Molecular insights into the aging-driven aroma evolution of Jian flavor Baijiu

Kouzijiao (KZJ) is a traditional Jian flavor Baijiu (JFB) that exhibits flavor characteristics typical of both soy sauce flavor Baijiu (SSFB) and strong flavor Baijiu (SFB). However, the key aroma compounds and compositional changes during aging have not been clearly characterized, and manufacturers lack objective criteria to determine the optimal aging period for peak KZJ flavor. A total of 58 aroma compounds were identified in the KZJ from different years using a combined approach of headspace solid-phase microextraction (HS-SPME) and liquid–liquid extraction (LLE) coupled with gas chromatography–olfactometry (GC-O). There were 19 important aroma compounds (FD≥9) with odor activity values (OAVs) ≥ 1 revealed by aroma extract dilution analysis (AEDA) and odor threshold calculations. Among them, ethyl 3-methylbutanoate and ethyl furfuryl ether were first identified as key aroma compounds in JFB. Recombination and omission experiments further confirmed that ethyl acetate, ethyl hexanoate, hexanoic acid, and dimethyl trisulfide made significant contributions to the characteristic aroma profile of KZJ. Moreover, one-way analysis of variance (ANOVA) showed that the levels of key aroma compounds remained relatively stable in KZJ3. This study provides critical insights into the quality control parameters and dynamic trends of key flavor compounds during the aging of KZJ.