A dehydrator works by exposing food to low temperatures of heat for a long period of time in order to remove the moisture from the food. Without moisture, bacteria, molds and yeasts are unable to grow. Food dehydrating also slows down enzyme action, although it does not stop it entirely. This means that when water is added back to some foods after drying, they return to its original size and weight.
This method of food drying, which preserves the food so that it can be consumed later, has been around for centuries. Today, the electric food dehydrator is used to prepare lightweight foods for camping, hiking or children's snacks, such as fruit leather made from dried strawberries.
Method of Removing Moisture
A dehydrator usually uses a temperature of 140 degrees F, because higher temperatures will cook the food rather than drying it. "Case hardening" is when the food is cooked on the outside, but still moist on the inside. This is caused by setting a dehydrator to a temperature higher than 140 degrees. Food like this will most certainly mold in a couple of days.
A food dehydrator also uses an air current to dry the food. As the food heats up slowly, moisture evaporates into the air. That humid air must be removed and replaced with dry air. Therefore, the faster the air current, the faster the food will be dehydrated. The best electric food dehydrators have adjustable air current speeds, along with strong fans and plenty of ventilation.
All food dehydrators feature racks that are stacked on top of each other, which space in between for the food to sit on the racks and for warm air to flow between the racks. Air that moves from the top to bottom of such dehydrators will mix the flavors of the foods on the racks. Some cooks do this on purpose. Other dehydrators have fans which make sure the air circulates from side to side, so as not to mix flavors.
A food dehydrator usually has double wall construction, allowing the air inside to stay warm with the outside of the container remaining cool. Some also feature heating elements on the sides rather than top and bottom, which dries the food faster and more evenly. This also prevents juices from dripping on any heating elements. Finally, many food dehydrators feature timers that will notify you when the drying process is complete, a handy feature due to the fact that dehydrating food can take up to 72 hours.