| Fresh vegetable and fruit are rich in nutrition and can be eaten conveniently. But they are highly perishable in normal ambient conditions. And organophosphorus pesticides residual in vegetable and fruit will be a potential risk to consumers. So it is a concerned problem that how to prolong the vegetable and fruit's shelf-life and degrade the organophosphorus pesticides residual. Although rare earth elements(REE), especially cerium ion , have good activities on antibiotic capability and cleavage of phosphoester bonds , easily form a gel of metal hydroxide under neutral physiological condition, lose their activities and this character limits its application in food industry, agriculture and life science. Therefore, it's important to look for an appropriate conjugant for its further application in biology scope. Chitosan can be as supporting ligand to combine lanthanide and transition metal ions because of having many active groups such as amino and hydroxyl groups. So the complex (named SCC-Ce) made from chitosan and Ce(â…£) was prepared and used in vegetable and fruit's preservation and degradation of organophosphorus pesticides. Some satisfying results have been obtained which will be theoretic base for the further applications. This research refers to following aspects:1. SCC-Ce is straw yellow powder. It can't dissolve in organic solvents. but prone to dissolving in acetic acid, citric acid, formic acid, oxalic acid and can dissolve in perchloric acid, hydrochloric acid and sulfuric acid. The results of ultraviolet spectra, infrared spectra, DSC, element analysis and X-ray diffraction show that a new complex is synthesized and Ce(â…£) reacted with the amino groups and hydroxyl groups of chitosan.2. Cucumbers were coated by SCC-Ce film and storage at room temperature. The sensory evaluation, the rate of weight loss, firmness, the content of chlorophyll and Vc, the activity of POD and PPO and the degradation of chlorpyrifos were measured. The results show that SCC-Ce could prolong the cucumber's shelf-life and degrade chlorpyrifos effectively. The SCC-Ce which contents 1% chitosan and 0.06% cerium ammonium nitrate has the best effect of degradation. The degraded rate could be above 73% after 12 days storage, 53% higher than control.3. SCC-Ce film was applied to preserve grapes. The results show that the quality of grapes that treated with SCC-Ce is better than that of no treated or treated with chitosan, and the storage time is relatively longer. That is say, SCC-Ce can be more beneficial in extending postharvest life and maintaining quality and, to some extent, controlling decay of grapes. SCC-Ce is also contributed to the degradation of omethoate. The degraded rate is 98.57% after 12 days, 25.8% higher than control.4. The degraded rates of organophosphorus pesticides by SCC-Ce, water and several detergents were determined. The results show that the degraded rates of chlorpyrifos on cucumber and tomato by SCC-Ce are notable higher than control, and evident higher than other detergents. And the qualities of cucumber and tomato are better than other treated.5. The degraded effects of dichlorvos, omethoate, dimethoate, chlorpyrifos in vitro by SCC-Ce were discussed. The results show that the degraded rate of every organophosphorus pesticide is increased when SCC-Ce formed. But the effects of degradation are varied because of the different molecule structures of organophosphorus pesticides.6. Gas chromatography-mass spectrometry (GC-MS) and Ion chromatography were used to analyse the degradation products of parathion by SCC-Ce. The chromatograms show that the intermediate product of parathion is aminoparathion and the toxicity is disappeared. As the prolong of reactive time, aminoparathion will be degraded to CO2,H2O and some inorganic negative ions at last. It is suggested that SCC-Ce acts a role of reducase in the beginning of reaction and then acts a role of phosphoester enzyme.SCC-Ce is mainly composed of chitosan and Ce(â…£). Chitosan is the safe material which is allowed to add in food, so it will not damage the health of customers. Ce(â…£) will not arouse the disadvantageous residual and the pollution of environment because of the trace content. The cost of SCC-Ce is low and the operation is simple, so, it is believed that SCC-Ce has better applied perspective in preservation of vegetable and fruit and degradation of organophosphorus pesticides.
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