Cellulose is commonly used for the removable casing on skinless hot dogs.
Although they are sold without an edible outer skin, skinless hot dogs still need a casing during production. A thin cellulose tube holds the emulsified meat mixture in shape while the sausage is cooked. After cooking, manufacturers remove the casing, leaving the smooth surface associated with a skinless frankfurter.
This process differs from a natural-casing hot dog, which uses an animal-intestine casing that remains on the sausage and provides a noticeable “snap” when bitten. Skinless varieties are generally more uniform in size and texture and are often less expensive to manufacture. The casing is therefore temporary rather than an ingredient intended to be eaten.
The commercial skinless casing process is closely associated with Chicago inventor Erwin O. Freund and the Visking company. The first products were marketed under the name Nojax, short for “no jackets,” and were sold to Chicago sausage makers. Collagen can also be used in some sausage products, but cellulose is the standard answer for the removable casing described in this question.