a number of conditions. In view of the close chemical relationship between nitrite and nitrate, we suggest that the value of inorganic nitrate in medicine is due, at least in part, to its conversion into nitrite during administration or contamination with nitrite because of the manner in which it was manufactured.

Niter occurs in natural deposits in desert regions. Fairly large amounts are found in the northwestern provinces of China, and it was well known to early Chinese alchemists. They called it xiao shi (solve stone), and it was first recognized in the 4th century CE. It was a component of some of the elixirs of immortality concocted by Daoist savants as they searched for a means of realizing the Daoist ideal of life without death.⁸⁴ Entirely by chance, they mixed it with sulfur and charcoal and thus created gunpowder, which was used by the Chinese not only for fireworks but also for civil engineering and warfare. The first printed formula for gunpowder occurs in a Chinese manual of war that appeared in 1044 CE.

One of the oldest accounts of the use of niter in Chinese medicine is as a treatment for what appears to be angina in an 8th century Chinese manuscript uncovered at the Buddhist grotto of Dunhuang.⁸⁵ The patient is instructed to take niter, hold it under the tongue for a time, and then swallow the saliva. The significance of the instructions is that under the tongue, even in a healthy mouth, nitrate-reducing bacteria convert some of the nitrate into nitrite.^77,86 So, if the patient follows the physician’s instructions fully, he or she will be taking in nitrite, known to be a treatment for the alleviation of anginal pain.

Arab physicians were among the most advanced of the medieval period, but there is no mention of niter in a book on cardiac drugs by Avicenna, born 980 CE. The first extant Arabic mention of niter occurs in a book by Kitab al-Jami’fi al-Adwiya al-Mufrada (Book of the Assembly of Medical Simples) finished by Abu-Muhammad al-Malaqi Ibn al-Baitar around CE 1240. Niter was called Thalji al-Sin (Chinese snow), indicating the contact between Chinese and Arab civilizations. It was about this time that Arabs started to use niter in gunpowder and as a component of prescriptions.

Niter does not occur naturally to any great extent in Europe, and the efficacious use of niter in early European medicine is easier to understand if one realizes how the niter was produced. When gunpowder became known in Europe (Roger Bacon mentions it in 1240 CE), there was enormous demand for niter, and much was shipped to Europe from India, where it occurs in natural deposits. But, the demand outstripped supply, and indigenous manufacture was started. It was made in plantations or “nitriaries,” particularly in France and Germany. Natural conditions were simulated by exposing heaps of decaying organic matter mixed with lime to atmospheric action.⁸⁷ Nitrates appeared as efflorescences and were converted into potassium salt by reaction with potassium carbonate (potash). Two groups of bacteria are responsible for this process: Nitrosomonas convert ammonia into nitrite, and Nitrobacter convert nitrite into nitrate.⁸⁸ It is quite possible that niter from nitriaries contained some nitrite, thus giving it medicinal value. This is unlikely in niter from natural deposits because they are old and aerial oxidation will, over time, convert all the nitrite into nitrate. So, the 8th century Chinese physician mentioned previously had to instruct the patient on how to generate nitrite, but European physicians of the 14th to 17th centuries, using niter from a different source, could prescribe it without further refinement because nitrite was there already.

However, such a prescription was rather hit-or-miss in that the amount of nitrite present was a matter of chance. In one of the most comprehensive accounts of the use of niter, methods of making it more effective are described. The book, by Challoner, was printed in London in 1584 and entitled A Short Discourse of the Most Rare and Excellent Vertue of Nitre.⁸⁹ The spelling of the English is idiosyncratic (rather like that of modern students) because spelling was not fully standardized until the publication of Johnson’s dictionary in 1775. Challoner’s book is concerned mainly with the value of niter in treating various dermatological conditions (“diseases of the skinne”), including “tawnie steynings, freckles, duskness and flegmatike evaporations.” It will, he claims, “restore the skinne and complexion to the native bewtie.” The key to understanding this claim lies in the first section of the book in which the author tells his readers how to make niter more effective (“yet more sharpe and subtile”). He describes 3 ways, all involving heating (called “calcination” by Challoner). Heat, of course, converts some of the niter into potassium nitrite, and so, without realizing it, Challoner anticipated the discovery of potassium nitrite by Scheele by nearly 200 years. As discussed above, nitrite has an antibacterial effect and accelerates wound healing, hence its effectiveness on infected skin blemishes (“skales, scrabbes, skurffe, dandruffe, pimples, tetters, bytes” and so on). Naturally occurring nitrite in saliva has the same effect and explains, in part, why most animals instinctively lick a wound.⁹⁰

Challoner does not stop with the application of niter to the skin. He claims that it can be used “for uncumbring and clensing of the lunges” and for the “remedie of hoarnesses, olde coughe and toughe coughe, weising in the windpipes,” and so on. For this use, he suggests making the niter into a pill and then “hold one of those pilles lounge under the tongue, to mixe thereof as much as may be with the moisture of the mouth … and lastlie swallow it,” a procedure curiously reminiscent of the Chinese prescription and anticipating some of the work of Lundberg et al.⁷⁷

Nitrate and the Treatment of Lung Diseases

For a time, amyl nitrite was used for relieving patients suffering an asthma attack. In an article⁹¹ in 1891, other nitrites, including sodium nitrite, were suggested for this purpose. The author remarks that the use of nitrites is not the treatment of choice but that it is said to be beneficial, probably by virtue of its smooth muscle–relaxing effects. However, relief could be delivered even better by a procedure using nitrate rather than nitrite. Blotting paper was soaked in a solution of niter and allowed to dry. Squares of the paper were burnt in a jar, and the patient inhaled the fumes. Apparently, this procedure was frequently successful in relaxing a bronchial spasm. It was first published as a patent in 1867,⁹² is described in detail in the Encyclopedia Britannica of 1911,⁹³ and occurred as recently as 1926 in the US Dispensatory.⁹⁴ The products of thermal decomposition of niter include NO, NO₂, and O₂.⁹⁵ Because NO is a poor bronchodilator and NO₂ is toxic, it is difficult to see how inhalation of this mixture brings relief. The combination possibly has an effect that is greater than the sum of its parts.

In addition to its use in asthma, sodium nitrate was given orally to treat chronic bronchitis.⁹⁶ It is unclear whether the apparent effectiveness of this treatment was secondary to its conversion to nitrite causing bronchial relaxation and antibacterial effects or due to an effect of nitrate itself.

Nitrates as Diuretics

Nitrates have been used as diuretics for centuries. One of the first descriptions of the medical use of potassium nitrate for the treatment of dropsy (edema) is found in Thomas Willis’ Pharmaceutice Rationalis of 1674.⁹⁷ Although it was long known that relatively large amounts (grams) were required to achieve effective diuresis, the dose-response relationship was first established in systematic “homeopathic provings” in 1825.⁹⁸ Clear differences in potency exist between various nitrate salts,⁹⁹ with ammonium nitrate being the most effective. Their mode of action was revealed by studies in dogs demonstrating an enhanced excretion of urinary chloride and sodium, resulting in a net loss of salt and water caused by increased glomerular filtration without an equivalent increase in tubular reabsorption.^100,101 Whether these effects are mediated by formation of nitrite or NO is unknown.

Extensive animal and human studies by Keith et al¹⁰² confirmed the superiority of the ammonium over the sodium salt of nitrate. They also demonstrated that nitrates can potentiate the effects of other diuretics and that toxic symptoms are remarkably rare, even when administered in doses of 10 to 15 g daily for several weeks. Thus, ammonium nitrate was introduced as a new, more effective diuretic in 1926 and was used with great success to treat various forms of edema in North America, particularly at the Mayo Clinic. After a time of exaggerated emphasis on possible toxic effects of nitrates during the preceding 2 decades, which led physicians to use lower, inadequate doses, it looked as though ammonium nitrate was here to stay as the diuretic of choice. What had triggered the fear of inducing severe cyanosis when potassium or sodium nitrate was used as a diuretic before was the toxicity associated with the use of massive amounts of bismuth subnitrate for diagnostic purposes,¹⁰³ which is somewhat surprising because the toxicity of large amounts of nitrate was well known for a long time.¹⁰⁴ Concerns about the safety of nitrates reached a new height with the appearance of case reports about transient methemoglobinemia after administration of ammonium nitrate.^105,106 The reasons for these rare complications (which disappeared on discontinuation of nitrate therapy in most cases) remain unclear but may have been due to contamination of the nitrate salt with nitrite, renal insufficiency causing elevated circulating levels of nitrate, or gastrointestinal disorders with enhanced reduction of nitrate to nitrite by the bacterial gut flora.¹⁰⁷ With alternative diuretics in the form of organic mercurials available, the therapeutic use of nitrates as diuretics was abandoned by the mid-1930s.

Nitrate in Other Medicinal Preparations

The fact that most nitrate salts are readily water soluble has been exploited to produce medicines that require quick dissolution or application in liquid form. Although the effects of most of these drugs (eg, cerium and silver nitrate) have little to do with the amounts of nitrate they contain, application of large enough quantities can cause methemoglobinemia.¹⁰⁸ Presumably, the same holds true for the excessive use of toothpastes aimed at treating dental hypersensitivity, some of which contain up to 10% potassium nitrate, although no intoxication from this source is documented in the literature.

Conclusions and Outlook

Despite the widespread use of sometimes astonishing amounts of nitrite and nitrate for different indications in medicine of the past, little use is made of them in contemporary medicine (except as antidote and solubility enhancer). This is a result of several factors, some of which we have described in this review. Apart from the replacement by more modern and effective medicines in some cases, the major driving force for this development appears to have been the fear fostered by discussions, in both the lay press and scientific literature, about the purported health risks of exposure to nitrite and nitrate. Reports about methemoglobinemia in infants caused by drinks or food prepared with nitrate-rich (and bacterially contaminated) well water and vegetables such as spinach, celery, and carrots (“blue baby syndrome”), intentional and occupational intoxications in adults, increasing nitrate levels in soil and lakes as a result of fertilizer overuse, and the formation of potentially carcinogenic N-nitrosamines all contributed to the negative image that nitrite and nitrate have held in recent years. As a result, major efforts have been made to remove as much nitrite and nitrate as possible from our drinking water, to advocate replacement of nitrite by other (often less effective) food preservatives, and to establish cultivation conditions that result in crops with reduced levels of nitrate. Although possible long-term consequences of a chronically reduced intake of nitrite and nitrate on human health are unknown, doubts have been raised about the general health risk of nitrite/nitrate intake.^76,109–112 Interestingly, the average dietary intake of nitrate roughly equals that produced by the endogenous production of NO.¹¹³ Thus, if nitrite truly were of concern to human health because of its propensity to form carcinogenic nitrosamines, then the human body would have a significant evolutionary design flaw because ≈5% of all ingested and endogenously produced nitrate eventually ends up as nitrite in the stomach, as pointed out by Archer¹⁰⁹ (so far about “intelligent design”). Despite the critical voices, the image of nitrite and nitrate remains stigmatized.

What appears to have the greatest potential to change our current perception of the risk and value of nitrite and nitrate is the most recent emergence of data on the physiological and pharmacological effects of relatively low concentrations/doses of nitrite. Previously considered a biologically inert oxidative decomposition product of NO, nitrite has been proposed to be a signalling molecule in its own right.55 Given its propensity for conversion into NO and related species, unequivocal evidence for this role may be difficult to provide unless nitrite-specific signalling pathways are identified. Although speculative, it is possible that the nitrite-based reaction channels of contemporary mammalian cells are a vestige of earlier bacterial pathways and that the evolutionarily more recent l-arginine/NO pathway uses signalling cascades originally evolved for nitrite, not the other way round. Regardless, surprisingly low amounts of nitrite have been demonstrated to exert potent cytoprotective effects against ischemia/reperfusion-related tissue damage in vivo,10,11 an action possibly mediated by modulation of mitochondrial function.113 Nitrate, which has been proposed to contribute to the health-promoting effects of the Mediterranean diet,114 has been demonstrated to inhibit platelet aggregation,115 to mildly lower blood pressure,116 to enhance gastric mucosal defence mechanisms,¹⁰⁷ and to reduce the oxygen cost of exercise.¹¹⁷ The last is perhaps one of the most surprising of the more recent findings across the spectrum of nitrate actions. This particular observation may explain why an enhanced production of NO, which not only elevates blood flow and thus oxygen transport to tissues but leads to increased levels of circulating nitrite and nitrate, is crucial for the adaptation of life to the chronic hypoxia experienced at high altitude.¹¹⁸ Taken together, these results have shifted the attention away from toxic and vasodilator properties to a focus on metabolic effects. Moreover, they make one wonder to what extent inorganic nitrate may contribute to the effectiveness of organic nitrates in the setting of heart failure, for example.

Although efforts are underway to assess the potential usefulness of inorganic nitrite in a number of clinical research studies at the US National Institutes of Health, none of these are likely to whet the appetite of the pharmaceutical industry to invest substantial amounts of money into drug development because not only are intellectual property claims related to simple inorganic compounds legally difficult to defend but the material itself is cheap and readily available. The situation may change if medicinal chemists come up with new prodrugs that allow targeted delivery of nitrite to specific tissues or organs or if nitrite/nitrate is intelligently used as an adjuvant to current therapeutics. Which of the many facets of nitrite and nitrate action is likely to form the basis for future pharmaceutical exploitation is difficult to predict at present. Although rational approaches to the pharmacological treatment of medical problems have a tendency to ridicule the wisdom of century-old folk medicine and to condemn the alchemist’s doing as quackery, there is much to learn from the past. In reviewing the therapeutic use of nitrite and nitrate over centuries, it appears that some of the potential that these simple compounds may hold for medical use has not been realized, often because the basis for some unwanted drug effects was not understood and thus could not be controlled at the time. But, even if the scare factor continues to dominate mainstream thinking, there is an obvious need for a careful reassessment of the health risks of nitrite and nitrate. If initiated soon, such activity may provide the necessary “activation energy” to overcome the fear and to stimulate the development of new therapeutic principles that use pathways regulated by nitrite and nitrate.

Sources of Funding

This work was supported by funds from the Guthrie Trust (a travel grant for visiting the Wellcome History of Medicine Library in London to Dr Butler) and the Medical Research Council (Strategic Appointment Scheme to Dr Feelisch).

Disclosures

None.

Footnotes

Correspondence to Anthony R. Butler, Bute Medical School, University of St. Andrews, St. Andrews, Fife, KY16 9ST, Scotland (e-mail arb3@st-andrews.ac.uk); or Martin Feelisch, Clinical Sciences Research Institute, Warwick Medical School, Gibbet Hill Rd, Coventry, CV4 7AL, England (e-mail mf@warwick.ac.uk).

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Chapter 12.04: The Direct Addition of Nitrites to Curing Brines – The Spoils of War

06/26/202106/27/2021 eben van tonder Bacon and the art of living, Bacon History, Best Bacon direct addition of nitrite, nitrite curing, sodium nitrite

Introduction to Bacon & the Art of Living

The Direct Addition of Nitrites to Curing Brines – the Spoils of War

September 1959

Dear Tristan,

I thought I would write your sister this time around but then realised that I have to finish my tale of how sodium nitrite became the most popular way to add nitrite to curing brines. It one of the most epic developments in the curing world.

From a scientific standpoint, using sodium nitrite as the source of nitrite is an important progression of the technology of bacon curing but there was a problem. The general public saw sodium nitrite as a poison and the cost was exorbitant. It would require more than just an energetic and brilliant Master Butcher from Prague to convince the world that it is an improvement in curing technology.

Early Public Perception about Nitrite

Between the mid-1800s and early 1900s, industry and informed members of the public knew nitrite as an ingredient in medication ^[8] (Vaughn E, et al.;2010; Jul–Aug; 18(4): 190–197) and sodium nitrite as an intermediary in the chemicals dye industry. (Concerning Chemical Synthesis and Food Additives) Most people, however, knew nitrite as a toxic chemical that kills livestock and people if the drinking water has even small traces of it. Such was the concern that nitrite levels in drinking water were reported in local newspapers every week to alert the public to possible contamination. It is, therefore, no wonder that the public and authorities were very skeptical about its use in food.

At the beginning of the 1900s, scientists developed a detailed understanding of the chemistry of curing which showed the priority of nitrites. In contrast to this, the general public and their elected officials were against the direct use of nitrites in food. As is many times the case, the scientific understanding was not general knowledge.

Three parts of the world now become the focus of our attention namely Prague, Germany and in the USA, Chicago. Events, dates, and places will start to overlap and two processes will become very important, the electric arc method of extracting nitrogen from the atmosphere and the Haber process.

As we do so, it is important to understand one more point in chemistry namely the close proximity of nitric oxide (), nitrous acid (), nitric acid (), nitrite (), nitrate () and ammonia (). All have a nitrogen atom as part of either the molecule or the ion. The Haber process yields ammonia () and the electric arc process, either nitrous acid () or nitric acid (). From any of these, nitrite () can be formed. (Webb, H. W.; 1923)

Germany 1910 – 1920 – the Race to Access Atmospheric Nitrogen

Austerity for the middle class in Germany during the Great War.

