Chemical profiling and metabolic mechanism of Pixian doubanjiang, a famous condiment in Chinese cuisine

Pixian doubanjiang (PXDB) is a famous fermentation condiment in China and throughout the world. However, detailed information regarding its metabolic mechanism remains scarce. This paper presents a comprehensive chemical profiling of PXDB during fermentation, to obtain a global understanding of the metabolite variations based on the untargeted metabolomics approach through ultra-performance liquid chromatography coupled with quadruple-time-of flight mass spectrometry (UHPLC-Q-TOF). Ninety-nine metabolites, including amino acids, small peptides, organic acids, fatty acids and phospholipids were proposed as key chemical markers for the first time. Meanwhile, the pathways' analysis revealed that the transformation of these metabolites was primarily associated with arginine biosynthesis, alanine, aspartic acid and glutamate metabolism, glycerol phospholipid metabolism, unsaturated fatty acid biosynthesis and citric acid cycle pathways. The comprehensive analysis of the metabolite changes is expected to help us explore the formation of the taste and flavor components in PXDB production.