Evaluation of Emulsion Stability. The Effect of a Natural Emulsifier, Soya Sterol, on w/o Type Emulsions

Abstract

Using soya sterol (chemical composition by weight : β-sitosterol 56% ; campesterol 28% ; stigmasterol 4% ; sterol hydrocarbons and cholesterol 6% ; triterpene alcohols, keto-steroids and other steroid-like constituents 6%) and Span 85 as emulsifiers, with liquid paraffin as the dispersed phase in water, the effect of soya sterol and Span 85 on emulsion stability was evaluated in terms of the following five physicochemical parameters : (1) particle size, (2) degree of dispersion, (3) separation rate of dispersed droplets, (4) rheology of emulsion products, (5) sedimentation rate of dispersed droplets. An agitator and a homogenizer were used to produce the emulsions. The following results were obtained. (1) The particle size of emulsions prepared with soya sterol was larger than that with Span 85, and consequently, soya sterol is a less effective emulsifier than Span 85. (2) Nevertheless, soya sterol has stronger stabilizing action on emulsions than Span 85, and this effect become especially marked when emulsification was carried out with a homogenizer at a high shear rate.