JP2020048419A - Method for suppressing growth of bacillus cereus, packaging container suitable for maintaining freshness of vegetables and fruits and package using the same, and method for maintaining freshness of vegetables and fruits - Google Patents

Abstract

To provide a method for suppressing growth of germs, in which the growth of germs including Bacillus cereus can extremely effectively be suppressed, and is suitable for maintaining the freshness of contents, such as cut vegetables, that are susceptible to germs, and to provide a packaging container using the method.SOLUTION: Provided is a method for suppressing growth of Bacillus cereus in packaging container, and in which, for the case of maintaining at a condition of 35 ± 2°C, the internal oxygen concentration 24 hours after sealing of the packaging container is 2.0 vol.% or more and 16.5 vol.% or less.SELECTED DRAWING: None

Description

The present invention relates to a method for suppressing the growth of Bacillus cereus, and a packaging container suitable for maintaining freshness of fruits and vegetables using the method.
Since the packaging container can effectively suppress the growth of various bacteria including Bacillus cereus, it is suitable for maintaining the freshness of fruits and vegetables stored in the packaging container, particularly for maintaining the freshness of cut vegetables and the like. It is suitable.

In recent years, so-called packaged cut vegetables in which cut vegetables are stored in a packaging container have been increasing in demand in recent years because they can be easily served for meals, and have high economic value.
In such packaged cut vegetables, spoilage is likely to progress due to the growth of various germs.For cut vegetables sold over-the-counter, conventionally, thorough sterilization treatment has been used to minimize the number of general viable bacteria as much as possible. It is desirable. For this reason, the cut vegetables before storage are sterilized with sodium hypochlorite or the like (for example, see Patent Document 1), and the amount of organic substances adhering to the surface of the cut vegetables by washing or the like is limited to a certain value or less. (For example, see Patent Document 2).
However, even if sterilization, washing, and the like are performed according to these techniques, the growth of various bacteria may not be sufficiently suppressed, and a technique capable of suppressing the growth of various bacteria at a higher level has been demanded. In addition, excessive sterilization, washing, etc. are not necessarily preferable in terms of quality, taste, cost, etc. of the cut vegetables, and do not require excessive sterilization, washing, etc., and various germs in the cut vegetable packaging container, especially, There has been a demand for a technique capable of suppressing the growth of Bacillus cereus, whose suppression is particularly important from the viewpoint of preventing food poisoning.

JP-A-6-46812 JP-A-2006-154552

  The present invention, in view of the limitations of the above-described conventional techniques, is capable of extremely effectively suppressing the growth of bacteria such as Bacillus cereus, and maintaining the freshness of contents susceptible to bacteria such as cut vegetables. It is an object of the present invention to provide a method for inhibiting the growth of microorganisms, and a packaging container using the method.

The present inventor has conducted intensive studies and found that, in a packaging container for maintaining the freshness of fruits and vegetables, when kept under a predetermined temperature condition, the oxygen concentration 24 hours after sealing is within a predetermined numerical range, The present inventors have found that the growth of Bacillus cereus in the packaging container is effectively suppressed, and have completed the present invention.
That is, the present invention
[1]
15. A method for suppressing the growth of Bacillus cereus in a packaging container, wherein the internal oxygen concentration of the packaging container after sealing for 24 hours is 2.0% by volume or more when kept at 35 ± 2 ° C. The above method, wherein the content is 5% by volume or less.

Hereinafter, each of [2] to [11] is one of preferred embodiments of the present invention.
[2]
When held at 35 ± 2 ° C., the ratio of the total area of the colonies of Bacillus cereus in the standard agar medium placed in the packaging container to the total area of the culture medium is determined by the sealing of the packaging container. The method according to [1], wherein the content is suppressed to 20% or less over the next 0 to 24 hours.
[3]
The method according to [1] or [2], wherein the internal oxygen concentration immediately after sealing of the packaging container is less than 15% by volume.
[4]
The method according to any one of [1] to [3], wherein the internal nitrogen concentration of the packaging container immediately after sealing is 50 to 98% by volume.
[5]
The method according to any one of [1] to [4], wherein the internal carbon dioxide concentration immediately after sealing of the packaging container is 20% by volume or more.
[6]
A packaging container for maintaining the freshness of fruits and vegetables, wherein the internal oxygen concentration of the packaging container after sealing for 24 hours is 2.0% by volume or more and 16.5% by volume or less when kept at 35 ± 2 ° C. And the ratio of the total area of the colonies of Bacillus cereus in the standard agar medium placed in the packaging container to the total area of the medium when the temperature is maintained at 35 ± 2 ° C. The above-mentioned packaging container, wherein the content is suppressed to 20% or less from 0 to 24 hours after the container is sealed.
[7]
A package comprising the fruits and vegetables stored in the packaging container according to [6].
[8]
A freshness maintaining method for fruits and vegetables, comprising a step of storing and sealing fruits and vegetables in the packaging container according to [6], and a step of maintaining the packaging containers at 35 ± 2 ° C.
[9]
The method for retaining freshness of fruits and vegetables according to [8], further comprising a step of enclosing carbon dioxide in the packaging container.
[10]
The method according to [8] or [9], wherein the internal oxygen concentration of the packaging container 24 hours after sealing is 2.0% by volume or more and 16.5% by volume or less.
[11]
The method according to any one of [8] to [10], wherein the internal oxygen concentration immediately after sealing in the packaging container is less than 15% by volume.

  According to the present invention, it is possible to extremely effectively suppress the growth of Bacillus cereus in a packaging container, and even at a relatively high storage temperature of about 35 ° C., such as cut vegetables stored in the packaging container. While maintaining the hygiene and safety of the fruits and vegetables, it is possible to effectively prevent deterioration in appearance, generation of an unpleasant odor, and the like.

Hereinafter, embodiments for implementing the present invention will be described.
The present invention relates to a method for inhibiting the growth of Bacillus cereus in a packaging container, wherein the internal oxygen concentration of the packaging container after sealing for 24 hours is 2.0 vol. % Or more and 16.5% by volume or less.

