Solubilization Mechanism of cis-3-Hexenol and Menthyl Acetate into Sodium Dodecyl Sulfate Micelles, and the Vapor Pressure of These Odorants

Abstract

The solubilization mechanism of cis-3-hexenol and menthyl acetate into sodium dodecyl sulfate (SDS) micelles, and the vapor pressure of these odorants were examined. Also, the electric cond uctivity and osmotic pressure of the SDS micelle dispersed system containing odorants were measured to determine the number of micelles and reveal the micelle formation condition. Lots of cis-3-hexenol molecules are solubilized into the palisade layer of SDS micelles to form composite micelles with the surfactant resulting in an increase in the number of micelles. In our examination, it was revealed that a little quantity of the odorant enters into the hydrophobic layer of the micelles after the solubility limit in the palisade layer is reached, but the solubilization mechanism is different from those of hydrophobic alcohol such as geraniol and citronellol. Menthyl acetate proved to be solubilized into SDS micelle hydrophobic layer only.
By using a sweeping method with nitrogen gas, the aroma of the dispersed system samples were collected and the partial vapor pressure of each odorants in the dispersed systems were determined through calculation on the quantity of collected aroma. The partial vapor pressure of cis-3-hexenol solubilized in palisade layer of the composite micelle with SDS indicated great negative deviation and the aroma of the dispersed system very much decreased in this solubilization area. The partial vapor pressure of menthyl acetate solubilized in the hydrophobic layer of SDS micelle extremely increases to be significantly larger than that based on the vapor pressure of pure liquid, because the intermolecular force of menthyl acetate is weakened in the hydrophobic layer. This accounts for an significant increase in the aroma strength of menthyl acetate solubilized in micelles.