Changes in polyphenol content and polyphenoloxidase activity of apple fruits during ripening process

We investigated the changes in polyphenol (PP) content and polyphenoloxidase (PPO) activity of apple fruits (flesh, core and peel) during ripening process. The apples were cultivated with the experimental hydroponics (water cultured fruit of Fuji:WCF) or sprayed with Ca-solution on conventional soil culture (Ca-solution sprayed fruit of Starking:CaF). The control apples of the same cultivar were cultivated by conventional soil culture (soil cultured fruit:SCF). These apples were harvested at 3 stages during ripening process at Morioka in 1993. The following results were obtained. (1) Total PP (TPP) contents in WCF and CaF, which had low browning degree were higher than that in SCF with high browning degree. (2) In peel of all apples, regardless of cultivar and culture condition, TPP was included four of five times the other parts. (3) The contents of chlorogenic acid and epicatechin in WCF and CaF were higher than those in SCF. In Fuji, regardless of culture condition, chlorogenic acid content was higher than epicatechin content in all parts. In Starking, same result was obtained in flesh and core, but reverse result was found in peel. (4) The contents of TPP, chlorogenic acid and epicatechin decreased during ripening process, and fell rapidly during the early stage of development. (5) The PPO activity in WCF was weaker than that in SCF significantly, but it was not affected the spraying of Ca-solution. (6) The PPO activity decreased rapidly during the early stages of development.