Oil for deep frying

[artzystuf]

How do I keep cooking oil after deep frying? I know it can be cleaned somehow, but I don't know how to do it, how to save it, how long I can keep it, and how to get rid of it. Can someone fill me in?

[Kitchen Witch]

I don't keep anything too long - if I am using it for fish - I use it only for fish and nothing else. I usually use shortening - sometimes vegetable oil.

I strain mine using a fine mesh strainer (some like to use a coffee filter in it or cheesecloth) after it has cooled; pour into a glass or porcelain (not plastic) bowl, cover and refrigerate.

Some people freeze their cooking oil - I've never done that. any ice crystals that form will breakdown the oil and you won't be deep-frying - you'll be boiling.

Getting rid of it is easy - just pour into a bowl and refrigerate. Once it solidifies I place in a plastic bag (from the grocery store) and put in the trash.

From my notes:

Yes, it can be re-used several times, but realize that each time you re-use it two important things happen:

1) You build up food particles and silt than can burn, turn black, and generally make everything taste bad like them. Careful filtration between uses can limit this quite a bit, but few people do it.

2) Every time you use the oil you lower its smoke point - the point at which the molecules break down into a funky stuff called acreolein and spread awful smoke around your kitchen in the process. Most common frying oils and vegetable shortenings start out with a smoke point in the 445F range with some lower (olive oil and lard @ 375F) and some higher (safflower @ 510F), so you have some wiggle room. But after you've used it a few times the smoke point starts to drop near your frying temperature, usually around 365F, and smoke begins to rise before you can even get the food in.


Everything you heat up oil to a high temperature, you lower it's 'flashpoint', the temperature that it can catch on fire. Some oils have a very high flashpoint to start with so you can reuse them if you don't abuse the oil. Peanut oil has the highest flashpoint. It's about 400° the first time you use it but then it goes down about 25° every time you reuse it if you heat it high like 375°. Soy and corn oil are not good longlasting oils. They degrade quite quickly.

[artzystuf]

Thanks for this wealth of information. More than I expected. Now I can fry, fry, fry!

[Kitchen Witch]

You're very welcomed! Happy frying! : )

[bennybbc]

Originally Posted by Kitchen Witch

I don't keep anything too long - if I am using it for fish - I use it only for fish and nothing else. I usually use shortening - sometimes vegetable oil.

Fish can certainly flavor fry oil but if you have a batch of oil and it's still clean and you don't want to toss it you don't necessarily have to. I've found that a batch or two of french fries can help remove some or nearly all of the fishy flavor from oil. Of course then the french fies have a little, "Extra flavor" but that's never stopped me from eating them anyway.

Originally Posted by Kitchen Witch

I strain mine using a fine mesh strainer (some like to use a coffee filter in it or cheesecloth) after it has cooled; pour into a glass or porcelain (not plastic) bowl, cover and refrigerate.

If the oil really has a lot of particles in it a fine metal strainer is a good start. But I've found a coffee filter to be way too slow. Multiple layers of cheesecloth works well though. But the best way to do it is the way I did it for years in restaurants and that is to use what we called a filter cone. You can buy them at any restaurant supply house. They're designed to fit inside of a, "China Cap" conical filter but they work fine in a larger wire mesh strainer or even a smaller metal colander. They are similar to a coffee filter but the weave isn't as tight. The oil is properly strained and it doesn't take so long.

There are a couple of things that will make oil go rancid more quickly. One is if it's stored in a cast iron or copper container. Steel and aluminum are fine though. Another is if it's exposed to air. Sealing it with very little surface area exposed to air is the best way to go. I will admit though that I regularly store used oil in one of my cast iron Dutch ovens with the lid on. I fry often enough and replace the oil enough that it doesn't usually have a chance to go rancid.

Originally Posted by Kitchen Witch

Some people freeze their cooking oil - I've never done that. any ice crystals that form will breakdown the oil and you won't be deep-frying - you'll be boiling.

I've never heard anything like this before. Between my kitchen science books and the internet, I've never seen a single mention of ice crystals being harmful to cooking oil. Where did you get this information?

There shouldn't be any water in the oil when you're done using it because it all quickly gets steamed out when the oil is hot. That's what the spattering is from. If somehow water did find it's way into the oil it will sink to the bottom and not stay mixed with the rest of the oil. Regardless, any hot oil that is hot enough will, still fry foods, not boil them no matter if it breaks down for any reason.

Originally Posted by Kitchen Witch

Getting rid of it is easy - just pour into a bowl and refrigerate. Once it solidifies I place in a plastic bag (from the grocery store) and put in the trash.

