JP6735250B2 - Package excellent in freshness-keeping performance of fruits and vegetables containing lettuce, and freshness-keeping method of fruits and vegetables - Google Patents

Description

The present invention relates to a package excellent in freshness retention performance of fruits and vegetables containing lettuce, and more specifically, it contains fruits and vegetables containing lettuce in a packaging container having a polymer film. The present invention relates to a package that can effectively suppress the occurrence of browning and odor.

A gas permeable film is provided in a polymer film base material, and a gas such as oxygen, carbon dioxide, and water vapor is permeable from the gas permeable part, in the food field, for fruits and vegetables, particularly fresh vegetables such as cut vegetables. It is preferably used as a packaging material. By packaging, for example, vegetables and fruits using such a gas-permeable film, it is possible to maintain an oxygen concentration suitable for keeping the freshness of the contents vegetables and fruits, for example, an oxygen concentration of about 1 to 4%. It is known that the contents can be stored while keeping the freshness for a relatively long period.
For example, in Patent Document 1, in a fruit and vegetable-containing package made of a polymer film in which fruits and vegetables are sealed, the package is composed of (A) a perforated polymer film and (B) a non-perforated polymer film, (A), (B) at least one of the film characteristics is 25 ℃, relative humidity of 75% measured water vapor transmission rate is 50 ~ 800gm ^-2 d ^{-1 based} on the effective surface area of the package There is 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, which is made of stretched polypropylene having a thickness of 35 μm, has 95 holes with an average pore diameter of 30 μm, and has 9 holes with an average pore diameter of 60 μm. It is used.

However, for some fruits and vegetables, discoloration cannot be sufficiently suppressed even by applying the above technique, and improvement thereof has been desired. For example, lettuce is liable to cause browning (a phenomenon of turning brown or red), and this tendency is remarkable especially in cut lettuce having many cut surfaces. Demand for cut lettuce has been increasing in recent years because it can be easily used for meals, and lettuce is one of the most popular vegetables for salads and the like, and thus has high economic value. From such a background, a technique capable of keeping the freshness of fruits and vegetables including lettuce, such as suppressing browning and offensive odor over a long period of time, has been proposed. For example, Patent Document 2 discloses oxygen per bag/lettuce 1 kg. A technique is described in which cut lettuce is put in a bag made of a film having a predetermined permeation amount, and a predetermined amount of oxygen is filled per 1 kg of lettuce during packaging. However, even with the above technique, it has not always been easy to achieve both suppression of browning of cut lettuce and prevention of odor over a long period of time.

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

In view of the limitations of the background art described above, the present invention is a package in which a fruit or vegetable containing lettuce is stored in a packaging container, which suppresses browning of the fruit or vegetable containing the lettuce and prevents an offensive odor for a long period of time. It is an object of the present invention to provide a package excellent in the function of keeping the freshness of the fruits and vegetables, which is compatible with the conventional art at a high level beyond the limit.
The present inventor, as a result of diligent studies, introduced a predetermined concentration of carbon dioxide into the package, and controlling the internal oxygen concentration of the package to be a predetermined value or more, the long-term browning of fruits and vegetables including lettuce. They have found that they are particularly effective in maintaining freshness such as suppressing and preventing offensive odors, and completed the present invention.

That is, the present invention is
[1]
A package in which fruits and vegetables containing lettuce are stored in a packaging container containing a polymer film, wherein the internal carbon dioxide concentration is 18% by volume or more and the internal oxygen concentration is 6% by volume or more. It is a package.

Hereinafter, each of [2] to [14] is one aspect or a preferred embodiment of the present invention.
[2]
The package according to [1], wherein the oxygen permeability of the packaging container is 4500 cc/m ² /atm/day or less at 20° C. and 90% RH.
[3]
The package according to [1] or [2], which suppresses browning of the lettuce and generation of an offensive odor for 72 hours under the condition of 10° C. after sealing the package.
[4]
The package according to any one of [1] to [3], which has an internal carbon dioxide concentration of 20% by volume or more after being kept for 72 hours under the condition of 10° C. after sealing the package.
[5]
The package according to any one of [1] to [4], which has an internal oxygen concentration of 10% by volume or more after being kept for 72 hours under the condition of 10° C. after sealing the package.
[6]
The package according to any one of [1] to [5], wherein nitrogen is further enclosed in the packaging container.
[7]
The packaging body according to any one of [1] to [6], wherein the packaging container does not have a through hole that can be confirmed by an ink leak checker.
[8]
The package according to any one of [1] to [7], wherein the polymer film has a thickness of 10 to 50 μm.
[9]
The package according to any one of [1] to [8], wherein the polymer film is a stretched polypropylene film, a polyethylene film, or a laminate of a stretched film and a polyethylene film.
[10]
The package according to any one of [1] to [9], wherein the polymer film contains at least one antibacterial agent or is coated with at least one antibacterial agent.
[11]
The package according to any one of [1] to [10], wherein the lettuce is cut lettuce.
[12]
The package according to any one of [1] to [11], which further contains a hygroscopic agent and/or an antibacterial agent.
[13]
A step of storing fruits and vegetables containing lettuce in a packaging container comprising a polymer film and having an oxygen permeability of 4500 cc/m ² /atm/day or less at 20° C. and 90% RH, and in the packaging container The method for maintaining freshness of fruits and vegetables, comprising the steps of: setting the carbon dioxide concentration to 20% by volume or higher and the oxygen concentration to 10% by volume or higher; and sealing the packaging container.
[14]
The freshness preservation method for fruits and vegetables according to [13], wherein nitrogen is also enclosed in the step of setting the carbon dioxide concentration in the packaging container to 20 vol% or more and the oxygen concentration to 10 vol% or more.

According to the present invention, by introducing a predetermined concentration of carbon dioxide into the package and controlling the internal oxygen concentration of the package to a predetermined value or more, suppression of browning of lettuce and prevention of off-flavor are compatible for a long period of time. However, there is provided a package having a practically high value that can effectively suppress the freshness of fruits and vegetables containing lettuce, and a method for maintaining the freshness of fruits and vegetables.

