Pulsed electric field processing device and method for producing food

Abstract

A pulsed electric field processing device (2) comprises: a pair of electrodes (22) installed in a processing chamber (21) through which an object to be processed passes; a pulsed power supply (23) that outputs, to the pair of electrodes (22), a voltage pulse having a first polarity, which is one of a positive polarity and a negative polarity, and a voltage pulse having a second polarity, which is the opposite polarity of the first polarity; a control unit (24) that controls the pulsed power supply (23); and a voltage sensor (28) that measures the voltage applied to the pair of electrodes (22) by the pulsed power supply (23). The pulsed power supply (23) has a first polarity main module and a first polarity sub-module that output voltage pulses of the first polarity, and a second polarity sub-module that outputs voltage pulses of the second polarity. When discharging at the second polarity, the control unit (24) causes the pulsed power supply (23) to output voltage pulses of the second polarity such that the discharge energy of the first polarity and the discharge energy of the second polarity per unit time are equal to each other.

Description

Pulse electric field treatment device and method for manufacturing food

[0001] The present disclosure relates to a pulse electric field treatment device that performs pulse electric field treatment on an object to be treated with a high-voltage pulse, and a method for manufacturing food.

[0002] Conventionally, pulse electric field treatment devices have been used for treatments such as sterilization and softening of objects to be treated. A pulse electric field treatment device generates a pulse electric field in a treatment liquid in a treatment chamber by applying a pulse voltage to an electrode pair installed in the treatment chamber through which the object to be treated passes, and performs pulse electric field treatment on the object to be treated. The object to be treated is generally food and food ingredients. When the object to be treated is a liquid, the pulse electric field treatment is performed using the object to be treated itself as the treatment liquid. When the object to be treated is a solid, the pulse electric field treatment is performed while passing the object to be treated through a liquid tank filled with the treatment liquid.

[0003] The liquid sterilization device disclosed in Patent Document 1 is a pulse electric field treatment device that sterilizes an object to be treated by pulse electric field treatment by applying a pulse voltage to a liquid object to be treated.

[0004] Japanese Patent Application Laid-Open No. 2021-114943

[0005] During pulse electric field treatment, a current flows through the treatment liquid, so the anode is consumed by electrolysis. Since the pulse electric field treatment device disclosed in Patent Document 1 uses a unipolar pulse power supply, among the electrode pairs installed in the treatment liquid, the anode connected to the positive electrode of the pulse power supply is consumed faster than the cathode connected to the negative electrode of the pulse power supply. For this reason, the pulse electric field treatment device disclosed in Patent Document 1 has a problem that maintenance must be performed frequently.

[0006] The present disclosure has been made in view of the above, and an object thereof is to obtain a pulse electric field treatment device that suppresses the consumption of electrode pairs.

[0007] To solve the above-mentioned problems and achieve the objective, the pulse electric field processing apparatus according to this disclosure comprises an electrode pair installed in a processing chamber through which an object to be processed passes; a pulse power supply that outputs a voltage pulse of a first polarity, which is either positive or negative polarity, and a voltage pulse of a second polarity, which is the opposite polarity to the first polarity, to the electrode pair; a control unit that controls the pulse power supply; and a voltage sensor that measures the voltage applied by the pulse power supply to the electrode pair. The pulse power supply has a first polarity main module and a first polarity sub-module that output a voltage pulse of the first polarity, and a second polarity sub-module that outputs a voltage pulse of the second polarity. During discharge in the first polarity, the control unit causes the pulse power supply to output a voltage pulse only from the first polarity main module. If the absolute value of the voltage applied by the pulse power supply to the electrode pair during pulse discharge in the first polarity using only the first polarity main module falls below a preset threshold, the control unit causes the pulse power supply to output a voltage pulse from both the first polarity main module and the first polarity sub-module. During discharge in the second polarity, the control unit causes the pulse power supply to output a voltage pulse of the second polarity such that the discharge energy of the first polarity per unit time is equal to the discharge energy of the second polarity.

[0008] According to this disclosure, it is possible to obtain a pulsed electric field processing device that suppresses the wear of electrode pairs.

[0009] Figure showing the configuration of a food manufacturing system using the pulse electric field processing device according to Embodiment 1. Figure showing the circuit configuration of the pulse power supply of the pulse electric field processing device according to Embodiment 1. Figure showing the circuit configuration of the positive electrode side unit module of the pulse electric field processing device according to Embodiment 1. Figure showing the circuit configuration of the negative electrode side unit module of the pulse electric field processing device according to Embodiment 1. Figure showing the energized state of the pulse electric field processing device according to Embodiment 1 during charging. Figure showing the energized state of the pulse electric field processing device according to Embodiment 1 during positive discharge. Figure showing the energized state of the pulse electric field processing device according to Embodiment 1 during negative discharge. Waveform diagram of the voltage pulse output by the pulse power supply of the pulse electric field processing device according to Embodiment 1. Figure showing the energized state of the positive discharge when the positive electrode side sub-module of the pulse electric field processing device according to Embodiment 1 is enabled. Pulse electric field processing according to Embodiment 2. A diagram showing the circuit configuration of the pulse power supply of the device. A diagram showing the energized state of the pulse electric field processing device during charging according to Embodiment 2. A diagram showing the energized state of the pulse electric field processing device during positive discharge according to Embodiment 2. A diagram showing the energized state of the pulse electric field processing device during negative discharge according to Embodiment 2. A diagram showing the energized state of the pulse electric field processing device during positive discharge when the positive electrode side submodule of the pulse electric field processing device according to Embodiment 2 is enabled. A diagram showing the energized state of the pulse electric field processing device during negative discharge when the negative electrode side submodule of the pulse electric field processing device according to Embodiment 2 is enabled. A waveform diagram of the voltage pulse output by the pulse power supply of the pulse electric field processing device according to Embodiment 2. A diagram showing the configuration of a food manufacturing system using the pulse electric field processing device according to Embodiment 3. A diagram showing an example of hardware configuration that realizes the control unit of the pulse electric field processing device according to Embodiments 1, 2 and 3.

