JP2000262261A - Sterilization with high electrical field pulse, and devic therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for sterilizing even relatively stubborn germ. SOLUTION: This method sterilizes germ by the aid of a device, which is provided with a flat plate 3a of an insulating material having, at the center, a through-hole 1 of sufficiently large diameter to contain a liquid 8 to be sterilization-treated, and fine pore 2 bored from the upper side of the flat plate 3a to run to and open to the upper side of the through-hole 1, wherein the fine pore 2 serves as the spacer 3 and sterilization container. The electrodes 4 for applying an electrical field are provided on both sides of the spacer 3 in such a way to close both ends of the through-hole 1, and to form a high electrical field applying region 5 between the inner peripheral area of the through-hole 1 and electrodes 4 for applying an electrical field. High-voltage pulses are generated by a short pulse generator 6, which is connected to the electrodes 4, and the high electrical field pulses are applied to the liquid 8 to be sterilization-treated, positioned in the high electrical field applying region 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for sterilizing high electric field pulses used for sterilizing liquids such as beverages, and more particularly to a method for sterilizing relatively robust spores such as heat-resistant bacteria. The present invention relates to a high-field pulse sterilization method and apparatus.

[0002]

2. Description of the Related Art As one of sterilization methods for liquids such as beverages, a liquid to be sterilized is disposed between a pair of electrodes arranged to face each other, and a high electric field pulse is applied between the electrodes to generate a relatively long pulse of 100 ns or more. By applying the pulse with the width of the pulse waveform and causing a shock wave or an electric field generated by the high electric field pulse to act on the microorganisms in the liquid to be sterilized,
A high-field pulse sterilization method has been already proposed in which the liquid to be sterilized is sterilized by causing physical damage to destroy the NA and the membrane (Japanese Patent Application Laid-Open No. 62-151).
174, JP-A-1-95751).

In the above-mentioned high electric field pulse sterilization method, generally, as shown in FIG. 3, the relationship between the electric field intensity of the applied high electric field pulse and the survival rate of the bacterium has the same pulse width (for example, 1 pulse width).
0 μs) and the same number of shots (for example, 100 shots)
In the case of ts), it has been confirmed that as the electric field intensity of the high electric field pulse applied to the liquid to be sterilized increases, the viability rate decreases, that is, the sterilizing effect increases.

[0004]

However, in the conventional high electric field pulse sterilization method, when a high electric field pulse is generated, a high electric field pulse having a relatively long pulse width of 100 ns or more is generated. If you try to increase the electric field strength of the high electric field pulse for the purpose of enhancing the sterilization effect, dielectric breakdown due to abnormal discharge (discharge of the entire discharge path)
Therefore, the electric field strength cannot be made too high, and therefore, the bactericidal effect cannot be made so high. Therefore, it is relatively robust such as Bacillus stearothermophilus which is a heat-resistant bacterium. There is a problem that it is not possible to sterilize various spores, and when sterilization is performed, it is easy to cause a change in the quality of not only microorganisms but also the liquid to be sterilized itself. There is also a problem that it is easy to cause.

Accordingly, the present invention is to provide a high-field pulse sterilization method and apparatus which can perform relatively robust sterilization treatment of spores as described above without causing deterioration or temperature rise of the liquid to be sterilized. It is assumed that.

[0006]

According to the present invention, in order to solve the above problems, a liquid to be sterilized is arranged in a high electric field application region formed between electric field application electrodes facing each other at a required interval, and the high electric field is applied. Set the rise time to 1 for the liquid to be sterilized in the application area.
00 ps to less than 20 ns, pulse width less than 100 ns,
A sterilization method is performed by applying a high electric field pulse having a fall time of 100 ps to 100 ns or less and an electric field intensity of 30 to 300 kV / cm, and both sides of a space in which a liquid to be sterilized can be stored. A pair of flat electric field applying electrodes facing each other at a required interval, a high electric field applying area between the electric applying electrodes, and a short pulse for applying a high electric field pulse to the high electric field applying area. An apparatus including a generator.

When a high electric field pulse is applied to the liquid to be sterilized injected into the high electric field application area, the microorganisms in the liquid to be sterilized are physically separated by a shock wave and an electric field generated by the applied high electric field pulse. Damage is given,
Will be sterilized. At this time, the applied high electric field pulse can end the pulse in a time before the dielectric breakdown due to the abnormal discharge, and can greatly reduce the occurrence of the abnormal discharge that causes the dielectric breakdown. The electric field strength of the high-voltage pulse applied can be increased without causing the above.

