Introduction to Bacon & the Art of Living
The story of bacon is set in the late 1800s and early 1900s when most of the important developments in bacon took place. The plotline takes place in the 2000s with each character referring to a real person and actual events. The theme is a kind of “steampunk” where modern mannerisms, speech, clothes and practices are superimposed on a historical setting. Modern people interact with old historical figures with all the historical and cultural bias that goes with this.
The Polenski Letter
My dear Son,
This weekend we had plans to visit the geology museum at the University of Copenhagen. It is summer in Denmark and the demand for our bacon is very good. We all agreed that we would go next weekend and put in extra work on Saturday to get through our work. Next weekend Uncle Jeppe will not be able to join us but we will all still go, capitalising on good weather we are having. I am not disappointed at all. The most unexpected set of facts became known to us.
There is much that we can learn from the Danish nation. Their food, the strange shops, elevated above the streets, the beer and the warm people. I realised that the culture of this amazing land is having just as big an impact on me as what I am learning about the curing of bacon. These people set their mind to a task and then work to achieve the goals. They not only learned from the Irish system of curing but took it to new heights by combining it with their powerful and unique cooperative model! I am learning the mechanics of a bacon curing business and spend a lot of time on the topic of saltpetre. Andreas gave me a word of caution that knowing the steps of a process and understanding the process are two different things. My understanding of the steps in bacon production will flow from my understanding of saltpetre.
No sooner did I hear those words from Andreas when the ever-resourceful Jeppe presented me with the next gold nugget in my education. How it happened that I came to Europe at this time, is remarkable. It is exactly in this epoch when humans are discovering that, despite the fact that saltpetre has been used for thousands of years to cure and preserve meat, there is an even more fundamental principle behind it that stems from the composition and nature of saltpetre. This fundamental principle is a relative of saltpetre or sodium nitrate, called sodium nitrite. The “a” changes to an “i“.
FOODS by Edward Smith
After supper, at the Østergaard home, we follow another great Danish tradition. We read together and discuss what was read. This is customary in many households. The Danes have a practicalness about them. As I have seen from their unique high school model, they never stop learning and if something works, they adopt it.
Andreas’ dad chose as a book to read every night after supper, called Foods, written over 20 years ago in the 1870s by an Englishman, Edward Smith. He helped me to see the curing of meat as both a necessity and a delicacy. We cure meats because, for the most part, using modern curing methods, cured meat tastes great. On the other hand, meat curing was started to impart longevity; to prevent spoilage.
Back home we are familiar with the value of meat that “last.” In Europe and England with their growing populations and vast navies that have to be fed, it has been an obsession and a priority to solve the problem of conserving meat for future use. Edward Smith says in his book that “the art of preserving meat for future use, with a view to increase the supply and lessen the cost of this necessary food (meat), is of very great importance to [England] and all the available resources of science are now engaged in it.” (Smith, 1876: 22) This meant that the best scientists of the time devoted at least part of their work to unravel the secret of meat curing in order to develop mechanisms to manipulate the process. The discovery that it is not actually saltpetre (nitrate) that cures meat but nitrite grows out of this focus.
Smith lists the main ways that meat preservation is done, as “by drying, by cold, by immersion in antiseptic gasses and liquids, by coating with fat or gelatin, by heat, salted meat and by pressure.” (Smith, 1876: 22 – 38) All have their benefits and disadvantages and I have a feeling that over the years, the technology within any one of these groups may develop, but these broad categories will remain and continue to be available to the public.
