Development of fish gelatin edible films using extrusion and compression molding

Fish gelatin was plasticized with 20% and 25% glycerol (w/w of gelatin) and used to develop edible films by twin-screw extrusion at 110 and 120 °C followed by compression molding at 80 °C. Tensile and moisture barrier properties and glass transition temperature were then measured and compared with solution-cast films. The films extruded at 110 °C and with 25% glycerol had the highest percent elongation at break of 293 ± 27%. The water vapor permeability values of extruded films (the highest value being 2.9 ± 0.2 g mm h⁻¹ cm⁻² Pa⁻¹) were higher than those of solution-cast films while the glass transition temperatures (T_g) of the extruded films were generally lower than those of solution-cast films. Films with 25% glycerol that were extruded at 110 °C had the lowest T_g (2.10 ± 0.31 °C). This investigation showed that extrusion processing followed by compression molding is a feasible method to produce fish gelatin films for commercial applications in a wide range of food products.