Question

milk contains protein but butter contains fat

Answer 1

milk contains fat too. while making butter most of the proteins are left out so the remaining fats stays in the butter.

Answer 2

Pure milk fat contains only fat; it does not contain any casein proteins, but milk does. Dairy products contain two types of protein, caseins and whey proteins. Caseins comprise around 80 percent of milk proteins, according to the University of Guelph in Ontario, Canada.