A special storage container called Mare Nectaris bears a close relationship with Feng-flavor Baijiu quality during aging. The goal of this work is to unveil molecular mechanism of the role of Mare Nectaris in the Feng-flavor Baijiu aging as well as establishes a classification method of vintage Baijiu. Based on ultra high performance liquid chromatography quadrupole-orbitaltrap high resolution mass spectrometry (UHPLC-Q-Orbitrap HRMS), most micromolecules especially nonvolatile molecules in Baijiu can be accurately identified and in total of 45 characteristic molecules were discovered through application of the principal component analysis (PCA), partial least square-discriminant analysis (PLS-DA), variable importance in projection (VIP). With the increase of aging year, in addition to 5-fluoro-2,3,4-three chlorobenzoic acid decreased, the other 44 components showed remarkable up-regulation, concretely comprising 10 kinds of esters, 6 organic acids, 8 amino acids , 11 bioactive components and 9 other components. By utilizing artificial neural network recognition model which used 45 characteristic molecules as inputs and 8 groups various aging years as outputs, the prediction accuracy of Baijiu vintage was up to 100%.
Ethyl carbamate (EC) is carcinogen occurring naturally in fermented foods, while the EC formation pattern in Feng-flavor Baijiu during Mare Nectaris storage and magnetic field treatment remains controversial. In this work, variation of EC in Mare Nectaris and magnetic field were investigated for the first time through ultra high performance liquid chromatography quadrupole-orbitrap high resolution mass spectrometry (UHPLC-Q-Orbitrap). Quantification results revealed that EC decreased significantly in the stage of 3–9 years and kept at 12.4 μg L −1 after 10 years of aging. Arginine succinate synthase (ASS) and urease were deemed as vital factors for EC decomposition. Degradation effetc of EC in 250 mT is simillar to that of EC in Baijiu stored in Mare Nectaris for 8 years. This is due to that aging process was accelerated by magnetic field and the content of total acid in Baijiu was increased, creating a favorable environment for decomposition of EC and urea.