Identification of phenols and their formation network during the brewing process of Shanxi aged vinegar.

Phenols are important functional compounds present in vineagr, however, their composition and formation pathways remain uncertain. Herein, non-targeted metabolomics and macrotranscriptomics methods were applied to identify phenols and analyze their formation network during the brewing process of Shanxi aged vinegar. A total of 82 phenols were detected from the raw material and the brewing process. Results indicated that phenolic acids were the major phenols and were mainly formed during acetic acid fermentation stages. Water, reducing sugars, lactic acid, and 7 amino acids influenced the formation and transformation of phenols, as shown through Spearman analysis. Furthermore, 16 genera and 38 enzymes were involved in substrates decomposition and phenols formation according to the metabolic pathway analysis, with Xenobiotics biodegradation and metabolism identified as the main pathway for phenols formation. Lactobacillus and Acetobacter were the key genera responsible for the phenols transformation. This study provides new insights into the phenols formation mechanisms in cereal vinegars and it is helpful for isolating the functional strains to reinforce the phenols formation.