Essential Oil-Enriched Chitosan Coatings for Postharvest Preservation of Citrus Fruits: A Review

Citrus fruits are among the most economically important horticultural commodities worldwide, yet postharvest losses remain a critical challenge, particularly in developing countries where losses can reach 30-40%. Conventional postharvest management using synthetic fungicides raises significant environmental and health concerns, driving research toward biodegradable alternatives. Chitosan-based edible coatings, enriched with plant essential oils (EOs), have emerged as a promising eco-friendly strategy for extending the shelf life and maintaining the quality of citrus fruits during storage. This review comprehensively examines the current state of knowledge on chitosan-EO composite coatings for citrus preservation, covering the physicochemical properties of chitosan as a coating matrix, the antimicrobial and antioxidant mechanisms of key essential oils (thyme, lemongrass, oregano, cinnamon, and citrus-derived EOs), their effects on postharvest quality parameters (weight loss, firmness, pH, titratable acidity, total soluble solids, total phenolic content (TPC), and antioxidant activity), and their efficacy against major citrus pathogens including Penicillium digitatum and Penicillium italicum. The review also discusses the challenges of EO incorporation into chitosan matrices, including film disruption at suboptimal concentrations, volatile loss during storage, and potential sensory impacts. Emerging technologies such as nanoemulsion-based delivery systems, microencapsulation, and combination treatments with modified atmosphere packaging (MAP) are highlighted as future directions. The evidence strongly supports chitosan-EO coatings as viable, GRAS-compliant alternatives to synthetic postharvest treatments for sustainable citrus preservation.