Comparison of nanofiltration and high pressure ultrafiltration of cottage cheese whey and whey permeate

A DDS LAB-20 unit was used for ultrafiltration (UF) or nanofittration (NF) of cottage cheese whey and whey permeate at 3 different transmembrane pressures (10, 20 and 30 bars) at constant temperature, flow rate and osmotic pressure. The flux rate increased significantly (p less than or equal to 0.05) with the pressure increase for NF, while it remained pressure-independent during high pressure UF (HPUF). The increased pressure resulted in substantial augmentation of the total solids rejection by the UF and NF membrane, ranging from 39.73 (+/-0.06) to 67.52% (+/- 1.87) during whey UF and 87.45 (+/- 0.36) to 96.16% (+/- 0.17%) during whey NF with the pressure rise from 10 to 30 bars. The presence of the secondary protein layer at HPUF of acid whey resulted in a significant effect (p less than or equal to 0.05), causing higher retention of the total solids. The rejection of the positively charged multivalent ions (Ca and Mg) was directly proportional to the pressure rise during whey UF. Retention of monovalent positive ions (Na and K) was affected only marginally. Phosphorus retention was the highest during whey UF trials, and its permeation ability increased 3 fold in the absence of whey proteins. During whey NF, the retention of all minerals increased significantly (p less than or equal to 0.05) with the increase of the transmembrane pressure. Without the whey proteins present, all minerals experienced substantially higher retention at high pressure NF.