That is, in the present invention, when the packaging container is kept under the condition of 35 ± 2 ° C., the oxygen concentration 24 hours after sealing of the packaging container is 2.0% by volume or more and 16.5% by volume or less. When the internal oxygen concentration is 2.0% by volume or more and 16.5% by volume or less, the growth of Bacillus cereus in the packaging container is effectively suppressed.
Bacillus cereus is a facultative anaerobic bacterium, and it has been considered that even when the oxygen concentration is low, energy is obtained by anaerobic respiration and the growth proceeds. However, in the present invention, when the oxygen concentration 24 hours after sealing of the packaging container is set to 2.0% by volume or more and 16.5% by volume or less when the packaging container is held at 35 ± 2 ° C. It was surprisingly found that the growth of Bacillus cereus was effectively suppressed.
The low oxygen concentration in the packaging container is also preferable in that the respiration of the fruits and vegetables can be suppressed, the fruits and vegetables can be kept in a dormant state, and the oxidation and discoloration of the fruits and vegetables can be suppressed.
When the packaging container of the present invention is held at 35 ± 2 ° C., the oxygen concentration 24 hours after sealing of the packaging container is preferably 2.2% by volume or more and 14.5% by volume or less. It is particularly preferable that the content be 2.3% by volume or more and 14.3% by volume or less.
The oxygen concentration inside the package can be specified, for example, by sampling the gas inside the package with a sampling needle tube and measuring the oxygen concentration with a zirconia oximeter for food packaging.
Here, “after sealing the packaging container” refers to an elapsed time when the packaging container is sealed and maintained at a predetermined temperature.

From the viewpoint that the oxygen concentration 24 hours after the sealing of the packaging container is 2.0% by volume or more and 16.5% by volume or less, the internal oxygen concentration immediately after the sealing of the packaging container is less than 15% by volume. Is preferred.
If the internal oxygen concentration immediately after the sealing of the packaging container is less than 15% by volume, oxygen is consumed by the respiration of fruits and vegetables contained in the packaging container and the respiration of bacteria, so that the packaging container is reduced to 35 ± 2. It is much easier to keep the oxygen concentration at 2.0 hours to 16.5% by volume 24 hours after the sealing of the packaging container when kept at the condition of ° C.
The internal oxygen concentration immediately after the sealing of the packaging container is more preferably less than 14.5% by volume, and particularly preferably less than 14.3% by volume.

From the viewpoint of achieving the desired internal oxygen concentration described above, it is preferable that nitrogen is further sealed in the packaging container. More specifically, the internal nitrogen concentration immediately after the sealing of the packaging container is preferably 50% by volume or more and 98% by volume or less. The internal nitrogen concentration immediately after sealing of the packaging container is more preferably from 53% by volume to 90% by volume, and particularly preferably from 55% by volume to 83% by volume.
By enclosing nitrogen when sealing the packaging container, the internal oxygen concentration immediately after packaging can be kept low. Further, by further enclosing nitrogen, it is possible to keep the pressure in the packaging container high, prevent the inflow of outside air having a higher oxygen concentration, and reduce the oxygen concentration 24 hours after the sealing of the packaging container to 2.0. It is much easier to set the volume percentage to 16.5% by volume or less.

From the viewpoint of achieving the above-mentioned desired internal oxygen concentration, it is also preferable to introduce carbon dioxide into the packaging container. More specifically, the internal carbon dioxide concentration immediately after the sealing of the packaging container is preferably 20% by volume or more, and more preferably 25% by volume or more.
The concentration of carbon dioxide in the packaging container can be measured, for example, by a Danmater O ₂ / CO ₂ analyzer for food packaging Check Mate 3.

When the packaging container of the present invention is held at 35 ± 2 ° C., the ratio of the total area of the Bacillus cereus colonies in the standard agar medium placed in the packaging container to the total area of the culture medium is determined by It is preferably suppressed to 20% or less over 0 to 24 hours after the container is sealed.
Therefore, the method for suppressing bacterial growth which satisfies the conditions of the present invention and a packaging container using the same are stored inside even at a relatively high storage temperature of about 35 ° C. without requiring a separate means for inhibiting bacterial growth. It can maintain the hygiene and safety of fruits and vegetables. Further, it is not necessary to perform excessive sterilization, washing, and other treatments on the fruits and vegetables stored therein. Further, it is possible to effectively prevent the appearance from being deteriorated due to the growth of bacteria, the generation of an unpleasant odor, and the like.
When the packaging container is kept at 35 ± 2 ° C., the ratio of the total area of the colonies of Bacillus cereus in the standard agar medium placed in the packaging container to the total area of the culture medium is the ratio of the packaging container. It is preferably controlled to 15% or less over 0 to 24 hours after sealing, and particularly preferably to 8% or less.
The total area of the Bacillus cereus colonies in the standard agar medium can be measured by taking an image of the bacterial colonies on the petri dish and analyzing the image.

The packaging used in the present invention as long as the internal oxygen concentration of the packaging container after sealing for 24 hours is 2.0% by volume or more and 16.5% by volume or less when the package is held at 35 ± 2 ° C. The container is not particularly limited, but is preferably a packaging container containing a polymer film from the viewpoint of cost, appearance, lightness, and the like. Here, "comprising a polymer film" means that the entire packaging container is composed of a polymer film, and that a part of the packaging container such as a lid is composed of a polymer film. The purpose is to include both.
Therefore, the above-mentioned preferable packaging container may be a flexible packaging container in which all or a main part is formed of a flexible polymer film, that is, a so-called packaging bag. It may be a flexible packaging container combining other flexible members such as paper, or a packaging container combining a flexible polymer film and a rigid member, for example, as a lid material And a rigid film such as a tray or a cup.

In an embodiment in which the packaging container is a so-called packaging bag, for example, three or two sides are heat-sealed in a state where two polymer films are overlapped with each other or one polymer film is folded. To form a packaging bag. The remaining one side can be sealed by arranging the contents such as fruits and vegetables in the packaging bag and then similarly fusing by heat sealing.
The shape of such a packaging bag in a plan view may be a circle, a triangle, a rectangle, or a polygon having a rectangle or more, but it is preferable to form a rectangle from the viewpoint of workability and ease of handling.