Hereinafter, modes for carrying out the present invention will be described.
The present invention is a package in which fruits and vegetables containing lettuce are stored in a packaging container containing a polymer film, the internal carbon dioxide concentration is 18% by volume or more, and the internal oxygen concentration is 6% by volume or more. The above-mentioned 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 that constitutes the package of the present invention comprises a polymer film. Here, "comprising a polymer film" refers to a case where the entire packaging container is made of a polymer film, and a case where a part of the packaging container such as the lid material is made of a polymer film. The purpose is to include both.
Therefore, the packaging container may be a flexible packaging container, a so-called packaging bag, which is wholly or principally composed of a flexible polymer film, such as a flexible polymer film and coated paper. It may be a flexible packaging container in which other flexible members other than the above are combined, or a packaging container in which a flexible polymer film and a rigid member are combined, for example, as a lid material. The molecular film may be combined with 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, two polymer films are superposed on each other, or one polymer film is folded, and three or two sides are heat-sealed. It is possible to form a packaging bag by fusing, for example. The remaining one side can be sealed by arranging the contents such as fruits and vegetables in the packaging bag and then similarly heat-sealing the contents.
The shape of such a packaging bag in a plan view may be a circle, a triangle, a quadrangle, or a polygon of a quadrangle or more, but it is preferably a rectangle from the viewpoint of workability and ease of handling.

The packaging container used in the present invention comprises a polymer film as described above, and the oxygen permeability thereof is not particularly limited, but it is 4500 cc/at an oxygen permeability of 20° C. and 90% RH. It is desirable to use a packaging container having m ² /atm/day or less.
By using a packaging container having an oxygen permeability in the above range, fluctuations in the internal gas composition due to internal gas, particularly outflow of carbon dioxide, inflow of outside air, respiration of fruits and vegetables, etc. are suppressed or mitigated, and of fruits and vegetables including lettuce. It becomes easy to maintain an environment suitable for maintaining freshness. The oxygen permeability of the packaging container is more preferably 3500 cc/m ² /atm/day or less, more preferably 2500 cc/m ² /atm/day or less, and 1500 cc/m ² /atm/day or less. It is particularly preferable that
There is no particular lower limit to the oxygen permeability of the packaging container, but from the viewpoint of allowing some breathing of fruits and vegetables containing lettuce and more effectively preventing the generation of offensive odors, it is 500 cc/m ² /atm/day or more. Is preferable, and 800 cc/m ² /atm/day or more is particularly preferable. Also, considering the cost, etc., the oxygen permeability will be 500 cc/m ² /atm/day or more as long as a commercially available polymer film is used and the packaging container is configured with a relatively simple structure. Is common.

The oxygen permeability of the packaging container can be measured, for example, by the following method.
First, a bag having an inner size of a (cm) x b (cm) is formed by the following method.
Fold one film into two almost evenly and set the scale of heating conditions to 3 with an impulse sealer (manufactured by Fuji Impulse Co., product number Fi-200-10WK) with a width of about 5 mm, and heat seal the film. Heat seal one entire side that is substantially perpendicular to the heat-sealed side so that the side is almost in the center, and the entire side except for about 2 cm of the end that is one of the communicating sides of the other side. A bag of (cm) x b (cm) is formed.
Next, nitrogen gas is injected from the communication section, and when the inside of the bag becomes saturated, almost all the gas in the bag is discharged from the communication section. After repeating this operation 5 times, nitrogen gas is injected to saturate the inside of the bag with nitrogen gas, and the communication part is heat-sealed under the same conditions with the impulse sealer. The bag saturated with nitrogen gas is left for 6 hours in a room at 22° C. and 40% relative humidity in 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 No. LC-750F, manufactured by Toray Engineering Co., Ltd.). Further, the volume of gas in the bag is measured, and the oxygen permeability is calculated from the following formula.
(Equation) Oxygen permeability=internal oxygen concentration change (%)/100×volume (cm ³ )×24×60/hour (360 minutes)×10000 cm ² /area (2×a×b×cm ² )/oxygen Partial pressure (0.21 atm)
The oxygen permeability of the packaging container can be adjusted to a desired range by appropriately selecting and adjusting the material, thickness, layer structure, presence/absence of coating, type, application area, etc. of the polymer film forming the packaging container. it can. Details of the polymer film will be described later.
Also, the oxygen permeability of the packaging container can be appropriately adjusted by providing (or not providing) an opening in the polymer film. The oxygen permeability can be appropriately adjusted depending on the size, shape and number of the openings. The details of the opening will also be described later.

Fruits and vegetables The package of the present invention contains fruits and vegetables containing lettuce in the packaging container. Here, that the fruit and vegetables "include" lettuce is meant to include both the case where all of the fruit and vegetables are composed of lettuce and the case where part of the fruit and vegetables is composed of lettuce. .. Therefore, the fruits and vegetables stored in the packaging container may or may not include vegetables, fruits, etc. other than lettuce. Furthermore, as long as it contains lettuce, it may contain components 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 (stored in a packaging container) is a concept that includes general vegetables belonging to the Asteraceae genus Chisha species, and the vegetables distributed under the name “lettuce” itself are Not limited.
That is, the "lettuce" referred to here is a type of scraping chisha or cutting lettuce typified by santu, which is a type of scraping leaves from the stem; typified by romaine lettuce, etc. All of the types called chisha; non-heading leaf lettuce (leaf chisha) typified by sunny lettuce and green leaf; and heading ball lettuce (ball chisha) typified by what is commonly called lettuce. Is a concept that includes.
Preferable specific examples of "lettuce" here are lettuce (tama lettuce), green leaf, romaine lettuce (cos lettuce), sunny lettuce, silk lettuce, pink roaster, salad vegetable, bouquet lettuce, green oak leaf (saranova lettuce), frills. Examples include, but are not limited to, lettuce, (chima) santu, stem lettuce, and the like.

