American cheese has a bad reputation, especially among foodies and health-conscious folks. (Think the bright yellow stuff at McDonald's.) You might hear claims that it's made of "plastic" or "chemicals," but it turns out the truth is nothing scary. American-style cheese is just cheese mixed with melting salts and ordinary ingredients like milk.
Photo by Henry Zbyszynski.
Technically, makers can't call it cheese, because it's a mixture of cheese and other things. The word cheese should still be on the label somewhere, though. Generally, the main main on the label will use a variation like "singles" or "slices" instead. As J. Kenji López-Alt puts it:
Saying "American cheese is not cheese" is like saying "meatloaf [or Spam] is not meat." Just as meatloaf is a product that is made by blending real meat with texture- and flavour-altering ingredients, so American cheese is a product made by blending real cheese with texture- and flavour-altering ingredients. In fact, percentage-wise, there's a good chance that there's more milk and cheese in your American cheese slices than there is meat in your meatloaf!
Over at Serious Eats, he delves into the ingredients in American cheese, and explains where the myths come from and why they're misleading. American cheese is a fine thing to put on top of your burger, and there's no shame — and certainly no health risk — in enjoying it.
What Is American Cheese? [Serious Eats]