Polysorbate 20 is a water-soluble, nonionic surfactant that acts as an emulsifier in oil-in-water (o/w) formulations and as a solubilizer for fragrance oils, oil-soluble vitamins, and essential oils. The exact amount of the material required to solubilize an essential oil or fragrance component depends on the chemical composition and polarity of the aroma chemicals, and must be determined experimentally. While PEG-40 hydrogenated castor oil is among the most widely used and effective solubilizers, polysorbate 20 is often a more economical alternative, requiring a higher dosage but coming at a lower cost. In many cases, such as when dissolving lavender, lemon, thyme, clove stem, bergamot, and rosemary essential oils, as well as citronellol and limonene, polysorbate 20 performs equally well or even better than PEG-40 hydrogenated castor oil.
A few examples are provided below:
- Approximately 40 wt% of lemongrass or peppermint essential oil* can be solubilized in a 3:1 polysorbate 20/water mixture [1].*
- Approximately 28 wt% of cinnamic aldehyde or 37 wt% of citral can be solubilized in a 3:1 polysorbate 20/water mixture [1].
The solubilization of hydrophobic substances is not a linear process; increasing the amount of the active ingredient often requires a disproportionately higher amount of solubilizer. For instance, dissolving 0.5% tocopheryl acetate in water may require around 4% polysorbate 20, but increasing the concentration to 1% can require over 20% of the same solubilizer.
Additionally, polysorbate 20 functions as a mildness additive in the formulation of gentle baby shampoos. It is approved as food additive E432 in Europe. The safety of this material depends on the concentration used in a product; however, it is generally considered safe for use in skin care products. Allergic reactions are rare and typically occur only with excessive use.
The critical micelle concentration (CMC) of polysorbate 20 has been reported to be 57.5 ppm.
* The exact chemical composition and, therefore, solubilization of essential oils depend on factors such as the place of origin, climatic conditions, etc.
[1] World Applied Sciences Journal 8 (1 ): 86-91, 2010
