Wet-milling, composition and functional properties of starch and protein isolated from buckwheat groats

Buckwheat greats, containing 75% starch and 14% protein, were wet-milled into starch, protein, fiber, tailings and steep-water fractions, with 79 and 64% extraction efficiencies for starch and protein, respectively. About 5-10% of the total starch was found in protein and tailings fractions, while 29% of the total protein was found in the fiber fraction. About 72% of total lipid was recovered in the fiber fraction, indicating the separation of embryo tissue into this fraction. The refined starch product contained 98% starch, 0.6% protein and 21.3% amylose. Buckwheat starch exhibited a typical A-type x-ray diffraction pattern. The amylogram of native buckwheat starch showed higher peak and set-back viscosities than regular corn and rice starches; the pasting temperature was similar to those of corn and rice starches. Acetylation of the native starch lowered pasting and gelatinization temperatures and significantly improved cold storage stability of the gel. Amino acid composition and functional properties of buckwheat protein concentrates showed similarities to soybean protein. Compared to a freeze-dried protein sample, the spray-dried buckwheat protein concentrate was more white in color and showed higher nitrogen solubility index at neutral pH, and higher water holding, emulsifying and foaming capacities. (C) 1998 Canadian Institute of Food Science and Technology. Published by Elsevier Science Ltd. All rights reserved.