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Among family, I have found radically different approaches to reheating food that has already been fully cooked. Some will not eat last night's leftovers unless they have been microwaved to the point where every single part of the food is piping hot. Said people consider food that is "cold in the middle" dangerous. Others are happy as long the the meal is sufficiently warmed for it to be safe to eat.

This gives me my question. Why do leftovers need to be reheated before they can be eaten? Is it just for pleasure or is there an actual safety benefit?

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    As someone with executive dysfunction, I will often eat cooked leftovers right out of the fridge, cold. Pizza, sausage, sliced turkey, whatever. There are a few things I won't do that with just because the taste/texture is unpleasant to me when cold, but that's about my limit. I've never had a case of food poisoning in my life that's sent me to the hospital, and the few times I have gotten food poisoning is more often attributable to going out to eat than eating cold leftovers. I never keep such things longer than 7 days though.
    – Doktor J
    Sep 30 at 14:08
  • I'd like to add to the comments pointing out that rewarming doesn't make leftovers safer: I saw a segment on TV about feeding pigs leftovers from hotel buffets, and they put everything into a stew and bring it to a boil. In the old days, stew (for people) made from leftovers on other peoples' plates was definitely re-cooked, not just warmed up.
    – JDługosz
    Sep 30 at 18:12
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The primary reason for reheating is just that warm food is more pleasant to eat. How warm, that is a personal preference - and stirring or heating longer can ensure more throughout heating.

Reheating does weaken and kill pathogens. However, properly stored food should not have a dangerous amount of pathogens to start with. And some pathogens can either tolerate high temperatures or excrete toxins that are not destroyed by heat. Thus reheating food that already has a high amount of pathogens is only partially effective. Heating before cold storage is much more effective, as the pathogens do not get the chance to grow in the first place.

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    Good on on the toxins: If stored food is old enough to have significant pathogens in it it also has a high chance of already having toxins in it, the latter isnt really affected by heating
    – Hobbamok
    Sep 28 at 8:29
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    You got to risk it for the cold biscuit!
    – blankip
    Sep 29 at 19:41
  • One could speculate about the reason why we prefer warm food - from an evolutionary perspective it might have been advantegeous to prefer meat that was still warm and therefore fresh over cold meat from an animal that had died long ago.
    – elzell
    Sep 30 at 7:56
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    @SeanDuggan it could be both evolutionary and chemical -- after having discovered cooking, those that cooked their food died of food poisoning less often than those that didn't, so those who evolved a taste preference for those released chemicals survived more often than those who didn't.
    – Doktor J
    Sep 30 at 14:02
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    For foods with oils whose melting points are within the range of heating, the mechanism for heated being preferable, if not the reason that came to be, is at least fairly clear. Sep 30 at 17:53
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You don't. Reheating food does not improve food safety, it is purely a matter of taste. Even "piping hot" is not hot enough to kill off any pathogens. If it's safe to eat warm, it's safe to eat cold. As an anecdote, my sister considers last night's leftovers, cold directly from the fridge, the most delicious of breakfasts. Regardless of if it's pizza, a curry, or a beef stew.

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  • Comments are not for extended discussion; this conversation has been moved to chat.
    – Stephie
    Sep 29 at 13:38
  • This isn't strictly correct. Piping hot food is likely to be somewhere around 60 °C, proteins denature at around 41 °C. Anything over 41 °C will be killing bacteria and breaking down viruses. But, as you say, previously cooked food is perfectly safe to eat cold as long as it has been stored correctly. Oct 1 at 0:46
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It's a personal preference. I preferfood at, below, or slightly above room temperature while my relatives like their food scalding hot.

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We don't need to reheat food. Cooked food can be eaten cold. We may want to reheat food if its something that would be easier to eat or tastes better hot; or to kill bacteria if its been sitting out at room temperature and may pose a food safety issue.

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    Unfortunately your assumption that unsafe food can be made safe by heating is false.
    – Stephie
    Sep 29 at 13:39
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    Technically, cooking certain foods in the first place can mean "unsafe food made safe by heating" :) Sep 29 at 20:38
  • Hmm... I think the point being made is that the initial cooking is what makes it safer (breaking down organic compounds, heating it to higher temperatures that eliminate pathogens) and that reheating it doesn't induce additional helpful changes. Sep 30 at 12:23

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