Deep-fat frying of foods

Deep fat frying is a cooking method that can be used to cook foods such as fried chicken, French fries, and potato chips. Fried foods have desirable flavor, color, and crispy texture, which make deep-fat fried foods very popular to consumers. Deep fat frying process involves submerging a food in extremely hot oil until a safe minimum internal temperature is attained.

It is a complex unit operation involving high temperatures, significant microstructural changes both to the surface and the body of the chip, and simultaneous heat and mass transfer resulting in flows in opposite directions of water vapor (bubbles) and oil at the surface of the piece.

The process is based on the oil-food interaction at high temperatures, which cooks and dehydrates the food, leading to physical and chemical changes, such as starch gelatinization, protein denaturation, flavoring, and color production via Maillard reaction.

Deep fried foods are hot and crispy on the outside and cooked safely in the center. The simultaneous heat and mass transfer of oil, food, and air during deep-fat frying produces the desirable and unique quality of fried foods.

Foods, such as chicken and fish, are coated with a breading or batter (cornmeal, flour, tempura) prior to being submerged in the hot oil. Once the coated food is submerged in the oil, the surface begins to dehydrate and undergoes Maillard reactions that break down sugars and proteins, creating the golden brown or brown exterior of the food.

Deep frying is very fast and, when performed properly, destroys bacteria. When water/moisture in food encounters very hot oil water vaporizes instantaneously turning into super-heated steam. It expands quickly and creates the crispy texture. Most of volatile compounds evaporate in the atmosphere with steam and the remaining volatile compounds in oil undergo further chemical reactions or are absorbed in fried foods.
Deep-fat frying of foods