[0010] The pulsed electric field processing apparatus and food manufacturing method according to the embodiment will be described in detail below with reference to the drawings.

[0011] Embodiment 1. Figure 1 shows the configuration of a food manufacturing system using a pulse electric field processing device according to Embodiment 1. The food manufacturing system 100 is a system that sterilizes a target object by pulse electric field processing, using the liquid target object itself as the processing liquid, in order to manufacture food. The food manufacturing system 100 includes a process control device 1 that controls the entire system, a pulse electric field processing device 2, a pre-processing tank 3 in which the target object before pulse electric field processing is stored, and a post-processing tank 4 in which the target object after pulse electric field processing is stored. The pulse electric field processing device 2 receives the target object supplied from the pre-processing tank 3 as a load 70, applies pulse electric field processing to the target object which is the load 70, and sends it to the post-processing tank 4.

[0012] The pulse electric field processing device 2 comprises a pipe-shaped processing chamber 21, an electrode pair 22 installed in the processing chamber 21, a pulse power supply 23 that outputs voltage pulses of a first polarity (positive) and a second polarity (negative) which is the opposite polarity to the first polarity to the electrode pair 22, a control unit 24 that controls the pulse power supply 23, a voltage sensor 28 that measures the voltage applied by the pulse power supply 23 to the electrode pair 22, a first temperature adjustment unit 25 that heats the object to be processed as it flows from the pre-processing tank 3 into the processing chamber 21, and a second temperature adjustment unit 26 that cools the object to be processed as it is sent from the processing chamber 21 to the post-processing tank 4.

[0013] Figure 2 shows the circuit configuration of the pulse power supply of the pulse electric field processing device according to Embodiment 1. The pulse power supply 23 comprises a charging power supply 231, a positive electrode side main module 232, a positive electrode side sub-module 233, a negative electrode side sub-module 235, and a voltage measuring unit 236 that detects the voltage of the positive discharge pulse and negative discharge pulse output to the electrode pair 22. The positive electrode side main module 232 and the positive electrode side sub-module 233 output a voltage pulse of positive polarity, which is the first polarity. The negative electrode side sub-module 235 outputs a voltage pulse of negative polarity, which is the second polarity.

[0014] The positive electrode side main module 232 and the positive electrode side sub-module 233 are composed of a positive electrode side unit module 40, which is a first polarity unit module. Figure 3 is a diagram showing the circuit configuration of the positive electrode side unit module of the pulse electric field processing device according to Embodiment 1. The positive electrode side unit module 40 has a capacitor 44, which is a first capacitor for positive discharge, that is stretched between the positive electrode wire 61 and the negative electrode wire 62, and a semiconductor switch 49 that switches whether to connect the capacitor 44 in series or in parallel with the capacitor 44 of another positive electrode side unit module 40. The semiconductor switch 49 includes a positive electrode wire switch 41 installed on the positive electrode wire 61, a negative electrode wire switch 42 installed on the negative electrode wire 62, and a discharge switch 43 that is stretched between the positive electrode wire 61 and the negative electrode wire 62. The capacitor 44 is stretched between the portion of the positive electrode wire 61 that is on the charging power supply 231 side of the positive electrode wire switch 41, and the portion of the negative electrode wire 62 that is on the charging power supply 231 side of the negative electrode wire switch 42. The discharge switch 43 is connected to the portion of the positive electrode wire 61 that is between the capacitor 44 and the positive electrode switch 41, and to the portion of the negative electrode wire 62 that is on the load 70 side of the negative electrode switch 42.

[0015] The positive-side unit modules 40 that constitute the positive-side main module 232 and the positive-side unit modules 40 that constitute the positive-side sub-module 233 have the same circuit configuration, but the capacitance of the capacitors 44 is different. The capacitance of the capacitors 44 in the positive-side unit modules 40 that constitute the positive-side sub-module 233 is larger than the capacitance of the capacitors 44 in the positive-side unit modules 40 that constitute the positive-side main module 232. The positive-side main module 232 is configured by connecting multiple positive-side unit modules 40 in series. Embodiment 1 shows an example in which three positive-side unit modules 40 are connected in series to constitute the positive-side main module 232.

