Valorization of Candy Industry Residues in Biopolymer Films: Development and Physicochemical Characterization

Abstract The growing demand for sustainable packaging materials has spurred the development of biopolymer-based films based on renewable resources and agro-industrial by-products. Therefore, this study aimed to valorize candy-industry residue as an ingredient for producing biopolymer-based films composed of sodium alginate, methylcellulose, and chia mucilage. Fifteen formulations were prepared and characterized regarding thickness, color parameters, and water-related and mechanical properties. Based on these, the selected formulation was characterized in terms of water activity, contact angle, barrier, thermal, and microstructural properties. The results showed that the polymeric composition had a considerable impact on the physicochemical and mechanical behaviors of the films. Moisture content ranged from 5.81% to 56.41%, while solubility varied from 19.75% to 100%, suggesting different interactions between the polymer matrices and water. The formulation significantly affected tensile strength and elongation at break ( p < 0.05), highlighting differences in the mechanical behavior of the developed films. Among all the formulations, blend 5 (sodium alginate: methylcellulose: candy residue, 50:50:100) exhibited the most balanced performance, combining low moisture content (7.66%), reduced water activity (0.608), low solubility (19.75%), high swelling capacity (80.60%), and flexibility (33.59% elongation at break). These results demonstrate that candy industry residues can be successfully incorporated into biopolymer matrices to produce biopolymer-based films with suitable physicochemical and mechanical characteristics for further investigation as sustainable packaging materials.