Lunch bag with two cooler blocks sticking out of it in front of an orange background

Lunchtime Tips: How to Keep Lunch Box Cold

Whether you’re packing a lunch for your little one or yourself, there’s a good chance that you need to keep lunch cool and don’t always have access to a refrigerator. Food that stays out too long at room temperature can cause dangerous bacterial growth levels, leading to foodborne illness. Lunches are safest when hot foods stay hot and cold foods stay cold.

Bacteria grow most rapidly in temperatures between 40 °F and 140 °F, doubling in number in as little as 20 minutes. This range of temperatures is often called the “Danger Zone.” That's why we’ve created this guide that’s full of suggestions to keep your food fresh and out of the danger zone. Some links in this post are affiliate links meaning we will be compensated if you purchase through them.

Containers to Keep Lunch Cold

The USDA recommends starting with food that's already cold and using an insulated container as part of your lunch packing system. These containers play a large part in ensuring that perishable foods you pack remain at a safe temperature for the hours between packing and eating.

1. Insulated Lunch Bags

Bento boxes with multiple compartments are one of the more popular lunch box options. Most bentos are non-insulated and will need an insulated lunch bag to stay cold. These lunch bags come in a broad range of shapes, sizes, and designs. If you're getting an insulated lunch bag to carry a bento box you'll want to make sure to choose a lunch bag that fits your bento.

Tips for Using Insulated Lunch Bags:

  • Make sure to look for easy to clean fabrics – typically you'll clean these bags by wiping them out with warm soapy water.
  • If you pack lunch into an insulated bag ahead of time then store it in the fridge, make sure to leave the bag open while it's refrigerated so cold air can circulate.
  • If you're packing a hot food like soup along with cold foods you'll want to keep the hot food as separate as possible from the cold. Some people achieve this by wrapping the insulated soup container in a towel to create more of a temperature barrier before placing it in the lunch bag.

2. Freezable Lunch Containers

The Bentgo Chill comes with a removable ice pack that's incorporated into the bento's design. Other options with an ice pack include Fit & Fresh and DaCool lunchbox containers. My experience from using the Fit & Fresh brand of food containers was that it's convenient to have the ice block that fits so nicely with your container, but you still needed an insulated bag, and possibly another cold source to really stay cold.

As far as freezable lunch bags go, the PackIt line of bags is great. Their lunch bags are lined with a freezable material. All you need to do is put the bag in the freezer before you pack them, and they can hold on to the cold for an impressive amount of time. The only struggle we've had with them is sometimes forgetting to put them back in the freezer after school.

3. Thermos's

Thermos containers aren’t just suitable for keeping beverages hot, they can also be used for keeping food and drinks cold. They're designed with the proper insulation to ensure food and drinks maintain a temperature within the safe zone.

Tip for keeping Thermos's cold: Depending on the diameter of your thermos you may be able to use a neoprene sleeve made for wide-mouth mason jars to add an extra layer of insulation.

4. Cooler Containers

If you are packing a large lunch that needs more space or packing for more than one person, a cooler could be a better option. They are made specially to provide more space, and the insulation acts as refrigeration of sorts to keep the content cool.

Lunch bag with two cooler blocks sticking out of it in front of an orange background
Photo via Shutterstock.com

Cold Sources and Ice Packs for Your Lunch Box

While using containers and lunch bags that are made to keep the contents cold is smart, that’s only one step when you need to keep a lunch box cold.

To keep lunch foods cold and maintain a temperature under 40 °F, lunch makers should include at least two cold sources in an insulated lunch box. These can be frozen gel packs, juice boxes, or bottled water. Frozen juice boxes or bottled water will thaw and should be ready to drink by lunchtime.

1. Ice or Frozen Gel Packs

Using an ice pack is almost imperative when packing a cold lunch. You want to ensure that it’s frozen, and not just cold. The slim ice packs made especially for lunches are easy to fit into your lunch bag and are quite affordable.

2. Frozen Water Bottles

Most people pack a water bottle in their lunch boxes. To maximize it, just freeze a water bottle overnight and pack it in the lunch bag. It acts as a great tool to keep the temperature down, and it’s refreshingly cold and thawed when it comes the time to drink it.

3. Do-It-Yourself Ice Packs

For those of you looking to keep lunch box cold with do-it-yourself methods, we’ve found two simple options for you, and you likely have the materials at home already.

  • Sponge Ice Packs

Get yourself a sponge, a plastic bag, and a glass bowl before starting. Fill the bowl with cold water and dunk the sponge into it until it’s thoroughly soaked. Make sure to let the excess water drip off the sponge first, and then place the fully wet sponge in a ziplock bag. Then, remove all the air from the bag, seal it up, and put it in the freezer overnight.

  • Dish Soap Gel Pack

To create a dish soap gel pack, you need to line the inside of a glass with a ziplock bag, but make sure that the seal is guarded so that no soap gets on the zipper. From there, add approximately ¾ cups of the soap to the empty bag and add some food coloring if you want to make it colorful. Make sure to remove all air bubbles from the bag before you remove it from the cup and seal it. After it’s sealed, lay it flat in the freezer overnight. Keep in mind that they won’t freeze to a solid, but to a gel-like consistency that can be reused.

A few more tips for how to keep lunch cold without refrigeration:

  • Store lunch in a cool spot out of the sun.
  • When packing lunch, keep food in the refrigerator until the last moment so it's as cold as possible going into the lunch bag.
  • Include multiple cold sources and place them close to perishable items in your lunch bag.
  • Keep lunch containers closed before eating.
  • Consider keeping non-perishable snacks in an outer pocket or otherwise separate from your cold lunch in order to access them without opening the insulated compartment.

FINAL VERDICT

There are plenty of ways to keep your lunch box and the contents of your lunch box cold. Start by making sure food is cold already when you're putting it into the lunch box. Use an insulated bag to hold the lunch box, and use two cold sources.

These tips should help to keep your food out of the danger zone, so you and your kid don’t get sick. The food should remain below 40F for cold and above 140F for hot. Happy eating!