Improvement of water solubility and humidity stability of tapioca starch film by incorporating various gums

Various gums including gum arabic, κ-carrageenan, gellan, and xanthan were tested to improve water solubility and humidity stability of a starch-based edible film. Aqueous tapioca starch pastes containing a gum (total 5.0% solids including 0.2 or 0.5% gum solids) were cast on a glass plate, and effects of the gum addition on the water solubility, humidity stability and mechanical properties of the films were examined. Solubility of the film specimen (20 × 20 mm) in distilled water or buffer solution with α-amylase (50 mL) at 37 °C within 60 s was significantly increased by the presence of the gums. Moreover, the starch-gum films were more stable to humidity than a pure pullulan film (20% solids) which was similar to popular commercial films. Under different RH conditions (23, 52, and 85%), the starch-gum films (0.2% gum addition) exhibited tensile strength values similar to those of the pure pullulan film. Among the gums tested, gellan gum at 0.2% addition appeared most effective in improving the mechanical properties and storage stability of the starch film.