Despite the fact that I am convinced that current processing methods of hams and bacon do not pose any health rish for consumers, the demand for nitrite free bacon is not going away. Bacon and ham have always been a product for the people and whatever our personal views on the matter, the clear and growing consumer demand must be catered for.
Over the years I have seen spice companies acting with great dishonesty. They develop curing mixes that they claim accomplish meat curing without nitrites. The way they did this was by using plant extracts which are naturally replete with nitrate. Through bacterial reduction, they achieved the conversion of nitrates to nitrites which was then sold as a “natural” curing agent due to the fact that no synthetic ntirite was added. They circumvented food labeling legislation by not adding synthetic nitrite. In reality they still add nitrites to curing brines.
I have friends from around the world who build their brands on the claim that it is nitrite free and having investigated those claims, I can confidently say that they definitely add nitrites to curing of meat. It is an embarrassment just waiting to be exposed!
The Spanish Case
A Spanish producer launched a new curing system in the early part of the 2010s. They claim great results and that only plant and fruit extracts are being used. Despite this being a step in the right direction, several aspects of the development did not sit well with me, in particular the fanatical secrecy surrounding the product.
We were preparing for sausage trails today and the interview with the CEO milled through my mind. I do not understand the secrecy! Certainly there is a place for protecting proprietary information, but when the way it is being done goes against the food legislation governing all of us, it does not sit well with me. If the entire commercial viability of the approach is based upon complete secrecy, how do they expect to win the hearts and minds of the very consumers they are trying to rich out to by its nitrite-free curing brine. How will “trust me, I’m a doctor” in terms of this product be different from “trust me when I say that nitrites is not really bad for you?”
In the absence of information, people speculate and since the company is creating an enviroemt where people will speculate, let me also “speculate”. I asked the question how I would have done it if I had to copy what they did. For starters, remember that my approach is predicated on science. I have extensively looked at the curing reaction in Reaction Sequence: From nitrite (NO2-) to nitric oxide (NO) and the cooked cured colour and the colour of fresh meat in Difference between Fresh Cured and Cooked Cured Colour of Meat. There is a fundamental reason why the world works the way it works and understanding nitrite curing is intimae associated with our most fundamental understanding of the universe. In Fathers of Meat Curing I review some of the key developments.
– What they get right.
The company claims that they address Listeria spp (broad spectrum), Listeria monocytogenes, E Coli H157, and Clostridium spp (broad spectrum). The organism responsible for the existence of the meat curing industry is Clostridium Botulinum. (Clostridium Botulinum – the priority organism) and the fact they address it in their research is significant. The curing brine is effective against Clostridium Botulinum is very important. Personally I would like to know how effective it is against damaging the spore and preventing its viability. I am not sure if the study looked at that. If not, I would ask for that detail.
– Questions about antimicrobial efficacy
Challenge tests were performed where the brines efficacy was tested against sodium nitrite and compounds such as sodium nitrite plus sodium erythorbate, and a control with no antimicrobial. They claim to have demonstrated that their product performs equally well against listeria mono and Clostridium botulinum. Still, my reservations will stand.
In reviewing references to the brine, I found a claim that it its anti-microbial activity is especially effective if used with dehydrated lactic acid. Dehydrated lactic acid will itself be effective against amongst other, Listeria Monosytogenes. The one that worries me is still the efficacy against Clostridium. The claim is that its efficacy is due to traditionally processed Mediterranean fruit and spice extracts. What bothers me is that through the ages of meat processing, the producer claim that extracts were used which until now has been hidden from science. There is a lack of understanding of the experimental character of the meat curer who would, over thousands of years, if not millennia, certainly have stumbled upon these miracle substances and have incorporated it into his or her processing techniques long ago.
A further claim is made that these extracts are high in naturally occurring compounds with antimicrobial and antioxidative capacities. There are indeed a number of extracts who claim exactly this. However, what is the role of these antioxidative agents in meat curing. The context of the claims seems to point to pathogen eradication when in actual fact its role is in the prevention of fat rancidity and the development of off flavours.
– Questions about colour
The claim is made that it is these extracts are responsible for the meat flavor as well as its typical reddish color and pathogen protection, without the risk of nitrosamine formation. It is the claims about antimicrobial efficacy of the compound that is the most worrying and second to this, is the claim about the fact that it imparts a cured colour to the meat.
The most fundamental question will be this – is it causing the meat to change colour or is it imparting a colour to the meat. Is it an external colour which is imposed upon the meat or is the meat itself changing colour as it does in the case of nitrite curing?
Identifying which one it is is very simple. Let me walk you through it. For the meat to change colour, it is a reversible reaction. During curing, meat often turns brown due to oxidation, just to turn the regular pinkish/ redish colour of cured meat. It the meat is able to go from brown to pinkish/ redish, back to brown and again back to pinkish redish, you are dealing with the meat changing colour.
Secondly, look at the fat. If the fat inside the meat change colour (to pink for example), it is an external colourant applied to the meat and whether this is a plant extract or not, it must be approved as a meat colourant by the relative legislative body.
Look for an accumulation of brine. Especially in pork belly (streaky bacon) this will be noticeable where the injected brines are often trapped between the horizontal layers of fat and connective collagen. If an external colour is used, the brine pockets will display a brighter colour than in the meat surrounding it. It is one of the many reasons why it is not advisable to use a colourant in ham or bacon injection.
No plant extract without nitrogen will cause the meat itself to change colour. This is one of the laws of nature. There are colours imparted to long term cured meats which forms a purplish colour, but as far as my knowledge goes, the exact mechanism is not well understood and despite a considerable effort, scientists have not been able to replicate this effect in short cured hams and bacon.
