Study On Fresh-keeping Technology And Change Of Postharvest Physiology Of Dong Jujube

Abstract: The fruit of Dong jujube is favorable for its wonderful fresh edible quality — thin pericarp,crisp pulp and toothsome sapor. It riches in not only vitamin C (about 300-500mg per 100g) , soluble solid substance (34-36%) , mineral and trace elements, but also cAMP and cGMP ,which were provided with various functions of physiological adjustment, such as preventing blood vessel from increasing frangibility, inhibiting artery from congelative sclerosis piece by piece, and certain effect of anticancer.In recent years, the supply of Dong jujube fell short of the demand in domestic and foreign markets,its return is several,or 10 times more than that of the other crops. For the inherent property of the fruit in biology , physiology, tissue configuration and postharvest physiological change, the storage period of Dong jujube is 4-5 days at routine temperature,50-60 days in cold storage. The rate of fine fruits is so small that it is difficult to commercialize it. The fresh-keeping technology of Dong jujube has being studied during recent years.but the technical parameters that obtained differ greatly from each other,and are not applicable to practice so far. Scholars had maken little progress on postharvest physiology of Dong jujube.The fruit of Dong jujube tends to softening, going moldy and decaying during storage period,so it is groundwork of fresh-keeping of the fruit to reveal hypostasis of the above phenomena. In the article,first of all,the indexes of physiology and biochemistry of the fruit at diverse period of time were mensurated, simultaneously, pulp and pericarp of the fruit were observed by scan and transmission electronic microscope, namely, change of the fruit quality was observed and studied in two aspects of physiology and microcosmos. Secondly, a series of single-factor tests,which consists of fresh-keeping reagents,controlled atmosphere and ozone, were carryed out to filtrate effective modes of treatment. Lastly.appropriate technical parameters were acquired by orthogonal experiment.The conclusions were turned out as follows:1. Although disposals of 3%CaCl2,l% ascorbic acid ,10% juice of ginger, 5g m^-3 TBZ, 0.03% gibberellin, 50mg L^-1TIBA,0-2%CO₂ and 4-10% O₂ controlled atmospherestorage all appear active effects on fresh-keeping of Dong jujube,it is hard to achieve long period of storage.2. Hypobaric storage (increasing humidity by filling water) has prominent effects on fresh-keeping of Dong jujube. The fruit was stored at 40.5KPa, the rate of fine fruits was up to 86.3% after 120 days.3. Dong jujube was supposed to belong to the kind of fruit without climacteric. Hypobaric could reduce respiratory intensity, however,when the pressure drops to lower than 40.5KPa, the effect is not remarkable.4. During storage of the fruit, activity of the amylase gradually goes up, by way of parenthesis,content of the starch declines and the fruit goes softening. Hypobaric could inhibit activity of the amylase, slow down degradation rate of the starch,and keep firmness of the fruit, however, the effect is not remarkable when the pressure is below 40.5KPa.5. During storage of the fruit, activity of the ascorbic acid oxidase gradually goes up, by way of parenthesis.content of the ascorbic acid declines. Hypobaric could inhibit activity of the ascorbic acid oxidase, slow down degradation rate of the ascorbic acid, however,when the pressure drops to lower than 40.5KPa, the function is not distinct.6. Hypobaric could resist reproduction of the mold spores, prevent rot of the fruit, and that,the lower the pressure is,the more prominent the effect is. When the pressure drops to lower than 40.5KPa, the function is not distinct.7. Hypobaric storage could slacken cold harm of the fruit. The storage temperature could be reduced to -2^-3"C under the pressure of 40.5KPa, which is 2'C lower than the storage temperature under the routine pressure.8. Hypobaric could inhibit degradation of inclusion and middle lamella of the fruit cell, and that,the lower the pressure is,the more prominent the effect is. The cell walls of pulp is intact when the fruit was storedfor 120 days (P<60.7KPa) .9. The pericarp stomas of Dong jujube are all open under the condition of hypobaric storage. As storage period extends, secretions of the stomas are increasing,and the stomas are much more open. The lower the pressure is,the fewer secretions of the stomas are,and the more fluent routeway of the stomas are.10. The freshness index of the fruit was up to 83.8% after 120 days when it was dealt with 300mg-m"3 ozone,once every 10 days and 30 minutes every time.The tissue of the fruit was damaged severely when the concentration of ozone is higher than...