Freeze-dried vs. dehydrated food: What’s the difference?Dried (or “dehydrated”) food has shed its moisture via heat and air circulation, usually in an oven or in a simple electric or solar dehydrator. You can even dry herbs and low-moisture foods atop racks outdoors on a hot, dry day. Most home-dried foods keep well if stored in airtight containers in a dark, dry, cool location.Freeze-drying food requires a more complicated process, wherein a machine freezes food to minus 40 degrees Fahrenheit. The freeze dryer then creates a vacuum and gradually warms the food, causing the ice to change directly into vapor — a process called “sublimation.” Finally, the unit causes the vapor to condense and freeze on its internal walls. After the food is removed, the unit warms up and the water drains. You can store the product in cans, jars or Mylar pouches.Both types of food are lightweight and thus popular with backpacking enthusiasts. According to Postharvest Technology and Food Process Engineering, freeze-dried foods have a longer shelf life, retain flavors and nutrients better, and rehydrate rapidly, but are much more expensive to produce than dried foods.