Introduction to Bacon & the Art of Living

The story of bacon is set in the late 1800s and early 1900s when most of the crucial developments in bacon took place. The plotline occurs in the 2000s, with each character referring to a natural person and actual events. The theme is a kind of “steampunk” where modern mannerisms, speech, clothes, and practices are superimposed on a historical setting. Characters interact with one another with all the historical and cultural bias that goes with this. The period of technology it covers is breathtaking. Beginning in pre-history, it traces the development of curing technology until the present, where bacon curing is possible without adding nitrites.

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The Development of Dry Curing from Salt Only to Salt, Saltpeter and Sugar

January 1920

Cape Town

Thirty years of learning teach you a lot! Since the diary entry in 1886 about Stillehoogte and my recollections as a young man, my understanding of dry curing developed much. I write this following in response to your request to put my diary entries and the letters I’ve sent you over the years about my adventures in chronological order so that you can present them as a book. A complete work on bacon. At times, chronology is not fair to the story. In this case, I had three decades to learn more about dry curing, and it would be unfair to leave my new insights till the end of the book that you want me to compile.

What did the march of time and exposure to good teachers reveal about dry curing that I did not know when I walked across the fields on Stillehoogte? For starters, dry-cured bacon has been a staple food for many years. It sustained workers, and armies marched on it.

Review of Dry Curing

I told the story of my parents and how we cured meat, but we did not discuss the mechanism working in the meat. Here, I want to pull the veil back so that you can look inside the meat. I present the system that developed throughout millennia, called dry curing. An Englishman living in Canada, Robert Goodrich later insisted on the same system handed down to him when he was taught the trade of meat curing while working at the Smithfield market in London over 50 years ago. He is arguably one of the world’s best proponents of dry curing today. So, to illustrate the intricate processes at work in achieving dry-curing, I rely on the method he taught me. As we look at this, remember that each step in this process had to be discovered through trial and error over centuries and even millennia.

Stepwise Evaluation of Dry Curing

This review becomes a one-chapter synopsis of everything we will cover in this book regarding the technical steps of curing. It is the application of Chapter 2, The Curing Molecule. Dry curing is foundational to the meat curing we do today. Various alternative methods exist to the Goodrich method I discuss here, but they all follow the same basic steps. Some may leave out saltpetre as an ingredient. Specific steps are slightly adjusted. An adaptation that has become popular presently is what is referred to as equilibrium curing, where the ratio of ingredients to meat is calculated and added to a vacuum bag. Meat is weighed off. The exact ratio of salt, sugar, saltpetre and other spices to the weight of the meat is determined and placed in a vacuum bag. The meat is placed in the bag, and the salt is rubbed on the meat. The bac is then vacuum sealed, preventing over-salting. Since I am an enthusiastic fan of Robert Goodrich, we follow his method in this discussion.

-> Mixing the dry cure

The salt mix used to this day typically consists of salt, sugar, and nitrate (saltpetre). This first statement seems ordinary. Three simple ingredients. The composition of these ingredients, however, fascinatingly changed over time. When humans worked out that salt preserves meat, they used just this one ingredient, possibly for millennia.

Early on, humans learned that meat is preserved by drying it in the wind and sun and rubbing salt on it. It is easy to see how they would have used these two in combination and that by leaving the meat for a few months, they would have noticed the curing colour of the meat developing.

In Chapter 2, we discovered that if meat is left sufficiently long and if enough water is removed from it to prevent spoilage, it will naturally develop the cured colour through the oxidation of the amino acid L-arginine, which forms nitric oxide and, in turn, is the curing molecule. This is the same molecule we still rely on to cure our bacon and hams today.

Very early on, I believe, even urine and sweat from humans and animals were used to speed up this process. Later, particular salts emerged that cured more effectively than salt-only, like saltpetre, as nitrate salts were called, or a salt like sal ammoniac. Their value was discovered accidentally. Over time, as saltpetre overtook sal ammoniac in terms of its availability, this became the curing salt of choice to be added with bay or rock salt.

-> Curing

Finally, when the value of a combination of salt, sugar and saltpetre was worked out, this dry mixture was rubbed onto the meat and kept at a temperature between 2 – 4^oC. The curing mix is completely dissolved in the moisture present in the meat. As a general guide, the salt penetration rate into the meat is estimated at around 2.5cm/ week. Micrococcal and Staphylococcus bacteria reduce the saltpetre or nitrate, as we call it today, to nitrite.

Through a sequence of chemical reactions or bacteria reduction, nitric oxide will form, which reacts with the haem protein, imparting the characteristic pinkish/ reddish colour and flavour to the meat. More than one salt application is required, and the meat must be turned over and restacked daily. In large curing operations, meat is salted and stacked in a curing bath. The following day, it’s re-stacked in a second bath. Meat at the top is taken off first and placed at the bottom of the second bath and continues to stack so that what was below, this time at the top, re-salting as you go.

-> Equalizing or post-salting resting

After the initial cure is complete, the excess cure is washed off with cold water. This facilitates the closing of meat pores, leading to a hardening of the surface and a considerable reduction in the drying rate. The equalizing step should be done for the same time period as the initial curing time and at the same refrigeration temperatures of 2 – 4^o C. This is to ensure that the cure spreads evenly through the meat.

