Author: Eben van Tonder
Salt – 7000 years of meat-curing
13 June 2017
Dedicated to Minette, my fellow explorer, and to Luani and Luan on their birthday.
The adventure starts here.
The story of salt is older than humanity itself. Our interest is in its use as a meat preservative. When did this start and how and what are its functional benefits? We begin very general by asking if there is any evidence that Homo Habilis or Neanderthal used salt to preserve meat. Then we consider Africa which leads to a surprising productive line of inquiry. From the life of David Livingston we learn that salt was not used in Africa to preserve, but as a condiment, added during or after cooking. Salt preservation of meat was known. We learn that from events surrounding Livingston’s death. I am not sure how wide-spread this knowledge was, but in this particular instance, it was applied to the preservation of Livingston’s corps.
This leads to the realisation that studying mummies and mummification technology through the ages may be a very productive way of searching for the oldest known meat preservation technology and the use of salts at a time before writing was invented. I applied this thinking and did an internet search of the oldest mummies on earth which yielded the most startling two results.
The oldest mummies on earth, dating from around 7000 BCE are the Chinchorro mummies from the one place on earth that is at the same time the dryest and is replete with the highest concentration of natural sodium nitrate, the Atacama Desert from Chili and Peru! I have always thought that the use of sodium nitrate in meat curing became popular due to the cured colour it imparts to meat and that its preserving ability was a secondary application. I also thought that its widespread use was a very recent development which reached a height in Europe at the end of the 1800’s when it was replaced by the use of sodium nitrite, starting from the early 1900’s. Following my logic about mummification technology, I was certainly not expecting a date of 7000 BCE for a known use of sodium nitrate in meat curing.
I turned my attention to Asia from where, in an iconic review article from Binkerd and Kolari (1975), they claim that the use of nitrates in the curing of meat was first used as meat preservative “in the saline deserts of Hither Asia and in coastal areas. Desert salts contained nitrates and borax as impurities.” I wanted to examine the veracity of their claims. I followed the same logic of mummification and again, I was startled by the results. The oldest mummies in China are found in the Taklimakan Desert in the Tarim Basin. Right here, in the region where the mummies are found, in the Turpan-Hami Basin, massive nitrate ore fields, close in proximity to the Tarim Basin exists. Nitrate deposits, so massive that it is estimated to be at least 2.5 billion tonnes and comparable in scale to the Atacama Desert super-scale nitrate deposit in Chile.
At the graves near Loulan, one of the bodies were subjected to radiocarbon dating which indicated that she died she died about 1200 BCE. This takes the known date for meat preservation, by our logic of linking this with mummification, to 3200 years ago in China.
The two areas in the Atacama Desert and the Taklimakan Desert in China share a striking similarity in weather. They are both some of the aridest regions on earth. A second factor that plaid a role in the natural mummification is rapid-freezing due to extreme cold conditions in the winter and then, of course, the very high sodium chloride content of the soil. The sodium nitrate content in the soil surrounding the mummies is something that must still be studied in great detail (if you are looking for me during my next vacation, I will be at the mummy sites, taking soil samples for analysis, and if you are joining me on the two expeditions, mail me at firstname.lastname@example.org)).
I honed in on this region in China for its geographical importance as being on the important Silk Road connecting Asia with the Middle East and Europe. I asked if there is any evidence of the development of sophisticated thinking pertaining to the use of sodium nitrate salt from this particular region. My reasoning is that if meat curing as an art developed here, that would have been a springboard for the development of related applications.
The results of my enquiry have been nothing less than startling and leave me with little doubt that I have identified the exact location on earth from where the art of curing of meat developed and was spread into Europe and back into Asia. Not that they were the only ones who would have discovered this. I am convinced the ancients in the Atacama Desert would have easily made the same link with meat preservation but it was here, in China’s Western front, on the Silk Road, where a level of sophistication in thought related to the application of sodium nitrate developed that is unrivaled, as far as I am aware off, by any other location on earth.
The first factor is then the enormous natural deposits of sodium nitrate deposits. Secondly, you have the mummies which are something that observant ancients would have noticed almost immediately. It won’t take you 3200 years to realise that something extraordinary is happening with the corpses. The third fact relates to the level of sophistication in the application of sodium nitrate.
The clue of such sophistication of thought comes to us in the discovery of an ancient medical prescription dating from some time between CE 456 and 536, during the life of the famous Daoist alchemist and physician Toa Hongjing in a cave close to the city of Dunhuang, right in our area of interest.
The text describes the treatment of a condition identified as a case of severe angina, i.e. restricted blood flow due to the narrowing of the cardiac arteries. The treatment was to place saltpetre (potassium nitrate) under the tongue.
The basic curing pathway that alleviates the condition by the ancient prescription is a reduction of the nitrate through bacteria under the tongue to nitrite and in the tissue, transported there by the blood, the nitrite is converted to nitric oxide. The role of nitric oxide as vasodilator was, amazingly, only discovered in 1987 simultaneously by a group of researchers at the Wellcome Research Laboratories in Beckenham led by Professor Salvador Moncada and by a group in the USA led by Professor Louis Ignarro. So momentous was this discovery that the 1998 Nobel Prize in Physiology and Medicine was awarded for the work. Once nitric oxide was identified as playing a role in physiological processes, it was found to be involved in many processes from inflammation to crying. So, here we have a text, detailing a medical prescription in 5th and 6th decade of the Christan Era, from China, that has only been fully understood by modern science in 1987! This by itself is an astounding fact!
