Fruits and vegetables freshness retaining bag, package containing fruits and vegetables, and method for retaining freshness of fruits and vegetables

Abstract

To provide a technology relating to a packaging bag that can achieve both good anti-fogging properties and improved bag strength while retaining the freshness of fruits and vegetables.SOLUTION: The fruit and vegetable freshness retaining bag of the present invention is made of a synthetic resin film, which contains polyethylene and polypropylene, and when the contact angle on the inner surface of the fruit and vegetable freshness retaining bag is defined as αi and the contact angle on the outer surface is defined as αo, αo / αi is 1.1 to 4.0, and the tensile elongation measured by the following procedure 1 is 200 to 500%. Step 1: Prepare a No. 1 dumbbell test piece according to JIS K 7127 so that the MD direction of the synthetic resin film is the test direction, pull the dumbbell test piece in the test direction at 23°C and a tensile speed of 500 mm / min, and measure the length L (mm) between the marked lines just before the test piece breaks, starting from 40 mm between the marked lines. The tensile elongation (%) is calculated as {(L - 40) / 40}×100 (%).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a freshness-keeping 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] A conventional method for preserving the freshness of harvested fruits and vegetables is to moderately suppress the respiration of the fruits and vegetables by adjusting the oxygen and carbon dioxide concentrations. This type of packaging used to preserve the freshness of fruits and vegetables is known as modified atmosphere (MA) packaging. In recent years, with the growing interest in MA packaging, there is a demand for packaging materials to have improved performance in various aspects, including gas permeability, processability, strength, packaging workability, and appearance.

[0003] For example, Patent Document 1 (JP 2023-106849 A) ​​discloses a film for freshness-keeping bags for fruits and vegetables in which the dynamic friction coefficient μ' between the inner surfaces at 40°C is controlled in order to prevent the film itself from reducing the freshness of the fruits and vegetables, taking into account that the packaging film may come into direct contact with the fruits and vegetables. Furthermore, Patent Document 2 (JP 2022-119289 A) discloses a freshness-keeping film that is thin and has excellent content tracking properties, yet does not reduce seal strength, is resistant to whitening due to anti-fog agent bleeding, and has deodorizing properties. Specifically, it discloses that the freshness-keeping film uses a specific polypropylene resin and a specific deodorizing nanofiller. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-106849 [Patent Document 2] Japanese Patent Application Publication No. 2022-119289 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the technologies disclosed in Patent Documents 1 and 2 do not focus on the state of the packaging bag after packaging fruits and vegetables in it. The inventors focused on the fact that after packaging fruits and vegetables in the packaging bag, the packaging bag may tear due to the weight of the fruits and vegetables or the impact during transportation. Further investigation revealed that using a resin material with relatively good stretchability to make the packaging bag less likely to tear tends to reduce the anti-fogging properties of the packaging bag.

[0006] Therefore, the inventor devised a new index relating to the contact angle on the inner surface and the contact angle on the outer surface of the packaging bag, and discovered that by simultaneously controlling the tensile elongation of the packaging bag, it is possible to achieve both good anti-fogging properties and improved bag strength, thereby completing the present invention. [Means for solving the problem]

[0007] According to the present invention, the following technology relating to packaging for fruits and vegetables is provided.

