Freshness preservation bags for fruits and vegetables, packaging containing fruits and vegetables, and method for preserving the freshness of fruits and vegetables.

Abstract

To provide a technique related to a packaging bag capable of suppressing local deformation while obtaining a freshness retaining effect of vegetables and fruits.SOLUTION: The fruit and vegetable freshness-keeping bag of the present invention is made of a synthetic resin film, the synthetic resin film contains polypropylene, and a ratio of elastic recovery rates (elastic recovery rate MD / elastic recovery rate TD) of the fruit and vegetable freshness-keeping bag measured by a predetermined procedure a is 1.00 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a freshness-preserving bag for fruits and vegetables, a package containing fruits and vegetables, and a method for preserving the freshness of fruits and vegetables. [Background technology]

[0002] Traditionally, a method for preserving the freshness of harvested fruits and vegetables has been known to be by adjusting the oxygen and carbon dioxide concentrations to appropriately suppress the respiration of the produce. Packaging materials used for preserving the freshness of fruits and vegetables in this way are known as MA (Modified Atmosphere) packaging. In recent years, with the growing interest in MA packaging, packaging materials are required to have improved performance in various aspects, including gas permeability, processability, strength, ease of packaging, and appearance.

[0003] For example, Patent Document 1 (Japanese Patent Application Publication No. 2023-106849) discloses a film for preserving the freshness of fruits and vegetables, in which the coefficient of dynamic friction μ' between the inner surfaces is controlled at a 40°C environment, taking into account that the packaging film may come into direct contact with the fruits and vegetables, and in order to suppress the deterioration of the freshness of the fruits and vegetables caused by the film itself. Furthermore, Patent Document 2 (Japanese Patent Publication No. 2022-119289) discloses a freshness-preserving film that is thin, has excellent conformability to contents, does not reduce seal strength, is less prone to whitening due to anti-fogging agent bleeding, and has deodorizing properties. Specifically, it discloses that the freshness-preserving film uses a specific polypropylene resin and a specific deodorizing nanofiller. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-106849 [Patent Document 2] Japanese Patent Publication No. 2022-119289 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, the technologies disclosed in Patent Documents 1 and 2 did not focus on the state of the packaging bag after the fruits and vegetables have been packaged in it. The present inventor focused on the fact that after the fruits and vegetables have been packaged in the packaging bag, a part of the packaging bag deforms due to localized loads such as when transporting heavy objects, resulting in a decrease in appearance.

[0006] Therefore, the inventors diligently conducted research to suppress deformation of the packaging bag in response to localized loads. As a result, they devised a new index related to the ratio of elastic recovery rates and found that by controlling this index, deformation in response to localized loads can be suppressed while maintaining good freshness preservation, thus completing the present invention. [Means for solving the problem]

[0007] According to the present invention, the following technologies relating to packaging bags for fruits and vegetables are provided.

[0008] [1] A fresh produce preservation bag made of synthetic resin film, The aforementioned synthetic resin film contains polypropylene, The ratio of the elastic recovery rates (elastic recovery rate) measured by the following procedure a of the fresh produce preservation bag MD / Elastic recovery rate TD A fresh produce preservation bag in which the ) is 1.00 or less. (Procedure a) (i) Cut out the fresh produce preservation bag so that the MD direction of the synthetic resin film is in the length direction, and prepare a strip-shaped sample with a width of 5 mm. Using a tensile testing machine, the distance between the chucks when both ends of the sample are fixed with chucks is defined as the gauge length L0 (mm) of the sample. Stretch the sample until the gauge length L0 (mm) is 1.2 times, and hold it in that position for 3 minutes. Then, release the fixation of the sample, and measure the gauge length L1 (mm) of the sample 20 seconds after release. The elastic recovery rate is calculated from the following formula (1). MD Calculate the percentage (%). [(L0×1.2 - L1) / L0]×0.2 (1) (ii) Except for cutting out the fresh - produce freshness - retaining bag such that the TD direction of the synthetic resin film becomes the length direction and preparing a strip - shaped sample with a width of 5 mm, the measurement is carried out in the same procedure as in (i), and the elastic recovery rate TD (%) is calculated from formula (1). [2] The fresh - produce freshness - retaining bag according to [1], where the elastic recovery rate TD (%) is 60.0% or more, a fresh - produce freshness - retaining bag. [3] The fresh - produce freshness - retaining bag according to [1] or [2], where the loop stiffness measured in the following procedure b of the fresh - produce freshness - retaining bag is 2.5 - 30 mN, a fresh - produce freshness - retaining bag. (Procedure b) Cut out the fresh - produce freshness - retaining bag such that the TD direction of the synthetic resin film becomes the length direction, and prepare a strip - shaped sample with a width of 25 mm. While making the two ends of the sample face each other, overlap them and roll them into a loop shape, and clamp and fix the two ends from the outside with a chuck so that the loop length becomes 55 mm. In the fixed state, compress the sample by 20 mm at a speed of 3.3 mm / s from the apex of the loop part toward the chuck direction with a pressure head, and measure the pressure applied to the pressure head. [4] The fresh - produce freshness - retaining bag according to any one of [1] to [3], where the synthetic resin film is a single - layer film containing polypropylene or a multi - layer film having a layer containing polypropylene, a fresh - produce freshness - retaining bag [5] The fresh - produce freshness - retaining bag according to any one of [1] to [4], where the synthetic resin film includes a stretched polypropylene film, a fresh - produce freshness - retaining bag [6] The fresh - produce freshness - retaining bag according to any one of [1] to [5], where the fresh - produce freshness - retaining bag has through - holes, a fresh - produce freshness - retaining bag. [7] A fresh - produce - containing package obtained by housing fresh - produce in the fresh - produce freshness - retaining bag according to any one of [1] to [6]. [8] In the fresh - produce - containing package according to [7], A package containing fresh produce, wherein the weight of the fresh produce is 300 g or more. [9] A method for maintaining the freshness of fresh produce, [1] to [6] A method for maintaining the freshness of fresh produce, comprising the step of storing fresh produce in the fresh produce freshness maintaining bag according to any one of the above. [Advantages of the Invention]

