{{short description|Cooking of food in oil or fat}} {{For|other uses of "fry" or "frying"|Fry (disambiguation){{!}}Fry}} [[File:PLAINTAIN.jpg|thumb|alt=Slices of plantain being fried in a wide pan outside in bubbling oil|Fried plantain]] '''Frying''' is the cooking of food in oil or fat.{{efn|Chemically, oils and fats are the same, differing only in melting point: oils are liquid at room temperature and fats are solid.<ref name="Industrial Frying">{{cite journal |last1=Rosseli |first1=J. B. |title=Industrial Frying Process |journal=Grasas y Aceites |date=30 August 1998 |volume=49 |issue=3-4 |doi=10.3989/gya.1998.v49.i3-4.729|url=https://grasasyaceites.revistas.csic.es/index.php/grasasyaceites/article/view/729 |access-date=3 April 2026|doi-access=free }}</ref>}}<ref>{{cite book |title=The New Larousse Gastronomique: The Encyclopedia of Food, Wine & Cookery |editor-last=Montagné |editor-first=Prosper |publisher=Crown |year=1977 |isbn=0517531372 |pages=299, 307}}</ref> Similar to sautéing, pan-fried foods are generally turned over once or twice during cooking to ensure that the food is evenly cooked, using tongs or a spatula, whereas sautéed foods are cooked by "tossing in the pan".<ref>{{Cite book| publisher = Artisan Books| isbn = 978-1-57965-236-4| last = Peterson| first = James| title = Essentials of Cooking| date = April 2003}}</ref> A large variety of foods may be fried. Frying is a dehydration process which involves the transfer of mass and heat. Different chemical changes take place during the frying process such as protein denaturation, starch gelatinization, surface browning, rapid water evaporation and oil absorption.<ref>{{Cite journal |last=Onigbogi |first=Isaac O |last2=Olatunji |first2=T.O |last3=Nupo |first3=S.S |last4=Bello |first4=T.K |date=December 2011 |title=Effect of Repeated Frying Operations on the Quality Attributes of Frying Oil and Acceptability of Sweet Potato Chips |url=https://www.researchgate.net/publication/304898163_Effect_of_repeated_frying_operations_on_the_quality_attributes_of_frying_oil_and_acceptability_of_sweet_potato_chips |journal=Journal of Sciences and Multidisciplinary Research |volume=3 |pages=10 |via=ResearchGate}}</ref>
==History== {{Expand section|date=December 2009}} Frying is believed to have first appeared in Ancient Egyptian cuisine during the Old Kingdom, around 2500 BC.<ref name='Tannahill'>Tannahill, Reay. (1995). ''Food in History''. Three Rivers Press.</ref> There is evidence of frying dating to c. 1500 BC in India, when ghee was used to fry appam.<ref>{{cite book |last1=Prakash |first1=Om |title=Food and Drinks In Ancient India: From Earliest Times To B.c. 1200 A.d. |date=1961 |publisher=Munshi Ram Manohar Lal |page=250 |url=https://archive.org/details/dli.ernet.103355/page/249/mode/2up |access-date=3 April 2026}}</ref> In China, the Book of Rites describes a Zhou dynasty-era recipe for fried rice and fat from a wolf's breast. It is hypothesised that stir frying emerged in field kitchens in the late Han dynasty, but evaded the literary record due to its informal nature.<ref name="Tannahill"/> In Leviticus, a distinction is made between baked bread and bread fried in a pan with oil.<ref name="Morton"/>
In Europe, frying pans begin appearing in Norwegian grave goods in the seventh century.<ref>{{cite book |last1=Bukkemoen |first1=Grethe Bjørkan |title=The Agrarian Life of the North 2000 BC–AD 1000: Studies in Rural Settlement and Farming in Norway |date=2017 |pages=117–132 |url=https://www.jstor.org/stable/jj.36233739.9 |access-date=3 April 2026}}</ref> Frying is mentioned in the Wife of Bath's Tale and a reference is made to fried eggs in Don Quixote in the 14th and 17th centuries respectively.<ref name="Morton">{{cite journal |last1=Morton |first1=I. D. |title=Geography and history of the frying process |journal=Grasas y Aceitas |date=30 August 1998 |volume=49 |issue=3–4 |doi=10.3989/gya.1998.v49.i3-4.745 |url=https://grasasyaceites.revistas.csic.es/index.php/grasasyaceites/article/view/745 |access-date=12 April 2026|doi-access=free }}</ref>
