Chitosan–carnauba wax composite edible coatings for shelf-life extension and quality preservation of guava (Psidium guajava L.) during cold storage

Guava is a nutrient-rich climacteric fruit that is highly perishable during storage. This study investigated the effect of an edible composite coating comprising chitosan and carnauba wax, plasticized with glycerol and emulsified with Tween 80 on the postharvest quality of guava. Coated fruits were evaluated for weight loss, color, firmness, decay percentage, titratable acidity, total soluble solids, ascorbic acid content, antioxidant activity, and total phenolic content at 0, 7, 14, and 21 days of storage. Results showed that fruits coated with a higher concentration of carnauba wax exhibited lower moisture loss and decay incidence, greater firmness retention, and better color preservation. Among the treatments, T3 (3% carnauba wax, 3% chitosan) showed the slowest decline in titratable acidity (0.85-0.75%) and ascorbic acid content (122.0-98.33 mg/100 g) over the 21-day storage period at 6 °C. The T3 also retained the highest radical scavenging activity (50.3%) and showed minimal reduction in thr total phenolic content (140.00-137.53 mg GAE/100 g). Sensory evaluation using a 9-point hedonic scale further confirmed that T3 achieved the highest overall acceptability among all treatments. These findings demonstrate that a composite edible coating of 3% carnauba wax and 3% chitosan effectively preserves the physicochemical properties, antioxidant potential, and sensory quality of guava stored at 6 °C, thereby extending its postharvest shelf life.