Thicken

To create a denser liquid or mixture by either adding a thickening agent or by boiling to reduce the existing volume of liquid. This procedure is commonly referred to as creating a "liaison," to disperse solids within a mixture, thus increasing the viscosity and making the substance less fluid. In other instances, the thickener is used to form an emulsion that suspends one liquid within another, such as egg yolks or gums. Heat can also be used to thicken foods by warming the ingredients to a point that stiffens the food or by boiling off excess liquid to reduce the volume and thus thickening the liquid.

Flour is one of the most often used thickening agents when cooking foods such as sauces, gravies, soups, stews, and gumbos. Two thickening agents prepared with flour – a roux and a beurre manié – are among the most popular methods for using flour as a thickener. A roux is a flour and fat combination that is cooked before it is used as a thickener, and beurre manié is a flour and fat paste that is not cooked before it is used.

Other commonly used thickening ingredients include: Agar, Arrowroot, Blood, Butter, Carrageenan, Cheese, Cornstarch, Cream, Crema, Egg Whites, Egg Yolks, Gelatin, Groats, Mayonnaise, Pectin, Sago, Seaweed, and Vegetable Purees.