Quantification and Distribution of Thiols in Fermented Grains of Sauce-Aroma Baijiu Production Process.

Five volatile thiol compounds (methanethiol, ethanethiol, 2-mercapto-1-ethanol, 2-furfurylthiol, and 2-methyl-3-furanethiol) in fermented grains of sauce-aroma baijiu were determined using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The samples were pre-treated using a modified QuEChERS method. 4,4'-Dithiodipyridine (DTDP) derivatization reaction improved the detectability and stability of volatile thiol compounds. From the end of the first round to the end of the seventh round of fermentation and different fermentation states from the fifth round of fermented grains of the sauce-aroma baijiu production process were analyzed. The results showed that the concentrations of methanethiol (67.64-205.37 µg/kg), ethanethiol (1.22-1.76 µg/kg), 2-furfurylthiol (0.51-3.03 µg/kg), and 2-methyl-3-furanthiol (1.70-12.74 µg/kg) were increased with the number of fermentation rounds. Methanethiol, 2-furfurylthiol, and 2-methyl-3-furanthiol increased during fermentation and distillation in the fifth round. Fermentation and distillation were important stages for their widespread production. After distillation, there were still a large number of volatile thiol compounds in the fermented grains. The thermal reaction was of great significance in the formation of these thiols.

Characterization of key aroma compounds in aged Qingxiangxing baijiu by comparative aroma extract dilution analysis, quantitative measurements, aroma recombination, and omission studies.

Aging aroma is an intriguing but an understudied phenomenon in baijiu. The aromatic characteristics of Qingxiangxing (QXX) baijiu stored for 45 years (aged) were investigated using the sensomics approach and were compared with those of young baijiu (0 year-old). Aroma extract dilution analysis revealed 59 odorants, with many long-retained components exhibiting greater flavor dilution values in the aged than the young sample. The analysis of variance of the quantitative data showed significant differences between the young and aged baijiu for 26 compounds. Based on the variations in the content of these compounds, QXX baijiu aged for 0, 5, 15, 20, and 45 years was analyzed and twelve compounds were significantly correlated with aging duration. Finally, eight positively correlated compounds were omitted from the recombinant model, and sotolon, methional, vanillin, dimethyl trisulfide, benzaldehyde, and 3-hydroxy-2-butanone were confirmed to primarily contribute toward the aging aroma of QXX baijiu.