This is a good way to do it. Another way that I dispose of old used oil is to pour it back into the container that it came in. Of course you have to wait until it cools down so that it won't melt the plastic. One thing to be aware of is that some towns my not want you pouring any oil into your garbage whether it's in a container or not. Restaurants typically store their used oil in large containers and either a rendering company or a, "Bio Diesel" company will pick it up and do whatever with it. This isn't practical for a home usually but you still might want to check with your local garbage company or city regulations if you're concerned about such things...I'm not, but I thought I'd mention it.

Originally Posted by Kitchen Witch

From my notes:

Yes, it can be re-used several times, but realize that each time you re-use it two important things happen:

1) You build up food particles and silt than can burn, turn black, and generally make everything taste bad like them. Careful filtration between uses can limit this quite a bit, but few people do it.

Depending on the restaurant I've worked in we reused our oil quite a few times. But as you pointed out, filtering the oil was the key. Most places I worked didn't do that much deep frying, or we didn't fry many breaded foods that dropped crumbs into the oil. French fries keep the oil clean for quite a while. But frying prawns or crab cakes would contaminate the oil quickly so we used those filter cones on a regular basis. Oil can be expensive if you toss it out after only a couple of uses. Filtering with a filter cone is pretty easy and it greatly extends the life of the oil, thus greatly lowering the net cost of the oil per usage.

Originally Posted by Kitchen Witch

2) Every time you use the oil you lower its smoke point - the point at which the molecules break down into a funky stuff called acreolein and spread awful smoke around your kitchen in the process. Most common frying oils and vegetable shortenings start out with a smoke point in the 445F range with some lower (olive oil and lard @ 375F) and some higher (safflower @ 510F), so you have some wiggle room. But after you've used it a few times the smoke point starts to drop near your frying temperature, usually around 365F, and smoke begins to rise before you can even get the food in.

While the smoke point for some oils may be well above 400 degrees, heating the oil up and frying at those temperatures is a good way to not only burn your food but also greatly shorten the useful life of the oil. I've seen a few recipes that call for frying temperatures at 400 degrees and above but I think that doing this is a mistake. 375 degrees is that standard temp that every restaurant I've ever worked in keeps it's oil.

The smoke point for vegetable shortening is the same as that for lard, 375 degrees. Neither lard or olive oil is really suitable for deep frying, primarily because of their relatively low smoke point. But vegetable shortening does have a redeeming quality in that it is very refined and it doesn't smell as much or transfer as much flavor to the food as other oils. I usually use it for frying chicken in a cast iron fry pan. It gets no where near it's smoke point since I fry chicken at around 325 derees or so.

Originally Posted by Kitchen Witch

Everything you heat up oil to a high temperature, you lower it's 'flashpoint', the temperature that it can catch on fire. Some oils have a very high flashpoint to start with so you can reuse them if you don't abuse the oil. Peanut oil has the highest flashpoint. It's about 400° the first time you use it but then it goes down about 25° every time you reuse it if you heat it high like 375°. Soy and corn oil are not good longlasting oils. They degrade quite quickly.

Actually, oil can catch on fire at any temperature and the hotter it gets the easier for it to ignite. The, "Flash point" of an oil is typically between 600 degrees to a little below 700 degrees, not 400 degrees. The flash point is the temperature at which tiny wisps of flame start to spontaneously appear on it's surface. The fire point is typically a little above 700 degrees and that's the point at which the whole surface of the oil will be on fire.

One very important thing to note about flaming oil is that you should never, never, never use water on an oil fire. It won't put out the fire, it will make it worse. The water basically explodes into steam and blasts the flaming oil all over. If possible the best method to extinguish an oil fire is to shut off the heat and put a lid on the pot. If the fires is too large to do either of those things a fire extinguisher, (Not a water type) is the next step. Baking soda tossed on the flames can help too but who has that much baking soda within easy reach. Every single kitchen should always have a working fire extinguisher labeled with A B C classifications within easy reach. Not the one out in the garage. Not the one in the closet. Not the one in your car. Get one for the kitchen and put it where you and anyone else can see it and reach it. If the fire is more than you can handle within less than 30 seconds you should get everyone out of the house and call 911.

There are some good ways to prevent an oil fire from ever occurring in the first place. Don't overfill the container in which you are frying. Leave plenty of room for the food you're going to add and a few more inches, (At least) for the oil to bubble up after you add the food. Try to dry the food before you add it. The moisture will cause it to bubble and spatter more. Monitor the temperature of your oil while you're heating it up and during the entire cooking process. There are various types of deep frying thermometers that work well. I use an electronic thermometer that works well for just about everything in the kitchen. Don't overheat your oil before you add the food. As was mentioned by KW, it will cause the oil to break down and it also causes it to boil up more when you first add the food and maybe boil over onto the heat source. Never leave the kitchen when you are deep frying. It's something that really requires your attention. Be careful.

