Specialty Fats

Shea Butter

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Shea (Vitellaria paradoxa) is small to medium sized tree spread over West African countries. The fruit is oblong in shape. The epicarp of the ripe fruit is initially green and when matured - yellowish green. The average fresh weight of the nut is 8-10 gms which makes shea nuts one of the heaviest butter seeds available. The fresh nut contains 43-68% moisture by weight and as much as 30-45% of the kernel can be recovered.

Shea tree kernels are the main source of Shea fat. The fat is obtained from these kernels through solvent extraction method. The obtained Shea fat is then fractionated by Solvent Fractionation method and other allied processes to obtain Shea stearic acid or Shea stearine. Like other fat substitutes, Shea stearine is also used as a substitute for Cocoa Butter Equivalents (CBE) and Cocoa Butter Replacers (CBR).

Shea Fat

Butter is made up of fatty acid and their glycerides, plus a characteristically high proportion of unsaponifiable matter. Unlike cocoa butter, shea butter contains a high proportion of di-and tri-unsaturated glycerides, which give it the softer consistency. The heavier carbon molecules (stearic and oleic acid) dominate which result in a high melting point of 37.8 degree C. The unsaponifiable fraction makes shea butter a useful ingredient in cosmetic products. Estimation of the proportion of unsaponifiables vary but their presence makes the fat prone to oxidation. Some of the triterpenes and sterols are characteristics of shea butter and can be used to detect its presence as an adulterant in cocoa butter.

Before shea can be used as a raw material for CBEs, removal of the unsaponifiables and fractionation of the di-and tri-unsaturated glycerides from the symmetrical mono-oleoglycerides butters is necessary. The saturated triglycerides are purified in a simple physical fractionation process (35-40% can be obtained from single fractionation), selectively filtered as they crystallize from a mass of triglycerides being cooled. This stearian fraction is then used in conjunction with fractions from other vegetable fats (eg.illipe, sal) to produce a cocktail with a chemical composition almost identical to that of CB; the olein fraction is used for margarine and baking. An alternative method of separating the constituents of Shea butter has been developed using super-critical carbon dioxide. This has the added benefit of removing all the isoprenic hydrocarbons (which act as pro-oxidants) and lowering the levels of ffa mono-and di-glycerics, iron, triterpene acetates and triterpene cinnamates.