These bags are not intended to be sealed before sterilization, however they can be successfully "pre-sealed" before sterilizing if all excess air is removed from the bag, excess bag material is neatly folded around the bag, and the bags are allowed to cool slowly and completely before removing them from the sterilizer. If the pressure cooker/sterilizer being used lacks an internal liner, caution should be taken to avoid contact with the internal walls of the unit, as the higher temperature retained by the walls can melt the bags.