JP6674407B2 - A package excellent in freshness keeping performance of fruits and vegetables, and a method of keeping freshness of fruits and vegetables - Google Patents

Description

  The present invention relates to a package excellent in freshness preserving performance of fruits and vegetables including lettuce, and more specifically, a product in which fruits and vegetables including lettuce are stored in a packaging container having a polymer film and having a specific oxygen concentration. It relates to a package.

By providing a gas permeable portion in the polymer film base material, a gas permeable film that allows gas such as oxygen, carbon dioxide, and water vapor to pass therethrough from the gas permeable portion is used in the food field to produce fruits and vegetables, particularly fresh vegetables such as cut vegetables. It is suitably used as a packaging material. When vegetables, fruits, and the like are packaged using such a gas-permeable film, for example, an oxygen concentration suitable for maintaining the freshness of the contents of vegetables and fruits, for example, an oxygen concentration of about 1 to 4% can be maintained. It is known that contents can be stored while maintaining freshness for a relatively long period of time.
For example, in Patent Document 1, in a package of fruits and vegetables comprising a polymer film in which fruits and vegetables are sealed, the package is composed of (A) a perforated polymer film and (B) a non-porous polymer film; (A), at least one of the film properties (B), the water vapor permeability measured at 25 ° C. and a relative humidity of 75% is 50 to 800 gm ⁻² d ^{−1 based} on the effective surface area of the package. There is described a package containing fruits and vegetables characterized in that the open area ratio of (A) is 3 × 10 ^{−6 to} 7 × 10 ⁻⁴ % with respect to the effective surface area of the package. Specifically, (A) a perforated polymer film made of stretched polypropylene having a thickness of 35 μm and having 95 holes with an average pore diameter of 95 μm, and having nine holes with an average pore diameter of 60 μm, etc. in use.

Demand for cut lettuce has increased in recent years because it can be easily served for meals, and cut lettuce has high economic value because lettuce is one of the most common vegetables for salads and the like. Against this background, a technique has been proposed that can maintain freshness of fruits and vegetables including lettuce, such as suppressing browning and off-flavors for a long period of time. For example, Patent Document 2 discloses oxygen per 1 bag / kg of lettuce. A technique is described in which a cut lettuce is placed in a bag made of a film having a permeation amount of a predetermined value, and oxygen is filled in a predetermined amount per 1 kg of lettuce during packaging. However, even with the technique described above, there are cases where the off-flavor from cut lettuce cannot be sufficiently suppressed.
From such a background, there has been a strong demand for a technique capable of maintaining freshness of fruits and vegetables including lettuce, exceeding the level of the prior art, such as suppressing browning for a long period of time.

JP-A-5-168400 JP-A-8-228674

The present invention has been made in view of the above-mentioned limitations of the background art, and is a package in which a fruit and vegetable containing lettuce is stored in a packaging container, such as suppressing the browning of the fruit and vegetable containing the lettuce, and maintaining the freshness of the fruit and vegetable. An object of the present invention is to provide an excellent package.
As a result of intensive studies, the present inventor has found that controlling the internal oxygen concentration of the package after a predetermined time has elapsed after sealing the package to a predetermined value or less is effective in maintaining freshness such as suppression of browning of fruits and vegetables including lettuce. They have found that they are particularly effective, and have completed the present invention.

That is, the present invention
[1]
Vegetables and vegetables containing lettuce are stored in a packaging container containing a polymer film, and the internal oxygen concentration after holding the package at 72 ° C. for 72 hours after sealing is 7.0% by volume or less. Body.

