Foaming behavior of colloidal whey protein isolate micro-particle dispersions

[Display omitted] •Soft WPI particles are good foam stabilizers.•Charge density of WPI particles is important on foaming properties.•At high charge density, WPI micro-particle dispersions have high foam stability.•At different pH, foam stability trend of dispersions and solutions is the opposite.•WPI particle dispersions showed longer foam stability than WPI solutions. The foaming properties of whey protein isolate (WPI) particle dispersions were investigated. These particles were produced by a two-step emulsification method through heat-induced aggregation. We prepared two types of micron-sized WPI particles, namely soft and hard particles at different network densities, by changing the electrostatic interaction between proteins. Foam stability behavior of the dispersions was analyzed considering the size, hardness, and charge density of the particles. Foaming properties of WPI particle dispersions were compared to those of native WPI solutions. Changing only size and only hardness of particles separately yielded comparable foaming properties. However, changing the charge density of the particles had an essential effect on foam stability. At acidic pH, soft WPI particle dispersions showed better foaming properties than hard WPI particle dispersions, possibly due to the high stretching ability of soft particles at the interface. At alkaline pH, both soft and hard particle dispersions showed high foam stability; whereas, at the iso-electric point of proteins, dispersions showed low foaming properties. At the interface, the WPI particles behaved like colloidal particles, which was different from the native proteins. In this study, the foaming properties WPI micro-particles at different network densities were discussed for the first time. The structuring and foam stabilizing abilities of WPI particles are promising in food products, and therefore the particles can be considered as an alternative food-grade Pickering stabilizer.