JP2018167891A - Package with excellent freshness retaining capacity for fruit and vegetables, and method for retaining freshness of fruit and vegetables - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a packaging body in which fruits and vegetables containing lettuce are stored in a packaging container, which has an excellent function of maintaining the freshness of the fruits and vegetables, such as suppressing browning of the fruits and vegetables containing the lettuce. SOLUTION: Fruits and vegetables containing lettuce are stored in a packaging container containing a polymer film, and the internal oxygen concentration after holding the package at 10 ° C. for 72 hours after sealing is 7.0% by volume or less. The packaging. [Selection diagram] None

Description

  The present invention relates to a package excellent in the freshness retention performance of fruits and vegetables containing lettuce, and more specifically, contains fruits and vegetables containing lettuce in a packaging container having a polymer film, and has a specific oxygen concentration. It relates to a package.

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.

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 and off-flavor can be suppressed over a long period of time. For example, Patent Document 2 discloses oxygen per 1 bag / kg of lettuce. 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-described technique, the off-flavor from cut lettuce may still not be sufficiently suppressed.
From such a background, there has been a strong demand for a technique capable of maintaining the freshness of fruits and vegetables including lettuce exceeding the level of the prior art, such as being able to suppress browning 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 packaged body containing fruits and vegetables containing lettuce in a packaging container, and the freshness maintaining function of the fruits and vegetables such as suppressing browning of the fruits and vegetables containing the lettuce. It is an object of the present invention to provide an excellent package.
As a result of intensive studies, the present inventor can control the internal oxygen concentration of the package after a predetermined time has elapsed after sealing the package to a predetermined value or less to maintain the freshness such as the suppression of browning of fruits and vegetables containing lettuce. The present invention has been found to be particularly effective, and the present invention has been completed.

That is, the present invention
[1]
Packaging containing fruits and vegetables containing lettuce in a packaging container comprising a polymer film, and having an internal oxygen concentration of 7.0% by volume or less after being held at 10 ° C. for 72 hours after sealing the package The body.

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

According to the present invention, by controlling the oxygen concentration inside the package after a predetermined time from packaging to a predetermined value or less, browning of lettuce and generation of odor are effectively suppressed, and the freshness of fruits and vegetables containing lettuce is made effective. A package that can be suppressed and a method for maintaining freshness of fruits and vegetables are provided.

Hereinafter, modes for carrying out the present invention will be described.
The present invention contains fruit and vegetables containing lettuce in a packaging container comprising a polymer film, and the internal oxygen concentration after holding the package at 10 ° C. for 72 hours is 7.0 vol% or less. It is a package. That is, the package of the present invention has at least a packaging container and fruits and vegetables stored therein.

Packaging container The packaging container 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 the polymer film described above, and its oxygen permeability is not particularly limited, but is within the range of, for example, 500 to 10,000 cc / m ² / atm / day. Can be preferably used, those within the range of 750 to 5000 cc / m ² / atm / day, more preferably those within the range of 900 to 2500 cc / m ² / atm / day More preferably, those within the range of 950 to 1500 cc / m ² / atm / day can be used particularly preferably, at 10 ° C. after sealing the amount and type of fruits and vegetables to be stored and the package. An appropriate oxygen permeability can be selected in accordance with a desired internal oxygen concentration after holding for 72 hours.

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 "a fruit and vegetable contains" lettuce "means that it includes both the case where all the fruits and vegetables are made of lettuce and the case where a part 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, mung bean sprout, soybean sprout, sprout such as cypress, fungi such as shiitake, shimeji, eringi, maitake, matsutake, broccoli , Spinach, komatsuna, pak choi, cabbage, lettuce, leafy vegetables such as asparagus, flower buds 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, the form of the 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.

  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 the lettuce, if present), the preferred oxygen concentration for maintaining freshness will vary to some extent within the scope of the present invention, and accordingly the preferred oxygen permeability, as well as such oxygen Although the aspect of the polymer film that gives the permeability is different, by appropriately setting them, the present invention effectively maintains freshness for any of the above lettuce (and the fruits and vegetables stored together with the lettuce, if present). It can be performed.

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

The internal oxygen concentration of the package of the present invention after being held at 10 ° C. for 72 hours after sealing the package is preferably 3.5% by volume or less, more preferably 1.5% by volume or less. , 0.5% by volume or less is more preferable, and 0.3% by volume or less is particularly preferable.
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 25 ° C. for 72 hours after sealing” means a state immediately after holding the fruit and vegetables containing lettuce in the packaging container and then holding the packaging container at 10 ° C. for 72 hours.

