Key Compounds and Metabolic Pathway Responsible for the Browning in Dangshan Pear (Pyrus spp.) Wine.

Based on hydrophilic interaction liquid chromatography (HILIC) liquid chromatography-mass spectrometry (LC-MS), untargeted differential metabolomics analysis was performed on the pear wine samples before and after browning to determine the key compounds that affect the browning of Dangshan pear wine. A total of 196 significantly differential metabolites were found, 22 of which might be related to the browning of Dangshan pear wine. d-(+)-glucose, l-phenylalanine, l-norleucine, methionine, d-(+)-proline, aloin, and rutin were the key differential metabolites in pear wine before and after browning. The Maillard reaction of d-(+)-glucose, l-norleucine, methionine, and the oxidation of aloin played critical roles in the browning of Dangshan pear wine. The reaction of aloin and glucose to form 5-hydroxyaloin A, 7-hydroxyaloin B, and elgonica-dimer A was one of the important metabolic pathways in which the phenolic compounds formed anthraquinone during the browning process of Dangshan pear wine.