Gelatinization

Heat starch in water and its granules lose their molecular order in the process called gelatinization. The change runs over a temperature range and varies with granule size: granules swell irreversibly, lose their birefringence under polarised light, leach amylose and shed crystallinity, until prolonged heating disrupts them entirely. Cooks see it as thickening: sauces, gravies and porridges body up as granules swell. Food scientists measure its onset temperatures to predict texture, since under-gelatinized starch tastes raw and overcooked starch turns gummy.