Nitrite Cured Meat: It’s Fantastic but is it also Bad?
By Eben van Tonder
15 February 2021
Introduction
I started my career in meat curing in 2008 when I founded the South African bacon brand Woody’s and the company Woody’s Consumer Brands with Oscar and Anton. I never imagined that the most exciting journey on earth would follow which I chronicled in Bacon & the Art of Living. I wanted to know as much as possible about the world of curing and the chemical, biological and bacterial reactions that fascinated me. One of the first books I consumed was Ronald Pegg and Fereidoon Shahidi’s work, Nitrite Curing of Meat: The N-Nitrosamine Problem and Nitrite Alternatives.
I delved into the matter with great interest. I discovered that nitrates are present in many vegetables, but they first need to change to nitrites through bacterial action before they change chemically into nitric oxide which then cures the meat. Nitrates are not very toxic, but once they change into nitrite and is fried, their reaction in the stomach is of particular concern.
As I learned more I discovered the importance of cured products in a world before refrigeration. They are extremely effective to protect us against pathogens, including the mother of all pathogens, Clostridium Botulinum. Its protective action extends into the age of refrigeration! Far from a villain chemical, it turns out that nitrite is an amazing compound that naturally occurs all around us and is, amongst others, formed in our mouths when we consume a wide variety of food including fruits and vegetables.
The question is now obvious. We know that adding nitrites to meat is doing a world of good in giving us safe food that lasts long without refrigeration and just happens to also taste delicious but are we causing more harm than good? Should we stop using it if we ingest far more nitrites from some vegetables than from cured meat? How do we evaluate a matter when scientists continually conclude any discussion on the matter with the words “more research on the topic is required?”
When did we realise that nitrite is not only beneficial but under certain conditions may be problematic? What exactly is the concern with its use? How did we end up using this? What physiological role does it play in humans? What benefits do we derive from ingesting it?
I will provide a brief overview. More than this, I use this as a landing page for material on the subject. Some of my consultancy work relates to exactly this topic and proprietary information is therefore restricted with password protection. Why “password” protected? Because the obvious next question is this: “Is there anything we can do to change it?” To manage the negative elements so that it is removed, and the product is wholly healthy! The answer is a resounding YES! But that is proprietary information! 🙂
A. How did we Realise there is a Problem?
What is the actual issue then and how did humans realise that there is a problem?
The Realization of Danger of Nitrites in Cured Meat and The Responses Since 1926
Nitrate was used as a curing agent for many thousands of years. The basic value initially related to the preventing of spoilage and in a world before refrigeration bacon soon became the staple meat source for the masses in a large part of the world. Curing with saltpetre, the common name for nitrate salts, takes about a month and apart from retarding spoilage, it imparts into meat a characteristic pinkish/ reddish colour and a very agreeable cured meat taste. In the 1800s a new method of curing was invented which reduced the time to cure meat considerably. It was called tank curing on account of the tanks that were used to cure the meat in or mild curing due to a reduced need for salt. It was invented in Ireland. When our understanding of chemistry and bacteriology matured, we realised the reason why tank curing sped meat curing up. For curing to take place nitrate (saltpetre) must first be converted to nitrite through bacterial action before it can be changed into nitric oxide which, we discovered, is the real curing molecule. So, nitrate (saltpetre) to nitrite curtesy of microorganisms (bacteria) and nitrite to nitric oxide through is a chemical reaction.
What was achieved through tank curing was that the step of bacteria changing nitrate into nitrite is cut out. Still, we do not add the nitrite directly. It is “added” through fermentation. The old brine is re-used and in doing so, the liquid is replete with nitrite that was already converted from nitrate. This, naturally, speeds the process up by cutting a step out. Before the late 1800’s curers did not have a clue what caused curing apart from saltpetre. They arrived at the process of tank curing through experimentation and observation without any inkling to microorganisms changing nitrate to nitrite.
The curing reaction was being unravelled by scientists late in the 1800s and early in the 1900s. As we learned that going from nitrite to nitric oxide is much quicker than going from nitrate first to nitrite and then to nitric oxide. We also realized that nitrite forms a salt with sodium to create sodium nitrite. Late in the 1800s and early in the 1900s sodium nitrite was being used in the dye industry and chemists stocked it because it became an important medication to treat some blood disorders. Butchers used it as the source of nitrite. It is easier and “cleaner” than the indirect creation of nitrite through fermentation (tank curing or mild curing). Sodium nitrite can be dissolved directly in a brine and will immediately start penetrating the meat and change to nitric oxide.
