Chillin' at the symposium with Plato: refrigeration in the ancient world.

INTRODUCTION

During the nineteenth century several methods of producing cold were developed and used for industrial purposes and have since become common. The three main methods were machines that operated by: compressing and evaporating refrigerants, pioneered by Perkins (1834); expanding compressed air, pioneered by Gorrie (1844), and absorption machines, pioneered by Carre (1859) (Thevenot R., 1979). Just preceding, and parallel, to the development of mechanical refrigeration systems a global trade in natural ice also developed. The pioneer of this trade was Frederic Tudor who first exported commercial quantities of ice from Boston Lakes to the Southern US in 1806 (Anon. 1932). By 1856, Tudor's company (and a small number of competitors) exported American ice to England, the Caribbean, South America, the Persian Gulf, India, Southeastern Asia, Hong Kong, Manila and Australia; in 1857 (the peak year) 146,000 tons of ice were exported from Massachusetts (Dickason, 1991). Ice was also exported from Norway (Thevenot R., 1979). As well as ice, some perishable products were exported such as fruit, and ice-creams (Anon. 1932), but these were in fact less profitable (about 30% profit) in comparison to selling the ice itself (about 40-50% profit; Dickason, 1991). The global ice trade eventually failed from about 1880 onwards, largely because mechanical refrigeration systems became cheaper and more reliable (Forbes, 1958).

However, the use of ice, or snow, in food has a much older pedigree than the nineteenth century, as throughout antiquity many civilizations made use of ice or snow. They were able to store ice and snow out of season and were even capable of engineering systems to produce ice or cool water. The ancients typically used this ice or snow to cool wine for drinking, (Curtis, 2001; Forbes, 1958; Fiske 1932). Possibly some fruit or vegetables were also preserved via chilling, and they certainly were in ancient China (Schafer, 1977) but, the very high cost of unseasonal ice seems to have restricted its use with low value products in Europe. Certainly meat was not chilled and was normally either slaughtered immediately prior to consumption or preserved through drying or salting (Curtis, 2001). In the following paper the reported use and manufacture of ice and snow are examined in a number of civilizations, which left either literature or artifacts describing their activities.

MESOPOTAMIA ICE-HOUSES

Some of the first literate, urban civilizations (Sumer, Babylonia, Assyria) arose in Mesopotamia and documentary evidence has been discovered that they stored ice in special ice-houses. There appears to have been a cold-house in the city of Ur, in about 2000 BC, ice-houses at the cities of Terqa and Saggaratum on the Eurphrates river, during the reign of king Zimri-lim of Mari (about 1700 BC), and an ice-house at the Assyrian capital of Assur (Sassons, 1984; Forbes, 1958). There is ambiguity about some of the references to ice-houses as the word for ice was also sometimes used for copper ores; however, it seems clear that at least some of the "ice-houses" really stored ice (Forbes, 1958). Many of the references to icehouses also occur alongside records of wine, which suggests that the ice was used primarily for cooling wine (Curtis, 2001). Interestingly, it seems that beer (which the Mesopotamians also brewed) was not served chilled (Sassons, 1984).

Where did this ice come from? Probably some was harvested in the mountainous regions, and certainly some of the ice-houses seemed to have been simple timber lined pits that would provide some insulation to keep the ice cool, and indeed such pits were still used in Syria in the twentieth century (Forbes, 1958). On the other hand, instructions for the construction of Zimri-lim's ice-house in Terqa detail a large, elaborate structure about 6 meters by 12 meters with special channels to remove melted water, which apparently took special expertise to construct: that is, it was more than just an insulated pit (Sassons, 1984). This ice-house may have been a large, shallow, walled pool, which would lose heat at night via radiation to the sky. On cloudless winter nights this would be sufficient to freeze the water, and the ice could then be harvested and stored in a storage pit (Sassons, 1984). This process is the same as that which causes a frost to naturally form on the ground. It is probable that observation of natural frost formation led to the development of this technique as the climate in Mesopotamia was suitable for such observations and there are many references to natural ice and frost in surviving Mesopotamian literature (Forbes, 1958). There is also a modern tradition of this process being used in the same region; similar ice-makers were used in Iran up until the twentieth century, when they were abandoned due to public health concerns (Bahadori, 1978).

