PROTEIN ISOLATE FROM HIGH‐PROTEIN OATS: PREPARATION, COMPOSITION AND PROPERTIES

Abstract

ABSTRACT An alkaline extraction process was developed to produce protein isolates and starch from defatted flour or defatted groats of high‐protein oats. Optimum extraction was at pH 9.2 in 0.02N sodium hydroxide with a solid:solvent ratio of 1:6. The defatted flour was extracted with sodium hydroxide solution, and bran was removed by screening the alkaline dispersion. After centrifuging the slurry that passed through the screen, the alkaline supernatant was adjusted to pH 5.0 to yield a precipitate (protein isolate) and supernatant. The defatted groats were first extracted with water followed by two sodium hydroxide extractions. Bran was removed by screening the second alkaline dispersion, and protein isolate was precipitated from the first alkaline extract at pH 5.7. Protein content (nitrogen × 6.25) of the isolate varied between 94 and 103% and accounted for 53–67% of total protein from defatted flour or groats. The isolate contained from 3.4–4.0g lysine and 2.2–4.2g total sulfur amino acids per 16g nitrogen. Minimum nitrogen solubility of the isolates was 3–4% near pH 5.5, and solubility was 78–83% near pH 2.2. All protein isolates had good hydration capacity (2.9–3.9) and two of the isolates had good emulsifying activity (around 50%) and good emulsion stability (near 50%).