Effects of Starch on the Improvement of Mechanical, Thermal, and Water-Solubility Properties of Films Developed with Gelatin/Starch/Procyanidins Blends

Sorghum-derived biopolymers, such as starch and procyanidins, combined with gelatin, are promising candidates for the development of sustainable, biodegradable, non-toxic, and functional films for various applications. This study aimed to evaluate the effects of starch on the improvement of mechanical, thermal, and water-solubility properties of films developed with gelatin/starch/procyanidins blends. Films were prepared using various gelatin (G)–starch (S) ratios (G-100, GS-75:25, GS-50:50, GS-25:75, S-100) and procyanidin concentrations (5–20 mg/mL), being plasticized with glycerol. Subsequently, the films were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), molecular docking, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and measurements of thickness, opacity, and water solubility. SEM, XRD, and FTIR analyses confirmed the compatibility among the film components, while molecular docking analysis supported these experimental findings. TGA and DSC analyses showed that most films maintained thermal stability up to 150 °C. The GS-25:75 formulation, in which starch predominated, exhibited the most favorable balance of mechanical and thermal properties. All the films obtained can be considered ultra-thin; opacity increased with the starch and procyanidin content, while maintaining low water solubility levels. In conclusion, the GS-25:75 formulation with 10–20 mg/mL procyanidins is particularly promising for applications that require films with structurally stable properties, as well as enhanced mechanical, thermal, and water-solubility properties.