JP4209857B2 - Sterilization method - Google Patents

Description

The present invention has directed to a method of sterilization by irradiation with flash pulse flash lamp to emit food container tray or bat or lunch boxes, cooking utensils, food containers, daily necessities, to the sterilization object, such as medical and nursing care is there.

As a non-heated sterilization method for food containers, daily necessities, medical / care items, etc., a method of spraying a disinfectant is widely used. For example, at a lunch center, in order to prevent food corruption and prevent food poisoning, spray a disinfectant solution on the tray container of the lunch box, place the lunch box in this disinfected tray container, or disinfect the bat container that separates the lunch box material. The liquid is sprayed and the lunch box material is placed in this sterilized vat container.
However, in these disinfection methods, there are concerns about the effects of the disinfectant on the human body, and the vaporized material of the disinfectant may have a unique odor that may cause discomfort to humans, is flammable, and is safe. There is also a problem. In addition, there is a disadvantage that the work cost is considerably high.

Ultraviolet irradiation is known as one of the sterilization methods used in factories and the like.
As a typical example of this ultraviolet irradiation sterilization method, there are a method of irradiating radiation of a low-pressure mercury lamp (sterilization lamp) and a method of irradiating a flash pulse of a xenon flash lamp.
The germicidal lamp emits light having a main wavelength of 254 nm. A xenon flash lamp has a wavelength distribution from 200 nm to 2000 nm and emits light that includes an abundant ultraviolet wavelength region of 220 nm to 300 nm. In either case, sterilization is performed by damaging the bacterial DNA.
However, the sterilization lamp has weaker illuminance than the xenon flash lamp (instantaneously about 1/1000), and has recently been converted to sterilization of the xenon flash lamp.

In the flash operation of the xenon flash lamp, assuming that the flash discharge voltage of the xenon flash lamp is V, a capacitor charging voltage V is applied to the main discharge portion. flash pulse is generated at time intervals, power energy W per flash pulse, given by W = CV ^2/2.
Conventionally, in the xenon flash sterilization method, an ultraviolet irradiation means is installed in a storage (see, for example, Patent Document 1), an ultraviolet irradiation means is arranged in the middle of a conveyor line, and a workpiece being conveyed, for example, before carcass processing. It is used in the form of sterilizing the carnivorous soul (see Non-Patent Document 1), etc., the power energy per one flash pulse is large, the xenon flash lamp and the condenser are large, the tray container, bat or lunch box container It is difficult to apply to the sterilization of equipment.

  Patent Document 2 discloses that the half-wave value of the supply power waveform for one flash pulse is set to 60 μs to 2000 μs. In order to perform satisfactory sterilization under these conditions, the supply power energy per one flash pulse is disclosed. Is required to be at least 25 J. For the sterilization of the lunch box tray container, the food sorting bat or the lunch box container, the xenon flash lamp is too large to perform a handy sterilization process, and the intensity of reflected light is high. It is too strong and it is difficult to guarantee the safety of those who work near the tray container, bat or lunch box container.

FIG. 5 of JP-A-12-342626. Japanese Patent No. 3037936 Food machinery equipment, 2001-vol7, p48-54, flash pulse sterilizer

  The object of the present invention is to use a small xenon flash lamp with a supply power energy per flash pulse of 0.5 to 20 J, food container tray or bat or lunch box, food container, daily necessities, medical / nursing goods, etc. Is to enable sterilization with high sterilization efficiency.

The sterilization method according to claim 1 is a method of sterilizing an object to be sterilized moved on a belt conveyor by irradiation of a flash pulse from a flash lamp on the belt conveyor, and a power supply amount per pulse of 0.5 to 20 J And 30 to 120 flash pulses per second are generated and the half width of the supply power waveform per flash pulse is adjusted to 10 to 40 μs .

The sterilization method according to claim 2 is the sterilization method according to claim 1 , wherein the flash lamp is a xenon flash lamp.

The sterilization method according to claim 3 is characterized in that, in the sterilization method according to claims 1-2 , the object to be sterilized is a food container tray, a bat or a lunch box.

