Environmental parameters-dependent rheological behaviors of whey protein fibril dispersions: Shear and extensional flow behaviors

Abstract

This study characterized the shear and extensional rheology properties of whey protein fibril (WPF) dispersions under different heating times (1, 2, 4, 8, and 16 h), fibril lengths obtained from mechanical stirring times (2, 4, 6, and 8 h), and pH values (2.0, 3.5, 7.0, and 9.0). The WPF dispersions in the steady shear flow, exhibited shear-thinning and the dominant elastic behavior. The WPF dispersions' apparent extensional viscosity and characteristic relaxation times increased as the heating time was extended, and the strain hardening occurred after heating for 8 h. Fibril length had no significant impact on the WPF dispersions’ shear rheology properties but greatly influenced their extensional flow behaviors, including the decreased break-up time and relaxation time of the filament after decreasing fibril length. The WPF dispersions at pH 3.5 showed the highest break-up time and relaxation time. In light of fibril entanglement and association in the strong flow field, these results provide a useful guideline for WPF applications in the food industry. • The shear and extensional rheology properties of WPF dispersions were compared. • Effects of heating time, fibrils length and pH on the rheology were investigated. • Extensional flow was more sensitive to WPF dispersions alteration than shear flow.