Some hams call for this step to be a few months. It depends on the ham size, the ratio of lean surface to mass, pH, and the presence of intramuscular fat. The relative humidity is progressively decreased as this step progresses. Weight loss of between 4 to 6% can be expected. French hams are usually heated to 22^oC and 24^oC for a week to dry them and “fix” the colour. The air velocity should be kept low, but the air circulation must be uniform to ensure uniform air temperature and relative humidity through the curing chamber. Otherwise, microorganisms could spoil the meat.

-> Drying

If smoke is applied, the meat is first dried for 2 – 3 days, with high humidity of around 66% to 75%, with a very light breeze/airflow. High air velocities will influence the quality of dry-cured ham negatively. This will lead to the surface layer of ham or bacon drying out and collapsing. Internal and external diffusions should be identical for efficient and uniform drying.

The meat must be tacky to the touch for the smoke to adhere during the next step. An ambient temperature for dry-cured bacon of between 7 – 13^oC is recommended. After drying, the meat will be well prepared for smoking or ripening.

-> Smoking

Traditionally, smoking was done in regions where drying was more difficult. It imparts a characteristic flavour to the hams and acts as a preservative. In bacon production, it is interesting that smoking was applied as an additional preservative for bacon destined for long sea journeys. This is one of the reasons why countries far from England, accessed by such long voyages by sea, became accustomed to smoked bacon, and green, unsmoked bacon is not generally known in those countries. It is a well-known version of bacon in England and Europe, enjoyed even today. Here in South Africa, I had the request from many British Expats to produce unsmoked bacon for them, which is never an option for South Africans.

When doing cold smoking, there is “no” heat at all. This development took place in Westphalia in Germany, and we will delve into this fascinating history when we focus on the smoking of meat in Chapter 13.02.02: Robert Henderson and the invention of the smokehouse. It produced superior bacon and hams compared to hot smoking.

According to this method, no heat is run through the chamber. All you need is a thin blue smoke. Smoke duration is between 8 and 48 hours. Rest overnight at room temperature. In between cold smoking, hang back at room temperature and not in the fridge; if you do, this will make the product wet again.

Smoking is typically done for a total of 48 hours:

Day one, 8 hours, rest overnight; Day two, 8 hours, rest overnight; Day three, 8 hours, rest overnight; Day four, rest all day and overnight; Day five, 8 hours, rest overnight; Day six, 8 hours, rest overnight; Day seven, 8 hours. This gives you 48 hours (6 x 8 = 48). The fact of a 48-hour curing time is very interesting. Why so long? The reason and the profound implications will be discussed later when we look at the role of smoking.

Keep an eye on the colour of the bacon/meat when you take it out of the smokehouse and again the following morning before placing it into the smokehouse — this alone will give you an indication of the depth/colour of the smoke you like — keep records.

-> Ripening and Maturing

The meat is now held in an air-conditioned chamber and ripened. Depending on the objective of the product, this can take anywhere from 14 days to 3 years. The longer it takes to mature, the better the quality will be. “Increased time of ripening gives a higher degree of enzymatic degradation, contributing to taste and flavour of the final product and as a consequence yields a higher quality of dry-cured ham.” (Petrova et al., 2015) Generally, temperatures vary between 5^o C, and some take this up to as high as 14 or even 20^o C. Relative humidity is between 70 and 90%.

Temperatures for the drying-ripening of hams are different since the drying and ripening stage flows one another, and there is not usually a smoking step for most hams (there are some with a smoking step, and bacon will usually have a smoking step). Even so, drying-ageing temperatures for hams vary greatly. Iberian ham, for example, has the “drying–ripening split into three-time intervals: the first phase is maintained at 6 – 16^oC, the second at 16 – 26^oC and the third at 12–22^oC. This temperature range with the adjusted air relative humidity provides necessary moisture diffusivity. It allows the adequate activity of meat enzymes that leads to the formation of the distinctive quality of the final product.” (Petrova, et al., part 2, 2015) The higher the temp, the lower the humidity and the higher the airspeed, the dryer the end product and the greater the weight loss.

-> Evaluation of Final Product

Developing a process like this took millennia and was the province of artisan guilds where secrets were tightly guarded and passed on from generation to generation. One thing we know for sure is that initially, meat was cured with salt only. One of the oldest complete descriptions of this is from ancient Greece.

Cato the Elder

A record exists from Cato the Elder, who described in 160 BCE how a ham should be cured. In his Latin work, De Agricultura (On Farming), this Roman statesman and farmer gives an ancient recipe for curing pork with salt.

“After buying legs of pork, cut off the `feet. One-half peck ground Roman salt per ham. Spread the salt in the base of a vat or jar, then place a ham with the skin facing downwards. Cover completely with salt. After standing in salt for five days, take all hams out with the salt. Put those that were above below, and so rearrange and replace. After a total of 12 days take out the hams, clean off the salt and hang in the fresh air for two days. On the third day take down, rub all over with oil, hang in smoke for two days…take down, rub all over with a mixture of oil and vinegar and hang in the meat store. Neither moths nor worms will attack it.” (economist.com)

Cato may have imitated a process whereby hams are smoked over juniper and beech wood. The Roman gourmets probably imported the process from Germania. (economist.com) It is possible that the process of curing itself was brought to Rome by the military stationed in Germany. Many years later, it would be in Westphalia where the cold smoking of meat was invented.

