What is whey protein made of?
I’m glad you asked. It’s made of cow’s milk. The end.
No, it’s more complicated than that, I’m just kidding! After the cow’s milk is collected, rennet, or other enzymes, are added to curdle the milk. The solid component of the curdled milk is called curds, and the liquid component is whey. (Miss Muffet ate both, of course.)
While the curds are whisked off to make cheese, the whey is dried and processed in one of several ways. Filtration is used to make whey protein concentrate (the inexpensive Optimum Nutrition Gold Standard Whey, for example.) Whey Protein Isolate contains fewer carbohydrates and fats than concentrate, but it’s made in specialized equipment like an ion exchange tower. Some whey protein is processed both ways, such as the great (and only slightly more expensive) Isopure Zero Carb whey protein.
Whey protein can also be hydrolyzed, to make (surprise) Whey Protein Hydrolysate. The hydrolysis process breaks down the longer protein chains into shorter ones, making it easier and faster to digest, at the price of tasting fairly gross.
The upside to all of this intense processing is that whey protein is one of the proteins with the highest bioavailability of anything edible on Earth. What does this mean? For every gram of whey protein you eat, your body can process more of it than any other protein source. Pound for pound, whey protein beats beef, chicken, fish, pork, soy, pea, rice, and hemp protein in its bioavailability.