JPH08332035A - Production of cooked rice grains excellent in preservability and sterilization of rice grains - Google Patents

Abstract

PURPOSE: To provide a method capable of pre-sterilizing rice grains to an extent capable of storing for a long period even by heat treatment carried out at 100 deg.C for 20-30min in producing a container packed cooked rice. CONSTITUTION: In this method for sterilizing rice grains using a gas or a mixture of the gas with a liquid in which at least part is ionized by an electric field or an energy converter to which electromagnetic wave is irradiated, the gas or the mixture whose at least part is ionized is brought into contact with whole surface of rice grains. Rice grains sterilized by the method is cooked in aseptic state and packed and sealed into a packing container.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing cooked rice grains and a method for sterilizing rice grains. More specifically, the present invention efficiently and pre-sterilizes rice grains that are stored for a long time after processing such as cooked rice, and uses rice grains sterilized by this method, The present invention relates to a method for producing a container-packaged cooked rice grain, particularly a container-packaged cooked rice, which can be stored for a long period of time and has a good taste.

[0002]

2. Description of the Related Art "Container-wrapped rice" has been commercialized in which cooked rice is packaged and retorted to withstand long-term storage. The "container-wrapped rice" is obtained by aseptically wrapping rice in a container after cooking the rice, or by filling the container with rice and then cooking the rice together with the container, and at the same time performing heat sterilization. In order to sterilize it to a state where it can be stored for a long time, it is usually 120 ° C
For 20 to 30 minutes. However, 120
Heating at ℃ requires a pressure vessel, and generally has a drawback that the apparatus becomes large-scale.

[0003]

However, sterilization at 100 ° C., which is a temperature at which a pressure vessel is unnecessary, requires long-time heating and is not practical. Therefore, it is generally practiced to add a small amount of acid to the rice cooking water as a bacteriostatic agent or a sterilization aid. By adding a small amount of acid such as citric acid, by heat treatment at 100 ° C. for 20 to 30 minutes,
Sufficient sterilization is possible. However, cooked rice to which a small amount of acid has been added has a weak acidity, and there is a problem in that the taste is reduced compared to rice cooked without adding acid. Further, it is necessary to use a freshness-retaining agent such as an oxygen scavenger together, which causes a problem of cost increase.

By sterilizing rice before cooking rice to some extent and then cooking the rice and packaging in a sterile state, 1
It is known that a heat treatment at 00 ° C. for 20 to 30 minutes can provide “sealed rice in containers and packaging” that can be stored for a long period of time.
However, a practical method that can sterilize rice before cooking to some extent has not been known so far.

It is possible to sterilize rice by irradiation with ultraviolet rays, which is widely used as a sterilization method. However, the sterilizing power of ultraviolet rays is weak, and even if rice that has been sterilized by irradiating ultraviolet rays is used, it is not possible to obtain "container-wrapped rice" that can be stored for a long period under the above heat treatment conditions. In addition to rice for cooking rice, it is desired to provide a method for easily and efficiently sterilizing particulate foods in consideration of long-term storage and the like.

Therefore, an object of the present invention is to provide a method for producing cooked rice grains such as "container-wrapped rice" which can be stored for a long period of time without retorting under high temperature and high pressure and which has a good taste. To do. Further, the object of the present invention is that retort treatment by high temperature and high pressure is unnecessary,
100 ° C, 20-30 at the time of production of "packaged rice"
Another object of the present invention is to provide a method capable of pre-sterilizing rice grains to such an extent that they can be stored for a long period of time even by heat treatment for a minute.

[0007]

The present invention provides an electric field
Or a gas or a mixture of a gas and a liquid, at least a part of which is ionized by an energy converter irradiated with an electromagnetic wave,
The present invention relates to a method for producing cooked rice grains, which comprises bringing the sterilized rice grains obtained by bringing the whole surface of the rice grains into contact with the rice to be aseptically filled, and filling and sealing in a container and packaging.

Further, the present invention is a method for sterilizing rice grains using a gas or a mixture of a gas and a liquid, at least a part of which is ionized by an energy converter irradiated with an electric field or an electromagnetic wave. The present invention relates to a sterilization method, which comprises bringing a gas or a mixture of which at least a portion is ionized into contact with the surface. The present invention will be described in detail below.

In the method for producing cooked rice grains of the present invention, the rice grains sterilized by the sterilization method of the present invention are cooked, and the containers and packaging are filled and sealed. Therefore, first, the sterilization method of the present invention will be described.

In the sterilization method of the present invention, a gas or a mixture of a gas and a liquid, at least a part of which is ionized by an electric field,
Alternatively, a gas or a mixture of a gas and a liquid, at least a part of which is ionized by an energy converter irradiated with an electromagnetic wave, is used.

The former method using an electric field is specifically
It can be divided into the following three methods. A method of passing a gas or a mixture of a gas and a liquid through an electric field to ionize at least a part of the gas or the mixture, and then contacting the rice or cereal with the gas or the mixture of which the at least a part is ionized outside the electric field. (First method). A method of passing at least a portion of a gas through an electric field, mixing the obtained at least partially ionized gas with a mixture of a gas and a liquid, and contacting the obtained mixture with a rice grain outside the electric field ( Method 2). A method of introducing a mixture of a gas and a liquid into an electric field to ionize at least a part of the mixture, and bringing the mixture at least partially ionized in the electric field into contact with rice grains (third method).

The latter method using the energy converter is
Specifically, the following method may be mentioned. It is a method of bringing a gas containing a rare gas into contact with the energy converter irradiated with electromagnetic waves, then mixing the gas containing the rare gas with a mist-like liquid, and bringing the resulting mixture into contact with rice grains (No. Method 4).

