JP6694846B2 - Package excellent in freshness-keeping performance of fruits and vegetables containing lettuce, and method of keeping freshness of fruits and vegetables containing lettuce - 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 offensive 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. 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 package containing fruits and vegetables which is composed 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 75% measured water vapor transmission rate is 50 ~ 800gm ^-2 d ^{-1 based} on the effective surface area of the package There is described the packaged body containing fruits and vegetables, wherein the open area ratio of (A) is 3 × 10 ^{−6 to} 7 × 10 ⁻⁴ % with respect to the effective surface area of the packaged body. 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 if the above technique is applied, 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 particularly remarkable 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 maintaining 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 whose permeation amount is a value between a predetermined upper limit value and a lower limit value, and oxygen is filled between the predetermined upper limit value and the lower limit value per 1 kg of lettuce during packaging. ing. 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. For example, it has been known that browning can be suppressed by setting the oxygen permeation amount and the oxygen filling amount to be lower and setting the environment in the bag to have a low oxygen concentration, but in that case, an offensive odor associated with anoxic breathing occurs. It is unavoidable that the suppression of browning and the prevention of off-flavor are not compatible with each other in the prior art.

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 fruits and vegetables containing lettuce are stored in a packaging container, and even in an environment of low oxygen concentration in which browning of fruits and vegetables containing the lettuce is suppressed. Another object of the present invention is to provide a package excellent in the function of keeping the freshness of the fruits and vegetables, such that it can effectively prevent an offensive odor.
The present inventor, as a result of diligent studies, by introducing a predetermined concentration of carbon dioxide, the offensive odor from fruits and vegetables containing lettuce is prevented even in an environment of low oxygen concentration, and by utilizing this, the limit of the prior art is reduced. The inventors have found that it is possible to simultaneously suppress browning of fruits and vegetables containing lettuce and prevent off-flavor at an exceedingly high level, and have 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 1 to 98% by volume and the internal oxygen concentration is 1 to 19% by volume. The above-mentioned package.

Hereinafter, each of [2] to [12] 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 20 000 mL / m ² / atm / 24 hr or less at 20 ° C. and 90% RH.
[3]
The package according to [1] or [2], which suppresses browning of fruits and vegetables containing the lettuce and generation of an offensive odor at 72 ° C. for 72 hours after sealing the package.
[4]
The package according to any one of [1] to [3], which has an internal carbon dioxide concentration of 6 to 90% by volume after holding the package at 10 ° C for 72 hours.
[5]
The package according to any one of [1] to [4], which has an internal oxygen concentration of 19 vol% or less after the package is sealed and kept at 10 ° C. for 72 hours.
[6]
The packaging body according to any one of [1] to [5], wherein the packaging container does not have a through hole that can be confirmed by an ink leak checker.
[7]
The package according to any one of [1] to [6], wherein the polymer film is a stretched polypropylene film, a polyethylene film, or a laminate of a stretched film and a polyethylene film.
[8]
The package according to any one of [1] to [7], wherein the polymer film contains at least one antibacterial agent or is coated with at least one antibacterial agent.
[9]
The package according to any one of [1] to [8], wherein the lettuce is cut lettuce.
[10]
The package according to any one of [1] to [9], which further contains a hygroscopic agent and / or an antibacterial agent.
[11]
A step of storing fruits and vegetables containing lettuce in a packaging container comprising a polymer film and having an oxygen permeability of 20 000 mL / m ² / atm / 24 hr or less at 20 ° C. and 90% RH, and the packaging container A method for maintaining freshness of fruits and vegetables, comprising a step of setting the carbon dioxide concentration in the container to 50% by volume or more, and a step of sealing the packaging container.
[12]
The method for maintaining freshness of fruits and vegetables according to [13], wherein the oxygen concentration is 20 vol% or less in the step of setting the carbon dioxide concentration in the packaging container to 50 vol% or more.

  According to the present invention, by introducing a predetermined concentration of carbon dioxide into the package, suppression of browning of lettuce and prevention of offensive odor are both achieved at a high level exceeding the limit of the prior art, and freshness of fruits and vegetables containing lettuce. Provided is a package having a practically high value that can effectively suppress the above-mentioned effects, and a method for maintaining freshness of fruits and vegetables.