Hereinafter, each of [2] to [13] is one aspect or one of preferred embodiments of the present invention.
[2]
The package according to [1], wherein browning of the lettuce and generation of an odor are suppressed at 10 ° C. for 72 hours or more after sealing of the package.
[3]
The package according to [1] or [2], wherein the oxygen concentration in the package immediately after sealing of the package is 0.0 to 12.0% by volume.
[4]
The package according to any one of [1] to [3], wherein nitrogen is further sealed in the packaging container.
[5]
The package according to any one of [1] to [4], wherein the polymer film has an oxygen permeability of 10,000 cc / m ² / atm / day or less at 20 ° C. and 90% RH.
[6]
The package according to any one of [1] to [5], wherein the packaging container does not have a through hole that can be confirmed with an ink leak checker.
[7]
The package according to any one of [1] to [6], wherein the thickness of the polymer film is 15 to 45 μm.
[8]
The package according to any one of [1] to [7], wherein the polymer film is a stretched polypropylene film, a polyethylene-based film, or a laminate of a stretched film and a polyethylene-based film.
[9]
The package according to any one of [1] to [8], wherein the polymer film contains at least one antibacterial agent, or has at least one antibacterial agent applied thereto.
[10]
The package according to any one of [1] to [9], wherein the lettuce is a cut lettuce.
[11]
The package according to any one of [1] to [10], further containing a hygroscopic agent and / or an antibacterial agent.
[12]
6. A step of storing and sealing the fruits and vegetables including lettuce in the packaging container containing the polymer film, and keeping the oxygen concentration in the packaging container at 2 to 15 ° C. for 72 hours or more after the packaging is sealed. A method for maintaining the freshness of fruits and vegetables, comprising the step of maintaining the volume at 0% or less.
[13]
The method for maintaining freshness of fruits and vegetables according to [12], further comprising a step of enclosing nitrogen in the packaging container.

According to the present invention, by controlling the oxygen concentration inside the package after a predetermined time from the packaging to a predetermined value or less, it is possible to effectively suppress the occurrence of browning and odor of the lettuce, and to effectively increase the freshness of fruits and vegetables including the lettuce. Provided are a package that can be suppressed and a method for maintaining freshness of fruits and vegetables.

Hereinafter, embodiments for implementing the present invention will be described.
According to the present invention, fruits and vegetables containing lettuce are stored in a packaging container containing a polymer film, and the internal oxygen concentration after holding the package at 10 ° C. for 72 hours after sealing is 7.0% by volume or less. Is a package. That is, the package of the present invention has at least a packaging container and fruits and vegetables stored therein.

Packaging Container The packaging container constituting the package of the present invention contains a polymer film. 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 packaging container may be a flexible packaging container in which all or a main part is formed of a flexible polymer film, a so-called packaging bag, such as a flexible polymer film and coated paper. May be a flexible packaging container in which other flexible members are combined, or a packaging container in which a flexible polymer film and a rigid member are combined, for example, as a lid material. It may be a combination of a molecular film and a rigid member 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 packaging container used in the present invention comprises the above-described polymer film, and its oxygen permeability is not particularly limited, but is, for example, in the range of 500 to 10000 cc / m ² / atm / day. And preferably those in the range of 750 to 5000 cc / m ² / atm / day and those in the range of 900 to 2500 cc / m ² / atm / day. Those which can be used more preferably and have a range of 950 to 1500 cc / m ² / atm / day can be used particularly preferably, and the amount and kind of the fruits and vegetables to be stored and at 10 ° C. after sealing of the package. An appropriate oxygen permeability can be selected according to a desired internal oxygen concentration after holding for 72 hours.

Fruits and Vegetables The package of the present invention contains fruits and vegetables including lettuce in the packaging container. Here, "comprising" and the fruits or vegetables are lettuce, if all of the fresh produce is composed of lettuce, and if the part of the fruits or vegetables is composed of lettuce is the spirit encompasses both . Therefore, the fruits and vegetables stored in the packaging container may or may not include vegetables and fruits other than lettuce. Furthermore, as long as it contains lettuce, it may contain ingredients other than fruits and vegetables, for example, foods other than fruits and vegetables, seasonings, food additives, and the like.

The “lettuce” that constitutes the package of the present invention (contained in a packaging container) is a concept that encompasses vegetables that generally belong to the Asteraceae Akinonogeshi genus Chisha species. Not limited.
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).

  In the present invention, there is no particular limitation on fruits and vegetables other than lettuce that can be stored together with the lettuce in the packaging container, and non-heated or heated fruits and vegetables that can be edible with the lettuce can be appropriately stored. Specific examples of such fruits and vegetables include fruits such as banana, mango, plum, apple, strawberry, orange, grape, Japanese pear, pear, root vegetables such as radish, carrot, yam, burdock, tomato, Fruits and vegetables such as cucumber, eggplant, pepper, edamame, okra, mushrooms such as mung bean sprouts, soy bean sprouts, syrup, shiitake mushrooms, shimeji mushrooms, fungi and mushrooms such as mushrooms, broccoli , Spinach, komatsuna, pak choi, cabbage, lettuce, asparagus, but not limited to leafy vegetables, flowers and seedlings. The effect of the present embodiment of controlling and maintaining the oxygen concentration is particularly effective for maintaining the freshness of a fruit or vegetable in a substantially breathing mode.

