While it isn’t common to hear about them, self heating meals are actually a bit more common than you think. However, the first thing that most people think when they hear about them is “how do they work?” or “what is the secret behind self-heating meals”. After all, food needs heat to be cooked, and generally heat needs to be produced somewhere. The process by which these meals heat themselves is actually really interesting and actually ties directly into the processes that allow them to stored safely as well.
The only thing that you need when you are going to use one of these meals is water, and often that is even included. Most of the time it will be salt water, which is actually important to the process. Outside of that, the meal, the heating bag, and even the utensils are usually provided. These meals were originally designed to make it easier for soldiers and people in disaster situations to eat and stay healthy.
The process of heating starts when you open the bag, making sure not to tear it too much, and giving yourself enough space to fold it over later. Usually this means that there will be a guide line for opening it, and some are simply sealed with a removable tape or something similar.
Next the food is places inside the bag, making sure that the heating pad is touching the food. There may be arrows on the top to indicate which direction is up, or you may just need to look for the big lump that is the heating pad. Water is added, either measured from your own stores or from the water that is included in the kit, before the bag is closed and then rolled as tight as possible.
Once the bag is closed, it needs to be placed on a heat safe surface and should be left alone for at least 10 minutes, before a steaming hot meal can be pulled out of the bag. Because the process does involve water, it is a good idea to be careful when opening the bag to make sure that you don’t get a steam burn or spill water all over everything.
So that’s how the bags work on a day to day level, but what makes it so that they function, and why can they only be used once? The answer is science, and the key to the chemistry behind the reactions power the heat is actually water, and element not well known for causing heat, but that can be used to conduct heat rather well in cooking and other applications.
The heating packet that was mentioned earlier is the most important part of the process, as it contains calcium oxide, sodium carbonate and aluminium powder in pre-measured quantities. When these come into contact with water, they cause something called an exothermic reaction, which creates heat and allows the meal to be warmed. Once the reaction has happened, the calcium and other ingredients have already been activated, explaining why you can’t use them to heat another meal. Instead, they are safe for disposal and won’t create heat or any other reaction when exposed to water.
The bag, pouch, or box that the food is in is also important as it is specially made to conduct heat. The water reaction will generally only get up to around 100 degrees, but when placed against a bag that helps conduct heat, the food is subjected to much higher temperatures for a short period of time. This also makes it so that you can keep leftover food in the bag for a few hours without it getting cold, prolonging the life of your meal.
Finally, the box that the meal comes in is often put around the heating bag to give another layer of insulation, just like you might wrap food in tin foil and then place it inside of a cooker. The result is that any steam that escapes has yet another barrier to go through before the energy becomes lost.
The entire process that it takes to cook a self heating meal only takes a few minutes and can be done anywhere in the world. As long as you have access to water and a stable surface that won’t have a problem with 100 degree heat, you can make yourself a meal. This is important for people who work in emergency care, people in disaster situations, and people who like to go into the great outdoors. It provides a cooking option were there wasn’t one before, but also doesn’t add much bulk to the cooking process.
While the selection of self heating meals is a bit limited at present, the technology behind it is catching the attention of many groups of individuals who simply want to eat a hot meal in situations that wouldn’t otherwise allow for that to happen.