== Process == When in contact with oil heated to {{convert|150|{{ndash}}|200|C}}, food undergoes heat and mass transfer.<ref name="Changes in food" /> The food's water content reaches boiling point and begins to vaporise, creating pores in its cell walls which enable it to absorb oil.<ref name="Food Safety and Health">{{cite journal |last1=Valle |first1=Consuelo |last2=Echeverría |first2=Francisca |last3=Chávez |first3=Vilma |last4=Valenzuela |first4=Rodrigo |last5=Bustamante |first5=Andrés |title=Deep-frying impact on food and oil chemical composition: Strategies to reduce oil absorption in the final product |journal=Food Safety and Health |volume=2 |issue=4 |pages=414–428 |doi=10.1002/fsh3.12056 |url=https://iadns.onlinelibrary.wiley.com/doi/10.1002/fsh3.12056 |access-date=3 April 2026|doi-access=free }}</ref> 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.<ref name="Food Safety and Health" />
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.<ref name="Changes in food">{{cite journal |last1=Bordin |first1=Keliani |last2=Tomihe Kunitake |first2=Mariana |last3=Kazue Aracava |first3=Keila |last4=Silvia Favaro Trindade |first4=Carmen |title=Changes in food caused by deep fat frying |journal=Órgano Oficial de la Sociedad Latinoamericana de Nutrición |date=2013 |volume=63 |issue=1 |url=https://ve.scielo.org/scielo.php?script=sci_abstract&pid=S0004-06222013000100001&lng=es&nrm=iso&tlng=en |access-date=5 May 2026 |issn=0004-0622}}</ref> Frying is complete when all water content in the food vaporises.<ref name="Food Safety and Health" /> When a fried food reduces in temperature below {{convert|100|C|F}}, water vapour inside condenses and internal pressure drops, causing oil absorption into the food via a vacuum effect.<ref name="Food Safety and Health" />
== Techniques == === Deep frying === {{Main|Deep frying}} [[File:Munkinpaisto.jpg|thumb|225px|alt=Rings of dough floating in bubbling oil, varying in colour from cream to dark brown|Smultring being deep fried]] In deep frying, food is submerged in hot oil or fat so that all sides are cooked simultaneously. A deep fryer or chip pan may be used, or, in an industrial frying operation, a pressure fryer or vacuum fryer. One method for preparing food for deep frying involves battering or breading, which adds colour and crunch to its surface.<ref name="Food prep NVQ2">{{cite book |last1=Stevenson |first1=Danny |title=Food Preparation and Cooking: Cookery Units |date=1996 |publisher=Nelson Thornes Ltd |isbn=0 7487 2566 0 |page=18 |edition=2nd |url=https://books.google.co.uk/books?id=vRcidxIUWYMC&pg=PA18&redir_esc=y#v=onepage&q&f=false |access-date=4 May 2026}}</ref> French fries, doughnuts, cong you bing, and tempura are common deep-fried foods.<ref name="Oxford Companion"/><ref>{{cite book |last1=Y. W. Ang |first1=Catharina |last2=Liu |first2=KeShun |last3=Huang |first3=Yao-Wen |title=Asian Foods: Science and Technology |date=1999 |publisher=Technomic Publishing Company, Inc. |isbn=1-56676-736-9 |page=94 |url=https://books.google.co.uk/books?id=C4cTXJYTE4QC&pg=PA94&redir_esc=y#v=onepage&q&f=false |access-date=4 May 2026}}</ref>
=== Sautéing === In sautéing, food is tossed over high heat in a frying pan with minimal oil to prevent sticking.<ref name="Frying Fats Boskou">{{cite book |last1=Boskou |first1=Dimitrios |title=Frying Fats |date=2011 |publisher=CRC Press |edition=2 |url=https://www.researchgate.net/publication/259575170_Frying_Fats_in_Chemical_Biological_and_Functional_Aspects_of_Food_Lipids |access-date=10 May 2026}}</ref><ref>{{cite news |last1=Ibitoye |first1=Tai |title=What’s the healthiest way to cook vegetables? |url=https://www.bbc.co.uk/food/articles/healthiest_vegetable_cooking_method |access-date=7 May 2026 |work=BBC Food |date=May 2024}}</ref> A sauté pan, which has higher sides to prevent food escaping during tossing, may also be used.<ref name="Oxford Companion">{{cite book |last1=Davidson |first1=Alan |title=The Oxford Companion to Food |date=1999 |publisher=Oxford University Press |isbn=0192115790 |url=https://archive.org/details/oxfordcompaniont0000davi_g3y4/mode/2up |access-date=11 May 2026}}</ref>
=== Shallow frying === In shallow frying, also known as pan frying, food is fried in shallow oil on one side until browned, then flipped to cook the other side.<ref name="Oxford Companion"/>
