Nano packaging with carbon quantum dots and essential oil nanocapsules prolongs shelf life of fresh cut Kale

Postharvest handling of fresh-cut leafy vegetables such as kale poses significant challenges due to rapid spoilage and nutrient degradation. This study explores the effectiveness of two nano-packaging strategies, carbon quantum dot (CQD) coatings and essential oil-based nano-capsules (EO-NCs), in preserving the quality and extending the shelf life of fresh-cut kale up to 40 days of refrigerated storage. CQD-treated samples demonstrated superior performance, exhibiting the lowest weight loss (5.50 g) compared to EO-NC treatments (11.92 g for Thymus daenensis Celak, 12.49 g for Bunium persicum) and the control (27.29 g). CQDs also retained higher levels of chlorophyll (12.61 mg g⁻¹ FW) and ascorbic acid (50.33 mg g⁻¹ FW), surpassing both EO-NC-treated and control samples. Microbial counts were significantly lower in CQD fresh-cut kale (130 CFU/ml), affirming its potent antimicrobial effect compared to EO-NCs and the untreated group (946 CFU/ml). CQDs effectively inhibited oxidative enzymes such as catalase (0.81 U/mg g FW) and polyphenol oxidase (0.79 U/g FW), contributing to reduced browning and spoilage. Antioxidant metrics, including total phenolic content (251.97 µg/ml) and DPPH radical scavenging activity (39.64%), were also enhanced with CQD treatment, highlighting its role in maintaining nutritional quality. While EO-NCs particularly those based on T. daenensis provided moderate preservation benefits, CQDs consistently outperformed them across all parameters. These findings underscore the potential of CQD-based nano-packaging as a promising strategy for enhancing food preservation, reducing waste, and supporting sustainability. Further studies are needed to evaluate commercial scalability, safety, and cost-effectiveness.