2004,Harold McGee, chapter 1, inOn Food and Cooking: The Science and Lore of the Kitchen, Scribner,→ISBN:
It’s the clumping nature of thecaseins that makes possible most thickened milk products, from yogurt to cheese. The whey proteins play a more minor role; they influence the texture ofcasein curds, and stabilize the milk foams on specialty coffees.