Hereinafter, modes for carrying out the present invention will be described.
The present invention is the above-mentioned package, wherein a vegetable containing lettuce is contained in a packaging container containing a polymer film, and the internal carbon dioxide concentration is 1 to 98% by volume. 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 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. It is meant to include both.
Therefore, the packaging container may be a flexible packaging container in which all or a main part is made of a flexible polymer film, that is, a so-called packaging bag, and the flexible polymer film and the coated paper, etc. It may be a flexible packaging container in which other flexible members other than that 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 polygonal shape of a quadrangle or more, but a rectangular shape is preferable from the viewpoint of workability and easy 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 at an oxygen permeability of 20 ° C. and 90% RH, 20000 mL is used. It is desirable to use a packaging container having a / m ² / atm / 24 hr or less.
By using a packaging container whose oxygen permeability is in the above range, fluctuations in the internal gas composition due to the outflow of internal gas, especially carbon dioxide, the outside air, especially the inflow of oxygen, are suppressed or alleviated, and the freshness of fruits and vegetables including lettuce. It becomes easy to maintain an environment suitable for retention. The oxygen permeability of the packaging container is more preferably 15000 mL / m ² / atm / 24 hr or less, and particularly preferably 12000 mL / m ² / atm / 24 hr or less.
There is no particular lower limit to the oxygen permeability of the packaging container, but from the viewpoint of allowing the fruits and vegetables containing lettuce to breath to some extent and preventing the generation of offensive odors more effectively, 500 mL / m ² / atm / 24 hr It is preferably not less than 800 ml , more preferably not less than 800 mL / m ² / atm / 24 hr . In addition, considering the cost and the like, as long as the packaging container is configured with a relatively simple structure using a commonly available polymer film, the oxygen permeability thereof is 500 mL / m ² / atm / 24 hr or more. 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 (Fuji Impulse Co., Ltd., 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 excluding about 2 cm of one end of the other side, which is the communicating portion, and then the inside dimension a ( 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 by a zirconia oxygen concentration meter for food packaging (Model 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.
(Formula) Oxygen permeability = internal oxygen concentration change (%) / 100 × volume (cm ³ ) × 24 × 60 / hour (360 minutes) × 10000 cm ² / area (2 × a × b × cm ² ) / of 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, and application area of the polymer film forming the packaging container. it can. Details of the polymer film will be described later.
Further, the oxygen permeability of the packaging container can be adjusted appropriately 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 a case where all of the fruit and vegetables are composed of lettuce and a case where a 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.
In other words, the "lettuce" referred to here is a type of scraping chisha or cutting lettuce, which is typified by Sanchu and is a type of scraping leaves from the stem; All of the type 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 (stem lettuce), and the like.

  In the present invention, there is no particular limitation 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 banana, mango, plum, apple, strawberry, mandarin orange, grape, Japanese pear, fruits such as 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, sprouts such as tokyo, mushrooms such as shiitake, shimeji mushrooms, eringi, maitake, matsutake mushrooms, broccoli Examples include, but are not limited to, leafy vegetables such as spinach, spinach, komatsuna, bok choy, cabbage, asparagus, flowers or seedlings. From the effect of the present embodiment of controlling and maintaining the oxygen concentration, it is particularly effective in maintaining the freshness of fruits and vegetables in the form of substantially breathing.

In the present invention, the form of fruits and vegetables containing lettuce stored in a packaging container and kept fresh is not particularly limited. Therefore, fruits and vegetables containing lettuce may be as-harvested, may be so-called pre-treated with outer leaves removed, or may be so-called cut vegetables (cut lettuce) that have been cut. May be. The fruits and vegetables may be those that have undergone any or all of the treatments such as washing, cooling, dehydration, and those that do not undergo 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, the cut lettuce is washed at 80 to 120 ppm for 10 to 20 minutes with hypochlorous acid 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 reduction 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 used for meals, and has high economic value. Cut lettuce is a typical cut vegetable and can be easily used as a salad or the like for meals, and thus 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 the fruit and vegetables stored with lettuce, if present), the preferred carbon dioxide concentration for freshness retention will vary to some extent within the scope of the present invention, with which the preferred carbon dioxide permeability is indirectly The specified oxygen permeability, and the aspect of the polymer film that gives such oxygen permeability are also different, but by properly setting these, the above lettuce (and fruits and vegetables stored with the lettuce when present) In any case, the freshness can be effectively maintained by the present invention.

