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How often can I re-use vegetable oil?

We have a countertop fryer — the kind with a basket that submerges into a deep well full of oil. It is designed to store the cooled oil in the well, between uses. How often can we re-use the same oil that was used for frying? How long can we safely store this oil? How do you know when vegetable oil is starting to turn rancid?

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  1. I reuse my oil a few times, but that is because I usually cook the same thing in the fryer (chicken wings, and I make alot of em in football season). You really should put new oil in if you are going to be cooking something drastically different (ie: fish to chicken to fries). Veg. Oil has no problem keeping for a week or two, but then again I don't really want to eat that much fried food...

    1 Reply
    1. re: MattInNJ

      We don't fry that often either, which is the problem. My husband is willing to store the oil for several months, using it 3-4 times during that long period to fry different things. He's the cook. I'm the scullery maid who wants to throw out the old oil and use fresh.

    2. Smell the oil to determine if it is rancid. You will know - it will not smell appetizing. To extend the number of times you can use it, you can strain the oil after each use (but if one goes to this effort one might as well throw it out). Three to four months sitting on the countertop is probably too long for decent or even edible quality; I'd advise refrigerating it if you wish to keep it that long.

      1. If your kitchen is not too hot and you've skimmed off the bits of food from the oil, it should keep a couple of weeks, otherwise, I would refrigerate it. I find that after 3 uses, the heat has caused the oil to break down and too much water has leeched out of the food into the oil. This makes the food less crispy. One can tell when french fries take longer to brown than the previous time. I always add some fresh oil to the old batch before I reuse it. Food comes out crispier.

        1 Reply
        1. re: PBSF

          i thought one should not add fresh oil to old oil because the latter has "broken down".

        2. There is much confusion about this point, and much mis-information. The answer is, without question, "it depends." Mostly it depends on how hot you have heated the oil, how old it is, and whether you have taken the trouble to keep it clean.

          Commercial (ie restaurant) oil is re-used many times. It is called "fry life" in the biz. But these oils are formulated with additives and stabilizers for commercial use which extend their life. A typical heavy duty decent quality commercial oil has a "fry ratio" of maybe 15 or 16, meaning that you can fry 15+ lbs. of stuff (typically french fries) per pound of oil. Thus, a 35 lb. box of oil will fry maybe 600 lbs. of potatoes. This will take many fryings possibly over many days. Many restaurants have a rule of thumb of changing their oil on the same day every week, but of course it depends..... Good restaurants are diligent about keeping their oil clean, by filtering to get the charred bits out. And of course commercial fryers are built to not overheat the oil. Hopefully home electric fryers similarly avoid overheating, but for those who fry on the stovetop this requires careful watching.

          At home, with typical oils available to home cooks, you certainly can re-use the oil, but you have to be careful to not let it overheat and you should filter it before putting it away. I use a simple fine-mesh coffee filter (plastic and metal). Of course, I have to let the oil cool before I filter it. Basically the oil is OK so long as the food comes out tasting OK and so long as it isn't showing signs of smoking, (since the heating will lower the smoke point and eventually make it dangerous). Inevitably some oil will be lost each time, and I top my used oil up with new oil.

          I think throwing oil away each time is not only wasteful, but how do you dispose of it? Too often it goes down the drain, and that is a bad idea for many reasons, especially IMO the impact it may have on the local sewer system and sewage treatment plant.

          BTW, as to freshness, experts claim absolutely fresh oil isn't the best--it needs to be used to be optimum, and some chefs add a little old oil to achieve this effect from the getgo.

          2 Replies
          1. re: johnb

            UPDATE----Wonder of wonders. About an hour after I typed the above, Alton Brown comes on the tube with a show about oil. He says you can reuse the deep fry oil about 7 times, assuming you strain it, and he says you should keep it in the freezer (I think that's what he said--I got distracted). I'm not so sure about the freezer part anyway, even if he really did say it..

            He also confirmed the "add a little old oil to the new oil" trick. It helps the new oil better absorb the water from that which is being fried and you get a better result.

            1. re: johnb

              thanks so much for all the info you've given me. I feel more confident about re-using and will filter the oil when it is cooled. (The freezer? I don't know about that part.)
              Thanks for everyone's input on this.

          2. Add a brick of lard to your oil to stabilize it. It'll last longer.
            Always strain your oil and don't bother trying to save the bottom of the barrel where all the sediment is after you've let it cool down enough to handle.
            Keeping the oil in a sealed container and in the freezer between uses will allow you to maintain it much longer. Also, if breading, make sure to shake off any excess flour or bread crumbs before frying. The excess will fall off anyways and just contribute to turning your oil back since it'll stay in oil for a longer period of time thus burning away and turning into carbon.
            If you fry often it is worth investing in a fine metal strainer (with a long handle) to sift the oil between frying batches. The time it takes you to strain it will also allow the oil to return to proper frying temperature for the next batch anyway and the less free floating carbonized particles you have in the oil, the 'cleaner' your food will look after frying.

            4 Replies
              1. re: bullysf

                I ended up using my French coffee press to filter the oil. Efficient, easy to clean, reusable. Makes the choir of filtering oil somewhat fun.

                1. re: arktos

                  Now there's an idea. I keep a coffee mill in the barn to pulverize big tablets of medicine for my horse, but I guess that tip is for another sort of blog

                2. re: bullysf

                  Thanks for the tip bullysf.

                  My question for everybody is, why freeze is instead of refrigerating it? Is it necessary to if you are not going to use it for a long period?

                  Thanks for the this thread.

                3. From the days of my Dh and his brother owning a Chicken Delight, I watch the oil for foaming, and change it after that occurs. I do strain it and refrigerate it in between uses, and if you use it for fish, for fish only it is from then on, as the fishy flavor will be imparted to the next food cooked.

                  2 Replies
                    1. re: Bossmare

                      I have been freezing cooking oil for years. Find a good quality vegetable oil and cook as normal. When done I let it cool enough to where it no longer will burn (but still a little warm) then I have a large screen strainer that I line with two layers of cheesecloth and strain into a large bowl. I let that cool a little more then have a large filter that I put some NEW cheesecloth in and pour from the bowl, through the funnel/cheesecloth, directly back into the plastic oil container it came in (although my fryer holds about 1/2 gallon so I clean 2-liter bottles and refill those).

                      Then I put in the spare freezer in the garage (where I keep my "bulk" purchases of chicken/etc. - always good to save money:)!!). I found I can use the oil about 6 - 7 times before I make the decision to dispose of so it appears I fall in line with what Alton Brown has said too.

                      BTW, when you know you are going to use simply take out of the freezer, twist the top (just to confirm it is tight), fill the sink with as hot of water you can get out of your kitchen faucet, and lay your oil bottles in there and let them float in the hot water. I have found within about 15 to 20 minutes it should be close to "thawed" and can start to pour out (sometimes still a "chunk" and have to put the bottle back in the sink with the remaining "solid" oil and let the remainder thaw). Of course if you have more time that is better but I have "rushed" the process, refilled sink once or twice more, and put the bottle with some solid oil back in the sink and stil have the fryer going within about 20 to 30 minutes. Straining and freezing cooking oil has worked for me for about 15 years and never have had a problem. ENJOY!!

                  1. Columbia university has some good guidance about the possible dangers of reusing cooking oil:

                    http://goaskalice.columbia.edu/reusin...

                    1. EXCELLENT discussion. Thanks for the excellent notes each of you have posted. I am certain that many people will save a good deal of money, while maintaining a healthy diet, by using your suggestions.