Abstract
We investigated migration of Ag from model Ag nanoparticle (AgNP)-loaded polyethylene films into bovine milks with varying milkfat content after storage for 10 days at 20 °C. Ag migration into 2% fat milk (2.18 ± 0.03 ng/cm2) was comparable to that observed in skim milk (2.16 ± 0.14 ng/cm²), while whole milk (4% milkfat) had the lowest migration (1.80 ± 0.07 ng/cm²). Notably, Ag migration into skim, 2%, and whole milk was 1.72, 1.69, and 1.40 times higher, respectively, than that into 50% aqueous ethanol, a common simulant for whole milk. At least a portion of the migrated Ag in milk existed as nanoparticles, suggesting that milk components influence the final form of migrated Ag. We explored the behavior of Ag+ ions in milks and observed efficient Ag+ transformation to Ag0 NPs and Ag2O NPs. Electron microscopy images revealed polydisperse, quasi-spherical Ag particles with sizes ranging from 5 to 70 nm. Milk proteins, particularly casein and whey, play a role in the transformation of dissolved Ag+ to nanoparticles, while lactose influences the nanoparticle composition. These findings highlight that Ag interactions with milk components affect Ag migration dynamics and emphasize the need for a better delineation of appropriate food simulants for migration studies with AgNP-containing polymers.
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Data availability
Experimental (ICP-MS and SP-ICP-MS) migration data are provided in table format in the Supporting Information section. Data used to generate X-ray diffractograms and Raman/UV–Vis spectra are available upon request to the corresponding author.
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Acknowledgements
This work was funded by the U.S. Food and Drug Administration. L.A. acknowledges an appointment to the Research Participation Program at the FDA, administered by the Oak Ridge Institute for Science and Education through an interagency agreement between the U.S. Department of Energy and the FDA. T.V.D. acknowledges support from the Nano CORES intramural grant program, which is operated through the FDA Office of the Chief Scientist. The authors are grateful for Reiner Bleher at the Northwestern University Atomic and Nanoscale Characterization Experimental (NUANCE) Center for assistance with electron microscopy imaging. The NUANCE Center has received support from the SHyNE Resource (NSF ECCS-2025633), the IIN, and Northwestern's MRSEC program (NSF DMR-2308691).
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L.A. and T.V.D. designed the experiments, interpreted data, made figures, and prepared the manuscript. S.P., R.M., and M.S. contributed to experimental work, which included nanoparticle synthesis, composite fabrication, and chemical analysis. All authors had an opportunity to review the manuscript prior to submission.
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Adhikari, L., Pansare, S.B., Mudireddy, R.R. et al. Milk proteins and fat influence Ag migration from model dairy packaging containing silver nanoparticles. npj Sci Food (2026). https://doi.org/10.1038/s41538-025-00684-5
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DOI: https://doi.org/10.1038/s41538-025-00684-5
