Filler effects of oil droplets on the viscoelastic properties of emulsion gels

Abstract

Filler effects of oil droplets on the viscoelastic properties of emulsion gels were investigated by small deformation mechanical measurements. The emulsions were made with soya oil and soy 11S globulin (15 wt% oil, 1.5–7% protein concentrations). The emulsion and soy 11S globulin solutions were gelled using Ca ++-independent transglutaminase from a microorganism. The shear storage modulus (G′) and loss modulus (G″) of the proteinous gels and emulsion gels depended on the protein concentration. The concentration dependence of the modulus was approximated by an exponential function of the form: G ∝ C n , n = 4 and n = 2 being found in the cases of the proteinous gels and the emulsion gels, respectively. Shear moduli of the emulsion gels were much higher than those of the proteinous gels. Gels made from a fine emulsion (containing smaller oil droplets) exhibited higher G′ and G″ values than corresponding gels from a coarse emulsion. Addition of Tween 20 was found to reduce G′ and G″ of emulsion gels even when the protein matrix was not significantly displaced from the oil—water interface by the surfactant.