[0008] [1] A freshness-keeping bag for fruits and vegetables made of synthetic resin film, The synthetic resin film includes polyethylene and polypropylene, When the contact angle on the inner surface of the fruit and vegetable freshness-keeping bag is αi and the contact angle on the outer surface is αo, αo / αi is 1.1 to 4.0, A freshness-keeping bag for fruits and vegetables having a tensile elongation of 200 to 500% as measured by the following procedure 1. Step 1: Prepare a No. 1 dumbbell test piece according to JIS K 7127 so that the MD direction of the synthetic resin film is the test direction. Pull the dumbbell test piece in the test direction at 23°C and a tensile speed of 500 mm / min. Measure the length L (mm) between the gauge lines just before breakage, starting from a point 40 mm between the gauge lines. The tensile elongation (%) is {(L - 40) / 40} x 100 (%). [2] The freshness-keeping bag for fruits and vegetables according to [1], Furthermore, the freshness-keeping bag for fruits and vegetables has a tear strength of 1000 to 2500 N / cm as measured in the following procedure 2. Step 2: Prepare a rectangular tear test piece as specified in JIS K 7128-3 and JIS K 6252 so that the MD direction of the synthetic resin film is the test direction, and pull the rectangular tear test piece in the test direction at 23°C and a pulling rate of 200 mm / min. The maximum load required to tear the rectangular tear test piece is defined as the tear strength (N / cm). [3] The freshness-keeping bag for fruits and vegetables according to [1] or [2], A freshness-keeping bag for fruits and vegetables, in which αi is 10° to 45°. [4] The fruit and vegetable freshness-keeping bag according to any one of [1] to [3], The synthetic resin film has a multi-layer structure. [5] The fruit and vegetable freshness-keeping bag according to any one of [1] to [4], The fruit and vegetable freshness-keeping bag has an inner surface made of a layer of polypropylene. [6] The fruit and vegetable freshness-keeping bag according to any one of [1] to [5], The freshness-keeping bag for fruits and vegetables, wherein the synthetic resin film contains an anti-fogging agent. [7] The fruit and vegetable freshness-keeping bag according to any one of [1] to [6], The fruit and vegetable freshness-keeping bag has through holes with a diameter of 4 mm or more. [8] A package containing fresh produce, in which fresh produce is contained in a fresh produce freshness-keeping bag described in any one of [1] to [7]. [9] A method for preserving the freshness of fruits and vegetables, comprising a step of storing fruits and vegetables in a fruit and vegetable freshness preservation bag described in any one of [1] to [8]. [Effects of the Invention]

[0009] According to the present invention, a technology is provided for a packaging bag that can achieve both good anti-fogging properties and improved bag strength while maintaining the freshness of fruits and vegetables. DETAILED DESCRIPTION OF THE INVENTION

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

[0011] In this specification, unless otherwise specified, the expression "X to Y" in the description of a numerical range means at least X and at most Y. For example, "1 to 5% by mass" means "at least 1% by mass and at most 5% by mass."

[0012] <Fruit and vegetable freshness preservation bag> The fruit and vegetable freshness-keeping bag (hereinafter also referred to as "packaging bag") of this embodiment is made of a synthetic resin film, which contains polyethylene and polypropylene, and when the contact angle on the inner surface of the fruit and vegetable freshness-keeping bag is αi and the contact angle on the outer surface is αo, αo / αi is 1.1 to 4.0, and the tensile elongation measured by the following procedure 1 is 200 to 500%. Step 1: Prepare a No. 1 dumbbell test piece according to JIS K 7127 so that the MD direction of the synthetic resin film is the test direction. Pull the dumbbell test piece in the test direction at 23°C and a tensile speed of 500 mm / min. Measure the length L (mm) between the gauge lines just before breakage, starting from a point 40 mm between the gauge lines. The tensile elongation (%) is {(L - 40) / 40} x 100 (%).

[0013] This makes it possible to obtain a packaging bag that is effective in preserving the freshness of fruits and vegetables while also achieving good anti-fogging properties and improved bag strength. The details of the reason for this are not clear, but it is thought to be as follows. In general, it is believed that polyethylene can impart flexibility, extensibility, moderate gas permeability, etc. to synthetic resin films, while polypropylene can impart mechanical strength, good bag-making properties, moderate gas permeability, transparency, etc. to synthetic resin films. Furthermore, a low contact angle generally indicates high wettability and easy water spreading. On the other hand, low wettability means that water is repelled, making it easier for water droplets to form. In other words, increasing wettability makes it harder for water droplets to form, which in turn makes it harder for condensation to occur. Therefore, it is believed that controlling the contact angle of a synthetic resin film can suppress condensation and make it easier to achieve anti-fogging properties. Therefore, in the packaging bag of this embodiment, by setting the ratio (αo / αi) of the contact angle (αi) on the outer surface of the packaging bag to the contact angle (αo) on the inner surface of the packaging bag to 1.1 to 4.0, it is thought that condensation caused by breathing of the fruits and vegetables inside the packaging bag can be suppressed, and that a decrease in freshness of the fruits and vegetables due to condensation can be suppressed.In addition, by using a synthetic resin film with a specific tensile elongation as an index and controlling it to be within a predetermined range, it is thought that tearing of the bag due to the weight of the fruits and vegetables can be suppressed while obtaining anti-fogging properties.