In the above first to third methods, it is preferable to sterilize by using a pulse voltage for generating an electric field and by using a mixture of a gas and a liquid at least a part of which is ionized.

The rising speed of the pulse voltage is suitably in the range of 0.01 kV / ns to 10 kV / ns. The rising speed of the pulse voltage is 0.01
When it is less than kV / ns, the bactericidal effect tends to be lowered.
Even if the rising speed of the pulse voltage exceeds 10 kV / ns, the sterilizing effect is not adversely affected, but voltage generation becomes difficult. The preferable range of the rising speed of the pulse voltage is 0.
It is in the range of 1 kV / ns to 1 kV / ns.

The pulse width of the pulse voltage is 10 ⁻⁹ seconds to 1
It is suitable to be in the range of 0 ^-1 second. Although the pulse width has no great influence on the sterilization effect, the pulse width capable of oscillating is within the above range. The preferable range of pulse width is 10 ^-8 seconds ~
It is 10 ^-6 seconds.

The peak voltage of the pulse voltage is 1 kVp-10
It is suitable to be in the range of 0 kVp. When the peak voltage is less than 1 kVp, the electric field strength is small and the peak voltage is 1
If it exceeds 00 kVp, there is a problem that the device needs to be upsized. The preferred range of peak voltage is 8 to 50
kVp.

The frequency of the pulse voltage is 1 Hz to 100 kHz.
Suitably it is in the range of z. If the frequency is less than 1 Hz, the sterilization efficiency is lowered, and if it exceeds 100 kHz, the temperature of the gas in the electric field is significantly increased. The preferable range of the frequency of the pulse voltage is in the range of 50 Hz to 500 Hz.

The ionization method includes a method of passing a gas or a mixture of a gas and a liquid in an electric field to ionize at least a part of the gas or the mixture (first and third methods), and a method of passing a gas in the electric field. There is a method (second method) in which a gas having at least a portion thereof ionized and a mixture of a gas and a liquid are mixed outside the electric field to obtain a mixture of a gas and a liquid having at least a portion thereof ionized.

The electric field can be generated, for example, by using at least one pair of high-voltage electrode and ground electrode and applying a voltage of a certain level or more between these electrodes. Such an electric field generator can use the high-voltage electrode and the ground electrode used for corona discharge or the like as they are, for example,
The surface of at least one of the high voltage electrode and the ground electrode may be covered with a solid dielectric.
The solid dielectric is not particularly limited, but for example, ceramics such as quartz, a laminated body of hypalon rubber, polyethylene terephthalate, or the like can be used. Further, both the high voltage electrode and the ground electrode may be metal electrodes.

The number and shape of the high-voltage electrode and the ground electrode are not particularly limited, and can be appropriately determined depending on how much the gas or the mixture of the gas and the liquid passing through the generated electric field needs to be ionized. . For example, when the flow rate of a gas or a mixture of a gas and a liquid is high, it is possible to adjust the residence time in the electric field to be long for the purpose of ionizing at a certain rate or more. A plurality of ground electrodes may be provided in parallel, or at least one of the high voltage electrode and the ground electrode may have a strip shape. Further, in order to prevent local discharge, in order to increase the surface area of the high voltage electrode, the electrode may be provided with protrusions or irregularities.

In the first and third methods of obtaining the ionized body of the mixture of gas and liquid in the present invention, the gas of the "mixture of gas and liquid" which passes an electric field is a gas which can be ionized in the electric field. Is. Examples of such a gas include oxygen, nitrogen, rare gases (argon, helium, and neon), hydrogen, air, and the like. Among rare gases, argon is preferable because it is easily ionized and is excellent in cost. Further, helium is preferable from the viewpoint that ionization tends to be continuous. In particular, argon has a specific gravity closer to that of air than helium and is easy to handle under atmospheric pressure, so that it can be used more preferably. Further, two or more kinds of the above gases can be mixed and used together.

The liquid is, for example, water, hydrogen peroxide,
It can be hydrogen peroxide water, ethanol, a mixture of ethanol and water and the like. When hydrogen peroxide water is used, it is suitable that the concentration of hydrogen peroxide is, for example, 50% or less from the viewpoint of being commercially available and easily available. When the concentration is lower than that, commercially available hydrogen peroxide solution may be diluted with water to appropriately adjust the concentration in consideration of sterilization conditions and the like. However, considering the bactericidal effect, it is preferable to use 1% or more hydrogen peroxide solution.

The liquid used for ionizing at least a part of the photocatalyst may be water irradiated with excitation light for the photocatalyst in the presence of the photocatalyst. Photocatalyst used herein, water hydroxyl ion (OH ^-) and hydrogen ions (H
⁺ ) Can be used without particular limitation as long as it has the ability to dissociate into ⁺ ). Examples of the photocatalyst include titania, strontium titanate, zinc oxide, and cadmium sulfide. These photocatalysts
They can be used alone or in combination.

Further, the photocatalyst is one or more selected from the group consisting of titania, strontium titanate, zinc oxide and cadmium sulfide, and one selected from the group consisting of platinum, rhodium, ruthenium oxide and nickel oxide.
It may be a species or a complex (support) with two or more species. For example, Pt / TiO ₂ , Rh / SrTiO ₂ , R
u / SrTiO ₂ , Pt / SrTiO ₂ , RuO ₂ / T
Examples thereof include iO ₂ / Pt and RuO ₂ / TiO ₂ . Further, the photocatalyst and the metal or metal oxide serving as a carrier can be used together without being complexed.

