Effect of enzymolysis on the antioxidant activity and functional properties of the soluble soy proteins

Since multiple functionality of the protein derivatives is widely needed, identifying tools for modulating it is highly desired. The aim of the present study was to test the influence of three different endopeptidases, namely bromelain, Neutrase and trypsin, on the antioxidant and functional properties of the soy proteins. The soluble proteins content of the obtained hydrolysates varied with the hydrolysis degree, which ranged between 1.85% (in case of trypsin) and 10.27% (in case of bromelain). The resulting peptide mixtures exhibited higher antioxidant activity values compared to the native soluble proteins. Both DPPH and ABTS-based methods indicated that the sample hydrolysed with Neutrase was the most bioactive, whereas the sample prepared with trypsin exhibited the lowest antioxidant activity. The bioinformatics tools revealed that mainly the hydrophobic di- and tripeptides were responsible for the increased antioxidant activity of the hydrolysates. The impact of enzyme assisted hydrolysis on the functional properties was estimated by determining the foaming and emulsion forming properties of the hydrolysates. The best foaming properties were registered for the hydrolysate obtained with Neutrase (the overrun was by 25-50% higher compared to the native proteins). All tested emulsions exhibited predominant viscous like behaviour. The results indicated that soy proteins hydrolysis with bromelain, Neutrase and trypsin could be exploited for the knowledge-based improvement of the antioxidant activity or for modulating the functional properties of the protein derivatives.