Frying
The art and science of cooking food in hot oil or fat.
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Frying is the cooking of food in oil or fat, a dehydration process involving the transfer of both mass and heat. Unlike sautéing, where food is tossed in the pan, pan-fried items are typically turned over once or twice with tongs or a spatula to ensure even cooking. A vast array of foods can be prepared this way. During frying, several chemical changes occur: proteins denature, starches gelatinize, the surface browns, water rapidly evaporates, and oil is absorbed.
History
The practice of frying is ancient, though pinpointing its exact origins is tricky. While some early cultures may have used hot oil, the earliest clear archaeological evidence of frying comes from later periods than once thought. Frying is believed to have first appeared in Ancient Egyptian cuisine during the Old Kingdom, around 2500 BC.
In China, stir frying is hypothesized to have emerged in field kitchens of the late Han dynasty, though it escaped literary record due to its informal nature. The biblical Book of Leviticus distinguishes between baked bread and bread fried in a pan with oil. In Europe, frying pans appear in Norwegian grave goods from the seventh century. Literary references to frying appear in works like Don Quixote (published in the early 17th century), which mentions fried eggs.
Process
When food contacts oil heated to a high temperature, heat and mass transfer begin. The food’s water content reaches boiling point and vaporizes, creating pores in cell walls that allow oil absorption. Greater heat exposure on the surface causes faster water vaporization there, forming a crisp crust that protects the interior from further oil uptake.
The crust browns due to melanoidin formation from caramelization and the Maillard reaction. Starch gelatinization softens the food’s interior, while the surface, with less water, remains crisp. Frying is complete when all water content has vaporized. As the fried food cools below 100°C, internal water vapor condenses, dropping pressure and drawing oil into the food via a vacuum effect.
Quick Facts
- Common oils
- Palm oil
- rapeseed oil
- sunflower oil
- olive oil
- peanut oil
Facts from the source article.
Lore & Background
Frying involves cooking food in hot oil or fat, a process that dehydrates the food while transferring heat and mass. During frying, the water within the food turns to steam and escapes, creating pores in the cell walls that allow oil to be absorbed. The surface, in direct contact with the hot oil, dehydrates fastest, forming a crisp crust. This crust browns due to caramelization and the Maillard reaction, which produce melanoidins.
Meanwhile, starches in the food gelatinize and soften, though the drier surface remains crisp. Frying is complete when all the food’s water has vaporized; as the food cools below 100°C, internal steam condenses, creating a vacuum that pulls more oil into the food. A wide variety of foods can be fried.
Different techniques exist: deep frying submerges food completely in hot oil, often after battering or breading; sautéing tosses food in minimal oil over high heat; shallow frying cooks food in shallow oil, flipping it once; and stir frying, a Chinese method, uses a wok placed directly over a fire, where constant stirring cooks ingredients in two to three minutes at temperatures up to 400°C. The earliest evidence of frying appears in Ancient Egypt around 2500 BC, and by about 1500 BC, ghee was used in India to fry appam. In China, a Zhou dynasty-era recipe from the Book of Rites describes fried rice with fat from a wolf’s breast. The Book of Leviticus distinguishes baked bread from bread fried in oil. Frying pans appear in seventh-century Norwegian graves, and a reference to fried eggs occurs in the early 17th-century novel Don Quixote.
Reader's Guide
When in contact with oil heated to high temperature, food undergoes heat and mass transfer. The food's water content reaches boiling point and begins to vaporise, creating pores in its cell walls which enable it to absorb oil. As heat exposure is greater on the surface of the food in direct contact with the oil, water vaporisation occurs more quickly. This dehydration effect causes a crisp crust to form which protects the centre of the food against further oil absorption.
The crust browns due to the formation of melanoidins caused by caramelisation and the Maillard reaction. The food's starch content gelatinises, causing it to soften; the surface contains less water and retains its crisp crust. Frying is complete when all water content in the food vaporises.
When a fried food reduces in temperature below 100°C, water vapour inside condenses and internal pressure drops, causing oil absorption into the food via a vacuum effect. Techniques include deep frying, sautéing, shallow frying (also known as pan frying), and stir frying. Stir frying is a Chinese, high-heat technique using a wok in which ingredients are constantly stirred for even cooking. The base of the wok is placed directly in the fire and its concave shape allows the flames to envelop the bowl; the base of the wok can reach 400°C. Frying is finished in two to three minutes.
Did You Know?
- A 2023 meta-analysis found that fried food consumption is linked to a 52% increase in the risk of stomach cancer.
- Up to 75% of calories can be from fat in fried foods due to oil absorption.
- Toxic compounds such as aldehydes (e.g. formaldehyde) are produced during frying and evaporate with steam, which can irritate lung tissue if inhaled.
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Sources
Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.
- Wikipedia: Frying (CC BY-SA 4.0).
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