Fractionation of κ-casein from caprine micellar caseins using differential precipitation

The effects of potentially important processing conditions at each step of differential precipitation on the yield and purity of κ-casein fractionated from caprine micellar casein concentrate (MCC) were investigated. The optimal conditions were: rehydrating (3% casein) MCC using homogenisation followed by dissociating micelles at pH 11.0; complexing caseins using 45 mm added Ca at 25 °C for 60 min, followed by precipitating β-/αS-caseins using 2 m acetic acid at pH 7.0 again at 25 °C for 60 min. Two fractionation cycles were used with 50 mm added Ca for the second cycle, followed by precipitating κ-casein at pH 3.8 and 50 °C. To increase processing capacity for scale-up, increased casein concentrations of 4–7% along with 60 mm added Ca resulted in comparable yields and purity of the κ-casein. Maximum yield and purity of 84.6% and 84.4%, respectively, were achieved for κ-casein from the MCC dispersions at 4% casein.