The effect of sugars on the gelatinisation of starch

It is well-known that the addition of sugars and other polyols to starch–water systems elevates the starch gelatinisation temperature, with the elevation being greater the higher the concentration of the aqueous solution and the larger the molecular weight of the added solute. Small angle X-ray scattering combined with wide-angle X-ray scattering and DSC are used to study the effects which aqueous solutions of low molecular weight sugars and other polyols have on starch gelatinisation. It is shown that adding sugars is not equivalent to moving into a regime of limiting water, with no broadening or splitting of the gelatinisation endotherm being observed, other than in limiting solution conditions. The results are interpreted within a phenomenological model of gelatinisation, based on the concept of a continuous plasticisation curve, with a degree of internal plasticisation and self-assembly being required before gelatinisation can proceed.