Edward Smith says that pork is particularly prized over beef and mutton because of the “taste, but chiefly perhaps [due] to the universal habit among the peasantry of feeding pigs, which has descended from Saxon times. Moreover, there is a convenience in the use of it, which does not exist with regard to beef and mutton, for in such localities the pork is always pickled and kept ready for use without the trouble of going to the butcher, or when money could not be spared for the purchase of meat.” Pigs proved to be an equally prized meat in the new world due to the “ease with which pigs are bred and reared, and the meat preserved, whilst there is great difficulty in obtaining a sufficient number of persons, in a thinly populated country or a small village, to eat a sheep or ox whilst meat is fresh. (Smith, 1876: 59)
“Bacon is made when cuts from the pig are preserved by salt and saltpetre.” (Smith, 1876: 64). This gives bacon its characteristic pinkish/ reddish colour, a nice flavour, and it lasts a long time before it tastes “off”. This is the kind of thing we learn at night. After a good supper, we discuss what has been read for an hour or two before retiring to bed.
At Uncle Jeppe’s bacon curing factory I started working in the curing department where we mix herbs, spices and salts. Uncle Jeppe is a knowledgeable man and it seems as if he has been around in the meat industry forever. I have not asked him any question that he did not know the answer.
Saltpetre is the curing salt for bacon and hams which I work with every day in the curing department. When we do dry curing, we use 1.25 st. (10 pounds) salt, 0.375 st. (3 pounds) of brown sugar, 0.04 st. (6 ounces) of black pepper and 0.02 st. (3 ounces) of saltpetre. We use 1.25 st. (10 pounds) of this mixture per 12.5 st. (100 pounds) of meat. (1, 2, 3) The Irish system of mild cured bacon calls for a liberal use of saltpetre and the purer form called sal prunella. It is military-grade refined saltpetre. This is the main curing system we use and in both dry curing and tank curing (as mild cure is also called), it is a key ingredient.
What confused me much about saltpetre was that Trudie’s dad, Anton, also talks about the value of phosphates and saltpetre in fertilizing their fields in the Transvaal. We know that it is the explosive power in gunpowder. I know that the Dutch East Indian Company, as well as the English East Indian Company, were created, in large part, for the purpose of transporting saltpetre from India to Amsterdam, London and other European cities like Copenhagen for fertilizer and to make gunpowder. How can this one substance be useful for such diverse applications?
The power of saltpetre is the fact that it contains nitrogen and nitrogen is one of only two elements, with carbon, that can exist in 8 oxidation states. This means that nitrogen can react in a diverse and complex way and, like carbon, is foundational to all of life. The two substances that contain nitrogen, most familiar to us, are saltpetre and ammonia.
The nitrogen in saltpetre makes it very reactive, giving it an explosive power. In saltpetre it has a particular effect on blood, explaining the fact that it gives cured meat its pinkish/ reddish colour. Nitrogen exists in the first place as a gas in our atmosphere and comes into our world in different ways. Remember the lecture I have Minette and the baboons on the Witels about how saltpetre is formed? I said that there are other ways in which atmospheric nitrogen is converted into a salt that we can use. The most important process is not through the action of lightning as I explained on the Witels but through microorganisms with the ability to take it from the air and convert it directly to plat food.
Dr. Eduard Polenski – Nitrate and Nitrite
Uncle Jeppe told Minette and me that he will return to the fascinating story of how this was discovered but must be patient to hear this another day. The first very tentative step to identify the “real” curing agent came when a friend of Uncle Jeppe discovered something remarkable. His friend’s name is Dr. Eduard Polenske (4), a chemist, working at the Imperial Health Office in Germany. Jeppe tells me that 1891 will forever be remembered as a watershed year for Woody’s since it is the year I arrived in Denmark and started learning about bacon curing; for the curing industry in South Africa since it is the year when Woody’s took the first steps to excellent bacon in Africa; and for the curing industry around the world because of Dr. Polenskis’ discovery.
He tested and saw that curing brine (the curing salts) and cured meat contain nitrite. This is remarkable since we know that saltpetre or nitrate does not contain nitrite. Nitrate is . The one oxygen atom in the nitrate composition is not as tightly bound as the other two and is easily stripped away. The new compound is nitrite. On the other hand, nitrite () has the affinity to combine with an extra oxygen atom to again form nitrate (). It is a very volatile compound. Nitrite is then when one of the three oxygen atoms is removed from the molecule and we have . It does not look like something important but it changes the nature of the compound.
