Deep frying

[Miss Chicken]

One of my sons has just bought a deep fryer which is something I have never owned. He has just asked me how many times he can re-use cooking/vegetable oil before he has to throw it out and put new cooking oil in. Can anyone tell me?

Myself, I only stir-fry with a little olive oil.

 

[MollyRoger]

One of my sons has just bought a deep fryer which is something I have never owned. He has just asked me how many times he can re-use cooking oil before he has to throw it out and put new cooking oil in. Can anyone tell me?

Myself, I only stir-fry with a little olive oil.

I saw on a the food network there's a place that has used the same vat of oil for over 50 years. As long as you strain the junk out, they say it's good.

 

[Capn Flukie]

Seeing 'Deep Frying Miss Chicken' is a little scary.

 

[CorporalClegg]

As long as you strain the junk out, they say it's good.

Except that's the hard part. You have to get everything or it'll start to solidify and start to sink.

It also depends on how much it gets used as heating it helps to keep it "cycled" (for lack of a better term).

I would say for normal household use change it weekly or bi-weekly at the most.

 

[Trekker4747]

It's a complicated answer. I would say no more than 3 or 4 times but as long as the oil never reaches its smoke point it can -theoreticaly- be used indefintely as long as its peroidclay strained through cheese cloth. I would make frying any fish in it the "last use" unless you want everything cooked in it afterwards to have a fishy taste. Really, that could probably be said for any fried meats.

But, all and all, I'd say four uses would be a good time to change it.

 

[Kirby]

I believe I heard Alton Brown say that you can use it up to three times, but you need to strain it through some cheese cloth after every use.
I had a roommate in college that would deep fry stuff every so often using a big cast iron pot. It stank up the apartment and made an awful mess everytime. Nasty stuff. Tasty, but nasty.

 

[USS Triumphant]

Seeing 'Deep Frying Miss Chicken' is a little scary.

Actually, it sounds like what my wife is cooking right now, and delicious.

 

[Amaris]

One of my sons has just bought a deep fryer which is something I have never owned. He has just asked me how many times he can re-use cooking/vegetable oil before he has to throw it out and put new cooking oil in. Can anyone tell me?

Myself, I only stir-fry with a little olive oil.

Can you do it? Certainly. Should you do it? No. Really you shouldn't. Health-wise, it's just very, very bad for your heart.
That said, if he's going to use oil, have him use Canola oil. It's a lot better on the heart. It's better than vegetable, palm or olive oil in that regard.

 

[Trekker4747]

If you fry the food right it should absorb very little, if any, oil. So any health issues shouldn't be of much concern.

 

[Timby]

Generally speaking, the rule of thumb I've always gone by is this: Lower a basket into the fryer so the third horizontal wire from the bottom is level with the top of the oil. If you can't see the bottom of the basket, you change the oil. I've followed this both in kitchens I've worked in, and with home fryers.

I've actually filtered oil with a China hat and a stock pot.

Don't get me started on the R2 unit used in my last restaurant kitchen, though. That may have been the most laughably unsafe piece of equipment I've ever seen in my life.

 

[Geckothan]

Don't get me started on the R2 unit used in my last restaurant kitchen, though. That may have been the most laughably unsafe piece of equipment I've ever seen in my life.

Did it have a bad motivator?

 

[Major Chord]

Generally, we change it after 4-5 uses. It depends on what you're cooking. Definitely change it after frying fish, or anything with a really crumbly, breaded coating, like cornmeal, as that stuff breaks off, and ends up floating in the oil. even after straining, it's hard to remove all the little pieces of corn meal. I believe I saw on the Food Network that as long as your food is emitting bubbles in the oil, it will absorb very little of the oil (as the water from inside is being expelled, bubbling, and preventing oil from entering). When it stops bubbling, the oil will start to be absorbed because there's nothing 'fighting' against it. At least, that's how I remember it, and the general rule I use when frying.

 

[Kirkman1987]

Don't get me started on the R2 unit used in my last restaurant kitchen, though. That may have been the most laughably unsafe piece of equipment I've ever seen in my life.

Did it have a bad motivator?

