Six specially constructed Early Celtic ditches previously excavated at Eberdingen-Hochdorf a 2,550-year-old settlement in Germany, were used to make high-quality barley malt, a key beer ingredient, says archaeobotanist Hans-Peter Stika of the University of Hohenheim in Stuttgart. Thousands of charred barley grains unearthed in the ditches about a decade ago came from a large malt-making enterprise, Stika reports.
     The researcher bases that conclusion on a close resemblance of the ancient grains to barley malt that he made by reproducing several methods that Iron Age folk might have used. He also compared the ancient grains to malt produced in modern facilities. Upon confirming the presence of malt at the Celtic site, Stika reconstructed malt-making techniques there to determine how they must have affected beer taste.
     The oldest known beer residue and brewing facilities date to 5,500 years ago in the Middle East, but archaeological clues to beer's history are rare. At the Celtic site, barley was soaked in the specially constructed ditches until it sprouted, Stika proposes. Grains were then dried by lighting fires at the ends of the ditches, giving the malt a smoky taste and a darkened color. Lactic acid bacteria, stimulated by slow drying of soaked grains, added sourness to the brew.
     Unlike modern beers, the Eberdingen-Hochdorf brew probably contained spices such as mugwort, carrot seeds or henbane, in Stika's opinion. Excavations at the Celtic site have yielded a few seeds of henbane, a plant that also makes beer more intoxicating. "These additives gave Celtic beer a completely different taste than what we're used to today," Stika says. Heated stones placed in liquefied malt during the brewing process - a common practice later in Europe - would have added a caramelized flavor to this fermented Celtic drink, he adds. Stika suspects that fermentation was triggered by using yeast-coated brewing equipment or by adding honey or fruit, which both contain wild yeasts.
     Classics professor Max Nelson of the University of Windsor in Canada, an authority on ancient beer, largely agrees with Stika's conclusions. Other stages of brewing occurred either at the site, as suggested by Stika, or nearby, in Nelson's view. "Stika's experiments go a long way toward showing how precisely barley was malted in ancient times," he remarks. Beer buffs today would regard Celtic beer as a strange brew not only for its flavor but because it would have been cloudy, contained yeasty sediment and been imbibed at room temperature, Nelson notes.

Edited from ScienceNews (14 January 2011)