Oriented or Non-Oriented (Straight) Casings
Casing orientation considerably enhances its mechanical and barrier properties. It becomes less stretchable but stronger and stable. For the same reasons, an oriented casing is normally thinner than a non-oriented one. Biaxial orientation builds up a shrink force in the casing, which can be released by exposing the casing to heat, e.g., during sausage processing. The shrinkage combined with a special plastic resin in the inner layer contributes to the adhesion between the meat and the casing during processing and to the elimination of wrinkle formation later on. An oriented casing normally forms straighter shoulders than a non-oriented casing, and this translates to increased yields and throughputs in sliced applications.
When manufactured in a line that includes only one extruder feeding the die, the resultant tubing consists of only one layer and forms a casing called monolayer or single-layer. It can be either non-oriented or oriented, and it can still be combined with several components to improve its properties.
When manufactured in a line that includes several extruders feeding the die, the resulting tubing consists of several layers and forms a casing called multilayer or coextruded. The main component of a multilayer casing is often polyamide which provides such properties as oxygen barrier, mechanical resistance, expandability and shrinkability. Polyolefin provides a water barrier and acts as a tie layer or an adhesive that creates the bond between the adjacent layers and keeps them together.
ViskoTeepak casings have a multilayer structure design that can be tailor-made to fit any application or production process through the combination of different materials in each layer for the required properties. A single layer of material that alone has all the required performance properties is extremely rare. Co-extrusion allows us to combine, in one casing, the good properties of various raw materials such as mechanical strength, oxygen and water-vapor barrier for increased shelf life and zero weight loss, lower water-vapor permeability for reduced weight loss during processing and storage, etc. Moreover, each casing can be adapted to suit the customer's unique processing conditions.