Influence of storage and in vitro gastrointestinal digestion on total antioxidant capacity of fruit beverages

Eight fruit beverages containing grape, orange and apricot, with/without iron and/or zinc and with/without milk added were analyzed for total antioxidant capacity (ORAC and TEAC methods), ascorbic acid content, and total polyphenols. The influence of cold storage (2–4 °C) during the product shelf-life (135 days) and antioxidant capacity after an in vitro gastrointestinal digestion were evaluated. Antioxidant capacity for all beverages together increased significantly (p < 0.05) at the end of storage (16.4% and 12.8% for ORAC and TEAC, respectively), whereas ascorbic acid remained stable. Regarding in vitro digestion, antioxidant values of bioaccessible fractions of fruit beverages increased (p < 0.05) 59% and 20% for ORAC and TEAC, respectively, while ascorbic acid and polyphenol content fell 36% and 16%, respectively (p < 0.05). Supplementation of fruit beverages with milk and/or Fe/Zn did not modify total antioxidant capacity of samples during either cold storage or during in vitro digestion.