Effects of drying temperature on barrier and mechanical properties of cold-water fish gelatin films

Abstract

Fish gelatin films made from Alaska pollock (Theragra chalcogramma) and Alaska pink salmon (Oncorhynchus gorbuscha) were dried at 4 °C, 23 °C, 40 °C, and 60 °C. The tensile, thermal, thermal stability, water sorption, and water vapor permeability properties were examined for cold-cast gelatin films (dried below gelation temperature at 4 °C) and hot-cast gelatin films (dried above gelation temperature at the higher temperatures). Cold-cast gelatin films retained helical-structured gelatin, whereas hot-cast gelatin films were amorphous. This resulted in cold-cast gelatin films having higher tensile strength and percent elongation values than hot-cast gelatin films. Also, water sorption isotherms indicated cold-cast gelatin films had higher equilibrium moisture contents than hot-cast gelatin films, except at low and high relative humidity. In addition, cold-cast gelatin films had water vapor permeability values two to three times higher than those of hot-cast gelatin films. The higher water vapor permeability values might in part be due to higher moisture contents found in cold-cast gelatin films.