Package The internal carbon dioxide oxygen concentration of the package of the present invention is 1 to 98% by volume, and the internal oxygen concentration is 1 to 19% by volume. By having an internal carbon dioxide oxygen concentration of 1 to 98% by volume, it is possible to effectively prevent generation of an offensive odor from lettuce in fruits and vegetables contained in a packaging container in a low oxygen concentration environment suitable for suppressing browning, It is possible to achieve both suppression of browning of fruits and vegetables containing lettuce and prevention of off-flavor at a high level that exceeds the limit of the prior art.
It has been conventionally known that by adjusting the oxygen concentration in the package to be within a predetermined range, deterioration of appearance such as browning of fruits and vegetables contained in the package can be suppressed. However, if the oxygen concentration is below a predetermined value, there is a problem in that anomalous odor such as alcohol odor is generated due to anoxic breathing of fruits and vegetables. Among the fruits and vegetables, lettuce is particularly prone to browning, and there is a strong demand for a low oxygen concentration for its inhibition. Therefore, in keeping the freshness of fruits and vegetables containing lettuce, it is possible to achieve both suppression of browning and prevention of off-flavor. It has been particularly difficult in the past.
In the present invention, in a package containing fruits and vegetables containing lettuce, carbon dioxide is introduced, and by setting the internal carbon dioxide concentration within a predetermined range, the suppression of browning and the prevention of off-flavor are limited by the prior art. The amazing effect of achieving both at an extremely high level is realized.
In the present invention, the internal carbon dioxide oxygen concentration is within a predetermined range, the suppression of browning of lettuce in fruits and vegetables contained in the packaging container and the prevention of off-flavor, at a high level beyond the limit of the prior art. It is not clear what mechanism they are compatible with, but it has something to do with having an effect on the respiration equilibrium state of fruits and vegetables containing lettuce by excessively increasing the amount of carbon dioxide, which is a product of normal respiration. It is estimated to be.

The internal carbon dioxide concentration of the package is preferably 3% by volume or more, more preferably 5% by volume or more, and even more preferably 10% by volume or more.
The internal carbon dioxide concentration of the package is more preferably 50% by volume or less.
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 concentration of carbon dioxide in the gas filled in the packaging container when the package is manufactured. For example, when producing a package, the carbon dioxide concentration in the gas filled in the packaging container is preferably 50% by volume or more, more preferably 70% by volume or more, and 90% by volume or more. Is particularly preferable.
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 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, for example, by a food packaging O ₂ / CO ₂ analyzer Check Mate 3 manufactured by Dansensor.

The upper limit of the internal oxygen concentration of the package is 19% by volume, but from the viewpoint of more effectively suppressing the deterioration of appearance such as browning of fruits and vegetables containing lettuce, it is 18.5% by volume or less. More preferable.
The lower limit of the internal oxygen concentration of the package is 1% by volume, but from the viewpoint of allowing the minimum breathing of fruits and vegetables containing lettuce and more effectively suppressing the offensive odor caused by anoxic breathing, 1.2% by volume It is preferably not less than 1.3%, more preferably not less than 1.3% by volume.
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 to set the oxygen concentration in the gas filled in the packaging container to 19 vol% or less when producing the package.
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 flowing in 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 fruits and vegetables containing lettuce and generation of an offensive odor for 72 hours when the package is kept at 10 ° C after the package is sealed.
This preferred embodiment suppresses browning of lettuce-containing fruits and vegetables and generation of offensive odors for 72 hours after the packaging is sealed, so that the freshness of the lettuce-containing fruits and vegetables can be maintained for a long period of time considered to be sufficient for distribution. Since it can be maintained at a high level, it has a high practical and economic value.
In this preferred embodiment, when the browning of fruits and vegetables containing lettuce and the generation of offensive odor are kept at 10 ° C. after the packaging is sealed, it is more preferable to suppress it for 96 hours. It is more preferable to suppress over time, and it is particularly preferable to suppress for 144 hours after sealing the package.

