Final answer:
Freeze-dried food is lightweight and has a long shelf life, making it popular among campers and soldiers. It is prepared using freeze-drying technology, which removes water from the food in a vacuum chamber.
Step-by-step explanation:
Freeze-dried food is commonly used by campers and soldiers due to its lightweight and long shelf life. It is prepared using freeze-drying technology where the food is cooked, frozen, and then dehydrated in a vacuum chamber, resulting in a final product that retains 98 percent of its nutrition and weighs only 20 percent of its original weight. The vacuum speeds up the dehydration process by lowering the boiling point of water, causing the frozen water in the food to sublime directly into gas without going through the liquid phase, thus preserving the food's structure and nutrients.