Chapter 15.10: Meat Curing – A Review.

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.


Meat Curing – A Review
Cape Town, November 1959

Dear Lauren,

Over the years I covered the progression of both curing techniques and the understanding of how curing takes place in great detail. There is a need with so much information given, to summarise everything to enable you to have a birds-eye view of the progressions. If you have a good grasp of both the process and the development of the various curing systems you will be well on your way to become a good meat curer yourself.

I, therefore, set out to give a historical overview of the development of meat curing. This review spans many millennia. From the dawn of humanity to our current time where we touch on modern developments in meat curing technology. Curing started out as a way of managing food scarcity by providing a means of fortifying meat against spoilage and over time became a culinary craft. This review is done from the perspective of a commercial high throughput bacon plant and not from the viewpoint of artisan curing operations, some of which is itself large and service an expansive client base. These operations are, however, almost exclusively restricted to developed countries. It must also be said that what was yesterdays most advanced and quickest way of producing bacon became today’s artisan curing techniques.

The Curing Process

A modern understanding of the benefits of curing is that it fixes a pinkish-reddish cured meat colour. It endows the meat with unique longevity, even if left outside a refrigerator, many times longer than that of fresh meat. It is powerful enough to prevent the deadly toxin formation by Clostridium botulinum. It prevents the formation of rancidity in fat. It lastly gives meat a unique cured taste.

What is completely mesmerising in meat curing is that the basic process follows physiological processes, essential for human life. The fact that humans stuck, as it were, to the evolutionary playbook in its practice of curing in that it mimics these physiological processes to the smallest details is completely astounding! I will write to you separately about how the basic processes in curing are exactly the processes essential for life that happens every moment in our bodies! Far from a villain that causes health trouble, nitrate, nitrite and nitric oxide are indispensable molecules to life on earth. Of course, its overuse, in proportions greater than what nature dictates, is extremely unhealthy, as we discussed in Chapter 12.06: Regulations of Nitrate and Nitrite post-1920’s: the problem of residual nitrite. By and large, meat curing is a safe and essential technique of preserving meat.

Discovering the mechanics behind meat curing was a slow process that took hundreds of years. (For an overview of some of the people behind the most important discoveries, see Fathers of Meat Curing)  A survey of farm curing methods conducted in 1951 by the US Department of Agriculture among farmers in the US revealed the following brining methods used:

  • Dry cure – no pumping,
  • Brine cure – no pumping (the use of cover brine),
  • Brine cure – pumped, and
  • Dry cure – pumped.  (Dunker and Hankins; 1951: 4)

We can add the following to this list from 1951:

  • Sweet Curing (Stitch Pumping with dry curing and with hot smoking)
  • Mild Curing (the re-use of cover brine with or without stitch pumping, with or without dry salting)
  • Pale Dry Bacon (Sweet curing with no smoking, only drying)
  • The direct use of nitrites in curing brines
  • Grid or Formed Bacon

For a discussion on the mechanics of curing, please review the letter I sent you previously Chapter 12.09: The Curing Reaction.

Salt Only (Dry cure – no pumping – salt only – using a dry rub or brine)

Exactly where salt curing of meat started is an interesting question. There is ample evidence that salt preservation of meat was done from the earliest of times. Despite the fact that there are records of fish being salt-cured in China going back to 2000 BCE and from Egypt and Mesopotamia, the practice is much older.

Ancients consumed their food raw before it was discovered how to make fire. (How did Ancient Humans Preserve Food?) Even after fire-making was invented and this technology became universally part of human culture, humans only cooked their food intermittently for a very long time. There are cultures to this day that eat raw meat in one form or the other. Besides this, hanging meat to dry in the sun, the wind or over a fireplace without adding any curing agent such as salt was practised in southern Africa, North America, and Nepal, to mention just a few places that I am personally aware of. It was likely universally practised at some point in the past. 

Salt was without question the first curing agent and in all likelihood, salt in the form of seawater. It seems that as people migrated from coastal regions, inland, they developed solar evaporation to extract the salt from seawater along with techniques such as boiling the water off when it became more difficult to access seawater when communities started to settle further away from the coast. It is often claimed that salt did not play a significant role in southern Africa. Nothing could be further from the truth! After a careful investigation of the use of salt for meat preservation in southern Africa, the evidence points to the fact that the power of salt to preserve meat was known by for example the Khoe and the San people, but they preferred to simply hang meat in the sun and the wind to dry. Still, salt played a significant role in the diets of ordinary people. They understood it and used it!  (Salt and the Ancient People of Southern Africa) A direct link can be made to every great civilisation that existed in antiquity in the fact that they all knew the value and uses of salt.

China

One of the greatest and oldest civilisations that ever existed (and still exist) is the Chinese! What we know for sure is that salt curing of meat occurred in China from very early on. Flad, et al. (2005) showed that salt production was taking place in China on an industrial scale as early as the first millennium BCE at Zhongba. “Zhongba is located in the Zhong Xian County, Chongqing Municipality, approximately 200km down-river along the Yangzi from Chongqing City in central China. Researchers concluded that “the homogeneity of the ceramic assemblage” found at this site “suggests that salt production may already have been significant in this area throughout the second millennium B.C..” Significantly, “the Zhongba data represent the oldest confirmed example of pottery-based salt production yet found in China.”  (Flad, et al.; 2005)

Salt-cured Chinese hams have been in production since the Tang Dynasty (618-907AD). First records appeared in the book Supplement to Chinese Materia Medica by Tang Dynasty doctor Chen Zangqi, who claimed ham from Jinhua was the best. Pork legs were commonly salted by soldiers in Jinhua to take on long journeys during wartime, and it was imperial scholar Zong Ze who introduced it to Song Dynasty Emperor Gaozong. Gaozong was so enamoured with the ham’s intense flavour and red colour he named it huo tui, or ‘fire leg’. (SBS) An earlier record of ham than Jinhua-ham is Anfu ham from the Qin dynasty (221 to 206 BCE).

In the middle ages, Marco Polo is said to have encountered salt curing of hams in China on his presumed 13th-century trip. Impressed with the culture and customs he saw, he claims that he returned to Venice with Chinese porcelain, paper money, spices, and silks to introduce to his home country. Polo alleges that it was from his time in Jinhua, a city in eastern Zheijiang province, where he found salt-cured ham. Marco Polo is a controversial figure in that there is great uncertainty if he ever actually undertook the voyages he wrote about. Still, these stories, either first hand from Polo or from someone else who compiled it, the reports certainly had a basis in reality.

The reach of Chinese technology of salt production was impressive. On a trip to New Zealand, I learned that the Māori never developed salt extraction in any form. I did a short review of the colonization of Indonesia and salt extraction technology in an article, “Concerning the lack of salt industry in pre-European New Zealand and other tales from Polynesia and the region.” A brief survey of the history of salt extraction from Fiji, Samoa, New Guinea, Vanuatu, and Taiwan shows the large influence of China on regional salt production technology.

This study also revealed a possible forerunner of more formal salt production around the world, including in China. One of the earliest ways that salt found itself in food preparations was undoubtedly through the fact that seafood was consumed that naturally had added salt which came from the water. Another way would have been if meat was stored in seawater. Immersing carcasses of animals and fish in water would have been one of the earliest forms of preservation and since earliest communities gravitated to coastal regions, salt water would have been used and in addition to seafood which is rich in salt, it would have entered early human culture when food was cooked in seawater. It is likely that carcasses were stored in water at first to hide them from predators and its preserving power would soon have been discovered. Migrating groups would have noticed how seawater preserved meat better and changed (improved) the taste of the meat.

Polynesia

The study of salt in Polynesia shows that as groups migrated inland, away from the sea, saltwater was boiled to evaporate the water and leave the salt as a very basic salt extraction technique. The salt was then traded with the inland communities. This was widely practised in Taiwan until fairly recently. The references of it in Polynesia and Asia offer a suggested progression of the extraction of salt from seawater. Studies from Fiji identified population size, even of coastal communities to be a key driver of salt extraction technology. 

It seems that migrants from Taiwan spread their technology throughout the lands of Polynesia. Every evaluation of salt on the islands I looked at supports this. China would undoubtedly have been a key driver in the region in progressing salt extraction technology with Pappa New Guinea playing a large role where a multitude of techniques to extract salt was (and still is) in use. Solar evaporation of seawater, extracting salt through plant material and burning plants, naturally high in salt are a few of the developments from the region, which all presumably have their roots in the practice of simply boiling seawater; in turn, this was probably a progression of the practice of cooking food in seawater; which, in turn, had its roots in storing meat in saline solutions; which had its roots in simply immersing carcasses in bodies of water for storage. When we are at this point, we are clearly at the very early age of the existence of cognitive modern humans who were cognitively similar to modern humans.

New Zealand

In a discussion with a curator from the Canterbury Museum about the matter of salt production and trade in salt being absent from New Zealand’s ancient history, he drew my attention to the interesting practice of the Maori to slow boil large quantities of shellfish in freshwater. Had they not done so, it would not have been possible to consume large quantities at a time. There seems to be evidence that they did, in fact, consume large quantities of this at a time. It supports the notion that they knew about salt and the possibility exists that this was true across the world from very early. Like the people of southern Africa, people probably knew at least some of the techniques for extracting it, but some local populations, as was the case in New Zealand and many of the southern African populations, may have opted not to use the technology simply because it was not necessary. In the case of the Maori, they definitely knew to remove some of the salt from shellfish before consuming it. They have a word for salt which shows that they definitely knew about its taste. In southern Africa, most would have gotten their salt from meat or milk and when they could only eat plant material, they knew that a bit of salt would cure the ailments which resulted from a lack of salt.

Salt as a condiment

One can not talk about salt curing and not at least make mention of its use as a condiment. Even though too much salt alters the taste negatively, preservation through salt and altering (enhancing) the taste go hand in hand. Evidence is emerging about the use of condiments in food, the earliest discovery so far which dates in Europe going back 6000 years ago in Germany and Denmark. Archaeology magazine (Nov/ Dec 2013) reports that “a team of researchers has found phytoliths, small bits of silica that form in the tissues of some plants, from garlic mustard seeds, which carry strong, peppery flavour but little nutritional value. Because they were found alongside residues of meat and fish, the seed remnants represent the earliest known direct evidence of spicing in European cuisine. According to researcher Hayley Saul of the University of York, “It certainly contributes important information about the prehistoric roots of this practice, which eventually culminated in globally significant processes and events.” (Archeology)  Salt would undoubtedly have been part of their arsenal of taste enhancers.

It seems that our relationship with salt has never been static and to this day, it continues to evolve. More importantly, the discoveries in Denmark and Germany brings into focus innovations in the European lands of Germany, Austria, Hungary, the Czech Republic, Switzerland, Denmark, Holland, Belgium, Spain, France, and Poland. Besides these, there is Irland. What was happening in these regions while cities and kingdoms covering Mesopotamia, India, Pakistan, Nepal were developing salt industries and very sophisticated meat curing technologies based on salt, nitrate, and sal ammoniac? I am filling in the gaps over the years to come.

Origins of Nitrate/ Nitrite curing?

This study of salt also brings me back to my work on nitrite/ nitrate curing which has been a major focus for me over many years. While people living in desert areas would have discovered that certain salts have the ability to change the colour of meat from brown, back to pinkish/ reddish, along with increased preservation power and a slightly distinct taste, coastal dwellers would have observed the same. They would have noticed that sea salt or bay salt have the same ability.

Dr Francois Mellett, the renowned South African food scientist, sent me the following very interesting theory about the earliest discovery of the curing process in private communication between us on the matter. He wrote, “I have a theory that curing started even earlier by early seafarers: when a protein is placed in seawater, the surface amino acids are de-aminated to form nitrite for a period of 4 to 6 weeks. Nitrite is then converted to nitrate over the next 4 weeks. Finally, ammonia and ammoniac are formed from nitrate. It is possible that they preserved meat in seawater barrels and that the whole process of curing was discovered accidentally.”

I think he is on the right track. I suspect that people discovered this even long before barrels were invented. The use of seawater for meat storage and further preparation was so widespread that it would have been impossible not to have noticed meat curing taking place. If it is generally true that the earliest humans first settled around coastal locations before migrating inland, and if the seaside communities first noticed curing, it would push the discovery of curing many thousands of years earlier than we ever imagined, to a time when modern humans started spreading around the globe. When did it develop into an art or a trade is another question altogether, but I think we can safely push this back to the earliest cognitive and cultured humans whom we would have recognized as thinking “like us” if we could travel back in time and meet them.

We know that dry-curing of pork takes around 5 to 6 weeks under the right conditions and if the meat is not cut too thick. It must be cool enough that the meat doesn’t spoil before it is cured.  Even though I now suspect that curing was first noticed by communities living by the sea as I just explained, I suspect that curing salts in deserts were discovered since natural salts always appear as a mix of various salts and under certain conditions, these salt deposits contain small amounts of nitrate salts and ammonium chloride. This would have aided its development into an art by the much larger availability of nitrate and related salts.

