Influence of peroxyl radical-induced oxidation on structural characteristics, emulsifying, and foaming properties of α-lactalbumin

In this research, 2, 2′-azobis (2-amidinopropane) dihydrochloride (AAPH) was chosen to evaluate the influences of peroxyl radical-induced oxidation on structural characteristics, emulsifying, and foaming properties of α-lactalbumin. Oxidative modification of α-lactalbumin resulted in the gradual increase of protein carbonyl groups from 1.7 to 5.5 nmol/mg and dityrosine concentration from 33.5 to 225 but the gradual decrease of free sulfhydryl groups from 8.2 to 2.0 nmol/mg. Moderate oxidation led to slight decreases of surface hydrophobicity of α-lactalbumin, whereas excessive oxidation resulted in the increase of surface hydrophobicity. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) demonstrated the formation of α-lactalbumin aggregates partly through the disulfide bond, consistent with the increase of particle size after oxidative modifications. Moderate oxidation was beneficial to interfacial properties, whereas exorbitant oxidation (AAPH>1 mmol/L) could lead to the reduction. Peroxyl radical-induced oxidative modification exhibited great potential to ameliorate the emulsifying, and foaming properties of α-lactalbumin.