Ultrasound-Enhanced Ionotropic Gelation of Pectin for Lemon Essential Oil Encapsulation: Morphological Characterization and Application in Fresh-Cut Apple Preservation

The global demand for natural bioactive compounds has increased interest in essential oils, particularly for applications in the food and nutraceutical industries. However, their volatility, instability, and susceptibility to environmental factors pose significant challenges for formulation and storage. This study focused on the extraction and characterization of essential oil from Citrus limon (Eureka variety), followed by evaluation of its antioxidant and antifungal activities and encapsulation via ionotropic gelation. The oil, obtained through hydrodistillation of lemon peel, yielded 3.85% and was rich in limonene (56.18%), β-pinene (9.89%), γ-terpinene (9.75%), and other monoterpenes. Antioxidant assays (DPPH, ABTS, FRAP, phenanthroline, and SNP) demonstrated moderate to strong radical scavenging capacities. Antifungal activity was also con-firmed against Aspergillus niger, Botrytis sp., Fusarium oxysporum, and Penicillium sp., with the highest in-hibition rates observed at 0.3% concentration. To enhance oil stability, ultrasound-assisted pretreatment of pectin was applied before encapsulation via calcium ionotropic gelation. Scanning Electron Microscopy (SEM) revealed improved morphology and homogeneity of capsules treated with ultrasound. Encapsula-tion efficiency reached up to 82.3% at 0.5% oil concentration. To demonstrate food application potential, the encapsulated oil was applied to fresh-cut apples. Results showed a significant reduction in browning, microbial growth, and water loss, along with enhanced firmness during storage. These findings support the use of ultrasonic-assisted pectin encapsulation as an effective method for enhancing essential oil delivery systems in food preservation and pharmaceutical applications.