I deal with these salts below under separate headings, but the most important two curing salts that appear to us from antiquity are saltpetre (sodium nitrate) and sal ammoniac (ammonium chloride).  Both salts were well known in Mesopotamia and references to them appear alongside references to salt curing of fish mentioned earlier and both salts were used in meat curing.

The ancients developed basic techniques of separating out the different salts. In particular, sal ammoniac was by far the more important salt of the bronze age (2000 BCE). It was produced in Egypt and mined in Asia where it occurs naturally. There are features of sal ammoniac that favour it as a salt for people who had a motivation to exploit new lands due to population pressure and climate changes or just curiosity. When the horse was domesticated around 5000 BCE, a food source was needed to sustain humans on long expeditions and I believe sal ammoniac fits the requirement perfectly.

Both salts cure the meat in a week which obviously had huge advantages over salt-only curing. This, I speculate, was the first incentive to change to a dedicated curing salt. Secondly, sal ammoniac, as far as I can find, was globally traded from much earlier on than saltpetre. Ancient Macedonian records indicate that even 2000BCE saltpetre was preferred in food over sal ammoniac on account of the better taste of saltpetre.

There is a modern era example of a curing technique that was good for a time and was then replaced with more agreeable methods as soon as supply lines were established. This technique, I believe actually existed from very early after the horse was domesticated and was re-introduced by various cultures, at various times. One such culture was the Boers who left the Cape Colony and moved into the interior of South Africa. The technique they used to cure their meat disappeared as soon as conventional supply lines were established.

The technique is curing of meat by hanging it over the neck of the horse or placing it under your saddle so that the sweat of the horse cure the meat. (For a discussion on this, see my article, Saltpeter, Horse Sweat and Biltong)  My point is that this is a good example of a curing technique that was used for a time only and then disappeared, only to be re-appear when conditions required it. Such was the case, I suspect when sal ammoniac was used for a time in curing until the requirement subsided, salt curing became popular again and much later economic factors re-introduced an improved curing salt which by this time was saltpetre. The inclusion of saltpetre into curing salt mixes goes hand in hand with its increased availability.

German and Austrian cookbooks pre-1600’s reveal that vegetable dyes were used to bolster colour in this time and speak of curing with salt only. It is well known that the Germans and Austrians were familiar with nitrate curing and, I will argue, they would have been acquainted with sal ammoniac as a curing salt also, but for whatever reason, these fell out of common practice. When the requirements disappeared for nitrate and sal ammoniac curing of the ancient world, the nations of Europe and China reverted to salt curing.

The many references to salt curing are therefore not surprising in the context of a mature and stable society. A record exists from Cato the Elder who described in 160 BCE how a ham should be cured.  In his Latin work, De Agricultura (On Farming), this Roman statesman and farmer, gives an ancient recipe for curing pork with salt.

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

Cato may have imitated a process whereby hams are smoked over juniper and beech wood. The process was probably imported by the Roman gourmets from Germania. (economist.com) It is possible that the process of curing itself was brought to Rome by the military stationed in Germany.

Salt curing remains an important technique for high-end hams and certain bacon. Like nitrite curing, it yields a particular cured colour, but one that is a deeper purple than pink.  For the mechanism behind this, refer to a section in my article on the mechanisms of nitrite curing, Bacterial/ Enzymatic Creation of Cured Colour. This is entirely restricted to long term curing which was the norm at a certain time.

Sal Ammoniac

In 2017 I did an article where I speculated that nitrate curing originated from either the Turpan area in western China or from the Atacama desert in Chile and Peru. In this article, I suggest that nitrate curing of meat is thousands of years old. (Salt – 7000 years of meat-curing) I was working on the assumption that nitrate salts are the only salts that will yield nitrite and nitric oxide, required for meat curing. Between the Atacama desert and Turpan in Western China, Turpan is by far the best candidate for the birthplace of meat curing as it is practised around the world. I recently review further evidence from this area in an article, Nitrate Salts Epic Journey and And then the mummies spoke!

In the course of researching the article, I discovered that sal ammoniac was far more vigorously traded than saltpetre in the early Christian era and possibly for thousands of years before that. Fascinatingly enough, I realised that ammonium chloride will, like nitrates, undergo bacterial transformation into nitrites which will then in the meat matrix yield nitric oxide which will cure the meat. I further discovered that it is an excellent meat preservative, even better than nitrates. Turpan is also probably the only place on earth where sal ammoniac and nitrate salts in the form of sodium nitrate occur in massive quantities side by side.

Chinese authors of antiquity are unanimous that sal ammoniac came into China from Turpan, Tibet, and Samarkand and through Samarkand, it was traded into the Mediterranian along the silk road. There are similar records that it was traded from Turpan along the silk road through the city of Samarkand that had strong trading ties with the Mediterranean. It all makes for an appealing case for sal ammoniac as the actual curing salt from antiquity that was used in meat curing when the practice spread around the world. There is even a tantalizing link between Turfan and the ancient city of Salzburg in that a very particular stitch was found in jerseys on mummies in Turfan and in salt mines in Salzburg. This leads me to speculate that the trade of sal ammoniac was done into the heart of Western Europe, into what became known as Austria. This leads me to believe that the actual technological progressions may have come from Austria. Whether it was Salzburg or Turfan is not clear. More work remains to be done to gain greater insight.

We are not familiar with this salt in the context of meat curing and it will be in order for me to dwell on the topic a bit. I reviewed modern references dating back to the 1700s, 1800s, and 1900s where it continued to be used in meat preservation in Nitrate Salts Epic Journey. Several minerals exist composed of ammonium (NH4). Ammonium is formed by the protonation of ammonia (NH3). Sal ammoniac is the most well known and was named by the ancient Romans.  They collected this salt which was found around the temple of Jupiter Ammon in Egypt and called it salt (sal) of Ammon (ammonocius). The name ammonia was subsequently derived from it. It forms in volcanic vents and after volcanic eruptions before it has rained which dissolves it. It is highly soluble. It is unique in that the crystals are formed directly from the gas fumes and bypass the liquid phase, a process known as sublimation.

Ammonium readily combines with an acid thus forming a salt such as hydrochloric acid to form ammonium chloride (sal-ammoniac) and with nitric acid to form ammonium nitrate. Recent studies have shown that volcanos release a “previously unconsidered flux of nitric acid vapour to the atmosphere. (Mather, T. A., et al, 2004) It is a fascinating and insightful fact that the Turfan area, both the basin and the mountains are replete with different salts containing nitrogen (nitrate salts and ammonium) any one of which could be used effectively in meat curing.

Sal ammonia was mined from openings in the sides of volcanic mountains where steam from underground lava flows created the ammonium chloride crystals. These were traded across Asia, Europe and India. Massive sodium nitrate deposits occur in the Tarim Basin, the second-lowest point on earth. I then speculate that traders used some of these deposits to forge ammonium chloride since the ammonium chloride crystals did not survive in crystal form on long voyages due to their affinity for water that breaks the crystal structure down. Once this happened, the sodium nitrate and the ammonium chloride look similar in appearance. Due to the fact that it is known that almost all the sal ammonia mined in Samarkand was exported, I deduce that demand outstripped supply and this provided the incentive for such forgery. I find support for the likelihood of such a forgery, not just in the limited supply of sal ammoniac compared to nitrate salts, but also in the fact that mining then sal ammoniac was a seasonal affair and extremely dangerous and a difficult undertaking.

It seems likely that sal ammonia was the forerunner of saltpetre as the curing agent of choice. It is composed of two ions, ammonium, and chloride. The ammonium would be oxidized by ammonia-oxidizing bacteria (AOB) into nitrites and the well-known reaction sequence would result. (Reaction Sequence)

Not only would it result in the reddish-pinkish cured colour, but it was an excellent preservative. In my personal experience, it is a better preservative than salt and nitrites alone but more work is needed to confirm this. There is, however some evidence of this fact from history. An 1833 book on French cooking, The Cook and Housewife’s Manual by Christian Isobel Johnstone states that “crude sal ammonia is an article of which a little goes far in preserving meat, without making it salt.” (Johnstone, C. I.; 1833: 412) It is, of course, the sodium which tastes salty in sodium chloride and ammonium chloride will have an astringent, salty taste. I know exactly what ammonium chloride tastes like since it was added to my favourite Dutch candy “Zoute Drop” with liquorice. I believe it was none other than my old friend, Jan Bernardo who first gave me Zoute Drop. As a boy, I used to ride my bicycle once a month to the only Greek Caffe in Vanderbijlpark which sold it for my monthly fix. My favourite was the double strength version called “Dubbel Zoute Drop.”

Subsequent to these discoveries, I did two small tests with sal ammoniac. Refer to The Sal Ammoniac Project.  Here I show that sal ammoniac stands up to its reputation as an excellent preservative and definitely cures meat in two weeks at a 5 deg C temperature.

Salt with a little bit of saltpetre

Saltpetre is the curing salt that most of us are familiar with that preceded sodium nitrite as curing agent. By far the largest natural known deposits of saltpetre to the Western world of the 1600s were found in India and the East Indian Companies of England and Holland plaid pivotal roles in facilitating its acquisition and transport. The massive nitrate fields of the Atacama desert and those of the Tarim Bason were still largely unknown. In 1300, 1400 and 1500 saltpetre had, however, become the interest of all governments in India and there was a huge development in local saltpetre production.

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

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

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

The pivotal area where I believe saltpetre technology spread from across Asia, India and into Europe, is the Turpan-Hami Basin in the Taklimakan Desert in China. Here, nitrate deposits are so substantial, that an estimated 2.5 billion tons exist, comparable in scale to the Atacama Desert super-scale nitrate deposit in Chile. (Qin, Y., et al; 2012)  (The Tarim Mummies of China) Its strategic location on the silk road, the evidence of advanced medical uses of nitrates from very early on and the ethnic link with Europe of people who lived here, all support this hypothesis.

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

To the South East, in China, the largest production base of saltpetre was discovered dating back to a thousand years ago. Here, a network of caves was discovered in 2003 in the Laojun Mountains in Sichuan Province – possibly the largest production base of saltpetre in China from 1000 years ago. Meat curing interestingly enough is also centred around the west and southern part of China. Probably a similar development to the Indian progression.

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

The Dutch and English arrived in India after 1600 with the first shipment of saltpetre from this region to Europe in 1618. Availability in Europe was, generally speaking, restricted to governments who, in this time, increasingly used it in warfare. (Frey, J. W.;  2009) This correlates well with the proposed time when it became generally available to the European population as the 1700s from Lauder. I believe that a strong case is emerging that the link between Western Europe and the desert regions of Western China was the place where nitrate curing developed into an art. The exact place, I believe, in Western China is the Tarim depression.

Dry curing of meat changed from salt only to a mixture of salt and saltpetre, liberally rubbed over the meat.  As it migrates into the meat, water and blood are extracted and drained off.  The meat is usually laid skin down and all exposed meat are plastered with a mixture of salt and saltpetre.  Pork bellies would cure in approximately 14 days. (3) (Hui, Y. H.,  2012: 540)

Salt, Saltpeter, and Sugar

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

Science later revealed that the sugars contribute to “maintaining acid and reducing conditions favourable” for the formation of nitric oxide.” (Kraybill, H. R..  2009)  “Under certain conditions reducing sugars are more effective than nonreducing sugars, but this difference is not due to the reducing sugar itself. The exact mechanism of the action of the sugars is not known. It may be dependent upon their utilisation by microorganisms or the enzymatic systems of the meat tissues.” (Kraybill, H. R..  2009)

Ralph Hoagland, Senior Biochemist, Biochemie Division, Bureau of Animal Industry, United States Department of Agriculture, discovered that saltpetre’s functional value upon the colour of meat is its reduction to nitrites and the nitrites to nitric oxide, with the consequent production of NO-hemoglobin. He showed that the reactant is nitrous acid (CodeCogsEqn (19)) or one of its metabolites such as nitric oxide (CodeCogsEqn (13)).

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

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

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

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

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

Denitrifying bacteria are facultative anaerobes, that is, they will only use nitrate (codecogseqn-2) if oxygen (CodeCogsEqn (3).gif) is unavailable as the terminal electron acceptor in respiration.”  “The codecogseqn-2 is sequentially reduced to more reduced forms although not all bacteria form gas. ” “Many bacteria can only carry out the reduction of codecogseqn-2 to CodeCogsEqn (5).gif, and this process is referred to as dissimilatory nitrate reduction. There is also evidence emerging that certain bacteria can denitrify, even if codecogseqn-3  is present.  (Seviour, R. J., et al..  1999:  31)

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(Seviour, R. J., et al..  1999:  31)

“The rate of denitrification is affected by several parameters including temperature, dissolved oxygen levels and the concentration and biodegradability of carbon sources available to these cells” (Seviour, R. J., et al..  1999:  223) Examples of such carbon sources are sugar, oxygen and plant oils.

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

Double Salting

In order to dry the meat quicker, a practice developed to salt it multiple times. During the first salting, meat juices are pulled from the meat. This was cleared away and a second “salting” was administered. Later on, several “saltings” were administered. Right here from the southernmost point of the African continent comes a great illustration of this from the early 1700s which then, easily extends back several hundred years.