[0016] Each of the positive electrode unit modules 40 constituting the positive electrode main module 232 and the positive electrode sub-module 233 has the circuit configuration shown in Figure 3. The positive electrode main module 232 is constructed by arranging a plurality of individually formed positive electrode unit modules 40 in series using positive electrode wires 61 and negative electrode wires 62. The plurality of positive electrode unit modules 40 are arranged in series by connecting terminal P2 of the positive electrode unit module 40 located on the charging power supply 231 side to terminal P1 of the positive electrode unit module 40 located on the load 70 side, and by connecting terminal N2 of the positive electrode unit module 40 located on the charging power supply 231 side to terminal N1 of the positive electrode unit module 40 located on the load 70 side.

[0017] The negative electrode submodule 235 is composed of a negative electrode unit module 50, which is a second polarity unit module. Figure 4 is a diagram showing the circuit configuration of the negative electrode unit module of the pulse electric field processing device according to Embodiment 1. The negative electrode unit module 50 has a capacitor 54, which is a second capacitor for negative discharge, that is stretched between the positive electrode wire 61 and the negative electrode wire 62, and a semiconductor switch 59 that switches whether to connect the capacitor 54 in series or in parallel with the positive electrode submodule 233. The semiconductor switch 59 includes a positive electrode switch 51 installed on the positive electrode wire 61, a negative electrode switch 52 installed on the negative electrode wire 62, and a discharge switch 53 that is stretched between the positive electrode wire 61 and the negative electrode wire 62. The capacitor 54 is stretched between the portion of the positive electrode wire 61 that is on the charging power supply 231 side of the positive electrode switch 51, and the portion of the negative electrode wire 62 that is on the charging power supply 231 side of the negative electrode switch 52. The discharge switch 53 is connected to the portion of the positive electrode wire 61 that is on the load 70 side of the positive electrode wire switch 51, and to the portion of the negative electrode wire 62 that is between the capacitor 54 and the negative electrode wire switch 52. The capacitance of the capacitor 54 of the negative electrode unit module 50 that constitutes the negative electrode submodule 235 is the same as the capacitance of the capacitor 44 of the positive electrode unit module 40 that constitutes the positive electrode submodule 233.

[0018] Each of the negative electrode unit modules 50 constituting the negative electrode submodule 235 has the circuit configuration shown in Figure 4. The negative electrode submodule 235 is constructed by arranging a plurality of individually formed negative electrode unit modules 50 in series using positive electrode wires 61 and negative electrode wires 62. The plurality of negative electrode unit modules 50 are arranged in series by connecting terminal P4 of the negative electrode unit module 50 located on the charging power supply 231 side to terminal P3 of the negative electrode unit module 50 located on the load 70 side, and by connecting terminal N4 of the negative electrode unit module 50 located on the charging power supply 231 side to terminal N3 of the negative electrode unit module 50 located on the load 70 side.

[0019] The control unit 24 is connected to each positive-side unit module 40 and negative-side unit module 50, and controls each positive-side unit module 40 and negative-side unit module 50 individually. Note that, to avoid making the diagram complex, the connection lines between each positive-side unit module 40 and negative-side unit module 50 and the control unit 24 are omitted from the diagram.

[0020] In Embodiment 1, an example is shown in which the positive electrode submodule 233 is composed of one positive electrode unit module 40. However, the positive electrode submodule 233 may be composed of two or more positive electrode unit modules 40 connected in series. Also, in Embodiment 1, an example is shown in which the negative electrode submodule 235 is composed of two negative electrode unit modules 50. However, the negative electrode submodule 235 may be composed of two or more negative electrode unit modules 50 connected in series.

[0021] Figure 5 shows the energized state of the pulse electric field processing device according to Embodiment 1 during charging. The arrows in Figure 5 indicate the flow of current. The positive electrode switches 41, 51 and the negative electrode switches 42, 52 are in the ON state, and the discharge switches 43, 53 are in the OFF state. Therefore, the capacitors 44 of each positive electrode unit module 40 and the capacitors 54 of the negative electrode unit module 50 are connected in parallel with each other. The charging current supplied from the charging power supply 231 charges the capacitors 44 sequentially, starting with the positive electrode unit module 40 closest to the charging power supply 231, followed by the charging of the capacitors 54 of the negative electrode unit module 50. The capacitors 44, 54 are charged until the voltage across them equals the voltage of the charging power supply 231.

[0022] Figure 6 shows the energized state of the pulse electric field processing device according to Embodiment 1 during positive discharge. The arrows in Figure 6 indicate the flow of current. During positive discharge, the control unit 24 causes the pulse power supply 23 to output a voltage pulse only from the positive electrode main module 232. Of the positive electrode unit modules 40 constituting the positive electrode main module 232, the positive electrode unit module 40 closest to the charging power supply 231 has the positive electrode wire switch 41 and the discharge switch 43 in the off state, and the negative electrode wire switch 42 in the on state. On the other hand, of the positive electrode unit modules 40 constituting the positive electrode main module 232, the positive electrode unit modules 40 other than the positive electrode unit module 40 closest to the charging power supply 231 have the positive electrode wire switch 41 and the negative electrode wire switch 42 in the off state, and the discharge switch 43 in the on state. In addition, the positive electrode unit modules 40 constituting the positive electrode sub-module 233 have the positive electrode wire switch 41 and the negative electrode wire switch 42 in the on state, and the discharge switch 43 in the off state. Furthermore, in the negative electrode unit module 50 that constitutes the negative electrode submodule 235, the positive electrode switch 51 and the negative electrode switch 52 are in the ON state, and the discharge switch 53 is in the OFF state. For this reason, the capacitors 44 of the positive electrode unit modules 40, except for the one closest to the charging power supply 231, are connected in series. Consequently, the load 70 receives a positive discharge pulse with a voltage whose absolute value is less than or equal to the voltage of the charging power supply 231 multiplied by one (N-1) which is one less than the number N of the positive electrode unit modules 40.

