WET-MILLING, COMPOSITION AND FUNCTIONAL-PROPERTIES OF STARCH AND PROTEIN ISOLATED FROM BUCKWHEAT GROATS

Buckwheat greats, containing 75% starch and 14% protein, were wet-mill ed into starch, protein, fiber, tailings and steep-water fractions, wi th 79 and 64% extraction efficiencies for starch and protein, respecti vely. About 5-10% of the total starch was found in protein and tailing s fractions, while 29% of the total protein was found in the fiber fra ction. About 72% of total lipid was recovered in the fiber fraction, i ndicating the separation of embryo tissue into this fraction. The refi ned starch product contained 98% starch, 0.6% protein and 21.3% amylos e. Buckwheat starch exhibited a typical A-type x-ray diffraction patte rn. The amylogram of native buckwheat starch showed higher peak and se t-back viscosities than regular corn and rice starches; the pasting te mperature was similar to those of corn and rice starches. Acetylation of the native starch lowered pasting and gelatinization temperatures a nd significantly improved cold storage stability of the gel. Amino aci d composition and functional properties of buckwheat protein concentra tes showed similarities to soybean protein. Compared to a freeze-dried protein sample, the spray-dried buckwheat protein concentrate was mor e white in color and showed higher nitrogen solubility index at neutra l 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.