Strategic Integration of Alkali Lignin Into Citrus Pectin–Gelatin Films for Sustainable Food Packaging With Enhanced Barrier and Antioxidant Performance

ABSTRACT The sustainable transformation of agro‐industrial residues into high‐value functional materials is central to advancing circular biorefinery and bioeconomy frameworks. This study presents a green valorization strategy wherein alkali lignin (AL), a polyphenol‐rich byproduct of the Kraft pulping process, is incorporated into citrus pectin–gelatin (CPG) biopolymer films to develop multifunctional, biodegradable packaging materials. Incorporation of AL at low concentrations (0.5%–2% w/w) resulted in significant enhancements in UV‐blocking capacity, moisture barrier performance, surface hydrophobicity, and antioxidant activity, while maintaining favorable mechanical and structural integrity. These effects stem from lignin's chromophoric and phenolic structures, which absorb UV light and scavenge free radicals, while its aromatic backbone reinforces the matrix. All films exhibited substantial biodegradation under soil burial conditions, with only a slight reduction observed upon lignin incorporation. The formulation with 1.5% AL exhibited the most balanced overall performance, while higher loading led to aggregation‐induced limitations. This work demonstrates a novel and scalable approach to agro‐waste valorization, showcasing the synergistic integration of polysaccharide, protein, and phenolic components into functional food packaging systems that support sustainability and circular resource utilization.