[0009] According to the present invention, there is provided a technique related to a packaging bag that can suppress deformation against local loads while maintaining good freshness retention of fresh produce. [Embodiments for Carrying out the Invention]

[0010] Hereinafter, embodiments of the present invention will be described in detail.

[0011] In this specification, the notation "X to Y" in the description of a numerical range represents X or more and Y or less, unless otherwise specified. For example, "1 to 5 mass%" means "1 mass% or more and 5 mass% or less". Also, in this specification, the MD direction represents the Machine Direction, which is intended to be the flow direction of the resin, and the TD direction represents the Transverse Direction, which is intended to be the direction perpendicular to the MD direction.

[0012] <Fresh Produce Freshness Maintaining Bag> The fresh produce freshness maintaining bag of the present embodiment (hereinafter also referred to as "packaging bag") is made of a synthetic resin film, and the synthetic resin film contains polypropylene. The ratio of the elastic recovery rate (elastic recovery rate MD / elastic recovery rate TD [[ID=X]] (Procedure a) ​(i) Cut out the fresh fruit freshness-keeping bag so that the MD direction of the synthetic resin film becomes the length direction, and prepare a strip-shaped sample with a width of 5 mm. Using a tensile testing machine, set the distance between the chucks when both ends of the sample are fixed with the chucks as the gauge length L0 (mm) of the sample. Stretch the sample until the gauge length L0 (mm) becomes 1.2 times, and hold it for 3 minutes as it is. Then, release the fixation of the sample, and measure the gauge length L1 (mm) of the sample 20 seconds after the release. Calculate the elastic recovery rate MD (%) from the following formula (1). [L0×1.2 - L1] / L0×0.2 (1) (ii) Measure in the same procedure as in (i) except that the fresh fruit freshness-keeping bag is cut out so that the TD direction of the synthetic resin film becomes the length direction, and a strip-shaped sample with a width of 5 mm is prepared, and calculate the elastic recovery rate TD (%) from formula (1).

[0013] As a result, a packaging bag that can suppress deformation against local loads while obtaining the freshness-keeping effect of fresh fruits can be obtained. Although the details of such reasons are not clear, it is considered as follows. The elastic recovery rate intends the recoverability of the synthetic resin film against tension. If there is a bias in the elastic recovery rate, it is considered that the packaging bag is likely to deform against local stress. Therefore, it is presumed that by reducing the ratio of the elastic recovery rates (elastic recovery rate MD / elastic recovery rate TD ), it is possible to highly suppress the packaging bag from being locally deformed. Also, by using polypropylene, good bag-making property and appropriate gas permeability can be obtained in a balanced manner, and it becomes easier to obtain a packaging bag having freshness-keeping property.

[0014] The ratio of the elastic recovery rates (elastic recovery rate MD / elastic recovery rate TD ) is 1.00 or less, preferably 0.99 or less. By setting the ratio of the elastic recovery rate to be below the above upper limit value, it becomes easier to suppress deformation against local loads.

[0015] Elastic recovery rateMD The percentage is preferably 60.0-70.0%, more preferably 62.0-68.0%, and even more preferably 62.0-66.0%. Elastic recovery rate TD Preferably, it is 61.0% or more, more preferably 62.0 to 70.0%, and even more preferably 63.0 to 69.0%.

[0016] The packaging bag is further preferably such that the loop stiffness measured by the following procedure b is 2.5 to 30 mN, and more preferably 2.6 to 29 mN. stomach. (Procedure b) Cut out the fresh produce preservation bag so that the TD direction of the synthetic resin film is the length direction, and prepare a 25 mm wide strip-shaped sample. Overlap the two ends of the sample facing each other and roll it into a loop shape so that the loop length is 55 mm, and secure both ends by clamping them from the outside with a chuck. With the sample secured, compress it by 20 mm at a speed of 3.3 mm / s from the top of the loop towards the chuck using an indenter, and measure the pressure applied to the indenter.

