Studies on protein hydrolysis. IV.—Further Observations on the Taste of Enzymic Protein Hydrolysates

Enzymic hydrolysates have been prepared from α‐, β‐ and γ‐fractions of the casein complex by use of trypsin, and from commercial muriatic casein by use of crystalline trypsin and of crystalline chymotrypsin. These hydrolysates had a bitter taste. Muriatic casein was incubated with dilute sodium hydroxide so as to split off orthophosphate before digestion with ‘Protease’ (Takamine). Muriatic casein was also treated with crude proteolytic enzyme preparations and the degree of liberation of orthophosphate was measured. In these experiments the taste of the hydrolysates was improved in parallel with the liberation of orthophosphate. However, a similar improvement in taste was not observed when the orthophosphate was removed by use of intestinal phosphatase following the tryptic hydrolysis. A series of fractionations of a tryptic casein hydrolysate yielded a product that had an extremely bitter taste. Chromatographic and electrophoretic studies have suggested that this material was a single polypeptide. Use of 2: 4‐dinitrofluorobenzene failed to reveal the presence of N‐terminal amino‐acids; the material yielded leucine, valine, and glutamic acid on hydrolysis with carboxypeptidase.