Polyphenoloxidase activity and polyphenol levels in organically and conventionally grown peach (Prunus persica L., cv. Regina bianca) and pear (Pyrus communis L., cv. Williams)

Polyphenoloxidase (PPO) activity and total polyphenol content were tested in organically and conventionally grown whole fruits, peach (Prunus persica L., cv. Regina bianca) and pear (Pyrus communis L., cv. Williams), in order to evaluate the existence of a relationship between these parameters and of differences between fruits obtained with the two cultivation practices. Organic fruits were obtained on three different grounds: subterranean clover (sample A), spontaneous weed cover (sample B) and tilled (sample C). From the latter soil, the conventionally grown fruits were produced. All organic peach samples showed a highly significant (P<0.001) increase in polyphenols (mg equivalents of tannic acid/100 g fresh sample) compared with conventional peaches, while, of the three organic pear samples, samples B and C displayed an increased polyphenol content with respect to the conventionally grown sample (P<0.05). Activity of PPO (U.E./100 g fresh sample), extracted in appropriate conditions and tested towards 1 mM chlorogenic and caffeic acid, was significantly higher in most of the organic peach and pear samples analyzed with respect to the conventional samples.