Page 15 - The Lost Book Preserving Food Naturally

The Lost Book of Preserving Food Naturally

Dehydrating vs. Freeze Drying
Most dried foods throughout history have been dehydrated. This is a process where

sunlight or heat are used to draw the moisture out of the food. Of the two, sunlight has

historically been more common, although modern dehydration techniques use heat.

Freeze drying is a newer process, which has been developed for use with foods that don’t

dehydrate well. Some fruits, like berries, don’t turn out well when dehydrated, but are
shriveled and hard. While they can be rehydrated, they really can’t be eaten as they are.

Freeze drying provides an option in those cases, providing dried foods that appear more

appetizing (because they look more like the moist version) and are edible without
rehydration.

Freeze drying can also be used for some foods that one would not expect to be able to be

dried, like ice cream. The invention of freeze drying coffee revolutionized the coffee

industry, providing a means of making instant coffee that tasted almost as good as fresh

brewed.

While it is possible to freeze dry foods at home, the equipment is considerably more

expensive than dehydrating. The three-step process for freeze drying is also more
complicated. It consists of freezing the food, then placing it in a vacuum chamber. Low

heat is applied, along with the vacuum. This causes the water crystals to evaporate

directly in a process known as sublimation. After this, the food undergoes secondary
drying, in which remaining water is removed under higher temperature.

In a survival situation, freeze drying probably wouldn’t be effective, because it requires

much more electricity than dehydrating does. Since dehydrating food can be

accomplished with nothing more than solar power, it would be much more effective in a

survival situation.

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