JP2019176796A - Food sterilization method - Google Patents

Abstract

To provide a food sterilization method capable of effectively sterilizing fungus and microorganism that have entered structures of food, such as vegetables.SOLUTION: A food sterilization method includes: an introduction step of introducing a bactericidal substance into a container accommodating therein food whose surface includes fine pores; and a sterilization step of impregnating the bactericidal substance into the fine pores of the food by increasing a pressure in the container.SELECTED DRAWING: None

Description

  The present invention relates to a method for sterilizing food having fine pores on the surface, and particularly to a method for sterilizing vegetables having pores.

  Conventionally, sterilization and sterilization with hypochlorous acid and the like are generally known as means for washing food such as vegetables. However, in the sterilization method using a drug such as hypochlorous acid, after the sterilization process, a process such as washing with water is necessary to prevent the drug from remaining in food. As a technique that makes such treatment unnecessary, a method is known in which ozone is used as a bactericidal substance instead of a chemical such as hypochlorous acid (see Patent Documents 1 and 2 below). In these methods, by supplying ozone (ozone water) in a reduced-pressure atmosphere, ozone is efficiently adhered to voids or the like caused by unevenness on the food surface, and the sterilizing effect is enhanced.

JP-A-2006-204106 JP2015-128388A

  As described above, in the sterilization method according to Patent Documents 1 and 2, etc., decompression is performed in a sealed space, so that ozone can be efficiently delivered to the surface of the food to be sterilized without leaking out of the system. On the other hand, many foods such as vegetables have fine pores such as pores on the surface. However, in the above-described sterilization method, it is difficult to kill bacteria and microorganisms that have penetrated into tissues (hereinafter, these may be simply referred to as “bacteria”). For example, in the case of vegetables having pores, bacteria may enter not only the bacteria attached to the surface but also soil from the soil through the pores. From the viewpoint of freshness and hygiene, it is desirable to kill bacteria that have entered these cell gaps. However, there is no method other than the current heat sterilization to kill the bacteria that have invaded the inside of the vegetables, and there has been a demand for the development of a method that can effectively sterilize the bacteria that have penetrated into the vegetable tissue in a non-heated state. .

  In order to solve the above-described problems, an object of the present invention is to provide a food sterilization method capable of effectively sterilizing bacteria and microorganisms that have entered a food tissue such as vegetables.

<1> An introduction step of introducing a bactericidal substance into a container containing food having fine pores on the surface, and a sterilization for increasing the pressure in the container and impregnating the bactericidal substance into the fine pores of the food And a method for sterilizing food comprising the steps.
<2> The method for sterilizing food according to <1>, wherein the food is a vegetable having pores as the fine pores.
<3> The method for sterilizing food according to <1> or <2>, wherein the bactericidal substance is in the form of a gas, a solution, or a mixture thereof.
<4> The food sterilization method according to any one of <1> to <3>, wherein the introduction step introduces a gas containing the bactericidal substance into the container.
<5> The food sterilization method according to any one of <1> to <4>, wherein the introduction step includes a step of irradiating the food with blue light.
<6> The method for sterilizing food according to any one of <1> to <5>, wherein the bactericidal substance is ozone.
<7> The method for sterilizing food according to any one of <1> to <6>, wherein the introducing step introduces a liquid containing fine bubbles having a diameter of less than 100 μm containing the bactericidal substance into the container.
<8> The method for sterilizing food according to any one of <1> to <7>, wherein the introducing step introduces the bactericidal substance into the container after decompressing the inside of the container.
<9> The food sterilization method according to any one of <1> to <8>, wherein the sterilization step raises the pressure in the container with a gas containing the bactericidal substance introduced in the introduction step.
<10> The food sterilization method according to any one of <1> to <8>, wherein the container is a vacuum precooling chamber of a vacuum precooling facility.

  ADVANTAGE OF THE INVENTION According to this invention, the sterilization method of the food | food which can effectively sterilize the microbe and microorganisms which entered into the structure | tissue of foods, such as vegetables, can be provided.

  Hereinafter, the contents of the present invention will be described in detail using embodiments. However, the following embodiments are examples, and the present invention is not limited to these embodiments.

