Enhancing post-harvest quality of tomato fruits with chitosan oligosaccharide-zinc oxide nanocomposites: A study on biocompatibility, quality improvement, and carotenoid enhancement

In this study, a new composite with combination of chitosan oligosaccharide (COS) and zinc oxide nanoparticles (ZnO NPs), termed Chitosan Oligosaccharide-Zinc Oxide Nanocomposites (COS-ZnO NC), was designed to enhance the quality of tomato fruits during postharvest storage. SEM analysis showed a uniform distribution of COS-ZnO NC films on tomato surfaces, indicating high biocompatibility, while the FTIR spectrum confirmed the interaction of COS and ZnO NPs via hydrogen bonds. The COS-ZnO NC exerts positive effects on post-harvest quality of tomato fruits, including significantly reduced water loss, fewer skin wrinkles, increased sugar-acid ratio, and enhanced vitamin C and carotenoids accumulation. Furthermore, COS-ZnO NC induces transcription of carotenoid biosynthesis genes and promotes carotenoids storage in the chromoplast. These results suggest that the COS-ZnO NC film can significantly improve the quality traits of tomato fruits, and therefore is potential in post-harvest storage of tomato fruits. Schematic illustration for preparation of COS-ZnO NC. The results indicate reduced water loss, increased sugar-to-acid ratio, and enhanced carotenoid accumulation in tomato fruits. [Display omitted] •Innovative COS-ZnO nanocomposites (COS-ZnO NC) improves tomato fruit quality.•Uniform COS-ZnO NC film reduces water loss of tomato fruits.•Sugar-acid ratio is improved by COS-ZnO NC treatment.•Increased carotenoid accumulation due to enhanced biosynthesis and plastid storage.