A sausage is a prepared food, usually made from ground meat, animal fat, salt, and spices (sometimes with other ingredients such as herbs), typically packed in a casing. Sausage making is a traditional food preservation technique. Traditionally, sausage casings are made of animal intestines, though in modern times the casings are often synthetic. Some sausages are cooked during processing, and the casing may be removed after that. Sausages may be preserved by curing, drying in cool air, or smoking. Care must be taken when cooking to avoid burning sausages unless they are desired in that state, as with all burnt meats, burnt sausages are possibly carcinogenic (can cause cancer) due to elevated levels of benzopyrene.