JP2005278543A - Packaging method for retaining freshness of strawberry - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for excellently retaining freshness of strawberry through suppressing mold and decay. <P>SOLUTION: This packaging method for strawberry comprises using a film having no hole. The atmosphere in a package after 3-9 days from packaging strawberries has an oxygen concentration of 2-10%, a carbon dioxide concentration of 5-10% and a relative humidity of ≥95 %RH. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a packaging method for maintaining the freshness of strawberries satisfactorily. More specifically, the present invention relates to a packaging method that suppresses the occurrence of mold and spoilage and maintains the freshness of strawberries well.

  Strawberries are generally said to be fruits and vegetables that are difficult to last. This is partly because mold and rot are likely to occur during storage. Therefore, it is necessary to shorten the time from harvesting to consumption as much as possible. As a result, when the growth of strawberries is poor, the supply of strawberries may not be in time, and the ball may run out. Therefore, a method that can be stored for a long time in the market has been desired.

  In the current circulation of strawberries, a packaging method that suppresses the generation of mold by keeping the humidity in the pack low by a packaging method in which the upper surface of the pack is pressed with a film so as not to be sealed is generally performed. However, the reality is that mold has not been sufficiently suppressed.

In general, rot of fruits and vegetables may occur due to disease, but it often occurs as a result of advanced aging due to active respiratory action. In order to prevent aging, a technique to suppress respiratory action under low oxygen concentration and high carbon dioxide concentration environment has been performed, but the appropriate oxygen concentration and carbon dioxide concentration differ depending on the type of fruits and vegetables, strawberry It is necessary to find an appropriate concentration.
In addition, since mold tends to propagate in high humidity, it is known that storage at low humidity is a method for preventing mold as described above. However, a low humidity environment is unsuitable for preserving the freshness of strawberries because it promotes the loss of moisture in fruits and vegetables and causes wilt.

Studies on maintaining the freshness of strawberries have already been conducted in many ways. For example, a method is disclosed in which a perforated synthetic resin film is packaged and stored in a high carbon dioxide concentration, low temperature environment, thereby tightening the skin before the strawberries become soft and suppressing mold generation. (For example, refer to Patent Document 1). However, in this method, problems such as an increase in the temperature of the packaging environment and intrusion of foreign substances due to the outside air entering through the holes of the film for imparting air permeability have been pointed out.
Further, a freshness-maintained package using a porous synthetic resin film and an ethanol generator has been proposed (see, for example, Patent Document 2), but the packaging process becomes complicated and the cost increases. Is hard to say.

JP 2000-21003 A JP 2003-250443 A

  The present invention has been studied to solve the above-mentioned problems in the current distribution of strawberries, and an object of the present invention is to provide a method for maintaining good freshness of strawberries by suppressing mold and rot.

  As a result of intensive studies, the present inventor is a method for packaging strawberries sealed with a film having no holes, and the environment in the packaging 3 to 9 days after packaging the strawberries has an oxygen concentration of 2 to 10%, carbon dioxide It has been found that this problem can be solved by a packaging method having a concentration in the range of 5 to 10% and a relative humidity of 95% RH or more, and the present invention has been completed based on this finding.

The present invention is constituted by the following.
1. It is a packaging method for strawberries that is sealed with a film that is not provided with a hole, and the environment in the packaging for 3 to 9 days after packaging the strawberries is in the range of oxygen concentration 2 to 10%, carbon dioxide concentration 5 to 10%, And the freshness maintenance packaging method of the strawberry characterized by being 95% RH or more of relative humidity.

2. Oxygen permeability at 23 ° C. is 5,000 to 11,000 nmol / (m ² · s · 100 kPa), carbon dioxide permeability at 23 ° C. is 15,000 to 35,000 nmol / (m ² · s · 100 kPa) , 40 ° C., the moisture permeability 90% RH is used a film having a property of 35~80g / ^{m 2} · d, and wherein the packaging at the film strawberry 300g per 0.1 to 0.2M ² The freshness-keeping packaging method for strawberries according to 1 above.

3. The method for maintaining and packaging freshness of strawberries according to 2 above, wherein the film is a polyolefin resin film.

4). 2. The film according to claim 2, wherein the film has a concavo-convex shape consisting of at least a convex part substantially continuous on one side and a discontinuous concave part partitioned by the convex part, and the concavo-convex shape satisfies the following conditions: 4. The method for maintaining and packaging freshness of strawberries according to item 3 or 3.
1) The thickness da of the concave portion is 0.003 to 0.05 mm, and the ratio da / db of the thickness da of the concave portion to the thickness db of the convex portion is 0.01 ≦ da / db ≦ 0.8.
2) The ratio Sa / Sb between the concave area Sa and the convex area Sb on the film surface on which the concavo-convex shape is formed is 0.1 ≦ Sa / Sb ≦ 5.