[0008] Further, the liquid to be sterilized disposed in the insulator container is irradiated with a microwave having a frequency of at least 50 MHz or more, so that the liquid to be sterilized has a high electric field intensity of 30 to 300 kV / cm. A method in which a pulse is applied to sterilize, and a high electric field application area is provided outside the insulator container which is configured to accommodate a liquid to be sterilized, and the high electric field application area has at least 50 MHz.
As described above, an apparatus provided with a microwave generator for applying an electric field generated by a microwave having a certain frequency.

When a microwave generated by a microwave generator is applied to a high electric field application region, a high electric field pulse is generated in the high electric field application region because the microwave is a spatially propagating wave including an electric field and a magnetic field. Thus, a high electric field pulse is applied to the liquid to be sterilized in the high electric field application region, and physical damage is given to microorganisms in the liquid to be sterilized.
At this time, the frequency of 50 MHz or more in the microwave is 10 ns at the maximum in the applied high electric field pulse.
Since the pulse width is equivalent to a short pulse width, the electric field intensity of the high electric field pulse applied without causing dielectric breakdown can be increased.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 (a) and (b) show an embodiment of the high electric field pulse sterilization method and apparatus according to the present invention. The flat plate 3a made of an insulator having a required plate thickness, for example, a thickness of 5 mm.
A through-hole 1 is provided at the center of the plate, the size of the through-hole 1 being large enough to hold a liquid to be sterilized. 2, a spacer 3 is formed as a sterilization container through which the liquid to be sterilized is put into one through-hole through the fine hole 2, and the above-described through-hole 1 is formed on both side surfaces of the central portion of the spacer 3. The plate-shaped electric field applying electrodes 4 are respectively symmetrically arranged in contact with both side surfaces of the spacer 3 so as to be closed from both sides, and are formed between the inner peripheral surface of the through hole 1 and both electric field applying electrodes 4. A space portion to be formed is a high electric field application region 5, and a short pulse generator 6 for generating a voltage pulse having a required pulse width and a required intensity on each of the electric field application electrodes 4 is connected via a wiring 7. Connected configuration,
The liquid 8 to be sterilized is injected into the high-voltage application area 5 through the pores 2 of the spacer 3 and the short pulse generator 6
The voltage pulse generated in step (1) is led to each of the electric field applying electrodes 4 through the wiring 7, so that the rising time of the liquid 8 to be sterilized disposed between the electric field applying electrodes 4 is reduced by one.
00 ps to less than 20 ns, pulse width less than 100 ns,
A high electric field pulse with a fall time of 100 ps to 100 ns or less and an electric field intensity of 30 to 300 kV / cm is applied.

Each of the electric field applying electrodes 4 is formed in a disk shape having a diameter larger than the diameter of the through hole 1 of the spacer 3, and a round projection 4 a is formed on the outer peripheral edge of the surface on the side opposite to the spacer 3.
Is formed so that a uniform electric field can be generated between the two electric field applying electrodes 4.

The wiring 7 is made of a copper plate having a thickness of up to about 1 mm.
The physical and three-dimensional structural distance between the wiring 7 and the short pulse generator 6 is reduced as much as possible, and the inductance, capacitance and pure resistance of the wiring 7 are reduced so that the impedance becomes low.

Reference numeral 9 denotes a housing for holding the spacer 3 and the electric field applying electrodes 4 integrally by a pair of supporting devices 10 provided on the facing surface.

When sterilizing the liquid 8 to be sterilized, the liquid 8 to be sterilized is first injected into the high electric field application region 5 of the through hole 1 through the fine holes 2 of the spacer 3, and then the short pulse generator 6 is used. To generate a voltage pulse to apply the high electric field pulse to the liquid 8 to be sterilized in the high electric field application region 5. As a result, the shock wave or the electric field generated by the applied high electric field pulse causes physical damage such as destroying the DNA or cell membrane of the microorganisms in the liquid 8 to be sterilized, thereby sterilizing the liquid.

In the above, the applied high electric field pulse has a rise time of 100 ps to less than 20 ns, a pulse width of less than 100 ns, and a fall time of 100 ps to 100 ps.
It is set to 100 ns or less. Here, in a pair of parallel plate electrodes generally provided with a gap length of 5 mm, tens of ns means that electrons emitted by discharge from one plate electrode move to reach the other plate electrode. The high electric field pulse used in the present invention terminates the pulse to be applied before the dielectric breakdown due to abnormal discharge, that is, before the entire discharge breakdown occurs, since it is only in the time unit of the region of whether or not. And therefore
Since the possibility of occurrence of abnormal discharge that causes dielectric breakdown can be significantly reduced, the electric field strength of the high-voltage pulse applied without causing dielectric breakdown can be increased.

