2.4. Microfiltration
Skimmed milk, previously heated to 50 8C in a double jacketed tank was subjected to a MF module (Model MFS-1, Tetra Pak 15 Filtration Systems, Colombes, France) with 0.8 mm pores in a tubular ceramic membrane (Sterilox1). The MF separation was circulated at a velocity of 7.0 m/s along the membrane with a total area of 0.24 m2 and a uniform trans-membrane pressure in the range of 0.5 bar. The obtained flux was approximately 33.3 mL/s and 1:20 concentration factor was used. Cleaning was carried out before and after the MF process, with two cleaning cycles, alkaline and acidic, respectively, as described by Saboya and Maubois (2000). The microfiltered milk was packaged in plastic bottles (LDPE of 200 mL) and then stored at 4 8C and 14 8C.