The internal carbon dioxide concentration of the package of the present invention after holding at 10 ° C. for 72 hours after sealing the package is preferably 6 to 90% by volume. Since the internal carbon dioxide concentration after holding at 10 ° C. for 72 hours after sealing is 6 to 90% by volume, suppression of browning of lettuce in fruits and vegetables contained in the packaging container and prevention of offensive odor can be prolonged. A higher level of compatibility can be achieved over a period of time.
The internal carbon dioxide concentration after holding the package of the present invention at 10 ° C. for 72 hours after sealing is more preferably 6.5 to 90% by volume, and particularly preferably 6.8 to 89% by volume. ..
Here, "after sealing the package" refers to the elapsed time from sealing the packaging container after storing the fruits and vegetables containing lettuce in the packaging container. That is, "after holding the package at 10 ° C for 72 hours after sealing" means that after storing fruits and vegetables containing lettuce in the packaging container, after sealing the packaging container, 72 hours under the condition of 10 ° C. The state immediately after holding.

  In the package of the present invention, since the internal carbon dioxide concentration is 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 in which the internal carbon dioxide concentration after holding at 10 ° C. for 72 hours is 6% by volume or more, the internal carbon dioxide concentration is 6% by volume or more from 0 to 72 hours after the sealing. Most likely there is. Such a history of carbon dioxide concentration is particularly preferable in order to more effectively suppress browning of lettuce in fruits and vegetables and generation of off-flavor.

The internal carbon dioxide concentration after holding the package at 10 ° C. for 72 hours after sealing 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 with which the packaging container is filled when producing the package. For example, when producing a package, it is preferable that the concentration of carbon dioxide in the gas filled in the packaging container is 50% by volume or more.
In addition, the internal carbon dioxide concentration after holding the package at 10 ° C. for 72 hours is 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 also possible to adjust to a predetermined concentration by adjusting. 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 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 holding the package of the present invention at 10 ° C. for 72 hours after sealing is preferably 19% by volume or less. Since the internal oxygen concentration is 19% by volume or less after being kept at 10 ° C. for 72 hours after sealing, generation of offensive odor from lettuce in fruits and vegetables contained in the packaging container is more effectively suppressed for a long period of time. To be done.
The internal oxygen concentration of the package of the present invention after being kept at 10 ° C. for 72 hours after sealing is more preferably 18% by volume or less, and particularly preferably 17% by volume or less.
The internal oxygen concentration of the package of the present invention after holding at 10 ° C. for 72 hours after sealing is preferably 1% by volume or more, more preferably 2% by volume or more, and 3% by volume or more. It is particularly preferable that

The internal oxygen concentration after holding the package at 10 ° C. for 72 hours after sealing 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, when producing a package, it is preferable that the oxygen concentration in the gas filled in the packaging container is 20% by volume or less.
In addition, the internal oxygen concentration after holding the package at 10 ° C. for 72 hours is determined by the amount of oxygen flowing out of the package or flowing from the outside of the package, and / or the respiration of 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. 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 It is possible to adjust the amount of oxygen consumed by respiration of fruits and vegetables by adjusting the amount of oxygen filled in the packaging container.

  From the viewpoint of achieving the desired internal carbon dioxide concentration and internal oxygen concentration described above, other gas such as nitrogen may be further enclosed in the packaging container. This is because the internal carbon dioxide concentration and the internal oxygen concentration can be adjusted independently by enclosing another gas such as nitrogen at the time of sealing the packaging container.

Polymer Film Also, in order to realize the above-mentioned 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 20000 mL / m ² / atm / 24 hr or less at 20 ° C. and 90% RH. By using a polymer film whose oxygen permeability at 20 ° C. and 90% RH is equal to or lower than the above value, a preferred embodiment has an oxygen permeability of 20000 mL / m ² / atm / at 20 ° C. and 90% RH. A packaging container of 24 hours or less 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 preferably 15,000 mL / m ² / atm / 24 hr or less at 20 ° C. and 90% RH, and is 12000 mL / m ² / atm / 24 hr or less. Is particularly preferable.
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, at 20 ° C. and 90% RH, 500 mL / m ² / atm / It is generally 24 hours or more.
Further, from the viewpoint of more effectively preventing the generation of offensive odor from the stored fruits and vegetables, it is preferable that the polymer film have an oxygen transmission rate that allows the fruits and fruits to breathe at a minimum level. From this viewpoint, the oxygen permeability of the polymer film at 20 ° C. and 90% RH is preferably 750 mL / m ² / atm / 24 hr or more, and is 900 mL / m ² / atm / 24 hr or more. Is particularly preferable.