[0017] By controlling the loop stiffness in this way, the packaging bag gains appropriate rigidity, which is thought to distribute and reduce localized stress on the packaging bag and suppress deformation.

[0018] Furthermore, the loop stiffness (mN) measured in step b with respect to the thickness (μm) of the synthetic resin film is preferably 0.13 to 1.00, and more preferably 0.14 to 0.8. This allows for more precise control over the stiffness of the packaging bag, which is thought to enable more stable distribution of local stresses and suppress deformation.

[0019] In this embodiment, the above elastic recovery rate MD , elastic recovery rate TDPackaging bags that meet loop stiffness requirements can be achieved, for example, by selecting polypropylene, adjusting the polyethylene content, modifying the layer structure of the synthetic resin film, or improving the manufacturing method of the synthetic resin film. Examples of manufacturing methods for synthetic resin films include adjusting the stretching conditions of the synthetic resin film and annealing the synthetic resin film.

[0020] [Bag shape] The packaging bag of this embodiment is a bag formed from a synthetic resin film, and its shape is not particularly limited; it can be a two-sided bag, a three-sided bag, a back-sealed bag (gusseted bag), a pouch, a gusseted bag, etc. A two-sided bag is a bag in which a synthetic resin film is folded in half, with the folded part as the bottom and both sides sealed. A three-sided bag is a bag in which two layers of synthetic resin film are overlapped and the bottom and both sides are sealed.

[0021] The size of the packaging bag in this embodiment can be approximately 100mm x 100mm to 250mm x 350mm for packaging fresh produce intended for general consumers.

[0022] [Through hole] The packaging bag may or may not have through holes. The presence or absence of through holes allows for stable adjustment of water vapor permeability and oxygen permeability.

[0023] The planar shape of the through-hole may be, for example, circular, polygonal, or a slit. Circular is not limited to a perfect circle, but includes approximately circular shapes. In addition to circular shapes, semicircular or crescent shapes are also acceptable. A polygon is any shape enclosed by three or more line segments, such as a triangle, quadrilateral, or pentagon. A slit is a cut or narrow gap that penetrates the synthetic resin sheet constituting the packaging material, and may be a straight line, curve, L-shaped, or X-shaped, with no particular limitations on its length.

[0024] If through-holes are formed, the average diameter of the through-holes is preferably 10 μm to 200 μm, more preferably 20 to 100 μm, even more preferably 40 to 80 μm, and especially preferably 60 to 75 μm. Setting it above the lower limit improves the oxygen permeability of the packaging and makes it easier to suppress the generation of off-odors. On the other hand, setting it below the upper limit prevents the entry of foreign matter while maintaining the MA effect, making it easier to preserve the freshness of fruits and vegetables. The average diameter of the through-hole is calculated by assuming the through-hole is a perfect circle, based on the area of ​​the opening.

[0025] Furthermore, the packaging bag may have through holes with a diameter of 4 mm or more. It may also have so-called punch holes.

[0026] The number of punch holes is preferably 1 to 20 per packaging bag, more preferably 1 to 10, even more preferably 1 to 5, and especially preferably 1 to 2, in order to suppress increased respiration and drying due to excessive gas permeability and to help maintain freshness.

[0027] The above-mentioned through holes may be formed in the resin film beforehand when manufacturing the packaging bag, may be formed after the resin film has been formed into a packaging bag, or may be formed before or after the resin film has been formed into a packaging bag.

[0028] The method for forming the through-hole described above is not particularly limited, and known methods can be employed. Examples of such known methods include laser processing, needle processing including a hot needle, and methods using molds such as a roll cutter.

[0029] [Oxygen permeability] Oxygen permeability of packaging bags at 23°C and 60% RH (cc / m³) 2 The day ATM is preferably 500 to 30,000, more preferably 600 to 20,000, and even more preferably 800 to 10,000.

[0030] Oxygen permeability can be calculated, for example, by measuring the oxygen concentration inside a packaging bag immediately after filling it with nitrogen and then measuring the oxygen concentration inside the packaging bag after it has been left for a certain period of time after filling it with nitrogen, and then calculating the oxygen concentration gradient.

[0031] [Water vapor transmission rate] The water vapor permeability of the packaging bag at 40°C is preferably 1 g / (m³) from the viewpoint of releasing water vapor due to the respiration of fresh produce. 2 (day) or more, more preferably 3g / (m 2 It is more than (day) On the other hand, the water vapor permeability of the packaging bag at 40°C is preferably 300 g / (m³) from the viewpoint of suppressing the respiration of fresh produce. 2 • day) or less, more preferably 100g / (m 2 • day) or less, and more preferably 50 g / (m 2 • day) or less, and more preferably 9 g / (m 2 It is less than or equal to (day).

[0032] Water vapor transmission can be measured using a method compliant with JIS Z 0208 (Cup method).

