Characterisation of some underutilised vegetable oils and their evaluation as starting materials for lipase-catalysed production of cocoa butter equivalents

Abstract

Oils were extracted from the inner skin of Strychnos madagascariensis fruit shell, Trichelia emetica seed and Ximenia caffra seed. Gas chromatography analysis of methyl esters of the glycerides of these oils was used to determine the fatty acid profiles of the oils. S. madagascariensis and X. caffra oils were found to contain high oleic acid levels, 68 and 59% respectively, while T. emetica oil was found to contain 53% palmitic acid. Pancreatic lipase digestion was used to perform structural analyses on the triglycerides of oils. Oleic acid was found to be concentrated at the 2-position of the triglycerides of the X. caffra and T. emetica oils. The three oils were evaluated for use as starting materials in lipase-catalysed production of cocoa butter equivalents using transesterification reactions. A 1,3-specific lipase from Rhizomucor miehei was used to incorporate stearic acid and palmitic acid into the 1- and 3-positions of the triglycerides. The products of the transesterifications in the case of X. caffra and S. madagascariensis compare well with those produced using lipase-catalysed transesterifications of other oils.