Tank curing soon lost its place as the quickest way to cure meat in favour of the direct addition of nitrites to curing brines. There was an issue with nitrites though in that most people at this time knew that nitrite was a potent toxin. Understandably, from very early, humans who did not “see” the conversion of nitrate to nitrites and did not understand that nitrites were in any event present in cured meat grappled with the concept of a toxic substance being introduced in food preparations.
During the First World War, curing brines came onto the market which included nitrites. The days of tank curing were numbered, and a controversy was born about how healthy this is. Several investigations were made into the matter. No sooner was the matter of the toxicity of nitrites settled through scientific investigation when another, far more dangerous issue came onto the scene in the 1970s of n-nitrosamines. Let’s run through the chronology of some of the key studies and some of the important ways that governments around the world responded to it.
We picked the investigations into this matter up in 1926 which looked at the matter of nitrite as a toxin. If it was simply a matter of concentration, it would be easily settled because we regularly use substances if food which, in too high dosages can harm or even kill us. Alcohol is a very good example. The way to mitigate the risk is to determine the “safe” levels and to ensure that producers use the appropriate dosages.
1926
A 1926 study by Kerr and co-workers was based on the general knowledge of nitrite’s toxicity and the publics very negative perceptions about it. In the report, they state that public health was the primary motivation behind the study. (Kerr, et al, 1926: 543) I quote from their report. “The first experiment involving the direct use of nitrite was formally authorized January 19, 1923, as a result of an application by one of the large establishments operating under Federal meat inspection. Before that time other requests for permission to experiment with nitrite had been received but had not been granted. The authorization for the first experiment specified that the whole process was to be conducted under the supervision of bureau inspectors and that after the curing had been completed the meat was to be held subject to laboratory examination and final judgment and would be destroyed if found to contain an excessive quantity of nitrites or if in any way it was unwholesome or unfit for food. This principle was rigidly adhered to throughout the experimental period, no meat being passed for food until its freedom from excessive nitrites had been assured, either by laboratory examination or through definite knowledge from previous examinations, that the amount of nitrite used in the process would not lead to the presence of an excessive quantity of nitrites in the meat. By “excessive” is meant a quantity of nitrite materially in excess of that which may be expected to be present in similar meats cured by the usual process.” (Kerr, et al, 1926: 543)
“The maximum nitrite content of any part of any nitrite-cured ham [was found to be] 200 parts per million. The hams cured with nitrate in the parallel experiment showed a maximum nitrite content of 45 parts per million.” (Kerr, et al, 1926: 543) The conclusion was that “hams and bacon could be successfully cured with sodium nitrite, and that nitrite curing need not involve the presence of as large quantities of nitrite in the product as sometimes are found in nitrate- cured meats.” (Kerr, et al, 1926: 545)
Related to the health concerns, the report concluded the following:
- “The presence of nitrites in cured meats, was already sanctioned by the authoritative interpretation of the meat inspection and pure food and drugs acts sanctioning the use of saltpeter; as shown previously, meats cured with saltpeter and sodium nitrate regularly contain nitrites. (Wiley, H, et al, 1907) (Kerr, et al, 1926 : 550)
- The residual nitrites found in the nitrite-cured meats were less than are commonly present in nitrate-cured meats. The maximum quantity of nitrite found in nitrite-cured meats, in particular, was much smaller than the maximum resulting from the use of nitrate. (Kerr, et al, 1926 : 550)
- The nitrite-cured meats were also free from the residual nitrate which is commonly present in nitrate-cured meats. (Kerr, et al, 1926 : 550)
- On the contrary, the more accurate control of the amount of “nitrite and the elimination of the residual or unconverted nitrate are definite advantages attained by the substitution. (Kerr, et al, 1926 : 550)
Following further studies, the Bureau set the legal limit for nitrites in finished products at 200 parts per million. (Bryan, N. S. et al, 2017: 86 – 90) Conventional wisdom that surfaced in the 1920s suggested that nitrate and nitrate should continue to be used in combination in curing brines (Davidson, M. P. et al; 2005: 171) as was the case with the Irish curing method or the tank curing concept of the previous century. Nitrite gives the immediate quick cure and nitrate acts as a reservoir for future nitrite and therefore prolongs the supply of nitrite and ensures a longer curing action. This concept remained with the curing industry until the matter of N-nitrosamines came up in the 1960s and ’70s, but remarkably enough, it persists in places like South Africa where to this day, using the two in combination is allowed for bacon. More about this later.
