Researchers at the University of Jiroft in Kerman Province, Iran, set out to test whether aloe vera gel, used as an edible coating and enriched with fennel or lime peel essential oils, could extend the shelf life and microbial safety of table eggs stored under refrigeration. The team, led by Zahra Ranjbarinasab and Fatemeh Shahdadi, noted that although aloe vera gel and various essential oils have each been explored for egg preservation before, no previous study had investigated this particular combination for maintaining both the physicochemical quality and microbial stability of refrigerated eggs. Their findings point toward a natural, additive-free approach that could reduce food waste and economic losses in one of the world’s most consumed animal products.

The experimental design was straightforward but rigorous. The researchers obtained 300 fresh white-shelled chicken eggs from a local retail center, with an average weight of 62.39 grams, and excluded any showing cracks, shell defects, or surface contamination. The eggs were randomly divided into six groups: an uncoated control, eggs coated in pure 100 percent aloe vera gel, and four groups coated with aloe vera gel containing either 500 or 1000 parts per million of fennel essential oil or the same concentrations of lime peel essential oil. The essential oils were extracted by steam distillation using a Clevenger-type apparatus for three hours, following European Pharmacopeia guidelines, from dried Mexican lime peel and ground fennel seed. Each egg was dipped in its assigned coating for one minute, dried, dipped again, and dried once more before all samples were stored at 5 degrees Celsius for 30 days, with quality assessments performed on days 1, 15, and 30.

The choice of coating ingredients was far from arbitrary. Aloe vera gel is a transparent, viscous substance rich in carbohydrates, proteins, fibers, soluble sugars, vitamins, minerals, amino acids, organic acids, and phenolic compounds, and it has established antioxidant and antimicrobial credentials in food applications. Fennel essential oil, dominated by trans-anethole at roughly 65 to 78 percent of its composition, has demonstrated bacteriostatic effects against Escherichia coli, Bacillus subtilis, and Staphylococcus aureus. Lime peel essential oil is an even more complex mixture of more than 100 compounds, including limonene, citral, and linalool, and is prized for its potent antioxidant and antibacterial properties. By embedding these oils within the aloe vera matrix, the researchers aimed to create a coating that was simultaneously a physical barrier and an active antimicrobial delivery system.

The results on weight loss were striking. After 30 days of refrigerated storage, uncoated control eggs had lost 4.81 percent of their initial weight, while every coated group lost only about 3.35 percent, a roughly 30 percent reduction. The researchers attribute this to the formation of a semipermeable barrier on the shell surface that limits the diffusion of water vapor and carbon dioxide through the shell’s pores. Interestingly, adding essential oils provided no additional weight-loss benefit beyond the aloe vera gel alone, suggesting that the moisture barrier was supplied entirely by the gel matrix and that the oils’ contribution lay elsewhere, primarily in antimicrobial activity.

Internal quality told a similar story. The Haugh unit, the standard industry measure of albumen quality based on the height of the thick egg white, declined in all groups over the month, but coated eggs fared markedly better. Uncoated eggs fell from a Haugh unit of 76.21 on day one to just 54.17 by day 30, while eggs coated with aloe vera gel containing 1000 ppm of fennel essential oil retained a value of 65.74, and those with 1000 ppm lime peel oil reached 65.40. The mechanism is rooted in egg chemistry: as carbon dioxide escapes through the shell during storage, the albumen becomes more alkaline, protein structures break down, and the thick white thins into a watery state. By slowing carbon dioxide loss, the coatings delayed this alkalization and preserved the ovomucin network responsible for albumen viscosity.

The pH measurements reinforced this picture. Fresh albumen contains about 0.5 percent dissolved carbon dioxide, and its loss during storage can push albumen pH from around 7.2 toward 8.5 or higher. In this study, uncoated eggs climbed to an albumen pH of 8.26 after 30 days, whereas eggs coated with aloe vera gel plus 1000 ppm fennel oil reached only 7.60, and those with 1000 ppm lime peel oil reached 7.64. Yolk pH followed the same pattern, rising to 6.91 in controls but only to 6.54 and 6.57 in the highest-concentration fennel and lime peel treatments, respectively. Because yolk and albumen pH are both recognized freshness indicators, these numbers translate directly into longer commercial shelf life.

