High internal phase emulsions stabilized by adsorbed sucrose stearate molecules and dispersed vesicles

Abstract

Sucrose esters are nonionic surfactants which are non-toxic and biodegradable. In this work, aqueous dispersions of a hydrophilic sucrose stearate (C-1815) and their stabilization of both dilute and high internal phase oil-in-water (O/W) emulsions are studied. The results show that C-1815 forms vesicles at concentrations above the critical aggregation concentration (CAC) of 2.0 × 10−4 wt%, and can then stabilize hexadecane or edible O/W emulsions (φo = 0.5) above 0.1 wt%, where vesicles dispersed in aqueous lamellae surrounding oil droplets improve the emulsion stability. Moreover, high internal phase emulsions (HIPEs) with φo = 0.8 can also be formed at C-1815 concentrations as low as 0.05 wt% (relative to whole emulsion). After three freeze-thaw cycles between −20 °C and 30 °C, HIPEs with hexadecane stabilized by C-1815 at concentrations >0.5 wt% are extremely stable to creaming and coalescence. In HIPEs, the vesicles constitute a wall surrounding the oil droplets hindering the oil crystals from approaching each other and coalescing after melting during the harsh freeze-thaw cycles. Although the HIPEs with edible oils stabilized by C-1815 at 0.5 wt% are not stable after similar freeze-thaw cycles, they are stable at room temperature and after cooling-heating cycles between 5 °C and 30 °C. This characteristic makes sucrose stearate a good food-grade emulsifier in various food emulsion products.