Mechanical and barrier properties of edible starch-protein-based films

The present investigation dealt with the mechanical properties, water-vapor transmission behavior at different relative humidity conditions, and DSC thermograms of edible films formulated using various proteins (casein, gelatin, albumin) in combination with starch and nonthermal as well as intense thermal blending. Nonthermal blended film showed in the DSC thermogram a double T-g, indicating poor miscibility of the components and, hence, a poor film-forming property. However, the DSC thermogram of all the films based on intense thermal blending showed a single T-g, indicating the complete molecular miscibility of the components. Casein-based film showed a lower watervapor transmission rate, water gain at different relative humidity conditions, and higher tensile strength compared to counterparts containing gelatin and albumin. Since the casein-starch blend gave better film properties, a blend of hydrophobic carnauba wax and casein was prepared to compare the properties of hydrophilic-hydrophilic and hydrophobic-hydrophilic blends. Both these blends compared well with respect to the water-vapor transmission rate. Wax-based film showed multi-phased behavior in the DSC thermograms and the percent elongation was lower as compared to the casein-starch blend. (C) 2003 Wiley Periodicals, Inc.