Like many of the greatest advancements in human history, nobody knows who invented reheating food. It is strange to even think of the practice as an “invention”, but consider this: How often was food “reheated” before the gas oven was invented? And even then, how long before that oven was used to make leftovers?
But how many times can that common individual reheat food?
You can reheat food as many times as you can within the shelf life of the food if it is homemade. Anything from a restaurant, however, should be reheated no more than once.
Risks Of Reheating Food
You run a few risks when you reheat anything. These risks are all about playing a balancing act between two opposing forces: The growth of bacteria in your food, and the ability of the food to withstand being reheated.
Do not be alarmed, for as scary as “the growth of bacteria in your food” may sound, it takes a lot of growth under specific circumstances for there to be enough to hurt you.
Bacterial growth in food occurs constantly. In fact, our bodies are filled with bacteria that helps us live. This is why foods that are technically mold, like cheese and yogurt, can actually be quite good for us. The bacteria you need to worry about is the kind that gives you food poisoning. It won’t kill you, but it can make you sick.
Bacterial growth is only ever going to occur in significant amounts when the food is left exposed to bacteria.
So, when is food “exposed to bacteria”? Well, any time it is sitting in the open air unprotected. That might make it sound like food is exposed to bacteria all the time, but that is not necessarily the case.
The heat caused by cooking the food will protect it from bacteria for as long as it remains hot, and the cold of a freezer will slow the speed of bacterial colonization and growth down to such a crawl that it is barely happening at all. This means that whenever your food is cooked or frozen, it is far less likely to develop bacteria.
Part of this is simply due to the nature of bacterial life: There is bacteria that can survive in the cold, and bacteria that can survive in the heat. This is why you move your leftovers from the freezer, which has killed hot bacteria and propagated cold bacteria, to the stove, which kills cold bacteria.
Then, once you have eaten it, you store it back in the freezer again.
The Limits Of The Freezer
There is a limit to how much you can do this, however. Especially with restaurant food, there is a point where your meal will be more bacteria than food, and no change in environment will kill all the bacteria.
This will usually happen after three days of storing the food in the freezer. The National Health Service recommends leftovers be consumed within four days for this reason.
Even further than the growth of bacteria though, how many times you can reheat food is a matter of the food’s integrity itself. Pasta and meat are durable to heat, though both can develop some pretty nasty bacteria.
Reheating food is one of the greatest value-saving methods ever developed. Just be sure to eat your leftovers within three days of storing them, heat them up properly when you do, and be careful for what might have grown on or in them in that time.