Whey protein microgels for stabilisation of foams

Rheological, foaming and foam textural properties of whey protein isolate (WPI) microgels formed via cold-set gelation were investigated and compared with those of native WPI foams. The effect of CaCl ₂ concentration and cross-linking time on microgel formation was studied assessing particle size, rheology and foamability. Foams, produced by mechanical whipping, were assessed by overrun, stability and texture. WPI had lower viscosity than the microgels, producing foams with greater overrun. For microgels, higher concentrations of CaCl ₂ formed smaller particles and decreased microgel viscosity, causing higher overrun. Increasing cross-linking time from 0 to 24 h significantly (P < 0.05) increased G′ and G″ of the microgels, resulting in decreased overrun. Native WPI foams drained within 60 min. In contrast, negligible amounts of liquid drained from microgel foams, which remained stable for >2 years. This demonstrates that WPI microgels can be used as a novel functional application for creating ultra-stable foams for use in the food industry.