The excitation light of the photocatalyst varies depending on the type of the photocatalyst, but is usually ultraviolet light having a wavelength of 200 to 400 nm. The amount of the photocatalyst per unit amount of water, the contact time between the photocatalyst and water was irradiated with excitation light, temperature, etc., the amount of water that is dissociated from the action of a photocatalyst (generated hydroxide ions (OH ^-) and hydrogen ions ( H ⁺ ) amount) is taken into consideration. Further, water hydroxide ion (OH ^-) and hydrogen ions (H ⁺⁾
Since the amount of the above influences the bactericidal effect, it is appropriately adjusted in consideration of the desired bactericidal effect.

The shape and structure of the photocatalyst are not particularly limited, but may be, for example, powder or plate. The powdery photocatalyst has, for example, a particle size of 20 to 5
It can be in the range of 000 Angstroms.

The plate-shaped photocatalyst is effective in continuously producing photodissociated water, and ultraviolet light (254 nm, 400 nm) is used.
When W) is used, for example, dissociated water obtained by contacting a photocatalyst having an area of 100 cm ² with 1 liter of water for about 60 to 180 minutes can be used. Photodissociated water can also be obtained by irradiating a column or the like filled with photocatalyst particles with excitation light and further circulating water.

In the present invention, water is photodissociated, but an additive may be added to water as long as the photodissociation of water is not hindered. For example, examples of the additive include alcohol and hydrogen peroxide.

The liquid is preferably in the form of a mist,
The atomized liquid can be generated by passing the gas as a carrier gas through a nebulizer connected to a liquid supply source. The atomized gas can also be generated by bubbling a carrier gas through them. Also, "a mixture of gas and liquid"
Can also be prepared by using a part of the gas as a carrier gas and mixing the atomized substance obtained by the gas and the carrier gas with the rest of the gas.

Gas (all gases including carrier gas)
The ratio of the liquid to the liquid is not particularly limited, but the range of 1 mg to 100 mg per liter of gas is appropriate from the viewpoint of sustaining the discharge and the pressure on the sterilized object. Further, the particle size of the atomized material is preferably in the range of, for example, about 5 to 3000 μm from the viewpoint of preventing local discharge.

In the second method of obtaining the ionized body of the mixture of gas and liquid in the present invention, the gas passing through the electric field is a gas ionizable in the electric field. Such a gas can be appropriately selected from the gases that can be used for the “mixture of gas and liquid”. In the second method, a gas that is at least partially ionized and a mixture of a gas and a liquid are mixed to obtain a mixture of a gas and a liquid that is at least partially ionized. The mixing ratio of the gas at least a part of which is ionized and the mixture of the gas and the liquid can be appropriately determined depending on the desired degree of sterilization.

At least a part of the gas or the mixture of the gas and the liquid which is passed through the electric field needs to be ionized. Therefore, at least a part of the gas or the mixture of the gas and the liquid can be ionized, such as the flow rate of the gas or the mixture of the gas and the liquid, the amount of voltage and current (electric power) applied to generate the electric field, the number and shape of the electrodes, and the like. As appropriate. Further, it is preferable that the gas pressure is usually around atmospheric pressure because the operation is easy. However, as described later, it is possible to enhance the sterilization effect by operating the sterilization container so that the inside of the sterilization container is slightly pressurized (atmospheric pressure up to 1 atm). It is preferable from the viewpoint that it is possible to sterilize the inside of a thick body to be sterilized.

In the fourth method, a gas containing a rare gas is brought into contact with the energy converter irradiated with electromagnetic waves. Here, the energy converter is one that absorbs the energy of electromagnetic waves and then releases the energy to excite the rare gas. Therefore, the energy converter having a crystal lattice defect and easily absorbing and releasing energy can be preferably used. Examples of the energy converter include ceramics such as oxides, carbides, nitrides, borides, and silicides, and carbon materials. In addition to these, as long as the energy of the electromagnetic wave is absorbed and then the energy is released and the rare gas can be excited, it can be used without limitation.

As a more specific example of the energy converter, the general formula is MO.Fe ₂ O ₃ (M = Ba ²⁺ , M
n ²⁺ , Fe ²⁺ , Co ²⁺ , Ni ²⁺ , Cu ²⁺ , Zn ²⁺ ) ferrites, SiO ₂ , Al ₂ O ₃ , Na
₂ O, K ₂ O, Fe ₂ O ₃ , FeO, CaO, MgO,
An oxide containing at least one kind of ZrO ₂ , BeO, Y
Examples thereof include superconducting substances such as BC (yttrium, barium, copper) oxides.

Furthermore, the combination of the A site and the B site is monovalent and pentavalent, bivalent and tetravalent, trivalent and trivalent, or singularly hexavalent, and the general formula is ABO ₃ (A = Na ⁺ ,
K ⁺ , Li ⁺ , Rb ⁺ , Ag ²⁺ , Ba ²⁺ , Sr ²⁺ , Cd
²⁺ , Pb ²⁺ , Ca ²⁺ , La ³⁺ , Y ³⁺ , Sm ³⁺ , Lu ³⁺ ,
Gd ³⁺ , Pr ³⁺ , Nd ³⁺ , Bi ³⁺ , Ce ⁴⁺ , Th ⁴⁺ , B
= Mo ⁶⁺ , W ⁶⁺ , Re ⁶⁺ , Ta ⁵⁺ , Nb ⁵⁺ , Ti ⁴⁺ , Z
r ⁴⁺ , Sn ⁴⁺ , Ce ⁴⁺ , Cr ⁴⁺ , Mn ⁴⁺ , Hf ⁴⁺ ,
V ⁴⁺ , Mo ⁴⁺ , Fe ⁴⁺ , Ru ⁴⁺ , Ir ⁴⁺ , Pt ⁴⁺ , Sc
³⁺ , Ti ³⁺ , Ru ³⁺ , Rh ³⁺ , Mn ³⁺ , Cr ³⁺ , N
i ³⁺ , Co ³⁺ , Y ³⁺ , V ³⁺ , Fe ³⁺ , Mg ²⁺ , Cu ²⁺ )
A perovskite complex oxide represented by can also be used as an energy converter.