5). The polyolefin resin is a propylene-based block copolymer comprising a crystalline propylene polymer (A) and a propylene-α-olefin copolymer (B), and the propylene-α-olefin copolymer (B) propylene polymerization component content is 40 to 95 wt%, the ratio of the intrinsic viscosity [eta] _B having an intrinsic viscosity [eta] propylene -α- olefin copolymer of _a to the crystalline propylene polymer (a) (B) 5. The method for maintaining and packaging freshness of strawberries according to 3 or 4 above, wherein [η] _B / [η] _A is a propylene-based block copolymer having a range of 0.5 to 1.3.

  The strawberry freshness-keeping packaging method of the present invention is an excellent freshness-keeping packaging method capable of suppressing mold and spoilage by sealing with a film having no holes and packaging the strawberry under specific environmental conditions. . In addition, by sealing and packaging strawberries with a film having specific characteristics, it is possible to achieve the specific environmental conditions described above, and no other materials are required. It is.

Hereinafter, embodiments of the present invention will be described.
In this invention, the environmental temperature in a package becomes like this. Preferably it is 0-15 degreeC, More preferably, it is 0-13 degreeC. If the environmental temperature in a package is said range, there is no possibility that a strawberry will freeze, and the freshness of a strawberry will not fall remarkably with a raise in temperature.
Further, in the present invention, since the film is sealed with a film having no holes, the environment in the package is less affected by the outside air temperature than in the case of a perforated film, is not invaded by foreign matters, and is maintained well over a long period of time. The

  In general, in order to control the gas permeability of the film, a method of forming a through hole having a hole diameter on the order of several μm to several mm is taken. However, the “film without a hole” of the present invention has a hole diameter of 1 μm. The above-described film having no through-hole may be formed with a gas flow path having a pore diameter of less than 1 μm in a molecular level gap, a seal part of a package, or the like.

  In the present invention, the packaging environment 3 to 9 days after packaging the strawberry is an oxygen concentration of 2 to 10%, a carbon dioxide concentration of 5 to 10%, and a relative humidity of 95% RH or more. If the oxygen concentration is in the above range, the anaerobic breathing of the strawberry does not impair the taste and odor, and the strawberry breathing is activated and the freshness maintaining effect and the effect of inhibiting mold and decay are not impaired. Moreover, if a carbon dioxide concentration is said range, the inhibitory effect of mold | fungi and decay will be enough, and the color of a strawberry will not darken. Furthermore, if the relative humidity is 95% RH or more, there is little loss of weight due to the loss of moisture, and there is no risk of losing commercial value by causing wilt in a short time. The environmental conditions in the packaging are defined as 3 to 9 days after packaging because it takes 3 days for the oxygen and carbon dioxide concentrations to stabilize, especially due to the air volume in the bag during packaging. Yes, if it exceeds 9 days, depending on the storage temperature, the freshness of the strawberry may be significantly reduced and rot may occur. There is no particular problem when packing with the usual method, but if there is too much air capacity, it will take time to stabilize and it may be difficult to obtain the effect. May be packaged.

In order to make the environment in the packaging after 3 days after packaging strawberries the above-mentioned conditions, in the present invention, the oxygen permeability at 23 ° C. is 5,000 to 11,000 nmol / (m ² · s · 100 kPa. ), Preferably 6,000 to 10,500 nmol / (m ² · s · 100 kPa), carbon dioxide permeability at 23 ° C. of 15,000 to 35,000 nmol / (m ² · s · 100 kPa), preferably 20, 000-33,000 nmol / (m ² · s · 100 kPa), 40 ° C., and a film having a characteristic of moisture permeability at 90% RH of 35-80 g / m ² · d, 0.1 to 0 per 300 g of strawberries Preferably it is hermetically packaged with ² m ² of the film. If the oxygen permeability, carbon dioxide permeability, and moisture permeability of the film are in the above ranges, and the amount of the film used is in the above ranges, the strawberry packaging environment is appropriately maintained, and the effect of suppressing mold and spoilage Is obtained.

  The form of the film may be a general flat film or a film having a concavo-convex structure on one side or both sides, but the form of packaging is hermetic packaging. Sealing packaging includes gas permeable film, general film, tray, etc. and heat sealing method to heat and fuse the gas permeable film, gluing method to avoid heating, rubber band, special jig etc. There are known methods such as a tightening method for closing the tape, a tape fixing method for fastening the opening with a tape, and a chuck method, and any method may be used. If it cannot be sealed, the environment in the package cannot be properly maintained, and there is a possibility that a stable effect cannot be obtained. Since the appearance and the like may be impaired by water droplets adhering to the inner surface of the film, an antifogging treatment may be performed.