The oxygen permeability of the packaging container containing the polymer film used in the present embodiment is not particularly limited. For example, the oxygen permeability is 10000 cc / m ² / atm / day or less at 20 ° C. and 90% RH. It is preferred that When the oxygen permeability of the packaging container is within the above range, the control of the oxygen concentration in the packaging container is further facilitated, and the oxygen concentration 24 hours after sealing of the packaging container is 0 vol% or more and 5 vol% or less. This is because it becomes even easier.
Oxygen permeability of the packaging container is more preferably at most ^{6000cc / m 2 / atm / day} , even more preferably at most ^{3500cc / m 2 / atm / day} .
Although there is no particular lower limit to the oxygen permeability of the packaging container, the use of a polymer film having a realistic cost and thickness often results in 500 cc / m ² / atm / day or more. It is preferable to select an appropriate oxygen permeability in consideration of the shape and size of the packaging container, the type and amount of contents to be stored in the packaging container, and the like.

Polymer Film As described above, the packaging container used in the present invention preferably contains a polymer film. At this time, the oxygen permeability of the polymer film is 10,000 cc at 20 ° C. and 90% RH. / M ² / atm / day or less is particularly preferred. That is, in this embodiment, in order to achieve the above-described desired internal oxygen concentration, it is desirable to configure the packaging container using a polymer film having an oxygen permeability of a predetermined value or less.
Oxygen permeability of the polymer film is more preferably at most ^{6000cc / m 2 / atm / day} , even more preferably at most ^{3500cc / m 2 / atm / day} .
When the oxygen permeability at 20 ° C. and 90% RH is equal to or less than a predetermined value, invasion of oxygen from the outside air is prevented, and the oxygen concentration 24 hours after sealing the packaging container is 2.0% by volume to 16.5%. It is easier to make the volume% or less.
Although there is no particular lower limit to the oxygen permeability of the polymer film, as long as a normal polymer film not subjected to gas barrier coating or the like is used, 500 cc / m ² / atm / day at 20 ° C. and 90% RH is used. Generally, this is the case.
Further, from the viewpoint of preventing generation of odor from the stored fruits and vegetables, it is preferable that the polymer film has an oxygen permeability enough to allow the fruits and vegetables to breathe. From this viewpoint, the oxygen permeability of the polymer film at 20 ° C. and 90% RH is preferably 500 cc / m ² / atm / day or more, and more preferably 1000 cc / m ² / atm / day or more. More preferably, it is particularly preferably at least 3,500 cc / m ² / atm / day.

The oxygen permeability of the polymer film used in the present embodiment can be measured, for example, by the following method.
First, a bag having an inner dimension a (cm) × b (cm) is formed by the following method.
One film is almost equally folded in half and is about 5 mm wide. The scale of the heating condition is set to 3 with an impulse sealer (manufactured by Fuji Impulse, part number Fi-200-10WK), and heat sealing is performed. One of the sides substantially perpendicular to the heat-sealed side is heat-sealed so that the side is substantially at the center, and the other side is heat-sealed except for an end of about 2 cm, which is one communicating part of the other side. (cm) x b (cm).
Next, nitrogen gas is injected from the communicating portion, and when the inside of the bag becomes saturated, almost all the gas in the bag is discharged from the communicating portion. After repeating this operation 5 times, nitrogen gas is injected to saturate the inside of the bag with nitrogen gas, and the communicating portion is heat-sealed with the impulse sealer under the same conditions. The bag saturated with nitrogen gas is left for 6 hours in a room at 22 ° C. and a relative humidity of 40% in the air (1 atm, oxygen concentration: 21%, nitrogen concentration: 79%).
Next, about 20 cc is sampled with a sampling needle tube, and the oxygen concentration in the bag is measured with a zirconia oxygen concentration meter for food packaging (model number LC-750F, manufactured by Toray Engineering Co., Ltd.). Further, the volume of the gas in the bag is measured, and the oxygen permeability is calculated from the following equation.
(Formula) Oxygen permeability = internal oxygen concentration change (%) / 100 × volume (cm ³ ) × 24 × 60 / hour (360 minutes) × 10000 cm ² / area (a × b × 2 cm ² ) /0.21 ( Partial pressure of oxygen)

By appropriately selecting the material, thickness, processing method, and the like of the polymer film, the oxygen permeability of the polymer film can be appropriately adjusted. For example, in the case of a biaxially stretched polypropylene (OPP) film, by setting the thickness to 45 μm or less, the oxygen permeability at 20 ° C. and 90% RH can be 500 cc / m ² / atm / day or more. . In consideration of mechanical strength and the like, the thickness of the polymer film is more preferably 15 to 45 μm, and particularly preferably 20 to 40 μm.

As described above, the oxygen permeability of the polymer film can be adjusted by appropriately selecting the material, thickness, processing method, and the like of the polymer film. It is not necessary to provide an opening in the polymer film. In particular, from the viewpoint of realizing an oxygen permeability of 10,000 cc / m ² / atm / day or less in a preferred embodiment of the present invention, it is preferable not to make openings in the polymer film.
Since it is not necessary to provide an opening in the polymer film, the manufacturing process becomes simpler and lower in cost, and it is not necessary to precisely control the size, shape, and the like of the opening.
The absence of an opening in the polymer film can be confirmed, for example, by the fact that the polymer film forming the packaging container does not have a through hole that can be confirmed by an ink leakage checker.

