Effect of enzymes addition on the fermentation of Chinese rice wine using defined fungal starter

A higher fermentation capability and quality of a rice wine was achieved, using mixed fungal (Rhizopus chinonsis R01, Asperigillus niger A20, Mucor pusillus M05 and Saccharomyces cerevisiae S10) starter fermentation of japonica rice supplemented with a-amylase (AM), glucoamylase (GAM) and acid protease (AP). Results showed that alcohol content, free amino acids (FAA) and volatile flavor substances concentrations were increased by 49.22%, 85.54%, and 25.71% compared with the control group respectively. To understand the role of enzymes during rice wine brewing, the effects of hydrolases on chemical and physical properties of cooking rice, on the yeast growth, enzyme productivity of molds were determined. Rice starch was hydrolyzed effectively by AM and GAM, the viscosity reduced significantly, the enzyme contact area expanded, which accelerated the further hydrolysis of japonica rice. Increase of hydrolysate promoted the fungi growth, while improved the ability of molds to produce enzymes. AP promoted the protease activity of M. pusillus M05 and A. niger A20, improved protein utilization, increased the content of FAA and formed higher level of flavor substances in rice wine. The results indicate that hydrolase addition can change the physic-chemical state of the mash to enhance microbial biotransformation and modify flavor metabolism.