JP6309444B2 - Sterilization method - Google Patents

Description

  The present invention relates to a sterilization method suitable for sterilizing a container filled with a liquid such as drinking water.

A rotary filling device is known as a system for filling a container such as a PET (Polyethylene terephthalate) bottle, a glass bottle, or a bottle can with a liquid such as drinking water. This rotary filling device is provided with a plurality of filling valves on the outer periphery of the rotating body, and the filling from the filling valve into the container is carried out while the rotating body rotates almost once and the container is conveyed in the circumferential direction. I do. Then, after filling the container, the lid is attached to the container by a capper or a stopper.
Inside the container, the PET bottle is formed by blowing air into a test tubular precursor called a preform. For this molding, a biaxial stretch blow molding method is mainly used. The biaxial stretch blow molding method is a molding method in which a heated preform is inserted into a mold and then expanded in the circumferential direction by blowing pressurized air while being stretched in a vertical direction with a rod called a stretch rod.
A beverage filling system for PET bottles has a PET bottle molding device on the upstream side, and there is a form in which the molded PET bottle is supplied to the filling device. There is also a form of supplying to

By the way, when filling liquids such as drinking water, it is necessary to prevent contamination of bacteria in the container as much as possible. For this reason, in a clean room, container sterilization / rinsing, cap sterilization, liquid filling and cap attachment A so-called aseptic filling method that performs such a series of processes is employed. In the case of a beverage filling system equipped with a PET bottle molding device on the upstream side, it may be required to sterilize the PET bottle molded by this molding device and supply it to the filling device.
As sterilization in the aseptic filling method, it is mainstream to use a peracetic acid-based disinfectant composed of an aqueous solution containing a drug, for example, peracetic acid (PAA) or hydrogen peroxide (H ₂ O ₂ ) (for example, Patent Document 1). , 2).
However, when peracetic acid is used as a bactericidal agent, the problem is that resistant bacteria against peracetic acid are created. In addition, with hydrogen peroxide, although there are few problems with resistant bacteria, there is a problem that when PET bottles are targeted, they are absorbed by PET and remain in the container.

Sterilization using ozone (O ₃ ) is known as a technique that does not have a problem of resistant bacteria and does not have a problem of remaining in the sterilization target region (for example, Patent Documents 3 and 4).

JP 2014-181039 A JP 2014-080207 A Japanese Patent Laid-Open No. 63-59961 JP-A-4-33658

Although the conventional sterilization method using ozone does not have the problem of the sterilization method using a peracetic acid-based disinfectant comprising an aqueous solution, it takes a long time to obtain the desired sterilization performance. Any object that allows a long time is acceptable, but in the case of a beverage container, the time that can be spent to sterilize the container in seconds, depending on the speed at which the beverage is filled into the container. is there.
Therefore, an object of the present invention is to provide a sterilization method capable of obtaining desired sterilization performance in a short time when sterilizing using ozone.

The present inventors have studied the sterilization of containers in a beverage filling system in view of the fact that it is necessary to obtain a predetermined sterilization performance within a very short time, for example, within a few seconds per bottle. As a result, the sterilization method of the present invention supplies ozone gas to the region to be sterilized, and supplies the ozone gas and moisture that have been individually conveyed to the region to be sterilized when sterilizing the bacteria present in the region to be sterilized. A first sterilization method for supplying ozone gas and water vapor as moisture toward the region to be sterilized , and a method for supplying ozone gas and spray water as moisture toward the region to be sterilized following the first sterilization. 2 sterilization is performed .

In the sterilization method of the present invention, the ozone gas and moisture that have been individually conveyed may be mixed before the sterilization target region or inside the sterilization target region, and the mixed ozone gas and moisture may be supplied to the sterilization target region. preferable.
In this case, ozone gas and moisture can be supplied inside the chamber in which the object to be sterilized is continuously conveyed.

  In the sterilization method of the present invention, when the object to be sterilized is a beverage container, ozone gas and moisture are supplied through the mouth of the container, and inside the container that forms a closed space except for the mouth, Ozone gas and moisture can be mixed. Although this assumes that the inner peripheral surface of a container is sterilized, in order to sterilize the outer peripheral surface of a container, it does not prevent supplying ozone gas and a water | moisture content to the said outer peripheral surface.