  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.

By appropriately selecting the material, thickness, processing method, etc. of the polymer film, the oxygen permeability of the polymer film can be appropriately adjusted. For example, in the case of a biaxially oriented polypropylene (OPP) film, the oxygen permeability at 20 ° C. and 90% RH can be set to 5000 mL / m ² / atm / 24 hr or less by setting the thickness to 10 μm or more. It is preferable because it is possible. Considering 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 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. Particularly, in the preferred embodiment of the present invention, 20 ° C., a relatively low oxygen permeability of 20000 mL ^/ m 2 ^/ 24hr or less of oxygen permeability at 90% RH, without providing openings in a polymer film Can be realized.
If it is not necessary to provide an opening in the polymer film, the manufacturing process becomes simpler and less expensive, and it is not necessary to precisely control the size, shape, etc. of the opening.
The absence of openings in the polymer film can be confirmed, for example, by the polymer film forming the packaging container having no through holes that can be confirmed by an ink leak checker.

Meanwhile, in an embodiment of the present invention, 20 ° C., and if it is necessary to realize a relatively high oxygen permeability of 20000 mL ^/ m 2 ^/ 24hr or less of oxygen permeability at 90% RH, thick high When it is necessary to use a molecular film or a polymer material having a low oxygen permeability, the openings provided in the polymer film may be used together in order to achieve a desired oxygen permeability. 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 guideline. 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 providing things, it has the effect of increasing the about ^{1000 mL / m 2 / 24hr /} atm oxygen permeability of each existing one for packaging containers of 200 mm × 200 mm, is required on the basis of such findings It is preferable to determine the number of slit openings from the oxygen permeability of the entire packaging 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, economy, the amount of oxygen permeation provided by the opening. From the viewpoints 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 50 μm, more preferably 15 to 45 μm, and particularly preferably 20 to 40 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. Furthermore, one of these materials may be used alone, or a plurality of these materials may be blended and / or laminated and used.

  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 a polyolefin 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 polymeta-xylene adipamide, polyvinyl chloride, polyimide, ethylene acetic acid. Examples thereof include vinyl copolymers or saponified products thereof, polyvinyl alcohol, polyacrylonitrile, polycarbonate, polystyrene, ionomer, 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. 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 referred to as homo PP), which is manufactured and sold under the name of polypropylene, propylene / α-olefin random copolymer (also referred to as random PP). , A propylene-based crystalline polymer such as a mixture of propylene homopolymer and low crystalline or amorphous propylene / ethylene random copolymer (also called 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 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 a copolymer thereof with at least one or more α-olefins having 3 to 8 carbon atoms, an ethylene / vinyl acetate copolymer, Examples include 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 Examples of the copolymer include a copolymer, ethylene / 1-octene copolymer, and the like, which has ethylene as a main monomer, and at least one 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-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 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 one of the above-mentioned polymers, and any one 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.

In the present invention, the polymer film constituting the packaging container may be either a non-stretched film or a stretched film.
From the viewpoint of mechanical strength and the like, stretched films of various polymers can be 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 therefore can be particularly preferably used in the packaging container used in the present invention.
Further, the film using the 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 in the machine direction and the transverse direction by 5 to 10 times (25 to 100 times in area magnification), 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 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-based 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, dry lamination is performed in which a stretched film and a polyethylene-based film that have been prepared in advance are attached with an adhesive, and the stretched film surface to which the adhesive is applied here is subjected to corona treatment. preferable. Specifically, the surface tension of the film surface after corona treatment is preferably 35 mN / m or more, and more preferably 40 mN / m or more, from the viewpoint of adhesion stability.

