Pink discoloration of coconut water caused by heating rather than the enzyme activity or Maillard reaction under pasteurized conditions
【摘要】：Composition, effect of heat treatment, pH, mental ion, polyphenol oxidase(PPO) and peroxidase(POD) activities, coconut variety on pink discoloration of coconut water were investigated in this study. Results showed that composition of the coconut water vary with varieties of coconut fruits. Pink discoloration of coconut water would be accelerated significantly with the increasing of heat temperature and time from 75℃-95℃ for 2-32 min, which could not be relieved by decreasing pH and accelerated by adding Cu~(2+) and Fe~(2+) after heating. However, PPO and POD activities in coconut water were decreased or inactivated by thermal treatment at 75-95℃ for 2-32 min. A significant negative correlation also was observed between pink discoloration and relative PPO/POD activities at p≤ 0.01 and p≤0.05. Meanwhile, there was no pink color changes appearing when coconut water was stored at room temperature or 4 ℃ during storage, and adding extra PPO and POD didn't accelerated the pink discoloration.