Key flavor compounds in different grades of strong-flavor Baijiu analyzed based on GC×GC-MS

In this study, the volatile flavor components components in original samples (numbered as A, B and C) of special grade, first grade, and second grade strong-flavor (Nongxiangxing) Baijiu were analyzed by comprehensive two-dimensional gas chromatography-mass spectrometry (GC×GC-MS). The key flavor compounds (OAV≥1) were screened based on odor activity value (OAV), and key differential flavor compounds (OAV≥1,VIP>1) were screened by the variable importance in projection (VIP) values of orthogonal partial least squares-discriminant analysis (OPLS-DA). Furthermore, the correlation analysis was conducted between the key differential flavor compounds and the sensory characteristics, combined with the sensory evaluation of the Baijiu samples. The results shown that the contents of ethyl caproate, ethyl acetate and ethyl butyrate in grade A wine samples and the types of key flavor substances were higher than those in grade B and C wine samples. Combined with the VIP values, a total of 11 key differential flavor compounds were obtained, which were mainly hexyl caproate, ethyl caproate, propyl caproate, and so on. The sensory scores of grade A Baijiu sample were higher, with floral, fruity, and sweet aromas and mellow flavors with discernible aftertastes. The correlation analysis results showed that esters (ethyl caproate, isobutyl acetate, hexyl caproate, propyl caproate, etc.) were positively correlated with spiciness, mellowness, sweetness, and aftertaste in general. Alcohol compounds (2-methyl-1-butanol, 3-methyl-1-butanol) were positively correlated with grain aroma and sour taste, but negatively correlated with alcohol sweetness and coordination.