A SMALL-ANGLE X-RAY-SCATTERING STUDY OF THE ABSORPTION OF WATER INTO THE STARCH GRANULE

Analysis of the shape of the small-angle X-ray scattering (SAXS) inten sity profiles obtained from suspensions of wheat starch granules in wa ter gives information on the amount of absorption into the different r egions of the granule. At room temperature, less water is absorbed int o the granules the higher the starch concentration. At 51-degrees-C, t he beginning of the gelatinisation region, lower amounts of water are absorbed when the concentration of starch is high and there is less lo ss of crystalline order. In an excess of water, co-operative melting o ccurs, whereas, with less water, the absorption is insufficient to des tabilise the crystalline order. The beam damage at room temperature is reflected in a slight increase in order, possibly due to rearrangemen t after chain scission.