JP3037936B2 - Sterilization method by light irradiation - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light for irradiating an object to be sterilized such as food, tableware, fluid, gas or the like with a pulse light such as a strobe light to sterilize bacteria adhered or mixed into the object to be sterilized. about the sterilization how by irradiation.

[0002]

2. Description of the Related Art Conventionally, sterilization methods are roughly classified into physical methods and chemical methods. Examples of the physical method include a boiling method, a steam sterilization method, a high-pressure sterilization method, and a sterilization method using ultraviolet irradiation or radiation. The chemical method is a method using a disinfectant such as alcohol, hydrogen peroxide, and cresol. In the sterilization of foods, boiling and steam sterilization methods are the mainstream. In recent years, there is a high-temperature short-time sterilization method. .

[0003]

However, the sterilization method using the heating method is not preferable depending on the object because the composition of the object may be altered when exposed to a high temperature for a long time. Similarly, the sterilization method using ultraviolet irradiation or ozone is also not preferable depending on the target object, and may have an adverse effect on the human body such as skin and eyes, and has a drawback that requires careful handling. Further, the disinfectant is usually used for disinfecting resins and rubber products which are unsuitable for heat disinfection, and is clearly not preferable for disinfecting food. Of course, there is a sterilization method by irradiation, but care must be taken with the treatment and it is not a general sterilization method.

[0004] In the sterilization of chicken eggs, a method has been adopted in which eggs are washed with water to remove bacteria adhering to the surface of the shell and then exposed to ozone for sterilization. However, ozone is an oxidizing gas, And oxidizes it to cause problems such as corrosion. Also,
When sterilizing by exposure to high temperature for a short time, which is a conventional sterilization method, there is a possibility of altering egg white and the like, which is not necessarily a preferable sterilization method, and depending on the sterilization target, still another sterilization method is desired. I have.

[0005] The present invention has been made in view of the above problems, and has as its object to provide a sterilization method by light irradiation that can sterilize without damaging the composition of the sterilization target.

[0006]

Means for Solving the Problems The present invention has achieved the above-mentioned object, and the invention of claim 1 is to transport a liquid, gas, or solid object to be sterilized into a partitioned area, 250 to the sterilization target transported in the area
Light having a wavelength of 1100 nm and a flash time of 1/500 to 1/17000 seconds has a steep rise.
When sterilizing by irradiating the pulsed light, the liquid is set by setting the transport speed of the sterilization target passing through the region, setting the number of flashes per unit time of the pulsed light , and irradiating the liquid. This is a sterilization method by light irradiation, wherein sterilization is performed by giving a steep temperature rise to bacteria to be mixed, bacteria floating in a gas, or bacteria attached to a solid surface. According to the present invention, bacteria that adhere to or enter the object to be sterilized in a short time, such as by flash irradiation (pulse light) with a strobe light, cannot be achieved by a normal high-temperature and short-time sterilization method. This is a sterilization method of irradiating light including infrared rays to kill bacteria by a sharp rise in temperature. This flash is light from, for example, a xenon lamp, and its spectral distribution has many continuous spectrum portions, has a wavelength range similar to natural light even in the visible range (about 380 to 760 nm), and has all absorption characteristics. be capable of corresponding to a bacterium having, can provide <br/> sufficient energy to you disrupt the cells. In addition, although the strobe light by the xenon lamp is the wavelength most suitable for bacteria, the strobe light may be a combination of various wavelengths.

[0007]

[0008]

