Sift or stir flour, salt and pepper together in a shallow dish and set aside. In a bowl, beat egg whites until white and frothy. In another bowl, combine bread crumbs with polenta and basil.
To coat the fillets, dip first into flour, shaking off any excess, then into egg whites, then into bread crumb mixture.
Spray a shallow baking dish with non-stick cooking spray. Lay fillets flat in the dish, tucking under any thinner ends or edges for more even cooking. Bake in the preheated oven for 10 to 15 minutes, or until fish flakes easily with a folk.