Foaming Properties of Whey Protein Isolate and λ-Carrageenan Mixed Systems

Heating protein with polysaccharide under neutral or near neutral pH can induce the formation of soluble complex with improved functional properties. The objective of our research was to investigate the effects of -carrageenan (C) concentrations and pH on foaming properties of heated whey protein isolate (WPI) and C soluble complex (h-cpx) in comparison to heated WPI with added C (pWPI-C), and unheated WPI with C (WPI-C). In all 3 WPI-C systems at pH 7, increasing C concentration led to improved foamability until a certain concentration before it decreased. Despite their higher viscosity, both heated systems (pWPI-C and h-cpx) showed significantly better foamability and foam stability compared to WPI-C. Rheological results of foams with 0.25% C suggested that higher elasticity and viscous films were produced in h-cpx and pWPI-C systems corresponding to better foam stability. Foam microstructure images indicated that foams produced from h-cpx had thicker film and consisted of smaller initial bubble area and more uniform bubble size. Results from the effect of pH (6.2, 6.5, and 7.0) further confirmed that stronger interactions between WPI and C during heating contributed to the improved foaming properties. Foam stability was higher in h-cpx system at all 3 pH levels, especially under pH 6.2 where there were strongest interactions between the biopolymers. Practical Application With enhanced protein and polysaccharide interactions, heated complex between whey protein isolate and -carrageenan can be utilized to increase stability of food foams.