As described above, since a high electric field pulse having a higher electric field intensity can be applied to the liquid 8 to be sterilized as compared with the related art, the intensity of physical damage to the microorganisms in the liquid 8 to be sterilized is increased. It is possible to sterilize relatively robust spores such as Bacillus stearothermophilus that could not be sterilized by the conventional high electric field pulse sterilization method, and to increase the electric field intensity of the high electric field pulse. Accordingly, a high sterilizing effect can be obtained even if the pulse width is shortened. Therefore, the total time required for applying an electric field to the liquid 8 to be sterilized, which is required to obtain a sterilizing effect equivalent to the conventional one, is shortened. It is possible to perform the sterilization treatment without heating, and since the pulse width of the high electric field pulse is shortened, the time for the electrons and ions in the liquid 8 to be sterilized to move is reduced. No longer, therefore it can restrict the electronic and ionic movement and reaction, sterilized liquid 8
Deterioration of itself can be prevented.

By the way, the reason why the electric field intensity of the high electric field pulse applied to the liquid 8 to be sterilized is 30 to 300 kV / cm is that when the electric field exceeds 300 kV / cm in the air, the insulation is performed even if the pulse width is less than 100 ns. It is difficult to prevent destruction, and the apparatus is not practical with the current technology. On the other hand, when the pressure is 30 kV / cm or less, it is possible to effectively apply physical damage to microorganisms to sterilization. This is because spores cannot be sterilized.

Next, FIG. 2 shows another embodiment of the present invention, in which ceramics having a required length so as to accommodate a liquid 8 to be sterilized flowing at a predetermined flow rate from one direction for a predetermined time. On the outer periphery of a tube 11 as an insulating container made of glass, plastic, or the like, a large-diameter conductor resonance cavity 12 surrounding an intermediate portion of the tube 11, and a small-diameter conductor waveguide surrounding both ends of the tube 11, respectively. 13 are arranged coaxially and connected integrally, and the resonance cavity 12 and the tube 1 are connected together.
The space formed between the first and second intermediate portions is a high electric field application region 14.
The microwave input unit 17 for guiding the microwave 16 from the microwave generator 15 is provided, and the microwave 16 having a certain frequency of at least 50 MHz generated by the microwave generator 15 is supplied to the microwave input unit 17. The electric field intensity of the liquid to be sterilized 8 guided to the high electric field application region 14 through the tube 11 by the microwave 16 is increased by 30 to 300 k.
A high electric field pulse of V / cm is applied.

When sterilization is performed using the apparatus of the present embodiment, first, the microwave 16 generated by the microwave generator 15 is supplied to the tube 11 while the liquid 8 to be sterilized is passed through the tube 11 at a predetermined speed. When input into the resonance cavity 12 via the wave input unit 17, the microwave 16
Is a spatially propagating wave including an electric field and a magnetic field, and is focused by the waveguide 13 and the resonance cavity 12 so as to generate a high electric field pulse in the high electric field application area 14, and therefore, the inside of the high electric field application area As a result, a high electric field pulse is sequentially applied to the liquid 8 to be sterilized flowing in the tube 11, thereby causing physical damage to the microorganisms in the liquid 8 to be sterilized as in the above embodiment. As a result, the liquid 8 to be sterilized is continuously sterilized.

At this time, 50 MHz in the microwave 16
Since a frequency of z or more corresponds to a short pulse width of about 10 ns at the maximum in an applied high electric field pulse, the electric field intensity of the high electric field pulse applied without causing dielectric breakdown can be increased. it can.

Therefore, according to the present embodiment, the same effect as in the above embodiment can be obtained.

The present invention is not limited to the above embodiment. In the embodiment shown in FIGS. 1A and 1B, the high electric field application region 5 is different from the through hole 1 provided in the spacer 3. Although it is shown as being formed by a pair of electric field applying electrodes 4 having a Rogowski electrode structure, the liquid 8 to be sterilized is opposed for a predetermined time between the pair of electric field applying electrodes for generating a uniform electric field at a predetermined interval. If it can be arranged, the high electric field application region 5 may be formed freely, and the interval between the pair of electric field application electrodes 4 is determined by the electric field intensity of the desired high electric field pulse and the short pulse generator. May be freely determined according to the voltage of the voltage pulse generated in
Further, in the embodiment of FIG. 2, in order to form a high electric field application region 14, a microwave 13 is provided by providing a waveguide 13 and a continuous resonance cavity 12 on the outer periphery of a tube 11 through which the liquid 8 to be sterilized passes. The microwaves 1 were condensed, but the microwaves 1 were placed in an insulating container that contained the liquid 8 to be sterilized for a predetermined time.
If it is possible to focus and irradiate 6, an open-type resonant cavity or a traveling-wave tube may be used, and an antenna such as a dipole or a parabola is installed in a large room and directed toward a container for containing a liquid to be sterilized. The bacteriostatic action that suppresses the microbial activity can be achieved by controlling the pulse width of the high electric field pulse, the electric field intensity, the number of shots, and the like to act on the microorganisms. Thus, it can be applied to long-term preservation of food, control of fermentation, and brewing, and, of course, various changes can be made without departing from the gist of the present invention.

