Silver Nanoparticles Paired with Antifungal Peptides Show Promise for Fruit Preservation

A new review published in Agricultural Products Processing and Storage examines how silver nanoparticles, particularly when combined with natural antifungal peptides and plant-derived compounds, could extend the shelf life of perishable fruits and vegetables. The review, published on 1 September 2026, synthesizes current knowledge on how these nanoparticles are made, how they are characterized, how they attack fungal pathogens, and what safety and regulatory hurdles stand between the laboratory and the supermarket.

The motivation is stark. According to Food and Agriculture Organization estimates cited in the review, roughly 8.2 percent of the global population, about 653 million people, faced chronic hunger in 2024, while a mid-range figure of 733 million represents a 35.1 percent increase compared with 2019 levels. Postharvest losses are a major contributor: approximately 1.3 billion tons, roughly one third of global food production, is lost or wasted within the supply chain. Fruits and vegetables are especially vulnerable because of their high perishability, and fungal pathogens such as Penicillium expansum, Botrytis cinerea, and Alternaria alternata are identified as the leading drivers of postharvest decay. In some developing countries, more than 90 percent of perishable goods are still not refrigerated, and inadequate cold chain infrastructure is responsible for over 20 percent of postharvest losses.

Silver nanoparticles have emerged as promising antimicrobial agents because of their high stability and broad-spectrum activity. The review explains that during synthesis, silver ions derived from a precursor such as silver nitrate are reduced to elemental metallic silver, forming nanoparticles whose high surface area-to-volume ratio distinguishes them from dissolved silver ions. Synthesis routes fall into three broad categories. Chemical methods, using reductants such as sodium borohydride, sodium citrate, and ascorbic acid, offer precise control over particle size and morphology but rely on toxic reagents that raise environmental and safety concerns for food applications. Physical methods, including evaporation-condensation and laser ablation, produce high-purity particles without chemical contaminants but are energy-intensive and costly to scale. Biological, or green, synthesis uses plant extracts, microorganisms, and biopolymers as reducing and stabilizing agents, offering reduced toxicity and biocompatibility, though with less control over particle size and challenges in scalability.

The review catalogs numerous specific examples. Sonochemical decomposition of silver nitrate under sonication in an argon-hydrogen environment produced amorphous particles of about 20 nanometers. Electrochemical dissolution of a silver anode yielded particles of 2 to 7 nanometers, with size tunable through current density. Zeolite nanocages confined particles to 1 to 2 nanometers, while graphene oxide substrates with polyethylene glycol under microwave irradiation produced particles up to 20 nanometers dispersed within a mesoporous matrix. Plant extracts from species including Salacia chinensis, Brassica rapa, and Cannabis sativa yielded particles ranging from roughly 5.7 to 80 nanometers, with reaction conditions such as pH and temperature strongly influencing outcome. Alkaline pH enhances reduction kinetics and produces smaller, more uniform particles, while higher temperatures accelerate reduction; in one temperature-sensitive method, the conversion of silver ions to nanoparticles rose from 45 percent at 60 degrees Celsius to 100 percent at 90 degrees Celsius.

Characterization relies on a suite of complementary analytical techniques. Ultraviolet-visible spectroscopy tracks surface plasmon resonance to monitor particle formation and aggregation, with smaller spherical particles absorbing near 400 nanometers. Fourier transform infrared spectroscopy identifies carbonyl, amide, and hydroxyl functional groups involved in reduction and capping. Dynamic light scattering measures hydrodynamic diameters, scanning electron microscopy reveals surface morphology and aggregation, transmission electron microscopy delivers high-resolution images of size, shape, and crystal defects, and X-ray diffraction confirms crystalline phase using standard reference cards. The review notes that X-ray photoelectron spectroscopy and zeta potential analysis remain underused in plant-based synthesis studies, and calls for their wider adoption to fully elucidate surface composition and colloidal stability, which directly influence biological activity and aggregation behavior.

