冷冻-复温过程中葡萄细胞结晶变化研究

Research on Crystallization Change of Grape Cells during Freezing-thawing Process

利用低温显微镜系统对葡萄进行了冷冻-复温实验,研究了葡萄细胞在冷冻-复温过程的结晶变化。通过分析冷冻-复温过程的葡萄细胞显微图像、细胞体积、内压、渗透率的变化,发现：葡萄细胞的结冰温度随冷冻速率的增加而降低;葡萄细胞的体积变化总趋势是随温度的降低而减小,但由于细胞内自由水体积的变化,在-5~0℃细胞体积会有所增大。在14℃/min、50℃/min冷冻速率下细胞体积分别减小了54.5%,26.3%。冷冻速率越大,细胞体积变化越小;冷冻过程中葡萄细胞的渗透系数随温度的降低而降低,随冷冻速率的降低而降低。在葡萄细胞的冷冻-复温过程中,提高复温温度能有效减少细胞的破损。

The freezing-thawing phenomenons of fruits and vegetables are inevitable during the refrigerated transport process. The quality of fruits and vegetables will also be changed. Grapes as test objects are used to test the quality change during the freezing-thawing process. The cryomicroscope system（ including CCD camera,BCS 196 cryostage,the liquid nitrogen tank,the crystage temperature control system） was used to test the grape sample during the freezing-thawing process. The temperature range of cryomicroscope system is- 196℃ to 125℃. The crystallization change of grape cells has been researched. The freezing-thawing rate is 2,6,8,11,14,20,50,90℃ / min. Micrograph,volume,internal pressure and permeability coefficient of grape cells were analyzed during the freezing-thawing process.The result shows that the formation process of crystallization in the intercellular space depends on the freezing rate. Grape cell freezing temperatures will decrease with increasing freezing rate and the general trend of change in volume of grape cells will decrease with the decreasing of temperature. However,grape cells volume will increase at- 5 ~ 0℃ due to the volume changes of intracellular free water. Grape cells volumes were reduced by 54. 5%,26. 3% respectively at 14℃ / min and 50℃ / min freezing rates. The larger the freezing rate is,the smaller the cell volume changes to be. During the freezing process,the permeability coefficient of grape cells will decrease with the decreasing temperature and freezing rate.Increasing thawing temperature can effectively reduce the damage of the grape cells during freezing-thawing process. This research will optimize the temperature gradient of fruit and vegetable during cold storage.