Protein Isolate From High‐protein Oats: Preparation, Composition and Properties

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 x 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.Og 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%).

Effect of Extraction Conditions on the Recovery and Potency of Antioxidants in Oat Fiber

“…Similar to whole meal oat flour (Wu et al, 1977) the protein and total fatty acid contents of the oat fiber extract were high, 24% and 6%, respectively, when the extraction pH was alkaline, while carbohydrate was prominent in the extract obtained at the lower pH. The amounts of salts introduced as buffers or during pH adjustments contributed between 30% and 50% to the total dry matter in aqueous extracts.…”

The impact of alkaline conditions on storage proteins of cereals and pseudo-cereals

“…Alkaline extraction at pH 11 has a strong effect on the secondary structure and techno-functional properties of barley proteins [27]. Rye and oat proteins are well soluble at pH 10.0 (rye) [28] and pH 9.2 (oat) [29]. Maize (Zea mays L.) proteins, mainly zein, are in practice not extracted in alkali but in alcohol containing media.…”

Oat Protein Concentrates with Improved Solubility Produced by an Enzyme-Aided Ultrafiltration Extraction Method

“…Oat protein concentrates and isolates are commonly produced using alkaline extraction or dry fractionation [ 6 , 7 ]. The most effective procedure to extract proteins from grain material, such as oat bran, is the former [ 8 ].…”