Shea butter, the fat obtained from the kernels of shea seeds (nuts), has several useful properties for a wide range of food, personal care and other applications. Its fatty acid composition makes its use healthy. Shea butter is soft solid or fatty oil at room temperature.
Shea kernels contain about 40 to 57 % wt/wt fat or butter. The fat content varies depending on the regions where the shea trees are grown. Shea butter is extracted by various methods and the yield varies from 25 to 35% depending on the extraction method. Generally, significant residual amount of butter remains in the kernels during extraction by mechanical press or expellers. Therefore, the oil cake from expellers is fed to solvent extraction plants to extract the residual shea butter, leaving only minute quantities of shea fat in the oil cake.
Typical or standard properties of raw or unrefined and refined shea butter grades are listed in the following table:
TABLE 1: TYPICAL PROPERTIES OF UNREFINED AND REFINED SHEA BUTTER
|PROPERTIES||UNREFINED SHEA BUTTER||REFINED SHEA BUTTER|
|Refractive Index at 44 deg. C||1.4620 – 1.4650||1.4620 – 1.4650|
|Iodine Value||30 – 75||30 – 75|
|Saponification Value||160 – 200||160 – 200|
|Unsaponifiable Matter||19% by wt. max.||10% by wt. max.|
|Free Fatty Acids (as Oleic Acid)||8% max.||0.25% max.|
|Peroxide Value, meq/kg||10 max.||10 max.|
|Flash Point (PenskyMarten Closed Method)||NA||250 deg. C min.|
|Test for Argemone Oil||Negative||Negative|
The African Standard specific quality criteria for three different unrefined shea butter types or grades are presented in the following table:
TABLE 2: AFRICAN STANDARD FOR UNREFINED SHEA BUTTER GRADES
African Standard identity characteristics of unrefined shea butter are listed in the following table:
|PARAMETERS||TYPE 1||TYPE 2||TYPE 3|
|Moisture Content, (%) m/m||0.05 max.||0.05 – 0.2||0.2 – 2.0|
|Free Fatty Acid / FFA (%) m/m||1.0 max.||1.0 – 3.0||3.0 – 8.0|
|Peroxide Value, meq/kg||10 max.||10 – 15||15 – 50|
|Insoluble Impurities (%) m/m||0.09 max.||0.09 – 0.2||0.2 – 2.0|
TABLE 3: IDENTITY CHARACTERISTICS OF UNREFINED SHEA BUTTER AS PER AFRICAN STANDARD
|Relative Density, g/ml (40 deg. C )||0.89 – 0.93|
|Saponification Value, mg KOH/g||160 – 190|
|Iodine Value (Wijs)||30 – 75|
|Unsaponifiables (%)||1 – 19|
|Refractive Index at 44 deg. C||1.4620 – 1.4650|
|Melting Point (deg. C)||32 – 40|
|Volatile Matter at 105 deg. C (% m/m)||0.2 max.|
|Soap Content (% m/m)||0.005 max.|
|FATTY ACID COMPOSITION (% m/m)|
|Lauric Acid (C12:0)||1 max.|
|Myristic Acid (C14:0)||0.7 max.|
|Palmitic Acid (C16:0)||2 – 10|
|Palmitoleic Acid (C16:1)||0.3 max.|
|Stearic Acid (C18:0)||25 – 50|
|Oleic Acid (C18:1)||36 – 62|
|Linoleic Acid (C18:2)||1 – 11|
|Linolenic Acid (C18:3)||1 max.|
|Arachidic Acid (C20:0)||3.5 max.|
The typical levels of the major fatty acids present in shea butter are – oleic acid (C18:1) 34 to 62%, stearic acid (C18:0) 20 to 55.7%, palmitic acid (C16:0) 1.9 to 10% and linoleic acid (C18:2) 1 to 11%.
Shea butter has approximately 50% by weight of unsaturated fatty acids and about 50% by weight of saturated fatty acids. It has higher stearic acid content than palmitic acid. The higher content of unsaturated fatty acids accounts for its higher iodine value.
The unsaponifiable matter in shea butter contains high levels of tocopherols (vitamin E) and polyphenols, which have antioxidant properties. About two-thirds of the vitamin E occurs as Alpha-Tocopherol, which has the highest antioxidant activity among tocopherols.
