Experimental Study On Evolution Of Mechanical Injury Of Biological Tissue During Cryopreservation

To ensure fresh perseveration by reducing the metabolic rate, lowering the temperature of the cell or the whole organization is required by low temperature preservation of Cells, tissues, organs and other biological materials, as well as cryogenic operations of frozen food, fruits and vegetables storage. Therefore, the study of cryopreservation biological group textile mechanical injury has significant importance.In this paper, the low temperature system and high speed camera were used to record the image of mouse kidney cells during the cooling process. And through these images, the digital image correlation method(DICM) was used to calculate the growth process of the extracellular ice crystals and the intracellular ice crystals in the mouse kidney cells. Results show that: as the temperature decreased, extracellular ice crystals first appear and cells with large rigid displacement, ice increased gradually, until the whole cells surrounded. Then the cells will no longer occur displacement of a rigid body. When the extracellular ice crystals no longer grow, there will be ice crystals inside the cell, and the intracellular ice crystals from the cell membrane near the initiation, and then to the nucleus of the growth, until the whole cell is filled with.Secondly, in this paper, the design of the cryogenic tensile system, to study the mechanical behavior of potato tissue under different environment temperature(room temperature, 0℃,-3℃,-5℃,-8℃,-10℃,-15℃,-20℃), and through the cryogenic microscopy to study the potato cells in the corresponding temperature of morphological parameters. In addition, this paper also studies the potato tissue at a temperature of 4℃, relative humidity 65% environment, storage on different days(fresh, 5 days, 10 days, 15 days, 20 days,25 days) and the variation of mechanical parameters and texture parameters. The results showed that the potato tissue elastic modulus will be increased with the decrease of temperature, and when the temperature reached-20℃, the modulus of elasticity will produce dramatic changes. This is because when the temperature of-20℃, potato tissue has produced ice crystals, resulting in potato tissue elastic modulus increases sharply. With the decrease of temperature, the stress of the failure of the potato tissue increased, and the strain at the corresponding place of the failure stress would be reduced. And potato cell area, length, width and perimeter will decreases with the decrease of temperature, but at-20℃, the parameter of potato will increase slightly, which is because in-20℃, potato cells produce crystals, the cell boundary outward diffusion, resulting in cell area increases. But there was no significant change in the plane shape and roundness of the potato cells, which showed that the deformation of the cells in the process of temperature drop was uniform. In addition, from the potato storage test can be found, increase with storage time, maximum of potato tissue should stress and elastic modulus are reduced, which indicates that the potato in storage in the process of mechanical parameters in reducing. And along with the increase of storage time, potato tissue elasticity, hardness, resilience, chewiness, adhesiveness and cohesiveness are in decreasing, which shows potato tissue in the storage process texture parameters is also reduced. The consistency of the mechanical parameters and the texture parameters is fully explained, with the increase of storage time, the quality of the potato tissue is gradually reduced.Finally, for a comprehensive understanding of the biological tissue in frozen storage in the process of deformation severity, explore the cooling rate effects on cell deformation. In this paper, the design of the three different cooling rates(0.5℃/min,1.2℃/min,2℃/min), to study in the freezing process in onion epidermal cells of deformation and cooling rate of the relationship and application of digital image correlation methods for measuring cell deformation, and mapped the entire cell area of the deformation field before and after freezing. The results showed that the changes of cell deformation and cell area were different in different regions. In the central region of the cell, the cell’s deformation and cell area changes are often relatively small. In addition, with the increase of cooling rate, the changes of cell deformation and cell area were decreased. This conclusion has important significance in evaluating the quality of frozen vegetables.