JP2019177917A - Package storing vegetables and fruits, and method for retaining freshness of vegetables and fruits - Google Patents

Abstract

To provide a package that stores vegetables and fruits, including lettuce, in a packaging container, wherein it can suppress browning of the vegetables and fruits including lettuce effectively, without requiring excessive low oxygen concentrations.SOLUTION: The present invention provides a package that stores vegetables and fruits, including lettuce, in a packaging container composed of a polymer film. The ratio between a vitamin C content C(ppm) and a chlorophyll content C(ppm) of the lettuce, C/C(ppm/ppm), 144 hours after the sealing of the package, is 0.85-2.00.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 containing a polymer film, and the lettuce contains The present invention relates to a package having a specific relationship between the amounts of vitamin C and chlorophyll.

In order to maintain the freshness of fruits and vegetables such as lettuce, and in particular to prevent discoloration such as browning, it has traditionally been possible to suppress the respiration of fruits and vegetables by controlling the oxygen concentration in the packaging container containing the fruits and vegetables. It was broken. For example, Patent Document 1 proposes that the oxygen concentration in the packaging container be 1 to 3%.
However, even if the oxygen concentration is strictly controlled, the browning of lettuce may still not be suppressed, and a technique that can stably suppress the browning of lettuce for a long period of time has been demanded.
In addition, if the oxygen concentration is kept low, there is a problem that anaerobic breathing such as lettuce produces alcohol and aldehyde, resulting in off-flavors, and there is a strong demand for a technique for preventing discoloration that does not require an excessively low oxygen concentration. It was.

Japanese Patent Application Laid-Open No. 8-228673

In view of the limitations of the prior art described above, the present invention is a package that contains fruits and vegetables containing lettuce in a packaging container, and the browning of the fruits and vegetables containing lettuce without requiring excessively low oxygen concentration. It is an object of the present invention to provide a package that can more effectively suppress the above.
As a result of intensive studies, the present inventors have found that the amount of chlorophyll and vitamin C contained in lettuce and the like have a strong correlation with discoloration of lettuce, and further, the content of chlorophyll in lettuce and vitamin C It has been found that browning of lettuce is stably suppressed when the ratio to the content is within a predetermined range, and the present invention has been completed.

That is, the present invention
[1]
A package formed by containing fruits and vegetables containing lettuce in a packaging container containing a polymer film, and the vitamin C content C _vc (ppm) of the lettuce at 144 hours after sealing of the package the ratio _C vc _/ C ch of the chlorophyll content _{C ch (ppm) (ppm /} ppm) is from 0.85 to 2.00, the package is.

Hereinafter, [2] to [16] are each one aspect or preferred embodiment of the present invention.
[2]
The package according to [1], wherein the lettuce has a chlorophyll content of 19.5 ppm or more and 22.5 ppm or less, and a vitamin C content of 30 ppm or more.
[3]
The packaging according to [1] or [2], wherein the lettuce has a chlorophyll content of 18 ppm or more and 22.5 ppm or less and a vitamin C content of 30 ppm or more at 144 hours after sealing the packaging. body.
[4]
The package according to any one of [1] to [3], which effectively suppresses browning of the fruits and vegetables containing the lettuce over 144 hours after sealing the package.
[5]
The package according to any one of [1] to [4], wherein the oxygen concentration in the packaging container is 0.0 to 10.0% by volume.
[6]
The package according to any one of [1] to [5], wherein a carbon dioxide concentration in the packaging container is 2.0 to 7.0% by volume.
[7]
The packaging body according to any one of [1] to [6], wherein nitrogen is further enclosed in the packaging container.
[8]
The package according to any one of [1] to [7], wherein the polymer film has an oxygen permeability of 10,000 cc / m ² / atm / day or less at 20 ° C. and 90% RH.
[9]
The packaging body according to any one of [1] to [8], wherein the packaging container does not have a through hole that can be confirmed by an ink leakage checker.
[10]
The package according to any one of [1] to [9], wherein the polymer film has a thickness of 15 to 45 μm.
[11]
The package according to any one of [1] to [10], wherein the polymer film is a stretched polypropylene film, a polyethylene film, or a laminate of a stretched film and a polyethylene film.
[12]
The package according to any one of [1] to [11], wherein the polymer film contains at least one antibacterial agent or is coated with at least one antibacterial agent.
[13]
The package according to any one of [1] to [12], wherein the lettuce is cut lettuce.
[14]
The package according to any one of [1] to [13], further containing a hygroscopic agent and / or an antibacterial agent.
[15]
Maintaining the freshness of fruits and vegetables, comprising the steps of storing fruit and vegetables containing lettuce in a packaging container comprising a polymer film, forming a package and sealing the package, and holding the package at 2 to 15 ° C. A ratio C _vc / C _ch (ppm / ppm) of vitamin C content C _vc (ppm) and chlorophyll content C _ch (ppm) of the lettuce 144 hours after sealing of the package The freshness preservation method of the said fruits and vegetables which is 0.85-2.00.
[16]
The method for maintaining freshness of fruits and vegetables according to [15], further comprising the step of enclosing nitrogen in the packaging container.