It gets even more startling. It turns out that this exact reaction sequence of nitrate ion that is reduced to nitrite through bacterial reduction and changed to nitric oxide, along with the influence of acidity and various reductants on the speed of the process is something that is well known in meat science. Humphrey Davy, in 1812 (cited by Hermann, 1865) was the first one to note the action of nitric oxide upon haemoglobin. On 7 May 1868, Dr. Arthur Gamgee from the University of Edinburgh, brother of the famous veterinarian, Professor John Gamgee (who contributed to the attempt to find ways to preserve whole carcasses during a voyage between Australia and Britain), published a groundbreaking article entitled, “On the action of nitrites on the blood.” He observed the colour change brought about by nitrite. He wrote, “The addition of … nitrites to blood … causes the red colour to return…” Over the next 30 years, it would be discovered that it is indeed nitrites responsible for curing and not the nitrates added as saltpeter. It was Polenski who first speculated that saltpeter is reduced to nitrite in the curing of meat in 1891 and 1901 Haldane showed that nitrite is further reduced to nitric oxide (NO). (Fathers of Modern Meat Curing)
Meat curing has been known to follow this exact pathway since 1901. The tantalising possibility, now presents itself that the preserving nature of the salt was recognised in aspects of everyday life such as natural mummification in this exact region in China. The salt was applied to meat in which it had an amazing preserving impact as well as, what must have been, a mysterious reddening effect. To the ancients, it probably looked as if the meat was coming to life again. The Chinese alchemists in all likelihood naturally gravitated to this as a possible key component of the elusive elixir of immortality. Finding such an elixir was the goal of Chinese alchemy. They probably applied its preserving power to all kinds of ailments and in a process of trial and error, a treatment for angina must have been especially effective.
Such experimentation takes years and if this was a known cure and part of a medical prescription by CE 400 or CE 500, it means that curing of meat must have been very advanced in terms of it being practised in this region by this time. From here, in terms of its key position on the Silk Road, the curing technology would have spread across Asia and into Europe.
This is then the introductory article on one of the greatest journeys of discovery into the nature of salt in curing. Later, in subsequent articles, we will follow the search for understanding the different salts and what accounts for their power and different characteristics. We will follow developments in China and in Europe until the brilliant Antoine-Laurent de Lavoisier arrives on the scene, pulls all available data together and formalise a scientific discipline, we today know as chemistry. We go beyond this and see how modern science is only now unlocking the secrets in Chinese applications of nitrate, showing a level of sophistication millennia ago in China that is staggering.
In the process, our understanding of our world will be enriched, our view of history challenged and as meat curing professionals, we will become more proficient in our trade. We may even develop a bacon brine, based on the results of our discovery. What an adventure!!
There is another reason why this story is important. High throughput factories are constantly being accused that they are not “authentic”. By this, it is meant that the old, original and by implication, the “healthier” and better tasting way of meat curing has been abandoned and is now in the exclusive domain of “artisan curers”. What I will show is that a proper historical view thoroughly debunks this myth. That humans, throughout the ages, have used current prevailing meat technology to its fullest in order to create meat such as hams, of excellence. When Ladislav Machtmulner invented the ham press in the early 1900’s, I am sure he was accused of the same. Or when meat curers started incorporating saltpetre into their brine mix as opposed to salt only. Far more important is to identify the broader trends such as the application of technology with an “artisan flair,” which can and should be done even if one is producing 20 000 metric tonnes of bacon each day. I will argue, in other articles, that such artistic principles include matters such as a thorough understanding of the technology, a meticulous and rigorous methodology in application and wide collaboration. (see related article published on Linkedin)
Edward Smith writes in his 1867 publication, Foods, “the oldest and best-known preserving agent (for meat) is salt, with or without saltpetre.” (Smith, E, 1867: 34) (1)
It is reported in the American Encyclopedia of 1858, that “Very excellent bacon may be made with common salt alone, provided it is well rubbed in, and changed sufficiently often. Six weeks in moderate weather, will be sufficient for the curing of a hog of 12 score.” (Governor Emerson . 1858: 1031)
This introduces us to the use and function of salt in bacon. What is the earliest use of salt as a food preservative and flavour enhancer? What is a salt exactly and when was the composition of different salts identified? How does salt preserve food and what is the mechanics behind its enhancement of flavour and taste?
Salt has been in wide use from the earliest time, but fixing the earliest date by when we can, with confidence claim that salt was used to preserve meat is not easy. The use of salt in food probably predates the existence of modern humans. Sodium chloride may have been collected and stored by one of the oldest species of the genus Homo, Homo Habilis who existed between 1.4 and 2.4 million years ago. (Munas, F.; 2014 :213) From this, we can however not conclude that salt was used to preserve meat.
