Calcium Reduced Skim Milk Retentates Obtained by Means of Microfiltration

The purpose of this study was to characterize processes for the manufacture of calcium reduced skim milk retentates (8.5% (w/w) protein), only using microfiltration (MF, 0.06 mu m pore size) or ME in the diafiltration (DF) mode, at different temperatures and pH, regarding the i) effectiveness of calcium reduction, ii) flux and iii) generated amount of permeate (pH >= 6.0), that can be processed like sweet whey. It was observed that both low pH and low temperature decreased the flux during MF, while operating the MF in the DF mode at the initial pH 6.7 enhanced the flux. Furthermore, pH adjustment from 6.7 to <= 5.8 facilitated an increase of the maximum volume reduction ratio from 10.1 to >= 12.2 during MF. In order to avoid initial fluxes of < 40 Lm(-2) h(-1), it is recommended to operate MF at temperatures >= 50 degrees C and pH >= 5.6. By concentrating skim milk via MF at pH 6.2, acidifying the resulting retentate to pH 5.6 and eluting the serum calcium via a six stage MF in the DF mode, the retentate calcium content could be decreased by 52%.