When meat is cured with saltpetre, nitrate () is added. If Dr. Polenski tested the brine and meat and found nitrite () present, the only way this could occur is if somehow the one oxygen atom was stripped of the saltpetre molecule to form nitrite ().
The fact that he discovered nitrite in the curing brine is of concern because nitrite is toxic. I know nitrite very well! In Cape Town, as is done around the world, the local water is tested for nitrites every day and if the levels are too high, one can not drink the water. It is so important that newspapers report the nitrite counts in the water on a weekly basis. Farmers can suffer loss if their livestock drinks from this contaminated water. For humans and animals, it can be fatal.
The Value of Speed
Before Uncle Jeppe learned about Dr. Polenskis’ findings in 1891, what we knew is that only saltpetre or nitrate is used to cure meat. We also know that the Irish system of curing compared to dry curing cures the meat much faster. This matter of the speed of curing is important. Dry curing is accomplished in 28 days where mild cured bacon can be produced in 19 days. On farms, long curing is generally not a problem, but for a commercial curing operation, it means that you keep large stocks of bacon that are in the process of curing. If you produce bacon for household consumption, that is one thing, but when you have an army to feed, speed is of the essence.
The question has been asked why mild curing cures meat faster than dry curing and various possible answers have been discussed.
The Wiesbaden Meetings
Jeppe and Ed met up in Wiesbaden, Germany, earlier this year. This has been an annual winter ritual for the two men taking their annual retreats at the same time. They became acquainted at the General Congress on Hygiene in Brussels in 1852. It is exactly the hygienists that Dr. Ed fears will be most concerned about the fact that he found nitrites in cured meat.
Both men attended the conference and struck up a friendship based on their shared passions. Wiesbaden is famous for its hot springs since ancient Roman times and the second shared love between these men, besides meat technology and science, is their love for hot springs.
They have been hosted each year by an equally interesting man, Francois Blanc, at one of his gambling resorts in Wiesbaden. It is said that he is the man who made Wiesbaden what it is today. Jeppe describes Blanc as a mighty wizard with an eye, quick to see the possibilities of a situation, with a brain to plan and a hand to execute. His ambitions and achievements are great across Germany, yet, Jeppe tells me that his tastes are simple.
His clothes do not attract any attention and he wears his spectacles on the tip of his nose. He does not pay attention to flattery, yet, he is a hard-headed, silent man without any enthusiasm and equally without any weaknesses. He keeps lavish tables, yet he himself eats sparingly. His wine cellar rivals those of the autocrats in Russia, yet, he himself only drinks mineral water. He is one of the largest gambling hall owners in Europe, yet, for entertainment, he may occasionally play Dominoes and frequently goes on a drive through the countryside with his wife.
It was at their annual retreat at Wiesbaden, earlier this year, where Dr. Ed told Jeppe about a monumental discovery. Dr. Ed is not a fan of cured meat since, in the process of making it, nutrition is lost. The entire matter of the relationship between nutrition and nitrogen is introduced by this statement. Unfortunately, the subject is of such a nature that, again Jeppe said that we will deal with this over the next two weeks. For the time being, we take Jeppe at his word of such a relationship (nitrogen and nutrition).
Without looking too much into the subject, my suspicion is that this has to do with the meat juices that are lost in dry curing. I also suspect that in the loss of meat juices, nitrogen is lost which explains the loss of nutrition, if indeed the relationship between the two is linear. The new Irish system largely overcomes the loss of meat juices by filling the tank with liquid brine and placing the meat inside it.
This means that pressure is created around the meat with brine wanting to draw into the meat instead of drawing the albumen (protein-rich protein) out of the meat. If the meat is not placed in liquid brine, as is done in dry curing where the meat is only rubbed with salt, in the mild curing technique, brine seeps into the meat as opposed to albumen (meat juices) being drawn out of it. In mild curing, no albumen is lost.
