Interaction between Casein and Carboxymethyl Cellulose in the Acidic Condition

The stabilizing action of carboxymethyl cellulose (CMC-1 and CMC-2) on caseins was studied in the acidic pH region. CMC-1 stabilized 1% whole, α-, α_S- and β-casein at pH 4.6 and 5.0, and at 5°C. But CMC-2 could not completely stabilize these caseins at pH 5.0. Interaction between κ-casein and CMC-1 commenced when pH was adjusted to 6.3, but CMC-2 interacted with κ-casein below pH 5.6. An α_S- and κ-casein mixture (4 : 1) with CMC-2 was destabilized by the addition of 0.02 m NaCl or NaH₂PO₄ at pH 5.0. The α_S/κ ratio of the precipitated casein was about 10. But the same system with CMC-1 was not destabilized by the salts.