Chitosan and carboxymethyl chitosan nanocarriers enhance mango seed extract stability and antimicrobial activity to improve strawberry postharvest quality

Strawberries are highly perishable fruits due to moisture loss, intense metabolic activity, and microbial contamination, leading to rapid quality deterioration during storage. In this study, mango seed extract (MSE), a natural antioxidant source, was loaded with chitosan (CS) and carboxymethyl chitosan (CCS) nanoparticles to develop edible coatings for postharvest quality enhancement. Nanoparticles were characterized by dynamic light scattering (DLS) to determine particle size and zeta potential, revealing stable formulations with average sizes of 68.1 nm (CS LM) and 91.3 nm (CCS LM). Antioxidant capacity was assessed using ABTS and DPPH radical scavenging assays, where CCS LM exhibited superior activity (> 92%, p < 0.05) compared to free MSE and CS LM. Antimicrobial properties were evaluated by microbial inhibition tests against Staphylococcus aureus, Escherichia coli, and Candida albicans, showing significant inhibition rates at 800 µg/mL. Storage performance was assessed over 21 days at 2 °C by monitoring weight loss, firmness, color preservation, pH, titratable acidity, and microbial counts. Results demonstrated that CCS LM-coated strawberries had minimal weight loss (5.7%, p < 0.05), retained firmness, and showed reduced bacterial (1.2 log₁₀ CFU/g) and fungal counts (1.3 log₁₀ CFU/g) compared to uncoated fruits. These findings suggest that MSE-loaded CCS nanoparticles, through their antioxidant and antimicrobial functions, offer a promising sustainable strategy to improve the postharvest quality and storage performance of strawberries.