For the most part, dry curing is practised with an accompanying loss of nutrition. At a time when most families across the world can not afford to eat meat more than two days a week and where most children go to bed hungry, at least a couple of times a week any loss of nutrition is a problem in any food. In the current world context, Dr. Polenske believes the most important consideration in evaluating methods of preservation is its effect on the nutritional value of the preserved food. He is obviously not very familiar with the Irish mild cure and in his work, he mainly considered dry curing. His observations about the formation of nitrites are, however, volcanic!
The Polenski Experiment
Dr. Polenski designed an experiment to study just how much nutrition is lost. The brine he prepared was a combination of salt, sugar, and saltpeter. (5) He put this in three jars with three pieces of meat which he sealed and opened again after 3 weeks, 3 months and 6 months respectively. When he tested for nitrite, he unexpectedly found it in the brine and the meat, despite the fact that he did not add any. (6)
The Foundational work of Ulysse Gayon and Gabriel Dupetit
Dr. Polenske told Jeppe that he was not really surprised to find nitrite in the brine since he knew that saltpetre is a compound of potassium or sodium nitrate. Nine years earlier a drama unfolded with a discovery by French scientists of bacteria that changes nitrate into nitrite and further into nitric oxide. What this means is that certain bacteria, under certain conditions is able to remove one oxygen molecule from nitrate () to form nitrite (). It is further able to remove another oxygen atom from the nitrite () to form Nitric Oxide (NO). Thus, it is clear that the conditions that favours such a removal or “reduction” as it became known of nitrate to nitrite must exist in curing brines and must occur in the meat.
In 1882 a team of researchers, Ulysse Gayon from the French commune or town, as we call it, Bouëx in Charente and his 22-year-old collaborator, Gabriel Dupetit, from the town of Auch, Gers, coined the term denitrifying bacteria. This formidable research team went on to make a number of very important discoveries about denitrifying bacteria. (7)
Nitrification starts with nitrogen gas which is one of the most abundant gasses in our atmosphere and through the nitrification process, bacteria create more complex compounds such as nitrate (). An example of nitrification is ammonia () which is changed into nitrite () and finally into nitrate () which serves as the nutritional source for plants.
Denitrification is the reverse where a more complex molecule is broken down to the point where it ends up with a simple molecule like nitric oxide (NO) or pure nitrogen gas (). Denitrification is, therefore, the reverse of nitrification. This time it starts with a complex compound of nitrate () which is changed into nitrite (), into nitric oxide (NO), into nitrous oxide () and finally back into nitrogen gas or molecular nitrogen (). Note the gain or loss of the oxygen atom in both processes.
The Mentorship of Louis Pasteur
Louis Pasteur, the renowned French chemist, and microbiologist urged Gayon to follow what happens with the oxygen of the nitrite utilised in the process of denitrification. They heeded his advice paid close attention to this. They conclusively refuted an old notion that nitrate was reduced through chemical means by hydrogen, generated during fermentation. As to the purpose of the loss of oxygen they believed that the bacteria used the oxygen from nitrogen for the combustion of organic matter to generate carbon dioxide (CO2). (8)
Based on their very thorough work, Dr. Polenske believes that nitrite is present through this process of denitrification of nitrate by bacteria. He expects there to be much public concern following his discovery. (9)
Jeppe and the Main Point
Jeppe was now becoming particularly excited. “Eben, Minette!” he said and put his hands around our shoulders. “In dry curing, we start with nitrate. Sodium or potassium or calcium or magnesium nitrate, depending on where you harvest the nitrate from. Nitrogen and THREE oxygen atoms. We mix it into salt and rub it on the meat to cure in dry curing. What is happening?”