From Salt only to Salt, Salpeter and Sugar

The question arises of how salt-only curing progressed to include salt, saltpetre and sugar. I decided that it is appropriate to take you on an abbreviated journey through history and to arm you with more key background knowledge about bacteria and enzymes, which, like Chapter 2’s discussion on the curing molecule, will arm you to appreciate the rest of this work more fully.

-> The Mechanics of Salt-Only Curing

Salt-only curing is more than just producing salted meat. The mechanisms responsible for meat with a pinkish colour and a cured taste are fascinating. There are two equally important matters to consider. One is the mechanism of curing, and the second is how these “mechanisms” spread through the meat.

>> The Mechanism of Dry Curing Without Nitrate Salts

The curing of meat in a salt-only system happens through the oxidation of L-arginine either through enzymes in the meat or through enzymes in bacteria that penetrate the meat. One of the products created is nitric oxide, which is the curing molecule.

The reaction is driven by both enzymes in the meat and bacteria, which accomplish the oxidation through enzymes. An enzyme accelerates the rate of reaction in which different substrates are converted to products through the formation of an “enzyme-substrate complex.” An enzyme is very specific in terms of its activity. Generally speaking, each enzyme will speed up (catalyses) only one type of reaction and will only do this for one type of substrate. This highly specific mechanism is often called a “lock and key” mechanism. Enzymes are highly specific and discriminate between slightly different substrate molecules. Another essential feature of enzymes is that their function as a catalyst is optimal over a narrow range of temperatures, ionic strength and pH. (Natureclean)

Bacteria are tiny living things made up of just one cell. They have a tough outer layer and an inner part without specific parts like a nucleus. Bacteria can make different kinds of special helpers called enzymes. These helpers help bacteria deal with what’s around them. Enzymes can break down fats, oils, plant stuff (like cellulose and xylan), proteins, and starches. All these things are like long chains that need more than one kind of enzyme to be broken down properly. (Natureclean)

To do this, bacteria have a specific group of enzymes for each job, like a team for each task. For example, there are three kinds of enzymes (endocellulases, exocellulases, cellobiohydrolases) needed to break down cellulose, which is a type of plant material, into simple sugar bits. All these enzymes are called cellulases, but they each work on a different part of the plant material. If one of these enzymes tries to do the job alone, it won’t work well. Bacteria can make all the right enzymes they need to break down and use the things around them. They can even have more than one team working at the same time.

Another important thing about how bacteria make enzymes is that they start doing it as soon as they grow. When bacteria want to eat, they need food from their surroundings. So, they release enzymes that can break down the food they find. The amount of enzymes they make can differ from one type of bacteria to another. It also depends on how much food there is, how warm it is, how acidic or basic the environment is, and how fast the bacteria are growing.

Some of these enzymes, like proteases (for proteins), amylases (for starches), and cellulases (for plant stuff), can be made in small amounts, like milligrams, or in more significant amounts, like grams, for every litre of liquid where the bacteria are growing.

These particular conditions required for bacteria to multiply are equally important. Bacteria require a particular environment to thrive, closely associated with temperature and pH.

Unlike bacteria, enzymes are not living things. They are like tools made of protein and don’t last forever. Enzymes can stick around for a short time, from a few minutes to a few days, depending on the situation. Just like bacteria, enzymes work best under certain conditions, affecting how well they do their job. (Natureclean)

Enzymes can be easily broken down by other enzymes called proteases, as well as by chemicals, extreme pH levels (like really acidic or basic environments), and very high or low temperatures. One crucial difference between products based on enzymes and bacteria-based products is that enzymes can’t fix themselves or make more of themselves. In contrast, living bacteria can keep making new enzymes constantly, even if they face some environmental challenges.

>> How Bacteria Spreads Through Meat

The fascinating question from the discussion above is how the bacteria get into the meat. How they spread now becomes essential.

Bacteria can be either proteolytic or non-proteolytic. Proteolytic bacteria is a type of bacteria that can produce protease enzymes, which are enzymes that can break down peptide bonds in protein molecules. The result of proteolysis is, therefore, the breakdown of proteins into smaller molecules catalyzed by cellular enzymes called proteases. (Shirai, 2017)

Proteolysis in dry-cured meat products has been attributed mainly to natural enzymes inside the meat. On the other hand, Rodríguez (1998) found that the breakdown of proteins on hams may be due not only to enzymes inherently part of the meat, but also to microbial enzymes.” A researcher from New Zealand who did a lot of work to understand the penetration of bacteria into meat is C. O. Gill. Gill (1977) came to the same conclusion years earlier when they found that bacteria are confined to the surface of meat during the initial multiplication or logarithmic growth phase. Still, when proteolytic bacteria approach their maximum cell density, they secrete enzymes that can break cells down, including a breakdown of the connective tissue between muscle fibres, allowing the bacteria to penetrate the meat. Further, non-proteolytic bacteria do not penetrate meat, even when grown in association with proteolytic species. (Gill,1977)

