Abstract: Enzymatic browning has a significant impact on the quality of fruits and vegetables during processing and preservation, and increasing studies have been devoted to the mechanism of enzymatic browning. This article summarizes recent studies on the mechanism of enzymatic browning from the perspectives of polyphenol oxidase (PPO) and its phenolic substrates, including the types and catalytic sites of PPO and the methods used to extract, separate and purify PPO and determine its activity; changes in the types and contents of phenolics and the cause thereof; enzymatic oxidation of phenols, quinone production pathway, secondary metabolism process, oxidation end product characteristics and the mechanism of the inhibition of enzymatic browning by anti-browning agents. We hope that this review will provide a reference for systematic and in-depth studies on the mechanism of enzymatic browning.

Key words: enzymatic browning mechanism; polyphenol oxidase; phenolic compounds; oxidation products