EVAPORATION IN EGYPT

The Egyptians also manufactured wine. This was kept in semi-porous pottery amphorae, which were stored in large underground cellars insulated with mud brick to maintain a cool environment (Curtis, 2001). By comparison, mud brick has a thermal conductivity value of about one quarter that of typical woods (used by Greeks for insulating ice pits) and a thermal conductivity of about ten times typical modern insulating panels (Holman, 1992). Thus, pits could be effectively insulated with mud bricks or wood.

There are also Egyptian tomb paintings (dating from as early as 1400 BC) that show servants fanning racks of wine jars (Darby et al., 1977). Figure 1 is an example of these paintings. For this system to effectively cool the wine jars, the fanning motion would have to assist the evaporation of water from the surface of the jars. Different archaeologists experimenting with this procedure have recorded achieving quite different drops in temperature (Forbes, 1958). This may be because the wine jar temperature would approach the wet bulb temperature-much like a modern evaporative condenser cools refrigerant by passing air over wet coils-the fact that the wet-bulb temperature varies according to both the dry bulb temperature and the air humidity could explain why the observed temperature drop created by this cooling method varies. The low humidity of the Egyptian environs, ideal for preserving mummified corpses, would also improve the efficacy of this cooling method.

[FIGURE 1 OMITTED]

Where did this evaporating surface water come from? It could be that, as the amphorae were semi-porous, it is due to some of the wine seeping through to the exterior (Curtis, 2001), but this does not sit entirely comfortably alongside evidence that at least some Egyptian amphorae had their inner surface sealed with resins precisely to stop such seepage of product (Darby et al., 1977). However, there is also literary evidence that water was deliberately sprayed onto the surface of the amphorae. Athenaeus of Nauratis (an Egyptian writing in the third century AD) writes that the ancient Egyptians cooled water by:

  "...exposing it to the air in earthernware water-jugs on the highest
  parts of their houses, and all night long two slaves sprinkle the
  jars with water." (Athenaeus).

DRINKING WINE IN GREECE AND ROME

An important feature of Greek culture was the symposium, whose beginnings date back to at least the Homeric period (Vetta, 1999). At the symposium the Greeks would meet, discourse, and drink wine. Wine was also a prominent feature of Roman banquets. There is considerable evidence that both the Greeks and Romans sometimes served wine chilled. For example, Athenaeus of Nauratis provides numerous quotations from the ancient Greeks that demonstrate that wine was both mixed directly with snow to cool it and that wine was also cooled by lowering amphorae into wells (Athenaeus). Likewise, the Roman epigramist Martial (writing in the first century AD) mentions the drinking of both wine and water chilled with snow (Martial). Martial also provides this direction, which clearly suggests that ice was a very expensive commodity:

  "Do not, my slave, mix the smokey wine of Marseilles with iced water,
  lest the water cost you more than the wine." (Martial).

As well as direct mixing of wine with either snow or chilled water, the Greeks used a device called a psykter to provide cooling. The word is related to our word psychrometry. Very early, rare examples of psykters (dating from the seventh and sixth century BC) were sleeved pottery amphora. The inner chamber was filled with wine that was poured in through the neck, and the sleeve, which was accessed via a spout on one side, was filled with chilled water (Karo, 1899). It is also possible that these pottery vessels were preceded by similar devices made of metal (Forbes, 1958). After the late sixth century BC, double walled psykter are no longer found (Karo, 1899) but a new type of psykter became popular (Moore, 1997). This new type was single walled pottery vessel, with a bulbous body supported by a long stem (Figure 2). Wine was placed in the psykter and the whole vessel was then placed in a larger vessel called a krater, which was filled with cooling (or sometimes heating) liquid. The psykter's long stem acted like a keel to prevent it from tipping over (Moore, 1997). The new style of psykter have been rarely found in bronze, and terracotta examples date between 525 BC and 460 BC (von Bothmar, 1961). Some archaeologists hold that the fluids were reversed (the wine was held in the krater and the coolant in the psykter) but this seems unlikely from both a practical perspective and extant illustrations of psykters in use (Moore et al., 1986).