In the present invention, there are no particular restrictions on fruits and vegetables other than lettuce that can be stored together with lettuce in the packaging container, and unheated or heated fruits and vegetables that can be edible with lettuce can be stored as appropriate. Specific examples of such fruits and vegetables include fruits such as banana, mango, plum, apple, strawberry, mandarin orange, grape, Japanese pear, pear, Japanese radish, carrot, potato, root vegetables such as burdock, tomato, Fruit vegetables such as cucumber, eggplant, peppers, edamame, okra, mung bean sprouts, soybean bean sprouts, buds such as tokyo, mushrooms (mushrooms) such as shiitake, shimeji, eringi, maitake, matsutake, and broccoli. , Leaf spinach, komatsuna, bok choy, cabbage, leafy vegetables such as asparagus, flower or seedling, but are not limited thereto. From the effect of the present embodiment of controlling and maintaining the oxygen concentration, it is particularly effective for maintaining the freshness of fruits and vegetables that are substantially breathing.

In the present invention, there is no particular limitation on the form of fruits and vegetables containing lettuce stored in a packaging container and kept fresh. Therefore, the fruits and vegetables containing lettuce may be as-harvested, may be so-called pretreated with outer leaves removed, or may be so-called cut vegetables (cut lettuce) already cut. May be. The fruits and vegetables may have been subjected to any or all of the treatments such as washing, cooling and dehydration, or may be those without any of these treatments.
When the lettuce stored and kept fresh is cut, it is preferable that the lettuce is cut, washed, dehydrated and/or dried to be adjusted to an appropriate water content. More specifically, for example, cut lettuce is washed with hypochlorous acid at 80 to 120 ppm for 10 to 20 minutes based on the "Massive Cooking Facility Hygiene Management Manual" (Ministry of Health and Welfare) and then "Analysis of nutrition labeling etc. according to nutrition labeling standards." Based on the "Method" (Consumer Affairs Agency), the amount of water measured based on the weight loss when dried under reduced pressure at 70°C for 5 hours is in the range of 20 to less than 30% to prevent odor generation and browning. It is particularly preferable from the viewpoint of the balance of prevention of deterioration of external appearance.

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 cut vegetable, and since it can be simply served as a salad as it is, it has a particularly high economic value. On the other hand, when vegetables, especially lettuce, are cut, the respiratory action and metabolic reaction are rapidly activated, and the quality tends to be sharply reduced. Since the present embodiment can be effectively used to maintain the freshness of such cut lettuce, it has a particularly high economic value.

Depending on the type and form of lettuce (and fruits and vegetables stored with lettuce, if present), the carbon dioxide concentration and oxygen concentration that are preferable for maintaining freshness will vary to some extent within the scope of the present invention. Although the aspect of the polymer film that gives such oxygen permeability is also different, by appropriately setting these, according to the present invention, any of the above lettuce (and fruits and vegetables to be stored together with the lettuce if present) can be obtained. The freshness can be effectively maintained.

Packaging Body The packaging body of the present invention has an internal carbon dioxide oxygen concentration of 18% by volume or more and an internal oxygen concentration of 6% by volume or more. When the internal carbon dioxide oxygen concentration is 18% by volume or more and the internal oxygen concentration is 6% by volume or more, suppression of browning of lettuce in fruits and vegetables contained in the packaging container and prevention of offensive odor, It can be compatible for a long time.
It has been conventionally known that by adjusting the oxygen concentration in the package to a predetermined value or more, it is possible to prevent the offensive odor of the fruits and vegetables contained in the package due to anoxic breathing. However, when the oxygen concentration is higher than a predetermined value, there is a problem in that the normal breathing of fruits and vegetables causes deterioration in appearance such as browning. Among the fruits and vegetables, lettuce is particularly prone to browning, and in keeping freshness of fruits and vegetables containing lettuce, it has hitherto been difficult to achieve both suppression of browning and prevention of offensive odor.
In the present invention, in a package containing fruits and vegetables containing lettuce having an internal oxygen concentration of a predetermined value or more, carbon dioxide is also introduced, and the internal carbon dioxide concentration is set to a predetermined value or more, thereby suppressing browning. The surprising effect that both the prevention of unpleasant odor and the prevention of offensive odor are achieved at a high level over the limit of the conventional technique and for a long period of time is realized.
In the present invention, the internal carbon dioxide oxygen concentration is a predetermined value or more, and, by the internal oxygen concentration is a predetermined value or more, suppression of browning of lettuce in fruits and vegetables contained in the packaging container and prevention of off-flavor However, the mechanism that can be compatible for a long period of time is not always clear, but rather than limiting the supply of oxygen consumed by breathing, by making the amount of carbon dioxide generated by breathing excessive, the respiration of fruits and vegetables including lettuce. It is presumed that there is some relationship with the fact that normal breathing can be restricted while suppressing anoxic breathing of the dog as much as possible.

The internal carbon dioxide concentration of the package is preferably 20% by volume or more, more preferably 23% by volume or more.
There is no particular upper limit to the internal carbon dioxide oxygen concentration of the package, but from the viewpoint of effectively suppressing odor, it is preferably 50% by volume or less, and more preferably 45% by volume or less. preferable.
The internal carbon dioxide concentration of the package can be adjusted to a desired range by adjusting the carbon dioxide concentration immediately after packaging. More specifically, it can be appropriately adjusted by adjusting the carbon dioxide concentration in the gas to be filled in the packaging container when the package is manufactured. For example, when producing a package, it is preferable that the concentration of carbon dioxide in the gas filled in the packaging container is 30% by volume or more.
The internal carbon dioxide concentration of the package is adjusted to a predetermined concentration by adjusting the amount of carbon dioxide flowing out of the package and/or the amount of carbon dioxide generated by respiration of fruits and vegetables containing lettuce inside the package. It is possible. More specifically, by adjusting the gas permeability of the packaging container, it is possible to adjust the amount of carbon dioxide flowing out of the package, the amount of fruits and vegetables to be stored in the packaging container and / or in the packaging container. By adjusting the amount of oxygen to be filled, it is possible to adjust the amount of carbon dioxide generated by respiration of fruits and vegetables.
The oxygen concentration and the carbon dioxide concentration in the packaging container can be measured by, for example, an O ₂ /CO ₂ analyzer Check Mate 3 for food packaging manufactured by Dansensor.