The sterilization method according to claim 4 is characterized in that, in the sterilization method according to claims 1 to 3 , the object to be sterilized is any one of a cooking utensil, a food container, a daily necessities, and medical / care items.

The sterilization method according to claim 5 is characterized in that in the sterilization method according to claims 1 to 4 , bacteria attached to an object to be sterilized are sterilized.

The half-value width of the supply power waveform per one flash pulse is set to 40 μs or less under the supply power energy 0.5 to 20 J per one flash pulse, and the sterilization efficiency can be made higher than when the half-value width exceeds 40 μs.
And since the number of flash pulses per second is set to 30 to 120, the power energy per flash pulse is small (0.5 to 20 J). The sterilization energy given by the product of the illuminance and the number of irradiations can be sufficiently increased to ensure a predetermined sterilization efficiency.
Further, since the power supply energy per one flash pulse is as low as 0.5 to 20 J, a sufficiently small flash lamp can be used because of shortening the discharge gap of the flash lamp, light insulation, and the like.
Thus, instead of partially sterilizing food container trays or bats or lunch boxes, cooking utensils, food containers, daily necessities, medical / care products, etc. with a disinfectant spray, sterilization treatment is performed by flashing a small flash lamp. It becomes possible to do.
Therefore, the above-mentioned article can be easily and quickly sterilized at low cost by eliminating the influence on the human body, discomfort, danger of ignition, and the like.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an example of a sterilizer used in the present invention.
In FIG. 1, 1 is a commercial power supply, 2 is a DC power supply unit comprising a step-up transformer, an AC / DC converter, and a DC voltage setting unit, C is a capacitor charged by the DC power supply unit, R is an adjustment resistor, and P is an anode-cathode. And a small xenon flash lamp having a trigger probe tr, and generates a flash pulse every time a trigger voltage is applied from the trigger circuit 3 with energy supplied from the capacitor C. The trigger circuit 3 can be set to a predetermined number of trigger voltage generations within a range of 30 to 120 times per second, and the xenon flash lamp P is connected via the flexible cord 4 and easily moved. It is possible. The xenon flash lamp P is provided with a reflecting mirror. In addition, when the supply energy per pulse reaches nearly 20 J, cooling means such as air cooling is required, but it can be done with weak air cooling, and the handy property of the xenon flash lamp can be sufficiently secured even with the supply energy of 20 J. .

When the set value of the DC voltage V, and capacitance of the capacitor is C, the energy W stored in the capacitor is given by W = ^CV 2/2, and 0.5~20J supply energy per this 1 pulse Thus, the DC voltage V and the capacitor capacitance C are set. For example, for a supply energy of 1 J per pulse, V is set to 1000 volts and C is set to 2 μF.
The trigger voltage generation frequency per second of the trigger circuit is set to 30 to 120 flash pulses per second.
Light irradiation can be performed while adjusting the trigger voltage application count of the trigger circuit in accordance with the sterilization effect. That is, when the bactericidal effect is insufficient, the trigger voltage generation frequency is increased to increase the number of flash pulses per second, and when the bactericidal effect is excessive, the number of flash pulses per second is decreased. Therefore, it is possible to irradiate light while reducing the number of trigger voltages generated by the trigger circuit. In this case, the trigger voltage generation frequency adjustment controller of the trigger circuit can be collectively attached to the xenon flash lamp.

When the supply energy per pulse is about 1 J, the supply energy generation unit can be made sufficiently small by setting the DC voltage to 1000 volts and the capacitor to 2 μF as described above. Thus, the supply energy generating unit may be installed in the xenon flash lamp in a lump, and the rear end of the flexible cord may be detachably connected to the AC commercial power supply with a plug.
The xenon flash lamp can be detachably attached to the tip of the handle. In the case where the supply energy generation unit is collectively mounted on the xenon flash lamp, the handle can be a cylindrical case type, and the supply energy generation unit can be accommodated in the cylindrical case. In this case, the flexible cord is pulled out from the cylindrical case, and the plug at the end of the cord is inserted and connected to a commercial AC power outlet. A battery may be used as the DC power source.

