Internal and external factors affecting the stability of glycerol monostearate structured emulsions

Abstract

Monoglyceride (MG) structured emulsions have been developed for use in diverse food and cosmetic applications. However, these MG-structured emulsions undergo a polymorphic transformation from the α-gel phase to the coagel phase, resulting in emulsion destabilization and water syneresis. In this study, the stability of emulsions containing 60–70% (w/w) water structured with 5% (w/w) of a blend of the emulsifier glycerol monostearate (GMS) and co-emulsifier sodium stearoyl lactylate (SSL), was assessed. The internal factors examined were concentrations of co-emulsifier and the addition of the polysaccharide xanthan gum. External factors examined included cooling rate and applied shear. The methods used to study the polymorphic transition were differential scanning calorimetry, X-ray diffraction, and pulsed proton nuclear magnetic resonance. In this work, the sub-α Coagel Index was successfully used to characterize the degree of coagel formation in MG-structured emulsions. Results showed that the stability of the α-gel phase was improved by using 1 : 9 w/w SSL : GMS ratios and by adding 0.1% xanthan gum. Slow cooling rates without shear could also increase the stability of the α-gel phase in the structured emulsion system.