Gill (1977) found that the “penetration of meat by nonmotile bacteria (i.e. not mobile) and the rapid rate of advance of invading microorganisms indicate that physical forces are involved in the movement of bacteria through meat. Non-proteolytic species do not invade in company with proteolytic species probably because, with mixed cultures, penetration originates in the area of growth of a microcolony of the proteolytic species so that the non-proteolytic bacteria are excluded.” The production of enzymes that can break cells down by the bacteria does not occur until the end of the initial growth phase or logarithmic growth when the meat is in an advanced stage of spoilage. Therefore, unless the meat has been treated with chemicals designed to break the muscle structure down, bacteria should not be penetrated into fresh, healthy meat. Penetration of meat by bacteria, therefore, apparently results from the breakdown of the connective tissue between muscle fibres by proteolytic enzymes secreted by the bacteria.” (Gill, 1977) Shirai (2017) quotes Gill (1984) when he stated that bacteria migrate into meat via gaps between muscle fibres and endomysia. 

It has been shown that meat from a healthy animal is intrinsically sterile. The question then arises of how bacteria can penetrate this very compact structure in a matter of days and weeks during the curing of hams and bacon in dry-curing. Without some outside force, bacteria will spread through a meat muscle only when the meat is almost written. How is it possible for the meat to remain relatively “healthy” and bacteria penetrate it completely? What can this outside force be that facilitates its spread through the meat?

The answer is in the spread of the salt through the muscle. The salt molecule is large but splits into two ionic compounds, sodium and chloride, which are much smaller and can travel through the meat at a higher rate. The salt dehydrates the meat cells, and the meat fibres shrink. Water migrates from the cells, and a large quantity lodges itself in the enlarged extra-cellular spaces inside the meat. This creates waterways for the bacteria to spread into the inner parts of the muscle much faster than it would have if it relied on its ability to “bore” into the meat.

>> Combining the Mechanism of Curing and Migration of Bacteria in the Meat

Let’s put these two aspects we just looked at together now and see how they work in synergy. In meat processing, when oxygen availability varies, Staphylococcus xylosus and Staphylococcus carnosus, known for their versatile metabolic abilities, adapt accordingly. As these bacteria are injected into the meat, they encounter different oxygen levels within the muscle tissue. In areas where oxygen is limited, these bacteria switch to anaerobic metabolism. The deeper they penetrate the meat, the lower the oxygen levels become. During this transition from aerobic to anaerobic respiration, these bacteria require a nitrogen source for their metabolic processes.

At this critical juncture, the bacteria turn to L-arginine, an amino acid naturally present in the meat, as their nitrogen source. Through enzymatic pathways, they convert L-arginine into nitric oxide (NO). This nitric oxide production occurs both under aerobic conditions, closer to the meat’s surface where some oxygen may be present, and in anaerobic regions deeper within the meat, where oxygen is scarce.

The enzymatic conversion of L-arginine into nitric oxide is critical in the curing process. Nitric oxide serves multiple purposes: it helps preserve the meat by inhibiting the growth of spoilage bacteria and contributes to the development of the meat’s characteristic flavour and colour. Importantly, this process is achieved without adding extra nitrite or nitrate to the brine, making it an intrinsic aspect of the curing method.

Key factors to consider are food for the bacteria, the optimal pH range, and temperature. The optimal temperature for meat curing with these bacteria is typically 15°C to 24°C. Maintaining a consistent temperature within this range is best throughout the curing process. The time required for curing will vary and typically lasts 7 to 14 days. This duration allows the bacteria to convert L-arginine into nitric oxide gradually. Aim for a pH range of 5.2 to 6.2. This slightly acidic environment promotes the activity of nitrate-reducing bacteria while inhibiting unwanted bacterial growth. An adequate bacterial population will be essential to support effective nitric oxide production. Small amounts of sugars, like glucose, can be naturally present in the meat or added to support bacterial growth and metabolism.

-> Salt with a little bit of saltpetre

We know by now that nitric oxide can also be produced from nitrate salts such as sodium or potassium nitrate. One of the ancient nitrate salts is called Saltpeter. It was found that the curing reaction was sped up if a little bit of Saltpeter was added to the salt when rubbing it onto the hams or bacon. The reason was that the bacteria now had a more accessible and more readily available source of nitrogen, namely nitrate, which is three oxygen atoms joined with one nitrogen atom. Saltpetre is the curing salt that most of us are familiar with that predates sodium nitrite as curing agent. 

By far, the largest natural known deposits of saltpetre to the Western world of the 1600s were found in India, and the East Indian Companies of England and Holland played pivotal roles in facilitating its acquisition and transport. The massive nitrate fields of the Atacama Desert and those of the Tarim Bason were still largely unknown. In 1300, 1400, and 1500, saltpetre had, however, become the interest of all governments in India, and there was a considerable development in local saltpetre production.

In Europe, references to natron emerged in the middle of the 1500s and were described by scholars who travelled to the East, where they encountered the substance and the terminology. Natron was originally the word that referred to saltpetre. Later, the word natron was changed, and nitron was used.