[0033] Furthermore, in the present invention, the oxygen permeability and water vapor permeability (moisture permeability) of the packaging bag can be adjusted by controlling the selection of the synthetic resin film material, the film manufacturing method, the film layer structure, the presence or absence of through holes and the average diameter of the through holes, the presence or absence of unpenetrated grooves, and so on.

[0034] [Synthetic resin film] (raw materials) The synthetic resin film is preferably transparent or semi-transparent, and more preferably transparent, from the viewpoint of allowing the fruits and vegetables to be seen from the outside. It may also be printed with information for the purpose of identifying the fruits and vegetables. The synthetic resin may also use biomass-derived raw materials in part.

[0035] The synthetic resin constituting the synthetic resin film does not need to contain polypropylene, and is not particularly limited as long as it can be used for packaging fruits and vegetables; known synthetic resins can be used. This allows for good freshness preservation while suppressing deformation under localized loads.

[0036] Examples of polypropylenes mentioned above include homopolymers, random copolymers, and block copolymers. More specifically, examples of homopolymers include isotactic polypropylene, syndiotactic polypropylene, and atactic polypropylene, while examples of random copolymers include ethylene-propylene copolymers, propylene-1-butene copolymers, and propylene-octene copolymers. Among these, homopolymers are preferred.

[0037] The synthetic resin film may have a film made of polypropylene, or it may have a film made of a resin material which is a mixture of polypropylene and other resins.

[0038] Other resins include, for example, polyethylene resin, polyamide resin, polyvinyl chloride, polystyrene, acrylic resin, polyester resins such as polyethylene terephthalate and polylactic acid.

[0039] Examples of polyethylene resins mentioned above include various polyethylenes and ethylene copolymers. Specific examples include high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene (L-LDPE), metallocene-linear low-density polyethylene, ethylene-vinyl alcohol copolymer, ethylene-vinyl acetate copolymer, ethylene-(meth)acrylic acid copolymer, ethylene-α-olefin copolymer, and other copolymers or ionomers. The linear low-density polyethylene described above is typically a copolymer of ethylene and a small amount of α-olefin. The type of α-olefin is not particularly limited. Typical α-olefins include 1-propylene, 1-butene, 1-hexene, 4-methylpentene-1, and 1-octene, which have 3 to 10 carbon atoms. The ethylene content of ethylene-propylene copolymers is typically 4.5% or less.

[0040] Examples of the polyamide resins mentioned above include nylon. Nylon can be nylon 6, nylon 11, nylon 12, nylon 66, nylon 6-10, nylon 6-12, nylon 6-T, nylon 6-I, nylon 9T, nylon M5T, polymetaxylylene adipamide (MXD nylon), etc., and can be used individually or in combination of two or more. Among these, nylon 6, nylon 11, nylon 12, and nylon 66 individually or in combination of two or more are preferred, and nylon 6 and nylon 66 individually or in combination of two are even more preferred.

[0041] The synthetic resin film may contain additives such as antifogging agents, antiblocking agents, heat stabilizers, lubricants, impact modifiers, processing aids, antistatic agents, ultraviolet absorbers, antioxidants, weather degradation inhibitors, fillers, and pigments, as needed, to the extent that they do not impair the performance of the synthetic resin film.

[0042] The anti-fogging agents mentioned above include those that wet and spread water through hydrogen bonding by hydroxyl groups. Specific examples of anti-fogging agents include glycerin laurate, diglycerin laurate, decaglycerin laurate, glycerin monostearate, and sorbitan stearate.

[0043] Examples of the above antiblocking agents include particulate inorganic compounds such as silica, alumina, alumina silicate, and diatomaceous earth; and particulate organic compounds such as polyethylene, cross-linked polyethylene, polymethyl methacrylate, and cross-linked polymethyl methacrylate. By using an antiblocking agent, the handling properties of synthetic resin films can be improved, such as when winding the film into a roll during molding.

[0044] (Film manufacturing method) The method for obtaining the synthetic resin film is not particularly limited. Examples of known methods for obtaining a synthetic resin film include extrusion, inflation, and calendering. Furthermore, the synthetic resin film may be subjected to stretching or annealing. Stretching is typically biaxial stretching. The stretching ratio is not particularly limited, but for example, it can be approximately 2 to 10 times in both the MD and TD directions. Annealing can be performed at a temperature of 130 to 175°C for several tens of seconds to several hours. Furthermore, the above elastic recovery rate MD , elastic recovery rate TD The conditions may be adjusted as needed to achieve loop stiffness.

[0045] (Layer composition) The synthetic resin film may be a single layer or a multilayer film of two or more layers. It may be a single layer film made of polypropylene, a multilayer film including a layer made of polypropylene, a single layer film made of a resin material mixed with polypropylene and another resin, or a multilayer film including a layer made of a resin material mixed with polypropylene and another resin. Among these, a single layer film made of polypropylene or a multilayer film including a layer made of polypropylene is preferred, and a single layer film made of polypropylene is more preferred. Furthermore, it is even more preferable that the film be a stretched polypropylene film.

