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 (+...