IDENTIFICATION OF PROANTHOCYANIDINS IN BEER AND THEIR DIRECT MEASUREMENT WITH A DUAL ELECTRODE ELECTROCHEMICAL DETECTOR

A sensitive and reliable method was developed for the measurement of simple flavanols in beer by direct-injection High Performance Liquid Chromatography using dual-electrode electrochemical detection. When operated in the amperometric mode the detector was extremely sensitive for readily-oxidized substances such as polyphenols, so that sample preparation was minimal. The dimeric flavanols in a commercial beer were positively identified as procyanidin B3 and prodelphinidin B3. Tentative identifications for three trimeric proanthocyanidins were made also. Collectively, monomeric, dimeric and trimeric flavanols accounted for only about 4% of the colorimetrically determined total polyphenol content, and about 35% of the total flavanol content of a non-haze stabilized beer. The improved chromatographic method was applied to measuring the decreases in simple flavanols caused by treatment of beer with polyvinylpolypyrrolidone.