If I make a skillet full of bacon, how long can I leave the grease sitting out before it is unsafe/rancid? Is the answer different for ground beef grease?

3 Answers 3


Fat doesn't spoil like other foods. No bacteria can live in fat. Going rancid is a chemical reaction in which the fat molecules break down. So "leaving out" is not a problem.

The major factors in going rancid are light and air. The more light hits your fat, the sooner it goes rancid. Also, rancidity occurs when the fat is oxidized, meaning that if you prevent contact with air, your fat will last longer.

Both factors are minimized by transferring the fat to a tightly closed opaque container. With liquid oils, you use a dark colored bottle. As bottles are impractical for solid fat, just strain your grease into a jar, close it, and put it in a cupboard. The shelf life should be many months, probably more than a year.

Also, don't worry that you can get something nasty when the grease goes bad unnoticed. Rancid fat isn't a big safety risk, and ingesting it in small amounts is not problematic. If it stinks, throw it out. Before that, there is no problem eating it.

The above assumes pure, well-strained fat. Pieces of fried meat left over in the fat are a safety risk, even tiny ones.

  • 4
    Then what is so bad about rancid oils? If they can't infect you? Just it just taste unpleasant?
    – Chloe
    Commented Jun 19, 2015 at 0:08
  • 2
    @Chloe yes exactly, people avoid them because they dont like the taste.
    – rumtscho
    Commented Jul 4, 2015 at 10:14
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    Actually, there is evidence of negative health effects in animal models, and there are also case reports of rancidity-caused illness in humans. See this article (citations included): nutritionnutsandbolts.com/2012/08/01/rancid-fat
    – Stew
    Commented Sep 23, 2015 at 20:51

Grease makes an anaerobic environment —that is, that it lacks oxygen— and while that may prevent many types of bacteria from growing in it (Staph.,E. coli,etc.), Clostridia species (including the kind that causes botulism) are obligate anaerobes— they need to have an oxygen poor environment in which to live.

Now, will all that scalding grease allow bacteria to live in it? As more is collected, it mixes and rapidly cools when it melts the existing grease.

Although our grandmothers may have collected grease and kept reusing it, people used to die a lot younger "back in the day" as well, just saying.

When it comes to food handling, better safe than sorry. Once it cools, store it in the refrigerator where it will keep for up to a month without fear of bacterial overgrowth.



I've been using the same fish grease for 5 years....my mother did the same for even longer...and so did my grandmother who just turned 92. We're all in great health, no prescriptions. So skip all the talk, I'm living proof you can reuse over and over again.

  • Skip all what talk? The other answers provided insights in why exactly you can keep fat a very long time. That is what this forum is for. Nice of you to also add anectotal evidence, but it hardly makes the answers above superfluous. Commented Jun 20, 2015 at 8:29
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    I dont think the guy meant other answers were the "talk" he wanted to skip. I believe he mant he didnt have to go into detail as to why, just that he has seen it true.
    – user36595
    Commented Jul 3, 2015 at 23:03
  • @user36595 Richard ten Brink's comment is still spot-on: explaining why is a core part of an answer. Without that, this answer could just as easily be one person getting lucky as a solid fact. What if "why" is an important part of the answer? Maybe he's actually been keeping it in a dark, airtight container, and that's why it's working so well.
    – Cascabel
    Commented Jul 4, 2015 at 0:26
  • And he might also be in a colder climate (which would tend to have smaller windows, which means less light in the kitchen as well). It's also possible that there's something different about 'fish grease'. (I assume this is grease from frying fish, as other than the lion fish, fish doesn't get to be as fatty as other animals)
    – Joe
    Commented Jul 4, 2015 at 12:42

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