In the present invention, there is no particular limitation on the form of the lettuce stored in the packaging container and kept fresh. Therefore, fruits and vegetables including lettuce may be as-harvested, so-called pre-processed ones from which outer leaves have been removed, or cut so-called cut vegetables (cut lettuce). You may. 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 the case of cut lettuce that is stored and kept fresh, it is preferable that cut, washing, dehydration and / or drying are performed to adjust the water content to an appropriate level. And / or specifically cut and cut lettuce after washing with hypochlorous acid at 80 to 120 ppm for 10 to 20 minutes based on the "Manual for Mass Cooking Facilities Sanitation 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 appearance.

  Here, the demand for cut vegetables has been increasing in recent years because they can be easily served for meals, and has high economic value. Cut lettuce is a typical example of cut vegetables, and has a particularly high economic value because it can be easily served as a salad or the like as it is. On the other hand, vegetables, especially lettuce, tend to sharply activate their respiratory action and metabolic reaction when cut, and their quality tends to decrease sharply. The present embodiment has a particularly high economic value because it can be effectively used for maintaining the freshness of such cut lettuce.

  Depending on the type and morphology of the lettuce (and the fruits and vegetables that are stored with the lettuce, if present), the preferred oxygen concentration for keeping freshness will vary to some extent within the scope of the present invention, and accordingly the preferred oxygen permeability and such oxygen Although the mode of the polymer film giving the transmittance is also different, by properly setting these, the above lettuce (and fruits and vegetables stored together with the lettuce if present) can be effectively kept fresh according to the present invention. It can be performed.

Package The internal oxygen concentration of the package of the present invention after holding the package at 10 ° C. for 72 hours after sealing is 7.0% by volume or less. When the internal oxygen concentration after holding the package at 10 ° C. for 72 hours after sealing is 7.0% by volume or less, browning of the lettuce in the fruits and vegetables contained in the packaging container is effectively suppressed. In a preferred embodiment of the package of the present invention, the browning of the lettuce in the fruits and vegetables and the generation of an odor can be suppressed for a long time after the package is sealed, preferably for 72 hours or more.

The internal oxygen concentration of the package of the present invention after holding the package at 10 ° C. for 72 hours after sealing is preferably 3.5% by volume or less, more preferably 1.5% by volume or less. , 0.5 volume% or less, more preferably 0.3 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 the package is sealed" refers to the elapsed time when a vegetable or vegetable containing lettuce is stored in the package, and the package is sealed and held at a predetermined temperature, and then "package". “After holding at 25 ° C. for 72 hours after sealing”, refers to a state immediately after storing vegetables and fruits including lettuce in a packaging container, sealing the packaging container, and then holding at 10 ° C. for 72 hours.

In the package of the present invention, since the internal oxygen concentration is significantly lower than the atmospheric oxygen concentration, the internal oxygen concentration often rises with the passage of oxygen from the outside. Therefore, in the present invention, in which the internal oxygen concentration after holding the package at 10 ° C. for 72 hours after sealing is 7.0% by volume or less, the internal oxygen concentration is maintained at 10 ° C. for 0 to 72 hours after the package sealing. The oxygen concentration is likely to be 7.0% by volume or less. Such a history of the oxygen concentration is particularly preferred in order to further effectively suppress the generation of browning and odor of lettuce in fruits and vegetables.
In addition, from the viewpoint of suppressing breathing and keeping a dormant state and suppressing oxidation (browning) of the cross section of the lettuce, the holding temperature of the package is preferably 2 to 15 ° C, and particularly preferably 3 to 10 ° C.
Regarding the history of oxygen concentration, fruits and vegetables including lettuce immediately after sealing of the package, that is, lettuce preferably cut, washed, dehydrated and / or dried to adjust the water content to an appropriate level. It is preferable that the oxygen concentration in the packaging container immediately after sealing the packaging container after storing the container is 0.0 to 12.0% by volume. The oxygen concentration in the packaging container immediately after packaging is more preferably from 0.0 to 6.0% by volume, and particularly preferably from 0.0 to 0.5% by volume.
In addition, the integrated value of the elapsed time from the sealing of the packaging container and the internal oxygen concentration for 72 hours after the sealing of the package is 504 (time × vol%) (72 hours × 7.0 vol%) or less. It is preferably 252 (time × volume%) (72 hours × 3.5 vol%) or less, and more preferably 36 (time × volume%) (72 hours × 0.5 vol%). Is particularly preferred.