  In the sterilization method of the present invention, it is preferable that the supply of ozone gas and moisture to the region to be sterilized is started at the same time, or ozone gas is supplied to the region to be sterilized prior to moisture.

In the sterilization method of the present invention, granular water can be used as water. The method for producing granular water is arbitrary, but water vapor can be used as it is, or liquid phase water can be sprayed for use. Further, by supplying ozone gas and moisture to the two-fluid nozzle, a mixed fluid of ozone gas and spray water can be generated and supplied to the region to be sterilized.
In the sterilization method of the present invention, the ozone gas can be either dry ozone gas or wet ozone gas.

In the sterilization method of the present invention, following the first sterilization for supplying ozone gas and moisture toward the sterilization target region, and following the first sterilization, ozone gas and a different kind of moisture from the first sterilization are directed to the sterilization target region. And second sterilization to be supplied.
In the sterilization method of the present invention, ozone gas and water vapor or heated spray water as moisture can be supplied toward the sterilization target region. As this water vapor, low-temperature wet water vapor can also be used.

  ADVANTAGE OF THE INVENTION According to this invention, when sterilizing using ozone, the sterilization method which can obtain the desired sterilization performance in a short time can be provided.

It is a figure which shows typically the mechanism of sterilization by this embodiment. It is a figure which shows the example of a combination of the ozone gas and water | moisture content of disinfection by this embodiment. It is a figure which shows the supply form of ozone gas by this embodiment, and a water | moisture content. It is a figure which shows the process example in the case of applying this invention to disinfection of a PET bottle. It is a figure which shows the other example of a process in the case of applying this invention to disinfection of a PET bottle. It is a graph which shows the result of the experiment example (bacteria species: Bacillus atrophaeus) which evaluated bactericidal performance. It is a graph which shows the result of the other experiment example (bacteria species: Chaetomium globosum) which evaluated bactericidal performance.

Hereinafter, the present invention will be described based on embodiments.
[Mechanism for improving sterilization performance]
This embodiment presupposes supplying ozone gas and a water | moisture content with respect to the area | region to sterilize. For example, when the region to be sterilized is a beverage container, ozone gas and moisture are supplied into the container. As shown in FIG. 1 (a), this sterilization involves hydroxyl radical (hereinafter referred to as OH radical) generated by the reaction of ozone (O ₃ ) contained in ozone gas with water (H ₂ O). It is said that it attacks the bacteria B and is made by its oxidation action. The OH radical has the strongest oxidizing power among molecular species called so-called active oxygen. However, OH radicals have a short half-life and disappear quickly after generation.
Here, bacterial cells have a chromosome that controls the function of genetic information in the central core, a soft cell membrane composed of proteins and lipids on the outside, and a cell wall composed of proteins, polysaccharides, and lipids on the outside. Yes. The sterilization mechanism of bacteria by OH radicals starts from oxidative destruction of this cell wall with a strong oxidizing power. Thus, sterilization using ozone is understood to be different from a mechanism in which, for example, chlorine passes through cell walls and cell membranes to destroy enzymes.
In the present invention, the region to be sterilized includes not only the region that needs to be directly sterilized but also the periphery thereof. For example, in the case of a PET bottle, the outer peripheral surface and inner peripheral surface of the PET bottle are areas that require direct sterilization, but in the case of the outer peripheral surface, the external space in which the PET bottle is processed is In the case of the peripheral surface, the internal space of the PET bottle surrounded by the inner peripheral surface is included in the sterilization target region.

According to the study by the present inventors, in order to obtain the desired sterilization performance, it is not sufficient to increase the ozone concentration in the ozone gas, and it is necessary to secure the amount of moisture supplied together with the ozone gas. This state is shown in FIG. In addition, this is based on the fact that there is a significant difference in sterilization performance due to an increase or decrease in the amount of water supplied together with ozone gas, as will be described in the examples described later. For example, in the case of sterilization using wet ozone gas with humidity added to ozone gas, the amount of water that can be supplied is limited to saturated humidity or less, so ensure sufficient water amount to generate OH radicals necessary for high sterilization ability. I can't. The specific amount of water is determined by the ozone gas concentration and the sterilization target such as the sterilization target, but the ozone concentration of the 500 mL PET bottle 1 is 10 vol. % Ozone gas is used in the range of 0.3 to 10 mL, preferably 2 to 8 mL.
Therefore, in the present invention, ozone gas and moisture are individually supplied to the region to be sterilized so that the amount of water to be supplied can be arbitrarily adjusted.