Further, 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.
Further, a specific surfactant may be present on the surface of the polymer film in a specific amount, or the polymer film may contain a specific surfactant in a specific amount to 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, at least 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, bacteria By suppressing the reproduction of the bacteria, the growth of various bacteria in the dew condensation (drip) 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 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 linear low density polyethylene (LLDPE) polystyrene and EVA on polyethylene terephthalate (PET) 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 internal carbon dioxide concentration thereof is appropriately adjusted to produce the package of the present invention. The freshness preservation method for fruits and vegetables which is one embodiment of the invention can be implemented.
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 a pretreatment step, the outer leaf is manually removed, divided into 2 to 4, and the lettuce from which the core has been 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 or the like. The dehydrated cut lettuce is packed in 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 and reduce scratches on the cut surface.
Further, the narrower the cut width, the larger the cutting area and the more difficult it becomes to maintain 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.
Furthermore, if a large amount of bacteria adheres to the cut lettuce from the beginning, it will be more difficult to maintain the freshness. Therefore, it is preferable to thoroughly clean the cut lettuce to reduce the adhesion of 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 liquor containing highly active enzymes and the like that may cause discoloration and the like.
In addition, it is important for keeping the freshness to sufficiently remove the water adhering to the surface of the cut lettuce after washing.
This is because the growth of miscellaneous bacteria in the excessively adhered minute water droplets can be suppressed by adjusting the water content appropriately. 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 the nutrition labeling standard" (consumer It is preferable that the water content, which is measured based on the weight reduction when dried under reduced pressure at 70 ° C. for 5 hours, is in the range of 20% or more and less than 30%. Even after draining after standing still after washing, since much water still adheres to the surface of cut lettuce, use a centrifugal dehydrator to remove water and dry with dry air. Is effective.

In the production of the package for freshness preservation of fruits and vegetables of the present embodiment, after the fruits and vegetables containing lettuce are stored, a gas having a predetermined composition, for example, a gas having a carbon dioxide concentration of 50% by volume or more is introduced and then sealed. May be. By introducing a gas having a predetermined composition, it becomes possible to quickly reach a desired carbon dioxide 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 70% by volume or more, and particularly preferably 90% by volume or more. The oxygen concentration of the gas having the above-mentioned predetermined composition is not particularly limited, but it is preferably 15% by volume or less, and more preferably 10% by volume or less because it is advantageous for maintaining the appearance of fruits and vegetables containing lettuce. It is more preferably 5% by volume or less, still more preferably 1% by volume or less, and particularly preferably 0.5% by volume or less. 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 the human body, fruits and vegetables and the like.
Further, from the viewpoints of improving efficiency in the distribution process, saving space, and eliminating a specific gas, degassing may be performed before or during 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, for example, 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 influence on fruits and vegetables and use near fruits and vegetables which are 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 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 non-woven fabric made of synthetic resin, but as long as it has water vapor permeability and the activated carbon does not spill, it may be paper, natural fiber, etc. no problem.

  There is no particular limitation on the antibacterial agent, and substances having an antibacterial effect can be appropriately used, but a natural antibacterial agent with relatively little concern about the effect on fruits and vegetables and the use near fruits and vegetables that are foods 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, 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 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 the 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 (Fuji Impulse Co., Ltd., product number Fi-200-10WK) with a width of about 5 mm, and heat seal the film. Heat-seal so that the side is almost in the center, and one side that is almost perpendicular to the heat-sealing side is heat-sealed, except for the end of about 2 cm that 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 communication part was heat-sealed under the same conditions with the impulse sealer. The bag saturated with nitrogen gas was left to stand in a room at 22 ° C. and 40% relative humidity in air (1 atm, oxygen concentration: 21%, nitrogen concentration: 79%) for 6 hours.
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.
(Formula) 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 )
(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 seal of 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 with n = 3.
The evaluation criteria are as follows.
A: There is no browning and there is no problem.
A ×: No browning, but part of the cross section is thin and red, but hardly noticeable B: Browning, but 10% or less of the entire cross section is slightly noticeable B ×: 20% of the entire cross section, although browning Conspicuous state below: C: Browning but 30% or less of the whole cross section, quite noticeable but marketable D: Browning but 50% or less of the whole cross section, remarkably conspicuous and unsellable by consumers State (odour)
When the seal of the package was opened, the face was brought close to the package and the internal odor was smelled to perform a sensory evaluation 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. C: A state with a strong odor but in the same state as on the market, and in a state where it can be sold. E: A state in which the odor is stronger and unsellable In the present application, it was evaluated that an offensive odor was generated in the case of the evaluation of C, D and E, and an offensive odor that lost the commercial value was generated in the case of D and E. To do.