[0014] αo / αi is 1.1 to 4.0, preferably 1.2 to 3.5, and more preferably 1.2 to 3.0. From the viewpoint of improving bag strength while obtaining higher antifogging properties, αo / αi is preferably 1.4 to 2.5.

[0015] αo is preferably 20 to 70°, more preferably 30 to 65°, and even more preferably 35 to 60°.

[0016] On the other hand, αi is preferably 45° or less, more preferably 40° or less, and even more preferably 38° or less. By making αi lower than the above upper limit value, wettability is increased and water droplets are less likely to form, thereby suppressing the occurrence of condensation inside the bag. The lower limit of αi is not particularly limited, but may be 10° or more, or 15° or more.

[0017] The contact angle with water can be determined, for example, using a commercially available contact angle meter (such as DROPMASTER-501 manufactured by Kyowa Interface Science Co., Ltd.) by the sessile drop method, by depositing 2 μL of purified water on the surface to be measured and measuring the water contact angle after 7 seconds.

[0018] The tensile elongation measured in procedure 1 is 200 to 500%, preferably 300 to 450%, and more preferably 350 to 400%. By setting the tensile elongation measured in step 1 to fall within the above numerical range, it becomes easier to achieve both good anti-fogging properties and improved bag strength.

[0019] The packaging bag preferably has a tear strength of 1000 to 2500 N / cm as measured by the following procedure 2. Step 2: Prepare a rectangular tear test piece as specified in JIS K 7128-3 and JIS K 6252 so that the MD direction of the synthetic resin film is the test direction, and pull the rectangular tear test piece in the test direction at 23°C and a pulling rate of 200 mm / min. The maximum load required to tear the rectangular tear test piece is defined as the tear strength (N / cm).

[0020] The tear strength measured in procedure 2 is 1000 to 2500 N / cm, preferably 1100 to 2000 N / cm, and more preferably 1200 to 1800 N / cm. By setting the tear strength measured in step 2 to fall within the above numerical range, it becomes easier to achieve both good anti-fogging properties and improved bag strength.

[0021] In this embodiment, a packaging bag that satisfies the above αo / αi and tensile elongation / tear strength can be realized by selecting a material such as polypropylene, adjusting the polyethylene content, or using additives such as an anti-fogging agent, or by devising the layer structure of the synthetic resin film or the manufacturing method of the synthetic resin film. Examples of the manufacturing method of the synthetic resin film include leaving the synthetic resin film unstretched and adjusting the roll temperature or cooling temperature.

[0022] [Bag shape] The packaging bag of this embodiment is a bag formed from a synthetic resin film, and the bag shape is not particularly limited, and can be a two-sided bag, a three-sided bag, a back-sealed bag (a palm-shaped bag), a pouch, a gusset bag, etc. A two-sided bag is a bag made by folding a synthetic resin film in half, using the folded part as the bottom, and sealing both sides. A three-sided bag is a bag made by sealing the bottom and both sides of two overlapping synthetic resin films. The seal can be a fusion-cut seal obtained by fusion-cutting a synthetic resin film. Fusion-cutting is a method of cutting the synthetic resin film with heat using a hot wire while melting and adhering the synthetic resin film at the cut portion. In this embodiment, a good fusion-cut seal can be obtained by including polyethylene in the synthetic resin film.

[0023] The size (length and width) of the packaging bag of this embodiment can be about 100 mm×100 mm to 350 mm×400 mm when used to pack fruits and vegetables for general consumers.

