Effect of Green-Synthesized CaO-Based Nanoparticle Coatings on Postharvest Quality and Bioactive Compounds of Strawberry Fruits During Cold Storage

Postharvest quality losses limit the storage life of strawberries, highlighting the need for environmentally friendly preservation approaches. In this study, CaO-Based nanoparticles were green-synthesized using hemp (Cannabis sativa L.) leaf extract as a reducing and stabilizing agent, characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX), and applied to Portola and Monterey strawberries at concentrations of 50, 100, 150, and 200 ppm. XRD analysis confirmed CaO as the main crystalline phase, with CaCO3 identified as a secondary crystalline phase, whereas the presence of metallic Ca could not be confirmed unambiguously. The fruit were stored at 1 ± 0.5 °C and approximately 90% relative humidity for 21 days. The effects of CaO-NP treatments varied according to cultivar, concentration, storage period, and the quality parameter evaluated. In Portola, the 100 ppm treatment resulted in the lowest weight loss, while the 50 ppm treatment maintained the highest firmness and total monomeric anthocyanin content at the end of storage. The 200 ppm treatment produced the lowest numerical decay rate, although it was statistically similar to the control and 100 ppm treatments. In Monterey, the 50 ppm treatment maintained the highest firmness and showed the lowest weight loss among the nanoparticle treatments; however, it did not reduce weight loss below the control and resulted in the highest decay rate. The 100, 150, and 200 ppm treatments maintained decay rates comparable to the control. The 150 ppm treatment maintained comparatively high soluble solids content in both cultivars, while the 200 ppm treatment resulted in the highest total phenolic content in Monterey. No sustained improvement in total antioxidant capacity was observed. Overall, no single CaO-NP concentration was consistently effective across all quality attributes or both cultivars, indicating that these coatings require cultivar- and quality-target-specific optimization.