非酿酒酵母筛选及协同发酵对醪糟挥发性风味影响

Selection of Non-Saccharomyces Yeasts and Effect of Co-fermentation with Them and Rhizopus on the Volatile Flavor Components of Fermented Glutinous Rice Wine

为解决目前传统酒曲生产的醪糟品质不稳定、香气不突出、酒精度偏高等问题,通过微生物多样性分析传统酒曲的真菌群落结构,筛选具有产酯增香特性的非酿酒酵母菌株,探究协同发酵对醪糟挥发性风味物质含量的影响。结果表明,子囊菌门(Ascomycota)和毛霉门(Mucoromycota)是醪糟酒曲的优势真菌门,根霉属(Rhizopus)、复膜孢酵母属(Saccharomycopsis)是主要真菌属。分离纯化后得到4株非酿酒酵母JLY1~4,经测序鉴定JLY1、JLY2是扣囊复膜酵母(Saccharomycops fibuligera),JLY3和JLY4分别是德尔布有孢圆酵母(Torulaspora delbrueckii)和异常威克汉姆酵母(Wickerhamomyces anomalus)。将4株非酿酒酵母分别协同根霉菌发酵醪糟,其中挥发性风味物质种类从46种增加到62种,增加了酯类和醇类化合物的种类,并且明显提升了异戊醇、苯乙醇、乙酸苯乙酯等主要风味物质的相对含量。对醪糟共有的40种挥发性风味成分进行偏最小二乘判别分析,以变量投影重要性值≥1为条件筛选出20种差异风味物质,其中醇类5种、酯类10种、酸类3种、醛酮类1种、烷烃类1种。经差异物质和感官评定分析,JLY1和JLY2产酯增香效果优于其他菌株,协同发酵能够显著提升醪糟的挥发性风味物质含量,改善醪糟品质。

To solve the current problems of fermented glutinous rice wine produced with traditional Jiuqu as a fermentation starter such as unstable quality,weak aroma and high alcohol content,this study selected non-Saccharomyces yeast strains with ester-producing and aroma-enhancing characteristics from traditional Jiuqu by analyzing the structure of its fungal community,and explored the effects of co-fermentation with each selected strain and Rhizopus arrhizus on the volatile flavor components of fermented glutinous rice wine.The results showed that Ascomycota and Mucoromycota were the dominant fungal phyla in Jiuqu and Rhizopus and Saccharomycopsis were the major fungal genera.Four non-Saccharomyces yeast strains,JLY1–JLY4,were obtained,and JLY1 and JLY2 were identified by sequencing as Saccharomycopsis fibuligera,while JLY3 and JLY4 as Torulaspora delbrueckii and Wickerhamomyces anomalus,respectively.Co-fermentation with JLY2 and Rhizopus arrhizus increased the number of volatile components from 46 to 62 compared with the control group,increasing the numbers of esters and alcohols and significantly increasing the relative contents of major flavor compounds such as isoamyl alcohol,phenylethanol,and phenylethyl acetate.Partial least squares-discriminant analysis(PLS-DA) was performed on 40 volatile flavor components shared by fermented glutinous rice wines,and 20 differential flavor substances were selected using the cut-off of variable importance for the projection(VIP) value ≥ 1,including 5 alcohols,10 esters,3 acids,1 aldehyde or ketone,and 1 alkane.Differential substance analysis and sensory evaluation indicated that JLY1 and JLY2 were better than the other strains in terms of ester production and aroma enhancement,and synergistic fermentation significantly enhanced the contents of volatile flavor substances in fermented glutinous rice wine and consequently improved its quality.