Stability of Model Emulsion Prepared with Soybean Lecithin

Abstract

Stability of emulsion prepared by using of soybean lecithin was investigated. Better stability was obtained from the emulsion prepared by dispersing lecithin in oil phase than from that prepared by dispersing lecithin in water phase. The emulsion stability increased with an increase of the lecithin amount added in both static and dynamic tests. Of the emulsion containing more than 5% lecithin, no phase separation was observed during storage for two weeks at 25°C, moreover, it was noticed that the emulsion containing above 1% lecithin was very stable and did not break even by ultracentrifuging of 10, 100G at 30°C. Acid precipitated soybean protein increased the stability of the emulsion prepared with lecithin. Normal alcohols (C₁-C₇) also increased the stability of the emulsion and emulsions containing alcohols with higher molecular weight were more stable than those containing lower molecular weight alcohols. Higher the sodium chloride concentration, the emulsion became more unstable among samples prepared by dispersing lecithin in oil phase. On the other hand, in the case of samples prepared by dispersing lecithin in water phase, the worst stability was observed of the emulsion with lecithin content which was regarded as identical with salt content stoichiometrically. These results indicate that the electrical charge reversing caused the change of lecithin arrangement at the oil-water interface.