In the most simple definition, sulfuring helps to preserve the color of some dried foods, like apricots. Fumes from burning sulfur or gaseous sulfur dioxide penetrate the surfaces of foods before they are dried. I do not sulfur the foods I dry. I do not believe that it is necessary when drying foods in an electric food dehydrator. Sulfuring is mainly used as a pretreatment when foods are dried out-of-doors.