《Food sterilization method》
The food sterilization method of the present embodiment (hereinafter may be simply referred to as “the sterilization method of the present embodiment”) is an introduction step of introducing a bactericidal substance into a container in which food having fine pores is stored on the surface. And a sterilization step of increasing the pressure in the container and impregnating the microbicidal substance with the microbicidal substance.
In the sterilization method of the present embodiment, the sterilization treatment is performed with the sterilizing substance while increasing the pressure in the container, whereby the sterilizing substance can be impregnated into the structure of the food from the fine holes. Thereby, the microbe and microorganisms which invaded in the structure of food can be killed effectively. For this reason, by using the sterilization method of this embodiment, the number of viable bacteria such as raw vegetables can be reduced to the extent that it has been difficult to obtain in the past. The number of viable bacteria has a great influence on the freshness of raw vegetables. For example, the cut vegetables using the raw vegetables obtained by using the sterilization method of the present embodiment are conventional products (for example, the vegetables are immersed in a 200 ppm sodium hypochlorite aqueous solution for 5 minutes and then rinsed with sterile water. The number of viable bacteria can be sufficiently reduced as compared with cut vegetables using In addition, the cut vegetables using the vegetables sterilized by the sterilization method of the present embodiment have excellent flavor, and the shelf life is about twice as long as that of conventional products, and the quality is maintained without deterioration for about 10 days. It has excellent freshness maintenance ability.

The influence of ozone on the human body is generally known, but the exposure limit is said to be about 0.1 ppm (or 0.2 mg / m ³ ) as an allowable concentration. For this reason, in order to handle ozone as it is in a closed system such as a food factory, it is usually necessary to use a special device. For example, while strictly controlling so that ozone does not leak outside in a completely closed system, It is desirable to sterilize vegetables. From such a viewpoint, it is preferable to introduce ozone into a sealed container such as a sterilization tank or a fumigation tank. Moreover, in the sterilization methods as described in Patent Documents 1 and 2, it is considered that an effect of preventing ozone from leaking out of the system can be obtained.

  Hereinafter, the sterilization method of the present embodiment will be described for each step focusing on the introduction step and the sterilization step.

<Introduction process>
The introduction step is a step of introducing a bactericidal substance into a container in which food having fine pores is stored on the surface. The food stored in the container may be subjected to a process (preparation process) of removing non-edible portions or removing mud or the like before the introducing process. Moreover, the food stored in the container may be food before cutting, or may be food after being cut by a cutting process. Other processes such as a preparation process and a cutting process will be described later.
The container used for the introduction step can be used without any particular limitation as long as it is a container that can withstand the pressurization in the sterilization step and the decompression step described later and includes a means capable of introducing a bactericidal substance. Moreover, what has a mechanism in which an inside bactericidal substance does not leak out of a container, such as a container being sealed, is preferable. The size and shape of the container are not particularly limited, and can be appropriately selected and used according to the target food and the degree of pressure fluctuation in the container. Such containers include, for example, large devices such as a vacuum precooling chamber installed in a vacuum precooling facility in addition to a general pressure resistant container.

  As described above, a vacuum precooling chamber installed in a vacuum precooling facility can be used as a container. In particular, the vacuum pre-cooling facility is usually installed in a field of production area, and therefore, ozone is easy to handle and is preferable. In addition, if such a facility is installed in a field or the like, it can be processed immediately after harvesting vegetables, which is effective in maintaining freshness. Here, “vacuum precooling” means that food such as fruits and vegetables is cooled by the heat of vaporization due to decompression, and “vacuum precooling cabinet” is used for the vacuum precooling and is used for decompression means (gas is introduced into the chamber or It means a storage with a pump that can suck the gas in the storage. When the pressure in the vacuum precooling chamber decreases, the evaporation temperature of water decreases, so that moisture on the food surface can be vaporized and the inside of the vacuum precooling chamber can be cooled by the heat of vaporization. For example, since the evaporation temperature of water in the vacuum precooling chamber is determined by the relationship with the pressure, the cooling temperature in the vacuum precooling chamber can be set by adjusting the pressure in the vacuum precooling chamber. In addition, although not particularly limited, the cutting process and the packaging process described later may be performed in the vacuum precooling chamber, or the vacuum precooling facility of the vacuum precooling facility that performs the introduction process and the sterilization process is divided into the cutting process and the packaging. It may be an aspect in which these steps are performed outside the vacuum precooling chamber by being included in a part of the line together with the steps.