Shea butter unsaponifiable matter also contains relatively high levels (up to 6%) of phytosterols, which are generally regarded as cholesterol-reducing nutritional components.
Shea butter, an important product of sub-Saharan Africa, has long been used for culinary, medicinal and other applications.
High nutritive value and low cholesterol levels make shea butter a table oil equivalent. It is ideal raw material for cooking oil, margarine, cosmetics, soaps, detergents and candles due to the presence of solid fat or stearin and liquid oil, i.e., olein. Shea butter can also be used in various food preparations, replacing butter, olive oil, coconut oil, etc.
Shea butter is used as a cocoa butter equivalent (CBE) (after mixing with other oils) and improver in the manufacture of chocolates; but its taste is noticeably different. Due to the presence of natural antioxidants (tocopherols or vitamin E) in shea butter, increased stability and longer shelf-life are attributed to the final chocolate products.
Shea butter is fractionated either by dry fractionation method or by using solvents to separate the stearin (higher-melting or solid) and olein (lower-melting or liquid) fractions. These fractions have different applications. The stearin fraction is used in cocoa butter equivalents (CBE) and cocoa butter substitutes (CBS).
Shea butter melts at body temperature and therefore gets quickly absorbed into the skin. It acts as a “re-fatting” agent and has good water-binding properties. Its moisturizing and healing properties are beneficial in the treatment of many skin ailments. It is anti-inflammatory and, to some extent, antimicrobial as well.
Shea butter, rich in unsaturated fatty acids, has become an important ingredient in cosmetics and personal care products. Shea butter has gained significant popularity in the western developed countries due to its widespread use in many beauty products, such as moisturizers, shampoos, conditioners, lip gloss, lipsticks, creams, lotions, emulsions, etc. for skin and hair.
The unsaturated fatty acids including the essential fatty acids, significant content of unsaponifiable matter, vitamins E and D, phytosterols, provitamin A and allantoin, etc. in shea butter make it very beneficial in personal care and cosmetics products.
The American Shea Butter Institute (ASBI) has reported that 100% pure natural shea butter is effective as an all-natural vitamin A cream, which has been shown to be a superb moisturizer, with exceptional healing properties.
The beneficial effects of shea butter on the skin and hair are summarized here –
- Moisturizes dry skin
- Reduces skin inflammation, itchy skin, and peeling
- Reduces acne and blemishes
- Anti-ageing, anti-wrinkle and action against free radicals
- Reduces skin elasticity
- Reduces stretch marks and baby diaper rash
- Repairs damaged hair
- Prevents hair loss
- Effective natural hair conditioner
Shea butter is a natural sun screen and can protect the skin from harmful UV rays of the sun to a small extent, due to the presence of cinnamic acid. Generally, it is used in sun screen products (lotions and creams) along with other, stronger, sun screen agents.
Shea butter is also useful as a medicine in the treatment of various ailments – dry skin, skin rash, skin peeling after tanning, blemishes and wrinkles, itching skin, sunburns, shaving cream for a smooth silky shave, small skin wounds, skin cracks and tough or rough skin, cold weather, frost bites, muscle aches, muscle fatigue, stretch mark prevention during pregnancy, rheumatism, arthritis, nasal inflammation and congestion, diarrhea, lowering of cholesterol, wound healing, insect bites, skin allergies such as poison ivy or poison oaks, dermatitis, psoriasis, eczema, and skin damage from heat. It is also used as a raw material for drug formulations for the above ailments as well as for herpes lesions and nutraceuticals.
In Africa, shea butter and its byproducts (obtained during the production of shea butter) have been used as cooking oil and to make traditional cosmetics and other products, such as African black soap, skin moisturizers, hairdressing, for muscle sprains treatment (usually as an emollient along with medicinal herbs), for the management of sinusitis and relief of nasal congestion, for moisturizing new-born babies (including removal of the umbilical cord), for curing leprosy and other ailments, lubricating moving parts, waterproofing houses (using wax, or residue from shea butter), as an accelerant for fire lighting, and as a fuel in the traditional oil lamp. Shea butter candles are common at traditional funerals. Shea butter is applied on the skin after twice daily ablutions, particularly during the Harmattan period, i.e., when the dusty Saharan wind blows during the driest season and the humidity levels regularly fall below 5%. It is also used to increase the durability of wood in traditional African percussion instruments such as Calabash gourds and leather tuning straps.
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