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

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 charac-teristic 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.

Automated summary

This study characterized the shear and extensional rheology properties of whey protein fibril dispersions under different conditions. The results showed that heating time and fibril length had significant effects on the extensional viscosity and relaxation times of the dispersions. pH value also influenced the dispersion's break-up time and relaxation time. These findings provide useful insights for the application of whey protein fibrils in the food industry.