The Mother Brine

The Mother Brine
By Eben van Tonder
January 2015 (Updated Dec 2021)

Introduction

Nitrate salts occur naturally on earth and have been used for millennia to cure meat.  After WW1 sodium nitrite was used directly in meat curing, speeding the process up tremendously and making the entire process far more controlled. Before nitrite was directly added to curing brines, seeding the new brine with old, used brine was a way of adding nitrite directly to the curing brine, thus speeding up the curing process. The old, used brine that contained the nitrite was called the mother brine. The process was  “industrialized” by the Irish, exported to Denmark where the Danes improved on it and integrated it into their cooperative bacon factories.  They, in turn, exported the system to England as tank curing.  It seems as if the Irish also introduced it directly to Australia. In England, the most famous adaptation of the system became known as the Wiltshire cure. Wiltshire curing was exported around the world to countries like Canada, Australia, New Zealand, and South Africa.

We examine the process, its history, and it’s probable stone age roots. We also compare it with the mother dough concept and offer a possible role it could have played in stone age chemistry and the precursor understanding of microbiology.

Two Roads to Curing

The scientific understanding that it was not saltpetre (nitrate) that is curing bacon but somehow, nitrite was directly involved came to us in the work of Dr Edward Polenski (1891) who, investigating the nutritional value of cured meat, found nitrite in the curing brine and meat he used for his nutritional trails, a few days after it was cured with saltpetre (nitrate) only. He correctly speculated that this was due to bacterial reduction of nitrate to nitrite. (Saltpeter: A Concise History and the Discovery of Dr Ed Polenske)

What Polenski suspected was confirmed by the work of two prominent German scientists.  Karl Bernhard Lehmann (1858 – 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. (Fathers of Meat Curing)

In the same year, another German hygienist, one of Lehmann’s assistants at the Institute of Hygiene in Würzburg, Karl Kißkalt (1875 – 1962), confirmed Lehmann’s observations and showed that the same red colour resulted if the meat was left in saltpetre (potassium nitrate) for several days before it was cooked.  (Fathers of Meat Curing)

This laid the foundation of the realisation that it was nitrite responsible for curing of meat and not saltpetre (nitrate). It was up to the prolific British scientist, Haldane (1901) to show that nitrite is further reduced to nitric oxide (NO) in the presence of muscle myoglobin and forms iron-nitrosyl-myoglobin. It is nitrosylated myoglobin that gives cured meat, including bacon and hot dogs, their distinctive red colour and protects the meat from oxidation and spoiling. (Fathers of Meat Curing)

Identifying nitrite as the better (and faster) curing agent was one thing.  How to get to nitrite and use it in meat curing was completely a different matter. I have, in great detail, explained how sodium nitrite came to be added directly into curing brines. The most complete is The Naming of Prague Salt.

There was, however another method, made popular in Denmark. This was before the scientific understanding just given became known. It involved “seeding” new brine with old brine. The results were “magical” and worked much faster than simply using new brine. Instead of simply looking at the beautiful chemistry behind the method, one must frame it within the context of the development of the Danish bacon industry. The Danes, however, did not invent it.

Tank Curing Originated in Ireland

In Ireland, just before 1837, a wet curing method was invented by William Oake. He was probably from Northern Ireland and trained as a chemist. He set up a very successful bacon curing operation based on this system in Limerick, Ireland. The British firms, using dry salt curing were unable to compete with the lower cost of the new system. The UK was their largest client and his son, WH Oake, had a business selling his dad’s bacon in England for some years prior to 1885 in Gillingham, Dorset. The British Navy awarded him at least one bacon contract for production in Limerick. (Tank Curing was invented in Ireland)

A crisis moment came for Denmark in 1887/ 1888 that would cause them to shift their pork production to bacon curing. Up to that time they sold their pigs live in England and Germany. These sales of live pigs were halted due to the outbreak of swine flu in Denmark. The Danes set out to accomplish one of the miracle turnarounds of history by converting their pork industry from the export of live animals to the production of bacon (there was no such restriction on the sale of bacon). The turnaround took place in 1887 and 1888. They used the cooperative model that worked so well for them in their abattoirs.

One would expect that the Irish system of curing was imported to Denmark at this time. This is, however, incorrect. The first cooperative bacon curing company was started in Denmark in 1887. Seven years earlier, in 1880, the Danes visited Waterford and “taking advantage of a strike among the pork butchers of that city, used the opportunity to bring those experts to their own country to teach and give practical and technical lessons in the curing of bacon, and from that date begins the commencement of the downfall of the Irish bacon industry. . . ” (Tank Curing was invented in Ireland)

This is astounding. It means that they had the technology and when the impetus was there, they converted their economy. It also means that Ireland not only exported the mild cure or tank curing technology to Denmark but also to Australia. We have this information from an Australian publication that talks about a local company that has been using the same brine for 16 years, starting in the 1880s. It was probably Irish immigrants that brought the technology to Australia during the 1850s and 1860s gold rush, between 20 and 30 years before it came to Denmark. Many of these immigrants came from Limerick in Ireland where William Oake had a very successful bacon curing business. Many came from Waterford.

One further note must be made about the invention of tank curing by Oake from Ireland. He apparently was a chemist and his invention had as much to do with the brine makeup as it had to do with the fact that tanks were used and the brine re-used. Morgans work shows clearly that curing brine was a priority in Ireland in the mid-1800s. The focus of work by scientists at that time in Ireland was on preservation and not curing the meat as we know it today. Oake clearly had preservation in mind in the exact makeup of his brine which included refined nitrate. Besides this, he used salt and saltpetre (unrefined nitrate). The genius of the system was to re-use the old brine which was “reduced” by bacteria to nitrite. When this was applied to a new batch for curing there was nitrite already in the brine which resulted in quick curing. The rest of the reaction sequined that cures the meat is further driven by chemistry and not bacterial action.

The possibility that Oake and Morgan interacted and possibly influenced each other is a tantalizing likelihood that emerges from the data. This speaks to the issue of whether stitch pumping was used by the Irish, but it falls outside the scope of this article.

In what city was it developed?

This is a fascinating question. The Danes got the technology from Waterford, but is this where it was invented? The Journal of Agriculture and Industry of South Australia says that invention was done in Ulster, Northern Ireland. There is another account of the invention of Irish Mild Cured bacon I stumbled upon from a 1913 reprint of much older work from the Times. It says that Irish mild-cure was discovered by accident when a curer in Limerick, hard-pressed for money, took his imperfectly cured bacon to the market before curing was completed. The short-cured bacon was an instantaneous success, and the method was soon developed. (Ireland of Today).

