HARDNESS MEASUREMENT AND GLIADIN POLYACRYLAMIDE GEL ELECTROPHORESIS IDENTIFICATION OF WHEAT GRAINS

The Instron Universal testing machine was used to determine the time needed to cut, and to crush, kernels of hard and soft wheat. The total cutting time on large sized kernels at "as is" moisture content distinguished best the difference between hard and soft wheat kernels.;Bulk wheat samples were ground on a Wiley mill. The amount of meal passing the screen as a function of time was plotted on log-log paper. The data produced a straight line following the function Y = aX('b). Small sized, dark hard vitreous, and hard wheat kernels manifested harder texture than the larger size, floury appearing, and soft wheat kernels.;The scanning electron microscopy showed that the broken endosperm of soft wheat has a loose structure with a rough surface. The broken endosperm of hard wheat has a compact structure. When illuminated with laser light, the degree of roughness could be measured but the varying degree of light absorption of opaque and translucent kernels had a detrimental effect on this measurement. Coating the endosperm surface with a reflecting metal reduced this inter-kernel variation.;Polyacrylamide gel electrophoresis of individual kernels from one single wheat sample showed a lack of uniformity in gliadins patterns. Some of the varieties studied had more than one biotype for the same wheat sample. Endosperm appearance and kernel size, shape, and texture are not related to the gliadin patterns of individual wheat kernels. Floury appearing endosperms contained fewer gliadins and fewer total proteins than the dark hard vitreous kernels of the same variety. The PAGE test was used to identify twenty-eight Tunisian wheat varieties.