(Comparative Example 1)
Two OPP (biaxially oriented polypropylene) films with a thickness of 40 μm are stacked, three sides are sealed by heat sealing 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 mL / m ² / atm / 24 hr .
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 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 Example 1 except that a polyethylene film having a thickness of 30 μm was used in place 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 mL / m ² / atm / 24 hr .
The results are shown in Table 1.

(Example 3)
A package was prepared and evaluated in the same manner as in Example 1 except that an 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 10000 mL / m ² / atm / 24 hr .
The results are shown in Table 1.

(Example 4)
A package was prepared and evaluated in the same manner as in Example 1 except that an OPP (biaxially oriented polypropylene) film having a thickness of 40 μm was provided with three holes having a diameter of 300 μm.
The oxygen transmission rate of the film was 15000 mL / m ² / atm / 24 hr .
The results are shown in Table 1.

(Comparative example 2)
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 transmission rate of the film was 30,000 mL / m ² / atm / 24 hr .
The results are shown in Table 1.

  In the packages of the respective examples satisfying the conditions of the predetermined internal carbon dioxide concentration and internal oxygen concentration of the present invention, browning of cut lettuce and generation of offensive odor are effectively suppressed for at least 72 hours after sealing, and the offensive odor is detected. Was suppressed up to 144 hours. On the other hand, in Comparative Example 1, an offensive odor was generated after 96 hours had passed, and in Comparative Example 2, the appearance deteriorated after 72 hours had passed, and the commercial value of cut lettuce was partially impaired.

  The package of the present invention is compatible with suppression of browning of fruits and vegetables containing lettuce such as cut lettuce having a high economic value and prevention of off-flavor at a high level exceeding the limit of the prior art, and is particularly effective in maintaining freshness. Therefore, it has high practical value, and has high availability in various fields of industry such as food processing, distribution, and restaurant.

Claims (7)

Oriented polypropylene film, polyethylene film, and saw including a polymeric film selected from the laminate of the stretched film and the polyethylene film, the state superposed the polymer film into two each other, or one the polymer film A package in which fruits and vegetables containing cut lettuce are contained in a packaging container formed by fusing in a folded state , the internal carbon dioxide concentration is 1.0 to 97.6% by volume, and the internal oxygen concentration is Is 0.386 to 20.2% by volume,
The internal carbon dioxide concentration after holding the package at 10 ° C. for 24 hours is 23.3% by volume or more and 97.6% by volume or less,
The above-mentioned package, wherein the oxygen permeability of the packaging container is 500 mL / m ² / atm / 24 hr or more and 15000 mL / m ² / atm / 24 hr or less at 20 ° C. and 90% RH.   The package according to claim 1, wherein the internal carbon dioxide concentration after the package is kept at 10 ° C for 72 hours after being sealed is 3.0 to 87.8% by volume.   The package according to claim 1 or 2, wherein the internal oxygen concentration after the package is sealed and held at 10 ° C for 72 hours is 3.29 to 18.5% by volume.   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 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 5, further containing a hygroscopic agent and / or an antibacterial agent. Oriented polypropylene film, polyethylene film, and saw including a polymeric film selected from the laminate of the stretched film and the polyethylene film, the state superposed the polymer film into two each other, or one the polymer film Fused in a folded state, in a packaging container having an oxygen permeability of 500 mL / m ² / atm / 24 hr or more and 15000 mL / m ² / atm / 24 hr or less at 20 ° C. and 90% RH. A step of storing fruits and vegetables containing cut lettuce, a step of sealing the packaging container, and a step of adjusting the internal carbon dioxide concentration in the 24 hours after sealing the packaging container from 23.3% by volume to 97.6% by volume. A method for maintaining freshness of fruits and vegetables, which comprises: