In the poor student or youth worker days it was popular to have never ending soup; a large pot on the stove that was topped up with new and leftover ingredients when available.

Normally the pot was stored in the fridge overnight.

Food items added were sometimes plate leftovers from fellow flat (share house) mates, who would in turn be eating the soup, too.

Most days other ingredients would be fresh(ish) vegetables, beans, grains, and fresh meat products sourced from the local butcher as money allowed.

Brussels sprouts where banned, and so were strong spices (you added those to your bowl before serving).

Also, for irony, a large (cleaned) stone is always left in the pot.

Fresh bread was sometimes baked in the oven while cracked bones were browning, but the oven was often an electrical and environmental death trap.

The pot kept going till the summer holidays, and no one got food poisoning in my time, or from any student stories I have ever heard.

This sort of activity is recorded in history as being a popular resource-saving idea.

Are there any real food safety implications with this method of cooking? And have any actual studies of this technique ever been published?

I still recommend this money-saving idea to current students, not keen on bad practices being continued though.

  • 11
    That's hilarious... and kind of disgusting. I assume that the pot was actually heated and not just sitting there, right? It's a bit similar to the question Can one preserve food by periodically re-heating it?.
    – Aaronut
    Feb 1, 2012 at 13:42
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    I think there are some modern day inexpensive buffet restaurants that still work sort of like this. There may be one piece of pasta in the mac n cheese that has been traveling in there for months... Shudder.
    – renegade
    Feb 1, 2012 at 17:20
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    Put was pulled out of fridge (it was usually in there), and then put on the stove to boil. If we got too tanked and no one put it away, the cat would start eating it when it had cooled sufficiently by the middle of the night. The cat ate at our table anyway, so no biggie
    – TFD
    Feb 1, 2012 at 19:56
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    We had stone soup as a kid, but the soup was always made fresh. We had a "soup stone" that was re-used, a nice smooth river rock. Feb 2, 2012 at 23:02
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    If you'd left it going all the time on the stove, it would be perfectly safe... ironically the refrigeration is what makes it unsafe. Also... the cat eating from the pot. Nasty!
    – BobMcGee
    Jul 6, 2012 at 19:22

5 Answers 5


It takes quite a while for a pot of hot soup to cool down to 40°F in the fridge. Several hours, sometimes, depending on the shape of the pot and the volume of soup. If you're heating and re-chilling the same soup daily, it's going to spend a lot of time in the danger zone. From a safety perspective, you'd be much better off making a pot of soup every few days and then reheating just the portion that you're actually going to eat.

I still recommend this money saving idea to current students

Soup is a great food for stretching a dollar, but I don't see how it's any more expensive to make a fresh pot twice a week and it shouldn't take much time either. I understand that you were adding scraps each night, but you could as easily save those scraps for a day or two until you make the next pot of soup.

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    Good point about the amount of time in the 'danger zone'. If someone insisted on doing this it would be a good idea to use a "cold paddle" or "ice wand" to speed up the cooling process. But I agree that just being in a routine of starting over again every so often is the best policy. Saving up scraps and even peelings is not at all unusual. I do this myself with chicken parts for example and make a big batch of stock whenever I have material and time.
    – renegade
    Feb 10, 2012 at 18:39
  • If you cool the soup in many smaller containers it won't take so long to cool and be in the danger zone.
    – user37554
    Aug 13, 2015 at 20:11
  • @CrawfordChristopher Agree, and that'd prevent the need to reheat the entire pot of soup each night as well. But the question is really about cooling and reheating the same pot of "never-ending" soup every night indefinitely, so the small container option doesn't really apply to the question.
    – Caleb
    Aug 15, 2015 at 1:29
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    @AndrewMattson I missed the bit about "plate leftovers" being added -- that's just gross. I envisioned adding bits and pieces left from preparing other dishes. I'll also point out that making a fresh pot every few days instead of endlessly extending the existing pot affords the opportunity to periodically wash the pot, which would be another step forward from a sanitation perspective.
    – Caleb
    Nov 29, 2016 at 15:29
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    @renegade And the stone is the exact opposite of a cold paddle: it's a large thermal mass that does nothing more than keep the soup warmer for longer. Jan 17, 2017 at 10:37

Officially, its unsafe.
This is largely due to the fact that the time spent in "the danger zone" is cumulative. You may be killing off bacteria, but during their lifespan they may release toxins and spores that you may not kill. Every time you reheat the bits of leftovers, they're adding up time in the 'danger zone'.

Addionally, soup is only good in the fridge 3-4 days - so unless it was fully reheated every 3-4 days, its unsafe that very first 5th day , irrespective of any other debate. Bacteria still grow in the fridge, just slower.

