Interfacial and emulsifying behaviour of crayfish protein isolate

Abstract

The interfacial behaviour of adsorbed protein films constituted with a crayfish protein derivate that is typically produced as by-product from the food industry, has been studied at the air–water and oil–water interfaces. An analysis of the surface pressure under compression-expansion cycles of this protein was carried out as a function of time, concentration and pH (2 and 8). Besides, interfacial tension and adsorption kinetics also were determined as a function of time at different concentrations and pH values. Interfacial rheological properties were studied under dilatational deformations applied to a single droplet, either at the initial step of film formation or once the interfacial tension was at equilibrium and the film was completely formed. The contribution of the interfacial properties to the behaviour of oil-in-water emulsions stabilised with this protein derivative were also analysed. Finally, droplet size distributions obtained for concentrated emulsions stabilised by crayfish protein were analysed and related to the interfacial tension behaviour. We have demonstrated that crayfish proteins at pH 8 show higher solubility, smaller aggregates and better interfacial activity (higher surface pressure and lower interfacial tension) with higher interfacial viscoelasticity, than at pH 2. A two-dimensional model of the results showed that oil–water and air–water interfaces are clearly related to the improved stability of emulsion made with crayfish proteins at pH 8.