[FIGURE 2 OMITTED]

Clearly, to provide snow for either mixing with wine or to create chilled water to fill psykters, the Greeks must have had some method of storing snow. This probably took the form of covered pits. Athenaeus describes how during the siege of the Indian city of Petra:

  "...Alexander [the Great] dug thirty large trenches close to one
  another, and filled them with snow, and then he heaped on the snow
  branches of oak; for in that way snow would last a long time."
(Athenaeus).

The Romans apparently transported snow from the mountains in carts insulated with straw, and contamination with the straw could result in either discoloration or bad taste (Curtis, 2001). In Rome, the harvested snow was probably also placed in covered pits, and there were special shops that sold snow and ice (Curtis, 2001). There is no evidence that the Romans or Greeks deliberately used techniques like evaporation to cool water or create ice, although they did record the techniques used by the Egyptians in antiquity (Athanaeus). Covered pits continued to be used in parts of Europe for the storage of ice harvested in mountainous regions through-out the medieval period and up until the early nineteenth century (Fiske, 1932).

ICE IN INDIA

Mediterranean and North African civilizations were not the only ancients to use ice. For example, in India, cold water and ice were produced through radiation into the sky (Forbes, 1958). Fiske (1932) reports more details: shallow trenches were dug, insulated with straw, into which shallow water pans were placed. On cold, windless, winter nights heat is radiated from the pans into the sky and ice forms which can be collected in the early morning (Figure 3). This is similar to the method described above in use in Mesopotamia, and ice can be formed using this system even when the air temperature is above freezing (as high as 6[degrees]C or 43[degrees]F; Fiske, 1932). In more modern times, Indian Mughal's also imported ice from the Himalayas up until the 1600s (Dickason, 1991), and under British rule the use of water in shallow pans to create ice was used until the mid-1800s (Fiske, 1932). It is interesting to note that British working in India record that 25-30 tones of ice were produced in a night, but that it took in excess of 2,000 workers and many acres of land, for the ice trenches, to achieve this (Dickason, 1991).

[FIGURE 3 OMITTED]

ICE-CREAM AND REFRIGERATED BARGES IN CHINA

In China ice has also long been used for refrigeration and was used for many food products other than just wine-in a seventh century king's palace roster out of the 2271 personnel who handled food and wine, 94 of them were tasked with the procurement and serving of ice (Chang, 1977). There are also documents that record that the wealthy used chunks of ice to cool their houses at least as far back T'ang dynasty (618 AD-907 AD) (Schafer, 1977). Even earlier, during the Han Dynasty (206 BC - 220 AD) ice was harvested in winter and used in special ice chambers for the storage of meat (Yu, 1977), and Chinese poetic references to ice houses date back as far as 1100 BC (Thevenot R., 1979).

In the T'ang dynasty there are the first records of a dish similar to modern ice-cream which was made from fermented milk mixed with flour and camphor and then refrigerated in ice chambers. Also during this period it is recorded that the imperial palace contained a number of pits for the storage of ice and many other wealthy Chinese also used chunks of ice to prevent the spoilage of fruit and vegetables, especially melons (Schafer, 1977). Documents from 1618, during the late Ming Dynasty, indicate that the Directorate of Foodstuffs (part of the imperial household) routinely shipped perishable goods such as plums, loquats, bamboo shoots, and shad (a type of fish) in barges that were refrigerated with blocks of ice that had been cut in winter and then stored in caves and trenches until needed (Mote, 1977).

SALT SOLUTIONS

Adding certain salts to water can cause a drop in temperature, and from the sixteenth century onwards more solutions were discovered and increasingly lower temperatures were obtained. Temperatures as low as - 40[degrees]C (- 40[degrees]F) were reached in 1760 with mixtures of snow and calcium chloride (Thevenot R., 1979). Indeed, Fahrenheit set the zero of his temperature scale because it was the lowest temperature he could achieve with a mixture of snow and ammonium nitrate (Fiske, 1932). The first written references to such mixtures were by the thirteenth century Arab writer Ibn Abi Usaibia (Thevenot R., 1979), but (maybe because of difficulty in precisely identifying and purifying such salts) they do not seem to have been used in the ancient world (Forbes, 1958).

