Solubilization of essential oil components and orange oil in microemulsions

Emulsions used to stabilize flavor materials in water are often ineffective. Microemulsions can greatly increase the solubility of flavor components that are insoluble or marginally soluble in water. The solubility of four classes of flavor components in 0.1M sodium dodecyl sulfate (SDS), 0.1M sodium laurate, 0.1M polyoxyethylene sorbitan monolaurate (Tween 20) and 0.0022M poly(ethylene oxide-propylene oxide 3:1) (block copolymer) was determined. The maximum additive concentration of aldehydes, ketones, alcohols and ethyl esters in these microemulsions ranged from 0.07 to 77.2 mg/ml. Models expressing solubility as a partition coefficient, mole fraction, volume fraction and molar solubilization ratio were calculated to describe solubility based on the chemical characteristics of the solubilizate and the surfactant. Decreasing the microemulsion pH from 7 to 2 increased the solubilization capacity of SDS but did not affect that of Tween 20. Temperature had a greater effect on the solubilization capacity of Tween 20 than of SDS but the effect was dependent on the solubilizate. Pasteurization of the surfactant-gum arabic system affected solubilization but was dependent on the solubilizate as well as the surfactant. Long-chain components had the largest relative increase in solubility when gum arabic was added to the microemulsion. Solubility of cold-pressed orange oil increased as the essential oil was concentrated 5-fold or 10-fold. This increase in solubility was due to a selective solubilization of limonene over the more desirable flavor components.