Effects Of Oxygen Partial Pressure And Treatment With GA₃ On Physiological And Biochemical Changes In Postharvest Jujube Fruit During Cold Storage

In this experiment six cultivars of Chinese jujube fruits (Zizyphus jujuba Mill.) named Jinsi small jujube, Li jujube, Shuai jujube , Mu jujube, Dong jujube and Cui jujube were harvested at the half-red stage for studying the respiratory type. Applications of hypobaric and high C>2 storage were investigated to maintain the jujube quality. We not only studied on the postharvest physiological and biochemical changes of Dong jujube ; but also analyzed the mechanism of alcoholism, softness and flesh browning and the changes of storage quality during the hypobaric storage and GAs treatment. At the same time we studied water loss of jujube fruit and water requirement of hypobaric installation, put forward appropriate hypobaric parameter, provided a theoretical basis for jujube storage technology.1. The results showed that there were clear differences in the respiratory intensity among the four different ripening phases of Jinsi small jujube during cold storage. Furthermore, significantly higher at the all-red stage than the other mature stages. According to the experiment, Jinsi small jujube, Li jujube, Shuai jujube and Mu jujube fruits, which had not significant climacteric peak. The similarity of Li jujube to ascent pattern of respiratory final phase, while the similarity of shuai jujube, Mu jujube and Jinsi small jujube to respiratory gradual descent pattern. Dong jujube and Cui jujube had characteristic of climacteric pattern.2. Hypobaric storage significantly kept firmness and vitamin C content, reduced acetaldehyde and ethanol contents in pulp and respiratory intensity of jujube fruit, inhibited ascorbic acid oxidase and alcohol dehydrogenase activities, slowed down the rate of ethylene production in fruit. The effect of hypobaric storage on flesh browning was not obvious.3. Effect of postarvest treatment with GA3 (30mg L-1) on physiological and biochemical changes of Cui jujube fruit during cold storage was studied. The results showed that the GA3 treatment not only reduced respiratory intensity and rate of ethylene production, but delayed the decrease of jujube fruit firmness, inhibited the increase in contents of acetaldehyde and ethanol and the activities of alcohol dehydrogenase and polyphenol oxidase, slowed down the occurrence of alcoholism and flesh browning. Compared with control fruit, the content of ascorbic acid of the treated fruit was observed with no significant difference.4. This investigation showed that hypobaric treatment can significantly keep the quality of Dong jujube fruit during cold storage. Under appropriate hypobaric parameter the hypobaric treatment reduced the decrease of jujube fruit firmness, delayed the development of jujube fruit to become red, had an effective role in fruit fresh protection, reduced the rot indices, browning indices and peculiar smell indices, slowed down the mature and senescent process of Dong jujube. The hypobaric condition with the adding water installation may avoid water loss of jujube fruit.5. The different kinds of concentrations and times in the high O2 treatment (30% O2,50%O2,70%O2, 90%O2/10d, 20d, 30d ) were applied to the jujube fruit, with significant difference. The shorter time treatment had a better effect than the longer time; raised fresh fruit rate and firmness value in pulp; reduced becoming red indices, rot indices, browning indices and peculiar smell indices. But the high O2 (100% O2) treatment of the long time is disadvantageous to the fresh life of Dong jujube fruit.