  According to the present invention, the browning of lettuce is stably and effectively suppressed over a long period of time without depending on excessively low oxygen concentration and beyond the limits of the prior art, and the freshness of fruits and vegetables containing lettuce is maintained. 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 comprising a vegetable container containing a lettuce in a packaging container comprising a polymer film, and the vitamin C content C _{vc of the} lettuce at 144 hours after the package is sealed. the ratio between (ppm) and the chlorophyll content of _{C ch (ppm) C vc /} C ch (ppm / ppm) is 0.85~2.00 (ppm / ppm), a packaging body.
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, for example, within the range of 500 to 10,000 cc / m ² / atm / day. In the range of 750 to 5000 cc / m ² / atm / day, more preferably in the range of 900 to 2500 cc / m ² / atm / day. A thing within the range of 950-1500cc / m < ² > / atm / day can be used especially preferably. An appropriate oxygen permeability may be selected in consideration of the amount and type of fruits and vegetables to be stored, a desirable internal oxygen concentration, and the like.

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 the case where all of the fruits and vegetables are composed of lettuce and the case where some of the fruits and vegetables are composed 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.
In other words, “lettuce” here is a type called scraping chisha or cutting lettuce typified by sanchu, etc., where the leaves are scraped from the stem; typified by romaine lettuce, etc. 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, roots such as yams, 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. In view of the advantage of the invention that oxygen concentration and respiration can be controlled by the packaging container, the present invention can be particularly suitably used for maintaining the freshness of fruits and vegetables that are substantially respiring.

In the present invention, the form of lettuce stored in the packaging container and kept fresh is not particularly limited. 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. And / or specifically and / or cut the lettuce after washing with hypochlorous acid for 10 to 20 minutes based on the “Manufacturing Sanitation Management Manual” (Ministry of Health and Welfare). Analytical method "(Consumer Affairs Agency) Based on the weight loss when dried under reduced pressure at 70 ° C for 5 hours, the moisture content measured based on the range of 20-30% is to prevent odor generation and browning It is particularly preferable from the viewpoint of the balance of preventing the appearance deterioration.
In these cutting, washing, dehydration and / or drying processes, since the vitamin C content and chlorophyll content of lettuce can fluctuate, the conditions of these processes can be set appropriately. It is one method for appropriately controlling the vitamin C content and the chlorophyll content of sucrose.

  Here, the demand for cut vegetables has increased in recent years because they 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 stored with lettuce, if present), the preferred oxygen concentration for maintaining freshness varies to some extent, and accordingly, preferred oxygen permeability, and a polymer film that provides such oxygen permeability However, setting these appropriately is one method for appropriately controlling the vitamin C content and chlorophyll content of the lettuce.

The ratio C _vc / C _ch between the vitamin C content C _vc and the chlorophyll content C _ch of lettuce in the fruits and vegetables stored in the package of the present invention 144 hours after sealing the package is 0.85. -2.00 (ppm / ppm).
When the ratio of the vitamin C content C _vc to the chlorophyll content C _ch in the lettuce is within the above range, the browning of the lettuce should be stably prevented for a long period of time at a high level exceeding the limit of the prior art. Can do. For example, lettuce browning can be prevented for 144 hours after sealing the package. At that time, it is not necessary to excessively reduce the oxygen concentration in the package.
The ratio C _vc / C _ch between the vitamin C content C _vc and the chlorophyll content C _ch of lettuce 144 hours after sealing of the package is preferably 0.90 to 1.98, more preferably 0.92. ˜1.96, particularly preferably 0.94 to 1.94.

