JP2018167897A - Package with excellent freshness retaining capacity for fruit and vegetables including lettuce, and method for retaining freshness of fruit and vegetables - Google Patents

Abstract

To provide a package which is comprised of a packaging container storing fruit and vegetables including lettuce, and which can achieve both inhibition of browning of the fruit and vegetables including lettuce, and prevention of malodor, for a long time and at a high level, and thus has an excellent freshness retaining function for the fruit and vegetables.SOLUTION: A package is comprised of a packaging container provided with polymeric film and storing fruit and vegetables including lettuce, and its internal carbon dioxide concentration is 18 volume% or higher, whereas its internal oxygen concentration is 6 volume% or higher.SELECTED DRAWING: None

Description

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

A gas permeable film that is provided with a gas permeable portion on a polymer film substrate and allows gas such as oxygen, carbon dioxide, and water vapor to pass through the gas permeable portion is used in the field of foods, particularly for fresh vegetables such as fruits and vegetables. It is suitably used as a packaging material. Using such a gas permeable film, for example, when packaging vegetables, fruits, etc., the oxygen concentration suitable for maintaining the freshness of the vegetables, fruits, etc., for example, an oxygen concentration of about 1 to 4% is maintained. It is known that contents can be stored while maintaining freshness over a relatively long period of time.
For example, in Patent Document 1, in a package containing fruits and vegetables made of a polymer film in which fruits and vegetables are sealed, the package is composed of (A) a porous polymer film and (B) a non-porous polymer film, The water vapor transmission rate measured under the conditions where the film characteristics of at least one of (A) and (B) are 25 ° C. and the relative humidity is 75% is 50 to 800 gm ⁻² d ^{−1 based} on the effective surface area of the package. There is described a packaged product with 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 porous polymer film made of stretched polypropylene having a thickness of 35 μm, having 95 holes with an average pore diameter of 30 μm, 9 holes with an average pore diameter of 60 μm, etc. It is used.

  However, for some fruits and vegetables, discoloration could not be sufficiently suppressed even when the above technique was applied, and an improvement was desired. For example, lettuce tends to be browned (a phenomenon that turns brown or red), and this tendency is particularly noticeable in cut lettuce having many cut surfaces. Cut lettuce has increased in demand in recent years because it can be easily provided for meals, and has high economic value because lettuce is one of the most common vegetables for salads. From such a background, a technique capable of maintaining the freshness of fruits and vegetables including lettuce has been proposed, such as browning, off-flavor, etc. can be suppressed over a long period of time. A technique is described in which cut lettuce is put into a bag made of a film having a predetermined permeation amount, and oxygen is filled in a predetermined amount per 1 kg of lettuce during packaging. However, even with the above technique, it has not always been easy to achieve both the suppression of browning of cut lettuce and the prevention of odor over a long period of time.

JP-A-5-168400 Japanese Patent Application Laid-Open No. 8-228673

In view of the limitations of the above-mentioned background art, the present invention is a packaging body that contains fruits and vegetables containing lettuce in a packaging container, and prevents browning and prevention of off-flavors of the fruits and vegetables containing the lettuce for a long time. It is an object of the present invention to provide a package excellent in the function of maintaining the freshness of fruits and vegetables, such as being compatible at a high level exceeding the limits of the conventional technology.
As a result of intensive studies, the inventor has introduced carbon dioxide of a predetermined concentration into the package body, and controlling the internal oxygen concentration of the package body to a predetermined value or more can reduce browning over a long period of fruit and vegetables including lettuce. It has been found that it is particularly effective in maintaining freshness such as suppression and prevention of off-flavors, and the present invention has been completed.

That is, the present invention
[1]
A package comprising a vegetable container containing lettuce in a packaging container comprising 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. Packaging.

Hereinafter, [2] to [14] are each one aspect or 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], wherein browning of the lettuce and generation of a strange odor are suppressed for 72 hours under conditions of 10 ° C. after sealing of the package.
[4]
The package according to any one of [1] to [3], wherein the internal carbon dioxide concentration after being held at 10 ° C. for 72 hours after sealing the package is 20% by volume or more.
[5]
The package according to any one of [1] to [4], wherein the internal oxygen concentration after being held at 10 ° C. for 72 hours after sealing the package is 10% by volume or more.
[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 leakage 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], further containing a hygroscopic agent and / or an antibacterial agent.
[13]
A step of storing fruit 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; A method for maintaining the freshness of fruits and vegetables, comprising: a step of adjusting the carbon dioxide concentration of the product to 20% by volume or more and an oxygen concentration of 10% by volume or more; and a step of sealing the packaging container.
[14]
The method for maintaining freshness of fruits and vegetables according to [13], wherein nitrogen is sealed together in the step of setting the carbon dioxide concentration in the packaging container to 20% by volume or more and the oxygen concentration to 10% by volume or more.

