how to use a food flask

Food flasks are great for keeping food cold or hot for longer. You can use them for work or school lunches. What’s more, these containers allow you to pack nutritious meals so you and your kids can enjoy tasty meals despite having busy schedules.

Whether you already own a food flask or are searching for information to help you decide if you need one, we’ve got you covered. Either way, we’re sharing our favourite tips on how to use a food flask the right way.

Using a Food Flask

In order to use a Thermos properly, there are some instructions you’ll need to follow to retain the heat and enjoy hot meals. Food flasks are designed with double-wall vacuum insulation that allows them to retain the temperature, keeping your food hot or cold for several hours. It’ll keep food hot or cold depending on its original temperature of it before being in the food jar.

For cooler recipes, one thing you can do is add an ice pack in your bag next to the Thermos.

How to Preheat a Food Flask

There are things you can do to keep meals hot for longer in your food flask. For the best results when wanting food to stay hot, pour boiling water into the Thermos and screw on the lid. Leave the hot water for around five minutes, although you can leave it for a longer period to keep your lunchtime meal piping hot.

Then, reheat your food in a microwave or pan. Empty the water from the flask and place your food inside the jar. Place the lid on securely and keep it in a lunch bag until you’re ready to leave the house.

How to Clean a Food Flask

Once you bring your Thermos home from work or kids, bring it home from school, and empty any leftovers into the bin, rather than letting the remaining food build up and create stains in the Thermos flask.

Once you’ve emptied any leftovers from lunches, fill the flask with warm water and some dish detergent. Avoid submerging your flask into deep water, but choose to fill it with water instead. Allow this mixture to soak for up to five minutes to remove any stubborn stains.

Next, wrap a microfibre cloth around a bottle scrubber and gently scrub the inside of the container. This technique will help to remove any stuck-on food in the Thermos flask without scratching the surfaces. Next, rinse with warm water. Wipe the inside of the Thermos with a towel and air dry.

How to Prevent Hot Food from Spoiling

hot soup

A Thermos flask is great for keeping food piping hot and allowing you to explore new and exciting lunch ideas. The best way to prevent food from spoiling is not to let it sit for long periods before taking it with you. Doing so means that you’ll keep food in the lunch container for longer than you have to.

Fortunately, flasks won’t spoil food as long as it stays above 15 degrees Celsius or 23 degrees for meat. It’ll usually keep your food warm for up to six hours before it begins to cool down. After this point, there’s a chance that harmful bacteria will start to grow, which then becomes unsafe for you to eat.

It would be best if you also considered that some foods would naturally spoil more quickly than others. For example, chicken, fish, and meats won’t last as long as vegetables, making them more prone to attracting bacteria. With this in mind, opt for spoil-friendly ingredients if you won’t be consuming your lunch for over five hours. This could include pasta, stew, and soups—all without meat.

Preparing School Lunches the Night Before

If you plan to prepare meals the night before, you need to follow the proper precautions to prevent any chances of your child getting sick due to food poisoning. When you prepare the food after dinner each night, ensure that you place it into a food jar or container almost immediately. Then, place the food in the fridge. The faster the food cools down, the safer it will be to eat.

The following day, you can then reheat the dish before adding it to your food flask to make a hot lunch that won’t attract bacteria. Whether you’re storing it in the work fridge or your children are keeping their lunches in their backpacks, this is the safest way to prepare your food flask meals.

What to Look for When Buying a Food Flask

One of our best tips to consider when buying a Thermos flask is to choose among high-quality ones so you can enjoy your favourite lunch ideas without any leaks.

To help you discover the best stainless steel Thermos, we’ve devised a buying guide to remember during your search. When in the market for a flask, look at the following:


Whether you’re using the Thermos for hot food or drinks, make sure that it’s the right capacity for your needs.

Most products range between 300 and 700ml, but the capacity depends on how big your lunchtime meals are. For example, if your children don’t eat much for lunch, it may be a waste to buy a 700ml Thermos.

But if you’ll use a Thermos for a long-distance journey, make sure you get something bigger.

Lid Options

Whether they are from Thermos or by a different manufacturer, the lid of food flasks should fit securely and prevent your soup, drinks, and liquids from seeping through. Check out past customer reviews for feedback on the ones you are eyeing to ensure that the Thermos lid remains tight and keeps liquids firmly inside.

In addition, some products feature lids that include a spoon, which is ideal for keeping utensils clean when the kids are eating at school or for transporting lunches without any mess. This means that they can eat your pasta or other dishes without worrying about forgetting or losing cutlery on the way.

Heat Retention

An essential feature of a Thermos is that it keeps foods hot or cold—even if you let it sit for long periods. As opposed to regular food jars, most flasks can keep your lunch hot or cold for 4–5 hours, while some can retain heat for up to 12 hours. The latter is ideal if you’ll be embarking on a long journey and need the flask to retain the heat for longer.

Final Thoughts

We hope this guide on how to use a food flask has been helpful to you. There are so many recipes to explore with a Thermos; from hot food to cold desserts, these items are great for school lunches, days out, and packing hot meals for a working day, so knowing how to utilise one is always helpful!

If you have any tips or ideas on using vacuum-insulated steek food containers or exciting recipes for the family, share your thoughts in the comments.

Additional Resources

One Comment

  1. When one must have used a flask without putting warm water in it for time, can the person still do it after using it for like two or three times?

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