泸型酒酿造过程中各层酒醅挥发性物质变化规律

采用顶空固相微萃取（HS-SPME）结合气相色谱-质谱（GC-MS）联用技术，对泸州老窖浓香型白酒（泸型酒）酿造过程中上、中、下层酒醅的主要挥发性风味物质的变化规律进行分析，并基于酯类物质进行主成分分析（PCA）。结果表明，三层酒醅的主要挥发性风味物质为醇类、酸类和酯类，其在不同层酒醅发酵过程中的变化趋势相似，醇类物质相对含量变化不明显；发酵前期（0～15 d），酯类物质相对含量上升，酸类物质相对含量下降，发酵后期（18～39 d）这两种物质变化趋于平稳。发酵结束时，上层酒醅主要挥发性风味物质含量最高，下层酒醅次之，中层酒醅最低。PCA结果表明，泸型酒发酵过程分两个阶段，发酵前期特征酯类物质为乙酸乙酯和丁酸乙酯等，发酵后期特征酯类物质为己酸乙酯、乳酸乙酯等。

Changes of volatile compounds in different layers of fermented grains during Lu-flavor Baijiu brewing

Changes rule of main volatile flavor compounds in upper, middle and lower layer of fermented grains during Luzhoulaojiao strong-flavor Baijiu (Lu-flavor Baijiu) brewing were analyzed by headspace solid-phase micro-extraction (HS-SPME) combined with gas chromatography-mass spectrometer (GC-MS), and principal component analysis (PCA) was carried out based on ester compounds. The results showed that the main volatile compounds in three layers of fermented grains were alcohols, acids and esters, their change trend in fermentation process of different layers of fermented grains was similar, and the relative contents of alcohols did not change significantly. In the early stage of fermentation (0-15 d), the relative contents of esters increased, while the relative contents of acids decreased. In the late stage of fermentation (18-39 d), the changes of these two substances tended to be stable. At the end of fermentation, the contents of main volatile flavor substances in the upper layer of fermented grains were the highest, followed by those in the lower layer of fermented grains, and the middle layer of fermented grains was the lowest. The results of PCA showed that the fermentation process of Lu-flavor Baijiu could be divided into two stages, the characteristic esters in the early stage of fermentation were ethyl acetate and ethyl butyrate, and the characteristic esters in the late stage of fermentation were ethyl caproate and ethyl lactate.