  According to the present invention, carbon dioxide of a predetermined concentration is introduced into the package body, and the internal oxygen concentration of the package body is controlled to a predetermined value or more, so that browning of lettuce and prevention of off-flavor can be prevented over a long period of time. In addition, there are 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, and the internal carbon dioxide concentration is 18% by volume or more and the internal oxygen concentration is 6% by volume or more. It is the said 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 which comprises the package of this invention comprises a polymer film. Here, “comprising a polymer film” means that when the entire packaging container is made of a polymer film and when a part of the packaging container such as a lid is made of a polymer film, It is intended to include both.
Therefore, the packaging container may be a flexible packaging container, or a so-called packaging bag, whose whole or main part is 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 are combined, or a packaging container in which a flexible polymer film and a rigid member are combined, for example, as a lid material. It may be in the form of a combination of a molecular film and a rigid member such as a tray or cup.

In an embodiment in which the packaging container is a so-called packaging bag, for example, three or two sides are heat-sealed in a state where two polymer films are overlapped with each other or one polymer film is folded. A packaging bag can be formed by, for example, fusing. The remaining one side can be sealed by arranging the contents such as fruits and vegetables in the packaging bag and then fusing it by heat sealing.
Such a packaging bag may have a circular shape, a triangular shape, a quadrangular shape, or a polygonal shape equal to or more than a quadrangular shape in a plan view, but is preferably rectangular from the viewpoint of processability and ease of handling.

The packaging container used in the present invention comprises a polymer film as described above, and there is no particular limitation on the oxygen permeability thereof, but the oxygen permeability is 4500 cc / at 20 ° C. and 90% RH. It is desirable to use a packaging container that is m ² / atm / day or less.
By using a packaging container whose oxygen permeability is in the above range, fluctuations in the internal gas composition due to outflow of internal gas, especially carbon dioxide, inflow of outside air, breathing of fruits and vegetables, etc. are suppressed or alleviated, and the fruits and vegetables including lettuce It is 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 preferred.
Although there is no particular lower limit to the oxygen permeability of the packaging container, 500 cc / m ² / atm / day or more from the viewpoint of allowing some respiration to the fruits and vegetables including lettuce and preventing the generation of off-flavors more effectively. It is preferable that it is 800cc / m < ² > / atm / day or more. In view of cost and the like, as long as the packaging container is configured with a relatively simple structure using a normally available polymer film, the oxygen permeability thereof should be 500 cc / m ² / atm / day 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 a (cm) × b (cm) is formed by the following method.
One film is folded almost equally into two, approximately 5 mm wide, and heat sealing is performed with an impulse sealer (manufactured by Fuji Impulse Co., product number Fi-200-10WK) with the heating condition scale set to 3, and the heat sealing is performed. Heat seal the whole of one side that is almost perpendicular to the heat seal side so that the side is almost in the middle, except the end of about 2 cm that is one communicating part of the other side, and the inner dimension a ( cm) × b (cm).
Next, nitrogen gas is injected from the communication portion, and when the inside of the bag becomes saturated, almost all the gas in the bag is discharged from the communication portion. After repeating this operation five times, nitrogen gas is injected to saturate the inside of the bag with nitrogen gas, and the communicating portion is heat-sealed with the impulse sealer under the same conditions. The bag saturated with nitrogen gas is left 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 is sampled with a sampling needle tube, and the oxygen concentration in the bag is measured with a food packaging zirconia oxygen concentration meter (model number LC-750F, manufactured by Toray Engineering Co., Ltd.). Furthermore, the volume of the gas in the bag is measured, and the oxygen permeability is calculated from the following formula.
(Expression) Oxygen permeability = change in internal oxygen concentration (%) / 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 configuration, presence / absence of coating, type, application area, etc. of the polymer film constituting the packaging container. it can. Details of the polymer film will be described later.
Also, the oxygen permeability of the packaging container can be adjusted as appropriate by providing (or not providing) an opening in the polymer film. The oxygen permeability can be adjusted as appropriate depending on the size, shape, and number of openings. Details of the opening will also be described later.

Fruits and vegetables The package of the present invention is obtained by storing fruits and vegetables containing lettuce in the packaging container. Here, the phrase “including fruits and vegetables” “includes” lettuce includes both the case where all of the fruits and vegetables are made of lettuce and the case where some of the fruits and vegetables are made of lettuce. . Therefore, the fruits and vegetables stored in the packaging container may or may not contain vegetables, fruits and the like other than lettuce. Furthermore, as long as lettuce is included, components other than fruits and vegetables, for example, foods other than fruits and vegetables, seasonings, food additives and the like may be included.

The “lettuce” constituting the package of the present invention (contained in a packaging container) is a concept that includes vegetables in general belonging to the Asteraceae genus Chisha species, and the vegetable distributed under the name “lettuce” itself It is not limited.
That is, "lettuce" here is a type called scraping chisha or cutting lettuce typified by sanchu, etc., where the leaves are scraped off from the stem; All of the types called chisha; non-headed leaf lettuce (leaf chisha) represented by Sunny lettuce and green leaf; and the ball-letting lettuce (ball chisha) typically represented by lettuce It is a concept that includes
Preferable specific examples of “lettuce” here include lettuce (ball lettuce), green leaf, romaine lettuce (kos lettuce), sunny lettuce, silk lettuce, pink low star, salad vegetables, bouquet lettuce, green oak leaf (sarano ballet), frills. Examples include, but are not limited to, lettuce, (Cima) sanchu, stem lettuce (stem lettuce), and the like.

