Sausage links are a mixture of ground meat, fat, seasoning, and sometimes fillers that is packed into a casing and then tied or twisted at intervals to create individual links. Traditionally, link sausage is stuffed into natural casings made from the intestines of animals, but artificial casings are also available on the market. These days most commercial sausages use synthetic casings. Before you make your own sausage links—or just want to know what you're eating—learn about the differences between natural and artificial casings.
The natural casing's origin may have begun around 4,000BC where cooked meat was stuffed into the stomach of a goat, but today natural casings are made from the submucosa, a layer (which consists of naturally occurring collagen) of a farm animal's intestine. The intestines mainly come from pigs, cattle, goats, sheep, and sometimes a horse. This method of encasing sausage has been around for centuries—although machinery has replaced the need to clean the intestines by hand before use—and is the only form of casing that can be used in organic sausage production.
The benefits of the natural casing are flavor and visual appeal. Because the natural casing breathes, it results in a deeper flavor and richness in the sausage—the smoking and cooking flavors can permeate the casing and infuse the meat. Since the casings are all-natural, the sausages are very natural looking, being somewhat irregular in shape and size.
Artificial sausage casings can be made from materials such as collagen, cellulose, and plastic and may not always be edible. Collagen casings have been around the longest and are produced from animal collagen, mostly from the hides of cows and pigs. Sometimes the bones and tendons are included, and the casings can also be made from poultry and fish. An inexpensive choice, collagen casings are easier to use than natural casings as they provide better weight and size control of the sausage.
Cellulose casings are made of viscose, a material comprised of the cellulose from wood pulp or cotton linters (the fibers that cling to the cotton seeds after being separated from the cotton). These casings are strong and sheer, and permeable to smoke; they are peeled off after cooking. Plastic casings are not edible, and since they are impermeable, they are used for non-smoked, high-yield products.
Some artificial casings require soaking in hot tap water before use and need to be punctured with a knifepoint before stuffing to eliminate air pockets. The advantages of using synthetic casings are their strength and uniformity.
If you do not have access to natural or artificial casings, or just don't want to use them but still want to make sausage links, you can make casings from strips of muslin. To form casings about 1 1/2 inches in diameter, cut strips about 6 inches wide and 16 inches long. Fold lengthwise and stitch edges together to form tubes.
If you do not use casings at all, you can still form links by rolling up the mixture in foil or plastic wrap and refrigerating until firm. You will need to add a binder (bread crumbs, soy protein concentrate, etc.) to the sausage mix, normally 5% to 10% of the mix, to keep the meat from separating during cooking.