Studies On The Effects And Mechanisms Of Pressurized Argon And Its Combined Treatments On Fresh-keeping Of Fresh-cut Green Pepper And Cucumber

The tissue structure of fresh fruits and vegetables can be destroyed by the fresh-cut process which triggers the plant physiological reaction, leading to microbial growth and the deterioration of fresh-cut fruits and vegetables. It leads to the reduced shelf-life of fresh-cut fruits and vegetables. For extending the shelf life of fresh-cut fruits and vegetables, some treatments are neccessary. In this study, the effect of pressurized inert gases treatments, such as argon (Ar) and krypton (Kr), on physiological characteristics, quality parameters and microbial growth of fresh-cut green peppers&cucumbers was investigated. Moreover, the mathematical model was developed to evaluate the relation between the storage conditions and quality characteristics.In order to explore the effect of pressurized inert gases treatments on fresh-cut vegetables, the changes in respiration rate, ethylene production, browning, nutritional properties and physicochemical indexes were investigated. The results showed that pressurized argon treatments could inhibit respiratory metabolism, and the activities of peroxidase (POD), phenylalanine ammonialyase (PAL) and ascorbic acid oxydose (AAO) of fresh-cut green peppers treated with pressurized argon were lower than that of control samples. In addition, pressurized argon treatmentscould reduce the loss of VC, total phenols and beta-carotene. Furthermore, the antioxidant activities of fresh-cut green peppers treated with pressurized argon werehigher than that of control samples.In order to further explore the role and mechanism of pressurized argon treatments on preservation of fresh-cut vegetables, pressurized argon was used to treat fresh-cut cucumbers. The changes in water mobility, water loss, physiological metabolism and quality characteristics were investigated. The results showed that pressurized argon treatments were effective in reducing water mobility the loss of water. In addition, the respiratory metabolism of fresh-cut cucumbers was inhibited by pressurized argon treatments. Moreover, pressurized argon treatments maintained cell membrane integrity and delayed the senescence of fresh-cut cucumbers.In order to explore the effect of inert gas mixture treatments on fresh-cut vegetables, the effect of pressurized inert gas mixture (argon+krypton) on quality and physiological characteristics of fresh-cut green peppers during cold storage was investigated. The results showed that pressurized inert gas mixture of argon and krypton was effective in inhibiting respiration rate, ethylene production and the loss of water and firmness. In addition, it was found that the treatments of pressurized inert gas mixture could maintain the integrity of the cell membrane of fresh-cut green peppers, and reduce the production of malondialdehyde (MDA). Moreover, the treatments of pressurized inert gas mixture could reduce the loss of VC content and delay the incidence of browning of fresh-cut green peppers. By comparison, it was found that the effects of pressurized inert gas mixture treatments on fresh-cut green peppers were inferior to that of pressurized argon treatments, but superior to that pressurized krypton treatments.Based on quality deterioration and microbial growth characteristics of fresh-cut cucumbers, the effects of pressurized argon, nano-zinc oxide (ZnO) coating and their combination in maintaining the quality of fresh-cut cucumbers during storage were investigated. The results showed that pressurized argon treatments, nano-ZnO coating, especially mixed treatments were effective in inhibiting respiration rate and ethylene production of fresh-cut cucumbers. In addition, pressurized argon treatments, nano-ZnO coating and mixed treatments could inhibit the activity of peroxidase (POD) and polyphenol oxidase (PPO) of fresh-cut cucumbers. Furthermore, the combined treatments of pressurized argon and nano-ZnO coating were found to be more effective in reducing the population of Escherichia coli., Salmonella, molds and yeasts than other two treatments (pressurized argon, nano-ZnO coating), resulting in lower deterioration and higher edible security of fresh-cut cucumbers.In order to predict the quality of fresh-cut green peppers treated with pressurized argon, a multiple linear regression model and a nonlinear neural network model based on back propagation arithmetic were developed. The results showed that the three layers (4-5-4) BP neural network model has good predictive ability which was superior to that of multiple linear regression model. Based on the developed neural network model, the prediction of b value, VC content, water loss and firmness of fresh-cut green peppers was close to the measure values.