Mechanism of Digestion of Bitter Peptide from a Fish Protein Concentrate by Wheat Carboxypeptidase

Abstract

A bitter peptide fraction from the peptic hydrolysate of a fish protein concentrate was treated with crystalline wheat carboxypeptidase. The bitterness of the bitter fraction lessened with an increase in free amino acids. The enzymatic hydrolysate obtained from the digest of the bitter peptide fraction by wheat carboxypeptidase was chromatographed on Sepandex G-15 and separated into three fractions: high molecular weight fraction, dipeptide fraction and free amino acid fraction. Glutamic and aspartic acids costituted 50% of all amino acids in the dipeptide fraction. When the release percentage of total free amino acids was approximately 38%, those of hydrophobic amino acids with a Δf value (cal/mol)>1600 were 40-84% except for proline, and amino acids with a Δf value<1600 had a tendency to be released less than hydrophobic amino acids. The wheat carboxypeptidase seems to eliminate bitter taste under the cooperative effects of the selective release of hydrophobic amino acids and the formation of acidic dipeptides from the bitter peptides.