Chapter 09.06 From the Sea to Turpan

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.

From the Sea to Turpan

University Geology Museum (1), Copenhagen, June 1891

The day has finally arrived, our much-anticipated visit to the University of Copenhagen’s Geology Museum. It is located on Nørregade. The museum is part of the Natural History Museum of Denmark.  It was truly exceptional. The exhibition of minerals is, from what I am told, one of the finest in Europe! There are exhibitions on meteorites, volcanoes, continental drift, the geology of Denmark, the geology of Greenland, fossils (including the largest bivalves such as clams, mussels, oysters, and scallops), and an exhibition on the origin of humans. The fact that we had to postpone the trip for a week worked out well. Despite Uncle Jeppe being unable to join us, the Curator of the Museum was there and what happened was exceptional! He proved to be just the man to bombard with my many questions!

Bezeklik caves on mountain slopes near Turfan

Wondering About Meat Preservation

For as long as I can remember, I have been wondering about meat curing. As a child, I tried to imagine how people discovered that dry meat lasts longer. It seems self-evident to us now, but someone had to “discover” it! There is a difference between dry meat and cured meat. Cured meat is identified by three things. Its look, taste, and longevity.  When an animal is killed, the meat blooms a beautiful red colour. If you do not rub it with saltpetre, it changes to a dull brown colour. If you, however, rub it with a mixture of salt and saltpetre, it retains the pinkish-reddish colour. If you rub it onto meat that already turned brown, after a few days the entire piece of meat will return to its pinkish-reddish colour, resembling fresh meat. This probably conjured up images of the power of immortality in the minds of the ancients endowing saltpetre with seemingly magical powers.

Is Curing possible without Saltpeter

Using saltpetre does not guarantee you good bacon, but without it, curing does not happen. When you dry meat, this can be done without saltpetre and the meat will also last a long time but the meat will be dry and without juices. In South Africa, the old Dutch farmers fused their knowledge of drying meat in the chimnies in Holland and the North European practice of using vinegar in their hams with the indigenous practice of hanging meat out in the sun and wind to dry. They add coriander with salt to the vinegar to create what they call biltong. This is a good example where drying works well to preserve meat with or without saltpetre. Saltpetre can only be left out of the recipe if vinegar is used and lots of salt and provided that the temperature where the meat is hung is not too high.

It is possible to cure meat with salt only, but the process takes a long time. Longer even than dry-curing with saltpetre. Communities in Italy that does this often have to carry the hams or bacon higher up the mountain to parts where it is still cold if the weather turns warmer and where humidity is lower. For our curing plant in Cape Town, similar to Uncle Jeppes’ plant, time is a luxury that we will not have and besides, we do not have high mountains. The process of curing it without saltpetre is a special skill.

The Friendly Curator and My Research Partner

The curator of the museum was on duty this weekend which was must fortuitous. He agreed to have coffee with us and answer our questions. This is the thing about the Danish that I notice wherever I go – they don’t have inflated egos.  If this was in Cape Town, I can not imagine that someone with his position would have taken the time to have coffee with us and answer a novice in the area of minerals and chemistry’s many questions. Minette is a research partner second to none! She asks simple but powerful questions. She is never afraid to ask for clarification on points of seeming contradiction.

From Sea to Dry Deserts

The curator patiently listened to my questions before he started speaking. It was as if he did not really listen to my questions but decided to rather address the topic of the origins of curing more generally. Not one of us minded his approach. It was all fascinating and he had Minette, Andreas, his dad, his mom and me hanging on his every word.

First, the professor had to set me right in a wrong perception I had about how salts naturally occur on earth. I did not understand that today our salts are very refined. Impurities are removed before it is sold. Different salts are neatly separated but in nature that is not how they occur. Salts occur in nature as a mixture of various minerals.  When the ancients talk about saltpetre, for example, there were many different grades of purity. The nitrate salts may be mixed with what we refer to as table salt or sodium chloride along with many other chemical compounds. The opposite also occurs. If salt is mined from a salt pan, for example, there may be small amounts of nitrate salts mixed in with the table salt. There may even be some nitrite salts present in very small quantities from game urinating in the pan.

After setting me straight, the professor continued. “While people living in desert areas would have noticed 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, it is certainly true that coastal dwellers would have observed the same. They would have seen that sea salt or bay salt has the same ability. It is possible that curing was first noticed by early seafarers: meat proteins contain nitrogen. When the meat is placed in seawater, the surface proteins start to break down and forms nitrites for a period of 4 to 6 weeks. Nitrite is then converted to nitrate over the next 4 weeks through bacteria. It is possible that they preserved meat in seawater barrels and that the whole process of curing was discovered accidentally.”

Our friendly curator ordered a second cup of strong coffee! We all remained spellbound. My note-keeping was put to the test and there was no time for me to even take a sip of coffee! I had to keep up and did not want to miss a single point. “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, it could 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 the time when it was noticed 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. I think the question of recognition in different regions we can safely put at the time when these areas were populated.”

“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 inland dwellers discovered salt that cures meat in deserts also. Salt in nature almost always appear as a mix of various salts and under certain conditions, these salt deposits contain small amounts of nitrate salts and ammonium chloride. The ancients would have noticed that these salts cure meat.”

Sal Ammoniac

He then introduced me to something that I did not expect. Another curing salt! “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.”

