Unlike the good old plastic lunch bag, insulated bags can keep your food hot or cold much longer and prevent it from going stale. They're even better at keeping warm and cool than traditional lunch boxes because of their built-in insulation. But how do they work? In a nutshell, they are made up of several layers.
How do you carry your nomad meals ? By Isothermal Bag, of course ! But ... How do insulated bags work?
Most insulated bags have multi-layer insulation. They usually have an outer layer, a lining and a middle layer that provides insulation. The middle layer is the most important because without it, an insulated bag would be no better than your lunch box.
While thermoses and lunch boxes rely on a vacuum created between the outer and inner layer to prevent energy dissipation, insulated bags keep food and drinks hot or cold with a middle layer made of dense foam. The thicker and denser the foam, the better the insulation.
The foam layer prevents heat from seeping into the outer layer and keeps the surrounding cold or heat from reaching the contents of the bag. You may notice that the outside of insulated lunch bags do not warm up when filled with heated items, because the heat cannot dissipate. (The outer layer of most lunch bags is usually made of non-woven fabric, vinyl or heavy fabric.)
As an added layer of protection, many insulated lunch bags have an inner layer or lining made of foil, heavy vinyl or plastic that is waterproof and heat reflective.
This means that the inner layer of the bag, which resembles foil, reflects the heat energy radiated by the food, rather than absorbing it and allowing it to escape from the bag. As a result, the food inside retains its original temperature, flavor and moisture for longer than in a regular bag.
This means that this type of bag also prevents food from going stale, as foil does, but to a much greater extent.
That's why insulated lunch bags are a must for people who like to pack their own lunches on the go, for kids who take their home-cooked meals to school, and for anyone who prefers to eat a hearty home-cooked meal rather than play Russian roulette with their health when ordering takeout or fast food.
How long does an insulated bag stay cold/hot?
There is no easy answer to this question. The length of time food can be kept in an insulated lunch bag varies depending on several factors:
- The type of bag
- Whether or not there is a heated or frozen gel in the cooler bag
- Outside temperature
As a general rule, without added gel, food in a lunch bag should still be warm after two to three hours in hot weather and four to five hours in cold weather. A heated or frozen gel pack can give you an extra three to four hours. An ice bread mini can adapt the temperature lower in the bag before enjoying your meal.
But these numbers depend largely on the quality of the bag and the ambient temperatures. So it's best to test your cooler bag at home before taking it out for lunch.
How to improve the performance of a cooler bag?
Here are some tips if you want to keep your food hot or cold longer in an insulated lunch bag:
- Place a cold or hot source in the bag, such as a heated gel pack/water bottle if the food is hot or a frozen gel pack/water bottle/juice box if the food needs to stay cool.
- Reheat food just before packing or place chilled food directly from the refrigerator or freezer into the lunch bag.
- Wrap the food in aluminum foil for an extra layer of insulation; then you can wrap a tea towel around the food to prevent heat from dissipating.
- Do not open the bag until you have actually eaten the food to prevent heat energy from escaping from the bag.
- Place the lunch bag in an air-conditioned area (the trunk of your car on a hot summer day is not an ideal place for a lunch bag if you want to keep the contents cool)
- Use the right size lunch bag for your needs; a partially filled insulated container is less effective than a full one.
- Keep hot and refrigerated foods separate, even if some foods are inside the bag and others outside.
We hope that with all theses tips, you can now manage to choose your isothermal bag.