Effect and mechanism of calcium ions on the gelation properties of cellulose nanocrystals-whey protein isolate composite gels

This study aimed to evaluate the effect of calcium ions (Ca2+) on the thermal gelling properties of cellulose nanocrystals-whey protein isolate composite gels, as well as to propose a corresponding ion-induced gelation mechanism. It was found that the gel strength, viscoelasticity, and thermal stability of the mixed gels gradually improved with an increase in the Ca2+ concentration from 0 M to 0.15 M. The addition of an appropriate Ca2+ could induce the conformational transformation from α-helix to β-sheet, increase the content of tryptophan residues and reactive sulfhydryl groups, and enhance the hydrophobic interactions and the amide II band, which promoted the full unfolding and orderly aggregation of protein molecules to form a stable three-dimensional gel network. However, 0.20 M Ca2+ resulted in the formation of a coarse gel structure with some irregular aggregates, thereby leading to the decreased water holding capacity and gel strength. This research offers a theoretical foundation for the design and development of novel composite food gels with various functional properties.