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