Ozone (O ₃ ) is chemically unstable, and the presence of water promotes decomposition accompanied by the generation of OH radicals. As described above, OH radicals disappear rapidly when generated. Therefore, if ozone and moisture are in contact with each other for a long time before being supplied to the area to be sterilized, the OH radicals generated before reaching the area to be sterilized will rapidly decrease, and the OH radical will be insufficient in the area to be sterilized. And cannot contribute to sterilization. On the other hand, if ozone is consumed to generate OH radicals before reaching the sterilization target area, the amount of OH radicals generated in the sterilization target area decreases.
Therefore, in the present invention, ozone gas and moisture are separately supplied to the region to be sterilized to approach the region to be sterilized, or after reaching the region to be sterilized, OH radicals are generated therein. It is preferable to be able to start.

[Combination of ozone gas and moisture]
The ozone gas used in the present embodiment can be a dry (dry) ozone gas or a wet (wet) ozone gas. Here, the dry state is a relative expression with respect to the wet state, and does not mean that no humidity is provided, but means that no humidity is intentionally provided. In order to suppress consumption of ozone and moisture necessary for generating OH radicals before reaching the bacteria target region, it is preferable to keep humidity low even if wet ozone gas is used. From this viewpoint, it is preferable to use dry ozone gas in the present invention.

The moisture used in the present embodiment is preferably in the form of fine particles having a particle size of about 1 to 1000 μm. This is to ensure contact with ozone while suppressing the amount of water as much as possible.
As the granular moisture, water vapor that is gas phase water can be used, and spray water that is generated by spraying liquid phase water can be used. When using only water vapor, either saturated water vapor or unsaturated water vapor can be used. Moreover, this water | moisture content may be used at normal temperature, and may be used as heated warm water. For hot water, it is necessary to set the temperature in consideration of, for example, heat resistance of the sterilization target region. For example, when a PET bottle is used as the sterilization target region, the current PET bottle has a heat resistance of about 70 ° C. Therefore, when using warm water, it is preferable that the temperature of the spray water adhering to the PET bottle does not exceed 70 ° C.

  FIG. 2 shows an example of a specific combination of ozone gas and moisture, but the present invention may be any of those shown in FIGS. 2 (a) to 2 (d). As shown in FIG. After supplying, in addition to the form of supplying dry ozone gas and spray water, as shown in FIG. 2 (d), after sterilization with dry ozone gas and water vapor, sterilization with dry ozone gas and spray water is continuously performed. You can also.

[Ozone gas]
Next, the ozone gas used in the present invention will be described.
The dry ozone gas is typically generated as a mixed gas of ozone (O ₃ ) and oxygen (O ₂ ) using oxygen (O ₂ ) gas as a raw material. Therefore, the ozone gas in the present invention means a mixed gas of ozone and oxygen. In the present invention, the ozone concentration in the ozone gas is selected from the range of 5 to 20% by volume, preferably 8 to 15% by volume. In addition, as a raw material which produces | generates ozone gas, not only pure oxygen but the gas containing oxygen as a raw material, for example, air, can also be used. In this case as well, the ozone gas is still a mixed gas of ozone (O ₃ ) and oxygen (O ₂ ).

As a method for generating dry ozone gas, there are a silent discharge method, an electrolysis method, an ultraviolet lamp method, and the like. The silent discharge method is used for industrial use, and it is preferable to apply the silent discharge method in the present invention, but it does not prevent other methods from being adopted. Here, silent discharge is a discharge phenomenon observed when a dielectric is provided between parallel electrodes, oxygen gas is supplied therebetween, and an alternating high voltage is applied between the two electrodes. . Electrons e are emitted into the gas by this silent discharge. A first step of causing the electrons e to collide with stable oxygen molecules O ₂ to dissociate the oxygen molecules O ₂ into oxygen atoms O; an oxygen atom O, an oxygen molecule O _2, and a third substance M (for example, a nitrogen molecule) Ozone is generated by the second step in which a three-body collision including) occurs. Therefore, the ozone gas in the present invention may contain this third substance M.
First step: O ₂ + e → 2O + e
Second step: O + O ₂ + M → O ₃ + M

