Constructing aqueous foams from milk components: structure and interfaces

Milk foams are complex colloid systems including protein dispersion foam, emulsion foam, and oleofoam. Bovine milk is a unique colloid mixture containing diversified surface-active components ranging from mesoscopic to molecular scales, such as proteins, milk fat globules (MFGs), fat crystals, phospholipids, etc. A comprehensive understanding about their foaming behaviors in the context of milk foam would result in cleaner-label opportunities and superior stability. Regarding practical foaming processes, interfacial adsorption or foam film formation is a net effect resulted from both thermodynamic equilibrium and kinetic aspects, in which surface tension, gravity, physicochemical properties, hydrodynamics, etc. are involved. This has a significant meaning to the W-A entering phenomenon for MFGs and to the milk (emulsion) foaming capacity and stability due to MFGs may act as both foaming and antifoaming agent. This mini review elaborates foaming mechanisms for milk components, knowledge gaps and opportunities are discussed based on recent research findings.