Cooking oil#Refinement

While consumption of small amounts of saturated fats is common in diets,{{cite journal|journal=J Clin Med Res|year=2015 |volume=7|issue=3|pages=145–9|doi=10.14740/jocmr2030w|pmid=25584098|title= Effects of Dietary Fat Intake on HDL Metabolism|vauthors=Yanai H, Katsuyama H, Hamasaki H, Abe S, Tada N, Sako A|display-authors=3|pmc=4285059}} meta-analyses found a significant correlation between high consumption of saturated fats and blood LDL concentration,{{cite journal |pmid=9006469 |year=1997 |last1=Clarke |first1=R |last2=Frost |last3=Collins |last4=Appleby |last5=Peto |title=Dietary lipids and blood cholesterol: quantitative meta-analysis of metabolic ward studies |volume=314 |issue=7074 |pages=112–7 |journal=BMJ |first2=C |first3=R |first4=P |first5=R |display-authors=3|pmc=2125600 |doi=10.1136/bmj.314.7074.112}} a risk factor for cardiovascular diseases.{{cite journal |pmid=12716665 |year=2003 |last1=Mensink |first1=RP |last2=Zock |last3=Kester |last4=Katan |title=Effects of dietary fatty acids and carbohydrates on the ratio of serum total to HDL cholesterol and on serum lipids and apolipoproteins: a meta-analysis of 60 controlled trials |volume=77 |issue=5 |pages=1146–55 |journal=Am J Clin Nutr |first2=PL |first3=AD |first4=MB|doi=10.1093/ajcn/77.5.1146 |doi-access=free }} Other meta-analyses based on cohort studies and on controlled, randomized trials found a positive,{{cite journal |last1=Jakobsen |first1=M. U |last2=O'Reilly |first2=E. J |last3=Heitmann |first3=B. L |last4=Pereira |first4=M. A |last5=Balter |first5=K. |last6=Fraser |first6=G. E |last7=Goldbourt |first7=U. |last8=Hallmans |first8=G. |last9=Knekt |first9=P. |display-authors=3|title=Major types of dietary fat and risk of coronary heart disease: a pooled analysis of 11 cohort studies |journal=American Journal of Clinical Nutrition |volume=89 |issue=5 |pages=1425–32 |year=2009 |pmid=19211817 |pmc=2676998 |doi=10.3945/ajcn.2008.27124}} or neutral,{{cite journal |last1=Katan |first1=Martijn B. |last2=Mozaffarian |first2=Dariush |last3=Micha |first3=Renata |last4=Wallace |first4=Sarah |title=Effects on Coronary Heart Disease of Increasing Polyunsaturated Fat in Place of Saturated Fat: A Systematic Review and Meta-Analysis of Randomized Controlled Trials |journal=PLOS Medicine |volume=7 |issue=3 |pages=e1000252 |year=2010 |pmid=20351774 |pmc=2843598 |doi=10.1371/journal.pmed.1000252 |editor1-last=Katan |editor1-first=Martijn B. |doi-access=free }} effect from consuming polyunsaturated fats instead of saturated fats (a 10% lower risk for 5% replacement).

Mayo Clinic has highlighted certain oils that are high in saturated fats, including coconut, palm oil and palm kernel oil. Those having lower amounts of saturated fats and higher levels of unsaturated (preferably omega-3) fats like olive oil, peanut oil, canola oil, soy and cottonseed oils are generally healthier.{{cite web|url=http://www.mayoclinic.com/health/fat/NU00262|title=Dietary fats: Know which types to choose|publisher=Mayo Clinic Staff|date=2015}} The US National Heart, Lung and Blood Institute{{cite web|url=http://www.nhlbi.nih.gov/chd/Tipsheets/satfat.htm|title=Choose foods low in saturated fat|publisher=National Heart, Lung, and Blood Institute (NHLBI), NIH Publication No. 97-4064. 1997|access-date=2009-09-28|archive-url=https://web.archive.org/web/20091213184426/http://www.nhlbi.nih.gov/chd/Tipsheets/satfat.htm|archive-date=2009-12-13|url-status=dead}} urged saturated fats be replaced with polyunsaturated and monounsaturated fats, listing olive and canola oils as sources of healthier monounsaturated oils while soybean and sunflower oils as good sources of polyunsaturated fats. One study showed that consumption of non-hydrogenated unsaturated oils like soybean and sunflower is preferable to the consumption of palm oil for lowering the risk of heart disease.{{cite journal|last1=Kabagambe|name-list-style=amp |url=http://jn.nutrition.org/cgi/content/abstract/135/11/2674|first1=EK |last2=Baylin|first2=A|last3=Ascherio|first3=A|last4=Campos|first4=H|title=The Type of Oil Used for Cooking Is Associated with the Risk of Nonfatal Acute Myocardial Infarction in Costa Rica|journal=Journal of Nutrition|volume=135|edition=135|issue=11|pages=2674–2679 |date=November 2005|pmid=16251629|doi=10.1093/jn/135.11.2674 |doi-access=free}}