Figure 2 shows the waveform of the supply power (current) for one flash pulse is raised with a time constant until the time t ₀ is restricted by the insulation resistance of the capacitor and the capacitor C of the capacitor C, the capacitance of the capacitor at the time t ₀ after The waveform is regulated by the voltage V, the capacitance C of the capacitor, and the adjustment resistor R, and the half-value width tb is adjusted by the capacitance C and the adjustment resistor R. it can.
In the present invention, the reason why the full width at half maximum tb is set to 10 to 40 μs is that it is difficult to make it less than 10 μs from the viewpoint of the circuit, and if it exceeds 40 μs, the sterilization efficiency cannot be improved by adjusting the full width at half maximum tb. Because.

In the present invention, a flash pulse is generated under a supply energy of 0.5 to 20 J, preferably 4 to 18 J, per pulse, and the half-value width tb of the supply power waveform per flash pulse is set to 10 to 40 μs. The number of flash pulses per hit is 30 to 120, preferably 30 to 70. The distance between the xenon flash lamp and the irradiation surface is ± 30 mm with respect to 50 mm.
The reason why the supply energy per pulse is 0.5 to 20 J is that the illumination intensity is too low at less than 0.5 J, and incomplete sterilization cannot be avoided (in this specification, sterilization is 99.9% or more, In other words, it means that the order of 10 ³ or more is killed), and if it exceeds 20 J, the discharge gap becomes large, the size of the cooling means is increased, and the size of the flash lamp cannot be avoided. This is because it becomes difficult and the ultraviolet illuminance applied to the worker by reflecting the irradiated surface is increased, which hinders the safety of the worker. Even in the case of 20J, the size of the xenon flash lamp can be made to have an outer diameter of about 165 mmφ and a height of about 50 mm (in the case of a ring shape), and the size of the xenon flash lamp can be made sufficiently small.

The capacitance of the capacitor C, and a DC voltage voltage application to the capacitor to is V, the stored energy of the capacitor is given by CV ^2/2, the supply energy per this energy per pulse, 0.5～20J the supply energy As a result, the capacitor can be downsized or the DC voltage can be reduced, and the energy supply device can be downsized and the cost can be reduced. If it is 2.0 J or less, the xenon flash lamp can be collectively equipped with the energy supply device by downsizing.

  In the present invention, the reason for setting the number of flash pulses per second to 30 to 120 is that if the number is less than 30, the amount of accumulated ultraviolet rays per unit time is too small and effective sterilization becomes difficult. This is because the cumulative amount of ultraviolet irradiation per unit time becomes too large, the flash lamp generates heat significantly, and a large cooling means is required, making it difficult to ensure substantial miniaturization or handicap of the flash lamp.

