Enzymatic Browning of Apples on the Market: Relationship between Browning, Polyphenol Content, and Polyphenol Oxidase.

Relationship between content of such polyphenols as chlorogenic acid, (-)-epicatechin, and (+)-catechin, polyphenol oxidase (PPO) activity, and browning in five cultivars of apples 'Fuji', 'Kogyoku (Jonathan)', 'Jona Gold', 'Mutsu', and 'Tsugaru' on the market was examined. Polyphenol was determined by high-performance liquid chromatography. Chlorogenic acid was found to be the major polyphenol (3-25mg/100g fruit). Chlorogenic acid and catechins rapidly decreased by browning. Catechins contributed to browning more than chlorogenic acid. PPO activity was measured using chlorogenic acid or (+)-catechin as the substrate. Cultivar Tsugaru contained polyphenols the least and turned brown the least among five cultivars, while it kept high PPO activity. Cultivar Mutsu showed the highest polyphenol content, the highest PPO activity and the most intense browning. The polyphenol content showed correlation with the browning.