Studies On Softening And Decay Disease And Precautionary Methods In Storage Of Dong Jujube Fruit

Dong jujube fruit is favorable for its particular flavor, deliciousqualities and high economy value. However, it is liable to suffer mechanicaldamnification and microbial approaching because of its thin pericarp, crisp pulp andhigh containing water. These factors result in blet and metamorphosis of Dong jujubefruit. In order to study the infected pathogen and select some effective methods for itsprevention, we used the Zizyphus Jujuba Mill cv. Dong jujube grown in ShandongProvince as our study material. The pathogen which resulted in decay at roomtemperature and in the poststorage at low temperature was identified and colonygrowth and sporulation of the pathogen were controlled by different treatments. Thebest treatment was educed by trend surface analysis. The effects of differenttreatments on storage quality and physiological metabolism of Dong jujube fruit werestudied. Lastly, appropriate technical parameters for prevention of Dong jujube fruitdisease were acquired. The conclusions were turned out as follows:1. Main pathogenic fungi are Alternaria Nees ex wallr by identifying.Thepathogen could be restrained but not be terminated at -2℃. The pathogen is thepathogenic fungal which lead to decay of Dong jujube fruit in low temperaturestorage. The pathogen could grow and sporulate in the condition of neutral, weak acidand alkalescence. However, its tolerance is better in alkalinity condition than in acidcondition.2. The inhibitory action of chitosan on sporulation of the pathogen is conspicuous.There is also a positive correlation between log inhibition of growth and log chitosanconcentration (R=0.9921) when chitosan concentration is 0.5～2.0mg/ml. Ozone couldinhibit propagation of the spore. The effect of sterilization by 300μg/L ozone on thepathogen is obvious. However, the bactericidal effect is the same as that of 300μg/Lozone when the concentration of ozone is higher than 300μg/L. Hypobaric could resistreproduction of mold spores, the lower the pressure is, the more prominent the effectis. The inhibiting effect is optimal when the pressure drops to 40KPa.3. The orthogonal experiment based on single factor of chitosan and ozone restraining growth of the pathogen and trend analyzes were proceeded. A enlargeexperiment was done in condition of excellent results. The experimenting outcome isnear to its theories. Accordingly, the best combination for repressing sporulation of thepathogen is ozone concentration 323μg/L, chitosan concentration 1.25mg/ml.4. The treatment of chitosan and ozone sterilization on depressing rotten rate andrepressing patulous speed of the disease spot surpasses two of handles alone, but theeffect of two of combination for derepressing patulous speed of the disease spot is thesame. However, the treatment of 0.75mg/ml chitosan and 323μg/L ozone for loweringrotten rate of Dong jujube fruit surpasses the treatment of 1.25mg/ml chitosan and323μg/L ozone.5. The treatment of 0.75mg/ml chitosan and 323μg/L ozone has prominent effecton fresh-keeping of Dong jujube fruit. The freshness index of the fruit is up to 95.2%after 125 days.6. The treatment of 0.75mg/ml chitosan and 323μg/L ozone could inhibit theincreasing of soluble solids and reducing sugar during initial stages and staveascending during anaphase and inhibit the decreasing of TS and V_C during storage. Soit could keep good quality of Dong jujube fruit under room temperature and lowtemperature.7. The treatment of 0.75mg/ml chitosan and 323μg/L ozone could reducerespiratory intensity and relative conductivity of Dong jujube fruit. Accordingly, itcould delay effectively the consenescence of Dong jujube fruit at low temperature.8. The treatment of 0.75mg/ml chitosan and 323μg/L ozone could restrainremarkably the degression of phenols contents, activate rapidly the activation ofprotective enzyme system POD, furthermore the high level activation could maintainlonger time, restrain decreasing of PAL activity during initial stages and staveascending during anaphase and inhibit PPO activity. Accordingly, it could improvethe disease resistance ability of Dong jujube fruit.