The sterilization method by light irradiation of the present invention
Irradiates the target object with the optimal number of pulsed
It is carried out by a light sterilizer that can
Conveying means for sending, and sterilization conveyed by the conveying means
A light emitting means for irradiating the object with pulsed light;
The object to be sterilized is transported, and the light emitting means is operated to
Control means for setting the timing of irradiating the pulsed light.
Depends on the provided light sterilizer. This light disinfection device
Photosterilization that irradiates the elephant with the optimal number of pulsed light
It is a device that generates pulsed light in a short flash time on the object to be sterilized.
Irradiate a suitable number of times to kill bacteria. The control means can control the output of the strobe light or the like and the transfer means by operating the light emitting means, and the transfer means is provided if the object to be sterilized is a fluid such as a liquid or a gas. , A flow control device and a blower.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the sterilization <br/> how by irradiation of the present invention will be described with reference to the drawings and tables. The sterilization method by light irradiation of the present invention is a method of sterilizing bacteria by irradiating light to an object to be sterilized. The wavelength of this light is from 250 nm to 1100 nm, which is an ultraviolet wavelength range to an infrared wavelength range. This is a method of irradiating an object to be sterilized such as food or tableware with the use of a sterilizer to sterilize it. In particular, the light source is most preferably a strobe light that emits light including visible light to near-infrared light, and the light flash time of this light source is in the range of 1/500 to 1/17000 seconds. Preferably, the flash time is 1/5000 to 1/16
Light with a sharp rise in the range of 000 seconds is desirable. The sterilization is performed for about 1 second at a frequency of, for example, 8 Hz. Of course, the number of flashes (frequency) per second and the irradiation time are not limited to these, and may be set according to the sterilization irradiation target.

Next, a light sterilizer capable of achieving the present embodiment will be described in detail with reference to FIG. FIG. 1 is a schematic diagram of a photosterilizer used in the present embodiment, which is composed of a strobe device and a transport means 5, and the strobe device is composed of a strobe light 1 and its circuit device. In the strobe light 1, a discharge tube 2 such as a xenon lamp is provided in the center of the reflector, and a glass plate 3 is provided in front of the strobe light 1. It is not necessary to provide the glass plate 3 depending on the wavelength of the light of the strobe light 1. The circuit device of the strobe light 1 includes a charging / discharging circuit 6 including a capacitor and a trigger circuit, a power supply circuit 7 for charging the capacitor of the charging / discharging circuit 6, a number of flashes, an irradiation time, and a light emission timing. And a control circuit 8.

The conveying means 5 is a device driven by a driving device 9 based on a control signal from a control circuit 8 to continuously convey the sterilized object 4 directly below the strobe light 1. When the object 4 to be sterilized is conveyed to a position directly below the strobe light 1, a flash light (hereinafter, referred to as pulse light) from the strobe light 1 is applied to the object 4 to be sterilized. The strobe light is light in which pulse light is continuous, and the strobe light is applied to the surface or the inside of the sterilization target 4. When the pulsed light is applied, it is absorbed by bacteria and its temperature instantaneously rises and is killed by damaging bacterial cells.

The conveying means 5 may be stopped while the object to be sterilized 4 is conveyed to the irradiation position and the object to be sterilized 4 is irradiated with the pulse light, or as shown in FIG. When irradiating the sterilized object with the energy that has been applied, the flash time is illuminated with light having a very short flash time of 1/16000 seconds, so that pulse light is applied to the sterilized object 4 while maintaining a predetermined transport speed. Sterilization may be performed by irradiation.

The control circuit 8 sets the output of the strobe light 1, the number of irradiations per second, the irradiation time, the setting of the conveying speed of the conveying means 5 operated by the driving device 9, and the setting of the strobe light 1. The setting of the irradiation timing and the operation such as driving / stopping of the transport unit 5 by the driving device 9 are performed based on the control signal. Of course, the irradiation time during which the pulse light is substantially irradiated may be set by adjusting the conveyance speed at which the sterilization target object 4 is conveyed by the conveyance means 5.

Further, a plurality of strobe lights 1 may be arranged in the conveying direction of the object to be sterilized, and the object to be sterilized 4 may be conveyed and sterilized. The strobe light is irradiated several times, for example, once or more per second, preferably about two to twenty times, to kill bacteria that adhere to or enter the sterilization target 4. Of course, depending on the object 4 to be sterilized, it may be sterilized by irradiating a strobe light several times after irradiating the surface with ultraviolet rays.

Further, the strobe light 1 may be arranged at the upper part and the lower part, or may be arranged at the left and right.
Further, the entire area irradiated with the strobe light 1 may be covered with a reflector so that the strobe light does not leak outside.