By the end of the war, the largest stockpiles of nitrite in the history of humanity were in Germany. It was created by the most productive chemicals industry in the world. How this happened is fascinating!

By the late 1800s, it was apparent that the world’s growing populations will not be fed unless atmospheric nitrogen can be harvested. Solving the problem of how to achieve this became one of the biggest priorities of science. After an intense search and various processes tested on an industrial scale, including the electric arc method, the German chemist, Fritz Harber finally solved the problem with the help of Robert Le Rossignol who developed and build the required high-pressure device to create ammonia from atmospheric nitrogen.

The process was first demonstrated in 1909. The German dyes manufacturer, BASF acquired the technology and under the leadership of Carl Bosch, the first Haber-process factory went into operation in Oppau, Germany in 1913. (Concerning the direct addition of nitrite to curing brine) As a direct consequence of this development, Germany was no longer reliant on saltpetre from Chili (sodium nitrate) as fertilizer to feed its massive agriculture industry. Another consequence of the Haber process is that it made World War One possible on an industrial scale. Nitrogen is key in ammunition production. Germany and its allies could escalate the war to a never before seen level.

When ammonia is made from atmospheric nitrogen, it was possible to produce nitrates and nitrites. The concept of using nitrites as a preservative in food was not something new. There are good examples of Germans toying with the use of nitrite in food, even before the war. The German scientist, Glage (1909) wrote a pamphlet where he outlined the practical methods for obtaining the best results from the use of saltpetre in the curing of meats and in the manufacture of sausages. (Hoagland, Ralph, 1914: 212, 213)

Glage gives for the partial reduction of the saltpetre to nitrites by heating the dry salt in a kettle before it is used. It is stated that this partially reduced saltpetre is much more efficient in the production of colour in the manufacture of sausage than is the untreated saltpetre (Hoagland, Ralph, 1914: 212, 213), pointing to the fact that nitrite was being considered as a preservative and for its effect of meat colour, from the earliest times. This means that by the 1910s, German scientists tried to solve the problem by still using saltpetre as a starting point to the reaction but getting to a reduced state faster. The line of thinking of using nitrate as the starting point was finally perfected by the Irish, Danes, and British who allowed the reduction to take place at the normal pace through bacterial means. In developing tank curing, there is no indication that they had any inkling of why it worked. They merely joined different known methods which resulted in faster curing in one cohesive system.

The main obstacle to using nitrite directly was still its cost. When BASF’s new Haber process came into operation, sodium nitrite became generally and cheaply available which meant for curing of meat that it could be added directly without allowing a bacterial reduction of nitrate to nitrite first. Solving the problem by using sodium nitrite was now a serious possibility. The Great War provided the environment to “motivate” the entire meat-curing industry to change from saltpetre to sodium nitrite when saltpetre was suddenly not available for curing and survival was linked to the speed of curing which all resulted in the fact that public perceptions were put aside.

It was a document from the University of Vienna which was the first breakthrough in my research which unlocked the mechanism of how sodium nitrite became the curing chemical of choice. According to it, saltpetre was reserved for the war effort and was consequently no longer available as curing agent for meat during World War One. (University of Vienna). It was reserved for the manufacturing of explosives, and for example, the important industry of manufacturing nitrocellulose, used as a base for the production of photographic film, to be employed in war photography. (Vaupel, E., 2014: 462) It gets even better. The prohibition on the use of saltpetre gives us the background of why people started using sodium nitrite as curing salt instead of saltpetre in Germany.

In August 1914, the War Raw Materials Department (Kriegsrohstoffabteilung or KRA) was set up under the leadership of Walther Rathenau. It was Rathenau who was directly responsible for the prohibition on the use of saltpetre. (11) He, therefore, is the person in large part responsible for creating the motivation for the meat industry in Germany to change from saltpetre to sodium nitrite as a curing medium of choice. It was the vision and leadership of Walther Rathenau, the man responsible for restricting the use of saltpetre, which drove Germany to produce synthesized Chilean Saltpeter. He saw this as one of the most important tasks of his KRA. He said: “I initiated the construction of large saltpetre factories, which will be built by private industries with the help of government subsidies and will take advantage of recent technological developments to make the import of saltpetre entirely unnecessary in just a few months“. (Lesch, J. E., 2000: 1)

Fritz Harber was one of the experts appointed by Rathenau to evaluate a study on the local production of nitric acid. During World War One production was shifted from fertilizer to explosives, particularly through the conversion of ammonia into a synthetic form of Chile saltpetre, which could then be changed into other substances for the production of gunpowder and high explosives (the Allies had access to large amounts of saltpetre from natural nitrate deposits in Chile that belonged almost totally to British industries; Germany had to produce its own). It has been suggested that without this process, Germany would not have fought in the war, or would have had to surrender years earlier.” (www.princeton.edu)

So it happened that Germany became the leader in the world in synthesised sodium nitrate production and it effectively replaced its reliance on saltpetre from Chile with synthesised sodium nitrate, produced by BASF and other factories. As a result of the First World War, sodium nitrite was produced at levels not seen previously in the world and in large factories that were built, using the latest processing techniques and technology. Sodium nitrite, like sodium nitrate, was later used in the production of explosives. Nitroglycerin is an example of an explosive used extensively by Germany in World War One that uses sodium nitrite in its production.

Ball-and-stick model of Amyl nitrite used in the production of nitroglycerin. Amyl nitrite is produced from sodium nitrite. The diagram shows the amyl group attached to the nitrite functional group.

Sodium nitrite and the coal-tar dye industry

The importance of the manufacturing cost of nitrite and the matter surrounding availability can be seen in the fact that sodium nitrite has been around since well before the war. Despite the fact that it was known that nitrite is the curing agent and not nitrate, and despite the fact that sodium nitrite has been tested in meat curing agents, probably well before a clandestine 1905 test in the USA, it did not replace saltpetre as the curing agent of choice. This was due to cost restrictions as much as public opinion.

The technology that ultimately is responsible for synthesising Chilean Saltpeter and made low-cost sodium nitrite possible was incubated in the coal-tar dye and textile industry and in the medical field. The lucrative textiles and dye industry was the primary reason for German institutions of education, both in science and engineering to link with industry, resulting in strong, well-organised skills driven German economy. For example, “Bayer had close ties with the University of Göttingen, AGFA was linked to Hofmann at Berlin, and Hoechst and BASF worked with Adolph Baeyer who taught chemists in Berlin, Strasbourg, and Munich.” (Baptista, R. J.. 2012: 6)

“In the late 1870s, this knowledge allowed the firms to develop the azo class of dyes, discovered by German chemist Peter Griess, working at an English brewery, in 1858. Aromatic amines react with nitrous acid to form a diazo compound, which can react, or couple, with other aromatic compounds.” (Baptista, R. J.. 2012: 6) Nitrous acid (HONO) is to nitrite (NO2-) what nitric acid (NO3) is to nitrate (NO3-). According to K. H. Saunders, a chemist at Imperial Chemical Industries, Ltd., Martius was the chemist to whom the introduction of sodium nitrite as the source of nitrous acid was due. (Saunders, K. H., 1936: 26)

The Economic Imperative

The simple fact is that ammonia can be synthesized through the direct synthesized ammonia method at prices below what can be offered through Chilean Saltpeter. (Ernst, FA. 1928: 92 and 100) Sodium Nitrite can be supplied at prices below Chilean saltpetre and this made sodium nitrite the most effective curing agent at the lowest price since World War One.

As an example of the cost differences, the price of Nitric Acid (HNO3) from direct synthesis in 1928 was $23.60 per ton HNO3 plus the cost of 606 lb. of NH3 by-product and from Chilean Nitrate at $32.00 per ton of HNO3, plus the cost of 2840 N NO3 by-product. (Ernst, FA. 1928: 112)

The Advantage of Scale and Technology

By 1927, Germany was still by far the world’s largest direct syntheses ammonia producer. Production figures for the year 1926/ 1927 exceeded Chilean saltpetre exports even if compared with the highest levels of exports that Chilean saltpetre ever had in 1917. A total of 593 000 tons of nitrogen was fixed around the world in 1926/27. Of this figure, Germany produced 440 000 tons or 74%. The closest competitor was England through the Synthetic Ammonia and Nitrates Ltd. with a total capacity of 53 000 tons of nitrogen per year. (Ernst, FA. 1928: 119, 120) In the USA, seven direct synthesis plants were in operation with a combined capacity of 28 500 tons of nitrogen per year. (Ernst, FA. 1928: 120)

Supporting Evidence from the USA

The thesis that before the war, the production of sodium nitrite was not advanced enough for its application in the meat industry (resulting in high prices and low availability) is confirmed when we consider the situation in the USA. The first US plant for the fixation of atmospheric nitrogen was build in 1917 by the American Nitrogen Products Company at Le Grande, Washington. It could produce about one ton of nitrogen per day. In 1927 it was destroyed by a fire and was never rebuild. (Ernst, FA, 1928: 14)

An article in the Cincinnati Enquirer of 27 September 1923 reports that as a result of cheap German imports of sodium nitrite following the war, the American Nitrogen Products Company was forced to close its doors four years before the factory burned down. The imports referred to, was as a result of Germany selling their enormous stockpiles of sodium nitrite at “below market prices” and not directly linked to a lower production price in Germany, even though this was probably the case in any event. (The Cincinnati Enquirer ( Cincinnati, Ohio), 27 September 1923. Page 14.)

The meat curers initially used sodium nitrite directly (i.e. not mixed with sodium chloride). It looks similar to regular table salt. Several cases of poisoning were reported including the mass poisoning of 34 people including a child who died in Leipzig. The Government promptly banned its use (Hans Marquardt , et al, 1999:21), but in the prevailing war conditions, and with the Government’s inability to stamp out the massive black market in foods, there can be no doubt that this practice persisted throughout the war.

The practice of colouring curing salt containing sodium nitrite pink, probably stems from this indecent or incidents like this, in order to prevent people from confusing sodium nitrite with table salt. The practice became law in most countries in subsequent years and the remains to this day. The Vienna University document indicates that the fast curing of sodium nitrite was recognised and after the war, the ban was lifted. Walter Rathenau’s actions may have motivated the change, but it was the developments in synthesizing ammonia, sodium nitrate and sodium nitrite which provided the price point for the compound to remain the curing agent of choice, even after the war and after the prohibition on the use of saltpetre was lifted.

By 1909, the world production of inorganic nitrogen by the electric arc method and some miscellaneous processes were standing at a combined 3000 metric tons. The Haber process was not invented yet. One year after Ladic started working as a meat curer, by 1913, the arc and miscellaneous processes yielded 18 000 metric tons and the Haber process, 7000 metric tons.

By 1917, the arc and miscellaneous processes delivered 30 000 metric tons and the Haber process, 100 000 metric tons. This was 5 years after Ladic learned the art of curing and possibly started using sodium nitrite in meat curing. Over these five years, he has seen a dramatic increase in the availability of nitrite and therefore a reduction in nitrite prices. In 1920, the Haber process delivered a staggering 308 000 metric ton of nitrogen, compared to the 33 600 metric tons of the arc and miscellaneous processes. (Scott, E. Kilburn. 1923; : 859–76)

World War One broke out on 28 July 1914 and lasted until 11 November 1918. When the war ended, Germany had huge stockpiles of sodium nitrite (along with many other war chemicals). They had to pay a massive war debt and raise the German economy from the dead. These were desperate times and Germany threw its full energy and industriousness behind this effort. The effort focused on the lucrative market of the USA.

The USA – 1910’s – Nitrite on Trial

The drama of the sale of German nitrites played itself out in the USA and particularly in Chicago. This directly led to the creation of a legendary curing salt, Prague Salt, which later became Prague Powder. We used Prague Powder during all the years that I was with Woodys. These events played out in America.

We begin our US story by looking at public and government views on nitrite. During the 1910s, the USA wrestled with the question of whether nitrites in food constitute adulteration and its consideration created its own epic drama. Vastly opposing views were held in relation to preservatives and colourants generally. Prof. Julius Hortvet, a chemist at the Minnesota Dairy and Food Commission said in an address delivered on 16 July 1907, at the Eleventh Annual Convention of the Association of State and National Food and Dairy Departments, in Jamestown, “Some state laws go so far as to inflict fine and imprisonment for making an article appear better than it really is.” He presented the opposing view when he said that he believes that “if we must have legislation in regards to this, it would be wiser to reserve it and punish the man who did not make his food product as attractive as possible.” (American Food Journal; 1907)

In his speech, he made the following prophetic comment about saltpetre which in years to come would become one of the dominant arguments for the use of nitrite in foods. He said that “we know . . that certain substances, as salt and saltpetre, have caused death from the effects of large doses.” He then draws a brilliant comparison between these products and alcohol when he said that “alcohol is classed as a poison.” His point was that what is good for alcohol, which is a poison if consumed in high concentrations and large volumes, should be good for saltpetre (i.e. limit the amount of nitrate and nitrite in foods instead of banning it altogether, as is the case with alcohol). “In short,” he said, “the whole question sometimes is relative.” (American Food Journal; 1907)

He was “not contending that certain articles commonly used in . . . . food may or may not under certain circumstances act as a poison.” He was “simply defending . . . against two possible evils: first, the addition to . . . food of any substances that will tend to augment the possibilities of harm arising from our daily diet.” His second point sounds like one directed to the use of nitrite and its medicinal use when he said that “he is secondly defending against,” the addition to . . . foods of substances having therapeutic or even toxic properties by persons unqualified to prescribe such substances.” (American Food Journal; 1907) He is possibly tripped up by a lack of scientific understanding about nitrites at the time, but both cautionary notes are commended and points that I have for years lived by.

In the 1910s, the US Department of Agriculture had the right to promulgate “standards of purity for food products and to determine what is regarded as adulteration therein.” (American Food Journal; 1907 vol 2 no 2, 15 Feb 1907, p43) Whether these standards would become law was an open question at this stage. If there was a dispute about a substance, it was heard by a special organ of the US Department of Agriculture, the Referee Board of Consulting Scientific Experts, created in 1908. The battleground about the use of nitrites itself was not the meat industry. It seems that the meat industry considered and possibly used it in secret. The battle played out in its use as a bleaching agent in flour. The controversy came to a head in a landmark court case in 1910 related to flour.

The millers were infuriated because the attorney general opted for a jury trial instead of referring the matter to the Referee Board of Consulting Scientific Experts. (Chicago Daily Tribune; 7 July 1910; Page 15) I can only suspect that the attorney general was himself against the use of nitrites in food and probably did not want scientists to decide.

A court case was brought by the US Federal Government against the Mill and Elevator Company of Lexington, Nebraska. The charge was that they adulterated and misbranded flour and sold it to a grocer in Castle, Missouri. The government seized as evidence 625 sacks of flour from the grocer. The court case lasted five weeks. The case was brought by the government under the pure food and drug act of 1906. (Chicago Daily Tribune; 7 July 1910; Page 15) This is an act “for preventing the manufacture, sale, or transportation of adulterated or misbranded or poisonous or deleterious foods, drugs, medicines, and liquors, and for regulating traffic therein, and for other purposes.” (www.fda.gov)

The government contended that “poisonous nitrites are produced in the flour by bleaching.” They did not share the view of Prof. Julius Hortvet that we looked at earlier who said that these matters are relative to the amount of the substance used since alcohol is also a poison if used in the right quantity. The Federal Government said that “any amount of poison introduced into food is an adulteration.” (Chicago Daily Tribune; 7 July 1910; Page 15)

The issue was that as much as 80% of the flour produced in the USA during that time was bleached with a nitrogen peroxide process. Flour naturally has a creamy tint. The cheaper the grade, the more creamy it is. In ages past, flour was bleached simply by age. The chemical bleaching process with nitrogen peroxide instantly changes the yellowest flour whiter than the highest grade. The process results in residue traces of nitrous and nitric acid being left in the flour which produce nitrites and nitrates. (Chicago Daily Tribune; 7 July 1910; Page 15)

The defence argued that “nitrates (and nitrites) were present in such small quantities that no man could eat enough bread at one time to be poisoned by them.” (Chicago Daily Tribune; 7 Jul 1910; Page 15) The government contended that “if this view were upheld by the courts all foodstuffs manufactured could introduce quantities of poison into their products, infinitely small in each case, but devastating in their cumulative effect.” (Chicago Daily Tribune, 7 Jul 1910, Thu, Page 15) (I will look at the arguments and provide an overview of how the international food industry answered it in the years following 1910 in a separate letter)

This was a case of huge importance to the industry as can be seen from the list of people called upon by the defence. Pierce Butler of St Paul acted as a special attorney for the defence. (Chicago Daily Tribune; 7 Jul 1910; Page 15) Whether he still had the position in 1910 when the case was heard must be verified, but he was a lawyer of such stature that in 1908, Butler was elected President of the Minnesota State Bar Association. From 1923 to 1939 he served as Associate Justice of the Supreme Court of the United States. (saintpaulhistorical.com)

Apart from Butler, “a large staff of distinguished lawyers fought for the company whose flour was seized, and for the millers of Nebraska, the millers of Kansas, and the company who makes the bleaching machines. Among the experts who testified were all the toxicologists who testified in a previous landmark case (the Swope case), professors of chemistry and medicine from twenty universities, doctors, bakers, millers, and housewives.” (Chicago Daily Tribune; 7 Jul 1910; Thu, Page 15) After seven hours of deliberation, the jury returned a verdict in favour of the government upholding the charge that the bleached flour was both adulterated and misbranded. (Chicago Daily Tribune; 7 Jul 1910; Thu, Page 15) It is fair to conclude that by 1910, nothing was more sensitive in food production than the presence of nitrites and the use of sodium nitrite in food was highly controversial.