Of course, this account may be true, but I have serious doubts. I give the full mild cure method below as note 1. It fits none of the technical aspects of mild curing. I do not even think it influenced the actual invention.

I did a survey of the uses of the phrase “mild cure” on the online platform newspapers.com with all of the major newspapers from Britain and Ireland on the platform dating back several hundred years. There are many references from Limerick and Waterford from the 1840s and 1850s onwards. The very first reference, however, goes back to 1837 to a report from Antrim, Northern Ireland. It is fascinating that following this initial reference, Antrim completely disappears from the map and Limerick and Waterford takes over completely. The report simply said about bacon arriving from Ireland, that the Bacon market was dull the past week but for “a small parcel of mild cure.” (Belfast News-Letter (Belfast, Antrim, Northern Ireland) 21 July 1837)

From this, it would seem that we are justified in retaining the most likely place for the invention of mild cure to have been in Northern Ireland. (see my addendum to this work, Addendum A, Occurrences of “mild cure” in English Newspapers)

What was the Inspiration for Oake’s re-use of the Old brine?

William Oake was not the first person to re-use old brine, nor was it “accidentally discovered” as one tends to think when we run out of historical information to refer to. Reality is far more interesting. In Russia, Catherine the Great became the ruling empress of Russia in 1762 and she reigned until 1796. The Russia she inherited expanded its territory and became one of the great European powers of the time. Funding these expansions was a mammoth task for an economy that was still trapped in the dark ages. They have been using indirect taxes to fund these and one of their major sources of revenue was the taxation of salt. Salt became expensive. Catherine was by all accounts a good ruler and sought ways to reduce its price and the accompanying misery the high prices caused especially to the poorer people.

One of the ways that she did this was by increasing the supply of salt. Not just did she do this by making more salt available for the market, she also taught people how not to waste salt. Whether it was her (who had a history of inquisitiveness) or someone working for her, they produced the idea of “recovering the salt” of old brines by boiling it, adding more salt, sugar, and saltpetre to get the concentrations right and reusing it. This idea was nothing new. Boiling seawater down where solar evaporation was impeded due to weather conditions was a known recovery method of salt. “Cleaning” old brine in this same way is a logical extension but in salt used for curing, and where a liquid brine is used, there is no need to boil all the water off. So was born what became known as the Empress of Russia’s brine.

This technology was spread to the West through a famous ham and bacon curing region in Germany called Westphalia. They were known to make some of the best hams on earth which were readily exported to the rest of the world. The Empress of Russia’s brine was introduced to Westphalia from where the technology was exported to the rest of Europe including Ireland. Westphalia Ham, which relied heavily on a unique cold smoking process, has been linked with the Empress Brine from very early on by various authors and newspaper reporters. I discuss this in Westphalia Bacon and Ham & the Empress of Russia’s Brine: Pre-cursers to Mild Cured Bacon. An 1841 reference (Antrim, Northern Ireland), 26 Oct 1841) to the Empress of Russia’s Brine in Antrim is interesting since it was also the city from where we find the earliest reference for mild cured bacon which we know was invented by William Oake and that relied on the re-use of old brine in 1837. Is it possible that the editors of the newspaper knew that the people of Antrim will have a high interest in the Empress Brine based on the work of William Oake who progressed her idea?

The original concept of the re-use of old brine is Russian but they had a boiling step before the salt levels were adjusted and re-used. William Oake likely progressed this idea and discovered that he could leave the boiling of the brine out. I say “discovered” because we know that he did his work through experimentation.

Peeling back the pages of history to understand what his methods entailed is fascinating. Theodore (2014) wrote about the 1700s, “The period of enlightenment and reason was led by philosophers John Locke, Diderot, Voltaire, Rousseau, and others. These men produced a new approach to science and knowledge derived from observations and systematic testing and philosophical debate of ideas as opposed to instinctive or innate knowledge as the basis for human progress.” (Theodore, 2014)

There were many questions to be answered with this notion of experimentation and proof. One of the enduring enigmas that existed from the ancient time of the Romans was the question of whether certain life forms arose spontaneously from non-living matter. It directly applied to the discipline of meat and was very closely connected to the reality of brines. Levine and Evers (1999) set the debate out as follows. They wrote that “such ‘spontaneous generation’ appeared to occur primarily in decaying matter. For example, a seventeenth century recipe for the spontaneous production of mice required placing sweaty underwear and husks of wheat in an open-mouthed jar, then waiting for about 21 days, during which time it was alleged that the sweat from the underwear would penetrate the husks of wheat, changing them into mice. Although such a concept may seem laughable today, it is consistent with the other widely held cultural and religious beliefs of the time.” (Levine and Evers, 1999)

We follow their account of the history of this through. They wrote, that “the first serious attack on the idea of spontaneous generation was made in 1668 by Francesco Redi, an Italian physician and poet. At that time, it was widely held that maggots arose spontaneously in rotting meat. Redi believed that maggots developed from eggs laid by flies. To test his hypothesis, he set out meat in a variety of flasks, some open to the air, some sealed completely, and others covered with gauze. As he had expected, maggots appeared only in the open flasks in which the flies could reach the meat and lay their eggs.” (Levine and Evers, 1999)

We look at Redi’s 1668 experiment. It is as fundamental as the next one we will look at from Lazzaro Spallanzani. Both experiments show that life did does not come from non-life.

-> Redi’s Experiment

Where do maggots come from? Hypothesis: Maggots come from flies.

Redi’s experiment design: Put meat into three separate jars.