At first, the saltpetre fields of Bihar were the focus of the Dutch East Indian Company (VOC) and the British East Indian Company (EIC). The VOC dominated the saltpetre trade at this point. In the 1750s, the English East Indian Company (EIC) was militarised. Events soon took place that allowed for the monopolization of the saltpetre trade. In 1757, the British took over Subah of Bengal; a VOC expeditionary force was defeated in 1759 at Bedara; finally, the British defeated the Mughals at Buxar in 1764, securing the EIC’s control over Bihar. The British seized Bengal and took possession of 70% of the world’s saltpetre production during the latter part of the 1700s. (Frey, J. W.; 2009: 508 – 509)

The application of nitrate in meat curing in Europe rose as it became more generally available. Later, massive deposits of sodium nitrate were discovered in the Atacama Desert of Chile and Peru and became known as Chilean saltpetre. Curing with this was only a re-introduction of technology that existed since well before 2000 BCE.

The pivotal area where I believe saltpetre technology spread from across Asia, India and into Europe is the Turpan-Hami Basin in the Taklimakan Desert in China. Its strategic location on the Silk Road, the evidence of advanced medical uses of nitrates from very early on and the ethnic link with Europe of people who lived here all support this hypothesis.

Large saltpetre industries sprang to the South in India and the Southeast in western China. In India, a large saltpetre industry developed in the north on the border with Nepal – in the state of Bihar, in particular, around the capital, Patna; in West Bengal and Uttar Pradesh (Salkind, N. J. (edit), 2006: 519). Here, it was probably the monsoon rains that drenched arid ground, and as the soil dries during the dry season, capillary action pulls nitrate salts from deep underground to the surface, where they are collected and refined. It is speculated that the source of the nitrates may be human and animal urine. Technology to refine saltpetre probably only arrived on Indian soil in the 1300s. Both the technology to process it and robust trade in sal ammoniac in China, particularly in western China, predate the development of the Indian industry. It is, therefore, unlikely that India was the birthplace of curing. Saltpetre technology probably came from China. However, India, through the Dutch East Indian Company and later, the English East Indian Company, became the primary source of saltpetre to the West.

To the Southeast, in China, the most extensive production base of saltpetre was discovered dating back to a thousand years ago. Here, a network of caves was discovered in 2003 in the Laojun Mountains in Sichuan Province. Interestingly, meat curing is also centred around China’s western and southern parts.

In China, in particular, a very strong tradition of meat curing developed after saltpetre was possibly first introduced to the Chinese well before 2000 BCE. Its use in meat curing only became popular in Europe between 1600 and 1750, and it became universally used in these regions towards the end of 1700. Its usage most certainly coincided with its availability and price. I have not compared price and availability in Europe with the findings on its use in meat curing, based upon an examination of German and Austrian kook books by Lauder (1991). Still, I am confident that the facts will prove the same when I get to it one day.

The Dutch and English arrived in India after 1600, with the first shipment of saltpetre from this region to Europe in 1618. Availability in Europe was generally restricted to governments who, at this time, increasingly used it in warfare. (Frey, J. W.; 2009) This correlates well with the proposed time when it became generally available to the European population in the 1700s from Lauder. A strong case is emerging that the link between Western Europe and Western China’s desert regions was where nitrate curing developed into an art. It is hard to tell whether it happened here or in the lands surrounding the Black Sea. Which region influenced this is uncertain, but that both regions are very strong contenders for developing curing into an art is certain.

That these regions had a hugely symbiotic effect on one another is evident. Significantly, that sea beat, the form of beetroot that existed before it was cultivated and became the plant we know today, comes from the northern shores of the Caspian Sea, with the Caucus Mountains stretching from this water body to the Black Sea. In Turkey, still today, beetroot is a highly important crop, and the industry stretches back to a time before historical records were kept.

Dry-curing of meat changed from salt only to a mixture of salt and saltpetre, liberally rubbed over the meat. Water and blood are extracted and drained as it migrates into the meat. The meat is usually laid skin down, and all exposed meat is plastered with salt and saltpetre. Pork bellies would cure in approximately 14 days. (Hui, Y. H., 2012: 540)

-> Salt, Saltpetre, and Sugar

The addition of sugar favouring nitrate reduction to the active agent nitrite became common practice during the 19th century.” (Lauer K. 1991.) At first, sugar was added to reduce the meat’s saltiness and make it more palatable. Curers soon discovered that when sugar is added, the meat cures faster and improves colour development.

Science later revealed that the sugars contribute to “maintaining acid and reducing conditions favourable” for forming 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 utilisation by microorganisms or the enzymatic systems of the meat tissues.” (Kraybill, H. R.. 2009)

Ralph Hoagland, Senior Biochemist, Biochemie Division, Bureau of Animal Industry, United States Department of Agriculture, discovered that saltpetre’s functional value upon the colour of meat is its reduction to nitrates and the nitrites to nitric oxide, with the consequent production of NO-hemoglobin.

