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Abstract
Accurate, simple methods are needed to determine tannic acid (gallotannin), which is present endogenously in many foods and fermented beverages such as wine and cider. A method complementary to thin-layer chromatography (TLC) uses high performance liquid chromatography (HPLC) on Corasil-II, with a multisolvent gradient system. The calibration curves are made with both monomeric and dimeric gallic acid. The latter is isolated from tannic acid by preparative HPLC and identified by nuclear magnetic resonance spectroscopy and TLC. Tannic acid is then determined in a beer ethyl acetate extract by quantitative chromatography of its gallic and digallic acid components. Because endogenous digallic acid has not been reported in beer, determination of this component in beer confirms the presence of tannic acid and its use in beer processing. The HPLC method offers an alternative to the TLC method and can be used to confirm TLC results.