# Dual-Modified A- and B-Type Wheat Starch–PCL Composite Films: Antibacterial and HACCP-Oriented Biodegradable Packaging from Kazakhstani Resources

## TL;DR

Researchers developed biodegradable packaging from Kazakhstani wheat starch and PCL, finding that different starch types affect mechanical and composting properties.

## Contribution

The study introduces dual-modified A- and B-type wheat starch–PCL composites with tailored antibacterial and composting properties.

## Key findings

- A-type starch composites showed better mechanical strength and smoother surfaces.
- B-type starch composites degraded faster in compost and had higher water vapor permeability.
- A-type starch films exhibited stronger antibacterial activity against E. coli and S. aureus.

## Abstract

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.