The internal oxygen concentration of the package is preferably 6.5% by volume or more, and more preferably 7.2% by volume or more.
There is no particular upper limit to the internal oxygen concentration of the package, but from the viewpoint of more effectively suppressing deterioration of appearance such as browning, it is preferably 80% by volume or less, and 70% by volume or less. Is more preferable.
The internal oxygen concentration of the package can be adjusted to a desired range by adjusting the oxygen concentration immediately after packaging. More specifically, it can be appropriately adjusted by adjusting the oxygen concentration in the gas filled in the packaging container when the package is manufactured. For example, it is preferable that the oxygen concentration in the gas filled in the packaging container at the time of producing the package is 12% by volume or more.
In addition, the internal oxygen concentration of the package is also determined by adjusting the amount of oxygen flowing out of the package or flowing from outside the package, and/or the amount of oxygen consumed by respiration of fruits and vegetables containing lettuce inside the package. It is possible to adjust the concentration of. More specifically, by adjusting the oxygen permeability of the packaging container, it is possible to adjust the amount of oxygen flowing out of the packaging body, or from the outside of the packaging body, the amount of fruits and vegetables to be stored in the packaging container and By adjusting the amount of oxygen to be filled in the packaging container, it is possible to adjust the amount of oxygen consumed by respiration of fruits and vegetables.

In the package of the present invention, it is preferable to suppress browning of lettuce and generation of an offensive odor for 72 hours under the condition of 10° C. after sealing the package.
This preferred embodiment suppresses browning of lettuce and generation of offensive odor for 72 hours after the packaging is sealed, so that the freshness of fruits and vegetables containing lettuce can be maintained at a high level for a long period considered to be sufficient for distribution. Since it can be maintained, it has a high practical and economic value.
In this preferred embodiment, the browning of lettuce and the generation of offensive odor are more preferably suppressed for 96 hours after the sealing of the package, and further preferably suppressed for 120 hours after the sealing of the package. It is especially preferred to suppress for 144 hours after the body is sealed.

The internal carbon dioxide concentration of the package of the present invention after holding for 72 hours at 10° C. after sealing the package is preferably 20% by volume or more. Since the internal carbon dioxide concentration after holding for 72 hours under the condition of 10° C. after sealing is 20% by volume or more, the browning of lettuce in the fruits and vegetables contained in the packaging container can be suppressed and the offensive odor can be prevented. , Can be compatible at a higher level for a long period of time.
The internal carbon dioxide concentration after holding the package of the present invention for 72 hours at 10° C. after sealing is more preferably 22.5% by volume or more, and particularly preferably 23.0% by volume or more. preferable.
Here, "after sealing the package" refers to the elapsed time from sealing the packaging container after storing fruits and vegetables containing lettuce in the packaging container. That is, “after holding the package at 10° C. for 72 hours after sealing the package” means that after storing fruits and vegetables containing lettuce in the packaging container, the packaging container is sealed and then the condition of 10° C. State immediately after holding for 72 hours.

In the package of the present invention, since the internal carbon dioxide concentration is not higher than the atmospheric carbon dioxide concentration, the internal carbon dioxide concentration often decreases over time due to the outflow of carbon dioxide to the outside. Therefore, in the present embodiment where the internal oxygen concentration at 10° C. for 72 hours after sealing is 10% by volume or more, the internal carbon dioxide concentration may be 10% by volume or more for 0 to 72 hours after sealing. high. Such a history of carbon dioxide concentration is particularly preferable for more effectively suppressing browning of lettuce in fruits and vegetables and generation of off-flavor.

The internal carbon dioxide concentration at 72° C. for 72 hours after sealing the package can be adjusted to a desired range by adjusting the carbon dioxide concentration immediately after packaging. More specifically, it can be appropriately adjusted by adjusting the carbon dioxide concentration in the gas to be filled in the packaging container when the package is manufactured. For example, when producing a package, it is preferable that the carbon dioxide concentration in the gas filled in the packaging container is 12% by volume or more.
In addition, the internal carbon dioxide concentration at 72° C. for 72 hours after sealing the package adjusts the amount of carbon dioxide flowing out of the package and/or the amount of carbon dioxide generated by respiration of fruits and vegetables containing lettuce inside the package. Even with this, it is possible to adjust to a predetermined density. More specifically, by adjusting the gas permeability of the packaging container, it is possible to adjust the amount of carbon dioxide flowing out of the package, the amount of fruits and vegetables to be stored in the packaging container and / or in the packaging container. By adjusting the amount of oxygen to be filled, it is possible to adjust the amount of carbon dioxide generated by respiration of fruits and vegetables.

The internal oxygen concentration after the package of the present invention is kept for 72 hours under the condition of 10° C. after sealing is preferably 10% by volume or more. Since the internal oxygen concentration after holding for 72 hours under the condition of 10° C. after sealing is 10% by volume or more, generation of offensive odor from lettuce in fruits and vegetables contained in the packaging container is more effective for a long period of time. Suppressed to.
The internal oxygen concentration of the package of the present invention after holding for 72 hours under the condition of 10° C. after sealing is more preferably 13% by volume or more, and particularly preferably 15% by volume or more.

The internal oxygen concentration after holding the package for 72 hours under the condition of 10° C. after sealing can be adjusted to a desired range by adjusting the oxygen concentration immediately after the packaging. More specifically, it can be appropriately adjusted by adjusting the oxygen concentration in the gas filled in the packaging container when the package is manufactured. For example, when producing a package, it is preferable that the oxygen concentration in the gas filled in the packaging container is 50% by volume or more.
In addition, the internal oxygen concentration after holding the package for 72 hours under the condition of 10° C. is the amount of oxygen flowing out of the package or flowing out of the package, and/or fruits and vegetables containing lettuce in the package. It is also possible to adjust to a predetermined concentration by adjusting the amount of oxygen consumed by respiration. More specifically, by adjusting the oxygen permeability of the packaging container, it is possible to adjust the amount of oxygen flowing out of the packaging body, or from the outside of the packaging body, the amount of fruits and vegetables to be stored in the packaging container and By adjusting the amount of oxygen to be filled in the packaging container, it is possible to adjust the amount of oxygen consumed by respiration of fruits and vegetables.