I told him that the nitrate will be turned into nitrite by bacteria. “Yes, yes, yes!” He said impatiently. “But what else? What do you see?” Still, I had no clue what he was talking about.
“Time!” Jeppe exclaimed, “It will take time! Bacteria are living organisms and it will take time to achieve the reduction of the nitrate. Think about fermentation – it takes time!”
“What is the faster process? Dry curing or mild curing”, he asked.
That one I gladly knew. “Mild curing!” “Correct!”, he exclaimed. “Correct!” “But why?”
Suddenly Minette and I saw what he was driving at! She answered, “The time it takes the bacteria to convert the nitrate to nitrite . . .” “And what?”, he spurred her on. “What does this points to?” “What is doing the curing?'”
I suddenly saw it and a bolt of energy hit me. “It is the nitrite doing the curing and not the nitrate!” “The time difference between the old system of dry curing using nitrates and the new system which re-uses old brine is that in the old brine, the nitrate has been converted to nitrite! This is the power of the old brine! This is why it is so much faster!”
His secretary walked in at that moment announcing that his next appointment is there. “Oh, let him wait”, Uncle Jeppe exclaimed! “”Get us coffee! There is some hope for South Africa after all!” He gave me an enthusiastic slap on my back!
He walked around his desk and sat down. “I did not discuss this with Polenski but I saw it immediately! If I told him the entire Germany would convert to mild curing and Denmark’s competitive edge would be lost. I sat there thinking of what Andreas told me. That I will find that my greatest discovery won’t be the mild curing process, but why it works the way it works. The “why?” And “how?” of curing. I was exhilarated!
Tristan, I know you love biology and the natural sciences. This is why I address this mail to you and I have no worry that I become too technical. The reaction sequence and mode are beautiful. I can honestly say that I am completely in love with the natural world and my fellow explorer in all this is Minette!
I now want to know every element present in the brine, and its exact function. What is the chemistry in the meat itself? How does curing happen? When we know this, we will be in a position to manipulate the process and improve it.
A Bigger Point
Jeppe had something very important to share with Minette and I that flows the discovery of denitrifying bacteria. Right at the start of this journey, I realised that what we are discovering is much more than simply learning how to cure bacon. This journey back to the lands of my forefathers is a big deal! In a way, it was already an end in itself for me. History and context if of enormous importance. Our lives are never in isolation. We come from the soil of Denmark and the fact that it is here where we find the answers is hugely important to me!
Bacon is in the centre of scientific research of Europe, America, and the United Kingdom, and the combined scientific focus of these countries are directed at unlocking its secrets which are bound up with that of agriculture and superior technology in warfare. Besides these, there are many human stories that are part of the story of bacon. Real people who each contribute small parts of a very large jigsaw puzzle that is coming together. They teach us about life. We do not live in isolation, my son! What I am recounting is not fiction! I tell you real stories of real people! Jeppe taught us that life is more than bacon. The journey of discovering its secrets are far more important than just the factory we will one day set up.
Within the same year of publishing a major paper on denitrifying bacteria by Gabriel and Ulysse, tragedy struck. The young Gabriel Dupetit ended his own life. He travelled to the Italian city of Savano and booked in at the Albergo Svizzero under the false name, Gaston Denault. Overcome by anxiety of all sorts, on the evening of 28 December 1886, he injected poison into himself. He was discovered, barely alive and despite many efforts to save his life, he passed away on the morning of the 29th. He left a note in French explaining some of his worries. The use of the false name was done to hide his identity and spare his parents’ embarrassment. Both Minette and I sat silently as Jeppe told us what had happened.
Minette had to fight away the tears. We are both humbled and saddened by this story. His work directly contributes to our quest of understanding bacon and still, his death reminds me that our lives are bigger than our goals and dreams. Despite our ambitions, we must pay attention to each sunset and sunrise and never make the mistake of thinking that achieving goals define us. Francois Blanc got it right. He found fulfilment in small things, despite his success. His success does not define him. He finds the greatest fulfilment in the ordinary in life. In this, bacon and life become inseparable and I am never sure when I stop learning about the one and start learning about the other.
