Determination of Tannic Acid in Beer by Thin-Layer Chromatography¹

1 Presented at the 44th Annual Meeting, Toronto, Canada, May 1978.

Abstract

Chillproofing and antioxidant activities of tannic acid and its availability from natural sources make it a stabilizing agent of substantial interest. This paper describes accurate methodology for determining tannic acid used in beer production. Because the polymeric components of tannic acid (gallotannins) react with complex nitrogenous beer constituents, the gallic acid monomer component can be measured. Beer is extracted with ethyl acetate and subjected to thin-layer chromatography on silica gel. A rapid visual test (Prussian blue) determines if tannic acid has been used in beer production. If the test is positive, spectrodensitometric measurement of the gallic acid monomer determines tannic acid added to beer after kettle boiling. Residual gallotannins and those removed during processing are determined similarly in the beer hydrolysate. Digallic acid carries over to finished beer with the gallic acid monomer if tannic acid is added after kettle boiling. Tannic acid that is added before kettle boiling hydrolyzes, since no digallic acid is detected in finished beer. Oxidation browning of gallic acid on silica gel plates also is shown.

• Gallic acid
• Gallotannins
• Silica gel
• Spectrodensitometry
• Prussian blue