PARTIAL-PURIFICATION OF COCOA SEED PROTEINS AND STUDIES INTO THE DEGRADATION OF COCOA STORAGE PROTEIN

Cocoa seed proteins have been extracted and semi-purified without the use of mercaptoethanol as mercaptoethanol may cause problems due to fo rmation of colourless adducts between proteins and polyphenols. A non- storage protein with molecular weight 21 kDa was purified using conven tional techniques of gel chromatography and electrophoresis. The stora ge protein itself proved difficult to purify because of its solubility and its tendency to aggregate or to form complexes. Partially purifie d storage protein was hydrolysed using commercial enzymes but this gav e no cocoa-like aroma on roasting with a model sugar mixture. Incubati on of cocoa acetone powders containing cocoa proteins and proteinases resulted in proteolysis of the storage protein. The products of proteo lysis on roasting with sugars resulted in cocoa-like aromas. This woul d suggest that specific cocoa proteinases are required to breakdown co coa storage protein to produce cocoa flavour precursors.