Complex coacervation with Lippia sidoides essential oil improves thymol encapsulation in chitosan-based antifungal coatings for Fuji apples.

This study investigated the development of chitosan (CH)-based active films incorporating free and encapsulated thymol-Lippia sidoides essential oil (EO) systems and their effectiveness in preserving Fuji apple quality during postharvest storage. Gelatin-gum arabic (P1) and CH-gum arabic (P2) microparticles were produced by complex coacervation using a formulation in which pure thymol was associated with L. sidoides EO to improve its dispersion and functional incorporation. Both encapsulation systems exhibited high efficiency, achieving 92.12% for P1 and 96.74% for P2. Films containing encapsulated systems displayed modified optical characteristics while maintaining barrier and mechanical properties comparable to pure CH films. In vitro antifungal assays demonstrated that films containing free thymol-EO systems and P2-based microparticles were the most effective in inhibiting mycelial growth and reducing the viability of Penicillium expansum spores. However, in coated apple storage tests, films containing free systems caused undesirable changes in fruit color, texture, and weight loss, with a total color difference (ΔE) of 14.53 after 14 days of storage, whereas encapsulated systems maintained ΔE values below 4.2. The CH/P2-2 formulation exhibited the best in vivo performance, reducing fungal counts by 2.7 log CFU g-1 compared with the control while preserving the physicochemical quality of Fuji apples. Overall, CH-films incorporating P2 microparticles showed the highest in vivo antifungal effectiveness combined with improved preservation of fruit quality, highlighting the potential of thymol-EO combined with encapsulation as a natural strategy for postharvest fungal control.