Bruce

[Kitchen Witch]

Seasoned or flavored oils (walnut, olive oil, lard, drippings) should not be used because they have a low smoke point. Blended vegetable oils, pure corn oil, sunflower oil, soybean oil, rape seed oil (canola oil) have a high smoke point. Peanut oil will greatly impact flavor. Never mix oils.

Everyone knows that high heat, water and burnt food particles break down the oil's smoke point. Oil should be replaced immediately if you notice excessive smoking at normal temperatures, strong oil discoloration, a rancid smell, excessive foaming around the food.

Many foods are battered with bread crumbs, flour, spices, salt, egg and the like. Many frozen foods have ice crystals on their surface which adds water and volatility to the deep frying. All of these are extraneous to the food and to the oil, creating an oxidation environment that can be detrimental to food and oil quality. These extraneous materials can be considered "pro-oxidants" which catalyze, in the high temperature agitating environment of deep frying, undesirable break down of components in the oil.

Oil darkens with use because the oil and food molecules burn when subjected to high/prolonged heat. The more you use the oil, the more slowly it will pour. Its viscosity changes because of changes to the oils molecular structure. When smoke appears on the oil's surface before the temperature reaches 375* F, the oil will no longer deep fry properly.

Filtering helps to keep the oil fresher. The cones are nice - not all households have the use for a cone. The large filtering machines in the restaurant are nice too - just not for the average kitchen.

For home use, some will refrigerate the oil to be used again. It is not recommended because bringing chilled oil to room temp causes excessive splattering during the heat up process.

Some recommend just cooling, covering and storing in a cool dark place for up to 3 months. To me (and this is my opinion) that is much too long.

Always check the oil before using it - check for color, smell, or excessive foaming. If you see any of this - discard.

And there are those that say only use the oil once if frying fish or chicken.

Once I use oil for fish - I don't use it for anything else except fish. It's not "flavor" to me to fry a batch or two of fries (or anything else) in that oil.

[Kitchen Witch]

previously posted on site:

The Smoke Point

Knowing the smoke point can also save you money, because each time you deep-fry, you lower its smoke point irreversibly. If your oil's smoke point is just above 190 degrees C (375 degrees F), which is the normal deep-frying temperature, chances are its smoke point will drop below 190 degrees C (375 degrees F) after its first use, rendering it useless. If you want to save money by reusing an oil as many times as possible, select one with a high smoke point.

Smoke Points
Safflower 265 degrees C
Sunflower 246 degrees C
Soybean 241 degrees C
Canola 238 degrees C
Corn 236 degrees C
Peanut 231 degrees C
Sesame 215 degrees C
Olive 190 degrees C
Lards 183 to 205 degrees C

A number of factors will decrease the smoke point of any fat:

* combination of vegetable oils in products
* presence of foreign properties (batter)
* temperature to which oil is heated
* presence of salt
* number of times oil is used
* length of time oil is heated
* storage of oil (exposure to oxygen, light, temperature)
* Knowing the smoke point will also warn you about, because of its proximity to, the flash point and fire point. An oil reaches its flash point (about 320 degrees C (600 degrees F) for most oils) when tiny wisps of fire begin to leap from its surface. If the oil is heated to its fire point (slightly under 400 degrees C (700 degrees F) for most oils), its surface will be ablaze.
* Never use water to put out an oil fire: the water will splatter the burning oil and spread it more quickly. Instead, smother the flames with a tight-fitting lid or sheet of aluminum foil. If the fire has spread outside the pan, suffocate it with baking soda or a fire extinguisher formulated for oil fires.

[bennybbc]

Originally Posted by Kitchen Witch

Seasoned or flavored oils (walnut, olive oil, lard, drippings) should not be used because they have a low smoke point. Blended vegetable oils, pure corn oil, sunflower oil, soybean oil, grape seed oil (canola oil) have a high smoke point. Peanut oil will greatly impact flavor. Never mix oils.

Since lard and vegetable shortening have about the same smoke point then they should be treated the same when it comes to deep frying.

You have, "Grape seed oil" mixed up with, "Rape seed oil". Grape seed oil is just that, the oil from grape seeds. Canola oil comes from the Rape seed. The folks who grow them decided that if they want to market their product, (and a good one it is!) they had better come up with a better name than, "Rape seed oil". I guess they figured some people might be put off by the name. Grape seed oil is very useful though. It has a very long shelf life because for some reason it's resistant to becoming rancid. If you wanted to make a flavored or infused oil like chili oil, for example, grape seed oil would be the perfect choice because it lasts so long.

Most modern peanut oils are more refined now and they have very little if any detectable flavor. I've used it a few times in my turkey fryer, (On sale in those big 3 gallon jugs) and I couldn't taste any more flavor than with canola oil. I have bought peanut oil from some Asian markets that were apparently less refined and I could taste the peanut flavor in them. Personally, I like the peanut flavor in many dishes.