Cashew oil and other nut-based oils do not present a danger to persons with a nut allergy, because oils are primarily lipids, and allergic reactions are due to surface proteins on the nut.{{cite book | last = Urry | title = Campbell Biology | publisher = Pearson}}

The seeds of most cultivated plants contain higher levels of omega-6 fatty acids than omega-3, with some notable exceptions. Growth at colder temperatures tends to result in higher levels of omega-3 fatty acids in seed oils.{{cite journal |last1=Sands |first1=David C. |last2=Morris |first2=Cindy E. |last3=Dratz |first3=Edward A. |last4=Pilgeram |first4=Alice |title=Elevating optimal human nutrition to a central goal of plant breeding and production of plant-based foods |journal=Plant Sci. |date=2009 |volume=117 |issue=5 |pages=377–389 |doi=10.1016/j.plantsci.2009.07.011|pmid=20467463 |pmc=2866137 }}

{{Main|Trans fat}}

Unlike other dietary fats, trans fats are not essential, and they do not promote good health.{{cite book | last = Food and nutrition board, institute of medicine of the national academies | title = Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients) | publisher = National Academies Press | year = 2005 | page = [https://archive.org/details/isbn_9780309085250/page/423 423] | url = https://archive.org/details/isbn_9780309085250/page/423 | isbn = 978-0-309-08537-3 }} The consumption of trans fats increases one's risk of coronary heart disease{{cite book | last = Food and nutrition board, institute of medicine of the national academies | title = Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients) | publisher = National Academies Press | year = 2005 | page = [https://archive.org/details/isbn_9780309085250/page/504 504] | url = https://archive.org/details/isbn_9780309085250/page/504 | isbn = 978-0-309-08537-3 }}{{dead link|date=August 2017 |bot=InternetArchiveBot |fix-attempted=yes }} by raising levels of LDL cholesterol and lowering levels of HDL cholesterol.{{cite web | title = Trans fat: Avoid this cholesterol double whammy | publisher = Mayo Foundation for Medical Education and Research (MFMER). | url = http://www.mayoclinic.com/health/trans-fat/CL00032 | access-date = 2007-12-10 }} Trans fats from partially hydrogenated oils are more harmful than naturally occurring oils.{{cite journal |last1=Mozaffarian |first1=Dariush |last2=Katan |first2=Martijn B. |last3=Ascherio |first3=Alberto |last4=Stampfer |first4=Meir J. |last5=Willett |first5=Walter C. |display-authors=3|title=Trans Fatty Acids and Cardiovascular Disease |journal=New England Journal of Medicine |volume=354 |pages=1601–113 |year=2006 |doi=10.1056/NEJMra054035 |pmid=16611951 |issue=15}}

