Soy proteins with various surface properties prepared by limited enzymatic hydrolysis and their potential on emulsion thickening and controlling lipolysis

In recent years, proteins with designed surface properties as interfacial stabilizers to obtain functional emulsions with controlled lipolysis has received increasing attention. In this work, four types of soy proteins (I, II, III, IV) with different surface properties were obtained by controlled enzymatic hydrolysis (Neutrase). Protein particle size, morphology, surface hydrophobicity and interfacial wettability were analyzed along with changes in subunits composition and secondary structure, aiming to establish a certain relationship between protein surface properties and its capacity in modulating emulsion properties. Specifically, Type I (α', α, β, A and B subunits) as protein nanoparticles showed high surface hydrophobicity (+84%) and could form a thick interface to delay lipolysis (k1-24.0%, k-24.2%) through Pickering effect. Type II (α, β, A and B subunits) as protein aggregates in larger size showed high surface hydrophobicity (+45%) and roughness, which could enhance viscosity (equivalent to that of φ0.3–0.4 oil fraction) and delay lipolysis (k1-24.0%) by bridge flocculation. Further hydrolysis caused partial precipitation (originated from β and B subunits) and the soluble portion (Type III and IV) with decreased surface hydrophobicity and increased structural flexibility showed poor emulsification capacity and formed weak interface. It can be concluded that regulating subunit composition by enzymatic hydrolysis is an effective way to obtain proteins with multi-surface properties, which plays a vital role in modulating emulsion viscosity and lipolysis behavior. Results from the present study could provide a new strategy for the design of low-calorie emulsions for weight management.