  The vitamin C content of lettuce in the fruits and vegetables stored in the package of the present invention is preferably 30 ppm or more. Since the vitamin C content of lettuce may vary with the passage of time after sealing, if the elapsed time after sealing is specified, for example, the vitamin C content of lettuce at 144 hours after sealing of the package is 30 ppmg. The above is preferable.

Vitamin C content C _vc of lettuce is adjusted to a certain degree of accuracy by adjusting the initial vitamin C content of lettuce stored in the package, assuming changes in vitamin C content during storage in the package. Can be adjusted to a desired value. For example, since vitamin C often decreases over time during storage, lettuce containing vitamin C more frequently than desired may be selected in anticipation of the decrease, or the lettuce before storage Lettuce containing vitamin C more frequently than desired may be prepared in steps such as cutting, washing and dehydration.

Moreover, you may adjust the vitamin C content after predetermined time progress to a desired value by adjusting the storage temperature of a package, the oxygen concentration in a package, etc. suitably.
For example, vitamin C tends to decrease with time as the internal oxygen concentration of the package increases, so that the initial vitamin C content of lettuce and the desired vitamin C content are taken into account. The oxygen concentration can be set.
Further, since vitamin C tends to decrease with time as the storage temperature increases, the storage temperature can be set in consideration of the initial vitamin C content of lettuce and the desired vitamin C content.

  The vitamin C content of lettuce in the fruits and vegetables contained in the package can be measured by a method conventionally known in the art. For example, lettuce is extracted from the package, and after extraction with metaphosphate, It can be measured by liquid chromatography, and more specifically, for example, can be measured by the method described in the examples of the present application.

  The chlorophyll content of lettuce in the fruits and vegetables stored in the package of the present invention is preferably 19.5 ppm or more and 22.5 ppm or less. Since the chlorophyll content of lettuce may vary with the passage of time after sealing, if the elapsed time after sealing is specified, for example, the chlorophyll content of lettuce at 144 hours after sealing of the package is 19.5 ppm. As mentioned above, it is preferable that it is 22.5 ppm or less.

The chlorophyll content C _ch of lettuce is desired to a certain degree of accuracy by adjusting the initial chlorophyll content of lettuce stored in the package, assuming changes in the chlorophyll content during storage in the package. Can be adjusted to the value. For example, chlorophyll often decreases over time when stored in the air at a temperature of about 10 ° C., so even if lettuce containing more chlorophyll than the desired value is selected in anticipation of the decrease. Alternatively, lettuce containing chlorophyll more than desired may be prepared in steps such as cutting, washing and dehydrating lettuce before storage.

Moreover, you may adjust the chlorophyll content after predetermined time progress to a desired value by adjusting the storage temperature of a package, the carbon dioxide in a package, etc. suitably.
For example, since chlorophyll tends to increase with time if the internal carbon dioxide concentration of the package is high, the internal chlorophyll content of the package is considered in consideration of the initial chlorophyll content of lettuce and the desired chlorophyll content. The carbon concentration can be set.
Moreover, since chlorophyll tends to decrease with time as the storage temperature is high, the storage temperature can be set in consideration of the initial chlorophyll content of lettuce and the desired chlorophyll content.

  The chlorophyll content of lettuce in the fruits and vegetables contained in the package can be measured by methods conventionally known in the art. For example, lettuce is taken out from the package, and after acetone extraction, the spectrophotometric method is used. More specifically, for example, it can be measured by the method described in Examples of the present application.

Packaging The internal oxygen concentration of the packaging body of the present invention is not particularly limited, but is preferably, for example, 0.0 to 10.0% by volume.
Since the internal oxygen concentration may vary with the passage of time after sealing, if the elapsed time after sealing is specified, for example, the internal oxygen concentration after holding for 72 hours at 10 ° C. after sealing of the package is 0. The content is preferably 0 to 10.0% by volume, particularly preferably 7.0% by volume or less. When the internal oxygen concentration of the package is within the above range, it becomes easy to control the vitamin C content and chlorophyll content of lettuce in the fruits and vegetables contained in the packaging container, and the browning of the lettuce is more effectively suppressed. it can. In this preferred embodiment, the browning of lettuce in the fruits and vegetables and preferably further the generation of odor can be suppressed for a long period of time after sealing the package, preferably over 144 hours.

