You have a pot of leftover stew on the stove. Should you let it cool down a bit before transferring it to a plastic container and putting it in the refrigerator? Or should you place it in the fridge as soon as possible, to get it cold more quickly?
Do Hot Foods Placed in the Refrigerator Warm Up the Fridge?
The reason many people say you should not place hot or warm foods in the refrigerator, especially large amounts, right away is that doing so will only release heat into the refrigerator and warm up everything else. Thus, not only will your hot food not cool down very quickly, but anything else, such as your milk, will become warmer. Thus, there is no advantage to placing overly warm foods in the refrigerator and you are only going to cause other foods to spoil faster.
Some folks say this depends on the type of food, as well. For example, while it is fine to place leftover meat in the refrigerator right away, you should wait for a large pot of stew or other such food to cool down to room temperature, first.
Is any of this true?
While it is logical to expect a large amount of hot food placed in the refrigerator to release heat into the refrigerator and thus warm up its interior, modern refrigerators can recover from this very quickly. This is, after all, what a refrigerator is meant to do. The danger of letting hot foods sit out at room temperature is much greater than the threat of a temporary warming trend in your fridge.
Place Leftover Cooked Foods in the Refrigerator Quickly
As stated in safe temperatures for foods, there is a golden rule for storing food: keep hot foods hot and cold foods cold. Returning to that pot of leftover stew, if you keep it on the heat, at just below a simmer, it will be safe to eat and you can leave it there and have another helping later if you’d like.
But once you turn the heat off and allow the stew to start cooling down, it quickly enters the danger zone and will stay in this zone, becoming a paradise for foodborne pathogens, until it is chilled.
A Little Cooling Science with Your Stew
This may need some further explanation. The hotter an item is compared to the environment it is in, the faster it will cool down. A very hot item, sitting at room temperature, will start cooling down very rapidly at first. Then, as it reaches closer to room temperature, this energy loss will slow down quite a lot, meaning that the item, while you are waiting for it to be “cool enough” will stay in the danger zone for more time than it stayed “hot.” By that time, the bad bugs are already there, and the refrigerator will not kill them.
Placing it in the fridge will mean that it cools down more quickly and spends less time in the danger zone because the relative difference in temperatures is more extreme.
Find out more about the danger zone by reading the article linked above. Meanwhile, just know that the people who say to let hot foods cool down to room temperature first, to keep from warming up the fridge, are wrong. Place all leftovers in the refrigerator as soon as possible. You want to cool them down through the danger zone and past it quickly.
How Long Before Harmful Bacteria Starts to Grow?
The length of time you have before you must put leftovers in the refrigerator depends on the volume of the food and its composition. A huge pot of boiling soup, with its cover on, may remain hot longer than a few servings of leftover casserole, for example.
Although there is no point in waiting until the last minute, the general rule of thumb is that bacteria will start to grow in around two hours. The hotter the temperature in the room, the more the food will be kept at a temperature that is just right for bacteria to multiply out of control. This does not mean that they will not grow at lower temperatures but that they will grow faster if food is kept warm, but not hot. So, if the room the food is sitting in is very hot, especially above 90˚F, you need to refrigerate it even faster, within an hour, at most.
Let the Food Stop Steaming First?
I have recently come across the assertion that hot food should be allowed to stop steaming before it is put into a sealed container, whether it be one container or smaller containers as explained below. The reason, apparently, is because the steaming food will cause condensation, which will then drip back onto the food to cause little pools of water. This water, then, will be the perfect breeding ground for bacteria. I have no idea whether there is direct evidence supporting this assertion, or if it is just an assumption. Warm food, whether steaming or not, will cause some condensation in a plastic container, but unless we compare many samples of the same food, and measure the bacteria growth on food left out for 30 minutes and then sealed, versus the bacteria growth on foods sealed right away and refrigerated right away, we have no way of knowing whether this is true. Pursuant to further evidence put forth by food safety specialists or microbiologists, I would advise you to continue refrigerating foods as soon as is practical.
Separate Large Amounts of Hot Food into Small Containers for Chilling
If you have a large amount of food, like our stew, and you have enough room in the refrigerator and enough containers, you can separate out the food into smaller containers. This is better because the food will cool down much faster in smaller amounts, thus getting it down to the safe temperature of 41° F or below faster. Another tip I’ve read from quite a few sources is to place stew or soup into a flat container, to allow heat to dissipate more quickly. This may be a good idea, but I would advocate that unless you plan to store your dish in this flat container, adding an extra step is not likely to make a big difference in the overall outcome.
As well, the smaller containers allow for conveniently reheating small amounts for later. This is good because you want to avoid warming up portions that you do not eat.
To keep your leftovers for longer periods, you may want to consider purchasing a food vacuum sealer.
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