[0024] [Through hole] The packaging bag may have through holes formed therein, or may have no through holes. Depending on whether or not there are through holes, the water vapor permeability and oxygen permeability can be stably adjusted.

[0025] The planar shape of the through-hole may be, for example, a circle, a polygon, or a slit. The circle is not limited to a perfect circle and includes an approximate circle. In addition to a circle, the through-hole may be a semicircle or a crescent shape. The polygon may be any shape surrounded by three or more line segments, such as a triangle, a rectangle, or a pentagon. The slit is a cut or narrow gap that penetrates the synthetic resin sheet that constitutes the packaging material, and may be a straight line, a curve, an L-shape, an X-shape, or the like, and its length is not particularly limited.

[0026] When 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 even more preferably 50 to 70 μm. By making the diameter equal to or greater than the above lower limit, the oxygen permeability of the package is improved and the generation of unpleasant odors is easily suppressed. On the other hand, by making the diameter equal to or less than the above upper limit, the MA effect can be maintained while preventing the intrusion of foreign matter, making it easier to maintain the freshness of fruits and vegetables. The average diameter of the through holes is calculated from the open area of ​​the through holes, assuming that the through holes are perfect circles.

[0027] The packaging bag may have through holes with a diameter of 4 mm or more. It may also have so-called punched holes. The diameter of the punched holes is preferably 4 to 8 mm, more preferably 4 to 6 mm, from the viewpoint of maintaining freshness while obtaining bag strength. In order to further improve freshness retention, it is preferable that the packaging bag does not have punch holes.

[0028] The number of punched 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 make it easier to maintain freshness.

[0029] The above-mentioned through holes may be formed in the resin film in advance when manufacturing the packaging bag, or may be formed after the resin film is formed into the packaging bag, or may be formed before or after the resin film is formed into the packaging bag.

[0030] The method for forming the through holes is not particularly limited, and any known method can be used, such as a laser processing method, a needle processing method including a hot needle, or a method using a mold such as a roll cutter.

[0031] [Synthetic resin film] (raw materials) The synthetic resin film is preferably transparent or translucent, more preferably transparent, so that the fruit or vegetable can be visually recognized from the outside. It may also be printed with information for identifying the fruit or vegetable. The synthetic resin may be partially made from biomass-derived raw materials.

[0032] The synthetic resin constituting the synthetic resin film is not particularly limited as long as it contains at least polyethylene and polypropylene, and any known synthetic resin can be used as long as it can be used to package fruits and vegetables. This allows for flexibility and stretchability while maintaining appropriate strength, and can achieve both good anti-fogging properties and improved bag strength while maintaining the freshness of fruits and vegetables. In addition, good adhesiveness and weld-sealing properties can be obtained during bag production, improving the strength of the entire bag.

[0033] Polyethylene and polypropylene may be mixed in the same layer, may be an ethylene-propylene copolymer as described below, or the layer containing polyethylene and the layer containing polypropylene may be separate layers. The synthetic resin film may have a multilayer structure containing these layers.

[0034] The polyethylene mentioned above includes various polyethylenes and ethylene copolymers, and specific examples include copolymers such as 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, and ethylene-α-olefin copolymer, as well as ionomers. The linear low-density polyethylene is usually a copolymer of ethylene and a small amount of an α-olefin. The type of α-olefin is not particularly limited. Typical α-olefins include α-olefins having 3 to 10 carbon atoms, such as 1-propylene, 1-butene, 1-hexene, 4-methylpentene-1, and 1-octene. Of these, 1-propylene is preferred. The ethylene content of the ethylene-propylene copolymer is typically 4.5% or less.

[0035] The polypropylene may be a homopolymer, a random copolymer, or a block copolymer. More specifically, the homopolymer may be an isotactic polypropylene, a syndiotactic polypropylene, an atactic polypropylene, or the like, and the random copolymer may be an ethylene-propylene copolymer, a propylene-1-butene copolymer, a propylene-octene copolymer, or the like. Of these, the random copolymer is preferred.

[0036] Examples of other resins include polyamide resins, polyvinyl chloride, polystyrene, acrylic resins, and polyester resins such as polyethylene terephthalate and polylactic acid.

