Effect of acetone soluble fraction from various fruits on enzymatic browning.

Polyphenol oxidase (PPO) of each fruit was added to each of acetone soluble fractions (AFs) prepared from various fruits, and the extent of browning of the reaction mixtures was determined.When the AFs from three fruits ('Delaware' grape, 'Sordum' plum, 'Hakuho' peach), containing the same amount of polyphenol, were added to PPO of each fruit, the AF of grape markedly inhibited PPO activity of all three kinds of fruit.The oxidation of the AF of peach was the strongest of the three and that of plum was intermediate.The PPO and AFs of 'Kosui' pear and 'Tsugaru' apple were also prepared by the same method as the other three fruits.Since the PPO of all five fruits had high substrate specificity for chlorogenic acid, the oxidation of chlorogenic acid was used as an index of the browning.The AF of grape inhibited PPO activity of peach, apple and grape, whereas the AF of plum inhibited PPO activity of peach and apple, but accelerated the PPO activity of pear, plum and grape.The AF of peach and apple was appeared to have a stimulative effect on PPO activity.