Shoyu(Soy Sauce) Flavor Components: Acidic Fractions and the Characteristic Flavor Component

From the volatile flavor concentrate of shoyu, acidic I and acidic II fractions were separated. Shoyu was also directly extracted with CH2C12 in order to cover the components that were not obtained by the above method, and the extract was separated into ten (A~J) fractions. C~I fractions were acidic ones. The above fractions were successively analyzed by gas chromatography and combined gas chromatography-mass spectrometry. Consequently, 93 components were identified, 36 of which have not been reported previously as constituents of shoyu. The identified compounds were 15 alcohols, 15 carbonyls, 9 esters, 4 lactones, 6 furans, 3 furanones, 5 pyrones, 7 phenols, 13 acids and 16 other compounds. Organoleptically, the caramel-like aroma compounds among them are important for the characteristic flavor of shoyu. 4-Hydroxy-2(or 5)-ethyl-5(or 2)-methyl-3(2H)-furanone (HEMF) and 4-hydroxy-5-methyl-3(2H)-furanone seem to be important, and particularly, in view of the content and the organoleptic property, HEMF is concluded to be the main and most important constituent of the characteristic flavor of shoyu.