Preparation of chitosan-based coating enriched with zinc oxide nanoparticles for inhibiting Alternaria alternata on tomato fruits

Fresh tomatoes have a short shelf life of 4-8 days due to dehydration, aging and microbial infection, resulting in serious decay and waste. In this study, an edible chitosan (CS)-based coating was prepared by incorporating nano zinc oxide (nano-ZnO) biosynthesized using Cinnamomum camphora (L.) leaf extract, known for their antimicrobial and antioxidant properties. Structural characterization revealed that hydrogen bonding formed between CS and nano-ZnO significantly enhanced the mechanical and barrier properties of the composite film, especially 40 mg<middle dot>L- 1 nano-ZnO (CTS-40). Compared with pure chitosan, CTS-40 exhibited a 1.61- and 14.46-fold increase in tensile strength and elongation at break, respectively. Meanwhile, water vapor transmittance, light transmittance, and water solubility decreased by 25.98%, 8.35%, and 29.47%, respectively. Furthermore, in vitro test showed the CTS-40 film inhibited the mycelial growth of Alternaria alternata by 99.02%. After 7 days of storage, CTS-40-coated tomatoes exhibited significantly reduced disease incidence and lesion diameter accompanied by increased the activities of antioxidant enzymes and accumulation of total phenols, flavonoids and anthocyanins. Overall, nano-ZnO/chitosan coating film can serve as a promising, efficient, environmentally friendly and easy to operate alternative to pesticides for the preservation of tomatoes and other fresh fruits.