Characterisation of a whey protein hydrolysate as antioxidant

A whey protein hydrolysate was fractionated by size-exclusion chromatography to investigate the effectiveness of individual peptide fractions as (i) deactivators of hypervalent haeme iron, (ii) as radical scavengers, and (iii) as iron chelators. The reduction of ferrylmyoglobin, MbFe(IV)O, to metmyoglobin, MbFe(III), by the peptide fractions was found to follow first-order kinetics for excess peptide. The fractions with the highest rate of reduction of ferrylmyoglobin also exhibited most efficient radical scavenging as determined for the stable Fremy's salt radical. Inactivation of catalytic free ion by peptide fractions, as examined by their ability to inhibit formation of the ferrozine-Fe2+ complex, showed highest inhibition for the fractions with least scavenging capacity of the Fremy's salt radical. Radical scavenging of 1-hydroxylethyl radicals generated in Fenton reactions showed antioxidant activity for low peptide concentration, but prooxidative activity for increasing concentration. Specific whey peptide fractions, may be combined as a food additive to optimise antioxidative activity.