Among them, the perovskite type complex oxide is particularly suitable for use because it releases energy and easily generates plasma. As the perovskite-type composite oxide, LaCoO ₃ , LaT in which the A site is lanthanum
iO ₃ , LaMnO ₃ , LaFeO ₃ , LaNiO ₃ ,
LaCrO ₃ etc. and A site is strontium,
Preferred are SrMoO ₃ , SrTiO ₃ , and YNiO ₃ in which the A site is yttrium. Further, a perovskite-type composite oxide in which a part of the metal ions forming the A site and the B site are replaced with metal ions having different valences has a defect in the crystal lattice and easily emits energy to generate plasma. , More preferably used as an energy converter.

Further, since the carbon material has a layered structure, it vibrates between layers, or a defect in the layered structure causes strain between layers,
It is considered to release energy easily and can be used as an energy converter. Gas carbon as a carbon material,
Examples thereof include amorphous carbon such as soot, charcoal, animal charcoal, and coke, and a substance containing a carbon atom or graphite obtained by graphitizing amorphous carbon. Further, if the surface of the carbon material is coated with a compound having a high melting point such as iron, nickel, chromium, tungsten, stainless alloy, titanium nitride, etc., there is no loss of the carbon material, which is a more preferable use mode. The energy converter may be used not only in one kind but also in a mixture of two or more kinds.

The above energy converter can be supported on a support such as a honeycomb-shaped one, a porous woven fabric, a knitted fabric, a non-woven fabric or a felt. In particular, it is preferable to use a support, because when the rare gas or the like passes through the support, energy is easily received from the energy converter to excite the rare gas or the like. In addition, when such a support is used, plasma is generated on the opposite side of the energy converter, so that it is possible to continuously treat the sterilized object without disturbing the irradiation of the electromagnetic wave to the energy converter. Becomes

The carbon material is also porous woven fabric, knitted fabric, non-woven fabric,
Hold felt such as a holding body, honeycomb-shaped, porous woven fabric, knitted fabric, non-woven fabric using carbon material,
Can be processed into felt. When a carbon material having voids is used in this way, when a rare gas or the like passes through the voids of the carbon material, it receives energy from the carbon material,
Excitation of a rare gas or the like is likely to occur, which is preferable. In addition, when a carbon material with voids is used, plasma is generated on the opposite side of the carbon material in the flow path of a rare gas or the like, so that the base material is continuously treated without disturbing the irradiation of electromagnetic waves to the carbon material. It becomes possible to do.

The electromagnetic wave used in the present invention may be any one as long as it gives energy to the energy converter and releases the energy from the energy converter. As such an electromagnetic wave, an electromagnetic wave having a frequency of several kilohertz (kHz) to several hundred gigahertz (GHz) can be used. Among them, microwaves having a frequency of 1 to several tens of gigahertz (GHz) are particularly preferably used because the energy converter has sufficient energy to emit energy. Irradiation of electromagnetic waves to the energy converter can be performed continuously using a DC power supply, or pulsed electromagnetic waves can be irradiated using an AC power supply. In this case, as the pulse, for example, a pulse having a frequency of 100 kHz or less, and a pulsed electromagnetic wave of 50 Hz or 60 Hz which is generally used in an AC power supply can be used. By irradiating with pulsed electromagnetic waves, the bactericidal effect can be enhanced.

It is appropriate that the gas containing the rare gas and the energy converter are brought into contact with each other to such an extent that at least a part of the rare gas is in a plasma state. Therefore, the gas flow rate, the electromagnetic wave irradiation amount, the energy converter amount, the shape, and the like can be appropriately determined so that at least a part of the rare gas is in a plasma state. Further, it is preferable that the gas pressure is usually around atmospheric pressure because the operation is easy. However, as described later, it is possible to enhance the sterilization effect by operating the sterilization container so that the inside of the sterilization container is slightly pressurized (atmospheric pressure up to 1 atm).

The rare gas is excited by the energy released from the energy converter to generate plasma. Examples of the rare gas include argon, helium, neon and the like. Among them, argon is preferable because it easily becomes plasma and is excellent in cost. Helium is preferable from the viewpoint that the plasma state is likely to be continuous. In particular, argon has a specific gravity closer to that of air than helium and is easy to handle under atmospheric pressure, so that it can be used more preferably. Also, two or more rare gases can be used together.

The gas containing a rare gas may be a gas composed of only a rare gas, or a rare gas and nitrogen,
It can also be a mixed gas with a gas such as oxygen or air. However, from the viewpoint of easily obtaining a plasma state, a mixed gas containing 50% by volume or more of a rare gas is preferable.

In the fourth method, a gas containing a rare gas brought into contact with an energy converter irradiated with electromagnetic waves (hereinafter, referred to as
(Excited gas) is mixed with a nebulized liquid. Nebulized liquids can be generated by passing carrier gas through a nebulizer that is connected to these sources.
The atomized liquid can also be generated by bubbling a carrier gas through them. Further, as the carrier gas, rare gas, nitrogen, oxygen, air, hydrogen or the like can be used. The ratio of the liquid to the carrier gas is preferably in the range of 10 to 0.01 parts by volume with respect to 1000 parts by volume of the carrier gas, from the viewpoint of stably generating plasma. further,
The particle size of the atomized material is preferably in the range of, for example, about 5 to 3000 μm from the viewpoint of the sustainability of plasma generation.