On the other hand, another embodiment of the light sterilizer according to the present invention .
The state will be described with reference to FIGS.
Although the strobe device is not illustrated in FIG. 2A, the sterilization target 4 a is a fluid, and the strobe light is emitted while the liquid or gaseous sterilization target 4 a flows from the supply device to the flow path 10. By irradiating the sterilization target 4a under the light emission conditions described in the above section, bacteria mixed into the sterilization target 4a can be sterilized. In addition, the sterilization target 4 flowing through the flow path 10
“a” is adjusted so that the light is transmitted at a thickness that allows the strobe light to pass therethrough and the light is sufficiently transmitted. When the flow path 10 is tubular, a transparent material such as glass or resin may be used so that strobe light can be transmitted. In addition, these are connected to the flow path 10.
May be covered with a reflector. Furthermore, when sterilizing a liquid, it is also possible to sterilize while circulating the fluid through a light sterilizer.

FIG. 2B shows a photosterilizer in which the object 4b to be sterilized is a gas such as air. In this light sterilizing apparatus, a filter 13 is provided at one end of an air passage 11 having a blower 12 and a filter 14 is provided at the other end.
The strobe light 1 is provided halfway. Blower 1
When the 2 is driven, the air to be sterilized passes through the filter 13 and is sent into the air passage 11. When the blower 12 is driven, the air in the air passage 11 passes through the filter 14. While the air, which is the sterilization target 4b, passes through the air passage 11, a strobe light is irradiated to sterilize the sterilization target 4b. The strobe light is continuously emitted at a predetermined frequency.

The blower 12 may be provided on the air discharge side, or may form a flow using cooling air sent from the strobe light 1. The filter 13,
14 is not necessarily required. In addition, FIG.
As the light sterilizer of (b), the one described in the above embodiment is used. When the photosterilizer is installed in an air purifier or the like, it is preferable that pulse light is continuously emitted at, for example, 8 Hz to sterilize the light.

Next, a test for verifying the sterilization effect of the sterilization method using the strobe light of the present embodiment will be described with reference to FIG. 3 and a table. First, a sterilization method by light irradiation according to the present embodiment will be described. Sterilization target 4
The test was performed using a sample in which the test bacterium was applied to the surface of a petri dish medium. The surface of this sample was irradiated with strobe light, and the sterilizing effect of the strobe light irradiation was confirmed. This strobe device used strobe lights 1a and 1b shown in FIGS. 3 (a) and 3 (b).

FIG. 3A shows a multi-type strobe light 1a which emits strobe light containing a relatively large amount of ultraviolet light.
And a xenon lamp was used. The flash time of the light waveform of this multi-type strobe light is, as shown in FIG. 4, the half width of the light waveform is 64 μs.
1/15625 seconds. FIG. 3B shows a strobe light 1b mainly for photographing, which emits strobe light including visible light and near-infrared light, and is different from the multi-type strobe light 1a of FIG. 3A. The rising of the light pulse was slow, and irradiation was performed at an emission interval of about 8 times in 5 seconds.

The sample was irradiated with light by four methods. Multi-type strobe light 1a shown in FIG.
(MULT-200) output 25 Ws at one time, and irradiated strobe light at a frequency of 8 Hz for 1 second (8 flashes per second). The light irradiation was performed in the case where a glass plate 3 for blocking ultraviolet rays was provided on the front surface of the strobe light 1a and in the case where it was not provided. On the other hand, a strobe light 1b (CA-1600) shown in FIG.
The irradiation was performed by a method of irradiating Ws once.

FIGS. 5 and 6 show the spectral distribution characteristics of the multi-type strobe light 1a shown in FIG. 3 (a). This strobe light 1a is a xenon lamp (helical type).
And the light emission condition is 915V. FIG.
The spectral distribution of the strobe light 1a in the wavelength region of 1100 nm, where the light intensity at 550 nm is 100%.
The horizontal axis indicates each wavelength, and the vertical axis indicates relative intensity. The solid line in FIG. 5 indicates the case where no glass plate is provided, and the dotted line indicates the light intensity when the glass plate is provided. Also,
FIG. 6 shows the light intensity in the region of 200 to 400 nm, and the solid line in the drawing indicates the case where no glass plate is provided, and the dotted line indicates the light intensity when the glass plate is provided.