Jar 1 was left open 

Jar 2 was covered with netting

Jar 3 was sealed from the outside

Jar-1

Left open 

Maggots developed

Flies were observed laying eggs on the meat in the open jar

Jar-2

Covered with netting 

Maggots appeared on the netting

Flies were observed laying eggs on the netting

Jar-3

Sealed 

No maggots developed

(The summary from the 1668 experiment of Francesco Redi is from Dr Dan Trubovitz’s, A Brief History of Microbiology)

“This was one of the first examples of an experiment in the modern sense, in which controls are used. In spite of his well-executed experiment, the belief in spontaneous generation remained strong, and even Redi continued to believe it occurred under some circumstances. The invention of the microscope only served to enhance this belief. Microscopy revealed a whole new world of organisms that appeared to arise spontaneously. It was quickly learned that to create “animalcules,” as the organisms were called, you needed only to place hay in water and wait a few days before examining your new creations under the microscope.” (Levine and Evers, 1999)

“The debate over spontaneous generation continued for centuries. In 1745, John Needham, an English clergyman, proposed what he considered the definitive experiment. Everyone knew that boiling killed microorganisms, so he proposed to test whether or not microorganisms appeared spontaneously after boiling. He boiled chicken broth, put it into a flask, sealed it, and waited – sure enough, microorganisms grew. Needham claimed victory for spontaneous generation.” (Levine and Evers, 1999) Objections would later be raised that he did not boil the chicken broth long enough.

Notice, however, the general belief that prevailed in 1745 about microorganisms. Levine and Evers (1999) reported that “everyone knew that boiling killed microorganisms.” This not only takes us to a time before William Oake lived but into the imperial time of the reign of Catherine the Great (1762 – 1796). Hippocrates of Cos (460-377 BC), for example, advocated irrigation of wounds with wine or boiled water. “Galen (130-200 AD), a Greek who practised medicine in Rome and was the most distinguished physician after Hippocrates, boiled instruments used in caring for wounded Roman gladiators. Denis Papin, a French physicist, invents the “Digester” (pressure cooker) in 1680. Pressure cookers work by creating a tight seal between pot and lid. This seal traps the air inside the pot as it gets heated. As the air gets heated, it expands but because it is trapped, pressure increases. As pressure increases, so does the boiling point of the water inside: An increase of about 15 pounds per square inch (psi) above standard atmospheric pressure (a typical pressure-cooker setting) boosts the water boiling point from its normal 212°F (100°C) to about 250°F (121°C). The superheated steam trapped in the cooker circulates around the items inside quickly penetrating them, or in the case of food, quickly cooking it.” (Skellie, 2010)

Russia was, in her time, already making its mark in the field of science and technology. Theodore (2014) writes that “Peter the Great (1682–1725) [of Russia] initiated political, cultural, and health reforms. He sent young aristocrats to study sciences and technology, including medicine, in Western Europe. He established the first hospital-based medical school in St. Petersburg and subsequently in other centres as well, mainly to train military doctors. He established the Anatomical Museum of the Imperial Academy of Sciences in St. Petersburg in 1717.” Kahn (2020) writes that during the reign of Catherine’s husband, Peter III, “experimental science had been given a prestigious place, physically and symbolically” and was at the heart of Peter III’s new government complex, in the Academy of Sciences.”

The fact that organisms like bacteria existed was well known in the time of Catherine the Great. “In the 1670s and the decades thereafter, a Dutch merchant named Anton van Leeuwenhoek made careful observations of microscopic organisms, which he called animalcules. Until his death in 1723, van Leeuwenhoek revealed the microscopic world to scientists of the day and is regarded as one of the first to provide accurate descriptions of protozoa, fungi, and bacteria.” (A Brief History of Microbiology) This is an important first point because it means that the world of organisms that cannot be seen with the naked eye was known from the time of the invention of the microscope by Van Leeuwenhoek and his discovery of microorganisms in 1675.

The progress of microbiology was slow following the death of Van Leeuwenhoek because microscopes were not widely available yet to scientists. Scientists like Lazzaro Spallanzani had microscopes at their disposal for research. He obtained an adequate one in 1762 and began repeating Needham’s experiments. This work was interrupted by his departure for the northern Italian city of Reggio Emilia. It is said that he received offers for academic positions from as far afield as Coimbra, Moderna, Cesena and interestingly enough for our purposes, St Petersburg is Russia. (Dolman, 2018)

This means that his work was known throughout the world, including in Russia of Catherine the Great!

Levine and Ehlers (1999) write that Spallanzani “was not convinced [that spontaneous generation took place and nor that Needham’s experiment proved it], and he suggested that perhaps the microorganisms had entered the broth from the air after the broth was boiled, but before it was sealed. To test his theory, he modified Needham’s experiment – he placed the chicken broth in a flask, sealed the flask, drew off the air to create a partial vacuum, then boiled the broth. No microorganisms grew. Proponents of spontaneous generation argued that Spallanzani had only proven that spontaneous generation could not occur without air.” (Levine and Evers, 1999)

-> Spallanzani’s Experiment

Let us look at the simple, yet powerful 1767 experiment of Spallanzani. The question he posed was this: is life from nonlife possible? Could microorganisms be killed by boiling? His hypothesis was that microbes come from the air and that boiling will kill them. He put beef broth into four flasks:

Experiment design – Four flasks with beef broth.

Flask 1 was left open 

Flask 2 was sealed

Flask 3 was boiled and then left open

Flask 4 was boiled and then sealed

Flask-1

Left Open 

Turned cloudy

Microbes were found

Flask-2

Sealed 

Turned cloudy

Microbes were found

Flask-3

Boiled and left open 

Turned cloudy

Microbes were found

Flask-4

Boiled and sealed 

Did not turn cloudy

Microbes not found

(The summary from the 1767 experiment of Lazzaro is from Dr Dan Trubovitz’s A Brief History of Microbiology)

“The theory of spontaneous generation was finally laid to rest in 1859 by the young French chemist, Louis Pasteur (Levine and Evers, 1999)., but for our purposes, it is enough to understand that by the time Catherine’s brine came onto the scene and definitely by the time when Oake invented mild curing, there was good proof, despite the objection by some, that boiling did indeed kill bacteria even before Pasteur! This means that the presence of microorganisms in brine would have been known to Oake, probably even to Catherine the Great and her advisors.

The person or people responsible for the idea that the brine had to be boiled could have done so based on the known technique of “recovering brine” but there is a significant difference. In the case of salt recovery, it is to boil off the water and end up with dry salt and in the case of Catherine the Great, it was to prepare the brine for re-use. The only correlation with salt recovery is that boiling brine was a known practice. Another well-established technique was “roasting” dry salt before it is applied to meat which, in all likelihood, had to do with “cleaning” the salt before it was applied. So, did they boil the brine to “clean it”? Certainly, Catherine and her advisors knew enough about the micro world to understand that it would have cleaned the brine!

