The present invention provides a functional additive transferring (co)extrudedthermoplastic food casing having a water vapor barrier and/or oxygen barriereffect wherein an inside surface of the thermoplastic food casing has atexturedsurface which forms a three-dimensional pattern of higher and lower retainingcapacity for a functional additive, wherein the thermoplastic food casinghaving a textured surface in case of a monolayer casing or an inner layercomprising the inside surface having a textured surface in case of amultilayercasing comprises as a main component at least one thermoplastic polymermaterial selected from the group consisting of (co)polyamides,(co)polyolefins, (co)polyester and vinylidenchloride (co)polymers, whereinthe (co)extruded thermoplastic food casing does not comprise a net and/or amaterial forming a net or any other three dimensional structure on its outsidesurface, wherein the average thickness of the thermoplastic food casing in theareas having a higher retaining capacity is in a range of from 1 to 100 µm,wherein the average thickness of the thermoplastic food casing in the areashaving a lower retaining capacity is in a range of from 191 to 2000 µm,provided that the thickness difference between the average thickness in theareas having higher retaining capacity and the average thickness in the areashaving a lower retaining capacity is in a range of from 160 to 1950 µm andthat a ratio of the average thickness of the thermoplastic food casing in theareas having a higher retaining capacity and the average thickness of thethermoplastic food casing in the areas having a lower retaining capacity is ina range of from 0.002 to 0.25.
