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Enzymatic hydrolysis leads to improved functional and biological properties of protein by-products, which can be further used as nutraceuticals and protein ingredients for food applications. The present study evaluated ACE-inhibitory, antioxidant and immunostimulating activities in hydrolysates of egg-yolk protein by-product (YP), generated during industrial process of delipidation of yolk. The protein substrate was hydrolyzed using non-commercial protease from Asian pumpkin (Cucurbita ficifolia). The reaction was conducted in 0.1 M Tris-HCl buffer (pH 8.0) at temperature of 37°C for 4 hours using different enzyme doses (100-1000 U/mg of substrate). The protein degradation was monitored by the determination of the degree of hydrolysis (DH), release of free amino groups (FAG) and by RP-HPLC. In the obtained hydrolysates we also evaluated biological activities. It was shown that the highest DH of substrate (46.6%) was obtained after 4h of reaction at the highest amount of enzyme. This hydrolysate exhibited antioxidant activity, including ferric ion reducing (FRAP) (56.41 μg Fe2+/mg), ferric ion chelating (695.76 μg Fe2+/mg) and DPPH free radical scavenging (0.89 μmol troloxeq/mg) as well as ACE-inhibitory (IC50=837.75 μg/mL) activities. The research showed improved biological properties of enzymatically modified YP by-product. [ABSTRACT FROM AUTHOR]

The antioxidant activity of denaturated egg white protein preparation (EP) was evaluated by enzymatic hydrolysis. The EP treated with digestive and microbial proteases resulted in different degradation products confirmed by degree of hydrolysis (DH) and free amino groups concentration (FAG) measurement. The highest free radical scavenging activity reached 0.21 µmol troloxeq/mg and was exhibited by tryptic hydrolysate. EP hydrolysates showed significant, enzyme-dependent ferric reducing activity. The highest chelating activity was observed for protein preparations hydrolyzed with neutrase (397.0 µg Fe2+/mg). Antioxidative peptide fractions were isolated from tryptic hydrolysate by reserved phase high pressure liquid chromatography (rP-HPLc). Among the obtained fractions, we identified: ISQAVHAHAEINEAGr, SVL, QL and AP, KVr antioxidative peptides corresponded to ovalbumin and ovotransferrin fragments, respectively. [ABSTRACT FROM AUTHOR]