[0046] By creating a multilayer structure for synthetic resin films, desired functionality can be enhanced. For example, by adding functions such as slipperiness to the surface layer of the synthetic resin film, the handling and heat-sealing properties of the synthetic resin film can be improved, and packaging bags with an excellent balance of stretchability and rigidity can be reliably obtained. Furthermore, for example, by creating a two- or three-layer structure for the synthetic resin film and making at least one of the surface layers a layer containing an antiblocking agent, slipperiness can be obtained.

[0047] In the case of a multilayered synthetic resin film, the base resins of each layer may be the same or different. From the viewpoint of obtaining good adhesion between layers, it is preferable that each layer uses the same resin.

[0048] When a synthetic resin film is multilayered, the thickness of each layer may be the same or different. For example, in a three-layer structure, the thickness of the intermediate layer may be the greatest, and the thickness of the surface layer may be the lowest. The surface layer is preferably 10-20% of the total thickness of the synthetic resin film, and more preferably 12-17%.

[0049] Known methods such as dry lamination, extrusion lamination, co-extrusion, and coating can be used as appropriate to obtain multilayer films. From the viewpoint of improving interlayer adhesion and controlling layer thickness, co-extrusion is preferable.

[0050] (Thickness) The thickness of the synthetic resin film is preferably 5 to 200 μm, more preferably 10 to 100 μm, even more preferably 15 to 80 μm, and most preferably 20 to 50 μm. By making the thickness of the synthetic resin film greater than or equal to the lower limit mentioned above, the strength of the packaging bag is increased, suppressing deformation due to external stress while ensuring a stable freshness preservation effect. By making the thickness of the synthetic resin film greater than or equal to the upper limit mentioned above, the flexibility (suppleness) of the packaging bag can be maintained.

[0051] [Fruits and vegetables] In this embodiment, "fresh produce" refers to uncooked vegetables from which non-edible parts of soil-grown or hydroponically grown vegetables, such as roots, peels, cores, stems, seeds, and flowers, have been removed, with the edible portion of the vegetable being prepared with consideration for ease of eating and simple preparation.

[0052] As for fruits and vegetables, there are no particular limitations, but for example, semi-heading and heading vegetables such as cabbage, Chinese cabbage, lettuce (lettuce, leaf lettuce, romaine lettuce, sunny lettuce, salad lettuce, ssamjang, etc.), and Brussels sprouts; spinach, komatsuna, mizuna, bok choy, rapeseed (kakina), non-heading lettuce (romaine lettuce, sunny lettuce, etc.), garland chrysanthemum, stem vine, santouna, rapeseed, curly lettuce, kousaitai, urui, field wasabi, flower wasabi, watercress, arugula, shepherd's purse, petit vert, ice plant, leaf radish, etc.; root vegetables such as sweet potato, potato, nagaimo, yamaimo, taro, jinenjo, and yamatoimo, radish, carrot, burdock, turnip, ginger; leeks, ta Examples include: onions, chives and other Allium vegetables; broccoli and cauliflower; cucurbitaceous fruits and vegetables such as cucumbers and pumpkins; nightshade fruits and vegetables such as eggplants, tomatoes, cherry tomatoes, bell peppers, and paprikas; and fruits and vegetables such as okra, bitter melon, zucchini, and sweet corn; immature beans such as edamame, snow peas, green beans, and broad beans; stem vegetables such as celery, asparagus, and wasabi; herbs such as myoga ginger, perilla, water dropwort, mitsuba, and herbs (thyme, sage, parsley, Italian parsley, rosemary, oregano, lemon balm, chives, lavender, salad burnet, lamb's ear, arugula, dandelion, and nasturtium); and mushrooms. These may be packaged individually or in combination of two or more types.

[0053] Fresh produce may be cut as appropriate, taking into consideration purchasing and consumption, and may be roughly divided into 1 / 8 to 1 / 2 portions, for example, in terms of purchasing appeal, such as cabbage, Chinese cabbage, and pumpkin. Furthermore, it may be cut into bite-sized pieces or julienned for raw consumption in salads, or for cooking in stir-fries.

[0054] <Packaged fresh produce> The fruit and vegetable packaging of this embodiment (hereinafter also referred to as "packaging") contains fruit and vegetable in the fruit and vegetable freshness preservation bag described above. This improves the freshness preservation effect of the fruit and vegetable.

[0055] It is preferable that the packaging has a sealed opening after the fruits and vegetables have been packaged. Sealing may be achieved, for example, by heat-sealing the opening of the bag, or by using materials such as back sealing tape, cable ties, rubber bands, or crimping.

[0056] The amount of produce contained in the packaging bag may vary depending on the size of the container, the type of produce, and the intended use of the packaging. For produce intended for general consumers, for example, from the viewpoint of easy consumption immediately after opening and ease of carrying and handling, the amount is preferably 50 to 1000 g, more preferably 100 to 800 g. Furthermore, from the viewpoint of obtaining a more significant effect in suppressing deformation against localized loads, the amount of produce contained in the packaging bag is preferably 300 g or more, and more preferably 400 g or more.