Wet ozone gas can be obtained by applying humidity to dry ozone gas.
The method of applying humidity is arbitrary, such as a bubble dissolution method, a mixing method in which wet gas such as generated wet oxygen and ozone gas are mixed, and a shower method in which ozone gas is supplied to water sprayed in a shower form. Can be adopted. Moreover, after producing | generating ozone water by arbitrary methods, this can be vaporized and wet ozone gas can also be produced | generated, water vapor | steam can be produced | generated by arbitrary methods, and ozone gas can also be made to contact this.

[moisture]
Next, the moisture used in the present invention will be described.
As the water vapor which is one form of the water of the present invention, saturated or unsaturated water vapor at atmospheric pressure can be used. Further, as this water vapor, wet water vapor which is a mixture of liquid phase water and water vapor can be used. Since saturated steam has a temperature in the vicinity of 100 ° C., it is effective for sterilizing bacteria having poor heat resistance by raising the temperature of the region to be sterilized in a short time.
On the other hand, the spray water which is the other form of the water | moisture content of this invention can be produced | generated using an atomizing nozzle. In this case, as shown in FIG. 3A, it is preferable to use a two-fluid nozzle 6 capable of atomizing liquid water. The two-fluid nozzle can inject the liquid into a fine mist by mixing the gas and the liquid. The particle size of the spray water by the two-fluid nozzle is on the order of several tens of μm, and can be easily realized as 10 μm or less.
In the case of the present invention, the gas can be ozone gas and the liquid can be water, so that it can be supplied to the region to be sterilized as a mixed fluid of ozone gas and fine water. When the type of moisture is switched from the middle, as shown in FIG. 3B, a three-fluid nozzle 7 having three fluid inlets in one nozzle can also be used.
However, the present invention allows ozone gas and moisture to be supplied using individual nozzles 8 and 9, respectively, as shown in FIG. In this case, if one gas nozzle is used to discharge water in the form of a mist while ozone gas is supplied toward the discharged water, ozone gas and fine granular water are used in the same manner as when using the two-fluid nozzle. And a mixed fluid can be generated. As shown in FIG. 3 (d), the tips of nozzles 8 and 9 from which fluid is discharged can be inserted into the PET bottle 1, and the mixed fluid can be fed into the PET bottle while raising and lowering the tips of the nozzles 8 and 9. 1 can also be supplied.
Although water vapor and spray water are preferred forms of water for the present invention, the present invention is not limited to this, and shower-like watering can also be used.

As described above, if the mixed fluid of ozone gas and fine granular water is supplied to the region to be sterilized, a stirring action is generated, which contributes to improvement in sterilization performance. That is, as shown in FIG. 1 (c), ozone gas and moisture particles coexist and are stirred together, increasing the chance that ozone and moisture come into contact with each other, and the opportunity for the generated OH radicals to touch bacteria B. It contributes to the improvement of sterilization performance.
The effect of this agitation becomes significant when the region to be sterilized is a space that is closed except for a part, and the ozone gas and moisture that are sent individually agitate each other in the space to promote mixing. When an object to be sterilized is a container for beverages as an example of a region to be sterilized consisting of such a closed space, the internal space of the container filled with beverages corresponds, and the inner peripheral surface of the container is sterilized In addition, mixing of ozone gas and moisture is promoted in this internal space. As another example, if a container is accommodated in a chamber when an object to be sterilized, for example, a beverage container, is sterilized, the inner space of the chamber corresponds to the outside of the container. In this case, when the outer peripheral surface of the container is sterilized, mixing of ozone gas and moisture is promoted in the internal space.

