Sauce Thickening Agents. Flour is a common thickening agent for homemade gravy and is used in some hot sauces. Egg yolk can also be used as thickening agent in different sauce.

Egg yolks are used in three main areas as a thickening agent. To thicken a sauce or soup with the consistency of water to a traditional nape stage (coats the back of a spoon), you will need 2 oz of corn starch for every 1 qt of sauce or soup. Some common thickeners are flour, cornstarch, xantham gum, egg yolk, and tomato paste.