Final answer:
Milk contains two types of protein, casein and whey. Casein makes up about 80% and is slow to digest, whereas whey is the remaining 20% and digests quickly, aiding in muscle recovery.
Step-by-step explanation:
The two types of protein found in milk are casein and whey protein. In cow's milk, casein accounts for approximately 80% of the milk protein, while whey represents the remaining 20%. Casein protein contains glutamine and casomorphin and is known for its slow digestion, making it ideal for consumption before sleeping. Whey protein, on the other hand, is rich in essential amino acids and is rapidly digested, which makes it popular for muscle recovery especially among bodybuilders.