  From the viewpoint of achieving the desired internal oxygen concentration described above, it is preferable that nitrogen is further sealed in the packaging container. This is because, by sealing the packaging container with nitrogen, the internal oxygen concentration immediately after packaging can be kept low. Further, by further enclosing nitrogen, it is possible to keep the pressure inside the packaging container high, to prevent the inflow of outside air having a higher oxygen concentration, and to keep the internal oxygen concentration low 72 hours after the sealing of the package. Can be.

Polymer Film In order to realize the above-mentioned 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.
That is, the oxygen permeability of the polymer film used in the present invention is preferably 10,000 cc / m ² / atm / day or less at 20 ° C. and 90% RH. When the oxygen permeability at 20 ° C. and 90% RH is equal to or less than the above value, intrusion of oxygen from outside air is prevented, and even after 72 hours from the sealing of the package, a low internal volume of 7.0% by volume or less. It is suitable for maintaining the oxygen concentration. The oxygen permeability of the polymer film used in the present invention at 20 ° C. and 90% RH is more preferably 5000 cc / m ² / atm / day or less, and preferably 3000 cc / m ² / atm / day or less. More preferably, it is particularly preferably at most 1500 cc / m ² / atm / day.
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. In this respect, 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 900 cc / m ² / atm / day or more. More preferably, it is particularly preferably at least 1000 cc / m ² / atm / day.

The oxygen permeability of the polymer film used in the present invention 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. It is preferred. 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 raining 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, the oxygen permeability of 500 cc / m ² / atm / day or more at 20 ° C. and 90% RH in a preferred embodiment of the present invention can be realized without providing an opening 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, in order to achieve a desired oxygen permeability, for example, when it is necessary to use a thick polymer film or a polymer material having a low oxygen permeability, May be used together. 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 invention, when a laser is used for micropore opening, it is preferable that the target film efficiently absorbs 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 present invention does not have physical contact with metal, so there is no risk of mixing of missing blades, needles, etc. 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 ×. .

  The thickness of the polymer film used in the present invention is not particularly limited. Suitable oxygen permeability, flexibility when forming a packaging container, strength, transparency, economy, etc. From the viewpoints of accuracy and easiness in forming the portion, 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.

  There is no particular limitation on the material of the polymer film, but a polymer used for a conventional film for packaging 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 invention, the polymer film constituting the packaging container may be any of a non-stretched film and 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 used in the present invention.
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 invention include a stretched polypropylene film, a polyethylene-based film, and a laminate of a stretched film and a polyethylene-based film.

<Stretched polypropylene film>
The stretched polypropylene film preferably used in the present invention 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 invention 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>
The laminate of a stretched film and a polyethylene-based film preferably used in the present invention is obtained by laminating the above-mentioned polyethylene-based film layer and the stretched film layer. 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.
Further, a specific surfactant may be present on the surface of the polymer film in a specific amount, or the polymer film may have a specific amount of a specific surfactant to 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.

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 vegetables and fruits containing lettuce in the packaging container of the present invention and appropriately adjusting the internal oxygen concentration, the package of the present invention can be manufactured, and the freshness of the fruits and vegetables which is one embodiment of the present invention can be maintained. The method can be performed.
Hereinafter, the manufacturing method of the package of the present invention 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%.

Note that, in the package for maintaining freshness of fruits and vegetables of the present embodiment, nitrogen may be sealed and / or degassed after storage of the fruits and vegetables including lettuce and sealing of the packaging container. By performing nitrogen filling and / or degassing, it becomes possible to quickly reach a desired oxygen concentration designed as an equilibrium state between the oxygen permeability of the packaging container and the respiratory volume of the fruits and vegetables, which 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.

