Studies of Bitter Peptides from Casein Hydrolyzate. IV. Relationship between Bitterness and Hydrophobic Amino Acids Moiety in the C-Terminal of BPIa (Arg–Gly–Pro–Pro–Phe–Ile–Val)

In the synthetic studies of bitter peptide BPIa (Arg–Gly–Pro–Pro–Phe–Ile–Val), we synthesized several BPIa analogs to elucidate the participation of the hydrophobic amino acids moiety in the C-terminal in the bitter taste exhibited by BPIa. The syntheses of the peptides were performed by the usual MA (mixed anhydride) and DCC (dicyclohexylcarbodiimide)–HOBt (1-hydroxybenzotriazole) method, and the bitterness of the peptides was organoleptically determined. The BPIa analogs in which more than two hydrophobic amino acids were located in the C-terminal exhibited a bitter taste as strong as that of BPIa.