ehydration is all about removing water from food. Doing this helps to preserve the food (bacteria need water) and concentrate flavor. It’s a common misconception that you need heat to dehydrate food. But low humidity, not heat, is the driving force behind dehydration. Warming the air surrounding the food helps keep it dry, but if the air doesn’t move, the food will stay wet. So when dehydrating food in the kitchen, make certain that air can freely circulate around it.
Sidenote: You can achieve the same preservation of dehydration by leaving the water in food but making it unavailable to bacteria. Just add substances like sugar and salt, which bind to water molecules and lock them away. Lox (salt-cured salmon) and salted butter are safe to keep at room temperature for this reason—but unsalted butter is not!