Sodium Nitrite Tested in Meat Curing in Chicago

In the early 1900s, in Chicago, the powerful meatpacking companies set up by Phil Armour, Gustav Swift, and Edward Morris were all looking for ways to reduce steers to beef and hogs to pork in the quickest, most economical and the most serviceable manner.” (The Indiana Gazette. 28 March 1924). The earliest reference to a test of meat curing with sodium nitrite in the USA places a secret experiment conducted where sodium nitrite was used to cure meat in 1905. ^[11] This was probably done in Chicago. When the “Pure Food and Drug Act and Meat Inspection Act” of 1906 was promulgated, it made the use of sodium nitrite in food illegal. It was not specifically forbidden, but the act was applied, for example in the 1910 court case we just looked at, in such a way that it was seen as making its use in food illegal.

During the 1910s a very interesting article appeared in Chicago that places a company with the technology to produce sodium nitrite in the same city. It appeared in the American Food Journal of 15 February 1907 entitled “Cheap Nitrogen.” It said that a Chicago-based company was producing nitric acid by the electric arc method invented by Prof. Mościcki of the University of Freiburg, Switzerland, that we looked at before. The method, in reality, was able to produce both nitric and nitrous acid (US patent US1097870) and dates back to 1901. (cesa-project.eu) The article states that the process made its production “cheap enough to be commercially applicable.” (American Food Journal. Vol 2. No 2. 15 Feb 1907, p29) The entrepreneur behind this company was William M. Thomas, who set an experimental plant up in Marshfield Avenue, Chicago. His main goal was probably to produce fertilizer. (Chicago Sunday Tribune, Nov 10, 1907)

We have already referred to the electric arc method several times. Mościcki, the inventor of the process was the former assistant to Józef Wierusz-Kowalski (1896), professor of physics, and rector (provost) at Albert-Ludwigs University in Freiburg, Switzerland. Prof Mościcki was an interesting person. After a very successful academic career and a career as an inventor, he became the 3rd president of the second Polish Republic. He was in office from 4 June 1926 to 30 September 1939. Another interesting fact relates directly to his invention is that in Bern, Switzerland, his patent application was handled by none other than Albert Einstein.

“In 1905 Einstein evaluated Prof Mościcki’s special arc furnace which employed a rotating electric arc and was used for the production of nitric (and nitrous) acid…” ”The field generated by an electromagnet was used to rotate the arc. The 26-year-old physicist (Einstein) and the still young (38) but already renowned inventor and scholar (Prof Mościcki’s) met and discussed the patented idea. Einstein was curious to know why an electric arc changed its orientation in a magnetic field.” Prof Mościcki’s became a successful businessman in Switzerland. (Zofia Gołąb-Meyer Marian. 2006) ^[12]

When we looked at the career of Ladic Nachtmullner, we have seen that the first production of nitrous acid in Switzerland was in 1910, during World War One based on the invention of Prof Mościcki. This happened “immediately after his procedure was patented.” “A factory was opened in Chippis in Wallis canton, Switzerland.” “In the subsequent years, this procedure was substantially perfected and nitrous acid could be supplied not only to Switzerland but also to neighbouring countries.” (cesa-project.eu)

What is interesting in relation to Chicago is that the American Food Journal article says that the Chicago company was already in production by 1907 manufacturing nitric acid “in a small way” from free nitrogen, using the technology invented by Mościcki’s. (American Food Journal. Vol 2. No 2. 15 Feb 1907, p29) In the USA the fixation of atmospheric nitrogen was a priority and they knew they lagged behind Germany. The first US plant for the fixation of atmospheric nitrogen was built in 1917 by the American Nitrogen Products Company at Le Grande, Washington. It could produce about one ton of nitrogen per day. In 1927 it was destroyed by a fire and was never rebuild. (Ernst, FA, 1928: 14)

We can conclude then with great certainty that there was at least one company in Chicago by 1907 that could produce sodium nitrite. Was this venture funded by the meatpacking companies? It is a question for further discovery. A much larger project got underway in 1917, but by 1923, the USA was not in a position to supply material quantities of sodium nitrite.

Nitrite Curing Known in the USA Pre-1925

A document, published in the USA in 1925 shows that sodium nitrite as a curing agent has been known well before 1925. The document was prepared by the Chicago based organisation, The Institute American Meat Packers and published in December 1925. The Institute started as an alignment of the meatpacking companies set up by Phil Armour, Gustavus Swift, Nelson Morris, Michael Cudahy, Jacob Dold and others with the University of Chicago.

A newspaper article about the Institute sets its goal, apart from educating meat industry professionals and new recruits, “to find out how to reduce steers to beef and hogs to pork in the quickest, most economical and the most serviceable manner.” (The Indiana Gazette. 28 March 1924). The document is entitled, “Use of Sodium Nitrite in Curing Meats“, and it is clear that the direct use of nitrites in curing brines has been practised from earlier than 1925. (Industrial and Engineering Chemistry, December 1925: 1243) The article begins “The authorization of the use of sodium nitrite in curing meat by the Bureau of Animal Industry on October 19, 1925, through Amendment 4 to B. A. I. Order 211 (revised), gives increased interest to past and current work on the subject.” Sodium Nitrite curing brines would therefore have arrived in the USA, well before 1925.

It continues in the opening paragraph, “It is now generally accepted that the saltpetre added in curing meat must first be reduced to nitrite, probably by bacteria, before becoming available as an agent in producing the desirable red colour in the cured product. This reduction is the first step in the ultimate formation of nitrosohemoglobin, the colour principle. The change of nitrate to nitrite is by no means complete and varies within considerable limits under operating conditions. Accordingly, the elimination of this step by the direct addition of smaller amounts of nitrite means the use of less agent and a more exact control.”

Aftermath of the Great War

At the end of World War One, England had its own stockpiles of nitrite to dispose of Sodium nitrite in the UK appeared for sale in an advertisement in the Times of London on 1 May 1919, 6 months after the armistice. (The Times, London)

The stockpile of the English was dwarfed by what was available from Germany. The German Government did not wait long before they started selling their war stockpile. An article appeared in The Watchman and Southron on 19 Feb 1921 and shows that German goods, especially chemicals have been making its way to the USA in such quantities that it was seen as a threat to the local industry.

Restrictions on German Sodium Nitrite in the USA

Our three worlds of Germany, Prague, and the USA now merge. The Detroit Free Press (Detroit, Michigan) reported on 14 Jan 1921 that “large stocks of imported sodium nitrite are offered at extremely low prices by agents of German manufacturers.”

Some of the tactics used by Germany to get goods into the USA, including goods subjected to presidential restrictions, were to import goods through the “concealment of the origin of shipment.” German chemicals, subject to such restrictions have been making their way into the USA “appearing as having been shipped from Switzerland, Italy and elsewhere. “Also, there has been extensive smuggling.” The article states that the German plans to sell their products in the USA and economic domination have been made as early as May 1919. (The Watchman and Southron, 19 Feb 1921, page 3)

Great emphasis is placed on sodium nitrite. The author of an article that appeared in The Watchman and Southron, 19 Feb 1921, misread its importance when it was reported that “sodium nitrite would seem to be of minor importance.” “Since the first of the year (Jan 1921), the Germans have glutted the American sodium nitrite market, threatening to destroy the hitherto prosperous American industry, and no relief has yet been obtained through the war trade board.” (The Watchman and Southron, 19 Feb 1921, page 3)

In April 1921, the call made in February for greater control over the import of sodium nitrite was answered when the war trade board in the USA placed an embargo on the importation of sodium nitrite. In the future, it could only be imported under license.

An article that appeared in the Detroit Free Press, 22 April 1921, reported that the goal of the embargo was to “check the heavy imports from Germany and Norway which have swamped the market in the country and reduced prices to a level below the cost of manufacture in the United States. (Detroit Free Press, 22 Apr 1921, Page 18) On 7 May 1924, The Indianapolis News, reports that the tariff for importing sodium nitrite was increased by a massive 50% from 3 cents a pound to 4.5 cents per pound. This was the maximum duty permitted under the Fordney-McCumber tariff act. The additional duty was levied in response to a petition filed by the American Nitrogen Products Company of Seattle, Washington. (Detroit Free Press, 22 Apr 1921, Page 18) In June it is reported that the measures were effective and that sodium nitrite prices were increasing. (Detroit Free Press, Detroit, Michigan, 11 June 1921, p4)

German Sodium Nitrite Appears as Curing Agent in the USA – Ingredients for Deceit.

Union Stock Yard, Chicago, 1910

Then arrived 1925 and everything seems to change as sodium nitrite became available through the Griffith Laboratories in a curing mix for the meat industry. They described Prague Salt and how they came upon the concept in official company documents as follows, “The mid-twenties were significant to Griffith as it had been studying closely a German technique of quick-curing meats. Short on manpower and time, German meat processors began curing meats using Nitrite with salt instead of slow-acting saltpetre, potassium nitrate. This popular curing compound was known as “Prague Salt.” (Griffith Laboratories Worldwide, Inc.)

In Canada, Prague Salt was classified as food adulteration. A progress report from the Canadian department of agriculture in 1925 lists the fact that “one sample of Prague salt” was tested and it was found to contain “5.87 % of potassium nitrite.” It calls it an adulteration. (Progress Report for the Years Canada. Dept. of Agriculture. Division of Chemistry, 1912)

In 1925 in the USA however, the fortunes of nitrite seem to change overnight. If the courts continue to find against the use of an ingredient in food that is seen as a food adulteration, the easiest way to solve the problem is to change the law. In Oct 1925 the American Bureau of Animal Industries legalised the use of sodium nitrite as a curing agent for meat. In December of the same year (1925) the Institute of American Meat Packers document appeared which we already referenced, “created by the large packing plants in Chicago,” entitled “The use of sodium Nitrite in Curing Meats.”

A key player suddenly emerges onto the scene in the Griffith Laboratories, based in Chicago and very closely associated with the powerful meatpacking industry. In that same year (1925) Hall was appointed as chief chemist by the Griffith Laboratories and Griffith started to import a mechanically mixed salt from Germany consisting of sodium nitrate, sodium nitrite and sodium chloride, which they called “Prague Salt.”

Probably the biggest of the powerful meat packers was the company created by Phil Armour. You will recall that Phil was the mentor who set David de Villiers Graaff on his course to build refrigerated railway cars to transport meat which became the backbone of his Anglo Boer War supply to the English forces. More than any other company at that time, Armour’s reach was global. It was said that Phil had an eye on developments in every part of the globe. (The Saint Paul Daily Globe, 10 May 1896, p2) He passed away in 1901 (The Weekly Gazette, 9 Jan 1901), but the business empire and network that he created endured long enough to have been aware of developments in Prague in the 1910s and early ’20s.

Could one of the offers of employment that Ladislav received before 1926 have been from Armour or one of the other meatpackers in Chicago? Griffith Laboratories is formed in the year following the armistice in 1919. This is the same year when the United Kingdom starts selling its sodium nitrite stockpile. Two years later, even cheaper German and Norwegian sodium nitrite start arriving in the USA. In response to this, import duties are levied against German sodium nitrite.

By April 1921, the import duties have been bolstered by a blanket embargo on importing sodium nitrite, except where a special permit is granted. In 1924, the tariffs on sodium nitrite are increased by 50% to the maximum allowed level permitted under the law. By this time, the use of sodium nitrite in curing brines were in all likelihood the norm in Chicago and the 50% increase would have impacted the bottom line of these companies.

Is it possible that by calling it the curing mix from Germany, Prague Salt (as opposed to German Salt or German Nitrites), did Griffith sidestep the import tariff and the required permit for importing sodium nitrite completely? My thesis is that it is entirely possible, even probable. It probably misrepresented the content in Prague Powder (mislabeling) as well as misrepresenting the country of origin.

Just as a side note, I have over the years seen the same trend returning to the meat industry. More and more companies pack their products without declaring the ingredients and apart from protecting the exact composition, I have seen many illegal ingredients going into meat curing in this way.

When Phil Armour passed away, his personal fortune was estimated at $50 000 000. This is almost $1,500,000,000 in 2016. So powerful were the packing companies that US anti-trust legislation was created to break these companies up. The point is that big money was at stake and a big influence on parts of the American government.

Prague Salt

Is it possible that Prague Salt is no more than a clever name given to a curing brine? Taking the full weight of the historical context of events in Prague, Germany, and the USA into account in the 1910s and 1920s; particularly the severe measures to keep German sodium nitrite out of the USA, with the last blow being dealt, in 1924; understanding the extreme pressure on the packing houses to deliver huge volumes of bacon faster, I seriously doubt it. The name was probably deliberate in referring to the salt invented by Ladic in Prague but instead of giving him credit for the invention, it was in all likelihood a ruse to distract the attention from the real issue that German sodium nitrite was still coming into the USA despite a ban.

It seems that the name, Prague Salt was crafted to misrepresent the country of origin and possibly its real composition. Importing salt was no problem. There is a possibility, of course, based on the popularity of salt from Bohemia, and the fact that we know it was widely exported, including to Germany, that the original mix was done in Germany, could even have contained salt from Prague, mixed with German sodium nitrites. Whether this was so or not, the name had enough of a basis in reality in Ladislav Nachtmullner, Praganda and the famous salts from Prague to get it past the customs officers at the American harbours and into the meatpacking plants of Chicago and later, around the world. The fact that it was tested in Canada and found to contain nitrite shows that this was not declared at borders, at least in one of the events of the import into Canada and even though this does not prove that it was done in the US also, it builds the case for the theory that it was imported into the US without disclosure of its nitrite content at the borders.

Prof. Julius Hortvet, in his address in Pittsburgh, had these prophetic concluding remarks about the future of science in the food industry. He said that “…it is imperative that the use of colouring matter should be kept under intelligent control. Regulations of the food industries will in future depend more than ever before on the results of scientific investigations, and the laboratory will become the dominant factor in the shaping of food standards and food laws.” (American Food Journal; 1907)

The legal status of nitrites as food additive was clarified in 1925 through proper legislation, based on Prof. Hortvet’s principle of “intelligent control” when science decided the matter and it was taken out of the hands of “the court of popular opinion.” However, the involvement of the packing plants and Griffith in everything that happened in 1925 raises suspicion of collusion with the US government.

The real hero in the story is the master butcher from Prague who through practical application and the exact scientific inquiry that Prof Hortvet spoke about, developed the first commercially successful curing mix, Praganda. Unknowingly, he became the central figure in the saga about the naming of Prague Powder and the worldwide phenomena of the direct addition of nitrites to curing brines. Finally, there is Griffith Laboratories. The way in which Prague Salt came into the USA was probably not above board. They did, however, became pivotal around the world in making the direct addition of sodium nitrite through Prague Salt and later, Prague Powder a worldwide phenomenon. If Ladislav was the messiah to the bacon industry with his nitrite containing curing mix, Griffith was his St. Paul, the evangelist to the gentiles!

They preached the gospel of a new curing brine that swept the world. So much so that today, it is universally used as the curing brine of choice and only a handful of artisan curing operations still use the tank curing method. Several British processors, including Direct Table Foods from Bury St Edmunds, United Kingdom, retain Tank Curing as one of the methods used to cure bacob.

This was one of the most significant developments in the world of bacon curing. As I have said many times before, understanding the limitations and the mechanics of the system is very important to the modern-day curing plant manager. The tale of nitrite and how sodium nitrite became the curing salt of choice is riveting and involves some of the most important names in scientific history.

Well, my son, there you have it. A story of suspense, intrigue, and risk-taking! Remarkable! I am excited to see you soon during your upcoming vacation. There is a chance that Lauren may come home over the same time. What a blessing that will be to Minette and me. Liam is finishing school this year as Luan is going to Grade 1. We can all go up in Kirstenbosch with Skeleton Gorge one morning and spend the day in the Botanical Gardens in Cape Town. I can not wait to see you!

Lots of love from Cape Town,

Dad and Minette.