The internal oxygen concentration of the package of this preferred embodiment after holding the package for 72 hours at 10 ° C. is more preferably 3.5% by volume or less, and 1.5% by volume or less. Is more preferably 0.5% by volume or less, and particularly preferably 0.3% by volume or less.
The oxygen concentration inside the package can be specified by, for example, sampling the gas inside the package with a sampling needle tube and measuring the oxygen concentration with a zirconia oxygen concentration meter for food packaging.
Here, “after packaging” means the elapsed time when the packaging container is stored and then kept at a predetermined temperature after storing the fruit and vegetables containing lettuce. “After holding at 10 ° C. for 72 hours after sealing” means a state immediately after holding the vegetables and fruits containing lettuce in the packaging container and then holding the packaging container at 10 ° C. for 72 hours.

In the package according to this preferred embodiment, the internal oxygen concentration is remarkably lower than the oxygen concentration in the atmosphere. Therefore, the internal oxygen concentration often increases over time due to the intrusion of oxygen from the outside. Therefore, for example, in an embodiment in which the internal oxygen concentration after holding for 72 hours at 10 ° C. after sealing the package is 10.0% by volume or less, for 0 to 72 hours at 10 ° C. after sealing the package, There is a high possibility that the internal oxygen concentration is 10.0% by volume or less. Such a history of oxygen concentration is particularly preferable in order to more effectively suppress browning of lettuce and odor generation in fruits and vegetables.
In addition, from the viewpoint of suppressing respiration such as lettuce and maintaining a dormant state and suppressing oxidation of the lettuce cross section that contributes to browning, the holding temperature of the package is preferably 2 to 15 ° C, and particularly preferably 3 to 10 ° C. .
As for the history of oxygen concentration, fruits and vegetables containing lettuce immediately after sealing of the package, that is, lettuce that has been cut, washed, dehydrated and / or dried and adjusted to an appropriate amount of water after being packaged. It is preferable that the oxygen concentration in the packaging container immediately after the packaging container is sealed is 0.0 to 12.0% by volume. The oxygen concentration in the packaging container immediately after packaging is more preferably 0.0 to 6.0% by volume, and particularly preferably 0.0 to 0.5% by volume.
In addition, the integrated value of the elapsed time from the sealing of the packaging container and the internal oxygen concentration at 72 hours after sealing of the package is 504 (time × volume%) (72 hours × 7.0 volume%) or less. It is preferable that it is 252 (time x volume%) (72 hours x 3.5 volume%) or less, and 36 (time x volume%) (72 hours x 0.5 volume%). It is particularly preferred.

  From the viewpoint of realizing the preferable internal oxygen concentration described above, it is preferable that nitrogen is further enclosed in the packaging container. It is because the internal oxygen concentration immediately after packaging can be kept low by sealing nitrogen at the time of sealing the packaging container. Furthermore, by further enclosing nitrogen, the pressure in the packaging container can be kept high, the inflow of outside air having a higher oxygen concentration can be prevented, and the internal oxygen concentration can be kept low.

Although there is no restriction | limiting in particular in the internal carbon dioxide density | concentration of the package of this invention, For example, it is preferable that it is 2.0-7.0 volume%.
Since the internal carbon dioxide concentration may vary with the passage of time after sealing, if the elapsed time after sealing is specified, for example, the internal carbon dioxide concentration after holding for 72 hours at 10 ° C. after sealing of the package is determined. It is preferably from 2.0 to 7.0% by volume, particularly preferably from 1.8 to 6.8% by volume. When the internal carbon dioxide concentration of the package is within the above range, it becomes easier to control the vitamin C content and chlorophyll content of lettuce in the fruits and vegetables contained in the packaging container, and the browning of the lettuce is more effective. Can be suppressed.
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. 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.