On the other hand, in one embodiment of the present invention, when maintaining the freshness of fruits and vegetables with a large amount of respiration, when it is necessary to use a thick polymer film and / or a polymer material having a low oxygen permeability, In order to achieve a desired oxygen permeability, an opening provided in the polymer film may be used in combination. The shape of the opening is not particularly limited, and may be circular, substantially circular, or slit-like. A circular or substantially circular opening is preferable in that processing is easy, and the like, and a slit-shaped opening is preferable in that foreign substances can be effectively prevented from entering.
As a method for forming the micropores, any of a physical means such as a heating needle and an optical means such as a laser can be used. If the pore diameter is 100 to 300 μm, it is within a range where the pores can be sufficiently opened even by using physical means, which is advantageous in terms of cost. Needless to say, the hole can be opened even by a laser or the like. In this case, the hole diameter can be controlled more precisely. In the present embodiment, when a laser is used to form the fine holes, it is preferable that the target film efficiently absorbs the laser light. For example, a carbon dioxide laser, a YAG laser, a helium neon laser, an excimer laser, a UV laser light oscillator, and a semiconductor laser light oscillator can be used, but are not particularly limited thereto.
In addition, unlike the slit processing, the laser hole processing preferably used in the production of the package of the embodiment does not have physical contact with metal, so there is no risk of missing blades, needles and the like being mixed, and the opening area is limited to the slit. It is preferable because quality control (management of gas permeability) is easy because it is constant.
As slit processing, the size of each opening and the number of openings can be appropriately set and changed as long as the oxygen permeability of the polymer film is appropriate. The number of openings in the area is a guide. For example, it is a slit-shaped opening having a length of 2 mm, and in a closed state, the width as a through hole cannot be visually recognized by an optical microscope (manufactured by Olympus, model SZH-131) at a magnification of 4 ×. In the case where a package is provided, there is an effect of increasing the oxygen permeability of about 1000 cc / m ² / day / atm every time one package is present in a 200 mm × 200 mm package. It is preferable to determine the number of slit openings from the oxygen permeability of the whole container.
As the laser processing, it is preferable to provide about 1 to 5 holes having a diameter of 50 to 200 μm φ, and the opening holes can be visually recognized by an optical microscope (manufactured by Olympus Corporation, model SZH-131) at a magnification of 4 ×. .

  There is no particular limitation on the thickness of the polymer film used in the present embodiment, and suitable oxygen permeability, flexibility when forming a packaging container, strength, transparency, economy, etc., when an opening is provided. From the viewpoints of accuracy and easiness in forming the openings, a suitable thickness may be appropriately selected in relation to the material for forming the polymer film. Typically, the thickness of the polymer film is preferably from 15 to 45 μm, more preferably from 20 to 40 μm.

Further, 20 ° C. of the polymer film used in this embodiment, it is preferable that carbon dioxide permeability at 90% RH or less ^{10000cc / m 2 / atm / day} , or less 8000cc ^/ m 2 ^/ atm ^/ day Is more preferable, and it is especially preferable that it is 7500 cc / m < ² > / atm / day or less.
When the carbon dioxide permeability at 20 ° C. and 90% RH is equal to or less than a predetermined value, intrusion of carbon dioxide from the outside air is prevented, and the carbon dioxide concentration 24 hours after sealing of the packaging container is within a preferable range. Is easier.
Although there is no particular lower limit to the carbon dioxide permeability of the polymer film, 5000 cc / m ² / atm / at 20 ° C. and 90% RH as long as a normal polymer film without gas barrier coating or the like is used. Generally, it is not less than day.

  The carbon dioxide permeability of the polymer film used in the present embodiment can be measured by the same method as the oxygen permeability.

  The material of the polymer film is not particularly limited, but a polymer used for a conventional film for packing fruits and vegetables can be appropriately used. For example, polyethylene, polypropylene, polyethylene terephthalate, polystyrene, nylon (polyamide), ethylene vinyl acetate copolymer (EVA), polybutylene succinate, polybutylene succinate adipate, polylactic acid and the like can be mentioned. Also, for example, a natural polymer such as cellophane can be used. Further, any one of these materials may be used alone, or a plurality of these materials may be blended and / or laminated.

  From the viewpoint of easiness of processing and cost, the material of the polymer film is preferably a thermoplastic resin. Examples of the thermoplastic resin include homopolymers or copolymers of α-olefins such as ethylene, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene. Specifically, ethylene polymers such as high-pressure low-density polyethylene, linear low-density polyethylene (LLDPE), and high-density polyethylene, propylene homopolymer, propylene / α-olefin random copolymer, and propylene block copolymer And polyolefins such as poly 1-butene and poly 4-methyl / 1-pentene. Examples of the thermoplastic resin include polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, polyamides such as nylon-6, nylon-66, and polymethaxylene adipamide, polyvinyl chloride, polyimide, and ethylene / acetic acid. Biodegradable resins such as vinyl copolymers or saponified products thereof, polyvinyl alcohol, polyacrylonitrile, polycarbonate, polystyrene, ionomer, polylactic acid, polybutylene succinate, and mixtures thereof. One of these thermoplastic resins may be used, or two or more of them may be used in combination. Among these, as the thermoplastic resin, polyolefin, polyester, polyamide and the like are preferable because of their excellent rigidity and transparency. Further, as the thermoplastic resin, an ethylene polymer or a propylene polymer is more preferable because of its light weight and excellent film processability, and a propylene polymer is more preferable from the viewpoint of flexibility and transparency.

<Propylene polymer>
As the propylene-based polymer, propylene homopolymer (also referred to as homo PP) manufactured and sold under the name of polypropylene, propylene / α-olefin random copolymer (also referred to as random PP) And a crystalline polymer containing propylene as a main component, such as a mixture of a propylene homopolymer and a low-crystalline or amorphous propylene-ethylene random copolymer (also called a block PP). . The propylene-based polymer may be a mixture of propylene homopolymers having different molecular weights, and a propylene homopolymer and a random copolymer of propylene and ethylene or an α-olefin having 4 to 10 carbon atoms. It may be a mixture.

  As the propylene-based polymer, specifically, polypropylene, propylene / ethylene copolymer, propylene / ethylene / 1-butene copolymer, propylene / 1-butene copolymer, propylene / 1-pentene copolymer Propylene as a main monomer, such as propylene / 1-hexene copolymer or propylene / 1-octene copolymer, and copolymerized with this and at least one or more selected from ethylene and α-olefins having 4 to 10 carbon atoms. Coalescence. These may be used alone or in combination of two or more.

The density of the propylene-based polymer is preferably 0.890 to 0.930 g / cm ³ , more preferably 0.900 to 0.920 g / cm ³ . The MFR (ASTM D1238, load 2160 g, temperature 230 ° C.) of the propylene polymer is preferably 0.5 to 60 g / 10 min, more preferably 0.5 to 10 g / 10 min, and 1 to 5 g / 10 min. Is more preferred.

