Effects Of Postharvest Heat Treatment And Ultrastructural Changes In The Cell Of Chinese Jujube Fruits During Ripening And Senescence

The effects of heat treatment on respiration rates, the rates of ethylene production, the contents of starch, water-soluble pection, propection, the activities of anylase, PG enzyme and the qualities of jujube variety "Li zao"(Zizyphus jujuba Mill) fruits were studied in this thesis. The physiological and biochemical mechanism of ripening and softening of jujube treated with heat treatment were also discussed. In addition to, the relationship between the structure and the physiological metabolism of jujube fruits during ripening and senescence was discussed. All above provided theoretical bases for improving techniques in jujube fruits storage.Half-red jujube fruit, Green-white jujube fruit and Whole-red jujube fruit were respectively treated 1 hour after 34C, 42C, 50C and 58C heat treatments. The results of study showed that "Li Zao" jujube was non-climacteric fruit, and had not significant peaks of respiration. Heat treatment could delay the hydrolysis of protein, Vc, Starch, Propectin, inhibited the activities relating to fruit softening such as amylase, PG enzyme. It also could improve storage of jujube. But it had no effects on total solublesolids and titri table acids in jujube. There were obvious effects for different ripening stage fruits in jujube. Half-red stage jujube remained highest content of Vc and storage was the best.The electron microscopy observation showed a series of ultrastructuralchanges in the cell wall structure, the subcellular structure and the intercellular structure of mesocarp cells of jujube fruits. These structural changes happened at different ripening stages and different cellular locations, apparently and regularly. There was a close relationship between the ultrastructural changes and the physiological metabolism, especially jujube fruits softening .There were some characters of the ultrastructural changes: During softening, cell contents decreased, middle lamella between cell wall degenerated adherent cells separated. But cell wall remained unchanged.