In a number of instances where the Empress of Russia’s Brins is given, rock salt is specified. Rock salt was known to be replete with impurities. It would be logical for them to boil the brine to get rid of these impurities as was done with dry salt. There is a problem with this view though in that the boiling of the brine before use was only done when the brine was re-used and not when it was used the first time. If the purpose was to sterilize the salt, surely it would be done for the first brine usage!

I have looked at the nature of the salt and possible explanations for this in much greater detail in my article, Westphalia Bacon and Ham & the Empress of Russia’s Brine: Pre-cursers to Mild Cured Bacon. The solution for this enigma may not be very difficult. Decay in organic matter was, at this time, associated with microorganisms. The link with microorganisms would have been with meat and not with salt. My suspicion is that they associated the contamination of the brine with microorganisms with contact with the meat and not the salt. The sterilization was therefore required only after the brine has been in contact with the meat and not before.

If the question of possible sources of contamination were framed in this way, a scientist, worth his salt (pardon the pun!) would design simple experiments to test for this. In fact, a control would be part of the experiment design where no sterilization of the brine would be done. The control would have shown to be as effective as the other. In fact, the control would have been more effective in subsequent brining experiments of meat because the microbial load would be higher in the unboiled brine which would have facilitated the presence of a higher concentration of nitrites in the brine.

As a chemist, well versed in microbiology (as understood at the time), and experimental techniques and procedures would without question have asked the question: “What would the result be if we do not boil the brine?” Did the brine spoil the meat in any way and if not, why was it necessary to boil the brine at all?

Incorporating the Mother Brine into the Danish Cooperative Model

A next step in the development of the mother brine concept is its Danish adoption. The impetus for such assimilation is important. A fascinating article appeared in the Chicago Tribune (Chicago, Illinois) of 3 October 1897 entitled Why Ireland is in Want. The Recess Committee, established by the British Parliament to consider the creation of a department of agriculture and industry for Ireland, set out to look at the Danish model of agriculture as a possible solution for turning the Irish industry around. A comparison was made between Ireland and Denmark’s economies based on the fact that both countries are dependant on exports to Great Britain with more or less the same mix of agricultural products being pork, butter, and bacon. (Tank Curing Came from Ireland)

It sets the development of the bacon market in Denmark as having taken place beginning in 1889. Before 1888, Danish farmers relied on selling their pigs live to Germany. Swine Fewer hit Denmark in the autumn of 1887 which halted the export of live pigs. Exports to Germany fell from 230 000 in 1886 to only 16 000 in 1888.  The creation of large bacon curing cooperatives was born out of the need to switch from exporting live pigs to processed pork in the form of bacon. (Tank Curing Came from Ireland)

This was stunningly successful. In 1887 the Danish bacon industry accounted for 230 000 live pigs and in 1895, converted from bacon production, 1 250 000 pigs.

The Parliamentary Committee made an interesting observation that may shed light on a possible progression of events namely that due to the impoverished nature of the economy of Ireland, many people were forced to emigrate to seek a better life elsewhere.  The people who emigrated were described by the committee as “the more energetic elements of the population” emigrated, taking with them skills that in the past was responsible for making Ireland a formidable rival of Great Britain in commerce and manufacturing.  The committee examined the causes for the change of fortunes of the individual Irishmen and the lack of competitiveness of its economy.  It sought to juxtapose this with the much smaller and imminently more successful Danish economy. (Tank Curing Came from Ireland)

The state of its bacon industry is of particular interest. The committee compared it to the Irish butter industry where the newest technology was introduced, but despite this, never achieved the competitiveness expected due to structural shortcomings in the system of agriculture. Bacon, it reported, was in a similar situation. The reason for the decline in bacon exports was due to the ability of the cooperatives of the Danish farmers (the chief competitor to Irish bacon) to produce better breeds of pigs, “a more rational system of feeding while the quality of the Irish pig has remained stationary.” (Tank Curing Came from Ireland)

Another reason for the poor showing of Irish Agriculture, related to the pork trade, was the large trade between Ireland and Great Britain in live animals.  Switching to dead meat would be far more profitable for Ireland due to the inherent inefficiencies in selling live animals. (Tank Curing Came from Ireland)

Just as important as the fact that they implemented tank curing is the fact that they did it within the context of the development of their cooperative bacon curing model which again, in turn, is a development from their abattoir industry. Before we look at the use of the mother brine it is, therefore, important to set the scene for the industrialization of the bacon industry generally with cooperation.  It is only within this context that tank curing can properly be understood.  The Danes were renowned dairy farmers and producers of the finest butter. They found the separated milk from the butter-making process to be excellent food for pigs. The Danish farmers developed an immense pork industry around it. (Daily Telegraph, 2 February 1901: 6) Part of the process was to re-think bacon curing and to industrialize it to the point where they could compete with the British producers.

“On 14 July 1887, 500 farmers from the Horsens region joined forces to form Denmark’s first cooperative meat company. The first general meeting was held, land was purchased, building work commenced and the equipment installed.  On 22 December 1887, the first co-operative abattoir in the world, Horsens Andelssvineslagteri (Horsen’s Share Abattoir), stood ready to receive the first pigs for slaughter.” (Danishcrown.com)

The cooperative model very soon became the dominant organizational model for bacon factories around the world.  In the UK, Ireland and as far afield as in South Africa. Let us meet the man behind the world first cooperative abattoir, the concept which very quickly spilt over into the creation of large bacon curing plants, Peter Bojsen.

Peter Bojsen

Peter_Bojsen
Peter Bojsen

The dynamic Peter Bojsen (1838-1922) took centre stage in the creation of the abattoir in Horsens. He served as its first chairman. (2) He created the first shared ownership slaughtering house.  In years to follow, this revolutionary concept of ownership by the farmers on a shared basis became a trend in Denmark.  Before the creation of the abattoir, he was the chairman of the Horsens Agriculture Association and had to deal with inadequate transport and slaughtering facilities around the markets where the farmers sold their meat at.  (Horsensleksikon.dk.) Peter was a visionary and a creative economist. The genius of this man transformed a society.

Peter believed in investing in young minds. He founded Gedved College in an old, abandoned school building.  His creativity and energy led him to create the Horsens Folkeblad in 1866 and in the same year were elected as MP for Vejle circuit while at Gedved College he still remained on as superintendent.  (Horsensleksikon.dk.  Gedved Seminarium)

Denmark started bacon exports to England in 1887 and the corporate structures created by Peter would soon establish Denmark as the premium bacon producer in the world.  By 1890 Denmark exported 59 084 270 Lbs of bacon and ham (26 800 metric tons) (Daily Telegraph, 2 February 1901: 6) 1887 is the exact same year when the first cooperative curing company was created.

