Freeze-dried and dehydrated food has always been popular with backpackers do to the convenience, light weight, and resistance to spoilage at room temperature.
It's now becoming popular as a critical disaster preparedness item.

About:
Freeze-drying, or lyophilization, is like "suspended animation" for food. In this process, fresh or cooked food is rapidly frozen and placed in a vacuum.
Virtually any food item and ingredient can be freeze-dried. To do this however, specialized equipment is required, making it a costly option.
Cell structure, nutrients, shape, and color are all preserved because of this rapid change, allowing the food to keep a “fresh” look and nutrition.
When it is added to boiling water, freeze-dried food can reconstitute in only a few minutes.

Freeze-drying may keep the food's original look, but it takes up substantially more room than compact dehydrated food.

Dehydrated, or dried, food is made by applying heat to the desired food item, resulting in 98% of the substance's water being lost to evaporation.
This technique has been performed, though through different methods (air drying, sun drying, etc.), for years to preserve foods.

Source: Freeze-drying & Dehydration at Wild Backpacker

Freeze-dried Food Dehydrated Food
Weight Reduction
Nutritional Content
Space Savings
Taste
Cost $$$ $
Rehydration 5 min. in boiling/hot water;
5-10 min. in cold water
1-2 hours in cold water;
5-20 min. in boiling water
From Packit Gourmet via Wild Backpacker

Dehydrated food:
Air Dried Vegetables at NorthBayTrading.com
Dehydrated Vegetables | HarmonyHouseFoods.com
Dehydrated Vegetables & Freeze Dried Meat at BackPackingChef.com

Freeze Dried:
Freeze-Dried Food at REI
Eastern Mountain Sports
MOUNTAIN HOUSE: Standup Pouch: Main Entrees

Links:
Dehydrated Food vs. Freeze Dried Food

last updated 23 Apr 2013