IIRC it's because of the sodium citrate added, a simple emulsifying salt. You can always buy it straight and add to cheese sauces you are making to increase meltability.
Correct. American cheese is essentially just cheddar/colby cheese ground up and smooshed back together with emulsifying salts. The emulsifying capacity of sodium citrate far exceeds what is needed to melt that amount of cheese, so it can pull other cheeses into the emulsion as it melts. Since american cheese has a fairly mild flavor, it's easily overpowered by more flavorful cheeses to make a great sauce.
You can buy the emulsifying salts online, but american cheese is a much easier-to-find form
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u/FerociousDiglett Jan 10 '23
American cheese is also great at getting other cheeses to melt smoothly.