The material of the film is not particularly limited as long as the oxygen permeability, carbon dioxide permeability, and moisture permeability of the film are in the above ranges, but a thermoplastic resin film is preferable. Examples of the thermoplastic resin include polyolefin resins, polystyrene resins, polyvinyl chloride resins, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, urethane resins, acrylic resins, polyamide resins, polycarbonate resins, and fluorine resins.
Among these, a polyolefin resin typified by a polyethylene resin or a polypropylene resin is preferable from the viewpoint of processability and economy. Further, when used in an automatic packaging machine, a certain degree of rigidity is required for the film, and therefore a polypropylene resin is preferable.

Examples of the polyethylene resin include an ethylene homopolymer, a random or block copolymer of two or more with a monomer other than ethylene having ethylene as a main component, and a mixture of two or more of these. In the present invention, the main component means the most abundant component. Although it does not specifically limit as said monomers other than ethylene, C3-C12 alpha olefins, such as propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, Vinyl esters, such as vinyl acetate Examples thereof include acrylic acid esters such as ethyl acrylate, methacrylic acid esters such as methyl methacrylate, and carbon monoxide. These may be used alone or in combination of two or more.
Examples of the polypropylene resin include a homopolymer of propylene, a random or block copolymer of two or more with a monomer other than propylene mainly composed of propylene, and a mixture of two or more of these. Although it does not specifically limit as monomers other than the said propylene, C2-C12 alpha olefins, such as ethylene, 1-butene, 1-pentene, 1-hexene, 1-octene, etc. can be illustrated. These may be used alone or in combination of two or more.

Among them, the polyolefin resin is a propylene-based block copolymer composed of a crystalline propylene polymer (A) and a propylene-α-olefin copolymer (B), and the propylene-α-olefin copolymer (B ) Of the propylene polymerization component is 40 to 95% by weight, and the intrinsic viscosity [η] _B of the propylene-α-olefin copolymer (B) with respect to the intrinsic viscosity [η] _A of the crystalline propylene polymer (A) _B When the ratio [η] _B / [η] _A is a propylene-based block copolymer in the range of 0.5 to 1.3, the resulting film has a packaging workability, transparency, and fluoroscopy necessary as a packaging film. In the state which maintained the property, since the gas permeability and moisture permeability suitable for the freshness maintenance packaging method of a strawberry are expressed, it is preferable.

  The α-olefin component used in the propylene-α-olefin copolymer (B) is not particularly limited, and for example, ethylene, butene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 4-methyl. Examples thereof include -1-pentene and 3-methyl-1-pentene. In addition, the α-olefin can be used alone or in combination of two or more thereof. Of these, ethylene and butene are preferred from the economical aspect.

  Further, the propylene-based block copolymer comprises 40 to 95% by weight of the crystalline propylene polymer (A) and 5 to 60% by weight of the propylene-α-olefin copolymer (B), and propylene-α- When the olefin copolymer (B) is an ethylene-propylene-butene random copolymer (B ′) containing 10 to 30% by weight of an ethylene polymerization component and 3 to 40% by weight of a butene polymerization component, the propylene-based copolymer A film obtained from the block copolymer exhibits higher gas permeability and moisture permeability.

  In the present invention, when the crystalline propylene polymer (A) constituting the propylene-based block copolymer is a propylene-α-olefin copolymer containing an α-olefin polymerization component, the polymer (A The film obtained from the propylene-based block copolymer is particularly suitable as a packaging film for strawberries that require gas permeability and state confirmation of the freshness and quality of the contents as well as gas permeability. It is.

  When a film obtained from the propylene-based block copolymer requires further excellent transparency and transparency, the crystalline propylene polymer (A) constituting the propylene-based block copolymer is α- It is a propylene-α-olefin copolymer containing an olefin polymerization component, and the propylene-α-olefin copolymer (B) has an ethylene polymerization component of 10 to 30% by weight and a butene polymerization component of 3 to 40% by weight. The ethylene-propylene-butene random copolymer (B ′) is preferably contained.

  When the crystalline propylene polymer (A) is a propylene-α-olefin copolymer, the α-olefin component is not particularly limited. For example, ethylene, butene, 1-hexene, 1-octene, 1-decene, Examples thereof include 1-dodecene, 4-methyl-1-pentene, and 3-methyl-1-pentene. In addition, the α-olefin can be used alone or in combination of two or more thereof. Of these, ethylene and butene are preferred from the economical aspect.