Maybe, I wonder, the biggest and most important act of his life was the drives he took through the countryside with his wife. His relationship with his sons and the evenings that Uncle Jeppe and Dr. Polenski spent with him. Uncle Jeppe told me how much he enjoys it!
We see glimmers of the full mechanisms of curing brought about by microorganisms, nitrate, nitrite, salt, sugar, and spices. I would love to know much more to take back to Cape Town a curing method where curing can be done in a shorter time than 19 days, yielding a product that tastes just as exquisite as Irish or Danish Mild Cured bacon. I have many friends in the curing industry who would rather cut off their one hand than do anything quickly. This is a discussion for another day. There are those who believe that in order to cure bacon in the “right” way, one needs time, but my quest is centred around understanding a process that fits with a bacon curing plant that is capable of supplying bacon in large quantities. We do not envisage setting up something small in Cape Town.
Even so, with all the excitement from our quest, never forget the priority of each sunset. Knowing that we are but small parts of a very big whole. That our highest achievements will be measured in whom we loved and how content we were with whatever life offers us. My heart goes out to that young man and his parents! Imagine his final moments – alone, in a foreign land!
With these, my dear son, it is time for me to go. Know that, no matter what, my love for you and your sister is eternal. You guys will be my last thought when I die. The vision of you and my dear Minette! You guys are my entire world and as certain as I write these words today, one day you will read it and I will be gone. Know that my life was not just about bacon, but like Gabriel Dupetit, it is also about the art of living! Imitate me, my son! Live!!
Be well, my boy! Take care of Lauren!
Lots of love from Denmark,
(c) eben van tonder
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(1) “St” is the abbreviation for “stone.” Until as recent as the Second World War, the Smithfield market in London used the 8 lb to a stone measurement. (hansard.millbanksystems)
The stone weight differed according to the commodity weighed. Animals were weighed in 14 lb to a stone before they were slaughtered and once slaughtered, the carcass and meat would be sold in 8 lb to a stone measure. Spices were also sold in 8 lb to a stone weights. (Newman, 1954)
(2) A survey was done in the US in the 1950’s to determine the most common brine mix used for curing bacon at the time. (Dunker and Hankins, 1951: 6) Even though it is 60 years after this letter was presumably written, I include it since methods and formulations in those days seemed to have a longevity that easily would have remained all those years later. The survey was also done among farmers, in an environment where innovation are notoriously slow.
(3) How salty was this bacon in reality? The recipe is used by most US farmers by the 1950’s was 10 lb (4.54kg) salt, 3 lb (1.36kg) of brown suger, 6 ounces (170g) of black pepper and 3 ounces (85g) of saltpeter. 10 pounds (4.54kg) of this mixture per 100 pounds (45.36kg) of meat.
The total weight of dry spices is therefore 6.07kg of which salt is 74% or 3.4kg. This was applied at a ratio of 3.4kg salt per 45kg of meat or 1 kg salt per 13 kg of meat. Not all salt was absorbed into the meat, but the meat was regularly re-salted over the curing period which means that this ratio would be applied many times over before curing was complete. Compare this with the salt ratio targeted by us in 2016 of 25g per 1kg final product, this means that the bacon made with this recipe would be extremely salty, irrespective of the use of sugar to reduce the salty taste. The bacon would have to be soaked in water first to draw out some of the excess salt, before consumed.