On the other hand, four types of bacteria were selected and applied to separate media on the surface of the medium of the petri dish, which is the object 3 to be sterilized. Escherichia coli (Gram-negative bacteria), Salmonella bacteria (Gram-negative bacteria), Staphylococcus aureus (Gram-positive bacteria), and Bacillus subtilis spores were selected as test strains.
First, the bacteria (1) to (4) were applied to culture media of different petri dishes, respectively, and irradiated with strobe light. Thereafter, the petri dish irradiated with strobe light was cultured in a sterile constant temperature bath. After a predetermined time had elapsed, the number of colonies generated was counted, and the sterilizing effect of the strobe light irradiation was confirmed.

These test bacterial strains were passaged several times from the stock strain, and cultured for one day and one day before the test was used as a test solution. As for Bacillus subtilis, those cultured for several weeks on a slant medium were subjected to a heat treatment at 80 ° C., and spore formation was confirmed under a microscope to obtain a test bacterial solution. These adjusted bacterial solutions were diluted to 10 ⁵ CFU / ml using a saline solution. 0.1 ml of this test solution was applied on a tryptic case soy agar (BBL). Five test strains were produced, one was cultured before irradiation, and the remaining four were used as irradiated samples.

As shown in FIGS. 3 (a) and 3 (b), the light irradiation method is as follows. The light emitting portion of the multi-type strobe light 1a is directed downward, and a culture medium (irradiation target 4) is placed directly below the light source. did. The distance D between the light emitting portion and the irradiation target 4 was set by measuring the EV value with a flash meter so that the brightness of the light irradiated on the surface was constant. As shown in Table 1, the distance D is 60 mm in the case of FIG.
In the case of (b), it was set to 90 mm.

The light emission conditions A1, A2, B1, B2 in Table 1 will be described. The light emission condition A1 is a case where the strobe light 1a with a glass plate shown in FIG. 3A is used.
The experimental conditions are set to 0 mm. The light emission condition A2 is
This is a case where a glass plate is not used for the strobe light 1a in FIG. 3A, the distance D is set to 60 mm, and the output is 2
The experiment conditions of irradiation at 5 Ws and 8 Hz for 1 second are shown. The light emission condition B1 is as follows.
The experimental condition is shown in which the strobe light 1b shown in (b) is used, the output is 50 Ws, and irradiation is performed eight times in 5 seconds. The light emission condition B2 is the strobe light 1b in FIG. 3B, and shows the experimental conditions in which the output was 400 Ws and the irradiation was performed once.

[0028]

[Table 1]

Table 2 shows the test results of the sterilization method by light irradiation of the present invention. As is clear from Table 2, in the case of non-irradiation, it was 10 ⁵ CUF or more. In the table, ○ indicates an example in which a bactericidal effect was observed, X indicates an example in which the bactericidal effect was not observed, and △ indicates a case in which the effect was slightly observed by visually observing the petri dish surface. ing. In the case of Bacillus subtilis, no decrease in the number of bacteria was observed under all conditions.

On the other hand, for Escherichia coli and Salmonella, an effect was observed under the luminescence condition A1 with a glass of the multi-type strobe light 1a (A1). E. coli is 8.8 x 1
Salmonella became 3.5 × 10 ² CFU in O ² CFU, and a bactericidal effect was observed. Under the luminescence condition A2, the bactericidal effect was reduced against staphylococcus aureus to 8.8 × 10 ² CFU, but no effect was observed on other bacteria.

Under the luminescence condition B1, the bactericidal effect was reduced against Staphylococcus aureus to 2.4 × 10 ² CFU. No remarkable effect was observed for other bacteria, but for Salmonella and Escherichia coli indicated by △ marks, sparse growth was observed on the surface of the culture medium of the dish, and some effects were observed. Admitted. Under luminescence condition B2, no effect was observed on all the bacteria. No effect was observed on B. subtilis under any of the luminescence conditions, but the spores of B. subtilis had higher resistance to physical actions such as disinfectants, heating, and ultraviolet rays than vegetative forms. It seems to be a natural result.