  When the crystalline propylene polymer (A) is a propylene-α-olefin copolymer, the α-olefin polymerization component content is preferably 0.1 to 5% by weight based on the polymer (A). . If the α-olefin polymerization component content is in this range, a film having a concavo-convex shape described later obtained from the propylene-based block copolymer composed of the polymer (A) is excellent in transparency and transparency. The contents to be packaged are easily visible, and the film has sufficient rigidity so that it is excellent in automatic packaging suitability and packaging workability.

  If the ethylene polymerization component content of the ethylene-propylene-butene random copolymer (B ′) is in the range of 10 to 30% by weight, the film having a concavo-convex shape described later obtained from the propylene-based block copolymer. The gas permeability is sufficiently large, and transparency and transparency are at a level that can sufficiently confirm the state of the strawberry to be packaged.

  When the butene polymerization component content of the ethylene-propylene-butene random copolymer (B ′) is in the range of 3 to 40% by weight, the film having a concavo-convex shape to be described later obtained from the propylene-based block copolymer. Transparency and transparency are at a level at which the state of the strawberry to be packaged can be sufficiently confirmed, and there is no problem in the production of the propylene block copolymer due to the deterioration of the powder properties of the propylene block copolymer.

  The proportion of the propylene-α-olefin copolymer (A) and the ethylene-propylene-butene random copolymer (B ′) in the propylene-based block copolymer is such that the copolymer (A) is 40 to 95% by weight. The content of the copolymer (B ′) is preferably 5 to 60% by weight, and more preferably 10 to 50% by weight. When the proportion of the copolymer (A) and the copolymer (B ′) is in the above range, the film having an uneven shape composed of the propylene-based block copolymer is used as a heavy weight packaging film. Rigidity and gas permeability.

The propylene-based block copolymer used in the present invention comprises a propylene-α-olefin copolymer (B) constituting the intrinsic viscosity [η] _B measured in 135 ° C. tetralin and a crystalline propylene polymer (A The intrinsic viscosity ratio [η] _B / [η] _A to the intrinsic viscosity [η] _A is 0.5 to 1.3, preferably 0.5 to 1.1.

The intrinsic viscosity ratio [η] _B / [η] _A affects the dispersibility of the propylene-α-olefin copolymer (B) in the crystalline propylene polymer (A). If the intrinsic viscosity ratio [η] _B / [η] _A is in the above range, the film obtained from the propylene-based block copolymer has sufficient transparency and transparency, and can be used as a heavy weight packaging film. Has the rigidity to withstand.

The propylene-based block copolymer used in the present invention preferably has an intrinsic viscosity [η] _{WHOLE in} the range of 1.6 to 3.6 dl / g from the viewpoint of ease of molding during film molding. More preferably, it is in the range of 1.8 to 2.5 dl / g.

  The propylene block copolymer used in the present invention may be produced by any method as long as the above conditions are satisfied. Of course, the propylene block copolymer may be produced by mixing the separately produced crystalline propylene polymer (A) and the propylene-α-olefin copolymer (B) using a mixing device. However, it can be suitably produced by employing a two-stage continuous polymerization method in the gas phase.

  Examples of the two-stage continuous polymerization method include those disclosed in WO 97/19135 and JP-A-10-316810, that is, in the presence of an olefin polymerization catalyst component having an average particle size of 30 to 300 μm. The first polymerization step for producing the crystalline propylene polymer (A) in the gas phase, and then the second polymerization step for producing the propylene-α-olefin copolymer (B) are successively carried out in order. A method for continuously producing the system block copolymer can be exemplified. The propylene-based block copolymer can be produced by the above-described method, and a commercially available product having a desired specification can be selected and used.

In the case where a crystalline propylene polymer (A) and a propylene-α-olefin copolymer (B) are continuously produced to obtain a propylene-based block copolymer, propylene-α in the propylene-based block copolymer is obtained. -The intrinsic viscosity [η] _B of the olefin copolymer (B) cannot be directly measured, so the intrinsic viscosity [η] _{A of the} crystalline propylene polymer (A) and the intrinsic viscosity of the propylene block copolymer as the final product _{[η] WHOLE,} and is obtained by the following equation from the weight% _{W B} of the propylene block copolymer of propylene -α- olefin copolymer (B).
[η] _B = {[η] _WHOLE− (1−W _B / 100) [η] _A } / (W _B / 100)
In the two-stage continuous polymerization method, the olefin polymerization catalyst component is not particularly limited. For example, it can be produced using a titanium-based catalyst or a metallocene-based single site catalyst. Of these, titanium-based catalysts are preferred.

