The drying process removes moisture from the food. This also hinders the growth of mold, bacteria and yeast and ensures the dehydrated fruit and vegetables don't easily spoil. A major contributor to drying food is humidity. As drying involves removing the moisture from the food and releasing it into the surrounding air, low humidity helps the drying process. This is why the drying of foods originated in the warmer and drier countries around the planet. Higher humidity will slow down the drying process as the air would also be heavy with moisture. Increasing air flow can speed up the drying process.