The role of amyloid fibrils in the modification of whey protein isolate gels with the form of stranded and particulate microstructures.

Adding fibers to hydrogels is a modern strategy for producing tough hydrogels. Nanofibers usually perform well in hydrogels due to their unique properties. The purpose of this study was to investigate the effects of whey protein amyloid fibril (WPF) on the properties ofheat-set whey proteinisolate (WPI)gels with fine-stranded or particulate microstructure (at pH 7). The results show that by adding WPF, a homogenous and dense network was observed in fine-stranded gel, while the formation of a coarse and amorphous structure with microphase separation intensified in particulate gel. By adding 1% WPF, the elastic modulus of gels increased about 10.6 and 3.6 times in the case of fine-stranded and particulate gels, respectively. In fine-stranded gels, adding WPF to the gel led to a decrease in the T value (from 66.33 to 59.36 °C) and a decrease in tan δ (from 0.2328 to 0.0837), indicating an increase in gel strength because of WPF. In contrast, adding WPF to particulate gels did not cause significant changes in the T and tan δ. There was a decrease in the water holding property of particulate gels when WPF was added, whereas it did not change significantly in fine-stranded gels. These findings imply that the efficiency of WPF in WPI gels depends not only on the WPF concentration but also on the type of the WPI gel. In sum, WPF enhances order in the structural network of fine-stranded gels, while accelerating the formation of inhomogeneous random aggregates in particulate gels. Creating fiber-hydrogels with different microstructures and rheological properties can be possible by controlling WPI aggregation (as in amyloid fibril, fine-strand or particulate aggregates).