  In the present invention, there are no particular limitations on the fruits and vegetables other than lettuce that can be stored together with the lettuce in the packaging container, and unheated or heated fruits and vegetables that can be used for food together with the lettuce can be appropriately stored. Specific examples of such fruits and vegetables include fruits such as bananas, mangoes, ume, apples, strawberries, mandarin, grapes, Japanese pears, pears, radish, carrots, yams, root vegetables such as burdock, tomatoes, Fruits and vegetables such as cucumber, eggplant, bell pepper, green beans, okra, sprouts such as mung bean sprout, soybean sprout, cypress, fungi (mushrooms) such as shiitake, shimeji, eringi, maitake, matsutake, broccoli , Spinach, komatsuna, chinensai, cabbage, leafy vegetables such as asparagus, florets or seedlings, but are not limited thereto. The action of the present embodiment of controlling and maintaining the oxygen concentration 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 including lettuce stored in the packaging container and kept fresh. Therefore, the fruits and vegetables containing lettuce may be as-harvested or so-called pre-treated from which outer leaves have been removed, or cut so-called cut vegetables (cut lettuce). May be. In addition, the fruits and vegetables may be those that have been subjected to any or all of the treatments such as washing, cooling, and dehydration, and may be those that do not perform any of these treatments.
In addition, in the case of lettuce in which the lettuce stored and kept fresh is cut, it is preferable that the amount of moisture is adjusted by performing cutting, washing, dehydration and / or drying. More specifically, for example, cut lettuce is analyzed according to the “nutritional labeling standard in the nutrition labeling standard” after 80 to 120 ppm for 10 to 20 minutes of hypochlorous acid based on the “Manufacturing Sanitation Management Manual” (Ministry of Health and Welfare). Method ”(Consumer Affairs Agency) Preventing the generation of odor and browning when the water content measured based on weight loss when dried under reduced pressure at 70 ° C. for 5 hours is within 20-30% It is particularly preferable from the viewpoint of the balance of preventing the appearance deterioration.

  The demand for cut vegetables has increased in recent years because it can be easily used for meals, and has high economic value. Cut lettuce is a typical cut vegetable and has a particularly high economic value because it can be simply used as a salad for meals. On the other hand, when vegetables, especially lettuce, are cut, the respiratory action and metabolic reaction are rapidly activated, and the quality tends to decrease rapidly. Since this embodiment can be used effectively for maintaining the freshness of such cut lettuce, it has a particularly high economic value.

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

Package Body The package 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, the suppression of browning of lettuce in the fruits and vegetables contained in the packaging container and the prevention of off-flavors are obtained. Can be compatible over a long period of 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 generation of a strange odor due to oxygen-free breathing of the fruits and vegetables contained in the package. However, when the oxygen concentration is set to a predetermined value or more, there is a problem that appearance deterioration such as browning occurs due to normal respiration of fruits and vegetables. Among fruits and vegetables, lettuce is particularly susceptible to browning, and it has heretofore been difficult to prevent browning and prevent odor when maintaining the freshness of fruits and vegetables containing lettuce.
In the present invention, in a packaging body containing fruits and vegetables containing lettuce having an internal oxygen concentration of a predetermined value or higher, carbon dioxide is introduced together, and the internal carbon dioxide concentration is set to a predetermined value or higher, thereby suppressing browning. As a result, a surprising effect is achieved in which the prevention of off-flavors and the prevention of off-flavors are achieved at a high level exceeding the limits of the prior art and for a long period of time.
In the present invention, the internal carbon dioxide oxygen concentration is a predetermined value or more, and the internal oxygen concentration is a predetermined value or more, thereby suppressing the browning of lettuce in the fruits and vegetables contained in the packaging container and preventing the off-flavor. However, the mechanism that is compatible over a long period of time is not always clear, but rather than restricting the supply of oxygen consumed by respiration, the respiration of fruits and vegetables including lettuce is increased by excessing the amount of carbon dioxide generated by respiration. It is presumed that there is some relationship with the ability to restrict normal breathing while suppressing anaerobic breathing as much as possible.

The internal carbon dioxide concentration of the package is preferably 20% by volume or more, and more preferably 23% by volume or more.
Although there is no particular upper limit to the internal carbon dioxide oxygen concentration of the package, it is preferably 50% by volume or less and more preferably 45% by volume or less from the viewpoint of effective suppression of odor. 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, when producing a package, it is possible to appropriately adjust the carbon dioxide concentration in the gas filled in the packaging container. For example, when producing a package, the carbon dioxide concentration in the gas filled in the packaging container is preferably 30% by volume or more.
The internal carbon dioxide concentration of the package is also 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 including lettuce in 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, and 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, the amount of carbon dioxide generated by the respiration of fruits and vegetables can be adjusted.
The oxygen concentration and the carbon dioxide concentration in the packaging container can be measured by, for example, Dansensor's food packaging O ₂ / CO ₂ analyzer, Check Mate 3.

