The popularity of natural oils in skin care and color cosmetics industries has been on the rise since the entry of Argan oil as an ingredient. A quick scan of beauty magazines reveals product claims like “extraordinary oil” and “gel meets oil” texture. The of use these raw materials has continued to expand into just about every category including cream oil moisturizers, oil cleansers, and even primer oils.
INCI names for natural oils require the genus and species of the plant the oil is derived from. This helps the formulator to easily identify the source of the raw material. Natural oils are complex mixtures of triglycerides, the distribution of these components and their individual structures drive sensory and performance attributes. The selected plant seed and the processing impact the final properties of the oil as well. Derivatives oils formed by reactions with molecules like silicones can provide enhanced functionally.
Oils can be subject to rancidity so it is important to understand and monitor the details of specifications like iodine value and peroxide value. You can find a more detailed discussion of these evaluation methods in one of my previous posts on cosmetic certificate of analysis.
A great guide primer on natural oils can be found in the book Oils of Nature by Tony O’Lenick, David C. Steinberg, Kenneth Klein and Carter LaVay. Below is some information about two oils that I have found useful.
Castor oil is a vegetable oil made by pressing the seeds of Ricinus communis, the castor oil plant. Castor oil is a pale yellow liquid comprised mostly of ricinoleic acid, a monounsaturated, 18-carbon fatty acid. Ricinoleic acid is unusual for a fatty acid due to the presence of a hydroxyl group on the twelfth carbon this makes castor oil more polar than most fats. The chemical reactivity of the alcohol group also allows chemical derivatization that is not possible with most other seed oils. Castor oil has low been used as a dispersant for pigments in lipstick and lip balm because castor oil is often already part of the base formulation and it is cost effect, although many new approaches to pigment dispersion exist today.
Meadowfoam Seed Oil
Meadowfoam seed oil is derived from the seeds of meadowfoam (Limnanthes alba).The plant was named because of its beautiful white flowers that resemble a meadow of foam. This relatively new material is distinctive due to a high concentration of fatty acids with chain lengths of 20 carbons or more and unique arrangement of double bonds. Meadowfoam seed oil contains with occurring tocopherols and has a high level of oxidative stability. Meadowfoam seed oil has a lighter skin feel than some other natural oils but still provides a high level of emollience. This oil has also found application in hair care for its ability to provide gloss without weighing hair down.