Several large studies{{cite journal |doi=10.1016/0140-6736(93)90350-P |last1=Willett |first1=WC |last2=Stampfer |first2=MJ |last3=Manson |first3=JE |last4=Colditz |first4=GA |last5=Speizer |first5=FE |last6=Rosner |first6=BA |last7=Sampson |first7=LA |last8=Hennekens |first8=CH |display-authors=3|title=Intake of trans fatty acids and risk of coronary heart disease among women |journal=Lancet |volume=341 |issue=8845 |pages=581–5 |year=1993 |pmid=8094827|s2cid=2616254 }}{{cite journal |last1=Hu |first1=Frank B. |last2=Stampfer |first2=Meir J. |last3=Manson |first3=Joann E. |last4=Rimm |first4=Eric |last5=Colditz |first5=Graham A. |last6=Rosner |first6=Bernard A. |last7=Hennekens |first7=Charles H. |last8=Willett |first8=Walter C. |display-authors=3 |title=Dietary Fat Intake and the Risk of Coronary Heart Disease in Women |journal=New England Journal of Medicine |volume=337 |issue=21 |pages=1491–9 |year=1997 |pmid=9366580 |doi=10.1056/NEJM199711203372102|doi-access=free }}{{cite journal |last1=Hayakawa |first1=Kyoko |last2=Linko |first2=Yu-Yen |last3=Linko |first3=Pekka |title=The role of trans fatty acids in human nutrition |journal=Starch - Stärke |volume=52 |pages=229–35 |year=2000 |doi=10.1002/1521-379X(200007)52:6/7<229::AID-STAR229>3.0.CO;2-G |issue=6–7}}[http://www.channing.harvard.edu/nhs/ The Nurses' Health Study (NHS)] indicate a link between the consumption of high amounts of trans fat and coronary heart disease, and possibly some other diseases. The United States Food and Drug Administration (FDA), the National Heart, Lung and Blood Institute and the American Heart Association (AHA) all have recommended limiting the intake of trans fats. In the US, trans fats are no longer "generally recognized as safe", and cannot be added to foods, including cooking oils, without special permission.{{cite web|url=https://www.fda.gov/food/ingredientspackaginglabeling/foodadditivesingredients/ucm449162.htm |title=Final Determination Regarding Partially Hydrogenated Oils (Removing Trans Fat) |website=Food and Drug Administration |access-date=March 29, 2019}}

File:Marchand d’huile a Lisbonne (âne en profil).jpg

File:Olive oil.jpg

File:Sunflowerseed oil.jpg oil]]

Heating, as well as heating vessels rapidly change characteristics of cooking oil.{{Cite journal|last1=Doureradjou|first1=P.|last2=Koner|first2=Bidhan Chandra|date=2008|title=Effect of Different Cooking Vessels on Heat Induced Lipid Peroxidation of Different Edible Oils|journal=Journal of Food Biochemistry|language=en|volume=32|issue=6|pages=740–751|doi=10.1111/j.1745-4514.2008.00195.x|issn=1745-4514|doi-access=free}} Oils that are healthy at room temperature can become unhealthy when heated above certain temperatures, especially when heating repeatedly. The toxic risk is linked to oxidation of fatty acids and fatty acids with higher levels of unsaturation are oxidized more rapidly during heating in air.[https://www.ift.org/news-and-publications/food-technology-magazine/issues/2018/may/features/do-cooking-oils-present-a-health-risk Crosby (2018) Do Cooking Oils Present a Health Risk?]

So, when choosing a cooking oil, it is important to match the oil's heat tolerance with the temperature which will be used.{{cite journal | url=https://www.thefreelibrary.com/Oil+right%3a+choose+wisely+for+heart-healthy+cooking.+(Eating+Right).-a098469943 | title=Oil right: choose wisely for heart-healthy cooking - Eating Right | journal=E: The Environmental Magazine | author=Orna Izakson}} and to change frying oil a few times per week.

Deep-fat frying temperatures are commonly in the range of {{convert|170-190|C|F}}, less commonly, lower temperatures ≥ {{convert|130|C|F}} are used.

Palm oil contains more saturated fats than canola oil, corn oil, linseed oil, soybean oil, safflower oil, and sunflower oil. Therefore, palm oil can withstand deep frying at higher temperatures and is resistant to oxidation compared to high-polyunsaturated vegetable oils.{{cite journal |doi=10.1002/ejlt.200600192 |title=Frying performance of a sunflower/palm oil blend in comparison with pure palm oil |year=2007 |last1=De Marco |first1=Elena |last2=Savarese |last3=Parisini |last4=Battimo |last5=Falco |last6=Sacchi |journal=European Journal of Lipid Science and Technology |volume=109 |pages=237–246 |first2=Maria |first3=Cristina |first4=Ilaria |first5=Salvatore |first6=Raffaele |issue=3 |url=https://www.academia.edu/download/35415139/de_marco_et_al._frying.pdf }}{{dead link|date=July 2022|bot=medic}}{{cbignore|bot=medic}} Since the 1900s, palm oil has been increasingly added into food by the global commercial food industry because it remains stable in deep frying, or in baking at very high temperatures,{{cite journal |doi=10.1111/j.1745-4522.1999.tb00142.x |year=1999 |last1=Che Man |first1=YB |last2=Liu |last3=Jamilah |title=Quality changes of RBD palm olein, soybean oil and their blends during deep-fat frying |volume=6 |issue=3 |pages=181–193 |journal=Journal of Food Lipids |first2=J.L. |first3=B. |last4=Rahman |first4=R. Abdul}}{{cite journal |doi=10.1002/ejlt.200600294 |title=Use of palm oil for frying in comparison with other high-stability oils |year=2007 |last1=Matthäus |first1=Bertrand |journal=European Journal of Lipid Science and Technology |volume=109 |pages=400–409 |issue=4}} and for its high levels of natural antioxidants, though the refined palm oil used in industrial food has lost most of its carotenoid content (and its orange-red color).{{cite journal|url=http://apjcn.nhri.org.tw/server/apjcn/12/3/355.pdf |year=2003 |last1=Sundram |first1=K |last2=Sambanthamurthi |last3=Tan |title=Palm fruit chemistry and nutrition |volume=12 |issue=3 |pages=355–62 |journal=Asia Pacific Journal of Clinical Nutrition |first2=R |first3=YA|pmid=14506001}}

