Effect of lecithin on the viscoelastic properties of beta-lactoglobulin-stabilized emulsion gels

Oscillatory shear viscoelastic measurements have been carried out on beta-lactoglobulin oil-in-water emulsions (7 wt% protein, 32.5 wt% n-tetradecane, pH 7) subjected to a standardized thermal processing treatment (30 min at 90 degrees C). The influences of lecithin (egg-yolk phosphatidylcholine) on the storage and loss moduli (at 1 Hz) of heat-set emulsion gels cooled at 30 degrees C has been compared with that for the equivalent beta-lactoglobulin systems (10-11 wt% protein, pH 7) without emulsion droplets present. It has been found that the addition of lecithin after emulsification leads to an increase in the mechanical strength of the heat-set emulsion gel with no significant protein displacement from the oil-water interface. This contrasts with previous literature reports for whey protein emulsion gels which indicated the opposite effect for the case when lecithin was present during emulsification.