Functional characterization of enzyme-hydrolysed soy and whey protein isolates: A comparative approach

Abstract

In the present study, the soy protein and whey protein isolates were hydrolysed using food-grade endoenzymes (papain and pancreatin) for different time periods (10, 30, 60, 90, and 120 min) at 35 °C. Several functional properties were examined at various times of hydrolysis. Papain hydrolysed both the isolates better than pancreatin throughout the hydrolysis period. The degree of hydrolysis of papain hydrolysed soy protein isolate was 1.12 after 120 min of hydrolysis. During the hydrolysis, the particle size of the isolates was decreased initially followed by slight increase. The particle size of whey protein isolate was higher than the soy protein isolate. Zeta potential was decreased during hydrolysis for both isolates. The particle size and zeta potential were inversely proportional to the degree of hydrolysis. SDS-PAGE has shown that, soy protein isolate had a greater number of peptide bands after hydrolysis than whey protein isolate. Emulsifying activity increased with hydrolysis time. Emulsion stability increased after enzyme addition and decreased with time. From this study it was evident that, enzymatic hydrolysis of defatted soy protein isolate enhances its functional properties. Hence, this hydrolysed soy protein isolate can be used as a cost-effective alternative to whey protein isolate, for vegans and patients.

Keywords

• Soy protein isolate
• Whey protein isolate
• Degree of hydrolysis
• Foaming properties
• Emulsifying properties