Pepperoni casing is made from one of three materials: natural animal intestines, edible collagen derived from animal hides, or inedible fibrous and plastic casings that get removed before the pepperoni is sliced and packaged. The type of casing depends on whether you’re buying a whole pepperoni stick or pre-sliced pepperoni, and it affects everything from texture to whether the pepperoni cups up on a pizza.
Natural Casings
Traditional pepperoni uses natural casings made from the intestines of pigs, sheep, goats, or cattle. These are the same casings used for centuries in sausage making. The intestines are cleaned, salted, and processed into thin, flexible tubes that are entirely edible. You’ll find natural casings most often on whole pepperoni sticks sold at delis or specialty shops rather than on mass-produced supermarket pepperoni.
Natural casings shrink when heated. On a pizza, that shrinkage is what causes pepperoni slices to curl into little cups, with the edges pulling upward and crisping while rendered fat pools in the center. Slices between about 1.3 and 6.4 millimeters thick all cup to some degree, with the best curling happening around 2.5 millimeters. If you’ve ever wondered why some pizza pepperoni curls into crispy bowls while other slices stay flat, the casing is the biggest factor.
Collagen Casings
Collagen casings are the most common edible casing on pepperoni you’d buy at a grocery store. They’re manufactured from collagen extracted from cow or pig hides, processed into a uniform tube. Unlike natural casings, which vary slightly in diameter and thickness, collagen casings are consistent in size, which makes them ideal for automated production lines.
These casings are edible and stay on the pepperoni when it’s sliced. Like natural casings, collagen shrinks during cooking, so pepperoni stuffed in collagen casing will also cup on a pizza. The shrinkage tends to be even more pronounced than with natural casing, since the collagen tightens uniformly around the edges of each slice.
Fibrous and Cellulose Casings
A large share of commercially produced pepperoni is stuffed into fibrous casings that are not edible. These casings are made from regenerated cellulose reinforced with a paper-like web, typically using fibers from wood pulp, hemp, or cotton. The paper is formed into a tube, soaked in a chemical solution called viscose, and hardened into a sturdy shell that holds its shape during the curing process.
Fibrous casings give pepperoni a perfectly round, uniform shape, but they’re peeled off before the pepperoni is sliced. That’s why pre-sliced pepperoni from a package typically has no visible casing at all. If you buy a whole pepperoni stick with a tough, papery skin that doesn’t feel like it belongs on food, that’s a fibrous casing and you should remove it before eating. Products sold with inedible casings still attached are required by the USDA to carry a label stating “Remove casing before eating.”
Pepperoni cured in fibrous casings tends to lay flat when cooked on pizza rather than cupping, precisely because the casing has already been stripped away and there’s nothing left to shrink around the edges.
Plastic and Synthetic Casings
Some pepperoni, particularly products made at industrial scale, uses fully synthetic casings made from food-grade plastics like polyamide (nylon), polypropylene, or polyethylene. These are always inedible and always removed before the product reaches the consumer as sliced pepperoni. Multilayer casings that combine several polymers are also common, engineered to control how much oxygen and moisture pass through during curing.
Synthetic casings now represent the largest segment of the sausage casing market, holding roughly 48% of global revenue. Their dominance comes down to manufacturing efficiency: they’re uniform in size, easy to load onto automated filling equipment, carry lower microbial risk than natural casings, and extend shelf life. For large pepperoni producers turning out millions of sticks, those advantages outweigh the artisanal appeal of natural or collagen casings.
Plant-Based Casings
Vegan and plant-based pepperoni products use casings made without any animal-derived materials. The most common option is calcium alginate, a gel-like substance made from alginates extracted from the cell walls of brown seaweed. When sodium alginate is exposed to calcium, it forms a strong, elastic coating that mimics the texture of traditional collagen casings. Some manufacturers add pea protein or plant-based emulsifiers to the alginate mixture to improve flexibility and mouthfeel. These casings are edible and compatible with automated co-extrusion equipment, where the casing and filling are formed simultaneously.
How to Tell What’s on Your Pepperoni
If you’re buying a whole pepperoni stick, the casing type matters for both eating and cooking. Here’s how to identify what you’re dealing with:
- Edible, slightly irregular skin: Natural casing. It will have subtle variations in texture and may feel slightly slippery. Safe to eat.
- Edible, smooth, uniform skin: Collagen casing. It looks and feels consistent along the entire stick. Safe to eat.
- Tough, papery, or plastic-feeling skin: Fibrous or synthetic casing. It won’t tear easily and feels distinctly different from the meat underneath. Peel it off before slicing.
Pre-sliced pepperoni sold in packages has almost always had its casing removed already, whether it was fibrous or synthetic. If you see a thin, translucent skin on sliced pepperoni, that’s likely a collagen casing and it’s edible. When in doubt, check the packaging for any “remove casing” language, which the USDA requires on products sold with inedible casings still attached.