Temperature effect on behavior of minerals during ultrafiltration of skim milk and acid whey

Pasteurized skim milk and untreated cottage cheese whey were ultrafiltered on a bench-top ultrafiltration (UF) tubular metallic membrane (0.016 m(2), molecular weight cut-off 20,000 Da) with an inorganic, porous carbon-type support, at 5, 20, 35, and 50 degrees C (+/-1 degrees C), 400 kPa cross-membrane pressure, and a flow rate of 3x10(-3) m(3)/min. Analyses of minerals in skim milk, acid whey, skim milk and acid whey permeate were used to determine their retention. Higher temperature gave greater flux, but caused significantly higher membrane fouling after 60 min. The retention of calcium and inorganic phosphorus was higher during UF of skim milk than acid whey. The retention of inorganic phosphorus was inversely correlated with the temperature and calcium retention during UF of skim milk. During UF of acid whey, the retention of calcium and inorganic phosphorus was lower than that of other minerals. The retention of calcium was independent of the temperature changes during UF of acid whey, while the retention of phosphorus was significantly higher at lower temperatures.