The non-linear rheological properties of fresh wet foams based on egg white proteins and selected hydrocolloids

Abstract

The study focuses on analysis of non-linear properties of foams consisting of egg white protein, xanthan gum and gum Arabic. The measurements of the G′ and G″ values as the function of the deformation amplitude were carried out. The yield stress values τ0 were determined by two methods, and the flow curves investigation were carried out as well. Distributions of characteristic times were determined. It has been proven that xanthan gum is a major factor forming non-linear image of the studied foams. The rheological behavior of xanthan gum-containing systems can be explained by the theory of soft glass, which implies that the studied foams are in a metastable state. The changes of the deformation amplitudes or the changes of the shear rate values cause the transition among subsequent metastable states. These phenomena are not present in foams, which consist of egg white protein only and which are supplemented with gum Arabic only. Furthermore, it has been noticed that there are no evident differences between the correlations of β/δ (G′~γ0−β, G″~γ0−δ) and computer simulation for the hard sphere-type systems, presented in the literature. The systems containing higher concentrations of xanthan gum exhibit very complex behavior during the performance of a qualitative test of the hysteresis loop. This results in the extension of the spectrum of characteristic times. Conformity between two methods of yield stress τ0 estimation has been obtained. Furthermore, it has been shown that xanthan gum causes the increase in τ0. This phenomenon was not observed in the case of gum Arabic.