IN-VITRO STUDIES ON THE PROTEOLYTIC FORMATION OF THE CHARACTERISTIC AROMA PRECURSORS OF FERMENTED COCOA SEEDS - THE SIGNIFICANCE OF ENDOPROTEASE SPECIFICITY

The proteolytic formation of the cocoa-specific aroma precursors was studied in vitro using the vicilin-class globulin from cocoa seeds as protein substrate and different proteases. Cocoa-specific aroma precursors were obtained by degradation of the cocoa globulin with the aspartic endoprotease from cocoa seeds followed by post-treatment with carboxypeptidase A from porcine pancreas. Proteolysis products derived from the cocoa globulin by successive digestion with pepsin and carboxypeptidase A also revealed a typical, but less pronounced cocoa aroma upon roasting in the presence of reducing sugars. No cocoa-specific aroma precursors were, however, generated by degradation of the cocoa globulin with chymotrypsin and carboxypeptidase A. Therefore, the specific mixture of oligopeptides and hydrophobic free amino acids required for the formation of the typical cocoa aroma components is not only determined by the structure of the protein substrate but also dependent on the specificity of the endoprotease.