How to Keep Food Warm for Lunch

If you want to have hot food for your lunch, remember that you need to keep the food warm at 1400F (600C) or over. Hot food that is below this range of temperature for 2 hours and more may contain harmful bacteria and mold, especially in hot, moisture days. And if you eat this food, you can get a stomach ache, or worse, a food poisoning. Therefore, it’s important to figure out how to keep food warm for lunch. It’s easy. You will know how after reading this article.

How to keep food warm for lunch with a thermos

A thermos is a container with two metal walls; one is inside the other one. Between these two walls is a vacuum. The vacuum, with no air, prevents the heat from the things that kept inside the thermos from escaping. That is why a thermos can keep hot food warm. You can use it by following these steps:

How to keep food warm for lunch with a thermos

Image source: MightyNest

Step 1: Preheat the thermos

Pour boiling water into the thermos and keep it for 10 minutes to heat the container. This step is for keeping your food warm enough to eat until lunchtime.

Step 2: Heat your food

Heat your food in the microwave or stove until it reaches at least 1000C (2120F) before pouring it into the thermos.

Step 3: Place the food into the thermos

Pour out the boiling water and put the hot food immediately into the thermos.

Step 4: Close the thermos immediately

Seal it tight to make sure the heat won’t escape from it.

If the food is for your children, tell them not to open the thermos by themselves but as an adult to do it for them.

Step 5: Keep it closed until lunch time

Only open the container right when you’re ready to eat. Otherwise, the food will be cool before lunchtime. And it’s an opportunity for harmful bacteria to grow and damage your food.

How Long Is It Safe To Keep Hot Food In A Thermos

It depends on the container that you use and the way you heat up the food. A perfect thermos can keep the hot food up to 5 hours.

In the temperature below 1400F (600C), bacteria grows quicker. Hot food should not stay at that range of temperature longer than 2 hours. Make sure that you heat your hot food at 1000C or more so it won’t be cool to this range of temperature after 3-4 hours. Don’t worry if the food is too hot to eat. We don’t heat it to eat immediately but in 3-5 hours later.

The secret of how to keep food warm for lunch is keeping an eye on the temperature. If you heat it with perfect temperature, but the food is still not warm enough to eat, consider changing a new thermos.

Food that put into the thermos must be cooked thoroughly. That’s mean no raw egg, raw onion, undercooked meat or fish or whatever can help the bacteria to grow easily.

You must throw away any leftover from the thermos at the end of the day. They are not safe to eat.

Always preheat the thermos before filling it with hot food. And always test the new thermos before using it.

How Long Is It Safe To Keep Hot Food In A Thermos

Image source: Today Show

Testing The Thermos For Heat Retention

This test is for making sure that the food packed in your thermos is still warm enough and safe to eat after 3-5 hours.

First, place the heated food or water in a preheated thermos and close the thermos tightly. Then note the time you close the thermos and determine the waiting time. This waiting time is exactly how long you and your children would usually have lunch after packing the food in the container.

For example, if you usually pack your lunch bag at 8 am, and eat it at 12 pm, you need to wait for exact 4 hours. This way, you can check if your thermos works efficiently.

After the exact waiting time, open the thermos and check the temperature of the food.

You will know that you have a good thermos if the food is still warm enough to eat. If the food is cold, you better find a new one.

It would be perfect if you have a thermometer and check the exact temperature of the food. Therefore, you can make sure it is over 1400F (600C). 1 or 2 degrees lower is acceptable. But if it’s much lower, the bacteria might already grow, and the food might not be safe to eat.

Testing The Thermos For Heat Retention

Image source: Tested

Packing a hot-and-cold lunch bag

You might want both hot and cold foods. How can we keep the hot food warm for lunch but not change the temperature of the cold food while putting them in the same bag? The key is an insulated lunch bag and the following easy method:

Step 1: Use a lunch bag that has separate rooms for different food.

Step 2: Cover the thermos with a napkin. The napkin is an extra protective layer for preventing your hot food from being cool down from the cold temperature of the cold food. Use an elastic band to lock the napkin.

Step 3: Place the thermos and the cold items onto two separated sides. Your insulated bag might already have a divider to separate warm and cold foods. If not, or if you want to ensure they are well-separated, you can put into the bag a cardboard.

Step 4: Close the bag. And keep it closed until lunchtime.

Packing a hot-and-cold lunch bag

Image source: The Sweethome

Some Ideal Hot Food For Lunch

Here is some hot food you can make for you and your children to make the lunch time more fun and enjoyable:

  1. Fried chicken. Put an oil absorbing paper into the thermos before putting the food into it to keep it crunchy and not too oily to eat.
  2. Pizza Rolls.
  3. Fried egg rice.
  4. Sandwich. Cut into strips to fit inside a thermos.
  5. Soup.
  6. Pasta served with meatballs.
  7. Hamburger. Take out the veggies and put them in a small container to keep them fresh.
  8. Mashed potatoes with bacon and veggies.
  9. Leftover hot food from last night dinner.
  10.  Ramen soup.


Keeping hot food warm is important for your safety! Hope that this article can help you to keep it nice and warm easily and have more fun while creating lunch-packing food for you and your kids.

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