Functional properties also benefited. Albumen foaming capacity, which matters for baking and culinary performance, declined with storage in all groups, but coated eggs retained significantly more foaming ability than controls, with coated samples reaching about 7.5 milliliters of foam per gram of albumen at day 30 compared with 6.28 for uncoated eggs. The researchers explain that ovomucin stabilizes foam by forming insoluble films around air bubbles, and that coatings preserve this functionality by limiting the water and carbon dioxide losses that drive pH-driven protein degradation. Shell thickness, by contrast, was unaffected by either coating or storage time, indicating that the coatings act as surface barriers rather than altering the mineralized structure of the shell itself.

Perhaps the most compelling results came from the microbiological analysis. Total microbial counts rose in all groups over the storage period, but coated eggs consistently carried lower loads than controls. By day 30, uncoated eggs had reached 5.40 log CFU per gram, while eggs coated with aloe vera gel alone reached 4.67. The essential oil treatments pushed the counts down further still: 4.16 log CFU per gram for 1000 ppm fennel oil and 4.17 for 1000 ppm lime peel oil. The authors attribute this to a dual mechanism, in which the coating acts as a physical barrier against microbial penetration while simultaneously serving as a carrier for natural antimicrobial compounds. Aloe vera’s activity stems from anthraquinones, saponins, phenolics, and organic acids, while limonene and gamma-terpinene in lime oil disrupt bacterial cell membranes, and trans-anethole, fenchone, and methyl chavicol in fennel oil inhibit a wide range of pathogens and even biofilm formation.

The study does have limitations that the authors themselves acknowledge. Only two concentrations of each essential oil were tested, storage was confined to a single refrigerated condition for 30 days, and sensory properties and consumer acceptance of the coated eggs were not evaluated. Industrial scalability, long-term performance, and economic feasibility remain open questions. Nevertheless, the overall conclusion is clear: aloe vera gel enriched with 1000 ppm of either fennel or lime peel essential oil represents a promising natural coating for extending egg shelf life and maintaining quality during refrigerated storage. As food scientists worldwide search for alternatives to synthetic preservatives, this simple dip-and-dry treatment, built from ingredients with long histories of safe human use, offers an elegant demonstration that sometimes the best packaging material may already be growing in a garden.

Subject of Research: Edible aloe vera gel coatings enriched with fennel and lime peel essential oils for extending the shelf life and microbial safety of refrigerated eggs

Article Title: Enhancing the Shelf Life and Microbial Safety of Refrigerated Eggs Using Edible Coatings of Aloe Vera Gel Combined With Fennel and Lime Peel Essential Oils

Article References: Ranjbarinasab, Z., Shahdadi, F., Yousefi, M., Seyedimarghaki, Z., & Omidi, S. (2026). Enhancing the Shelf Life and Microbial Safety of Refrigerated Eggs Using Edible Coatings of Aloe Vera Gel Combined With Fennel and Lime Peel Essential Oils. Food Science & Nutrition, 14(10), Article e72389. https://doi.org/10.1002/fsn3.72389

Image Credits: AI Generated

DOI: 10.1002/fsn3.72389

Keywords: edible coatings, aloe vera gel, essential oils, fennel, lime peel, egg preservation, shelf life, microbial safety, Haugh unit, food science, natural preservatives, refrigerated storage

The research, published in the Journal of the Saudi Chemical Society by a team led by Mohamed S. Abdelwahab of Matrouh University together with colleagues at Qassim University, Alexandria University, and the National Institute of Oceanography and Fisheries, describes a green synthesis route for what the researchers call CQDs-F: carbon quantum dots functionalized with an extract of fennel seed, Foeniculum vulgare. The approach is disarmingly simple. Sucrose was dissolved in water, purified by liquid-liquid extraction, and then subjected to a staged thermal decomposition in a sealed crucible—five minutes at 300 degrees Celsius, five minutes at 400, and twenty minutes at 500. The resulting black carbonaceous residue was ground, sieved, and then blended with a methanolic fennel seed extract in a mortar, where the extract’s phytochemicals passivated and decorated the nanoparticle surfaces as the mixture dried at room temperature.