In the present invention, the significance of setting the half-value width tb of the supply power waveform per one flash pulse to 40 μs or less is verified.
FIG. 3 shows the verification results for E. coli.
The measurement method is as follows. That is, the culture liquid diluted 10 ^1x glass watch glass of φ45mm dispensed 0.5m liters, spread the dispensed liquid to about 32 mm, sterilized by irradiation under the conditions 1-4 below To do. The culture solution recovered after irradiation is diluted 10-fold in stages, and 0.5 ml is dispensed into a normal agar medium (Nissui Pharmaceutical Co., Ltd.) at each stage, and the number of viable cells (viable cells after irradiation) is determined by the pour method. Number) N was measured, and Log (N ′ / N) was determined from the number of unirradiated viable bacteria (cultured bacteria) N ′, which was used as an evaluation value of the bactericidal effect. The Escherichia coli NBRC3972 was cultured in an ordinary bouillon (manufactured by Eiken Chemical Co., Ltd.) with shaking at 30 ° C. as the E. coli culture solution. Viable count of the culture solution is 10 ⁹ order.
[Condition 1] The supply energy per pulse of the xenon flash lamp is 18 J, the half-value width of the supply power waveform for one pulse is 38 μs, and the number of flash pulses per second is 40. A flash pulse was applied for 0 seconds.
The xenon flash lamp has a diameter of about 12 mm and a length of about 500 mm. A reflection mirror is provided. The gap between the xenon flash lamp and the irradiated surface was 50 mm.
[Condition 2] The supply energy per pulse of the xenon flash lamp is 18 J, the half-value width of the supply power waveform for one pulse is 31 μs, and the number of flash pulses per second is 40. A flash pulse was applied for 625 seconds.
The xenon flash lamp has a diameter of about 12 mm and a length of about 500 mm. A reflection mirror is provided. The gap between the xenon flash lamp and the irradiated surface was 50 mm.
[Condition 3] The supply energy per pulse of the xenon flash lamp is 4 J, the half width of the supply power waveform for one pulse is 11 μs, and the number of flash pulses per second is 60. A flash pulse was applied for 667 seconds.
The xenon flash lamp has a diameter of about 12 mm and a length of about 180 mm. A reflection mirror is provided. The gap between the xenon flash lamp and the irradiated surface was 50 mm.
[Condition 4] The supply energy per pulse of the xenon flash lamp is 18 J, the half width of the supply power waveform for one pulse is 49 μs, the number of flash pulses per second is 40, and 0.375 to 1.5 A flash pulse was applied for 2 seconds.
The xenon flash lamp has a diameter of about 12 mm and a length of about 500 mm. A reflection mirror is provided. The gap between the xenon flash lamp and the irradiated surface was 50 mm.

If FIG. 3 is verified, from the comparison between the condition 1 or 2 where the supply energy per pulse is the same 18 J and the condition 4, the irradiation time is 0 for the half-value width of 31 to 38 μs and the half-value width of 49 μs of the supply power waveform. The sterilization number magnification is 10 ^1.5 to 10 ^2.5 times in 5 seconds to 1.0 seconds, and the former is remarkably superior.
Further, from comparison between Condition 3 and Condition 4, when the half-value width of the supply power waveform is approximately 1/5 from 49 μs to 11 μs, the supply energy per pulse is approximately 1/5 from 18 J to 4 J. Nevertheless, the sterilization number magnification is dramatically increased.
The reason why the sterilization efficiency can be improved by setting the half-value width of the supply power waveform for one pulse to 40 μs or less is that the rise of the supply power waveform can be made steep and the xenon gas can be excited efficiently. It is estimated to be.

  If FIG. 3 is verified, sterilization of Escherichia coli having an order of 6 or more (99.9999% or more) by irradiation with a xenon flash lamp having a supply energy per pulse of about 4 to 18 J for 0.4 to 0.7 seconds. It is clear that food container trays or bats or lunch boxes, cooking utensils, food containers, daily necessities, medical / care products can be performed more quickly and easily and more powerfully than conventional spray or cloth methods. is there.

The present invention can be implemented in the following forms.
Conventionally, to prevent food corruption and prevent food poisoning, the lunch box is sprayed with a disinfectant and then placed in the tray container. However, there is concern about the disinfectant's effect on the human body, and the amount of disinfectant Many are expensive.
Thus, if the tray container is irradiated with light according to the present invention, the influence of the disinfectant residue on the human body can be eliminated, and the tray container can be sterilized at low cost.
4A is a top view of a conveyor type sterilizer used for the sterilization treatment of the tray container, and FIG. 4B is a cross-sectional view of the roller in FIG.
In FIG. 4, 51 is a quadruped stand that is adjusted to the height of the operator, 52 is a belt conveyor installed at the top of the stand 51, and 53 is a light shielding hood that is attached to the center of the top of the stand across the width of the conveyor. , 54 is a light-shielding curtain attached to the entrances at both ends of the hood, 55 is a reflective curved plate supported on the ceiling in the hood, P is a xenon flash lamp mounted in the reflective curved plate 55, and 56 is on the back of the stand. The installed transformer and capacitor are shown respectively.
57 ... is a reflector erected on the hood ceiling between the reflective curved plate and both ends of the hood, and prevents the flash from leaking from the curtain when the tray container passes through the entrance / exit of the hood by running the belt conveyor. .