[0037] Examples of the polyamide resin include nylon. Nylon includes nylon 6, nylon 11, nylon 12, nylon 66, nylon 6·10, nylon 6·12, nylon 6·T, nylon 6·I, nylon 9T, nylon M5T, and polymetaxylylene adipamide (MXD nylon), which can be used alone or in combination of two or more. Among these, nylon 6, nylon 11, nylon 12, and nylon 66, either alone or in combination of two or more, are preferred, and nylon 6 and nylon 66, either alone or in combination, are more preferred.

[0038] The synthetic resin film may contain additives such as anti-fogging agents, anti-blocking agents, heat stabilizers, lubricants, impact modifiers, processing aids, anti-static agents, ultraviolet absorbers, antioxidants, weather-resistant agents, fillers, and pigments, as needed, within the range that does not impair the performance of the synthetic resin film.

[0039] The anti-fogging agent may be one that wets and spreads water by hydrogen bonding through hydroxyl groups. Specific examples of the anti-fogging agent include glycerin laurate, diglycerin laurate, decaglycerin laurate, glycerin monostearate, and sorbitan stearate. The antifogging agent is preferably contained in at least the layer that will become the inner surface of the packaging bag in order to prevent water droplets from forming inside the packaging bag. Depending on the use of the packaging bag, the antifogging agent may be contained on both sides of the synthetic resin film in cases where the packaging bag has double-sided sealing properties or in order to enable bag production without considering the front and back of the synthetic resin film.

[0040] Examples of the antiblocking agent include fine particle inorganic compounds such as silica, alumina, alumina silicate, and diatomaceous earth; and fine particle organic compounds such as polyethylene, cross-linked polyethylene, polymethyl methacrylate, and cross-linked polymethyl methacrylate. Use of an anti-blocking agent can improve the handling properties of the synthetic resin film when it is wound into a roll during molding.

[0041] [Oxygen permeability] Oxygen permeability (ml / m) of synthetic resin film at 23°C and 60% RH 2 ·day·atm) is preferably 500 or more and 30,000 or less, more preferably 800 or more and 20,000 or less, and even more preferably 1,000 or more and 10,000 or less.

[0042] For example, oxygen permeability can be calculated by making a bag using a synthetic resin film, measuring the oxygen concentration inside the bag immediately after filling it with nitrogen and after leaving it for a certain period of time, and then calculating the oxygen concentration gradient.

[0043] [Water vapor permeability] The water vapor permeability of the synthetic resin film at 40°C is preferably 1 g / (m 2 ·day) or more, and more preferably 3g / (m 2 ·day) or more. On the other hand, the water vapor permeability of the synthetic resin film at 40°C is preferably 300 g / (m 2 ·day) or less, and more preferably 100g / (m 2 ·day) or less, and more preferably 50 g / (m 2 ·day) or less, and particularly preferably 10 g / (m 2 ·day) or less.

[0044] The water vapor permeability can be measured by a method in accordance with JIS Z 0208 (cup method).

[0045] (film manufacturing method) The method for obtaining the synthetic resin film is not particularly limited, and examples of the method for obtaining the synthetic resin film include known methods such as extrusion, inflation, and calendering. The synthetic resin film may be stretched or annealed, or may be left unstretched. When stretched, the stretching ratio is not particularly limited, but may be, for example, about 2 to 5 times in both the MD and TD directions. The conditions may be adjusted as appropriate so as to achieve the above-mentioned contact angle, tensile elongation, and tear strength.

