Hog casings are made from the small intestines of pigs, specifically a single layer called the submucosa. This is a thin, collagen-rich tissue that sits between the inner lining and the outer muscular wall of the intestine. During processing, every other layer of the intestinal wall is stripped away, leaving only this one tough, elastic sheet of natural collagen.
Why the Submucosa Specifically
A pig’s intestinal wall has four distinct layers: the inner mucosa (which absorbs nutrients during digestion), the submucosa, two muscle layers that move food along, and an outer layer called the serosa. Of these, only the submucosa has the right combination of strength and flexibility for sausage making. Its structure is a woven mesh of wavy collagen fibers, which gives it natural elasticity so it can stretch during stuffing without tearing. That same collagen structure is what creates the characteristic “snap” when you bite into a natural-casing sausage.
The submucosa is also highly permeable to both moisture and smoke, which is why natural hog casings remain the standard for smoked sausages. Smoke and seasoning flavors pass through the casing and penetrate the meat, something plastic casings cannot do.
How Intestines Become Casings
The transformation from raw intestine to finished casing involves several steps of cleaning and stripping. After slaughter, the small intestines are separated, and their contents are squeezed out. The fat and connective tissue (mesentery) attached to the outside are removed in a step called “running.”
Next comes the critical part. The intestines are turned inside out and soaked in water at around 20° to 24°C until the mucosa and muscle layers soften enough to be removed. They’re then passed between sets of rollers or scrapers that crush and strip away every layer except the submucosa. This process is called “sliming,” and it’s what turns a multi-layered organ into the thin, translucent tube you’d recognize as a sausage casing. The finished product is essentially a collagen sleeve, nothing more.
Sizes and What They’re Used For
Hog casings come in graded diameter ranges measured in millimeters. A standard package, called a “hank,” contains about 110 yards of casing. The diameter determines which type of sausage the casing is suited for and how much meat it holds:
- 30 to 32 mm: Holds roughly 105 pounds of meat per hank. Used for thinner link sausages.
- 32 to 35 mm: Holds about 125 pounds. A common size for bratwurst and Italian sausage.
- 35 to 38 mm: Holds around 135 pounds. Works well for kielbasa and smoked Polish sausage.
- 38 to 42 mm: Holds about 150 pounds. Suited for larger links and ring bologna.
Beyond the small intestine, other parts of the pig’s digestive tract are also used. The large intestine yields “caps” and “middles” for wider sausages, and the terminal end (the bung) is used for larger specialty products like liver sausage. But when people refer to “hog casings” without further detail, they almost always mean the small intestine rounds.
How They Compare to Artificial Casings
Natural hog casings are entirely edible, and they remain the preferred choice for traditional sausages like bratwurst, Italian links, kielbasa, and landjäeger. The main alternatives are collagen casings, cellulose casings, and plastic casings, each with different properties.
Collagen casings are manufactured from processed animal collagen (often from hides) rather than harvested from intestines. They’re edible but tend to be more tender and lack the firm snap of a natural casing. Cellulose casings, made from plant fiber, are permeable to smoke and water but are peeled off before eating. You’ll find these on products like bologna and sliced deli meats. Plastic casings block smoke and moisture entirely, making them useful only for non-smoked products where maximum yield matters. They’re always removed before consumption.
The reason natural casings still command a premium comes down to that collagen fiber structure. The interwoven, wavy pattern lets the casing breathe, absorb smoke, and deliver a bite texture that manufactured alternatives haven’t fully replicated.
Storage and Shelf Life
Hog casings are preserved in salt or brine, which gives them a surprisingly long shelf life. Salted casings stored at 40°F or below will last a year or more. Preflushed casings packed in brine typically last six months to a year. The key rule is to never freeze them. Freezing damages the collagen structure and makes the casings brittle and prone to tearing during stuffing.
If you buy a hank and only use part of it, cover the leftover casings in granulated salt or brine solution and return them to the refrigerator. Before your next use, rinse off the salt and soak the casings in warm water (80° to 100°F) for about an hour. This rehydrates the collagen, making the casings pliable and easy to slide onto a stuffing tube.
Safety and Inspection
In the United States, natural casings fall under FDA jurisdiction rather than USDA inspection. They don’t carry the USDA mark of inspection by default, though a facility can voluntarily request USDA certification, which is often required for export. Whether domestic or imported, casings must come from animals that passed veterinary inspection before and after slaughter, and they must be handled under sanitary conditions. Imported casings require a certificate from a government official in the exporting country confirming these standards were met.