[Application example to beverage containers]
Hereinafter, the present invention will be described with reference to FIG. 4 and FIG.
This example is based on the premise that the inner peripheral surface and the outer peripheral surface of the PET bottle 1 continuously conveyed from the upstream process are sterilized, and the PET bottle 1 is delivered to the downstream process. The process described here includes a sterilization process for performing sterilization itself, and a rinsing process for rinsing the sterilized PET bottle 1. The sterilization process is divided into first sterilization and second sterilization. In addition, it is preferable to accommodate the PET bottle 1 in the chamber 10 through the sterilization process and the rinse process. When the PET bottle 1 to be transported is continuously processed, the chamber 10 is formed in a tunnel shape connected to the transport path, and forms a sterilization region including a closed space except for the entrance and the exit of the PET bottle 1. Is preferred.
In the present embodiment, as shown in FIG. 4, the PET bottle 1 is sterilized in an inverted state with the mouth portion 2 facing downward. This is because when a considerable amount of water is supplied for sterilization, the supplied water is expected to be discharged from the PET bottle 1 by gravity.

As the first sterilization, ozone gas and water vapor are supplied from the opening of the mouth part 2 of the inverted PET bottle 1 toward the internal space of the body part 3. Here, it is assumed that the PET bottle 1 at room temperature is supplied.
By supplying ozone gas and water vapor, OH radicals generated inside the PET bottle 1 sterilize the inner peripheral surface of the PET bottle 1. Further, since water vapor is supplied into the PET bottle 1, the temperature of the PET bottle 1 is increased as shown in FIG. 4, and this embodiment uses this temperature increase for sterilization. In other words, there are bacteria that are vulnerable to heat among the bacteria that are to be killed, and it is assumed that these bacteria will be killed by heating.

  Next, as the second sterilization, ozone gas and spray water are blown to promote sterilization inside the PET bottle 1 by OH radical generation, particularly sterilization against heat-resistant bacteria. In particular, since the first sterilization uses water vapor as water, the absolute amount of water that can be supplied is limited. Therefore, in the second sterilization, the generation of OH radicals is accelerated using spray water, and the sterilization performance is improved. Improve. During the second sterilization, ozone gas and spray water are blown into the inner space of the chamber 10 outside the PET bottle 1 to sterilize the outer peripheral surface of the PET bottle 1. In order to sterilize the outer peripheral surface, ozone gas and spray water may be blown during the first sterilization or through the first sterilization and the second sterilization.

When the sterilization process including the first sterilization and the second sterilization is completed, the process proceeds to the rinsing process.
In the rinsing step, air is supplied to the inside of the PET bottle 1 in order to discharge ozone gas remaining inside the PET bottle 1.
The supplied air may be cold air at normal temperature or warm air. Moreover, in order to wash away the inner peripheral surface of the PET bottle 1, spray water may be blown together with air.

  In the above, sterilization of the inner peripheral surface of the PET bottle 1 has been described. However, the outer peripheral surface of the PET bottle 1 can be sterilized by supplying ozone gas and water vapor and / or spray water into the chamber 10. In the case of the sterilization process including the first sterilization and the second sterilization described above, a mechanism capable of supplying ozone gas and spray water used for the second sterilization to the outside of the PET bottle 1 inside the chamber 10 is provided. It can be sterilized in the same manner as the inner peripheral surface.

  Here, it is assumed that a molding apparatus for the PET bottle 1 is provided as an upstream process, and the PET bottle that has just been molded is sterilized. This molding apparatus uses a prototype of a PET bottle 1 called a preform, and molds the PET bottle 1 by a blow molding method that involves heating. The molded PET bottle 1 has a temperature of about 70 ° C. doing. Therefore, in this case, it is assumed that heat sterilization has been performed, and the sterilization for supplying ozone gas and spray water is performed as shown in FIG. 5 without performing the processing corresponding to the first sterilization described above. Can do. In this case, in order to maintain the temperature of the PET bottle 1 in the sterilization process, it is preferable to supply low-temperature wet steam or spray water made of hot water. In this case, the heat resistant temperature of the PET bottle 1 should be considered.