The Danish Curing Process

The Horsens share slaughterhouse around 1900. Courtesy of the Danish Agricultural Museum, Gl. Estrup.

The Horsens share slaughterhouse around 1900. Courtesy of the Danish Agricultural Museum, Gl. Estrup.

In Denmark, during the 1800s, the Irish wet curing or mild cure (tank curing) method was incorporated into the Danish industries where they used a combination of stitch pumping and curing the meat in curing tanks with a cover brine.  (Wilson, W, 2005:  219) Evidence would show that the concept was known to farmers, but never before was it used on an industrial scale. The system had several advantages over the mainly dry-curing market in England.  It was a lot quicker and much cheaper!

Danish Crown describes the process as follows in their literature. The bacon was packed into bales.  Each bale was a half carcass weighing around 100kg. Before packing it, the bacon was cured first.  The process is started by injecting the pork side with salt through a needle. They were then placed in a basin for further curing. Here a special mother brine was used that was many years old.  The brine consisted of salt, water, nitrite, and potassium nitrate. After use, the brine was strained so it can be reused. The brine had a reddish colour because it had drawn so much blood out of the meat. (Danishcrown.com)

The old brine contained the nitrite which was reduced through bacterial action from nitrate.  It was the nitrite that was responsible for the quick curing of the meat. The Danish method, therefore, obtained the nitrite by allowing saltpetre to be reduced to nitrite and then using the nitrite-rich brine again in the next curing batch, along with new saltpetre brine. In so doing, they mixed nitrite and nitrate with the result a much faster curing time.

The salt brine was poured over the sides of the bacon, covering them completely. It was important that there is enough brine for the side of bacon to be completely immersed so they are properly cured. The sides of the bacon were placed in the basins meat side up and staggered so that each top end of the carcass sits above the thigh bone joint on the side of the bacon underneath. The brine was then poured over.  The only matter remaining now is the time it will take the brine to diffuse through the meat. This is helped along by injecting the salt solution into the meat with a needle. Once the side of bacon soaks in the brine for the prescribed time, the brine was drained off.  (Danishcrown.com)

Transferring the process across the English Channel

The Danes imported the system into Denmark in 1880 and made it part of the agricultural turnaround of the pork industry in 1887 and 1888.  It is quite possible that the Harris Bacon Company changed to the same system during this time.  The British Journal of Commerce reported in January 1889 that Calne was ‘the chief seat of the bacon-curing industry of England’. Harris bacon was being exported to many parts of the world including most European countries, America, Australia, India, China, the Cape of Good Hope, and New Zealand.

Ten years later, by 1897/1898, mild cured or tank cured bacon was available at all major cities in Europe and Australia. It was probably taken to Australia by immigrants from Limerick.  During the gold rush in the 1850s and 1860s, many Irish immigrants came to Victoria from amongst others, Limerick. It would not surprise me if such an immigrant were the source for Molineux or whoever wrote the section on Mild Curing in the Journal of Agriculture and Industry of South Australia. The descriptions are too vivid and crisp not to be from someone with intimate knowledge of the origin of the system. It may have been that the account came from someone who saw the system in Northern Ireland.

It was the use of tank curing or mild curing as it also became known that made the Danish bacon so much cheaper than the traditional dry-cured English bacon. At a time before the direct addition of nitrite to curing brines, the only two ways to cure bacon were either dry curing or tank curing. Dry curing requires about 21 days as against 9 days for tank curing. The Bacon Marketing Scheme officially established tank curing in the UK. (Walworth, 1940)

The dating of the Irish invention

The Journal of Agriculture and Industry of South Australia, edited by Molineux, General Secretary of Agriculture, South Australia, Volume 1 covering August 1897 – July 1898 and printed in Adelaide by C. E. Bristow, Government Printer in 1898.  This publication gives the inventor of mild curing or tank cure as William Oake and it is said by date of publication that he was deceased already.

There is a reference The Freeman’s Journal (Dublin, Dublin, Ireland), 23 September 1853 reporting that the previous Wednesday, letters from London “announced the disposal of the provisions contract for the royal navy, 12 000 tierces (casks) of pork and 4000 tierces (casks) of beef.”  The short notice says that “we have the satisfaction to add that half the pork contract was taken for Irish account, and a considerable portion will be made up in Limerick, by Shaw and Duffield, William G. Gubbins, William Oake, and Joseph Matterson.” The article is quoting the Limerick Chronicle.

The information from Australia is clear that William Oake who invented tank curing is from Ulster and Limerick is in Munster, but we are on the right island. A notice was posted in Manchester Weekly Times and Examiner (Manchester), Saturday, 28 September 1889 of the death of William Horwood Oake from Gillingham, Dorset “elder son of the late William Oake of Limerick“, aged 49. This means that WH Oake was born in 1849 and if we presume William Oake from Limerick had him when he was 20, William was probably born around 1820.  We, however, know that mild cure was shipped to England at least by 1837.  Let’s take another 5 years off for the invention of the system and let’s pin a date for argument’s sake at 1832 for the invention of the cure.  (Tank Curing Came from Ireland)

Let’s also assume that William, if he was the inventor, was 25 when he completed his studies and invented the system.  That means he must have been born around 1807.  We have the fixed date of the death of WH Oake.  To make both sides work, would mean that William was 33 in 1840 when his first son was born.  It seems a bit late, but if his first two children were daughters, it works well. (Suggested timeline for William Oake is then:  Born:  1807;  Invented mild cure: 1832 (aged 25); WH born in 1840 (William, aged 33); 1889 WH passes (aged 49) (William would have been 82).  By 1897/1898 when the account is given in Australia, William Oake was deceased. If he was still alive, he would have been 90.

Let’s go back to the 1837 date for the first reference to mild cured bacon shipped to England and see how it develops.  This first reference in English and Irish newspapers to mild cured bacon shipped to England in an 1837 report from Antrim, Northern Ireland.  It is fascinating that following this initial reference, Antrim completely disappears from the map and Limerick and Waterford takes over completely.  The report simply said about bacon arriving from Ireland, that the Bacon market was dull the past week but for “a small parcel of mild cure.” (Belfast News-Letter (Belfast, Antrim, Northern Ireland) 21 July 1837)

Now, was this just a mispronunciation or a description that disappeared or do we have here the first instance of a concept that grew? A technical term that is loaded with meaning with specifically mild cured bacon from Ireland in mind or a vague reference?

