Surface properties and rheology of concentrated oil in water emulsions stabilized by heat modified -lactoglobulin
Special Symposium - Innovations in Food Technology (LMC Congress)
Innovations in Food Technology - Poster Session (LMC/Food - P1)
Keywords: emulsions, rheology
A wide range of food systems are emulsions where oils droplets and/or air cells of various volume fractions are dispersed in a continuous water phase. Modification and control of particle interactions are of interest to obtain desired properties of food emulsions with respect to stability and rheology. In the present study oil in water emulsions were made with an oil volume fraction of 0.6, which renders the oil droplets rather close packed. The effects of modifying the oil droplet interactions through heat modification of the emulsifier, -lactoglobulin, were investigated. Mild heating was applied to modify -lactoglobulin prior to emulsification followed by molar mass determination of the species formed upon heating. The microstructure of the emulsions were studied by confocal laser scanning microscopy and sizes of oil droplets were measured by light scattering together with determination of the amount of protein adsorbed to surfaces of oil droplets. Furthermore, oil droplet interactions in the emulsions were quantified rheologically including steady shear, and small and large amplitude oscillatory shear measurements. The rheological properties of the emulsions stabilized by heated -lactoglobulin were remarkably different compared to the emulsions stabilized by native -lactoglobulin and a fifty-fold increase in the zero-shear viscosity and moduli was observed for the emulsions stabilized by heat-modified -lactoglobulin. Thus, mild heat modification of milk protein based ingredients containing -lactoglobulin may be applied to induce major enhancement in viscosity and visco-elastic properties of concentrated food emulsions stabilized by milk proteins.
