A food dehydrator dries out the food so no moisture can develop and thus no bacteria can grow. It’s a small oven that circulates air at very low temperatures.
A freeze dryer is a bit more scientific: the food is placed into a vacuum-sealed chamber. The temperature is lowered and then raised again until the water in the food changes from liquid to gas.
Nope! You can dehydrate or freeze dry simple fruits and veggies as well as soups, casseroles, even pet foods – you simply soak them in water or, in the case of soups.
Freeze-dried food lasts longer. Food can be stored for 25-30 years. Dehydrated food can last over a year if not vacuum-sealed.