The second reference I found was in 1842. Reporting in the Provisions section of Jackson’s Oxford Journal which would regularly report on bacon prices from Ireland.  In a mention about produce from Ireland, it reports, “in the bacon market there is no great alterations; heavy bacon is more inquired after, and all fresh mild cure meets a fair demand.”  Heavy bacon seems to be used as opposed to mild cure.  (Jackson’s Oxford Journal (Oxford, Oxfordshire, England) 17 September 1842, p4)

In 1842 I found one reference and in 1844, two. The progression in the references, all related to bacon from Ireland and all focused on amongst other, Limerick and Waterford continue. A 1945 report said that “choice mild-cured Bacon continues brisk.” (Jackson’s Oxford Journal (Oxford, Oxfordshire, England) 26 July 1845, p4.)  In total, I found 5 references to mild cured bacon from 1845. All indications were that the supply was limited.  All with the specific reference of mild cured bacon from Ireland.

An 1853 report from Ireland itself is very instructive. From Dublin, a report says “We are glad to observe that several Dublin curers are now introducing the system of mild cure in bacon as well as hams, in consequence of the great difference had in price. (The Freeman’s Journal, (Dublin, Dublin, Ireland) 11 Feb 1853, p1)

In total, I found 5 references to mild cured bacon from 1845. All indications were that the supply was limited. From this, we are justified in retaining the most likely place for the invention of mild cure to not only have been in Northern Ireland but that it must have taken place just before 1837. (See my addendum to this work, Addendum A,  Occurrences of “mild cure” in English Newspapers.

Historical Instances of Seeding

The remarkable thing is that there are other historical instances of seeding. Seeding substances with something old to create a desired product or outcome are something known in antiquity. It must have conjured up proof of the magical.  The power of one product, magically contained in its fabric, is transferred to a new. Sometimes the link back to the old was maintained for hundreds of years.

I read modern-day accounts of brine used for pickling fish that was developed when a factory was built and was never completely replaced for the, sometimes, hundreds of years of existence of the company.  New brine would always be added, but the old brine never completely discarded.

Back Slopping in Fermented Sausages

Some fermented sausages were famously produced using back slopping. Part of the last batch of fermented sausages was used in the next sausage mix. By “inoculating” the next batch with the same micro-flora from the previous batch, a consistent product was created of similar quality. The negative side is that defects were also transferred. (Marianski, 2009)

Another instance of the concept is the mother yeast from sourdough.

Mother Yeast

Prof. Erick Pallant does a beautiful lecture, The Rise and Fall of Sourdough: 6000 years of Bread. Taken from this lecture, Prof. Pallant begins by looking at humans, 100 000 years ago. We would have been recognized as the same kind of creatures we are today, and our primary food source was meat.

Starting around 10 000 years ago we have the last ice age receding. The last glaciers are moving back into the mountains and a blooming of grasslands takes place. The gathering of seeds was done by women.  The hard work was to know which seeds are edible and which are not. This is before domestication. The seeds are tiny and hard to pull off. We know this because if we look at caves where prehistoric people lived from this time, we find these seeds there that they collected.

The invention of agriculture happens around the world, almost at the same time when the last ice age receded at around 8 000 to 10 000 years ago. He sketched a scenario of how agriculture could have developed. I agree with him that it was probably a woman who was responsible for this. Someone with remarkable insight and an amazing mind. She could very well have been the Galloleo or Copernicus of her generation.

Pallant sketches a scenario that allows us to see how the discovery could have been made.

She possibly lived in a cave in what became known as the fertile crescent next to a dry wadi.  For generations, her grandparents and parents left the cave every morning and went into the fields to pick seeds. One day she is walking back from the field.  There was possibly light rain that morning. Crossing the waddy close to her cave she noticed, in the mud, the same seeds that she picked that morning.  Possibly what she dropped there yesterday on her way home or that her mom dropped or her sister.

She possibly wondered to herself if she must pick them up and wash them clean or is it not worth the trouble? She decided not to go to the trouble. She did, however, make a mental note of it. Possibly three days when she walked home, she saw a bursting forth of small leaves from the seeds. She must have made the connection between the seeds and the plants which look exactly like the ones that she knows she collects seeds from.  If those seeds could be edible, she could think about growing them where she wants to grow them and not way out into the fields.

She maybe decided to test her theory. She possibly took a stick and drew a circle in the mud and threw the seed in the circle and three days later, they grew. The same lush plants. That becomes the discovery of a lifetime.

Scientists are able to date within 25 years from a layer in a cave with mostly bone and a small number of wild seeds, 25 years later, they find the same seeds, but much bigger. It means that humans figured out that we are not going to eat the biggest and fattest seed, but we are going to use it to plant new crops.  Making them grow where we want it to be, close to our homes and growing the size of seeds that suit us.

Civilization changed forever! For the first time, we are able to produce more food through agriculture than we would have done if we went out and hunted a buck.  Specialization of labour took place. One person protects the seeds, another makes the furrows; another waters the plants; another collects them and distributes them. Religions are invented in the fertile crescent to try and reduce the bad years for growing crops and increase the good years.

For the first 3000 years after the domestication of plants, we still didn’t have bread. People were eating a soupy porridge of grain and water.

In Egypt, we have amazing records of the making of bread.  It was invented, probably by a woman who made a bowl of porridge and left it in a room. The room would have been full of yeast and bacteria.  Maybe it was right next door to a room where beer was being brewed. The yeast and bacteria fell into the bowl of soupy porridge and after three days it started to bubble. It would have been wheat which is the only cereal to contain enough gluten so that as it rises, the strands would still hold it together as the microorganisms exhale carbon dioxide and it starts to rise.  It would smell a bit fermented. The woman probably put it in the oven to try and bake it and when she served it to her family, they liked it.  Friends would have been invited to try it a revolution took place.

At the archaeological digs, the Amarna excavation site behind the great pyramids, the most common artefacts are bread ceramic cones (dated to between 4000 and 5000 years ago). They found an estimated 500 000 of these cones from one dig. This was the fuel you feed workers to build the pyramids.

The simple ingredients to make bread turn out to be wheat flour, water, salt, and a leavening agent. The leavening agent is all around us.  Yeast and bacteria, which fall out of the atmosphere. Put it in the oven and you have bread.

