Some Experiments on Formation of Bitter Taste Peptide During Casein Hydrolyses

The peptides capable of causing bitter taste, which is unpleasant taste, in fermented milk products and soy bean products resulting from some actions of microorganisms and proteolytic enzyme are causative substances. It has also assumed that the bitter taste peptide has a unique cyclic structure such as Azlacton or Oxazolone, and that the unique structure is an origin of the bitter taste. However, the structure is in general uncertain yet. From simple discussion of Author\u27s electrone theoretical view, some experiments on the nonenzymatic formation, the unique structure and the prevention from its forming by chemical agents of the bitter taste peptide were carried out. This report was results on findings support the view, and it was quite possible to add some conclusions and conciderations to the informations on the bitter taste peptide. 1. The bitter taste peptide is produced during proteolyses not only by enzymatic action but also by nonenzymatic action, and its unique structure, it is presuming with its solubility in organic solvents and other properties, is formed by some of chemical reactions, which are take placed as an inevitable consequence at the time of decomposition of peptide bonds in protein. The decomposition, which depends on enzymatic or nonenzymatic actions, gives then to raise similar chemical energy. Therefore, it seems to be possible to use chemical preventers, which have properties of ion-exchangeable or disperseable operation, for the for-mation of bitterness. 2. The two kinds of the bitter taste peptides, which were prepared from enzymatically and nonenzymatically hydrolyzed casein, were observed by infrared spectroscopy on their secondary structures. It was found from the results that the two bitter peptides had no essential differences in their structures. The unique structure of these was formed partly by cyclic amide, γ-lactam or other lactams structures consisting with -NH and -CO groups produced by dehyd-ration and hydrolysis during proteolyses. 3. Three kinds of chemical agents were used as a preventer for the formationof the bitter taste during trypsin hydrolysis. From the results, about 2 % of polyphosphoric acid was a useful and effective preventable concentration in the reaction mixture, and it seems also a nonenzymatic decompositor of the bitter structure. Then 2.0 M sodium phosphate and 0.5 M potassium phosphate buffer solutions were also effective preventable concentration in it for the formation of bitter taste during proteolysis, especially potassium ion was more effectiveness than the other agents