Natural casings made from the intestines of animals have been traditionally used to encase sausage meat for millennia. High-quality sausages will have a natural casing. It looks better and it’s permeable, allowing smoke and cooking flavors to infuse the meat. Artificial casings are also available. Collagen casings are produced from animal hides and are edible. Cellulose casings, made of viscose, are permeable so flavor can pass through during cooking, but not edible. Plastic casings are impermeable and inedible, and typically used for non-smoked, high-volume sausage production.