[0032]

[Table 2]

From the above results, it was clarified that bacteria can be killed by pulsed light. That is,
Sterilization by strobe light is extremely short (light emission condition A1
It has been clarified that bacteria can be killed by irradiating the object to be sterilized with light having a wide wavelength distribution by a xenon lamp with a flash time of 1/15625 seconds). On the other hand, since the flash time of the pulse light is extremely short, the composition of the surface of the sterilization target does not change due to heat. Of course, by adjusting the flash time of the pulse light, the number of light irradiations, or the output according to the sterilization target, it is possible to sterilize various sterilization targets without altering the composition.

The number of times the strobe light is irradiated is not limited to eight times a second as described above. By reducing the capacity of the condensate, the flash time can be shortened. Under such conditions, the sterilizing effect can be obtained even if the number of irradiations is one. As is clear from Table 2, the shorter the flash time, the higher the bactericidal effect.

Further, even if the pulsed light by the strobe light is applied to the surface of the object to be sterilized or the liquid or gas through which the pulsed light is transmitted, the same sterilizing effect can be obtained. It is possible, and air sterilization is also possible by mounting the light sterilizer on the air purifier.

Further, in the above-described embodiment, the strobe light is used as the pulse light, but it is apparent that the radiation light by other gas discharge may be used.

[0037]

According to the above description, according to the present invention, bacteria are sterilized by irradiating bacteria with pulse light having a wavelength including near-ultraviolet light, visible light, and near-infrared light. A photosterilization method and a photosterilizer thereof, by irradiating bacteria with pulsed light, the bacteria absorb the pulsed light, the temperature rises sharply, and the cells are damaged and killed. Since the irradiation time of light is short, the object to be sterilized has an advantage that its heat capacity is large and the absorbed heat is dissipated to prevent the composition of the object to be sterilized from being denatured.

Further, according to the present invention, sterilization is performed using strobe light, and the strobe light is an extremely effective sterilization method that is easy to handle and does not affect the human body.

According to the present invention, for example, bacteria to be sterilized can be used to kill bacteria adhering to the surface of food such as chicken eggs and meat, bacteria contained in air, and bacteria mixed in liquids such as drinking water. Extremely effective.

[Brief description of the drawings]

Is a diagram for explaining a sterilizing how by irradiation of the present invention; FIG.

FIG. 2 (a) shows an example of a light sterilizer according to the present invention, and FIG. 2 (b) shows an example of another light sterilizer.

3 (a) shows a strobe light light disinfection device of the present invention, (b) are diagrams showing the strobe lights of the comparative example.

FIG. 4 is a diagram for explaining a flash time of strobe light.

FIG. 5 is a diagram showing a spectral distribution of a xenon lamp.

FIG. 6 is a diagram showing a spectral distribution of a xenon lamp in an ultraviolet wavelength region.

[Explanation of symbols]

 1, 1a, 1b Strobe light 2 Discharge tube 3 Glass plate 4 Sterilization target 4a Fluid sterilization target 4b Gas sterilization target 5 Transport means 6 Charge / discharge circuit 7 Power supply circuit 8 Control circuit 9 Driving device 10 Flow path 11 Wind Road 13,14 Filter

Claims (1)

(57) [Claims] An object to be sterilized, which is a liquid, a gas, or a solid, is transported in a partitioned area, and the object to be transported in the area is light having a wavelength of 250 to 1100 nm and flashing. Time is 1/500 to 1/170
At the time of sterilization by irradiating a pulse light having a steep rise of light of 00 seconds, a conveying speed of the sterilization target passing through the region is set, and a flash of the pulse light per unit time is set.
Sterilization by light irradiation characterized by applying a steep temperature rise to bacteria mixed in the liquid, bacteria floating in a gas, or bacteria attached to a solid surface by irradiating by setting the number of times of light. Method.