It is speculated that a much closer ancestor, the Neanderthal who lived between 40 000 and 400 000 years ago, dried meat as a way to preserve it. Bent Sørensen suggests that in order for Neanderthal to have carried large carcases to their settlements (after hunting), they could have employed a technique used by later hunter-gatherer societies in Africa and American Indiens of drying the meat at the site and carrying it home by threading a stick through it. He speculates that solar energy could have been used in the summer for drying and wind energy with low air moisture during the winter. Such techniques could have reduced the meat mass that had to be carried by a third.” He also suggests that “storing times could have been prolonged by smoking or salting the meat. Smoking seems fully accessible to Neanderthal societies.” He adds that “we do not know if they used salt.” (Soresen, B.. 2012) The likely use of smoke to preserve meat along with drying is important when we ultimately will apply all this to bacon curing, which remains our primary subject of interest, but so far, we do not have a definite date for the preservation of meat through salting.
There is clear evidence that salt was mined since before the last ice age, some 12 000 years ago in the hills of Austria and Poland, the shores of the Mediterranean and the Dead Sea, the salt springs and sea marches across Europe and Asia. (Bitterman, M, 2010: 16) Similar evidence exists for salt mining across Africa and South America. It seems as if there is not a time known to humans when salt was not mined, in all likelihood to amend our diet, as an ingredient in the manufacturing of a range of products including pottery making and quite possibly to preserve meat. Again, we know that salt was used, but no automatic connection to meat preservation is established for any of these.
In Africa pre-salting of meat, for preservation was not known until Europeans introduced the practice during colonialization. The need to preserve meat was not there. When an animal was killed, the animal was slaughtered and the meat consumed by the tribe, that same day. If salt was added, it was done after cooking the meat as a condiment.
Salt, in precolonial Africa, as was the case around the world at some point, was a scarce and expensive commodity. Ordinary people, generally speaking, had little or no access to salt. For many years it was reserved for royalty and the elite of society. David Livingston, for example, refers to the poor in Africa in the 1840’s with the adjective, “who had no salt” and to salt, as that which “the rich alone could afford to buy.” (Hyde, A., et al.; 1867: 150)
Livingston makes an interesting observation about salt. He was working among a tribe, the Bakwains, while living at Kolobeng, approximately 20kms west of Gaborone in the present day Botswana. He described how the poor often suffered from indigestion on account of their lack of salt. The region has no natural sources of salt. Native doctors who, according to Livingston, was aware of the fact that the lack of salt, was the reason for the malady, prescribed salt along with other ingredients. The doctors themselves did not have any salt and so, the missionaries were approached for help. They “cured” the disease by giving them a teaspoon of salt (minus the other ingredients). He mentions that either milk or meat had a similar effect, but not as rapid as salt. (Hyde, A., et al.; 1867: 150) This has subsequently been well described and explained by modern science. Another important observation from this account is that Livingston confirms the use of salt in food as a condiment only and not to preserve.
The lack of information on meat preservation by ancient societies is challenging. It was probably initiated at a time before these things were written down. Linking salt works of the ancient world and salt preservation of meat, as most authors on the subject do, is not valid as is clear from the African example. There are locations in Southern Africa where archaeologists have traced the mining of salt back to 4000 years ago and yet, preserving of meat with salt is a very recent, post-colonial development in Africa. They mined salt, but they did not preserve the meat using the salt. Salt was simply used in other ways.
This does not mean that the technology of using salt for preserving meat was unknown in Africa. Livingston’s life becomes an example of this knowledge. When he passed away in Zambia in 1875, the tribe used salt to preserve his body after which his body was exposed to the sun for 14 days to dry in an embalming ceremony. Livingston’s embalming was done in order to facilitate repatriation of the body. (Hyde, A., et al.; 1867: 150) How far South down the African continent this was known is an interesting question and the Livingston example indicates that the technology and practice were known further South than one would have expected.
MUMMIFICATION – KEY TO PRESERVATION TECHNOLOGY
The use of salt in embalming is an obvious application of the preserving power of salt to meat. It also seems reasonable to speculate that salt for preserving meat for domestic consumption came first and the application of the technology to mummification was probably a later development. One obvious reason for this is that meat preservation for consumption would have been a daily requirement. An immediate need, for a large group of people. So, many people, over a long time would have been engaged in experiments with various salts and ingredients to determine by a simple process of observation which salts ingredients and combination of factors preserved meat best. Burying the dead and mummification, on the other hand, was a far more infrequent event, with very few people working on solving the problem resulting in a much slower development trajectory. It is far more probable that techniques for meat preservation in general use would have been applied to the preservation of human bodies after death and in the art of mummification.
If one assumes this logic, it becomes an important tool to establish a date by which food preservation with salt was done by a society. The use of salt in embalming leaves us with clear records with precise dates and exactly what was used in meat preservation. If one assumes that meat preservation for general consumption would have predated the use for embalming, we can fix precise dates by what time a society used which salts to preserve meat.
I found support for this reasoning from Valerie Wohl. She writes, “While we do not know exactly how embalming began, it is likely that methods common at the time for preserving meat, fowl or fish probably suggested a clue for early techniques. One might bleed a fish, for example, then preserve it by salting, smoking, sun drying or otherwise heating it to prevent decomposition and store it for a later time. By the time of the very earliest documentation of the process of embalming (in about 500 BCE), it had become a sophisticated technique that had been evolved over hundreds of years.” (Wohl, V.)
As soon as this logic occurred to me after my reading about the embalming of David Livingston, and thinking through the implications of the African example, I realised that I have to follow the trail of mummification.