The molecule responsible for the cured colour of meat is Nitric Oxide. Without Nitric Oxide being produced somehow by the magical concoction of spice extracts, the meat itself will not change colour and a colourant will be used. The fact that this may be a natural colourant is then a matter for consumers to decide whether they are satisfied with this, but that the meat is not “cured” in the traditional sense of the word is a fact. At best you can call it fresh and coloured meat.
– Questions about flavour
If the plant extracts impart flavour to the meat and it is not natural, does this mean that meat prepared in this way is “flavoured meat?”
For starters it would have been very easy if one used nitrates. I see no mention of it in their literature. If I had to guess how the cure is made, I would say they possibly could be using reduced amount of nitrates but my guess would be that if this is used, residue nitrites are disposed of during the curing process. How to convert the nitrate quickly to nitrite would have been the challenge. I would have used techniques developed through the celery and beetroot juice developments where nitrates in plant extracts were converted to nitrite. In salami manufacturing, the use of starter cultures have become so commonplace that it will be easy to impregnate the brine with bacterial cultures who can achieve the conversion quickly. I would have elevated the levels of ascorbic acid, to ensure that nitrites are rapidly converted to nitric oxide which achieves the cure. I would add plant extracts to bolster the reduction to NO, to add flavour, to assist in the colour and to confuse the issue. Paprika, red chili’s, red pepper, etc are good colour enhancers especially for a darker, reddish colour. In terms of micro I would rely on nitrite, nitrate and the anti microbial action of the plant extracts which I would add. I would set out a tight schedule in terms of how long the product must be cured before the important test is done for nitrites.
From correspondence with the company, I learned that they say that the meat itself does not change colour which means that they are not using nitrate, but in the absence of full disclosure, how do we know? Who says that the statement is not purposefully vague? However, lets take them at their word. Lets assume that nitrates are not used. Like them, I would reply on plant extracts.
Supporting Correspondence
Remember that I have no knowledge if this is actually how the curing brine is being made. I discovered one bit of information that I can use to get some idea if I am on the right track or not.
I looked at mail communication that was made public related to the product under the access to information law. In this communication, regulators are asking questions which I echo.
The company has to make known the materials used (more detail than edible spice and fruit extracts) and if they claim that the meat colour is changed itself, show how by which mechanism this is achieved. Failing which, it is an external colourant and must comply with colouring legislation. Failing such disclosure is against the letter and spirit of our food laws. (Refer to my article Concerning Chemical Synthesis and Food Additives)
The question is asked as to “what kind of processes are being used e.g. physical, chemical or microbiological for the extracts? How many steps are there in the extraction process?”
Another good question that came up was for a “simple flowchart”. The company claimed, I assume, that “simple ethanol water extraction, using traditional methods of extraction and no selective physical or chemical extraction of constituents” are used. The legislature ask for “further detail, for example, is the extract a standardized product? How do you prevent variation?” These questions would be asked from us who use the product in processing and the company has to comply.
The all important question is then asked related to the “active component or components that are being used as a substitute for nitrite/nitrate preservatives to prevent the growth of harmful microorganisms and/or increase shelf-life? If this is considered commercially sensitive information can you describe how it kills or prevents the growth of microorganisms? These are the same questions I have raised above. Meat science is not an isolated discipline being pursued in dark corners any longer. It is done at almost every university and high profile meat institutes and if another product was available for curing meat apart from nitric oxide, television programs would have been made about the discovery and every scientist on earth would have known about it.
Related to the colour of the meat, it seems as if the company stated that the meat does not actually change colour. The legislator asks, “Does any component impart a colour change in the pork meat?” The statement is then made that the company has said that “no component used imparts a colour change in the pork meat.” This being the case, the follow up question is then “Does any component prevent colour change?”
In terms of flavour, using the plant extracts will certainly qualify the products as flavoured bacon? How does the plant extracts not impart their flavour to the meat and how is the flavouring natural?
A Better Way
I am of the opinion that the use of pant extracts is warranted. I am working on a completely new direction that may or may not include plant extracts. Even if I opt for plant extracts, I have an ongoing problem with current extraction processes and prefer the products to be used in the form in which it is found in nature. The discussion from the legislator with the Spanish company bears this preference up. Resent equipment developments make a better raw material possible. Another key lesson to learn from the Spanish example is the importance of taking the consumer and industry along in the process. A man walking too far ahead of the people he is trying to lead is a man out for a walk and not a leader. He will achieve nothing! Bacon and ham and health – they all belong to all of us!
Mechanisms of Meat Curing – From Hoagland in 1914 to Pegg and Shahidi in 2000.
By: Eben van Tonder
14 August 2016
Ralph Hoagland
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)
“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.
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 postWWI 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.
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 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.
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 salpeter. (5) He therefore is the person in large part responsible creating the motivation for the meat industry in Germany to change from saltpeter to sodium nitrite as curing medium of choice for the German meat industry during Wold War One.
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 ofthe 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 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)
“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 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.
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 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 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 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.
(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
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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
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The Food Packer. Vance Publishing Corporation. 1954
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The Indiana Gazette. 28 March 1924.
The Nebraska State Journal Lincoln, Nebraska. Wednesday, June 29, 1910. All for bleached flour. No harm can come from its consumption says experts. Page 3.
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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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Whittaker, CW, et al. July 1932. A Review of the Patents and Literature on the Manufacture of Potassium Nitrate with notes on its occurrence and uses. United Stated Department of Agriculture. Miscellaneous Publications Number 192.
, bright red, 
– ferrous state)
ferric state)
) 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)
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)
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 
