Dehydrated and freeze-dried food: what it is, how long it lasts and whether it's worth it

Our grandparents dried plums, apples and mushrooms in the attic or in the sun. The idea is the same today: without water, bacteria and mold can’t grow, and food keeps for months or years. The difference is that we now have faster and safer methods.

Dehydrated or freeze-dried?

	Dehydrated	Freeze-dried
How it’s made	Warm air, 40-70°C, several hours	Fast freezing, then ice removed under vacuum
Water left	5-20%	1-4%
Texture	Chewy or crisp, shrinks	Crisp, keeps its shape
Taste and nutrients	Some vitamins lost	Very well preserved
Shelf life	6 months-2 years	10-25 years in sealed packs
Price	Low, can be done at home	High
Rehydration	15-60 minutes, sometimes boiling	A few minutes with hot or cold water

What’s worth having in a home supply

Dried fruit: prunes, apricots, raisins, figs, dates, cranberries, apple and banana chips. Eaten as they are, sweet, rich in fiber and energy. Watch store-bought cranberries and banana chips: they’re often sweetened or fried in oil.

Dried vegetables: onion, carrot, celery, leek, peppers, mushrooms, sun-dried tomatoes, potato flakes. A handful turns an instant soup or a bowl of rice into a complete meal.

Beans and grains: these are also dried foods, and have the best ratio of price, calories and shelf life. See the non-perishable food list.

How to dry your own

You need a dehydrator or your oven (on its lowest setting, door slightly open).

1. Wash and slice fruit or vegetables into thin, even slices (3 to 6 mm).
2. Pre-treat: fruit that browns (apples, pears, bananas) goes into water with lemon juice for a few minutes. Vegetables like carrots, green beans and peas are blanched for 2 or 3 minutes first.
3. Dry at 50 to 60°C (120 to 140°F) for fruit and vegetables. Times vary from 4 to 12 hours.
4. Check: fruit should be pliable with no moisture when torn; vegetables should be crisp.
5. Condition: put them in a loosely closed jar and shake daily for a week. If condensation appears, dry them more.
6. Store in airtight jars or vacuum bags, somewhere dark and cool.

For jerky, follow tested recipes and higher temperatures, for food safety reasons.

Freeze-dried emergency meals

“Survival food” packs contain complete freeze-dried meals (pasta with sauce, stews, breakfasts) that you prepare by pouring hot water into the pouch. Pros: light, tasty, very long shelf life, no rotation needed. Cons: high price and the need for hot water.

They make sense in two situations:

• for the go bag, where weight matters;
• for a long-term supply you don’t want to track and rotate.

Otherwise, a pantry of ordinary food rotated properly is much cheaper.

Don’t forget water

Any dried food needs water to be eaten. A freeze-dried meal needs 250 to 500 ml, a portion of lentils or rice even more. When you work out your water supply, add the water for cooking.