Restoration of Choujiu Koji and evaluation of its brewing performance

Koji is used as a fermentation starter in Choujiu manufacture in northwestern China. Traditional natural Koji (NK) cultivates in open environments, which probably leads to diverse microflora, causes inconsistent quantities in Koji, then results in instable qualities of Choujiu. A native Choujiu producer has been purchasing NK from local workshop, while their Choujiu qualities fluctuate by the stability of NK. As a request from the producer, this study aimed for stable Koji and inheriting sensory traits of current products. Strains of mold, yeast, and LAB, separated from NK, were selected for Restored Koji (RK) making. Brewing performance of RK and NK were compared by analysis of the physicochemical properties and volatile flavor compounds (VFCs) in fermented mash, combined with sensory evaluation in corresponding Choujiu. Pure Koji from individual strains was separately cultured at 28 °C for 48 h, and then reconstituted for RK II at the proportion of mold Koji (M7 Koji): yeast Koji (Y3 Koji: Y4 Koji = 1:1): LAB Koji (L1 Koji) = 1:1:1, where M7 was Rhizopus oryzae , Y3 was Saccharomyces cerevisiae , Y4 was Saccharomycopsis fibuligera , and L1 was Pediococcus pentosaceus . Results showed RK II could meet the desired purpose of this study.