Hydrophilic and lipophilic antioxidant activity changes during on-vine ripening of tomatoes (Lycopersicon esculentum Mill.)

Abstract

Changes in antioxidant activity during the on-vine ripening of tomatoes (Lycopersicon esculentum) were studied at four different ripening stages (green, breaker, pink and red ripe). Hydrophilic and lipophilic antioxidant activities (HAA and LAA, respectively) were determined and their relationships to ascorbic acid, total phenols, lycopene and β-carotene contents were analysed. HAA and ascorbic acid remained practically unchanged, while the levels of aqueous phenols increased during ripening. The levels of ascorbic acid and HAA were strongly correlated (r=0.90, P<0.1). β-Carotene increased until breaker and pink stages, decreasing afterwards. In contrast, lycopene accumulated throughout the ripening period. The LAA followed the same pattern as lycopene and a good correlation was found (r=0.91, P<0.05). There was less difference between the measured and calculated LAA as the lycopene level increased, the discrepancy being lowest at the red-ripe stage, indicating the importance of lycopene as a lipophilic antioxidant in tomatoes.