What makes this functionalization more than a gimmick is the chemistry of fennel itself. Before making any nanoparticles, the team ran the fennel extract through ultra-performance liquid chromatography coupled to high-resolution mass spectrometry, operating in both positive and negative electrospray ionization modes to catch the widest possible range of molecules. The dual-mode analysis revealed a rich phytochemical arsenal: chlorogenic acid and its isomers, coumarin, p-coumaric acid, anethole and estragole derivatives—including a glycosylated form—the flavonoids quercetin and kaempferol, sesquiterpene oxides, epoxy fatty acids, and unsaturated fatty acids such as linoleic acid. These are precisely the classes of compounds associated with antioxidant, antimicrobial, and anticancer activity in the ethnobotanical literature, and the researchers hypothesized that anchoring them to the carbon dot surface would imbue the nanoparticles with biological functions that bare carbon dots lack.

The characterization data told a compelling story of successful marriage between plant chemistry and carbon nanostructure. Fourier-transform infrared spectroscopy of CQDs-F showed the characteristic 852 per centimeter band of para-disubstituted benzene rings—the unmistakable fingerprint of trans-anethole, fennel’s principal phenylpropanoid—alongside aryl-ether stretches and broadened hydroxyl absorption indicating reinforced hydrogen-bonding networks from adsorbed polyphenols. X-ray diffraction revealed that the (002) graphitic peak had broadened relative to the pristine dots, shrinking the crystallite size to roughly 0.8 to 1.0 nanometers by the Scherrer equation, evidence that the adsorbed plant molecules were distorting the carbon lattice. High-resolution transmission electron microscopy confirmed quasi-spherical particles spanning 4.05 to 6.9 nanometers, averaging 5.6 nanometers, well dispersed without large aggregates. Energy-dispersive X-ray spectroscopy found a carbon- and oxygen-dominated composition with no intentional metal doping, and nitrogen physisorption measured a spacious BET surface area of about 232 square meters per gram for the functionalized dots, with a predominantly mesoporous texture.

Then came the biology. Against a panel of four bacterial pathogens, CQDs-F showed a striking selectivity for Gram-negative Escherichia coli. At the highest tested concentration of 1000 micrograms per milliliter, the nanoparticles produced an inhibition zone of 23.33 millimeters against E. coli—roughly four times the effect seen against the Gram-positive strains Staphylococcus aureus and Bacillus subtilis and the Gram-negative opportunist Pseudomonas aeruginosa. The minimum inhibitory concentration told the same story: 62.5 micrograms per milliliter for E. coli versus 125 for the other three organisms. Critically, the minimum bactericidal concentrations—125 micrograms per milliliter for E. coli, 250 for S. aureus and B. subtilis, and 500 for P. aeruginosa—yielded MBC-to-MIC ratios between 2 and 4, all within the accepted bactericidal threshold, meaning the dots do not merely stall bacterial growth but actually kill the cells.

Why would a sugar-derived carbon dot wrapped in fennel phytochemicals be such an effective antibacterial agent? The authors point to a two-pronged mechanism. Carbon quantum dots are known to disrupt bacterial membrane permeability and integrity, and their heteroatom content promotes the generation of reactive oxygen species that damage microbial cells. Layered on top of that is the chemical firepower of the fennel-derived surface molecules, which can interact directly with microbial membranes and modulate oxidative stress. The pronounced susceptibility of E. coli, with its outer membrane architecture, suggests the phytochemical-functionalized surface may interact particularly well with Gram-negative cell envelopes, although the precise molecular basis remains a question for future work.