(Food with micropores on the surface)
In the sterilization method of the present embodiment, food having fine pores on the surface is targeted for sterilization. Here, “micropore” means a hole having a diameter of 1.0 mm or less. Examples of the micropores include plant pores, but are not limited thereto. Similarly, foods having fine pores on the surface include, for example, vegetables and fruits having pores as fine pores. As for the pores, not only leaves but also stems and fruits are observed, and examples include leafy vegetables such as lettuce and cabbage, cucumber, asparagus glass, broccoli, green onion, onion and the like. In addition, when it calls "vegetables" in a present Example, in addition to vegetables, fruit is also included. However, the food having micropores in the present embodiment is not limited to vegetables and fruits.

  Plant stomata are vents between two guard cells and provide a passage for water vapor and gas during transpiration, respiration, and assimilation. A plant having a pore has a cell space immediately inside the pore, and further leads to a cell space in a leaf. For this reason, the cells inside the leaves can also directly touch the air entering through the pores. In general, there are more pores on the back surface than the front surface of the leaf, and soil microorganisms may enter the leaf from the pores. Thus, the bacteria and microorganisms that have entered the plant body from the pores may grow in the cell space. According to the sterilization method of the present embodiment, it is possible to effectively kill bacteria, microorganisms and the like that have proliferated in the pores.

(Bactericidal substance)
The bactericidal substance means a substance having an effect of killing target bacteria or microorganisms. Examples of the “bacteria” removed by the sterilization method of the present embodiment include, for example, bacteria that adhere to soil-derived germs and vegetables and reduce the freshness thereof, Escherichia coli, Salmonella, Staphylococci that cause health hazards. Including bacteria and fungi in general.

The bactericidal substance is not particularly limited as long as it has an effect of killing these bacteria, but a compound that does not have a bactericidal activity and disappears after use in a bactericidal treatment in a plant tissue is desirable. For example, when a compound that finally changes to oxygen molecules, such as ozone, is used, after the sterilization treatment, a treatment such as washing the sterilizing substance itself is not necessary. Similarly, a hydroperoxy radical (HOO.) Generated by a reaction between a superoxide anion radical (O ₂ ⁻ ·) generated by plasma and a proton in a liquid, or pernitric acid described in International Publication WO2016 / 035342A1 (HOONO ₂ ) and the like also become inactive and stable after sterilization, and the reaction is terminated. Therefore, it is not necessary to remove them out of the system like chlorinated compounds. Can be suitably used.

  The state of the bactericidal substance introduced into the container is not particularly limited, and may be any state of a gas, a solution, or a mixture thereof (a mixture of a gas and a solution). For example, when a gaseous sterilizing substance is introduced into a container, a pressure gradient is created so that the sterilizing substance is introduced into the container together with a gas such as air, nitrogen gas, or a mixed gas thereof alone. Is done. Similarly, when the bactericidal substance is in the form of a solution, the solution-like bactericidal substance may be introduced alone into the container, or may be introduced into the container together with a gas such as air. In addition, when using gaseous bactericidal substances or gas, such as air, and a bactericidal substance together, these can be used as a means to raise the pressure in the container in a sterilization process. In addition, the means for introducing the bactericidal substance into the container is not particularly limited, and it may be introduced so that the bactericidal substance can be uniformly distributed in the food to be sterilized. A known introduction means can be appropriately selected according to the above. For example, when a gaseous sterilizing substance is introduced together with a gas such as air, if the inside of the container has been previously depressurized as will be described later, the sterilizing substance is placed in the container using the negative pressure in the container. It can be configured to be introduced into. On the other hand, when the inside of the container is in a normal pressure (atmospheric pressure) state, it is configured to introduce a bactericidal substance into the container together with a gas such as air and pressurize the container by means of a pump or the like. Can do. Further, when the bactericidal substance is in the form of a solution, it may be introduced into the container together with air or the like as in the case of the gaseous form, or ozone water or the like is made into a shower and continuously on the sterilized object. May be sprayed.