THE CHINCHORRO MUMMIES OF ATACAMA DESERT
This line of reasoning yielded the most surprising results imaginable. Not in my wildest imagination did I think that the oldest mummies and their preservation would be linked, not with sodium chloride, but with what has been the curing salt of choice up until at leat 1905, namely sodium nitrate. I have always thought, based on research on the subject, that sodium nitrate was used for preserving meat from the 1600’s and reached its height in Europe in the 1700’s and 1800 before it was replaced with sodium nitrite from around 1905 and in particular after World War 1. I thought it was used in isolated places around the world where various cultures re-discovered the reddening effect it had on meat, independently and over a long time and that this slowly filtered through to Europe where it gained popularity over time until it became a general practice. Never did I expect sodium nitrite to have been used for meat preservation since between 5000 and 7000 years BCE and not due to its reddening effect, but for its preserving properties. Let’s look at this case.
It turns out that the oldest mummies on earth are the Chinchorro mummies from the Atacama Desert in Chile and Peru, dating from as early as 7000 BCE. (Guillén, S. E.; 2005) Gypsum, a sulphate mineral, was later used with clay (3000 – 1300 BCE), but mud and clay played an important role from as early as 5000 BCE.
The fascinating link is between this region and sodium nitrate. Nowhere on earth are such large natural deposits of this salt found. The soil here is rich in sodium nitrate salt which is known as Chilean Saltpeter to distinguish it from potassium nitrate or regular saltpeter. A war was fought over these deposits and securing it was a major consideration of Germany going into World War 1. The second important factor is that the Atacama desert is the dryest place on earth. The soil is so rich in saltpeter and it is so dry that mummification occurred naturally, leaving mummies that exist since 7020 BCE.
Two of the most important ingredients in meat preservation namely heat/ drying and saltpeter were present in the mummifications rituals of the Chicharro people of then Atacama Desert since as early as at least 5000 BCE. I do not think that it is a too far a stretch to assume that these people knew about the meat preserving ability by drying in combination with their special salts (sodium nitrate). Even though it is completely conjecture, I am comfortable to say that preserving of meat through sodium nitrate salt and drying was probably known since at least 5000 BCE in Chile and parts of Peru. It is then not a stretch to say that this was likely to be known in the other two main regions in the world where saltpeter is found naturally namely in China and India. This is, of course, a fascinating possibility since this particular salt became the curing agent of choice in the 1700’s which gave rise to the food category of cured meats and directly resulted in our use of sodium nitrite in meat curing today. This date of between 5000 and 7000 BCE is completely in line with a date proposed by Binkerd and Kolari.
Despite this tantalising possibility, the actual sodium nitrate concentrations at the burial sites in the Atacama Desert has never been studied. The degree of mummification varies tremendously (Aufderheide, A. C.; 2003: 141) which will indicate that various factors have been present in varying degrees.
THE TARIM MUMMIES OF CHINA
This date of between 5000 and 7000 BCE is completely in line with a date proposed by Binkerd and Kolari. According to their iconic 1975 review article about the history and use of nitrates and nitrites in the curing of meat, “it appears that meat preservation was first practised in the saline deserts of Hither Asia and in coastal areas. Desert salts contained nitrates and borax as impurities. However, the reddening effect of nitrates was not mentioned until late Roman times.” (Binkerd, E. F. and Kolari O. E.; 1975: 655) A probable time for this discovery is however not given.
I first thought that what they were talking about was salt preservation generally, but the more I look at events in the Atacama desert, the more I wondered if the particular preserving power of sodium and potassium nitrate was not known from the earliest times and the discovery, focussed on its preserving power and not on its reddening effect on cured meat.
A further elaboration of what Binkerd and Kolari may have been talking about comes to us from a 1977 newspaper article. According to it, the suspicion is that prehistoric nomadic hunters in Western Asia began carrying salt containing nitrate with them to preserve the hunting catch. (The Indianapolis Star; 1977) The focus was indeed on nitrate and its preserving ability and not just on salt generally. I learned that nitrate deposits occur and precipitate as an efflorescent crust in amongst other the Egyptian and Namibian deserts, the Abu Dhabi sabkhas, and deserts of the Mojave, Death Valley and of course, the Atacama Desert and the Gobi Desert. (Warren, J. K.; 2016: 1278)
It is, however, the largest desert in China, the Taklimakan Desert of Western China that offers the biggest surprise when I find the oldest examples of natural mummification in China, right in this desert region, replete with natural nitrate deposits. The conditions are almost identical to those of the Atacama desert.
Like the Atacama desert, the Taklimakan Desert is at the same time one of the aridest regions on earth and massive nitrate ore fields exist in the Turpan-Hami Basin, close in proximity to the Tarim Basin, in the Xinjiang province, where the oldest mummies in China was found. The 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 mummification happened, as was the case with the mummies of the Atacama Desert between 5000 BCE and 7020 BCE, spontaneously.
