A deep-frying revelation (for me at least)

[Fat Guy]

Maybe you're like me: I don't do a lot of deep frying. When I do it, I do it at home without any special equipment. I don't have a restaurant-quality fryer or even a home fryer. I just fill a pot with oil, stick a thermometer in, get the oil up to temperature and drop in whatever needs to be fried.

If you're like me, you also experience a significant drop in temperature as soon as you add, say, cool chicken or potatoes or whatever to the pot of oil. The pot is small, the burner is weak, you don't have the kind of volume and energy of a dedicated fryer. So you heated the oil to maybe 350, assuming that's the called-for frying temperature for whatever you're frying, but as soon as you put the food in you suddenly have 275-degree oil. Ten minutes later it's back up to 350, but by then the food is irreversibly less crispy and more saturated with oil than is desirable.

A comment by Rocco DiSpirito, however, has totally changed the way I fry. Rocco suggested that, if the oil drops 75 degrees (or whatever the number is in your case -- you'll have to experiment, but 75 is pretty normal) when you add food to oil, that you start by heating your oil 75 degrees hotter than you need it. So, if you want to fry at 350, you heat your oil to 425. You then add the food and -- voila! -- you have 350-degree oil. Then it's easy to hold the 350-degree temperature.

So, the other day I tried this trick while making some breaded chicken cutlets. And it worked! For the first time I can remember, I achieved totally professional deep-frying results at home with no special equipment. It's really amazing how much better things come out when you preempt the temperature drop in this manner.

Now feel free to tell me you always do it this way. But for me it was a revelation.

Thanks Rocco.

Needless to say, in order for this trick to work, you need to use an oil with a smoke point higher than 425 (assuming that's the magic number for your particular task and equipment -- it may be a little lower or higher for you). Most refined cooking oils (corn, peanut, Canola, safflower, whatever) will work just fine. Don't try it with unrefined oils, like virgin olive oil, though.

[kbjesq]

A comment by Rocco DiSpirito, however, has totally changed the way I fry. Rocco suggested that, if the oil drops 75 degrees (or whatever the number is in your case -- you'll have to experiment, but 75 is pretty normal) when you add food to oil, that you start by heating your oil 75 degrees hotter than you need it. So, if you want to fry at 350, you heat your oil to 425. You then add the food and -- voila! -- you have 350-degree oil. Then it's easy to hold the 350-degree temperature.

Yep, been using this technique for years . . . works great.

My latest deep-frying revelation is that more is not always better. I had always been led to believe that in order to maintain temperature and achieve a quick recovery after foods are added to the oil, you must start with a large quantity of oil. In other words, you need a large fryer and lots of oil.

A couple of months ago, on a whim, I picked up a relatively shallow electric deep-fryer for $20 at Walmart, similar to this one, but a little shorter. Anyhow, this thing holds less than 2 liters of oil, but because the heating element is the same size as the other ones that hold 3+ liters of oil, the small fryer has nearly instant recovery of temperature after foods are added. You must work in smaller batches, of course, but because the recovery time is so quick, there is no waiting between batches for the temperature to recover. And you don't need to "overheat" the oil, either. Just set at 375 F or whatever, and you're good to go.

[Chris Hennes]

This is part of the reason I prefer to use a dutch oven and thermometer to using a deep fryer - home deep fryers are generally limited to heating the oil to 375 or 400, so it is difficult to allow for the food bringing the temperature down and you are therefore required to fry in small batches. If you overheat the oil in the stockpot you can basically deep fry as much stuff at a time as you want.

[deltadoc]

And then you have home deep fryers like Rival, where the dial says 350 and the candy thermometer says 200, and the dial says 375 and the candy thermometer says 220.

They'll send you a new one, but you have to send the old one back and pay postage both ways. Estimate postage was more than the original cost of the fryer and on the internet, I found 22 pages of people who had the same trouble with their Rival deep fryer. Yep, bet the company is really glad to send you more of their junk, since no one is going to buy a second one anyway, they might as well give 'em away and make money on the postage and handling!

