How to Reuse Olive Oil for Sautéing and Frying

Deep frying with olive oil is healthier than frying with other oils, and it can be reused several times, with some caution, to reduce waste and enhance flavors.

By Paolo DeAndreis
Jul. 7, 2023 00:08 UTC
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Consumers are increas­ingly aware of olive oil’s health ben­e­fits. While many use olive oil to pan-fry or sauté at home, only a frac­tion of deep-fry­ing enthu­si­asts turn to olive oil.

Still, a grow­ing body of research shows that olive oils are the most bal­anced, safe and healthy fat for both pan-fry­ing and deep-fry­ing.

Moreover, when reusing fry­ing oil more than once, noth­ing is bet­ter than olive oil.

See Also:Olive Oil Basics

I do not usu­ally deep fry at home, but should I do that, I would cer­tainly use olive oil, which I com­monly use for all of our house­hold cook­ing,” Guy Crosby, a pro­fes­sor at the Harvard T.H.Chan School of Public Health’s nutri­tion depart­ment, told Olive Oil Times.

One of the rea­sons many shun olive oils for deep-fry­ing is their rel­a­tively higher prices than other com­mon cook­ing oils.

Whether it is canola oil, corn oil or sun­flower oil, most cook­ing oils usu­ally come with a lower price tag than olive oil, let alone the high­est grade: extra vir­gin olive oil.

On top of that, fry­ing oils are cum­ber­some, as rel­e­vant vol­umes are used for deep-fry­ing and need to be ade­quately dis­posed of after use. This, and their price tag, make reusing fry­ing oils a highly sen­si­tive sub­ject.

Why EVOO’s unique pro­file makes it the best deep-fry­ing oil

In the past few decades, many researchers have focussed on how olive oil is affected by fry­ing.

For exam­ple, a 2022 study pub­lished in Food Chemistry found that fry­ing with vir­gin olive oil results in French fries with some of the oil’s healthy qual­i­ties; fry­ing with vir­gin olive oil proved to be more ben­e­fi­cial than using less antiox­i­dant-rich cook­ing oils to fry.

The antiox­i­dants in extra vir­gin olive oil and unique anti-inflam­ma­tory com­pounds such as oleo­can­thal make it the ideal can­di­date for deep-fry­ing.

Olive oil and extra vir­gin olive oils are cer­tainly used for deep-fat fry­ing, and you can cer­tainly reuse them, as they are some of the most sta­ble fry­ing oils that you can buy,” Crosby said.

When sautéing or fry­ing, all veg­etable oils are sub­jected to mod­i­fi­ca­tion and oxi­da­tion. These reac­tions are mit­i­gated in olive oils because of the high pres­ence of monoun­sat­u­rated oleic acid.

See Also:Cooking With Extra Virgin Olive Oil

Extra vir­gin and vir­gin olive oils also boast a high vol­ume of antiox­i­dant polyphe­nols, such as tyrosol and hydrox­y­ty­rosol. In dif­fer­ent mea­sures, they show resilience to fry­ing.

Crosby cited a lab exper­i­ment that showed how fry­ing pota­toes in vir­gin olive oil for 10 min­utes at 180 °C (356 ºF) halved hydrox­y­ty­rosol lev­els, which fell to 10 per­cent of the orig­i­nal amount after being reused for fry­ing six times.

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On the other hand, tyrosol degraded by only 20 per­cent even after being reused for fry­ing 12 times.

What hap­pens there is that the antiox­i­dants in vir­gin olive oils pro­tect the fatty acids from oxi­da­tion,” Crosby said.

Oxidation

In the con­text of health and biol­ogy, oxi­da­tion refers to a process that occurs in the body involv­ing the pro­duc­tion of reac­tive oxy­gen species (ROS) or free rad­i­cals. These are highly reac­tive mol­e­cules that con­tain oxy­gen and can cause dam­age to cells, tis­sues, and bio­log­i­cal mol­e­cules like pro­teins, lipids, and DNA.

