Toward sustainable LDPE packaging films from cotton straw: barrier–moisture–microenvironment coupling for food preservation

Sustainable food packaging that preserves quality without migratory additives is highly desirable. While CS–LDPE composites have been widely studied for structural applications, their role in food packaging remains limited. Herein, cotton straw (CS) is used as a bio-filler in LDPE films via melt blending compatible with conventional processing. With LDPE-g-MA compatibilization, interfacial densification and modified surface morphology are achieved, enabling coupled regulation of gas transport, moisture behavior, and the local microenvironment. Surface roughness variation further reflects these interfacial changes and their influence on moisture interaction. At moderate CS contents (10–15 wt%), oxygen transmission is reduced by up to ~55% while maintaining balanced water vapor permeability. These effects translate into improved preservation, including reduced weight loss, delayed deterioration, stabilized pH, and reduced microbial growth. The effect is attributed to structure-regulated mass transport rather than direct antimicrobial activity, offering a scalable strategy for LDPE-based food packaging. • Cotton straw serves as a multifunctional bio-filler in LDPE packaging films. • LDPE-g-MA improves interfacial densification and filler dispersion. • Moderate cotton straw loadings reduce oxygen transmission. • Water vapor permeability remains balanced, limiting excessive dehydration. • Structural regulation delays food deterioration and microbial growth without added antimicrobial agents.