ABSTRACTCottonseed wheys resulting from protein isolation from cottonseed flour were processed by semi‐permeable ultrafiltration (UF) and reverse osmosis (RO) membranes. The UF membrane fractionated the soluble whey constituents by retaining protein and passing through salts, carbohydrates and other non‐protein components along with most of the water. The UF membrane effluent was then processed through an RO membrane to recover a secondary product containing the whey materials not retained in the protein product from the UF membrane.The feasibility of recycling effluent from the RO membrane for reuse in subsequent protein extractions was demonstrated. Thus, the threat of water pollution from effluent disposal could be eliminated completely and process water requirements drastically reduced.Spray‐dried UF protein concentrates were tested for utilization in protein fortification of breads and noncarbonated beverages and as whipping products. They exhibited commercial potential for use in these food applications.The economics of processing the whey‐type liquids by the membrane process under investigation were analyzed. Membrane processing of wheys by each of two alternative whey processing systems proved to be economically att