Improvement of antioxidant properties of egg white protein enzymatic hydrolysates by membrane ultrafiltration

The production of bioactive peptides from egg white proteins (EWPs) and their separation are emerging areas with many new applications. The objective of this study was to com-pare antioxidant activity of three distinct EWP hydrolysates and their peptide fractions pre-pared by membrane ultrafiltration using membranes with 30, 10 and 1 kDa molecular weight cut-off. The hydrolysates were obtained by thermal and ultrasound pretreated EWPs hydrolyzed with a bacterial protease, Alcalase. It appeared that the pretreatment significantly affected peptide profiles and antioxidant activity of the hydrolysates mea-sured by ABTS, DPPH and FRAP methods. The hydrolysate prepared using alcalase and ultrasound pretreatment at 40 kHz – 15 min has shown to be the most effective in sca-venging both DPPH and ABTS radicals (28.10±1.38 and 79.44±2.31%, respectively). It has been noticed that this hydrolysate had a nutritionally more adequate peptide profile than the other hydrolysates with a much lower amount of peptides <1 kDa (11.19±0.53%) and the greatest content of the peptide fraction in the molecular weight (MW) range of 1–10 kDa (28.80±0.07%). This peptide fraction has shown the highest DPPH and ABTS antioxi-dant activity compared to all other fractions having a potential to be used as a functional food ingredient. The importance of oxidation processes in the body and foodstuffs has been widely recognized. It is well known that the formation of free radicals and other reactive oxygen species (ROS), which can induce oxi-dative damage, is a consequence of the oxidation metabolism which is indispensable for the survival of cells [1]. An important role in the preservation of human health has inhibition of oxidative reaction and scavenging of free radicals which take place under the influence of antioxidants. Synthetic antioxidants like butylated hydroxytoluene (BHT) and butylated hyd-roxyanisole (BHA) which were ordinarily applied for radical scavenging in biological systems pose a risk for human health. Accordingly, the contribution of many studies was aimed to isolate natural antioxidants such as tocopherols, catechin, phenolic compounds and pep-tides [2–5].