PILOT-SCALE PREPARATION OF WHEAT GLUTEN PROTEIN-FRACTIONS I-INFLUENCEOF PROCESS PARAMETERS ON THEIR PROTEIN-COMPOSITION

Commercial wheat gluten was fractionated on a pilot plant scale to pro duce gliadin- and glutenin-rich fractions. Acetic acid solutions (0.01 -0.05 M) were blended with dry gluten (16, 10 or 7 volumes unit(-1) of dry gluten ratio) and the slurry was separated by continuous centrifu gation to yield a gliadin-rich supernatant, which was then concentrate d by ultrafiltration and spray-dried. The pellet obtained was optional ly rinsed by water or acetic acid and separated in a second stage. The second supernatant was treated as the first one, and the final residu e, insoluble and glutenin-rich, was then dispersed in ammonia and spra y-dried. The protein distributions in supernatants and residues depend ed on pH and ranged from 20/80 to 40/60 for the first stage, and from 40/60 to 80/20 for the sum of the two stages. The compositions of the fractions were measured by solubility tests and size exclusion high pe rformance liquid chromatography (SE-HPLC) profiles. A [-1, +1] selecti vity scale was created: each fraction was compared to pure gliadins (- 1), gluten (0) and pure glutenins (+1). The best combination between y ields of soluble and insoluble fractions (40/60 distribution) and sele ctivities for gliadins and glutenins (-0.32 and +0.26 respectively) wa s obtained at ratio 16 and a 0.01 M molarity. Though the selectivities were limited because gliadins and medium-size glutenin polymers have similar solubilities in acid solutions, this process permits preparati on of fractions which differ widely from gluten in contents of high mo lecular weight glutenin polymers.