1. Natural Casings

Natural casings are processed from the digestive or urinary systems of animals such as pigs, cattle, and sheep. Depending on the processing method, they are categorized into salted casings and dried casings. Natural casings appear light red, white, or milky white, while dried casings are typically pale yellow and possess a characteristic aroma. The diameters are graded in 2mm increments, ranging from 24mm to 40mm, etc. Salted casings require thorough soaking and cleaning before use; otherwise, salt efflorescence may appear after cooking.

Advantages:

Good elasticity and moisture retention.

Safe for consumption (edible).

Excellent permeability to water vapor and smoke flavor.

Good thermal shrinkage and adhesion to the meat filling.

Possess good toughness and firmness.

High nutritional value.

Disadvantages:

Irregular in(size/caliber) and shape.

Limited and variable supply.

Susceptible to insect infestation if processed or stored improperly.

Prone to developing holes, spoilage, and off-flavors.

2. Artificial (Synthetic) Casings

These are flat or tubular films processed from materials like animal hides, plastic, fibers, or paper. They include the following types:

(1) Cellulose Casings: Made from natural fibers like cotton linters, wood pulp, flax, or other plant fibers.

Advantages:

Excellent toughness and breathability (gas permeability).

Stable during rapid heat treatment.

Can be smoked and colored even when moist.

Disadvantage:

Not edible.

Do not shrink with the meat filling.

(2) Collagen Casings: Produced from raw materials like the hides and tendons of livestock.

Advantages:

Edible (Note: may not be palatable with coarse fillers).

Good breathability.

Takes color easily.

Disadvantage:

Requires careful control of heating temperature during thermal processing, as they can become soft if overheated.

(3) Plastic Casings: Often used as outer packaging casings or for product shaping.

Advantages:

Act as a barrier against air and water permeation.

Relatively high impact resistance.

Wide variety of types and specifications available.

Suitable for printing.

Convenient to use, with a smooth and aesthetically pleasing appearance.

Suitable for cook-in products.

Disadvantage:

Not edible.

(4) Cellophane Casings: A type of cellulose film, soft and flexible. The cellulose microcrystals are arranged parallel longitudinally, resulting in high strength lengthwise and lower strength crosswise.

Advantage:

Lower cost compared to natural casings.

Disadvantage:

Prone to tearing if not handled correctly.