Originally Posted by Kitchen Witch

Everyone knows that high heat, water and burnt food particles break down the oil's smoke point. Oil should be replaced immediately if you notice excessive smoking at normal temperatures, strong oil discoloration, a rancid smell, excessive foaming around the food.

In my previous post I was addressing your statement that ice crystals that form during freezing would break down the oil and you would be boiling instead of deep frying. My belief is that there should be no water in the oil when it freezes to make those ice crystals. And if for some reason there are ice crystals I don't think they will harm the oil. I'm not sure I understand the boiling versus deep frying thing but that's ok.

Originally Posted by Kitchen Witch

Filtering helps to keep the oil fresher. The cones are nice - not all households have the use for a cone. The large filtering machines in the restaurant are nice too - just not for the average kitchen.

Anyone who wants to filter their oil has a use for a paper filter cone. I think I paid maybe $5 for a box of them at a local restaurant supply store. I don't have a China cap at home so I just put the filter into a larger wire mesh strainer. I put the strainer over another pot and pour the oil through. It's no different than using the coffee filter or cheese cloth that you suggested other than it is designed for this purpose and it works much better. Especially better than a coffee filter which clogs up quickly. The average kitchen would do well to pick up a box of oil filter cones and use them to greatly prolong the life of their oil. The filters I'm talking about look like this: 10" Paper Grease Filter Cone 50/BX Product details $6.50 for 50 of them is a pretty great deal. There's also a holder that I've never seen before that I just might order. 10 1/2" Fryer Oil Cone Filter Holder Product details $6 is pretty cheap. For $12.50 plus whatever shipping is you can have a professional filter setup that is easier and better than any other filtering method a home cook is likely to find. Use it only a few times and you've easily paid for the price of the filter and holder in the saved expense of buying more oil so often.

I've worked in about a dozen restaurants over the years. I've visited numerous others. I've never used or even seen any kind of filtering machine. I've only seen them in large restaurant supply houses. I guess they might use them in places that deep fry huge amounts of food but I've never worked in or visited those places.

Originally Posted by Kitchen Witch

For home use, some will refrigerate the oil to be used again. It is not recommended because bringing chilled oil to room temp causes excessive splattering during the heat up process.

Can't you just let the chilled oil come back to room temperature slowly by sitting on the counter? Then you use the oil as usual. I don't usually refrigerate my deep fryer oil but only because I don't usually have enough room in either of my refrigerators. However, when I fry chicken in a cast iron pan I use Crisco and I do let that cool mostly and then pour it back into the can it came in. I then refrigerate that and use it only for frying chicken. Yes, I do filter it when I'm pouring it back into the can.

Originally Posted by Kitchen Witch

Some recommend just cooling, covering and storing in a cool dark place for up to 3 months. To me (and this is my opinion) that is much too long.

Agreed. It gets rancid if I leave it too long. Yuk!

Originally Posted by Kitchen Witch

Always check the oil before using it - check for color, smell, or excessive foaming. If you see any of this - discard.

And there are those that say only use the oil once if frying fish or chicken.

Once I use oil for fish - I don't use it for anything else except fish. It's not "flavor" to me to fry a batch or two of fries (or anything else) in that oil.

I don't know what else other than a flavor that frying fish adds to oil. The frys are a cheap way to remove most of that flavor. Most restaurants use the same oil for everything that they fry. The only time I've ever noticed extra flavor in the other foods fried in that oil is when the restaurant isn't changing their oil often enough. Everyone has their own ways though so whatever works for you is the right way to do it.

I hope I've clarified some of my points regarding fry oil. I think it's important to discuss and exchange information like this so that people looking for answers on this forum get the best and most complete information. There is so much to know about food and cooking that I'm always trying to learn more. I appreciate it when I learn a new technique or recipe from someone else and I hope the same is true when I share my knowledge.

Bruce

[Kitchen Witch]

grape/rape seed oil - typo on my part - one of these days I will have letters on my worn out keyboard! LOL

regarding the ice crystals - take a restaurant that doesn't prep their fries (most places that use frozen fries - especially fast food restaurants - fill their fry baskets with frozen fries and place them on the fry rack and let them sit at room temp to allow the ice crystals to melt off and the water to run down the rack - just for this reason) without this process their is a definite difference in fry flavor, texture, etc.

any restaurant I ran I would not allow the fish oil to be used for anything except fish! my belief has always been - no everyone wants the taste of fried fish in their food - I know I don't - the chefs in my family are the same way

fry filtering machines are great! a bit of work - but they do such a great job!

keep sharing - that is the only way for others to learn!