  • 3
    Are you sure about this? Assuming the food is being reheated to cooking temperature each time - we're talking about the very bottom of an exponential growth curve, combined with regular consumption and replacement (i.e. dilution).
    – Aaronut
    Feb 1, 2012 at 19:05
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    @Aaronut - I'm definitely sure that the danger zone is cumulative and there is food that is being reheated well beyond 2 hours in it. The problem is you never know if you're consuming the toxins or just making it more concentrated. You then re-dilute it, but you could be just bring it back to the strength it was. Would I personally do it? Sure. Is anything likely to happen? Probably not. Could I in good conscious call it 100% safe to a stranger on the Net? No.
    – rfusca
    Feb 1, 2012 at 19:12
  • @Aaronut - The difference here between this and Bob's answer on cooking.stackexchange.com/questions/16872/… is that they're keeping it out of the danger zone by periodically reheating it and they might cool it down and reheat it again for a day or maybe two. Not indefinitely.
    – rfusca
    Feb 1, 2012 at 19:29
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    If a pot of soup is boiled for an extended period of time, left covered and put away, is time spent in the "danger zone" really all that accurate? The contents of the pot were thoroughly heated, pathogens killed by the heat, and then, while it is cooling, covered, there is very little opportunity for new pathogens to get introduced. I guess part of it depends on whether it remains heated beyond the time when people are taking out servings or adding ingredients. It's quite different than adding hot food to a container, because the pot, itself, has been heat-treated, as a container, right? Nov 29, 2016 at 15:14
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    @PoloHoleSet : the problem is when you don't bring it up to a high enough temperature for long enough. Like if someone heats it up to an eating temperature and then cools it back off. Bacteria can produce spores or toxins that can't be killed off at high heat. That's why you can't just boil something if you suspect botulism.
    – Joe
    Sep 28, 2018 at 18:28

Ok, I have been making never ending soup for many years. I do not put it in the refrigerator at all. We really eat very luxuriously. So, it is not the savings that we are after. There is nothing like hot soup whenever you want it, if the soup is good enough. We do not put left overs from other people into the soup (it’s safe because of the temperatures, we just don’t like to) except from time to time I freeze bones until I have enough to make bone broth. For our never ending soup if we really like it, we keep it at 180°F. It hardly changes and I don’t worry about the top being hotter than the bottom or having to stir it as you do when at 140°F. If adding ingredients for over night cooking I keep it at 200°F. If adding ingredients to be done in 1/2 to 1 hour 210°F (simmer). Although, you can keep it going indefinitely because 180°F is like freezing it, I usually keep it going only about 5 days. I find the fresh soup seems to taste a bit better then to keep adding to the old soup, although I have done it many times and have had it going for months, over time I found 5 days is enough.

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    180? 140? 200? What are these numbers, and how do you keep the soup there? Feb 6, 2019 at 14:21
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    Keeping a pot of soup at 180°F for five days sounds incredibly wasteful of energy unless you have some method of insulating the pot. Also, the OP's situation was quite different than what you describe... there, the soup was repeatedly heated and chilled, passing through the danger zone many times, and so the safety considerations are also very different.
    – Caleb
    Jul 11, 2019 at 17:42
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    @Caleb For me, if I was doing it in the winter, it would not be a waste of energy. Since my house is heated with electricity anyway, and my stove is electric. The electricity "wasted" by the stove would be pretty much exactly counteracted by energy saved on my electric baseboard heaters. For the same reason, where I live, energy-efficiency of light-bulbs, appliances, etc., doesn't matter at all 5 months per year. But I admit this is an uncommon situation.
    – JBGreen
    Jul 1, 2020 at 19:37

The good thing about soup is it is hot enough to kill all potential pathogens. It is also unlikely to be a low-acid low-oxygen environment long enough for botulism to rear its head. Sounds completely practical and the safest possible way to make use of left overs and questionable cuts (the other way is curries I guess).

Seems to me a "cup of brown" was available from soup vendors in the distant past. Maybe that's just in fantasy novels :-).

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    I'm not entirely sure that that soup vendors in the distant past would hold up to modern food safety standards...
    – KatieK
    Feb 8, 2012 at 2:10
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    It doesn't sound like the safest possible way of doing anything. For example, one could refridgerate or even freeze the leftovers and make them into soup in batches, rather than continuously. Also? Plate scraps, ew. Jan 17, 2017 at 10:39

The danger zone is between 40 and 140 F, where bacteria can grow. While simmering, it's above 140. After the fridge chills it, it's below 40. Theoretically, you could perpetually chill it or perpetually simmer it and it would be preserved, but that's not practical (too expensive to keep it simmering all the time, and on the other hand you wouldn't want to eat it cold). Also, the time any part of it spends between those temps is where bacteria grows, so the shape of the container you're chilling it in is also important. Never put the pot in the fridge, as that will leave the soup in the center of that shape retaining some heat longer -- as the periphery chills, the center will be in the danger zone too long. So it's best when refrigerating to transfer it to flatter or smaller containers to eliminate this warm center. This is why restaurants transfer soup from the pot to flatter pans like those in a steam table, not because they need the pot for the next batch, but because a pot of warm soup in the fridge becomes a bacteria incubator.

  • 6
    Keeping food colder than 40°F or hotter than 140°F is important for food safety, but your theoretically, you could perpetually chill it...and it would be preserved statement is misleading. Even food kept well chilled will spoil eventually, and simmering the soup and then refrigerating it again doesn't reset the clock (see rfusca's answer for why).
    – Caleb
    Jul 11, 2019 at 17:01

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