What is the difference between freeze dried and dehydrated food?
Freeze-drying removes 98% of the water in food 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.
See also:
Freeze Dried vs. Dehydrated Backpacking Meals and Ingredients