Changes in Polyphenol Concentrations and Polyphenol Oxidase Activity of Loquat (Eriobotrya japonica Lindl.) Fruits in Relation to Browning.

Polyphenols and polyphenol oxidase (PPO) activity in the fruits of loquat (cv. Mogi) during development and storage were studied in relation to browning of the pulp. The concentration of total phenolics decreased sharply during fruit growth and then increased significantly during maturation and ripening. But, it varied slightly during the two months of cold storage. Chlorogenic acid increased rapidly during fruit maturation and ripening and became a predominant compound in ripe fruits. Chlorogenic acid decreased slightly while the fruit was stored at 5°C. PPO activity declined concurrent to fruit growth and ripening. In cold storage, PPO activity decreased gradually, but from 68.8 to 92.2% of the browning in the reaction mixture prepared from pulp juice occurred within the first hour. Chlorogenic acid oxidation proceeded quickly and played an important role in browning of ripe fruit. Total phenolics was highly related to the degree of browning.