What do you picture when you think of freeze drying? A pot of stroganoff, rendered to dry pasta and powders? A bag of life-saving blood, ready for transport to needy soldiers? Or perhaps you picture the high mountains of Peru and majestic ancient cities like Machu Pichu? Today we’ll walk through the history of freeze drying, and what the process is actually doing to your emergency food.
If you want to show off you can call freeze drying by its other name: lyophilization. Lyophilization is the process of completely removing water from a material (in our case, food.) For some foods, dehydration and proper storage are all that is needed to achieve this, but for wetter food, like fruits and veggies, freeze drying is often the better route.
The principle that sets freeze drying apart from other methods of food preservation is sublimation. Sublimation occurs when conditions allow a molecule to break free from those around it. We see a similar effect, evaporation, every time we boil a pot of water. In sublimation however, the water molecules skip a step, going directly from a solid into a gas.
What state a molecule takes is dependant on two factors: temperature and pressure. Water, for example, is a solid when frozen, a liquid when tepid, and a gas when it gets hot. What they might not have taught you in science class however, is that if you lower the pressure enough you can turn ice directly into vapour, without melting the water to liquid form.
For more details on how this is achieved, check out this helpful page from a company that makes lyophilizers.
Although this technique was made famous by NASA and their astronaut ice cream, it has a history dating back to the fifteenth century. The Inca people of Peru stored their crops in the mountain heights where the altitude creates a low-pressure environment that is cold enough to freeze the food quickly. The water inside then vaporized over time in a rudimentary form of freeze drying.
In World War II technology was introduced to the freeze drying process for life-saving results. In order to keep blood from spoiling on the journey from the US to Europe, scientists began experimenting with lyophilization with excellent results. It wasn’t long until the technique was being used to preserve bone and penicillin.
After the war freeze drying found its niche in the medical and food industries. It gave full meals, fruits, vegetables, and even meat shelf lives of up to 30 years when combined with the correct packaging, making it a no-brainer for emergency preparedness.
Why Freeze Dry?
Besides the long shelf lives there are other reasons to use the freeze drying process for preserving food. Removing all of the water from a meal or other material makes it very light weight. For some foods, they can become up to two thirds lighter from having the water inside removed. The lightweight and compact nature of freeze dried meals, combined with no need for refrigeration, makes them a popular choice for camping, backpacking, boating, and other outdoor pursuits.
When food is frozen slowly and stored with the water inside (like in your freezer) the process can cause large ice crystals to form and degrade the quality of food (freeze burn). Because freeze-dryers freeze their food rapidly, these crystals do not form. This keeps food as fresh as the day it was frozen, even if it isn’t reconstituted for decades.
All in all, freeze drying is the perfect way to preserve emergency stores. If you have any questions or comments about the process or history of this fascinating method, please let us know in the comments – we’d love to hear from you!
Thank you for reading.
This article was written by Zenia Platten – Author and emergency preparedness professional.