Skim Milk Membrane Filtration Protocols

Prior to filtration, the membrane was conditioned with caustic Ultrasil 69 (0.4% v/v, Ecolab Deutschland, Monheim am Rhein, Germany) at 50 °C for 20 min to charge the membrane negatively. Then, 150 L of skim milk (native pH of 6.8 at 10 °C) were heated from 4 °C to the process temperatures of 10 °C and 50 °C, respectively. The filtration plant was flushed with 50 L skim milk without permeate production (permeate valve closed). Pressure was adjusted to the target Δp_TM and the permeate and retentate streams were recirculated. After the start-up procedure, flux was measured continuously and filtration tests were run with one of the following filtration protocols:

Stepwise increasing and subsequently stepwise decreasing Δp_TM

Setting Δp_TM directly to target level and keeping it constant during the experiment