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

Upham reports on the following course of events from 1709. A detailed treatment of the reference can be seen at Saltpeter, Horse Sweat and Biltong. What was happening in the sweltering heat of March in Cape Town was that meat that was salted for sale to ships were off. A certain Michiel Ley then suggested that the meat should be salted in a two-step process. In other words, salt it and let it lay for a couple of days, giving time for blood and meat juices to be drawn out. Then, give it a second salting. Lay originally came to the Cape as a soldier employed by the Dutch East Indian Company but he changed his occupation to that of a master butcher. Certainly, this was his trade which he received in Europe.

An extract from 28 March 1709 from a Broad Council Meeting at the Cape of Good Hope gives us the rest of the story. It is clear from the entry that they were under pressure to supply due to both supply and increased demand. They noted, “Not one hardly offered himself for the supply of dried or smoked meat. Only 2,500 or 3,000 Ibs. were offered – a quantity very little among so many vessels. The necessity of supplying the ships properly is re-iterated.” The reason for the short supply was the prices offered by the Company which was too low and consequently the farmers were reluctant to sell.

The small quantity of meat that they received was itself unsuited for sale. They minuted that the “Governor and flag officers inspect some meat salted 8 days ago by the contractor Husing. The lean parts were found good, but the thick parts already spoiling“.

Michiel Ley came up with a plan that was accepted. “Decided that the treat should first lie some days in the brine to draw out the blood, and after that placed in new salt. That was not the idea of Husing but of his fellow contract or Michiel Ley. The former believed that the meat should be left in its first salt and not pickled beforehand; And was prepared to guarantee supply remaining good.” This dispute clearly shows that double salting was by no means an accepted technique in the 1600s and early 1700s.

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

So it happened that Lay was contracted to supply all the meat required by the Company together with Willem Basson, Jan Oberholster, and Anthony Abrahamsz. The issue of the supply of meat was major and shaped the immediate political landscape of the colony. Remember that we said that the prices offered by the Company for meat was too low and the farmers refused to sell. South Africans are well familiar with the fact that Van der Stell was recalled and that Adam Tas was involved in the saga. Adam Tas was one of these farmers and he took it upon himself to collect signatures for a petition against the governor at the Cape. Governor Van der Stel was eventually recalled to Holland. Van der Stel’s reply to the petition against him was a document drafted by him in his defence and signed by among other Ley and Oberholster. The four partners requested that their meat contract be cancelled which was granted and it was taken over by Claas Henderiksz Diepenaar. Adam Tas was locked up in the Castle’s notorious dungeon and finally, Van der Stel was recalled to Holland in 1708. The meat contract was the issue at the heart of Van der Stel’s recall.  (Linder) Ley acted as one of Van der Stel’s representatives to finalize the sale of his assets. (Stamouers)

Notice the black pepper which was added. The reason for this was probably to keep flies and other insects away.

Brine-soaking (brine cure – no pumping)

Brine-soaking followed dry-salt-curing. Note that dry or wet curing is defined by what the meat is left in to cure and not what is applied to the meat. Wet brine curing is still relatively slow and meat pieces are placed in a mixture of salt, saltpetre, and water. It is important to take temperature into account since spoilage may occur before the brine had a chance to penetrate the meat. (Hui, Y. H.,  2012: 540) Here the temperature is very important and is the reason why curing was only done in the winter months.

An 1830 description of a “wet cure” survived where a farmer describes the dry cure method as “tedious.” He credits Europe as the birthplace of the wet-cure method. One of the benefits of this simple system is that it can be used for mutton and beef also. The downside is that it is more expensive than dry-cure, but the wet cure could be re-used and taking everything into account, would work out cheaper in the long run than dry-cure. (The Complete Grazier, 1830:  304) It seems then that wet-curing was invented in the late 1700s or early 1800s.

This re-using of the brine would turn out to become the cornerstone of the industrial revolution for bacon curing and the country credited for this development is Ireland. Before we get to that, we have to first look at barrel pork.

Barrel pork

Barrel pork was an easy way to cure pork that involved liquid brine. It had the benefit that it could be put in barrels, loaded onto a wagon or a ship for transport and cure in transit. It could also be stored in the cure which would render it safe from flies and other insects. References to it show that it was practised already by the second half of the 1700s and well into the 1800s.

In the 1800s, this was the main way that the packing plants in the USA exported pork to England as bacon. There are many accounts in newspapers of the time where advice is given to the bacon producers on how to make sure that the meat arrives in England unspoiled. One of the main points was the importance of using good, new wood for the barrels.

A 1776 description is given on how barrel pork was produced. “After the meat has cooled < probably after the hair was removed >, it is cut into 5 lb. pieces which are then rubbed well with fine salt. The pieces are then placed between boards a weight brought to bear upon the upper board so as to squeeze out the blood. Afterwards, the pieces are shaken to remove the surplus salt, [and] packed rather tightly in a barrel, which when full is closed. A hole is then drilled into the upper end and brine allowed to fill the barrel at the top, the brine being made of 4 lb. of salt (1.8kg or 10%), 2 lb. of brown sugar (0.9kg or 5%), and 4 gallons of water (15L or 84%) with a touch of saltpetre. When no more brine can enter, the hole is closed. The method of preserving meat not only assures that it keeps longer but also gives it a rather good taste.” (Holland, LZ, 2003: 9, 10)

Again, notice the brine make-up of salt, saltpetre, sugar mixed with water. The role of the sugar was to break the hard salt taste.

Barrel pork would remain an important curing method throughout the 1700s and would make a spectacular return almost 100 years later when pressure pumps were introduced to inject the brine into the meat through needles.  A plank would be run across the barrel opening. The meat is placed on the plank for injection with between one and three needles. The three needles are fed brine through a hand pump that would pump brine directly from the barrel.  The barrel is half-filled with brine. After the meat has been injected, it is pushed off the plank, to fall into the brine which acts as a cover brine.  It would remain in the cover brine the prescribed time before it is removed and smoked.

The invention of Mild Cured Bacon by William Oake

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Ham press from the 1910s

Sometime before 1837 William Oake, a chemist from Ireland invented Mild Cured Bacon. (Chapter 09.01 – Mild Cured Bacon) This was the first major development in curing technology following barrel curing. The essence of mild curing is the continued re-use of the old brine. Oake was investigating what was responsible for the preservation power in the salt/saltpetre mix. He correctly concluded that salt plays a very limited role in preservation and today we know that its main function in old dry curing systems was to reduce the moisture in the meat and thus lowering the water activity. He also found no great preserving power in saltpetre but he knew that “nature” provided somehow a preserving power to the meat. It was known that the re-use of old brine had a large benefit and we know that this probably came to England from the German region of Westphalia. (Mild Cured Bacon) So, at this time, there was a practice in England to re-use brine twice. One would cure the meat with the liquid brine, boil it to “clean it”, and re-use it a second time. (For a full discussion on this, see William and William Horwood Oake)

After a careful and detailed investigation of the curing techniques used in Westphalia, I came to the realisation that this, the key feature of William Oake’s Mild Cures system was a progression of a system developed years earlier, not in Westphalia but in the Russia of Catherina the Great! She (or someone in Russia or even possibly in her court) happened upon the idea that since salt is a scarce and very expensive commodity, as was the case in Russia at that time, a way to re-use, not the brine but the salt would be to boil the brine down after it was used, add sugar, saltpetre and salt to it with fresh spring water. The brine was called the Empress of Russia’s Brine and for a comprehensive discussion on the link between this brine and Westphalia, see Westphalia Bacon and Ham & the Empress of Russia’s Brine: Pre-cursers to Mild Cured Bacon. The clue to the close connection between a knowledge of this brine, possibly through Westphalia and Northern Ireland where William Oake invented mild cured bacon is discussed in great detail in Mild Cured Bacon.

William Oake, a trained chemist must have worked out that boiling the brine was not necessary which is the only substantive change he made to the method of Catherina the Great! This is the key feature of his brilliance. Yes, a second and vital contribution is to look at the full process and reorganise it in a way that makes sense in a factory environment. He industrialised bacon production. This made great bacon affordable and available to the general public. His system incorporated the following elements.

  • Lightly salting the meat to draw out the blood on the concrete factory floor
  • Tanking or brining (stacking and pickling) for 7 days which involved sprinkling the bottom of the tank where the meat would be cured with salt. Stack the flitches on the bottom. Lightly sprinkle saltpetre over it with sugar and salt. The next layer of flitches is stacked on top of the first but done crosswise. This is again sprinkled exactly as was done with the first and so it is repeated till the tank is full. A lid is now placed inside the tank with an upright on top and pickle is poured into the tank. The lid and upright serve the purpose of keeping the bacon sides submerged. The pickle is made as follows: To every 10lbs. of salt we add 8lbs. of dark-brown sugar; 1 lib. of spice, and 1/2lb. of sal-prunella.” Sal prunella a mixture of refined nitre and soda.  Nitre is refined saltpetre used in the manufacturing of explosives. Saltpetre plays a very important role as does the grade of saltpetre used. It is important to turn the meat over after forty-eight hours into another tank.  The meat that was on top is placed at the bottom of the next tank. Salt, sugar, and saltpetre are again used exactly as it was done during the first salting. Now the real trick comes in. The same pickle is used!”
  • Maturing/ Resting and Drying for 21 days. After seven days the flitches are removed and stacked on the floor putting some salt between each layer. Be careful not to stack it higher than four sides deep, until it has been on the floor for some days when it should be turned over, and stacked higher each time until the fourth week from the day it went into the tanks; the bacon will then be cured.”
  • Washing, drying, trimming and smoking. Place the bacon in tanks of cold water. Here it is soaked overnight. The next morning we wash them well with a brush. Whether smoking is done or not after tank curing the meat should be rinsed off and dried before aging or maturation. The reason for this is that the meat pores should be closed leading to a hardening of the surface and a considerable reduction in the drying rate. The meat is trimmed and hung till it is properly dried. It is then smoked. 

Two aspects should be noted. One is the rigid stepwise process which addressed efficiency, speed and hygiene and the second is the re-use of the old brine. Oakes genius was combining existing curing steps in a new way and the quality of his brine. His lasting contribution is, however, without any doubt, the creation of the live brine system which became the cornerstone of tank curing.

The system was next adopted by the Danes. The year was 1880. Denmark is a tiny nation. To remain competitive, they realised years earlier to learn as much as they can from other nations and peoples and adapt. Every industry in Denmark was constantly looking where new discoveries were being made and how they can adopt and adapt it.

Denmark had large dairy farmers and a sizable pork industry developed from the by-products of dairy farming. It was very simple and profitable. Raise pigs on the byproducts from milk and sell it to England and Germany. Someone from the pork industry learned about the new mild cured bacon produced in Ireland. They tried many times to sent people to learn the techniques, but the Irish were careful not to employ the young Danish men who were sent over for employment in the large bacon plants in Ireland. They needed an opening in the Irish market to learn their techniques. Such an opening was presented through industrial action by the Irish workers. The thing about Ireland is that the workers often go on strike and how they are treated by the companies they work for is often very harsh. Those on strike do not get paid and stand a large chance to be laid off.

In 1880 there was a strike among butchers in the Irish town of Waterford. Some shrewd members of the Danish pork processing guild happened to be in Ireland at that time, in Waterford and at the promise of lucrative employment in Denmark managed to persuade a number of the striking men to return with them to Denmark. In Denmark, they quickly arranged for them to train the Danish butchers. Mild Cured Bacon became the new Danish bacon.

Sweet Cured Bacon by C & T Harris (Dry-salt-curing in combination with injection)

In Calne, a small settlement in Wiltshire, England, the firm C & T Harris was becoming the world leader in producing exceptional mass-produced bacon. For a complete discussion, please read Chapter 10.02 – Sweet Cured Harris Bacon.

Their invention was very similar to the general method of William Oake’s Mild Cured Bacon with the notable exception of the re-use of the old brine. Very importantly, they hot smoked their bacon after curing. Even more importantly was the fact that this invention in the 1840s used stitch pumping. Stitch pumping itself was invented around this time and it allowed for much quicker curing of the meat which together with hot smoking cut the curing time down and was a major improvement on the taste. It was not a had salted taste, but a mild cure taste and from there the name.

It seems that the basic distinguishing between dry and wet curing is not based on whether injection is applied or not, but the state of the salts that the meat is left in, even after it has been injected with a brine (mixture of salt and water). So, if it is packed in a dry mix, it is dry curing and if it is soaked in a brine, it is wet curing.

It was reported by some bacon curers that they used the dry-curing in conjunction with injection. In this case, the meat is injected with approximately 10% saturated brine solution and the injected meat is then treated the usual way in the application of dry-salt-cure. There is a record showing that C & T Harris (Calne) used injection with their bacon from 1843. After it was dry-cured, the meat was smoked at a temperature of not higher than 38 deg C (100 deg F) in order to prevent nitrate burn which presents itself as green spots that appear on the meat. In the report, mention is also made that care should be taken if these products are stored to prevent damage from insects such as cheese skippers, mites, red-legged ham beetles, and larder beetles.  (Hui, Y. H.,  2012: 540) The result was sweet cured bacon!

