Characterization of Milk Proteins in Ultrafiltration Permeate and Their Rejection Coefficients

The most widespread method applied for standardization of milk protein in cheese production isultrafiltration. In the current study, pasteurized, unhomogenized whole milk was ultrafiltered with APVultrafiltration system, 51 spiral wound, polysulfone membrane with 20000 Da molecular weight cut off (DDS,Nakskov, Denmark) at 50 ˚C, such that the pressure difference between the two sides of membranes was notmore than 3.6 bar. Permeate that was collected, contained (w/w٪) 0.01 ٪ proteins. The protein was isolated fromcrystalline TCA to the concentration of 12.5٪ (w/v), and then characterized by discontinuous SDS-PAGE (10-20٪ acryleamide). The products of proteolysis contained α-lactalbumin (49.95±2.25 %), β- lactoglubolin(22.30±2.3 %) and casein proteolysis products (30±4 %) and (96.68±1.725), (99.18±0.46) and (98.39±1.005) %were rejected by ultrafiltration membrane, respectively. Casein micelles were rejected completely (100 ٪),therefore, they couldn’t penetrate to permeate from retentate. Incomplete rejection of casein and penetration ofcasein into permeate indicates the leakage of retentate in to permeate.