Vegetable oils and fats differ significantly in their consistency. Fats are commonly referred to as “oils” if they are in a liquid state at room temperature. Fats that are solid at room temperature are called “fats”. The melting point of oils and fats is determined by the type of fatty acids they contain. A high content of unsaturated fatty acids leads to a liquid consistency, whereas a high content of saturated fatty acids leads to a semi-solid or solid consistency.
Extraction of vegetable oils and fats
Vegetable oils and fats are obtained from seeds or fruits of various plant species. The main methods for gaining vegetable oil are cold pressing and extraction. In cold pressing, the seeds or fruits are ground to a pulp at a low temperature, resulting in a high-quality, natural oil.
During extraction, the oil is extracted using solvents. This results in a higher yield than pressing, but it is difficult to remove the solvents afterwards. For this reason, a subsequent refining process is necessary, which can affect the quality of the oil however. During the refining process, the oils are cleaned, dyed and steamed. This will remove pollutants, but important nutrients in the oil may be lost as well.
Important components of vegetable oils
The monounsaturated oleic acid can be found in different amounts in each oil. Since unsaturated fatty acids make oils liquid and easily spreadable, vegetable oils containing oleic acid are often used for skin care. When processed into an emulsion, oils containing oleic acid ensure good spreadability and a pleasant feeling on the skin.
The double-unsaturated linoleic acid is, besides arachidonic acid, the most frequently occurring poly fatty acid of the skin. The acid supports the regeneration of the skin and forms a protective film on the upper skin layer. This ensures that the skin is always supplied with moisture. Linoleic acid also has anti-inflammatory effects and thus reduces skin problems based on inflammatory processes.
The triple unsaturated α-linolenic acid is one of the essential fatty acids that cannot be produced by the body itself. This acid has a wide range of effects. Notable is its anti-inflammatory effect and its support of the repair mechanism of the skin. Especially walnut and rapeseed oil are rich in α linolenic acid.
The triple unsaturated γ-linolenic acid is extremely rare in nature. It has an anti-inflammatory and itch-relieving effect. It is therefore used for the care of very dry skin and also to reduce skin diseases such as neurodermatitis. Oils rich in γ-linolenic acid are for example borage seed oil, black currant seed oil and evening primrose oil.
Vegetable oils with a high proportion of saturated lauric acid can be distributed very well on the skin, absorb well into the skin and provide a pleasantly soft skin feeling. This acid is also said to have an antimicrobial and cooling effect (while melting on the skin). An oil containing lauric acid is, for example, coconut oil.
The saturated palmitic acid is a natural component of our skin barrier. As its proportion decreases with age, palmitic acid oils are often used for the care of mature skin. Like stearic acid, palmitic acid has a slight replenishing effect, is comedogenic and, due to its high melting point, also consistent. It is contained in cocoa butter and sea buckthorn oil for example.
As a saturated fatty acid, stearic acid can be used in emulsions as a consistency enhancer, which improves the even distribution of the care product. It forms a film on the skin and protects it from external influences. Since stearic acid is said to have a comedogenic effect, it is less suitable for oily and impure skin. The acid is contained in a high proportion in cocoa butter for example.
Vitamin E (α-Tocopherol)
Vitamin E is used as an umbrella term for tocopherols and tocotrienols with vitamin E activity. Vitamin E is used in small doses as an antioxidant. It acts as a radical absorber and can reduce a variety of inflammatory diseases and degenerative processes. Thus, vitamin E is said to have effects such as the prevention of skin aging, increase in the moisture retention capacity of the horny layer, accelerated wound healing, scar reduction, improvement of inflammatory skin processes and alleviation of itching.
Vitamin A appears in various forms. A distinction can be made between retinol, retinal and retinoic acid. The latter should not be used in cosmetics due to its negative side effects. A deficiency of vitamin A leads to a thickening of the horny layer, making the skin appear leathery and wrinkled. Vitamin A is said to counteract skin aging by stimulating cell growth. Vitamin A preparations should be stabilized with an antioxidant and UV filter to protect the Rentinol and ensure its effectiveness.
Shelf life and storage
Essential for the shelf life of an oil is the fatty acid composition and the number of antioxidants it contains. As soon as all antioxidants in the oil have been exhausted, various reactions in the oil quickly lead to so-called “rancidity”. The fatty acid composition has an influence on the shelf life, whereby saturated fatty acids are regarded as relatively stable. Unsaturated fatty acids have a shorter shelf life.
The shelf life of an oil can be favorably influenced externally with dark and cool storage, but also with added antioxidants.
Effect of vegetable oils in cosmetics
Vegetable oils and fats are among the most important ingredients in cosmetics. They are more or less water soluble and support the protective function of the skin. As a lipid substance they make the skin water resistant and protect it against dehydration. They can also fill small skin indentations and thus smooth the skin and reduce wrinkles. The accompanying substances of the oils are also important. Many vegetable oils contain vitamins, provitamins and phytosterols. Phytosterols are able to strengthen the skin barrier and lead to a good nourishing effect, especially for older skin.
Use of vegetable oils in cosmetics
Creams containing oils that have a low melting point are easier to spread on the skin. Fats with a higher melting point lead to a firmer consistency. Since vegetable oils and fats are not water-soluble, they must be converted into an emulsion to be used in a water-containing cream. This is done with the aid of emulsifiers. Processing oils into oleogels is also possible. These are anhydrous (waterfree) and are considered more stable. Oils can also be used as auxiliary materials in cosmetics, for example as carriers for fragrances or fat-soluble vitamins.
Krist, Sabine (2013): Lexikon der Pflanzlichen Öle und Fett. Vienna: Springer.
Niestroj, Irmgard (2000): Praxis der Orthomolekularen Medizin. Suttgart: Hippokrates.