In the package of the present invention, since the internal oxygen concentration is significantly lower than the oxygen concentration in the atmosphere, the internal oxygen concentration often increases with time due to the entry of oxygen from the outside. Therefore, in the present invention in which the internal oxygen concentration after holding the package for 72 hours at 10 ° C. for 72 hours or less is 0 to 72 hours at 10 ° C. for 0 to 72 hours after sealing the package. The oxygen concentration is likely to be 7.0% 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.
Moreover, 2-15 degreeC is preferable and the holding | maintenance temperature of a package is especially preferable 3-10 degreeC from a viewpoint of suppressing respiration and keeping it in a dormant state and suppressing the oxidation (browning) of a lettuce cross section.
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 above-mentioned desired internal oxygen concentration, 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, it becomes possible to keep the pressure in the packaging container high, prevent the inflow of outside air with a higher oxygen concentration, and keep the internal oxygen concentration at 72 hours after sealing the package. Can do.

In addition, in order to realize the above-described desired internal oxygen concentration, it is desirable to configure the packaging container using a polymer film having an oxygen permeability of a predetermined value or less.
That is, the oxygen permeability of the polymer film used in the present invention is preferably 10000 cc / m ² / atm / day or less at 20 ° C. and 90% RH. Oxygen permeability at 20 ° C. and 90% RH is not more than the above value, so that intrusion of oxygen from the outside air is prevented. It is suitable for maintaining the oxygen concentration. 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 ( Oxygen partial pressure)

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. Therefore, it is preferable. 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 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 500 cc / m ² / atm / day or more at 20 ° C. and 90% RH in a preferred embodiment of the present invention can be realized without providing an opening in the polymer film.
Since it is not necessary to provide an opening in the polymer film, the manufacturing process 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, 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.

A method for producing a package and a method for maintaining freshness In addition, 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, thereby providing an antibacterial function. You may have. 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.
The package of the present invention can be produced by storing the fruit and vegetables containing lettuce in the packaging container of the present invention and adjusting the internal oxygen concentration as appropriate, and the freshness maintenance of the fruits and vegetables that is one embodiment of the present invention The method can be carried out.
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, 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 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 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 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 (1232 cm ² ) /0.21 (partial pressure of oxygen )
(Oxygen concentration / carbon dioxide concentration)
The measurement was performed using an O ₂ / CO ₂ analyzer, 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 a little conspicuous at 10% 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: Browning Although it is 50% or less of the entire cross section, it is extremely conspicuous and cannot be sold by consumers. E: Large browning and clearly unsaleable to consumers (odor)
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

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: 1232 cm ² ).
When the presence or absence of an opening in the film was confirmed, it was confirmed that there was no opening. The oxygen permeability of the film was 1000 cc / m ² / atm / day.
<Cut lettuce>
After removing 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 then heat sealed 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 and odor of cut lettuce.
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 three holes having a diameter of 300 μm were provided in a 40 μm thick OPP (biaxially oriented 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 3)
A package was prepared and evaluated in the same manner as in Example 1 except that 10 holes having a diameter of 300 μm were provided in 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: 5% by volume / nitrogen: 95% by volume was filled.
The results are shown in Table 1.

(Example 3)
A package was prepared and evaluated in the same manner as in Example 1 except that 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.

(Comparative Example 4)
A package was produced and evaluated in the same manner as in Example 1 except that instead of nitrogen gas, a mixed gas of oxygen: 15% by volume / nitrogen: 85% by volume was filled.
The results are shown in Table 1.

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

  The packaging body of the present invention has an appropriate value for the internal oxygen concentration of the packaging body after a predetermined time has elapsed after sealing of the packaging body, so that browning of fruits and vegetables containing lettuce such as cut lettuce having high economic value is achieved. It has a high value in practical use, such as being particularly effective in maintaining freshness such as suppression, and has high applicability in various fields of industry such as food processing, distribution, and dining out.

Claims (13)

  Packaging containing fruits and vegetables containing lettuce in a packaging container comprising a polymer film, and having an internal oxygen concentration of 7.0% by volume or less after being held at 10 ° C. for 72 hours after sealing the package body.   The package of Claim 1 which suppresses browning of the said lettuce and generation | occurrence | production of an odor for 72 hours or more at 10 degreeC after sealing of a package.   The package according to claim 1 or 2, wherein the oxygen concentration in the packaging container immediately after sealing the package is 0.0 to 12.0% by volume.   The package according to any one of claims 1 to 3, wherein nitrogen is further enclosed in the packaging container. The package according to any one of claims 1 to 4, wherein the oxygen permeability of the polymer film is 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 5, 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 6, wherein the polymer film has a thickness of 15 to 45 µm.   The package according to any one of claims 1 to 7, 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 8, 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 9, wherein the lettuce is cut lettuce.   The package according to any one of claims 1 to 10, further comprising a hygroscopic agent and / or an antibacterial agent.   6. A process of storing and sealing lettuce-containing fruits and vegetables in a packaging container comprising a polymer film, and an oxygen concentration in the packaging container at 2 to 15 ° C. for 72 hours or more after sealing the package. A method for maintaining the freshness of fruits and vegetables, comprising the step of maintaining the volume at 0% by volume or less. The method for maintaining freshness of fruits and vegetables according to claim 12, further comprising the step of enclosing nitrogen in the packaging container.