Tropical fruit peel powders as functional ingredients: Evaluation of their bioactive compounds and antioxidant activity

Fruit by-products such as peel often contain more bioactive compounds than the edible portion. Extracts of eleven tropical fruit peels were found to have high bioactive compound contents and high antioxidant activity. Green sugar apple and purple sugar apple peels had the highest total phenolics content, total flavonoids and antioxidant activity values. Total flavonoids and total phenolic compounds content were highly correlated to antioxidant activity as quantified by the ABTS, DPPH and reducing power assays. The three antioxidant activity assays were highly correlated (P <= 0.05) (ABTS vs. DPPH, R = 0.98; ABTS vs. Reducing power, R = 0.97; DPPH vs. Reducing power, R = 0.96). Purple sugar apple peel had the highest catechin content. The eleven analysed tropical fruit peels are promising sources of bioactive ingredients with antioxidant properties and potential applications in the design of functional foodstuffs or as food preservatives. (C) 2017 Elsevier Ltd. All rights reserved.