=== Stir frying === {{Main|Stir frying}} [[File:Wok cooking.jpg|225px|thumb|right|A wok being used to stir fry]] 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 {{convert|400|C|F}}.<ref>{{cite web |last1=Lam |first1=Lan |title=The Science of Stir-Frying in a Wok |url=https://www.americastestkitchen.com/articles/2189-the-science-of-stir-frying-in-a-wok |website=America's Test Kitchen |access-date=7 May 2026}}</ref><ref name="Chinese cooking">{{cite book |last1=Lo |first1=Eileen Yin-Fei |title=Mastering the Art of Chinese Cooking |date=2009 |publisher=Chronicle Books LLC |isbn=0811859339 |page=76}}</ref> Frying is finished in two to three minutes.<ref name="Chinese Cooking (1945)">{{cite book |last1=Chao |first1=Yang Buwei |title=How to Cook and Eat in Chinese |date=1945 |publisher=The John Day Company |url=https://archive.org/details/howtocookeatinch00cha0/mode/2up |access-date=7 May 2026}}</ref>
== Health effects == A 2021 meta-analysis found that the highest category of fried food consumption compared to the lowest is associated with a 3% increase in the risk of all-cause mortality, as well as with a 2% increase in the risk of cardiovascular mortality.<ref name=qin-mortality>{{cite journal |vauthors=Qin P, Zhang M, Han M, Liu D, Luo X, Xu L, Zeng Y, Chen Q, Wang T, Chen X, Zhou Q, Li Q, Qie R, Wu X, Li Y, Zhang Y, Wu Y, Hu D, Hu F |title=Fried-food consumption and risk of cardiovascular disease and all-cause mortality: a meta-analysis of observational studies |journal=Heart |volume=107 |issue=19 |pages=1567–1575 |date=October 2021 |pmid=33468573 |doi=10.1136/heartjnl-2020-317883 |url=}}</ref> Compared to participants with a low intake, those who ate the most fried food had a 37% increased risk of heart failure, a 28% increased risk of major cardiovascular events, and a 22% increased risk of coronary heart disease.<ref name=qin-mortality /> The risk of stroke, heart failure, and heart attack modestly increased with the increase of weekly servings of fried food.<ref name=qin-mortality /> The study concluded that fried food consumption may increase the risk of cardiovascular disease and presents a linear dose-response relation.<ref name=qin-mortality /> The researchers theorized the main reasons behind these associations are the high trans fat and calorie content of fried foods and their pro-inflammatory nature.<ref name=qin-mortality /> It was also noted that eating hyperpalatable crisp-fried foods may entice people to engage in routine overeating.<ref name=qin-mortality />
A 2023 meta-analysis found that fried food consumption is linked to a 52% increase in the risk of stomach cancer.<ref>{{cite journal |vauthors=Zhang T, Song SS, Liu M, Park S |title=Association of Fried Food Intake with Gastric Cancer Risk: A Systemic Review and Meta-Analysis of Case-Control Studies |journal=Nutrients |volume=15 |issue=13 |date=June 2023 |page=2982 |pmid=37447308 |pmc=10347084 |doi=10.3390/nu15132982 |doi-access=free |url=}}</ref> Fried food intake is also associated with prehypertension,<ref name=provido>{{cite journal |vauthors=Provido SM, Abris GP, Hong S, Yu SH, Lee CB, Lee JE |title=Association of fried food intake with prehypertension and hypertension: the Filipino women's diet and health study |journal=Nutr Res Pract |volume=14 |issue=1 |pages=76–84 |date=February 2020 |pmid=32042377 |pmc=6997139 |doi=10.4162/nrp.2020.14.1.76 |url=}}</ref> hypertension<ref>{{cite journal |vauthors=Sayon-Orea C, Bes-Rastrollo M, Gea A, Zazpe I, Basterra-Gortari FJ, Martinez-Gonzalez MA |title=Reported fried food consumption and the incidence of hypertension in a Mediterranean cohort: the SUN (Seguimiento Universidad de Navarra) project |journal=Br J Nutr |volume=112 |issue=6 |pages=984–91 |date=September 2014 |pmid=25201306 |doi=10.1017/S0007114514001755 |url=}}</ref><ref>{{cite journal |vauthors=Kang Y, Kim J |title=Association between fried food consumption and hypertension in Korean adults |journal=Br J Nutr |volume=115 |issue=1 |pages=87–94 |date=January 2016 |pmid=26449129 |doi=10.1017/S000711451500402X |url=}}</ref><ref name=provido /><ref name=qin-diseases>{{cite journal |vauthors=Qin P, Liu D, Wu X, Zeng Y, Sun X, Zhang Y, Li Y, Wu Y, Han M, Qie R, Huang S, Zhao Y, Feng Y, Yang X, Liu Y, Li H, Zhang M, Hu D, Hu F |title=Fried-food consumption and risk of overweight/obesity, type 2 diabetes mellitus, and hypertension in adults: a meta-analysis of observational studies |journal=Crit Rev Food Sci Nutr |volume=62 |issue=24 |pages=6809–6820 |date=2022 |pmid=33825582 |doi=10.1080/10408398.2021.1906626 |url=}}</ref> and obesity.