Antioxidant peptides released from gastrointestinal digestion of “Stracchino” soft cheese: Characterization, in vitro intestinal protection and bioavailability

Stracchino is a typical Italian soft cheese, widely consumed and appreciated for its flavour and freshness. With the aim to follow the release of health-promoting peptides, an in vitro gastro-intestinal digestion of Stracchino was carried out. The digest was fractionated by semi-preparative RPLC and tested for its antioxidant properties in H2O2-treated intestinal epithelial cell line (IEC-6). The most active fraction was characterized by UHPLC-MS/MS, showing the presence of two abundant β-casein hexapeptides: EAMAPK (f: 115–120) and AVPYPQ (f: 192–197), which were synthesized and tested, showing antioxidant activities in a wide concentration range (5–150 µg/mL), involving ROS reduction, SOD expression increase and Nrf2 antioxidant response activation. Hence, bioavailability studies were carried out through Caco-2 monolayers cells on the two hexapeptides, which revealed a significative concentration in the basolateral side. The results highlight the potential of Stracchino as health promoting food, and the possible employment of casein peptides in nutraceutical formulations.