The Effect of pH on the Orientation of Rennet Casein

Abstract

A study on the effect of pH (4.5-6.8) was conducted to clarify the characteristics of the orientation behavior of rennet casein. As a result, the orientation of rennet casein was observed at pH5.3-5.4 after squeezing out the casein from a syringe by shear stress. A maximum pellet volume of rennet casein at 10°C was given at about pH5.4. On the other hand, calcium and phosphate in rennet casein tended to transfer to the serum at low pH, but the degree of their transfers decreased gradually above pH5.4. From the relation between the change of pellet volume and the shift of protein fraction to the serum, the maximum degree of hydration of rennet casein was observed at about pH5.3-5.4. The phenomena of the orientation of rennet casein could be explained from the behavior of hydration of rennet casein and of the transfer of calcium and phosphate to the serum.