The role of glutamic acid addition in the functional and biodegradation properties of starch–pectin films

Environmental concerns and the need for sustainable alternatives to synthetic polymers have fostered the development of biodegradable materials from renewable sources. This study explores the incorporation of glutamic acid (GA) into starch–pectin films, aiming to enhance their mechanical and physicochemical properties. Films were produced via casting and evaluated for ultimate tensile strength (UTS), solubility, swelling, wettability, color, morphology, crystallinity, and thermal behavior. The incorporation of GA significantly improved film cohesion, increasing UTS from 1.8 to 6.4 MPa, and reducing water solubility from 65% to 41%. All films remained hydrophilic, but GA-modified films showed better stability, uniformity, and reduced water uptake. Fourier Transform Infrared spectroscopy and X-ray diffraction analyses revealed enhanced molecular interactions and increased crystallinity from 15.1% to 38.8%. Thermogravimetric analysis and differential scanning calorimetry confirmed a thermal stability improvement. Soil burial tests showed complete degradation within 7 and 35 days, reinforcing the potential of these films as short-life biodegradable packaging. Overall, GA acts as a multifunctional additive that enhances the structural, mechanical, and environmental performance of the films, positioning them as strong candidates for eco-friendly packaging.