Effect of Organic Farming Practices on the Level of Latent Polyphenol Oxidase in Grapes

The levels of polyphenol oxidase (PPO) in organic as compared with conventional Monastrell grapes were examined in this study. The enzyme was partially purified using the Triton X‐114 method, and in both cases it was obtained in a latent state, being activated by different methods (acid shocking, detergents, and proteases). PPO purified from both organic and conventional Monastrell grapes had the same isoenzymatic form, appearing as the same single band in polyacrylamide gel electrophoresis. However, diphenolase activity of activated PPO in organic grapes was 2 times higher than in conventional grapes, independent of the activation method used. Moreover, the proteolytic activation method, using trypsin, was the most effective for this latent PPO.