Native and Modified Gelatin Films Produced by Casting, Extrusion, and Blowing Extrusion Processes

Samples of native gelatin and gelatin modified by acylation and esterification were processed by casting and thermoplastic extrusion to produce laminated and tubular films. Extruded films containing sorbitol showed homogeneity and flexibility. Thinner films were obtained with the addition of sorbitol to the formulation. Tubular films prepared from gelatin modified with stearic acid were easily processed, had reduced friction, and were able to withstand bubble formation without fracturing after preparation. Films prepared by casting or thermoplastic techniques showed a decrease in tensile strength with the addition of plasticizer, and this also resulted in a substantial increase in their elongation ratio. The stearic acid modified gelatin-based films processed by blown extrusion showed higher tensile strength. Films fabricated by casting were, in general, less soluble than those prepared by extrusion except the films modified with stearic acid with or without the addition of plasticizer.