The internal oxygen concentration of the package is preferably 6.5% by volume or more, and more preferably 7.2% by volume or more.
Although there is no particular upper limit to the internal oxygen concentration of the package, it is preferably 80% by volume or less, and preferably 70% by volume or less from the viewpoint of more effectively suppressing deterioration of the appearance such as browning. It 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, when producing a package, the oxygen concentration in the gas filled in the packaging container can be adjusted as appropriate. For example, when producing a package, the oxygen concentration in the gas filled in the packaging container is preferably 12% by volume or more.
Also, the internal oxygen concentration of the package can be determined by adjusting the amount of oxygen that flows out of or out of the package and / or the amount of oxygen consumed by respiration of fruits and vegetables including lettuce in the package. It is possible to adjust to the density 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 packaging body, and the amount of fruits and vegetables 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.

In the package of this invention, it is preferable to suppress browning of lettuce and generation | occurrence | production of a strange odor over 72 hours under the conditions of 10 degreeC after sealing of a package.
This preferred embodiment suppresses the browning of lettuce and the generation of off-flavor for 72 hours after sealing the package, thereby maintaining the freshness of the fruits and vegetables containing lettuce at a high level over a long period considered to be sufficient for distribution. Since it can be maintained, it has high practical and economic value.
In this preferred embodiment, it is more preferable to suppress browning of lettuce and generation of off-flavor over 96 hours after sealing of the package, and more preferable to suppress over 120 hours after sealing of the package. It is particularly preferred to suppress for 144 hours after body sealing.

The internal carbon dioxide concentration of the package of the present invention after being held for 72 hours under the condition of 10 ° C. after sealing of the package is preferably 20% by volume or more. Inhibition of browning of lettuce in fruits and vegetables contained in the packaging container and prevention of off-flavor by having an internal carbon dioxide concentration of not less than 20% by volume after holding for 72 hours at 10 ° C. after sealing. It is possible to achieve both at a higher level over a long period of time.
The internal carbon dioxide concentration after holding for 72 hours under the condition of 10 ° C. after sealing the package of the present invention 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 since the packaging container was sealed after the fruits and vegetables containing lettuce were stored in the packaging container. That is, “after holding the package body at 10 ° C. for 72 hours” means that after storing the fruit and vegetables containing lettuce in the packaging container, the packaging container is sealed and then the condition at 10 ° C. The state immediately after holding for 72 hours.

  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 with time due to the outflow of carbon dioxide to the outside. Therefore, in this embodiment in which 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 from 0 to 72 hours after sealing. high. 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-flavors.

The internal carbon dioxide concentration in 72 hours at 10 ° C. after sealing the package can be adjusted to a desired range by adjusting the carbon dioxide concentration immediately after packaging. More specifically, when producing a package, it is possible to appropriately adjust the carbon dioxide concentration in the gas filled in the packaging container. For example, when producing a package, the carbon dioxide concentration in the gas filled in the packaging container is preferably 12% by volume or more.
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 including lettuce in the package. Of course, 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, and 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, the amount of carbon dioxide generated by the respiration of fruits and vegetables can be adjusted.

The internal oxygen concentration after holding for 72 hours under the condition of 10 ° C. after sealing of the package of the present invention is preferably 10% by volume or more. Generation of off-flavor from lettuce in the fruits and vegetables contained in the packaging container is more effective over a long period of time when the internal oxygen concentration after holding for 72 hours at 10 ° C. after sealing is 10% by volume or more. To be suppressed.
The internal oxygen concentration of the package of the present invention after holding for 72 hours at 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 for 72 hours under the condition of 10 ° C. after sealing the package can be adjusted to a desired range by adjusting the oxygen concentration immediately after packaging. More specifically, when producing a package, the oxygen concentration in the gas filled in the packaging container can be adjusted as appropriate. For example, when producing a package, the oxygen concentration in the gas filled in the packaging container is preferably 50% by volume or more.
In addition, the internal oxygen concentration after holding for 72 hours under the condition of 10 ° C. after sealing the package 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 flowing in from the packaging body, and the amount of fruits and vegetables 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 realizing the above-mentioned desired internal carbon dioxide concentration and internal oxygen concentration, it is preferable that nitrogen is further enclosed in the packaging container. This is because the internal carbon dioxide concentration and the internal oxygen concentration can be independently adjusted by sealing nitrogen together when the packaging container is sealed.

In addition, in order to achieve 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, 4500 cc / m ² / atm / day at 20 ° C. and 90% RH, which is a preferred embodiment The following packaging containers can be manufactured at a relatively low cost with a relatively simple configuration 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, and particularly preferably 2500 cc / m ² / day or less at 20 ° C. and 90% RH.
Although there is no particular lower limit to the oxygen permeability of the polymer film, it is 500 cc / m ² / day or more at 20 ° C. and 90% RH as long as a normal polymer film without gas barrier coating or the like is used. It is common to become.
Further, from the viewpoint of more effectively preventing the generation of off-flavors 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 is preferably 750 cc / m ² / day or more, particularly preferably 900 cc / m ² / day or more at 20 ° C. and 90% RH.

