Improvement of Cocoa Blends by Enantiomeric and Melting Point Modification

Cocoa butter (CB) is the foremost ingredient in chocolate, holding responsibility for the products’ functional and sensorial characteristics. Numerous studies have investigated the crystallisation and polymorphism of its component triacylglycerols (TAGs), yet no correlation has been made between their stereochemistry and crystalline behaviour; even though the predominant TAG, 1-palmitoyl-2-oleoyl-3-stearoyl-glycerol (POSt), is reportedly present in a racemic mixture. Moreover, several TAGs have higher melting points than human body temperature and their behaviour in the biophysical environment of the gastrointestinal tract is yet to be reported. In this multi-faceted project, three areas of research were investigated; enantiomeric ratio elucidation of CB POSt, the effect of high melting TAGs in the digestion process and organic synthesis measures for the formulation of enantiopure POSt. For the first parameter, two approaches were assessed using a rac-POSt standard for method development, chiral HPLC and derivatisation. Both were ineffectual for enantiomeric resolution, leaving unanswered questions on the enantiomeric composition of CB. For the second parameter, an in vitro analysis procedure was used successfully in an original study on the amount of free fatty acids (FFAs) released, comparing a range of initial melt temperatures (Tm), 37, 50 and 80 oC: temperatures intended to correlate with melting points of various constituent TAGs. Similarities in total FFA release were evident, indicating high melting components had no effect on the lipolysis of CB. Finally, transesterification and chemoenzymatic procedures were undertaken for the synthesis of enantiopure POSt. Difficulties in glycerol deprotection during the latter saw a novel approach introduced in the form of a small-scale reactor (fReactor), which proved consistent in removal of the benzyl protecting group. A near identical NMR spectra of the final product with that of rac-POSt allows determination that the synthesis of (R)-POSt was a success.