Sausage casing is the outer skin that holds the ground meat filling together, and it comes in several varieties: natural casings made from animal intestines, collagen casings made from animal skin, cellulose casings made from plant fiber, and plastic casings made from synthetic polymers. Some are edible, some aren’t, and knowing the difference matters when you’re biting into a bratwurst or peeling the wrapper off a stick of bologna.
Natural Casings: Animal Intestines
The most traditional type of sausage casing comes from the intestinal lining of sheep, hogs, or cattle. Specifically, it’s the submucosa layer of the small intestine, a thin, flexible membrane that’s been used for centuries. These casings give sausages their characteristic snap when you bite through them.
Each animal produces a different size casing, which is why certain sausages always look a certain way. Sheep casings are the smallest and most tender, ranging from 16 to 28 millimeters in diameter. They’re what you’ll find on breakfast links, snack sticks, and hot dogs from specialty butchers. Hog casings run from 30 to 44 millimeters and are the standard for Italian sausage, bratwurst, and Polish kielbasa. Beef casings are the largest and toughest of the three.
Both sheep and hog casings are fully edible. You eat them along with the sausage without even thinking about it. Beef casings, however, are tough enough that they’re typically peeled off after cooking rather than eaten.
If you’re buying natural casings for home sausage making, they come packed in salt. Before use, you rinse the salt off, then soak them in warm water (around 80 to 100°F) for about an hour. After soaking, you slide the softened casing onto a stuffing tube and you’re ready to go.
Collagen Casings: Processed but Often Edible
Collagen casings are manufactured from the proteins found in cattle hides. The collagen is extracted, processed into a paste, and then formed into uniform tubes. This gives manufacturers a consistent product that’s easier to work with than natural casings, since every casing comes out the same diameter and thickness.
Some collagen casings are designed to be edible and eaten with the sausage. Others are made thicker for larger products and need to be peeled. A more advanced version uses co-extrusion technology, where a thin collagen layer is applied directly onto the sausage filling as it’s formed, creating a nearly invisible casing that you’d never notice while eating.
Federal labeling rules require that sausages in collagen casings disclose this on the package, either on the front label or in the ingredient statement.
Cellulose Casings: Peel Before Eating
Cellulose casings are made from plant-based material, primarily wood pulp that’s been processed into a thin, paper-like tube. They’re widely used for skinless hot dogs and frankfurters. During production, the sausage is stuffed into the cellulose casing, cooked, and then the casing is mechanically peeled off before packaging. That’s why grocery store hot dogs often appear to have no casing at all.
If you encounter a cellulose casing that hasn’t been removed (which sometimes happens with smaller producers), peel it off before eating. It’s not harmful, but it has a papery texture that’s not pleasant to chew.
Fibrous casings are a sturdier cousin of cellulose casings, made from the same plant-based material but reinforced for larger products like summer sausage and salami logs. These are always removed before eating.
Plastic Casings: Always Remove
Plastic casings are made from synthetic polymers, most commonly polyamide (nylon), polypropylene, or polyethylene. They are never edible and must always be removed before eating.
You’ll find plastic casings on products like bologna, luncheon meat, and some cooked hams. They’re chosen because they create a tight, uniform seal and produce high yields with minimal moisture loss. Unlike natural and collagen casings, plastic doesn’t allow smoke or water to pass through, so these casings are reserved for non-smoked products.
Polyamide casings are the most common in commercial production. Shrinkable versions tighten around the meat during cooking to reduce water loss, while non-shrinkable versions allow the filling to expand slightly as it heats. Either way, you peel them off before slicing or eating.
Plant-Based and Vegan Casings
For sausages that avoid animal products entirely, manufacturers use casings based on alginate, a gel-like substance derived from seaweed. The process works by combining sodium alginate or potassium alginate with ingredients like cellulose gum, carrageenan, or plant-based starches (potato, rice, or tapioca). When this mixture contacts a calcium solution, it gels into a firm, flexible casing.
Some plant-based casings also incorporate fibers from wheat, citrus, soy, or pea to add structure and chew. These casings are edible and designed to mimic the snap of a natural casing, though the texture is noticeably different.
How to Tell What’s on Your Sausage
The simplest way to know your casing type is to check the label. USDA regulations require that natural casings from a different animal than the filling be identified. For example, a pork sausage in sheep casings must say so. Collagen casings must also be disclosed on the label.
If you don’t have the package handy, a few visual and tactile clues help. Natural casings have slight irregularities in shape and a visible sheen. They snap when you bite them. Collagen casings look more uniform and feel slightly tougher. Cellulose and fibrous casings have a papery, matte appearance. Plastic casings are obviously synthetic, often printed with branding, and peel away cleanly in sheets.
As a general rule: if the casing looks like skin and came on a fresh sausage from a butcher, it’s almost certainly edible. If it looks like plastic or paper and came on a large deli-style product, remove it.