Preserving food has been a problem since people started eating. Now, fortunately, we have a variety of ways to preserve food. Take the Florida Food & Farm quiz on “dehydrated” vs. “freeze-dried” foods. / Photo courtesy of

The practice of dehydrating foods — the oldest method of food preservation — has been around for centuries. The freeze-drying process, of course, is far more recent. Its first major use was during World War II — not to preserve food but, rather, blood that needed to be sent from the U.S. to Europe.

Below are five questions about freeze-dried and dehydrated foods. How many can you answer correctly? (Answers at bottom.)

1) Which words below are other names for “freeze-drying”?
a) lyophilisation
b) lyophilization
c) cryodesiccation
d) comestibleusdessicus

2) How low is the temperature when freeze-drying foods? *

3) How do “dehydrated” foods differ from “freeze-dried”? *

4) How long will properly prepared freeze-dried foods last … how long will dehydrated foods last? *

5) What is the major advantage that freeze-dried foods have over dehydrated? *

* Source:

Answers: 1) a, b, c; * 2) “Fresh or cooked foods are placed in the dryer where they are frozen to -40 degrees Fahrenheit or colder”; * 3) Though freeze-dried foods are subjected to subfreezing temperatures, dehydrated foods are “heated with warm air for a period of time, which evaporates the moisture in the food”; * 4) Freeze-dried “foods are shelf-stable for 25+ years. The color, taste and texture remain the same (after rehydrating) similar to frozen foods.” Dehydrated foods have about the same shelf life; * 5) “The most important positive about freeze-dried foods is the convenience of using them in everyday recipes as well as long-term use. … these foods can be prepared quickly with either hot or cold water. … (The main problem with) dehydrated foods is the time it takes to prepare them, which can take from 20-30 minutes, usually in boiling water. This isn’t an issue unless, in a crisis situation, time is short and fuel for cooking is scarce or non-existent.”