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

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

As described above, the oxygen permeability of the polymer film can be adjusted by appropriately raining the material, thickness, processing method, etc. of the polymer film. 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 a preferred embodiment of the present invention can be realized without providing an opening in the polymer film.
Since it is not necessary to provide an opening in the polymer film, the manufacturing process is simpler and less expensive, and it is not necessary to precisely control the size, shape, etc. of the opening.
The absence of an opening in the polymer film can be confirmed, for example, by the fact that the polymer film constituting the packaging container does not have a through-hole that can be confirmed with an ink leak checker.

On the other hand, in one embodiment of the present invention, when it is necessary to use a thick polymer film or a polymer material having a low oxygen permeability, the polymer film is used to achieve a desired oxygen permeability. You may use together the opening provided in. The shape of the opening is not particularly limited, and may be circular, substantially circular, or may be slit. 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 substances 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. In that case, the openings occupying the effective area of the polymer film The number of For example, a slit-like opening having a length of 2 mm, and in the closed state, the width as a through-hole cannot be visually recognized with an optical microscope (Olympus, model SZH-131) at a magnification of 4 times. When a product is provided, there is an effect of increasing the oxygen permeability of about 1000 cc / m ² / day / atm for every 200 mm × 200 mm packaging container. 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 this embodiment, suitable oxygen permeability, flexibility when forming a packaging container, strength, transparency, economy, oxygen permeation caused by the opening. From the viewpoint of accuracy and ease in forming the opening, a suitable thickness may be selected as appropriate 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, and particularly preferably 15 to 45 μm.

  The material of the polymer film is not particularly limited, but a polymer used in a 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, natural polymers 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 polymer film is preferably made of a thermoplastic resin. Examples of the thermoplastic resin include homopolymers or copolymers of α-olefins such as ethylene, propylene, 1-butene, 1-hexene, 4-methyl / 1-pentene, and 1-octene. Specifically, ethylene polymers such as high pressure method low density polyethylene, linear low density polyethylene (LLDPE), high density polyethylene, propylene homopolymer, propylene / α-olefin random copolymer, propylene block copolymer. And propylene-based polymers 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 polymetaxylene adipamide, polyvinyl chloride, polyimide, and ethylene / acetic acid. Examples thereof include a vinyl copolymer or a saponified product thereof, polyvinyl alcohol, polyacrylonitrile, polycarbonate, polystyrene, ionomer, polylactic acid, polybutylene succinate and the like, 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 are excellent in rigidity and transparency. As the thermoplastic resin, an ethylene polymer and a propylene polymer are more preferable because they are lightweight and excellent in film processability, and a propylene polymer is more preferable from the viewpoint of flexibility and transparency.

<Propylene polymer>
Examples of the propylene polymer include a propylene homopolymer (also referred to as homo PP) manufactured and sold under the name of polypropylene, and a propylene / α-olefin random copolymer (also referred to as random PP). And crystalline polymers mainly composed of propylene such as a mixture of propylene homopolymer and low crystalline or amorphous propylene / ethylene random copolymer (also called block PP). . Further, the propylene-based polymer may be a mixture of propylene homopolymers having different molecular weights, and is composed of 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 polymer include polypropylene, propylene / ethylene copolymer, propylene / ethylene / 1-butene copolymer, propylene / 1-butene copolymer, and propylene / 1-pentene copolymer. Copolymer of propylene such as propylene / 1-hexene copolymer and propylene / 1-octene copolymer as a main monomer and at least one selected from ethylene and α-olefin having 4 to 10 carbon atoms Coalescence is mentioned. These may use 1 type and may use 2 or more types together.

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 propylene-based polymer MFR (ASTM D1238 load 2160 g, temperature 230 ° C.) is preferably 0.5 to 60 g / 10 minutes, more preferably 0.5 to 10 g / 10 minutes, and more preferably 1 to 5 g / 10 minutes. Is more preferable.

<Ethylene polymer>
Examples of the ethylene polymer include a homopolymer of ethylene, a copolymer of ethylene as a main monomer and at least one α-olefin having 3 to 8 carbon atoms, an ethylene / vinyl acetate copolymer, Saponifications 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 thereof include copolymers of ethylene as a main monomer, such as a copolymer and an ethylene / 1-octene copolymer, and at least one kind of an 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 method 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 polymer may be an ethylene homopolymer 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 laminate may be a blend and / or laminate of any of the above polymers, and any of the above polymers and a material other than the polymer. Blends and / or laminates. That is, the polymer film is a material other than a polymer, such as a heat stabilizer (antioxidant), a weather stabilizer, an ultraviolet absorber, a lubricant, a slip agent, a nucleating agent, an antiblocking agent, an antistatic agent, an antifogging agent. In addition to pigments and dyes, various fillers such as talc, silica, and diatomaceous earth may be included, or a laminate of a polymer film and metal foil, paper, nonwoven fabric, or the like may be used.

