Edible films based on gum tragacanth and gelatin

Gelatin (GL) is one of the most utilized biopolymers due to its versatile physicochemical properties. However, replacing animal-based proteins in food and drug formulations has become a significant research area due to environmental and health concerns. Gum tragacanth (GT) is a promising polysaccharide with water-soluble and water-swellable parts. In this study, edible films were prepared using two methods, where different GT:GL volumetric ratios (1:0, 1:1, 1:3, 3:1, and 0:1) were prepared based on 1% w/v GT and 5% w/w GL. The dried films were exposed to distilled (DI) water and salt solution (0.5 M CaCl2 or NaCl). The effects of preparation methods and the film thickness on the swelling properties of the films were investigated. The films were characterized via dimensional analysis, weight, and absorbance at 600 nm. The film-forming solutions exhibited non-Newtonian behavior. Gel-like behavior was observed only for 3GT1GL, and the rest of the solutions exhibited liquid-like behavior. The thickness of the films was in the range of 0.040–0.45 mm, and the weight of the films was between 0.040 and 0.55 g. 3GT1GL-5 was identified as the best-performing film in DI medium, H1GT1GL-5 and H1GT3GL-5 in CaCl2 and H1GT1GL-5, H1GT3GL-5, and H3GT1GL-10 in NaCl solutions. The swelling rate of composite films was dependent on the biopolymer mixing ratio, the thickness of the films, and the swelling media (p < 0.05). 5GL can be replaced by 3GT1GL, leading to 60% less biopolymer use. Hence, GT is a good alternative to replace GL with reduced overall biopolymer concentration.