The technical aspects of sourdough are beautifully simple. We discovered that fresh flour naturally contains a wide variety of yeast and bacteria. “When yeast flour contacts water some of the gluten and starch is degraded by naturally occurring enzymes in the flour providing sugars and amino acids that yeast and bacteria can metabolise. Initially, a wide variety of microorganisms starts to grow – the dough becomes sour and may even develop a bad smell. Only after repeated feeding with fresh flour and water does the mixture a balanced, symbiotic culture.”  (Renneberg, 2006)

We learned that “all sourdough starters contain a stable symbiotic culture of yeast and lactic acid bacteria, most typically the yeast Candida humilis and the bacterium Lactobacillus sanfranciscensis, isolated first from San Francisco sourdough.  An active sourdough enables bread baking with only three ingredients – flour, water, and salt.  Sourdough bread is made by using a small amount of “starter” dough with active yeast and lactobacilli and mixing it with new flour and water. Part of this resulting dough is then saved for use as started next time. As long as the starter dough is fed flour and water daily, the sourdough remains healthy and usable almost indefinitely. It is not uncommon to have baker’s starter dough that has had years of history from many hundreds of previous batches.”  (Renneberg, 2006)

“Yeast and lactobacilli in the dough will metabolise sugars in the dough – mainly maltose and sucrose – to produce the gas CO2, which leavens the dough.  Obtaining a satisfactory rise from sourdough, however, is more difficult than with packaged baker’s yeast.  To leaven a dough with baker’s yeast, a large number of yeast cells is added (usually more than 100 million cells per g of dough), which rapidly produce enough gas to leaven the dough.  In sourdough, not as many yeast cells are present (about 10 million cells per gram), and although they are supported by lactobacilli, it takes a longer time to produce enough gas.  Additionally, proteolysis also results in weaker gluten, and a denser finished product.” (Renneberg, 2006)

“An advantage of gluten breakdown by enzymes in the flour during sourdough fermentation is the liberation of amino acids:  their transformation to flavour compounds by yeast and lactobacilli as well as during baking contributes to the special flavour of sourdough bread.” (Renneberg, 2006)

“Bread made from rye flours, which is very popular in the northern and eastern parts of Europe is leavened with sourdough.  Rye flour has a high amylase activity (an enzyme that catalyses the hydrolysis of starch into sugars). Unless rye amylases are inhibited by the acidity of the sourdough, they degrade the starch during baking, converting the bread crumb to a slimy mess.  In those parts of Europe where bread is produced from wheat, flour sourdough was replaced by baker’s yeast in the last century.  Only for special products such as baguette in France and panettone in northern Italy the use of sourdough remained a must to achieve the right taste and aroma.”  (Renneberg, 2006)

“American pioneers heading west on their covered wagons also carried sourdough – an active culture enables bread baking with flour, water, and salt only, and spared the need to carry other leavening agents. For the same reason “sourdough” was used by the gold prospectors in the 1848 California Gold Rush. In Northern California sourdough bread was so common that sourdough became the common nickname for the gold diggers.  In 1998, the sourdoughs and their “sourdough” moved to the Yukon in the Klondike Gold Rush but their sourdough bread remains a major part of the culture of San Francisco.  Baking was probably more lucrative than gold mining and a lot steadier. . . .” (Renneberg, 2006)

“Today in San Francisco alone, almost a thousand men and woman work around the clock to produce sourdough bread.  They annually produce 60 000 000 salable units a year (a unit can be anything from a loaf of bread to a bag of rolls, of which 70% is sourdough, 25% sweet French, and 5% specialty items like focaccia and ciabatta.  Together they serve around 4000 retail outlets in Northern California.” (Renneberg, 2006)

“Yeast and bacteria are symbiotic partners and their cells occur in a ratio of about 1:100.  Many species of yeast and lactobacilli were isolated from sourdough but Candida humilis (previously C milleri) L. sanfranciscensis remains the most fascinating.  L. sanfranciscensis has to date only been found in sourdough.  Moreover, it populates sourdoughs around the world and is used to make Westphalian Pumpernicle (in Northern Germany), Italian Panettone, and of course, the famous San Francisco Sourdough bread.” (Renneberg, 2006)

“The reason for its success in sourdough is that dough abounds in maltose which is formed through startch through the action of amylase enzymes. L. sanfranciscensis uses maltose-phosphorylase to cleave maltose to glucose-l-phosphate and glucose without the expenditure of ATP – the energy-rich glucose-l-phosphate is converted to lactate, CO2, and ethanol, the glucose is thrown out.  Fructose, the second most abundant sugar in dough, is not used as carbon source but reduced to a sugar alcohol, mannitol.  This process allows L. sanfranciscensis to gain more energy from maltose and to produce acetate instead of ethanol.  This and other metabolic features ensure that L. sanfranciscensis is the fastest growing bacterium in sourdoughs that are propagated daily, and thus outcompetes all other bacteria. The yeast cannot use maltose but utilizes all other sugars present in dough (including the glucose thrown out by the lactobacilli). Thus the two critters do not compete for a carbon source. Moreover, C humilis is much more resistant to lactic and acetic acid than bakers yeast.” (Renneberg, 2006)

“It’s taste is due mainly to lactic and acetic acids produced by the lactobacilli, but the flavours are the result of teamwork between yeast and lactobacilli. There are about 20 important flavour compounds in sourdough bread.  One example is 2-acetyl-i-pyrroline, a compound generated during baking from the amino acid ornithine, which imparts the roasty odour to the fresh crumb of wheat bread  (and contributes much to the smell of the bakery).  Wheat flour contains very low levels of amino acids. During sourdough fermentation, wheat proteins are degraded to amino acids by flour enzymes. Sourdough lactobacilli convert arginine to ornithine which accumulates in the dough.  Ornithine, which is not a proteinogenic amino acid, is converted during baking to 2-acetyl-i-pyrroline.” (Renneberg, 2006)

There are amazing similarities in the approach of using the mother dough and the mother brine, but what fascinates me is this. “What would this have taught me?” What could ancients have gleaned from this information?  The two processes are sufficiently different to have evoked interesting questions.

The Eskort Case in South Africa

(see A Most Remarkable Tale:  The Story of Eskort)

There is an interesting case about the hay-days of tank curing of the bacon branding of the South African producer, Eskort.  They are, to this day the largest producer of bacon in South Africa and was the first cooperative bacon producer. The plant opened in 1918 and was modelled on the Danish system as a cooperative.

