T. Vasiljevic et P. Jelen, Comparison of nanofiltration and high pressure ultrafiltration of cottage cheese whey and whey permeate, MILCHWISSEN, 55(3), 2000, pp. 145-149
A DDS LAB-20 unit was used for ultrafiltration (UF) or nanofittration (NF)
of cottage cheese whey and whey permeate at 3 different transmembrane press
ures (10, 20 and 30 bars) at constant temperature, flow rate and osmotic pr
essure. 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 substan
tial 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), caus
ing higher retention of the total solids. The rejection of the positively c
harged multivalent ions (Ca and Mg) was directly proportional to the pressu
re rise during whey UF. Retention of monovalent positive ions (Na and K) wa
s affected only marginally. Phosphorus retention was the highest during whe
y UF trials, and its permeation ability increased 3 fold in the absence of
whey proteins. During whey NF, the retention of all minerals increased sign
ificantly (p less than or equal to 0.05) with the increase of the transmemb
rane pressure. Without the whey proteins present, all minerals experienced
substantially higher retention at high pressure NF.