【作者】 丹阳；

【导师】 李里特；

【作者基本信息】 中国农业大学 ， 食品科学与工程， 2005， 博士

【摘要】 本研究在前人报道和研究的基础上,借助电磁物理学、果蔬采后生理学和生物化学等方面的专业知识,从工程实际的角度,针对典型呼吸跃变型果实番茄（Lycopersicon esculentum）,以呼吸强度、内源乙烯释放量、组织自由基产生及清除系统活性变化为标识,系统探讨了高压静电场处理对果实采后成熟及衰老的调控作用,结合电场作用条件的改变对宏观及微观指标变化的影响,分析了电磁场作用对番茄采后成熟、衰老过程抑制作用的机理,实验结果表明: 1 利用高等电磁学理论对保鲜操作中电场内各部位电场参数进行了理论分析,在此基础上明确了可能对保鲜效果产生影响的静电场参数为电场强度、极板富集电荷及电介质介电常数,并得出了不同情况下各电场参数改变的理论公式。通过对理论公式的分析,提出了表观电场强度的概念。 2 表观电场强度处理能够降低番茄贮藏过程中的失重率,调控果实的呼吸变化,减缓果实破断应力的下降,同时能够有效延缓L*、a*的变化,产生了显著的颜色差异。较高表观电场强度对番茄贮藏品质的影响高于较低表观电场强度。表观电场强度处理能够推迟番茄呼吸高峰并降低乙烯释放量,从贮藏中期开始降低超氧自由基发生速率,降低过氧化氢（H₂）₂)含量,在贮藏中后期保持较高的超氧化物歧化酶（SOD）、过氧化物酶（POD）活性,从而减低了组织膜脂过氧化程度,较高表观电场强度作用效果好于较低表观电场强度。 3 单纯场强及接触负电极处理能够有效控制果实采后的重量损失,分别比对照低4%及11%,呼吸高峰有所推迟,果实破断应力下降缓慢。接触接地极处理各观测指标与对照无显著差异。说明单纯场强能够产生保鲜效果,与负极板接触能够增加场强的保鲜效果,而与接地极板接触则消除了单纯场强的作用。 4 单纯极板电荷能够影响番茄的失重率等贮藏品质指标,负电荷能够在一定程度上抑制番茄的品质下降,但作用程度较小,而因感应产生的正电荷则会促进番茄的失重及颜色转化。负极板电荷可以推迟超氧化物歧化酶（SOD）活性峰值出现的时间,对过氧化物酶（POD）及过氧化氢酶（CAT）活性无显著影响,能够减少丙二醛（MDA）积累量,而因感应产生的正极板电荷对SOD、CAT及POD除少数实验点外,无显著影响。 5 在高压静电场番茄保鲜中,在极板与番茄之间衬垫电介质能够干扰保鲜效果,介电常数较小,对保鲜效果的干扰较大。介电常数为3.7的纸板隔绝处理在控制番茄贮藏过程中的失重率,调控果实的呼吸变化,减缓果实硬度的下降,延缓果实颜色转化上的作用显著高于介电常数1.9～2.2的塑料板隔绝处理。 6 通过对短时高压静电场下番茄失重率及果皮颜色变化的观测,证实在高压静电保鲜操作中采用采后仅处理一次的处理方式不能产生明显的保鲜效果。采后立即进行一段时间的高压静电场处理,番茄的重量损失及破断应力等标识贮藏品质的指标明显好于对照、自贮藏中期开始处理和自贮藏后期开始处理,有效延缓了果实成熟的启动。 7 在绿熟番茄的正常贮藏温度,高压静电场处理能够有效抑制番茄的采后失重、呼吸强度、乙烯释放量及果实颜色转化。而在临界贮藏温度,对照果实能够正常转红,高压静电场显著抑制了果实乙烯释放,从而抑制了果实的正常后熟,在宏观上表现为颜色转化受到抑制,果实不能正更多还原

【Abstract】 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.更多还原