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May 8, 2020

Beer was here! A new microstructural marker for malting in the archaeological record

The bowl-shaped charred cereal product ("brei mit napfförmiger oberfläche") from Hornstaad--Hörnle IA.Find no. Ho 45/43-28. Top: light micrograph (red square: location of SEM subsample), bottom: SEM images. Left: patch of regularly arranged aleurone cells (A) with a conspicuous intercellular space (*) in between. L... longitudinal cells, right: fracture through the outer caryopsis layers, the multiple aleurone layers (A1 -A3) identify the material as cultivated barley (Hordeum vulgare) as do the thin-walled transverse cells (T). SE... starchy endosperm (fused remains), N? ... probably nucellus tissue, L?... probably longitudinal cells, E... epidermis (abraded).. Images: ÖAW-ÖAI / N. Gail (light micrograph), A. G. Heiss (SEM) Credit: Heiss et al, 2020 (PLOS ONE, CC BY)
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The bowl-shaped charred cereal product ("brei mit napfförmiger oberfläche") from Hornstaad--Hörnle IA.Find no. Ho 45/43-28. Top: light micrograph (red square: location of SEM subsample), bottom: SEM images. Left: patch of regularly arranged aleurone cells (A) with a conspicuous intercellular space (*) in between. L... longitudinal cells, right: fracture through the outer caryopsis layers, the multiple aleurone layers (A1 -A3) identify the material as cultivated barley (Hordeum vulgare) as do the thin-walled transverse cells (T). SE... starchy endosperm (fused remains), N? ... probably nucellus tissue, L?... probably longitudinal cells, E... epidermis (abraded).. Images: ÖAW-ÖAI / N. Gail (light micrograph), A. G. Heiss (SEM) Credit: Heiss et al, 2020 (PLOS ONE, CC BY)

A new method for reliably identifying the presence of beer or other malted foodstuffs in archaeological finds is described in a study published May 6, 2020 in the open-access journal PLOS ONE by Andreas G. Heiss from the Austrian Academy of Sciences (OeAW), Austria and colleagues.

A beverage with prehistoric roots, beer played ritual, social, and dietary roles across ancient societies. However, it's not easy to positively identify of cereal-based like beer, since most clear markers for beer's presence lack durability or reliability.

To explore potential microstructural alterations in brewed , Heiss and colleagues simulated archaeological preservation of commercially-available malted barley via charring (malting is the first step in the beer-brewing process.). They compared these experimental grains with ancient grains from five dating to the 4th millennium BCE: two known beer-brewing sites in Predynastic Egypt, and three central European lakeshore settlements where cereal-based foods were found in containers, but the presence of beer was not confirmed.

Using , the authors found their experimental barley grains had unusually thin aleurone cell walls (specific to grains of the grass family Poaceae, the aleurone layer is a tissue forming the outermost layer of the endosperm). The archaeological grain samples across all five prehistoric sites showed the same aleurone thinning.

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Although there are other potential reasons for this type of thinned cell wall (such as fungal decay, , or degradation during heating—all of which can be ruled out with careful analysis), these results suggest that this breakdown in the grain's aleurone layer can serve as a general marker for the malting process.

This new diagnostic feature for confirming the presence of beer (or other malted beverages/foodstuffs) in artifacts works even if no intact grains are present. A novel tool for identifying the possible presence of beer in where no further evidence of beer-making or -drinking is preserved, this method promises to broaden our knowledge of prehistoric malting and brewing.

The authors note: "Structural changes in the germinating grain, described decades ago by plant physiologists and brewing scientists alike, have now successfully been turned into a diagnostic feature for archaeological malt, even if the grains concerned are only preserved as pulverized and burnt crusts on pottery. A "small side effect" is the confirmation of the production of malt-based drinks (and beer?) in central Europe as early as the 4th millennium BC." Dr. Heiss adds, "For over a year, we kept checking our new feature until we (and the reviewers) were happy. However, it took us quite a while to realize that en passant we had also provided the oldest evidence for malt-based food in Neolithic central Europe."

More information: Heiss AG, Azorín MB, Antolín F, Kubiak-Martens L, Marinova E, Arendt EK, et al. (2020) Mashes to Mashes, Crust to Crust. Presenting a novel microstructural marker for malting in the archaeological record. PLoS ONE 15(5): e0231696.

Journal information: PLoS ONE

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