The initial discovery was made in 1939 by the Swedish archaeologist Bergman Folke. A set of tombs were discovered the Chinese province of Xinjiang, known as the Xiaohe Tombs. For 60 years the tombs were forgotten until in 2000 a researcher, head of the Xinjiang Cultural Relics and Archaeology Institute, found the tombs again. It wasn’t until 2005 that the excavations were complete. (www.ancient-origins.net)
The size of the area is unprecedented. So far there have been 330 tombs found in multiple different layers. The tombs include adults and children as well as 15 intact mummies. About half of the tombs were looted by grave robbers. It is the first time anywhere on Earth that so many mummies have been found. (www.ancient-origins.net)
“Several bodies have been excavated from graves near Loulan, a site that once bordered a still shrinking lake fed by the Kongi River. Among these is the body of a young female with remarkably well-preserved facial features, whose radiocarbon date indicates that she died she died about 1200 BCE.” Subsequently, more than 500 tombs have been studied. Dr Wang Bing Hua, director of the Ürümxi’s Archeological Research Institute, attributes the spontaneous mummification to three factors: arid climate, salty soil and shallow, winter burial. Average salt content of the desert soil near Turpan is about 10g/ L but in the very surface layer, it can be five times greater. At Hami the soil contains layers of gypsum and at Cherchen actual salt blocks are obvious within the soil, especially near the surface. Most burials are only about a meter below the surface. (Aufderheide, A. C.; 2003: 268, 269) The nitrate in Xinjiang Lop Nur exists in two forms: natural sodium nitrate mine and natural potassium nitrate. (en.cnki.com.cn)
The Turpan Basin is a “fault-bounded trough located around and south of the city-oasis of Turpan, in the Xinjiang Autonomous Region in far western China, about 150 kilometres (93 mi) south-east of the regional capital Ürümqi.” “The surrounding mountain ranges are the central Tian Shan in the west, the Bogda Shan in the north-west, the Haerlike Shan in the north-west, and the Jueluotage Shan in the south. Beyond the surrounding mountain ranges lie the Junggar Basin in the north and the Tarim Basin in the south.” (www.revolvy.com)
“Some geographers also use the term Turpan-Hami Basin, which is understood as including the Turpan Depression along with the Hami Depression (located to the east of the Turpan Depression, and to the south-west of the city of Hami) and the Liaodong Uplift separating the two depressions.” (www.revolvy.com)
One of these mummies may hold a further clue to their preservation. She became famous for her “excellent preservation and beauty and it is known as the Beauty of Xiaohe. It is a white person with round eyes, perfect eyelashes, and long hair and has features that are more similar to a European person than a Chinese person.” (www.ancient-origins.net)
According to Elizabeth Wayland Barber, her “beautiful eyelashes finally proves an earlier hypothesis, deduced from little detail at Zaghunluq, that those bodies that mummified had to have died in early winter, flash freezing and gradually freeze drying over the next few months whereas other bodies decomposed.” She was dismayed at people’s acceptance or refutation of his arguments without dealing with the arguments posed. In the Beauty of Xiaohe she, at last, had hard evidence. “Eyeballs, being wet, cause rapid decomposition of both themselves and the eyelash-holding eyelids when warm; but by the same token, being wet, cause rapid decomposition of both themselves and the eyelash holding eyelids when warm, but by the same token, being wet, both they and the thin overlaying eyelids will freeze rapidly when being very cold, thus securing the eyelashes in place. Unlike putrefaction, the gentle process of freeze-drying will not dislodge eyelids.” (Mair, V. H., Hickman, J.; 2014: 35)
It has been known from earliest times that meat curing could be done only in the winter in the absence of refrigeration. If not, the putrefying and decomposing forces would overtake the preserving action of saltpetre and decomposition would be unstoppable. It is the combination of cold and dry conditions along with the use of sodium nitrate to preserve and ordinary salt (sodium chloride) to aid in drying out the meat, that forms a link between the earliest forms of mummification and modern meat-curing techniques. It seems unreasonable to think that the result of these forces, in combination, would have gone unnoticed. I further suspect that the power of these forces would have been practised in relation to fish, fowls, game and domesticated animals for centuries before they found inclusion in earliest mummification practices.
THE SILK ROAD
The location of the Turpan-Hami and Tarim Basins are very important. Crossing the Taklimakan Desert is possible at the foot of the mountains surrounding the Turpan-Hami Basin or along its streams such as the Tarim, “that spring from the mountains to enter the desert from its periphery but soon vanish into the sand. As ancient caravans from Eastern China approached Dunhuang at the edge of this segment of what eventually came to be part of the Silk Road to the Medditeranian, the near absence of water in the desert’s centre forced them to make a choice. The southern option skirts the desert along its southern edge at the foot of the steep Kunlun slopes descending from Tibet’s high plateau. Alternatively, the northern route passes through Hami and those communities living along the Kongi and Tarim rivers that lead to Loulan and Lop Nor. It is along these routes that mummies from the Tarim Basin have been found.” (Aufderheide, A. C.; 2003: 268, 269)
The caravans on the Silk Road approached Dunhuang, crossing vast sodium and potassium nitrate deposits. If the knowledge of its power was developed in this region and exported to Europe, I am sure that there should be remnants of this ancient knowledge in this city.
“One of the people who has extensively studied the Caucasian mummies of China, Professor Victor Mair of Pennsylvania University, said that he believes that early Europeans long ago spread out in different directions. He believes that some of these peoples travelled west to become the Celts in Britain and Ireland, others went north to become the Germanic tribes, and still, others journeyed east to find their way to Xinjiang. These ancient European settlers are believed to represent some of the earliest human inhabitants of the Tarim Basin, and Mair has stated that from around 1800BCE the earliest mummies to be found here are exclusively Caucasoid or Europoid rather than Chinese in origin.”
