If I leave fully-cooked food (particularly meat) out at warm temperature – say on the counter or in a crock pot that's been turned off – how long will it stay safe to eat?
Does it make any difference if I re-cook the food afterward?
food-safetymeat
If I leave fully-cooked food (particularly meat) out at warm temperature – say on the counter or in a crock pot that's been turned off – how long will it stay safe to eat?
Does it make any difference if I re-cook the food afterward?
As you mention, cooking the steak to medium rare does indeed kill the bacteria on the surface of the steak which is where most of the risk of contamination exists, so immediately after you've cooked the steak, if you eat it, you're probably pretty safe unless there happened to be bad organisms living inside the meat.
Assuming that you've got a good piece of meat, with nothing terrible inside it, after you cook the meat, what you need to worry about most is bacteria that you introduce to the meat, and so to answer your question, cutting meat shouldn't affect the safety of storing meat after cooking at all (as long as you use a clean knife/cutting board).
While cooking the meat does initially kill all of the surface bacteria, the fact that the surface was once cooked doesn't really do anything to deter new bacteria from moving in and going to town on the meat. What this means is that you need to be very careful to keep meat in sanitary conditions regardless of whether the exposed surface has been previously cooked or not if you're planning to eat it without cooking it again.
So, to recap, if you take a piece of meat where all bacteria has been killed via cooking, and seal it without introducing new bacteria, you should be safe to eat it.
The one remaining issue is that we're not talking about a steak that's necessarily had all bacteria killed. There's a possibility that some bacteria survived the cooking inside the meat. If this is the case, you may be safe to eat the meat right away if there are very few of these bacteria present (depending on what they are), but the longer you wait - even if you seal the whole thing up - the longer you're giving those bacteria to multiply into large enough quantities that they can destroy the meat and/or sicken you. To avoid this, you want to put the meat in the refrigerator, as soon as possible to slow bacterial action, and eat it as soon as possible. Like John, I've had success with around 3-5 days, but it really depends on what you're starting with, so I'd highly recommend that you have a good look/sniff before you eat to see if there are any signs of spoilage and discard if so. Again, this is a risk whether you cut the meat or not, so that isn't really a factor here.
Regarding partially eaten steaks, this is just introducing one more place where bacteria can get on the steak before it's sealed up and refrigerated. I could see this being no issue (if you're cutting off a piece of the steak, and sealing/refrigerating the rest while eating), or a significant issue if you're cutting the steak with utensils that have been in your mouth, or worse, trying to store a piece of steak that's been in your mouth. In those cases you're almost certainly introducing more bacteria and decreasing the amount of time you'll have before spoilage occurs.
So, in summary, cut the meat if you like - that should make no difference. Get it sealed up as soon as possible without exposing it to anything non-sterile. Put it in the refrigerator as soon as possible. Throw it out if at any point you detect spoilage. Following these steps you should be safe to keep your leftovers for 3-5 days and only rarely need to discard spoiled food.
Just to provide an official source, the USDA's National Advisory Committee on Microbiological Criteria for Foods (NACMCF) says this (unit conversion added):
Question 4: What minimum time/temperature parameters for hot holding would ensure food safety?
. . . For non-continuous temperature and time monitoring, a minimum hot holding temperature of 130°F / 54.4°C for a maximum time of 4 hours, based on information provided by FDA regarding the limitation of growth of Clostridium perfringens to no more than 1 log_10 in food, would be adequate to ensure food safety. In addition, the Committee concluded that a minimum temperature of 135°F / 57°C for a maximum of 8 hours, or a minimum temperature of 140°F / 60°C indefinitely also would be adequate to ensure food safety. . . .
You can read further details in the link and the detailed report which is linked on that page. But, basically as long as your food stays above 140°F / 60°C, according to this report, it should remain safe "indefinitely."
I would say that the main issue arises in the fact that you might add things to this endless soup/stock. It would only become potentially dangerous if the additions are below 140°F / 60°C when added (and thus cool parts of the food into the danger zone before they recover) or if the additions already contain toxins that might then be concentrated as the liquid evaporates off. Food above 140°F / 60°C should not be producing new toxins (from bacteria at least), but whatever is in there already may not necessarily be destroyed. Adding water though shouldn't pose a problem as long as it's heated before adding or is only added in a small quantity which wouldn't reduce the temperature below 140°F / 60°C.
My main other concern would be that any cooking vessel or utensils used be VERY non-reactive. Elevated temperatures will make it easier for metals or other substances to dissolve more quickly. A pot or pan or other vessel that might be fine for simmering for a few hours could leach more significant quantities of metals or coatings over days or weeks. If your cooking vessel AT ALL reacts with the liquid inside of it, this could pose a long-term issue.
(It's possible that some foods themselves might break down into less desirable components, but this will mostly be a quality issue than a safety issue at temperatures below boiling. At much higher temperatures -- which would be impossible in a liquid stock -- you could also potentially produce carcinogens over time as things break down, but this is probably unlikely for food kept in your proposed temperature range. If you were to let the stock reduce at some point to the point that it went past the demi-glace stage and became drier and temperature began to rise significantly, this could theoretically pose a problem. But in that case you'd probably get smoke and bad smells that would be a clue that your endless soup should be tossed because it had... well, met its end.)
Best Answer
The USDA has this to say on it:
You'll find similar statements from government agencies around the world. The safe limit for raw or cooked food is 2 hours in the danger zone (40-140° F or 4.4-60° C).
If you're a restaurant owner or cook, you must follow this rule, hold hot foods above 60° C and quick-cool other foods before refrigerating. If you are not working in a professional capacity then you are not legally required to follow it, but if you are serving guests then it would be irresponsible (and possibly actionable, if someone gets sick) to do otherwise.
If you're an individual serving only yourself, then take whatever liberties and break whatever rules you want; it's your food, and your body. But there's no table or chart anyone can give you; there's no single specific point at which a food transitions from "not entirely safe" to "probably will kill you" because it depends entirely on the food, the environment, your immune system, and a plethora of other variables. The rule is 2 hours, period; any longer and there is some non-trivial risk to your health.
Some hints, tips, and warnings:
The 2-hour rule is a conservative estimate with a safety margin. Don't ask what that margin is. It's like asking what the "real" speed limit is on a posted road; you might know from experience, but it could change depending on circumstances and exceeding it by any amount means you take your chances and accept the risks.
Don't put large, hot items (such as an entire pot of soup or chili) directly into the fridge. The residual heat will warm up and potentially spoil other items in the refrigerator.
To quickly cool large cooked items, use an ice-water bath and/or divide them into small containers. (Note: Don't use an ice-water bath for cast iron.)
Don't assume that re-cooking an improperly-stored item will make it safe. Most bacteria produce protein toxins, which are actually the primary agents responsible for food poisoning, and several of these toxins are heat-resistant. Cooking will not kill or inactivate these toxins and eating the re-cooked food will still make you sick.
Don't assume that cooking "kills everything" and that a cooked food or cooking surface is absolutely sterile. Cooking kills enough to make the food safe to eat, but some organisms - such as bacterial spores from bacillus and clostridium - can survive the cooking process and immediately start producing more bacteria. Sous-vide bags, crock pots, etc. are not safe environments for cooked food in the temperature danger zone.