Dual-Modified A- and B-Type Wheat Starch-PCL Composite Films: Antibacterial and HACCP-Oriented Biodegradable...

Biodegradable packaging based on starch-polycaprolactone (PCL) composites is a promising route to reduce reliance on petroleum-derived plastics. Here, wheat starches with A- and B-type crystallinity-sourced from Kazakhstani varieties-were dual-modified by electron-beam irradiation followed by acetylation and incorporated into PCL (30-50 wt%) via melt extrusion and compression molding. The resulting films were characterized for morphology, mechanical performance, water-vapor permeability (WVP), thermal behavior, antibacterial activity, and biodegradation under soil and composting conditions. Acetylated A-type starch dispersed more uniformly within the PCL matrix, yielding smoother surfaces, higher tensile strength, and moderate WVP. In contrast, B-type starch produced a more porous microstructure with increased WVP and accelerated mass loss during composting (up to ~45% within 10 days at higher starch loadings). Incorporation of starch slightly decreased thermal stability relative to neat PCL, while agar-diffusion assays against Escherichia coli and Staphylococcus aureus showed loading-dependent inhibition zones, with A-type composites generally outperforming B-type at equivalent contents. Taken together, A-type starch-PCL films are better suited for applications requiring mechanical integrity and controlled moisture transfer, whereas B-type systems favor breathable packaging and rapid compostability. These results clarify how starch crystalline type governs structure-property-degradation relationships in PCL composites and support the targeted design of sustainable packaging materials using regionally available starch resources.