Studies on the shape of casein particle and its denaturation in milk I

The normal shape and its denaturation of the casein particle in milk was investigated with the 50kV. electron-microscope. Principal results obtained are as follows: 1) The size of casein particles was about 20 to 200 mμ in diameter in cow's and goat's milk, but it was much smaller in human milk than in cow's milk. 2) Some absorbed substance was observed around casein particles in the normal milk and seemed to have some relationship with calcium in milk. 3) At the iso-electric point of casein in milk, same casein particles were agglutinated, forming bigger particles, and the absorbed substance observed around the original casein particles disappeared in the newly formed particles. At pH 2.4, the casein particles underwent transformation and looked like "swelling particles", 4) When the pH value was adjusted to normal by adding alkali, these acid-denaturated, casein particles did not restored their original shape. Accordingly, this type of transformation was irreversible.