The Interaction of γ-Casein Fraction with Other Caseins

Abstract

The turbidity and the casein components of turbid material and supernatant were investigated when α_s-, κ-, β- and whole caseins were mixed with the γ-casein fraction (UAM) both in the absence and presence of Ca²⁺.
1. In the absence of Ca²⁺, the turbidity of UAM was restrained by mixing with other caseins; κ-casein was the most effective, and next in order were whole, β- and γ_s-caseins.
The turbid material at the ratio of 3.0 was mainly composed of S-, TS- and γ•B-casein and trace amounts of α_s-, κ- and β-casein were also, contained. In the supernatant, the amount of γ•A-casein was more than that in the turbid material, and there were also plenty of α_s-, κ- and β-caseins in the supernatant.
2. When α_s- and β-caseins were mixed respectively with UAM in the presence of Ca²⁺, both mixtures precipitated and it was impossible to measure their turbidity. When κ-casein was mixed with UAM, its turbidity slightly decreased in comparison with the case of the absence of Ca²⁺. On the other hand when whole casein was mixed, the mixture became turbid on account of the presence of Ca²⁺ and α_s- and β-caseins, and it was stabilyzed by κ-casein.
When the mixture ratio of UAM to whole casein was small, the turbidity was large on account of the presence of whole casein and it decreased near at the ratio of 1.0. But at higher ratio, the turbidity increased.
Even if UAM increased in the casein solution, most of it existed in the turbid material and hardly increased in the supernatant.