<Ethylene polymer>
As the ethylene polymer, a homopolymer of ethylene, ethylene as a main monomer, a copolymer thereof with at least one kind of α-olefin having 3 to 8 carbon atoms, an ethylene / vinyl acetate copolymer, Saponified products and ionomers. Specifically, polyethylene, ethylene / propylene copolymer, ethylene / 1-butene copolymer, ethylene / 1-pentene copolymer, ethylene / 1-hexene copolymer, ethylene / 4-methyl-1-pentene Copolymers and copolymers of ethylene as a main monomer and at least one or more α-olefins having 3 to 8 carbon atoms, such as an ethylene / 1-octene copolymer, may be mentioned. The proportion of α-olefin in these copolymers is preferably from 1 to 15 mol%.

  Examples of the ethylene-based polymer include ethylene polymers manufactured and sold under the name of polyethylene. Specifically, high-pressure low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and high-density polyethylene (HDPE) are preferred, and LLDPE is more preferred. LLDPE is a copolymer of ethylene and a small amount of propylene, butene-1, heptene-1, hexene-1, octene-1, 4-methyl-pentene-1, and the like. Further, the ethylene polymer may be a homopolymer of ethylene or a polymer mainly composed of ethylene such as LLDPE.

Density of the ethylene polymer is preferably ^{0.910~0.940g / cm 3, 0.920~0.930g / cm} 3 is more preferable. When the density is 0.910 g / cm ³ or more, heat sealability is improved. When the density is 0.940 g / cm ³ or less, workability and transparency are improved.

  The blend and / or laminate may be a blend of any of the above polymers and / or a laminate, and may be any of the above polymers and a material other than the polymer. And / or a laminate. That is, the polymer film is made of a material other than a polymer, such as a heat stabilizer (antioxidant), a weather stabilizer, an ultraviolet absorber, a lubricant, a slip agent, a nucleating agent, an antiblocking agent, an antistatic agent and an antifogging agent And various fillers such as talc, silica, and diatomaceous earth, in addition to pigments and dyes, or a laminate of a polymer film and metal foil, paper, nonwoven fabric, or the like.

In the present embodiment, the polymer film preferably used for the packaging container may be either a non-stretched film or a stretched film.
From the viewpoint of mechanical strength and the like, stretched films of various polymers can be suitably used.
In particular, a stretched film (stretched polypropylene film) using a propylene-based polymer is excellent in mechanical strength, transparency, heat resistance and the like, and therefore can be particularly preferably used in the packaging container of the present embodiment.
In addition, a film using an ethylene-based polymer (polyethylene-based film) may be either a non-stretched film or a stretched film, but from the viewpoint of heat sealing properties and the like, a non-stretched film is particularly preferably used. be able to.
Examples of particularly preferable polymer films constituting the packaging container in the present embodiment include a stretched polypropylene film, a polyethylene film, and a laminate of a stretched film and a polyethylene film.

<Stretched polypropylene film>
The stretched polypropylene film preferably used in this embodiment may be composed of a film stretched in at least one direction, or the stretched polypropylene film itself may be stretched in at least one direction. When a biaxially stretched film is obtained as the stretched polypropylene film, it can be easily produced by, for example, sequentially or simultaneously biaxially stretching it. When a biaxially stretched film is obtained as a stretched polypropylene film, it is usually stretched 5 to 8 times in the machine direction, and then 8 to 10 times in the transverse direction by using a tenter mechanism, and the film thickness is finally adjusted. It can be manufactured by a method in which the thickness is 20 to 40 μm, or the film is stretched in the longitudinal and transverse directions by 5 to 10 times (25 to 100 times in area ratio), respectively.
<Polyethylene film>
The polyethylene-based film preferably used in the present embodiment is a film containing the ethylene-based polymer. Although various known molding methods can be used for the polyethylene-based film, cast molding by extrusion with an extruder is preferable from the viewpoint of production efficiency.

<Stretched film>
Polyamide film made of nylon 6, nylon 66, etc., film made of polyester represented by polyethylene terephthalate, polyethylene naphthalate, polycarbonate film, ethylene-vinyl alcohol copolymer film, polyvinyl alcohol film, polyvinyl chloride film, polyvinylidene chloride It is a uniaxially or biaxially stretched film made of a film, a polystyrene film, a polyolefin such as polypropylene, poly-L-lactic acid, poly-D-lactic acid, or a stereocomplex polylactic acid in which poly-L-lactic acid and poly-D-lactic acid are precisely coordinated.

<Laminated body of stretched film and polyethylene film>
A laminate of a stretched film and a polyethylene film, which is preferably used in the present embodiment, is obtained by laminating a layer of the polyethylene film and a layer of the stretched film. The polyethylene film may be stretched in one or two directions, but is preferably a non-stretched film from the viewpoint of the stability of the mechanical strength of the packaging bag.
Dry lamination is performed to attach a stretched film and a polyethylene-based film that have been prepared in advance using an adhesive, but it is necessary to perform a corona treatment on the stretched film surface where the adhesive is applied from the viewpoint of adhesion stability. preferable. Specifically, the surface tension of the film surface after corona treatment is preferably 35 mN / m or more, more preferably 40 mN / m or more, from the viewpoint of adhesion stability.

Further, these polymer films may be subjected to a stretching process, an anti-fogging process or printing, and may be an inorganic antibacterial agent such as silver or copper, or an organic antibacterial agent such as chitin, chitosan or allyl isothiocyanate. Agents may be applied, or they may be kneaded in a film.
From the viewpoint of maintaining the freshness of contents such as fruits and vegetables, it is preferable that the polymer film contains at least one antibacterial agent.
In addition, the surface of the polymer film, particularly the surface on the side inside the packaging container, a specific amount of a specific surfactant is present, or the polymer film contains a specific amount of a specific surfactant, It may have an antibacterial function. For example, palmityl diethanolamine, stearyl diethanolamine, at least one compound selected from the group consisting of glycerin monolaurate and diglycerin monolaurate is preferably present on at least one surface of the polymer film, It is particularly preferred that one compound is present at 0.002 to 0.5 g / m ² . Alternatively, it is preferable that the polymer film contains at least one compound selected from the group consisting of palmityl diethanolamine, stearyl diethanolamine, glycerin monolaurate and glycerin monocaprate, and 0.001 to 3 parts by mass. It is particularly preferred that it be contained.
When a specific amount of a specific surfactant is present on the surface of the polymer film, or when the polymer film contains a specific amount of the specific surfactant, dew condensation on the surface of the polymer film is suppressed, and various bacteria Is suppressed, the growth of various bacteria in dew (drip) is suppressed, and an antibacterial function is exhibited.