The origins of the mummies have been studied extensively using DNA technology. Writing in the journals BMC Genetics and BMC Biology, Chunxiang Li, an ancient DNA specialist at Jilin University, and colleagues report on their analysis of human remains from the Xiaohe tomb complex also on the eastern edge of the basin.
They conclude that reconstructing a possible route by which the Tarim Basin was populated, Li and colleagues concludes that “people bearing the south/west Asian components could have first married into pastoralist populations and reached North Xinjiang through the Kazakh steppe following the movement of pastoralist populations, then spread from North Xinjiang southward into the Tarim Basin across the Tianshan Mountains, and intermarried with the earlier inhabitants of the region, giving rise to the later, admixed Xiaohe community.” (Killgrove)
“The populations from the Russian steppe seem to have contributed more genetically to this population than did the populations from the oases of Bactria. “The groups reaching the Tarim Basin through the oasis route,” the researchers note, “may have interacted culturally with earlier populations from the steppe, with limited gene flow, resulting in a small genetic signal of the oasis agriculturalists in the Xiaohe community.”” (Killgrove)
The question is if there is any evidence that anything was done with the nitrate deposits and the clear evidence of its preserving power in the mummification. If this was the region where curing of meat was progressed into the art that we know it as today, is there any evidence of this? Any ancient document or reference, not just from China generally, but linked to this region. These were the actual questions I asked myself as I was searching. This is not a device I employ after the fact for the sake of creating drama.
I knew my general geographic area of focus was the one I show below featuring the Tarim Basin.
I started plotting the important points.
Looking at the map above, the saltpetre deposits are the largest at Yuli, marked as NO3-. Loulan is the city where many of the mummies have been found. Dunhuang is a major city before the trip past or across the desert was undertaken on the Silk Road past the Tarim Basin.
I did an internet search for any reference to saltpetre from the city of Dunhuang which would have been a key trading city in the area and important in terms of its location on the Silk Road. Not in my wildest imagination did I expect to uncover what I found!
It is here, in the Mogao Caves, where a remarkable find was made by the Daoist monk, Wang Yuanlu on 25 June 1900. The mix of religious and secular documents date from the 5th to the early 11th centuries. One text is of particular interest to us, the Dunhuang Medical Text. “The text has been carefully studied by China’s leading experts in traditional Chinese medical literature and ancient manuscripts. The text is attributed to the famous Daoist alchemist and physician Toa Hongjing (CE 456 – 536).” (Cullen, C, Lo, V.; 2005) There is evidence that it relies on earlier traditions from the Han and Sui Dynasties. “The original was decorated with images of the Three Daoist Lords and the Twelve Constellations, indicating links with Doist traditions. In Translation, it reads as follows:
(Cullen, C, Lo, V.; 2005)
Until the 1500’s this is the only script of its kind that we know off. “The symptoms described by the patient, as described in the Dunhuang manuscript, suggests an advanced case of cardiovascular distress. The colour of the fingernails (cyanosis) indicates ischaemia (lack of oxygen in the tissue) due to restricted blood flow. Cold hands and feet are additional symptoms of this condition. Also, acute pain suggests that the patient may be suffering from severe angina, i.e. restricted blood flow due to the narrowing of the cardiac arteries.” (Cullen, C, Lo, V.; 2005)
“Modern treatment for angina is glyceryl trinitrate or isosorbide dinitrate. So, at first glance, there seems to be a similarity in treatment. All three remedies contain the all important nitrate. Salpeter is, however, an inorganic compound that exists as a positively charges potassium cation (K+) and a negatively charged nitrate anion (NO3-). Concerning organic nitrate, such as glyceryl trinitrate, there is a covalent bond or a molecular bond between the nitrate moieties (NO3) where they share electron pairs which form the bond with the rest of the molecule (CH2). Where glyceryl trinitrate relaxes the muscle lining of the artery to relax, enlarging the vessel and so allowing more blood flow, saltpetre by itself will have no effect on the treatment of angina.(Cullen, C, Lo, V.; 2005)
This is however not the full story. The remarkable feature of the Dunhuang text is that the combination of the use of saltpetre, not on its own, but when applied according to the dictates of the text, becomes a remedy for exactly the condition described.
