Elucidating the organometallic interactions in Baijiu will promote a deeper understanding of the flavour formation mechanism during Baijiu aging. However, the organometallic interactions during aging are difficult to explore because the concentration and status of metals in Baijiu samples are affected by other substances (such as organic acids), and the concentrations of these substances also change dynamically. Hence, the flavour formation mechanism of aged Baijiu was investigated based on a multi-method analysis (i.e. electrochemistry, ICP-MS/OES, and UPLC-Q-Orbitrap-MS/MS), which enabled us to solve the difficulty above. The key finding is that, in the aging period, the organic acids induce the transformation of the metal ion state from the complex state to the free state. As a result, the flavour compound (i.e. the esters) contents in aged Baijiu are regulated by the free metal ion-catalyzed reactions.
The oxygen-based oxidation process is leading toward the understanding of the flavour formation mechanism of aged Baijiu. However, the oxygen-based oxidation process in Baijiu aging is difficult to explore because of (1) the composition of Baijiu produced in different batches varies a lot and (2) the spontaneous oxidation needs several years or even decades to occur. Hence, the flavour formation mechanism of Baijiu aging was investigated using electrochemistry and UPLC-Q-Orbitrap-MS/MS, which enabled us to solve the two difficulties above. The oxidation reaction on gold surface could accelerate Baijiu aging by catalyzing the transformation from alcohols to acids. Although natural aging contributed more diverse compound changes to Baijiu, the oxygen-based oxidation process during natural aging was similar to that in the electrochemical oxidation as a whole. This study provides new insights to flavour formation mechanism of aged liquors and provides a new way for liquor-related enterprises to optimise the aging process.
Fingered citron ( Citrus medica L. var. sarcodactylis Swingle) is a medicinal and edible citrus fruit cultivated in several major production regions of China. However, comprehensive information on its regional metabolite variation and its chemical differentiation from chayote ( Sechium edule ), a botanically unrelated commodity that may be confused with fingered citron because of partially overlapping Chinese vernacular names, remains limited. In this study, untargeted UPLC‐Q‐Orbitrap MS/MS was used to profile fingered citron samples from Zhejiang (CF1), Sichuan (CF2), Guangdong/Guangxi (CF3), and Yunnan (CF4), together with chayote samples used as a targeted authentication comparator (CFM). A total of 380 metabolites were putatively annotated, including 47 secondary metabolites comprising 23 flavonoids, 8 terpenoids, 8 phenols, 3 coumarins, 3 alkaloids, and 2 steroids. Multivariate analyses and hierarchical clustering identified 65 differential metabolites, including 19 secondary metabolites, that clearly separated the five sample groups within the present dataset. The very high cross‐validated Q 2 values should nevertheless be interpreted cautiously because of the large taxonomic and metabolic distance between C. medica and S. edule and the limited sample size. The interspecific separation was therefore interpreted as an expected chemotaxonomic difference with practical authentication value, rather than as a comparison between biologically equivalent taxa. Phenylalanine metabolism and flavone and flavonol biosynthesis showed the strongest nominal enrichment, although neither remained significant after FDR correction. These results provide a metabolite reference for regional quality discrimination of fingered citron and identify candidate chemical features for its targeted authentication against chayote. Further validation using independent samples, additional production years, and other potential comparator commodities is required before routine application. Untargeted UPLC‐Q‐Orbitrap MS/MS metabolomics was used to profile fingered citron ( Citrus medica ) from four Chinese production regions (CF1–CF4) and chayote ( Sechium edule , CFM). Of 380 putatively annotated metabolites, 65 differential metabolites distinguished the five groups, clearly separating chayote from fingered citron and highlighting regional chemical variation among fingered citron cultivars.
危险品化学品经营许可证（带存储）