Bitterness of Phenylalanine- and Tyrosine-containing Peptides

In order to investigate the role of phenylalanine and tyrosine residues in the bitter taste of peptides, some oligopeptides containing phenylalanine or tyrosine were synthesized and their taste was evaluated. The hydrophobicity of the phenylalanine or tyrosine molecule markedly caused the bitter taste in peptide. The bitterness was more intense when phenylalanine was located at the C- terminus and when the content of phenylalanine or tyrosine was increased in peptides. The hydrophobic residue in peptides functioned as a bitter taste determinant site. The experimental results suggest the existence of an additional site for the bitter taste of peptides.