I found an interesting question on the Cooking subreddit and it reminded me of an issue I’ve had at home involving the reheating of things like chili, spaghetti sauce, soup, etc. When storing leftovers in the refrigerator, is it better to reheat the entire pot or to reheat only the amount you want to eat? Will reheating the entire pot over and over make it last longer?
Quote: “Reheating chili on the stove? So I’m a broke college student trying to make bulk foods over winter break. I went with chili cause I’ve been craving it for a while. The issue, my recipe made 8 servings, and I’m only one person. I’ll probably only eat a bowl a day, so 8 days. Wayyy longer than chili will last for in the fridge. So, the question is, if every time I go to grab a bowl, I reheat the entire pot on the stove, would it last longer or am I accidentally gonna give myself botulism and die?” — gayspaceanarchist
I understand the logic. My wife, in the past, used to always heat up the entire pot of whatever leftover she wanted to eat, only to take out one serving and leave the rest to be put back in the refrigerator. She did it for no reason at all it was just a habit. But here, the OP is wondering whether reheating the leftover chili will make it last longer by killing the germs in it. In other words, if you “sterilize” the leftovers over and over again, will they last longer? Or, is it better to just remove the portion you want to reheat and put the rest of the leftover chili back into the refrigerator immediately?
The first thing to consider is how this affects the sensory qualities of the food. Reheating food and cooling it back down again and again is not likely to do anything good for the taste and texture of the food. But the question here is not about taste. It’s about safety.
The answer is that, while it does seem logical to want to heat the food and thus keep the bacteria population at bay, in reality, you are probably not doing that.
When you reheat leftovers, you are probably not sterilizing them or “disinfecting” them. They will be safe to consume, but to kill all pathogens, you would have to boil the chili or other leftovers for at least 10 full minutes, and perhaps more, to make sure all the contents reach a sufficient temperature, for long enough, to kill all the bacteria. So, unless you really want to boil your leftover chili or soup for ten full minutes or longer multiple times, it’s not a very practical way to reheat them.
And, if you don’t manage to kill all the pathogens, even if you put the remaining food that you don’t eat back in the refrigerator immediately, some of the bacteria will begin to multiply as the food cools through the danger zone. Then, even once the food has reached the typical refrigerator temperature, 40 F, this bacteria will continue to live and slowly divide. This is not to mention any other bacteria that may have been introduced into the leftovers as it was heating up and still outside the refrigerator.
So, in essence, by reheating the entire pot of chili, you are waking up the bacteria, potentially introducing more, and giving both spoilage bacteria and potentially harmful pathogens just the type of environment they need to thrive and divide. And this can occur very quickly. Bacteria can double in number every hour under the right conditions.
This is why the golden rule is to “keep hot foods hot and cold foods cold.” This is meant to minimize time in the danger zone, which is the temperature range between 41° F to 135° F (5° to 57° C). Bacteria will not die below 41° F, but they will not thrive. Above 135° F may not destroy all pathogens, but it will keep them from reproducing. Quoting from my article What Are Safe Temperatures for Foods in Restaurants, “Between these two temperatures, however, is the danger zone, where bacteria enjoy conditions perfect for their life cycle. They will begin reproducing at an astonishing rate. Once present in high numbers, it is too late — the food is considered adulterated and not fit to serve.”
And here is the important bit for our question, once food has spent 4 hours in the danger zone, it is considered unfit to serve in a restaurant. However, this period is cumulative! So, each time our Reddit friend reheats his pot of chili, he is letting it spend more time in the danger zone. Despite the fact that he is refrigerating it, more and more bacteria add up until the chili becomes, officially speaking, unsafe to eat.
It is not likely that anyone would get sick doing this. Let’s be honest, we’ve all done worse. As for botulism, it thrives in an oxygen-free environment, so it isn’t a worry when reheating foods. But the question was which way is the safest. The safest way to reheat leftovers is to only reheat the portion you intend to eat and put the rest of the leftover food directly back into the refrigerator so that it stays at the same cold temperature the entire time you are finishing it, even if that takes a few days.
Will the chili last 8 days? Probably not. He seems to be storing the chili in the pot which is not airtight. Chil or any leftovers will last longer when refrigerated in an airtight container. This way, the chili will probably last about four days.
