Silver (Ag)

Overview

Silver (Ag) occupies a position in the food safety literature that parallels gold: it appears overwhelmingly as an engineered nanomaterial serving as an analytical reagent or antimicrobial agent rather than as a dietary contaminant. The 12 papers ingested for this deposit divide into four functional domains. The largest group, six papers, describes silver nanoparticle (AgNP) or silver/gold nanocluster platforms developed to detect food contaminants including antibiotic residues, food dyes, food adulterants, and silver ions migrating from packaging. A second group covers nano-silver antimicrobial packaging and silver nanoparticles against food-borne pathogens. A third group covers aquatic ecotoxicology: two papers document the effects of AgNPs on fish liver function and sperm motility. Two additional papers describe silver carp (Hypophthalmichthys molitrix), a freshwater food fish whose common name contains the word silver but which is unrelated to the metal element. One dental paper adds peripheral context on AgNP use in medical materials.

No food occurrence dataset for silver as a naturally occurring dietary contaminant is contributed by any source in this deposit. The closest the deposit comes to a measured food-contact concentration is Lu et al. 2019, which reports 1.352 mg/L Ag+ in an extract from one nano-silver food packaging sample by flame atomic absorption spectrometry. Ufelle & Barchowsky 2021 notes silver among minor toxic metals for which toxicity has been described, without a dedicated silver subsection.

Toxicological context

Ufelle & Barchowsky 2021 places silver in the chapter-level category of minor toxic metals in the Casarett and Doull toxicology textbook. No dose-response data, mechanism, target organ, or regulatory limits for silver in food are provided by that source. The aquatic toxicology papers in this deposit provide the most mechanistic detail available here: Naguib et al. 2020 documents hepatotoxic effects of AgNPs in catfish at 10 to 100 µg/L water concentrations, and Oliveira et al. 2024 documents seabream sperm motility reduction at concentrations as low as 0.25 µg/L. These findings characterize the ecotoxicological hazard profile of AgNPs released into aquatic environments, which is relevant to assessing secondary exposure pathways in aquatic food chains, though no tissue residue data for edible fish flesh are reported.

Silver nanoparticles as food safety sensing platforms

The dominant finding from this evidence deposit is that silver nanoparticles and their structural variants serve as versatile analytical platforms for food safety target classes. Silver’s strong localized surface plasmon resonance, centered near 400 nm for AgNPs approximately 20 to 60 nm in diameter, shifts measurably when AgNPs aggregate, and the ease with which silver surfaces can be functionalized makes them adaptable across analyte classes.

Food adulterant detection

Liu et al. 2021 demonstrate that gallic acid-capped AgNPs detect melamine in raw milk at a LOD of 0.099 µM (0.012 ppm), more than 80 times below the Chinese safety limit of 1.0 ppm and more than 160 times below the EU limit of 2.0 ppm. The mechanism is AgNP aggregation induced by hydrogen bonding between melamine and gallic acid, shifting the solution color from yellow to brown. This sensor addresses the principal food safety target of the 2008 Chinese infant formula adulteration incident.

Food allergen detection

Mercadal et al. 2018 demonstrate an enzyme-free immunoassay using AgNPs of 58 and 78 nm diameter for detecting gliadin, the celiac disease antigen, at femtomolar concentrations, achieving 1,000 to 10,000 times greater sensitivity than ELISA. The method exploits the inhibition of Ag nanoparticle dimer formation by free antigen and reads extinction at 450 nm.

Antibiotic residue monitoring

Goda et al. 2025 develop dithioerythritol-capped silver/gold nanoclusters (DIT@AgAuNCs) as a ratiometric fluorescence probe for detecting fluoroquinolone antibiotics (ciprofloxacin, norfloxacin, enrofloxacin) in spiked egg and milk. LODs of 31, 38, and 44 nM respectively were achieved with recoveries of 94.0 to 106.0% and RSD below 4.09%.

Food dye detection

Pham et al. 2021 synthesize Ag/Au alloy nanoparticles for surface-enhanced Raman spectroscopy detection of rhodamine B, an illegal synthetic food dye. The Ag3Au composition (highest silver fraction) achieved a LOD of 10^-11 M rhodamine B with an enhancement factor exceeding 10^10, the highest SERS sensitivity for rhodamine B reported at the time of publication.

