Antimicrobial food packaging shows promise, but could come with contamination risks.

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Silver Nanoparticles in Packaging Can Contaminate Dry Foods

Antimicrobial food packaging shows promise, but could come with contamination risks.

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Published: January 28, 2025 

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Alexander BeadleA package of oranges in shrink-wrap plastic.

Credit: Wander Fleur / Unsplash.

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Incorporating silver nanoparticles (AgNPs) into plastic packaging has been proposed as a novel way to protect against foodborne disease and extend the shelf life of food.  

Despite their demonstrated promise for this purpose, nanoparticle-infused polymers are not yet authorized in the United States or European Union for use as food packaging. This is largely due to the need for further studies proving that silver nanoparticles and ions will not migrate into the food they contact.

New research led by scientists at the US Food and Drug Administration (FDA) suggests that AgNPs can leach out of plastic packaging and into solid foods. The study, published in ACS Food Science & Technology, found evidence of nanoparticle migration into dry goods (flour and ground rice), moist solid foods (cheese slices) and leafy greens (spinach leaves).

Understanding nanoparticle migration

Studying the migration of nanoparticles out of these plastic matrices is not a new endeavor. Early assessments concluded that nanoparticles larger than a few nanometers in diameter would be too large to diffuse through and out of plastic packaging under commercially relevant timescales.

However, subsequent studies using beverages, gelatinous foods (such as yogurt) and liquid food simulants have shown that AgNP-containing plastics can release dissolved silver ions into the food they contain. In some cases, these ions were found to induce silver nanoparticle formation in foods during long-term storage.

One significant limitation of past studies is that they have mainly assessed liquids or liquid food simulants rather than packaged foods like dry goods (grains, cereals) or moist solids (cheese slices, deli meat).

This is an important distinction to make, as solid foods will have different interactions with their packaging than a beverage or liquid simulant. There is normally less contact area between solid food and its packaging due to air bubbles, for example, which may make the direct migration of nanoparticles more difficult. Solid foods are also likely to have a harder time penetrating or degrading the polymer, which would otherwise increase the likelihood o

f nanoparticle migration or silver ion release.