<ref name=qin-diseases /><ref>{{cite journal |vauthors=Guallar-Castillón P, Rodríguez-Artalejo F, Fornés NS, Banegas JR, Etxezarreta PA, Ardanaz E, Barricarte A, Chirlaque MD, Iraeta MD, Larrañaga NL, Losada A, Mendez M, Martínez C, Quirós JR, Navarro C, Jakszyn P, Sánchez MJ, Tormo MJ, González CA |title=Intake of fried foods is associated with obesity in the cohort of Spanish adults from the European Prospective Investigation into Cancer and Nutrition |journal=Am J Clin Nutr |volume=86 |issue=1 |pages=198–205 |date=July 2007 |pmid=17616781 |doi=10.1093/ajcn/86.1.198 |url=|doi-access=free }}</ref>
=== Nutrition === Due to oil absorption during frying, the nutritional profile of the oil used becomes part of the final product; up to 75% of calories can be from fat in fried foods.<ref name="Changes in food" /> 15% of battered chicken or fish’s final weight is absorbed frying oil, compared to 20% when breaded. Doughnuts’ final weight is between 15{{ndash}}20% frying oil, and this figure increases to up to 35{{ndash}}40% for potato chips.<ref name="Industrial Frying">{{cite journal |last1=Rosseli |first1=J. B. |title=Industrial Frying Process |journal=Grasas y Aceites |date=30 August 1998 |volume=49 |issue=3-4 |doi=10.3989/gya.1998.v49.i3-4.729|url=https://grasasyaceites.revistas.csic.es/index.php/grasasyaceites/article/view/729 |access-date=3 April 2026|doi-access=free }}</ref>
Vitamins like thiamin, riboflavin, and vitamin A are unstable at high temperatures and vitamin C is water soluble, meaning they can be lost from fried foods during water evaporation. Vitamin A is particularly unstable{{mdash}}24% of vitamin A is destroyed during frying compared to 14% when boiled due to oxidation. Fibre increases in fried foods due to the formation of brown melanoidins, which form part of the crust. The proportion of protein also increases due to the concentrating effects of dehydration, with the exception of amino acid lysine due to its role in the Maillard reaction. Minerals increase in concentration in the same way, but this means that heavy metals found in some fish are also concentrated during frying.<ref name="Changes in food" />
=== Fume inhalation === Toxic compounds such as aldehydes (e.g. formaldehyde) are produced during frying and evaporate with steam, which can irritate lung tissue if inhaled.<ref name="Frying Fats Boskou"/> Fumes from frying have been classified as "probably carcinogenic to humans" by the International Agency for Research on Cancer.<ref name="Food Veg Oils">{{cite journal |last1=Abrante-Pascual |first1=Susana |last2=Nieva-Echevarría |first2=Barbara |last3=Goicoechea-Oses |first3=Encarnacion |title=Vegetable Oils and Their Use for Frying: A Review of Their Compositional Differences and Degradation |journal=Foods |date=23 December 2024 |volume=13 |issue=24 |pages=4186 |pmid=39767128 |url=https://pmc.ncbi.nlm.nih.gov/articles/PMC11675685/#B11-foods-13-04186 |access-date=13 May 2026}}</ref>
== Effects of oil == During frying, oil is exposed to water from food, high temperatures, and oxygen from the surroundings, which cause degradation. Hydrolysis causes an oil's smoke point to decrease and oxidation causes the formation of volatile compounds which change the flavour, quality, and texture of the food.<ref name="Chemistry of Oils"</> These are mostly toxic aldehydes, of which some amount is required to achieve a characteristic fried smell and taste.<ref name="Changes in food" /> Oils have varying proportions of saturated, monounsaturated, and polyunsaturated fats which change their performance during frying.<ref name="Chemistry of Oils">{{cite journal |last1=Choe |first1=E. |last2=Min |first2=D. B. |title=Chemistry of Deep-Fat Frying Oils |journal=Journal of Food Science |date=1 May 2007 |volume=72 |issue=5 |doi=10.1111/j.1750-3841.2007.00352.x |url=https://ift.onlinelibrary.wiley.com/doi/full/10.1111/j.1750-3841.2007.00352.x |access-date=13 May 2026}}</ref>
=== Monounsaturated fats ===
