Tapioca starch от John Spottiswood

Tapioca is a good choice for thickening pie fillings, since it thickens at a lower temperature than cornstarch, remains stable when frozen, and imparts a glossy sheen. Many pie recipes call for instant tapioca instead of tapioca starch, but instant tapioca doesn't dissolve completely and leaves small gelatinous blobs suspended in the liquid. This isn't a problem in a two-crust pies, but the blobs are more noticeable in single-crust pies. Tapioca starch is finely ground so that it dissolves completely, eliminating the gelatinous blob problem. The starch is also sometimes used to thicken soups, stews, and sauces, but the glossy finish looks a bit unnatural in these kinds of dishes. It works quickly, though, so it's a good choice if you want to correct a sauce just before serving it. Some recipes for baked goods also call for tapioca flour because it imparts a chewier texture.