Breading usually falls off for 3 reasons: the food’s surface is wet, the flour-egg-breadcrumb sequence is incomplete or out of order, or the coated piece is placed in the oil without resting. All 3 lead to the same result: the coating does not adhere to the food and comes off in a sheet the first time it is turned. When the steps are done in the right order and the coated food is chilled, the problem is completely eliminated. All 3 precautions take only a few minutes.
Each of the 3 layers has a separate job, and none can be skipped. Flour absorbs moisture from the surface of the food and creates a dry base for the egg to adhere to. Egg acts as a binder; when heated, it coagulates and locks the flour and breadcrumbs together. Breadcrumbs form the outer crust and create the browning surface. If the flour is skipped, the egg slides over the wet surface; if the egg is skipped, the breadcrumbs have nothing to adhere to; if the breadcrumbs are skipped, no crust forms. The order is always the same and should not be changed. Bread crumbs, cornflakes, or semolina can also be used instead of breadcrumbs; as long as the order is unchanged, the coating will adhere in the same way.
The most common mistake happens at the outset: the surface of the food has not been dried. Chicken taken from the refrigerator, marinated meat, washed eggplant, or fish left wet can form a dough-like muddy layer even after flour is added, and that layer comes off entirely during cooking. That is why the food should be patted dry with a paper towel, then floured. Shake off excess flour as well; a thick layer of flour creates a separation plane within itself and makes the coating come off entirely.
The second common mistake is putting the coated food into the oil immediately. The coating needs time for the layers to settle together: arrange the coated pieces in a single layer on a rack or wide plate and rest them in the refrigerator for 15–30 minutes. During this time, the egg moistens the breadcrumbs from within, the mixture firms up and behaves like a single piece when it enters the oil. Pieces piled on top of one another stick together and peel off the coating, so arrange them in a single layer with space between them.
The final cause is the oil. If the oil is not hot enough, the coating cannot set immediately; it absorbs oil, becomes heavy, and falls off the food under its own weight. The correct temperature range is 170–180°C / 340–355°F. If the pan is crowded, the oil cools and the same result follows. After placing the coated food in the oil, do not touch it for the first 2 minutes because the crust has not set yet. Turn it just once, holding the edge with tongs; pressing it with a spatula or moving it around in the oil directly loosens the coating. The same rules apply when baking in the oven, except that a thin layer of oil is drizzled over the coating; dry breadcrumbs do not brown in the oven and remain white and floury.