There are two broad categories of sausage casing: natural and artificial. Natural sausage casing is made from the intestines or stomachs of various animals and is permeable to air and outside flavorings while also being very strong and edible. An artificial sausage casing can be made from collagen, cellulose, cotton or plastic and is generally not edible or as flexible as a natural casing, but is much more cost effective and consistent in size and quality. The type of sausage casing used is usually determined by the type of sausage being made, with artificial casings used for larger or mass-produced sausages, and natural casings being a more popular choice for home sausage making and links that will be processed with smoke.
There are actually several varieties of natural sausage casing based on the type of animal from which it is made. Hog casings, made from the intestines of pigs, provide a very meaty flavor to sausages and are often used to make breakfast links. Sheep casings tend to be smaller than the other types of natural casings and are used for small or thin sausages.
Beef casings are very durable, can be very large and can be used for a variety of large sausages or salamis. One benefit of using a beef casing is that it can be stripped of a large amount of fat, leaving a very lean container for the sausage meat. Some beef casings are actually made from the lining of the stomach of the cow and can be used to wrap larger sausage products.
Artificial sausage casings come in a variety of forms and have been designed to function in some specific ways. Plastic casings are thick and prevent moisture and bacteria from reaching the meat inside while also helping to hold the shape of tough sausages. Fibrous casings can be made from different types of fibers and are very strong; a lining of proteins inside the casing also gives them the ability to shrink as a sausage dries. Neither type of casing is usually edible.
Another type of artificial sausage casing is made from cellulose and is formed from materials that are meant eventually to dissolve in moisture or over time, meaning a sausage can be wrapped and protected during production or aging and then be free of any casing when delivered to the consumer. The final type of artificial sausage casing is made from collagen that is derived from the cartilage and animal bones. This is one of the most widely used casings, closely matching many properties of the natural variety. Collagen casings can be edible or, like other artificial casings, might be intended to be removed before the sausage is eaten.
