Sausage casing is the edible membrane, natural or synthetic, that holds the meat filling of a sausage in shape while it cooks, cures, or smokes. Natural casings are traditionally made from animal intestines, such as sheep or hog casing, and remain common in sausage-making traditions in Germany, Italy, and Eastern Europe; modern alternatives include synthetic and collagen- or cellulose-based casings.
Casings are generally neutral in flavor, letting the seasoned filling (garlic, onions, paprika, mustard, and regional spice blends) come through, though some natural casings add subtle texture and flavor of their own.