Microplastic release from flexible food packaging: Effects of simulants and package structure

Flexible food packaging is widely used in daily life, yet the potential risk of microplastics release, especially under common heating scenarios remains poorly understood. In this study, the release behavior of microplastics from two common flexible food packaging materials was investigated under three treatment conditions: ultrapure water at 100 ℃ for 30 min, 4% acetic acid at 70 ℃ for 30 min, and 10% ethanol at 100 ℃ for 30 min. The results showed that the polyamide(PA)/polyethylene(PE) co-extruded pouch and the polyethylene terephthalate(PET)/aluminum(Al)/PA/retort cast polypropylene(RCPP) retort pouch released 97 ± 14-377 ± 11 MPs/500 mL and 72 ± 10-167 ± 6 MPs/500 mL, respectively, with significant differences among packaging types and treatment conditions. The major released polymers were PA, PE, and PP, and most microplastics were in the size range of 20-50 μm, with particles being the dominant morphology. Scanning electron microscopy(SEM) further revealed that microplastic release was jointly driven by surface/interfacial weakening, thermal stress, and local structural failure. Scenario-based estimates suggested that the dietary intake of detectable microplastics ranged from approximately 106-754 MPs/week. This study demonstrates that microplastic release from flexible food packaging is jointly influenced by package structure and usage conditions, and provides useful evidence for food packaging safety evaluation and human exposure assessment.