Optimization of nanochitosan coating and modified atmosphere packaging for bacterial load control and quality preservation of strawberry during postharvest storage

Microbial spoilage and quality deterioration are major challenges limiting the postharvest life of fresh strawberries. This study evaluated the combined effects of nanochitosan edible coating and modified atmosphere packaging (MAP) on aerobic bacterial load and quality preservation of strawberries during storage. A face-centered central composite design based on response surface methodology was applied to investigate the effects of CO₂ concentration (0–70%), nanochitosan concentration (0–2%), and storage duration (0–10 days) on total aerobic mesophilic bacterial counts (TAMB), antioxidant activity, vitamin C, total phenolic content, and anthocyanin retention. The developed quadratic models exhibited high predictive accuracy for all measured responses (R² ≥ 0.975). The combined nanochitosan-MAP treatment significantly reduced TAMB and delayed quality deterioration compared with individual treatments, indicating a potential complementary preservation effect. Multi-response optimization identified 54.6% CO₂, 2.0% nanochitosan, and 6.1 days of storage as the optimal conditions for the measured microbial and quality responses. These findings suggest that the integration of nanochitosan coating and MAP may provide a promising approach for postharvest preservation of fresh strawberries and a predictive framework for optimizing preservation conditions.