  As described above, ozone can be used as the bactericidal substance in the present embodiment. Ozone may be used as ozone gas or ozone water. The ozone water can be obtained by a known method such as dissolving ozone gas in water or utilizing electrolysis of water. Ozone water can exhibit a bactericidal effect by the oxidizing power of the hydroxyl radicals generated from ozone itself and ozone. For example, it is said that 3 ppm to 5 ppm of ozone water can exhibit the same degree of bactericidal power as slightly acidic electrolyzed water of 1 ppm effective chlorine. In addition, since the stability of ozone is low, it is quickly decomposed into oxygen after being used in the sterilization process. For example, the ozone concentration (10 ppm) gas is reduced to about one third in about 3 minutes.

When ozone gas is used as the bactericidal substance, the ozone concentration in the ozone gas is preferably 1 ppm to 20 ppm, more preferably 2.0 ppm to 5.0 ppm.
Similarly, when ozone water is used as a bactericidal substance, ozone water has a higher oxidizing ability than ozone gas and may damage vegetables themselves, so the ozone concentration in ozone water is preferably 1 ppm to 10 ppm. 0 ppm to 5.0 ppm is more preferable. The supply amount of the bactericidal substance is not particularly limited. For example, when the bactericidal substance is introduced into the container together with a gas such as air, the bactericidal substance is appropriately sterilized depending on the relationship between the container size and the pressure to be increased. What is necessary is just to adjust the density | concentration and supply amount of a substance.

(Liquid containing fine bubbles)
Further, the introducing step may be an aspect in which a liquid containing microbubbles having a diameter of less than 100 μm containing a bactericidal substance is introduced into the container. Thus, by using the liquid containing fine bubbles, the bactericidal effect can be improved more effectively against the bacteria and microorganisms in the micropores. In the case of using a liquid containing fine bubbles, the bactericidal substance may be contained in a gaseous state (for example, ozone gas) or in a solution state (for example, ozone water).

Here, the “fine bubbles” are fine bubbles having a diameter of less than 100 μm, and micro-sized fine bubbles called “micro bubbles” can be used. Further, from the viewpoint of obtaining a sufficient bactericidal effect, the diameter of the fine bubbles is preferably less than 100 μm, more preferably fine bubbles having a diameter of less than 1 μm (so-called “ultra fine bubbles”), and 10 nm to 500 nm. It is particularly preferred.
The presence of fine bubbles in the liquid can be confirmed, for example, by using laser light scattering.

  The method for measuring the diameter of the fine bubbles is not particularly limited. For example, dynamic light scattering (DLS), particle tracking analysis, laser analysis, resonance mass measurement (RMM), etc. These known methods can be used as appropriate. The average diameter of the fine bubbles measured by these known methods can be regarded as the diameter of the fine bubbles.

Further, the concentration of fine bubbles in the liquid used in the washing step is not particularly limited, but from the viewpoint of washing and sterilization efficiency, it is preferably 10 ⁵ / ml or more, and 10 ⁷ / ml or more. More preferably, 10 ⁸ pieces / ml or more is particularly preferable. The concentration of the fine bubbles can be measured by, for example, Zetaview (registered trademark) manufactured by Microtrack Bell.

  The liquid containing fine bubbles is not particularly limited, and deionized water generally used for washing fruits and vegetables, potable well water, tap water, and the like can be used. Moreover, it is not restricted to these, Aqueous solution, such as ozone water, ethanol, acetic acid, an organic acid, can also be used.