He wrote an important article in 1921, Substitutes for Sucrose in Cured Meats. Writing at this time, this formidable meat scientist is ideally placed to comment on the use of sugar in meat curing in the 1800s since the basis of its use would have been rooted in history.

He writes about the use of sugar in meat curing in the USA and says it is used “extensively.” He reveals that according to government records, 15,924,009 pounds of sugar and 1,712,008 pounds of syrup, totalling 17,636,017, were used in curing meats in pickle establishments inspected by the US Government in 1917. If one added the estimated use of sugar in dry cures in the same year, he placed the usage at an estimated 20,000,000 pounds. This estimate excludes the use of sugar in meat curing on farms. (Hoagland, R. 1921)

Hoagland says that the functional value of sugar in meat curing at this time (and probably reaching back into the 1800s) was entirely related to product quality and not preservation. “Sugar-cured” hams and bacon were viewed as being of superior quality. He states that a very large portion of bacon and hams produced in the USA are cured with sugar or syrup added to the cure. The sugar used in the curing mix is so tiny that it does not contribute to meat preservation.  He wrote, “meat can be cured in entire safety without the use of sugar, and large quantities are so cured.”  (Hoagland, R.  1921.)

The contribution to quality that he speaks about is probably related to both colour and flavour development. The colour development would have been related to the formation of the cured colour of the meat (The Naming of Prague Salt) as well as the browning during frying.

The role of sugar in bacon curing of the 1800s when saltpetre was used was elucidated in 1882 by Gayon and Dupetit, studying and coining the term “denitrification” by bacteria. The process whereby nitrate is changed to nitrite is through the process of bacterial denitrification. They demonstrated the effect of heat and oxygen on this process and, more importantly for our present discussion, “they also showed that individual organic compounds such as sugars, oils, and alcohols could supplant complex organic materials and serve as reductants for nitrate.” (Payne, 1986)

Want to Know More?

The phrase used by Payne in his 1986 review article in celebration of a “Centenary of the Isolation of Denitrifying Bacteria,” quoted above caught my attention. “Individual organic compounds such as sugars, oils, and alcohols could supplant complex organic materials and serve as reductants for nitrate.” Did they mean to say that the environment becomes favourable for such reduction or did they mean to say that each of the organic compounds including sugars, oils, and alcohols could supplant the “complex organic material?” Did they mean this, that these materials somehow play a role in the actual reduction of nitrate or merely that it creates an environment for the existence of the bacteria required for the reduction to exist? It could only have been the latter because sugar plays no role in the actual reduction apart from being favourable for the microorganisms to exist which accomplish the reduction. Even Lauer (1991) whom we referred to above said that “the addition of sugar . . . favours the reduction of nitrate to the active agent nitrite. Payne in his review of the 100 years since denitrifying bacteria has been named mentions that Gayon and Dupetit were at this point being mentored by Pasteur and this fact alone necessitates that we pause for a moment and consider the word very carefully.

What is the exact nature of the “benefit” of sugar and is there something for us to learn here? The fact that sugar does not play any direct part in the reduction of nitrate is true but the fact that nitrate reduction takes place more rapidly when sugar has been added required more investigation.

Bacteria, like the cells of animals and plants rely on ATP as energy. Bacteria cannot process something without resources and the right environment. Temperature and pH accordingly are two very important environmental factors in the rate of microbial action. Another important factor is the availability of chemical nutrients. Jurtshuk (1996) puts it like this. “The uptake and utilization of the inorganic or organic compounds required for growth and maintenance of a cellular steady state (assimilation reactions)” is very important and lacking any of these can be a limiting factor on the microbes role such as nitrate reduction. They continue that “these respective exergonic (energy-yielding) and endergonic (energy-requiring) reactions are catalyzed within the living bacterial cell by integrated enzyme systems, the end result being self-replication of the cell. The capability of microbial cells to live, function, and replicate in an appropriate chemical milieu (such as a bacterial culture medium) and the chemical changes that result during this transformation constitute the scope of bacterial metabolism.” (Jurtshuk, 1996)

“The bacterial cell is a highly specialized energy transformer. Chemical energy generated by substrate oxidations is conserved by formation of high-energy compounds such as adenosine diphosphate (ADP) and adenosine triphosphate (ATP). . . ” (Jurtshuk, 1996) In order to do this, the bacteria requires a constant feed of particular chemicals. Carbon, nitrogen, Oxygen and Hydrogen are required. Our focus is on the conversion of nitrogen from Nitrate to Nitrite, but if carbon, for example, is not available, it becomes a limiting factor as the bacteria will stop converting nitrate to nitrite or the process will be slowed down considerably. Sugar turns out to be an excellent source of carbon for bacteria and adding sugar to a solution will increase the rate of nitrate conversion to nitrite in cases where the availability of carbon is limited. Seviour (1999) commented on the same phenomenan when he wrote that “the rate of denitrification is affected by several parameters including temperature, dissolved oxygen levels and the concentration and biodegradability of carbon sources available to these cells” (Seviour, 1999) Examples of such carbon sources are sugar, oxygen and plant oils. (FM)

Denitrifying bacteria are facultative anaerobes, that is, they will only use nitrate if oxygen is unavailable as the terminal electron acceptor in respiration.”  “The nitrate is sequentially reduced to more reduced forms although not all bacteria form gas. ” “Many bacteria can only carry out the reduction of nitrate to nitrite, and this process is referred to as dissimilatory nitrate reduction. There is also evidence emerging that certain bacteria can denitrify, even if oxygen is present.  (Seviour, 1999)

What we have here are then two important reasons for adding sugar to the brine. In a Wiltshire live-brine system it will be to supplement the carbon for the bacteria’s diet which will enable them to convert nitrate to nitrite at an increased rate. In the past sugar was also added to reduce the “saltiness” of the bacon but in modern curing plants this is not a consideration any more. The fact that sugar adds to the taste and flavour of the bacon remains, however a reason why it is included in many brine cures.