The liquid may be, for example, water, hydrogen peroxide, hydrogen peroxide solution, ethanol, a mixture of ethanol and water, or the like. When hydrogen peroxide water is used, it is suitable that the concentration of hydrogen peroxide is, for example, 50% or less from the viewpoint of being commercially available and easily available. When the concentration is lower than that, commercially available hydrogen peroxide solution may be diluted with water to appropriately adjust the concentration in consideration of sterilization conditions and the like. However, considering the bactericidal effect, it is preferable to use 1% or more hydrogen peroxide solution.

The mixing ratio of the exciting gas and the atomized liquid is preferably as small as possible because the exciting gas generator can be downsized. However, considering the flow rate of the nebulizer carrier gas, etc., when the flow rate of the excitation gas (main gas) per unit time is 1 volume part, the atomized liquid should be in the range of 0.1 to 10 volume parts. Is appropriate. Mixing of the excitation gas and the atomized liquid can be performed by introducing the atomized liquid near the exit of the energy converter from which the excitation gas flows.

The at least partially ionized gas or the mixture of gas and liquid obtained by the above method is brought into contact with rice grains. This contact is carried out so that the gas or mixture obtained by ionizing at least a portion of the rice grain comes into contact with the entire surface of the rice grain.

The contact as described above is carried out, for example, by
It can be carried out by vertically or obliquely dropping into an at least partially ionized gas or mixture, or by bouncing through at least partially ionized gas or mixture on a horizontally moving support. .

The rice grain is vertically dropped in a chamber in which a gas flow of at least a part of ionization or a gas flow of a mixture flows or is filled, thereby ionizing at least a part of the whole surface of the rice grain. The gas or mixture can be contacted. The amount of fall, distance, etc. can be set as appropriate in consideration of the degree of sterilization. When a gas or a gas flow of a mixture is passed, this gas flow can flow countercurrently or in parallel with the falling object.

In addition, the rice grain is dropped obliquely on a surface having an inclination set in consideration of the residence time in a chamber in which a gas flow of at least a part of ionization or a gas flow of a mixture flows or is filled. Then, the gas or mixture obtained by ionizing at least a part of the rice grains can be brought into contact with the entire surface of the rice grain. When a gas or a gas flow of a mixture is made to flow, this gas flow can be made to flow countercurrently or in parallel with the falling object on the slope.

A vibrating belt conveyor or the like can be used for moving the rice grains while bouncing them on a support that moves in the horizontal direction.

The contact with rice grains is performed outside the electric field in the first and second methods, and in the electric field in the third method. In addition, including the fourth method, the contact with rice grains can be performed in a sterilization chamber other than the ionization chamber. Further, it is preferable to operate the inside of the sterilization chamber such that the pressure is slightly higher than atmospheric pressure (1 atmospheric pressure at maximum), as described above, from the viewpoint that the sterilizing effect can be enhanced. In addition, it is possible to maintain a sterile condition in the chamber by setting the positive pressure in the chamber.

The sterilization method of the present invention can be carried out, for example, by the apparatus shown in FIG. FIG. 1 is a cross-sectional explanatory view. In the figure, 1 is a quartz-coated electrode, 2 is a metal electrode that constitutes a ground electrode, and 3 is a rod-shaped metal electrode that constitutes a high-voltage electrode. Reference numeral 4 is an inlet pipe (pipe A) for a gas or a mixture of a gas and a liquid, 5 is an inlet pipe for a mixture of a gas and a liquid (pipe B), and 6 is an entrance / exit of a belt conveyor 53 which is a means for delivering sterilized rice grains 54. It is also an exhaust port that doubles as. Further, 7 is a sterilization chamber, 52 is a rice grain hopper, 51 is a supply port to the sterilization chamber 7, and 50 is rice grains. Although not shown, the pipe A communicates with a gas supply source via a nebulizer filled with a liquid such as hydrogen peroxide, or directly. Although not shown, the pipe B communicates with a gas supply source via a nebulizer filled with a liquid such as hydrogen peroxide.

In the first method of directly ionizing a gas or a mixture of a gas and a liquid, a gas-like mixture obtained by passing the gas through a nebulizer filled with a liquid such as hydrogen peroxide is introduced into an inlet pipe 4 (pipe A). ) To the electric field. At least a part of the gas that has passed between the ground electrode 2 and the high-voltage electrode 3 is ionized, and this gas also comes into contact with the rice grain 50, which is the object to be sterilized, that drops in the sterilization chamber 7 and sterilizes it. The sterilized rice grains 54 are transferred to the sterilization chamber 7 by the belt conveyor 53 at the bottom of the sterilization chamber 7.
Transferred outside. The sterilized gas is exhausted from the exhaust port 6.

Ionizing the gas, and then the ionized gas,
In the second method of mixing the mixture of gas and liquid, the gas for ionization is introduced through the introduction pipe 4 (pipe A), and the introduction pipe 5 is introduced.
From (Vape B), the atomized mixture obtained by passing the gas through a nebulizer filled with a liquid such as hydrogen peroxide is introduced. At least a part of the gas passing between the ground electrode 2 and the high-voltage electrode 3 is ionized, and this ionized gas is pipe B.
It is mixed with the mist-like mixture supplied from the above, and this mixture is contacted with the rice grain 50 which is the sterilization target falling in the sterilization chamber 7 and sterilized. Sterilized rice 54
Is a belt conveyor 53 at the bottom of the sterilization chamber 7.
Is carried out of the sterilization chamber 7. The sterilized gas is exhausted from the exhaust port 6. The sterilized rice grains carried out can be stored in, for example, a sterile silo.