“The thing about glyceryl trinitrate is that this too, in itself, is not a vasodilator (relaxing of the arterial lining). It is transformed, probably in the arterial wall, into a chemical species which is the vasodilator. Under very special circumstances, exactly as detailed in the Dunhuang text, the nitrate ion from saltpetre also converts to exactly the same species which is the vasodilator. Despite the fact that glyceryl trinitrate has been in use for over a hundred years, the identity of this species has only been discovered in 1987.” (Cullen, C, Lo, V.; 2005)
“Lining almost all blood vessels on the inside is a layer of cells known as the endothelium. A very important function of the endothelium was first reported in 1890 by Furchgott and Zawadzki. The presence of acetylcholine (a small biologically active molecule) in the blood stream effects vasodilation and it was generally assumed that acetylcholine acted directly upon vascular muscle. However, this was found not to be the case. Furchgott and Zawadzki showed convincingly that that acetylcholine acted, not upon the muscle of the artery, but upon the endothelium and the endothelium produces a “second messenger” which then acts upon the muscles to effect relaxation. This second messenger was christened “the endothelium-derived relaxing factor” (EDRF).” (Cullen, C, Lo, V.; 2005)
During the 1980’s, an intense effort was effected to identify the EDRF. It was initially assumed that it would turn out to be a complex molecule like a hormone. This speculation enhanced the surprise when the chemical nature of the molecule was finally determined. It turned out to be a small diatomic molecule called Nitric Oxide (NO). “That it had a physiological role, in a process as important as vasodilation, came as a complete surprise.” (Cullen, C, Lo, V.; 2005)
“The discovery was made simultaneously by a group at the Wellcome Research Laboratories in Beckenham led by Professor Salvador Moncada and by a group in the USA led by Professor Louis Ignarro. The 1998 Nobel Prize in Physiology and Medicine was awarded for this discovery. Once nitric oxide had been detected in one physiological process it was found to have roles in many others, from inflammation to crying. That it should have remained undetected during a hundred years of intense scrutiny of human physiology is astonishing. Glyceryl trinitrate is a vasodilator because it is transformed by an enzymatic process (possibly by the enzyme xanthine oxidoreductase) into nitric oxide.” (Cullen, C, Lo, V.; 2005)
Let us now return to the Dunhuang text. Is there any way that the inorganic nitrate could be transformed into nitric oxide? “In a healthy body it is very unlikely, that nitrate which is present in the blood plasma, is converted to nitric oxide. However, there is a species, nitrite (NO2-), very closely related to nitrate (NO3-), for which conversion into nitric oxide is quite possible. Do humans ever convert nitrate into nitrite? Such a conversion can occur in the mouth and it is this aspect of the Dunhuang prescription that is so interesting. The saliva contains many bacteria, some of which contain the enzyme nitrate reductase, which converts nitrate into nitrite.” (Cullen, C, Lo, V.; 2005)
“Experiments on rats have shown that reduction of nitrate to nitrite is confined to a specialised area on the posterior surface of the tongue. If the same applies to humans, the Dunhuang procedure, which specifies that the saltpetre should be placed under the tongue will maximise the conversion of nitrate into nitrite. The retention of saliva as described would also enhance nitrite production. Unlike nitrate, nitrite is physiologically active. It is an antiseptic and a vasodilator, although not a powerful one. It has been suggested that animals, particularly cats, lick wounds because of the antiseptic effect of nitrite in the saliva. Although not a powerful vasodilator, there is now direct evidence that rat hearts, when subjected to global ischaemia, generate nitric oxide and that a significant proportion comes from nitrite present in the tissue. Ischaemic tissue is very acidic and the acid effects the conversion of nitrite to NO via the following equalibia:”
(Cullen, C, Lo, V.; 2005)
“Calculations, assuming only a modest level of nitrite in ischaemic tissue, show that enough nitric oxide from the above equalibria to activate guanylate cyclase, the enzyme responsible for the initiation of the cascade of reactions which lead, eventually, to vasodilation. So, if nitrite enters the plasma, as a result of administration of sublingual saltpetre, it could generate nitric oxide in ischaemic tissue. Because of the abundance of blood vessels under the tongue sublingual administration of a drug is a good way of getting a drug into the bloodstream and bypassing the stomach. Also, the tongue, in traditional Chinese medical theory, is linked to the function of the heart.” (Cullen, C, Lo, V.; 2005)
“The interaction of saliva and nitrate to generate nitrite before conversion to nitric oxide in ischaemic tissue gives considerable credence to the Dunhuang procedure as a treatment for cardiovascular distress.” (Cullen, C, Lo, V.; 2005)
Here, in the Tarim Basin, we have three things present. One of the world’s largest natural salpeter deposits. Natural mummification dating back to just over 3000 years ago. From these, the preserving power of these soils would have been evident to all since the mummies existed then already. The longevity of the corpses would have been evident to the ancients. We have a record of very sophisticated use of saltpetre from very early in the Christian Era from this exact region. In fact, some of the most sophisticated use of the salt on record and the exact mechanics is even today mirrored in the act of curing itself which has been until the early 1900’s when the direct addition of sodium nitrite replaced saltpeter as curing agent of choice.
Until that happened, curing was done by the addition of saltpetre which was reduced, through bacterial action to nitrite which diffused into the muscle for the purpose of preservation. The similarity in the curing action and the mechanism relied on, in the utilisation of saltpetre in the Dunhuang Medical Manuscripts is startling, to say the least. Of course, I am not suggesting that the full or even a partial understanding of the mechanism was known to the ancients, but the application did suggest a much more detailed understanding of saltpetre and its efficacy on meat muscles which could easily have originated from the experience with curing! Seeing the preserving power of the salt and the reddening effect of the meat could have led them to an application of the salt for heart conditions even though the reduction steps may not have been fully understood.
This is without a doubt the best possible location from anywhere in the world where curing of meat could have originated. The picture is not of wondering hunters who stumbled upon the salt and early farmers using it for preserving meat – or at leat, it could have started like this. But if it happened in this exact region, it soon found itself in the most advanced society on earth of its time with the most sophisticated thinking about chemistry. The Chinese alchemists in all likelihood gravitated to this as a possible key component of the elusive elixir of immortality. Finding such an elixir was the goal of Chinese alchemy. They probably applied its preserving power to all kinds of ailments and in a process of trial and error, a treatment for angina must have been especially effective.
Here, at a key location on the silk road, the knowledge of curing and the power of saltpetre could easily have been spread through India and China to the East and right into the heart of Europe to the West.
