Isolation of Bitter Peptides from Tryptic Hydrolysate of Casein and their Chemical Structures

Bitter peptides were isolated from the tryptic hydrolysate of casein. Fractionation and isolation were carried out using n-butanol extraction, acidic precipitation at pH 5.4, gel filtration with Sephadex G-25, ion exchange chromatography with Dowex 50W and paper chromatography. Three kinds of bitter peptides were purified. The primary structures of these peptides were proposed as follows; BP-I, Gly-Pro-Phe-Pro-Val-Ileu; BP-II, Phe-Phe-Val-Ala-Pro-Phe-Pro-Glu-Val-Phe-Gly-Lys; BP-III, Phe-Ala-Leu-Pro-Gln-Tyr-Leu-Lys. These peptides were very bitter in a 0.1% solution. L-Tyrosine, L-phenylalanine and their derivatives were also tasted. The importance of the position of bitter amino acids in the peptide in the development and strengthening of its bitter taste is discussed.