Optimum Nutrition | Gold Standard Casein 2IbWhile rapid protein absorption is desirable immediately before or after exercise, delayed release is probably more beneficial throughout the remainder of the day. Casein proteins are pH sensitive and gel in the acidic environment of the stomach. As a result, it can take more than twice as long for caseins to be broken down into their amino acid subcomponents than whey and other proteins. Casein is the most abundant protein present in milk. It is