The Injection of Meat

A short review of the invention of the practice of brine injection with needles is appropriate at this time. The practise started as a way to preserve cadavers. I remember an account I read of how Von Hombult and Guthrie went from house to house after a particularly heavy thunderstorm buying up the copses of the deceased for their own medical studies. Before the age of refrigeration, preserving human remains to study the make-up of the human body would have received considerable attention and this was the first area where injection of meat was done for the purpose of preservation.

The link between meat preservation for sustenance and meat preservation for the study of anatomy is, as the link between meat injection and the medical establishment, one that is abundantly obvious if you just think about it for a minute, but not necessarily the first connection you make when you look at the different disciplines separately. The man who took front and centre stage in the development and progressed the practice of injecting preserving fluids into dead animal muscles for the purpose of preservation was Morgan.

Morgan’s Patent

It was a certain Mr Morgan, in England, who had a significant impact on popularising the technique of injecting a liquid brine into the meat in the first place. The motivation was to increase the rate of curing by getting the brine faster into the meat in order to reduce the time required for processing which became the basis of sweet cured bacon.

In temperatures above 20 deg C, pork spoils in three days. By injecting a liquid brine into the meat at evenly spaced intervals, the brine diffuse quicker through the meat. Morgan’s interest was the preserving of meat generally but included meat preservation for long sea voyages before the advent of refrigeration and not the curing of meat by farmers.

We encountered Mr Morgan in the work of Edward Smith, Foods, (1873). Smith wrote that “Mr Morgan devised an ingenious process by which the preserving material, composed of water, saltpetre, and salt, with or without flavouring matter, was distributed throughout the animal, and the tissue permeated and charged. His method was exemplified by him at a meeting of the Society of Arts, on April 13, 1854, when I [Edward Smit was] presided.” (Smith, 1873)

He describes how an animal is killed in the usual way, the chest opened and a metal pipe connected to the arterial system. Brine was pumped through gravity feed throughout the animal. Approximately 6 gallons were flushed through the system. Pressure was created to ensure that it was flushed into the small capillaries. Smith reported overall good results from the process with a few exceptions. He himself seemed unconvinced.

An article appeared in the Sydney Morning Herald that mentions Dr Morgan and his arterial injection method. An important observation from the article is the date of 1870. By this time, he is referred to as “Dr Morgan”, cluing us in about the timeline of Morgan’s life.

A second observation is a drawback of the system. The article states that “salting is the most common and best-known process of preservation (of meat), the principal modern novelty being Dr Morgan’s plan of injecting the saline solution into the arterial system – the principal objection to which has been that the meat so treated has been over-salted.” (Sydney Morning Herald, 1 March 1870, p 4) The brine mix that Mr Morgan suggested was 1 gallon of brine, ¼ to ½ lb. of sugar, ½ oz. of monophosphoric acid, a little spice and sauce to each cwt of meat. (Smith, E, 1873: 36)

Seventeen years after Smith met Morgan at the Society of Arts meeting, in 1871, Yeats reported that a certain “Professor Morgan in Dublin, proposed a method of preservation by injecting into the animal as soon as it is killed, a fluid preparation, consisting, to every hundredweight of meat, of one gallon of brine, half a pound of saltpeter, two pounds of sugar, half an ounce of monophosphoric acid, and a small quantity of spice.” (Yeats, J, 1871: 225)

The plan was widely tested at several factories in South America and by the Admiralty, who had reported that they had good results from the technique. (Yeats, J, 1871: 225, 226) It was in all likelihood the same Morgan that Smith reports on who, by 1871, became a professor in Dublin. Notice, as a matter of interest that he used the same basic brine mix of salt, water, saltpetre, sugar, monophosphoric acid and spices. This, together with the similarity in surname makes it quite certain that Mr Morgan, Dr Morgan and Prof. Morgan is the same person. In itself, this is an example of perseverance! In 1854 his arterial injection was met with scepticism where Yeats reports in 1871 that the Admiralty viewed his improved method.

Was this Morgan’s Invention?

The concept of arterial injection was not new. By the time Morgan demonstrated it to the Society of Arts, on April 13, 1854, it may have been as old as 150 years, used for embalming corpses for the purpose of medical studies. This invention is credited by some to the Dutch physician, Frederik Ruysch (1638 – 1730). He injected a preservative chemical solution, liquor balsamicum, into the blood vessels, but his technique remained largely unknown for some time. (Bremmer, E.; 2014)

British scientists who used arterial injection and from whom Morgan could have learned the system were the Hunter brothers William (1718–1783) and John (1728–1793) and their nephew, Matthew Baillie (1761–1823). The injection was into the femoral arteries. They all injected different oils, mainly oil of turpentine, to which they added Venice turpentine, oil of chamomile, and oil of lavender. Vermillion was used as a dye to create a more life-like skin colour, but would also have added preservation to the final solution. (Bremmer, E.; 2014)

There is a reference from 1837, on an essay delivered on the operation of poisonous agents upon the living body by Mr John Morgan (1797 – 1847), F.L.S Surgeon to Guy’s Hospital. (1837; Works on Medicine) The same publication contains an article by Dr Baillie, M.D. on the morbid anatomy of some of the most important parts of the human body. John Morgan was undoubtedly well familiar with arterial injection. Not only due to the fact that he was a contemporary of Baillie, but he was also a demonstrator of anatomy at the private school near Guy’s Hospital. (livesonline.rcseng.ac.uk/) The late 1830 article that is referenced means that it fits the timeline perfectly for a late 1830 or early 1840 technology transfer for the use of the same general technique of injecting preserving fluids into the meat of a pigs carcass which presumably became stitch pumping, a precursor for Morgans invention.

John Morgan is in all likelihood the father of Dr John Morgan (Circa 1863), who was professor of anatomy at the University of Dublin. A process of arterial injection is described that was used by Dr John Morgan from the University of Dublin. ” John Morgan, a professor of anatomy at the University of Dublin in Ireland, formally established two principles for producing the best embalming results: injection of the solution into the largest artery possible and use of pressure to push the solution through the blood vessels. He also was among the first to make use of a preinjection solution as well as a controlled drainage technique. Morgan’s method required that the body be opened so the heart was visible, then an 8-inch pipe was inserted into the left ventricle or aorta. The pipe was connected to yards of tubing ending in a fluid container hung above the corpse. The force of gravity acting on the liquid above the body would exert about 5 pounds of pressure, adequate to the purpose of permeating the body.” (Wohl, V.) This process described here is applied, not to the preservation of animal carcass, but for embalming a human body! It is, however, the exact same process that he demonstrated years earlier in London to Smith at the Society of the Arts meeting on 13 April related to carcass preservation.

From the process description, it is clear that we have identified Morgan, father of the arterial injection method in meat curing as Dr John Morgan, professor of anatomy at the University of Dublin, son of John Morgan, Surgeon to Guy’s Hospital. The original inventor of the system was the Dutch physician, Frederik Ruysch and the application was embalming.

Henry Denny and the claim of a Return to Dry Salting

No review of curing history will be complete without mentioning the legendary Henry Denny and the equally legendary company founded by him.

From the official website of Henry Denny & Sons.

Ireland in the first half of the 1800s was a fertile field for innovation. An excellent example is found in the person of Henry Denny. Part of his remarkable legacy is a firm that once was the largest bacon producer in Europe, Henry Denny & Sons. Henry was born in Waterford, Ireland in 1790.

Denny started out as a provisioner merchant in Waterford. The first reference to him as a bacon merchant comes to us from 1846. In 1854 he started using ice in bacon curing which allowed him to cure meat all year round like his colleagues in Calne. The bacon he cured was also referred to as mild cured bacon and a patent was granted in 1857 on his process. Like the process invented by C & T Harris, which they called Sweet Cured Bacon, Henry’s process used much less salt. The priority for inventing the first mild cured system, however, goes to William Oake from Ulster whom we know invented this at around the time when Denny had his merchant business or shortly after this and well before Denny entered the pork processing trade.

Henry’s curing system is described in Geocaching where the post seems to be a copy from another work that is unfortunately not referenced and all my attempts to locate the original publication has been in vain. The author describes it as follows: “Until the early 19th century, pork was cured by soaking large chunks of the meat in barrels of brine for weeks. Shelf life was poor, as often as the inside of the chunks did not cure properly, and meat rotted from the inside out. Henry Denny and his youngest son Edward Denny introduced a number of new innovations – he used long flat pieces of meat instead of chunks; and they dispensed with brine in favour of a dry or ‘hard’ cure, sandwiching the meat in layers of dry salt. This produced well cured bacon with a good shelf life and revolutionised Ireland’s meat industry. Irish bacon and hams were soon exported to Britain, Paris, the Americas and India“.

Reference is made to the fact that Denny invented several curing techniques and if the description given is correct, it would be one of several inventions. Taken at face value I doubt the superiority of his system over Oakes invention. It also comes so late in terms of dates that I seriously doubt if this could be the patent that was awarded in 1957. By this time meat injection was already well established which solved the shortcomings of William Oakes invention in his mild cured system of simply filling the curing tanks with brine to diffuse into the meat “naturally.” If this was in fact the patent that was granted in 1857, it would represent a serious step backwards.

The greatest contribution to this review article of Denny is the fact that he acquired a meat curing company in Denmark in 1894. The reference is Lets-Look-Again who also seems to quote an uncredited source. They make a statement that this purchase “introduced Irish meat curing techniques to Denmark.” I have over the years come across several authors who made the same claim that the Irish meat curing system was introduced to Denmark in the late 1800s after an Irish firm acquired a Danish processing company. They never gave the name of the Irish firm in question. The end of the 1800s is, however, the wrong time for the introduction of the Irish system to Denmark. By this time it was already well established in Denmark and the likely transfer of the technology to C & T Harris took place from Denmark either at this time (closing years of the 1800s) or in the opening few years of the 1900s. For this reason, I never used the reference but I was always curious who the Irish firm was, wrongly credited for the transfer of the technology to Denmark. Now I know and for this reason, as well as the widespread nature of the erroneous claim, I include it here.

Denny was undoubtedly a creative man. He is credited with the invention of the pork rasher. Geocaching quotes an unnamed source that “the rasher (a piece of bacon to be cooked quickly or rashed) was reportedly invented in 1820 by Henry Denny, a Waterford butcher who patented several bacon curing techniques still used to this day.” It must be mentioned that Denny’s career only started in 1820 but that was not as a butcher. It was as a merchant and he entered the pork processing business only in 1854. There could still be credibility to the claim which I base on the widespread nature of the story in Ireland. Maybe he was a young man with unusual interest and creativity in selling pork at his trading business. The claim may however be apocryphal.

Related to the inventions of Henry Denny in bacon curing in particular, is there any clue as to what this may have been exactly? It was when I studied the life of another man who claimed to have invented a unique curing system, the Dutch Orthodox Jewish bacon curer Aron Vecht, that I discovered the great contribution to the art of curing made by Denny. One aspect of pork curing that I overlooked for years was the importance of singeing. It is exactly in this area where Henry Denny made his greatest contribution to curing.

Singeing pork was nothing new. Removing the hair off the carcass and retaining the “rind” was done with straws for centuries. The old method is beautifully illustrated by Тихомир Давчев in their set of photos featured below.

Henry Denny automated this process. He re-looked at the process in light of the latest industrialised equipment available. One publication from 1866 describes it as follows. “Each pig is hoisted by the hind leg, it is hooked on to a lever, which suspends the animal head downwards, and its throat is slit with a sharp knife; the blood caught in a receiver flows into an external tank, from whence it is carted away. The leg is then fixed to a hook, which slides on a round iron bar placed overhead on an incline. A push of the hand sends the dead pig with railway speed to the singeing furnace, a distance of 30 to 50 feet. Here it is taken by a crane, placed on a tramway, and run into the furnace, where the flame impinges on it, and in a moment all the hair is removed. The carcass is re-hooked by the leg, passes into another room, where it is disembowelled, the entrails being transferred to an underground region or be dealt with. The head is next removed, and then the backbone is cut out, thus dividing the carcass into two flitches, which pass, suspended on the round bars and without handling, into the cooling room, where it hangs until the meat is firm.” (Fraser’s Magazine for Town and Country, Vol. LXXIV July to December 1866) 

Molander (1985)

His fame was in the first place due to his invention of the automated process of pork singeing. He may have, of course, also called his process “mild cured” as with the aid of refrigeration he would have obtained the same result as did William Oake who actually invented the original mild cured process.

Was this disingenuous for him to also have called it “mild cured”? I think not. It illustrates the inherent problem in using the result of the process (i.e. milder bacon) as the name of your product. If the result is the same but a different process was used to arrive at it, how would the consumer know (or care)! From a trademark perspective, it makes it tricky since the words seem to be difficult to protect as it would be the general way people would refer to the bacon, not heavily salted. It is like trying to trademark the phrase “well cooked.”

The Dutch Orthodox Jew, Aron Vecht and His Secret Curing System

If we have spoken about Henry Denny, we most certainly have to stop for a minute and look at Aron Vecht who essentially copied the system of Denny and passed it on as his own invention.