Oxidative stress is a con­di­tion that arises when there is an imbal­ance between the pro­duc­tion of ROS and the body’s antiox­i­dant defenses. Normally, the body has built-in defense mech­a­nisms, such as antiox­i­dants, that help neu­tral­ize and remove ROS. However, when there is an excess of ROS or a defi­ciency in antiox­i­dants, oxida­tive stress can occur.

Oxidative stress has been impli­cated in var­i­ous health con­di­tions and dis­eases, includ­ing aging, car­dio­vas­cu­lar dis­eases, neu­rode­gen­er­a­tive dis­or­ders (such as Alzheimer’s and Parkinson’s), can­cer, dia­betes, and inflam­ma­tory con­di­tions. ROS can ini­ti­ate chain reac­tions that dam­age cel­lu­lar struc­tures and impair nor­mal cel­lu­lar func­tions, lead­ing to tis­sue dam­age and dis­ease pro­gres­sion.

Antioxidants, both endoge­nous (pro­duced within the body) and exoge­nous (obtained from diet or sup­ple­ments), play a cru­cial role in com­bat­ing oxida­tive stress by neu­tral­iz­ing ROS and min­i­miz­ing their harm­ful effects. Common antiox­i­dants include vit­a­mins C and E, beta-carotene, sele­nium, and var­i­ous phy­to­chem­i­cals found in fruits, veg­eta­bles, and other plant-based foods.

Maintaining a bal­ance between oxida­tive stress and antiox­i­dants is impor­tant for over­all health and well-being. Lifestyle fac­tors such as a healthy diet rich in antiox­i­dants, reg­u­lar exer­cise, stress man­age­ment, and avoid­ing expo­sure to envi­ron­men­tal tox­ins can help mit­i­gate oxida­tive stress and pro­mote good health.

While re-use for deep fry­ing will even­tu­ally decrease polyphe­nols and antiox­i­dants found in EVOOs, this will only par­tially affect a cru­cial anti-inflam­ma­tory agent found in EVOO and in vir­gin olive oils only, which is oleo­can­thal,” Crosby said.

Oleocanthal is one of the most inter­est­ing phe­no­lic com­po­nents of extra vir­gin olive oil.

Its impact on health is the sub­ject of many ongo­ing stud­ies. Those stud­ies show evi­dence of highly sig­nif­i­cant effects, from its anti-can­cer prop­er­ties to pre­vent­ing neu­rode­gen­er­a­tive dis­or­ders.

Even if heated for long peri­ods at very high tem­per­a­tures, such as 240 °C (464 ºF) in a lab exper­i­ment, oleo­can­thal only par­tially degrades its bio­log­i­cal activ­ity.

How to safely reuse EVOOs for deep-fry­ing

Reusing extra vir­gin olive oils for deep fry­ing requires the same care when other fry­ing fats are brought into play.

When food is deep-fried, some of its par­ti­cles end up in the fry­ing oil, con­t­a­m­i­nat­ing it. To reuse it more than once, oil should then be care­fully fil­tered. Contamination is a major aspect to con­sider,” Crosby noted.

Think of what might hap­pen in some fast foods. If you do not ade­quately fil­ter and change what­ever fry­ing oils you are using, if you do not keep it fresh, that can become an issue,” he added, refer­ring to research link­ing exces­sive con­sump­tion of fast foods’ fried serv­ings to heart prob­lems.

See Also:Extra Virgin Olive Oil Better for Frying Fish

Correctly fil­ter­ing deep fry­ing oil before reuse is cru­cial, as this pre­vents those oil’s smoke points from being reduced dra­mat­i­cally after each use.

The smoke point for fil­tered extra vir­gin olive oil is 207 °C (405 ºF), which is well above the deep-fry­ing tem­per­a­ture, which rarely exceeds 190 °C (374 ºF). The smoke point is highly rel­e­vant as triglyc­eride mol­e­cules break apart, and the toxic acrolein alde­hyde is formed above this thresh­old.

