Abstract
The differences of the electrophoretic patterns, electric conductivities and proteolytic activities between individual acid-coagulable and acid-noncoagulable human skim milk samples were investigated to find factors related to the acid coagulability of human milk. From the observation of electrophoretic pattern of human skim milk, it appeared that acid-noncoagulable milk was poorer in casein content than acid coagulable milk. In the case of acid-noncoagulable milk, the concentration of salt ion determined by electric conductivity and the proteolytic activity were generally higher than those of acidcoagulable milk, and the 10% TCA soluble material content spectrophotometrically determined by treatment with Folin-Ciocalteu's reagent was also seemed to be higher. The coagulation by acid of human milk was inhibited by adding 21 mM NaCl, but was not affected by adding 3.5 or 7% lactose. These results suggest that the acid coagulability of human milk is related closely to the complicated factors which comprise mainly casein content, nonprotein nitrogen content or ionic concentration of the human milk.