Silver ion migration monitoring

Lu et al. 2019 synthesize nitrogen-doped carbon quantum dots (N-CQDs) as a fluorescent probe for detecting Ag+ ions in food packaging extracts. As a validation step, the probe was applied to a food packaging material sample and measured Ag+ at 1.442 mg/L (N-CQDs) versus 1.352 mg/L by flame AAS, a relative error of 6.24%. This measurement confirms that nano-silver antimicrobial packaging releases detectable silver ions. The paper frames Ag+ migration from packaging as a recognized food safety concern, citing mammalian cytotoxicity literature for AgNPs at the same molecular entity.

Silver in antimicrobial food packaging

Tavakoli et al. 2017 evaluate nano-silver packaging films at 1, 2, and 3% silver concentration for nuts stored over 24 months in Iran. All three concentrations significantly reduced total microbial count, mold count, and coliform count relative to controls and prevented aflatoxin production. Control groups developed aflatoxin contamination reaching 2.0 mg/kg in pistachios and almonds and 2.5 mg/kg in hazelnuts and walnuts after 24 months; nano-silver packaging prevented this entirely in all treatment groups. Shelf life extended from a control mean of 13 months to 18 to 20 months depending on nut type, with 3% nano-silver producing the strongest effect. Silver migration from packaging into the nuts was not measured in this study.

Silver nanoparticles against food-borne pathogens

Ahmed et al. 2023 characterize ESBL-producing E. coli from 250 retail meat samples in Egypt, finding prevalence of 81.1% in duck meat and workers and 61.5% in camel meat. All isolates were multidrug resistant with an average multiple antibiotic resistance index of 0.7. REP-PCR genotyping showed 100% similarity between human and meat isolates within clusters, documenting a zoonotic transmission pathway. Silver nanoparticles combined with hydrogen peroxide (AgNPs-H2O2) achieved complete growth inhibition of these MDR strains at concentrations of 0.625 to 5 µg/mL. This paper demonstrates both the food safety burden of drug-resistant pathogens in retail meat and the in vitro efficacy of AgNPs as an antimicrobial alternative, without quantifying silver residues in treated meat.

Aquatic ecotoxicology of silver nanoparticles

Two papers characterize the effects of AgNPs on fish, relevant to assessing secondary exposure pathways in aquatic food sources.

Naguib et al. 2020 expose African catfish (Clarias gariepinus) to AgNPs at 10 and 100 µg/L (20 nm and 40 nm diameter) or silver nitrate at 1.5 mg/L for 15 days. Liver enzyme concentrations (AST, ALT, ALP), total lipids, and glucose were significantly elevated in all exposed groups; total proteins, albumin, and globulin were significantly reduced. Liver Ag concentration increased significantly. Histopathological changes included hepatocyte proliferation, necrosis, apoptosis, blood vessel dilation, and melanomacrophage aggregation. A 15-day clean-water recovery period improved but did not fully normalize these parameters. This study is relevant because African catfish is a commonly consumed food fish in Africa and the Middle East, and the findings indicate that environmental AgNP exposure at concentrations not far above ambient levels (Ag background concentrations in natural waters are typically less than 0.1 µg/L) causes organ damage that persists through the recovery window examined.

Oliveira et al. 2024 expose gilthead seabream (Sparus aurata) sperm ex vivo to AgNPs and Ag+ ions at 0.25, 25, and 250 µg/L and find that total and progressive sperm motility was significantly reduced at all three concentrations, including the lowest (0.25 µg/L), which the authors characterize as within the realistic environmental range for AgNPs in coastal waters. The percentage of fast sperm subpopulations fell from 53.4% in controls to 34.8% at AgNP 250 µg/L. This study is notable because it identifies a reprotoxic effect at an environmentally relevant concentration for a commercially important marine aquaculture species.

Silver carp food science

Two papers in this deposit study silver carp (Hypophthalmichthys molitrix), a freshwater fish species farmed at large scale in Asia, whose common name contains the word silver but which does not involve the metal element.

Naseri et al. 2013 characterize changes in fatty acid composition of silver carp fillets fried in four culinary oils. Raw silver carp lipids contained 26.1% SFA, 52.1% MUFA, and 15.1% PUFA with 8.9% omega-3 and 6.1% omega-6. Frying in sunflower, soybean, and corn oil increased MUFA, PUFA, and omega-6 by oil exchange. Long-chain omega-3 content (EPA and DHA) was largely preserved except in soybean oil.