From the viewpoint of achieving the desired internal carbon dioxide concentration and internal oxygen concentration described above, it is preferable that nitrogen is further enclosed in the packaging container. This is because by enclosing nitrogen together when the packaging container is sealed, the internal carbon dioxide concentration and the internal oxygen concentration can be adjusted independently.

Polymer Film Further , in order to realize the above-described preferable oxygen permeability in the packaging container used in the present invention, 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 4500 cc/m ² /day or less at 20° C. and 90% RH. By using a polymer film having an oxygen permeability at 20° C. and 90% RH of not more than the above value, a preferred embodiment having an oxygen permeability of 20° C. and 90% RH is 4500 cc/m ² /atm/day. The following packaging container can be manufactured at a relatively low cost with a relatively simple structure and manufacturing method.
The oxygen permeability of the polymer film used in the present invention is more preferably 3500 cc/m ² /day or less at 20° C. and 90% RH, and particularly preferably 2500 cc/m ² /day or less.
There is no particular lower limit to the oxygen permeability of the polymer film, but as long as a normal polymer film that is not subjected to gas barrier coating or the like is used, it is 500 cc/m ² /day or more at 20° C. and 90% RH. It is common to become
Further, from the viewpoint of more effectively preventing the generation of offensive odor from the stored fruits and vegetables, the polymer film preferably has an oxygen permeability that allows the fruits and vegetables to breathe. From this viewpoint, the oxygen permeability of the polymer film at 20° C. and 90% RH is preferably 750 cc/m ² /day or more, and particularly preferably 900 cc/m ² /day or more.

The oxygen permeability of the polymer film used in the present invention can be measured, for example, by the same method as described above for the oxygen permeability of the packaging container.

The oxygen permeability of the polymer film can be appropriately adjusted by appropriately selecting the material, thickness, processing method, and the like of the polymer film. For example, in the case of a biaxially oriented polypropylene (OPP) film, by setting the thickness to 10 μm or more, the oxygen permeability at 20° C. and 90% RH can be set to 4500 cc/m ² /day or less, which is preferable. .. In consideration of mechanical strength and the like, the thickness of the polymer film is more preferably 10 to 50 μm, particularly preferably 15 to 45 μm.

As described above, the oxygen permeability of the polymer film can be adjusted by properly controlling the material, thickness, processing method, etc. of the polymer film, so that it is not always necessary to adjust the oxygen permeability. It is not necessary to provide an opening in the polymer film. In particular, the oxygen permeability of 4500 cc/m ² /day or less at 20° C. and 90% RH in the preferred embodiment of the present invention can be realized without providing an opening in the polymer film.
Since it is not necessary to provide openings in the polymer film, the manufacturing process becomes simpler and less expensive, and it is not necessary to precisely control the size and shape of the openings.
The absence of an opening in the polymer film can be confirmed by, for example, the polymer film forming the packaging container having no through hole which can be confirmed by an ink leakage checker.

On the other hand, in an embodiment of the present invention, in order to achieve a desired oxygen permeability, such as when a thick polymer film or a polymer material with low oxygen permeability needs to be used, the polymer film You may use together the opening provided in. The shape of the opening is not particularly limited, and may be circular, substantially circular, or slit-shaped. A circular or substantially circular opening is preferable because it is easy to process, and a slit-shaped opening is preferable because it can effectively prevent foreign matter from entering.
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, and in that case, the openings occupying the effective area of the polymer film. The number of is a guide. For example, in the case of a slit-shaped opening having a length of 2 mm, the width as a through-hole cannot be visually recognized by observation with an optical microscope (manufactured by Olympus, model SZH-131) at a magnification of 4 times in a closed state. When one is provided, it has the effect of increasing the oxygen permeability of about 1000 cc/m ² /day/atm for each one present in a 200 mm×200 mm packaging container, and the packaging required based on such knowledge. It is preferable to determine the number of slit openings from the oxygen permeability of the entire container.

There is no particular limitation on the thickness of the polymer film used in the present embodiment, suitable oxygen permeability, flexibility when forming a packaging container, strength, transparency, economic efficiency, the amount of oxygen permeation provided by the opening From the viewpoint of accuracy and easiness in forming the opening, etc., a suitable thickness may be appropriately selected in relation to the material forming the polymer film. Typically, the thickness of the polymer film is preferably 10 to 120 μm, more preferably 12 to 50 μm, particularly preferably 15 to 45 μm.

The material of the polymer film is not particularly limited, but the polymer used in the conventional film for packaging fruits and vegetables can be appropriately used. Examples thereof include polyethylene, polypropylene, polyethylene terephthalate, polystyrene, nylon (polyamide), ethylene vinyl acetate copolymer (EVA), polybutylene succinate, polybutylene succinate adipate, and polylactic acid. Further, 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 ease 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, high-pressure low density polyethylene, linear low density polyethylene (LLDPE), high density polyethylene and other ethylene polymers, propylene homopolymers, propylene/α-olefin random copolymers, propylene block copolymers. And propylene polymers such as poly-1-butene, and polyolefins such as 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 polymeta-xylene adipamide, polyvinyl chloride, polyimide, ethylene acetic acid. Examples thereof include vinyl copolymers or saponified products thereof, polyvinyl alcohol, polyacrylonitrile, polycarbonate, polystyrene, ionomers, polylactic acid, polybutylene succinate, and other biodegradable resins, or a mixture thereof. These thermoplastic resins may be used alone or in combination of two or more. Among these, as the thermoplastic resin, polyolefin, polyester, polyamide and the like are preferable because they have excellent rigidity and transparency. Further, as the thermoplastic resin, ethylene-based polymers and propylene-based polymers are more preferable because they are lightweight and have excellent film processability, and propylene-based polymers are more preferable from the viewpoint of flexibility and transparency.

<Propylene polymer>
As the propylene-based polymer, propylene homopolymer (also called homo PP), which is manufactured and sold under the name of polypropylene, propylene/α-olefin random copolymer (also called random PP). , 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 referred to as block PP). .. The propylene-based polymer may be a mixture of propylene homopolymers having different molecular weights, and includes 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.

