Modification of walnut shell lignin nanoparticles through deep eutectic solvent for application in active food...

Area of Science:

• Biomaterials Science
• Sustainable Chemistry
• Food Packaging Technology

Background:

• Fossil fuel depletion and plastic pollution necessitate renewable resource utilization.
• Lignocellulose, a biomass component, faces challenges in efficient extraction and application.
• Agricultural waste, like walnut shells, presents an opportunity for valorization.

Purpose of the Study:

• To develop a sustainable method for extracting bioactive lignin nanoparticles (LNPs) from walnut shells using a ternary deep eutectic solvent (DES).
• To create a composite active packaging film incorporating LNPs and ε-polylysine (ε-PL) for enhanced food preservation.
• To evaluate the efficacy of the active packaging in extending the shelf life of fresh walnuts.

Main Methods:

• Extraction of lignin nanoparticles (LNPs) from walnut shells using a continuous processing platform with a ternary DES and anti-solvent precipitation.
• Characterization of LNPs, including ζ-potential, particle size, and antioxidant activity.
• Fabrication of a composite film using LNPs, ε-polylysine (ε-PL), and polyvinyl alcohol (PVA) matrix.
• Assessment of the composite film's mechanical properties, UV-blocking efficiency, and antimicrobial activity.
• Application of the active film to walnut packaging to evaluate its effect on mold inhibition and nutrient preservation.

Main Results:

• A ternary DES successfully converted 56.84% of lignin into LNPs with preserved side-chain functionality, enhanced antioxidant activity, and optimal particle size (203.48 nm).
• The composite film exhibited a tensile strength of 33.32 MPa, 90% UV-blocking efficiency, and 60% microbial growth inhibition.
• Active packaging with the LNP-based film demonstrated mold suppression, reduced nutrient oxidation, and extended shelf life of fresh walnuts through gradual LNP release.

Conclusions:

• A scalable and circular approach was established for repurposing agricultural waste (walnut shells) into valuable lignin nanoparticles.
• The developed biodegradable active packaging offers a sustainable solution for food preservation, aligning lignin valorization with reduced environmental impact.
• This technology presents a promising strategy for enhancing food safety and reducing spoilage through innovative packaging materials.