Abstract: In the present study, litchi and litchi wine were used as the materials to study the properties of polyphenol oxidase (PPO) in litchi, and explore browning mechanisms and controlling strategies of litchi wine during fermentation process. The isoenzymes of PPO were observed in litchi and the optimal substrate of PPO in litchi was gallic acid. The optimal pH and temperature for PPO from litchi were 8.0 and 50 ℃ using gallic acid as the substrate. Kinetic parameters such as Km and Vmax of PPO from litchi were 26.033 mmol/L and 34.816 g/(L·min), respectively. The PPO from litchi was not stable at the conditions of 50－80 ℃, strong acid and strong alkali. Higher PPO activity in litchi was the major browning cause of litchi wine during fermentation process. Therefore, low-temperature storage and heating treatment can effectively inhibit the browning of litchi and litchi wine.

Key words: litchi, litchi wine, polyphenol oxidase, browning