Variation of activities of polyphenol oxidase and perioxidase in enzymatic browning of Chinese chestnut(Castanea Mollissima)

Chestnuts were peeled, sliced and then the browning degree, total polyphenol concentration, activities of polyphenol oxidase(PPO) and perioxidase(POD) were measured over time. The results showed that browning reaction of fresh-cut chestnut was slow. After three days, the browning degree only increased by 44%. The total polyphenol concentrations decreased by 34% in the first two days, then fluctuated slightly. The specific activity of PPO increased by 42% in the fist day, and decreased to 13% of that of fresh chestnut in the following three days. In addition, the specific activity of POD decreased by 50% in the first two days, and then remained stable. It can be inferred that PPO was the main enzyme in relation with browning reaction of Chinese chestnut, while peroxidase played a smaller role. There was also a synergistic effect between these two enzymes, which cooperatively catalyzed the oxidation of polyphenols.