1931
The USDA progressed the ruling on nitrate and nitrites further in 1931 by stating that where both nitrites and nitrates are used, the limit for nitrite is 156 ppm nitrite and 1716 nitrate per 100lb of pumped, cured meat. (Bryan, N. S. et al, 2017: 86 – 90)
1960’s – N-Nitrosamine
Up to the 1960’s the limit on the ingoing level of nitrites was based on its toxicity. In the late 1950s an incident occurred in Norway involving fish meal that would become a health scare rivalled by few in the past. 1960’s researchers noticed that domestic animals fed on a fodder containing fish meal prepared from nitrite preserved herring were dying from liver failure. Researchers identified a group of compounds called nitrosamines which formed by a chemical reaction between the naturally occurring amines in the fish and sodium nitrite. Nitrosamines are potent cancer-causing agents and their potential presence in human foods became an immediate worry. An examination of a wide variety of foods treated with nitrites revealed that nitrosamines could indeed form under certain conditions. Fried bacon, especially when “done to a crisp,” consistently showed the presence of these compounds. (Schwarcz, J) In bacon, the issue is not nitrates, but the nitrites which form N-nitrosamines.
This fundamentally sharpened the focus of the work of Kerr and co-workers of the 1920s in response to the general toxicity of nitrites to the specific issue of N-nitrosamine formation. Reviews from 1986 and 1991 reported that “90% of the more than 300 N-nitroso compounds that have been tested in animal species including higher primates causes cancer, but no known case of human cancer has ever been shown to result from exposure to N-nitroso compounds.” However, despite this, there is an overwhelming body of indirect evidence that shows that a link exists and “the presence of N-nitroso compounds in food is regarded as an etiological risk factor. It has been suggested that 35% of all cancers in humans are dietary related and this fact should not surprise us. (Pegg and Shahidi, 2000)
Studies have been done showing that children who eat more than 12 nitrite-cured hot dogs per month have an increased risk of developing childhood leukaemia. The scientists responsible for the findings themselves cautioned that their findings are preliminary and that much more studies must be done. It may nevertheless be a good approach for parents to reduce their own intake of such products along with that of their children in cases where intake is high. (Pegg and Shahidi, 2000)
These studies must be balanced by the fact that an overwhelming amount of data has been emerging since the 1980s that indicate that N-nitroso compounds are formed in the human body. What is important is that we keep on doing further research on N-nitrosamines and the possible link to cancer in humans. Not enough evidence exists to draw final conclusions.
1970 – The response to the N-Nitrosamine scare.
Back in the 1970s, so grave was the concern of the US Government about the issue that in the early 1970’s they seriously considered a total ban on the use of nitrites in foods. (Pegg and Sahidi, 2000) The response to the N-nitrosamine issue was to go back to the approach that was implemented following the work of Kerr and co-workers in 1926.
The first response was to eliminate nitrate from almost all curing applications. The reason for this is to ensure greater control over the curing. Meat processors continued to use nitrate in their curing brines from 1920 until the 1970s. One survey from 1930 reported that 54% of curers in the US still used nitrate in their curing operations. 17% used sodium nitrite and 30% used a combination of nitrate and nitrite. By 1970, 50% of meat processors still used nitrate in canned, shelf stable. In 1974 all processors surveyed discontinued the use of nitrates in these products including in bacon, hams, canned sterile meats, and frankfurters. One of the reasons given for this change is the concern that nitrate is a precursor for N-nitrosamine formation during processing and after consumption. (Bryan, N. S. et al, 2017: 86 – 90)
The reason for the omission in bacon, in particular, is exactly the fact that the nitrates will, over time continue to be converted to nitrites which will result in continued higher levels of residual nitrites in the bacon compared to if only nitrite is used. The N-nitrosamine formation from nitrites is a reaction that can happen in the bacon during frying or in the stomach after it has been ingested. It will not happen from the more stable nitrates.