  The film obtained using the propylene-based block copolymer may be a single layer film or a multilayer film. A multilayer film can be obtained by laminating a film made of another thermoplastic resin on a film made of the propylene-based block copolymer. The thermoplastic resin constituting the laminated film is not particularly limited, but propylene homopolymer, propylene-ethylene copolymer, propylene-α-olefin copolymer, propylene-ethylene-α-olefin copolymer, propylene- An olefin resin such as an ethylene block copolymer, a propylene-α-olefin block copolymer, an ethylene-α-olefin copolymer, an ethylene homopolymer or an ethylene-vinyl acetate copolymer is preferred, and the propylene homopolymer, propylene -Ethylene copolymer, propylene-α-olefin copolymer, propylene-ethylene-α-olefin copolymer, ethylene-α-olefin copolymer or ethylene homopolymer is particularly preferred.

The form of the film may be a general flat film or a film having a concavo-convex structure on one side or both sides, but the film is a convex part substantially continuous on at least one side as exemplified in FIG. 1 and FIG. The film has a concavo-convex shape composed of discontinuous concave portions partitioned by the convex portions, the concavo-convex shape satisfies the following conditions, and is a stretched film stretched at an area magnification of 4 to 60 times, the film is While satisfying the above-mentioned oxygen permeability, carbon dioxide permeability, and moisture permeability, it is preferable because it is excellent in strength and rigidity.
1) The thickness da of the concave portion is 0.003 to 0.05 mm, and the ratio da / db of the thickness da of the concave portion to the thickness db of the convex portion is 0.01 ≦ da / db ≦ 0.8.
2) The ratio Sa / Sb between the concave area Sa and the convex area Sb on the film surface on which the concavo-convex shape is formed is 0.1 ≦ Sa / Sb ≦ 5.

  In the case of a thermoplastic resin film, as a method for forming the above-described uneven shape, a thermoplastic resin film is manufactured by a calendar device, a T-die device, an inflation device, or the like, which is a known processing technique, and then the thermoplastic resin film is paired. A method of cooling by sandwiching between heated embossing roll units, a method of melting and softening the thermoplastic resin film and pressing and cooling between a pair of cooling embossing roll units, and a molten state of the thermoplastic resin with an extruder or a calender roll And a method of cooling by pressing between the pair of cooling embossing roll units.

  When providing an uneven shape only on one side of the thermoplastic resin film, one roll surface formed with an uneven shape opposite to the film surface, the other roll uses a metal roll or rubber roll with a smooth surface, When forming uneven | corrugated shape on both surfaces of a thermoplastic resin film, the two embossing rolls which have uneven | corrugated shape are used.

  Further, when the thermoplastic resin film requires further rigidity or tensile strength, a uniaxial stretching or biaxial stretching method is used. In this case, it is desirable to form a concavo-convex shape in advance in the thermoplastic resin film or sheet before stretching, and in order to form a concavo-convex shape in the film after stretching, it is necessary to remelt the film, The effect of stretching may be lost and the desired rigidity and tensile strength may not be obtained.

  In the biaxial stretching method, the thermoplastic resin film or sheet having a concavo-convex shape is usually stretched 2 to 8 times in the longitudinal (machine) direction and the biaxial direction in the transverse direction (4 in area magnification). The simultaneous biaxial stretching method in which the film is stretched in the biaxial direction at the same time is stretched in the longitudinal direction and then stretched in the transverse direction, or the stretching is performed in the transverse direction and then stretched in the longitudinal direction. It does not matter. If the area magnification is 4 to 60 times, uniform stretching is possible, and it is difficult to break during stretching. In addition, the stretched film thus obtained may be subjected to relaxation treatment in a heating environment at a melting temperature or lower for the purpose of removing internal residual strain.

  Although the thickness of the concavo-convex portion formed on the thermoplastic resin film varies depending on the required gas permeability, the area ratio of the concavo-convex portion, etc., the thickness da of the concave portion is 0 from the film strength, workability, economy, etc. 0.003 to 0.05 mm, preferably 0.004 to 0.03 mm, and more preferably 0.004 to 0.01 mm. If the thickness of the recess is in the above range, it is difficult for stretch cuts or perforations to be formed, and the desired gas permeability can be obtained as a strawberry packaging film.

The ratio da / db between the thickness da of the concave portion formed in the thermoplastic resin film and the thickness db of the convex portion is 0.01 ≦ da / db ≦ 0.8, preferably 0.01 ≦ da / db ≦. 0.6, more preferably 0.01 ≦ da / db ≦ 0.4. When the thickness ratio da / db is in the above range, gas permeability suitable for strawberry packaging is obtained, and the strength of the recesses is insufficient, and perforation is unlikely to occur during film formation or stretching.
The thickness db of the convex portion is a value within a range obtained from the thickness da of the concave portion and the thickness ratio da / db, and is preferably 0.02 to 0.2 mm. When the thickness is in the above range, tearing or the like hardly occurs when an unstretched film is formed or when a stretched film is stretched, and the rigidity of the film does not become too high.

