Studies On Control Of Postharvest Diseases And Hypobaric Storage Of 'Dongzao' Jujube Fruit

This paper deals with three problems in postharvest storage of 'Dongzao'jujube (Zizyphus jujuba Mill.): (1) Studies on the tolerance of three primary bacterial pathogens (Pseudomonas sp., Xanthomonas sp. and Erwinia sp.) obtained from 'Dongzao'jujube to temperature and pH value; (2) Studies on the effects of different agents treatment on fruit diseases, storage quality and physiological metabolism of 'Dongzao'jujube during storage and shelf-life; (3) studies on the changes of quality and physiology of 'Dongzao'jujube in different low pressure conditions during hypobaric storage. According to the experiments, some conclusions were drawn as follow: The study on the tolerance of three bacterial pathogens to temperature showed that the tolerance of Pseudomonas sp. to low and high temperature was 0℃and 57.5 ℃, Xanthomonas sp.'s was -2℃and 55℃, Erwinia sp.'s was 0℃and 57.5℃respectively. The tolerance of the three pathogens to alkalescence were more resistant, Pseudomonas sp. could not growth until pH value was 10, Xanthomonas sp. and Erwinia sp. could still growth normally when pH value was 12; at the range of acidity, when pH value was 2~4, the growth of three pathogens were inhibited. 　The growth of the three bacterial pathogens treated by different concentrations of sodium silicate, sodium hypochlorite and fresh-keeping-reagent were investigated in vitro. The results showed that the diameter of no-colony of the three bacterial pathogens treated by different agents were longer than that of ck, that means all of the reagents could inhibit the three pathogens'growth in different degree. The higher the concentration of reagents, the better the inhibiting effects. In all reagents, 5000 mg·L-1 sodium hypochlorite was the best, followed by 3000 mg·L-1 sodium hypochlorite, 1/100 and 1/50 fresh-keeping-reagent, while 100 mg·L-1 sodium hypochlorite and 3% sodium silicate had no obvious inhibiting effect on the growth of the three bacterial pathogens. In the experiment of agents selection during shelf-life and storage in vivo, organic acid treatment was the best in all treatments, and among the acids, the treatments by 1000mg·L-1 malic acid and 2000mg·L-1 oxalic acid were the best which decreased the decay rate of jujube fruit obviously, maintain the fruit firmness, soluble sugar, vitamin C and protopectin content, and inhibited the increase of water-solublepectin content, PE and PG activity of the fruits. Thereby the senescence of 'Dongzao'fruits was delayed, and the decay was inhibited effectively during shelf-life and storage. Five different air pressures were used in hypobaric storage, which were 86.1Kpa, 70.9KPa, 55.7KPa, 40.5KPa, and 25.3KPa. Compared with ck, hypobaric treatment inhibited respiratory intensity of 'Dongzao'jujube fruits, decreased the hydrolyzation of non-water-soluble pectin. The treatment of 55.7Kpa could hold fruits firmness, organic acid content and vitamin C content, inhibited the development of red-changing of jujube fruit, decreased the weight loss, hold the appearance and postponed the senescence.