The food casing having a porous outer layer

Described is a coextruded thermoplastic food casing composed of at least two layers including an outer layer (Z), having a porosity of at least 5 vol .-%, as measured by bubbles or pores are substantially in the plane of the surface. The surface of the outer layer (Z) In the production of the food casing at least one propellant and / or propellant gas is added prior to extrusion or composition is chosen such that in the plastic compound by chemical reactions between the components of gas. Upon pressure relief during and / or after discharge from the extruder, the melt is foamed by at least a part of the gas forms pores or bubbles which remain at least partially received in the solidifying melt or on their surface. Disclosed is also a manufacturing method in which at least two plastic components for the outer layer (Z) and optionally used for at least one further layer. The at least two plastic components have significantly different properties and bond poorly to one another, so that arise at the interfaces between the components of pores and / or bubbles that remain at least partially received in the solidifying melt or on their surface.