BTW: It is a simple case of thermodynamics. The more volume of heated oil to product to be fried, the less the temperature drop. Also, as was pointed out, the bigger the heating element in relation to the amount of oil to be kept at a certain temperature, the faster the recovery time.

doc

[Hiroyuki]

A comment by Rocco DiSpirito, however, has totally changed the way I fry. Rocco suggested that, if the oil drops 75 degrees (or whatever the number is in your case -- you'll have to experiment, but 75 is pretty normal) when you add food to oil, that you start by heating your oil 75 degrees hotter than you need it. So, if you want to fry at 350, you heat your oil to 425. You then add the food and -- voila! -- you have 350-degree oil. Then it's easy to hold the 350-degree temperature.

Yep, been using this technique for years . . . works great.

My latest deep-frying revelation is that more is not always better. I had always been led to believe that in order to maintain temperature and achieve a quick recovery after foods are added to the oil, you must start with a large quantity of oil. In other words, you need a large fryer and lots of oil.

A couple of months ago, on a whim, I picked up a relatively shallow electric deep-fryer for $20 at Walmart, similar to this one, but a little shorter. Anyhow, this thing holds less than 2 liters of oil, but because the heating element is the same size as the other ones that hold 3+ liters of oil, the small fryer has nearly instant recovery of temperature after foods are added. You must work in smaller batches, of course, but because the recovery time is so quick, there is no waiting between batches for the temperature to recover. And you don't need to "overheat" the oil, either. Just set at 375 F or whatever, and you're good to go.

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How much oil do you actually use for deep-frying? In Japan, we usually put 600-ml or more oil to have a oil depth of 5-6 cm (about 2 inches).

I've never heard of the overheating trick. Isn't it potentially dangerous? I don't think this trick works for tempura.

[Toliver]

We deep fried a turkey for Thanksgiving on a propane burner and used the "overshoot" trick but not to such an extreme. Our goal temp was 375 (below that you risk getting a greasy bird). So we cranked the burner til we hit 400 and lowered the turkey in which dropped the oil temp to 350 (not too bad of a drop). Because the propane burner was like a freakin' jet engine, we got it quickly back to the optimum 375. We used peanut oil so we didn't worry about a flash point in our temp ranges.

Because we used such a vast quantity of oil, one problem we ran into was that there was a delay between flame adjustment and temperature reaction. We'd get it back to 375 only to watch it continue to creep up even after turning the burner down.

Live and learn (and eat your mistakes).

[slkinsey]

"Overheating" the liquid is a technique that is familiar to most all-grain homebrewers, where this is called the "strike temperature." When you're using relatively known elements (water and cracked malt in the case of homebrewing) it's easy to predict how high you need to heat a certain amount of liquid in order to arrive in the ballpark of another temperature after mixing in a certain amount of room temperature grain.

To really figure out how much to overshoot you need to know how much oil you have, how much food you want to fry, the temperature of that food, and to a certain extent the nature of that food (a pound of french fries will have a different effect than a pound of chicken thighs). Of, of course, you can just do it by the seat of your pants. One way would be to put in a small amount of food and keep on adding food in small amounts until the thermometer drops down to your target temperature.

[Batard]

"Overheating" the liquid is a technique that is familiar to most all-grain homebrewers, where this is called the "strike temperature." 

This is a very good analogy. Only thing I would add that when you are mashing, the temperature can be very unforgiving. With oil you have a lot more wiggle room.

[Holly Moore]

Recovery time is one issue. And since it is the rare home fryer that can achieve 375 degrees in the first place, much less recover once the cold food goes in, stove top pan and a gas flame seem the only solution. The bigger the pan, the more oil, and the quicker the recovery time.

One note on smoke point. It gets lower with use, as the oil breaks down.

I have two other issues with deep fat frying.

1. Waste of oil. I deep fat fry maybe every once every two or three months. I don't trust oil held that long so end up starting with new oil every time. Which means I fry even less because I don't like wasting the oil.

