Viscoelastic properties of heat-set whey protein-stabilized emulsion gels with added lecithin

Our objective was to determine how lecithin affects the small-deformation shear rheology of heat-set emulsion gels made from whey protein concentrate (WPC). Fine oil-in-water emulsions were prepared with WPC, lecithin or WPC; lecithin present during homogenization. Storage and loss moduli were measured in situ during thermal processing at temperatures up to 90 degrees C and afterwards at 30 degrees C. The positive influence of pure egg lecithin added after emulsification on the elastic modulus of the WPC emulsion gel was attributed to lecithin-protein complexation. Crude egg lecithin gave a broadly similar increase in gel strength, but pure soybean lecithin was not so effective in reinforcing the network, and crude soybean lecithin was ineffective. Using lecithin as sole emulsifier, with WPC added after homogenization, gave a lower modulus for the heat-set WPC emulsion gel. With protein + lecithin present during emulsification, the considerable loss of gel strength was attributable to some WPC displacement from the emulsion droplet surface.