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To characterize bitter peptides in fermented protein foods, peptides were extracted with 2:1 (v/v) chloroform-methand from various samples and separated into fractions I, II, and III by Sephadex G-25 gel chromatography. Amino acid compositions of Mozzarella cheese, soybean paste, and each fraction from the two samples were analyzed to calculate the average hydrophobicity. All the solvent extracts of the food samples had strong bitter taste, although the original samples did not taste bitter. The yield of solvent extraction ranged from 0.08 to 62.50% of total nigrogen of food samples. The average hydrophobicity calculated from the amino acid composition of Mozzarella cheese was 1376 ㎈/mole, solvent extract 1,623 ㎈/mole, gel chromatography traction I, 1,797 ㎈/mole, fraction II, 2,454 ㎈/mode, and fraction III, 1,559 ㎈/mole. In the case of soybean paste, the average hydrophobicity of original sample, solvent extract, gel chromatography fraction I, II, and III wre 1,229, 1,654, 1,900, 998 ㎈/mole, respectively. The important amino acids in bitter peptides were leucine, 2016, phenylalanine, proline, and voline.
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