Hong et al. 2023 demonstrate that adding black tea powder at 0.3% to silver carp surimi fish balls increases DPPH scavenging to 57.93%, ABTS scavenging to 89.24%, and significantly improves gel strength, hardness, and chewiness after seven days of frozen storage.

Neither paper measures silver (Ag) or any heavy metal, and neither is relevant to heavy metal contamination in food.

Silver nanoparticles in dental materials

Nikanjam et al. 2023 demonstrate that adding AgNPs at 250 and 500 ppm to feldspathic porcelain ceramic disks improves color stability under thermocycling in tea, orange juice, and artificial saliva. This paper is a dental biomaterials study; it has no relevance to dietary silver exposure or food safety but documents the broader use of AgNPs as functional additives in materials in contact with saliva.

What remains uncertain

No source in this deposit provides food occurrence data for silver as a naturally occurring dietary contaminant in crops, animal-derived foods, drinking water, or other food matrices. The packaging migration value from Lu et al. 2019 (1.352 mg/L Ag+ in a packaging extract) is a single-sample validation measurement under unspecified extraction conditions, not a standardized regulatory migration test. The concentration of dietary silver intake from consumption of foods packaged in nano-silver antimicrobial materials remains uncharacterized in this deposit. Regulatory frameworks for nano-silver food contact materials (EU Framework Regulation 1935/2004, FDA food contact guidance) are not documented in any source here. The aquatic ecotoxicology findings from catfish and seabream identify hazard at concentrations potentially relevant to aquaculture and wild fish, but the deposit contains no residue data for edible fish tissue that would allow dietary intake estimation.

Frequently asked questions

Sources

• Ufelle & Barchowsky 2021 : Ufelle AC, Barchowsky A, 2021. Toxic Effects of Metals, Ch 23 in Casarett & Doull’s Essentials of Toxicology, 4th ed.
• Lu et al. 2019 : Lu Z et al., 2019. Nitrogen-doped carbon quantum dots detect Ag+ in food packaging material. Int J Environ Res Public Health.
• Goda et al. 2025 : Goda MN et al., 2025. Silver/gold nanoclusters for fluoroquinolone detection in egg and milk. RSC Advances.
• Mercadal et al. 2018 : Mercadal PA et al., 2018. Enzyme-free AgNP immunoassay for gliadin detection. ACS Omega.
• Pham et al. 2021 : Pham TTH et al., 2021. Ag/Au alloy nanoparticles for SERS detection of rhodamine B. RSC Advances.
• Tavakoli et al. 2017 : Tavakoli H et al., 2017. Nano-silver packaging extends shelf life of nuts. Italian J Food Safety.
• Ahmed et al. 2023 : Ahmed HA et al., 2023. ESBL E. coli from retail meat and AgNP antimicrobial activity. BMC Microbiology.
• Liu et al. 2021 : Liu X et al., 2021. Gallic acid-capped AgNPs as colorimetric sensor for melamine in milk. ACS Omega.
• Naseri et al. 2013 : Naseri M et al., 2013. Frying effects on fatty acid composition of silver carp. Food Science & Nutrition.
• Naguib et al. 2020 : Naguib M et al., 2020. Hepatotoxic effects of AgNPs on African catfish. Toxicology Reports.
• Hong et al. 2023 : Hong J et al., 2023. Black tea powder effects on silver carp fish balls gel. Gels.
• Oliveira et al. 2024 : Oliveira CCV et al., 2024. AgNPs reduce seabream sperm motility at realistic concentrations. Fish Physiology and Biochemistry.
• Nikanjam et al. 2023 : Nikanjam S et al., 2023. Silver nanoparticles improve color stability of dental porcelain. Dental Research Journal.

References

Works cited in this page’s text, in first-appearance order. See Sources for this page’s source inventory. Each title links to a source record with bibliographic details, reported findings, and document provenance.

