熊秀芳, 李靓, 杨兴胜, 李星恕. 中压电场预处理对苹果组织损伤程度及微观结构的影响[J]. 农业工程学报, 2018, 34(14): 272-279. DOI: 10.11975/j.issn.1002-6819.2018.14.035
    引用本文: 熊秀芳, 李靓, 杨兴胜, 李星恕. 中压电场预处理对苹果组织损伤程度及微观结构的影响[J]. 农业工程学报, 2018, 34(14): 272-279. DOI: 10.11975/j.issn.1002-6819.2018.14.035
    Xiong Xiufang, Li Jing, Yang Xingsheng, Li Xingshu. Effect of moderate electric field pretreatment on damage degree and microstructure of apple tissue[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2018, 34(14): 272-279. DOI: 10.11975/j.issn.1002-6819.2018.14.035
    Citation: Xiong Xiufang, Li Jing, Yang Xingsheng, Li Xingshu. Effect of moderate electric field pretreatment on damage degree and microstructure of apple tissue[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2018, 34(14): 272-279. DOI: 10.11975/j.issn.1002-6819.2018.14.035

    中压电场预处理对苹果组织损伤程度及微观结构的影响

    Effect of moderate electric field pretreatment on damage degree and microstructure of apple tissue

    • 摘要: 为了探究中压电场预处理(<100 V/cm)对苹果组织结构损伤程度的影响,从宏观层面上分析了电场强度(15~90 V/cm)、温度(30~70 ℃)、频率(50~1000 Hz)等处理参数对苹果组织结构损伤率的影响规律,解析了温度对苹果组织损伤过程的影响;从微观层面上对不同温度和电场强度下苹果组织微观结构进行了电镜扫描观察。结果表明,同样温度下,中压电场预处理时的苹果组织结构损伤率远高于水浴加热处理(P<0.05);场强较高(>45 V/cm)时苹果组织结构损伤率随温度的升高而线性增大;场强较低(<30 V/cm)处理时与水浴处理均呈现先缓慢上升再急剧增大的变化趋势,但中压电场预处理增速更快。温度低于70 ℃时,苹果组织结构损伤率随电场强度升高而增加,随频率的增大而减小。苹果组织结构损伤率随时间的变化符合一级反应动力学模型;中压电场强度30 V/cm时,通过组织损伤速率常数、特征损伤时间计算所得活化能分别为122.88和157.01 kJ/mol;水浴处理时组织损伤速率常数所得活化能为143.82 kJ/mol。苹果组织细胞微观结构观察显示,中压电场电、热协同作用更易损伤苹果组织。研究结果可为改进苹果深加工预处理工艺提供参考。

       

      Abstract: Abstract: Apple deep processing in China is developing rapidly with the increasing demand of apple slices, fresh apple juice and apple canned products in recent years. All necessary processing technologies such as dehydration, diffusion, pressing and drying essentially require acceleration of two-way mass transfer into or out of the apple tissue. Apple tissue consists of thousands of cells and cell structure is the key factor that influences the mass transfer from inside to outside and vice versa. Therefore, the pretreatment method for damaging the apple tissue cell is needed before further deep processing. In recent years, moderate electric field (MEF) is receiving more and more significant attention due to its characteristics with the advantages of thermal and electrical treatment. To explore the effect of MEF pretreatment parameters such as electric field intensity, frequency and temperature on the damage degree and damage process of apple tissue, the paper analyzed the structural change of apple tissue under different MEF conditions, and evaluated the influence of pretreatment temperature on the damage process at macro and micro scale by detection of disintegration index of apple tissue structure and scanning electron microscope (SEM) observation respectively. The results indicated that apple tissue structure disintegration index from MEF was greater than that resulted from thermal treatment of waterbath. For waterbath pretreatment, the disintegration index of apple tissue structure firstly increased slowly with increasing temperature and then raised sharply when the temperature was above 60 ℃. The same tendency was observed for low electrical field intensity pretreatment (<30 V/cm), but the disintegration index increased more rapidly. The disintegration index changed slowly under hot water bath and low electrical field intensity treatment (< 30 V/cm), but when the temperature was above 60 ℃, the disintegration index increased sharply. The disintegration index increased linearly with increasing temperature when electrical field intensity was higher than 45 V/cm, and a greater disintegration index could be obtained under lower temperature and higher electric field intensity (90 V/cm). The reason was that the thermal and electrical synergistic effect of MEF pretreatment applied to the apple tissue simultaneously brought up the electroporation of cell membrane and the degradation of cell wall. In addition, the disintegration index of apple tissue structure increased with the increase of electric field intensity and decreased with the increase of frequency when the temperature was lower than 70 ℃. All the curves of disintegration index with holding time could be approximated using the first-order reaction kinetics model which could describe the characteristics of the damage process. The rate constant of the first-order model increased with the increasing treatment temperature and the characteristic damage time showed contrary tendency. The rate constants at different temperatures could be formulated by the Arrhenius equation, the same as the characteristic damage time. The activation energy calculated from the rate constant was 122.88 kJ/mol, and that from the characteristic damage time was 157.01 kJ/mol. The activation energy obtained from the hot water bath pretreatment was 143.82 kJ/mol.The micro-structure observation of apple tissue indicated that MEF pretreatment can effectively destroy the apple tissue at lower temperature. Apple tissue is destructed more easily by moderate electric field treatment because of the synergistic effect from electrical field and temperature field. The findings are useful to analyze the electro-thermal synergistic regime from MEF pretreatment and improve the deep processing technology of apple products.

       

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