The HPLC analysis of the concentration and enantiomeric purity of selectedamino acids in two highly fermented foods

A HPLC system linked to a variable wavelengths UV detector was used to sequ entially determine the total concentration and enantiomeric composition of two selected free amino acids (leucine, phenylalanine) in two highly fermen ted foods, bean curd and paste soy bean (i.e., miso), after their derivatiz ation with N-benzoyl chloride. As was expected, fermented bean curds tended to have a higher percentage of D-enantiomers and greater total amount of a mino acids than paste soy beans or fermented soy beans as reported previous ly. In one case, the relative amounts of D-phenylalanine and D-leucine exce eded 40% of the individual amino acids. Interestingly, paste soy bean made in Japan is found to be better than that made in Taiwan in terms of a highe r total level of amino acids and a lower percentage of D-enantiomers. In mo st samples, leucine was found to have a lower average percentage of D-enant iomer but higher total concentration than phenylalanine. This finding is co nsistent with what was observed for fermented soy beans. Only a trace of am ino acids (leucine, phenylalanine) was found in raw soy beans and bean curd , which was thought to be a result of a lack of microbial activities (e.g., fermentation, aging, etc.).