  In the present embodiment, a method for generating fine bubbles is not particularly limited, and a known method can be used. Examples of the known method include a method of generating fine bubbles by mixing a gas with a liquid and applying a high shearing force or the like to the liquid. More specifically, the liquid in which the gas is mixed can be sent to a mixer or the like having a complicated fluid path with a pump, and the bubbles can be refined by applying a shearing force to the bubbles in the liquid. Moreover, although it changes with apparatuses used, an ideal microbubble can be generated by repeating the bubble miniaturization process several times, for example. Although the gas mixed with the liquid is not particularly limited, for example, air, nitrogen gas, ozone gas or the like can be used, and it is particularly preferable to produce fine bubbles using ozone gas. As a microbubble generator, a commercially available ultra-high density ultrafine bubble generator or the like can be used. In addition, since carbon dioxide (carbon dioxide) has an action of closing the pores of vegetables, it is preferable to generate fine bubbles using a gas other than carbon dioxide. Further, it is preferable not to use carbon dioxide as much as possible in other steps including the introduction step (especially the steps before the introduction and sterilization step), and carbon dioxide (carbon dioxide) is removed (for example, 400 ppm) in a sealed space. Each step may be performed after the following.

(Irradiation process)
The introducing step in the present embodiment may include a step of irradiating food with blue light. According to the studies by the present inventors, it has been found that the opening and closing of the pores affects the sterilization efficiency. Since the pores can be opened by irradiating vegetables with blue light, the sterilization efficiency can be further improved by using the irradiation step in combination, and the viable bacteria rate recovered from the vegetables can be further reduced.

Here, blue light means light having a wavelength of 380 nm to 500 nm. The blue LED used has a maximum emission wavelength of 460 nm. Is not particularly limited dose of blue light in the irradiation step, from the viewpoint of the irradiation effect and irradiation efficiency, for example, preferably ^{50~500μmolm -2 s -1, 30~100μmolm -2 s} -1 it is particularly preferred. Although there is no particular limitation, the irradiation step is preferably performed before or while introducing the bactericidal substance. Further, the irradiation step may be continuously performed in the subsequent sterilization step following the introduction step. In addition, pulse irradiation is also effective in order not to raise the temperature of vegetables excessively. Furthermore, even if it is a vegetable such as a leafy vegetable that is tightly wound, it is possible to effectively prevent bacteria from entering the vegetable from the outside by irradiating the outer leaves with blue light. .

<Sterilization process>
The sterilization process is a process in which the sterilizing substance is allowed to coexist with the sterilization target, and then the pressure in the container is increased to impregnate the microbicidal substance of the food with the sterilizing substance. In the sterilization method of the present embodiment, the sterilization treatment is performed with the sterilizing substance while increasing the pressure in the container, whereby the sterilizing substance can be impregnated into the structure of the food from the fine holes. The means for increasing the pressure in the container is not particularly limited. For example, the pressure in the container is reduced in advance, and then the gas is introduced into the container using negative pressure to increase the pressure in the container to atmospheric pressure. And a means for increasing the pressure in the container from the atmospheric pressure by introducing gas into the container in a normal pressure (atmospheric pressure) state (pressurizing means). In this step, the increase in pressure is not particularly limited, but is preferably about 1 atm (1.01325 × 10 ⁵ Pa (760 torr) from the viewpoint of the burden on food and the temperature in the container. After the food is sterilized by the sterilization process, the food may be dehydrated to remove sterilizing substances, water, etc. Examples of the dehydration treatment include means such as centrifugal dehydration.

(Pressure reduction means)
When using a decompression means to increase the pressure in the container in the sterilization process, the pressure in the container can be increased by introducing a sterilizing substance into the container after reducing the pressure in the container in advance in the introduction process. . More specifically, first, the inside of the container containing the food is decompressed using a vacuum pump or the like in the introduction step. At this time, the degree of decompression is not particularly limited, but it is preferable that the decompression is performed so that the temperature in the container is reduced by the heat of vaporization and the water adhering to food is not frozen. From this point of view, for example, the pressure in the container at the time of depressurization can be 1.0 to 50 torr (about 133.322 Pa to about 6666.12 Pa), and preferably 5.0 to 10 torr (about 666. 61 Pa to about 1333.22 Pa). Then, the pressure in the container can be increased to atmospheric pressure by introducing the bactericidal substance together with the gas using the negative pressure in the container. That is, the sterilization process can raise the pressure in the container using the gas containing the sterilizing substance introduced in the introduction process. At this time, the time for depressurizing the inside of the container is not particularly limited, but is preferably 1 minute to 50 minutes from the viewpoint of preventing the temperature inside the container from being reduced by the depressurization and freezing of water adhering to food. 10 minutes is more preferable. Similarly, when using the decompression means, the temperature in the container is reduced when the decompression means is used from the viewpoint of preventing the temperature inside the container from being reduced by the decompression and preventing the water adhering to food from freezing. It is preferable to adjust the gas supply amount and the like so as to be 4 ° C to 30 ° C, preferably 5 ° C to 15 ° C.

