Shoyu (soy sauce) volatile flavor components: Basic fraction.

The volatile basic fraction concentrates were prepared from heated, and raw shoyu, separately. Each concentrate was successively analyzed by combined gas chromatography-mass spectrometry. In the above two concentrates, 35 components were identified, 27 of which have not been reported previously for their presence in shoyu. The identified compounds were 24 pyrazines, 5 pyridines, 2 oxazoles and 4 other compounds. Furthermore, the basic compounds of both heated and raw shoyu were quantitatively analyzed by GC, and the concentrations and odor units of major pyrazines which contained simple alkyl groups as the side chain were also determined. Consequently, the quantity of the basic compounds was found to increase during pasteurization; especially the total quantity of the above major pyrazines increased remarkably, Therefore, it is concluded that these confirmed pyrazines which have very low odor threshold values play an important role in the so-called “heated” flavor which is brought about by pasteurization of raw shoyu in the course of production. In addition, organoleptically, the basic compounds are considered to be indispensable to the shoyu flavor.