From the viewpoint of transparency, flexibility, cost, and the like, it is particularly preferable to use a stretched polypropylene film, which has been widely used in the related art, or a laminate of a stretched polypropylene film and a polyethylene-based film as a polymer film. . Since these films are generally excellent in heat sealability, productivity is good in the production of packaging containers.
In this case, when using a stretched propylene film alone, the thickness is preferably 10 to 100 μm, and when using a laminate of a stretched polypropylene film and a polyethylene-based film, the thickness of the former is 10 to 50 μm. The thickness of the latter is preferably from 10 to 120 μm.

  When a polymer film that is not always suitable for heat sealing is used, it may be formed by laminating or coating a sealant layer on all or a part of the polymer film. For example, a cellophane film coated with an acrylic resin, a film in which linear low-density polyethylene (LLDPE) polystyrene and EVA are laminated on polyethylene terephthalate (PET), and the like, can be used as a suitable polymer film.

Fruits and Vegetables The method for suppressing the growth of Bacillus cereus according to the present invention, and a packaging container using the method can be suitably used for maintaining freshness of fruits and vegetables.
There are no particular restrictions on the fruits and vegetables that retain freshness according to the present invention. Fruits and vegetables such as root vegetables, tomato, cucumber, eggplant, pepper, edamame, okra, mushrooms such as mung bean sprouts, soy bean sprouts, syrup, shiitake, shimeji, eryngii, maitake, matsutake (Mushrooms), broccoli, spinach, komatsuna, bok choy, cabbage, lettuce, leaf and stem vegetables such as asparagus, chrysanthemums, lilies, carnations and other flowers or seedlings.
In particular, the packaging container of the present embodiment is preferably used for maintaining the freshness of fruits and vegetables including at least one selected from the group consisting of lettuce, cabbage, and radish. This is because lettuce, cabbage, and radish are often eaten raw, and the need to suppress the growth of Bacillus cereus is particularly high.

The “lettuce” in this embodiment is a concept including general vegetables belonging to the Asteraceae, Agenda spp., And is not limited to vegetables distributed under the name of “lettuce” itself.
That is, the "lettuce" referred to here is a type called scraping chisha or cutting lettuce typified by a sanchu or the like, which scrapes leaves from the stem; standing such as romaine lettuce where the leaves hardly roll. Non-headed leaf lettuce (leaf chisha) represented by sunny lettuce and green leaf; and ball lettuce (ball chisha) typically represented by lettuce; Is a concept that includes
Preferable examples of the “lettuce” here include lettuce (ball lettuce), green leaf, romaine lettuce (cos lettuce), sunny lettuce, silk lettuce, pink roaster, salad greens, bouquet lettuce, green oak leaf (Saranova lettuce), frill Examples include, but are not limited to, lettuce, (chima) sanchu, and stem lettuce (stem lettuce).

The “cabbage” in this embodiment is a concept including general head vegetables belonging to the Brassicaceae Brassica genus, and is not limited to vegetables distributed under the name “cabbage” itself.
That is, the “cabbage” referred to here is, as a preferable example, a cold cabbage (winter) cabbage, a spring cabbage, a plateau cabbage, a red cabbage, a green ball (round ball), a savoy cabbage (crepe cabbage), a brussels sprouts, a petite veil, It is a concept that includes all of Misaki Kanai / Tongari Kyubetsu etc., but is not limited to these.

The “radish” in this embodiment is a concept including general vegetables belonging to the genus Brassicaceae, and is not limited to vegetables distributed under the name “radish” itself.
That is, the term "radish" used herein is generally known varieties such as blue radish, white radish, spicy radish, etc., but is not particularly limited to varieties and the like, and besides radish, Varieties such as radish, black radish, and Japanese radish may be used.
Further, the site of "radish" is generally a root, but is not particularly limited thereto, and may be a leaf or a stem, or a combination of these, for example, a radish with leaves. Such a thing may be used. In addition, the "radish" is not limited to a peeled one, and may include a part or all of the skin.

There is no particular limitation on the form of fruits and vegetables that maintain freshness in the packaging container of the present embodiment. Therefore, the fruits and vegetables may be as-harvested products, so-called pre-processed products from which outer leaves and the like have been removed, or may be cut fruits and vegetables, so-called cut vegetables. The fruits and vegetables may have been subjected to any or all of the processing such as washing, cooling, and dehydration, or may be those without any of these processings.
In addition, when the fruits and vegetables stored and maintained in freshness are cut vegetables, it is preferable that the vegetables are cut, washed, dehydrated, and / or dried to adjust the water content to an appropriate value. For example, if the cut vegetables are cut lettuce, the lettuce is washed with hypochlorous acid at 80 to 120 ppm for 10 to 20 minutes based on the "Manual for Mass Cooking Facilities Hygiene Management" (Ministry of Health and Welfare). Prevention of odor generation and browning can be achieved by controlling the water content within the range of 20 to 30% based on the weight loss when dried under reduced pressure at 70 ° C. for 5 hours based on “Analysis Method” (Consumer Affairs Agency). It is particularly preferable from the viewpoint of the balance of prevention of deterioration of the appearance.

  In recent years, demand for cut vegetables has been increasing because they can be easily served for meals, and has high economic value. On the other hand, when vegetables are cut, the respiratory action and metabolic reaction tend to be rapidly activated, and the quality tends to be rapidly reduced. The present embodiment has a particularly high economic value because it can be effectively used for maintaining the freshness of such cut vegetables.

