Study On Preservation Of Tropical Fruit By Using Chitosan And 1-Methylcyclopropene Treatment

Tropical fruits are easily loss their commercial values due to the fruits easily infected by phytopathogens, and their higher respiration rate,weight loss and colour loss. In order to select effective methods for reducing disease incidences and extending storage life, this study was carried out to investigate the antifungal activity of chitosan, pre-harvest inducement, and the treatment with the combination of 1-MCP and chitosan coating application to tropical fruits preservation, such as ber, avocado and sapodilla.Effects of chitosan on radial growth of fifteen phytopathogenic fungal from infected tropical fruits was investigated in vitro. The inhibitory action to fungal of chtosan oligomer was much stronger than chitosan, and their antifungal activities were increased as the chitosan concentration increased. Chitosan oligomer concentration exceeded at 5.0mg/ml inhibited the growth of pathogens, while chitosan at concentration exceeded 10.0mg/ml. The inhibitory ability decreased after the isolates were successively stimulated 10-40 times using chitosan oligomer and chitosan, indicating that the tested pathogens had some resistance. Chitosan induced morphological changes, including hyphal swelling, shortening of hypal segments in Botryodiplodia theobromae Pat. and Alternaria alternata pathogens using light microscope observation. Chitosan influenced greatly the relative permeability of B. theobromae Pat. and A. alternata, respectively. The mechanism of the antimicrobial activity is related to the changes in cell permeability due to interactions between the polycationic chitosan and the electronegative charges on the cell furfaces. This interaction leads to the leakage of intracellular electrolytes.In order to increase resistibility of harvested ber fruit to phytopathogens and reduce disease incidences, twice spraying 4mg/l of chitosan treated the developing ber fruit. The results showed that the developing ber fruit was induced an increasement in lignin and total phenolic content, POD, PPO, PAL, chitinase andβ-1,3-glucanase activities. The decay incidence of the sprayed-harvested ber fruit inoculated with Colletotrichum gloeosporioides decreased by 20% compared with control after 9d storage at 25℃.In order to improve preservative effects of chitosan, the introduction of gelatinized cassava starch and gelatin resulted chitosan-based blend film lower vapor permeability,good mechanical and improved gas barrier properties. An positive effect of chitosan-based coatings was observed. Coating treatment with chitosan-based could delay and reduce CO2 and...