A deep fryer (also referred to as a deep fat fryer) is a kitchen appliance used for deep frying. Deep frying is a method of cooking by submerging food into oil at high heat, typically between temperatures of .
While commonly used in commercial kitchens, household models are available and have become increasingly prevalent.
Deep frying has become well known in the United States, from frying sticks of butter to Twinkies, but the method can be traced back to Roman times.
Features
Deep fryers generally have a basket to lower the food into the oil tank and raise it when the food has finished cooking. Fryer baskets purchased separately are not standardized and when selected, need to fit into the deep fryer. There are timers and alarms, automatic devices to raise and lower the basket into and out of the oil, ventilation systems to exhaust frying odors from the kitchen, an oil filtration system or chemical treatment to improve the re-usability of the same amount of oil, and mechanical or electronic temperature controls that save energy and prevent fires by continuously sensing and adjusting the temperature of the oil.
Construction
The modern commercial fryer has improved energy efficiency, resulting from better heat transfer systems. Commercial fryers with infrared heating or convection heating are efficient, but often expensive. Infrared heating uses a radiant heat transfer process and convection heating operates through air circulating, while standard fryers utilize hot combustion gases. Most standard fryers are very hot which you would need to be careful while in use. The most common fryer models are electric and gas fryers.
Electric restaurant fryers are popular in counter top models, because of their mobility and easy installation. They lose less heat than gas fryers, because their heating elements are immersed in the oil and have a faster temperature recovery time between frying cycles. Gas fryers heat up more quickly and to a higher cooking temperature than electric fryers. They can be powered by either natural gas or propane, both of which are generally less expensive energy sources than electricity. This makes gas power especially popular in floor model fryers. Commercial fryers are generally available in mild steel or stainless steel. Stainless steel is less likely to corrode or stain than mild steel. Mild steel also expands under heat, which may damage the welds over time. Because of this, stainless steel fryers often come with a much longer warranty than mild steel fryers.
Some commercial fryers have a "cold zone" at the bottom of the fry pot. This is where food particles, such as breading, batter or broken off pieces of food, sink to, while the lower temperature keeps them from burning and tainting the oil. A tube-style fry pot has a large cold zone because the tubes are slightly above the bottom of the vat, leaving generous space for cooler oil and crumbs. This is particularly useful for cooking heavily breaded foods (such as a blooming onion). A tube-style fry pot is more difficult to clean than an open fry pot, but the tubes allow easy access to the heat source. Tube fryers are often less expensive than their open fry pot counterparts.
Open fry pots have an external heat source, which makes them easier to clean and affords better access to the oil, but they generally offer a smaller cold zone, so food particles could pollute the flavor of the oil. However, these fryers work very well for lightly breaded foods. Flat-bottomed restaurant fryers (another type of open fry pot fryer) can also be difficult to clean and have no cold zone, but they are highly effective for frying dough. Flat-bottom fryer pots may also be used with a batter trapping insert that keeps loose batter from quickly scorching on the bottom where the heat is applied normally. A batter trap can also help keep loose batter from being stirred up in the oil and adhering to subsequent batches of food in order to make foods taste better and extend the cooking oil's usability.
Some domestic fryers incorporate an angled motorized rotary basket that circulates its contents through the hot oil. This design reduces the amount of oil required to roughly half compared to a more traditionally designed fryer. Domestic fryers are generally much smaller than their commercial counterparts and typically have a capacity of two to four liters.