Metabolomic analysis reveals the browning related enzymes and metabolic pattern differences in apples of different storage periods

This study aimed to investigated metabolism and browning-related enzyme differences of Fuji apples in fresh (FC), browning pulp (BR), and browning inhibition pulp (CM) at 0, 4, 6, and 8 months of storage. Apples stored for 4-months exhibited the highest browning rate and color differences, with browning inhibition effectiveness decreasing over time. PPO and POD activity increased, while CAT and SOD decreased. Untargeted metabolomics revealed differential metabolites (445, 468, 265) in FC, BR, and CM among four-storage, mainly related to carbohydrate, lipid, and amino acid metabolism. In BR vs. FC, differential metabolites were primarily enriched in secondary metabolite biosynthesis (within 6-months) and energy metabolism (after 8-months). In CM vs. FC, differential metabolites were significantly enriched in nitrogen metabolism. Nitrogen metabolite accumulation induces browning, which can be mitigated by CaCl 2 through alleviating nitrosative stress and oxidative damage. These findings provide metabolic insights into quality control during apple storage and processing.