1. Potential Application of Nitrogen-Doped Carbon Quantum Dots Synthesized by a Solvothermal Method for Detecting Silver Ions in Food PackagingLu Z, Su T, Feng Y, Jiang S, Zhou C, Hong P, et al. · International Journal of Environmental Research and Public Health 16(14): 2518 · 2019 · doi.org/10.3390/ijerph16142518Peer-reviewed
2. Toxic Effects of Metals (Chapter 23), in Casarett & Doull’s Essentials of Toxicology, Fourth EditionUfelle AC and Barchowsky A · Casarett & Doull’s Essentials of Toxicology, Fourth Edition. McGraw Hill Education · 2021 · www.mhprofessional.comTextbook
3. Hepatotoxic Effects of Silver Nanoparticles on Clarias gariepinus; Biochemical, Histopathological, and Histochemical StudiesNaguib M, Mahmoud UM, Mekkawy IA, and Sayed AEH · Toxicology Reports 7: 133-141 · 2020 · doi.org/10.1016/j.toxrep.2020.01.002Peer-reviewed
4. Exposure to Silver and Titanium Dioxide Nanoparticles at Supra-Environmental Concentrations Decreased Sperm Motility and Affected Spermatozoa Subpopulations in Gilthead Seabream, Sparus aurataOliveira CCV, Ferrao L, Gallego V, Mieiro C, Oliveira IB, Carvalhais A, et al. · Fish Physiology and Biochemistry 50: 1959-1970 · 2024 · doi.org/10.1007/s10695-023-01218-0Peer-reviewed
5. In Situ Functionalization of Silver Nanoparticles by Gallic Acid as a Colorimetric Sensor for Simple Sensitive Determination of Melamine in MilkLiu X, Wang J, Wang Y, Huang C, Wang Z, and Liu L · ACS Omega 6(37): 23630-23635 · 2021 · doi.org/10.1021/acsomega.1c03927Peer-reviewed
6. Enzyme-Free Immunoassay Using Silver Nanoparticles for Detection of Gliadin at Ultralow ConcentrationsMercadal PA, Fraire JC, Motrich RD, and Coronado EA · ACS Omega 3(3): 2340-2350 · 2018 · doi.org/10.1021/acsomega.7b01840Peer-reviewed
7. Dithioerythritol-Capped Silver/Gold Nanoclusters for Determination of Ciprofloxacin, Norfloxacin, and Enrofloxacin in Food and Urine SamplesGoda MN, Alqarni LS, Ibrahim H, Ali AMBH, and El-Wekil MM · RSC Advances 15: 23364 · 2025 · doi.org/10.1039/d5ra02878gPeer-reviewed
8. Facile Synthesis of Silver/Gold Alloy Nanoparticles for Ultra-Sensitive Rhodamine B DetectionPham TTH, Dac Dien N, and Vu XH · RSC Advances 11: 21475 · 2021 · doi.org/10.1039/d1ra02576gPeer-reviewed
9. The Effect of Nano-Silver Packaging in Increasing the Shelf Life of Nuts: An In Vitro ModelTavakoli H, Rastegar H, Taherian M, Samadi M, and Rostami H · Italian Journal of Food Safety 6(3): 6874 · 2017 · doi.org/10.4081/ijfs.2017.6874Peer-reviewed
10. Extended-Spectrum Beta-Lactamase-Producing E. coli from Retail Meat and Workers: Genetic Diversity, Virulotyping, Pathotyping and the Antimicrobial Effect of Silver NanoparticlesAhmed HA, Elsohaby I, Elamin AM, Abd El-Ghafar AE, Elsaid GA, Elbarbary M, et al. · BMC Microbiology 23: 212 · 2023 · doi.org/10.1186/s12866-023-02948-0Peer-reviewed
11. Effect of Frying in Different Culinary Fats on the Fatty Acid Composition of Silver CarpNaseri M, Abedi E, Mohammadzadeh B, and Afsharnaderi A · Food Science and Nutrition 1(4): 292-297 · 2013 · doi.org/10.1002/fsn3.40Peer-reviewed
12. Effect of Black Tea Powder on Antioxidant Activity and Gel Characteristics of Silver Carp Fish BallsHong J, Wu J, Chen Y, Jiang Z, Zhu Y, Li Z, et al. · Gels 9(3): 215 · 2023 · doi.org/10.3390/gels9030215Peer-reviewed
13. The Effect of Adding Silver Nanoparticles on the Color Stability of Feldspathic PorcelainsNikanjam S, Firouz F, Farmany A, Farhadian M, Shishean A, and Masomian Z · Dental Research Journal 20: 71 · 2023 · pmc.ncbi.nlm.nih.govPeer-reviewed

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