[0023] Furthermore, the capacitor 44 of the positive electrode unit module 40 that makes up the positive electrode main module 232 and is closest to the charging power supply 231 cannot be connected in series with the capacitors 44 of other positive electrode unit modules 40 because there are no positive electrode wire switches 41 and negative electrode wire switches 42 further towards the charging power supply 231. For this reason, during positive discharge, the negative electrode wire switch 42 is turned on and the positive electrode wire switch 41 and discharge switch 43 are turned off in the positive electrode unit module 40 closest to the charging power supply 231, so the capacitor 44 of the positive electrode unit module 40 closest to the charging power supply 231 is disconnected from the capacitors 44 of other positive electrode unit modules 40.

[0024] Figure 7 shows the energized state of the pulse electric field processing device according to Embodiment 1 during negative discharge. The arrows in Figure 7 indicate the flow of current. The positive electrode unit module 40 constituting the positive electrode main module 232 has the positive electrode wire switch 41 and the negative electrode wire switch 42 in the ON state, and the discharge switch 43 in the OFF state. The positive electrode unit module 40 constituting the positive electrode submodule 233 has the positive electrode wire switch 41 and the negative electrode wire switch 42 in the ON state, and the discharge switch 43 in the OFF state. The negative electrode unit module 50 constituting the negative electrode submodule 235 that is closest to the charging power supply 231 has the positive electrode wire switch 51 and the negative electrode wire switch 52 in the OFF state, and the discharge switch 53 in the ON state. Furthermore, among the negative electrode unit modules 50 that make up the negative electrode submodule 235, all negative electrode unit modules 50 except the one closest to the charging power supply 231 have the positive electrode switch 51 and the discharge switch 53 in the off state, and the negative electrode switch 52 in the on state. The control unit 24 causes the pulse power supply 23 to output a negative polarity voltage pulse such that the positive polarity discharge energy and the negative polarity discharge energy per unit time are equal.

[0025] Figure 8 is a waveform diagram of the voltage pulse output by the pulse power supply of the pulse electric field processing device according to Embodiment 1. Since the charge that can be stored in the capacitor 44 is finite, the pulse voltage decreases over time even during discharge. In the example shown in Figure 8, at time T1, the absolute value of the voltage applied by the pulse power supply 23 to the electrode pair 22 in positive discharge is below a preset threshold. The control unit 24 monitors the voltage measured by the voltage measurement unit 236, and if the absolute value of the voltage applied by the pulse power supply 23 to the electrode pair 22 during positive polarity pulse discharge using only the positive electrode side main module 232 falls below a preset threshold, the control unit 24 activates the positive electrode side sub-module 233 to supplement the pulse voltage and restores the absolute value of the voltage applied by the pulse power supply 23 to the electrode pair 22 to above the preset threshold. Specifically, if the absolute value of the voltage applied by the pulse power supply 23 to the electrode pair 22 during positive polarity pulse discharge only in the positive electrode main module 232 falls below a preset threshold, the control unit 24 turns off the positive electrode wire switch 41 and the negative electrode wire switch 42 of the positive electrode unit module 40 constituting the positive electrode sub-module 233, and turns on the discharge switch 43. As a result, the pulse power supply 23 outputs voltage pulses in both the positive electrode main module 232 and the positive electrode sub-module 233. The preset threshold is the absolute value of the voltage at which the pulse electric field strength becomes the effective electric field strength threshold. The effective electric field strength threshold is the pulse electric field strength at which the degree of sterilization and softening of the object to be processed by pulse electric field treatment meets the minimum required specifications.

[0026] Figure 9 shows the energized state during positive discharge when the positive electrode side submodule of the pulse electric field processing device according to Embodiment 1 is enabled. The arrows in Figure 9 indicate the flow of current. By enabling the positive electrode side submodule 233, the capacitor 44 of the positive electrode side unit module 40 that constitutes the positive electrode side submodule 233 is connected in series with the capacitor 44 of the positive electrode side unit module 40 that constitutes the positive electrode side main module 232. As a result, during positive discharge with the positive electrode side submodule 233 enabled, the absolute value of the voltage applied by the pulse power supply 23 to the electrode pair 22 is supplemented by the positive electrode side submodule 233 to a threshold value set in advance, and the pulse electric field strength is maintained to be above the effective electric field strength threshold.

[0027] The electrical resistance of the processing solution during pulsed electric field processing is not uniform. When the object being processed is a liquid, the electrical resistance fluctuates due to variations in concentration, and when the object being processed is a solid, the electrical resistance fluctuates depending on the amount of object being processed passing through the liquid tank. If the resistance of the processing solution decreases during pulsed electric field processing, the pulse voltage decays more rapidly, and the intensity of the pulsed electric field decreases. In pulsed electric field processing, it is necessary to generate a pulsed electric field above the effective electric field strength threshold. If the pulsed electric field falls below the effective electric field strength threshold, the degree of sterilization and softening will be insufficient, and the object being processed will become a defective product due to insufficient processing. Therefore, continuing pulsed electric field processing under conditions that result in insufficient processing of the object will waste energy.

