Freeze Drying 101

So you want to know a little more about the freeze drying process and how it all works. Well we're here to help and try and make the process as easy to understand as possible.

Freezing

The process all begins as the name implies - by freezing the food. But this isn't like your home freezer, oh no. Freeze dryers remove all the air from the chamber and can take foods all the way down to -50 or even -70 degrees F (-56 C for those on the Celsius scale).

"Drying"

Once the food is frozen, it begins the "drying" cycle. The food is warmed, and because it is in a vacuum (with no air), the water in the food sublimates (i.e., goes directly from ice to water vapor). Given sufficient time, the moisture in the food is removed through the process of sublimation. Because low temperatures are involved, there is little change to the food's flavor, texture, and nutritional value. Speaking of which...

Nutrition

Freeze drying retains more of the food's nutritional value than any other method of preservation. Other methods, such as canning or dehydrating, use high temperatures that can destroy much of the food's value, not to mention changing the flavor and texture. Which leads us to...

Flavor and Texture

Preserving foods inevitably changes their flavor and/or texture. Canning often over saturates the food, making it soft and mushy, while dehydrating often makes the food tough, flavorless, and difficult to rehydrate. For most freeze dried foods, however, once rehydrated, it is hard to tell the difference from the original product.

Shelf life

Freeze dried foods have the longest shelf life of any preservation method. Oxygen, light, and moisture are the enemies of food storage. Freeze drying takes care of the moisture, removing 98-99% of it from the food. And so long as they are stored properly (in vacuum sealed bags/containers with oxygen absorbers), oxygen can be eliminated too. Lastly, protecting the food from light, whether by storing them in a dark place, or more commonly by using Mylar storage bags, light exposure can be easily controlled as well.

Shelf life of the average food (in years).