Specific examples of the propylene-based polymer include polypropylene, propylene/ethylene copolymer, propylene/ethylene/1-butene copolymer, propylene/1-butene copolymer, propylene/1-pentene copolymer. , A propylene/1-hexene copolymer, a propylene/1-octene copolymer, etc. as a main monomer, and a copolymerization of this with at least one or more selected from ethylene and α-olefins having 4 to 10 carbon atoms. An example is 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 , and more preferably 0.900 to 0.920 g/cm ³ . The MFR (ASTM D1238 load 2160 g, temperature 230° C.) of the propylene-based polymer is preferably 0.5 to 60 g/10 minutes, more preferably 0.5 to 10 g/10 minutes, and even more preferably 1 to 5 g/10 minutes. Is more preferable.

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

Examples of the ethylene 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 preferable, and LLDPE is more preferable. 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. The ethylene-based 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. Further, when the density is 0.940 g/cm ³ or less, workability and transparency are improved.

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

The polymer film forming the packaging container in the present invention 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 preferably used.
In particular, a stretched film using a propylene-based polymer (stretched polypropylene film) is excellent in mechanical strength, transparency, heat resistance and the like, and thus can be particularly preferably used in the packaging container used in the present invention.
Further, the film using an ethylene polymer (polyethylene film) may be either a non-stretched film or a stretched film, but from the viewpoint of heat sealability 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 film, and a laminate of a stretched film and a polyethylene 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 a stretched polypropylene film, it can be easily produced by, for example, sequential or simultaneous biaxial stretching. 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 to obtain the final film thickness. 20 to 40 μm, or by stretching 5 to 10 times (25 to 100 times in area magnification) in the machine direction and the transverse direction, respectively.
<Polyethylene film>
The polyethylene film preferably used in the present invention is a film containing the ethylene 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 typified by polyethylene terephthalate, polyethylene naphthalate, polycarbonate film, ethylene/vinyl alcohol copolymer film, polyvinyl alcohol film, polyvinyl chloride film, polyvinylidene chloride A uniaxially or biaxially stretched film comprising a film, a polystyrene film, a polyolefin such as polypropylene, and 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.

<Laminate of stretched film and polyethylene film>
The laminate of the stretched film and the polyethylene film preferably used in the present invention is obtained by laminating the layer of the polyethylene film and the layer of the stretched film. The polyethylene film may be stretched in one direction or in two directions, but it is preferably an unstretched film from the viewpoint of stability of mechanical strength of the packaging bag.
From the viewpoint of adhesion stability, it is necessary to perform a corona treatment on the surface of the stretched film on which the adhesive is applied. preferable. Specifically, the surface tension of the film surface after the corona treatment is preferably 35 mN/m or more, and more preferably 40 mN/m or more, from the viewpoint of adhesion stability.

In addition, these polymer films may be subjected to stretching processing, anti-fog processing or printing, and inorganic antibacterial agents such as silver and copper, and organic antibacterial agents such as chitin, chitosan and allyl isothiocyanate. The agent may be applied, or these may be kneaded into the film.
From the viewpoint of maintaining the freshness of contents such as fruits and vegetables, the polymer film preferably contains at least one antibacterial agent.
In addition, a specific amount of a specific surfactant is present on the surface of the polymer film, or the specific amount of the specific surfactant is included in the polymer film, so that the polymer film may have an antibacterial function. For example, at least one compound selected from the group consisting of palmityldiethanolamine, stearyldiethanolamine, 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 in an amount of 0.002-0.5 g/m ² . Alternatively, the polymer film preferably contains at least one compound selected from the group consisting of palmityldiethanolamine, stearyldiethanolamine, glycerin monolaurate and glycerin monocaprate, and 0.001 to 3 parts by mass. It is particularly preferable to contain.
There is a specific amount of a specific surfactant on the surface of the polymer film, or the polymer film contains a specific amount of a specific surfactant, dew condensation on the surface of the polymer film is suppressed, various bacteria By suppressing the reproduction of the bacteria, the growth of various bacteria in the dew condensation is suppressed and the antibacterial function is exerted.

From the viewpoint of transparency, flexibility, cost, etc., 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, they have good productivity in the production of packaging containers.
In this case, when the stretched propylene film is used alone, the thickness thereof is preferably 10 to 100 μm, and when the laminate of the stretched polypropylene film and the polyethylene-based film is used, the former thickness is 10 to 50 μm. The latter preferably has a thickness of 10 to 120 μm.

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

Package production method, and freshness retention method Vegetables and vegetables containing lettuce are stored in the packaging container of the present invention, and the package of the present invention can be produced by appropriately adjusting the internal carbon dioxide concentration and the internal oxygen concentration. In addition, the freshness maintaining method for fruits and vegetables which is one embodiment of the present invention can be carried out.
Hereinafter, the method for producing a package of the present invention will be described by taking as an example the case where the fruits and vegetables containing lettuce contained in the packaging container are cut lettuce.

First, in the pretreatment step, the outer leaves are manually removed, the leaves are divided into 2 to 4, and the lettuce from which the core is removed is supplied to the conveyor. The lettuce conveyed by the conveyor is cut with a slicer, and also serves as a cooling bath in a washing tank filled with cold water. Based on the "Massive Cooking Facility Hygiene Management Manual" (Ministry of Health and Welfare), 80-120 ppm, 10-20 minutes of hypochlorous acid It is washed with water, drained and then dehydrated with a centrifugal dehydrator, dry air or the like. The dehydrated cut lettuce is packed into a packaging container (one side of which is not sealed) containing the polymer film used in the present embodiment, and after weighing, the packaging container is sealed to retain 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 blade with good sharpness to reduce scratches on the cut surface.
Further, as the cut width is narrower, the cutting area is increased and it becomes more difficult to keep the freshness. Therefore, from the viewpoint of keeping the freshness, it is preferable that the cut width is wide as long as it meets the demand form.
Further, if a large amount of various bacteria adheres to the cut lettuce from the beginning, it becomes more difficult to maintain the freshness, so it is preferable to thoroughly clean the cut lettuce to reduce the adhesion of the other bacteria as much as possible. Washing is particularly effective for maintaining freshness because it not only reduces the attachment of bacteria, but also has the effect of removing cell fluid and the like that contains highly active enzymes and may cause discoloration.
In addition, it is important for keeping the freshness that the water adhering to the surface of the cut lettuce is sufficiently removed after washing.
This is because the proper water content can suppress the growth of various bacteria in the excessively adhered minute water droplets. More specifically, for example, based on the "Massive Cooking Facility Hygiene Management Manual" (Ministry of Health and Welfare), after "80-120ppm, 10-20 minutes of hypochlorous acid cleaning,""Analysis method of nutrition labeling in nutrition labeling standards" (consumer It is preferable that the water content, which is measured based on the weight loss when dried under reduced pressure at 70° C. for 5 hours, is in the range of 20% to less than 30%. Even if the dish is left standing after washing and drained, a large amount of water still adheres to the surface of the cut lettuce. Therefore, remove water using a centrifugal dehydrator and dry it by applying dry air. Is effective.

