Abstract: Bacillus amyloliquefaciens SWJS22 and Aspergillus oryzae were used as starters for soy sauce fermentation in this paper. To study the effects of koji making on soy sauce fermentation, soy sauces produced with koji containing Aspergillus oryzae alone (control) and in combination with Bacillus amyloliquefaciens SWJS22 and with mixed koji cultures of the strains were tested for physicochemical parameters and flavor compounds. Compared with the control group and soy sauce fermented by koji containing mixed strains, soy sauce fermented by mixed koji cultures showed higher amino acid conversion, lower color index and lower pigment content. Soy sauce fermented by mixed cultures had a significantly higher content of glutamic acid compared with the control group. Comparative analysis of flavor compounds by gas chromatograph-mass spectrometry (GC-MS) indicated that only a slight difference was seen in the flavor substances of three soy sauces and the important ones were detected in all of them. The content of acids was lowest in soy sauce fermented by mixed koji cultures.

Key words: Bacillus amyloliquefaciens SWJS22, koji containing mixed strains, mixed koji cultures