  The ratio Sa / Sb between the concave area Sa and the convex area Sb on the film surface on which the concavo-convex shape of the thermoplastic resin film is formed is preferably 0.1 ≦ Sa / Sb ≦ 5, more preferably 0.3 ≦ Sa /. Sb ≦ 4, more preferably 0.5 ≦ Sa / Sb ≦ 3. If this ratio Sa / Sb is in the above range, the effect of improving the gas permeability of the film can be obtained, and since the width of the convex portion is small, the contact area with the strawberry is also small, and the strawberry spoilage prevention effect is easily obtained. Further, the width of the convex portion is not too narrow, and it is not difficult to form the concave and convex shape on the embossing roll.

  Strawberries to which the strawberry freshness-keeping packaging method of the present invention can be applied are preferably those that have not yet been damaged from the viewpoint of maintaining freshness, but may be those that have been damaged after transportation. In particular, since strawberry after transporting molds early in the damaged part, it is preferable to wrap it as soon as possible and to take measures to stabilize the packaging environment early by degassing or the like. Moreover, the time for carrying out the packaging is preferably before transportation, but of course, it may be after transportation.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited by these.
In addition, the abbreviations and contents of the raw material resins for the films used in Examples and Comparative Examples are as follows.
[PP]
Propylene-based block copolymer (crystalline propylene polymer (A): ethylene-propylene random copolymer (ethylene) produced by the method disclosed in WO97 / 19135 pamphlet and JP-A-10-316810 Polymer component content 0.7 wt%, intrinsic viscosity [η] _A = 2.64 dl / g) 67 wt%, and propylene-α-olefin copolymer (B): ethylene-propylene-butene random copolymer ( Ethylene polymer component content 18 wt%, butene polymer component content 4.5 wt%, intrinsic viscosity [η] _B = 1.82 dl / g) 33 wt%, intrinsic viscosity [η] _WHOLE = 2.37 dl / g.Intrinsic viscosity ratio [η] _B / [η] _A = 0.69) Tetrakis- [methylene-3- (3 ′, 5′-di-t-butyl) as an antioxidant with respect to 100 parts by weight -4′-hydroxyphenyl) propionate] 0.15 parts by weight of methane and 0.10 parts by weight of calcium stearate as a neutralizing agent, and uniformly mixed by a Henschel mixer (trade name), The obtained mixture was melt-kneaded with an extruder and then used as a pellet-like composition. The intrinsic viscosity was measured using an automatic viscosity measuring device (AVS2 type, manufactured by Mitsui Toatsu Chemical Co., Ltd.) under a temperature condition of 135 ° C. using tetralin (tetrahydronaphthalene) as a solvent. The content of the butene polymerization component was measured by an infrared absorption spectrum method.
[PE]
Elite 5400G: (trade name, manufactured by Dow Chemical Japan, polyethylene).

Measurement methods and evaluation methods used in Examples and Comparative Examples are as follows.
(1) Oxygen permeability and carbon dioxide permeability of film: According to JIS K 7126, the permeability at 23 ° C. was measured using a differential pressure method gas permeation measuring apparatus (manufactured by Toyo Seiki Seisakusho).

(2) Moisture permeability of the film: According to JIS Z 0208, Condition B, the film is closely attached to the upper surface of a metal container containing calcium chloride, and left in a constant temperature and humidity chamber of 40 ° C. and 90% RH, and the weight change with time. Was converted to a value.

(3) Temperature and relative humidity in the package: Measured using a thermohygrometer (trade name; RS-10, manufactured by Tabay Espec Co., Ltd.).

(4) Oxygen concentration and carbon dioxide concentration in the packaging: Measured using an oxygen concentration / carbon dioxide concentration measuring device (trade name: CheckPointO2 / CO2, manufactured by PBI Dunsentor).

Example 1
[PP] is melt-kneaded with a 65 mm extruder with a thermoplastic resin composition containing 2.0% by weight of polyoxyethylene stearylamine monostearate as an antifogging agent, and is extruded into a film from a T-die. It was set as a shape. Next, the molten film is arranged in the machine direction of the roll surface with the concave portion depth, width and vertical and horizontal pitches of 0.8 mm, 0.8 mm and 3 mm, respectively, and the convex shape is a square. The thermoplastic embossed roll and the mirror-finished iron roll were cooled and solidified to obtain a thermoplastic resin sheet having a weight per unit area of 650 g / m ² . After the obtained thermoplastic resin sheet is heated so that the sheet temperature becomes 140 ° C., it is successively biaxially stretched under the conditions of a longitudinal stretching ratio × lateral stretching ratio of 5 × 6 times (area magnification 30 times), The concave portion thickness is 0.008 mm, the ratio da / db of the concave portion thickness da to the convex portion thickness db on the sheet surface is 0.19, and the ratio Sa between the concave portion area Sa and the convex portion area Sb on the sheet surface. A film having a / Sb of 0.99 and a basis weight of 21 g / m ² was obtained.
The obtained film had an oxygen permeability of 6,500 nmol / (m ² · s · 100 kPa), a carbon dioxide permeability of 21,800 nmol / (m ² · s · 100 kPa), and a moisture permeability of 49 g / m ² · d. .
300 g of strawberry (variety name; Tochiotome) was put in a bag using 0.1 m ^{2 of} the above film and heat-sealed, and then stored at 5 ° C. Mold, decay, odor, taste, discoloration, and wilting were evaluated until 18 days after packaging. The evaluation results are shown in Table 1.

