Seasonal Variation of Flavor Substances in Chinese Strong-Flavor Baijiu Base Liquor

In order to explore the flavor characteristics of strong-flavor baijiu base liquor in different seasons and different distillation stages, their organic acids and volatile components were analyzed using high-performance liquid chromatography and headspace solid-phase micro-extraction/gas chromatography-mass spectrometry (HS-SPME/GC-MS). The results showed that the contents of total acid and four major acids (caproic acid, acetic acid, lactic acid and butyric acid) in the second stage of distillation were lower than those in the third stage. The contents of total acid and all four organic acids in base liquor were higher in spring and summer than in autumn and winter. A total of 108 volatile compounds were detected, and the total content of volatile flavor substances in the second stage of distillation was higher than that in the third stage. The content of esters in the second stage was higher, while the contents of acids and ketones were lower. In different seasons, the content of alcohols in base liquor in decreasing order was as follows: spring > summer > autumn > winter, and the content of acids was higher in spring and summer than in autumn and winter. As the seasons went on, the content of aldehydes in base liquor increased in the second stage, but decreased in the third stage. Using partial least squares-discriminant analysis (PLS-DA), a classification model for volatile compounds in base liquor samples collected in different seasons and different distillation stages, which proved to be quite efficient. According to variable importance in the projection (VIP > 1) from the model, the key differential compounds were identified to characterize the volatile composition of strong-flavor baijiu. These results can provide data support for the adjustment of the distillation process in strong-flavor baijiu production in different seasons.