VISCOSITY AND CHEMICAL-COMPOSITION OF WATER EXTRACTS FROM BUCKWHEAT FLOUR

The viscous properties of the water extracts from buckwheat flour were investigated using a B-type viscometer. The viscosity of the extract solutions depended upon shear rate, and exhibited pseudoplasticity. And it decreased as ionic strength increased. The viscosity of supernatants prepared from the extract solution at different pHs provided a minimum value at pH 3.0-3.4. The viscosity of the supernatants prepared at different temperatures under 90-degrees-C was constant. It was revealed from measurements under some denaturation conditions that the viscosity of the supernatant corresponded to the content of total carbohydrate rather than that of protein. The water extract was fractionated by ion exchange chromatography on a DEAE-Shephadex column. One fraction of them was given higher viscosity over 18 times than that of the other fractions. The high viscous fraction was mainly composed of sugar. Composition of the sugar was galactose, xylose and mannose in the decreasing order of contents. On the basis of these results, it was concluded that the viscosity of the water extracts from buckwheat flour was attributable to polysaccharides.