Example 2
In the film production, longitudinal stretching ratio × transverse stretching ratio is 6 × 8 times (area magnification is 48 times), and biaxially stretched sequentially, the thickness of the recess is 0.006 mm, and the thickness of the recess on the sheet surface A film having a ratio da / db of da to a convex thickness db of 0.19, a ratio Sa / Sb of a concave area Sa to a convex area Sb on the sheet surface of 0.95, and a basis weight of 16 g / m ² is used. The same operation as in Example 1 was performed except that. The obtained film had an oxygen permeability of 10,200 nmol / (m ² · s · 100 kPa), a carbon dioxide permeability of 32,100 nmol / (m ² · s · 100 kPa), and a moisture permeability of 76 g / m ² · d. . The evaluation results are shown in Table 1.

Example 3
It was carried out in the same manner as in Example 1 except that it was evaluated at 9 ° C. after storage at 15 ° C. and packaging. The evaluation results are shown in Table 1.

Example 4
It was carried out in the same manner as in Example 2 except that the evaluation was made after storage at 15 ° C. and 9 days after packaging. The evaluation results are shown in Table 1.

Example 5
300 g of strawberries (variety name; Toyonoka) were put into a bag using 0.18 m ^{2 of} the film produced in the same manner as in Example 2, and then stored at 15 ° C. Mold, rot, nasty smell, taste, discoloration, and wilting were evaluated until 9 days after packaging. The evaluation results are shown in Table 1.

Example 6
A thermoplastic resin composition in which 2.0% by weight of polyoxyethylene stearylamine monostearate as an antifogging agent is blended with [PE] is melt-kneaded with a 40 mm extruder, and extruded from a T die into a film shape. It was set as a shape. Next, the molten film-like material is formed into a concave-convex shape in which the depth, width, and vertical and horizontal pitch of the concave portions are 0.05 mm, 1.0 mm, and 5 mm, respectively, and the convex shape is square, and the machine direction of the roll surface. (MD) is cooled and solidified by being sandwiched between an embossing roll made of iron arranged in (MD) and a rubber roll coated with a Teflon (registered trademark) tube, the thickness of the recess is 0.03 mm, and the thickness of the recess on the sheet surface A film having a ratio da / db of da to a convex thickness db of 0.38, a ratio of concave area Sa to convex area Sb on the sheet surface Sa / Sb of 1.83, and a weight per unit area of 43 g / m ² is obtained. It was.
The obtained film had an oxygen permeability of 5,100 nmol / (m ² · s · 100 kPa), a carbon dioxide permeability of 17,800 nmol / (m ² · s · 100 kPa), and a moisture permeability of 38 g / m ² · d. .
300 g of strawberry (variety name; Tochiotome) was put in a bag using 0.1 m ^{2 of} the above film and heat-sealed, and then stored at 5 ° C. Mold, decay, odor, taste, discoloration, and wilting were evaluated until 18 days after packaging. The evaluation results are shown in Table 1.

Comparative Example 1
It was carried out in the same manner as in Example 3 except that the evaluation was from 6 days after storage at 15 ° C. without packaging. The evaluation results are shown in Table 2.

Comparative Example 2
The film was stretched biaxially under the conditions of longitudinal stretch ratio × transverse stretch ratio of 3 × 4 times (area ratio of 12 times) in film production, the recess thickness was 0.019 mm, and the thickness of the recess in the sheet surface A film having a ratio da / db of da to a convex thickness db of 0.19, a ratio Sa / Sb of a concave area Sa to a convex area Sb on the sheet surface of 0.95, and a weight per unit area of 56 g / m ² is used. The same operation as in Example 3 was performed except that. The obtained film had an oxygen permeability of 3,500 nmol / (m ² · s · 100 kPa), a carbon dioxide permeability of 13,400 nmol / (m ² · s · 100 kPa), and a moisture permeability of 26 g / m ² · d. . The evaluation results are shown in Table 2.

