Biodegradable films based on alfalfa cellulosic residue and carrageenan blends for sustainable food packaging

Abstract

Plastic remains a dominant packaging material, but its non-biodegradability poses significant environmental and health concerns. Although starches, proteins, and lipids offer biodegradable alternatives, their primary role in food security necessitates exploring other sources. In this context, cellulosic residues from biowaste provide a promising option. This study examines the development of biodegradable packaging films from alfalfa cellulosic residue and investigates how their mechanical properties are improved through complexation with carrageenans. Alfalfa cellulosic residue (ACR) was extracted using alkaline and bleaching treatments, dissolved in 68% ZnCl₂, and then complexed with iota- (ι), kappa- (κ), and lambda- (λ) carrageenan solutions at concentrations of 0.5%, 1%, and 1.5%. The solutions were further crosslinked with calcium ions and plasticized with sorbitol, yielding nine different ACR-carrageenan films, with the ACR film serving as the control. The films were characterized for mechanical properties, water vapor permeability (WVP), color, UV-Vis-IR transmittance, water solubility, hydrophobicity, water uptake kinetics, antioxidant activity, and soil biodegradability. Incorporating carrageenan significantly increased tensile strength from 16.9 to 29.9 MPa, but decreased elongation at break, with a subtle effect on WVP. Water solubility and absorption increased by 20.1% and 173.9%, respectively, in the ACR-λ1.5% films. Water uptake followed Peleg's kinetics, while soil biodegradation exhibited second-order kinetics and reached complete degradation within 40 days at 24% soil moisture. These results demonstrate the potential of ACR-carrageenan films as innovative biodegradable packaging materials, offering an eco-friendly alternative to plastics in food packaging, promoting sustainability and a circular bioeconomy, and creating new income opportunities for alfalfa farmers.