Notes

1. The colour changes in meat.

The meat colour generally “changes” (either red, purple or brown), based on how many electrons are spinning around the iron atom which is part of myoglobin. Nitric oxide stabilizes or fixes the myoglobin colour through a reversible chemical bond. It does not colours the meat. (Pegg, B. R. and Shahidi, F.; 2000: 23 – 45) This is an important point to remember because, in the consideration of the use of nitrite in meat, nitrite can not be viewed as a meat colourant.

2. Rate of reaction.

The reaction of nitrite in meat is slow, in part due to the very small quantity used in the curing brine. The rate of reaction, as always, depends on the concentration of the reactants, the pH and temperature.

3. Nitrosating species from nitrous acid.
“The first step in the reaction sequence beginning with nitrous acid is the generation of either a nitrosating species or the neutral radical nitric oxide (NO).” (Sebranek, J. and Fox, J. B. Jn.. 1985)

The following list gives the relative reactivities of various nitrosating species, species 1 being the strongest and species 5 being the weakest.

Species 1:

Source: “From smoke which has many other phenolic compounds”

Species 2:

Source: From curing salt

Species 3:

Source: Found in the air.

Species 4:

Source: Nitrous acid anhydride

Species 5:

Nitrose derivatives of citrate, acetate, sulphate, phosphate.

Sources: Cure ingredients, weakly reactive under certain conditions.

I excluded those found under very acidic conditions. (Comparison by Sebranek, J. and Fox, J. B. Jn.. 1985)

4. The term “nitrite”

“The term nitrite is used generically to denote both the anion, , and the neutral nitrous acid , but it is the latter which forms nitrosating compounds.” (Comparison by Sebranek, J. and Fox, J. B. Jn.. 1985)

5. Reducing agents in the meat system.

One such mechanism for the conversion of “nitrite to nitric oxide in meat is by oxidation of myoglobin to metmyoglobin (brown coloured meat; Fe3+). This oxidation-reduction coupling produces both nitric oxide and metmyoglobin. It has been suggested by Kim et al. (2006) that metmyoglobin can be converted back to deoxymyoglobin through metmyoglobin reducing activity (MRA), a reaction facilitated by lactate. It is the enzyme activity of LDH that helps convert lactate to pyruvate and produce more NADH. Hendgen-Cotta et al. (2008) suggested that deoxymyoglobin can convert nitrite to nitric oxide and the generation of more deoxymyoglobin is likely to result in more nitric oxide (NO) from nitrite and less residual nitrite.” (Mcclure, B. N.; 2009: 28)

Several specific biochemical reducing systems have been the subject of intense investigation as far as their importance in the development of cured meat colour is concerned.

“Endogenous compounds such as cysteine, reduced nicotinamide adenine dinucleotide, cytochromes, and quinones are capable of acting as reductants for NOMb formation (Fox 1987). These reductants form nitroso-reductant intermediates with NO and then release the NO to Mb, forming a NOmetMb complex that is then reduced to NOMb. In model systems, the rate-limiting step in the production of NOMb was the release of NO from the reductant-NO complex (Fox and Ackerman 1968). Several researchers have investigated the effects of endogenous muscle metabolites including peptides, amino acids, and carbohydrates on the formation of NOMb. Tinbergen (1974) concluded that low-molecular-weight peptides such as glutathione and amino acids with free sulfhydryl groups were responsible for the reduction of nitrite to NO, which is subsequently complexed with Mb to produce NOMb. Similar work by Ando (1974) also suggested that glutathione and glutamate are involved in cured-meat colour formation. Depletion of these compounds in meat via oxidation occurs with time, but reductants such as sodium ascorbate or erythorbate are added to nitrite-cured meats before processing to ensure good colour development (Alley et al. 1992) The role of reductants in heme-pigment chemistry is somewhat ambiguous, but they can promote oxidation and even ring rupture under certain conditions. Thus to form cured meat pigment, two reduction steps are necessary. The first reduction of nitrite to NO and the second is conversion of NOmetMB to NOMb.” (Pegg, B. R., and Shahidi, F.; 2000: 44, 45)

6. Sugar as reducing agent.

“Sugars itself does not reduce dinitrogen trioxide in the way that ascorbate or erythorbate does, but it contributes to “maintaining acid and reducing conditions favorable” for the formation of nitric oxide.” (Kraybill, H. R.. 2009)”Under certain conditions reducing sugars are more effective than nonreducing sugars, but this difference is not due to the reducing sugar itself. The exact mechanism of the action of the sugars is not known. It may be dependent upon their utilization by microorganisms or the enzymatic systems of the meat tissues.” (Kraybill, H. R.. 2009)

7. Ascorbate or erythorbate supplements sugar.

An excellent reducing agent was discovered in the 1920s when ascorbate was isolated. As early as 1927, two German chemists, J. Tillmans and P. Hirsch (1927) observed that there is a correlation between the reducing capacity of animal tissue and their vitamin C content. (Concerning the Discovery of Ascorbate) . It reacts so aggressively (effectively) with nitrite, that a less effective, but more manageable cousin (an isomer of ascorbate), erythorbate turned out to be the most practical to use in curing brines along with nitrite and salt.

Ascorbate (vitamin C) reacts so aggressively (effectively) with nitrite, that a less effective, but more manageable cousin (an isomer of ascorbate), erythorbate turned out to be the most practical to use in curing brines along with nitrite and salt.

The old curing brines of the 1800s consisting of saltpeter (nitrate), sugar (create reducing conditions) (6) and salt are, therefore, equivalent to the current curing brines of nitrite (being added directly), erythorbate (reducing agent) and salt. The same general functionality at vastly reduced curing time.

Today, nitrate is still being added to many curing brines as a reservoir for future nitrite as bacteria continue to change nitrate into nitrite. This bolsters the residual nitrite levels in cured meat which is important since it was found that nitrite has a unique anti-microbial function in cured meat, in addition to its function of fixing the cured colour and contributing to the cured taste. It is unique in the sense that it is the most effective chemical control against a highly lethal pathogen, clostridium botulinum. (Concerning Nitrate and Nitrite’s antimicrobial efficacy – chronology of scientific inquiry)

Table salt remains the most important curing agent, but salt alone will not give the cured colour or taste and will not, on its own, be effective against clostridium botulinum. Sugar is still being used in many brines today, mostly to enrich the taste profile and to create browning during frying, especially in bacon. Its contribution to reducing conditions is now secondary and since the addition of ascorbate or erythorbate. Saltpeter has been replaced by sodium nitrite.

8. Nitrite as medicine.

“The organic nitrite, amyl of nitrite, was initially used as a therapeutic agent in the treatment of angina pectoris in 1867, but was replaced over a decade later by the organic nitrate, nitroglycerin (NTG), due to the ease of administration and longer duration of action.” BACK TO POST

9. Azo dye and textile colouring in 1895.

“Dyeing with Diazotised Dyestuffs

All the diazotised dyestuffs belong to the substantive group, and therefore, all that has been said with regard to these dyestuffs and their manner of application applies to the former also. In the majority of instances, however, the dyeings obtained directly are not sufficiently fast to be usable in that condition. Nevertheless, they can be converted into fast dyeings — provided the dyestuff contains free amino groups — by diazotising, followed by developing or coupling. The chemical reactions and method of procedure are just the sam.e as in the case of cotton.

In practice, the diazotising is effected in the following manner : —

The dyed and rinsed silk is entered at once into the cold diazotising bath and is worked about constantly for fifteen to thirty minutes. For every 100 parts of silk, the bath contains 3 parts of sodium nitrite dissolved in 1500-2000 parts of cold water, 8-10 parts of crude hydrochloric acid (20° Be.) being added. The operation must be conducted in wooden vats, metal vessels or fittings (lead excepted) being unsuitable. At one time, ice was used for cooling during the process, but this has been given up in favour of water at ordinary temperature, and in some cases, e. g. diazo indigo blue, the bath may be allowed to rise to 20-30° C. As a rule, the diazotisation will be complete in fifteen minutes, though some dyestuffs take longer and have to be left in the nitrite bath for half an hour. The goods are centrifuged or squeezed, contact with metal being avoided. A lead-lined hydro-extractor may be used, or else the goods must be wrapped in packing-cloth.

The intermediate diazo compound formed on the fiber is very unstable and sensitive to light, especially direct sunlight. The operation must therefore be carried on in a shady room, and care be taken to prevent any part of the diazotised goods from getting dry, or streaks and spots will be formed in the coupling stage. The diazotised material is rinsed and then immediately entered into the developing bath. The nitrite baths will keep for a considerable time and can be freshened up for use by the addition of one-third the original amounts of nitrite and acid. During the whole process the bath should smell strongly of nitrous acid. In the case of light shades, the bath may be weaker in nitrite and acid.” (Ganswindt, A; 1895: 98, 99) BACK TO POST

10. The Professional Career of Ladic

After his apprenticeship, he worked in several factories in Praha (Kracik, Beranek, Ugge-Sitanc and Miskovsky) as an assistant. His first work as a specialist in his field was with A. Chmel, Fr. Hlousek in Paha, Fr. Strnad in Lazne Luhacovice, and later in Germany, at the factories of Josef Sereda, Fr. Seidl, Zemka and Leopold Fisher in Berlin.

He worked as a “cellar man” at Josef Cifka, Vaclav Miskovsky in Praha, Kat. Rabus & Son in Zagreb, Jugoslavia,

Later he worked as a Foreman (Workman Leader) for the companies, Fr. Maly, Vacl. Havrda, A. Kadlec in Praha and Alexander Brero, Hard a/Bodensee Vorarlbersko and, in the end, he worked as a “Quick Production Specialist” for the export of hams for Carl Jorn A.-., Hamburg, Germany, Herrmann Spier, Elberfeld, Westfalsko, Karl Frank, Urach b/Stuttgart, Wurttemberg, A. Brero & Co, St. Margrethen, Switzerland.

11. The first War Raw Materials Department (KRA) in Germany was created (KRA) in mid-August 1914, as suggested by Walther Rathenau. (Vaupel, E. 2014: 462) Walter was the son of the founder of AEG and “one of the few German industrialists who realized that governmental direction of the nation’s economic resources would be necessary for victory, Rathenau convinced the government of the need for a War Raw Materials Department in the War Ministry. As its head from August 1914 to the spring of 1915, he ensured the conservation and distribution of raw materials essential to the war effort. He thus played a crucial part in Germany’s efforts to maintain its economic production in the face of the tightening British naval blockade.”

References:

Ladislav Nachmüllner vulgo Praganda. Nachmüllnerová, Eva, Editor, 2000, Translated by Monica Volcko

1907. American Food Journal. Volume 2.Chicago Daily Tribune, 7 Jul 1910, Thu. P15Chicago Sunday Tribune, Nov 10, 1907, The Cincinnati Enquirer ( Cincinnati, Ohio), 27 September 1923. Page 14

The Detroit Free Press (Detroit, Michigan) reported, 14 Jan 1921, p 16Detroit Free Press, Detroit, Michigan, 11 June 1921, p4

Detroit Free Press, 22 Apr 1921, Fri, Page 18Ernst, FA. 1928. Fixation of Atmospheric Nitrogen. D van Nostrand, Inc.http://www.fda.gov/RegulatoryInformation/Legislation/ucm148690.htm

Gamgee, A. 1867 – 1868. Researches on the Blood. On the Action of Nitrites on the Blood. Proceedings of the Royal Society of London. Vol. 16 (1867 – 1868), pp. 339-342. Published by: Royal Society.

Ganswindt, A. 1895. Dyeing. Silk, Mixed silk fabrics and artificial silks. Translated from German by Charles Salter. Scott, Greenwood & Son.Griffith Laboratories Worldwide, Inc. official company documents.

Hoagland, Ralph. 1914. Coloring matter of raw and cooked salted meats. United States Department of Agriculture. National Agricultural Library. Digital Collections.

Hiemstra-Kuperus, E. 2010. The Ashgate Companion to the History of Textile Workers, 1650–2000. Ashgate Publishing, Ltd.

The Indiana Gazette, 28 March 1924The Indianapolis News, 7 May 1924, Wed, Page 1

Jones, G. 1920. Nitrogen: Its Fixation, Its Uses in Peace and War. The Quarterly Journal of Economics. Vol. 34, No. 3 (May, 1920), pp. 391-431. Oxford University Press.

Kim-Shapiro, D. B., Schechter, A. N., Gladwin, M. T. 2006. Unraveling the Reactions of Nitric Oxide, Nitrite, and Hemoglobin in Physiology and Therapeutics. Arteriosclerosis, Thrombosis, and Vascular Biology. Published online before print January 19, 2006.

Kraybill, H. R.. 2009. Sugar and Other Carbohydrates in Meat Processing. American Meat Institute Foundation, and Department of Biochemistry, The University of Chicago, Chicago, Ill. USE OF SUGARS AND OTHER CARBOHYDRATES IN THE FOOD INDUSTRY. Chapter 11, pp 83–88. Advances in Chemistry, Vol. 12. Publication Date (Print): July 22, 2009 . 1955

Ladislav Nachmüllner vulgo Praganda Nachmüllnerová, Eva. OSSIS,2000Mcclure, B. N.; 2009.

The effect of lactate on nitrite in a cured meat system. Iowa State University.Packer, L. 1996. Nitric Oxide, Part 1. Academic Press.

Pegg, B. R. and Shahidi, F. 2000. Nitrite Curing of Meat. Food & Nutrition Press, Inc.

Polenske. E.. 1891 Works from the Imperial Health office, Volume 7, Springer, Berlin, S. 471-474Progress Report for the Years Canada. Dept. of Agriculture. Division of Chemistry.

Sebranek, J. and Fox, J. B. Jn.. 1985. A review of nitrite and chloride chemistry: Interactions and implications for cured meats. J. Sci. Food. Agric. 1985, 36, 1169 – 1182.

The Saint Paul Daily Globe, 10 May 1896,

http://saintpaulhistorical.com/items/show/183

http://www.stm-ke.sk/index.php/en/detached-expositions/solivar-near-presov

Scott, E. Kilburn. 1923. “NITRATES AND AMMONIA FROM ATMOSPHERIC NITROGEN. Lecture I”.

Journal of the Royal Society of Arts 71 (3702). Royal Society for the Encouragement of Arts, Manufactures and Commerce: 859–76.

http://www.jstor.org/stable/41356346.

Sullivan, G. A., 2011. “Naturally cured meats: Quality, safety, and chemistry”. Graduate Theses and Dissertations. Paper 12208.Sydney Morning Herald on 1 Mar 1870 (p4)

The Times, London, Greater London, England, 1 May 1919, Page 18Toldr, F.. 2010.

Handbook of Meat Processing. John Wiley & Sons Inc.Turmock, D.. 1989.

Eastern Europe: A Historical Geography 1815-1945.

RoutledgeVaughn E. Nossaman, Bobby D. Nossaman, Philip J. Kadowitz; Cardiol Rev. Author manuscript; available in PMC 2011 July 1; Published in final edited form as: Cardiol Rev. 2010 Jul–Aug; 18(4): 190–197. 10.1097/CRD.0b013e3181c8e14a

The Watchman and Southron, 19 Feb 1921, Sat, First Edition, page 3

The Weekly Gazette, 9 Jan 1901, Wed, Page 3

Webb, H. W.. 1923. Absorption of Nitrous Gasses. Edward Arnolds & Co, London.

Zofia Gołąb-Meyer Marian. 2006. Albert Einstein and Ignacy Mościcki’s, Patent Application. Smoluchowski Institute of Physics, Jagellonian University, Cracow, PolandImages

Image

1: Old Prague: Old Prague Logansport Pharos-Tribune Sat Oct 19, 1895Image

2: Ladislav Nachmüllner from Ladislav Nachmüllner vulgo Praganda Nachmüllnerová, Eva. OSSIS, 2000.Image

3: Ladislav Nachmüllner from Ladislav Nachmüllner vulgo Praganda Nachmüllnerová, Eva. OSSIS, 2000.Image

4: Sodium nitrite, photos by Prof Duchon.Image

5: Germany. http://theintersectionist.com/wp-content/uploads/2012/05/austerity-for-middle-class-meat-market.jpg

Image 6 and 7: Notice of sale by UK government: The Times, 1 May 1919, Thu, Page 18Image 8: Union Stock Yard, Chicago. The Modern Packing House. 1905, 1921. Nickerson & Collins.

Mechanisms of Meat Curing – From Hoagland in 1914 to Pegg and Shahidi in 2000

08/14/201608/16/2016 eben van tonder Nitrite, recent history, Sodium Nitrite history food science, Hoagland, Meat curing, Mechanisms of meat curing, nitrite curing, sodium nitrite

Mechanisms of Meat Curing – From Hoagland in 1914 to Pegg and Shahidi in 2000.
By: Eben van Tonder
14 August 2016

BACKGROUND AND OVERVIEW

Managing a meat curing operation in Cape Town at Woodys Consumer Brands (Pty) Ltd., the need exist to have a thorough understanding of meat curing mechanisms to ensure that conditions exist to optimise cured colour development, limit bacterial growth and deliver good product flavour and taste.