In the present invention, the polymer film constituting the packaging container may be an unstretched film or a stretched film.
From the viewpoint of mechanical strength and the like, stretched films of various polymers can be suitably used.
In particular, a stretched film (stretched polypropylene film) using a propylene-based polymer is excellent in mechanical strength, transparency, heat resistance and the like, and therefore can be particularly preferably used in the packaging container 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 a non-stretched film is particularly preferably used from the viewpoint of heat sealability and the like. be able to.
Examples of the polymer film that is particularly suitable as the polymer film constituting the packaging container in the present invention include a stretched polypropylene film, a polyethylene film, and a laminate of the stretched film and the 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. Moreover, when obtaining a biaxially stretched film as a stretched polypropylene film, it can also be easily manufactured 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 stretched 8 to 10 times in the transverse direction using a tenter mechanism, and the film thickness is finally adjusted. Or 20 to 40 μm, or by stretching 5 to 10 times (25 to 100 times in terms of surface magnification) in the longitudinal direction and the transverse direction, respectively.
<Polyethylene film>
The polyethylene film preferably used in the present invention is a film containing the ethylene polymer. Various known molding methods can be used for the polyethylene film, but cast molding by extrusion using an extruder is preferred from the viewpoint of production efficiency.

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

<Laminated body of stretched film and polyethylene film>
A laminate of a stretched film and a polyethylene film preferably used in the present invention is obtained by laminating the polyethylene film layer and the stretched film layer. The polyethylene film may be stretched in one or two directions, but is preferably an unstretched film from the viewpoint of the stability of the mechanical strength of the packaging bag.
Dry lamination is performed by adhering a stretched film and a polyethylene film prepared in advance with an adhesive. From the viewpoint of adhesion stability, the surface of the stretched film to which the adhesive is applied should be corona treated. preferable. Specifically, the surface tension of the film surface after the corona treatment is preferably 35 mN / m or more, more preferably 40 mN / m or more, from the viewpoint of adhesion stability.

These polymer films may be stretched, antifogged or printed, and include inorganic antibacterial agents such as silver and copper, and organic antibacterial agents such as chitin, chitosan, and allylisothiocyanate. The agent may be applied, or these may be kneaded in 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 amount of a specific surfactant is present on the surface of the polymer film, or the polymer film may have a specific amount of a specific surfactant to have an antibacterial function. For example, it is preferable that at least one compound selected from the group consisting of palmityl diethanolamine, stearyl diethanolamine, glycerol monolaurate and diglycerol monolaurate is present on at least one surface of the polymer film, it is particularly preferred that one compound 0.002~0.5g / ^{m 2} is present. Alternatively, the polymer film preferably contains at least one compound selected from the group consisting of palmityl diethanolamine, stearyl diethanolamine, glycerol monolaurate, and glycerol monocaprate, 0.001 to 3 parts by mass It is particularly preferable to contain.
When a specific amount of a specific surfactant is present 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, Suppression of the growth of bacteria suppresses the growth of germs in the dew (drip) and exhibits an antibacterial function.

From the viewpoints of transparency, flexibility, cost, etc., it is particularly preferable to use a stretched polypropylene film or a laminate of a stretched polypropylene film and a polyethylene film that has been widely used in the art as a polymer film. . Since these films are generally excellent in heat sealability, productivity is good in the production of packaging containers.
In this case, when the stretched propylene film is used alone, the thickness 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 thickness is preferably 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. Examples thereof include a cellophane film coated with an acrylic resin and a film obtained by laminating polyethylene terephthalate (PET) with linear low density polyethylene (LLDPE) polystyrene and EVA, and these can be used as suitable polymer films.

The packaging body of the present invention can be produced by storing the fruits and vegetables containing the lettuce in the packaging body of the present invention and appropriately adjusting the internal carbon dioxide concentration and the internal oxygen concentration. It is possible to carry out the method for maintaining the freshness of fruits and vegetables, which is an embodiment of the present invention.
Hereinafter, the manufacturing method of the package of this invention is demonstrated to the case where the fruits and vegetables containing the lettuce accommodated in a packaging container are cut lettuce.

  First, in the pretreatment process, lettuce is manually removed to remove the outer leaves, divide into 2 to 4 parts, and remove the core. Lettuce transported by the conveyor is cut by a slicer and cooled in a washing tank filled with cold water, and also cooled by hypochlorous acid at 80 to 120 ppm for 10 to 20 minutes based on the "Manufacturing Sanitation Management Manual" (Ministry of Health and Welfare). After washing with water, it is dehydrated with a centrifugal dehydrator or dry air. The dehydrated cut lettuce is packed in a packaging container (not sealed on one side) containing the polymer film used in this embodiment, and after packaging, the packaging container is sealed to maintain the freshness of the cut lettuce. A package is produced.

