Starch gelatinization in sugar solutions

In limited water (<30%), the gelatinization temperature of starch increases as the moisture content decreases. When sugar is dissolved in water, the sugar displaces part of the water. Therefore, the moisture content of a wheat starch granule in a sugar solution is always less than 30%; thus, the gelatinization temperature is increased. When sugar is dissolved in water, the Aw is decreased. This decreased Aw was shown to increase the onset melting point of crystallized dextrins. Thus, the well known effect of sugar increasing the onset temperature of starch gelatinization appears to be a result of the displacement of the water inside the starch granule and the lower Aw.