(Pressurizing means)
In the case of using a pressurizing means for increasing the pressure in the container in the sterilization process, the pressurizing means is not particularly limited. For example, a pump or the like is used in a container under an atmospheric pressure (atmospheric pressure) atmosphere. By introducing a gas containing a bactericidal substance, the pressure in the container can be increased. That is, also in this case, the pressure in the container is increased by the gas containing the bactericidal substance introduced by the introduction process. At this time, the degree of pressurization (the degree of increase in pressure) is not particularly limited, but from the viewpoint of work efficiency and container resistance, for example, the pressure in the container is about 2 atm (about 2.02650 × 10 ⁵ Pa). It is preferable to pressurize until). When the inside of the container is pressurized by the pressurizing means, the pressure in the container is released over a certain period of time so that the contents do not rupture after one point of time. In this case, the pressurization time is preferably 5 minutes to 60 minutes, and more preferably 1 minute to 30 minutes, from the viewpoint of reducing the load on food. Similarly, when using the pressurizing means, the temperature in the container is 3 ° C to 30 ° C, preferably 5 ° C to 10 ° C, from the viewpoint of reducing the load on food due to pressurization or temperature rise. It is preferable to adjust the gas supply amount and so on. In addition, the process consisting of pressure reduction and pressurization is not limited to once, and may be repeated.

<Other processes>
The sterilization method of the present embodiment may include a preparation process, a cutting process, a cleaning process, a packaging process, and the like in addition to the introduction process and the sterilization process described above. Moreover, the process of performing a dehydration process, a foreign material detection, a weight check etc. may be included between each process or each process itself.

Moreover, it is preferable that each process of this embodiment is performed aseptically as well as after a sterilization process.
Here, “aseptic condition” means practical sterility that is usually required according to the target food, and it is not necessary to be completely aseptic. Produce a microbially safe product within the set shelf life. Indicates the possible state (environment). For example, as the “sterile state”, as a general standard, the condition that the number of general viable bacteria in the environment is 5 CFU / cm ² or less and the coliform group is negative can be adopted (reference: BC Center for Disease) Control.Environmental hygiene monitoring: A guide for Environmental Health Offices, BC Center for Disease Control, October 5th, 2010 [NR / c / w, c / w rdonlyres / EF1461BE-0301-4A59-8843-4200724127721 / 0 / EnvMonitoringHygieneGuidef rEHOs.pdf>).

Specifically, although not particularly limited, for example, in order to carry out each process (at least the cutting process and the packaging process) in the “sterile state” in the present embodiment, there is a possibility of at least contact with the target food. A certain device and the surrounding environment can be based on the condition that the number of viable bacteria in the environment is 5 CFU / cm ² or less and the coliform group is negative.
In addition, examples of aseptic objects include the bacteria that are the targets of sterilization described above. The aseptic condition is, for example, the device used for the cutting process, the floor or wall of the room where the apparatus is installed, other installations, the person performing the cutting process, etc. This can be achieved by applying a sterilization treatment. Further, a clean bench or a clean room may be used in order to maintain aseptic conditions. The aseptic cutting process may be performed through a human hand in a clean bench, or may be automatically performed using an industrial robot or the like.
In order to ensure sterility, sterilization of equipment and facilities is based on the premise that products that enter the consumer's mouth and their raw materials will be exposed to chemical substances such as hypochlorous acid, or will be kept to a minimum. It is preferable to carry out by. That is, hypochlorous acid or the like can be used as a disinfectant for equipment facilities, and it is preferable to combine a plurality of disinfection treatments.

(Preparation process)
The sterilization method of this embodiment may include a preparation step. The preparation step is a step of performing a pre-cleaning process or the like in order to remove non-edible portions from the food material or to remove mud on the food surface. In the present embodiment, the preparation step is preferably performed before the introduction step.