From the viewpoint of maintaining the freshness of the cut lettuce, it is preferable to use a sharp blade and reduce the number of scratches on the cut surface.
In addition, as the cut width is narrower, the cutting area increases and it becomes more difficult to maintain freshness. From the viewpoint of maintaining freshness, it is preferable that the cut width is wider as long as it matches the form of demand.
Furthermore, if many germs are attached to the cut lettuce from the beginning, it is more difficult to maintain freshness. Therefore, it is preferable to reduce the adherence of germs as much as possible by washing the cut lettuce well. Washing is particularly effective for maintaining freshness because it not only reduces the adhesion of various bacteria, but also has the effect of removing cell fluids and the like that contain highly active enzymes and the like and can cause discoloration.
In addition, it is important for maintaining the freshness to sufficiently remove water adhering to the surface of the cut lettuce after washing.
This is because by making the water appropriate, the growth of germs in the extra small water droplets can be suppressed. More specifically, for example, based on the “Manufacturing Sanitation Management Manual for Large-scale Cooking Facilities” (Ministry of Health and Welfare), after 80-120 ppm for 10-20 minutes of hypochlorous acid cleaning, “Analytical Methods for Nutrition Labeling in Nutrition Labeling Standards” (consumers It is preferable that the moisture content measured based on the weight loss when reduced-pressure drying is performed at 70 ° C. for 5 hours based on the government) is in the range of 20% to less than 30%. Even if the water is drained by standing after washing, the surface of the cut lettuce is often still attached to the surface, so remove water using a centrifugal dehydrator, etc., and dry with dry air. Is effective.

In the production of the fruit and vegetable freshness-keeping package of this 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. Then, 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 of the packaging container, which is advantageous in maintaining freshness.
The carbon dioxide concentration of the gas introduced in the 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 embodiment is more preferably 10% by volume or more, more preferably 30% by volume or more, and particularly preferably 45% by volume or more. There are no particular limitations on the other components of the gas introduced in the above embodiment, but it is preferable to use nitrogen from the viewpoints of availability, small influence on the human body, fruits and vegetables, and the like.
Further, from the viewpoint of improving efficiency in the process of distribution, space saving, exclusion of specific gas, etc., deaeration may be performed before or at the time of sealing the packaging container.

The packaging body of the present invention may contain only fruits and vegetables containing lettuce in the packaging container, or may contain other members.
For example, in addition to fruits and vegetables, a hygroscopic agent and / or an antibacterial agent may be stored in the packaging container.
There is no limitation in particular in a moisture absorbent, The well-known or commercially available material which has a moisture absorption effect or a humidity control 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 calcined alum, or a mixture thereof. For example, but not limited to.
Among these, it is particularly preferable to use activated carbon which has relatively little concern about the influence on fruits and vegetables and the use of fruits and vegetables near foods. The activated carbon can be either powdered or granular, and the raw material can be anything from coconut husk, sawdust, charcoal, bamboo charcoal, lignite, peat, diamond, and petroleum pitch. The activated carbon is preferably wrapped in non-woven fabric, cellophane, paper, etc. for each unit used, but the activated carbon itself may be in the form of a fiber. The activated carbon packaging material is preferably a heat-sealable material such as a non-woven fabric made of a synthetic resin. However, any material such as paper or natural fiber can be used as long as it has water vapor permeability and does not spill activated carbon. no problem.

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

  Hereinafter, the present invention will be specifically described with reference to Examples / Comparative Examples. It should be noted that the present invention is not limited in any way by the following examples.

In the following examples / comparative examples, each characteristic was evaluated by the following method.
(With or without opening)
After injecting the red penetrant (Mitsubishi Gas Chemical Co., Ltd., trade name: Ageless Seal Check Spray) into the packaging container, set the scale of the heating condition 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 an opening was confirmed by the presence or absence of the transfer of the ink to paper.
(Oxygen permeability)
First, a bag having an inner size of 170 mm × 235 mm was formed by the following method.
One film is folded almost equally into two, approximately 5 mm wide, and heat sealing is performed with an impulse sealer (manufactured by Fuji Impulse Co., product number Fi-200-10WK) with the heating condition scale set to 3, and the heat sealing is performed. Heat seal the whole of one side that is almost perpendicular to the heat seal side so that the side is almost in the center, except the end of about 2 cm that is one communicating part of the other side, and the inner dimension is 170 mm × A 235 mm bag was formed.
Next, nitrogen gas was injected from the communication portion, and after the bag was saturated, almost all the gas in the bag was discharged from the communication portion. After repeating this operation five times, nitrogen gas was injected to saturate the inside of the bag with nitrogen gas, and the communicating portion was heat sealed with the impulse sealer under the same conditions. The bag saturated with nitrogen gas was left 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 the gas in the bag was sampled, and the oxygen concentration in the bag was measured with a zirconia oxygen concentration meter for food packaging (model number LC-750F, manufactured by Toray Engineering Co., Ltd.). Furthermore, the volume of the gas in the bag was measured, and the oxygen permeability was calculated from the following formula.
(Expression) Oxygen permeability = change in internal oxygen concentration (%) / 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 the 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 (model number LC-750F, manufactured by Toray Engineering Co., Ltd.).
(Carbon dioxide concentration / oxygen concentration)
It was measured by Dan Messor's food packaging O ₂ / CO ₂ analyzer, Check Mate 3.
(appearance)
The package was opened, the fruits and vegetables taken out were arranged, and the area of the entire browning portion was evaluated visually with n = 3 centering on the lettuce cross section.
The evaluation criteria are as follows. In addition, the presence or absence of mold was also observed.
A: No browning and no problem Ax: No browning but part of the cross section is thin and red but almost inconspicuous B: Although browning is present, it is slightly noticeable at 10% or less of the entire cross section Bx: Browning Although it is conspicuous at 20% or less of the entire cross section C: Although browning is 30% or less of the entire cross section, it is quite conspicuous but can be sold D: Although browning is present, it is 50% or less of the entire cross section Distinguishable by conspicuous consumers E: Large browning, clearly unsaleable to consumers (odour)
When the package was opened, the face was brought close to it and the inside smell was smelled, and sensory evaluation was performed with n = 3.
The evaluation criteria are as follows.
A: There is no problem in the fresh state B: There is a little smell but it can be said that it is fresh C: The state is strong but it is in the same state as the market and can be sold D: The state is more smelly and the consumer cares E: More smelly and unsaleable

