How To Thicken Whole Milk With The Other Dairy In Your Fridge

There are a number of ways and ingredients you can use to thicken whole milk. Whether you're making a sweet or savory whole milk-based sauce, one option includes cooking the sauce to thicken it. Another is to add a thickening agent such as flour or cornstarch. But if you don't want to introduce a dry ingredient to whole milk, you can add another form of dairy — just consider the flavor profile before selecting and adding another dairy product.

Savory, tangy milk sauces can be thickened using sour cream. While homemade sour cream is easy to make if you don't have any on hand, sour cream doesn't do well when boiled. So, be sure to heat it cautiously, toward the end of making the sauce, and keep a close eye on it. For sweet or savory sauces, cream cheese is another great option that can withstand heat better. (You can find more unusual uses for cream cheese here.) Finally, adding grated cheese to a sauce is another great option for thickening a milk sauce while bolstering the flavor. 

Why is it that these additional dairy products thicken milk sauce? It ultimately comes down to how much casein, a protein molecule, is present. Whole milk is easier to thicken because it has a higher percentage of fat, but the additional casein proteins help thicken the sauce. When whole milk is heated with other dairy products (whether it's sour cream, cream cheese, or grated cheese), the protein molecules in the melted dairy can combine more easily through protein coagulation. As the protein molecules coagulate, that's when you see the milk sauce begin to thicken. 

With an understanding of how dairy thickens milk and milk-based sauces, you can easily add different types into sauces. Whether you're making a creamy béchamel sauce (or any of the 11 sauces that are made from it), cheddar cheese sauce, or mornay sauce, you can quickly and easily thicken them with a dollop of cream cheese or whatever dairy you have on hand. Just don't forget to start with cold milk for lump-free results.