Concentration of skim milk using a multistage reverse osmosis, nanofiltration and ultrafiltration cascade and its influence on skim milk powder quality

The goal of this study is to develop a multistage membrane filtration cascade using reverse osmosis (RO), nanofiltration (NF), and ultrafiltration (UF) to produce skim milk concentrate. Using the cascade or evaporation, skim milk concentrates with a dry matter of 40 %, 45 %, and 50 % were produced before being spray dried to produce skim milk powder. Ceramic rotating disc membranes were used to process the highly viscous skim milk concentrate in the UF stage of the cascade. By recycling the permeates of the NF and UF stages of the cascade, the composition of the final UF retentate was close to that of regular skim milk concentrate. The flux of the membrane cascade ranged from 0.9–13 kg m -2 h -1 . The concentrates showed some differences in composition and viscosity, resulting in only minor variations in the functional properties of the skim milk powders. Membrane cascades are an emerging technology for concentrating skim milk. Compared to evaporators, membrane cascades mostly require electrical energy. This means that their use could reduce the environmental impact of the dairy sector. • A membrane cascade comprising reverse osmosis (RO), nanofiltration (NF) and ultrafiltration (UF) was developed to concentrate skim milk up to a dry matter of over 48 %. • Rotating ceramic membrane discs were essential to reach this dry matter. • Skim milk powders produced by membrane cascade had good functional properties. • Recycling of the NF and UF permeates produced an UF retentate composition comparable to skim milk.