[Experimental example]
An experiment for evaluating the bactericidal performance of a 500 mL PET bottle (specimen) using two types of bacteria, Bacillus atrophaeus and Chaetomium globosum, was performed as follows. The evaluation result about each microbial species is shown in FIG.6 and FIG.7.
As the sterilization step, the following treatments A, B and C were carried out alone or in combination. Processes B and C correspond to the present invention.
The evaluation of the sterilization performance was performed on specimens that had been rinsed inside after the sterilization process. When simultaneously supplying ozone gas and water vapor, ozone gas and water (liquid phase), a mixed fluid was blown into the specimen using a two-fluid nozzle.
Process A: Process for supplying ozone gas alone B: Process for supplying ozone gas and water vapor C: Supply of ozone gas and spray water

The specifications of ozone gas, water vapor and spray water used for sterilization, and air used for rinsing are as follows.
Ozone gas: dry (oxygen is the raw material), room temperature, ozone concentration; 10 vol. %, Flow rate; 20 mL / min.
Water vapor (vapor pressure): 0.3 MPa
Spray water: distilled water, room temperature air (rinse): dry, room temperature, flow rate; 20 mL / min.
Comparative example: wet ozone gas, 30 mL / min.

In FIG. 6, No. 7 is a comparative example in which sterilization is performed only by processing A that supplies ozone gas alone, and other Nos. 1 to 6 are examples of the present invention in which at least one of processing B and C is performed. is there. 7 is the same, No. 3 is a comparative example, No. 1 and No. 3 are comparative examples. 2 is an example of the present invention.
As shown in FIG.6 and FIG.7, the example of this invention has improved the bactericidal performance compared with the comparative example.
In addition, in FIG. 3 and no. 4 is compared, it turns out that sterilization performance improves markedly by increasing the quantity which supplies spray water.

[Effect]
As described above, according to the present invention in which ozone gas and moisture are individually supplied to the region to be sterilized, sterilization performance in a short time can be significantly improved. In particular, as shown in the experimental example, by selecting the moisture to be supplied together with the ozone gas, such as the process B for supplying ozone gas and water vapor and the process C for supplying ozone gas and spray water, the beverage can be obtained in a short time of about several seconds. The sterilization performance required for the PET bottle 1 can be obtained. This is due to the following reason.
First, by supplying ozone gas and water separately, the amount of water that can be supplied can be set arbitrarily, so that a sufficient amount of OH radicals necessary for sterilization can be secured.
Further, since water is supplied as a mist through the two-fluid nozzle, generation of OH radicals is promoted by efficiently contacting with ozone gas by a stirring action while avoiding supplying an excessive amount of water.

  Next, in the present invention, if water vapor is used as moisture supplied together with ozone gas, sterilization by heat can be performed in parallel with sterilization by OH radicals, so for example PET bottles conveyed at room temperature in a short time. It is effective to obtain a desired sterilization performance.

The preferred embodiments of the present invention have been described above. However, the configurations described in the above embodiments can be selected or changed to other configurations as appropriate without departing from the gist of the present invention. is there.
For example, although the PET bottle 1 is shown as the sterilization target area in the embodiment, the sterilization target in the present invention is arbitrary, and can be widely applied to containers and manufacturing equipment in the food field including beverages, instruments and equipment in the medical field, and the like. Can do.

1 PET bottle 2 mouth 3 body 6, 7, 8, 9 nozzle 10 chamber

Claims (6)

Supplying ozone gas to the area to be sterilized, and sterilizing the bacteria present in the area to be sterilized , the sterilization method of supplying the ozone gas and moisture that have been individually conveyed to the area to be sterilized ,
A first sterilization for supplying the ozone gas and water vapor as the moisture toward the sterilization target region;
Subsequent to the first sterilization, a second sterilization method of performing the second sterilization of supplying the ozone gas and the spray water as the moisture toward the sterilization target region is performed . The ozone gas and the moisture are mixed before the sterilization target area or inside the sterilization target area,
The sterilization method according to claim 1. Inside the chamber in which the object to be sterilized is continuously conveyed, the ozone gas and the moisture are supplied.
The sterilization method according to claim 2. The object to be sterilized is a beverage container,
The ozone gas and the moisture are supplied through the mouth of the container,
In the inside of the container that forms a closed space except for the mouth, the ozone gas and the moisture are mixed.
The sterilization method as described in any one of Claims 1-3. Supply of the ozone gas and the moisture to the sterilization target area is started at the same time, or
The ozone gas is supplied to the sterilization target area prior to the moisture,
The sterilization method as described in any one of Claims 1-4. The ozone gas is
A dry ozone gas or a wet ozone gas,
The sterilization method according to any one of claims 1 to 5 .

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