Abstract: Effects of temperature, pH, substrate, ascorbic acid, L-cysteine, sodium bisulfite, citric acid and sodium chloride on the activity of polyphenol oxidase (PPO) from Chaenomeles speciosa Nakai were studied. Results showed that PPO activity was obviously higher in core than in the peel and flesh. The browning of C. speciosa fruit was significantly correlated to PPO activity. The PPO from C. speciosa fruit had the optimum substrate of catechol, with the optimum temperature 20 ℃ and pH 5.5. The enzyme lost its activity substantially after exposure to 80 ℃ for 5 min. Its activity was suppressed effectively by ascorbic acid, L-cysteine, sodium bisulfite, citric acid and sodium chloride.

Key words: Chaenomeles speciosa Nakai, polyphenol oxidase, characteristic, inhibitor