In the next three articles we look at colour development. This first article sets the historical context by reviewing the 1914 landmark article by Hoagland; we briefly outline the current understanding of cured colour development from the work of Pegg and Shahidi and we overview one mechanism that has recently been described. Overall, we focus on the importance of nitric oxide (NO) in cured colour development for both fresh and cooked cured meat.

INTRODUCTION

The formation of cured meat colour takes place “by the reaction of nitrite with the natural meat pigment myoglobin to form dinitrosyl ferrochrome (DNFH). The pigment, which gives meat its characteristic cured-meat colour, is formed from the meat pigment myoglobin, which consists of an iron porphyrin complex, the heme group, attached to the protein globin. In the presence of nitrite, the bright red nitrosomyoglobin is formed, in which the H2O in the axial position on the heme iron is replaced by nitric oxide (NO). The NO is formed from nitrite by the natural reducing activity of the muscle tissue, which is accelerated by the addition of reductants such as ascorbic acid. In heatprocessed cured meat, the globin has been split off to a heat-stable pink pigment, nitrosyl hemochromogen.” (Soltanizadeh, N., Kadivar, M.. 2012)

This understanding of curing developed over many years with input from a variety of scientists. (The Fathers of Modern Meat Curing) One of these influential minds was Ralph Hoagland. His brilliance is seen in his academic work that helped to shape the meat curing industry. He had wide appeal in academic and industry circles as well as the popular press. He contributed immensely to the developing sciences of nutrition and meat processing with a special interest in pork processing and pork nutrition.

He was the Senior Biochemist, Biochemie Division, Bureau of Animal Industry, United States Department of Agriculture in Chicago who was, at this time, one of the curing centers of the world along with Denmark and Calne, in the United Kingdom where the Harris operation started.

He served as the department head of the Minnesota College of Agriculture (part of the University of Minnesota), appointed in 1909. The College of Agriculture later became the College of Biological Sciences. (http://cbs.umn.edu/ and The Bismarck Tribune; 1912)

In 1908 he published results obtained upon studying the action of saltpeter upon the colour of meat and “found that the value of this agent in the curing of meats depends upon its reduction to nitrites and nitric oxid, with the consequent production of NO-hemoglobin, to which compound the red color of salted meats is due.” He found that “saltpeter, as such, [had] no value as a flesh-color preservative.” (Hoagland, R. 1914)

In 1914 he published, Colouring Matter of Raw and Cooked Salted Meat. Reviewing this article has two important objectives.

1. It shows what was understood by 1914 about meat curing and colour formation in particular. This has important implication for determining an accurate chronology of developments around the direct addition of nitrite to curing brines, such as the invention of Praganda in Prague in 1915 and later, the introduction of Prague Salt in Chicago (The Naming of Prague Salt) where Hoagland worked for a time.

2. It is a novel way for an introduction into meat curing mechanisms and shows the progression in our understanding.

I interject the thoughts of Hoagland from 1914 with quotes on our current understanding by two of the leading scientists on the subject namely Ronald B. Pegg and Fereidoon Shahidi with quotes from their 2000 publication, Nitrite Curing of Meat.

Ronald Pegg is currently a professor at the Department of Food Science & Technology, University of Georgia. A great piece appeared about him in FST News (from the University of Georgia Department of Food Science and Technology). “He is a researcher who feels equally at home in the classroom and the laboratory. In addition to inspiring students with the chemistry of chocolate and coffee, he’s become one of the nation’s most sought-after experts on the nutrient content of food and the bioactive compounds that make blueberries, peanuts and other nutritionally dense superfoods so “super.” Pegg joined the faculty of UGA in 2006. He immediately saw the need for a more hands-on, practical approach to teaching food chemistry. His work with students has earned him Food Science and Technology Outstanding Undergraduate and Graduate Professor awards five times. Pegg has received a major teaching honor from his department, the college or the university every year since 2007.” “In addition to his time in the classroom, Pegg has received accolades from producer groups for his research into bioactive chemistry and the health benefits of pecans, peanuts, peaches and other crops.” (http://www.foodscience.caes.uga.edu/)

His research and publishing partner in Nitrite Curing of Meat is Fereidoon Shahidi. He is a university research professor at the Department of Biochemistry, Memorial University of Newfoundland St. John’s, Canada. This monumental food scientist “has received numerous awards, including the 2005 Stephen Chang Award from the Institute of Food Technologists, for his outstanding contributions to science and technology. Between 1996 and 2006, Shahidi was the most published and most frequently cited scientist in the area of food, nutrition, and agricultural science as listed by the ISI.” (wikipedia.org/wiki/Fereidoon_Shahidi)

THE COLOUR OF FRESH MEAT

Hoagland starts with the colour pigment of fresh meat, oxyhemoglobin. The word itself tells us what it is. Oxy is oxygen, connected to hem which is hamatin or the colouring group and globin, the protein. In Oxyhemoglobin, ogygen is connected to “hemoglobin, which is the protein molecule in red blood cells that carries oxygen from the lungs to the body’s tissues and returns carbon dioxide from the tissues back to the lungs.” (medicinenet)

Hoagland states that oxyhemoglobin, is “part of which is one of the constituents of the blood remaining in the tissues, while the remainder is a normal constituent of the muscles,” and “responsible for the red color of fresh lean meat, such as beef, pork, and mutton.” (Hoagland, R. 1914) Today we know that the colour of fresh lean meat is due to myoglobin, “the pigment in muscle that carries oxygen” (medicinenet), as opposed to protein in the blood.

The reason for using hemoglobin, instead, may have been “a matter of convenience” and “a matter of necessity since myoglobin was not isolated and purified until 1932,” (Theorell, 1932) a full 18 years after Hoagland published. “In spite of the differences between hemoglobin and myoglobin, Urbain and Jensen (1940) considered the properties of hemoglobin and its derivatives sufficiently like those of myoglobin to allow the use of hemoglobin in studies of meat pigments.” (Cole, Morton Sylvan, 1961: 2)

Despite the fact that it is oxymyoglobin that is responsible for the bright red colour of fresh meat, we follow his arguments using oxyhemoglobin since the same mechanisms of colour development applies in both proteins. Pegg and Shahidi uses myoglobin.

Our current understanding: Oxymyoglobin (Mb, bright red, – ferrous state)

Oxymyoglobin is the result of myoglobin’s affinity for and it results in a bright red bloom within minutes of fresh meat’s exposed to air. The reaction is rapid and reversible. The continued red bloom depends on a “continuing supply of .” (Pegg, R. B and Shahidi, F; 2000: 31) This is “because the enzymes involved in oxidative metabolism rapidly use the available .” (Pegg, R. B and Shahidi, F; 2000: 31)

“With time, the small layer of oxymyoglobin present on the surface of the meat propagates downward, but the depth to which diffuses depends on several factors, such as the activity of oxygen-utilizing enzymes (i.e., consumption rate of the meat), temperature, pH, and external pressure. In other words, as air diffuses inward, an and a color gradient are established throughout the meat. Muscles differ in their rates of enzyme activity which, in turn, regulate the amount of available in the outermost layers of tissue. As the pH and temperature of the tissue increase, enzymes become more active and the content is reduced. Consequently, maintaining the temperature of the meat near freezing point minimizes the rate of enzyme activity and the utilization and helps maintain a bright red color for the maximum possible time.” (Pegg, R. B and Shahidi, F; 2000: 31)

THE COLOUR OF CURED MEAT

Generally, Hoagland saw the cured colour of meat as “the same color as the fresh meat.” (Hoagland, R. 1914) There is a difference between the cured colour of fresh meat and the cured colour of cured-cooked meat. He recognised this difference and said that “the red color is not destroyed on cooking, but rather it is intensified.” (Hoagland, R. 1914)

The nature of these two different kinds of colour is the subject of his article, “undertaken for the purpose of obtaining more complete information concerning the color of raw and cooked salted meats.” (Hoagland, R. 1914)

HISTORICAL BACKGROUND

In his historical summary, he lists the following developments that lead up to his own work.

-> Weiler and Riegel

“Weiler and Riegel (1897), in the examination of a number of samples of American sausages, obtained a red coloring matter on extracting the samples with alcohol and other solvents, which color they concluded to be in some manner due to the action of the salts used in curing upon the natural color of the meat. On account of similarity of spectra, this color was considered to be methemoglobin.” (Hoagland, R. 1914)

Our current understanding: metmyoglobin (metMb, brown, ferric state)

Methemoglobin and metmyoglobin actually is the brown colour of meat which develops after meat has been standing for some time. Myoglobin exists within the interior of meat and has a purple-red colour. “This is the colour of Myoglobin” (Pegg, R. B and Shahidi, F; 2000: 31) Reductants generated within a cell by enzyme activity prevents the meat from turning brown, until this is no longer available. The heme iron (in the ferrous state – ) is oxidized to the ferric state () . (Pegg, R. B and Shahidi, F; 2000: 31)

It is generated as follows. The superoxide anion () is removed from the hematin. A water molecule is added. This gives a high-spin ferric hematin. “The ferric ion, unlike its ferrous counterpart, has a high nuclear charge and does not engage in strong bonding. Therefore, metmyoglobin is unable to form an oxygen adduct. (Pegg, R. B and Shahidi, F; 2000: 31)

-> Lehmann and Kisskalt

Lehmann (1899) identified nitrite as responsible for the red colour of meat and not nitrate. Kisskalt (1899) confirmed this and noted that “if the meat was first allowed to stand several days in contact with saltpeter and then boiled, the red color appeared” (Hoagland, R. 1914)

-> John Scott Haldane

John Scott Haldane (1901) made several important observations after an extensive study of the colour of cooked salted meat.

He attributed the colour of cooked salted meat “to the presence of the nitric oxide hemochromogen” (reduced hematin; Fe in reduced ferrous state, ; obtained by boiling oxymyoglobin/ oxyhemoglobin with a reducing agent). (Hoagland, R. 1914) He correctly concluded that nitric oxide hemochromogen is “resulting from the reduction of the coloring matter of the uncooked meat, nitric-oxid hemoglobin (NO-hemoglobin).” Hemochrome can be any of a number of complexes with the iron-porphyrin complex with one or two basic ligands (normally amines).

The terms nitric oxide hemochromogen, nytrosomyochrome, nitrosyl hemochrome, nitric oxide hemochrome, nitric oxide denatured globin hemochromogen, denatured globin nitric oxide ferrohemochrome, pigment of cured, heated meat, all as synonyms to refer to the same thing. (ICMSF; 1980: 140) Chromogen is a substance which can be easily converted into dye or other coloured compound for example through oxidation. Since the 1940’s, the term “hemochrome” (hem and chrome) has been used instead of “hemochromogen” and “parahematin.” “The term “hemochromogen” is associated historically with an erroneous conception of one of these substances as the colored component of hemoglobin. These compounds are in any case not “chromogens” in the chemical sense, i.e., ieuco compounds. The new term has the additional advantage of greater brevity.” (Lemberg, R. and Legge, J. W.; 1949: 165)

Linossier was the first to describe it and produced it by passing nitric oxide through hematin. (Haldane, J. S.. 1901) After careful study and observation, Haldene drew the following brilliant conclusions.

1. “The red colour of cooked salt meat is due to the presence of NO-haemochromogen.” (Haldane, J. S.. 1901)

2. “The NO-haemochromogen is produced by the decomposition by heat of NO-haemoglobin, to which the red colour of unsalted meat is due.” (Haldane, J. S.. 1901)

3. “The NO-haemoglobin is formed by the action of nitrite on haemoglobin in the absence of oxygen, and in presence of reducing agents.” (Haldane, J. S.. 1901)

4. “The nitrite is formed by reduction within the raw meat of the nitre used in salting.” (Haldane, J. S.. 1901)

5. “The nitrite is destroyed by prolonged cooking.” (Haldane, J. S.. 1901)

Our current understanding: nitric oxide hemochrome (Cooked Cured Meats – one nitric oxide molecule per heme).

When heated, NO-myoglobin (nitrosyl myoglobin) is transformed to nitrosyl myocromogen, which is denatured NO-myochromogen. This happens upon thermal processing. The globin unfolds (denatures); the iron atom comes loose from the globin; the unfolded globin folds itself around the heme functional part (moiety) which is the iron-porphyrin complex. This brings about the characteristic reddish-pinkish colour of cooked cured meat. (Pegg, R. B and Shahidi, F; 2000: 42)

By way of application, note that “there is a direct relationship between the concentration of NO-myoglobin in the muscle and the intensity of the cured colour” and NOT the nitrite level. “When muscle tissue are cured with equivalent amounts of nitrite, a more intense cured meat colour is produced in,” for example, corned beef as opposed to ham. “The addition of excess nitrite to that required to fix the pigment does not increase the intensity of the cured meat colour.” (Pegg, R. B and Shahidi, F; 2000: 42) This being the case, it is also true that if the concentration of nitrite and therefore nitric oxide formation is to low, that it will impact colour development.

He mentions Orlow (1903) who stated that “the red color of sausages is due to the action upon the color of the fresh meat of the nitrites resulting from the reduction of the saltpeter used in the process of manufacture.” (Hoagland, R. 1914)

“Humphrey Davy in 1812 (cited by Hermann, 1865) and Hoppe-Seyler (1864) noted the action of nitric oxid upon hemoglobin, but it appears that Hermann (1865) was the first to furnish us with much information as to the properties of this derivative of hemoglobin. He prepared NO-hemoglobin by first passing hydrogen through dog’s blood until spectroscopic examination showed that all of the oxyhemoglobin had been reduced to hemoglobin, then saturating the blood with pure nitric oxid prepared from copper and nitric acid, and finally again passing hydrogen through the blood to remove all traces of free nitric oxid.” (Hoagland, R. 1914)

By the time of publishing this article in 1914, he notes that NO-hemoglobin was mentioned very briefly in most of the texts on physiological or organic chemistry as being a hemoglobin derivative of “but little practical importance.” “Abderhalden (1911) and Cohnheim (1911), however, describe this compound quite fully.” (Hoagland, R. 1914)

Hoagland conducted several further experiments with NO-hemoglobin and outlined it in his 1914 paper.

COLOUR OF FRESH, CURED MEAT

He first deals with the Colour of Uncooked Salted Meats. “To a sample of finely ground fresh beef was added 0.2 per cent of potassium nitrate, and the material was placed in a refrigerated room at a temperature of 34 deg F (1 deg C) for seven days. At the end of that period the meat had a bright-red color, but gave evidences of incipient putrefaction.” (Hoagland, R. 1914) He did the same by curing the meat with nitrite. He correctly concluded that the colour of fresh meat, cured with nitrite, is due to NO-hemoglobin. (Hoagland, R. 1914)

Our current understanding: nitric oxide myoglobin (NOMb, red, ).

“When nitrite is added to comminuted meat, the meat turns brown because nitrite acts as a strong heme oxidant. The oxidizing capacity of nitrite increases as the pH of meat decreases, but nitrite itself may also partly be oxidized to nitrate during curing and storage. Myoglobin and are oxidized to metMb by nitrite. The ion itself can be reduced to . These products can combine with one another to form an intermediate pigment, nitrosylmetmyogloboin ().” (Pegg, R. B and Shahidi, F; 2000: 40)

“Nitrosylmetmyoglobin is unstable. It auto-reduces with time and in the presence of endogenous and exogenous reductants in the postmortem muscle tissue to the corresponding relatively stable Fe(II) form, nitrosylmyoglobin (NOMb).” (Pegg, R. B and Shahidi, F; 2000: 40)

A new suggestion was proposed as a mechanism for the meat curing process by Killday et al. (1988)

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“They suggested that is more adequately described as an imidazole-centered protein radical. This radical undergoes autoreduction yielding NOMb, and lacking exogenous reductants, reducing groups within the protein can donate electrons to the imidazole radical.” (Pegg, R. B and Shahidi, F; 2000: 40)

An interesting study by Corforth et al. (1998) strengthened the mechanism posed by Killday et al. (1988). “Cornforth and co-workers examined the relative contribution of CO and towards pink ring formation in gas oven cooked beef roast and turkey rolls. Data showed that pinking was not evident with up to 149 ppm of CO or 5 ppm of NO present in the burning gases; however, as little as 0.4 and 2.5ppm of was sufficient to cause pinking of the turkey and beef products, respectively. Cornforth et al. (1998) proposed that pinking previously attributed to CO and NO gas in ovens is instead due to which has much greater reactivity than NO with moisture at the surface of meats. Their argument was predicated on the fact that NO has a low water solubility unlike that of . Therefore on the basis of this consideration, NO would be an unlikely candidate to cause pink ring, since at the low levels typical of gas ovens or smokehouses, NO would be unable to enter the aqueous meat system in sufficient quantity to cause pink ring at depths up to 1 cm from the surface. On the other hand, reacts readily with water to produce nitrous and nitric acid.” (Pegg, R. B and Shahidi, F; 2000: 40, 42)

“Nitrous acid produced at meat surfaces would be free to diffuse inwards, where endogenous or exogenous meat reductants, including Mb itself may regenerate NO. Nitric oxide binds to MetMb followed by rapid autoreduction to NOMb as suggested by Killday et al. (1988).” (Pegg, R. B and Shahidi, F; 2000: 42)

NOMb is therefore responsible for the characteristic red colour of fresh cured meat before thermal processing. The NOMb pigment can be produced by the direct action of NO on a deoxygenated solution of Mb, but in conventional curing, it arises from the action of nitrite, as stated above. (Pegg, R. B and Shahidi, F; 2000: 42)

Hoagland’s conclusion in his 1914 article is, however, limited to NO formation and its role in cured colour formation. He states that “the evidence is ample to show that the action of saltpeter in the curing of meats is primarily to cause the formation of NO-hemoglobin ; but it is very possible that under certain conditions of manufacture or processing to which salted meats are subject, the NO-hemoglobin may undergo changes.”

