Studies of Bitter Peptides from Casein Hydrolyzate. X. Synthesis and Bitter Taste of H–Arg–Gly–Pro–Phe–Pro–Ile–Ile–Val–OH Corresponding to C-Terminal Portion of β-Casein

Abstract In order to ascertain the validity of the structure of bitter peptide BPIa (H–Arg–Gly–Pro–Pro–Phe–Ile–Val–OH) isolated from casein hydrolyzate by Minamiura et al., the C-terminal octapeptide of β-casein (H–Arg–Gly–Pro–Phe–Pro–Ile–Ile–Val–OH) determined by Ribadeau Dumas et al., which is assumed to correspond to BPIa, was synthesized and compared with the synthetic BPIa which was confirmed to be identical with the natural one. The two synthesized peptides, however, did not match on thin-layer chromatography. The result indicates that the structure of BPIa need not be converted to Ribadeau Dumas’ formula. The octapeptide possessed an extremely bitter taste, with a threshold value of 0.004 mM (1 M=l mol dm−3). It is the most bitter peptide.