This work aimed to prepare natural flavor oil emulsions by spontaneous emulsification by adding organic mixtures consisting of flavor oils, sucrose esters, and with/without ethanol into a stirred aqueous phase. Orange oil (OrO), peppermint oil (PpO), sucrose esters with mainly sucrose monostearate (S1670), and sucrose esters with mainly sucrose monopalmitate (P1670) were employed. The mean droplet sizes of emulsions were strongly dependent on flavor oil types, flavor oil concentrations, sucrose ester concentrations, and stirring speeds, but were lesser dependent on sucrose ester types. Higher sucrose ester concentrations and stronger convection created smaller oil droplets. The smallest mean droplet size of ~200 nm was achieved by the formulation of OrO emulsions containing 10.0 wt% oil, 7.5 wt% sucrose esters, and < 1 wt% ethanol. OrO emulsions stabilized by sucrose esters exhibited good physical stability over one month storage while PpO emulsions destabilized rapidly, suggested by Ostwald ripening. This study revealed that sucrose esters can be applied to form submicron emulsions without using any high energy homogenizers.
Spontaneous emulsification Sucrose esters Flavor oils Ostwald ripening Mass transfer
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This research project was funded by Assumption University research grants (RP59013). The sucrose esters used in this study were kindly donated by Caltech Corp., Ltd., Thailand. Special thanks to Ms. Dolina Millar for editing the manuscript.