Impact of Polymer Type, Storage Temperature, and Holding Times on the Release of Micro- and Nanoplastics from Food Packaging

Plastic packaging accounts for approximately 36-41% of global plastic production, with nearly half used in food and beverage applications. While packaging improves durability and shelf life, it also represents a potential source of human exposure to micro- and nanoplastics (MNPs). This study investigated the release of MNPs from polystyrene (PS), polypropylene (PP), and polyethylene terephthalate (PET) under realistic storage and heating conditions using a combined Raman imaging and ImageJ quantification workflow. Samples were incubated in 10% ethanol simulant at 4° C for 30 days or 80° C for 10 minutes, with six replicates per condition for statistical rigor. Quantitative analysis revealed substantially higher MNP release at elevated temperature for all polymers, with PP increasing from 501 ± 49 to 686 ± 55 particles per field, PS from 438 ± 30 to 838 ± 57, and PET from 454 ± 35 to 708 ± 53. ANOVA confirmed strong main effects for both temperature (F = 258.87, p < 0.001) and polymer type (F = 3.9966, p < 0.05), as well as a significant polymer × temperature interaction (F = 13.38, p < 0.001). PS exhibited the largest temperature-driven increase in particle shedding, nearly doubling from cold to hot conditions. Across all polymers and treatments, 75-80% of fragments were ‰¤10 µm, demonstrating that nanoscale fragmentation dominates and carries greater implications for tissue translocation and bioavailability. Raman identification of micro- and nanoplastic fragments ‰¤10 µm was achieved using the solvent-assisted extraction method; however, the resulting spectra exhibited markedly reduced peak intensities compared to the bulk PS reference. This attenuation is consistent with particle-size-driven reductions in scattering volume and enhanced surface-to-volume effects, where surface disorder and orientation effects dilute the net Raman response. These factors did not alter the underlying chemical fingerprint of PS but weakened its spectral expression. These findings demonstrate that temperature and polymer composition strongly influence MNP release from food packaging. The combined Raman-ImageJ workflow provides key quantitative insights to the formation and migration of MNPs, highlighting potential exposure risks during heating or prolonged warm storage of foods in plastic containers.