Ultrasound-induced changes in functional properties of egg white proteins and in their susceptibility to enzymatic hydrolysis

Abstract

The effects of the ultrasound pretreatment on functional properties of egg white proteins (EWPs) and their subsequent hydrolysis by Alcalase were investigated. Functional properties of the obtained hydrolysates were characterized in terms of solubility, turbidity, emulsification activity and foaming properties. The ultrasound pretreatment at 20 kHz for 15 min by using ultrasound probe has been shown to accelerate the hydrolysis process and generate more reproducible results, compared with both, heat treatment or treatment in an ultrasonic water baths at 40 kHz under similar conditions. It was also shown that the ultrasound pretreatment resulted in an increase in total and reactive thiol content, suggesting an unfolding of the protein molecules. Minor secondary and tertiary structural changes have also been confirmed by circular dichroism. The produced hydrolysate, under optimum condition, was characterized in terms of antioxidant properties and peptide composition. Industrial relevance: Egg producers are faced with problems of excess of egg white because mayonnaise industry and bakery industry use relatively high egg yolk amounts and egg white is remainder. In this work, EWPs was treated by high intensity ultrasound and then hydrolyzed by Alcalase. Effects of treatment time on the functional properties of EWPs and susceptibility to proteolysis were investigated. The results showed that the ultrasound technology could improve functional and antioxidant activity of EWPs under the controlled conditions.