Apple Peel Flavonoids as Natural Antioxidants for Vegetable Juice Applications
Document Type Article
European food research and technology. First online: 20 February 2016, Springer Verlag.
A phenolic extract from apple peels consisting mostly of flavan-3-ols (>50%), flavonol glycosides and dihydrochalcones was added as a natural antioxidant mixture to commercial carrot and tomato juices (final concentration: 90% juice, v/v) in order to transfer enhanced antioxidant capacity to the food matrix. The antioxidant contribution of the added extract to the capacity of the hydrophilic and lipophilic components of the juices was measured as ascorbic acid equivalents with FRAP and DPPH assays, and as inhibition against lipid peroxidation using an emulsified lipid in an oven test. Results showed that the addition of apple peel flavonoids at concentrations equal to or above 160 mg GAE/L as total phenolics in the juices led to significantly higher (p<0.05) radical scavenging capacity and to an increased protection against lipid peroxidation compared to control. The lipid radical inhibition of the enriched juices was comparable to synthetic antioxidants used for comparison. The antioxidant capacity of the enriched juices was mostly attributed to their hydrophilic components, particularly flavonoids with medium-to-high polarity such as catechins, dimers and quercetin glycosides. Nevertheless, it was suggested that oligomeric procyanidins with medium-to-low polarity could also contribute to the total antioxidant capacity as lipophilic components.