The Influence And Mechanism Analysis Of Dielectric Property On Fruit And Vegetable Pre-proccessed By High-voltage Pulsed Electric Field

Dielectric property is bound charge of matter molecules on the response characteristics of the applied electric field. Researching and utilizing dielectric property of fruit and vegetable can express and detection the quality of fruit and vegetable, and monitor and analyze organization, composition and state of fruit and vegetable in the processing. Related research has been widely concerned.High-voltage pulsed electric field (HPEF) can improve the freeze-dried rate of fruit and vegetable, and reduce the energy consumption and shorten freeze-dried processing time, still can farthest reserve the nutritional quality of fruits and vegetables as a kind of nonthermal technology, which is used in vacuum freeze drying process on fruit and vegetable after pretreatment. In recent years, we have carried on the thorough exploration in this respect. For the freeze-drying optimal process on fruit and vegetable preprocessed by HPEF, we monitor moisture content of fruit and vegetable in the freeze-dried process by using dielectric property of fruit and vegetable, which find HPEF has effect on dielectric property on fruit and vegetable. To select the rational electric field parameters and optimize the pretreatment technology on HPEF, we need to understand the influence mechanism of dielectric property on fruits and vegetables preprocessed by HPEF, so this paper specifically study the following research:(1) Based on the process of freeze-dried fruit and vegetable, electric field parameters were optimized after preprocessing fruit and vegetable by HPEF. To contrast experiment analysis, we use the response surface method and set the scope of the three parameters (pulse voltage, pulse frequency, pulse number) on high-voltage pulsed electric field, and analyze the changing of drying rate on different kinds of fruit and vegetable (apple, eggplant, green radish), which obtain the optimal process parameters after preprocessing fruit and vegetable by HPEF. The optimal process parameters combination for apple is pulse voltage830V, pulse frequency142Hz, pulse number64. The optimal process parameters combination for eggplant is pulse voltage710V, pulse frequency68Hz, pulse number83. The optimal process parameters combination for green radish cut by transverse is pulse voltage1284V, pulse frequency19Hz, pulse number66. The optimal process parameters combination for green radish cut by portrait is pulse voltage915V, pulse frequency110Hz, pulse number88.(2) The experimental study of high-voltage pulsed electric field on dielectric constant of fruit and vegetable. From the main factors on influencing the dielectric properties of fruit and vegetable, using the optimized processing parameter carry out pretreatment experiment on fruit and vegetable of different organization form, different organizations direction, different moisture content by HPEF. The capacitance and impedance of different fruit and vegetable are measured by LCR tester, and dielectric constant change curve is drawn by SAS. The influence law of experiment is analyzed on dielectric constant of different kinds of fruit and vegetable in the high-voltage pulsed electric field.(3)The Influence and mechanism analysis of dielectric property on fruit and vegetable proccessed by high-voltage pulsed electric field. On the basis of the theory of electromagnetic field, the influence of dielectric property on fruit and vegetable proccessed by high-voltage pulsed electric field, which is revealed from the mechanism. With apples as test materials, the influence of dielectric property on fruit and vegetable proccessed by high-voltage pulsed electric field, which is studied. The influence of pulse voltage, pulse frequency, magnetic field intensity, electric field intensity are analyzed and obtained on dielectric properties of apple. The influence mechanism is simply analyzed by the theory of electromagnetic field. The results show that:equivalent capacitance and equivalent impedance of apple is decrease with the increasing pulse voltage, pulse frequency, magnetic field intensity, electric field intensity. High-voltage pulsed electric field parameters have a certain effect on dielectric properties of fruits and vegetables, which is established the foundation to further study the effects of electric parameters on the different dielectric properties of fruit and vegetable and the optimal process parameters optimization pretreatment on fruit and vegetable proccessed by high-voltage pulsed electric field.(4)Correlation between electric parameters and dielectric properties of fruit and vegetable of high-voltage pulsed electric field. With apples as test materials, the electric field test frequency is set as1000Hz, different pulse voltage and different pulse frequency have influence on equivalent capacitance and equivalent impedance of apple, which is measured. Mathematical models of the equivalent capacitance, equivalent impedance and the three-dimensional figure of pulse voltage, frequency, dielectric properties are analyzed by using SAS software. The results show that three mathematical models and three-dimensional figure are shown dielectric characteristics of fruits and vegetables decreases with the increase of pulse voltage and pulse frequency, presenting a linear function relation.This paper analyzes the influence of dielectric property on fruit and vegetable proccessed by high-voltage pulsed electric field with the method combined theory with experiment. Biological effect mechanism is analyzed on fruit and vegetable proccessed by high-voltage pulsed electric field, which provides the basis of related analysis on fruit and vegetable in the process of vacuum freeze drying after high-voltage pulsed electric field pretreatment, and provides the important reference to explore low energy consumption on fruit and vegetable in the process of freeze-drying.