Valorization of potato peel waste into starch-based bioplastic films using glycerol and sorbitol plasticizers

The valorization of potato peel waste into biodegradable materials offers a sustainable route to reduce plastic pollution while utilizing agro-industrial residues. In this study, starch was extracted from potato peel waste by wet sedimentation, yielding 17.10% with high purity (ash 0.47%, moisture 14.00%, amylose 21.20%, amylopectin 78.80%). Three bioplastic films were prepared using glycerol, sorbitol, and a glycerol–sorbitol blend as plasticizers and evaluated for physical, mechanical, optical, structural, and biodegradation properties. Glycerol-plasticized films exhibited superior flexibility, high swelling (47.0 ± 3.0%) and water absorption (48.6 ± 3.40%), and the fastest biodegradation, reaching 95.62 ± 9.78% weight loss within 20 days under soil burial conditions. Sorbitol films showed the highest tensile strength (38.11 ± 1.52 N/cm ² ) and lowest water absorption (28.8 ± 1.15%), while blend films displayed intermediate strength (25.05 ± 1.20 N/cm ² ) and slower biodegradation (64.16 ± 5.41%). Fourier transform infrared ( FTIR) spectra confirmed preservation of the starch polysaccharide backbone with distinct hydrogen bonding patterns, where glycerol induced greater amorphous character while sorbitol enhanced molecular packing. X-ray diffraction (XRD) analysis of Glycerol-potato peel starch films indicated semi-crystalline structures with a crystallinity index of 91.6%. Application trials demonstrated that glycerol-based films adhered strongly as a leak-proof coating for paper cups and were mouldable into 3D products. Overall, glycerol-plasticized potato peel starch films were identified as the most promising formulation, combining desirable flexibility, rapid biodegradability, and practical applicability for sustainable packaging.