Freeze-drying removes 98% of the water in foods while dehydration removes about 80% giving freeze-dried products a much longer shelf-life. Freeze-dried food is flash frozen and then exposed to a vacuum, which causes all the water in it to vaporize. This requires expensive equipment and isn’t something you can do at home, but it makes it possible to store freeze-dried foods for 20 to 30 years, compared to dehydrated ones, which typically last one to five years.
But the biggest difference between freeze-dried and dehydrated foods is nutritional. Freeze-dried foods retain all of taste, smell, texture, and nutritional value they has in their original form before the freeze-drying process. Dehydrated foods lose about 50% of their nutritional value because they’re subject to heating during the drying process and can become somewhat chewier, since the heating process “cooks” them over a long period of time as they dry.
Freeze-dried foods also rehydrate more quickly, usually in 5 minutes or less (dried berries, almost instantly), in hot or cold water. Dehydrated foods usually take 10-20 minutes to rehydrate, provided you use boiling water, requiring a longer wait and more stove fuel, which are both anathemas for backpackers!
Mix and Match
I don’t dehydrate my own meals anymore, but I still eat commercial dehydrated backpacking meals (mainly dinners) made by Outdoor Herbivore because they taste good and are easy to prepare, even though I’m not a vegetarian. If you have the ability to make meals that taste as good as theirs, more power to you. But dehydrating and making my own dinners at home before each trip is not how I want to spend my free time. Being dehydrated, they do go off after about two years though, so I make a point to eat them all up in the calendar year that I buy them.
I still pack up my own ingredients on trips, but mainly as additives to the one pot breakfasts and some dinners I make myself, based around quick cooking grains and pasta like wheat cereal, oatmeal, ramen noodles, and angel hair spaghetti. But I’ve switched to freeze-dried ingredients out of convenience because they last longer without requiring refrigeration or going bad in our pantry if they’re not used promptly. I really hate throwing out food that’s expired and hasn’t been eaten, so the longer it can be stored and remain fresh, the better.