Dr James Anderson told me in New Zealand that Vecht claims that worldwide “only five firms possessed the right to use [his secret]’ one of which was his own, the London based Inter-Marine Supply Company. This means that William Oake’s company, Oake-Woods in Dorset was by far the most widely used curing system under a patent of the time. Still, what Vecht created was impressive.

Vecht took out patents in 1894 in New Zealand related to the singeing of pigs and the preservation of meat. His method of preservation was called the “Vecht Mild Cure Process.” He masterfully tied the patent was tied to his own bacon brand, York Castle. The patents were presumably owned by his business in New Zealand which he had with William Stokes called the Christ Church Meat Company, Ltd.

From a lawsuit following his death related to the York Castle trademark in New South Wales, Australia, we get insight into how he managed his intellectual property. The trademark and his secret method of curing went hand-in-hand. Only the Vecht Mild Cure Process could be used to produce the York Castle brand of bacon. Vecht would receive monetary compensation for every pig so cured in a territory.

When refrigeration was introduced into international trade, its impact on meat quality was an unknown. People opted for the less harsh conditions of chilling temperatures and tried to avoid freezing the meat. A drawback of mild cured bacon is that it did not last on long sea voyages under chilled conditions. The English market has, by the time Aron Vecht arrived on the scene, became used to mild cured bacon as opposed to heavy salted which was the kind of meat produced under the Rapid Cure process of Robert Davison. An attempt was made to use the sea voyage for the curing to take place and to pack the pork on ice. Famously the Harris brothers of Calne was involved in exactly this scheme. The Waikato Argus who reported on this in 1901 said that the lowering of the temperature below 32o Fahrenheit (0o C) has ‘invariably faded the flash into a pale, unpleasant colour and alienated the affections of the British matron.” What I think they meant was that lowering it to 0o C was ineffective in securing a good product that would arrive in London. At chilling schilling temperatures, when the meat has not been heated through hot smoking, the curing colour, resulting from the effect of nitric oxide on the meat proteins, giving it a bright pinkish/ reddish appearance would be reversed. If, however, the meat is frozen, such reversal would not take place. The meat would then be smoked when it arrived at its destination and the colour would be “fixed” through the unfolding of the proteins.

The Waikato Argus reported on this progression by Vecht as follows: “Now, however, by what may be called a triumph of transit and cure, a most promising and important trade has begun between New Zealand and England. By employing the Vecht curing process, a New Zealand firm is shipping pigs from that distant colony, placing them in refrigerators with a temperature of 20o Fahrenheit (-6o C), and curing them here on the banks of the Thames with apparently perfect success.

It was not well understood at the time and it was incorrectly believed that the method of sterilisation of the meat which was part of the Vecht process was responsible for preventing the cured colour from fading. What is true is not that it would have prevented the cured colour from fading, but that it would have stopped bacterial and enzymatic action which spoiled the meat and degraded the meat quality and this would undoubtedly also have affected the meat colour, even though it was by no means the only reason why the colour faded.

The article reported on this as follows. “This success is obtained by first treating the carcase*, before they leave New Zealand, by the Vecht curing process, which allays the action of the cold, and so sterilises the flesh as to prevent the changes which have hitherto interfered with the successful curing at Home of what is grown abroad.”

The Waikato Argus which we quoted above related to the use of temperature and the curing of meat made also provides us with another very valuable bit of information related to the trading of bacon cured with the Vecht method. It reported that “Messrs Trengrouse and Co., who are colonial shippers on a huge scale and the British agents of Armours, of Chicago, are encouraging this new process, and prophesy for it a vast influence on the bacon trade.” The mention of the agents of the legendary firm of Phil Armour is of extreme interest as is the link between Armour’s company and the propagation of Vecht’s method of curing. Armour was the pioneer of freezer technology for the distribution of meat in America and owned probably the largest curing works in Chicago in the world. Vecht was an expert in the refrigeration of meat in particular. Phil Armour was carefully plotting his way to introduce sodium nitrite directly as a curing brine but not wanting to be left out of the huge and lucrative international bacon trade, must have seen Vecht as a brilliant ally to secure bacon for his own trade while avoiding the expensive curing systems such as Auto Cure which Armour knew would be replaced by the direct addition of nitrite to curing brines.

– Messrs Trengrouse and Co

I told you that the one interesting aspect about Vecht was his method of curing. I referred you to the Waikato Argus which did an article on his life from where we got the all-important information on the temperature during the shipment of the meat. The same article mentions that Vecht’s products were sold through the firm of Messrs Trengrouse and Co.. They are described as colonial shippers on a huge scale and the British agents of the Armour Packing Company from Chicago, who are encouraging his new process. This brings us to the next fascinating aspect of this remarkable man’s life namely his link to the legendary provisions and general commission merchants of Messrs Trengrouse and Co.

The firm was officially called Trengrouse, H & Co., and was described as “Provision Agents and General Commission Merchants” Their address was 51, 55, Tooley Street, London, S.E. The firm was established in 1875 by Henry Trengrouse and his brother, who retired in 1908. They had agents in Liverpool, Manchester, Bristol, Cardiff, Melbourne, Sydney, Brisbane, Dunedin, (N.Z.), Monte Video, Buenos Ayres and they specialised in butter, cheese, bacon, eggs and canned goods. They claim to have pioneered the trade in New Zealand and Australia in dairy products. Most importantly for our purposes is that they were the agents for Armour & Co. from Chicago and by 1914 they have been Armour’s agents for upwards of thirty years. (1914 Who’s Who in Business) This means that Phil Armour probably set them up himself and dealt directly with them. Phil passed away at the turn of the century.

The grandfather Henery Trengrouse after whom he was named was a legendary figure in his own right. He devoted his life to the invention of a number of methods to improve safety aboard ships after he witnessed the sinking of a ship with a tragic loss of life close to his home town when he was a young man. (5) Adventure and perseverance ran in the family and, I am sure, accounted for their success in no small way!

– International Bacon War: Quest for Supremacy

I thought it important to deal with Vecht, Trengrouse and Denny in relation to each other since it speaks to the state of international competitiveness of the newly emerging superpower of the United States relative to the diminishing influence of England. We must not lose sight of the fact that Vecht’s process was a short-lived attempt by the Dutch (Vecht) and the Americans (Armour) to wrestle away control of the international bacon market from the British.

Over the years I have always wondered why Phil Armour did not try and assert his influence on the lucrative bacon trade not just through exports to Britain (which they did on a large scale), but in the international bacon trade. I never came across them in almost 10 years of research apart from sending bacon from the USA to England. This all changed with the mail from Dr Anderson and looking into the life and career of Vecht.

I speculate that their agents found an ideal ally in the Dutch curer, Aron Vecht. Vecht combined several known (and patented) curing processes, created his own version of mild cure, ostensibly predicated upon the use of refrigeration and an invention by the Irish firm of Henry Denny which automated the singeing process of the carcass. I suspect his allegiance with Armour either led him to become an expert in the newly developing art of refrigeration or he was already interested in this before he came into contact with the Armour Meatpacking company in Chicago. His curing process would have suited Armour in that it was far less capital intensive than Dorset based firm of Oake-Wood’s autocue and despite not being as fast in curing as was accomplished with the autocue equipment, it was a progression on the mild curing process of the inventor of the original process, William Oake, father of the Oake who was a partner in Oake-Woods.

The link with a unique bacon brand is a stroke of genius and something, I am sure, that was carefully deliberated. Before this time, bacon was differentiated by the particular method of curing. As I explained at the start, these would have been dry-cured, sweet cured, mild cured, pale dried or auto cured. There is evidence of Harris going after people using the name “pale dried bacon” but the advent of refrigeration, effectively levelled the playing field as many options became available to produce bacon with far less salt than was traditionally done under the dry-cured system.

Another very important point about Armour must be made. A few years ago, I came across a reference to a secret trial in the use of sodium nitrite done at a packing plant in Chicago. The year was 1905. This was done before its use was legal in any country on earth. I speculated that it was carried out by Phil Armour as very few people would have had the audacity to have tried it. I reported on this experiment in an article and shortly after this all references to it were removed from the publications I cited and I could not get hold of the source documents. I know the author of the article where this reference appeared. He is a prominent person in a leading role in European meat curing circles and I understand why this reference was removed.

This is pure speculation on my part, but it has a tone of credibility. I think that Armour or Armour with the key meatpackers in Chicago of Gustav Swift, and Edward Morris jointly performed the trial. I wrote extensively about this in The Direct Addition of Nitrites to Curing Brines – The Spoils of War. The experiment would have been spectacularly successful and I believe was done on the back of experiments done in German agricultural research centres for years before 1905.

With them having known about the work on nitrites, I believe the process of Vecht suited Armour well as a kind of a “placeholder” without engaging a firm like Oake-Woods and locking them into the Auto Curing system which was the leading system internationally at the time as far as it being patentable and indeed, it was the most widely used international patented system of the late 1800s and early 1900s.

There is an “air” of the thinking of Armour, Swift and Morris in the preamble to a meat science group formed by them, also in the early 1900s where their mission was stated as being “to reduce steers to beef and hogs to pork in the quickest, most economical and the most serviceable manner.” The process they had in mind here was nitrite curing.

It was a key turning point in the history of curing and the Americans spectacularly took the lead when, following the first world war, Griffith, the American Chicago-based company became the evangelists of the direct addition of nitrite to curing brines, a riveting saga which I uncovered and wrote extensively about in the article which I just now sited. So, anticipating what is to come in the direct addition of nitrites to curing brines, there would have been no point in investing in any of the “indirect curing processes” of the English, Danes or the Dutch. There is evidence that the Chicago meatpackers were preparing for this curing revolution for a number of years and the Griffith Laboratories was an important participant who had to be ready to handle the PR of what was to come. They have undoubtedly taken careful note of public perception related to nitrites and had to be careful how they introduce the matter to the public. Besides this, they had to ensure that using nitrites directly in meat curing was legalised. All this were carefully orchestrated and it completely explains why they never fully committed to curing systems that dominated through the rest of the world prior to 1905. Supporting the Vecht system would have been a perfect “placeholder.”

Was the use of the curing technique of Vecht as deliberate as I present it here? I suspect it but have no direct evidence to that effect. Is it a likely scenario, taking the full spectrum of information from that time into account? I believe so! At least it warrants keeping the possibility in mind as we progress our efforts to understand the grand story of the development of bacon!

Drying and Smoking of Bacon

Another aspect of bacon processing that we have not considered thus far is the drying and smoking of bacon. The oldest reference I can find of the smoking of bacon is a statement by the Scottish farmer, Robert Henderson that he created his own very simple design for a smokehouse in 1791. (Robert Henderson and the Invention of the Smokehouse) What is interesting about his account is that it deals with the establishment of the pork trade in Scotland.

Henderson recalls that in 1766 pigs were brought into Annandale in Scotland for the first time. Farmers bought them more out of curiosity than to make a profit. The pigs were small with bristles on their back. Between 1775 and 1780 both bacon flitches and hams became a considerable trade in this part of Scotland. By 1790 the pork trade was well established with buyers travelling throughout the region to buy pigs. Several markets were established for pigs. One such market was established at Dumfries where the Annadale curers meet the Galloway farmers. Events allowed Robert a birds-eye view on the birth of an industry!

Robert Henderson was a formidable pork trader. He distributed the carcasses among the farmers to dry and smoke them in the farmhouses. In one season he would cure no less than 500 animals in this way. He wrote, “I practised for many years the custom of carting my flitches and hams through the country to farm-houses and used to hang them in their chimneys and other parts of the house to dry, some seasons to the amount of 500 carcases.”

The system was accompanied by many difficulties. For starters, he often had to provide his own wood for hanging the flitches and hams on. This was only the start of the trouble. He wrote, “for several days after they were hung up, they poured down salt and brine upon the women’s caps, and now and then a ham would fall down and break a spinning wheel, or knock down some of the children; which obliged me to resort to the shop to purchase a few ribbons, tobacco, &c. to make up peace.”

The biggest problem of this system is related to weight loss. Henderson wrote, “there was a still greater disadvantage attending this mode; the bacon was obliged to hang until an order came for it to be sent off, which being at the end of two or three months, and often longer, the meat was overdried in most places and consequently lost a good deal of weight.”

In 1811 Henderson noted that this was still the way that bacon was cured in large quantities in Dumfriesshire. He lamented the fact that people are slow to abandon old ways of doing things in favour of better alternatives.

Robert Henderson claims that twenty years earlier, in 1791, he designed a simple, dedicated smokehouse for smoking hams and bacon. This simple statement would become my earliest reference to a smokehouse. He describes it as being twenty feet square (1.8m2) with the walls about seven feet (2.1m) high. Each wall allowed for 6 joints. Twenty-four flitches can be hung together in a row without them touching. Each one of the flitches was resting on a beam. There are five rows, allowing for a total of 120 flitches in the smokehouse. The flitches were hung between 21/2 to 3 feet (900mm) from the floor which is covered with sawdust of five or six inches (100 to 150mm), kindled at two different sides. (Henderson, 1811)

The door is kept closed with a small hole in the roof for ventilation. Bacon and hams smoked in this smokehouse were ready for dispatch within eight to ten days. An advantage of this system is that there is only a little loss in weight. (Henderson, 1811)

So, the system was that the bacon was kept in the salt-house till an order is received. At this point, it was moved to the smokehouse for drying and smoking before it was dispatched to the client. (Henderson, 1811)

During this time, the invention of the smokehouse by Robert Henderson had a dramatic impact on the quality of the bacon. One of the consequences of too much drying is very salty meat since water escapes, but salt is left in the meat.