A third possible reason why we want to include it is becasue nobody likes “pale” fried bacon. The best bacon has a dark golden colour when it is fried. The scandanavian countries, in particular are known for such bacon, but to some extent, it is a characteristic of good bacon the world over. This brings us to the topic of the reasons why these carours exist, as not all sugars are suitable for this and depending on the requirement, the optimal sugar must be selected.

There are two reasons why bacon turnes brown during frying. One is due to caramization and another is becasue of the Maillard reaction. In order to select the optimal sugar for these reactions, we devide sugars into two broad categories namely reducing and non-reducing sugars.

Redusing and non-Reducing Sugars and the Maillard Reaction

Sugars can be classified broadly into reducing and non reducing sugars.

>> Reducing Sugars

“Reducing sugars contain free aldehyde or ketone groups. They can transfer hydrogen electrons to other compounds and can cause the reduction of other compounds. the anomeric carbon of a sugar can be used to identify it. The first stereocenter of the molecule is an anomeric carbon. If the anomeric carbon has an OH group, it is a reducing sugar. When the sugar is in an open configuration, an alcohol molecule converts it to a ketone or aldehyde, which can reduce other compounds.” (Fernando)

Examples of reducing sugars:

– Glucose

– Fructose

– Galactose

– Maltose

– Lactose

– Dextrose

By this time you should have a proper headach trying to make sense of all of this. Dont worry. The only thing you actually need to remember is that for the Maillard reaction to take place, you need a redusing sugar. And a reducing sugar interacts with proteins during cooking or frying or baking which is what creates the brown/ caramel colour and apealing cooked flavours. For those who wonder, it is named after Louis Camille Maillard who first described it in 1912. We refer to it as the “browning reaction.” Other two important reasons why food turns brown is becasue of enzymes (called enzamic browning). You have seen when bacon is left uncovered in the freezer and it turnes brown. It is becasue of browning by enzymes. Another reason why bacon turns dark in colour upon frying is becasue of the caramalization of the sugars. Enzamic browning and caramalization has, however, nothing to do with the sugar being reducing or non-reducing. Caramalization occurs when reducing or non-reducing sugars are used.

>> Non-Reducing Sugars

“Non-reducing sugars do not contain any free aldehyde or ketone groups and are not capable of reducing other compounds because the anomeric carbon does not have an OH group attached to it.” (Fernando)

“Sucrose is the most common non-reducing sugar. It is also known as table sugar. Sucrose is a glucose carbon connected at the anomeric carbon to a fructose carbon. Because the bond involves both anomeric carbons, neither carbon has an OH group. Therefore, sucrose cannot reduce other compounds and is not a reducing sugar.”

Examples of non-reducing sugars:

– Sucrose

– Trehalose

– Raffinose

– Stachyose

– Verbascose

Caramalization

The publication, Food Science, does a great job simplifying caramalization. They write, “Sugar molecules begin to disintegrate at temperature above 170 degree C (340 degree F). They break up in various ways, and the number of different compounds which can thus be yielded is over a hundred.” (Food Science)

“Some of them are brown in color and bitter in taste producing the characteristic color and flavour of caramelization. If heating continued, caramelized sugars break down further into pure black carbon. The various types of sugar differ noticeably in the extended to which they caramelize. Fructose and sucrose caramelize readily but dextrose (or glucose – practically the same substance) hardly does so at all. The pentose sugars whose molecules contain only five carbon atoms instead of six, caramelize very well. Since small amounts of these are present in wheat bran and in rye, wholemeal and rye breads tend to color quickly when toasted.” (Food Science)

“Caramelization can take place both in air and away from it, as at the bottom of a saucepan. The sticky black coating in the bottom of an overhead pan is mostly caramel and carbon. Caramelized sugar can be used as a brown coloring and is the basis of ‘gravy browning’, which is made from glucose.” (Food Science)

“An example of pure caramelization is the well-known dessert Crème Caramel. Sugar and water are boiled until the sugar is caramelized and this is then use to line a small mould. A vanilla flavored custard is poured in and the mould is placed in a bain-marie in the oven.” (Food Science)

In the 1800s when the use of saltpetre was at its pinnacle, the use of sugar with saltpetre had then a much more prominent role in that it energizes denitrification bacteria which results in an increased rate of nitrate reduction to nitrite and therefore would speed up curing with saltpetre and result in a better overall curing process. Today, with the widespread use of sodium nitrite in curing brines, certain denitrifying bacteria are one mechanism for NO formation which directly leads to better curing. The use of sugar or dextrose in bacon production in the modern era has more to do with the browning effect through the well-known Millard reaction to give fried bacon a nice dark caramel colour when fried.

