Dromedary milk protein hydrolysates displayed enhanced antioxidant and functional properties

Abstract

Research background. Milk protein hydrolysates have received particular attention due to their health-promoting effects. Dromedary milk differs from the milk of other dairy animals in the composition and structure of its protein components, which give it unique properties. Whole dromedary milk proteins and their enzymatic hydrolysates have not received attention with respect to their bioactivity and functionality. Hence, this study aimed to investigate the effect of enzymatic hydrolysis of dromedary milk proteins on their antioxidant activities and functional properties. Experimental approach. Dromedary milk proteins were treated using four proteolytic enzymes (pepsin, trypsin, α-chymotrypsin and papain) and two mixtures of enzymes (pancreatin and pronase). The degree of hydrolysis was measured to verify the hydrolysis of the proteins. The SDS-PAGE and gel filtration chromatography were performed to determine the molecular mass distribution of the hydrolysates while Reversed phase-HPLC was conducted to explore their hydrophobicity. The antioxidant activities were evaluated using various in vitro tests, including DPPH and ABTS radical scavenging capacities, ferric reducing ability and chelating activity. Besides, functional properties in terms of solubility, foaming and emulsifying properties were assessed. Results and conclusions. Dromedary milk protein hydrolysates exhibited different degrees of hydrolysis ranging from 17.69 % to 41.86 %. Besides, the hydrolysates showed different electrophoretic patterns, molecular mass distribution and reverse phase-HPLC profiles demonstrating the heterogeneity of the resulted peptides in terms of molecular mass and polarity. The hydrolysates displayed significantly higher antioxidant capacities than the undigested proteins at all the tested concentrations. Ferrous chelating activity was the most improved assay after proteolysis and the hydrolysate generated with pancreatin had the highest chelating power. Dromedary milk protein hydrolysates possessed a good solubility (>89 %). Further, foaming and emulsifying properties of dromedary milk proteins were enhanced after their proteolysis. These interfacial properties were influenced by the enzymes employed during proteolysis. Novelty and scientific contribution. Enzymatic hydrolysis of dromedary milk proteins is an effective tool to obtain protein hydrolysates with great antioxidant and functional properties. These results suggest that dromedary milk protein hydrolysates could be used as a natural source of antioxidant peptides to formulate functional foods and nutraceuticals.