EFFECTS OF PH AND IONIC-STRENGTH ON DISTRIBUTION OF MINERAL SALTS IN MILK

Inorganic phosphate was solubilised at pH 5.2 but a complete solubilisation of calcium and magnesium was obtained only after acidification to pH 3.5. The increase of soluble sodium and potassium between 6.7 and 4.6 were respectively 35 and 128 mg/kg, these values representing 8% of the total amount. Ionic strength increase via addition of sodium chloride led to a solubilisation of calcium, magnesium, potassium and binding of sodium; there was an equivalence (in meq) between solubilized cations , and bound cations. At pH 6.6 an increase in ionic strength (0.8% Na) solubilized 90 mg calcium, 8 mg magnesium and 91 mg potassium and bound 160 mg sodium/kg. Ionic strength had no effect on phosphate solubilisation. It seemed that calcium phosphate was first solubilised when pH decreased; below pH 5.2, only calcium bound to phosphoserines and carboxyls was solubilised.