Flux rate performance for both rennet and cheddar wheys were similar to those described for acid casein whey beginning at 37–41 l m‐2h‐1and declining to 10 l m‐2h‐lat volume concentration ratio of 4. The chloride in dry matter reduction for these wheys was much greater at 71% compared to ∼41% for acid casein whey. Losses of organic solids from acid casein whey in terms of chemical oxygen demand were similar to those published for cellulose acetate membranes. Lactose and true protein nitrogen (total protein nitrogen less non‐protein nitrogen; NPN) losses amounted to 2.6% and 8.1% respectively. NPN constituted the main nitrogen loss (77%) through the HC‐50 membrane. True protein loss increased as pH was lowered to 3.6. Solubility index values obtained for nanofiltered powders produced from acid casein whey were comparable with those obtained for conventional spray dried powders and whey protein concentrates. In a case study based on the performance of the HC‐50 membrane the economic feasibility of nanofiltration along with other demineralization proce