November 8, 2010

Beer!

In the December issue of the Journal of Archaeological Sciences (quite possibly my favorite academic journal at the moment), there is an article on "Ergosterol as a potential biomarker for alcohol fermentation in lipid residues from prehistoric pottery." A generally-accepted theory is that fermentation (for beer/wine or for bread) is related to the advent and spread of agriculture. However, almost all of the research on alcohol in the past, according to the authors, is related to consumption rather than production. Arguments for the production of alcohol rely solely on indirect archaeological evidence.

The authors seek to remedy this gap in the methodological literature. Testing of lipid (fat) remains in archaeological ceramics has been around for at least a few years. It is possible to look for traces of sterols, cholesterol being the key animal lipid. Plants, on the other hand, produce phytosterols. One of the sterols specific to the fungus kingdom, which includes yeast, is ergosterol (think: ergot). The authors tested potsherds from 134 Bronze Age/Iron Age vessels from settled agricultural groups in Sweden and 115 potsherds from Neolithic hunter-gatherer sites in Sweden.

They did not find any ergosterol in the Neolithic vessels but did find it in 6 of the 134 potsherds from the Bronze/Iron Age. The pots, they concluded, were used for either baking or brewing. The vessels' form suggests a drinking bowl of some sort, however, suggesting it was for brewing or holding alcohol rather than for baking bread. Particularly interesting is their antepenultimate paragraph:

"There are ethnographic examples of ceramic vessels being used for the preparation and fermentation of beer. No addition of yeast is necessary as the pores of the vessels host the yeast between batches (Hayashida, 2008:167). The immobilization of yeast in a ceramic matrix has actually been successfully tried in connection with the development of modern continuous beer brewing systems (Nakanishi et al.,1989). Such impregnation of yeast into the ceramic matrix of the prehistoric vessel will have left detectable traces. Vessels used for fermentation are likely to have had a longer life time of use than for example cooking vessels due to thermal chocks and handling of the latter. Therefore we might expect there to be a smaller number of these vessels than of others in a given assemblage. The special character of these vessels may also be connected to their appearance in funerary contexts."

If yeast can survive in ceramic vessels in sufficient quantities to make beer, it will be exciting when this technique is applied more widely. We may learn more about the process of alcohol fermentation in the past - not to mention more about the people who consumed it and the situations in which they did so. At any rate, even with the low frequency of vessels that had evidence of ergosterol, their data provide direct evidence that fermentation was indeed associated with agricultural societies.

1 comments:

Supplements said...

Early fermentation processes are much different than today's systems.

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