It has been discovered that nitrate continues to be present in cured meats. Just as the view that if nitrate was added, no nitrite is present in the brine as was the thinking in the time before the early and mid-1800s, in exactly the same way it is wrong to think that by adding nitrite only to meat, that no nitrate is present. “Moller (1971) found that approximately 20% of the nitrite added to a beef product was converted to nitrate within 2 hours of processing. Nitrate formation was noted during incubation before thermal processing, whereas after cooking only slight nitrate formation was detected. Upon storage, the conversion of nitrite to nitrate continued. Herring (1973) found a conspicuous level of nitrate in bacon formulated only from nitrite. As greater concentrations of nitrite were added to the belly, a higher content of nitrate was detected in the finished product. They reported that 30% of the nitrite added to bacon was converted to nitrate in less than one week and the level of nitrate continued to increase to approximately 40% of the added nitrite until about 10 weeks of storage. Moller (1974) suggested that when nitrite is added to meat, simultaneous oxidation of nitrite to nitrate and the ferrous ion of 
to the ferric ion of metMb occurs.” Adding ascorbate or erythorbate plays a key role in this conversion. (Pegg and Shahidi, 2000) The issue is not the nitrate itself, but the uncontrolled curing that results from nitrate and the higher residual nitrites.
Secondly, the levels of ingoing nitrite were reduced, especially for bacon. The efficacy of these measures stems from the fact that the rate of N-nitrosamine formation depends on the square of the concentration of residual nitrites in meats and by reducing the ingoing nitrite, the residual nitrite is automatically reduced and therefore the amount of N-nitrosamines. (Pegg and Sahidi, 2000) Legal limits were updated in 1970 in response to the nitrosamine paranoia. A problem with this approach is however that no matter by how much the ingoing nitrite is reduced, the precursors of N-Nitrosamine still remain in the meat being nitrites, amines, and amino acids.
An N-nitrosamine blocking agent was introduced in the form of sodium ascorbate or erythorbate. “There are several scavengers of nitrite which aid in suppressing N-nitrosation; ascorbic acid, sodium ascorbate, and erythorbate have been the preferred compound to date. Ascorbic acid inhibits N-Nitrosamine formation by reducing 
to give dehydroascorbic acid and NO. Because ascorbic acid competes with amines for , N-Nitrosamine formation is reduced. Ascorbate reacts with nitrite 240 times more rapidly than ascorbic acid and is, therefore, the preferred candidate of the two. (Pegg and Sahidi, 2000)
More detailed studies identified the following factors to influence the level of N-nitrosamine formation in cured meats. Residual and ingoing nitrite levels, preprocessing procedure and conditions, smoking, method of cooking, temperature and time, lean-to-adipose tissue ratio, and the presence of catalyst and/ or inhibitors. It must be noted that in general, levels of N-nitrosamines formation have been minuscule small, in the billions of parts per million, and sporadic. The one recurring problem item remained fried bacon. In its raw state bacon is generally free from N-nitrosamines “but after high-heat frying, N-nitrosamines are found almost invariably.” One report found that “all fried bacon samples and cooked-out bacon fats analyzed” were positive for N-nitrosamines although at reduced levels from earlier studies. (Pegg and Sahidi, 2000)
Regulatory efforts since 1920 have shown a marked decrease in the level of N-nitrosamines in cured meats, even though it is still not possible to eliminate it completely. “Cassens (1995) reported a marked decrease (approx 80%) in residual nitrite levels in of US prepared cured meat products from those determined 20 years earlier; levels in current retail products were 7 mg/kg from bacon.” This and similar results have been attributed to lower nitrite addition levels and the increased use of ascorbate or erythorbate. (Pegg and Sahidi, 2000)
Despite the actions of governments and the curing industry, consumer demand has grown over the years to eliminate nitrites in food. Evidence has started to emerge that links the prevalence of colon cancer, for example, not just to the use of nitrites but to the use of saltpetre or the far less toxic cousin of nitrite called nitrate. Much of the evidence is either anecdotal or indirect but it is sufficient to fuel public suspicion and legitimate industry concerns.
B. Can’t we just Remove the Nitrites?
What is clear from our survey above is that it is a technical and complex field. Can we not just remove the nitrites and sell nitrite-free bacon? When we talk about nitrite-free bacon, it is important to know exactly what we are talking about. The term can imply several things.
