Structural modification of whey protein nanofibrils by a multiround induction pathway for enhancing the stability of Pickering emulsions

Abstract

In this study, a new fibrillation method, i.e., a multiround induction pathway, was proposed to modify the highly rigid structure of conventional whey protein nanofibrils and enhance the stability of Pickering emulsions. In contrast to the conventional self-assembly pathway, in which nanofibrils are formed by aggregation of polypeptides or monomers, the multiround induction pathway involves the use of multiple rounds of homologous seeds to induce whey protein nanofibril formation. The structure of nanofibrils formed by multiround induction was considerably different from that of conventionally self-assembled nanofibrils, with a greater or equal number of nanofibrils formed. Over 6 rounds of induction, the intersheet distance within the cross-β-sheet motifs of the nanofibrils increased (from 10.01 Å to 10.70 Å), and the intersheet stacking structure gradually became looser, consequently displaying a thicker morphology with greater height and periodicity. Compared to conventionally self-assembled nanofibrils, nanofibrils with this characteristic structure exhibited 4.04 times higher interfacial adsorption, an 83.24% lower flocculation index, and 61.29% higher emulsion stability. Differences in the emulsification properties of nanofibrils were attributed to multiround induction, which changed the nanofibril structure compared to conventional self-assembly. Some hydrophobic peptides at the β-sheet and α-helix positions were not involved in the construction of cross-β-sheet motifs, which made the nanofibrils more flexible and hydrophobic. These findings suggested that nanofibrils prepared via the multiround induction pathway had unique properties that might be significant for the fabrication of food-grade Pickering emulsions with excellent stability.