STUDY OF THE DISSOCIATION OF BETA-CASEIN FROM NATIVE PHOSPHOCASEINATE

Native phosphocaseinate is a relatively new product obtained from micr ofiltration of skim milk. The conditions used during the microfiltrati on of milk are believed to have only minor effects on micellar integri ty. The objective of the work was to study beta-casein solubilization from native phosphocaseinate in the conditions of cold storage as affe cted by different pH levels, calcium chelation and ionic strength. Nat ive phosphocaseinate powder was rehydrated to 2.0% (w/w) in the presen ce of NaCl (3.0, 6.0 and 9.0 g/kg) and trisodium citrate (0.4, 1.0 and 1.6 g/kg) before pH adjustment (4.0, 4.6 and 5.2) followed by cold st orage (0-degree-C). The amount of soluble casein was determined by RP- HPLC of ultracentrifugation supernatants. It was found that the solubi lization of beta-casein was optimal in the presence of 9.0 g/kg of NaC l at pH 5.2 and that calcium chelation did not have a marked effect.