In the production of the package for keeping freshness of fruits and vegetables of the present embodiment, a gas having a predetermined composition, for example, a gas having a carbon dioxide concentration of 30% by volume or more and an oxygen concentration of 50% by volume or more is introduced after storing the fruits and vegetables containing lettuce. After that, the sealing may be performed. By introducing a gas having a predetermined composition, it becomes possible to quickly reach the desired carbon dioxide concentration and oxygen concentration in the packaging container, which is advantageous for maintaining freshness.
The carbon dioxide concentration of the gas introduced in the above embodiment is more preferably 20% by volume or more, and particularly preferably 25% by volume or more. The oxygen concentration of the gas introduced in the above embodiment is more preferably 10% by volume or more, more preferably 30% by volume or more, and particularly preferably 45% by volume or more. The other components of the gas introduced in the above embodiment are not particularly limited, but nitrogen is preferably used from the viewpoint of easy availability and small influence on human bodies, fruits and vegetables.
Further, from the viewpoints of improving efficiency in the distribution process, saving space, and eliminating a specific gas, deaeration may be performed before or during the sealing of the packaging container.

In the package of the present invention, only fruits and vegetables containing lettuce may be stored in the packaging container, or other members may be stored.
For example, in addition to fruits and vegetables, a hygroscopic agent and/or an antibacterial agent may be contained in the packaging container.
The hygroscopic agent is not particularly limited, and known or commercially available materials having a hygroscopic effect or a humidity adjusting effect can be used. Suitable examples of the hygroscopic agent include activated carbon, silica gel, alumina gel, silica alumina gel, anhydrous magnesium sulfate, zeolite, synthetic zeolite, calcium oxide, calcium chloride, and burnt alum, or a mixture thereof. Examples include, but are not limited to:
Among these, it is particularly preferable to use activated carbon, which has relatively little concern about effects on fruits and vegetables and use near fruits and vegetables as foods. The activated carbon may be powdery or granular, and the raw material may be coconut shell, sawdust, charcoal, bamboo charcoal, lignite, peat, rice, petroleum pitch, or any other material. It is desirable that the activated carbon be packed in a unit such as a non-woven fabric, cellophane, paper or the like, but the activated carbon itself may be in a fibrous form. As the wrapping material for the activated carbon, it is preferable to use one having a heat-sealing property, such as a nonwoven fabric made of a synthetic resin, but as long as it has water vapor permeability and the activated carbon does not spill, it may be paper, natural fiber, or the like. no problem.

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

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

In the following Examples/Comparative Examples, the evaluation of each characteristic was performed by the following methods.
(Whether there is an opening)
After injecting a red penetrant (product name: AGELESS SEAL CHECK SPRAY, manufactured by Mitsubishi Gas Chemical Co., Inc.) into the packaging container, set the heating condition scale to 3 with an impulse sealer, heat seal with a width of about 5 mm, and then paper. (Kokuyo PPC paper, common paper A4) was pressed, and the presence or absence of the opening was confirmed by the presence or absence of the transfer of ink to the paper.
(Oxygen permeability)
First, a bag having an inner size of 170 mm×235 mm was formed by the following method.
Fold one film into two almost evenly and set the scale of heating conditions to 3 with an impulse sealer (manufactured by Fuji Impulse Co., product number Fi-200-10WK) with a width of about 5 mm, and heat seal the film. Heat-seal one side approximately perpendicular to the heat-sealed side so that the side is almost in the center, and heat-seal the entire other side except for the end of about 2 cm which is the communicating part of the other side, and the inside dimension is 170 mm × A 235 mm bag was formed.
Next, nitrogen gas was injected from the communication part, and after the bag was saturated, almost all the gas in the bag was discharged from the communication part. After repeating this operation 5 times, nitrogen gas was injected to saturate the inside of the bag with nitrogen gas, and the communicating portion was heat-sealed under the same conditions with the impulse sealer. The bag saturated with nitrogen gas was left for 6 hours in a room at 22° C. and 40% relative humidity in air (1 atm, oxygen concentration: 21%, nitrogen concentration: 79%).
Next, about 20 cc of gas in the bag was sampled, and the oxygen concentration in the bag was measured with a zirconia oxygen concentration meter for food packaging (Toray Engineering Co., Ltd., model number LC-750F). Further, the volume of gas in the bag was measured, and the oxygen permeability was calculated from the following formula.
(Equation) Oxygen permeability=internal oxygen concentration change (%)/100×volume (cm ³ )×24×60/hour (360 minutes)×10000 cm ² /area (799 cm ² )/0.21 (partial pressure of oxygen )
(Oxygen concentration)
About 20 cc of gas in the package 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 (Toray Engineering Co., Ltd., model number LC-750F).
(Carbon dioxide concentration/Oxygen concentration)
It was measured by an O ₂ /CO ₂ analyzer Check Mate 3 for food packaging manufactured by Dansensor.
(appearance)
The package was opened, the fruits and vegetables taken out were lined up, and the area of the entire browning part centering on the lettuce cross section was visually evaluated at n=3.
The evaluation criteria are as follows. In addition, the presence or absence of mold was also observed.
A: No browning and no problem A×: No browning, but part of the cross section is thin and red, but barely noticeable B: Browning, but 10% or less of the entire cross section is slightly visible B×: Browning Yes, but it is conspicuous in 20% or less of the entire cross section C: Browning is 30% or less of the entire cross section, and quite noticeable but can be sold D: Browning is 50% or less of the entire cross section, remarkably Conspicuously unsellable by consumers E: Browning is large and unsellable by consumers (odour)
When the seal of the package was opened, the face was brought closer to the inside to smell the inside and the sensory evaluation was performed with n=3.
The evaluation criteria are as follows.
A: There is no problem in a fresh state. B: There is a slight odor, but it can be said that it is fresh. E: The odor is stronger and the product cannot be sold.