CONCLUSIONS

Throughout the ancient world ice and snow were used to cool drinks and sometimes other foods. For this purpose pits insulated with timber, mud or straw were dug, to help keep the ice cool until needed. Evidence for ice pits date from the first civilizations in Mesopotamia (2000 BC) and were used up until the modern period in China and in parts of Europe. The ice or snow was sometimes merely harvested from cold regions, like mountains, and transported to more temperate regions. In other cases, the ice seems to have been generated via radiation of heat from shallow pools into the night sky-in imitation of the natural processes that form frost-such systems were used in India and Iran up until the introduction of mechanical refrigeration in the nineteenth century. Finally, there is evidence that evaporative cooling was used, for example in Egypt, to cool wine amphorae. Clearly, although mechanical refrigeration is a modern invention, the desire for a cool glass of wine at a symposium is an ancient desire which Plato would have been able to share with us.

REFERENCES

Anonymous. 1932. Frederic Tudor-Ice King. Bulletin of the Business Historical Society. 6(4):1-8.

Athanaeus. The Learned Banqueters. trans. Olson, S.D. 2006. Cambridge, MA: Harvard University Press.

Bahadori, M.N. 1978 Passive Cooling Systems in Iranian Architecture, Scientific American, Vol. 238(2):144-154.

Chang, K.C. 1977 Introduction. Food in Chinese Culture. Ed Chang, K.C., Binghamton, NY: Yale University Press: 1-21.

Curtis, R. 2001. Ancient Food Technology. Boston, USA: Brill.

Darby, W.J., Ghalioungui, P., Grivetti, L. Food: The Gift of Osiris. London: Academic Press.

Dickason, D.G. 1991. The Nineteenth-Century Indo-European Ice Trade: An Hyperborean Epic. Modern Asian Studies. 25(1):53-89.

Fiske, D.L. 1932. Refrigeration is Not New. Refrigerating Engineering. Vol. 24(4): 201-205.

Forbes, R.J. 1958. Studies in Ancient Technology, Vol. 6. Netherlands: Brill.

Holman, J.P. 1992. Heat Transfer. 7th Edition. London: McGraw-Hill Book Company.

Karo, G. 1899. Notes on Amasis and Ionic Black-Figured Pottery. The Journal of Hellenic Studies. Vol. 19:135-164.

Martial. Epigrams. trans. H.G.B. 1926. London: G.Bell and Sons, Ltd.

Moore, M.B., Philippides, M.Z.P., von Bothmer, D. 1986. Attic Black-Figured Pottery. The Athenian Agora: Vol 23. Lawrenceville, NJ: Princeton Academic Press.

Moore, M.B. 1997. Attic Red-Figured and White Ground Pottery. The Athenian Agora: Vol 30. Lawrenceville, NJ: Princeton Academic Press.

Mote, F.W. 1977 Yuan and Ming. Food in Chinese Culture. Ed Chang, K.C., Binghamton, NY: Yale University Press:193-257.

Sassons, J. 1984. Thoughts of Zimri-Lim. The Biblical Archaeologist. Vol. 47(2):110-120.

Schaffer, E.H. 1977 T'ang. Food in Chinese Culture. Ed Chang, K.C., Binghamton, NY: Yale University Press:85-139.

Thevenot, R. 1979. A History of Refrigeration throughout the world. (trans. Fidler, J.C.). Paris, France: International Institute of Refrigeration.

Vetta, M. 1999. The Culture of the Symposium. Food: A Culinary History from Antiquity to the Present. trans. Botsford, et al. New York: Columbia University Press:96-105.

Von Bothmar, D. 1961. Newly Acquired Bronzes-Greek, Etruscan, and Roman. The Metropolitan Museum of Art Bulletin: New Series. 19(5):133-151.

Yu, Y.S. 1977 Han. Food in Chinese Culture. Ed Chang, K.C., Binghamton, NY: Yale University Press:55-83.

Richard Love, PhD

Associate Member ASHRAE

Richard Love is a lecturer in food engineering at the Institute of Food, Nutrition, and Human Health at Massey University, Palmerston North, New Zealand.