Influence of processing temperature on flux decline during skim milk ultrafiltration

The flux decline behaviour during skim milk ultrafiltration (UF) was investigated at 10 °C, 30 °C and 50 °C. Despite higher fluxes, UF processing at higher temperatures resulted in higher magnitudes and rates of irreversible fouling. Fouling in this temperature range was primarily proteinaceous, consisting of mainly peptides and alpha-lactalbumin (α-LA), with minor amounts of beta-lactoglobulin (β-LG) present only at 50 °C. The increase in fouling resistance with processing temperature was concluded to be mainly due to increased pore fouling by α-LA deposition, and in part to β-LG deposition at 50 °C. These are attributed respectively to the thermal expansion of membrane pores and reversible conformational changes of β-LG.