(Comparative Example 1)
Two OPP (biaxially stretched polypropylene) films with a thickness of 40 μm are overlapped, three sides are sealed with heat sealing and cut, and one side is unsealed packaging bag (170 mm × 235 mm, inner dimension Area: 799 cm ² ).
When the presence or absence of an opening in the film was observed, it was confirmed that there was no opening. The oxygen transmission rate of the film was 1000 CC / m ² / atm / day.
78 g of lettuce was sealed in the packaging container, filled with nitrogen, and then heat sealed to prepare a package. The package was stored at 10 ° C., and the internal oxygen concentration and the internal carbon dioxide concentration were measured every day to evaluate the odor and appearance of cut lettuce.
The results are shown in Table 1.

Example 1
A package was produced and evaluated in the same manner as in Comparative Example 1 except that instead of nitrogen, a mixed gas of 70% oxygen and 30% carbon dioxide was enclosed.
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 instead of nitrogen, a mixed gas of 50% oxygen and 50% carbon dioxide was enclosed.
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 encapsulated instead 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 30 μm thick polyethylene film was used instead of the 40 μm thick OPP (biaxially stretched polypropylene) film.
When the presence or absence of an opening in the film was observed, it was confirmed that there was no opening. 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 hole having a diameter of 300 μm was provided in an OPP (biaxially oriented polypropylene) film having a thickness of 40 μm.
The oxygen permeability 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 holes having a diameter of 300 μm were provided in a 40 μm thick OPP (biaxially stretched polypropylene) film.
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 a 40 μm thick OPP (biaxially stretched polypropylene) film.
The oxygen permeability of the film was 30000 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 instead of nitrogen gas, a mixed gas of oxygen: 14.7% by volume / nitrogen: 55.3% by volume / carbon dioxide: 30% by volume was filled. And evaluated.
The results are shown in Table 1.

  In the packaging body of each example that satisfies the conditions of the present invention predetermined internal oxygen concentration and internal carbon dioxide concentration, browning of cut lettuce and generation of off-flavor are effectively suppressed for at least 72 hours after sealing, and the effect Was maintained until 144 hours. On the other hand, in each comparative example, at least 48 hours at the latest, deterioration occurred in at least one of the appearance and off-flavor, and the commercial value of cut lettuce was partially impaired.

  The package of the present invention has a practically high value, for example, it is effective for maintaining the freshness of the fruits and vegetables that contain lettuce such as cut lettuce, which has high economic value, for both long-term suppression of browning and prevention of off-flavors. It has high applicability in various fields of industries such as food processing, distribution, and dining out.

Claims (14)

  A package comprising a vegetable container containing lettuce in a packaging container comprising 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. Packaging body. The package according to claim 1, wherein the packaging container has an oxygen permeability of 4500 cc / m ² / atm / day or less at 20 ° C and 90% RH.   The package according to claim 1, wherein browning of the lettuce and generation of a strange odor are suppressed over 72 hours under a condition of 10 ° C. after sealing of the package.   The package according to any one of claims 1 to 3, wherein the internal carbon dioxide concentration after holding the package at 72C for 72 hours after sealing is 20% by volume or more.   The package according to any one of claims 1 to 4, wherein the internal oxygen concentration after holding for 72 hours at 10 ° C after sealing the package is 10% by volume or more.   The package according to any one of claims 1 to 5, wherein nitrogen is further sealed in the packaging container.   The package according to any one of claims 1 to 6, wherein the packaging container does not have a through-hole that can be confirmed by an ink leakage checker.   The package according to any one of claims 1 to 7, wherein the polymer film has a thickness of 10 to 50 µm.   The package according to any one of claims 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.   The package according to any one of claims 1 to 9, 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 10, wherein the lettuce is cut lettuce.   The package according to any one of claims 1 to 11, further comprising a hygroscopic agent and / or an antibacterial agent. A step of storing fruit 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; A method for maintaining the freshness of fruits and vegetables, comprising: a step of adjusting the carbon dioxide concentration of the product to 20% by volume or more and an oxygen concentration of 10% by volume or more; and a step of sealing the packaging container. The method for maintaining freshness of fruits and vegetables according to claim 13, wherein nitrogen is enclosed together in the step of setting the carbon dioxide concentration in the packaging container to 20% by volume or more and the oxygen concentration to 10% by volume or more.