Rules/Guidelines for storing used deepfryer oil [General]

2010 Jun 27
I got a T-Fal deepfryer recently that allows you to strain the oil and reuse it. Unfortunately, there does not seem to be alot on the internet in terms of how you should store the used oil, how many times you can use it and for how long can it be stored. So I am curious about the rules others follow on here.

Where do you store your used oil? Does it have to be stored in the refrigerator? In terms of the rules for refrigeration - does it matter if you were cooking vegetables or something like chicken?

How long can you store it for?

How many times can you use it?

Any thoughts or advice people have would be very much appreciated.


2010 Jun 27
Best way I've found to store used oil if it is filtered and relatively clear is to heat it in the MW in a mason jar til it is about 95C / 200F, and then put a lid on it and let it cool. For optimal deep fryer sized storage use bigger jars, obviously. 1L or even the 1.5 and 1.9L sizes.

I've found that like this you can store it indefinitely.

You can use it until it gets really dark and/or starts to smell rancid.


Found that one out the hard way. Boiling point of oil is pretty high obviously. So go slow the first time. For a 1L jar start with 2 minutes and then measure the temp. Then proceed accordingly in small increments.

At 95C / 200F there is no worry of bursting the jars - just your standard scalding hazards.

2010 Jun 27
Thanks for the tips Zymurgist. Couple of quick questions:

1) Once you have the oil in the mason jar, do you store it in the refigerator or is the pantry ok?

2) Where do you recommend getting the mason jars?

Cheers and thanks

2010 Jun 28
Just store on the shelf is fine.

Preston Hardware has the 1.9 liter ones - but check size as they may not fit in your microwave! Canadian Tire is my usual choice for selection and price.

2010 Jun 30
Thanks again Zym!

2010 Jun 30
I just checked, and the 1.9 litres do not fit in my mid-sized Panasonic MW, but the 1.5L do.

2010 Jun 30
Huh: I never thought of microwaving it after I'm done straining it. Does that help stabilize it somehow?

2010 Jun 30
Oh, and to filter my oil I picked up a cheapie funnel at Princess Auto with a built-in mesh filter. Ten bucks:

2010 Jun 30
I guess it kills anything that's in there - I do this with lots of stuff. For example, that jar of spaghetti sauce that you use only 1/3 of and want to store in the fridge only to come back 3 weeks later to find it moldy. In my case, of course, home made sauce. Anyway, I nuke it first to boil a bit, and put the lid back on while boiling hot. When cooled, into the fridge it goes. Keeps 2 or 3 times longer this way. Or more.

I believe oil goes rancid because or organisms, and this seems to take care of that problem.

I just use a regular small funnel with a coffee filter. Though it can sometimes take a long time to filter. I let the oil settle and pour out what i can without filtering. Usually that will be 90% of it. Then filter the rest through the funnel. Though coarse filtering first might be a better idea - maybe through a wire mesh sieve. Might make the fine filter go faster. But usually I have to let it sit overnight to complete.

2010 Jun 30
You may be right! I had always assumed that the oil goes rancid due to the heat breaking the oil down into smaller, errrr, more aromatic hydrocarbons, but there's no reason why little microbes wouldn't help out.

When I used to have cheesecloth in the house, I'd screw a small sheet of it into the bottom part of the funnel so that it'd have a finer filter on it.

It's a real pain to do for me, to be honest, because of the hand-holding the filtering step takes anyway. You kinda have to hold the funnel up above the neck of the bottle I use, so that you get air flow and the oil flows properly. Takes a couple pours, and makes a hell of a mess. I should get a vacuum filtration apparatus set up instead ;)

2010 Jul 3
Oil goes rancid because of oxidation, not microbes. To control the microbes, just make sure there are no traces of water introduced into the strained oil after deep frying...that would be a recipe for botulism.

Polyunsaturated fatty acids, the good stuff, are unfortunately also full of active sites that react with oxygen in the air, which results in the rancid taste. This is why flax oil, walnut oil,etc... have to be stored in the fridge in a tightly closed bottle to keep the oxygen out. Saturated fat, on the other hand, do not go rancid because there are no sites for oxidation. This is why Crisco never spoils, because the hydrogenation has removed most of the oxidation sites from the unsaturated fatty acids.

If you are using liquid vegetable oil, and not Crisco, for deep frying, the best way to avoid rancid oil is to choose one with low poly-unsaturated fatty acids, and high mono-unsaturated fatty acids. Olive oil or peanut oil are good bets. Mono-unsatured fatty acids only have one site for oxidation, so they will still eventually go rancid with time, but not nearly as fast as the polyunsaturated fatty acids. Canola oil is high in polyunsaturated fatty acids, which is very good for your health, but if you use it for deep frying, it won't last very long before going rancid.

2010 Jul 7
On the water issue a quick question. Prior to reading your response schtickyrice, I washed the mason jars and then gave them a quick dry with a paper towel. There certainly was not lots of water but its quite possible there was a spec here or there. Should I dump my oil? Or am I likely safe?

Cheers and thanks for the advice!

2010 Jul 7
Why dump if it does not smell rancid?

Any botulism in there will be killed next time you use the oil. Botulism toxin is destroyed by heat as well.

2010 Jul 8
You are probably OK, medicinejar. However, it really depends on how large the specs of water are, how clean the jar is, and how well strained the oil is. Clostridium botulinum spores are found in the air, and require moisture, food material to feed off, and anerobic conditions.

An infamous case in the 1980's involved garlic oil served in a Whitespot restaurant in BC. The kitchen staff made it in house with fresh garlic in a jar of olive oil. The oil cut off all oxygen from the garlic,which provided the perfect growth medium for the botulinum spores to germinate and grow in.

I make flavoured oils myself, but always use dried herbs or chilis, never fresh. I guess if you are only using the oil for more deep frying, there is less to worry about as any botox will be denatured, so zymurgist is right. It really comes down to your personal level of risk tolerance.

2010 Jul 9
Thanks for the tips Zym and schtickyrice!

2010 Jul 9
Let us know what you end up doing and how it works for you. I've been thinking about the oxygen thing and I guess it must work for me because the jars are full and when I heat up the oil it drives out a fair bit of air from expansion from the heat. Then when it gets sealed up there is only a finite amount of oxygen that will interact with the oil, and I guess that amount is small enough to not make it go rancid.

I could probably improve things by flushing the jars first with CO2 and then filling with oil, but given that my current method seems to work fine I'm not worried about it.

2010 Jul 15
I essentially followed your method Zym and had absolutely no problems it worked well. The heat from the microwave definitely sealed them in and everything was good. So thanks for the tips.

One other question - do I need to get new lids to seal them a second time?

I seem to recall someone who cans telling me you cannot reuse the lids but am not sure it applies here.


2010 Jul 15
You can reuse lids like this a good number of times. I would never reuse them for proper canning, but this is different as you suspect. With proper canning the top of the jar makes a pretty deep groove into the rubbery stuff on the lid, but doing this makes only a slight groove. The slight groove seems to allow reuse.

One part of my procedure that I did not mention was that after boiling and applying the lid, I invert my jars. I did not mention this because once recently I did that and the lid was not sealed well, and I had boiling hot stuff spraying everywhere. So I did not want to recommend something that was potentially dangerous, and besides I used this technique just fine for years without inverting - only started doing that a few months ago.

Anyway, upon further examination, the lid I'd used in that case was one that had been used for regular canning, and had the deep groove. Bad idea. I still do the inversion when storing half-full jars in the fridge. But I am a lot more careful with it, and do not necessarily recommend this to anyone else. Actually, come to think of it, I do not do it with oils though. Just things like pasta sauce and drippings.