大曲贮存过程中原核微生物群落结构及风味成分演替规律

The succession of procaryotic microbial community and the flavor components in the storage process of Daqu

【目的】研究大曲贮存过程中原核微生物群落结构及风味成分变化规律,阐述大曲贮存阶段的必要性和重要性,并探索不同微生物种属之间的相互关系,为更好地控制大曲品质提供微生物和风味方面的参考依据。【方法】通过Mi Seq高通量测序剖析大曲成熟过程中原核微生物群落结构变化;利用共存(Co-occurrence)模式方法分析不同种属微生物之间的相关关系,预测其相关性;利用SPME-GC-MS分析贮存过程中大曲风味成分的变化规律。【结果】采用Mi Seq测序方法共得到3 710个OTUs,除不能有效比对的序列外共鉴定出29个门和160个种属。其中,乳杆菌属、芽孢杆菌属、明串珠菌属、高温放线菌属、乳球菌属等是大曲中的优势菌群。随大曲贮存时间推移,贮存前期不断积累酸、醇类物质,后期酯类及含氮类等重要风味物质不断形成,而4-甲基苯酚等异味物质的含量却不断降低。相关性分析结果表明,乳酸菌与乳酸、乙酸等酸类物质之间存在显著的相关性,芽孢杆菌与酸类及含氮化合物之间存在显著的相关性。【结论】大曲贮存过程中,原核微生物结构不断发生调整,风味物质向更优质白酒风味进行变化。除环境因素外,原核微生物的代谢活动对风味物质的形成具有重要的影响,因此大曲贮存是白酒酿造过程中必不可少的环节。

[Objective] To expound the necessity and importance of the storage process of Daqu, and to control the quality of Daqu, we researched the succession of bacterial community and the flavor components of Daqu. The relationships between different bacterial genera were also analyzed. [Methods] We analyzed the bacterial community structure of Daqu in different storage processes through Mi Seq high-throughput sequencing technology; Co-occurrence pattern analysis method was used to analyze the relationships between different genera of bacteria; SPME-GC-MS was used to analyze the flavor compounds of Daqu in different storage processes. [Results] 3 710 OTUs were obtained through Mi Seq technology, which classified to 160 genera, 29 phyla. Lactobacillus, Bacillus, Leuconostoc, Thermoactinomyces and Lactococcus were the dominant genera in Daqu, which is the guarantee for the normal fermentation. During the storage process, acids, alcohols, esters and other components which good for the flavor of Chinese liquor were accumulated, while the off-odor compounds such as 4-methyl phenol were constantly reduced. The significant pairwise linear regressions for bacteria and flavor components indicated that lactic acid bacteria was closely correlated to lactic acid, acetic acid and other acid components. Besides acids components, Bacillus was correlated to nitrogen compounds also. [Conclusion] During the storage process, the bacterial community structure of Daqu was adjusted and the flavor components were changed for better flavor. In addition to the environmental factors, the metabolic activity of bacteria is the main influence of the formation of flavor components. Therefore, the storage of Daqu is necessary.