Extra vir­gin olive oil has a rea­son­ably high smok­ing point,” Crosby said. But again, the more any fry­ing oil is used, the more con­t­a­m­i­nated it will be from the food or the mois­ture of the food and more. As food par­ti­cles decom­pose and oxi­dize, the smoke point will decrease sub­stan­tially each time.”

This is also why fil­tered EVOOs have a higher smok­ing point than unfil­tered prod­ucts, as the lat­ter will con­tain olive par­ti­cles.

Keeping track of oxi­da­tion while deep-fry­ing once or more

EVOOs and refined olive oils come with dif­fer­ent price tags. They also bear sig­nif­i­cant dif­fer­ences in their qual­ity pro­files. These dif­fer­ences emerge when con­sid­er­ing deep-fry­ing and olive oil reuse.

Among cook­ing olive oils, extra vir­gin olive oil shows higher sta­bil­ity dur­ing cook­ing or fry­ing due to the sig­nif­i­cant pres­ence of antiox­i­dants.

See Also:Study Links Cooking Methods and Health

The oxi­da­tion process leads to the release of spe­cific com­pounds, which can impact health. Oxidation in a deep fat fryer is a sig­nif­i­cant issue,” Crosby said. Vegetable oils other than EVOOs com­monly used for fry­ing, such as soy­bean or canola oils, tend to oxi­dize a lot.”

The oxi­da­tion prod­ucts have not been thor­oughly proven to con­sti­tute a health haz­ard,” he added. Yet, it is pretty well accepted that such oxi­da­tion prod­ucts are a health risk as they begin to build up.”

Thanks to its polyphe­nols, EVOO tends to build up much fewer oxi­da­tion prod­ucts, allow­ing it to be reused at least sev­eral times before hav­ing to dis­card it and change it,” Crosby noted.

What about deep-fry­ing with the so-called light olive oils?

Refined olive oils are often sold as light” olive oil, and pro­duc­ers encour­age their use in sautéing and deep fry­ing.

These prod­ucts are usu­ally cheaper than extra vir­gin olive oil. They are meant to bring olive oil to the house­hold with­out the more robust fla­vors usu­ally found in vir­gin or extra vir­gin olive oil (which are pro­vided by polyphe­nols).

Some of those light olive oils that are usu­ally fil­tered might even have a higher smok­ing point than extra vir­gin olive oil,” Crosby said.

That is a favor­able char­ac­ter­is­tic when used in a deep fat fryer, but, on the other hand, they lack the polyphe­nols and antiox­i­dants of extra vir­gin olive oil,” he added.

The refined olive oil pro­duc­tion process implies using heat and chem­i­cals which allow the extrac­tion of oil from olives that have already been pressed. Such pro­duc­tion process reduces sub­stan­tially the healthy con­tents,” Crosby said.

That means that if you switch to the light olive oil, you are los­ing the health ben­e­fits of the high con­tent of polyphe­nols in extra vir­gin olive oil,” he con­cluded.


Know the Basics

Things to know about olive oil, from the Olive Oil Times Education Lab.

  • Extra vir­gin olive oil (EVOO) is sim­ply juice extracted from olives with­out any indus­trial pro­cess­ing or addi­tives. It must be bit­ter, fruity and pun­gent — and free of defects.

  • There are hun­dreds of olive vari­eties used to make oils with unique sen­sory pro­files, just as many vari­eties of grapes are used in wines. An EVOO can be made with just one vari­ety (mono­va­ri­etal) or sev­eral (blend).

  • Extra vir­gin olive oil con­tains healthy phe­no­lic com­pounds. Substituting a mere two table­spoons of EVOO per day instead of less healthy fats has been shown to improve health.

  • Producing high-qual­ity extra vir­gin olive oil is an excep­tion­ally dif­fi­cult and costly task. Harvesting olives ear­lier retains more nutri­ents and extends shelf life, but the yield is far less than that of fully ripe olives that have lost much of their healthy com­pounds.


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