JP2005040475A - Far-infrared sterilizing method and far-infrared sterilizer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for more enhancing the safety of food in addition to a conventional sanitation control method for suppressing the growth of bacteria bonded to processed and unprocessed foods of fishes, meats, vegetables and the like exposed to the open air to cause spoilage, food poisoning or the like. <P>SOLUTION: In a method for irradiating food with light having the absorbing wavelength of specific proteins constituting bacteria in a far-infrared region to kill or deactivate bacterial or to suppress the growth of bacteria, a means for selecting either one of a reflecting plate and a transmission plate or combining both of them according to necessity to use the same is provided as a far-infrared irradiation means of a specific wavelength. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a method for sterilizing microorganisms, particularly bacteria.

Sterilization simply kills bacteria, whereas sterilization kills all bacteria. Bacteriostasis is the inhibition or prevention of bacterial growth. There are various methods of sterilization and they are put into practical use. In general, a method of sterilizing an object by heat treatment is known. The problem in this case is that the temperature rise of the object is unavoidable, and the freshness and quality of foods may be deteriorated. Sterilization and sterilization are one of the main tasks in medical institutions. In this case, special methods such as high-pressure sterilization, gas sterilization, plasma sterilization, and radioactive sterilization have been adopted. It is often difficult to use. For this reason, heat treatment was adopted for sterilizing foods. In heat treatment, it is customary to raise the object directly to a predetermined temperature and hold it for a certain period of time. Heating in cooking includes processing of food sterilization in addition to the original purpose of cooking.

However, when continuous sterilization is required, such as frozen foods, a method capable of continuous sterilization is required, and some infrared heating treatments have been put into practical use. According to the published far-infrared food sterilization method, the applicable wavelength is 10-100 micrometers, and the action mechanism of sterilization is not clarified, such as whether it is due to a specific wavelength or due to temperature. However, there was a drawback that the sterilization treatment could not be performed efficiently. In "JP-A-6-137763", a wavelength of 3.6-6.5 micrometers was obtained from a far-infrared emitting sphere, and the object to be sterilized was irradiated. As a result, it was confirmed that colonies in the chalet became “0” after about 24 hours.

Even if the sterilizing effect is assumed to be based on far infrared rays, the applicable wavelength is as wide as 1-30 micrometers or 1-100 micrometers, and therefore, the temperature control range of the tropical zone or the far infrared rays generated The current situation is that the optimum wavelength cannot be specified. To compensate for this, various food additives have been added to foods and processed products for the purpose of sterilization and bacterial growth suppression in the food distribution process. However, there are the following problems. Due to the harmful effects of food additives on the body and the restrictions on the use of food additives, the growth of bacteria attached to food is promoted, and shortening the edible period of food is becoming a social problem. At present, in order to deal with these other than food additives, sterilization and sterilization methods using heat or ultraviolet light have been strengthened. However, repeatedly applying heat and ultraviolet light to foods has the problem of deteriorating the freshness and quality of foods as described above.
JP 56-164775 A No. 8-15420 JP-A-6-137763 Hironori Koryo "All about Antibacterials" Textile Company, 1997 Yokoyama and Tanaka "Sterilization and disinfection practical manual" Science Forum, 1997

As a result of various experiments on the effects that have not been elucidated in the past, the present inventor has confirmed the bactericidal effect by far infrared rays, and has completed the present invention.

The present invention clarifies the technology of sterilization, deactivation and growth inhibition of bacteria by far-infrared irradiation, and aims to put the device into practical use. As explained in detail in the background art, there is a need for a method of sterilization without adding or adding food additives to food, or without irradiating with heat load or ultraviolet rays that cause food deterioration. ing. In other words, the present invention
First, in addition to traditional hygiene management methods that suppress the growth of bacteria that cause spoilage, food poisoning, etc., which adhere to fish, meat, vegetables, etc., of processed and non-processed foods exposed to the open air. A method to further improve the safety of Secondly, sterilization, deactivation and growth control of foods covered with packaging materials etc. before packaging operations, or growth again in foods that have been sterilized or coated during packaging operations It provides a new method for the purpose of sterilization, deactivation, and growth control of bacteria.

In recent years, advances in infrared spectroscopy on living tissues, cells or bacteria have brought about the characteristics of the present invention. In addition, the present invention is characterized in that the bacteria are transformed with less energy by irradiating far-infrared light of a specific wavelength in order to solve the problems of the conventional sterilization method. In the conventional method, since the mechanism of action is not clear, a wide range of far-infrared irradiation dose and action amount are necessary for the sterilization target, and this has caused a problem that excessive action occurs.