(Cutting process)
The sterilization method of the present embodiment may include a cutting step. The cutting process is a process of cutting the target food. In the present embodiment, the cutting process may be performed before the above-described introduction process and the sterilization process, and the food after the cutting may be sterilized by the sterilization method of the present embodiment. It may be a flow that is performed later and cuts sterilized food. As described above, the cutting step is preferably performed in an aseptic state.

For the cutting (cutting) in the cutting process, a method that is usually used can be appropriately selected according to the target food. As a cutting method, for example, in the case of fruits and vegetables, various methods such as round cutting, diagonal cutting, strip cutting, chopping, diced cutting, and paste processing can be cited. Moreover, the apparatus used for a cutting process can also be suitably selected according to object food etc.
Further, the processing conditions at the time of cutting are not particularly limited. For example, under a carbon dioxide atmosphere, the humidity (RH) is about 50% to 90%, the temperature is about 1 ° C. to 15 ° C. (preferably 2 ° C. to 5 ° C. ) Is preferable.

(Washing process)
The sterilization method of this embodiment may include a cleaning step. The washing step is a step mainly aimed at washing food and removing bacteria from the surface of the food. Examples of the disinfectant used in the washing step include at least one selected from sodium hypochlorite, sodium chlorite, calcium nitrate, calcium hydroxide, pernitric acid, peracetic acid, and ozone. In the washing step, the target food can be washed by immersing it in at least one aqueous solution selected from these fungicides, preferably sodium hypochlorite, sodium chlorite, calcium nitrate and calcium hydroxide. The washing conditions when using the bactericide are not particularly limited, and can be appropriately determined according to the type of bactericide to be used, the size of the target food, and the type.
Further, in the cleaning step, cleaning may be performed using a liquid containing the above-described fine bubbles (micro bubbles, ultra fine bubbles) instead of the sterilizing agent or in combination with the sterilizing agent.

(Packaging process)
The sterilization method of the present embodiment may include a packaging process. The packaging process is a process of packaging the food that has undergone each process in a sterile state. The packaging of the target food in the packaging process is not particularly limited except that the aseptic condition is maintained, and a known method can be appropriately employed. For example, a method of sealing with a bag filled with an inert gas such as nitrogen gas or a packaging material can be employed, but it is preferable to employ a means that can ensure a sterilized state for a certain period even after packaging. . As such means, food packaging wraps made of vinylidene chloride resin or polyvinyl chloride resin are used, and an appropriate amount is stored in a tray and packed with a wrap film, or vacuum packed, sterilized packaging and removal. Examples include a method using an oxygen agent.

  Also, there are no particular limitations on the various conditions during packaging. For example, in a 3 to 10% carbon dioxide atmosphere, the humidity (RH) is about 50% to 90%, and the temperature is about 1 ° C to 15 ° C (preferably 2 ° C). It is preferable to carry out at ~ 5 ° C.

  As mentioned above, although the sterilization method of this invention was demonstrated with detailed embodiment, the structure of this invention is not limited to the above-mentioned embodiment.

  Hereinafter, the sterilization method of the present invention will be specifically described by way of examples. However, the present invention is not limited to the following modes.

[Comparative Example 1]
Circulating vegetables (cucumber, lettuce, cabbage) were obtained, and cut vegetables (vegetable samples) for salad bars were produced by conventional methods.
First, the vegetable material was washed with running water, sliced with a sterilized cooking tool (knife, cutting board), and finished for a salad bar. For sterilization, after slicing vegetables, they were immersed in a 150 ppm sodium hypochlorite aqueous solution for 5 minutes and washed with chiller water until the chlorine odor disappeared.

[Example 1]
Vegetables (cucumber, lettuce, cabbage) were obtained in the same manner as in Comparative Example 1, and all were stored in a glass vacuum desiccator. Next, the pressure in the desiccator was reduced to 5.0 torr. After depressurization, air containing 2 ppm of gaseous ozone was introduced into the desiccator using negative pressure, and the pressure in the desiccator was returned to atmospheric pressure (ie, the pressure was increased by 755 Torr). Then, each vegetable was taken out from the desiccator in the draft chamber, and it sliced with the sterilized cooking tool (a kitchen knife, a cutting board), and manufactured the vegetable sample. During decompression, the temperature in the desiccator was 18 ° C.

