We have recently developed a new polysulfone membrane GR70PE specifically for UF concentration of proteins with spiral wound module. Nonetheless, the membranes can also be used for plate and frame modules. Although the primary application of this membrane is for concentration of whey proteins, the test of concentration of gelatine also showed promising results. The membrane chemistry and structures have been optimized to minimize membrane fouling, gain high retention of macromolecules, e.g. proteins and high passage of small molecules such as lactose, organic acids and mineral compounds. In this work, we have conducted a long-term (up to 300 days) field test to compare the performance of GR70PE with two membranes from other manufacturers, which are commonly used for concentration of whey proteins. Moreover, the results of concentration of gelatine are also included in this report.