– Is the Problem Synthetic Nitrites Only (I.e. Sodium Nitrite Added Into the Brine)?
Is it that no synthesized nitrite must be used in the curing of the meat? Tank curing or fermented nitrate containing plant juices would then be an appropriate curing procedure. Celery and other plants are filled with nitrates which are part of plant nutrition, absorbed from the soil through the roots. Certain spice companies started using these plant extracts and then through a process of fermentation, allowed microorganisms to reduce the nitrite to nitrate like what was done in tank curing using old brine and they sold the plant extracts to be added to the meat as an ingredient. They called it a “natural curing agent” but in my opinion, they were actually deceiving the public. After the bacterial fermentation, the plant juices were now filled with nitrates. They cleverly circumvented the requirement to declare the use of nitrites in the curing process and in reality, nitrites were still present, now in usually much larger quantities as was the case using sodium nitrite.
– Is the Problem All Nitrites in the Brine and Meat, Including Either Sodium Nitrite or Nitrite that Formed Through Bacterial Action, Either through Reduction or Oxidation or Chemically and Irrespective of the Source?
Nitrite-free bacon can mean that no nitrites should be used in the curing process added directly or generated indirectly. Indirectly it can be generated through fermentation but there are other sources of nitrite which forms as a result of the decomposition of meat. In long-term curing, for example, the same colour, even a better taste and longer shelf life is achieved by the use of salt only. I mention this because it introduces a very important issue. For curing to take place, you don’t actually need nitrate or nitrite. You need nitrogen. The nitrogen must then react with oxygen to create nitric oxide (NO) which is a gas! Nitrate and nitrite are only the nitrogen source! Once Nitric Oxide is created, it must react with the meat proteins, myoglobin.
As the proteins of a dead animal or other constituents of meat are being broken down, nitrogen is made available and in long term curing, certain processes are involved and one of them is the combination of the nitrogen molecule, made available through decomposition, with an oxygen molecule and curing takes place if the overall destruction of the meat is managed through the removal of water which retards (even stops) the action of microorganisms and favours the effect of enzymes.
So, this can be done completely without any outside source of nitrogen but the process is very slow and there is no way that the world demand for cured meat will be satisfied through this. It will also be extremely expensive due to the weight loss involved in removing the moisture. No matter how you look at it, nitrogen must be accessed somehow, or it is not curing.
It is extremely important to know that curing is something that happens to the meat itself and it mimics a natural, biological process of nitric oxide being formed in our bodies. The meat protein in either its oxygenated state or with a nitric oxide molecule presents red. This is an extremely important concept to understand. Curing is a characteristic of meat itself and is a natural process. It is NOT the imposition upon the meat of a colouring agent. The fact that nitrogen is used in curing is completely consistent with natural biological processes. Even the reduction and interaction of nitrate and nitrite, including the chemical reduction to nitric oxide, is a biological process, essential to life!
I give one example from a review article by Shiva (2013). I anticipate that very soon consumers may demand food with high nitrate (NO3-) in a swing in perceptions of these molecules which will in all likelihood be driven by people who regularly work out. Shiva summarizes this work as follows. “Nitrite dependent inhibition of ccox also potentially regulates responses to physiological hypoxia (the absence of enough oxygen in the muscles), such as that present in the muscle during exercise. Larsen and colleagues recently demonstrated that ingestion of NO3- (nitrate) decreased whole-body oxygen consumption during exercise without changing maximal attainable work rate in human subjects.” Directly as a result of this work, several booster supplements are currently on the market and sold in gyms and health shops around the world containing nitrates.
Shiva continues, “This increase in exercise efficiency, which was associated with augmented plasma NO2- levels, has now been corroborated by a number of studies in various exercise models. While the underlying mechanism of this beneficial effect is not completely elucidated, a decrease in the rate of oxygen consumption due to proton leak and state 4 respiration in the skeletal muscle of subjects receiving NO3- was reported.” (Shiva, 2013)
Right there, the entire matter is resolved and in a few short years, the public will demand more nitrates in meat (and by implication, nitrite also)! 🙂 🙂
Furthermore, not only is the reaction of nitrite to nitric oxide not foreign in our physiology, the reaction of nitric oxide with myoglobin is an extremely important physiological reaction that is mimicked in curing. Jens Moller and Leif Skibsted write that “Nitrosylmyoglobin (MbFeIINO), the NO complex of iron (II) myoglobin, as formed in meat products, has now also been observed in vivo in rats. MbFeIINO thus seems important in controlling radical processes associated with oxidation”. (Møller and Skibsted, 2002)
The issue is that our best available source of nitrogen is through nitrite and nitrite itself but is both beneficial and problematic at the same time.