Beat me to it. lol

 

[Trekker4747]

Generally, we change it after 4-5 uses. It depends on what you're cooking. Definitely change it after frying fish, or anything with a really crumbly, breaded coating, like cornmeal, as that stuff breaks off, and ends up floating in the oil. even after straining, it's hard to remove all the little pieces of corn meal. I believe I saw on the Food Network that as long as your food is emitting bubbles in the oil, it will absorb very little of the oil (as the water from inside is being expelled, bubbling, and preventing oil from entering). When it stops bubbling, the oil will start to be absorbed because there's nothing 'fighting' against it. At least, that's how I remember it, and the general rule I use when frying.

That's pretty much it. If the oil is hot enough it'll flash-boil the water in the food which pushes outward preventing the oil from entering. Cook it too long or if the oil isn't hot enough this won't happen and the food will become greasy.

If you fry food properly and then re-measure the oil you'll discover that very, very little of the oil went into the food. Possibly only a couple tablespoons at the most.

I wouldn't reccomend cooking food "until it stops bubbling" that's probably inviting dry food or tempting greasy food too much. A good general rule of thumb for most food is to wait until it floats in the oul or looks "golden brown" taking the enternal temperature of the food is probably the most ideal way.

 

[Spot's Meow]

I use mine only for potstickers and change it about every 3 to 4 times I use it.

 

[sojourner]

I would imagine the amount of time between uses and the storage method should be taken into account as well as the number of uses.

 

[Timby]

Don't get me started on the R2 unit used in my last restaurant kitchen, though. That may have been the most laughably unsafe piece of equipment I've ever seen in my life.

Did it have a bad motivator?

The R2 (also known in the industry as "the dog" or "that busted piece of shit") unit refers to the grease pump. It was hilariously dangerous, for several reasons:

1) The power switch didn't work, so you had to plug and unplug it, instead of flipping a switch. So you had to hold the nozzle with one hand, and stre-ee-eee-eeeeetch to reach the plug and hopefully not slip and let go of the nozzle at the wrong moment.

2) The cord you had to plug in was insulated ... here and there. Plugging it in generally gave you about a 25 percent likelihood of a minor electrical shock. Considering the fact that you typically had to plug it in 4 or 5 times per piece of shit fryer, and we had 3 fryers, your odds worked out to 3 - 4 shocks a night.

3) It had a detachable hose, which in and of itself is not a bad thing. However, it had two fatal design flaws: First, instead of a collar which you pulled back to attach/remove the hose, it had 2 "wings." You spread them apart to unlock, and squeeze them together to lock it. They tended to work loose, so about once a week the hose would pop off. This lead to the second design flaw. Unlike typical hydraulic hoses or compressed air lines, disconnecting the coupler didn't cut off the flow. Instead, the fitting where the hose used to be directed the flow of grease into a horizontal torrent of pain.

I witnessed one cook run to the back and rip his pants off before the hot oil had a chance to soak through, and at least 3 or 4 other occasions where I was damn glad the salad bitch was in the walk-in, because otherwise he / she would have ended up in the burn unit.

I'm pretty sure my favorite experience with that R2 was when it electrocuted me, then caught on fire, then it caught me on fire.

 

[matthunter]

I'm not saying don't do it, just exercise common sense:

What Happens to Oil When it is Repeatedly Heated?

In frying the oil, it is usually heated to 170-220 °C (338-428 °F). When heated to these temperatures in the presence of oxygen (air), the oil undergoes chemical reactions such as hydrolysis, oxidation, and polymerization. In other words it changes its character. Degradation products can include free fatty acids, hydro-peroxides, and polymerized triglycerides. The oil viscosity increases, its color will grow darker, and rancidity begins to develop.

What is Rancidity?

Rancidity is the decomposition of fats, oils, and other lipids through oxidation. Oxidation of fats result in the replacement of an oxygen ion with a hydrogen ion in the fatty acid molecule. This substation destabilizes the molecule and makes it possible for other odd chemical fragments to find a place along the chain. Factors which accelerate fat oxidation are trace metals (iron, zinc, copper, etc.), salt, light, water, bacteria, and molds. Oxidation occurs primarily in unsaturated fats by a free-radical-mediated process. These chemical reactions generate highly reactive molecules in rancid food which also may destroy nutrients in the food. Free radicals formed by fatty acids react with oxygen to generate peroxides that enter into a multitude of reactions, producing numerous compounds such as aldehydes, ketones, acids, esters, and polymerized fats.

