INFLUENCE OF DISPERSING AGENTS ON MICELLE CONTENT OF MILK AND LIPID CONTENT OF CASEIN FRACTIONS

The action of several dispersing agents on casein micelles was studied. In whole milk, 89.1 to 93.3% of the total casein was in sedimentable micelles. When whole milk was dialyzed against distilled water, only 71.3% of casein was in centrifugate; dialyzed against phosphate only 22% of the casein was in centrifugate. Milk, dialyzed against a chelating agent such as ethylenediaminetetraacetate, gave 2% of the casein in centrifugate, but dialysis of this demineralized milk (by chelating agent) against 0.1M CaCl2 solution, gave 63.2% of the casein in centrifugate. When whole milk was dialyzed against 4M urea, 5.7% of casein was in centrifugate but when urea contained CaCl2, the centrifugate fraction was 43.7%. Treatment of milk with dodecyl sulfate and deoxycholate gave 2% centrifugate. The presence of CaCl2 in dialysis solution caused CMEP (chloroform-methanol extractable proteins) to migrate from the micelles to the nonmicellar casein fraction. The chelation decreased the lipid content of casein fractions from homogenized pasteurized milk considerably. All treatments decreased the micelle content in milk, but no treatment gave lipid-free centrifugate or supernatant casein fractions. Milk total lipid fraction, obtained with chloroform-methanol (2 to 1), contained calcium and magnesium. © 1969, American Chemical Society. All rights reserved.