Rapeseed oil, also known as canola oil, is the third most used frying oil, especially in northern Europe, Japan, Oceania, and Canada. Despite mostly comprising monounsaturated fat, its high linolenic acid content makes it prone to oxidation. Peanut oil, also known as groundnut oil, is commonly used in west Africa but, unlike rapeseed oil, is low in linolenic acid.<ref name="Chemistry of Oils"</> Olive oil is stable at high temperatures because of its high monounsaturated fat and antioxidant content, which make it less likely to oxidise during frying and improves the nutritional content of fried foods.<ref name="Food Safety and Health" /> It degrades two times as slowly as sunflower oil and ten times as slowly as linseed oil. Its widespread use may be the cause of fried food consumption not being linked to increased mortality in Mediterranean countries.<ref name="Chemistry of Oils"</>
=== Polyunsaturated fats === Polyunsaturated fats are most prone to oxidation and polymerisation, which form toxic compounds that are absorbed by food.<ref name="Chemistry of Oils"</> A 2022 WHO review and meta-analysis of 170 studies found that polyunsaturated fat consumption reduced overall mortality, but that higher quality evidence was needed.<ref>{{cite book |last1=J. de Souza |first1=Russell |last2=A. Zulyniak |first2=Michael |last3=Kazemi |first3=Mina |last4=Ali |first4=Rahim |last5=Bierbrier |first5=Rachel |last6=Williams |first6=Natalie |last7=Stennett |first7=Rosain |last8=Banfield |first8=Laura |title=Polyunsaturated fatty acids intake and risk of all-cause mortality, cardiovascular disease, breast cancer, mental health, and type 2 diabetes |date=2022 |publisher=World Health Organisation |isbn=978-92-4-006164-4 |url=https://iris.who.int/server/api/core/bitstreams/18dccfe5-6d1a-426c-a99a-29b664ee371e/content |access-date=6 May 2026}}</ref> Sunflower oil is most commonly used in eastern Europe. Despite being a source of vitamin E, its high polysaturated fat content makes it poor for frying. Sunflower oil is sold with added oleic acid to increase its monounsaturated fat content and therefore its stability.<ref name="Chemistry of Oils"</>
=== Saturated fats ===
Palm oil is the most common oil, especially in subsaharan Africa, southeast Asia, and some parts of South America. Its saturated and unsaturated fat content are nearly equal, but is slightly more saturated. It has a high palmitic acid content, which is linked to heart disease.<ref name="Chemistry of Oils"</>
=== Oil reuse === Oil is reused in industrial frying to reduce costs, but prolonged use causes oxidation, producing aldehydes that affect flavour and increase cancer risks.<ref name="Food Safety and Health" /> Unsaturated fats oxidise more quickly than saturated fats, and oils with high linolenic acid content can smell fishy.<ref name="Changes in food" /><ref name="Chemistry of Oils"</> Oil reuse reduces the nutritional value of foods and increases saturated and trans fats while reducing monounsaturated and polyunsaturated fats.<ref name="Food Safety and Health" /> Foods fried in reused oil absorb more.<ref name="Changes in food" />
=== Fire risks === Oil or fat with a smoke point below {{convert|200|C|F}} may foam and rise, spilling and causing a fire. Foaming can be distinguished from bubbles caused by water evaporation because the foam covers the whole surface of the oil, not just above the food.<ref name="Industrial Frying" /> Blended oils are more prone to foaming.<ref name="Frying Fats Boskou" /> Oil with a flash point below {{convert|315|C|F}} may explode.<ref name="Industrial Frying" />
== Gallery == <gallery widths="200px" heights="200px"> Gordurema.jpg|Fried polenta, French fries, and fried chicken at a Brazilian eatery Pakoras in Jaipur.jpg|Pakora is a fried snack, popular throughout the Indian subcontinent, served in Jaipur, India. Guasteddra dolce Caltanissetta 01.jpg|Guastedde a fried Sicilian dessert, in a shop window </gallery>
== See also == {{Portal|Food}} {{Div col|colwidth=35em}} * Air fryer * Vacuum fryer * List of fried dough foods {{div col end}}
==Notes== {{reflist|group=lower-alpha}}
==References== {{Reflist}}
==External links== {{Cookbook}} *{{Commons category-inline}} {{Cooking techniques}}
Category:Cooking techniques Category:Food preparation techniques Category:Culinary terminology Category:Fried foods