Quinoa protein concentrate was hydrolyzed with alcalase to obtain a hydrolysate that was fractionated by ultrafiltration using 10000-and 5000-molecular-weight cutoff membranes. Functional properties of the protein concentrate, protein hydrolysate, and membrane permeates were compared at different pH values. Protein solubility of the hydrolysate and membrane permeates were significantly higher (P = 0.05) than that of the protein concentrate. The protein concentrate had a significantly higher (P = 0.05) emulsifying activity index than the protein hydrolysate and membrane permeates. Membrane fractionation of the protein hydrolysate into lower-molecularweight peptides significantly reduced (P = 0.05) foaming properties, but it improved radical scavenging activity and the ability to inhibit the activity of angiotensin-converting enzyme.