Polyphenoloxidase Activity During Grape Maturation and Wine Production

Abstract

The activity of polyphenoloxidase (PPO) was studied during the maturation and wine production of several white grape varieties grown in the northeastern United States. The maturation studies revealed varieties with low, medium, and high levels of PPO activity. The PPO activity for any one cultivar fluctuated throughout the ripening period. No definite correlations between PPO activity and total phenolic content were found. During wine production the enzyme activity was highest immediately after the crushing of fresh grapes; enzyme activity ceased by the end of the final racking. Enzyme activity was prevented in wines prepared with adequate levels of sulfur dioxide, thereby minimizing brown discoloration; a higher phenolic content also was noted.