Abstract: This study was conducted to investigate the effect of thermal treatment temperature on physicochemical properties of gelatin-konjac flour composite films such as solubility, contact angle, microstructure and thermal stability. As a result, the film solubility (FS) and protein solubility (PS) in warm water at 30 ℃ were 45.62% and 28.83%, while those in hot water at 90 ℃ were 74.32% and 71.44%, respectively. Both FS and PS were gradually decreased with increasing thermal treatment temperature. The band intensities of α and β chains of proteins dissolved at 30 ℃ were decreased with increasing thermal treatment temperature, while no obvious changes were observed for the proteins dissolved at 90 ℃. The contact angles on the gelatin side and the konjac flour side of composite films were 107.14° and 88.53°, respectively, both of which were increased after thermal treatment. The water vapor permeability was decreased, whereas both the b* value and transparency were increased with the increase of thermal treatment temperature. Based on the results of scanning electron microscopy and differential scanning calorimetry, the gelatin and konjac flour layers in composite films were integrated gradually, and the thermal stability was increased as the thermal treatment temperature increased. It was concluded that the water resistance, surface hydrophobicity, moisture barrier properties and thermal stability of gelatin-konjac flour composite films could be improved by increasing thermal treatment temperature.

Key words: gelatin-konjac flour composite film, thermal treatment temperature, water resistance, water vapor permeability, contact angle, thermal stability