Effects Of Freezing Assisted By Magnetic Field On Freezing Characteristics And Quality Of Vegetables

With the intensive study of frozen food processing methods,non-thermal effect of magnetic field on food becomes a hot research direction,its good environmental protection,energy saving and the indubitable biological effects of magnetic field have caused widespread concern.In this paper,we mainly studied the biological effects of magnetic field assisted freezing on fruits and vegetables,and analyzed the law of freezing characteristics caused by magnetic field and the effect on the storage quality of fruits and vegetables.we put the magnetic field generator on both sides of the crystallization chamber in the middle of self-made quick freezer,which formed the experiment platform of magnetic field assisted freezing,after that placed them in the refrigerator of-18 oC for 70 days' storage,every ten days we would have the determination of indexes,and the morphological changes of cells could be observed by Olympus BX51 microscope.Compared the effect of different intensity of DC magnetic field with no magnetic field,we could get the general rules for the biological effects of different fruits and vegetables.In view of the fact that water occupied a large proportion in the fruits and vegetables,so the experimental study on water was carried out as well.The study found:1.Under different DC magnetic field intensity,the freezing assisted by magnetic field of vegetables showed the property of extreme value and different degrees of similar regularity for freezing process of water.However,compared with water,the composition of fruits and vegetables was much more complex,and the difference between different types of fruits and vegetables was also large,which led to differences in the effect of magnetic field.In this experiment,peas showed more obvious differences,and the uniformity of the freezing characteristics of carrots,potatoes,beans,broccoli and water was higher,the importance of moisture content in fruits and vegetables was further proved.2.For the freezing process of water,the magnetic field mainly had an effect on the hydrogen bond of water molecules,which could affect the phase transition time by weakening and enhancing the stability of hydrogen bonds between clusters.Macroscopically speaking,it could affect the heat conduction,convection heat transfer and latent heat of phase change in the process of freezing.Meanwhile,the constituent of each kind of fruits and vegetables was complex,and had great differences,so each vegetable had its own relatively independent freezing property assisted by magnetic field,which to some certain extent was not universal to others.3.The experiment showed that the magnetic field effect was significant compared to the control group(0Gs).For carrots and peas,it showed the best comprehensive storage quality under 4.6Gs,and in contrast to the freezing curves of the third chapter,the phase transition time change caused by magnetic field and the loss rate were positively correlated.For broccoli and bean,it showed the best comprehensive storage quality under 4.6Gs,which could maintain the overall quality at utmost;for potato,36 Gs also showed the advantage about loss rate,soluble solids and cell membrane permeability,but for the hardness and chewiness,it always had the lowest value.4.The writer put forward an index of the shrinkage rate of cells when analysing the cell changes through the figures got during the storage,after classification processing by the software of Photoshop,we can use the other software image J to calculate the valuecR,and then the above conclusions are further verified from microcosmic aspect.To sum up,freezing assisted by magnetic field has obvious effect to maintain the quality of fruits and vegetables,different fruits and vegetables imposing different magnetic field strength show the property of extreme value,the main reason is that the biological effects of magnetic field generated by the external magnetic field,not only related to the distribution and the frequency,but also to the type and level of living organisms under the effect of magnetic field.