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Deep-frying is a cooking method whereby food is submerged in hot oil or fat. This is normally performed with a deep fryer or chip pan; industrially, a pressure fryer or vacuum fryer may be used.

Deep frying is classified as a dry cooking method because no water is used. Due to the high temperature involved and the high heat conduction of oil, it cooks food extremely fast.

Contents 1 Technique 2 Oil deterioration 3 Disadvantages 4 See also 5 References 6 External links

If performed properly, deep-frying does not make food excessively greasy because the moisture in the food repels the oil: The hot oil heats the water within the food, steaming it from the inside out, oil cannot go against the direction of this powerful flow.^[1] As long as the oil is hot enough and the food is not immersed in the oil for too long, oil penetration will be confined to the outer surface. However, if the food is cooked in the oil for too long, too much of the water will be lost and the oil will begin to penetrate the food. The correct frying temperature depends on the thickness and type of food, but in most cases it lies between 175 and 190 °C (345–375 °F).

Some fried foods are given a coating of batter or breading prior to frying. The effect of these is that the outside of the food becomes crispy and browned while the inside becomes tender, moist, and steamed. Some foods, such as potatoes or whole, skin-on poultry, produce a natural coating and do not require breading or battering.

Overheating or over-using the frying oil, or undue exposure to air while hot, leads to formation of rancid-tasting products of oxidation, polymers and other deleterious, unintended or even toxic compounds such as acrylamide (from starchy foods). Researchers in many countries have found that of the three major market sectors, the most abused frying oils were (in order from the worst) those in the catering, domestic and industrial sectors^{[citation needed]}. Deep-frying under vacuum helps to significantly reduce the acrylamide formation, however this process is so far not widely used in the food industry due to the high investment volume involved.

Some useful tests and indicators of excessive oil deterioration are the following:

• Sensory: Darkening, smoke, foaming, thickening, rancid taste.
• Laboratory: Acidity (FFA), anisidine value, viscosity, total polar compounds, polymeric triglycerides.

Instruments that read the total polar compounds, currently the best single gauge of how deep fried an object is, are available with sufficient accuracy for restaurant and industry use.

• Deep frying produces large amounts of waste oil, which must be properly disposed.

• Deep fry shortenings contain trans fat. Overall this is very hazardous to your health.

• Cooking oil is flammable, and there have occasionally been fires caused by the oil igniting due to too high temperature. If one attempts to extinguish an oil fire with water, the water will boil, sending the burning oil in all directions and thus aggravating the fire. Instead, oil fires must be extinguished with dry powder or fire fighting foam. For this reason, most commercial deep fryers are equipped with automatic fire suppression systems using foam.

• French fried potatoes
• Banana chips
• Deep fried Twinkie
• Deep fried Mars Bar
• Deep fried pizza

• Christian Science Monitor: Backstory: If you can think of it, he can deep-fry it
• Deep Fryer Recipes

v • d • e Cooking techniques
Cooking under heat	Baking · Frying · Deep-frying · Boiling · Braising · Grilling/Broiling · Roasting · Sautéing · Stir frying · Poaching · Steaming · Pressure cooking · Pressure frying · Simmering · Clay pot cooking
Cooking without heat	Smoking · Marination
Food preservation	Canning · Drying · Pickling · Refrigeration · Salting · Smoking
Par-cook	Blanching · Parboiling
Other Techniques	Creaming · Fermenting · Outdoor cooking · Scalding · Tempering