Antioxidant and angiotensin-converting enzyme inhibitory activity of yoghurt fortified with sodium calcium caseinate or whey protein concentrate

Abstract

In this study, the effect of fortification of yoghurt with sodium calcium caseinate (SCC) and whey protein concentrate (WPC) on the antioxidant and angiotensin-converting enzyme (ACE) inhibitory activity was assessed. Milk was fortified with skim milk powder (SMP) as control, SCC, and WPC at 2% and 4% ratios. The antioxidant activity was determined using 2,2,-diphenyl-1-picrylhydrazyl (DPPH•) radical scavenging, hydrogen peroxide (H2O2) scavenging, and Fe2+ chelating activity methods. Yoghurt fortified with 4% WPC had the highest DPPH• scavenging activity, whereas there were no significant differences between yoghurt samples containing SMP and SCC at both fortification levels. In the Fe2+ chelating activity method, increase in incubation time (from 0 to 60 min, at room temperature) significantly improved the chelating effect of all yoghurt types. Yoghurts supplemented with WPC and 4% SMP showed higher Fe2+ chelating activity than those fortified with SCC for all incubation times. Experimental yoghurts also possessed antioxidant activity towards H2O2 except yoghurts fortified with WPC at a concentration of 0.2 g∙mL−1. Yoghurt containing 4% WPC showed higher H2O2-scavenging activity than those supplemented with 4% SCC at 0.05 and 0.1 g∙mL−1 concentrations, at 0 and 40 min. Addition of SCC or WPC caused an increase in the ACE inhibitory activity of yoghurt when compared to supplementation with SMP. Fortification of yoghurt with WPC was more effective than that of with SCC in terms of ACE inhibitory activity.