为探究清香型白酒立醅与挑醅两个发酵期的产酸环境差异,对两个时期发酵过程中不同关键时间节点的酒醅酸度、产酸菌生物量、短链脂肪酸及对应酒体的短链脂肪酸进行定量分析。研究结果表明,两个时期酸度均随发酵进程递增,挑醅期在整个发酵过程酒醅酸度高于立醅期,且递增速度更快,两个时期在出缸时酸度相差幅度最大为2.22。立醅期发酵过程乳酸菌总数呈马鞍形变化,存在二次发酵现象;挑醅期发酵过程乳酸菌总数变化呈先增后减趋势,产酸菌生物量高于立醅期。在短链脂肪酸差异上,整体来看,挑醅期发酵过程的短链脂肪酸含量均高于立醅各指标含量,且己酸、戊酸及丙酸在挑醅发酵起始含量就较高,其在整个挑醅发酵过程中高表达,尤其是丙酸,两时期发酵末期差异倍数最高,且立醅期产酸最高水平只接近于挑醅期7对(天,下同)时。同样的,对两个时期酒体短链脂肪酸进行对比发现,除己酸外,热季挑醅期的短链脂肪酸含量均高于立醅期各指标含量。显然,挑醅发酵环境对产酸水平有很大影响,尤其是除乙酸外的其他短链脂肪酸的变化。
In order to better understand the differences of acid producing environment in Lipei (LP) and Tiaopei (TP) of Fen flavor Baijiu,the acidity,biomass of acid producing bacteria,short chain fatty acids of fermented grains and corresponding liquor during different periods of fermentation in LP and TP were quantitatively analyzed.Results showed that the acidity of fermented grains in TP was higher than that in LP,and the increasing speed was faster.The maximum difference of acidity was 2.22 in the two stages.The biomass of lactic acid bacteria showed a saddle-shaped change during the fermentation process of LP,and there was a phenomenon of secondary fermentation;the total number of lactic acid bacteria increased first and then decreased during the fermenting period,and the biomass of acid-producing bacteria was higher than that during the fermenting period.On the whole,the content of short-chain fatty acids in the fermenting process during the TP was higher than that in the LP.The contents of caproic acid,valeric acid and propionic acid were higher at the beginning of the TP,and they were highly expressed in the whole fermenting process,especially propionic acid,which had the highest difference multiple at the end of the fermentation.The highest level of acid production in the LP stage was only close to 7 pairs (days) of time in the TP.Similarly,the content of SCFAs in fermenting period in TP was higher than that in LP except caproic acid.Obviously,the fermentation environment in TP has a great impact on the level of acid production,especially the changes of other SCFAs except acetic acid.
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