Whole-grain flours such as whole wheat and rye contain a small amount of fat which can quickly turn rancid. Store these flours in an airtight container in the refrigerator. Allow flour to warm to room temperature before using.
Aim for just a light coating of flour on the fish for minimal oil absorption--you should only use about 1/4 cup of the flour mixture. We attempted this recipe with whole-wheat flour, but the natural oils from the whole grain didn't allow the crust to crisp properly.