Mechanical Properties and Microstructure of Heat-set Whey Protein Emulsion Gels: Effect of Emulsifiers

A comparison of the viscoelastic properties of heat-set whey protein-stabilized oil-in-water emulsion gels in the presence and absence of added emulsifier has been complemented by structural information from confocal laser scanning microscopy (CLSM). Emulsions (300 mL/L triolein oil, pH 7.0) were prepared with pure -lactoglobulin (8 g/kg) or water-soluble surfactant (20 g/kg Tween 20) as emulsifier and commercial whey protein isolate (>95% -lactoglobulin) added to the emulsion aqueous phase (80 g/kg) before heat treatment (85°C). The differing effects of glycerol monopalmitate and Tween 20 (polyoxyethylene sorbitan monolaurate) on the emulsion gel rheology has been interpreted in terms of the reactivity of the filler particles as determined by the composition of the adsorbed layer around the emulsion droplets. There is evidence from the CLSM of enhanced coalescence of emulsion droplets during thermal treatment in the presence of the emulsifiers, and of an extensively phase-separated microstructure in the case of the emulsion gel containing Tween 20.