A method for manufacturing a package, and a method for maintaining freshness.Also , a specific surfactant is present on the surface of the polymer film in a specific amount, or the polymer film contains a specific surfactant in a specific amount, thereby having an antibacterial function. May be provided. For example, palmityl diethanolamine, stearyl diethanolamine, at least one compound selected from the group consisting of glycerin monolaurate and diglycerin monolaurate is preferably present on at least one surface of the polymer film, It is particularly preferred that one compound is present at 0.002 to 0.5 g / m ² . Alternatively, it is preferable that the polymer film contains at least one compound selected from the group consisting of palmityl diethanolamine, stearyl diethanolamine, glycerin monolaurate and glycerin monocaprate, and 0.001 to 3 parts by mass. It is particularly preferred that it be contained.

By storing the fruits and vegetables in the packaging container of the present embodiment, a package according to a preferred embodiment of the present invention can be manufactured, and a freshness maintaining method for fruits and vegetables according to another preferred embodiment of the present invention is implemented. be able to. At that time, it is preferable to appropriately adjust the internal oxygen concentration of the packaging container, and it is also preferable to encapsulate carbon dioxide or nitrogen.
Hereinafter, the manufacturing method of the package of the present embodiment will be described by taking as an example a package for maintaining the freshness of cut lettuce that has been cut, washed, dehydrated, and / or dried and adjusted to an appropriate water content.

  First, in a pretreatment step, lettuce is removed from the outer leaves by hand, divided into 2 to 4 parts, and the core is removed. The lettuce conveyed by the conveyor is cut by a slicer, and is also cooled in a washing tank filled with cold water, and is also used as a cooling tank. After dewatering, it is dehydrated by a centrifugal dehydrator or the like. The dehydrated cut lettuce is packed in a packaging container (one side not sealed) containing the polymer film used in the present embodiment, and after weighing, the packaging container is sealed to maintain the freshness of the cut lettuce. A package is manufactured.

From the viewpoint of maintaining the freshness of the cut lettuce, it is preferable to use a sharp blade and reduce the number of scratches generated on the cut surface.
In addition, as the cut width is smaller, the cut area increases, and it becomes more difficult to maintain freshness. Therefore, from the viewpoint of maintaining freshness, it is preferable that the cut width is wide as long as it conforms to the form of demand.
Further, if a lot of germs adhere to the cut lettuce from the beginning, it becomes more difficult to maintain the freshness. Therefore, it is preferable to reduce the adhesion of germs as much as possible by thoroughly washing the cut lettuce. Washing is particularly effective for maintaining freshness, since it not only reduces the adhesion of various bacteria, but also has the effect of removing cell fluids and the like that contain highly active enzymes and the like and may cause discoloration.
In addition, it is important to sufficiently remove moisture adhering to the cut lettuce surface after washing to maintain freshness. Even if water is drained by standing after washing, much water still adheres to the cut lettuce surface, so it is effective to remove water using a centrifugal dehydrator or the like.
This is because by adjusting the water content appropriately, it is possible to suppress the growth of various bacteria in extra small water droplets. More specifically, for example, after washing with hypochlorous acid at 80 to 120 ppm for 10 to 20 minutes based on the "Manual for Mass Cooking Facilities Hygiene Management" (Ministry of Health and Welfare), "analysis method of nutrition labeling in nutrition labeling standards" (consumer It is preferable that the water content measured based on the weight loss when dried under reduced pressure at 70 ° C. for 5 hours based on the Agency) is in the range of 20 to 30%.

The package for keeping freshness of fruits and vegetables of the present embodiment may be filled with nitrogen or carbon dioxide and / or degassed after storing fruits and vegetables and sealing the packaging container. By encapsulating and / or degassing nitrogen or carbon dioxide, it is possible to quickly reach a desired oxygen concentration or a preferable carbon dioxide concentration designed as an equilibrium state between the oxygen permeability of the packaging container and the respiratory volume of the fruits and vegetables. This is possible and is advantageous for maintaining freshness.
Degassing may be performed after the packaging container is sealed from the viewpoints of efficiency improvement, space saving, and elimination of a specific gas during the distribution process.

By carrying out the step of storing and sealing fruits and vegetables in the packaging container according to the method as described above, even when the packaging container is maintained at a relatively high temperature condition of 35 ± 2 ° C., the growth of Bacillus cereus can be achieved. Can be effectively suppressed, and the freshness of fruits and vegetables including lettuce and the like can be effectively maintained.
At that time, when the oxygen concentration in the packaging container is maintained at a temperature of 35 ± 2 ° C. for 24 hours after sealing, and is 2.0 vol% or more and 16.5 vol% or less, the growth of Bacillus cereus is more effective. It is preferable because it is suppressed. It is particularly preferred that the internal oxygen concentration immediately after sealing in the packaging container is less than 15% by volume.

In the package of the present embodiment, only fruits and vegetables such as lettuce may be stored in the packaging container, or other members may be stored.
For example, in addition to the fruits and vegetables, a moisture absorbent and / or an antibacterial agent may be contained in the packaging container.
There is no particular limitation on the hygroscopic agent, and known or commercially available materials having a hygroscopic effect or a humidity controlling effect can be used. Examples of those preferably used as a moisture absorbent include, for example, activated carbon, silica gel, alumina gel, silica alumina gel, anhydrous magnesium sulfate, zeolite, synthetic zeolite, calcium oxide, calcium chloride, and calcined alum, or a mixture thereof. But not limited thereto.
Among them, it is particularly preferable to use activated carbon which has relatively little effect on fruits and vegetables and concerns about use near foods such as fruits and vegetables. Activated carbon can be in any form of powder or granules, and the raw material can be coconut shell, sawdust, charcoal, bamboo charcoal, lignite, peat, stone, oil pitch, or anything else. The activated carbon is desirably packaged for each unit of use with a nonwoven fabric, cellophane, paper, or the like, but the activated carbon itself may be fibrous. The activated carbon packaging material is preferably a heat-sealing material such as a nonwoven fabric made of a synthetic resin, but any paper or natural fiber may be used as long as it has water vapor permeability and does not spill activated carbon. no problem.

  There is no particular limitation on the antibacterial agent, and a substance having an antibacterial effect can be used as appropriate.However, a natural antibacterial agent having relatively little concern about the effect on fruits and vegetables and the use near foods such as fruits and vegetables can be used. It can be preferably used. More specifically, chitosan, allyl isothiocyanate, hinokitiol, limonene, and the like, which are natural antibacterial agents, can be stored in a packaging container.

