| Nowdays, plastic made from polyethylene or PVC is widely used in various industries beause of its cheapness, stability, and convenience. However, because plastic could not be naturally degradated, waste plastic that was discarded and accumulated in environment was likely to cause white pollution. Until now, countermeasures to this problem were recycling, incineration, and using microbial degradable plastic combining with compost. Unfortunately, it's quite difficult to recycle watse plastic under current economic condition, and incineration would bring about second pollution. The concept of using microbial degradable plastic combining with compost seems to be good on the surface, but practice showed that it would take a long time for even paper ware and microbial degradable plastic to be completely decomposed, and the speed of degradation was largely depended on environmental condition. Moreover, because discardable packaging material and the field membrane are usually required to supply with large quantity and low price, microbial degradable plastic is too expensive to be accepted by market. Therefore, seeking for a wholenew type of material possessed the excellent properties of both conventional plastic and microbial degradable material becomes the most feasible solution. So biodegadable natural macromolecule, which is also a hotspot of this domain, turns out to be the best choice.Konjac Glucomannan is a type of natural macromolecule material with fine membrane characteristic, but it's poorly anti-microbial and highly hydrophilic. To imporove membrane and anti-microbe character of KGM, various experiments were conducted in this study by means of physical modification and addition of different additives, inhibitiors, and biologic inhibitors. Then it was applied on longan fruit storage.Considering the normal physiochemical condition of fruit or vegetable must be guaranteed, fruit-vegetable storage should reduce the function of metabolism and postpone the life cycle. After plastering composit membrane on the surface, microenvironment of low O2 and high CO2 concentration, which was semi-atmosphere controlled storage, was formed on longan pericarp exterior. In addition, with stabilization function of emulsification, the sucrose fatty ester could disperse with steady uniformity into the liquor, enhance water barrier and reduce the rate of water evaporation as well as reduce the rate of weightlessness. Compared to regular storage material, composite anti-microbe KGM membrane significantly lowered the concentration of PPO and POD in longan fruit, kept greater SOD activities, postoned the increase of MDA content, reduced the respiratory intensity of fruit and decomposition of pericarp pigment, maintian the total soluble solids.tiratable acid and vitamin c content, decreased the rate of fruit decay , thereby the storage life of fruit was prolonged . However, the restraining effect on respiratory intensity of fruit was not envident.As a kind of plant growth regulators, 2,4-D could strengthen the normal physiochemical metabolism activity of plants, and also improve the ability to resist plant diseases or pests. Cheliform thiourea could react to copper, and PPO contains copper enzyme. So with Thiourea chelated with PPO, activity of PPO could be restrained. Base on the former treatment, Thiourea (1.5%) and 2,4-D (0.02%) significantly displayed effects on freshness preseveration on longan, considerably reduced the activities and delayed the rise of PPO and POD in longan pericarp, kept greater SOD activities, postponed the increase of MDA, decreased the rate of fruit decay, postponed caducity, and storage life of fruit was improved.With the base of degradable pathogens inhibiter composit film material is considered, 2.5%thiourea and 0.05% 2,4-D for biology inhibitors to improve the film material properties is suggested. 0.2%Chitosan is suggested too, and then increased KGM degree.Because fruit or vegetables are still alive after pakcaging, the WVP of membrane must be accord with the special physical dem... |
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