The following oils are suitable for high-temperature frying due to their high smoke point:

• Avocado oil
• Mustard oil
• Palm oil
• Peanut oil (marketed as "groundnut oil" in the UK and India)
• Rice bran oil
• Safflower oil
• Olive oil
• Semi-refined sesame oil
• Semi-refined sunflower oil{{cite web |url= http://www.cookingforengineers.com/article/50/Smoke-Points-of-Various-Fats |title=Smoke Points of Various Fats - Kitchen Notes - Cooking For Engineers |work=cookingforengineers.com |year=2012 |access-date=July 3, 2012}}

Less aggressive frying temperatures are frequently used. A quality frying oil has a bland flavor, at least {{Convert|200|C|F}} smoke and {{Convert|315|C|F}} flash points, with maximums of 0.1% free fatty acids and 3% linolenic acid.{{cite journal |author=Rossell, J.B. |year=1998 |title=Industrial frying process |journal=Grasas y Aceites |volume=49 |issue=3–4 |pages=282–295 |url=http://grasasyaceites.revistas.csic.es/index.php/grasasyaceites/article/viewFile/729/742|doi=10.3989/gya.1998.v49.i3-4.729 |doi-access=free }} Those oils with higher linolenic fractions are avoided due to polymerization or gumming marked by increases in viscosity with age. Olive oil resists thermal degradation and has been used as a frying oil for thousands of years.{{cite book |author=Boskou, Dimitrios |year=2010 |title=Chemical and functional properties of food lipids |chapter=21 Frying Fats |pages=429 |chapter-url=https://www.researchgate.net/publication/259575170}}

All oils degrade in response to heat, light, and oxygen. To delay the onset of rancidity, a blanket of an inert gas, usually nitrogen, is applied to the vapor space in the storage container immediately after production – a process called tank blanketing.{{Citation needed|date=July 2021}}{{Cite journal |last1=Mishra |first1=Sundeep |last2=Manchanda |first2=S.C. |date=Feb 2012 |title=Cooking oils for heart health |url=https://ajeevan.in/Cooking-oils-for-heart-health.pdf |journal=J Prev Cardiol |volume=1 |issue=3 |pages=123–131 |via=Google Scholar |access-date=2022-06-21 |archive-date=2022-08-14 |archive-url=https://web.archive.org/web/20220814132901/https://ajeevan.in/Cooking-oils-for-heart-health.pdf |url-status=dead }}

In a cool, dry place, oils have greater stability, but may thicken, although they will soon return to liquid form if they are left at room temperature. To minimize the degrading effects of heat and light, oils should be removed from cold storage just long enough for use.{{Citation needed|date=July 2021}}

Refined oils high in monounsaturated fats, such as macadamia oil, keep up to a year, while those high in polyunsaturated fats, such as soybean oil, keep about six months. Rancidity tests have shown that the shelf life of walnut oil is about 3 months, a period considerably shorter than the best before date shown on labels.{{Cite journal|title = Oxidative stability and shelf-life evaluation of selected culinary oils|journal = International Journal of Food Sciences and Nutrition|date = 2009-01-01|issn = 1465-3478|pmid = 19634067|pages = 289–296|volume = 60|doi = 10.1080/09637480903103774|first1 = S. Parkash|last1 = Kochhar|first2 = C. Jeya K.|last2 = Henry| issue=Suppl 7 |s2cid = 44352150}}

By contrast, oils high in saturated fats, such as avocado oil, have relatively long shelf lives and can be safely stored at room temperature, as the low polyunsaturated fat content facilitates stability.

