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I left fully cooked lasagna out on the counter all night. My house is 72 degrees Fahrenheit (22 degrees Celsius). Is it safe to reheat and eat?

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    Aaronut has written some excellent food safety answers, such as cooking.stackexchange.com/questions/16665/… and cooking.stackexchange.com/questions/12992/… - have a look at those, before you even think about trusting the more "adventurous" (i.e. potentially dangerous) answers here.
    – Cascabel ♦
    Aug 22, 2011 at 23:23
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    There are a lot of similar questions out there. The fact you post it means you know, deep down, that it's not safe.
    – BaffledCook
    Aug 22, 2011 at 23:54
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    There is insufficient information in the question for anyone to give a definitive answer. For example, how was the dish covered? was is in a container or open for flies and cockroaches to crawl over while you slept.
    – Rincewind42
    Aug 24, 2011 at 13:44
  • I don't have any professional experience so just anecdotal and your mileage may vary: I have done so many times, with lasagne and spaghetti bolognese etc. also where it wasn't covered by any means. I have never been sick. Also, I know plenty of people (including my parents) who will always leave what remains of pizza, lasagne etc. in the oven for the next day so it is just a matter of turning on the oven to heat it up. Seems this is just how they were brought up, and has never caused problems. I will usually put in the refrigerator unless I forgot. But I do, I will eat it anywyay.
    – Morty
    Sep 17, 2018 at 10:37

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Throw this out. The general rule of thumb is that food that isn't otherwise preserved (through large quantities of acid or sugar for example) must not be in the danger zone from 40-140 degrees Fahrenheit for more than 2 hours. In practice this is an oversimplification - see the incredible and incredibly detailed food safety section in Modernist Cuisine for the whole story. Overnight is way too long. It is quite possible for bacteria to have multiplied and secreted toxins which are heat stable. E. Coli and Staph. Aureus both do this, for example. Reheating will not make this safe. It isn't worth making yourself or your family horribly ill. Order pizza.

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    It doesn't take "a bunch". One cell of these microorganisms, if allowed to thrive in a warm, moist environment for 12 hours could grown into billions of them. Unless of course your house is a surgical operating theater and your tomato sauce contains bleach.
    – Michael Natkin
    Aug 22, 2011 at 21:59
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    @michael: With a double rate of about 20 minutes, you'd need 10 hours just to get one billion, assuming the contamination was instant, the food was in the dangerzone, and also that the food was an ideal growth medium. In practice, you're more likely to get the e coli poisoning from your side salad. I'd put it at higher risk than raw eggs, but at a lower risk than raw chicken.
    – Satanicpuppy
    Aug 22, 2011 at 22:54
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    @Peter, this isn't an issue of agree or disagree, it's one of fact. There are at least a dozen common household bacteria that thrive in warm, moist environments and produce toxins within 2 hours. 4 hours is the absolute maximum time you can leave hot or warm food out and still be safe. Doesn't matter if it's cooked or not. Obviously the danger is greater with raw meat, but that's only because raw meat has a greater likelihood of being contaminated in the first place.
    – Aaronut
    Aug 22, 2011 at 23:12
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    @Satanicpuppy: Please, tone it down with your food safety rants. Unless you're an expert on microbiology, you have no basis from which to make such broad, sweeping claims. The fact is, tomato sauce does not have a high enough pH to stop bacterial growth, home kitchens are not sterile environments, and the type of cheese used in lasagna (mozzarella, ricotta, etc.) is more than moist enough to support bacteria, especially after being drenched in tomato sauce and water from the cooked pasta.
    – Aaronut
    Aug 22, 2011 at 23:23
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    @Satanicpuppy: Yes, exactly, they USDA and other agencies post guidelines that minimize risk. That is exactly what they do, and that is exactly what we need to do when answering food safety questions. It is the only responsible thing to do. We can certainly go into more detail and attempt to quantify the risk and let people make their own decisions if they wish to ignore the dangers, but simply telling people to ignore the guidelines because you think it's safe is extremely irresponsible and inappropriate. By all means add a caveat to the accepted guidelines but don't ignore them.
    – Aaronut
    Aug 22, 2011 at 23:35
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Was the pasta in a sealed container? If it was left open to the air or was touched by anything that could contaminate it, it might not be ok.

On the other hand, I have left rice and pasta out overnight in the pot with the lid on at room temperature numerous times and never had a problem. This "two hours at room temperature and throw it out" thing is really overkill almost all the time. Only if you are pretty unlucky will the food be unsafe to eat.

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    Food safety is not about being safe most of the time, or safe unless you're unlucky. There are a lot of people out there, and we want them all to be safe, not just the lucky ones. If everyone follows your advice, a lot of people will get seriously sick.
    – Cascabel ♦
    Sep 14, 2012 at 6:43
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If by reheat you mean get the internal temperature up over 140F for more than 10 minutes (and it won't really taste "hot" until you do so), then it's totally fine, provided that it was fully cooked originally.

That said, if you cooked it fully originally, unless there's something a little funky about your ingredients, you're probably fine to eat it cold right now. Of course "probably" is very different than definitely.

Hence, 140F if you wish to be sure. Alternately, touching 165F would be plenty; don't even have to wait the ten minutes.

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    I'm sorry, but this is dangerous, terrible advice. Bacteria can leave toxins that you can't destroy by reheating.
    – Michael Natkin
    Aug 22, 2011 at 21:34
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    @michael: Eh. I think the lasagna would be fine, but I agree that you shouldn't think heating makes you safer.
    – Satanicpuppy
    Aug 22, 2011 at 21:40
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    See my answer below, and read aggie-horticulture.tamu.edu/extension/poison.html if you have further doubt - there are several bacteria which produce toxins that you aren't going to destroy by reheating. This lasagna could make someone really sick.
    – Michael Natkin
    Aug 22, 2011 at 21:43
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    I have thoroughly reviewed the link you post, and stand by my general advice. Which bacteria listed on that link do you believe are at risk of growing here, (and note, at a rate which will cause significant toxins being left out 12 hours?) If the lasagna was safe to eat at first (and in this case, it seems to be, since the author has posted this question), there is nothing on that list that poses a health risk if the lasagna has been re-heated the following day. Food safety is important, but there's no point in spreading fear needlessly.
    – Peter V
    Aug 22, 2011 at 22:55
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    So there is lots of evidence that proves that this might be unsafe, but there is no evidence that actually proves that it is. The USDA regs are a ridiculous standard ... they introduce more harm by over-sterilization then they actually fix. If this was cooked properly to start with, and the food smells good, then eat it and stop wasting your money.
    – Kirk
    Aug 24, 2011 at 3:24

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