COLOUR OF COOKED, CURED MEAT

“Haldane has shown that the red color of cooked salted meats is due to the presence of NO-hemochromogen, a reduction product of NO-hemoglobin to which the color of uncooked salted meats is due.”… “While Haldane’s work seems to show clearly that the color of cooked salted meats is due to NO-hemochromogen, it has seemed desirable to study the subject further and to determine especially if the NO-hemoglobin of uncooked meats be reduced to NO-hemochromogen under other conditions than by cooking. The fact that in the examination of certain uncooked salted meats a coloring matter had been obtained similar to NO-hemoglobin yet not possessing all of the properties of that compound, as has already been noted, led the writer to believe that the coloring matter of some uncooked salted meats might be due, in part at least, to NO-hemochromogen. NO-hemochromogen is but briefly mentioned in the literature. The compound is described by Linossier (1887), Haldane (1901), and by Abderhalden (1911).” (Hoagland, R. 1914)

“The structural relation between NO-hemoglobin and NO-hemochromogen is simple. NO-hemoglobin is a molecular combination of nitric oxid and hemoglobin—the latter compound consisting of the proteid group, globin, on one hand, and the coloring group, hemochromogen, on the other. NO-hemoglobin and NO-hemochromogen differ from each other simply in that one contains the proteid group, globin, while the other does not. Apparently, then, a method of treatment which would split off the globin group from NO-hemoglobin should result in the production of NO-hemochromogen, provided, of course, that the procedure did not in turn change or destroy the NO-hemochromogen produced. As has already been noted by Haldane, it was found that when a solution of NO-hemoglobin was heated to boiling, a brick-red precipitate formed, in contrast to the dark-brown precipitate which formed on heating a solution of oxyhemoglobin or of blood. The brick-red precipitate was filtered off and was then extracted with alcohol, which gave a lightred colored extract showing a spectrum with a fairly heavy band just at the right of the D line. This spectrum corresponds with that of NO-hemochromogen. On standing, the color of the extract faded rapidly.” (Hoagland, R. 1914)

“The evidence seems to show very clearly that the color of cooked salted meats is due to the NO-hemochromogen resulting from the reduction of the NO-hemoglobin of the raw salted meats on boiling.” (Hoagland, R. 1914)

“It is very probable that in the case of meats which have been cured with saltpeter or of meat food products in which saltpeter has been used in the process of manufacture, the reduction of NO-hemoglobin to NO-hemochromogen takes place to a greater or lesser degree, depending upon conditions of manufacture and storage. The two compounds are so closely allied that their differentiation in one and the same product is not a matter of great importance.” (Hoagland, R. 1914)

Our current understanding: Nitrosylmyochromogen or nitrosylprotoheme.

Upon thermal processing, globin denatures and detaches itself from the iron atom and surrounds the hem moiety. Nitrosylmyochromogen or nitrosylprotoheme is the pigment formed upon cooking , and it confers the characteristic pink colour to cooked cured meats.” (Pegg, R. B and Shahidi, F; 2000: 44)

“Although the Cooked Cured Meat Pigment (CCMP) is a heat-stable NO hemochrome as evident by the fact that it doesnt undergo further colour change upon additional thermal processing, it is susceptible to photodissociation. Furthermolre in the presence of oxygen, CCMP’s stability is limited by the rate of loss of NO.

This effect is important if cured meats are displayed under strong fluorescent lighting while they are also exposed to air. Under these conditions, the surface colour of cured meat will fade in a few hours, whereas under identical conditions, fresh meat will hold its colour for a few days.” “A brownish-gray colour develops on the exposed meat surface during colour fading; this pigment, sometimes called hemichrome, has its heme group in the ferric state. The most effective way of preventing light fading is to exclude contact with the cured meat surfaces. It is routinely accomplished by vacuum packaging the meat in impermiable films. If is absent from the package, NO cleaved from the heme moieties by light cannot be oxidized and can recombine with the heme.” (Pegg, R. B and Shahidi, F; 2000: 44)

CONCLUSION

Hoagland and other researchers from that period laid the foundation to much of our current understanding of meat curing by drawing a distinction between fresh cured meat colour and cooked cured colour. The first detailed mechanism in the development of cured meat colour that started to emerge was through the action of nitric oxide. Pegg and Shahidi stated in 2000 that “to form cured meat pigment, two reduction steps are necessary. The first reduction of nitrite to NO and the second is conversion of NOmetMB to NOMb.” (Pegg, B. R. and Shahidi, F.; 2000: 44, 45)

An interesting side note. Hoagland wondered if it is possible to produce the cooked cured colour of meat in another way than curing with nitrite and heat treatment. Pegg and Shahidi has dedicated much work along similar lines – to identify a curing system that will replace nitrite curing. In meat curing, this has always been the holy grail which on the one hand will in all likelihood remain an unattainable concept and on the other hand, as our understanding of nitrite grows, will be deemed unnecessary.

The chemical reaction sequence from nitrite to NO, leading to the formation of NOMb will be described in the next article.

References:

The Bismarck Tribune (Bismarck, North Dakota); 10 July 1912; page 2.

Cole, Morton Sylvan, “Relation of sulfhydryl groups to the fading of cured meat ” (1961). Retrospective Theses and Dissertations. Paper 2402

Haldane, J. S.. 1901. The Red Colour of Salted Meat. Journal of Hygiene 1: 115 – 122

Hoagland, R. 1914. Cloring matter of raw and cooked salted meats. Laboratory Inspector, Biochemie Division, Bureau of Animal Industry. Journal of Agricultural Research, Vol. Ill, No. 3 Dept. of Agriculture, Washington, D. C. Dec. 15, 1914.

Lemberg, R. and Legge, J. W.. 1949. Hematin Compounds and Bile Pigments. Interscience Publishers, Inc.

Soltanizadeh, N., Kadivar, M.. 2012. A new, simple method for the production of meat-curing pigment under optimised conditions using response surface methodology. Meat Science 92 (2012) 538–547 Elsevier Ltd.

http://cbs.umn.edu/academics/departments/bmbb/about/history/timeline

http://www.foodscience.caes.uga.edu/documents/Newsletter2016June16colorforweb.pdfhttps://en.wikipedia.org/wiki/Fereidoon_Shahidi

http://www.medicinenet.com

Images:

Image 1: Ralph Hoagland. Oakland Tribune, 5 July 1927

Concerning the direct addition of nitrite to curing brine

12/17/201403/06/2020 eben van tonder Bacon and the art of living, Bacon History, meat processing, Nitrate, Nitrite, recent history, Sodium Nitrite, Woodys Bacon American Nitrogen Products Company, Antoine Lavoisier, atmospheric nitrogen, Bacon Curing, bacon processing, BASF, British Association for the advancement of Science, Chilean saltpeter, coal-tar dye industry, Doran, Dr E. Polenski, Fritz Harber, George F. Doran, Glage, Griffith Laboratories, John Scott Haldane, K. H. Saunders, K. Kisskalt, Karl Bernhard Lehmann, Kriegsrohstoffabteilung, Martius, nitrate, nitrite, Peter Griess, potassium nitrate, Prague Powder, Prague salt, Ralp Hoagland, Ralph Hoagland, Robert Le Rossignol, saltpeter, Sir William Crookes, sodium nitrate, sodium nitrite, The Institute American Meat Packers, US 1259376 A, Use of Sodium Nitrite in Curing Meats, Walther Rathenau, War Raw Materials Department, Wheat Problem

by Eben van Tonder

This article is available for download in pdf: Concerning the direct addition of nitrite to curing brines

See, Bacon & the Art of Living,

Chapter 11.03: The Direct Addition of Nitrites to Curing Brines – the Master Butcher from Prague

Chapter 11.04: The Direct Addition of Nitrites to Curing Brines – The Spoils of War

Introduction

Bacon and the art of living is a study in the birth of the elements of bacon curing. Neither the chemical reactions, nor the different mechanical processes are simple. Everything about bacon is complex and beautiful. One of the most amazing stories within the grand story of bacon, is the story of sodium nitrite.

Pork is changed into bacon by the reaction of nirtrite (NO2-). With salt, it is the curing agent. The meat industry uses nitrite in the form of an ionic compound, sodium nitrite. It is sold as Quick Cure or Insta’ Cure, Prague Salt, Prague Powder or simply Pink Salt or Curing Salt. It is coloured pink to distinguish it from ordinary salt (sodium chloride). Every spice company sells it. It is the essential ingredient in the meat curing process.

Meat changes colour from the red fresh meat colour to an unappetising brown colour within days. (1) If one injects nitrite into the meat or rubs a mixture of salt and a small percentage of nitrite onto it, the meat will develop an appatizing reddish/ pinkish fresh meat colour (Hoagland, Ralph. 1914) and a characteristic cured taste. It will retain this colour for weeks and months if packed in the right conditions. (1) Nitrite provides an indispensable hurdle against a particularly nasty food pathogen, clostridium botulinum. It also endows the meat with a distinct cured taste.

During ages past, it has however not been nitrite that was added to meat to accomplish this, but its cousin, nitrate (NO3-). They may be cousins, but are very different in characteristics. Nitrate takes several weeks or even months to cure meat where nitrite accomplishes the same task in 12 hours. How the change happened from using nitrate or salpeter in meat curing to nitrite is an epic story.

Overview

This article tracks the migration of the meat industry from the use of saltpeter (potassium or sodium nitrate) as curing agent to sodium nitrite. It gives an overview of the scientific discoveries which started to reveal the mechanisms of meat curing. This understanding lead to the realisation that a direct application of nitrite as the curing agent will be vastly superior to the use of saltpeter (nitrate).

This was a dramatic discovery since in the late 1800’s and early 1900’s, the world saw nitrite as a dangerous drug at best and a poison that polluted drinking water and cause death of cattle. Using this directly in food and meat curing was unthinkable.

Sodium nitrite was available in this time for application in the coal-tar dye and medical industries. Science and engineering have however not worked out its large scale production in a way that will make it a commercially viable proposition for direct use in meat curing from a price and availability perspective.

World War One provided the transition moments required to change everything. Germany invested heavily in nitrogen related technology for the war. The most organised scientific and engineering environment on the planet in the early 1900’s focused its full attention on overcoming the manufacturing challenges in the service of the manufacturing of munitions. It also required this technology to overcome the challenge of being cut off, as a result of the war, from the natural sodium nitrate deposits in Chili that it required as fertilizer to drive its enormous agriculture sector during the war. At the same time, the use of saltpeter in meat curing was prohibited under the leadership of Walther Rathenau so that the valuable nitrate could be reserved for manufacturing of munitions.

This prohibition, I believe, was the initial spark that caused butchers to change to the use of sodium nitrite. At the same time, sodium nitrite was being produced in large volumes since it had, in its own right, application in the manufacturing of explosives. Health concerns and probably the need to have it reserved for munitions, lead to a ban, similar to nitrate, on its use in meat curing. So, World War One solved the scientific challenges of large scale manufacturing of sodium nitrite, the engineering challenges of building production facilities and provided the impetus for the meat industry to change by banning the use of saltpeter in meat curing. The ban was lifted after the war.

Following the war, Germany had to find markets for its enormous war time chemical stock piles. One of the ways it “sold” sodium nitrite was as a meat curing agent based on its inherent benefits of curing consistency and the vastly shorter curing time required.

It was introduced to the world mainly through the Chicago based firm, Griffith Laboratories, who imported it as Prague Salt from Germany and later improved on it by fusing the sodium nitrite to sodium chloride and sold it as Prague Powder.

Early humans to Polenski (1891)

Early humans did not know they added nitrate to the meat. A mixture of salt and a small amount of saltpeter was used to cure meat in order to preserve it and to retain the fresh meat colour.

Saltpeter is found naturally around the world in typically dry areas. Deposits exist in India, China, Mexico, the USA, and the Middle East. Despite its wide occurrence, the concentration of natural saltpeter is low. (Whittaker, CW, 1932: 10)

Saltpeter is also made by human effort. Europe, particularly Germany and France, Great Britain, India and the United States all acquired the technology to produce satpeter. (Van Cortlandt, P, 1776: 7, 8)

In South Africa, saltpeter deposits are found in the Griquatown beds of the Transvaal geological system. It extends from just South of the Orange River Northwards to the Kalahari Desert and then Eastwards into the Old Transvaal from Zeerust to Polokwane. The nitrate deposits occur in the middle portions of these beds, in softer and more decomposed shale. These South African reserves have fortunately never been mined even though it was used on a small scale to make gunpowder for the old Boer government. (Whittaker, CW, 1932: 10)

Saltpeter was at the heart of the arms race of the middle ages. It was used mainly in gunpowder, but as the worlds population grew, it became indispensable as a fertilizer and for curing meat. (See Bacon and the art of living, chapters 2, 3 and 4)

The French chemist, Antoine Lavoisier worked out its chemical composition. It is an ionic compound consisting of the metal potassium and its power is nitrate. Potassium Nitrate. (Mauskopf, MSH. 1995: 96) Trade in Saltpeter around the world was done through companies such as the Dutch East Indian Company (Dutch abbreviation, VOC) who traded it for its main use as an ingredient in gunpowder. It was by volume one of the largest commodities traded by the Dutch East Indian Company who set up the trading post in 1652 that became Cape Town.

Major developments shifted the balance of power away from Indie, China and home grown saltpeter production to South America where huge deposits of sodium nitrate were discovered that would become the principal source of the worlds nitrate for much of the 1800’s.

A man walks down a dirt road in the Atacama Desert. Despite being one of the most inhospitable places on earth, the Atacama is still mined: in 2010 this made world-wide news, when the Copiapó mining accident led to the dramatic rescue of 33 trapped miners (AP Photo/Dario Lopez-Mills).

A popular legend tells the story of the discovery by two Indians in the Atacama desert in the South of Peru. According to the legend, after a hard day’s work, they camped in the Pampa and started a campfire to warm themselves. All of a sudden the ground started to burn and they ran away, thinking that they have seen the devil. They reported the event later to a priest in Camina who returned to the site. He had it analysed and found it to contain sodium nitrate (the same power as potassium nitrate, but linked to another common metal). The priest, according to the story, threw the rest of the soil in the courtyard of his house and saw the plants grew vigorously. He recommended the soil as an excellent tonic for the plant kingdom. (Wisniak, J, et al., 2001 :433)

So was discovered the enormous sodium nitrate deposits of the Atacama desert. The fertilizer properties of the salt was known long before the 1600’s. There are references to saltpeter and the nitrate ground in 1604. During the time of the Spanish Conquest, in the 1700’s, miners working in the South of Peru realised that gunpowder could be manufactured from the material in the soil instead of potassium nitrate. (Wisniak, J, et al., 2001 :433)

A report published in 1803 by Juan Egana, Secretary of the Royal Court of Mines in Chile showed the Huasco region is “covered in a large part by a crust of niter salt, well crystallized, and several inches thick” (Wisniak, J, et al., 2001 :434)

The region was developed and by 1850 exports reached 24 000 tons/ year. In 1910 it was 2.4 million tons per year and by 1916, 3 million tons per year from 97 plants. (Wisniak, J, et al., 2001 :434)

By the beginning of the 1900’s the country buying the largest quantity of the Chilean saltpeter was Germany (Wisniak, J, et al., 2001 :434) who used it aggressively in their agriculture sector as fertilizer.

There is a close correlation between sodium and potassium nitrate. Its difficult to distinguish between sodium and potassium nitrate just by tasting it. Scientists were able to distinguish between the two compounds from the mid 1600’s and knew that sodium nitrate had a much greater ability to attract water (Whittaker, CW, 1932: 3). This made sodium nitrate a much better curing agent than potassium nitrate.

