Interfacial properties of crayfish protein isolate/chitosan mixed films

Abstract

The interfacial properties of crayfish protein isolate (CFPI) and chitosan solutions (CH) at the air–water interface have been studied. An analysis of the surface pressure and interfacial shear rheology has been carried out as a function of CFPI and/or CH contents, at a fixed pH 2. The results indicate that a combination of CFPI and CH may produce a good strategy to stabilize systems. Both CFPI and CH are surface active, and synergistic effects may be obtained providing control over surface pressure. These effects are highly dependent on CFPI or CH contents. The former reduces surface tension whereas the latter enhances interfacial viscoelasticity. Previously, a transition from fluid-like behaviour to a gel-like behaviour was observed by increasing the CFPI content. However, interfaces composed of CH display a more pronounced viscoelastic nature, the effect however saturating at higher bulk concentrations. Furthermore, usage of highly sensitive interfacial shear techniques, such as the magnetic rod interfacial stress rheometer or the double wall ring, both of them providing consistent results, has proven to be highly useful to study the macroscopic viscoelastic properties of CFPI/CH interfacial films at levels that cannot be detected by other methods.