[0057] <Methods for maintaining freshness> The freshness preservation method of this embodiment includes the step of storing the produce using the above-described package containing the produce. Storage can be carried out by known methods, but it is preferable to store the packaged product at an ambient temperature of 2 to 20°C. Ambient temperature refers to, for example, the temperature setting of the refrigerator or refrigerator where the packaged product is stored, or the temperature control setting of the display case where the packaged product is displayed in a store. It does not refer to a precisely measured temperature around the packaged product. Furthermore, it is sufficient for the average ambient temperature to be between 2 and 20°C, and it may temporarily drop to around 10°C due to unavoidable circumstances such as opening and closing doors during transport of the packaged product.

[0058] Although embodiments of the present invention have been described above, these are merely examples, and various other configurations can be adopted. Furthermore, the present invention is not limited to the embodiments described above, and modifications, improvements, etc., within the scope that can achieve the objectives of the present invention are included in the present invention. [Examples]

[0059] The present invention will be described in detail below based on examples and comparative examples. It should be noted that the present invention is not limited to the examples provided.

[0060] <Measurement and Physical Properties> • Measurement of tensile elongation (i) Cut out a fresh produce preservation bag from a synthetic resin film so that the MD direction of the film was in the longitudinal direction, and prepared a 5 mm wide strip-shaped sample. Using a tensile testing machine, the distance between the chucks when both ends of the sample were fixed with chucks was defined as the gauge length L0 (mm) of the sample. The sample was stretched until the gauge length L0 (mm) was 1.2 times, and held in that position for 3 minutes. After that, the fixation of the sample was released, and the gauge length L1 (mm) of the sample was measured 20 seconds after release. The elastic recovery rate was calculated from the following formula (1). MD The percentage (%) was calculated. [L0×1.2-L1] / L0×0.2 (1) (ii) Except for cutting out the fresh produce preservation bag so that the TD direction of the synthetic resin film is the length direction, and preparing a 5 mm wide strip-shaped sample, the measurement was performed in the same procedure as in (i), and the elastic recovery rate was calculated from formula (1). TD The percentage (%) was calculated. • Tensile testing machine: TENSILON RTH-1225 (manufactured by A&D Company, Limited) ·Environment: 23℃, 50%RH

[0061] Loop stiffness A 25mm wide strip of the fruit and vegetable freshness preservation bag was cut out so that the TD direction of the synthetic resin film was the length direction. The ends of the sample were overlapped and rolled into a loop shape with a loop length of 55mm, and the ends were clamped and fixed from the outside with a chuck. With the sample fixed, it was compressed by 20mm at a speed of 3.3mm / s from the top of the loop towards the chuck using an indenter, and the pressure applied to the indenter was measured. Three test samples were used, and measurements were taken three times. The average value was defined as the loop stiffness (mN). • Device name: Loop stiffness tester (manufactured by Toyo Seiki Co., Ltd.) ·Environment: 23℃, 50%RH

[0062] Oxygen permeability at 23°C and 60% RH (cc / m³) 2 Measurement of ·day·atm) (1) Nitrogen gas filling A measurement bag was prepared using a synthetic resin film with the raw materials and thickness shown in Table 1. After sealing the bag by heat sealing or the like, the bag was degassed using an aspirator or the like. Degassing was continued until both sides of the bag stuck together. Next, nitrogen gas (purity 99.9% or higher) was filled into the bag using a white hard syringe. The amount of nitrogen gas injected was adjusted to the size of the bag, and as much as possible was injected while ensuring that the film constituting the bag was not under tension from the injected nitrogen gas, but was slightly loose. The amount was measured using the scale on the white hard syringe. Nitrogen gas degassing and injection were performed, for example, by piercing the bag with a needle. When piercing with a needle, double-sided tape was applied to the film constituting the bag, and then polypropylene film adhesive tape (hereinafter referred to as "PP tape") was applied on top of that. After removing the needle, the needle hole was quickly sealed with PP tape. The tape applied to the bag was 4.5 cm. 2 It was designed to fit within the following area. Furthermore, if the film constituting the bag is a microporous film, the tape was not used to block the micropores. (2) Measurement of initial oxygen concentration The initial oxygen concentration (C0) inside the bag immediately after filling with nitrogen gas (t=0) was measured. The gas inside the bag was sampled, and the initial oxygen concentration (C0) inside the bag was determined by gas chromatography (TCD). C0 was 0.2% or less; if it exceeded this, the procedure was repeated. The sampled gas for oxygen concentration measurement was 10cc or less. When injecting into the gas chromatograph, a constant amount of approximately 1cc was injected. In addition, measurements of standard gases (two or more points containing approximately 1% and 10% oxygen) were also performed by injecting the same amount of gas, and a calibration curve was created. (3) Storage of the bag The bags used for initial oxygen concentration measurement were stored at 23°C and 60% RH (in a temperature- and humidity-controlled cabinet). During this time, the bags were left undisturbed so that no objects were placed on top of them and the cabinet's fan did not directly blow air onto them. (4) Measurement of oxygen concentration inside the bag during storage and calculation of oxygen permeation rate The oxygen concentration inside the bag was measured at a total of 3 to 5 points, with at least two points measured immediately after nitrogen gas filling and again at least 3 hours later, within the range of 1% to 7%. A proportional relationship (correlation coefficient of 0.98 or higher) must be established between the elapsed time t (hr) and the oxygen concentration inside the bag. If the correlation coefficient was not established, the test was repeated. If the oxygen permeability rate of the film constituting the bag was too high, causing the increase in oxygen concentration inside the bag to be too rapid and failing to meet this condition, a bag could be created by laminating a portion of the film with a known oxygen permeability rate smaller than that of the film being measured, and the same procedure was followed. In this case, the surface area of ​​the bag was calculated excluding the portion laminated with the other known film, and the oxygen permeability rate of the measured film was obtained by subtracting the oxygen permeability rate of the known film portion from the calculated oxygen permeability rate. The oxygen permeation rate was calculated using the value obtained over the longer elapsed time, as shown in formula (i) below. F = 1.143 × (Ct - C0) × V / t (i) F: Oxygen permeation rate (cc / bag day atm) Ct: Oxygen concentration inside the bag (%) t time after nitrogen gas filling ( C0: Oxygen concentration inside the bag immediately after nitrogen gas filling (%) V: Amount of nitrogen gas filled (cc) t: Time elapsed since gas filling (hr)

