TRIHYDROXYOCTADECENOIC ACIDS IN BEER - QUALITATIVE AND QUANTITATIVE-ANALYSIS

Linoleic acid derived 9,10,13- and 9,12,13-trihydroxyoctadecenoic acids present in beer were subjected to stereochemical analysis by a method recently developed (Hamberg, M. Lipids 1991, 26, 407-415). Although all of the 16 possible isomers were detected, ca. 60% of total 9,10,13- and 9,12,13-trihydroxyoctadecenoates was accounted for by a single isomer, i.e., 9(S),12(S),13(S)-trihydroxy-10(E)-octadecenoic acid. A method for quantitative determination of 9,10,13- and 9,12,13-trihydroxyoctadecenoic acids was developed. Application of the method to five samples of beer showed that the mean concentration of 9(S),12(S),13(S)-trihydroxy-10(E)-octadecenoic acid was 5.9 +/- 1.1-mu-g/g and that the total concentration of 9,10,13- and 9,12,13-trihydroxyoctadecenoic acid isomers was 9.9 +/- 2.1-mu-g/g of beer.