In addition, in order to realize the above-described preferable internal oxygen concentration, it is desirable to configure the packaging container using a polymer film having an oxygen permeability of a predetermined value or less.
That is, the oxygen permeability of the polymer film used in the present invention is preferably 10000 cc / m ² / atm / day or less at 20 ° C. and 90% RH. When the oxygen permeability at 20 ° C. and 90% RH is not more than the above value, it is suitable for preventing oxygen from entering from the outside air and maintaining a low internal oxygen concentration of the package. The oxygen permeability of the polymer film used in the present invention is more preferably 5000 cc / m ² / atm / day or less at 20 ° C. and 90% RH, and preferably 3000 cc / m ² / atm / day or less. More preferably, it is particularly preferably 1500 cc / m ² / atm / day or less.
There is no particular lower limit to the oxygen permeability of the polymer film, but 500 cc / m ² / atm / day at 20 ° C. and 90% RH as long as a normal polymer film without gas barrier coating or the like is used. Generally, this is the case.
Moreover, from the viewpoint of preventing the generation of odor from the stored fruits and vegetables, the polymer film preferably has an oxygen permeability that allows the fruits and vegetables to breathe. From this viewpoint, the oxygen permeability of the polymer film is preferably 500 cc / m ² / atm / day or more at 20 ° C. and 90% RH, and more preferably 900 cc / m ² / atm / day or more. More preferably, it is particularly preferably 1000 cc / m ² / atm / day or more.

The oxygen permeability of the polymer film used in the present invention can be measured, for example, by the following method.
First, a bag having an inner 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 (a × b × 2 cm ² ) /0.21 ( (Partial pressure of oxygen)

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

As described above, the oxygen permeability of the polymer film can be adjusted by appropriately selecting the material, thickness, processing method, etc. of the polymer film. It is not necessary to provide an opening in the polymer film. For example, the oxygen permeability of 500 cc / m ² / atm / day or higher 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.
As a method of micropores, any of physical means such as a heating needle and optical means such as a laser can be used. If the hole diameter is 100 to 300 μm, the hole can be sufficiently opened even by using physical means, which is advantageous in terms of cost. Of course, it is possible to make a hole with a laser or the like, and in this case, it is possible to further precisely control the hole diameter. In the present invention, when a laser is used for micropore opening, it is preferable that the target film efficiently absorbs laser light. For example, a carbon dioxide laser, a YAG laser, a helium neon laser, an excimer laser, a U V laser light oscillator, and a semiconductor laser light oscillator can be used, but it is not particularly limited to these.
In addition, unlike the slit processing, the laser hole processing preferably used in the production of the package of the present invention has no physical contact with metal, so there is no possibility of mixing of missing blades, needles, etc., and the opening area is in the slit. Since it is constant, quality control (control of gas permeability) is easy and preferable.
For slit processing, the size of each opening and the number of openings can be appropriately set and changed as long as the oxygen permeability of the polymer film is appropriate. The number of openings in the area is a guide. For example, 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.
As laser processing, it is preferable to provide about 1 to 5 holes with a diameter of 50 to 200 μm, and the opening holes can be visually confirmed with an optical microscope (manufactured by Olympus, model SZH-131) at a magnification of 4 times. .

  There is no particular limitation on the thickness of the polymer film used in the present invention, and when an opening is provided such as suitable oxygen permeability, flexibility when forming a packaging container, strength, transparency, economy, etc. From the viewpoint of accuracy and ease in forming the part, 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 15 to 45 μm, and more preferably 20 to 40 μm.

  Although there is no restriction | limiting in particular in the material of the said polymer film, The polymer used for the film for conventional fruit and vegetables packaging can be used suitably. 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, 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-based 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.