On their packaging, they claim to cure the bacon using Wiltshire cure. It is a reference to the Harris method of tank curing and even though the actual Wiltshire curing method has not been used in South Africa since after the World Wars, it is a beautiful example of the extent of the use of the English and Danish tank curing method.

Walworth (1940) lists the countries that exported into the UK market in the 1930s.  The most important one was Denmark, followed by Canada, and in no particular order, Ireland (Eire), the USA, Germany, Latvia, Estonia, Poland, and Holland. He then states that “whilst there are other Empire sources of pig meat such as Australia, South Africa, Rhodesia, and Kenya”, his brief survey ends with New Zealand, presumably due to their small relative contributions.

The Canadian Case

A few years ago, someone mailed me claiming that he had information about a Canadian company that used the same tank curing system of the Harris operation in the UK.  Apparently, they were approached by Harris during one of the World Wars to produce Harris Bacon under license in case operations in England were disrupted by the war. I never got the promised information but wonder why someone will lie about such a random thing. The claim must have some basis in reality.

This means that we have examples from South Africa and Canada where tank curing was practised. I am sure there will be examples from Australia and New Zealand also. One can say that the Danes were the inventors, and the English were the evangelists of the new system which was popular from the early 1900s till after World War 1.

The Mother Brine in Australia

In Australia, there were several companies that followed the Danish cooperative model.   There was the Western and Murray Cooperative Bacon Curing Company which existed already in 1915 (The Age, 1915, p13), the Gippsland Cooperative Bacon Company (the Age, 1916, p9)

From the Journal of Agriculture and Industry of South Australia, it is clear that the system was widely in use in Australia by the end of the 1890s.  An interesting comment is made that one factory has been using essentially the same brine for the last 16 years, taking the date back to at least the early 1880s when we know for a fact that tank curing was used in Australia.

Conclusion

The other way that nitrite could be added to the meat is, if of course, by directly adding sodium nitrite to curing brines. If the Irish, Australians, Danes and the English favoured tank curing, the Germans and the Americans liked the concept of adding nitrite directly to the curing brines. This was, however, frowned upon due to the toxicity of sodium nitrite.  In America, the matter was battled out politically, scientifically and in the courts. The Naming of Prague salt deals in great detail with this fascinating history. It became the standard ingredient in bacon cures only after WW1. The Germans used it during the war due to a lack of access to saltpetre (nitrate) which was reserved for the war effort and the need to produce bacon faster to supply to the front.  The American packing houses in Chicago toyed with its use due to the speed of curing that it accomplishes.


Further Reading

Chapter 09.01 – Mild Cured Bacon, and

Chapter 11.04: Wiltshire Cured or Tank Cured Bacon

Tank Curing Came From Ireland

Westphalia Bacon and Ham & the Empress of Russia’s Brine: Pre-cursers to Mild Cured Bacon


Notes:

(1)  Bacon exported from Denmark to Britain doubled from 1876 to 1897.  In 1876, 3 560 176 cwt was exported compared with 1897 which was at least double.  The main countries that supplied England with cured bacon in 1901 were the USA, Canada, Sweden and of course, Denmark.  (Daily Telegraph, 2 February 1901: Page 6: Bacon curing)

(2)  Peter Bojsen remained chairman until 1913.  (Denstoredanske.dk  Peter Bojsen)

(3) In the ’70 and ’80 the Danish abattoirs and large processing companies consolidated and formed Danish Crown.  (Danmarkshistorien.dk)

(4)  A 1914 article in The Deming Headlight called the Danish cooperative bacon factory “the last word as to efficient scientific treatment of the dead porker.” (The Deming Headlight (Deming, New Mexico), Friday 8 May 1914, Page 6, A Cooperative Bacon factory)


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References

The Age (Melbourn, Victoria, Australia), 25 Sept. 1915, p13 and 26 June 1916, p 9.

www.bakersmaison.com.au/about-us/blog/the-history-of-sourdough

A Brief History of Microbiology – Cliffs Notes

The Complete Grazier.  1830.  Fifth edition.  Paternoster Row.  Baldwin and Cradock

www.british-history.ac.uk/vch/wilts/vol4/pp220-253

Daily Telegraph, Launceston, Saturday 2 February 1901.  Article:  Bacon curing.

http://www.danishcrown.com/Danish-Crown/125-years-of-food-history.aspx

http://danmarkshistorien.dk/leksikon-og-kilder/vis/materiale/fra-andelsslagterier-til-danish-crown-1887-2012/

The Deming Headlight (Deming, New Mexico), Friday 8 May 1914, Page 6, A Cooperative Bacon factory

http://www.denstoredanske.dk/Danmarks_geografi_og_historie/Danmarks_historie/Danmark_1849-1945/Peter_Bojsen

Dolman, C. E. 2018. Complete Dictionary of Scientific Biography. Cengage.

http://www.economist.com/node/8345876

http://www.horsensleksikon.dk/index.php%3Ftitle%3DGedved_Seminarium

Jaini, Padmanabh S. (1998) [1979], The Jaina Path of Purification

Kahn, A. 2020. How did Catherine the Great’s reign shape Imperial Russian history? British Acadamy of Science

Levine, R., Evers, C. (1999) The Slow Death of Spontaneous Generation (1668-1859) National Health Museum

Marianski, S., Mariański, A..  2009.   The Art of Making Fermented Sausages.  Bookmagic.

Renneberg, R..  2006.  Biotechnology for Beginners.   Elsevier.

Skellie, B. 2010. A brief history of sterilization.

Trubovitz, D. A Brief History of Microbiology)

Tulchinsky, T. H., & Varavikova, E. A. (2014). A History of Public HealthThe New Public Health, 1–42. https://doi.org/10.1016/B978-0-12-415766-8.00001-X

Varro On Agriculture 1, xii Loeb

Walworth, G..  1940.  Feeding the Nation in Peace and War.  London, George Allen & Unwin Ltd.

Pictures

Image 1:  Peter Bojsen.  http://commons.wikimedia.org/wiki/File:Peter_Bojsen.jpg

Image 2:  Horsens abattoir.  http://danmarkshistorien.dk/leksikon-og-kilder/vis/materiale/fra-andelsslagterier-til-danish-crown-1887-2012/

Featured Image:  From salt cured pig (https://www.facebook.com/groups/thesaltcuredpig), Salami