  Hereinafter, the present invention will be specifically described with reference to Examples / Comparative Examples. The present invention is not limited in any sense by the following examples.

In the following Examples / Comparative Examples, each characteristic was evaluated by the following methods.
(Internal oxygen concentration / carbon dioxide concentration)
Approximately 8 cc of the gas in the packaging container was sampled, and the internal oxygen concentration and the internal carbon dioxide concentration were measured using an O ₂ / CO ₂ analyzer for food packaging Check Mat 3 manufactured by Dansensor.
(Bacteria amount)
The bacterial colonies on the petri dish were photographed and subjected to image analysis to calculate the ratio of the bacterial colonies to the petri dish area.

(Example 1)
A standard agar medium (Standard Methods Agar, SMA, manufactured by Eiken Chemical Co., Ltd.) was placed in a Petri dish (manufactured by Atect, diameter: 90 mm), and Bacillus cereus was applied with a platinum loop to obtain a surface area of 1240 cm ² and a volume of 2243 cm ³ . Placed in a closed box. The oxygen permeability of the closed box was 600 cc / m ² / atm / day, and the carbon dioxide permeability was 7200 cc / m ² / atm / day.
After introducing carbon dioxide into the petri dish and adjusting the carbon dioxide concentration to 100% by volume, the petri dish was sealed and kept at 35 ± 2 ° C. In addition to observing the bacterial colonies during the holding, the internal oxygen concentration and carbon dioxide concentration 24 hours after the sealing were measured. Table 1 shows the results.

(Comparative Example 1)
An experiment was performed in the same manner as in Example 1, except that nitrogen was introduced into the dish instead of carbon dioxide, and the initial nitrogen concentration was set to 100% by volume and the carbon dioxide concentration was set to 0% by volume. Table 1 shows the results.

(Comparative Example 2)
An experiment was performed in the same manner as in Example 1, except that a mixed gas of oxygen and nitrogen was introduced into the dish instead of carbon dioxide, and the initial oxygen concentration was 15 vol% and the nitrogen concentration was 85 vol%. Was. Table 1 shows the results.

(Example 2)
A gas mixture of oxygen, nitrogen, and carbon dioxide was introduced into the dish instead of carbon dioxide, and the initial oxygen concentration was 14 vol%, the nitrogen concentration was 56 vol%, and the carbon dioxide concentration was 30 vol%. An experiment was conducted in the same manner as in Example 1 except for the difference. Table 1 shows the results.

In each of the examples in which the internal oxygen concentration was 2.0 vol% or more and 16.5 vol% or less when kept at 35 ± 2 ° C. for 24 hours after sealing, the total area of the Bacillus cereus colony was smaller than that of the medium. The percentage of the total area was suppressed to 20% or less. Therefore, when these conditions of the present invention are satisfied, the hygiene and safety of the fruits and vegetables stored in the packaging container can be maintained even at a relatively high storage temperature of about 35 ° C. In addition, it is possible to effectively prevent the appearance from being deteriorated due to the growth of bacteria, the generation of an unpleasant odor, and the like.
On the other hand, in each comparative example in which the internal oxygen concentration is less than 2.0% by volume or more than 16.5% by volume when kept at 35 ± 2 ° C. for 24 hours after sealing, the colony of Bacillus cereus was The ratio of the total area to the total area of the medium exceeded 20%, and the growth of Bacillus cereus could not be suppressed. Therefore, when the conditions of the present invention are not satisfied in this way, a separate means is required for suppressing the growth of Bacillus cereus on fruits and vegetables stored in the packaging container, and deterioration of appearance derived from bacterial growth, There is concern about the generation of off-flavors.

  The method for suppressing the growth of Bacillus cereus according to the present invention, and the packaging container using the method, can extremely effectively suppress the growth of Bacillus cereus inside, and the hygiene of cut vegetables stored in the packaging container. In addition to maintaining its properties and safety, it can effectively prevent deterioration of appearance, generation of off-flavors, etc., and thus has high applicability in various industrial fields such as food processing, distribution, and eating out.

Claims (11)

  15. A method for suppressing the growth of Bacillus cereus in a packaging container, wherein the internal oxygen concentration of the packaging container after sealing for 24 hours is 2.0% by volume or more when held at 35 ± 2 ° C. The above method, wherein the content is 5% by volume or less.   When kept at 35 ± 2 ° C., the ratio of the total area of the colonies of Bacillus cereus in the standard agar medium placed in the packaging container to the total area of the culture medium is determined by the sealing of the packaging container. 2. The method of claim 1, wherein the inhibition is less than or equal to 20% over the next 0 to 24 hours.   3. The method according to claim 1, wherein the internal oxygen concentration of the packaging container immediately after sealing is less than 15% by volume.   The method according to any one of claims 1 to 3, wherein the internal nitrogen concentration of the packaging container immediately after sealing is 50 to 98% by volume. The method according to any one of claims 1 to 4, wherein the internal carbon dioxide concentration immediately after sealing of the packaging container is 20% by volume or more.   A packaging container for maintaining the freshness of fruits and vegetables, wherein the internal oxygen concentration of the packaging container after sealing for 24 hours is 2.0% by volume or more and 16.5% by volume or less when kept at 35 ± 2 ° C. And the ratio of the total area of the colonies of Bacillus cereus in the standard agar medium placed in the packaging container to the total area of the medium when the temperature is maintained at 35 ± 2 ° C. The above-mentioned packaging container, wherein the content is suppressed to 20% or less from 0 hours to 24 hours after the container is sealed.   A package in which fruits and vegetables are stored in the packaging container according to claim 6.   A method for maintaining the freshness of fruits and vegetables, comprising: a step of storing and sealing fruits and vegetables in the packaging container according to claim 6; and a step of maintaining the packaging container at 35 ± 2 ° C.   The method for maintaining freshness of fruits and vegetables according to claim 8, further comprising a step of enclosing carbon dioxide in the packaging container.   The method according to claim 8 or 9, wherein the internal oxygen concentration of the packaging container after sealing for 24 hours is 2.0 vol% or more and 16.5 vol% or less. The method according to any one of claims 8 to 10, wherein the internal oxygen concentration immediately after sealing in the packaging container is less than 15% by volume.