Influence of carboxypeptidases on free amino acid, peptide and methylpyrazine contents of under-fermented cocoa beans

A study of the action of two carboxypeptidases on free amino acids, peptides and methyl-pyrazines in under-fermented cocoa beans was carried out. Carboxypeptidase B from porcine pancreas and carboxypeptidase Y from baker's yeast were used separately for digestion. Hydrophobic free amino acids (alanine, valine, isoleucine, leucine, phenylalanine and tyrosine) were predominantly produced in samples digested with both carboxypeptidase B and Y. The peptide patterns of samples digested with both carboxypeptidases were similar to that of the control. The concentration of 2,3,5,6-tetramethylpyrazine in samples with carboxypeptidase B addition was significantly higher than those of 2,5-dimethyl- and 2,3,5-trimethylpyrazine; the concentration of 2,3,5-trimethylpyrazine was highest (1727.86 mug per 100 g) in the sample with carboxypeptidase B addition that had been incubated for 24h. These findings indicate that carboxypeptidase B from porcine pancreas was more prominent in the formation of cocoa-specific aroma. (C) 2002 Society of Chemical Industry.