Biodegradable composite films from carrageenan, chitosan, and modified starch with enhanced mechanical strength and barrier properties for sustainable packaging

The development of biodegradable packaging materials from renewable biopolymers is increasingly important for reducing dependence on petroleum-derived plastics. This study investigated the design and characterization of composite bioplastic films based on carrageenan (CG), chitosan (CS), and modified starch (MS) as a sustainable polysaccharide matrix. Films were prepared using a solution-casting method by blending Kappaphycus alvarezii -derived carrageenan (0.5% w/v) with varying CS-MS ratios (1% w/v total solids) and glycerol (40% w/w of total solids) as a plasticizer. The CS-MS composition significantly influenced film performance, demonstrating the importance of polymer interactions within the ternary matrix. Optical properties varied among formulations, with MS100 (0% CS:100% MS) exhibiting the highest opacity (5 ± 0.6 mm − 1 ). The CS80 formulation (80% CS:20% MS) showed the highest tensile strength (12.71 ± 0.08 MPa), whereas MS100 presented the greatest elongation at break (22.6 ± 1.9%), indicating improved flexibility. Water vapor permeability was lowest in CS60 (1.3 ± 0.10 × 10 − 10 g m − 1 s − 1 Pa − 1 ) and CS40 (1.4 ± 0.12 × 10 − 10 g m − 1 s − 1 Pa − 1 ), suggesting enhanced moisture barrier performance. Thermal stability ranged from 303 to 325 °C, indicating resistance to thermal processing conditions relevant to food packaging. Biodegradation tests revealed rapid physical disintegration under modified compost conditions, with CS20 and MS100 films achieving complete mass loss within 7 days, while CS100 exhibited 42 ± 4% mass loss. Overall, the results demonstrate that integrating carrageenan with chitosan and modified starch produces a ternary polysaccharide matrix with improved mechanical strength, barrier properties, and biodegradability relative to most reported single-polysaccharide films. These findings provide insight into the design of multi-polysaccharide biodegradable films and highlight their potential as candidate materials for sustainable food packaging applications within a circular bioeconomy framework.