Shea oil is obtained from the kernels of the fruit of the Shea tree. The tree belongs to the Sapotaceae family (Sapotaceae species), which grows in a relatively broad strip on the southern fringe of the Sahel climate zone stretching from Senegal to eastern Uganda.
It is botanically divided into two subspecies, the West African subspecies Vitellaria paradoxa, which grows primarily in the Central African Republic and Senegal, and the East African subspecies Vitellaria paradoxa, which is mainly cultivated in Uganda and Sudan with small pockets in Ethiopia.
The average tree takes 20 years to flower and produces 4-inch, green fruit that contain brown seeds surrounded by a sweet pulp.
The nut kernels have a rough textured surface and contain 50% fat.
Shea butter, among other things, is produced from these kernels.
Native Shea butter (also called Beurre de Karité) has a high content of ingredients valued in the cosmetics industry, such as phytosterols, wax esters, tocopherols, antioxidant catechins, gallic acid and skin-friendly fatty acids.
Of particular interest is its high percentage of unsaponifiables, especially the aforementioned phytosterols (including campesterol, stigmasterol, β-sitosterol and α-Spinosterol), triterpenes (cinnamic acid ester, α-and β-amyrin, parkeol, cutyrospermol and lupeol) and tocopherols; their concentrations occur in West African Shea paradoxa at rates of 6-12%.
Of medical interest is allantoin, a substance found in the acqueous extract of the press cakes of the Shea nut and proven to prevent inflammation, regenerate cells, heal wounds, and help with skin perforations.
In addition to palmitic and linoleic acid, Shea butter contains stearic and oleic acids, which together make up about 85-90% of total fatty acids.
Within West Africa, the proportions of oil and stearic acids in the Shea butter vary by region - it may contain anywhere from 25-51% stearic acid and 39-62% oleic acid.
These differences result in vastly different product qualities in terms of consistency, melting point and processing characteristics. Varying climatic conditions are responsible for this variation. The plant produces cell-protecting antioxidant tocopherols more actively and has a lower oleic acid content in warmer climates.
In cosmetic use, a lower percentage of saturated fatty acids, combined with a higher proportion of saturated oleic acid, results in a slightly softer consistency and lower film formation on the skin because the oil acids influence absorbability. Saturated stearic acid, on the other hand, has a much more concealing effect.
Unsaponifiables occur in Shea paradoxa at a low percentage of 2% compared to about 6-11% in Shea nilotica, which means a less pronounced restructuring and regenerating effect. On the other hand, a high proportion of cell-protecting catechins is characteristic of Shea paradoxa.
Through its wide range of elements, Shea butter regulates the moisture content of the skin. It has a moisturizing, soothing and smoothing quality that is highly prized in the cosmetics industry.
The considerable amount of unsaponifiable components strengthens the lipid barriers of the skin’s horny layer. Shea butter is a preferred treatment of dry, hypersensitive and barrier-damaged skin.
The wide variation of Shea species allows for the reliable configuration of a desired drug profile.
The traditional method of producing Shea butter is hampered by various naturally occurring contaminants: Depending on the starting material, the production process, the quality of water used, storage temperatures and the care with which unwanted substances (from insects to pesticides in the water) are excluded from the process, the quality of the product can vary greatly.
This traditional process of manufacturing native butters, preferably overseas, is still not subject to controls to this day.
Laboratory analyses reveal significant deficiencies for the most part: high levels of free fatty acids (FFAs) and peroxide numbers as criteria for rancidity, microorganism contamination (bacteria, yeasts, fungi) and pesticide residues indicate a poor product quality.
A high-quality Shea butter has a homogeneous, smooth texture and is bright yellow in color.
An excellent chemical and microbiological criteria for a flawless product (this corresponds to an acid number of 4) is an FFA value of less than 2%, a peroxide number less than 15 meq/kg (values below 10 are desirable) and a microorganism contamination level within the legal limits for edible fats.
A low amount of residual moisture content is also important for minimizing the formation of mold and bacterial growth in the butters. Analyses show residual water (moisture content) to comprise 3.5 to 14.5% of traditionally produced Shea butter; excellent qualities are under 0.2%.
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