The conveyor type sterilizer shown in FIG. 4 was used.
The conveyor length was 1500 mm, the conveyor width was 300 mm, the conveyor height (stand height) was 700 mm, the size of the light shielding hood was 550 mm × width 550 mm, and the entrance / exit size of the hood was width 380 mm × height 50 mm. A xenon flash lamp with a diameter of about 12 mm and a length of 500 mm is used, the gap between the xenon flash lamp and the conveyor surface is 100 mm, a single-phase 100 V, 2 kW is used as the power source, The supply power energy was 18 J, the half-value width of the supply power waveform for one flash pulse was 31 μs, and the number of flash pulses per second was 40.
When an aluminum tray (size: 770 × 365 × H20 mm, E. coli number: 190,000 CFU / cm ² ) on which a Escherichia coli NBRC3972 was grown was treated at a conveyor belt speed of 200 mm / sec, the E. coli number was 0 CFU / cm. ^{Made 2}

Using the conveyor type sterilizer of Example 1, the supply power energy per one flash pulse is 18 J, the half width of the supply power waveform for one flash pulse is 31 μs, and the number of flash pulses per second is the same as in Example 1. There were 40 items.
When a glass fiber hard tray (size: 438 × 328 × H 20 mm, coliform number 40,000 CFU / cm ² ) on which Escherichia coli NBRC3972 was grown was treated at a conveyor belt speed of 180 mm / second, E. coli number 0 CFU / cm ² I was able to.

Using the conveyor type sterilizer of Example 1, the supply power energy per one flash pulse is 18 J, the half width of the supply power waveform for one flash pulse is 31 s, and the number of flash pulses per second is the same as in Example 1. There were 40 items.
Treatment of aluminum tray (size: 770 × 365 × H20mm, number of S. aureus tens of thousands of CFU / cm ² ) with staphylococcus aureus subsp. Aureus NBRC12732 grown at a conveyor belt speed of 200 mm / sec. As a result, the number of Staphylococcus aureus was 0 CFU / cm ² .

Using the conveyor type sterilizer of Example 1, the supply power energy per one flash pulse is 18 J, the half width of the supply power waveform for one flash pulse is 31 μs, and the number of flash pulses per second is the same as in Example 1. There were 40 items.
When an aluminum tray (size 770 × 365 × H20 mm, Salmonella count 50,000 CFU / cm ² ) on which a Salmonella enteritidis NBRC3313 was grown was treated at a conveyor belt speed of 200 mm / sec, the Salmonella count 0 CFU / cm ^{Made 2}

It is drawing which shows an example of the sterilizer used by this invention . It is drawing which shows the waveform of the electric power supplied with respect to one flash pulse. It is a graph which shows the bactericidal effect by this invention with respect to colon_bacillus | E._coli. It is drawing which shows the belt conveyor type sterilizer used in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Commercial AC power supply 2 DC power supply part 3 Trigger circuit 4 Flexible code C Capacitor P Xenon flash lamp 52 Belt conveyor 53 Light shielding hood 54 Light shielding curtain 55 Reflecting curved plate 57 Reflecting plate

Claims (5)

In a method of sterilizing an object to be sterilized moved by a belt conveyor by irradiation of a flash pulse from a flash lamp on the belt conveyor, 30 to 1 per second under a power supply amount of 0.5 to 20 J per pulse. A sterilization method characterized by generating 120 flash pulses and adjusting the half-value width of a supply power waveform per flash pulse to 10 to 40 μs . 2. The sterilization method according to claim 1 , wherein the flash lamp is a xenon flash lamp. The sterilization method according to any one of claims 1 to 2 , wherein the object to be sterilized is a food container tray, a bat or a lunch box. The sterilization method according to any one of claims 1 to 3 , wherein the object to be sterilized is any one of a cooking utensil, a food container, a daily necessities, and a medical / care item. The sterilization method according to any one of claims 1 to 4 , wherein bacteria attached to the object to be sterilized are sterilized.

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