The mechanism behind microstructure formation in mixed whey protein–polysaccharide cold-set gels

Microstructure formation in acidified mixed protein/polysaccharide gels is an important feature to control the mechanical properties of these gels. Previous work showed the relation between the charge density of the polysaccharide and the type of microstructure obtained. This manuscript deals with the mechanism behind the microstructure formation. This was studied with a combination of techniques, including light scattering, confocal microscopy (CLSM) and small deformation rheology. The microstructure obtained is a result of the competition between gelation of the protein aggregates and the phase separation between protein aggregates and polysaccharide molecules. The onset of gelation and microstructure formation occurs at a constant pH independent of the type and amount of polysaccharide added. The gelation of the protein aggregates induces the phase separation process that leads to the microstructure formation. The rate of gelation is controlled by the acidification rate, which can be used to modulate the microstructure of the mixed gels. A slower acidification rate results in a coarser microstructure because there is a longer time for the phase separation to occur.