Large amplitudes oscillatory shear (LAOS) behavior of egg white foams with apple pectins and xanthan gum

- LAOS and FTR measurement were done for wet foams.
- The foam containing only egg white generates the largest number of harmonics.
- The level of de and the pectin concentration in foam do not influence τ0.

The study presents the results of research on non-linear rheological properties of foams based on egg white protein, xanthan gum and apple pectin of various levels of methylation. The rheological studies were carried out by means of large amplitude oscillatory shear (LAOS) and Fourier transform rheology (FTR) methods. The obtained foams revealed elastoviscoplastic properties. The analysis of the results allowed determination of yield stress, shear exponents and the Fourier spectra, which enabled estimation of the quantity and intensity of individual harmonics. The Lissajous patterns as well as coefficients of energy dissipation were also demonstrated. The foam containing solely egg white revealed the largest number of harmonics in the Fourier spectrum (17th), whereas supplementation with hydrocolloids induced a decrease in the amount of harmonics (9th). The image of the Fourier spectra was reflected by the Lissajous curves, which gradually acquired an ellipsoidal shape as the hydrocolloid concentration increased. The coefficient of energy dissipation in the function of the deformation amplitude demonstrated a sigmoid dependence and tended towards the value of approximately 0.8 for higher amplitudes. This indicated that the investigated foams were in a flow area. The statistical analysis (two/three-way ANOVA) of the abovementioned values showed that neither the level of methylation nor the pectin concentration in foam influences the yield stress.