MASS BALANCE OF RESULTING FRACTIONS FROM SHEEP MILK FILTRATION PROCESS

Ultrafiltration (UF) is widely used membrane process in the dairy industry for fluid milk concentration, allowing the retention of high molecular weight solutes essentially proteins by removing part of the water, which makes up the milk. This separation is given by a semipermeable membrane with pores between 1-100 nm diameter. The aim of this work was to evaluate the difference in protein composition of concentrated and permeated fractions from Microfiltration (MF) and UF of semi-skimmed sheep milk, using 1.4 µm and 0.02 µm pore membranes. It was used 33.60 Kg of semi-skimmed sheep milk, heated to 45°C, 3 bar pressure and submitted to concentration process using the pilot filter unit with pore equal to 1.4µm and filtering area of 0.24 m². The milk was concentrated resulting in 16.90 Kg of concentrated fraction (CF1) and 15.60 Kg of permeated fraction (PF1). The PF1 was submitted to another concentration process using the same filtration unit and membrane pore equal to 0.02 µm, heated to 45°C, 3.5 bar pressure resulting in 7.40 Kg of concentrated fraction (CF2) and 8.71 Kg of permeated or whey milk (PF2). Samples of concentrated and permeated fractions for the two filtration processes (CF1, CF2 and PF2) were stored at 7°C ± 2 for 24h. The protein was determined by micro Kjeldahl method, according to AOAC. The volumetric concentration factors (VCF) showed that it was possible to concentrate the maximum amounts of sheep's milk at 2 and 0.85 for MF and UF, respectively. The protein fraction of CT1 represented 1.20 Kg or 7.10% of the total fraction obtained by filtering. Although CT2 represented 0.77 Kg or 10.46% of the concentrated fraction. The protein fraction in PF2 was 0.65 Kg or 0.75% of the total fraction. According to obtained data, the protein fraction from UF is 3.36% higher than MF.