In summary, the features of the present invention and the specific description of its implementation can be summarized by irradiating a far-infrared ray in a specific wavelength range on an object such as food that requires sterilization, that is, bacteria attached to the object. By irradiating far-infrared rays that match the absorption wavelength of the specific constituent molecules of the substance, it induces denaturation effects on bacteria with less energy, and is undesirably high in temperature, sterilization and inactivity, which is undesirable for food and other objects. It is to provide a method for suppressing the growth and growth.

However, it is necessary to experimentally confirm the sterilization, deactivation, and growth inhibition methods of bacteria because the definite mechanism of action has not been theoretically analyzed. According to previous reports, damage related to bacterial killing can be classified into DNA synthesis inhibition, RNA polymerase inhibition, protein synthesis inhibition, and cell membrane synthesis inhibition. Proteins present in the cell membrane can produce intracellular enzymes in response to transporters of substances, connections that connect intracellular actin filaments and extracellular matrix, receptors that transmit extracellular signals into cells, or extracellular signals. It functions as a catalyst. There are reports suggesting that damage to bacteria irradiated with far-infrared rays may be caused by inhibition of protein synthesis in RNA polymerase and ribosome.
JP-A-6-13776 Journal of Chemical Engineering of Japan, Vol 28, No 3, 294-299 pages, 1995

The hypothesis of the action of the present invention is to modify and denature molecular structures such as proteins and sugar chains that constitute various microprojections on the bacterial membrane surface by irradiation with far-infrared rays in a specific wavelength range. By reducing or breaking down, the function of bacteria is disabled or it leads to death.

The center temperature of the radiation temperature and its radiation spectrum is known as Planck's radiation law. When the temperature of the radiator decreases, the center wavelength of radiation shifts to the longer wavelength side. Therefore, the center wavelength of radiation is automatically determined depending on the temperature of the heating element that emits far infrared rays. Therefore, since it is known that vibration based on a general molecular structure exists in the infrared region, the present inventor has selected far infrared rays of 3 micrometers or more as a wavelength range in which the effect can be expected.

On the other hand, the resonance wavelengths of far-infrared water are theoretically required to be 2.74, 2.66, and 6.27 micrometers, respectively. However, it is actually quite wide. The far-infrared absorptivity has a deep relationship with the water layer thickness. Up to a layer thickness of 3 micrometers, absorption near 3 and 6 micrometers is large, but as the layer thickness increases, the absorption increases to 1 mm.
At this point, all far infrared rays longer than 3 micrometers are absorbed, and the wavelength dependence is lost. If sterilization, deactivation, and growth inhibition of bacteria are enhanced by irradiation with far-infrared rays in a specific wavelength range, absorption by slight moisture contained in or around bacteria as described in (0010) It is clear that this is due to the exothermic action. However, as described later, far-infrared rays with wavelengths longer than 10 micrometers have a low rate of killing bacteria, suggesting a different mechanism.

The action of light on an object is defined by the amount of light energy, light intensity, and action time. On the other hand, as described in (0011), when the temperature of the heating element is lowered, the radiation center wavelength at that time shifts to the longer wavelength side. Accordingly, the overall calorific value is reduced and the strength of action is reduced. Therefore, the important point is a means to ensure that sufficient energy and effect can be confirmed by requiring the energy and intensity of light in a specific wavelength range, and not simply setting the center wavelength to the specific wavelength range. At the same time, it is necessary to control the amount and intensity of light to the extent that quality degradation due to overheating of the object is prevented. In addition, since the irradiation of the target is insufficient, it is necessary to control the amount and intensity of light so that bacteria do not acquire resistance to far infrared rays.
Practical far-infrared rays, Human and History Company, 1999

As described above, the far-infrared irradiation in the specific wavelength range according to the invention of claim 1 suppresses the bacterial colony growth while maintaining the surface temperature of the object requiring sterilization at around 40 ° C. as described in the examples or It was possible to stop. It is considered that sterilization according to the present invention is possible even when the object to be sterilized is cooled or the object to be sterilized at a low temperature. In addition, it is possible to provide high-quality food that is free from the addition of disinfectants and heating operations in the sterilization process in food factories.

According to the inventions of claims 3 to 6, it is possible to select the irradiation method of far infrared rays, and it is possible to select the optimum method according to the sterilization target.

