The present work investigated the effects of whey protein concentrate (WPC) on probiotic yogurt. Five different concentrations of WPC (0 - 10%) were evaluated. The results showed positive effects of WPC on yogurt’s properties under simulated gastrointestinal (GI) transit and long-term storage. In vitro digestion of WPC-fortified yogurt during GI transit markedly promoted the antioxidant activities in a concentration-dependent manner. WPC supplementation was also shown to significantly enhance the viability of probiotics under GI transit and during refrigerated storage, to the recommended level for health benefits on daily intake. The optimal concentration for retention of physicochemical properties (water holding capacity and texture profile) of the yogurt during refrigerated storage for 28 days was 5% (w/w), while the addition of 10% (w/w) WPC yielded the highest radical-scavenging activity (15.3 ± 0.1 mg Trolox Eq./g), reducing power (575.3 ± 2.3 g Trolox Eq./g), and Fe2+-chelating ability (13.5 ± 0.02 mg EDTA Eq./g) under both gastric and pancreatic digestion conditions. The results obtained suggest that WPC-fortification promoted the overall quality of probiotic yogurt by improving its antioxidant activities and probiotic viability, as well as extending its shelf-life.
