Carnauba wax coating enriched with natural extracts, a potential strategy for citrus fruits

This research analyzes the innovative development of carnauba wax coatings enriched with essential oils (EOs: lemon, orange, grapefruit, clove, oregano, and cinnamon) or fruit by-products (FBPs: avocado, tomato, carrot, orange, lemon, and grapefruit) to improve
postharvest preservation of organic oranges and lemons.

Six EOs and six FBPs were evaluated for total phenolic content (TPC) and in vitro antifungal activity against Penicillium digitatum. Based on results, grapefruit, oregano, and clove EOs were selected for lemons, while avocado, orange, and grapefruit FBPs were selected for oranges.

Antifungal performance

An in vivo test at 20 ◦C for 15 days with carnauba wax coatings assessed antifungal performance. Clove EO and avocado FBP showed strong in vitro inhibition and consistent hyphal suppression (~100 and ~82%, respectively). In vivo, coatings with grapefruit EO and avocado FBP significantly reduced fungal decay and sporulation (~75%) in lemons and oranges, respectively. 

Lesser weight losses

Coated fruits also retained weight losses by ~25% compared to uncoated ones.

Phenolic-rich compounds, a promising strategy

These findings suggest that phenolic-rich natural extracts, especially from agro-industrial residues like avocado peels, offer a promising and sustainable strategy for postharvest citrus disease control. Further studies should test coating effectiveness in large-scale trials
under refrigeration combined with other preservation strategies.

Picture shows part A of Figure 4 of the original paper - Figure 4. Decay (%) and sporulation (%) percentage of inoculated organic lemon and oranges with P. digitatum and coated with waxes enriched in EOs (A) and FBPs (B). 
CTRL: control unwaxed;
CTRL-W: control waxed; 
OR-EO: wax enriched in 0.5% oregano EO;
CL-EO: wax enriched in 0.5% clove EO;
GEO: wax enriched in 0.5% grapefruit EO;
A-BP: wax enriched in 5% avocado FBP; O-BP: wax enriched in 5% orange FBP;
G-BP: wax enriched in 5% grapefruit FBP.
ns: no significant results compared to CTRL; *, **, and *** denotes significant results p < 0.05, p < 0.005, and p < 0.001, respectively, compared to CTRL. Bar charts of these data are shown in Figure S1.

Source

Carnauba Wax Coatings Enriched with Essential Oils or Fruit By-Products Reduce Decay and Preserve Postharvest Quality in Organic Citrus
Martínez-Zamora, L.; Zapata, R.; Cano-Lamadrid, M.; Artés-Hernández, F.
Foods 2025, 14, 2616.
https://doi.org/10.3390/foods14152616