[Formation of bitter peptides in cheese and from casein]

Whereas a slightly bitter taste is desirable in certain foods, it is an off-flavour in cheese which may even lead to unfitness for consumption. Bitter principles from cheese have been found to be peptides with molecular weights ranging from 2000 to 3000. For the purpose of further characterization, bitter peptides were isolated from enzymatic casein hydrolysates as well as from bitter cheese and purified. 30 proteases from different origins proved to be able to form peptides with bitter taste of varying intensity from casein. Present experience shows that the formation of bitter peptides during casein hydrolysis can be inhibited only to a very small measure. Bitter peptides are extrmely resistant to proteases, which is probably attributable to their high contents of hydrophobic amino acids and hydrophobic bonds. The detection of only N- or C-terminal amino acid in each of 11 different bitter peptides shows that peptide chains are present and not cyclic peptides as repeatedly assumed. It must be aimed at avoiding the cheese defect "bitter" by using appropriate starter cultures and rennet substitutes as little disposed as possible to produce bitter peptides.