Nitrite was described in 1864 by the English Physiologist, B. W. Richardson. He outlined how to manufacture it and its chemical properties. (Wells, D. A., 1865: 233) Much earlier, in 1777 the prolific Swedish chemist Scheele, working in the laboratory of his pharmacy in the market town of Köping, made the first pure nitrite. (Scheele CW. 1777) He heated potassium nitrate at red heat for half an hour and obtained what he recognized as a new “salt.” The two compounds (potassium nitrate and nitrite) were characterized by Péligot and the reaction established as 2KNO₃→2KNO₂+O₂. (Péligot E. 1841: 2: 58–68) (Butler, A. R. and Feelisch, M.)

The technology existed in the 1800’s to not only produce potassium nitrate (salpeter) and nitrite, but to also test for these.

Remember that curing up till 1890 has been attributed to saltpeter (potassium nitrate) or Chilean saltpeter (sodium nitrate). In 1891 a German food scientist, Dr Ed Polenski, working for the German Department of Health made an observation that would change the world while studying curing brines. When he tested the curing brine made from saltpeter and salt, days after it was made, he found nitrite to be present. This was surprising since saltpeter is potassium or sodium nitrate, not nitrite.

Dr Ed speculated that the nitrate (NO3-) was changed into nitrite (NO2-) through bacterial action, a reduction step between nitrate and nitrite that was well understood by this time. He had a hunch that nitrite is responsible for curing of meat and not the nitrate directly, as was previously thought.

From Polenski (1891) to WWI (1914 to 1918)

Following Dr Ed’s observations in 1891, considerable resources from around the world were dedicated to understand the chemistry of meat curing.

When World War One broke out, the concept of nitrite as curing agent (as opposed to nitrate) was firmly established.

Ralph Hoagland, Senior Biochemist, Biochemie Division, Bureau of Animal Industry, United States Department of Agriculture, published an article in 1914, Coloring matter of raw and cooked salted meats. In this article, he shows that nitrite as curing agent was a known and accepted fact by the outbreak of World War One (Hoagland, Ralph. 1914)

Readers who dont have an interest in the detailed description of the key discoveries may want to skip over the rest of this section altogether or glance over it generally. The goal of the section is to give the reader a sense of how firmly and universally the concept of nitrite as the curing agent was established by 1914. In the midst of the technical names and jargon, don’t lose the sense of the universal interest. The 1700’s, 1800’s and beginning of the 1900’s was a time when the average person was as interested in chemistry as we are today about communication and information technology.

The difference between nitrates and nitrites, for example, was taught in school curriculum. An article appeared in the Daily Dispatch in Brainerd, Minnesota in the 20’s, that gives as an example of a diligent high school student, that he or she would know the difference. (The Brainerd Daily Dispatch (Brainerd, Minnesota). 17 January 1923. Page 3.)

Following Dr. Polenski’s observation, the German scientist, Notwang confirmed the presence of nitrite in curing brines in 1892, as observed by Dr Polenski, but attributed the reduction from nitrate to nitrite to the meat tissue itself. The link between nitrite and cured meat colour was finally established in 1899 by another German scientist, K. B. Lehmann in a simple but important experiment.

Karl Bernhard Lehmann (September 27, 1858 – January 30, 1940) was a German hygienist and bacteriologist born in Zurich.

In an experiment he boiled fresh meat with nitrite and a little bit of acid. A red colour resulted, similar to the red of cured meat. He repeated the experiment with nitrates and no such reddening occurred, thus establishing the link between nitrite and the formation of a stable red meat colour in meat. (Lee Lewis, W., 1925: 1243)

In the same year, another German hygienists, K. Kisskalt, confirmed Lehmann’s observations but proved that the same red colour resulted if the meat was left in saltpeter (potassium nitrate) for several days before it was cooked. (Lee Lewis, W., 1925: 1243)

K. B. Lehmann made another important observation that must be noted when he found the colour to be soluble in alcohol and ether and to give a spectrum showing an absorption band just at the right of the D line, and a second band, often poorly defined, at the left of the E line. On standing, the color of the solution changed to brown and gave the spectrum of alkaline hematin, the colouring group (Hoagland, Ralph. 1914).

The brilliant British physiologist and philosopher, John Scott Haldane weighed in on the topic. He was born in 1860 in Edinburgh, Scotland. He was part of a lineage of important and influential scientists. (Lang, M. A. and Brubakk, A. O. 2009. The Haldane Effect)

J. S. Haldene contributed immensely to the application of science across many fields of life. This formidable scientist was for example responsible for developing decompression tables for deep sea diving used to this day. (Lang, M. A. and Brubakk, A. O. 2009. The Haldane Effect)

“Haldane was an observer and an experimentalist, who always pointed out that careful observation and experiments had to be the basis of any theoretical analysis. “Why think when you can experiment” and “Exhaust experiments and then think.” (Lang, M. A. and Brubakk, A. O. 2009. The Haldane Effect)

An interesting anecdote is told about him from the time when he was studying medicine in Jena. He apparently carefully observed the amount of beer being drunk, noting that the students on the average drank about 20 pints per evening.” (Lang, M. A. and Brubakk, A. O. 2009. The Haldane Effect)

Before we look at Haldene’s contribution, let us re-cap what has been determined thus far.

Polenski and Notwang discovered that nitrite were present in a mix of saltpeter and salt, after a while, even though no nitrite were present when the brine was mixed.

Karl Bernhard Lehmann linked nitrite conclusively with the reddening effect of fresh meat that was boiled in a nitrite and water solution with some free acid. He also showed that this does not happen if fresh meat is placed in saltpeter and water solution and boiled immediately. K. Kisskalt showed that the same reddening occurred if fresh meat is left in saltpeter for some time.

K. B. Lehmann managed to “isolate” the colour by dissolving it in ether and alcohol and analyze it spectroscopically.

What S. J. Haldele did was to apply the same rigor to cured meat and became the first person to demonstrate that the addition of nitrite to hemoglobin produce a nitric oxide (NO)-heme bond, called iron-nitrosyl-hemoglobin (HbFeIINO). (Lang, M. A. and Brubakk, A. O. 2009: 119)

Nitrite is further reduced to nitric oxide (NO) by bacteria or enzymatic reactions and in the presence of muscle myoglobin forms iron-nitrosyl-myoglobin. It is nitrosylated myoglobin that gives cured meat, including bacon and hot dogs, their distinctive red color and protects the meat from oxidation and spoiling. (Lang, M. A. and Brubakk, A. O. 2009: 119)

This is how he did it. He concluded (1901) that its red colour is due to the presence of the nitricoxid hemochromogen resulting from the reduction of the coloring matter of the uncooked meat, or nitric-oxid hemoglobin (NO-hemoglobin). (Hoagland, Ralph. 1914)

Remember the observation made by K. B. Lehmann that the colour of fresh meat cooked in water with nitrites and free acid to give a spectrum showing an absorption band just at the right of the D line, and a second band, often poorly defined, at the left of the E line. (Hoagland, Ralph. 1914)

Haldene found the same colour to be present in cured meat. That it is soluble in water and giving a spectrum characteristic of NO-hemoglobin. The formation of the red color in uncooked salted meats is explained by the action of nitrites in the presence of a reducing agent and in the absence of oxygen upon hemoglobin, the normal coloring matter of fresh meats. (Hoagland, Ralph. 1914)

Ralp Hoagland (1908) studied the action of saltpeter upon the colour of meat and found that its value as an agent in the curing of meats depends upon the nitrate’s reduction to nitrites and the nitrites to nitric oxid, with the consequent production of NO-hemoglobin. The red colour of salted meats is due to this compound. Hoagland conclusively shows that saltpeter, as such, has no value to preserve the fresh colour. (Hoagland, Ralph, 1914: 212)

The reason why the knowledge did not translate to a change in curing brines was very simple. The technology and infrastructure did not exist to produce enough nitrite commercially to replace saltpeter. This means that to produce nitrite was very expensive.

There were some attempts to capitalise on the knowledge gained. The German scientist, Glage (1909) wrote a pamphlet where he outlines the practical methods for obtaining the best results from the use of saltpeter in the curing of meats and in the manufacture of sausages. (Hoagland, Ralph, 1914: 212, 213)

Saltpeter can only effect the colour of the meat if the nitrate in the saltpeter is reduced to nitrite. Glage gives for the partial reduction of the saltpeter to nitrites by heating the dry salt in a kettle before it is used. It is stated that this partially reduced saltpeter is much more efficient in the production of color in the manufacture of sausage than is the untreated saltpeter. (Hoagland, Ralph, 1914: 212, 213)

The fear of nitrites

The lack of a large scale production process for sodium nitrite and the engineering to build these plants were however not the only factors preventing the direct use of sodium nitrite in meat curing brines. As one review literature from the late 1800’s and early 1900’s, one realises that a major hurdle that stood between the use of sodium nitrites in meat curing was the mistrust by the general public and authorities of the use of nitrites in food. The matter relate to the high level of toxicity of nitrite, a matter that will be dealt with separately in Bacon and the art of living.

The first recorded direct use of nitrite as a curing agent was in 1905 in the USA where it was used in secret. (Katina, J. 2009) The USDA finally approved its use as a food additive in 1906. (porkandhealth) This did not mean that the public would accept it.

Sodium Nitrite started to be used in this time as a bleach for flour in the milling industry. Several newspaper articles reveal public skepticism and the great lengths that the scientific community and industry had to go to in order to demonstrate its safety as a bleaching agent for flour. An article appeared in The Nebraska State Journal Lincoln, Nebraska on 29 June 1910 entitled, “All for bleached flour. No harm can come from its consumption says experts”. The article deals with a federal court case about the matter and interestingly enough, it seems from newspaper articles that the government was opposing its use. Many other examples can be sited.

There is a 1914 reference in the London Times that shows the general view of nitrite as not just restricted to the USA. The article appeared on 9 June 1914 and a reference is made to sodium nitrite where it is described as “a dangerous drug with a powerful action on the heart.” (The London Times. 1914. Page 118) The reference was to the use of nitrite for certain heart conditions.

It is interesting that sodium nitrite did not find an immediate application in the meat industry, even after it was allowed in 1906 in the USA.

In my view, this points to problems surrounding availability and price. If the issue was the public perception alone, this could have been overcome with a PR campaign by the meat industry as was successfully done by the milling industry.

On 13 Dec 1915 George F. Doran from Omaha, Nebraska, filed an application for a patent for a curing brine that contained nitrites. His application strengthens the evidence that it was not the knowledge of nitrite and its role in curing that was lacking, but availability and price. He states the objective of his patent application to “produce in a convenient and more rapid manner a complete cure of packing house meats; to increase the efficiency of the meat-curing art; to produce a milder cure; and to produce a better product from a physiological standpoint.”

One of Doran’s sources of nitrite is “sterilized waste pickling liquor which he [I have] discovered contains soluble nitrites produced by conversion of the potassium nitrate, sodium nitrate, or other nitrate of the pickling liquor when fresh, into nitrites. . .” “Waste pickling liquor is taken from the cured meats. Nitrites suitable for use in carrying out the present invention may be produced by bacterial action from nitrates and fresh pickling liquor by adding a small percentage of old used pickling liquor. The bacteria in old pickling liquor are reducing bacteria and change nitrates to nitrites.” (Process for curing meats. US 1259376 A)

The use of old pickle has been described much earlier than Doran’s patent. His usage of old pickle when he understood the reduction of nitrate to nitrite and nitrite’s role in curing along with the fact that sodium nitrite was available can point to only one reason – price. It comes 10 years after sodium nitrite was first tested in curing brines for meat and shows that it has never become the curing agent of choice most probably due to limited availability and price. Much more about this later.

The post WWI era (1918 and beyond)

After WWI something changed. Saltpeter (potassium or sodium nitrate) has been substituted by the direct addition of nitrite to the curing brines.

The question is who pioneered this. Why and how did sodium nitrite production become so commonplace that it became available to bacon curing plants around the world?

Industry developments like this do not happen “by itself.” Someone drives it in order for it to become general practice in an industry.

Chilean Saltpeter is a good case in point. Even though natural sodium nitrate deposits were discovered in the Atacama desert, it took a considerable effort on the side of the producers (mainly the Chilean Government) to work out the benefits of sodium nitrate and to market it to the world. It is, for example, famously reported that the first shipment to Britain was dumped in the sea before the ship docked on account that the cargo attracted customs duty and the ships owners could not see any commercial application for sodium nitrate. (2)

In the same way, the direct application of nitrite in curing brines must have been driven by someone.

The Griffith Laboratories, Inc.

The Chicago based company of Enoch Luther Griffith and his son, Carroll Griffith started to import a mixture of sodium nitrite and salt as a curing substitute for saltpeter from Germany in 1925. The product was called Prague Salt (Prague Powder, 1963: 3)

The Griffith Laboratories (3) played a key role in marketing the new curing brine in the USA. They took the concept of the Prague Salt (sodium nitrite) and in 1934 announced an improved curing brine, based on the simple use of sodium nitrite, where they fuse nitrite salt and sodium chloride in a particular ratio. They called it Prague Powder. Their South African agents, Crown Mills (4), brought the innovation to South Africa. (Prague Powder, 1963: 3, 4)

It is fair to assume that if Prague Salt was being sold to Griffith in the 1920’s, the German producers must have sold it to other countries and companies around the world also.

The benefits of Prague Salt and later Prague Powder over Saltpeter is dramatic. Prague Salt (sodium nitrite) does not have the slightly bitter taste of saltpeter (Brown, 1946: 223). It allows for greater product consistency since the same percentage of nitrate was not always present in the saltpeter and the reduction of nitrate to nitrite takes longer or shorter under various conditions (Industrial and Engineering Chemistry, December 1925: 1243). The big benefit was however in the curing time required. Instead of weeks or even months that is required with saltpeter, curing could now be done in days or even hours with sodium nitrite. (The Food Packer, 1954: 64) From there, brand names like Quick Cure or Instacure.

This means that we have narrowed the time line for invention of Prague Salt (Sodium Nitrite) to between 1914, the beginning of the Great War and 1925 when Griffith imported it from Germany.

However, a document, published in the USA in 1925 shows that sodium nitrite as curing agent has been known well before 1925.

The document was prepared by the Chicago based organisation, The Institute American Meat Packers and published in December 1925. The Institute started as an alignment of the meat packing companies set up by Phil Armour, Gustavus Swift, Nelson Morris, Michael Cudahy, Jacob Dold and others with the University of Chicago.

The document is entitled, “Use of Sodium Nitrite in Curing Meats“, and it it is clear that the direct use of nitrites in curing brines has been practiced from earlier than 1925. (Industrial and Engineering Chemistry, December 1925: 1243)

The article begins “The authorization of the use of sodium nitrite in curing meat by the Bureau of Animal Industry on October 19, 1925, through Amendment 4 to B. A. I. Order 211 (revised), gives increased interest to past and current work on the subject.”

Sodium Nitrite curing brines would therefore have arrived in the USA, well before 1925.

It continues in the opening paragraph, “It is now generally accepted that the salpteter added in curing meat must first be reduced to nitrite, probably by bacteria, before becoming available as an agent in producing the desirable red color in the cured product. This reduction is the first step in the ultimate formation of nitrosohemoglobin, the color principle. The change of nitrate to nitrite is by no means complete and varies within considerable limits under operating conditions. Accordingly, the elimination of this step by the direct addition of smaller amounts of nitrite means the use of less agent and a more exact control.”

Griffith describes the introduction and origin of Prague Salt and later, Prague Powder as follows in official company documents:

“The mid-twenties were significant to Griffith as it had been studying closely a German technique of quick-curing meats. Short on manpower and time, German meat processors began curing meats using Nitrite with salt instead of slow-acting saltpeter, potassium nitrate. This popular curing compound was known as “Prague Salt.” (Griffith Laboratories Worldwide, Inc.)

The World War One link

The tantalizing bit of information from Griffith sets World War One as the background for the practical and large scale introduction of direct addition of nitrite into curing brines through sodium nitrite.

There has to be more to the reason for saltpeter being replaced by sodium nitrite as curing agent than the reasons given by Griffith. For starters, the meat industry has always been under pressure to work fast with less people due to pressure on profit margins. The need to cure meat quicker due to short manpower and time as a result of the war could not be the full story.

The World War One link from Griffith does not give all the answers, but it puts the introduction of sodium nitrite to meat curing between 1914 and 1918, at least 7 years before Griffith started to import Prague Salt.

A document from the University of Vienna would fill out the story. According to it, saltpeter was reserved for the war effort and was consequently no longer available as curing agent for meat during World War One. (University of Vienna). It was reserved for the manufacturing of explosives, and for example, the important industry of manufacturing nitrocellulose, used as base for the production of photographic film, to be employed in war photography. (Vaupel, E., 2014: 462) It gets even better. Not only did the prohibition on the use of saltpeter expand the information from Griffith as to why people started using sodium nitrite (macro movements in culture does not take place because of one reason only), but it provide a name to the prohibition.