  After carrying out the step of storing fruits and vegetables including lettuce in the packaging container comprising the polymer film according to the method as described above, 2 to 15 ° C, more preferably 3 to 10 ° C, particularly preferably about 10 ° C By carrying out the step of maintaining the oxygen concentration in the packaging container at 7.0% by volume or less for 72 hours or more after sealing the package, the freshness of the fruits and vegetables including the lettuce can be effectively maintained.

In the package of the present invention, only fruits and vegetables including 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.
(With or without opening)
After injecting a red penetration liquid (manufactured by Mitsubishi Gas Chemical Co., Ltd., trade name: Ageless Seal Check Spray) into the packaging container, set the heating condition scale to 3 with an impulse sealer, heat seal with a width of about 5 mm, (Kokuyo PPC paper, paper A4) was pressed, and the presence or absence of the opening was confirmed by the presence or absence of transfer of the ink to the paper.
(Oxygen permeability)
First, a bag having an inner size of 220 mm × 240 mm was formed by the following method.
One film is folded almost evenly into two pieces, about 5 mm wide, and heat sealing is performed by setting the scale of the heating condition to 3 with an impulse sealer (manufactured by Fuji Impulse Co., Ltd., product number Fi-200-10WK). 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 entire side except for an end portion of about 2 cm, which is one communicating part of the other side, is heat-sealed to an inner dimension of 220 mm × A 240 mm bag was formed.
Next, nitrogen gas was injected from the communication portion, and after the inside of the bag became saturated, almost all of the gas in the bag was discharged from the communication portion. After repeating this operation five times, nitrogen gas was injected to saturate the inside of the bag with nitrogen gas, and the communicating portion was heat-sealed with the impulse sealer under the same conditions. The bag saturated with nitrogen gas was allowed to stand in a room at 22 ° C. and 40% relative humidity (1 atm, oxygen concentration: 21%, nitrogen concentration: 79%) for 6 hours.
Next, about 20 cc of the gas in the bag was sampled with a sampling needle tube, and the oxygen concentration in the bag was measured with a zirconia oxygen concentration meter for food packaging (manufactured by Toray Engineering Co., Ltd., model number LC-750F). Further, the volume of the gas in the bag was measured, and the oxygen permeability was 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 (1232 cm ² ) /0.21 (partial pressure of oxygen )
(Oxygen concentration / carbon dioxide concentration)
The measurement was performed using an O ₂ / CO ₂ analyzer for food packaging Check Material 3 manufactured by Dansensor.
(appearance)
The package was opened, the fruits and vegetables were taken out, and the area of the entire browned portion was visually evaluated with n = 3 centering on the lettuce section.
The evaluation criteria are as follows.
A: There is no browning and there is no problem. B: There is browning but a little noticeable at 10% or less of the whole cross section. C: There is browning but 30% or less of the whole cross section and it is quite noticeable but sellable. There is, but not more than 50% of the entire cross section, noticeably conspicuous Unsellable by consumers E: Big browning, clearly unsellable to consumers (smell)
When the package was opened, the face was approached and the internal odor was smelled, and the sensory evaluation was performed at n = 3.
The evaluation criteria are as follows.
A: No problem in fresh state B: Slightly smell but fresh state C: Smell strong but in the same state as on the market and available for sale D: Smell more strong and the consumer cares E: Smell more unsellable

(Example 1)
Two OPP (biaxially oriented polypropylene) films having a thickness of 40 μm are overlapped, three sides are sealed with heat sealing and cut, and one side is unsealed in a packaging bag (220 mm × 240 mm, inner size (Area: 1232 cm ² ).
When the presence or absence of an opening in the film was confirmed, it was confirmed that there was no opening. The oxygen permeability of the film was 1000 cc / m ² / atm / day.
<Cut lettuce>
After removing lettuce and removing the damaged portion, the cut lettuce was cut into approximately 4 cm squares, and was washed with hypochlorous acid at 100 ppm for 10 minutes based on "Manufacturing Manual for Mass Cooking Facilities" (Ministry of Health and Welfare). After that, moisture management was performed, and dehydration and drying were properly performed.
Further, the amount of water measured based on the weight loss when dried under reduced pressure at 70 ° C. for 5 hours based on “Analysis Method for Nutrition Labeling in Nutrition Labeling Standards” (Consumer Affairs Agency) was 24%.
78 g of the cut lettuce was sealed in a packaging container, filled with nitrogen, and then heat-sealed to produce a package. The package was stored at 10 ° C., and the internal oxygen concentration and carbon dioxide concentration were measured every day to evaluate the appearance and odor of cut lettuce.
Table 1 shows the results.

