Chitosan-coated nanoemulsions loaded with lemongrass essential oil: formulation and process optimization for postharvest quality retention and shelf-life extension of papaya

Abstract

Papaya fruits are highly susceptible to rapid postharvest deterioration, leading to substantial economic losses. This study aimed to develop an optimized chitosan-coated nanoemulsion (CC-NE) based functionalized coating by integrating bioactive lemongrass essential oils (LGEOs) into biopolymeric carriers to provide controlled release properties for extending the shelf-life of papaya. The effects of chitosan (0.5–1.5%), gum arabic (1–3%) and dispersed oil phase (0.01–0.15%) concentrations on the particle size, zeta potential, polydispersity index, and antifungal activity against Lasiodiplodia theobromae and Rhizopus stolonifer were evaluated by employing a Box–Behnken response surface methodology. The optimized formulation (0.5% chitosan, 2.5% gum arabic and 0.07% dispersed oil phase) produced a stable nanoemulsion with high encapsulation efficiency (87.4%) and excellent thermodynamic stability. The morphological analysis revealed spherical droplets with a uniform core–shell structure, indicating successful encapsulation of LGEO with the stabilized chitosan matrix. Further characterization revealed low viscosity, reduced turbidity and enhanced whiteness index properties, suggesting superior visual and functional properties. The shelf-life studies demonstrated that CC-NE coated papayas exhibited significantly lower weight loss (23.9%), delayed firmness reduction, slower peel colour changes, and controlled biochemical changes compared to the untreated control and fungicide-treated control groups. Moreover, the sensory evaluation confirmed superior colour, texture, aroma, and overall acceptability of the CC-NE treated fruits after 14 days of ambient storage. The findings ensure the CC-NE as a safe and effective alternative to synthetic fungicides, with strong potential for application in sustainable fruit coating and storage systems.