Walter Rathenau’s actions may have motivated the change, but it was the developments in synthesizing ammonia, sodium nitrate and sodium nitrite which provided the price point for the compound to remain the curing agent of choice, even after the war and after the prohibition on the use of saltpeter was lifted.

Atmospheric Nitrogen

One of the most important scientific riddles to be solved in the late 1800’s/ early 1900’s was how to produce ammonia and its related chemicals from atmospheric nitrogen. Sir William Crookes delivered a famous speech on the Wheat Problem at the annual meeting of the British Association for the advancement of Science in 1898.

In his estimation, the wheat production following 1897 would seriously decline due to reduced crop yields, resulting in a wheat famine unless science can step in and provide an answer. He saw no possibility to increase the worlds wheat yield under the prevailing agricultural conditions and with the increase in the world population, this posed a serious problem. He said, “It is clear that we are taxed with a colossal problem that must tax the wits of the wisest.” He predicted that the USA who produced 1/5th of the worlds wheat, would become a nett importer unless something change. He pointed to the obvious answer of manure, but observed that all available resources are being depleted fast.

Sir William saw a “gleam of light in the darkness” and that “gleam” was atmospheric nitrogen. (Otago Witness. 3 May 1900, Page 4)

It was the German Chemist, Fritz Harber who solved the problem, with the help of Robert Le Rossignol who developed and build the required high pressure device to accomplish this. (www.princeton.edu)

In 1909 they demonstrated that they could produce ammonia from air, drop by drop, at the rate of about a cup every two hours. “The process was purchased by the German chemical company BASF (a coal tar dye supplier), which assigned Carl Bosch the difficult task of scaling up Haber’s tabletop machine to industrial-level production. Haber and Bosch were later awarded Nobel prizes, in 1918 and 1931 respectively, for their work in overcoming the chemical and engineering problems posed by the use of large-scale, continuous-flow, high-pressure technology.” (www.princeton.edu)

“Ammonia was first manufactured using the Haber process on an industrial scale in 1913 in BASF’s Oppau plant in Germany.” (www.princeton.edu)

It was the vision and leadership of Walther Rathenau, the man responsible for restricting the use of saltpeter, that drove Germany to produce synthesized Chilean Saltpeter. He saw this as one of the most important tasks of his KRA. He said: “I initiated the construction of large saltpeter factories, which will be built by private industries with the help of governmental subsidies and will take advantage of recent technological developments to make the import of saltpeter entirely unnecessary in just few months“. (Lesch, J. E., 2000: 1)

Fritz Harber was one of the experts appointed by Rathenau to evaluate a study on the local production of nitric acid.

During World War One production was shifted from fertilizer to explosives, particularly through the conversion of ammonia into a synthetic form of Chile saltpeter, which could then be changed into other substances for the production of gunpowder and high explosives (the Allies had access to large amounts of saltpeter from natural nitrate deposits in Chile that belonged almost totally to British industries; Germany had to produce its own). It has been suggested that without this process, Germany would not have fought in the war, or would have had to surrender years earlier.” (www.princeton.edu)

So it happened that Germany became the leader in the world in synthesised sodium nitrate production and it effectively replaced its reliance on saltpeter from Chile with sythesised sodium nitrate, produced by BASF and other factories.

So, as a result of the First World War, sodium nitrite was produced at levels not seen previously in the world and in large factories that was build, using the latest processing techniques and technology from a scientific and an engineering perspective. Sodium nitrite, like sodium nitrate was being used in the production of explosives. Nitroglycerin is an example of an explosive used extensively by Germany in World War One that uses sodium nitrite in its production. (Wikipedia.org. Nitroglycerin and Amyl Nitrite)

Ball-and-stick model of Amyl nitrite used in the production of nitroglycerin. Amyl nitrite is produced with sodium nitrite. The diagram shows the amyl group attached to the nitrite functional group. — Ball-and-stick model of Amyl nitrite used in the production of nitroglycerin. Amyl nitrite is produced from sodium nitrite. The diagram shows the amyl group attached to the nitrite functional group.

Sodium nitrite and the coal-tar dye industry

The importance of the manufacturing cost of nitrite and the matter surrounding availability can be seen in the fact that sodium nitrite has been around since well before the war. Despite the fact that it was known that nitrite is the curing agent and not nitrate, and despite the fact that sodium nitrite has been tested in meat curing agents, probably well before the clandestine 1905 test in the USA, it did not replace saltpeter as the curing agent of choice. My hunch is that it did not enter the meat industry as a result of cost.

The technology that ultimately is responsible for synthesising Chilean Saltpeter and made low cost sodium nitrite possible was being incubated in the coal-tar dye and textiles industry and in the medical field. The lucrative textiles and dye industry was the primary reason for German institutions of education, both in science and engineering to link with industry, resulting in a strong, well organised skills driven German economy. For example, “Bayer had close ties with the University of Göttingen, AGFA was linked to Hofmann at Berlin, and Hoechst and BASF worked with Adolph Baeyer who taught chemists in Berlin, Strasbourg, and Munich.” (Baptista, R. J.. 2012: 6)

Nitrous acid (HONO) is to nitrite (NO2-) what nitric acid (NO3) is to nitrate (NO3-).

According to K. H. Saunders, a chemist at Imperial Chemical Industries, Ltd., Martius was the chemist to whom the introduction of sodium nitrite as the source of nitrous acid was due. (Saunders, K. H., 1936: 26)

The economic imperative

The simple fact is that ammonia can be synthesized through the direct synthesis ammonia method at prices below what can be offered through Chilean Satlpeter. (Ernst, FA. 1928: 92 and 100) Sodium Nitrite can be supplied at prices below Chilean saltpeter and this made sodium nitrite the most effective curing agent at the lowest price since World War One.

The advantage of scale and technology

By 1927, Germany was still by far the worlds largest direct syntheses ammonia producer. Production figures of the year 1926/ 1927 exceeded Chilean saltpeter exports even if compared with the highest levels of exports that Chilean saltpeter ever had in 1917. A total of 593 000 tons of nitrogen was fixed around the world in 1926/27. Of this figure, Germany produced 440 000 tons or 74%. The closest competitor was England through the Synthetic Ammonia and Nitrates Ltd. with a total capacity of 53 000 tons of nitrogen per year. (Ernst, FA. 1928: 119, 120)

In the USA 7 direct synthesis plants were in operation with a combined capacity of 28 500 tons of nitrogen per year. (Ernst, FA. 1928: 120)

Supporting evidence from the USA

The first US plant for the fixation of atmospheric nitrogen was build in 1917 by the American Nitrogen Products Company at Le Grande, Washington. It could produce about one ton of nitrogen per day. In 1927 it was destroyed by a fire and was never rebuild. (Ernst, FA, 1928: 14)

An article in the Cincinnati Enquirer of 27 September 1923 reports that as a result of cheap German imports of sodium nitrite following the war, the American Nitrogen Products Company was forced to close its doors four years before the factory burned down. The imports referred to, was as a result of Germany selling their enormous stockpiles of sodium nitrite at “below market prices” and not directly linked to a lower production price in Germany, even though this was probably the case in any event. ( The Cincinnati Enquirer ( Cincinnati, Ohio), 27 September 1923. Page 14.)

The Vienna University document indicate that the fast curing of sodium nitrite was recognised and the ban was lifted when the war ended. It was this fact that Griffith picks up on in their literature.

This is how it happened that sodium nitrite replaced saltpeter as curing salt.

Conclusion

The ban on the use of saltpeter for non military uses by Walther Rathenau is the likely spark that caused butchers to look at alternative curing systems. A known alternative was sodium nitrite. Despite a similar ban on the use of nitrite, later imposed for concerns over the safety of nitrite in meat and because sodium nitrite was also used to produce explosives, it was available in such large quantities around Germany that it was possible to defy the ban.

The likely consequence of the developments surrounding the production of atmospheric nitrogen is that sodium nitrite was being produced at prices that was previously not possible. These prices, combined with the volume of sodium nitrite now available made it a viable proposition to replace saltpeter in meat curing and to remain the curing brine of choice, following the war.

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Notes

(1) “The red color of fresh lean meat, such as beef, pork, and mutton, is due to the presence of oxyhemoglobin, a part of which is one of the constituents of the blood remaining in the tissues, while the remainder is a normal constituent of the muscles. When fresh meat is cooked or is cured by sodium chloride, the red color changes to brown, owing to the breaking down of the oxyhemoglobin into the two constituents, hematin, the coloring group, and the protein, globin.

On the other hand, when fresh meat is cured by means of a mixture of sodium chloride and a small proportion of potassium nitrate, or saltpeter, either as a dry mixture or in the form of a pickle, the red color of the fresh meat is not destroyed during the curing process, the finished product having practically the same color as the fresh meat. Neither is the red color destroyed on cooking, but rather is intensified.” (Hoagland, Ralph. 1914)

(2) The first export of salitre (sodium nitrate) was authorised by the Chilean government in March 1830 and went to the USA, France, and to Liverpool. It is the latter shipment which failed and was thrown overboard. Different sources give different reasons for the action. One, that price was not attractive, another, that the excise duties were to high, and a third that the Port captain did not allow the boat to come in because it was carrying a dangerous load. A few farmers in Glasgow received a few bags. They used it as fertalizer and reported a three fold increase in crop yield. (Wisniak, J, et al. 2001: 437)

(3) Steve Hubbard, Vice President, Global Marketing and Innovation at Griffith Laboratories Worldwide, Inc. graciously provided me with much of the information from company documents.

(4) Crown Mills was bought out by Bidvest and became Crown National.

(5) The first War Raw Materials Department (KRA) in Germany was created (KRA) in mid-August 1914, as suggested by Walther Rathenau. (Vaupel, E. 2014: 462) Walter was the son of the founder of AEG and “one of the few German industrialists who realized that governmental direction of the nation’s economic resources would be necessary for victory, Rathenau convinced the government of the need for a War Raw Materials Department in the War Ministry. As its head from August 1914 to the spring of 1915, he ensured the conservation and distribution of raw materials essential to the war effort. He thus played a crucial part in Germany’s efforts to maintain its economic production in the face of the tightening British naval blockade.”

References:

Baptista, R. J.. 2012. The Faded Rainbow: The Rise and Fall of the Western Dye Industry 1856-2000. From: http://www.colorantshistory.org/files/Faded_Rainbow_Article_April_21_2012.pdf

Brown, Howard Dexter et al. 1946. Frozen Foods: Processing and Handling

Butler, A. R. and Feelisch, M. New Drugs and Technologies. Therapeutic Uses of Inorganic Nitrite and Nitrate From the Past to the Future. From: http://circ.ahajournals.org/content/117/16/2151.full

Determination of nitrite in meat products. University of Vienna, Department of Analytical Chemistry, Food Analytical Internship for nutritionists.

Ernst, FA. 1928. Fixation of Atmospheric Nitrogen. D van Nostrand, Inc.

Griffith Laboratories Worldwide, Inc. official company documents.

Hoagland, Ralph. 1914. Coloring matter of raw and cooked salted meats. United States Department of Agriculture. National Agricultural Library. Digital Collections.

Hwei-Shen Lin. 1978. Effect of packaging conditions, nitrite concentration, sodium erythrobate concentration and length of storage on color and rancidity development of sliced bologna. Iowa State University Digital Repository @ Iowa State University

Katina, J. 2009. Nitrites and meat products. Czech Association of Meat Processors. http://www.cszm.cz/clanek.asp?typ=5&id=1136

Lang, M. A. and Brubakk, A. O. 2009. The Haldane Effect. The American Academy of Underwater Sciences 28th Symposium.Dauphin Island

Lee Lewis, W. December, 1925. Use of Sodium Nitrite in Curing Meat. Industrial and Engineering Chemistry.

Lesch, J. E.. 2000. The German Chemical Industry in the Twentieth Century. Kluwer Academic Publishers.

Mauskopf, MSH. 1995. Lavoisier and the improvement of gunpowder production/Lavoisier et l’amélioration de la production de poudre. Revue d’histoire des sciences

Otago Witness. 3 May 1900. Sir William Crookes and the wheat problem. Issue 2409, Page 4, from: http://paperspast.natlib.govt.nz/

Péligot E. 1841. Sur l’acide hypoazotique et sur l’acide azoteux. Ann Chim Phys.; 2: 58–68.

Prague Powder, Its uses in modern Curing and processing. 1963. The Griffith Laboratories, Inc.

Process for curing meats. US 1259376 A

Redondo, M. A.. 2011. Effect of Sodium Nitrite, Sodium Erythorbate and Organic Acid Salts on Germination and Outgrowth of Clostridium perfringens Spores in Ham during Abusive Cooling. University of Nebraska – Lincoln.

Salem, H. et al. 2006. Inhalation Toxicology, Second Edition. Taylor & Francis Group, LLC.

Saunders, K. H. The Aromatic Diazo-Compounds and their technical applications. Richard Clay and Company.

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The Brainerd Daily Dispatch (Brainerd, Minnesota). 17 January 1923. Page 3.

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The Times (London, Greater London). 8 June 1914. Adulteration. Examples of fraudulent manufacture. Page 118

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Van Cortlandt, P, et al. 1776. Essays upon the making of salt-petre and gun-powder. Published by order of the Committee of Safety of the colony of New-York.

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Krieg der Chemiker. Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

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Click to access freebies_SodiumNitriteFactSheet.pdf

http://www.princeton.edu/~achaney/tmve/wiki100k/docs/Haber_process.html

http://www.britannica.com/EBchecked/topic/491966/Walther-Rathenau

en.wikipedia.org/wiki/Nitroglycerin

http://en.wikipedia.org/wiki/Amyl_nitrite

Images:

Picture 1: Smoker trolly with pork belly taken by Eben

Picture 2: Curing salt taken by Eben

Picture 3: Atacama Desert. Photograph by Dario Lopez-Mills/AP. Source: http://www.theguardian.com/science/the-h-word/2014/jun/02/caliche-great-war-first-world-war-conflict-mineral

Picture 4: World War One: http://www.excaliburunit.org.uk/#/world-war-1/4580632440

Picture 5: US troops returning from World War One. http://www.ww1medals.net/WW1-US-Victory-medals.htm

Picture 6: Amyl nitrite. http://en.wikipedia.org/wiki/Amyl_nitrite

	eben van tonder on Saltpeter, Horse Sweat and Bil…
	eben van tonder on Saltpeter, Horse Sweat and Bil…
	William Ramwell on Saltpeter, Horse Sweat and Bil…
	eben van tonder on Rusk
	Des Basterfield on Rusk
	Kjell on Bacterial Migration Into Meat
	eben van tonder on Carcass Sanatising
	Klaas on Carcass Sanatising
	Tabitha Levine on Joshua Penny and Khoikhoi Ferm…
	eben van tonder on The Origins of Polony

Introduction to Bacon & the Art of Living

The Curing Molecule

What is Meat Curing?

How is Nitric Oxide formed?

Can we remove nitrogen (nitrate or nitrite) from our diets?

The Importance of Nitrogen

-> Reduction (losing oxygen atoms)

-> Oxidation (Gaining Oxygen Atoms)

The Ever-Presence of Nitrogen

Demonstrating Oxidation and Reduction

Changing Perceptions

It’s Present in our Bodies!

Conclusion

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Introduction

Nitrite

– Three Sources of Nitrite

Benefits of Nitrite

-> Contribute to protection against UV-induced cell damage.

-> Protection of gastric mucosa from hazardous stress.

-> Cardiovascular Benefits

-> The Brain

-> Protection of the Liver

-> Protection of the Lungs

-> Protection of the kidneys

-> Crush syndrome and shock

Conclusion

References

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EarthwormExpress Introduction

Circulation

Abstract

Discovery and Chemical Properties

Nitrite as a Vasodilator

Conversion of Nitrite Into NO and NO-Related Products

Nitrite as an Antidote for Cyanide and Hydrogen Sulfide Poisoning

Other Medical Uses of Inorganic Nitrite

Acidified Nitrite

Use of Inorganic Nitrate in Medicine

Nitrate and the Treatment of Lung Diseases

Nitrates as Diuretics

Nitrate in Other Medicinal Preparations

Conclusions and Outlook

Footnotes

References

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Introduction to Bacon & the Art of Living

The Direct Addition of Nitrites to Curing Brines – the Spoils of War

Early Public Perception about Nitrite

Germany 1910 – 1920 – the Race to Access Atmospheric Nitrogen

Sodium nitrite and the coal-tar dye industry

The Economic Imperative

The Advantage of Scale and Technology

Supporting Evidence from the USA

The USA – 1910’s – Nitrite on Trial

Sodium Nitrite Tested in Meat Curing in Chicago

Nitrite Curing Known in the USA Pre-1925

Aftermath of the Great War

Restrictions on German Sodium Nitrite in the USA

German Sodium Nitrite Appears as Curing Agent in the USA – Ingredients for Deceit.

Prague Salt

Further Reading

Notes

References:

Image

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