What are the two main proteins found in milk?

The two main proteins found in milk are casein and whey. Casein makes up about 80% of the total protein content in cow's milk and is responsible for the white color of milk and its ability to form curds. It is a key protein in cheese-making and provides essential amino acids, calcium, and phosphorus.

Whey, on the other hand, constitutes approximately 20% of the protein in milk and is a byproduct of cheese production. It consists of several different proteins, including lactalbumin and lactoglobulin, which are known for their high biological value and are often used in protein supplements.

In selecting the correct answer, while casein is clearly identified as one of the main proteins, the term "lactalbumin" refers to a component of whey proteins, rather than being a main protein on its own. Therefore, the two proteins most commonly recognized as the main constituents of milk proteins are casein and whey, making the best response about protein composition in milk revolve around casein and whey. However, the presence of casein in option A indicates an understanding of its significance in milk, even if the second part is not commonly referred to in relation to whey directly.