Research On The Fungicidal Mechanism Of Chlorine Dioxide And Its Effects On Preservation Of Fruits And Vegetables

Chlorine dioxide is a powerful oxidant, which can be used for the disinfection, sterilization, preservation and fresh-keeping of fruits and vegetables. Currently, it is internationally accepted as a disinfectant and food preservative with high level of performance and safety. Moreover, it does not produce any organic chloride and other harmful substances that may lead to carcinogenesis, teratogenesis and mutagenesis. Therefore, chlorine dioxide has many advantages over other disinfectants. However, the uncertainty of the germicidal mechanism of chlorine dioxide and the lack of technique of chlorine dioxide on fruit and vegetable storage have restricted its application in a more extensive field. The objective of this research was to investigate the fungicidal mechanism of chlorine dioxide by using S. cerevisiae and F. tricinctum spores as study objects. And the effects of chlorine dioxide treatment on storage quality of fruits and vegetables were also studied by using fresh-cut asparagus lettuce, mulberry fruit, plum fruit and chestnut kernel as study objects. This study would provide the theoretical foundation for the application of chlorine dioxide on fruits and vegetables.1. After the treatment by chlorine dioxide, changes in the fungal cells of S. cerevisiae and F. tricinctum spores were studied. And the correlation between these changes and the inactivation rates were then analyzed. Results showed that the genomic DNA was not the direct target of chlorine dioxide treatment on fungi. However, chlorine dioxide could damage cellular barrier function, which resulted in the ion leakages. The activities of key enzymes in some crucial metabolic processes were significantly inhibited. Moreover, the structures of cell wall, cell membrane and inner components were also destroyed by chlorine dioxide.2. The effects of chlorine dioxide treatment on the enzymatic browning and shelf-life of fresh-cut asparagus lettuce were studied. Results showed that the activities of polyphenol oxidase and peroxidase were inhibited by chlorine dioxide. Meanwhile, the process of degradation of color in the chlorine dioxide treated lettuce was also delayed. It was concluded that chlorine dioxide concentration and treatment time were two significant factors affecting chlorine dioxide treatment on enzymatic browning of fresh-cut asparagus lettuce. The treatment with 100 mg/L chlorine dioxide for 20 min could prolong its shelf-life for 10 d.3. The effects of aqueous chlorine dioxide treatment on the nutritional components and shelf-life of mulberry fruit were studied. Results showed that the chlorine dioxide treatment was effective in retention of flavonoid, ascorbic acid, reducing sugar, and titratable acid. Chlorine dioxide concentration and treatment time were two significant factors affecting chlorine dioxide treatment. The shelf-life of the samples treated by 60 mg/L chlorine dioxide for 15 min was extended for 6 d.4. The combined effects of aqueous chlorine dioxide and ultrasonic treatments on the postharvest storage quality of plum fruit were studied. Results showed that the combined treatments on maintaining the contents of total flavonoids, ascorbic acid, reducing sugars, and titratable acids were more beneficial than the individual treatments. The treatment with chlorine dioxide solution accompanied by simultaneous ultrasonic waves was more effective in reducing the initial microflora and retaining sensory qualities of plum fruit than applying them sequentially. The shelf-life of the simultaneously treated fruit could be extended for 25 d.5. The survival rate of D. gregaria and F. tricinctum spores inoculated onto chestnut kernel treated with chlorine dioxide were studied. And the models describing the survival curves were then established. The inactivation efficacy of chlorine dioxide treatment increased with chlorine dioxide concentration and treatment time. The Weibull model was the best model to describe the chlorine dioxide survival curves of D. gregaria, while the modified Gompertz model was most appropriate for fitting the survival curves of F. tricinctum.