Impact of steamed rice moisture content on solid-state saccharification, fermentation, and flavor profile of rice-flavor baijiu

We examined the impact of steamed rice moisture content during solid-state saccharification (SSS) on the fermentation process and the flavor profile of rice-flavor baijiu. Rice-flavor baijiu was produced using steamed rice with 60% and 36% moisture. The 60 % saccharified rice showed significantly higher levels of enzyme activities, lactic acid, and amino acids, as well as accelerating fermentation. The 60 % baijiu had stronger alcoholic and sour aromas, while 36 % baijiu exhibited sweeter, fruity, and floral aromas. Ethyl lactate levels, a key compound, showed no significant differences between treatments. Ethyl lactate production activity from lactic acid and ethanol was detected in the intracellular fraction of yeast, with a Km value of 22 mM for lactic acid. Since the lactic acid concentration in both the 60 % and 36 % mash was about twice the Km value, ethyl lactate levels became similar in both baijiu preparations. These results indicate that the 60 % moisture condition promotes alcohol fermentation and reduces the risk of contamination.