Refined starches such as cassava starch, and less-common alternatives including corn starch, are more recent arrivals in the pantry. All thickeners work in much the same way, but there are functional differences between flour and other starches, such as cassva starch.
Most plants contain starches in varying concentrations, with grains, root vegetables and some beans having especially large amounts. They’re usually stored in the plant in the form of fine, tightly wound granules. If they’re dispersed in water and heated, those granules absorb water and begin to swell. When they reach a specific temperature — different for each starch — they burst open, and the molecules of starch lose their compact shape. Instead they bond together in a large, open mesh, trapping and immobilizing the liquids to form a soft gel.