A sausage casing is a sheath that holds and forms the shape of the sausages. Ground meat, vegetables, and spices are stuffed inside these casings.
Types of casings:
Natural - made of intestines of pork, sheep, or cows and are edible
Artificial - made of collagen, or plastic and are not edible
Natural casings are made from the submucosa, a layer of the intestine that consists mainly of collagen. The fat and the inner mucosa lining are removed. Natural casings tend to be brittle once cooked and tend to "snap" when the sausage is bitten. They may also rupture during the cooking process; often, this indicates that the cooking was done too rapidly. Natural casings may be hardened and rendered less permeable through drying and smoking processes. Natural casings are generally made from porcine, bovine or ovine intestines.They can be flat or shirred, depending on application, and can be pretreated with smoke, caramel color, or other surface treatments.
Selecting and Buying
1 pound of meat will stuff about 2 feet of medium-size hog casing (32-35 mm)
1 pound of meat will stuff about 4 feet of medium-size lamb casing (20-22 mm)
1 ounce of medium-size hog casing (32-35 mm) will stuff about 8 feet of sausage
1 pound of medium-size lamb casing (20-22 mm) will stuff about 16 feet of sausage
Preparation and Use
The biggest volume of collagen casings are edible but a special form of thicker collagen casings is used for Salamis and large calibre sausages where the casing is usually peeled off the sausage by the consumer. Collagen casings are smoke and moisture permeable, and are less expensive to use, give better weight and size control, and are easier to run when compared to natural casings.
Conserving and Storing
Casings are normally bought soaking in brine or packed in salt. Remember that if you buy too much casing you can take the leftover casings, rinse, pack in salt and refrigerate for next time.