The effects of ethanol content and emulsifying agent concentration on the stability of vegetable oil-ethanol emulsions
Tóm tắt
In vegetable oil-ethanol emulsions ethanol is the polar phase and vegetable oil is the nonpolar phase. The primary advantage of vegetable oil-ethanol emulsions over conventional water-oil emulsions is that they enable the incorporation of water-and oil-insoluble or poorly soluble functional compounds and/or drugs into emulsions. A number of nonionic surfactants were used to select appropriate stabilizers for stable vegetable oil-ethanol emulsions. We found decaglycerol mono-oleate (MO750) to be the best stabilizer for ethanol-in-oil (E/O) emulsions. The effects of ethanol content and of emulsifying agent concentration on the stability of vegetable oil-ethanol emulsions were examined with MO750. After emulsification, two turbid layers formed simultaneously when ethanol content exceeded 20 wt%. The top layers (oil-in-ethanol emulsions; O/E emulsions) were very unstable, whereas the stability of the bottom layers (E/O emulsions) depended on the ethanol content. The stability of E/O emulsions is closely related to the effective concentration of MO750 aggregates, which play an important role in the film thickness stability of interfacial films formed by surfactant aggregates. Instability of E/O emulsion at 5 wt% MO750 is probably due to the polydispersity (i.e., nonuniform size and shape) of MO750 aggregates at high MO750 concentration. E/O emulsions prepared with 0.1, 0.5, and 1 wt% MO750 were stable, suggesting that the interfacial films formed were effective in protecting the droplets against coalescence and Ostwald ripening.
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