Processing is a term used to describe a step in the canning or jarring process. When a jar of applesauce is processed, it is rested in a water-bath canner to help destroy any micro-organisms. According to our research, you can process applesauce in an oven, but you have to add it to a tray filled with boiling hot water. Then, leave it at 200 degrees for 15-20 minutes.