山兰米醋发酵过程中理化指标及挥发性风味物质的变化规律

Changes of physicochemical parameters and volatile flavor substances in the fermentation process of Shanlan rice vinegar

以山兰黄酒为原料,添加醋酸菌发酵制备山兰米醋,分析测定其理化指标,并采用HPLC法和顶空固相微萃取气质联用法测定山兰米醋发酵过程中的游离氨基酸、有机酸和风味代谢物,分析其发酵过程中的变化规律。结果表明,山兰米醋发酵期间理化性质变化较大,发酵过程中总酸含量逐渐增加,而pH值呈现缓慢下降趋势。在山兰米醋发酵过程中,共检测到27种有机酸,其中乳酸和乙酸的含量较高,是米醋中主要的有机酸成分。游离氨基酸总含量在发酵的中期较高,成品米醋中呈味分布为甜味氨基酸>苦味氨基酸>鲜味氨基酸,甜味最为明显。基于主成分分析和正交偏最小二乘法判别分析发现,发酵不同阶段的代谢物差异较大,共检测到41种差异代谢物。通过对差异代谢物的代谢途径进行分析,筛选出17条关键代谢通路,且不同环境下的微生物代谢通路的富集程度最为显著,次生代谢产物的生物合成通路、植物次生代谢产物的生物合成通路和不饱和脂肪酸的生物合成通路的富集程度最高。

Shanlan yellow rice wine was fermented to develop Shanlan rice vinegar(SRV)using acetic acid bacteria as starter culture.The physico-chemical indexes of SRV were analyzed.The free amino acids,organic acids,and flavor metabolites in the fermentation process of SRV were determined by HPLC and headspace-solid phase micro-extraction-gas chromatography-mass spectrometry.The results showed that the physicochemical properties of the vinegar changed greatly during fermentation.The total acid content increased gradually during fermentation,while the pH value slowly declined.A total of 27 organic acids were detected in the fermentation process of SRV,among which lactic acid and acetic acid were the main organic acid produced.The total content of free amino acids was higher in the middle stage of fermentation.The flavor distribution in the finished SRV was sweet amino acids>bitter amino acids>umami amino acids as well as the sweetness showed the most obvious.Based on principal component analysis and orthogonal partial least squares-discriminant analysis results,there were significant differences in metabolites with 41 different metabolites screened out at different stages of fermentation.Screened out the 17 key metabolic pathways indicated that the enrichment degree of microbial metabolic pathways under different environments was most significant.The enrichment degree of secondary metabolites biosynthesis pathway,plant secondary metabolites biosynthesis pathway,and unsaturated fatty acid biosynthesis pathway were highest.