Shea butter triterpene alcohols

Much of the sterol component of shea butter is present as esters of cinnamic acid, which are less readily saponified than esters with glycerol (Peers, 1977) published data for this fat might therefore underestimate the hue value. Surprisingly measurement of cinnamic acid has not been used to test for the presence of shea butter in mixtures. Triterpene alcohols similar to those found in shea also occur in sal fat. Homberg and Bielefeld (1982) showed the presence of triterpene alcohols in illipe and sal fats and in commercial CBEs, and their analysis was proposed as a qualitative measure to detect cocoa butter adulteration. 

Reaction of shea triterpene alcohols with acetic anhydride and sulphuric acid to produce coloured products (Fitelson s reaction) was the basis of a sensitive early test for the presence of shea butter in cocoa butter (Fincke, 1975). Analysis of the triterpene fraction of a commercial cocoa butter by TLC fractionation followed by GC (Fincke, 1976), or argentation TLC followed by GC (Gegiou and Staphylakis, 1985), have been shown to have potential for detecting CBEs in chocolate based on the difference in levels of P-amyrin, butyrospermol and... 

No comprehensive comparison has been made of the proportions of the free and esterified sterols in cocoa butter with those of fats likely to be used in cocoa butter adulteration. However Gordon and Griffiths (1992) examined the sterol esters of palm kernel oil by isolation with TLC followed by GC and HPLC. They pointed out the problem of co-elution of triacylglycerols with steryl esters with GC. The characterization of esters of triterpene alcohols in CBA fats might well prove useful where the use of fats containing shea is suspected. 

The quantitative determination of sterenes has been used to detect added CBEs or refining in cocoa butter and to establish the presence of CBAs in retail chocolates (Crews et al., 1997). The high quantity of triterpene alcohols in shea butters means that dehydration products of these sterols are formed in detectable levels when shea is bleached. These triterpene sterenes, which have not be characterized, can be detected in the stearin fraction used in CBEs (Crews etal., 1999). 

Derbesy and Richert reported that HPLC of the unsaponifiables (sterol and triterpene alcohol fraction) revealed less than 1% of shea butter in cocoa butter. With measurement at 280nm, one specific peak area was linearly related to the percentage of shea butter. Homberg and Bielefeld suggested that sterols, methyl sterols, and triterpene alcohols be determined to identify cocoabutter adulteration. 

Sterols are separated as 3,5-dinitrobenzoic acid derivatives by thin layer chromatography and, after reaction with 1,3-diaminopropane, are determined quantitatively with high sensitivity in the form of a Meisenheimer adduct. Sterols and triterpene alcohols are silylated and then analysed by gas chromatography. One application of this method is illustrated by the detection of 5% coberine in cocoa butter (Fig. 3.44). The compounds a-amyrine and lup-20(29)-en-3P-ol (Formula 3.113a and 3.116) serve as indicators. They are present in much higher concentrations in some cocoa butter substitutes than in cocoa butter. Coberine is a cocoa butter substitute made by blending palm oil and shea butter (the shea is an African tree with seeds that yield a thick white fat, shea butter). 

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