(4) Eduard Polenske (1849-1911) was born in Ratzebuhr, Neustettin, Pommern, Germany on 27 Aug 1849 to Samuel G Polenski and Rosina Schultz. Eduard Reinhold Polenski married to Möller. He passed away in 1911 in Berlin, Germany. (Ancestry. Polenske)
The Imperial Health Office was established on 16 July 1876 in Berlin,focussing on the medical and veterinary industry. At first it was a division of the Reich Chancellery and from 1879, fell under the Ministry of the Interior. In 1879, the “Law concerning the marketing of food, luxury foods and commodities” was adopted, and the Imperial Health Office was tasked with the responsible for monitoring compliance with it. Established in 1900, the Reichsgesundheitsrat supported the Imperial Health Office in its tasks. (Wikipedia. Kaiserliches Gesundheitsamt)
(5) Brine is a solution of salt in water.
(6) Qualitative and quantitative techniques for measuring nitrite and nitrates in food has been developed in the late 1800’s. (Deacon, M; Rice, T; Summerhayes, C, 2001: 235, 236). The earliest test for nitrites is probably the Griess test. This is a chemical analysis test which detects the presence of organic nitrite compounds. The Griess reagent relies on a diazotization reaction which was first described in 1858 by Peter Griess.
Schaus and others puts the year of the discovery by Griess as 1879. According to him, Griess, a German Chemist used sulfanilic acid as a reagent together with α-naphthylamine in dilute sulfuric acid. In his first publication Griess reported the occurrence of a positive nitrite reaction with human saliva, whereas negative reactions were consistently obtained with freshly voided urine specimen from normal individuals. (Schaus, R; M.D. 1956: 528)
(7) Gayon and Dupetit’s discoveries include the following:
- they demonstrated the “antagonistic effect of heat as well as oxygen on the process.”
- “They also showed that individual organic compounds such as sugars, oils, and alcohols could supplant complex organic materials and serve as reductants for nitrate.”
- In 1886 they reported on “the isolation in pure culture of two strains of denitrifying bacteria.”
(Payne, W. J.. 1986)
(8) In reality, the key to understanding the function of the utalization of the oxygen atom is understanding cell respiration. The purpose of cell respiration is the formation of ATP. The organism needs nutrients for respiration which is obtained from sugar, amino acids, fatty acids and an oxidizing agent (electron acceptor), oxygen (). Now, in environments where oxygen is depleted (where the rate of oxygen consumption is higher than oxygen supply, the bacteria respire nitrate. The nitrate serves the purpose of the terminal electron acceptor, a function which is better performed by molecular oxygen, if it is available. It is not only nitrite that is used by microorganisms in respiration when molecular oxygen is depleted. Other electron acceptors are sulfate, iron and manganese oxides.
(9) Dr Ed Polenski’s findings has been published in “Arbeiten aus dem Kaiserlichen Gesundheitsamte , 7. Band, Springer, Berlin 1891, S. 471–474” (http://books.google.co.za/books?id=R_YAAAAAYAAJ&pg=PA471&redir_esc=y)
Asheville Citizen Times (Asheville, North Carolina), 20 August 1895. All information on Francois Blanc was from an article on page 3.
Dunker, CF and Hankins OG. October 1951. A survey of farm curing methods. Circular 894. US Department of agriculture
Jones, Osman, 1933, Paper, Nitrite in cured meats, F.I.C., Analyst.
Drs. Keeton, J. T.; Osburn, W. N.; Hardin, M. D.; 2009. Nathan S. Bryan3 . A National Survey of Nitrite/ Nitrate concentration in cured meat products and non-meat foods available in retail. Nutrition and Food Science Department, Department of Animal Science, Texas A&M, University, College Station, TX 77843; Institute of Molecular Medicine, University of Texas, Houston Health Science Center, Houston, TX 77030.
Payne, W. J.. 1986. 1986: Centenary of the Isolation of Denitrifying Bacteria.
Smith, Edward. 1876. Foods. D. Appleton and Company, New York.
Schaus, R; M.D. 1956. GRIESS’ NITRITE TEST IN DIAGNOSIS OF URINARY INFECTION, Journal of the American Medical Association.
A cargo ship at the Cape: https://en.wikipedia.org/wiki/Economy_of_the_Western_Cape