2. So I throw away the old oil. My method is to get hot water running through the sink drain and then slowly mix in the oil. Liquid oil, so it is not going to congeal. But still some inner sense tells me this is wrong.

[Marlene]

I pour the oil into an old container with a lid, (often the container the oil came in) then throw the container out usually. I have the same issues with deep fat frying. I don't do enough of it to justify all that oil wasted.

[plk]

I've done this before accidentally, but what happens to me is that the outer layer of the thing that is being fried gets done in about 2 seconds, leaving the inside nearly raw. The last time I deep fried (admittedly months ago, because I can't stand disposing of the oil) it was for eggplant katsu. So then the only real solution is to finish them in the oven, which takes forever and negates any speed advantage of frying.

[OliverN]

Yes! I'll definitely try this. I've deep fried twice in the last four months, once with some cornstarch-dredged chicken pieces for an oyster-sauce stir-fry and the second time for some katsu-don. Both times I used a wok with a candy-thermometer and both times the meals tasted good at the time.... but afterwards I felt like I had a brick in my stomach! I'm assuming that's cuz the oil temperature dropped and everything got sucked in. Does anybody what the mechanism is that keeps hot oil out of foods?

And also, alton brown mentioned that you should never use a cast iron pan to deep fry. Is that true???

[jayt90]

Used cooking oil really should be recycled. One or two steps and it can be used in diesels or refined into biodiesel.

[prasantrin]

2.  So I throw away the old oil.  My method is to get hot water running through the sink drain and then slowly mix in the oil.  Liquid oil, so it is not going to congeal.  But still some inner sense tells me this is wrong.

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It's very, very wrong.

From Wiki (believe at your own risk)

Proper disposal of used cooking oil is an important waste-management concern. Oil is lighter than water and tends to spread into thin and broad membranes which hinder the oxygenation of water. Because of this, a single liter of oil can contaminate as much as 1 million liters of water.[9] Also, oil can congeal on pipes provoking blockages.

Because of this, cooking oil should never be dumped on the kitchen sink or in the toilet bowl. The proper way to dispose of oil is to put it in a sealed non-recyclable container and discard it with regular garbage.[10]

Better yet, cooking oil can be recycled. It can be used to produce soap and biodiesel.[11]

In Japan you can buy a kind of powder that you put into warm oil that causes the oil to solidify. I usually use that, then throw my solidified oil out in the trash.

As for deep-frying, I, too, make my initial temperature about 20C higher than the temperature I want to fry at, so when I put my food in, the oil won't cool too much.

[Hiroyuki]

2.  So I throw away the old oil.  My method is to get hot water running through the sink drain and then slowly mix in the oil.  Liquid oil, so it is not going to congeal.  But still some inner sense tells me this is wrong.

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It's very, very wrong.

From Wiki (believe at your own risk)

Proper disposal of used cooking oil is an important waste-management concern. Oil is lighter than water and tends to spread into thin and broad membranes which hinder the oxygenation of water. Because of this, a single liter of oil can contaminate as much as 1 million liters of water.[9] Also, oil can congeal on pipes provoking blockages.

Because of this, cooking oil should never be dumped on the kitchen sink or in the toilet bowl. The proper way to dispose of oil is to put it in a sealed non-recyclable container and discard it with regular garbage.[10]

Better yet, cooking oil can be recycled. It can be used to produce soap and biodiesel.[11]

In Japan you can buy a kind of powder that you put into warm oil that causes the oil to solidify. I usually use that, then throw my solidified oil out in the trash.

As for deep-frying, I, too, make my initial temperature about 20C higher than the temperature I want to fry at, so when I put my food in, the oil won't cool too much.

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Really? I don't. I have sometimes wondered who wants to spend money just to dispose of waste. Like I said somewhere else, I usually use used milk cartons to dispose of used oil, and I try not to dispose of oil by reusing it.

[prasantrin]

Really?  I don't.  I have sometimes wondered who wants to spend money just to dispose of waste.  Like I said somewhere else, I usually use used milk cartons to dispose of used oil, and I try not to dispose of oil by reusing it.

