Thickening

In cooking, thickening is the process of increasing the viscosity of a liquid either by reduction, or by the addition of a thickening agent, typically containing starch.

Desserts are often thickened with sago, tapioca, gelatin or a gelatin substitute such as agar. Soups, sauces and stews are more often thickened with a starchy ingredient like cornstarch, arrowroot or wheat flour, or a fat and flour mixture such as roux or beurre manié. More rarely, savory dishes may be thickened with blood.