[Example 2]
Example 2 Example 2 was carried out in the same manner as Example 1 except that a blue LED (maximum emission wavelength: 460 nm; manufactured by Nippon Medical Instruments Co., Ltd.) was attached to a 500 W white light bulb and the vegetables in the desiccator were irradiated for 5 minutes from outside the desiccator. Of vegetable samples.

[Example 3]
Instead of “air containing 2 ppm gaseous ozone”, fine bubble water (manufactured by a device manufactured by NANOX) dissolved in 2 ppm ozone was sprayed together with air, and the pressure in the desiccator was returned to atmospheric pressure. Produced the vegetable sample of Example 3 in the same manner as Example 1. At this time, fine bubble water with several hundred million bubbles / ml of bubbles (diameter of fine bubbles has a peak near 100 nm) was used as fine bubble water. Fine bubble water was manufactured using a device manufactured by Nanocus Co., Ltd. (device name: Nano Fresher (registered trademark)). Specifically, 100 L of tap water was subjected to aeration treatment with ozone gas under a condition of room temperature and 2 hours by a nano flesher.

<Measurement of viable count>
Each vegetable sample was immediately poured into sterilized physiological saline, treated with a stomacher to prepare a bacterial solution, and the obtained bacterial solution was cultured at 37 ° C. for 2 days. The number of general viable bacteria was measured for the obtained bacterial solution with Compact Dry (manufactured by Nissui Pharmaceutical). Moreover, the same measurement was performed about the vegetable sample which has not performed sterilization treatment. These results are shown in the table below. In addition, the value in a table | surface is an average value of the result of having done the test 3 times.

  As is clear from the above table, the vegetable samples using the vegetables sterilized by the present technology were lower in the number of general viable bacteria than any of the vegetable samples of Comparative Example 1 sterilized by the conventional method. In particular, when Example 2 which was vacuum-treated by irradiating blue light having an effect of opening pores and fine bubble water containing ozone were used, the number of viable bacteria was further reduced as compared with Example 1. It was. From these results, there are bacteria in the vegetable tissue that cannot be sufficiently sterilized by surface sterilization by the conventional method, and in order to kill them, the pressure difference as in the present invention is used to put ozone in the pores. It can be seen that it is effective to impregnate a compound having no residual property.

  In the said embodiment, although the example of cucumber, lettuce, and a cabbage was shown, it is not restricted to this, It can apply also to other vegetables, such as an onion, a green onion, a palm, a bean seedling, and a honey bee.

Claims (10)

An introduction step of introducing a bactericidal substance into a container in which food having micropores on the surface is stored;
A sterilization step of increasing the pressure in the container and impregnating the microbicidal material with the microbicidal substance;
Method for sterilizing food containing   The method for sterilizing food according to claim 1, wherein the food is a vegetable having pores as the fine pores.   The method for sterilizing food according to claim 1 or 2, wherein the bactericidal substance is in the form of a gas, a solution, or a mixture thereof.   The method for sterilizing food according to any one of claims 1 to 3, wherein the introducing step introduces a gas containing the bactericidal substance into the container.   The method for sterilizing food according to any one of claims 1 to 4, wherein the introducing step includes a step of irradiating the food with blue light.   The method for sterilizing food according to any one of claims 1 to 5, wherein the bactericidal substance is ozone.   The said introduction | transduction process is a food sterilization method as described in any one of Claims 1-6 which introduce | transduces into the said container the liquid containing the microbubble with a diameter of less than 100 micrometers containing the said bactericidal substance.   The method for sterilizing food according to any one of claims 1 to 7, wherein the introducing step introduces the bactericidal substance into the container after decompressing the inside of the container.   The said sterilization process is the food sterilization method as described in any one of Claims 1-8 which raises the pressure in the said container with the gas containing the bactericidal substance introduce | transduced by the said introduction process.   The method for sterilizing food according to any one of claims 1 to 8, wherein the container is a vacuum precooling chamber of a vacuum precooling facility.