Partial purification and characterisation of the peptide precursors of the cocoa-specific aroma components

Essential precursors of the cocoa-specific aroma notes are formed during fermentation of the cocoa beans by acid-induced proteolysis. It has been shown that, in addition to free amino acids, hydrophilic peptides derived from the vicilin-class(7S) globular storage protein are required for the generation of the cocoa-specific aroma notes during the roasting process. To identify those peptides responsible for the generation of the cocoa-specific aroma components, we have developed a procedure for the fractionation of the aroma precursor extract from well-fermented cocoa beans by ligand-exchange and subsequent Sephadex-LH20 chromatography. The cocoa-specific aroma precursor fractions were characterised by matrix-assisted laser-desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF) and the determination of their amino acid sequences by electrospray ionisation mass spectrometry (ESI-MS/MS).