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In the late 1930s, a salesman for the Tenderoni Macaroni company began selling boxes of macaroni with packets of processed, grated cheese from Kraft. Kraft heard about it and began selling boxes of macaroni and cheese in 1937. Using chemistry, Kraft had created shelf-stable cheese that was also very creamy when melted into a sauce. But how did they do it?
Cheese, at its most fundamental, is an emulsion of milk fat in water. This means the globules of fat are suspended in water exactly like oil and water when shook up. When cheese is heated up, however, the emulsion breaks down causing all the fat to stick together. That makes good cheese for pizza, but not sauce. So an additional emulsifier is needed.
Many recipes use flour, but that tends to eliminate large portions of flavor. Other recipes call for oils, but then your macaroni and cheese is greasy. In 1916, James L Kraft discovered that adding sodium phosphate to cheese leads to the same emulsion result when the cheese melts. It was the first processed cheese in America, and has since been labelled “American Cheese”. But this wouldn’t be the last chemical innovation used by Kraft for their mac and cheese.
During World War II, the US military began experimenting with methods of stabilizing foods such as spray-drying. By spraying a product into a chamber filled with very hot air, the liquid evaporates leaving only powdered solids. This technique was used for eggs, ice cream, and, yes, cheese. Macaroni was put together with the powdered cheese for soldiers abroad and citizens at home. Boxes by Kraft only cost one rationing coupon for two boxes, so it caught on quickly!
If you would like to try your own emulsion experiment at home, sodium citrate (which you can find online or in a local Kosher store as “sour salt”) will work very well. Dissolve 11 grams of sodium citrate in 1 cup of simmering milk. Add 4 shredded cups of the cheese of your choice and enjoy the sauce over your favorite pasta.