Comparative Example 3
The film was stretched biaxially under the conditions of longitudinal stretch ratio × transverse stretch ratio of 7 × 8 times (area ratio of 56 times) in the film production, the recess thickness was 0.004 mm, and the thickness of the recess on the sheet surface A film having a ratio da / db of da to a convex thickness db of 0.18, a ratio Sa / Sb of a concave area Sa to a convex area Sb on the sheet surface of 0.90, and a basis weight of 11 g / m ² is used. And it implemented similarly to Example 1 except being evaluation until 12 days after packaging. The obtained film had an oxygen permeability of 12,900 nmol / (m ² · s · 100 kPa), a carbon dioxide permeability of 39,800 nmol / (m ² · s · 100 kPa), and a moisture permeability of 97 g / m ² · d. . The evaluation results are shown in Table 2.

Comparative Example 4
The concave portion thickness is 0.01 mm, the ratio da / db of the concave portion thickness da to the convex portion thickness db on the sheet surface is 0.17, and the concave portion area Sa to the convex portion area Sb ratio Sa on the sheet surface. This was carried out in the same manner as in Example 1 except that a film having a / Sb of 1.83 and a weight per unit area of 26 g / m ² was used and the evaluation was made after 12 days from packaging. The obtained film had an oxygen permeability of 15,600 nmol / (m ² · s · 100 kPa), a carbon dioxide permeability of 47,200 nmol / (m ² · s · 100 kPa), and a moisture permeability of 116 g / m ² · d. .

Comparative Example 5
Evaluation was conducted in the same manner as in Example 3 except for storage at 20 ° C. The evaluation results are shown in Table 2.

Comparative Example 6
It implemented like Example 4 except the area of the used film being 0.3 m < ² >. The evaluation results are shown in Table 2.

  The strawberry freshness maintaining and packaging method of the present invention is particularly useful for the distribution of strawberry.

An example of the film which provided the uneven structure used by this invention is shown. An example of the recessed part shape which looked at the film which provided the uneven structure used by this invention from the upper direction of the uneven | corrugated formation surface is shown.

Explanation of symbols

1: A concave portion of a film provided with a concavo-convex structure.
2: A convex portion of a film provided with a concavo-convex structure.
3: The concave width of the film provided with the concave-convex structure.
4 ... The pitch of the film provided with an uneven structure.
5: Thickness of the convex portion of the film having a concavo-convex structure.
6: Recess thickness of the film having a concavo-convex structure.

Claims (5)

  It is a packaging method for strawberries that is sealed with a film that is not provided with a hole, and the environment in the packaging for 3 to 9 days after packaging the strawberries is in the range of oxygen concentration 2 to 10%, carbon dioxide concentration 5 to 10%, And the freshness maintenance packaging method of the strawberry characterized by being 95% RH or more of relative humidity. The oxygen permeability at 23 ° C. is 5,000 to 11,000 nmol / (m ² · s · 100 kPa), and the carbon dioxide permeability at 23 ° C. is 15,000 to 35,000 nmol / (m ² · s · 100 kPa). in and, 40 ° C., the moisture permeability at 90% RH using a film which is 35~80g / ^{m 2} · d, and wherein the packaging at the film strawberry 300g per 0.1 to 0.2M ² The strawberry freshness-keeping packaging method according to claim 1.   The strawberry freshness-keeping packaging method according to claim 2, wherein the film is a polyolefin resin film. The film has a concavo-convex shape comprising at least one convex portion substantially continuous on one side and a discontinuous concave portion partitioned by the convex portion, and the concavo-convex shape satisfies the following conditions. 2. A method for maintaining and maintaining a freshness of strawberries according to 2 or 3.
1) The thickness da of the concave portion is 0.003 to 0.05 mm, and the ratio da / db of the thickness da of the concave portion to the thickness db of the convex portion is 0.01 ≦ da / db ≦ 0.8.
2) The ratio Sa / Sb between the concave area Sa and the convex area Sb on the film surface on which the concavo-convex shape is formed is 0.1 ≦ Sa / Sb ≦ 5. The polyolefin resin is a propylene-based block copolymer comprising a crystalline propylene polymer (A) and a propylene-α-olefin copolymer (B), and the propylene-α-olefin copolymer (B) propylene polymerization component content is 40 to 95 wt%, the ratio of the intrinsic viscosity [eta] _B having an intrinsic viscosity [eta] propylene -α- olefin copolymer of _a to the crystalline propylene polymer (a) (B) [5] The strawberry freshness-keeping packaging method according to claim 3 or 4, wherein [η] _B / [η] _A is a propylene-based block copolymer having a range of 0.5 to 1.3.

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