The molecular mechanisms of antimicrobial action are multifaceted. Silver ions can destabilize microbial cell membranes, potentially creating holes that allow penetration, and they interact with thiol groups in proteins and enzymes. Nanoparticles adhere to cell membranes, generate voids, and induce cell destruction through reactive oxygen species. Excessive accumulation of hydroxyl radicals, superoxide anions, hydrogen peroxide, and peroxide radicals causes oxidative damage to macromolecules, protein oxidation, DNA damage, and ultimately cellular apoptosis. Antifungal peptides operate through distinct but complementary mechanisms: being typically cationic, they bind strongly to negatively charged fungal membranes, promoting destabilization and pore formation through carpet-like or toroidal pore mechanisms. Fungal membranes contain ergosterol and a rigid cell wall of chitin and beta-glucans, key targets for peptide activity. Some peptides translocate into the cytoplasm, inducing oxidative stress, mitochondrial dysfunction, and inhibition of nucleic acid and protein synthesis, and can inhibit spore germination and hyphal growth, critical stages in postharvest infection.

Combination studies quantify synergy using the fractional inhibitory concentration index, where values below 0.5 indicate synergy, values above 2.0 indicate antagonism, and intermediate values indicate additive effects. In the reviewed microdilution assays, silver nanoparticles combined with polymyxin B acted synergistically against all Gram-negative bacteria tested, while gramicidin S showed synergy with the nanoparticles against selected strains. Against fruit spoilage fungi specifically, the evidence is encouraging. Chitosan films loaded with silver nanoparticles inhibited growth of Botrytis cinerea, Penicillium expansum, and Rhizopus stolonifer, with antifungal efficacy increasing as silver content rose. Nanoparticle-chitosan Janus particles showed significant activity against B. cinerea and A. alternata, and nanoparticles formed in situ with polycaprolactone in leaf extract hybrids inhibited Candida albicans and Aspergillus flavus at concentrations as low as 1 millimole per liter. However, aggregation of particles at higher concentrations reduced interaction with fungal cell walls, underscoring the importance of size and concentration control.

Safety remains the central caveat. Mouse studies cited in the review found harmful effects, including genotoxicity and histopathological indicators, after treatment with powdered silver nanoparticles at a dosage of 2.5 milligrams per mouse for particle sizes of 100 and 20 nanometers. Migration of nanoparticles from packaging into food depends on particle characteristics, polymer properties, pH, temperature, contact time, and food composition, and the solubility of metallic nanoparticles in aqueous solutions increases with temperature and decreases with pH, enhancing metal migration into the food matrix. Regulatory frameworks vary by region: in the European Union, nano-silver falls under European Food Safety Authority assessment and the Novel Food Regulation, requiring evaluation of migration, toxicity, and contact before approval in food packaging, while in the United States the Food and Drug Administration evaluates nano-silver under its Generally Recognized as Safe framework. Notably, neither agency has yet issued specific approvals for ingestible nano-silver applications in fresh produce, citing the need for more comprehensive toxicological and migration data.

Public acceptance presents another obstacle. A quantitative survey of 1,046 consumers found that approval and willingness to consume a hypothetical product diminished with the introduction of nanotechnology, with nano-outside packaging applications receiving mean scores above neutral and 64 percent of respondents willing to buy nano-wrapped products at a reduced price, while nano-inside applications, where nanoparticles are integrated into the edible portion of fruit, dropped to unsatisfactory levels. A separate United States poll of 1,131 respondents showed popular approval and willingness to pay for nano-foods, suggesting that consumer attitudes are nuanced and strongly influenced by trust in the food industry and perceived benefits. The review concludes that silver nanoparticle-based antifungal peptide systems show genuine promise as sustainable alternatives to traditional chemical preservatives, but that future research must standardize testing methodologies, develop hybrid synthesis approaches balancing chemical precision with green sustainability, and rigorously assess long-term safety, bioaccumulation potential, and human health impacts before widespread application can proceed.

Subject of Research: A review of silver nanoparticle and antifungal peptide systems for preserving fruit and their safety challenges

Article Title: A silver nanoparticles based anti-fungal peptides system for fruit preservation: synthesis, characterization, applications and safety

Article References: Akram, T., Jin, J., & Sani, A. I. (2026). A silver nanoparticles based anti-fungal peptides system for fruit preservation: synthesis, characterization, applications and safety. Agricultural Products Processing and Storage, 2(1), Article 45. https://doi.org/10.1007/s44462-026-00079-z

Image Credits: AI Generated

DOI: 10.1007/s44462-026-00079-z

Keywords: silver nanoparticles, antifungal peptides, fruit preservation, postharvest losses, green synthesis, chitosan coatings, food safety, nanotechnology, reactive oxygen species, food packaging regulation, fungal spoilage, shelf life