The fact that the reaction of oxygen (O2) and Nitric Oxide are both matters that all butchers work with daily is important. None of these reactions is “unnatural!” This is seen in the colour of fresh meat and cured meat. I dedicated a chapter to it in Bacon & the Art of Living, called Fresh Meat Colour vs Cooked Cured Colour.
I plan to do much more work about the physiological reason why nitric oxide fits onto the colouring site of a protein apart from the short quotes above, but I will deal with this separately and update this section with a link reference.
– If the Meat itself Does Not Change Colour (Curing), is the use of External Colourant Permitted/ Desirable?
There is another way of achieving a red colour in meat which we alluded to and that is through an artificial process that involves the use of an external colourant. Legally there are colourants that are allowed in meat, but how will consumer groups respond to this? This is not something natural and inherently part of meat itself. It is an external colourant that is brought to bear upon the meat matrix. This is even more objectionable to some than nitrite and the extreme objection against it goes back to the start of the meat trade where butchers used to disguise old and sometimes putrid meat as fresh by colouring it with an external colourant.
– Is the Real Issue Actually Residual Nitrite That We Must Eliminate? (I.e., Not Ingoing Nitrite but Nitrite Left in Meat After Curing)
Another possible meaning of nitrite-free bacon refers not to the fact that nitrite was somewhere involved in the supply of the nitrogen source to form nitric oxide, but the real meaning may refer to the question of whether any nitrite is left in the product when the consumer fries it in the pan. It is after all not the initial source of the nitrogen atom, which is the real issue, but how much nitrite is left after the meat has been cured. This is what is referred to as residue nitrite. The other question which goes hand in hand with this is to what degree can the consumer be guaranteed that no appreciable amount of nitrite is left in the product he buys?
– Is The Objective to Eliminate All Manipulation of Colour (Natural or Artificial) and Resign Ourselves to Selling Brown Bacon and Hams (uncured, salted only)?
A final solution for some is to simply omit accessing nitrogen in any shape or form altogether and not be concerned about the brownish colour that develops. I have over a few years followed the work of a New Zealand company, interestingly enough also called Woody’s who follow this approach and I am amazed at the success they have had with their brand positioning. Good old strict hygiene is used to sort shelf-life issues out and they educate their customers that the browner bacon is actually healthier bacon. The brown bacon they sell becomes a source of comfort for their clients. If this is advisable as a universal approach to bacon or ham is debatable in a world where not everybody shares the strict attention to detail of this company, but I applaud them for their honesty and the practical way in which they have dealt with this thorny issue (see Woody’s Free Range Farm) In the end, I feel much of the problems are self-inflicted in a world where bacon flitches are no longer wrapped in cloth, palletized and shipped any longer.
How to Explain it?
As you can see from this short overview, the matter is not simple but the fact that there is an issue to address is clear. For myself, I am satisfied that in the minuscule levels that nitrite is used and remains present in bacon and hams, these products are completely safe to eat. The consumer is, however, also not wrong to be concerned about the matter. The problem is that the explanation above is already so technical – who can follow this? Let alone a dissertation by Dr Sebranek or Dr Møller, two of the world authorities on the subject. If anybody must understand what they are saying before one can decide which bacon is healthy and not and which brine to use or not, only a handful of people will ever make a meaningful determination on the matter. This business of reduction and oxidation, bacterial, enzymatic reactions are all very confusing for people without an advanced degree in chemistry, like me. The only way that I could make any sense of it was to follow the story right from the beginning. As it unfolded. And what a story it turned out to be!
C. Review: How did we get here?
I will tell the story, at least the parts that are pertinent to the discussion about nitrite, from a series of articles I did on the subject over a few years and from extracts of a book I wrote about the history of bacon called Bacon & the Art of Living. One article where I deal with the full sweep of its history is Bacon Curing – a Historical Review.
Before we jump into the detail, let’s establish a timeline. Broadly speaking the development of bacon curing to where we are with the direct addition of nitrite to curing brine can be divided into the following timeline.