[0046] (Layer composition) The synthetic resin film may be a single layer or a multi-layer structure of two or more layers. As described above, it may be a single layer containing a mixture of polyethylene and polypropylene, or it may be two or more layers including a layer containing polyethylene and a layer containing polypropylene. Specifically, for example, in order to obtain good anti-fogging properties, it is preferable that the polypropylene-containing layer is disposed on the inside when the bag is made, and it is more preferable that the polypropylene-containing layer constitutes the inner surface. In addition, in order to obtain good anti-fogging properties, it is preferable that the polypropylene-containing layer contains an anti-fogging agent. The polyethylene-containing layer is preferably an intermediate layer. For example, the polyethylene-containing layer may be an intermediate layer, and the polypropylene-containing layers may be an inner and outer layer, forming a three-layer structure. Furthermore, it is preferable that the polyethylene and polypropylene are in the same layer. This provides good tear strength. Furthermore, in order to further increase tear strength, it is preferable to form a multilayer film in which a layer containing polyethylene and polypropylene is an intermediate layer and a polypropylene layer is an outer layer.

[0047] By making the synthetic resin film multilayered, it is possible to enhance the desired functionality. For example, by adding a function such as slipperiness to the surface layer of the synthetic resin film, the handleability and heat sealability of the synthetic resin film can be improved, and packaging bags with an excellent balance of elongation and rigidity can be consistently obtained. Furthermore, for example, by making the synthetic resin film into a two-layer or three-layer structure and making a layer containing an antiblocking agent at least one of the surface layers, slipperiness can be obtained.

[0048] When the synthetic resin film is multi-layered, the base resins of the layers may be the same or different from each other. From the viewpoint of obtaining good adhesion between the layers, it is preferable that the same resin is used for each layer.

[0049] When the synthetic resin film is multilayered, the thickness of each layer may be the same or different. For example, in the case of a three-layer structure, the thickness of the middle layer may be the greatest and the thickness of the surface layer may be the smallest. The surface layer preferably accounts for 10 to 20% of the total thickness of the synthetic resin film, and more preferably 12 to 17%.

[0050] As a method for obtaining a multilayer film, known methods such as dry lamination, extrusion lamination, coextrusion, coating, etc. can be appropriately used. From the viewpoint of improving adhesion between layers and controlling layer thickness, coextrusion is preferred. The synthetic resin film is preferably multi-layered in order to improve the anti-fogging property and the bag strength in a well-balanced manner.

[0051] (Thickness) The thickness of the synthetic resin film is preferably 5 to 300 μm, more preferably 10 to 200 μm, even more preferably 15 to 100 μm, and particularly preferably 20 to 70 μm. By making the thickness of the synthetic resin film equal to or greater than the above lower limit, the strength of the packaging bag is increased, suppressing deformation due to external stress, while stably achieving a freshness-preserving effect.By making the thickness of the synthetic resin film equal to or greater than the above upper limit, the flexibility (suppleness) of the packaging bag can be maintained.

[0052] [Fruits and vegetables] In this embodiment, fruits and vegetables refer to uncooked vegetables that have been grown in soil or hydroponically, from which inedible parts such as roots, skin, core, stem, seeds, and flowers have been removed, leaving the edible parts of the vegetables in a state that is easy to eat and can be easily cooked.

[0053] Examples of fruits and vegetables include, but are not limited to, semi-heading and heading vegetables such as cabbage, Chinese cabbage, lettuce (lettuce, leaf lettuce, cos lettuce, sunny lettuce, salad lettuce, and lettuce), and Brussels sprouts; spinach, komatsuna, mizuna, bok choy, turnip (kakina), non-heading lettuce (romaine lettuce, sunny lettuce, and the like); non-heading leafy vegetables such as chrysanthemum, kukitachina, shinobu-na, santona, rapeseed, chijirena, kousai-tai, urui, field wasabi, flower wasabi, watercress, arugula, shepherd's purse, petit vert, ice plant, and leaf radish; root vegetables such as sweet potato, potato, nagaimo (Japanese yam), yam, taro, jinenjo (Japanese yam), daikon radish, carrot, burdock, turnip, and ginger; leek, tuna, and the like. Examples of suitable vegetables include Allium vegetables such as onions and chives; Brassicaceae flower buds such as broccoli and cauliflower; Cucurbitaceae fruit vegetables such as cucumbers and pumpkins; Solanaceae fruit vegetables such as eggplant, tomato, cherry tomato, bell pepper, and paprika; okra, bitter melon, zucchini, bitter gourd, 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), myoba (Japanese parsley), Japanese water dropwort, mitsuba (Japanese parsley), and herbs (thyme, sage, parsley, Italian parsley, rosemary, oregano, lemon balm, chives, lavender, salad burnet, lamb's ear, rocket, dandelion, and nasturtium); and fungi and mushrooms. These may be packaged singly or in a mixture of two or more types.