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I reuse oil, too, but you can only reuse it so many times before it goes bad (stale or otherwise). You can't reuse it forever.

I prefer to recycle my milk cartons. By using the solidifying powder, I can still throw away my oil (neatly), and then recycle my milk cartons. That way I'm only throwing away one thing rather than two (and I buy my solidifying powder at the Y100 store, then recycle the carton it comes in).

I'm Canadian, so I believe in recycling as much as possible.

[project]

Recovery time:

Come on, guys: Suppose we have some hot oil, add some cold food, and want to know the time -- 'recovery' time -- it takes to get the oil back to its original temperature.

So, how long? Well, when lowered the temperature of the oil, took some energy from it. The recovery time is what is needed to add that much energy back to the oil.

So, a larger quantity of oil will have its temperature fall less, but the energy taken from the oil and, thus, the recovery time will be about the same.

So, a larger quantity of oil should not change recovery time significantly.

To reduce the recovery time, add less food or use a more powerful heat source.

[Toliver]

So I throw away the old oil.  My method is to get hot water running through the sink drain and then slowly mix in the oil.  Liquid oil, so it is not going to congeal.  But still some inner sense tells me this is wrong.

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Contact your waste disposal agency in your area to find out proper cooking oil disposal methods. Where my mom lives, residents can put the oil into a container with a tight lid and place it in their regular garabge bins.

I don't think pouring it down your sink is a good idea.

[johnder]

kitty litter is great for throwing out oil when you need to. put a scoop or two of kitty litter in a ziplock bag, pour cold oil in, and it seal it up. Keeps it from leaking.

[Restorer]

Recovery time:

Come on, guys:  Suppose we have some hot oil, add some cold food, and want to know the time -- 'recovery' time -- it takes to get the oil back to its original temperature.

So, how long?  Well, when lowered the temperature of the oil, took some energy from it.  The recovery time is what is needed to add that much energy back to the oil.

So, a larger quantity of oil will have its temperature fall less, but the energy taken from the oil and, thus, the recovery time will be about the same.

So, a larger quantity of oil should not change recovery time significantly.

To reduce the recovery time, add less food or use a more powerful heat source.

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You're right, recovery time will be the same. But the temperature drop will be smaller - you're taking the same amount of energy from a larger mass of oil. The total amount of heat transfer to the item you're frying will be greater over the recovery time.

[Fat Guy]

Cost of oil. I suppose if I deep fried often I'd develop more of a concern here, but vegetable oil is so cheap at places like Costco (something like $12 for 2 gallons) that I wind up using about $3-$4 worth of oil when I deep fry. Of course, if you deep fry often enough, you can reuse the oil. So either way it works out pretty economically. Plus, with this new-to-me method, I'm going to be able to use less oil because I'm not going to be worried about the temperature drop.

Tempura. If you're just cooking a few small, thin pieces of battered stuff at a time then you don't really have to worry about much of a temperature drop. The temperature drop is more of an issue when you cook a whole bunch of fries, or several pieces of chicken at once.

[Chris Hennes]

Cost of oil. I suppose if I deep fried often I'd develop more of a concern here, but vegetable oil is so cheap at places like Costco (something like $12 for 2 gallons) that I wind up using about $3-$4 worth of oil when I deep fry. Of course, if you deep fry often enough, you can reuse the oil. So either way it works out pretty economically.

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I agree - I think it's funny the way we think about cost. Even when I use peanut oil, and I'm doing large batches so using maybe $10 worth of oil, I'm making enough food to feed, say, 10 people. So that's like $1 each for the oil if I don't even re-use it once. It's a lot of oil, and it feels like a lot of money when you have to buy a 3 gallon jug for $25, but when you actually work out the math it's not really that outrageous. I spend way, way more on protein. And chocolate.

[Dianabanana]

I read somewhere that Japanese moms often use tiny pots for deep-frying just one or two items for bentos in the morning. I picked one up at Daiso for (what else) $1.50, but I haven't tried it yet. It's the cheapest possible aluminum with maybe a 2-cup capacity. They had a huge stock of them so I guess it's a big seller.