Hazards of Prolonged Heating

The amounts of degradation products increase with the duration of heating at high temperatures. The toxicity of these degradation products present a health concern. Other contaminants such as polycyclic aromatic hydrocarbons may be concentrated by prolonged heating. Some of these have been found to be potential carcinogens. Certain types of plant oils such as peanut oil are sometimes contaminated by naturally occurring aflatoxin which is a human carcinogen. Peroxides and other by-products are also formed, indicating a change in the oil on a molecular level. Secondary breakdown products of peroxides and hydro-peroxides are rapidly formed by prolonged heating. Trans-fatty acids and a substance called acrylamide are also produced.

If the oil starts to darken and the smell becomes acrid, it's probably time to replace it. As long as the oil remains clear and smells OK you can reuse it. Overuse will cause a buildup of acrylamide, which is the primary health concern.

 

[Amaris]

I'm not saying don't do it, just exercise common sense:

What Happens to Oil When it is Repeatedly Heated?

In frying the oil, it is usually heated to 170-220 °C (338-428 °F). When heated to these temperatures in the presence of oxygen (air), the oil undergoes chemical reactions such as hydrolysis, oxidation, and polymerization. In other words it changes its character. Degradation products can include free fatty acids, hydro-peroxides, and polymerized triglycerides. The oil viscosity increases, its color will grow darker, and rancidity begins to develop.

What is Rancidity?

Rancidity is the decomposition of fats, oils, and other lipids through oxidation. Oxidation of fats result in the replacement of an oxygen ion with a hydrogen ion in the fatty acid molecule. This substation destabilizes the molecule and makes it possible for other odd chemical fragments to find a place along the chain. Factors which accelerate fat oxidation are trace metals (iron, zinc, copper, etc.), salt, light, water, bacteria, and molds. Oxidation occurs primarily in unsaturated fats by a free-radical-mediated process. These chemical reactions generate highly reactive molecules in rancid food which also may destroy nutrients in the food. Free radicals formed by fatty acids react with oxygen to generate peroxides that enter into a multitude of reactions, producing numerous compounds such as aldehydes, ketones, acids, esters, and polymerized fats.

Hazards of Prolonged Heating

The amounts of degradation products increase with the duration of heating at high temperatures. The toxicity of these degradation products present a health concern. Other contaminants such as polycyclic aromatic hydrocarbons may be concentrated by prolonged heating. Some of these have been found to be potential carcinogens. Certain types of plant oils such as peanut oil are sometimes contaminated by naturally occurring aflatoxin which is a human carcinogen. Peroxides and other by-products are also formed, indicating a change in the oil on a molecular level. Secondary breakdown products of peroxides and hydro-peroxides are rapidly formed by prolonged heating. Trans-fatty acids and a substance called acrylamide are also produced.

If the oil starts to darken and the smell becomes acrid, it's probably time to replace it. As long as the oil remains clear and smells OK you can reuse it. Overuse will cause a buildup of acrylamide, which is the primary health concern.

Well, no one listens to the guy with the foreboding pronouncements of doom. Nooooo, you have to get word from a scientist!

Fickle!

 

[Franklin]

Can't add too much more other than to keep an eye on the smoking point. Bear in mind that the more you reuse an oil, the more you lower its smoking point. Start with an oil with a high smoking point, like Canola or Peanut. A lot of folks like peanut oil because of its neutral flavor.
And, peanut oil shouldn't be a problem with anyone who has a nut allergy. It's so refined, that the allergens are no longer in the oil. My oldest daughter is allergic to peanuts, but has no problem with food fried in peanut oil.

As far as frying foods (any foods) being unhealthy goes, it's not. It's improperly frying foods -- oil too cold, frying too long -- that makes it absorb fat. I think Trekker4747 said upstream that if you fry until there are no more bubbles, you've fried too long. That's the key. The bubbles mean steam is still escaping from the food, so no oil is getting in. When the bubbles slow or stop, it means the food can now take on on oil and become greasy.
I saw Alton Brown debunk the "frying is bad for you" myth when he poured the oil back into a container after frying some chicken (I think it was chicken), and all but the very smallest amount of oil was returned to the container.