Interfacial properties of highly soluble crayfish protein derivatives

An analysis of the interfacial behaviour of two alternative protein derivatives with high solubility has been carried out at two different pH values (2 and 8). The protein derivatives (protein content higher than 50 wt.%) have a globular protein fraction mainly consisting of sarcoplasmic proteins (CFS); and a protein hydrolysate, (CFH), both obtained from crayfish surpluses. The physicochemical characterisation included protein solubility (higher than 80%) and surface charge as well as chemical analysis (elementary, sulfhydryl and disulphide groups). This was complemented with an interfacial characterization included measuring the surface pressure and surface dilatational measurements with a drop tensiometer, and interfacial shear rheology measurements performed using a double-wall-ring geometry. Whereas both types of protein derivative have significant interfacial activity (surface pressure between 20 and 40 mN/m), the difference in their behaviour is small In contrast, a strong influence of pH on the interfacial behaviour has been found for both soluble protein fractions. At pH 2, globular sarcoplasmic protein fraction yields lower surface pressures but highly viscoelastic interfaces, with 2D gel-like behaviour. At pH 8, on the other hand, CF proteins form quite rigid and more brittle interfaces, being resistant to dilatational deformations and showing high sensitivity to shear. (C) 2016 Elsevier B.V. All rights reserved.