Effect Of High Voltage Electrostatic Field On Post Harvest Ripening And Senescence Of Tomatoes And Study On Its Mechanism

In order to study the effect of high voltage electrostatic field (HVEF) on the progress of ripening and senescence of tomato, Changes of weight loss, color, broken stress, respiration, ethylene production and super oxide species in tomato under HVEF were investigated. The results showed that:1. The theoretic analysis about parameters of HVEF under different configuration showed that the electric field strength, the electric charge and the dielectric of materials were the most important factors in the treatment of HVEF. Different equations were acquired to describe the change of electric parameters under different configuration of high voltage electrostatic field. The concept of apparent field strength was defined to represent the co-effect of field strength and electric charge.2. The weight loss of tomato was significantly controlled by the treatment of apparent field strength. Meanwhile the change of hardness, peel color and ethylene production was lowered by the treatment of apparent field strength. The respiration of tomato was retarded by apparent field strength as well. In general, the effect of higher apparent field strength was better than lower apparent field strength. The mechanism of fruit preservation under HVEF may be that HVEF controlled the super oxide species and kept a higher level of anti oxide enzymes when compared with control.3. The weight loss, broken stress and respiration of tomato were controlled by simple field strength. Meanwhile fruit contacting with electrodes showed an interesting result that fruit contacting electrode with negative charge were preserved, however the treatment of contacting with earth electrode showed no preserving effects.4. Single negative electric charge could control the decrease of tomato quality. On the contrary, single positive electric charge enhanced the weight loss and color change of tomato. The mechanism of this phenomenon may be the control of SOD by negative charge and the counteracting effect of positive charge.5. Materials with different dielectric could alter the effect of HVEF on tomato. The treatment with a piece of paper board placed between electrode and tomatoes could control the weight loss, rot ratio and control the change of color as well. However the treatment of HVEF with a piece of plastic board between electrode and tomatoes showed slight effect on post harvest physiology of tomato.6. Short time HVEF treatment showed no effect on tomato. The treatment of HVEF since harvest showed satisfactory effect on maintaining the quality of tomato. However, the treatment of HVEF since the middle period or the later period of the storage showed no effect on post harvest physiology of tomato.7. The treatment of HVEF could control the decrease of fruit quality under proper temperature usually used to store tomatoes. However HVEF could inhibit the change of color of tomato underlower temperature. Under room temperature the treatment of HVEF aroused unusual color change of tomato. These phenomena showed a limited usage of the treatment of HVEF.8. The effect of HVEF on tomato under proper humidity (RH 90%) was much significant than saturated humidity and low humidity. These phenomena showed another side of the limit usage of the treatment of HVEF.9. The investigation about tomato in higher level of harvest ripening showed that HVEF could not control the decrease of quality of tomatoes with high level of ripening.