The antioxidant results were equally impressive. In the standard DPPH assay, which tracks the fading of a deep violet free radical as it is quenched, CQDs-F achieved an IC50 of just 12.75 micrograms per milliliter—meaning that tiny amounts of the material neutralized half of the radicals present. Ascorbic acid, the vitamin C benchmark, was still stronger at 2.993 micrograms per milliliter, but the nanoparticles dramatically outperformed many previously reported carbon dots, such as those derived from pineapple waste or citrus peels, which required hundreds of times higher concentrations. The team attributes this potency to the synergistic radical-scavenging effects of the hydroxyl-rich polyphenols tethered to the nanoparticle surface, whose electron- and hydrogen-donating capacity is amplified by the oxygen-containing functional groups of the carbon core.

Perhaps the most medically significant findings came from the cell culture experiments. On Vero cells—normal African green monkey kidney cells used as a standard toxicity yardstick—CQDs-F was essentially harmless below 250 micrograms per milliliter, with measurable toxicity only appearing at 500 micrograms per milliliter and climbing steeply beyond that. But on human cancer cells the story was different. The dots showed an IC50 of 160.2 micrograms per milliliter against Caco-2 colon carcinoma cells and, most strikingly, 134.8 micrograms per milliliter against MCF-7 breast cancer cells. The resulting selectivity index of 3.56 for MCF-7 means the nanoparticles are preferentially toxic to the cancer cells relative to normal ones—a property the authors attribute to differences in cellular metabolism, membrane permeability, nanoparticle uptake, and sensitivity to oxidative stress between malignant and healthy cells. For a material made from table sugar and a spice, that is a remarkable therapeutic profile, even at this preliminary in vitro stage.

The context makes these results more than a curiosity. Antimicrobial resistance is one of the most pressing threats in modern medicine, and carbon quantum dots have attracted attention as low-toxicity alternatives or complements to conventional antibiotics, capable of breaking down biofilms and, in some studies, showing activity against drug-resistant pathogens without triggering detectable bacterial resistance. On the cancer front, carbon dots are being explored as drug-delivery vehicles, imaging agents, and even standalone therapeutics, with previous studies showing that functionalization—whether with glutathione, curcumin, doxorubicin, or plant metabolites—consistently enhances their therapeutic reach. This study adds fennel phytochemicals to that growing toolbox, and uniquely ties the biological activity to a fully mapped phytochemical inventory verified by dual-mode mass spectrometry.

The authors are careful to frame this as a preliminary study, and the caveats matter: the cytotoxicity work was done on cell lines in dishes, not in living organisms, and scaling a mortar-and-crucible synthesis to industrial volumes will require optimization of yield and reproducibility. Still, the synthesis itself is a persuasive argument for the green chemistry approach. It used inexpensive, renewable precursors, mild conditions, no hazardous reducing agents, and no elaborate instrumentation—the kind of process that could, in principle, be replicated almost anywhere. If subsequent in vivo studies validate the safety and efficacy suggested here, the idea that tomorrow’s antibacterial coatings, antioxidant supplements, or even cancer-targeted nanomedicines might begin life as caramelized sugar dusted with fennel extract will seem less like science fiction and more like the sensible future of sustainable nanotechnology.

Subject of Research: Green synthesis of fennel extract-functionalized carbon quantum dots and their antibacterial, antioxidant, and anticancer activities

Article Title: UPLC-MS analysis and green synthesis of fennel extract-carbon quantum dots: an assessment of antibacterial, anticancer, and antioxidant potentials

Article References: Abdelwahab, M. S., Al-Harby, N. F., El Batouti, M., & Metwally, R. A. (2026). UPLC-MS analysis and green synthesis of fennel extract-carbon quantum dots: an assessment of antibacterial, anticancer, and antioxidant potentials. Journal of Saudi Chemical Society, 30(4), Article 45. https://doi.org/10.1007/s44442-026-00096-4

Image Credits: AI Generated

DOI: 10.1007/s44442-026-00096-4

Keywords: carbon quantum dots, fennel, green synthesis, antibacterial, antioxidant, anticancer, UPLC-MS, nanotechnology, phytochemicals, E. coli, MCF-7, sucrose pyrolysis