[0063] • Water vapor transmission rate at 40°C (g / m³) 2 Measurement (day) The measurements were performed using synthetic resin films with the raw materials and thicknesses shown in Table 1, in accordance with JIS Z 0208 (cup method).

[0064] <Example 1> First, commercially available polypropylene resin (homopolymer) was prepared as the raw material. Next, the molten material was extruded from a T-die at a temperature of 230°C and stretched using a roll stretcher (5 times in the MD direction and 6 times in the TD direction) to obtain a biaxially oriented polypropylene film (synthetic resin film) with the thickness (μm) shown in Table 1. At this time, the temperature of the rolls of the roll stretcher was set to 140°C. After that, an annealing treatment was performed to obtain a synthetic resin film. Next, using the obtained synthetic resin film, two layers were stacked with the inner layers facing inward, and heat-sealed on three sides using an impulse sealer (Fuji Impulse Co., Ltd., FI-400Y-10PK) to form a 10 mm wide heat-sealed section at 160°C for 1 second, thereby producing a packaging bag with the bag size (inner dimensions) shown in Table 1.

[0065] <Example 2> A synthetic resin film was obtained in the same manner as in Example 1, except that the extrusion conditions from the T-die were adjusted to achieve the thickness (μm) shown in Table 1. Next, the synthetic resin form was cut to the bag size (internal dimensions) shown in Table 1, and a packaging bag was manufactured in the same manner as in Example 1.

[0066] <Example 3> A synthetic resin film was obtained in the same manner as in Example 1, except that the extrusion conditions from the T-die were adjusted to achieve the thickness (μm) shown in Table 1. Next, the synthetic resin form was cut to the bag size (internal dimensions) shown in Table 1, and a packaging bag was made in the same manner as in Example 1, with one through hole (hole diameter 70 μm) provided.

[0067] <Example 4> A synthetic resin film was obtained in the same manner as in Example 1, except that the extrusion conditions from the T-die were adjusted to achieve the thickness (μm) shown in Table 1, the stretching treatment was performed four times in the MD direction and four times in the TD direction, and no annealing treatment was performed. Next, the synthetic resin form was cut to the bag size (internal dimensions) shown in Table 1, and a packaging bag was made in the same manner as in Example 1, with one through hole (hole diameter 120 μm) provided.

[0068] <Example 5> A synthetic resin film was obtained in the same manner as in Example 1, except that the stretching treatment was performed four times in the MD direction and four times in the TD direction, and no annealing treatment was performed. Next, the synthetic resin form was cut to the bag size (internal dimensions) shown in Table 1, and a packaging bag was made in the same manner as in Example 1, with one through hole (hole diameter 120 μm) provided.

[0069] <Comparative Example 1> A synthetic resin film was obtained in the same manner as in Example 1, except that the extrusion conditions from the T-die were adjusted to achieve the thickness (μm) shown in Table 1, and stretching and annealing treatments were omitted. Next, the synthetic resin form was cut to the bag size (internal dimensions) shown in Table 1, and a packaging bag was manufactured in the same manner as in Example 1.

[0070] <Comparative Example 2> A synthetic resin film was obtained in the same manner as in Example 1, except that the stretching treatment was performed 6 times in the MD direction and 4 times in the TD direction, and no annealing treatment was performed. Next, the synthetic resin form was cut to the bag size (internal dimensions) shown in Table 1, and a packaging bag was made in the same manner as in Example 1, with one through hole (hole diameter 120 μm) provided.

