How long before protein breaks down?

I've heard that once protein powder is mixed, the protein only lasts for a short time before the protein is rendered useless. How long does it last? Also, how about the individual pre-mixed protein drinks such as Isopure glass bottles. How long does the protein last once the bottle is opened?

We greatly appreciate your interest in helping us build our Q&A database. To discourage vandals from posting garbage, however, we require people to register before posting.

You must be logged in to post an answer. Click here to log in.