Edible coatings inhibit plum rot and help preserve quality during cold storage

Plum preservation has a new avenue of research aimed at reducing post-harvest deterioration. A team from the Valencian Institute of Agricultural Research (IVIA) with the participation of the National University of Mar del Plata and CONICET (Argentina) has developed edible coatings containing antifungal compounds. These coatings reduced brown rot in trials and helped preserve fruit quality during cold storage.

The study, published in the journal *Foods*, highlights the potential of a geraniol-based formulation due to its combined effectiveness against the disease and weight loss. The research addresses an issue of particular interest to fruit and vegetable packing houses: limiting losses during storage without compromising the characteristics valued by consumers.

Brown rot caused in this study by the fungus Monilinia fructicola is one of the primary post-harvest diseases affecting stone fruit. Infections can begin in the orchard and remain latent until conditions favorable for development arise.

The researchers created coatings based on hydroxypropyl methylcellulose (a cellulose derivative) and lipid components, incorporating substances with antifungal activity. Following an initial screening, they evaluated formulations containing geraniol, as well as lemongrass and myrrh essential oils, on ‘Angeleno’ plums. The fruit was stored for up to six weeks at 1°C and 90% relative humidity, followed by four days at 20°C to simulate shelf life.

These formulations serve a dual purpose: on one hand, they create a semi-permeable barrier to gases and water vapor that slows the fruit's respiration and dehydration; on the other, they progressively release the active ingredients needed to inhibit spore germination and the pathogen's mycelial growth.

Antifungal efficacy and decay reduction during cold storage

The most notable results regarding incidence were observed after three weeks of refrigeration. Coatings containing geraniol and myrrh reduced the proportion of affected fruit by 45% and 70%, respectively, compared to the uncoated control. The tests were conducted on fruit artificially inoculated with the pathogen and treated 24 hours later, allowing for the evaluation of their effect on infections that had already begun.

At the end of the six-week cold storage period and an additional four days at 20°C, the antifungal coatings reduced lesion diameter by 35% to 50%. This result reflects a reduction in the extent of decay, although it does not equate to eliminating the disease or reducing the number of affected fruits by the same percentage.

The study also examined quality in a separate batch of non-inoculated plums. The geraniol formulation reduced weight loss by the end of the trial, while several coatings helped maintain firmness. Additionally, the coated fruit exhibited greater gloss.

Sensory evaluation by ten semi-trained panelists detected no negative effects on flavor attributable to the treatments, nor the emergence of off-flavors. No significant differences in soluble solids content were observed during storage either.

The authors identify the formulation containing 2 grams of geraniol per kilogram of coating as the most promising option among those studied. Commercial application requires further optimization of the formulations and expanded testing across other stone fruit varieties and species. These results thus pave the way for developing postharvest treatments that combine decay control with the maintenance of commercial quality.

A sustainable alternative for zero-waste programs

Implementing coatings formulated with food-grade matrices and plant-waste extracts facilitates the transition of packinghouses toward non-polluting, integrated management systems. By replacing or complementing conventional synthetic fungicides, this technology enables compliance with international food safety regulations and meets the demands of markets that prioritize fruit free from synthetic residues.

Sources:

Alvarez, M. V., Palou, L., Taberner, V., & Pérez-Gago, M. B. (2025).

Natural volatile compounds as antifungal agents against *Monilinia fructicola* in vitro and in composite edible coatings for sustainable disease reduction and fruit quality preservation during prolonged cold storage of fresh Japanese plums. Foods, 14(23), Article 4088.

https://doi.org/10.3390/foods14234088

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