(Comparative Example 1)
A package was prepared and evaluated in the same manner as in Example 1, except that one hole having a diameter of 300 μm was provided in an OPP (biaxially oriented polypropylene) film having a thickness of 40 μm.
The oxygen transmission rate of the film was 10,000 CC / m ² / atm / day.
Table 1 shows the results.

(Comparative Example 2)
A package was prepared and evaluated in the same manner as in Example 1, except that three holes having a diameter of 300 μm were provided in an OPP (biaxially oriented polypropylene) film having a thickness of 40 μm.
The oxygen permeability of the film was 15000 CC / m ² / atm / day.
Table 1 shows the results.

(Comparative Example 3)
A package was prepared and evaluated in the same manner as in Example 1, except that 10 holes having a diameter of 300 μm were provided in an OPP (biaxially oriented polypropylene) film having a thickness of 40 μm.
The oxygen permeability of the film was 30,000 CC / m ² / atm / day.
Table 1 shows the results.

(Example 2)
A package was prepared and evaluated in the same manner as in Example 1, except that a mixed gas of oxygen: 5 vol% / nitrogen: 95 vol% was charged instead of nitrogen gas.
Table 1 shows the results.

(Example 3)
A package was produced and evaluated in the same manner as in Example 1 except that a mixed gas of 10% by volume of oxygen / 90% by volume of nitrogen was charged instead of the nitrogen gas.
Table 1 shows the results.

(Comparative Example 4)
A package was prepared and evaluated in the same manner as in Example 1 except that a mixed gas of oxygen: 15 vol% / nitrogen: 85 vol% was charged instead of nitrogen gas.
Table 1 shows the results.

  In each of the examples in which the oxygen concentration inside the package after 72 hours from the sealing of the package was 7.0% by volume or less, browning was effectively suppressed and no odor was generated. On the other hand, in each comparative example in which the oxygen concentration inside the package 72 hours after packaging exceeded 7.0% by volume, browning occurred partially by 72 hours, and the commercial value of cut lettuce was partially impaired. Was.

  The package of the present invention has a suitable value for the internal oxygen concentration of the package after a predetermined time has elapsed after the sealing of the package, so that browning of fruits and vegetables including lettuce such as cut lettuce having a high economic value is reduced. It has high practical value, such as being particularly effective in keeping freshness such as suppression, and has high applicability in various industrial fields such as food processing, distribution, and restaurant.

Claims (8)

Oxygen permeability is from 500 cc / m ² / atm / day to 1500 cc / m ² / atm / day at 20 ° C. and 90% RH, including a polymer film selected from a stretched polypropylene film and a polyethylene film. A package containing a cut fruit lettuce and a fruit or vegetable in a packaging container obtained by fusing the two polymer films in a state of being overlapped with each other or in a state of folding one of the polymer films. A package having an internal oxygen concentration of 0.107% by volume or less after holding at 10 ° C. for 72 hours after sealing.   The package according to claim 1, wherein nitrogen is further sealed in the packaging container.   The package according to claim 1, wherein the packaging container does not have a through hole that can be confirmed by an ink leak checker.   The package according to any one of claims 1 to 3, wherein the thickness of the polymer film is 15 to 45 µm.   The package according to any one of claims 1 to 4, wherein the polymer film contains at least one antibacterial agent, or has at least one antibacterial agent applied thereto.   The package according to any one of claims 1 to 5, further comprising a moisture absorbent and / or an antibacterial agent. Oxygen permeability is from 500 cc / m ² / atm / day to 1500 cc / m ² / atm / day at 20 ° C. and 90% RH, including a polymer film selected from a stretched polypropylene film and a polyethylene film. A step of storing and sealing a fruit and vegetable including cut lettuce in a packaging container obtained by fusing the two polymer films in a state of being overlapped with each other or in a state where the one polymer film is folded. And maintaining the oxygen concentration in the packaging container at 0.107% by volume or less over 72 hours or more after sealing the package at 2 to 15 ° C.   The method for maintaining freshness of fruits and vegetables according to claim 7, further comprising a step of enclosing nitrogen in the packaging container.