PHYSICOCHEMICAL CHANGES OCCURRING IN GAMMA-IRRADIATED FLOURS STUDIED BY SMALL-ANGLE X-RAY-SCATTERING

Commercial samples of wheat, rye and potato flour and flaked oats, as well as ground flaked oats and fresh potatoes were gamma-irradiated (2 0 or 30 kGy dose). The products and appropriate control samples were i nvestigated by small-angle X-ray scattering (SAXS) in the range of 2th eta from 0.357 to 6.46 degree (Cu(Kalpha) radiation). The results were compared with those obtained for pure potato starch. Effects of grind ing and heating at 100-degrees-C on SAXS results were also examined. D ifferent scattering curves were obtained for various unirradiated prod ucts. Reflections derived from starch were detected for some unirradia ted as well as irradiated products. A reflection connected with long-r ange ordering in starch (corresponding to the distance d congruent-to 10 nm) was observed for potato, wheat, rye flour and potato powder. A reflection corresponding to the distance d congruent-to 1.6 nm (due to short-range ordering) was observed in the cases of potato flour and p otato powder. Comparison of diffractograms of gamma-irradiated and uni rradiated products, have revealed changes of the reflection correspond ing to d congruent-to 10 nm intensity and elevation of scattering curv es, connected with changes of long-range ordering in starch granules. The effect of gamma-irradiation on long-range ordering in starch was a lso observed after heating of starch at 100-degrees-C. Heating at 100- degrees-C as well as grinding, cause diminution of long-range ordering in starch granules.