This is apparently a new menu term. I saw it multiple times today, and I can't remember ever seeing it before. First was at lunch, at a local Thai restaurant, where the lunch specials came with "Your choice of Proteins chicken, beef, pork, tofu." (One doesn't expect perfect punctuation on the menu of a Thai restaurant. In fact, I think it's actually required to include a bunch of errors in order to be "authentic." The restaurant equivalent of "keeping it real.")
Then, when I got back to work, I read the flyer for the new, improved cafeteria menu, and the salad bar description said, "Crisp greens and hot Proteins". And the next menu item also described Proteins.
Yeah - "Proteins" needs to be capitalized, I guess.
Still, though, whenever I read "Proteins," I think this. It makes me not want to eat there.