This invention was “in the air” already since Henderson’s 1791 invention of the smokehouse. Losing weight results in more salty bacon as a large weight loss reduce the volume of meat to salt, making the remaining meat saltier. Smoking, at this time, was exclusively cold smoke.

Apart from better-tasting bacon, there was a significant reduction in cost. Henderson wrote that he “found the smoke-house to be a great saving, not only in the expense and trouble of employing men to cart and hang it through the country, but it did not lose nearly so much weight by this process.”

It is extremely unlikely that Robert Henderson was the first or only person who did away with the farmhouse-drying/ smoking of hams and bacon and opted for a built-for-purpose smokehouse. The following hundred years would see a plethora of ideas being shared and taken up by various companies and individuals, many claiming priority for their invention or progression. It is possible to get close to the people who pioneered these different progressions based on the dates for their inventions but if we are ever able to identify the very first person related to each invention is highly unlikely. It is, however, fascinating how close we can get to the first instance of an invention or progression.

It is interesting that the 1791 reference of Henderson (when he first designed his smokehouse) is still the earliest reference we can find anywhere to smokehouses. Following the indirect reference of Henderson, the next reference I was able to find was a 1796 reference to a smokehouse being part of an estate for sale. (The Philadelphia Inquirer1796) Several advertisements for properties in Pennsylvania with smokehouses on occurred in the 1790s and into the early 1800s. There is an 1813 reference to a smokehouse by a reader who complains that his measures against insects are not working. (Buffalo Gazette, 1813)

An 1820 account from Newbern Sentinel (New Bern, North Carolina), 1820 is my first reference where smoking and drying are specifically separated.

The author elaborates on the experience of his teacher who warned him about damp which leads to bitter-tasting bacon. He uses an interesting phrase to describe Mr A of Baltimore namely a man who “followed smoking for gain.” He is therefore squarely set in a commercial mindset.

The author continues. “one good fire per diem will smoke the pieces exactly in the same time they were salted viz. hams 4 weeks, shoulders 3 weeks, other pieces in two. When the bacon is smoked and all returned to the smokehouse, a floor, if not laid before should now be laid on the joist; by this means rats will be prevented from descending on the bacon, and the heat of the sun will be moderate so that the bacon will not drip in the summer heats. Darkness and coolness are necessary to preserve the bacon from flies – it may there hang in perfect safety till wanted!” (Newbern Sentinel (New Bern, North Carolina), 1820)

The fact that smokehouses were a new progression in the 1840s is seen from a newspaper report from Northern Ireland in 1841. The article points out that due to the misconstruction of the smokehouse and because the surface of the meat is not properly wiped dry and there is still saline matter on the outside of the meat, these cause the meat not to dry out but remain moist. Because of this a “pyroligneous acid taste and smell” is left on the meat.

The author gives the requirements for a good smokehouse:

  • it should be perfectly dry;
  • not warmed by the fire that makes the smoke;
  • the fire shall be sufficiently far from the meat so that any vapour from the smoke shall be “thrown off” and may be condensed before reaching the meat;
  • yet, close enough to prevent flies, mice, etc from feasting on the meat.

The art of building a proper smokehouse was still being disseminated through the British Isles by 1841. Not only in Britain but also in Germany smokehouses were not universally used to smoke bacon. The same article refers to smoking meat in Westphalia. Smoking Westphalia hams was done at this time in “extensive chambers in the upper stories of high buildings, some of four or five stories.”

In the constructions in Westphalia, the fire was made in the cellar and the smoke directed to the meat through pipes in which the heat was absorbed and the moisture removed. The smoke was dry and cool when it came into contact with the meat. The meat is, in this way, perfectly dried and had a flavour and a colour far superior to meat smoked in the “common method.” (Belfast News-Letter, 1841) Westphalian bacon and hams were notorious for what was later referred to as cold smoking. For a detailed discussion on this, see Westphalia Bacon and Ham & the Empress of Russia’s Brine: Pre-cursers to Mild Cured Bacon.

The strict aversion to heat of any kind in the smokehouse would not last and subsequent authors and experts found that a bit of heat produces a better environment for drying (less moist).

There is a reference from Lancaster Intelligencer (Lancaster, Pennsylvania), 1833 which states that during smoking the smokehouse should be warm but after smoking, it should be cool and dark. This “heating” of the smokehouse is an interesting reference and was by no means universally practised as we saw from the construction of the smokehouses as described from Westphalia. Another report from 1840 states that the smokehouse should be of a moderate temperature. The purpose is given as it will prevent dampness on the meat. (New England Farmer, 1840)

The Harris operation would progress this concept years later when they invented pale dried bacon where the bacon is dried in specially constructed ovens but not smoked (Harris Bacon – From Pale Dried to Tank Curing!)

– Smokehouse as the Storeroom for Finished Bacon

One system of storing the bacon was to keep it in the salt house till its sold. Then, smoke it and dispatch it to the client. Another system was to use the smokehouse as the storeroom for finished bacon. The system described in Winchester, Tennessee in 1856 calls for the bacon to be removed from the curing vats and the salt to be scraped off. Rub the bacon all over with hickory ash and hang it up for smoking, hock down. Smoke moderately for four weeks with only two fires a day made from hickory chips. On about the 1st of March, take them down, rub them with hickory ash again and hang them again. Here they remain the whole year. It makes an interesting comment that if little green mould appears on the outside of the bacon, it only insures against spoilage. (The Home Journal (Winchester, Tennessee)1856)

The hams and bacon can be wrapped in cotton bags for storage during the summer. Before use, dip the bag in strong salt brines to protect against insects. The next season, while bacon and hams are being smoked, hang the cotton bags in the middle of the smokehouse. The smoke will preserve the cotton.

During the summer, the bacon should not be hung against the roof, due to the heat, but in the middle of the smokehouse where it is cooler. The smokehouse should be dark and in the summer the ventilation holes must be closed to keep insects and rodents out.

– Was this customary in Wiltshire in the 1840s?

In asking this question, we look one more time at the possible nature of sweet cured bacon invented by Harris in the 1840s. (Sweet Cured Harris Bacon) An article from the Yorkshire Herald and the York Herald (1840) reports on the following method of curing used in Hants, Wilts, and Somerset.

The pork is singed by packing straw around the carcass and burning the bristles and hair off. Scalding tends to soften the meat and this method ensures the meat is left firm. The carcass is left to cool after which it is cut into flitches and salted and treated with saltpetre. The flitches are left for two to three weeks and turned three to four times. They are then wiped dry and suspended over a chimney over a wood or turf fire to dry out. A note is made that coarse sugar is used in Hampshire bacon but not in Wilts and Somerset. Hampshire bacon is imported with its particular flavour by the wood and turf smoke. During smoking, the flitches must be taken down and inspected for bacon-fly.

The 1840 newspaper report does not claim to be exhaustive, but it nevertheless creates the picture of a simple non-industrialised process and most certainly there is no mention of a dedicated smokehouse or salt house. In a dedicated butchers shop, as was run by the Harris family, one would expect a smokehouse and a curing room.

– Comparisons with William Oake’s Mild Cured System

We dealt with the mild cured system of William Oake in great detail (Mild Cured Bacon) and since he invented what later became known as tank curing, it is important that we reference his system again.

The first major difference with what we have seen so far relates to drying. Instead of hanging the bacon to dry, Oake used pressure when he re-stacked the flitches after curing, on a dry floor. The weight of the bacon is incrementally increased as the flitches are re-stacks with the ones at the bottom now on the top and by stacking them higher and higher every time it is restacked while always rotating the position of the meat pieces.

Oake called for a quick smoking of the bacon. According to his system between twenty-four and forty-eight hours will suffice to properly smoke the bacon if the weather is suitable, after which it may be packed and forwarded to market.” His smokehouse design is in line with what we have looked at thus far. He also used cold smoke.

Pale Dried Bacon and Wiltshire Cure or Tank Cured Bacon

The next major development in curing also came from C & T Harris (Calne). Pale Dried Bacon was invented by them just before they adopted tank curing. It was invented under John Harris in Calne in the 1890s. It is basically the same as Sweet Cured Bacon but instead of hot smoking the bacon, it was dried in special drying rooms and not smoked. The bacon was therefore pale on the outside of the flitches but it was properly dried. From there the name Pale Dried Bacon.

It was just after this, at the closing years of the 1800s or the very first few years of the 1900s that tank curing technology was transferred from Denmark to Calne in Wiltshire. The technology of mild cured bacon of Oake, invented in Ireland, adopted by the Danes finally spread to Calne, Wiltshire and became the famous British Wiltshire bacon curing or Tank curing in the closing years of the 1800s or early 1900s. For a detailed discussion, please refer to Chapter 10.06: Harris Bacon – From Pale Dried to Tank Curing!

Wet-curing in combination with injection (brine cure – with pumping)

stitch injection elmswell-bacon-factory

The first cooperative bacon curing company was started in Denmark in 1887. It was seven years after the visit to Waterford in Ireland in 1880 “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)

It means that the Danes had the technology and when the impetus was there, they used the technology. The impetus, as we already said, was the outbreak of swine flu which saw a ban on Danish pork. They had no choice but to change their export from live pigs to bacon. The detailed description of Oakes invention and his process came to me through an Australian publication from 1889. It means that Ireland not only exported the mild cure or tank curing technology to Denmark but also to Australia, probably through Irish immigrants 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. A report is given in 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. Apart from giving the complete system as invented by Oake and crediting him for the invention, it also sites one company who used the same brine for 16 years by 1897/ 1898 which takes tank curing in Australia to well before 1880 which correlates with the theory that immigrants brought the technology to Australia in the 1850s or 1860s.

One further note about the invention of tank curing by Oake from Ireland. He 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. Morgan’s work, already cited in great detail here, shows clearly that curing brine was a priority in Ireland in the mid-1800s. The possibility that Oake and Morgan interacted and possibly influenced each other is a tantalizing likelihood that emerges from the data.

founders

The original founders of the St. Edmunds Bacon Factory are shown in this old print of the laying of the factory’s foundation stone in 1911.

It was Denmark, however, who continued to expand on the tank curing system or mild cured system, as it was called, using a combination of stitch pumping and curing the meat in curing tanks with a cover brine.  (Wilson, W, 2005:  219) Brine consisting of nitrate, salt and sugar were injected into the meat with a single needle attached to a hand pump (stitch pumping). Stitch pumping was either developed by Morgan, whom we looked at earlier or became the forerunner of arterial injection which is solely credited to Morgan.

The meat was then placed in a mother brine mix consisting of old, used brine and new brine. The old brine contained the nitrate which was reduced through bacterial action into nitrite. It was the nitrite that was responsible for the quick curing of the meat. 

The Auto Cure System and the legendary Oak Woods & Co. Ltd. Bacon Curer

The auto cure system is an excellent example of the fact that the power of the used brine was known and who else to have invented it than the son of the man who pioneered the live brine system, namely Willaim Oake! 

William Horwood Oake set his curing operation up in Gillingham, Dorset with partners. It eventually became the famous Oak’ Woods & Co Ltd. Oake invented the system in which was eventually in use in England, Sweden, Denmark, and Canada. William Harwood Oake passed away on 28 September 1889 in his late 40s and Evan R Down took over the running of the company. There is a report that they exported their technology to New Zealand and South Africa also. They patented it around the world and licenced its use to companies in different countries. Down became the driving force for the international expansion on the back of solid patents. The Danes paid a £4,000 annual royalty for the use of the system which was probably applied in many factories across Denmark. They became the premium representation of Wiltshire bacon meaning the curing of whole bacon sides.

The process is as follows. The pig is slaughtered in the usual way and the sides trimmed and chilled. After chilling, it is laid out in rows on a sort of truck that exactly fits into a large cylinder of steel 32 feet long, 6 feet in diameter and which will hold altogether 210 sides. When the cylinder is filled, the lid, weighing 3 ½ tons (7000lb. Danish) is closed and hermetically sealed by means of hydraulic pumps at a pressure of 3 tons to the square inch.

A vacuum pump now pumps all the air out which creates a vacuum of 28 inches. It takes about an hour to pump all the air out. The brine channel which leads to the brine reservoir, holding around 6000 gallons of brine is now opened. The brine rush into the chamber and as soon as the bit of air that also entered has been extracted again, the curing starts.  It happens as follows.

The brine enters the cylinder at a pressure of 120 lbs. per square inch. It now takes between 4 and 5 hours for the brine to enter the meat completely through the pores which have been opened under an immense vacuum. When it’s done, the brine runs back into the reservoir. It is filtered and strengthened and used again.

An advantage of the system is given that the bacon can then be shipped overseas immediately. The time for the total process is around three days. On day 1 the pig can be killed, salted on day 2 and packed and shipped on day 3.

