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Solubilisation of soybean oil in microemulsions using various surfactants
John Flanagana'*, Katrine Kortegaarda, D. Neil Pinderb, Thomas Rades`, Harjinder Singha
aRiddet Centre, Massey University,Private Bag 11222, Pnlmerston North, New Zealand
"Institute of Fundanaenral Sciences, Massey University, Palmerston North, New Zealand
`School of Pharmacy, (Iniversiry of Otago, Dunedin, New ZealandAbstract
Microemulsions are transparent, isotropic solutions of oil, water and surfactant (and possibly cosurfactant) which are thermodynamically stable, and have been much studied in terms ofpharmaceutical and cosmetic applications. However, the application of microemulsions in foods has been limited both due lo toxic or irritant nature of ionic surfactants and the difficulty of solubilisinglarge triglycerides. Three surtactants, food-grade ethoxylated mono- and diglycerides (EMD) and phospholipids, and non-food-grade polyoxyethylene oleyl ether (POE) were examined for their ability loform microemulsions using soybean oil, and their areas of formation expressed on phase diagrams. Microemulsions prepared with EMD and phospholipids required the presence of a short-chain alcohol forformation. Both oil/water (o/w) and water/oil (w/o) microemulsions could be formed using ENID, and the microemulsion area of the phase diagram increased on addition of sucrose and increase intemperature. Depending on sucrose and ethanol concentrations, microemulsions formed with ENID were fotmd to retain their integrity at temperatures below which they formed. Microemulsions could be formed usingphospholipids, but only at high surfactant concentration and in the presence of a short-chain alcohol. O/w microemulsions containing 10% oil (w/w) were prepared with POE at surfactant concentrations of> 20% (w/w). Dynamic light scattering of microemulsion samples diluted with water indicated particle rada of 6.5 nm. Freeze-fracture SEM showed the structures lo be of a droplet type, however, this...