[0028] In the pulse electric field processing device 2 according to Embodiment 1, if the absolute value of the voltage applied by the pulse power supply 23 to the electrode pair 22 falls below a threshold, the control unit 24 activates the positive electrode side submodule 233 to compensate for the absolute value of the voltage applied by the pulse power supply 23 to the electrode pair 22 to be above the threshold, thereby setting the pulse electric field strength to be above the effective electric field strength threshold. Therefore, the pulse electric field processing device 2 according to Embodiment 1 does not continue pulse electric field processing under conditions where the object to be processed is under-processed. Accordingly, by using the food manufacturing system 100 equipped with the pulse electric field processing device 2 according to Embodiment 1, it is possible to manufacture food that has been subjected to sufficient pulse electric field processing.

[0029] On the other hand, in the pulse electric field processing device 2 according to Embodiment 1, during negative discharge, the negative electrode side submodule 235 discharges continuously. At this time, the pulse electric field processing device 2 performs negative discharge so that the positive discharge energy and negative discharge energy per unit time are equal. Furthermore, if the pulse electric field processing device 2 enables the positive electrode side submodule 233 during positive discharge and the absolute value of the voltage applied by the pulse power supply 23 to the electrode pair 22 is above a threshold, the pulse electric field processing device 2 performs negative discharge so that the positive discharge energy and negative discharge energy per unit time are equal, including the discharge from the positive electrode side submodule 233. As the pulse power supply 23 performs positive and negative discharge, the electrode pair 22 installed in the processing chamber 21 alternately becomes the anode and cathode. As a result, in the electrode pair 22 installed in the processing chamber 21, the components of the electrode that dissolved during positive discharge are deposited during negative discharge, thus suppressing electrolysis of the electrode pair 22.

[0030] The pulse electric field processing device 2 according to Embodiment 1 suppresses electrolysis of the electrode pair 22 associated with pulse electric field processing, thus reducing the maintenance frequency of the electrode pair 22. Furthermore, since the pulse electric field processing device 2 according to Embodiment 1 performs negative discharge only in the negative electrode side submodule 235, the number of unit modules in the entire pulse power supply 23 can be reduced, enabling miniaturization.

[0031] Embodiment 2. Figure 10 shows the circuit configuration of the pulse power supply of the pulse electric field processing device according to Embodiment 2. The pulse electric field processing device 2 according to Embodiment 2 differs from the pulse electric field processing device 2 according to Embodiment 1 in that the pulse power supply 23 includes a negative electrode side main module 234. In addition, the pulse electric field processing device 2 according to Embodiment 2 has a negative electrode side submodule 235 which is composed of one negative electrode side unit module 50. The negative electrode side unit module 50 that constitutes the negative electrode side main module 234 and the negative electrode side unit module 50 that constitutes the negative electrode side submodule 235 have the same circuit configuration, but the capacitance of the capacitor 54 is different. The capacitance of the capacitor 54 of the negative electrode side unit module 50 that constitutes the negative electrode side submodule 235 is larger than the capacitance of the capacitor 54 of the negative electrode side unit module 50 that constitutes the negative electrode side main module 234.

[0032] Figure 11 shows the energized state of the pulse electric field processing device according to Embodiment 2 during charging. The arrows in Figure 11 indicate the flow of current. The positive electrode switches 41, 51 and the negative electrode switches 42, 52 are in the ON state, and the discharge switches 43, 53 are in the OFF state. Therefore, the capacitors 44 of each positive electrode unit module 40 and the capacitors 54 of the negative electrode unit module 50 are connected in parallel with each other. The charging current supplied from the charging power supply 231 charges the capacitors 44 sequentially, starting with the positive electrode unit module 40 closest to the charging power supply 231, followed by the charging of the capacitors 54 of the negative electrode unit module 50. The capacitors 44, 54 are charged until the voltage across them becomes equal to the voltage of the charging power supply 231.

[0033] Figure 12 shows the energized state of the pulse electric field processing device according to Embodiment 2 during positive discharge. The arrows in Figure 12 indicate the flow of current. Of the positive electrode unit modules 40 constituting the positive electrode main module 232, the positive electrode unit module 40 closest to the charging power supply 231 has the positive electrode wire switch 41 and the discharge switch 43 in the OFF state, and the negative electrode wire switch 42 in the ON state. On the other hand, of the positive electrode unit modules 40 constituting the positive electrode main module 232, all positive electrode unit modules 40 other than the one closest to the charging power supply 231 have the positive electrode wire switch 41 and the negative electrode wire switch 42 in the OFF state, and the discharge switch 43 in the ON state. In addition, of the positive electrode unit modules 40 constituting the positive electrode submodule 233, the positive electrode wire switch 41 and the negative electrode wire switch 42 are in the ON state, and the discharge switch 43 is in the OFF state. Furthermore, in the negative electrode unit modules 50 that constitute the negative electrode main module 234 and the negative electrode sub-module 235, the positive electrode wire switch 51 and the negative electrode wire switch 52 are in the ON state, and the discharge switch 53 is in the OFF state. For this reason, the capacitors 44 of the positive electrode unit modules 40, except for the one closest to the charging power supply 231, are connected in series. Consequently, the load 70 receives a positive discharge pulse with a voltage whose absolute value is less than or equal to the voltage of the charging power supply 231 multiplied by (N-1), which is one less than the number N of the positive electrode unit modules 40.