The third method of ionizing the mixture of gas and liquid and sterilizing it outside the electric field can be carried out, for example, by the apparatus shown in FIG. The apparatus shown in FIG. 2 is configured so that the electric field region and the sterilization region are separated. In this method, as in the first method, a gas-like mixture obtained by passing a gas through a nebulizer filled with a liquid such as hydrogen peroxide is supplied into the electric field from the introduction pipe 4 (pipe A). Ground electrode 2
At least a part of the gas that has passed through the electric field region 8 between the high voltage electrode 3 and the high voltage electrode 3 is ionized. This gas further moves to the sterilization chamber 7 and comes into contact with the rice grains 50, which are the objects to be sterilized, that drop in the chamber 7 and sterilize them. Pasteurized rice 5
4 is a belt conveyor 5 at the bottom of the sterilization chamber 7.
3 is carried out of the sterilization chamber 7. Also,
The sterilized gas is exhausted from the exhaust port 6.

In the apparatus shown in FIG. 2, the gas for ionization is introduced through the introduction pipe 4 (pipe A) and the introduction pipe 5 (vip B).
From the above, by introducing the atomized mixture obtained by passing the gas through a nebulizer filled with a liquid such as hydrogen peroxide, it can also be used in the above-mentioned second method.

The apparatus shown in FIGS. 1 and 2 is one embodiment for carrying out the method of the present invention. For example, a sterilization chamber 7 is arranged in a room separate from the ionization region, and the gas obtained in the ionization region is obtained. Can also be introduced into the sterilization chamber 7 in a separate room via a pipe or the like, and the rice grain 50 and gas can be brought into contact therewith to sterilize.

In the above method, the scale and structure of the chamber are appropriately determined in consideration of the supply amount of rice grains, the degree of sterilization, the flow rate of gas, the residence time of rice grains and gas in the sterilization chamber, and the like. You can decide.

Further, FIG. 3 shows an apparatus used in an embodiment using a photocatalyst. Pipe A is nebulizer 10
Alternatively, it is in communication with the gas supply source 15. Further, the pipe B communicates with the nebulizer 10. The nebulizer 10 is connected to the photodissociation water generator 16. The photodissociation water generation device 16 arranges the light source 12 and the water 11 for photodissociation via the cooling water 13. The photocatalyst powder is dispersed in the water 11 for photodissociation, or a plate-shaped photocatalyst is immersed in the water 11. Water 11 for photodissociation is the light source 1
A part of it is dissociated as described above by the excitation light from 2. Although not shown, instead of the nebulizer, a mist can also be formed by passing a gas serving as a carrier gas through a bubbling container filled with photodissociated water.

FIG. 4 shows an apparatus used in the fourth method of the present invention. In the figure, 21 is an energy converter, 22
Is a pipe for introducing a gas containing a rare gas, 23 is a pipe for introducing a mist-like liquid, 24 is a space for mixing a gas containing a rare gas with an energy converter and a mist-like liquid, 25 is a nebulizer, 26 Is a liquid supply source, 27 is a carrier gas source, 28 is a sterilization chamber, 29 is a waveguide, 30 is a microwave generator, and 31 is also an entrance / exit of a belt conveyor 53 which is a means for carrying out sterilized rice grains 54. It is the exhaust port. Further, 50 is a rice grain to be sterilized, 51 is a rice grain supply port, and 55 is a sterile silo.

The noble gas-containing gas introduced from the introduction pipe 22 comes into contact with the energy converter 21 irradiated with the electromagnetic wave from the microwave generator 30. The gas containing the rare gas that is in contact with the energy converter 21 is mixed with the atomized liquid introduced from the introduction pipe 23 in the mixing space 24. The obtained mixture moves downward and comes into contact with the rice grains 50, which is the object to be sterilized, supplied from the supply port 51 in the sterilization chamber 28. The sterilized rice grains 54 are carried out by the belt conveyor 53 and stored in the aseptic silo 55.

The apparatus shown in FIG. 4 is one embodiment for carrying out the fourth method, and for example, a sterilization chamber 28 can be provided in a room separate from the mixing space 24. Further, the mixing space 24 may be provided with stirring means for the purpose of promoting mixing of the atomized liquid with the gas containing the rare gas that is in contact with the energy converter.

Further, the diameter of the energy converter 21 and the diameter of the mixing space 24 should be appropriately changed in consideration of the flow rate of the gas containing the rare gas, the flow rate of the atomized liquid, the residence time of the mixture of the two, and the like. You can In particular, the energy converter 21 preferably has a shape and structure capable of sufficiently absorbing electromagnetic waves, and for example, it is suitable to have a wide surface for receiving electromagnetic waves and a thickness that allows the electromagnetic waves to reach. Also, by reducing the volume of the energy converter per unit input power, the power density can be increased and electromagnetic waves can be generated stably.

Further, FIG. 5 shows a schematic view of an apparatus using a vibrating belt conveyor in the third method. In the figure,
Reference numeral 61 is a metal electrode covered with a dielectric and constitutes a high voltage electrode. 62 is a vibrating belt conveyor made of stainless steel, 63 is an introduction pipe of gas or a mixture of gas and liquid,
Reference numeral 64 is a high pressure bushing, 65 is a sterilization chamber, and 66 is a UV lamp. Rice grain, which is the raw material, is the raw material hopper 6
7 is supplied onto the vibrating belt conveyor 62. The rice grains 68 on the vibrating belt conveyor 62 are transferred into the sterilization chamber 67 while vibrating. The vibrating belt conveyor 62 may also be a mesh belt.