The Prehistory of Bacon Curing experimenting with various salts (sodium chloride, sal ammoniac, nitrate also called saltpetre) From antiquity to the end of the 1500s.
Saltpetre gained popularity as it becomes widely available as a vitalizer, an ingredient in gunpowder and as medication. 1600 to 1800.
William Oake invented Tank Curing/ Mild Curing around 1832 (aged 25) – an Indirect Addition of Nitrite to Curing Brines.
Dr. Ed Polenski’s Article on Nitrite in saltpetre brines, 1891.
The academic work of German and English researchers identifying Nitrate and Nitric Oxide as the curing agents. Notwang (1892), Lehmann (1899), Kiskalt (1899), Haldane (1901).
The work of Ladislav Nachmullner and the first curing brine containing sodium nitrite (1915).
The Impact of the First and Second World War in changing the indirect use of Nitrites to the direct addition of nitrites to curing brines.
The Griffith Laboratories as evangelists of the direct addition of nitrites to curing brines. Prague Salt (1925).
“Houston, we have a problem!” The n-nitrosamine problem and the response of the curing industry and world governments, late 1950s.
Must we Remove Nitrite from Food or Manage it?
D. Why do we use it at all?
Its anti-microbial ability now becomes important, especially as it relates to C Botulinum. Nitrite as a key hurdle in botulinum prevention remains relevant. I looked at the most important microorganism in a 2015 article, Clostridium Botulinum – the priority organism
The Anti-Microbial Efficacy of Nitrite
In 2015 I had the privilege to interact with Dr R. Bruce Tompkin on the issue of the antimicrobial efficacy of nitrate and nitrite. Dr Tompkin was one of the founders of the HACCP system. We had some correspondence about the possibility of replacing nitrite as a hurdle and his insights are still helpful to this day. For this, I will be eternally grateful. It was written before I discovered that tank curing came from Ireland and there are other sections where my understanding evolved. I nevertheless share it with you as I wrote five years ago. I am thankful for experts from around the world who continue taking the time to give input not just on the matter of nitrite replaces, but on a wide array of meat and processing-related subjects. I can honestly say that if you do not know in our trade you do not want to know! (or you have been so busy that there was no time to find out!) 
Which I fully understand!! 
I looked at this issue in 2015 in an article, Concerning Nitrate and Nitrite’s antimicrobial efficacy – chronology of scientific inquiry.
E. Further Work on Nitrite Free Bacon and its role in Human Physiology
- Literature: Removal of Nitrite from Meat Curing Systems
- Nitrite Free Bacon: Barriers against clostridium botulinum
- The Quest for Nitrite Free Curing
- Finally – nitrate, nitrite, nitric oxide as valuable molecules and the triumph of nature over foolish strawman positions
Conclusion
I have no doubt that this matter can be resolved scientifically. In terms of marketing, this can be done in a way that the consumer will be fully in-step, all the way and is taken along, not left behind or feel that half-baked ideas are thrust down his/her throat. This work is important, not just for the uncompromising drive to better and healthier food, but for the overall quest to be better in every way! To offer safe and delicious food should be the desire of every food producer on earth. Anything less both in terms of taste, quality, and safety is a crime! In this work, I can end with a quote from no finer man than Nelson Mandela who said that “what counts in life is not the mere fact that we lived. It is what difference we have made to the lives of others that will determine the significance of the life we lead!”
References
Jens K. S. Møller and Leif H. Skibsted. 2002. Nitric Oxide and Myoglobins. Chemical Reviews 2002102 (4), 1167-1178DOI: 10.1021/cr000078y
is formed and a very small amount of nitrite (less than 1% of the total nitrite) forms the neutral nitrous acid (
). It is nitrous acid that is responsible for the formation of nitrosating compounds which is the ultimate reaction of joining nitric oxide to an organic compound, in this case, the myoglobin protein (resulting in a nitroso derivative). (Sebranek, J. and Fox, J. B. Jn.. 1985)
). From nitrous acid, the neutral radical, nitric oxide is formed directly as well as a variety of nitrosating species or molecules that create such a nitrite-oxygen pair of atoms to link to an organic structure like a protein. [3] [4] (Sebranek, J. and Fox, J. B. Jn.. 1985)