I was riveted! “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 where it appeared around the kilns where camel dung was used as fuel for the fire and it was mined in Asia.  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 compared to salting the meat with normal table salt. In my experience, salt ammoniac is, however, a far better preservative than saltpetre. Sal ammoniac, as far as I can find, was globally traded from much earlier than saltpetre. Ancient Macedonian records indicate that even in 2000 BCE saltpetre was preferred in food over sal ammoniac on account of the better taste of saltpetre. 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.

He then introduced us to a region of the word that I did not even know existed. “Turpan is the name of an oasis in the far western regions of China. It is an extremely dry area. 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. 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 Turfpan and the ancient city of Salzburg and the salt mines which 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 related to meat curing may have come from Austria. Whether it was through Salzburg and initially from Turfan is not clear.”

“Around Turpan (also called Turfan), Sal Ammoniac forms in volcanic vents and after volcanic eruptions before it has rained which dissolves the crystals. 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. 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.”

“The 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 into 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 its affinity for water that breaks the crystal structure down. Once this happened, the sodium nitrate and the ammonium chloride look similar. Due to the fact that it is known that almost all the sal ammonia produced 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 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 follow.”

“Not only would it result in the reddish-pinkish cured colour, but it was an excellent preservative. 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.”

Flaming Mountains.jpg
Flaming Mountains of Turfan

More Information on Saltpeter

“Sal ammoniac may be the oldest curing salt, but saltpetre is the curing salt that most of us are familiar with. By far the largest known natural deposits of saltpetre of the 1600s were located in 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 in Chile and Peru and those of the Tarim Bason in western China 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 both the Dutch (VOC) and the British East Indian Company (EIC).  The VOC dominated the saltpetre trade. 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.”

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

“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’s super-scale nitrate deposit in Chile. 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 prominent 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 to the Western world.”

“To the south-east, in China, the largest production base of saltpetre existed dating back to a thousand years ago. Here, a network of caves was discovered in the Laojun Mountains in Sichuan Province. 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 the advent of the Christian era. 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 the 1700s. Its usage most certainly coincided with its availability and price.”

“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. 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.”

Everyone sitting around the table was hanging to his every word. I did not notice but by this time a small crowd had gathered around us. The curator raised his voice slightly to allow everyone to hear.

“There is another form of meat curing that I can tell you about.” As he started, Minette jabbed me in the ribs. “You see!” she said! “I told you!” Minette asked me before why the sweat of horses is also called saltpetre which is exactly the subject that he brought up.

Horse Sweat

“It may surprise you that one of the techniques used by ancient horseback riders to cure their meat was to hang strips over the neck of the horse or placing it under the saddle for the sweat of the horse cure the meat. Sweat contains nitrates and the same bacteria that reduce the nitrate to nitrite or that remove the one oxygen atom from the Salpeter to form nitrite is present on horses. This would result in the rapid curing of the meat. The fact that meat was placed under the saddles shows the importance of “softening the meat” in a time when people did not have many options in caring for their teeth.” It is the same mechanism, just in a less culturally acceptable way.”

“German and Austrian cookbooks pre-1600’s reveal that vegetable dyes were used to bolster colour 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 no doubt due to the effect of sal ammoniac on taste, it fell out of common use. Hanging meat around the nacks of horses had a limited lifespan and as the availability of nitrate salts in Europe increased due to its use as a pharmaceutical, for military use and to fertilise fields, the nations of Europe started using it to cure their meat instead of salt only.”

An Unforgettable Day

It was all over too soon. When the Curator of the Geology Museum was done, everybody applauded! I asked him how he knows so much about meat curing and not only geology and mineralogy. He told me that he grew up in a butcher’s family. His dad had a keen interest in mineralogy in particular since it deals with chemistry, crystal structure, and physical (including optical) properties of minerals and mineralized artefacts. His father inspired him to studied geology.

That evening we did not read from Edward Smith’s book after supper. Instead, we went over the notes I took and where our host was too fast for me to catch everything he said, Minette, especially, helped me to get the facts straight.  She has a very keen mind and a great memory.

We talked till very late into the night and all retired to bed, aware that we all experienced something very special today. There were two groups of people that I wanted to share this with. Tristan, Lauren, I could not go to bed without writing this letter. It is now 2:00 a.m.. Tomorrow I will share this with the second group of people or as in this instance, a person. Jeppe could not attend on account of the birthday celebrations of a grandchild. I can hardly wait for Minette and me to share this with him.

Now I am off to bed! I am exhausted but insanely excited! My Danish experience had just gone to another level! I can hardly believe the privilege I have to be here!

Lots of love from Denmark and a very happy father!


Turfan Depression.jpg
Turfan depression

Further Reading

From The Salt Bridge,

01. Salt – 7000 years of meat-curing

02. Nitrate salt’s epic journey: From Turfan in China, through Nepal to North India

03. And then the mummies spoke!

04. The Sal Ammoniac Project

05. An Introduction to the Total Work on Salt, Saltpeter and Sal Ammoniac – Salt before the Agriculture Revolution


(c) eben van tonder

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Note 1

Neither the University of Copenhagen, the Geology Museum or any other affiliated organisation had no input in any of the content in this chapter.  All research and conclusions are that of Eben van Tonder and the interaction with the curator of the museum, as portrayed here, is fiction.  Eben places it in this setting for literary and artistic reasons.


Bacon Curing – A Historical Review

Photo References

Featured Image: Bezeklik caves on mountain slopes near Turfan.

Flaming Mountains of Turfan:

Turfan Depression:

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