[0024]

EXAMPLES The results of experiments conducted by the present inventors will be described.

Example 1 A Bacillus stearothermophilus (A) was used as a sample of the liquid 8 to be sterilized in the high electric field application region of the apparatus shown in FIG.
By injecting a culture solution of TCC # 12980) and applying a voltage pulse generated by a short pulse generator to the electric field application electrode, the rise time of the sample is reduced by one.
A high electric field pulse of ns, a pulse width of 80 ns, a fall time of 2 ns, and an electric field intensity of 120 kV / cm was applied with a shot number of 10,000 shots.

This example confirmed the bactericidal effect on Bacillus stearothermophilus in the sample.

[0027]

As described above, according to the high electric field pulse sterilization method and apparatus of the present invention, the liquid to be sterilized is disposed in the high electric field application region formed between the electric field application electrodes facing each other at a required interval. The liquid to be sterilized in the high electric field application region has a rise time of less than 100 ps to less than 20 ns and a pulse width of 10
Less than 0 ns, fall time from 100 ps to 100 ns
The following, and a method of applying a high electric field pulse with an electric field strength of 30 to 300 kV / cm to perform sterilization, and
A pair of flat electric field applying electrodes facing each other at a required interval are disposed on both sides of a space portion capable of accommodating a liquid to be sterilized, and a high electric field applying region is provided between the electric field applying electrodes, and the high electric field The apparatus is provided with a short pulse generator for applying a high electric field pulse to an application area, and at least 50% of liquid to be sterilized is disposed in an insulating container.
By irradiating a certain microwave as a frequency above MHz,
An electric field strength of 30 to 300 kV / c is applied to the liquid to be sterilized.
m to apply a high electric field pulse to sterilize,
And, on the outside of the insulator container that is configured to accommodate the liquid to be sterilized, a high electric field application region is provided, and the high electric field application region is at least 50 MHz or more for applying an electric field by a microwave having a certain frequency or more. Since the device is equipped with a microwave generator, it is possible to increase the electric field strength of the high-voltage pulse applied without causing dielectric breakdown. Is applied to the liquid to be sterilized to increase the intensity of physical damage to the microorganisms in the liquid to be sterilized, and sterilization of relatively robust spores that could not be sterilized by the conventional high-field pulse sterilization method Can be performed, and by increasing the electric field strength of the high electric field pulse, a high sterilizing effect can be obtained even if the pulse width is shortened. The total amount of time during which an electric field is applied can be made shorter than before, sterilization can be made non-heating, and movement and reactions of electrons and ions can be restricted. And an excellent effect of preventing deterioration of the liquid to be sterilized itself.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the high electric field pulse sterilization method and apparatus of the present invention, wherein (a) is a schematic cut front view,
(B) is an AA arrow view of (A).

FIG. 2 is a partially cutaway schematic perspective view showing another embodiment of the present invention.

FIG. 3 is a graph showing the relationship between the electric field intensity of an applied high electric field pulse and the survival rate of bacteria in the high electric field pulse sterilization method.

[Explanation of symbols]

 4 Electric field application electrode 5 High electric field application area 6 Short pulse generator 8 Liquid to be sterilized 11 Tube (insulator container) 15 Microwave generator 16 Microwave

Claims (4)

[Claims] 1. A liquid to be sterilized is disposed in a high electric field application region formed between electric field application electrodes facing each other at a required interval, and the liquid to be sterilized in the high electric field application region has a rise time of 1 hour.
00 ps to less than 20 ns, pulse width less than 100 ns,
A high electric field pulse sterilization method characterized by applying a high electric field pulse having a fall time of 100 ps to 100 ns or less and an electric field intensity of 30 to 300 kV / cm to perform sterilization. 2. A liquid to be sterilized disposed in an insulator container is irradiated with a microwave having a frequency of at least 50 MHz or more, so that the liquid to be sterilized has an electric field intensity of 3 MHz.
A high electric field pulse sterilization method, wherein sterilization is performed by applying a high electric field pulse of 0 to 300 kV / cm. 3. A pair of flat electric field applying electrodes facing each other at a predetermined interval on both sides of a space portion capable of accommodating a liquid to be sterilized, and a space between the electric field applying electrodes is defined as a high electric field applying region. A high electric field pulse sterilizer comprising a short pulse generator for applying a high electric field pulse to the high electric field application region. 4. A high electric field application area is provided outside an insulator container adapted to contain a liquid to be sterilized, and an electric field by a microwave having a frequency of at least 50 MHz is applied to the high electric field application area. A high-field pulse sterilizer, comprising: a microwave generator for performing the method.