There are two brine reservoirs. The one is used with a stitch pump to inject brine into the sides as usual before they are placed in the cylinder and the second tank is used. The largest benefit of this system is the speed of curing and many people report that the keeping quality of the bacon and the taste is not the same as bacon cured in the traditional way.

For a full discussion on the father-son due of William and William Horwood Oake and their inventions, see William and William Horwood Oake.

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American Rapid Curing

Auto Curing was, however only a progression of the Rapid Curing system developed in Americ.

Clues as to the possible origin of the American report comes to us from an 1848 report in the Sydney Morning Herald. The author begins his explanation of a certain American curing system with an interesting statement. He says that “they (we) desire considerable satisfaction in promulgating the discoveries and inventions of our fellow labourers in the field of science, no matter whether they be transmitted to us from the shores of the Neva or the banks of the Mississippi, and we, therefore, hasten to lay before our agricultural friends an important American invention, which promises to with the greatest benefit in a particular branch of domestic economy, as well as in a commercial point of view, and which we are certain requires only to be generally known to be usually adopted.” (Sydney Morning Herald, 1848) In this, the author is completely right that adopting and adapting inventions are for the most part not very difficult. It clues us into something of the possibility that Auto Curing may well be an improvement of an American invention.

The author then turns his attention to a certain Mr Davison. Setting the 1848 report in the Sydney Morning Herald aside for a moment, we see if we can find evidence of who this Mr Davison was. A stunning description is given by Paul (1868) who records that Mr. Robert Davison attended the food committee meeting as a member of the Institution of Civil Engineers, in order to give information on the subject of desiccation as a preservative process which he studied since 1843. So, here we have Mr Davison’s first name given as Robert. He was an engineer by profession and he has been studying preservation since 1843. It definitely looks like the right man!

Paul (1868) gives us more information. He was not originally from the USA, but resided in London. He writes that Robert was of No. 33, Mark Lane, in the City of London, Civil Engineer, and James Scott Horrocks, of Heaton Norris, in the County of Lancaster, registered a patent for improvements in the means of conveying and distributing or separating granular and other substances.” The patent was sealed.

Paul then explains the basis of Roberts method of preservation being through heated air and using the newly emerging science of creating a vacuum. “The importance of hot blast had been discovered in the melting of metals, and it occurred to him that impelled currents of hot air might be advantageously applied to other processes of manufacture, especially as a purifying and desiccating process. In reference to its application to the purification of brewers’ casks, the question arose, in the first instance, as to the effect it would have upon the strength of the wood.” Here we pick up the similarities of Oake’s Auto Cure system with treating wood. “He (Robert) experimented on the subject and found that, so far from deteriorating the wood, it gave increased strength to it to a large extent. He saw that impelled currents of hot air were a valuable thing that had been overlooked, and he then turned his attention to the desiccation (the preservation of food by removing moisture) of vegetable and animal substances.

The key first observation is that his interest was in the removal of moisture and the application of heated air. You may very well wonder how on earth he brought those two together, but hang on. He did it in an interesting way. Paul (1868) writes that “he was successful in the first instance in desiccating potatoes and other table vegetables, which were preserved for a very long time; and he afterwards operated upon a quantity of rump steaks, and by depriving them of all their moisture, they were preserved in a perfectly sweet and wholesome condition for several months.” So far it sounds like standard drying and hot air would not be required. In fact, any air velocity would aid the evaporation process as is done today with fans, for example, in producing biltong. But using hot air which is moved around sounds very similar to what we use in smoking/ drying cabinets today where the air is indeed wam.

For all South African biltong lovers and American Jerky fans, he reveals something extraordinary. Paul (1868) writes that “at the time he was engaged in these experiments an intelligent young man, brother-in-law to Dr Livingstone. . .” Dr Livingston was of course the famous African explorer missionary who resided at the Cape for some time and laboured mostly in Botswana. He had an intimate knowledge of indigenous drying practices and the value of salt.

Paul (1868) continues describing the relationship with the brother-in-law of Livingston and Robert. He does not focus on information about the indigenous practice from Southern Africa but from North America, even though I am absolutely certain that he would have informed Robert about the drying techniques in Southern Africa also. He mentions that Livingston’s brother-in-law was “then his pupil, mentioned to him that he was doing by an artificial process precisely what the North American Indians did with their buffalo meat and venison by the natural heat of the sun in preserving their provisions, and at the same time, he gave him an extract from Catlin’s work on the subject. The Indian method of drying their meat was to cut it up into thin strips, which were hung upon the branches of trees for several days in the heat of the sun. The moisture was entirely evaporated. The meat was then stowed away, and would keep good for years. Salt they never used, notwithstanding the country abounded with it. What the Indians did by natural means, he did by artificial, by the employment of impelled currents of heated air. He cooked some of the steaks desiccated by this process three or four years after they had been operated upon, and they were perfectly good and retained their flavour. After it had been soaked in water the meat recovered nearly its original bulk. In the process of desiccation, nothing but the water was removed, the albumen being all retained in the meat.” (Paul, 1868)

Take special note of his views on the nature of what causes spoilage in meat and vegetables. “By depriving them of all their moisture, they were preserved in a perfectly sweet and wholesome condition for several months.” Mr. Davison said that “he had not entertained the idea of preparing meat in this way (through drying) for the tables of the gentry, but his idea was to have the meat cut into thin slices, thoroughly dried, and packed away for use as we should biscuits. In this way, he thought an excellent article of food might be prepared for shipping purposes, and for the poorer classes.” Not just is it clear that he targeted the moisture of the meat but also his method of work required cutting the meat into smaller cuts and inserting it into the apparatus manually which is similar to what the Indians (and the tribes of Southern Africa) did in cutting the meat into strips before hanging it.

“Mr Davison remarked that three or four years ago an article appeared in the Times, expressing a hope that some plan would be devised for desiccating meat in a better manner than had hitherto been done. The results of the process he had described were decidedly superior to any charqui (drying of meat) that he had seen. He had long since parted with the last portion of the steaks he had experimented upon. The apparatus for desiccation was at present largely in use for other purposes, such as the seasoning of wood, the purifying of casks, &c. It was extensively used for the former purpose in the royal dockyards. He had no doubt he should be able to make the experiment for the satisfaction of the Committee and should have great pleasure in doing so at the earliest opportunity. The heat of the air in his experiments was 180°, but he believed the desiccation would be effected equally well at a temperature of 120°, when the albumen would not be coagulated.”

Let’s now park Davison’s views of preservation which we know he worked on since 1843 for a minute and return to the Sydney Morning Herald’s 1848 article. Davison is described as, “prior to his present occupation, was long connected with the manufacture of salt.” We also learn that he resided in South America for a time, in a country “with greater capacities for the production of the hog and the ox” and his attention was turned to the preservation of meat. Mr Davison drew upon his knowledge of salt and after much investigation invented a method of curing which will sound very familiar to us. He is described as possessing an “inventive genius,” well educated and assisted in the matter of science by Dr Lardner, “whom he consulted upon his arrival in the United States.” (Sydney Morning Herald, 1848)

So, we learn that he did travel to the United States and there he solicited the assistance of a certain Dr Lardner. He was an authority on the subject of steam engines and the application of steam in industry.

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From William Douglas & Sons Limited, 1901, Douglas’s Encyclopedia, University of Leeds. Library.

Peters (1846) describes the system as follows: “The apparatus is very simple, consisting of a cylinder made airtight. It has a “mouthpiece” through which meat is loaded into the machine and closed with a lid that is screwed onto the machine. The lid has two air vents which are opened and closed by screws. Next to the machine is a large wooden vat holding the brine, connected to the machine through a pipe and elevated higher than the cylinder. A lifting pump circulated the brine from the cylinder back to the vat.” I imagine it looking something like the apparatus at the top of the three above which were associated with Auto Curing.

“Meat is cut and placed into the cylinder. Brine is allowed to fill the cylinder which is then closed. Brine is now pumped back into the vat till all the brine is out and a vacuum is formed in the cylinder with the meat pieces in. Blood, air and gasses are thus removed from the meat also. Brine is now run back into the cylinder. The air vents are opened and the liquid brine expels all air from the vessel. As soon as the vessel is full, the air vents are closed again, the brine pumped into the vat again and the meat is left in a vacuum. Again, blood, air and gasses are pumped out. The cycle is repeated. The initial intervals between the cycles are short but eventually, as all the blood, air and gasses have been removed from the meat, the brine is allowed to remain in the cylinder for as long as between 6 and 8 hours. The entire process is completed in about 12 hours.”

It is here where the explanation or the link that Davison found with meat curing and preservation moves from the factual to the fanciful. He believed that the blood, air and gasses in the meat created some kind of a “resisting power” to the brine which had to seep into the meat. The blood had an affinity for the brine and left the meat for brine to fill it. The pressure created by the elevated brine created relative pressure greater than the gasses and air. When the meat is under vacuum, the reporter writes that the meat is “swollen, its fibre distended and pores open and it readily admits the brine even at the pressure of the mere quantity of brine which the cylinder will hold.” One atmosphere was sufficient and where double and triple that was used, it would respectively close and completely close the pores.

So, he abandoned the use of hot air but instead used a vacuum and the pressure of the brine. Whether his explanation is accurate or not, his invention worked. The process cures the meat in hours as opposed to weeks and he patented it. The process is named Rapid Cure.

This means that Mr Davison’s invention or the application of a vacuum and pressure in curing has priority in terms of the Oake Woods invention which is a progression of the Davison invention. In all likelihood, what Ewart refers to in his 1878 publication is the American invention that was widely in use in America. The key object of the invention was the speed of curing and not the production of mild cured bacon as was the case with the Oake Woods patent.

The primary method of obtaining “mild cured bacon” from the USA was through the addition of sugar. Ewart writes that “it should, however, be stated, that American bacon, in its several forms of flitch, roll, and ham, and any of them of small and moderate weights, are also mildly cured in which sugar is in a considerable proportion an ingredient in the curing mixture used; and the article when so prepared is deservedly held in the highest esteem.” (Ewart, 1878)

Ewart also reports the formation of a bluish-green mould upon the flesh-cut portions of the flitches and hams from bacon or ham that are “perfectly cured and becomes thoroughly dried.” He states that the mould “most effectually prevents the rusting of the fat on these parts.” (Ewart, 1878)

It is clear that Aoto Cure for the meat industry is a progression of Rapid Cure, developed by Mr. Robert Davison which had huge success in the USA. Auto Cure quickly developed an impressive list of countries who participated in the technology.

Tank Curing

For a detailed treatment on tank curing or Wiltshire curing, please refer to The Wiltshire Cut.

Denmark was, as it is to this day, one of the largest exporters of pork and bacon to England. The wholesale involvement of the Danes in the English market made it inevitable that a bacon curer from Denmark must have found his way to Calne in Wiltshire and the Harris bacon factories. The tank-cured method, as it became known, was adopted by C & T Harris (Calne). The fact was that it was already in Wiltshire in the company Oake’ Woods & Co. Ltd.. Why it took C & T Harris till the second half of the 1800s to incorporate it into their processes is a good question to which I don’t have the answer yet.

A major advantage of tank curing, as it became known in England, is the speed with which curing is done compared with the dry salt process previously practised. Wet tank-curing is more suited for the industrialisation of bacon curing with the added cost advantage of re-using some of the brine. It allows for the use of even less salt compared to older curing methods. One of the biggest advantages was, however, the increased curing speed as nitrites were used which was already converted from nitrates through bacterial fermentation.

wiltshire injection

The question comes up if we have corroborating evidence that Denmark imported the Irish technology in 1880? Clues to the date of the Danish adaption come to us from newspaper reports about the only independent farmer-owned Pig Factory in Britain of that time, the St. Edmunds Bacon Factory Ltd. in Elmswell. The factory was set up in 1911. According to an article from the East Anglia Life, April 1964, they learned and practised what at first was known as the Danish method of curing bacon and later became known as tank-curing.

A person was sent from the UK to Denmark in 1910 to learn the new Danish Method. (elmswell-history.org.uk) The Danish method involved the Danish cooperative method of pork production founded by Peter Bojsen on 14 July 1887 in Horsens. (Horsensleksikon.dk. Horsens Andelssvineslagteri)

The East Anglia Life report from April 1964, talked about a “new Danish” method. The “new” aspect in 1910 and 1911 was undoubtedly the tank curing method. Another account from England puts the Danish invention of tank curing early in the 1900s. C. & T. Harris from Wiltshire, UK, switched from dry curing to the Danish method during this time. In a private communication between myself and the curator of the Calne Heritage Centre, Susan Boddington, about John Bromham who started working in the Harris factory in 1920 and became assistant to the chief engineer, she writes: “John Bromham wrote his account around 1986, but as he started in the factory in 1920 his memory went back to a time not long after Harris had switched over to this wet cure.” So, late in the 1800s or early in the 1900’s the Danes imported the Irish system and practised tank-curing which was brought to England around 1911. The 1880 date fits this picture well.