[0034] Figure 13 shows the energized state of the pulse electric field processing device according to Embodiment 2 during negative discharge. The arrows in Figure 13 indicate the flow of current. The positive electrode unit module 40 constituting the positive electrode main module 232 has the positive electrode wire switch 41 and the negative electrode wire switch 42 in the ON state, and the discharge switch 43 in the OFF state. The positive electrode unit module 40 constituting the positive electrode submodule 233 has the positive electrode wire switch 41 and the negative electrode wire switch 42 in the ON state, and the discharge switch 43 in the OFF state. The negative electrode unit module 50 constituting the negative electrode submodule 235 has the positive electrode wire switch 51 and the negative electrode wire switch 52 in the OFF state, and the discharge switch 53 in the ON state. A negative discharge pulse is output to the load 70 with a voltage value whose absolute value is less than or equal to the voltage of the charging power supply 231 multiplied by a value that is one less than (M-1) than the number M of the negative electrode unit module 50 constituting the negative electrode main module 234.

[0035] Figure 14 shows the energized state during positive discharge when the positive electrode side submodule of the pulse electric field processing device according to Embodiment 2 is enabled. The arrows in Figure 14 indicate the flow of current. By enabling the positive electrode side submodule 233, the capacitor 44 of the positive electrode side unit module 40 that constitutes the positive electrode side submodule 233 is connected in series with the capacitor 44 of the positive electrode side unit module 40 that constitutes the positive electrode side main module 232. As a result, during positive discharge with the positive electrode side submodule 233 enabled, the absolute value of the voltage applied by the pulse power supply 23 to the electrode pair 22 is complemented by the positive electrode side submodule 233 to be above a threshold, and the pulse electric field strength is maintained above the effective electric field strength threshold.

[0036] Figure 15 shows the energized state during negative discharge when the negative electrode side submodule of the pulse electric field processing device according to Embodiment 2 is enabled. The arrows in Figure 15 indicate the flow of current. By enabling the negative electrode side submodule 235, the capacitor 54 of the negative electrode side unit module 50 that constitutes the negative electrode side submodule 235 is connected in series with the capacitor 54 of the negative electrode side unit module 50 that constitutes the negative electrode side main module 234. As a result, during negative discharge with the negative electrode side submodule 235 enabled, the absolute value of the voltage applied by the pulse power supply 23 to the electrode pair 22 is complemented by the negative electrode side submodule 235 to be above a threshold, and the pulse electric field strength is maintained above the effective electric field strength threshold.

[0037] Figure 16 is a waveform diagram of the voltage pulse output by the pulse power supply of the pulse electric field processing device according to Embodiment 2. In the example shown in Figure 16, at time T2, the absolute value of the voltage applied by the pulse power supply 23 to the electrode pair 22 in positive discharge is below a preset threshold. The control unit 24 monitors the voltage measured by the voltage measurement unit 236, and when the absolute value of the voltage applied by the pulse power supply 23 to the electrode pair 22 in positive discharge falls below the threshold, it activates the positive electrode side submodule 233 to supplement the pulse voltage and restores the absolute value of the voltage applied by the pulse power supply 23 to the electrode pair 22 to above the preset threshold. That is, when the absolute value of the voltage applied by the pulse power supply 23 to the electrode pair 22 in positive discharge falls below a preset threshold, the control unit 24 turns off the positive electrode line switch 41 and the negative electrode line switch 42 of the positive electrode side unit module 40 that constitute the positive electrode side submodule 233, and turns on the discharge switch 43. Furthermore, in the example shown in Figure 16, at time T3, the absolute value of the voltage applied by the pulse power supply 23 to the electrode pair 22 via negative discharge falls below a preset threshold. The control unit 24 monitors the voltage measured by the voltage measurement unit 236, and when the absolute value of the voltage applied by the pulse power supply 23 to the electrode pair 22 via negative discharge falls below a preset threshold, it activates the negative electrode submodule 235 to supplement the pulse voltage and restores the absolute value of the voltage applied by the pulse power supply 23 to the electrode pair 22 via negative discharge to above a preset threshold. That is, when the absolute value of the voltage applied by the pulse power supply 23 to the electrode pair 22 via negative discharge falls below a preset threshold, the control unit 24 turns off the positive electrode switch 51 and the negative electrode switch 52 of the negative electrode unit module 50 that constitute the negative electrode submodule 235, and turns on the discharge switch 53.

[0038] As described above, in the pulse electric field processing device 2 according to Embodiment 2, if the pulse voltage or pulse electric field strength falls below the effective electric field strength threshold voltage during positive discharge, the control unit 24 activates the positive electrode side submodule 233 to supplement the pulse voltage and raise the pulse electric field strength to above the effective electric field strength threshold. Furthermore, in the pulse electric field processing device 2 according to Embodiment 2, if the pulse voltage or pulse electric field strength falls below the effective electric field strength threshold voltage during negative discharge, the control unit 24 activates the negative electrode side submodule 235 to supplement the pulse voltage and raise the pulse electric field strength to above the effective electric field strength threshold. In other words, the pulse electric field processing device 2 according to Embodiment 2 prevents the pulse electric field processing from continuing under conditions that would result in insufficient processing of the object to be processed, both during positive and negative discharge.