On the other hand, at least a part of the gas or the mixture of the gas and the liquid introduced from the introduction pipe 63 is ionized by the electric field in the sterilization chamber. The obtained ionized body is brought into contact with the rice grains 68 on the belt conveyor 62 and sterilized. The sterilized rice grains 69 are transferred to the sterile silo 70. U
The V lamp 66 is provided as necessary for the purpose of preventing contamination of various bacteria, and is not necessarily provided depending on the structure of the device and the degree of sterilization.

Although not shown, the introduction pipe 63 is connected to a gas supply source via a nebulizer filled with a liquid such as hydrogen peroxide, or directly. Further, the vibration frequency and vibration width of the belt conveyor 62, and further, the moving speed and the like can be appropriately determined in consideration of the size of rice grains, the degree of sterilization, and the like.

There is no particular limitation on the microorganisms that can be sterilized by the method of the present invention. According to the method of the present invention, for example, Escherichia coli (E. coli), Salmonella typhi (Sal.
typhi), B. subtilis, Staphylococcus. aure
us), Aspergillus niger
Microorganisms such as r) can be sterilized.

According to the present invention, various rice grains such as rice, wheat, soybeans, buckwheat seeds, spices (for example, pluck pepper grains) and corn grains can be sterilized easily and efficiently.

In the method for producing cooked rice grains of the present invention, the rice grains sterilized by the sterilization method of the present invention are cooked in an aseptic state, and the container packaging is filled and sealed. The rice grains before sterilization can be washed with water or the like in advance, if necessary. Also, rice grains after sterilization and before rice cooking can be washed with water or the like, if necessary. However, it is necessary to wash rice grains after sterilization and before cooking rice in an aseptic state, and for example, aseptic water or the like can be used. The cooked rice grains obtained by the production method of the present invention have a good taste,
And it can be stored for a long time.

The aseptic cooking of rice and filling and sealing of containers and packaging can be carried out by using, for example, the apparatus shown in FIG. In FIG. 6, 81 is a belt conveyor, and a container 82a on the belt conveyor 81 is filled with a predetermined amount of raw rice sterilized by the method of the present invention and sterile water. still,
It is appropriate that the container 82a is made sterile before filling with raw rice and sterile water. Furthermore, it is appropriate that the container 82a is made of a material having heat resistance that can withstand cooking rice. A container 82a filled with a predetermined amount of sterilized raw rice and sterile water is transferred to a steam chamber having a steam pipe 83, and the rice in the container is cooked. After the rice is cooked, the container 82b containing the cooked rice is further sealed under a sterile condition with a lid.

The container, lid, etc. used in the method for producing cooked rice grains of the present invention are not particularly limited. Further, the method of adhering the container and the lid is not particularly limited. However, it is appropriate for the container to have heat resistance because it is cooked with rice grains. Polypropylene can be mentioned as such a material. Further, from the viewpoint of preventing oxygen from penetrating into the container and improving the storage stability, it is preferable to use a material such as Eval having an excellent oxygen barrier property. Specifically, a laminated material of polypropylene and EVAL can be used for the container. Further, a laminated material of polypropylene, EVAL, and polyester can be used for the lid.

[0073]

EXAMPLES The present invention will be further described below with reference to examples. Example 1 Using the apparatus shown in FIG. 1, the sterilization method of the present invention was carried out under atmospheric pressure. However, a high voltage square wave pulse generator (peak voltage 16.4 kV, waveform: square wave, frequency: 240 Hz to 238.5 Hz) was used as a power source, and a nebulizer was used to mix the gas and the liquid, and the gas from the pipe A was used. And a mixture of liquid was fed into the electric field. The liquid supply rate was 2.5 g / hr. Rice to which 3 × 10 ⁷ Bacillus subtilis spores were attached per grain was used as the sterilization object, and the rice was placed in a sterile gauze at a distance of 8 cm from the electrode. Table 1 shows the experimental conditions of gas type and flow rate, liquid type and concentration, treatment time, and residual spore count.

Evaluation Method (Examination of Number of Remaining Spores) The rice grains subjected to the sterilization test were immersed in 10 ml of sterilized 0.2% Tween 80 physiological saline for 1 hour and then stirred to extract the remaining spores. The obtained residual spore extract was cultured at 35 ° C. for 48 hours using a standard agar medium. After culturing, the number of residual spores per rice grain was calculated from the number of appeared colonies. The results are shown in Table 1. Table 1
The number of residual spores of the control is 3.0 × 10 ⁷ (number of spores / rice grain).

[0075]

[Table 1]

Example 2 The sterilization method of the present invention was carried out under atmospheric pressure using the apparatus shown in FIG. Microwaves are used as electromagnetic waves, and perovskite complex oxides (LaC) are used as energy converters.
1 g of oO ₃ ) was used. The input voltage to the microwave generation source was set to 85 V, and the nebulizer was used to generate the atomized product of the hydrogen peroxide solution. Rice to which 3 × 10 ⁷ Bacillus subtilis spores were attached per grain was used as the substance to be sterilized, and the rice was placed in a sterile gauze at a distance of 12 cm from the electrode. Table 2 shows the flow rate of the rare gas (argon gas) brought into contact with the energy converter, the treatment time, the concentration of hydrogen peroxide solution or ethanol, the flow rate of the carrier gas (argon gas), and the number of remaining spores. Evaluation method (remaining spore count test)
Was the same as in Example 1. In Table 2, the number of residual spores of control is 3.0 × 10 ⁷ (number of spores / rice grain).

