Changes of yeast,enzyme activity and metabolites of fermented grains of sauce-flavor Baijiu during stacking
The physicochemical indicators,enzyme activity,total yeast count,and volatile flavor compounds of fermented grains stacked in different rounds in intelligent and traditional workshops were measured,and the stacking fermentation mechanism was analyzed by combining the stacking temperature system.The results showed that with the increase of stacking cycles,the moisture,acidity,ethanol,and L-lactic acid content of the fer-mented grains significantly increased(P＜0.05).The glucose content first increased and then decreased,and the starch content decreased.The stacking temperature was divergent from inside to outside,and the top temperature of the waist surface could reach 50 ℃.The activities of key enzyme systems,such as saccharifying enzymes and liquefying enzymes,were significantly reduced(P＜0.05).The total number of yeast and fermentation capacity decreased after reaching their peak in three rounds.There were 95 common aroma components detected in the intelligent and traditional workshop of stacking fermented grains,including acetic acid,ethyl lactate,benzyl alcohol,etc.The differences analysis of flavor substances between intelligent and traditional workshops showed that orthogonal partial least squares discriminant analysis(OPLS-DA)could effectively distinguish flavor differences between different types of workshops,and 14 key differential volatile flavor components(VIP＞1)were determined by variable importance in the pro-jection(VIP).The study elucidated the changes rules in physicochemical factors,enzyme activity,flavor substances,total yeast count,and viable bacte-rial in fermented grains of different stacking cycles in intelligent and traditional workshops,providing theoretical references for analyzing the mecha-nism of stacked fermentation and the differences in various indicators of fermented grains under two production modes.
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