Effect of microwave blanching on antioxidant activity, phenolic compounds and browning behaviour of some fruit peelings

Fruit peelings are increasingly being used as ingredients for the formulation of functional foods. In this study, the antioxidant activity and browning behaviour of free and bound phenolic fractions of mango, apple, orange and banana peelings microwave-blanched at 720 W for 1, 3 and 5 min were determined. The fractions were equally analyzed for their phenolic content and composition. Generally, increased microwave blanching was accompanied by a significant increase of total phenolics content in free and bound fractions. Increased antioxidant activities at 3 and 5 min of blanching varied with the type of fruit peelings. Browning rates decreased with microwave blanching time except in the case of apple peelings. Epicatechin, ferulic acid, caffeic acid, rosmarinic acid, p-coumaric acid and gallic acid were identified in fruit peelings. Generally, microwave blanching for 3 or 5 min was found to preserve antioxidant activities and reduce the browning rate.