Thickening: The Granules Leak Starch

Depending on how concentrated the starch granules are to begin with, the starch-water mixture may noticeably thicken at various points during their swelling and gelation. Most sauces are rather dilute (less than 5% starch by weight) and thicken during gelation, when the mixture begins to become translucent. They reach their greatest thickness after the gelated granules begin to leak amylose and amylopectin molecules into the surrounding liquid. The long amylose molecules form something like a three-dimensional fishnet that not only entraps pockets of water, but blocks the movements of the whale-like, water-swollen starch granules.