As means for ensuring such an appropriate irradiation condition, as heat generating means, for example, a generally known heat source such as a far-infrared heater, a ceramic heating element, a lamp light source, and a heating temperature control means capable of keeping the temperature of the heating element constant. Combined, keeps the surface temperature of the heating element constant. As a result, the center wavelength of the radiation spectrum is defined according to the Planck's radiation law. Since the radiation spectrum from the heating element maintained at a constant temperature has a wide wavelength distribution, in order to extract only the specific wavelength range, only the specific wavelength range is provided between the heating element and the irradiated body. There is a requirement for a structure to transmit the specific wavelength band transmitting material, or to irradiate the irradiated part through the specific wavelength band reflector that reflects the specific wavelength band once.

As is well known, materials that can transmit a specific wavelength range, especially far infrared rays, are very limited. The reason for this is that in general materials, the molecular vibration absorption spectrum due to vibration of the constituent molecules is limited to the far-infrared region. For this reason, commonly used materials such as glass, quartz glass, and plastic cannot normally transmit far-infrared rays of about 2 micrometers or more. Currently known far-infrared transmitting materials are limited to very expensive materials such as ZnSe, ZnS, GaAs and Ge. Therefore, when constructing a large-scale device, it is not appropriate to use a transmission material as a means to obtain a specific wavelength range. In addition, in order to transmit only a specific wavelength region, it is necessary to form a multilayer film so that only specific light can be transmitted to the surface of the material, and there is a disadvantage that it is expensive.

As another means of forming a specific wavelength range, a reflector that can reflect the specific wavelength range is sometimes used. The advantage in this case is that no special material is required for the reflective base material, and materials such as stainless steel, aluminum, copper, titanium, and glass that have been polished to the extent that no light scattering occurs on the surface can be used. Efficient reflection in a specific wavelength range can be realized by depositing a multilayer film as is well known.

As another means for forming a specific wavelength range, there is one realized by a combination of temperature setting conditions in the heat generation temperature control means and an infrared transmitting material. In this case, the infrared transmitting material has the advantage of not requiring vapor deposition with special wavelength selection. For example, CaF ₂
The crystal plate has no deliquescence and is a transparent crystal from the ultraviolet region to the far-infrared region, but in the far-infrared region of this optical crystal, the transmittance gradually begins to decrease from about 6 micrometers from the longer wavelength side to 10 microns. 10% near the meter
Decrease to the extent. Taking advantage of this characteristic, if the temperature of the far-infrared heating element is selected so that the center wavelength is from 7 micrometers to 10 micrometers, the far-infrared light transmitted through this optical crystal has a wavelength center from 7 micrometers. An optical filter having a tail portion corresponding to the Planck radiation spectrum on the short wavelength side and having almost no transmission beyond 10 micrometers can be constructed.
Science chronology, transmittance of optical crystal, Maruzen

As a similar means, there is a method using LiF ₂ crystal, but this case corresponds to the case where a center wavelength of 5-6 micrometers is required. Furthermore, it corresponds to the case where the center wavelength is 3-5 micrometers by using sapphire. Therefore, the simplest means of constructing a specific wavelength band was presented by a specific crystal optical material and a method of controlling the heating element temperature.

Although there are various definitions of the wavelength range of far infrared rays, the wavelength range from 3 micrometers to 1 mm is referred to as far infrared radiation according to the classification of the far infrared association.

FIG. 1 is a system diagram for explaining a method and apparatus of a sterilizing apparatus according to one embodiment of the present invention. 2 is an object to be irradiated and may be irradiated from one or more directions by one or a plurality of far-infrared radiation devices 1. 3 is a means of supplying power to the far-infrared radiation device and controlling the heat generation temperature. 1-3 are the same in Example 2.

FIG.

FIG. 2 is a cross-sectional view of the far-infrared radiation device body 1. The support 4 of the device is formed of aluminum, copper, glass, synthetic resin member or the like. A large number of cooling pipes 5 are provided inside to prevent heating of the support. 7 is a far-infrared radiation heating element, and 8 is a shield installed so that far-infrared radiation from the far-infrared radiation heating element does not reach the irradiated object directly. This shield is equipped with a cooling pipe inside to prevent unwanted far-infrared radiation by heating from an infrared radiation heating element. 6 is a part of the support 5 and has a structure in which infrared rays from a far-infrared radiation heating element are collected and vapor deposition is performed to reflect a specific wavelength. A fan for cooling the surface of 9 is attached to 5. 14 is a steam generator used to wet the surface of the irradiated object as needed. 9 is an irradiated body with or without a coating, and receives irradiation from various directions as necessary.
10 is a mechanism for changing the distance between the main body of the far-infrared radiation device and the object to be irradiated. By changing this distance, the irradiation field of the object to be irradiated and the far-infrared energy to be applied can be changed. 11 and 12 are far-infrared radiation control sensors, which are attached to the surfaces of 6 and 13. No. 13 has a structure that can be moved in a conveyor manner on the stage on which the irradiated object is placed, and a structure that can be irradiated from below.

