| 摘要: |
| 为探究不同场强的直流电磁场对植物组织细胞在冻结相变过程中细胞及冰晶形状和大小的影响，本文取洋葱第三层果肉为研究对象，切成0.5 cm×0.5 cm的方块，在低温冷台上放置样品切片进行细胞冻结实验，采用的降温速率：0 ℃之前为10 ℃/min；0 ℃之后为3 ℃/min；终温为﹣25 ℃。直流磁场强度分别为0 Gs（对比组）、4.6 Gs、18 Gs、36 Gs、72 Gs。实验过程中观察了不同场强作用下洋葱细胞及冰晶形态的变化，并提出“细胞二维保持率ζ”这一指标对果蔬细胞冻结效果进行评价，利用AutoCAD软件对显微图像进行数据计算得出ζ值。结果表明：磁场辅助冻结洋葱细胞冰晶形成趋向于雾化，沙粒化，抑制冰晶生长，从而减小冰晶尺寸，有利于保持细胞原有形态，使细胞损害率降低；随着磁场强度的增强，洋葱细胞相变时间逐渐缩短，过冷度逐渐降低，但始终高于无磁场下的过冷度。 |
| 关键词: 食品加工技术；直流磁场冻结；冰晶及细胞形态 洋葱 |
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| Effect of DC Magnetic Field on Freezing Process of Onion Cells |
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Song Jianfei1, Liu Bin1, Guan Wenqiang2, Zhang Dequan2
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| (1.Tianjin Key Laboratory of Refrigeration Technology, Tianjin University of Commerce;2.Institute of Agro-products Processing Science and Technology, Chinese Academy of Agriculture Science) |
| Abstract: |
| In order to explore the effect of DC electromagnetic field of different field strengths on the shape and size of cells and ice crystals during the freezing phase transformation process of plant tissue cells, the third layers of onion cut into squares of 0.5 cm×0.5 cm were studied. Put the onion slices on the cold platform and the cooling rate of the experiment was: 10 ℃/min before 0 ℃, 3 ℃/min after 0 ℃, and the final temperature was﹣25 ℃, the DC magnetic field strengths were 0Gs (the control group) , 4.6 Gs, 18 Gs, 36 Gs, 72 Gs respectively. In the experiment, the changes of morphology of the cells and ice crystals under different strengths were observed, and the index of "two-dimensional cell retention rate ζ" was put forward to evaluate fruit and vegetable cells’ freezing effect. AutoCAD software was used to calculate the micrograph and the value of ζ. The results show that the magnetic field assisted freezing of the onion cells can make the formation of ice crystals tend to atomization and sand grains, which can inhibit the growth of ice crystals, thus reduce the size of the ice crystals, and it will also be more conducive to maintain the original cell morphology and decrease the cell damage rate. With the increasing of the magnetic field strength, phase transformation time of the onion cells decreases, supercooling degree decreases gradually, but it is always higher than that of non magnetic field. |
| Key words: food processing technology DC magnetic field freezing morphology of ice crystals and cells onion |