[0039] Furthermore, the pulse electric field processing device 2 according to Embodiment 2 performs positive and negative discharges such that the positive discharge energy and negative discharge energy per unit time are equal. In addition, if the pulse electric field processing device 2 performs voltage supplementation during at least one of the positive and negative discharges, it performs positive and negative discharges such that the positive discharge energy and negative discharge energy per unit time are equal, including the discharge from the positive electrode submodule 233 and the negative electrode submodule 235.

[0040] Furthermore, it is sufficient that the positive discharge energy and negative discharge energy per unit time are equal; it is not necessary to alternate between positive and negative discharge. In other words, as long as the positive discharge energy and negative discharge energy per unit time are equal, the pulse field processing device 2 may output at least one of the positive discharge pulse and the negative discharge pulse two or more times in a row.

[0041] The pulse electric field processing device 2 according to Embodiment 2 performs pulse electric field processing so that the positive discharge energy and negative discharge energy per unit time are equal, thereby suppressing electrolysis of the electrode pair 22 and reducing the frequency of maintenance of the electrode pair 22.

[0042] Note that, here, an operation of performing pulsed discharge both during positive discharge and negative discharge is taken as an example. However, in either positive discharge or negative discharge, continuous discharge may be performed from the positive electrode side sub-module 233 or the negative electrode side sub-module 235, similar to the negative discharge of the pulsed electric field treatment apparatus 2 according to the first embodiment. In pulsed electric field treatment, heat is generated during the treatment. Therefore, if the treatment becomes excessive, the object to be treated may be heated, and the physical properties of the object to be treated may change. For example, when performing pulsed electric field treatment for the purpose of sterilizing an object to be treated that is a solid food, if the pulsed electric field treatment is excessive, the object to be treated may be heated and its physical properties may change, and the texture may deteriorate. For this reason, also in the pulsed electric field treatment apparatus 2 according to the second embodiment, by performing pulsed electric field treatment only in one of positive discharge and negative discharge, electrolysis of the electrode pair 22 can be suppressed without excessively performing pulsed electric field treatment on the object to be treated, and the maintenance frequency can be suppressed.

[0043] Embodiment 3. FIG. 17 is a diagram showing the configuration of a food manufacturing system using the pulsed electric field treatment apparatus according to Embodiment 3. The pulsed electric field treatment apparatus 2 according to Embodiment 3 is different from the pulsed electric field treatment apparatus 2 according to Embodiment 1 in that it includes a speed sensor 27 that measures the conveyance speed of the object to be treated. In Embodiment 3, since the object to be treated is a liquid and the object to be treated itself becomes the treatment liquid, the speed sensor 27 is a flow meter that measures the speed of the treatment liquid passing through the treatment chamber 21.

[0044] If the speed at which the object to be treated passes through the treatment chamber 21 is too fast, the number of voltage pulses contributing to the pulsed electric field treatment will decrease while the object to be treated is present in the treatment chamber 21, so there is a possibility that the pulsed electric field treatment will be insufficient. On the other hand, if the speed at which the object to be treated passes through the treatment chamber 21 is too slow, the number of voltage pulses contributing to the pulsed electric field treatment will increase while the object to be treated is present in the treatment chamber 21, so the treatment may become excessive and the object to be treated may be overheated.

[0045] Therefore, in the pulse electric field processing device 2 according to Embodiment 3, the pulse frequency is changed according to the transport speed of the object to be processed, and the number of voltage pulses contributing to the pulse electric field processing while the object to be processed is in the processing chamber 21 is kept within a preset range. As a result, the pulse electric field processing device 2 according to Embodiment 3 can prevent insufficient or excessive pulse electric field processing on the object to be processed.

[0046] Next, the hardware configuration of the control unit 24 of the pulse electric field processing device 2 will be described. Figure 18 is a diagram showing an example of the hardware configuration for realizing the control unit of the pulse electric field processing device according to Embodiment 1, Embodiment 2, and Embodiment 3. The control unit 24 is realized as a computer system by a processing circuit that includes a processor 91 that performs various processes, a memory 92 which is the main memory, and a storage device 93 that stores information.

[0047] The processor 91 may be an arithmetic unit, microprocessor, microcomputer, CPU (Central Processing Unit), or DSP (Digital Signal Processor). The memory 92 may be a non-volatile or volatile semiconductor memory such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), or EEPROM® (Electrically Erasable Programmable Read Only Memory). The storage device 93 stores a program for executing the process of controlling the pulse power supply 23. The processor 91 reads the program stored in the storage device 93 into the memory 92 and executes it. The functions of the control unit 24 are realized when the processor 91 reads the program stored in the storage device 93 into the memory 92 and executes it.

[0048] The configurations shown in the above embodiments are examples of the content, and it is possible to combine them with other known technologies, and it is also possible to omit or change part of the configuration without departing from the gist.

