If you made a coffee flavored protein drink with whey protein isolate, instant coffee, and approx. 90°c water would the heat have any negative effects on the protein?
No negative effects in terms of bioavailability (unless you are specially sensitive to caffeine ingestion, since it is quite irritating), bc whey is already hydrolyzed protein, but it will cause the powder to agglutinate which will require an extra stirr and could worsen the palatability (specially if it’s a low glycine formula).