It only stands to reason that the power of “old brine” must have been known from early after wet curing and needle injection of brine into meat was invented around the 1850s by Morgan. Before the bacterial mechanism behind the reduction was understood, butchers must have noted that the meat juices coming out of the meat during dry curing had special “curing power.” It was, however, the Irish who took this practical knowledge, undoubtedly combined it with the scientific knowledge of the time and created the commercial process of tank-curing which later became known as Wiltshire cure.

Why the system was brought over from Denmark when William Harwood Oake’s dad invented the system in Ireland remains a very good question. It is almost impossible to speculate on what exactly was happening in the Harris, Oake ‘ Wood & Co Ltd and in the St. Edmunds Bacon Factory Ltd., but I have a suspicion that Oake Wood was completely focused on their auto cure system in the 1890s and early 1900s and other companies were looking for a less expensive and equally efficient system which the Danish tank curing offered them. I can on the one hand understand why competitors were reluctant to buy into the Oake Wood system of auto curing and on the other hand, why Oake ‘ Woods was reluctant to sell it to strong opposition.

What we know for certain is that tank curing undoubtedly developed from the Oake Woods factory in Gillingham, Dorset and “diffused” into Wiltshire. It was probably independently incorporated into the Harris operation as was the case with the St. Edmunds Bacon Factory Ltd who both claim to have received the technology from Denmark.

Multi-Needle Injection and Vacuum Tumbling and The Direct Addison of Nitrites to Curing Brine

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Multi-needle injector, C & T Harris (Calne) Ltd. C 1960

The composition of the brine changed around 1915 by the direct addition of sodium nitrite. For a thorough discussion on this revolutionary development, see,

Where tank curing used the fermented brine which after fermentation contained nitrites, despite the fact that only nitrates were added to the brine to begin with, along with salt and sugar, nitrites became widely available through pharmacies at this time as it was used in treating certain heart related ailments. Nitrites were now being included directly into curing brines, bypassing the fermentation step.

Multi-needle injectors and vacuum tumblers became commonplace in any met curing operation. It is generally accepted that these developments took place in the mid to late 1900s, but an interesting US patent (number 23,141) was awarded to L. M. Schlarb from Allegheny, Pennsylvania on 3 June 1901 directly related to injection and vacuum machines for meat curing.  (Journal of the Society of Chemical Industry; 1902: 269)

The process is described as “injecting brine and carbon dioxide under pressure into the meat by means of suitable needles connected to a tank containing the brine and carbon dioxide, the pressure in the tank being about 2 atmospheres.” The nozzles it talks about maybe the three-needle injectors that were used until the middle of the 1900s and the unique aspect of the patent was the use of brine in conjunction with carbon dioxide. (Journal of the Society of Chemical Industry; 1902: 269)

The next bit is fascinating as it is possibly the earliest recorded date of the use of a vacuum machine in meat processing. The patent is described in a journal article that “the meat is now placed in a vessel from which the air is exhausted, and brine is then allowed to flow in. The meat is allowed to remain in the brine for about 10 hours, and may then be subjected to the action of carbon dioxide under pressure.” If one removes the presence of carbon dioxide, it is then reasonable to assume that a vacuum machine has been in use in one shape or another to facilitate the diffusion of brine into meat, as early as 1901. (Journal of the Society of Chemical Industry; 1902: 269) The process was, however, not new as auto curing was already in use in the second half of the 1800s in many countries across Europe.

Over the next 60 years, the multi-needle injector became bigger, with more needles until the present machines were being produced from the mid-1900s. Tumbling machines, as we know it today has been in use since the early 1970s.

Current Developments

Three major developments are currently taking root across the globe and the last one has the potential to change the way that bacon is being cured. One is a return to fermented brines where a natural carrier of nitrates is used as the start of brine preparations. A starter culture is then added to this “carrier” which will be something like celery powder or beetroot, high in nitrates and specially grown with high nitrate content in the soil. Salt and phosphates, where permitted, are added along with reducing and non-reducing sugar to complete the modern curing brines. This seems like a new curing system, but as we have seen, it is the resurrection of a curing method probably as old as humanity itself. Leafy green vegetables, spices, and many other plants are replete with nitrates and have been used in various forms to cure meat for millennia.

The second important development in commercial curing plants of the last decade is undoubtedly the introduction of what we call the grid system. According to this method, grids or bacon moulds are used to give the bacon a regular shape. The meat is normally wrapped in banking paper or some film before it is placed in the moulds and in one form or the other, an enzyme, Transglutaminase, is added to the product. The main purpose of this is to achieve higher slicing yields, but in reality, it also accounts for lower smoking losses. A detailed treatment of this method can be found at The Best Bacon System on Earth. I am inviting producers who are interested to interact with me on the process as long as developments will be used for our mutual benefit.

The third new development is about to make its entrance onto the bacon curing scene and it is this discovery that makes me particularly excited to be right at the forefront of the investigations and attempts to understand it and commercialise it. It is the use of bacteria that has the ability to oxidise certain nitrogen-containing components in meat to create nitric oxide directly which then cures the meat. Let’s spend some time looking at this development.

Bacterial Fermentation Curing

In a 2017 review, I did on the curing reaction, Reaction Sequence: From nitrite (NO2-) to nitric oxide (NO) and the cooked cured colour, I quoted Morita et al as referenced by Gasasira (2013) who found that nitric oxide (NO) formation in nitrite-free system is achieved from L-arginine due to nitric oxide synthase (NOS) in either Staphylococci or Lactobacilli.  (Gasasira, et al, 2013)  The nitric oxide-producing enzyme in cells is called, nitric oxide synthase (NOS) which converts L-Arginine into L-Citrulline and nitric oxide (NO).

This simple statement opens up the world as far as nitrite-free curing is concerned. I was doing a review of this matter again on the night of 24 June 2022 when the gravity of the work of Morita (1998) on the subject dawned upon me. I re-looked at the 2017 reference I made and thought about the implications. During the last year, I focused my own efforts on an enzymatic solution for the oxidation of nitrogen in L-Arginine by the application of extracted enzymes. The cost of these oxidizing enzymes was however prohibitively expensive and after consulting with Novozymes on the matter I realised that the direction is unfruitful.

For the first time ever I personally considered the use of bacteria to deliver the oxidation and found the species of staphylococcus most likely to be involved in the process. The earliest work on the subject I discovered was indeed Morita (1998), but his work was on low-pH salami. Li (2011) seems to be one of the earliest researchers to have noticed the formation and identification of nitrosylmyoglobin by certain Staphylococcus species in raw meat batters and suggested a potential solution for nitrite substitution in meat products. Again, I noticed that in 2017 already I quoted Møller and Skibsted (2001) who observed that “Parma ham is traditionally produced using only sodium chloride without the addition of nitrate or nitrite and develops a deep red colour, which is stable also on exposure to air. The identity of the pigment of Parma ham has not been established, but bacterial activity has been explored as responsible for transformation into nitrosylated heme pigments.  In one study, the stability of the pigment isolated from two different types of dry-cured ham (made with or without nitrite) was compared to that of the NO derivative of myoglobin formed by bacterial activity. Heme pigment from Parma ham made without nitrite was more stable against oxidation than the pigment from dry-cured ham with added nitrite.” (Møller and Skibsted, 2001)

They observed that “Heme pigments extracted from Parma ham and a bacterial (Staphylococcus xylosus) formed NO-heme derivative had similar spectral characteristics (UV/ vis spectra and ESR). ESR spectroscopy of heme pigment isolated from salami inoculated with bacteria had NO in a predominant pentacoordinate NOheme environment, whereas MbFeIINO, formed from nitrite and ascorbate, exclusively showed hexacoordinated iron, a difference which could be due to the decrease in pH during fermentation.”  (Møller and Skibsted, 2001)

Ras (2017) found evidence for Nitric Oxide Synthase Activity in Staphylococcus xylosus Mediating Nitrosoheme Formation.  

In Europe, Commission Regulation [EU], 2011, The conclusion was drawn that Staphylococcus xylosus has been shown to convert metmyoglobin to nitrosomyoglobin in a culture medium in salami (Morita et al., 1998) and in raw meat batter (Li et al., 20132016), without the addition of nitrate or nitrite.

NO production has been suggested to be linked to NO synthase (NOS) activity. Alderton (2001) also concluded that NOS catalyzes the production of NO from L-arginine and was initially described in mammals (Alderton et al., 2001). 

The all-important question of whether nitric oxide without nitrite will facilitate the inhibition of Clostridium botulinum was answered by Reddy by pointing out that NO2 is not the inhibiting factor against c. botulinum, but NO. He writes, “Vegetative cells of Clostridium botulinum were shown to contain iron-sulfur proteins that react with added nitrite to form iron-nitric oxide complexes, with resultant destruction of the iron-sulfur cluster. Inactivation of iron-sulfur enzymes (especially ferredoxin) by binding of nitric oxide would almost certainly inhibit growth, and this is probably the mechanism of botulinal inhibition by nitrite in foods.”

This all places us in a uniquely exciting time but much work must be done. For example, NO3, NO2 and NO are like the Christian concept of the Father, the Son and the Holy Spirit in that where you have one, you are likely to find the other. If we then cure meat without nitrites and nitrites develop post-curing, did we solve the matter? The second question is that knowing the facts that I just presented by no means results in a curing system that can be used in a commercial curing operation. What I just gave you have been available in the literature for a decade and a half. It is nothing new to science. Obstacles such as shelf life and colour stability pose daunting challenges and researchers are working tirelessly to solve the challenges.

In South Africa, the master curer, Richard Bosman and I partnered to take up the challenge with arguably one of the leading researchers in the world of nitrite curing from an esteemed American University. With partners in Europe we are starting our own attempt to crack the riddle and we are energised by existing work that has been done by our European partners. I am myself under restrictions by NDAs in terms of making anything public that is not in the public domain and both Richard and I will remain bound by relevant agreements and collaborations yet what has been in the public domain must be noted in a review of curing systems.

Richard and I are very aware that it took two world wars and the efforts of the Griffith Laboratories in Chicago to change the world from NO3- curing to NO2- curing. Only lab work will not spread the gospel nor will the simple facts that I stated above about the role of microbes in the generation of NO which cures the meat lead to a curing system that actually works.

There is an altogether different matter to consider and that is the avalanche of recent work conclusively showing the essential role of nitrite, nitrate and nitric oxide in human physiology. An understanding is emerging that these compounds are not inherently either good or bad for humans or other mammals. In fact, they are essential. Certain conditions, as it were, tip the scale for them to be either destructive or immensely constructive in essentially contributing to our health. Apart from nitrite-free curing, or, I should rather say, parallel to this, we have made it our goal to understand what these factors are and incorporate them into our food systems and we are developing a number of novel ways that we believe it can be done.

Especially related to this section, frustratingly for readers, I do not provide all the references below (work in progress)- I realise this and as I find time to return to this I will provide all references and cross check how I use them. I will confirm that all the references I give are actual work by the quoted scientists or are they stating facts which they have not verified themselves? I have to ask everybody to forgive me in this approach as research is not my primary occupation. I actually earn my living through meat processing and do this work in the minutes I am free in the day. As I always do, I will provide the full set of references and verify every comment over time. Accuracy is of the highest importance to me and so, if you spot any misquotes, please mail me at ebenvt@gmail.com. There is enough work done, however on the subject by others to present the general case and explain the direction of our future efforts along with a wide scope of international collaborators.

Finally

This review is done from the perspective of a commercial high throughput bacon plant. It, however, paints a rich picture and most of what is regarded as “artisan” today has been the way that large throughput factories of yesteryear have done it. In years to come, how bacon was cured even when we embarked on our current bacon project in 2008 will be regarded as “artisan curing” as we have seen the transition to moulds or grid curing over the last 10 years.

Consumer demands, perceptions and technology will remain the driving force behind this industry.  Many aspects will have to be added to this review article such as changes to health concerns which altered brining technology. I addressed most of these matters in this complete work.

I think back over the many years I have been engaged in this most glorious art and I realise that I am a fortunate man!  My deal La’tjie!  My prayer for you is that you too will find something insanely exciting to build your life around! The question still remains if the curing of bacon taught me the real secret of life? Through my quest, I am living a fulfilled and productive life, yes! That subject I have explored in great detail, but what about the link with what is fixed and eternal? Will meat curing allow me to touch the face of God? There is the most interesting answer to that question but it’s late and this letter is already very long. The answer to that question must remain till next time!

Just a few more days and both you and Tristan are with us!

Lots and lots of love from Cape Town,

Dad and Minette


Further Reading

Reaction Sequence: From nitrite (NO2-) to nitric oxide (NO) and the cooked cured colour.


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Reference

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

http://www.elmswell-history.org.uk/arch/firms/baconfactory/article2.html”>

http://www.elmswellhistory.org.uk/arch/firms/baconfactory/baconfactory.html

http://www.horsensleksikon.dk/index.php/Horsens_Andelssvineslagter

Images

Figure 1:  Founders of bacon plant:  http://www.elmswell-history.org.uk/arch/firms/baconfactory/article2.html

Figure 2:  Stitch pumping, http://www.suffolkheritagedirect.org.uk/resources/tours/made-in-suffolk.html