[0077]

[Table 2]

Example 3 The sterilization method of the present invention was carried out under atmospheric pressure using the apparatus shown in FIG. From the raw rice storage hopper 67, the raw rice having 3 × 10 ⁷ Bacillus subtilis spores attached to each grain was supplied onto the vertical vibration conveyor 62 at 0.1 to 0.4 g / cm ² . The vibration frequency of the vibration conveyor 62 is 600
The movement speed was 0.2 m / min, the temperature in the sterilization chamber was 50 ° C., and the residence time was 5 minutes. Plasma is generated by a high voltage square wave pulse generator (peak voltage 16.4 kV, waveform: square wave, frequency: 240 H) as a power source.
z ~ 238.5 Hz), and a nebulizer or pubring was used to mix the gas and the liquid, and a mixture of argon and the liquid (hydrogen peroxide, ethanol or acetone) was supplied from the pipe 63 into the electric field. The liquid supply rate was 2.5 g / hr. Table 3 shows experimental conditions such as gas type and flow rate, liquid type and concentration, vibration width, and residual spore number.

[0079]

[Table 3]

Example 4 100 g of the rice obtained in Example 3 was placed in a tray (polypropylene / Eval / polypropylene, total thickness 100 μm).
(300 ml), add 150 ml of sterile water, and
The rice was cooked at 00 ° C for 30 minutes. Then, a lid (polyester / Eval / polypropylene, total thickness 40 μm) was sealed to make a trial of packaged rice, and its storage condition was examined (No. 1 to 5). For comparison, adjust the pH with citric acid without sterilizing 100 g of raw rice (No6: pH
5.0, No7: pH 4.0) Soaked in 500 ml of water for 60 minutes, then steamed at 100 ° C for 30 minutes, filled in a tray and sealed to make a trial packaged rice, and examined its storage state (No6 ~ 7). Furthermore, for comparison, 100 g of raw rice was mixed with 500 ml of water without sterilization.
Steamed at 00 ° C for 30 minutes, filled the tray and sealed it to make a trial packaged rice, and examined its storage condition (No.
8). The results are shown in Table 4.

The taste was evaluated after storage at 30 ° C. for 30 days.
It was evaluated according to the following criteria. A: Very good B: Normal C: Sour taste and poor taste The storage test was carried out by storing bacteria at 30 ° C. for 60 days and then conducting a bacterial test by the SPC method (standard agar medium, culture at 35 ° C. for 48 hours).

[0082]

[Table 4]

[0083]

EFFECTS OF THE INVENTION According to the present invention, there is provided a method for producing cooked rice grains which can be stored for a long period of time without being retorted by high temperature and high pressure, and have a good taste, such as "packaged rice" which can be stored for a long time. Can be provided. Furthermore, according to the present invention, 100 ° C., 20-20
It is possible to provide a method capable of pre-sterilizing rice grains to such an extent that they can be stored for a long period even by heat treatment for 30 minutes.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view of an apparatus used for carrying out a sterilization method of the present invention.

FIG. 2 is a schematic explanatory view of an apparatus used for carrying out the sterilization method of the present invention.

FIG. 3 is a schematic explanatory view of an apparatus used for carrying out the sterilization method of the present invention.

FIG. 4 is a schematic explanatory view of an apparatus used for carrying out the sterilization method of the present invention.

FIG. 5 is a schematic explanatory view of an apparatus used for carrying out the sterilization method of the present invention.

FIG. 6 is a schematic explanatory view of a continuous rice cooking device for rice filled in a container.

[Explanation of symbols]

 1 ... Quartz coated electrode 2 ... Metal electrode (ground electrode) 3 ... Metal electrode (high voltage electrode) 4 ... Introducing pipe (pipe A) 5 ... Introducing pipe (pipe) B) 6, 31 ... Exhaust port 7, 28, 65 ... Sterilization chamber 10, 25 ... Nebulizer 11 ... Water for photodissociation 12 ... Light source 13 ... Cooling water 14, 15 ..Gas supply source 16 ... Photodissociation water generator 21 ... Energy converter 22 ... Introduction pipe for gas containing rare gas 23 ... Introduction pipe for atomized liquid 24 ... Mixing space 26 ... Liquid supply source 27 ... Carrier gas source 29 ... Waveguide 30 ... Microwave generator 50, 68 ... Rice grains 51 to be sterilized Grain supply ports 52, 67 ... Rice grain raw material hoppers 53, 62 ... Beltco Bears 54, 69 ... Sterilized rice grains 61 ... Dielectric-coated metal electrode (high-voltage electrode) 63 ... Introducing pipe of gas or mixture of gas and liquid 64 ... High-pressure bushing 66. ..UV lamp 70 ... Aseptic silo

Claims (4)

[Claims] 1. A sterilized rice grain obtained by bringing a gas or a mixture of a gas and a liquid at least a part of which is ionized by an electric field or an energy converter irradiated with an electromagnetic wave into contact with the entire surface of the rice grain. The method for producing cooked rice grains is characterized in that the rice is cooked in an aseptic state, and the container is packed and sealed. 2. The manufacturing method according to claim 1, wherein the electric field is generated by a pulse voltage. 3. A method of sterilizing rice grains using a gas or a mixture of a gas and a liquid, at least a part of which is ionized by an electric field or an energy converter irradiated with an electromagnetic wave, the method comprising the steps of: A sterilization method comprising contacting a gas or a mixture of which at least a part is ionized. 4. The sterilization method according to claim 3, wherein the electric field is generated by a pulse voltage.