When protein is heated, it can 'denature'- this means the protein molecules unfold or break apart. This is what your body does to protein anyway, breaking down the amino acids and digesting protein. Much like when you cook meat, the protein you gain is not altered by cooking.

Does protein powder go bad in the heat?

“It's best to store protein powder tightly closed in a cool, dry place,” she adds. “Heat, moisture, and air can spoil protein powders and cause molding.”

Does protein powder work if you cook it?

Cooking protein does not destroy it but could denature it. That denatured protein might be a little bit harder for your body to digest but likely isn't completely useless.