PROTEIN ISOLATE FROM AN EXPERIMENTAL HIGH-PROTEIN WHEAT AND FLOUR

An experimental high-protein (25 % protein, N x 5.7 dry basis) spring wheat (ND 643) and flour from that wheat were used to make protein isolate by alkaline extraction. Optimal extraction of protein was at pH 10.7 in 0.03 N sodium hydroxide with a solvent:solid ratio of 6:1. The alkaline extract after centrifugation was adjusted to optimal pH of 6.2 to yield a precipitate and a supernatant. Bran was separated from starch by screening the second alkaline dispersion. The protein contents of the isolates from ground wheat and flour were 90 and 95 %, respectively, and accounted for 65 and 68 % of the total nitrogen of the starting wheat and flour. Yields of protein isolate were 18 and 16 %, respectively, of starting high-protein wheat and flour compared with 10 % of starting wheat and flour from a typical hard red winter wheat. Protein isolate had a nitrogen solubility of 96 % at pH 2.6 and a minimum solubility of 5.7 % at pH 5.8, a hydration capacity of 2.5, an emulsifying activity of 51 %, and an emulsion stability of 50 %.