Method for manufacturing package and method for maintaining freshness Fruit and vegetables containing lettuce are stored in a packaging container, and the ratio C _vc / C _ch (ppm / ppm) of vitamin C content C _vc and chlorophyll content C _ch of the lettuce By adjusting within a predetermined range, the package of the present invention can be manufactured, and the method for maintaining the freshness of fruits and vegetables, which is an embodiment of the present invention, can be implemented.
Browning of fruits and vegetables containing lettuce can be effectively prevented when the ratio C _vc / C _ch (ppm / ppm) is in the range of 0.85 to 2.00. The reason is not necessarily clear, but when the ratio C _vc / C _ch (ppm / ppm) is less than 0.85, since chlorophyll is contained in a relatively large amount with respect to vitamin C, lettuce depends on vitamin C. Although the action of an enzyme that promotes browning of fruits and vegetables containing sucrose is inhibited, it is considered that browning occurs in some chlorophylls because vitamin C is not present in an amount sufficient to inhibit chlorophyll browning. On the other hand, when the ratio C _vc / C _ch (ppm / ppm) exceeds 2.00, vitamin C inhibits the action of the enzyme that promotes browning, but it is not complete, so browning is noticeable in lettuce with a small amount of chlorophyll. It is estimated that it will end up.
Hereinafter, the manufacturing method of the package of the present invention will be described by taking as an example a package for maintaining the freshness of cut lettuce that has been cut, washed, dehydrated and / or dried and adjusted to an appropriate amount of water.

  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 with a slicer and cooled in a washing tank filled with cold water. The hypochlorous acid is 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 the like. 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. Even if water is drained after standing after washing, it is often effective to remove water using a centrifugal dehydrator or the like because much water is still attached to the surface of the cut lettuce.
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” It is preferable that the water 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 30%.

In addition, the fruit and vegetable freshness-keeping package of the present embodiment may be filled with nitrogen and / or deaerated after storing the fruit and vegetables containing lettuce and sealing the packaging container. By performing nitrogen sealing and / or degassing, it becomes possible to quickly reach a desired oxygen concentration designed as an equilibrium state between the oxygen permeability of the packaging container and the respiration rate of fruits and vegetables, which is advantageous for maintaining freshness. .
In addition, deaeration may be performed after sealing the packaging container from the viewpoint of improving efficiency in the process of distribution, saving space, and eliminating a specific gas.

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

The 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, and limonene 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 220 mm × 240 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 220 mm × A 240 mm bag was obtained.
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 with a sampling needle tube, and the oxygen concentration in the bag was 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 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 (1056 cm ² ) /0.21 (partial pressure of oxygen )
(Oxygen concentration / carbon dioxide concentration)
The measurement was performed using an O ₂ / CO ₂ analyzer, Check Mate 3, for food packaging manufactured by Dansensor.
(appearance)
The package was opened, the fruits and vegetables taken out were 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.
A: No browning and no problem B: Browning but less than 10% of the entire cross section, no problem level C: Browning but less than 30% of the entire cross section D: Although there is browning, the cross section Less than 50% of total, notably conspicuous and unsaleable by consumers E: Big browning, clearly unsaleable to consumers (chlorophyll content: C _ch )
80% acetone was added to the lettuce taken out from the package, and the mixture was homogenized for about 1 minute for extraction, and then centrifuged at 3000 rpm for 10 minutes. The absorbance of 663.6 nm and 646.6 nm of the supernatant of the centrifugal separation was measured with a spectrophotometer, and the concentration of chlorophyll a was calculated.
(Vitamin C content: C _vc )
After extracting by adding metaphosphoric acid to the lettuce taken out from the package, it measured by the high performance liquid chromatograph method. Ascorbic acid in lettuce was reduced as reduced ascorbic acid, and oxidized dehydroascorbic acid was reduced, and these were quantified as total ascorbic acid.

Example 1
Two OPP (biaxially stretched polypropylene) films with a thickness of 40 μm are overlapped, three sides are sealed by heat sealing and cut, and one side is unsealed packaging bag (220 mm × 240 mm, inner dimension Area: 1056 cm ² ).
When the presence or absence of an opening in the film was confirmed, it was confirmed that there was no opening. The oxygen permeability of the film was 1000 cc / m ² / atm / day.
<Cut lettuce>
After removing the dirty and damaged portions of the lettuce, it was cut into approximately 4 cm square and washed with 100 ppm and 10 minutes of hypochlorous acid based on the Sanitation Management Manual for Large-scale Cooking Facilities (Ministry of Health and Welfare). Thereafter, moisture management was performed, and proper dehydration and drying processes were performed.
Moreover, the moisture content measured based on the weight reduction when reduced-pressure drying was performed at 70 degreeC for 5 hours based on "analysis method of nutrition labeling in nutrition labeling standards" (Consumer Agency) was 24%.
78 g of the cut lettuce was sealed in a packaging container, filled with nitrogen, and sealed with a heat seal to prepare a package. The package was stored at 10 ° C., and the internal oxygen concentration and carbon dioxide concentration were measured every day to evaluate the appearance of cut lettuce.
Six days after sealing (144 hours later), the cut lettuce was taken out, the vitamin C content C _vc and the chlorophyll content C _ch were measured, and the ratio C _vc / C _ch (ppm / ppm) was calculated.
The results are shown in Table 1.