Cooking oils are composed of various fractions of fatty acids.{{cite book |title=Lipid Biotechnology |author1=Kuo, T.M. |author2=Gardner, H. |isbn=9780824744182 |lccn=2001058440 |url=https://books.google.com/books?id=o_dOSHGDYgAC |year=2002 |publisher=Taylor & Francis |page=1 }} For the purpose of frying food, oils high in monounsaturated or saturated fats are generally popular, while oils high in polyunsaturated fats are less desirable.{{cite journal |last=Bouchon |first=Pedro |year=2009 |title=Chapter 5 - Understanding Oil Absorption During Deep-Fat Frying |journal=Advances in Food and Nutrition Research |volume=57 |pages=209–34 |issn=1043-4526 |doi=10.1016/S1043-4526(09)57005-2 |pmid=19595388 |url=https://www.researchgate.net/publication/26664126|isbn=9780123744401 }} High oleic acid oils include almond, macadamia, olive, pecan, pistachio, and high-oleic cultivars of safflower and sunflower.{{sfnp|The Lipid Handbook|2007|p=4}}

Cold-Pressed vs. Refined Cooking Oils

Cold-pressed oils are extracted mechanically without the use of heat or chemical solvents, preserving nutrients and natural flavors, whereas refined oils undergo additional processes like bleaching and deodorization, which can strip beneficial compounds.{{Cite web |date=2024-12-17 |title=Cold-Pressed vs Refined Cooking Oils: Which is Healthier for Your Family? {{!}} Adya Organics |url=https://adyaorganics.com/cold-pressed-vs-refined-cooking-oils-which-is-healthier-for-your-family/ |access-date=2024-12-17 |language=en-US}}{{Principal fatty acids of common cooking oils}}

The smoke point is marked by "a continuous wisp of smoke".{{sfnp|Vegetable Oils in Food Technology|2011|p=122}} It is the temperature at which an oil starts to burn, leading to a burnt flavor in the foods being prepared and degradation of nutrients and phytochemicals characteristic of the oil.

Above the smoke point are flash and fire points.{{sfnp|Vegetable Oils in Food Technology|2011|p=122}} The flash point is the temperature at which oil vapors will ignite but are not produced in sufficient quantities to stay lit. The flash point generally occurs at about {{convert|275-330|C|F}}.{{sfnp|Vegetable Oils in Food Technology|2011|p=90}} The fire point is the temperature at which hot oil produces sufficient vapors they will catch on fire and burn.{{sfnp|Vegetable Oils in Food Technology|2011|p=90}} As frying hours increase, all these temperature points decrease.{{sfnp|Vegetable Oils in Food Technology|2011|p=90}} They depend more on an oil's acidity than fatty-acid profile.{{sfnp|Vegetable Oils in Food Technology|2011|p=149}}

The smoke point of cooking oils varies generally in association with how oil is refined: a higher smoke point results from removal of impurities and free fatty acids.{{cite web|author1=Beck, Leslie|title='Smoke point' matters when cooking with oil|url=https://www.theglobeandmail.com/life/health-and-fitness/health/smoke-point-matters-in-cooking-with-oil/article26569060/|publisher=The Globe and Mail|access-date=11 April 2017|location=Toronto, Canada|date=28 September 2015}} Residual solvent remaining from the refining process may decrease the smoke point.{{sfnp|Vegetable Oils in Food Technology|2011|p=149}} It has been reported to increase with the inclusion of antioxidants (BHA, BHT, and TBHQ). For these reasons, the published smoke points of oils may vary.{{sfnp|Vegetable Oils in Food Technology|2011|p=149}}

{{Smoke_point_of_cooking_oils}}

Oils are extracted from nuts, seeds, olives, grains or legumes by extraction using industrial chemicals or by mechanical processes. Expeller pressing is a chemical-free process that collects oils from a source using a mechanical press with minimal heat. Cold-pressed oils are extracted under a controlled temperature setting usually below {{convert|105|°C|°F|abbr=on}} intended to preserve naturally occurring phytochemicals, such as polyphenols, tocotrienols, plant sterols and vitamin E which collectively affect color, flavor, aroma and nutrient value.{{cite book |last1=Ramadan |first1=Mohamed |title=Cold Pressed Oils: Green Technology, Bioactive Compounds, and Applications |date=2020 |publisher=Academic Press |page=311 |isbn=9780128181898 |url=https://books.google.com/books?id=X1TODwAAQBAJ&pg=PA311}}

{{Types of cooking oils and fats}}

{{Fat composition in different foods}}