How long have I got, doc?

How long does it take for good fry oil to turn bad you mean? That depends on a number of factors, chief among them the type of oil/fat you’re using. In general, you want a frying medium that’s fairly stable (i.e. resistant to breakdown) and neutral flavor-wise. For me that means either vegetable or canola oil. Solid fats like shortening or lard are even more resistant to breakdown, but are less convenient for the home fryer.

Assuming you don’t fry a whole lot of food at one time, you should get half a dozen uses out of a single pan full of oil (you’ll have to replenish some of course, since the food will soak some of it up). But use your nose. If the oil looks dark and/or has that telltale fishy ketone smell, dispose of it. You can do what I do and pour it out in a remote corner of the yard, or put it into disposable vessel and put it in the trash. Under no circumstances should you put it down the drain. Even liquid fat is hell on pipes.

Another important tip: if you want to re-use oil, don’t fry in an uncoated cast iron pan. Exposed iron acts as a catalyst that speeds up oil breakdown by many orders of magnitude. I know, grandma made fried chicken in that big cast iron pan you have. There’s no reason to break tradition, just don’t expect to use the oil again afterward.

7 thoughts on “How long have I got, doc?”

  1. Thank you! I’ve had oil go bad and didn’t think to smell it first before using it to fry food or baking with it. ruins whatever you are making. I’ve done the same with flour and bread crumbs; not good, either.

    Canola oil is not flavorless. It has an odor and flavor (that doesn’t suit me) in either baking or frying. I can’t even describe that flavor..but it’s there. I jumped on the band wagon when all the TV chefs were singing Canola Oil’s praises of healthfulness and neutral flavor so I tried it, several times. I can’t possibly have gotten ahold of 4 or 5 different bottles of canola that were going bad, so why does everyone say the flavor is neutral when (to me anyway) it’s clearly not? Plus it feels heavier (thicker or denser?) than veg oil. The ones I used were national brands..biggies!

  2. I have moved to lard! For me it is easier because I have a dedicated deep fryer, and the lard just sets in it making storage a lot easier. Sounds terrible, but it is a lot healthier fat than butter and you don’t eat it in nearly the same quantities.
    I have been trying to find somewhere local that will recycle old cooking oil but without success. I know there are places that use it for biodiesel, but unfortunately not near me – it’s worth checking out though. I’m thinking I might just pour a bit on some firewood and see how it burns in my log burner. Carefully.

    1. I know it wouldn’t use much but there’s always the business of mixing in a good amount of birdseed and letting it solidify in muffin tins or small cans with a loop or length of string embedded.

      Use the string to hang them or tie them to branches for the birds to eat over the hard winter months. They need the additional fat to metabolize into body heat.

  3. Interesting, since lard was the preferred fat in medieval times (they loved their pig). Turns out they may have been onto something.

    As for the cast iron pans – could this be why some people ‘season’ their pans? Would that reduce the effect of the cast iron?

    1. Hey Jim!

      No, seasoning doesn’t really impact fat breakdown very much. Indeed even a seasoned cast iron skillet can destroy a batch of fresh oil in 2-3 uses.

      – Jim

  4. I keep all of my used cooking oil and use it as weed killer. It is very effective. For small amounts of oil I pour it off into a coffee cup or measuring cup and dump it on any weed nearest to the kitchen. larger amounts I’ll store back in the container it came in and use a small gardening sprayer to spread everywhere. It works great when you string trim away the weed and apply it dirt where it was. An edgings best friend.

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