-> Double Salting

The curer’s task was still to remove moisture from the meat as far as possible through salting. When this proved ineffective, another salting step was added. As you will see from the steps I gave you about dry-curing at the beginning of this chapter, double salting is incorporated there, but it has not been part of even dry-curing for many decades. During the first salting, meat juices are pulled from the meat. This was cleared away, and a second “salting” was administered. Later, several “salting’s” were administered as per the method of dry curing given. Right here, from the southernmost point of the African continent, comes a great illustration of this from the early 1700s, which then easily extends back several hundred years.

Remember that the settlement, which became Cape Town, was, in the first place, set up as a refreshment station for the Dutch East Indian ships that rounded the African continent en route to India from Amsterdam. It became a stop-over for any friendly ship, and Cape Town soon got the name Tavern of the Sea. Here, the summers are extremely hot from December to March or mid-April. Winter starts when the first Arctic cold fronts arrive in April and lasts till at least September. From September to December, it’s technically summer, but it’s often very cold and rainy with intermitted very hot spells. This means that April to August would be the only four months to properly cure meat, which was very important for the Cape economy as it would be sold to passing ships. The pressure would have been relentless to find ways to cure meat in the other months. This is then the background to the account of multiple salting’s.

Upham reports on the following course of events from 1709. A detailed treatment of the reference can be seen at Saltpeter, Horse Sweat and Biltong.

Michiel Ley, who plays a vital role in the story, comes up with a plan to address the problem of the meat going bad before it is cured. He suggests double salting. “Decided that the treat should first lie some days in the brine to draw out the blood, and after that placed in new salt. That was not the idea of Husing but of his fellow contract or Michiel Ley. The former believed that the meat should be left in its first salt and not pickled beforehand and was prepared to guarantee supply remaining good.” This dispute clearly shows that double salting was not a generally accepted and practised technique in the 1600s and early 1700s.

The decision was made. “Decided, however, to adopt the plan of double salting, recommended by Ley; Husing ordered to supply in that manner; “Meervliet” having brought sufficient casks for the purpose. Ley to supply his share according to his plan. Company to supply the pepper.” The meat previously salted by Husing was also given over to Ley. “Decided to take over for the Company, the meat already salted by Husing. The good portions to be distributed among the crews, & the tainted ones among the slaves …”

So it happened that Lay was contracted to supply all the meat required by the Company together with Willem Basson, Jan Oberholster, and Anthony Abrahamsz. The issue of the meat supply was major and shaped the immediate political landscape of the colony. Notice the black pepper which was added. The reason for this was probably to keep flies and other insects away.

-> Using Salt with Salpeter (or Sodium Nitrite): An Excellent Strategy

In the curing reaction we have been looking at, we begin with nitrate (NO₃^–) converted through microorganisms into nitrite (NO2-). Nitrite is then converted through a series of chemical reactions or through bacteria to nitric oxide (NO). Salt is one of the most important things we can add to nitrite that is dissolved in water to “motivate” the solution to form nitric oxide. We will see that there are a few “motivators” to form nitric oxide. I will point this out every time we talk about it because this will allow the factory manager or supervisor to pay special attention to those steps in the factory. This is because it is the simplest thing we can do to ensure that we cure the meat as completely as possible so that it is uniform in colour and tastes great. Another “motivator” we introduced in the chapter is smoking the meat, which we will look at in much greater detail later. How smoking meat was “formalised” in the dry curing system, which Robert Goodrich taught me and in our modern systems, is itself a fascinating story.

Want to Know more:

The most important additive that influences nitric oxide formation is salt, due to the formation of nitrosyl chloride (NOCl), which is a more powerful agent than dinitrogen trioxid. (Dikeman, M. and Devine, C..  2014: 417)  It was Ridd (1961) who first reported that nitrous acid and hydrochloric acid will generate nitrosyl chloride (NOCl).   (Ridd, J. H.; 1961: 418)

Conclusion

Curing is an art as old as humanity itself. It developed around the noblest of human pursuits to fuel our inquisitive nature to explore the unknown. By itself, the story of meat curing stands in the annals of human achievement as a high point. This chapter briefly discusses every step in dry-curing and is a step-by-step guide for those who want to make their own dry-cured bacon or hams.

This brief introduction to bacteria and enzymes, along with historical background, provides the background, with chapter 2’s discussion on the curing molecule, to follow and appreciate the rest of this work.

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References

CHR Hansen – pamphlet and private communication, 2021 and 2022.

Fernando, R. A Comparison of Reducing Sugar vs. Non-Reducing Sugar. Food Science

http://www.natureclean.com/bacteria-enzymes.htm

Gill CO, Penney N. Penetration of bacteria into meat. Appl Environ Microbiol. 1977 Jun;33(6):1284-6. doi: 10.1128/aem.33.6.1284-1286.1977. PMID: 406846; PMCID: PMC170872.

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(c) eben van tonder

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