Abstract: In this study, we evaluate the quality and antioxidant activity of raw sauce produced by high-salt liquid-state fermentation of rice dregs with mixed starter cultures. The results showed that all four rice sauces fermented by different mixed starters reached the quality requirements of the Chinese national standard GB 18186-2000 for first-grade soy sauce. The sauce fermented by soy sauce koji containing Aspergillus oryzae and Aspergillus niger plus Zygosaccharomyces rouxii (S4) contained 41.81 g/L total free amino acids. The rice sauces had higher contents of total amino acids, essential amino acids, flavor amino acids and antioxidant amino acids than soy sauce fermented by Aspergillus oryzae (S5). The antioxidant activity of the rice sauces fermented by soy sauce koji containing Aspergillus oryzae alone (S3) and both Aspergillus species (S4) plus Zygosaccharomyces rouxii was higher than that of their counterparts (S1 and S2) obtained without the use of Zygosaccharomyces rouxii. S3 was found to have the strongest antioxidant activity, showing a 175.42- and 2.16-fold increase in hydroxyl and DPPH radical scavenging capacity compared with VC, respectively. The antioxidant activity of rice sauce was strongly influenced by fermentation temperature, reaching a peak at 35 and 50 ℃. In conclusion, the quality and antioxidant activity of rice sauce fermented with mixed cultures could be considerably improved compared with single culture fermentation, which is greatly attributed to Zygosaccharomyces rouxii.

Key words: raw sauce produced from rice dregs, quality, antioxidant activity, mixed strains, Zygosaccharomyces rouxii