FIG.

Figure 3 shows other far-infrared irradiation conditions. In the figure, the device shown in Fig. 3 is positioned roughly on the object to be irradiated, and forms a structure that irradiates the object with far-infrared rays from multiple directions.

FIG.

Next, an example of the bactericidal effect of the present invention is shown. The test bacterium is Escherichia coli (JMC1649) sold by RIKEN. E. coli cultured overnight
The bacterial solution diluted with 0.85% saline was seeded on LB agar plates and irradiated with far infrared rays. The far-infrared heater temperature was kept at 730 ° C., and CaF ₂ window material use group and non-use group were compared as window materials.
After irradiation, the cells were cultured at 37 ° C. for 18 hours, and the number of colonies formed was counted. The surface temperature of the agar plate during the far-infrared irradiation was 40 ° C. Count the number of colonies formed in both groups, and “irradiation group colonies /
Figure 4 shows the ratio of the number of non-irradiated group colonies. In the figure, the solid line shows an example of using CaF ₂ window material, and the dotted line shows an example of non-use. From this result, the irradiation 180 is performed even though the surface temperature of the agar plate during the far infrared irradiation is 40 ° C.
The survival rate became “0.1” after 2 seconds, and almost “0” after 300 seconds. Since the killing temperature of E. coli is around 60 ° C, it is thought that the cause of the decrease in the survival rate is the action of far-infrared rays.
Moreover, since colonies of E. coli have decreased due to the use of CaF ₂ window material, it is considered that far-infrared rays having a wavelength shorter than 10-12 micrometers are involved in killing bacteria.

FIG.

The example which shows the effect of other sterilization by this invention is shown. The test bacteria and culture method are the same as in the previous section (Section 0028). As shown in FIG. 5, the relative humidity (RH) was changed to 23.5 and 43.5%, and the survival rate was calculated. CaF ₂
Is not used. The survival rate decreased with increasing humidity. It was clarified that far-infrared sterilization effect can be enhanced by the method of forming a thin film of moderate humidity on the surface of the irradiated body.

FIG.

Application to fields where it is necessary to suppress or stop bacterial sterilization or bacterial growth where it is not desirable to raise the surface temperature, such as food manufacturing, food processing, food distribution, food preservation. Application to sterilization of objects to be sterilized by cooling or low temperature. In addition, application in fields where it is not necessary to add disinfectants or heat in the sterilization process in food factories, etc., and it is necessary to provide high-quality food. Furthermore, it can be applied in the medical field where sterilization is necessary.

Schematic of the far-infrared sterilizer of the present invention FIG. 1 is a schematic cross-sectional view of the far-infrared radiation device shown in FIG. 1 (Example 1). Schematic cross-sectional view of another far-infrared radiation device shown in FIG. 1 (Example 2) Far-infrared irradiation results for Escherichia coli Effect of humidity during far-infrared irradiation on Escherichia coli

Explanation of symbols

1 Far-infrared radiation device 2 Object to be irradiated
3 Control device
4 Supporting components for far-infrared radiators
5 Cooling pipe
6 Reflective vapor deposition layer for specific wavelengths
7 Far infrared radiation heater
8 Shield with built-in cooling pipe
9 Subject
10 Distance variable mechanism
11 Far-infrared radiation control sensor
12 Far infrared radiation control sensor
13 Platform and irradiated object moving device
14 Water vapor generator

Claims (6)

Method and apparatus for sterilization by irradiating a target object with far-infrared rays of a specific wavelength In the method of sterilization, the specific wavelength of far infrared rays applied to an object is in the range of 3-10 micrometers, and the method and apparatus The method and apparatus according to the first or second aspect, wherein the far infrared ray of a specific wavelength is constituted by a heat generation means, a heat generation temperature control means, a specific wavelength range reflector, and an object irradiation setting means. The method and apparatus as described in the above paragraphs 1 to 2, characterized in that far infrared rays of a specific wavelength are composed of heat generating means, heat generation temperature control means, specific wavelength range transmission plate, and object irradiation setting means. 5. The method and apparatus according to claim 1, wherein far infrared rays in a specific wavelength range are emitted by combining a set temperature condition in the heat generation temperature control means and a far infrared ray transmitting material. 6. A method and apparatus as claimed in claim 1, comprising a device for generating water vapor.

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