Gas chromatographic detection of D-amino acids as common constituents of fermented foods

Significant amounts of free D-amino acids (D-AA) have been found in fermented foods. Amino acids (AA) were extracted from sour milk, Emmentaler cheese, lactic acid fermented juices of carrots and celery, beer, wine, fermented black beans and a commercial liquid spice obtained by acidic hydrolysis of certain proteinaceous plants. The absolute amounts of free AA in foods were determined by automated ion-exchange chromatography according to Stein and Moore, and the ratios of AA enantiomers were determined as theirN(O)-pentafluoroproprionyl 1- (and 2-) propyl esters by capillary gas chromatography on the chiral stationary phases Chirasil-L-Val and XE-60-L-Val-(S)-α-phenylethylamide. Since D-AA were found in all fermented foods investigated and also on the basis of biochemical considerations of the orgin of D-AA in microorganisms, it may be assumed that D-AA are quite common in fermented foods.