Sausage Casings Explained: Natural, Collagen and Fibrous

Natural hog casings (32-35 mm) for brats and fresh venison links; collagen casings (19-21 mm) for snack sticks and (32 mm) for no-prep brats; fibrous casings (1.5 to 2.5 inches) for summer sausage. Natural and collagen are edible; fibrous is not and gets peeled. Those three lines cover almost every decision a home sausage maker has to make.

NDSU Extension's sausage publication is the clearest source on why: natural casings “are digestible and are very permeable to moisture and smoke,” and generally “hog casings are the most suitable for home use and work quite well for Polish and breakfast-type sausages.”

The three families

Natural casings. NDSU: “Natural casings are the gastrointestinal tracts of cattle, sheep and hogs.” Hog casings at 32-35 mm are the standard home size. They give the snap people associate with a good brat, they let smoke and moisture through, and they are edible. The cost is preparation and refrigeration.

Collagen casings. NDSU describes them as carrying “the attributes of both natural and fibrous casings,” used for products such as fresh pork sausage and pepperoni sticks, and “uniform in size, relatively strong and easy to handle.” In practice that uniformity is the selling point: they slide onto the tube dry, no soaking, and every stick comes out the same diameter. LEM's 19 mm collagen is the snack-stick workhorse; its 32 mm is the brat-size option for people who do not want to flush natural casings.

Fibrous casings. NDSU: they “are more suitable for summer sausage and similar products because of their greater strength and the variety of sizes available. They are permeable to smoke and moisture and can easily be removed from the finished product.” They are plant cellulose, non-edible, string-tied at one end so a chub hangs in a smoker, and they store in a cupboard.

There is a fourth family you will not want. NDSU notes that for cooked products that are water-cooked, like braunschweiger, “plastic casings impermeable to water are used” — the opposite of what you want for anything smoked.

Casing by product

Soaking and flushing, by type

This is where most first batches go wrong, and the instructions differ sharply by family. NDSU: “All casings preserved in salt must be soaked in lukewarm water for at least 30 minutes before use. Flush each casing under cold water, running cold water through the casing. This removes excess salt.” For fibrous, it specifies soaking “in 80 to 100 F water for at least 30 minutes, but not more than four hours before use.”

Diameter, and the tube it needs

A casing you cannot load is a casing you cannot use. Match the casing to the stuffing tube before you buy either. LEM recommends a tube of 1/2 inch outside diameter or smaller for its snack-stick collagen, and most stuffers ship with nothing below 5/8 inch — which is why a dedicated 3/8 inch (10 mm) tube is the common aftermarket purchase. At the other end, a 2.5-inch fibrous casing needs the biggest tube in the set.

A horizontal or vertical stuffer will take whatever tube fits its canister base, so measure the base rather than guessing. Our LEM versus Hakka comparison lists exactly which tubes each of those two big stuffers includes, and stuffer versus grinder attachment covers the trade if you were planning to stuff through the grinder head.

How much a pack covers

Makers publish fill figures, which makes planning easy. LEM's 32-35 mm hog casings fill about 30 lb; its 19 mm collagen about 16 lb a pack, its 21 mm about 20 lb, its 32 mm about 21 lb; its clear 2.5 x 20 inch fibrous casings hold about 3 lb each, and the 1.5 x 12 inch ones about 1 lb each. Bearded Butchers gives 25-30 lb for its pre-flushed hog casings.

Against a season, that is generous. At the Ohio DNR average of about 52 lb of venison a deer, a two-deer season is roughly 104 lb of venison, and sausage is a share of it. One pack of hog casings and one pack of collagen will usually see out a household season — but buy a spare strand anyway, because a casing that tears mid-batch stops the whole afternoon.

Air pockets, and the pin trick

NDSU: “If the casings are not pre-stuck they should be punctured with a knife point or pin to eliminate air and fat pockets in the finished sausage.” Clear casings, fibrous or collagen, show every pocket you leave, which is an argument for the mahogany version if presentation matters to you and an argument for the clear one if you want to see your own mistakes.

Stuff firm but not to the bursting point, and let the stuffer do the work rather than forcing the crank. An air release valve on the stuffer handles the air inside the cylinder; the pin handles what gets trapped against the casing wall.

Storing casings between seasons

Natural casings stay refrigerated in their salt or brine, and LEM says do not freeze them. Collagen goes back in an airtight bag or it dries out and splits on the tube. Fibrous casings are the easy ones: a cool, dry cupboard, no refrigeration, and they will be there next November.

Whatever you are stuffing into them, finish to a temperature rather than a time. USDA's safe minimum internal temperature chart is the reference; NDSU's own worked examples hold water at 170 °F until the sausage reaches 155 °F, and finish summer sausage at 155 °F internal. The whole mixing, stuffing and cooking sequence is in how to make venison sausage.