[0049] 1 Process management device, 2 Pulse electric field treatment device, 3 Pre-treatment tank, 4 Post-treatment tank, 21 Treatment chamber, 22 Electrode pair, 23 Pulse power supply, 24 Control unit, 25 First temperature adjustment unit, 26 Second temperature adjustment unit, 27 Speed sensor, 28 Voltage sensor, 40 Positive electrode side unit module, 41, 51 Positive electrode line switches, 42, 52 Negative electrode line switches, 43, 53 Discharge switches, 44, 54 Capacitors, 49, 59 Semiconductor switches, 50 Negative electrode side unit module, 61 Positive electrode line, 62 Negative electrode line, 70 Load, 91 Processor, 92 Memory, 93 Storage device, 100 Food manufacturing system, 231 Charging power supply, 232 Positive electrode side main module, 233 Positive electrode side sub-module, 234 Negative electrode side main module, 235 Negative electrode side sub-module, 236 Voltage measurement unit.

Claims

1. The apparatus comprises an electrode pair installed in a processing chamber through which an object to be processed passes, a pulse power supply that outputs a voltage pulse of a first polarity, which is either positive or negative polarity, and a voltage pulse of a second polarity, which is the opposite polarity to the first polarity, to the electrode pair, a control unit that controls the pulse power supply, and a voltage sensor that measures the voltage applied by the pulse power supply to the electrode pair, wherein the pulse power supply has a first polarity main module and a first polarity sub-module that output a voltage pulse of the first polarity, and a second polarity sub-module that outputs a voltage pulse of the second polarity, and the control unit causes the pulse power supply to output the voltage pulse using only the first polarity main module when discharging with the first polarity, and when the absolute value of the voltage applied by the pulse power supply to the electrode pair falls below a preset threshold during pulse discharge with the first polarity using only the first polarity main module, the control unit causes the pulse power supply to output the voltage pulse using both the first polarity main module and the first polarity sub-module. A pulse electric field processing device characterized in that, when discharge in the second polarity, the pulse power supply outputs the voltage pulse of the second polarity such that the discharge energy of the first polarity per unit time is equal to the discharge energy of the second polarity.

2. The pulse electric field processing device according to claim 1, wherein the first polarity main module and the first polarity submodule are composed of first polarity unit modules equipped with a first capacitor that outputs a voltage pulse of the first polarity by discharge, the first polarity main module is composed of a plurality of first polarity unit modules connected in series, and the first capacitor of the first polarity unit module constituting the first polarity submodule has a larger capacitance than the first capacitor of the first polarity unit module constituting the first polarity main module.

3. The pulse electric field processing apparatus according to claim 1 or 2, wherein the pulse power supply has a second polarity main module that outputs a voltage pulse of the second polarity, and the control unit causes the pulse power supply to output the voltage pulse using only the second polarity main module when discharging in the second polarity, and causes the pulse power supply to output the voltage pulse using both the second polarity main module and the second polarity sub-module when the absolute value of the voltage applied by the pulse power supply to the electrode pair falls below a preset threshold during pulse discharge in the second polarity using only the second polarity main module.

4. The pulse electric field processing apparatus according to claim 3, wherein the second polarity main module and the second polarity submodule are composed of second polarity unit modules equipped with a second capacitor that outputs a voltage pulse of the second polarity by discharge, the second polarity main module is composed of a plurality of the second polarity unit modules connected in series, and the second capacitor of the second polarity unit module constituting the second polarity submodule has a larger capacitance than the second capacitor of the second polarity unit module constituting the second polarity main module.

5. The pulse electric field processing apparatus according to any one of claims 1 to 4, comprising a speed sensor for measuring the speed of the object to be processed passing through the processing chamber, wherein the control unit changes the output period of the voltage pulse based on the measurement value of the speed sensor.

6. A method for manufacturing food products, comprising a pulse power supply having a first polarity main module and a first polarity submodule that output voltage pulses of a first polarity which is positive or negative, and a second polarity submodule that outputs voltage pulses of a second polarity which is the opposite polarity to the first polarity, wherein a pulse electric field treatment is performed on an electrode pair installed in a processing chamber by applying a pulse voltage from the pulse power supply, the method comprising: a first step of causing the pulse power supply to output the voltage pulse only with the first polarity main module when discharging with the first polarity; and a second step of outputting the voltage pulse of the second polarity when discharging with the second polarity such that the discharge energy of the first polarity per unit time and the discharge energy of the second polarity are equal, wherein in the first step, if the absolute value of the voltage applied by the pulse power supply to the electrode pair falls below a preset threshold, the pulse power supply is caused to output the voltage pulse with both the first polarity main module and the first polarity submodule.

7. The method for manufacturing food according to claim 6, wherein the pulse power supply has a second polarity main module that outputs a voltage pulse of the second polarity, and in the second step, the pulse power supply is made to output the voltage pulse using only the second polarity main module, and in the second step, if the absolute value of the voltage applied by the pulse power supply to the electrode pair falls below the preset threshold, the pulse power supply is made to output the voltage pulse using both the second polarity main module and the second polarity sub-module.

8. The method for producing food according to claim 6 or 7, characterized in that the pulse period of the voltage pulse is changed according to the speed of the object to be processed passing through the processing chamber.

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