Deep frying is a very fast way to cook foods in comparison to other methods such as boiling, due to the high temperature of the shortening in the fryer. Deep frying does not make food greasy since the dampness in the food repels the oil. (Oil and water do not mix.) Frying is actually a dry cooking method. The hot oil heats the moisture within the food to the boiling point, and steams the food from the inside out. Typically the frying temperature will range between 300 and 375 degrees Fahrenheit. Thicker / denser foods fry better at a lower temperature which allows them to heat through without scorching the outside.

Electric fryers heat the oil by immersing elements into the oil itself. Gas fryers have burners either encased in tubes running through the shortening or on the lower, outside sides of the fry pot. There are benefits and drawbacks to both methods and fuel types

The nature of the construction of gas fired fryers places the heat source above the base of the fry pot. This creates what is called a cold zone in the bottom of the vessel. Operations preparing high volumes of breaded, fried foods benefit from this type fryer as the crumbs from the product settle into the cold zone and do not continue to cook and burn in the shortening. This reduces the transfer of flavor from the food to the oil and also reduces carbonization (browning). This sediment can be easily drained off as well. The trade off with most gas fryers is a radical drop in the shortening temperature when a load of product is dumped in and a rather slow recovery to optimum frying temperature.

Some electric fryer manufacturers are now creating small cold zones within their fryers. Generally speaking, though, the heating elements are flush against the bottom of the fry pot which necessitates frequent oil filtering when cooking heavily breaded products. Electric fryers are very precise in temperature control and quick to recover after a load of cold or frozen product has been placed in the fry pot. High efficiency electric fryers in side by side comparison to standard gas fryers consistently provide more product throughput. While instant recovery gas fryers are available, they are priced out of the reach of most operators.

As with all grease-producing, commercial cooking appliances; fryers require dedicated exhaust ventilation in accordance with local mechanical and fire codes. At a minimum, this entails a class I grease exhaust hood built in accordance to UL 710 specifications. Additionally, an automatic fire suppression system and ductwork in compliance with NFPA96 standards are required.