Optimization of ultrasound-assisted microemulsions of citral using biopolymers: characterization and antifungal activity

Citral is an essential oil with antimicrobial activity against a broad range of microorganisms. However, its low solubility and susceptibility to environmental conditions difficult the use of citral in the food industry. In this study, the formulation of an eco-friendly emulsion of citral obtained by ultrasound was optimized using a Box-Behnken design. The effect of arabic gum (AG), sodium alginate (SA), maltodextrin (MD), and their concentration on the droplet size of the emulsion was evaluated. Based on the droplet size (1 μm), the emulsion formulated using 7.5% of AG and 0.4% of SA was selected as optimal with viscosity 34.63 cP, pH 5.76, and conductivity 1.426 mS. This emulsion retains the 92% volatile fraction of citral and contributes to increase the thermal stability of the essential oil from 37 to 185 °C. Besides, it has antifungal properties against Fusarium sp., contributing to reduce in 66% of the disease incidence caused by this fungus in bananas. Therefore, the optimal emulsion formulated in this research can be used to control the postharvest decay in fruits. Moreover, it can be used to obtain microcapsules and microfibers that can be used as edible coatings in the food industry.