[0071] <Comparative Example 3> A three-layer synthetic resin film was obtained by co-extruding commercially available polypropylene resin (homopolymer) and ethylene-propylene copolymer (random copolymer, ethylene content 3%) from a T-die (multi-die) at a temperature of 230°C, with the layer structure shown in Table 1, without stretching or annealing treatment. Next, the synthetic resin form was cut to the bag size (internal dimensions) shown in Table 1, and a packaging bag was made in the same manner as in Example 1, with one through hole (hole diameter 120 μm) provided.

[0072] <Rating> The following evaluations were performed on the obtained packaging. [Freshness preservation] 150g of fresh shredded cabbage was placed in each of the resulting packaging bags, and the bags were sealed to create fruit and vegetable packages, which were then stored at 10°C for 3 days. Afterward, the cabbage was removed, its appearance was observed, and its freshness retention was evaluated according to the following criteria. • Freshness preservation (standard) ◎: No loss of freshness whatsoever ○: Slightly reduced freshness △: Clearly shows a decline in freshness. ×: Significant deterioration in freshness

[0073] [Deformation resistance] After grasping only a portion of the packaged goods preserved using the freshness-preserving properties described above, and shaking it up and down 10 times to the point where the fruits and vegetables inside moved vigorously, the strength of the packaging bag was evaluated according to the following criteria. ·Bag strength (standard) ◎: No deformation of the bag ○: The bag is slightly deformed. △: The bag is deformed. ×: The bag has noticeable deformation.

[0074] [Table 1]

Claims

1. A fresh produce preservation bag made of synthetic resin film, The aforementioned synthetic resin film contains polypropylene, The aforementioned synthetic resin film is a single layer, The oxygen permeability of the aforementioned fresh produce preservation bag at 23°C and 60% RH is between 1900 (cc / m²·day·atm) and 30000 (cc / m²·day·atm). The water vapor permeability of the aforementioned fresh produce preservation bag at 40°C is 1 g / (m²·day) or more and 300 g / (m²·day) or less. The ratio of the elastic recovery rate (elastic recovery rate) measured by the following procedure a of the fresh produce preservation bag ＭＤ / Elastic recovery rate ＴＤ A fresh produce preservation bag having a coefficient of 1.00 or less and an elastic recovery rate TD (%) of 61.0% or more (excluding fresh produce preservation bags with a breathable material covering holes with a diameter of 1 to 10 mm). (Procedure a) (i) Cut out the fresh produce preservation bag so that the MD direction of the synthetic resin film is in the length direction, and prepare a 5 mm wide strip-shaped sample. Using a tensile testing machine, the distance between the chucks when both ends of the sample are fixed with chucks is defined as the gauge length L of the sample. ０ (mm) Let the gauge length be L. ０ Stretch the sample until its (mm) is 1.2 times its original size, and hold it in place for 3 minutes. Then, release the sample, and measure the gauge length L of the sample 20 seconds after release. １ Measure (mm). From the following formula (1), the elastic recovery rate ＭＤ Calculate the percentage (%). [7] ０ ×1.2-L １ ] / L ０ ×0.2 (1) (ii) Except for cutting out the fresh produce preservation bag so that the TD direction of the synthetic resin film is the length direction, and preparing a 5 mm wide strip-shaped sample, the measurement was performed in the same procedure as in (i), and the elastic recovery rate was calculated from formula (1). ＴＤ Calculate the percentage (%).

2. A fresh produce preservation bag according to claim 1, A fresh produce freshness preservation bag, wherein the loop stiffness measured by the following procedure b is 2.5 to 30 mN. (Procedure b) Cut out the fresh produce preservation bag so that the TD direction of the synthetic resin film is the length direction, and prepare a 25 mm wide strip-shaped sample. Overlap the two ends of the sample facing each other and roll it into a loop shape so that the loop length is 55 mm, and secure both ends by clamping them from the outside with a chuck. With the sample secured, compress it by 20 mm at a speed of 3.3 mm / s with an indenter, from the top of the loop towards the chuck, and measure the pressure applied to the indenter.

3. A fresh produce preservation bag according to claim 1 or 2, The aforementioned synthetic resin film is made of stretched polypropylene film, and is used for fresh produce preservation bags.

4. A fresh produce preservation bag according to claim 1 or 2, The aforementioned fresh produce preservation bag is a fresh produce preservation bag having through holes.

5. A package containing fresh produce, wherein fresh produce is contained in a fresh produce preservation bag according to claim 1 or 2.

6. In the package containing fresh produce according to claim 5, A package containing fresh produce weighing 300g or more.

7. In the package containing fresh produce according to Claim 5, The aforementioned produce is cabbage; the package contains produce.

8. A method for preserving the freshness of fruits and vegetables, A method for preserving the freshness of fruits and vegetables, comprising the step of placing the fruits and vegetables in a freshness-preserving bag for fruits and vegetables described in claim 1 or 2.

9. In the method for preserving the freshness of fruits and vegetables according to Claim 8, A method for preserving the freshness of fruits and vegetables, wherein the process of storing the fruits and vegetables is carried out under atmospheric pressure.

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