(Comparative Example 1)
A package was prepared and evaluated in the same manner as in Example 1 except that one hole having a diameter of 300 μm was provided in an OPP (biaxially stretched 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.

(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 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 2)
A package was prepared and evaluated in the same manner as in Example 1 except that instead of nitrogen gas, a mixed gas of oxygen: 10% by volume / nitrogen: 90% by volume was filled.
The results are shown in Table 1.

Each implementation in which the ratio C _vc / C _ch (ppm / ppm) of vitamin C content C _vc and chlorophyll content C _ch of the lettuce within 144 hours after sealing of the package is within the range defined in the present invention In the example, browning was suppressed to a level with no problem over a long period of 144 hours after sealing. In particular, Example 2 has a relatively high internal oxygen concentration, and according to the present invention, it has been found that browning can be effectively suppressed over a long period of time without requiring an excessively low oxygen concentration.
On the other hand, in some of the comparative examples in which the ratio C _vc / C _ch (ppm / ppm) was out of the range specified in the present invention, browning was already noticeable after 72 hours from sealing, and all after 144 hours. In the comparative example, the browning reached an unsaleable level.

  The package of the present invention includes lettuce such as cut lettuce having high economic value by controlling the ratio of chlorophyll content and vitamin C content in the lettuce stored in the package within a predetermined range. It has practically high value, such as suppressing browning of fruits and vegetables for a long period of time stably and effectively, and has high applicability in various fields of industry such as food processing, distribution, and eating out.

Claims (16)

A package formed by containing fruits and vegetables containing lettuce in a packaging container containing a polymer film, and the vitamin C content C _vc (ppm) of the lettuce at 144 hours after sealing of the package the ratio _C vc _/ C ch of the chlorophyll content _{C ch (ppm) (ppm /} ppm) is from 0.85 to 2.00, the package.   The package according to claim 1, wherein the lettuce has a chlorophyll content of 19.5 ppm or more and 22.5 ppm or less, and a vitamin C content of 30 ppm or more.   The package according to claim 1 or 2, wherein the lettuce has a chlorophyll content of 18 ppm or more and 22.5 ppm or less and a vitamin C content of 30 ppm or more at 144 hours after sealing of the package.   The package in any one of Claims 1 thru | or 3 which suppresses browning of the fruits and vegetables containing the said lettuce effectively over 144 hours after sealing of the said package.   The package in any one of Claims 1 thru | or 4 whose oxygen concentration in the said packaging container is 0.0-10.0 volume%.   The package in any one of Claims 1 thru | or 5 whose carbon dioxide concentration in the said packaging container is 2.0-7.0 volume%.   The package according to any one of claims 1 to 6, wherein nitrogen is further enclosed in the packaging container. The package according to claim 1, wherein the polymer film has an oxygen permeability of 10,000 cc / m ² / atm / day or less at 20 ° C. and 90% RH.   The package according to any one of claims 1 to 8, 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 9, wherein the polymer film has a thickness of 15 to 45 µm.   The package according to any one of claims 1 to 10, 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 11, 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 12, wherein the lettuce is cut lettuce.   The package according to any one of claims 1 to 13, further comprising a hygroscopic agent and / or an antibacterial agent. Maintaining the freshness of fruits and vegetables, comprising the steps of storing fruit and vegetables containing lettuce in a packaging container comprising a polymer film, forming a package and sealing the package, and holding the package at 2 to 15 ° C. A method,
The ratio C _vc / C _ch (ppm / ppm) of vitamin C content C _vc (ppm) and chlorophyll content C _ch (ppm) of the lettuce at 144 hours after sealing of the package is 0.85 The method for maintaining the freshness of fruits and vegetables, which is 2.00.   The method for maintaining freshness of fruits and vegetables according to claim 15, further comprising the step of enclosing nitrogen in the packaging container.