Suitable films include food casings which are generally flexible films which are preferably tubular and may be formed of polymeric materials including cellulosic materials such as regenerated cellulose or cellulose carbamate or of plastics such as homopolymers or copolymers of polyolefins e.g. polypropylene, polyethylene, or polyamides, polyethylene terphthalate, polyvinylidene chloride copolymers