Binkerd and Kolari may be correct in speculating that the preserving power of sodium and potassium nitrate was discovered in the deserts of Asia between 5000 and 7000 years ago. Nomadic hunters probably took this salt with them on hunting expeditions if the hunt took them to a region where these salts do not naturally occur. It was in all likelihood discovered in many other regions around the world where these salts naturally occur, including in the Atacama Desert and India. Of all these possible locations, the one region on earth with all the hallmarks of being the birthplace of our modern meat curing is Tarim Basin, in the Xinjiang province. The Silk Road probably was the perfect transport mechanism for the technology and the culture was spread. It is a remarkable glimpse back into human history and turns our gaze decidedly east towards China. Years will be spent building on this one single possibility!
Egypt becomes an interesting case since here the preserving salt of choice was not sodium or potassium nitrate, but natron. We will consider natron in a future article. We will also look at how the ancient knowledge of preservation was transferred from region to region, transforming our modern understanding of migration and travel in the ancient world. We will consider how and when this knowledge arrives in Eastern and Central Europe. What was known in China about potassium and sodium nitrite and how sophisticated were their understanding of these salts. It will be proposed that it was so sophisticated that in certain respects, their technology of 1500 years ago is only being properly understood today and incorporated in the most modern understanding of human physiology. We will trace the Western discovery of the composition of these salts and the formalisation of the scientific discipline of Chemistry. We will look at the role of these different salts in meat curing.
It will be proposed that the modern obsession with hydrocolloids and phosphates in meat processing is misplaced and how a re-evaluation of salts and their efficacy in meat can yield surprisingly beneficial results.
Please mail me with any comments, corrections or contributions or if you are interested in joining me on a trip to China and Chili at email@example.com As always, we will combine such a trip with amazing hikes!
(c) Eben van Tonder/ firstname.lastname@example.org
References (applicable to the entire work, still being written)
The Age, Melbourne, Australia, 3 June 1975, Page 1
Aufderheide, A. C.. 2003. The Scientific Study of Mummies. Cambridge University Press.
Bertman, S.. 2010. The Genesis of Science: The Story of Greek Imagination. Prometheus Books.
Brenner, E.. 2014. Human body preservation – old and new techniques Erich Brenner. J. Anat.(2014) 224, pp316–344 doi: 10.1111/joa.12160
Binkerd, E. F. and Kolari O. E.. 1975. The history and use of nitrate and nitrite in the curing of meat. Fd Cosmet. ToxicoL Vol. 13. pp. 655–661. Pergamon Press 1975. Printed in Great Britain
Cullen, C, Lo, V.. 2005. Medieval Chinese Medicine: The Dunhuang Medical Manuscripts. Routledge Curzon.
Davy, H. 1840. The Collected Works of Sir Humphry Davy …: Elements of chemical philosophy. Smith, Elder & Co.
Freedman, P. H.. 2007. Food: The History of Taste. Thames & Hudson Ltd. London.
Guillén, S. E. “Mummies, Cults, and Ancestors: The Chinchorro Mummies of the South Central Andes.” Interacting with the Dead: Perspectives on Mortuary Archaeology for the New Millennium. Gainesville: University of Florida, 2005. 142-49.
Gouverneur Emerson . 1858. The American Farmer’s Encyclopedia. A O Moore.
Heilbron, J. L.. 2003. The Oxford Companion to the History of Modern Science. Oxford University Press.
Hui, YH, Wai-Kit Nip, Rogers, R. 2001. Meat Science and Applications. Marcel Dekker, Inc.
Hyde, A., Bliss, F. C., Tyler, J.. 1867. The Life and Life-Work of Dr David Livingston. Columbian Book Company.
Mair, V. H., Hickman, J.. 2014. Reconfiguring the Silk Road: New Research on East-West Exchange in Antiquity. University of Pensylvania Press.
The Indianapolis Star (Indianapolis, Indiana) 21 November 1977, page 16
Krebs, RE. 2006. The History and Use of Earths Chemical Elements. Greenwood Press.
Laszlo, P. 1998. Salt, Grain of Life. Columbia University Press.
Lavoisier, A. 1965. Elements of Chemistry. Dover Publications, Inc. (Translated by Robert Kerr)
Leicester, H. M., Klickstein, H. S.. 1952. A Source Book in Chemistry, 1400-1900. Harvard University Press.
Munas, F.. 2014. Mission To Earth. New Authors Press.
Pearson, AM, et al. 1997. Healthy Production and Processing of Meat, Poultry and Fish Products, Volume 11. Chapman & Hall
Qin, Y., Li, Y., Liu, F. et al. Sci. China Earth Sci. (2012) 55: 213. doi:10.1007/s11430-011-4358-z
Rahman, SM. 2007. Handbook of Food Preservation. Second edition. CRC Press.
Siegfried, R. 2002. From Elements to Atoms: A History of Chemical Composition, Volume 92, Issues 4-6. American Philosophical Society
Soresen, B.. 2012. A History of Energy: Northern Europe from the Stone Age to the Present Day. Earthscan.
Warren, J. K.. 2016. Evaporites: A Geological Compendium. Springer.
Wohl, V. History of Embalming and Restorative Arts.
The Guardian, London, Greater London, 13 Oct 1934, page 13