Comprehensive Investigation of Grade-Specific Aroma Signatures in Nongxiangxing Baijiu Using Flavoromics Approaches

At present, the classification of nongxiangxing baijiu (NXB) predominantly relies on the subjective expertise of distillers and tasters, in the absence of scientifically standardized criteria. This reliance poses challenges for achieving precise classification. Consequently, there is an urgent need to employ flavoromics technology to identify the key characteristic aroma compounds that distinguish different grades of NXB. This study uses sensory evaluation, an electronic nose, and three-dimensional fluorescence spectroscopy to determine the significant differences in aroma profiles among different grades of NXB. Further, 112 compounds were identified by GC-MS, and quantitative analysis was conducted on 33 major volatile compounds. Using odor activity value (OAV) analysis, it found 21, 23, and 26 key aroma compounds (OAV ≥ 1) in Grade 2 (G2), Grade 1 (G1), and prime-grade (GP), respectively. Aroma recombination successfully simulated the aroma distribution of different grades of NXB, and omission experiments identified 11 key aroma compounds as the foundation for NXB. Additionally, each grade exhibited a unique profile of key compounds. G2 was characterized by the presence of octanoic acid, which imparts sweaty and cheesy aromas. G1 contained benzoic acid ethyl ester, phenethyl acetate, pentanoic acid, 2-methyl-1-propanol, and furfural, contributing to sweet, floral, sweaty/cheesy, alcoholic, and roasted aromas. GP demonstrated higher concentrations of aroma compounds compared to G1 and G2, with distinctive compounds such as decanoic acid ethyl ester, dodecanoic acid ethyl ester, 3-methyl-1-butanol, and 1-hexanol, which are associated with sweaty/cheesy, fruity, and alcoholic aromas. This study elucidated the role of these compounds in determining the flavor profiles of various NXB grades, thereby providing a theoretical foundation for the quality grading of NXB.