Emulsifying properties of milk proteins crosslinked with microbial transglutaminase

Oil-in-water emulsions containing 20% oil were prepared with n-tetradecane and sodium caseinate or beta-lactoglobulin in the aqueous phase. The proteins had been cross-linked with microbial transglutaminase prior to emulsification or were cross-linked in the emulsions after emulsification. Extensive cross-linking reduced the stability of the emulsions to coalescence or strong flocculation, as determined by droplet size measurements, whereas limited cross-linking improved coalescence stability. The creaming stability of milk protein stabilized emulsions was improved even with relatively extensive cross-linking and this was ascribed to changes in the adsorbed layer or increased viscosity of the continuous phase. Cross-linking greatly reduced Ostwald ripening or aggregation of the milk protein stabilized emulsions in the presence of ethanol, probably due to a reduction of the diffusion of oil from the emulsion droplets because of increased viscosity/elasticity of the adsorbed layer or due to hindering of the aggregation of protein, that in the non-cross-linked state probably results in a collapse of the surface protein layer. (C) 1998 Elsevier Science Ltd. All rights reserved.