Study On Inducing Resistance Of Chitosan/Nano-SiO_x And Its Application

Signal molecules play important roles in maintaining many life activities of the plants. Using inducing technology by exogenous singaling molecules to improve leveles in organisms has become an important research focus at home and abroad. Research in the role of resistance to aging, disease and other defense mechanism of signaling molecules, it can provide some theoretical basis for improving the effect of preservation.Chitosan(CTS) which showed good film-forming effect and ideal anti-bacterium effect as well is a kind of macromolecule cationic polymes. At present, many studies has shown that as singaling molecule chitosan can inhibit the growth of pathogenic microorganism,stimulate enhance disease resistance and delay senescence of fruits and vegetables. Fruits after harvest and during storage were treated with chitosan can improve the activities of PAL,POD and inhibit the freeradical generation and reduce the occurrence of disease.Nano-Si Ox has good properties such as O2, CO2 and H2 O barrier properties, antibacterial, absorb ultraviolet, inducing the resistance response to pathogens of plant,especially the resistance to biotrophic and can undertake modification to macromolecular organic compounds.In the subject, nano-Si Ox was added to the chitosan solution for improving the performance of chitosan membrane, such as mechanical strength, antimicrobial, permeability.And then the inducing resistance mechanism, antibacterial activity and property of chitosan/nano-Si Ox composite coating are investigated in details.And applied to fresh-keeping of Yanhong peach. Primary coverage and conclusions of this thesis are as follows: 1. Effect of chitosan/nano-Si Ox on superoxide anion production rate and relative enzymes of peach fruits:After receiving dipping treatment with composite chitosan/nano-Si Ox(CTSS) for 30 s, Yanhong peach fruits were stored under the condition of 27℃(±1℃). Results indicate that after 12 days,CTSS reduced the superoxide anion(O2-·) production rate and respiration rate. Compared to control peaches,superoxide dismutase(SOD), catalase(CAT),ascorbate peroxidase(APX) and ascorbate oxidase(AAO) of chitosan/nano-Si Ox treated peaches increase by 11.02%, 90.07%, 57.46%, 49.88%. These indicators appeared, in turn, 2.93%, 19.02%, 9.27%, 10.09% compared with the CTS group. Hence it can be concluded that chitosan/nano-Si Ox has the significant potential to preserve valuable attributes and prolong the shelf life postharvest Yanhong peach fruits. 2. Effects of composite chitosan/nano-Si Ox on browning and senescence of peach: The results showed: Polyphenol oxidase(PPO), and malondialdehyde(MDA) content of the fruits coating with chitosan/nano-Si Ox(CTSS) reduced by 11.92 % and 7.04%, at the same time, phenols compound increased by 9.09% respectively compared with coating with CTS. These indicators appeared, in turn, 24.26, 24.32%, 29.10% compared with the control group. Compared with control, PPO activity of Yanhong peach coated with CTSS were lower. Moreover, phenols compound were higher than control. 3. Antibacterical activity of composite chitosan/nano-Si Ox :To investigate the target of the antibacterial activities of chitosan/nano-Si Ox, E.coli and Yeast were selected as the tested bacteria. The results indecated that the UV absorption, relative electrical conductivity, and the activity of β-glycosidase in cell suspension increased at different degree. Chitosan/nano-Si Ox can opened the ion channel decreasedand changed the permeability of membranes. Resutts of SEM showed that chitosan/nano-Si Ox damaged the integrity of membrane which lead to the leakage of nuclear materical and death of the cell. 4. Attenuation Performance of Chitosan Nano-Si Ox Composite Membrane in Preservation: They were placed at 4 ℃,14 ℃,24 ℃,34 ℃ and 44 ℃,then were prepared by flow casting method. The p H value, the viscosity, the oxygen permeability(OP), carbon dioxide permeability(CP) and water permeability of the prepared CTSS/nano-Si Ox film were examined; The CTSS composite preservation agent was placed in the constant temperature of 25 ℃ and and the antibacterial properties of Penicillium,Yeast at different temperatures were examined.The results show that after 10 storage at 4 ℃,the decay index of strawberries was 24.3% lower than that of the Yanhong Peach coated with CTS. in comparison with the CTSS coating placed at 4 ℃,the OP 、 CP and WVP of CTSS coating which were placed at 44℃ were increased respectively13.02 mg·cm-2·d-1、27.54 mg·cm-2·d-1、25.56 mg·cm-2·d-1; the p H value and the viscosity increased,and the antibacterial properties of Penicillium,Yeast decreased.Permeability of preservative film to gas molecules was reduced,resulting in the attenuation of preservation properties of chitosan composite solution.