Elucidating the effect of chitosan microgel characteristics on the large amplitude oscillatory shear (LAOS) behavior of their stabilized high internal phase emulsions using the sequence of physical processes (SPP) approach and comparison with mayonnaise.

Chitosan microgels (h-CSMs) were prepared by cross-linking hydrophobically modified chitosan with sodium phytate (SP). Emulsions stabilized by h-CSMs with different inter-phase fraction, microgel concentration and cross-linking density were studied of their microstructural and rheological properties. In particular, the large amplitude oscillatory shear (LAOS) of the high internal phase emulsions (HIPEs) stabilized by h-CSMs were systematically analyzed using the Fourier transform with Chebyshev polynomials (FTC) and sequence of physical processes (SPP) methods to explore their nonlinear rheological properties. It was found that the HIPEs showed Type III LOAS response with weak strain overshoot depending on the emulsion parameters and microgel characteristics. The FTC method enabled the extraction of nonlinearity measures at limiting conditions (γ → 0, γ → γ) showing intracycle strain-hardening and intracycle shear thinning of the HIPEs under LOAS. By providing a detailed process of the emulsion microstructure transformation in each oscillation cycle, the SPP analysis showed that the HIPEs underwent a 3-step gradual sequence of physical processes, and magnified the influence of microgel characteristics on the rheology of the HIPEs. Comparing with commercially available traditional and low-fat mayonnaise samples, the h-CSM stabilized HIPEs exhibited higher flow compliance but stronger thixotropic recovery ability.