Peptides, Amino Acids and Amines Liberated from β-Casein by Micrococcal Cell-Free Preparations

Decomposition products derived from the action of cell-free preparations of Micrococcus #eudenreichii, Micrococcus caseolyticus and Micrococcus candidus on t-casein were studied for their contribution to the mechanism of /3-casein degradation and to flavor development in cheese.Peptide patterns were similar in each of the three micrococcal cell-free preparations reacting with t-casein.Variations induced by length of incubation, temperature, and sodium chloride were observed.Peptides from /3-casein degradation by micrococcal cell-free preparations neither stimulated nor inhibited growth of six bacterial species.Amino acids freed by M. freudenrelchii preparations were mostly lysine, glutamie acid, proline, valine and leueine; similarly, by M. caseolyticus preparations, glutamic acid, proline, leucine and phenylalanine; and by M. candidus preparations, lysine, valine, leucine and phenylalanine.Lysine, methionine, alanine, proline and leucine in the M. #eudenreichil mixture; methionine and phenylalanine in the M. caseolyticus reaction mixture; and phenylalanine in the M. candidus mixture were removed preferentially from t-casein.The freed amino acids contributed significantly to the complex flavor of the reaction mixtures, imparting sweet, brothy and bitter flavors whereas some peptides produced bitter flavors.