(Comparative Example 1)
Two OPP (biaxially oriented polypropylene) films with a thickness of 40 μm are stacked, three sides are sealed with heat seal and then cut, and one side is an unsealed packaging bag (170 mm×235 mm, inside size) Area: 799 cm ² ) was produced.
Observation of the presence or absence of openings in the film confirmed that there were no openings. The oxygen transmission rate of the film was 1000 CC/m ² /atm/day.
78 g of cut lettuce was enclosed in a packaging container, filled with nitrogen, and then heat-sealed to produce a package. The package was stored at 10° C., the internal oxygen concentration and the internal carbon dioxide concentration were measured every day, and the off-flavor and appearance of cut lettuce were evaluated.
The results are shown in Table 1.

(Example 1)
A package was prepared and evaluated in the same manner as in Comparative Example 1 except that a mixed gas of 70% oxygen and 30% carbon dioxide was enclosed in place of nitrogen.
The results are shown in Table 1.

(Example 2)
A package was prepared and evaluated in the same manner as in Comparative Example 1 except that a mixed gas of 50% oxygen and 50% carbon dioxide was enclosed in place of nitrogen.
The results are shown in Table 1.

(Reference example 1)
A package was prepared and evaluated in the same manner as in Comparative Example 1 except that carbon dioxide was enclosed in place of nitrogen.
The results are shown in Table 1.

(Reference example 2)
A package was prepared and evaluated in the same manner as in Reference Example 1 except that a polyethylene film having a thickness of 30 μm was used instead of the OPP (biaxially oriented polypropylene) film having a thickness of 40 μm.
Observation of the presence or absence of openings in the film confirmed that there were no openings. The oxygen transmission rate of the film was 5000 CC/m ² /atm/day.
The results are shown in Table 1.

(Reference example 3)
A package was prepared and evaluated in the same manner as in Reference Example 1 except that one OPP (biaxially oriented polypropylene) film having a thickness of 40 μm was provided with one hole having a diameter of 300 μm.
The oxygen transmission rate of the film was 10,000 CC/m ² /atm/day.
The results are shown in Table 1.

(Reference example 4)
A package was prepared and evaluated in the same manner as in Reference Example 1 except that three OPP (biaxially oriented polypropylene) films each having a thickness of 40 μm were provided with three holes each having a diameter of 300 μm.
The oxygen transmission rate of the film was 15000 CC/m ² /atm/day.
The results are shown in Table 1.

(Comparative example 2)
A package was prepared and evaluated in the same manner as in Reference 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 transmission rate of the film was 30,000 CC/m ² /atm/day.
The results are shown in Table 1.

(Example 3)
A package was prepared in the same manner as in Comparative Example 1 except that a mixed gas of oxygen: 14.7% by volume/nitrogen: 55.3% by volume/carbon dioxide: 30% by volume was filled in place of the nitrogen gas. , Evaluated.
The results are shown in Table 1.

In the packages of the respective examples, which satisfy the conditions of the predetermined internal oxygen concentration and internal carbon dioxide concentration of the present invention, browning of cut lettuce and generation of off-flavor are effectively suppressed for at least 72 hours after sealing, and the effect thereof is obtained. Was maintained until 144 hours. On the other hand, in each Comparative Example, at least 48 hours later, at least one of the appearance and the offensive odor was deteriorated, and the commercial value of cut lettuce was partially impaired.

The package of the present invention has a high practical value such as suppression of browning of fruits and vegetables containing lettuce such as cut lettuce having high economic value and prevention of offensive odor for a long period of time, and being particularly effective in maintaining freshness. In addition, it has high availability in each field of industry such as food processing, distribution, and restaurant.

Claims (9)

Fused polypropylene film, polyethylene-based film, or two polymer films, which are a laminate of a stretched film and a polyethylene-based film, stacked on each other, or one polymer film folded on top of another Is a package in which fruits and vegetables containing cut lettuce are stored in a packaging container having a carbon dioxide concentration of 19.2% by volume or more and 45.1% by volume or less and 10 after sealing the package. internal oxygen concentration 17.6 vol% 67.1 vol% der less in after holding for 72 hours under the conditions of ° C. is, the oxygen permeability of the packaging container, 20 ° C., in 90% RH, 1500cc / m ² / atm / day Ru der below, the above-mentioned package. The package according to claim 1, which has an internal carbon dioxide concentration of 20% by volume or more after being kept for 72 hours under the condition of 10°C after sealing the package. The package according to claim 1 or 2 , wherein nitrogen is further enclosed in the packaging container. The package according to any one of claims 1 to 3 , 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 4 , wherein the polymer film has a thickness of 10 to 50 µm. The package according to any one of claims 1 to 5 , wherein the polymer film contains at least one antibacterial agent or is coated with at least one antibacterial agent. The package according to any one of claims 1 to 6 , further containing a hygroscopic agent and/or an antibacterial agent. Fused polypropylene film, polyethylene-based film, or two polymer films, which are a laminate of a stretched film and a polyethylene-based film, stacked on each other, or one polymer film folded on top of another The process of storing fruits and vegetables containing cut lettuce in a packaging container having an oxygen permeability of 1500 cc/m ² /atm/day or less at 20° C. and 90% RH, and carbon dioxide in the packaging container. Freshness preservation of fruits and vegetables, which has a step of adjusting the concentration to 30% by volume or more and 50% by volume or less and an oxygen concentration of 14.7% by volume or more and 70% by volume or less, and then further sealing the packaging container. Method. The 50 vol% to 30 vol% of carbon dioxide concentration in the packaging container below, and in the step of the oxygen concentration is 70 vol% or more 14.7% by volume, together to enclose the nitrogen, according to claim 8 , How to maintain freshness of fruits and vegetables.