Some food can be pre-cooked before frying. When pre- cooked, food needs less time in the fryer, saving energy and lowering the fat absorbed by the food. Food cooks quickly, because very hot shortening surrounds the food on all sides and drives moisture from the food. During the cooking process, the food absorbs some shortening, which adds the desirable flavor and texture. The hot shortening seals the outside of the food with a crisp crust.
Heat moves quickly to the center of the food because the crust holds in some of the hot moisture.
Pressure Frying Hot shortening is the cooking medium in pressure frying, but moisture released from the food is kept under the tightly sealed lid. When the cooking cycle is complete, the pressure drops, and the food is ready. When shortening is filtered, suspended food particles are strained out from the hot shortening, by forcing the mixture through a porous barrier. Filtering shortening can be a chemical process, a mechanical process, or a combination of both. In chemical filtering, absorbent powder soaks up the by-products of frying.