[0054] Fruits and vegetables may be appropriately cut in consideration of purchase and consumption, and may be roughly divided into 1 / 8 to 1 / 2 in the case of cabbage, Chinese cabbage, pumpkin, etc. Furthermore, they may be cut into bite-sized pieces or shredded for eating raw in salads or for cooking in stir-fries.

[0055] <Packaging containing fruits and vegetables> The fruit and vegetable package of this embodiment (hereinafter also referred to as "package") contains fruit and vegetables in the fruit and vegetable freshness-keeping bag described above, thereby improving the freshness-keeping effect of the fruit and vegetables.

[0056] It is preferable that the opening of the package be sealed after packaging the fruits and vegetables. The sealing may be achieved, for example, by heat sealing the opening of the bag, or by using a back sealing tape, a cable tie, a rubber band, or a member such as a caulking member.

[0057] The amount of fruit or vegetable contained in a packaging bag may vary depending on the size of the container, the type of fruit or vegetable, the purpose of the package, etc. For fruit or vegetable intended for general consumers, the amount is preferably 50 to 1000 g, more preferably 100 to 800 g, from the viewpoints of ease of consumption immediately after opening and convenient carry-out and handling.

[0058] <How to maintain freshness> The freshness preservation method of this embodiment includes a step of storing fruits and vegetables in the above-described package containing the fruits and vegetables. Storage can be carried out by known methods, but it is preferable to store the package at an ambient temperature of 2 to 20°C. The ambient temperature refers to, for example, the temperature setting of a refrigerator or refrigerated room in which the package is stored, or the temperature setting of a showcase in which the package is displayed in a store, etc. It does not refer to a strict measurement of the temperature around the package. Furthermore, the average ambient temperature should be 2 to 20°C, and temporary temperatures of around 10°C are acceptable due to unavoidable circumstances such as the opening and closing of doors during transport of the package.

[0059] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations may be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications and improvements within the scope of achieving the object of the present invention are included in the present invention. [Example]

[0060] The present invention will be described in detail below with reference to examples and comparative examples. However, it should be noted that the present invention is not limited to the examples.

[0061] (1) Measurement and physical properties ·Measurement of contact angles (αi, αo) Using a DROPMASTER-50 manufactured by Kyowa Interface Science Co., Ltd., the water contact angle was determined by the sessile drop method, by depositing 2 μL of purified water onto the surface to be measured and measuring the water contact angle after 7 seconds.

[0062] Tensile elongation measurement A JIS K 7127 No. 1 dumbbell test piece was prepared so that the MD direction of the synthetic resin film was the test direction. The dumbbell test piece was pulled in the test direction at 23°C and a tensile speed of 500 mm / min. The length L (mm) between the gauge lines just before breakage was measured, starting from a point 40 mm between the gauge lines. The tensile elongation (%) was calculated as {(L-40) / 40} x 100 (%). The test machine used was a mechanical strength measuring instrument (Tensilon universal material testing machine RTF-1250, manufactured by A&D Co., Ltd.).

[0063] Tear strength A rectangular tear test piece according to JIS K 7128-3 and JIS K 6252 was prepared so that the MD direction of the synthetic resin film was the test direction, and the rectangular tear test piece was pulled in the test direction at 23°C and a pulling rate of 200 mm / min to obtain an SS curve and calculate the tear strength (N / cm). If the tear point was clearly identified on the SS curve, the tear strength was calculated from the maximum stress before and after the point. If the tear point was unclear, the tear strength was calculated from the intersection of two tangents drawn from points before and after the inflection point on the SS curve. The test machine used was a mechanical strength measuring instrument (Tensilon universal material testing machine RTF-1250, manufactured by A&D Co., Ltd.).

[0064] (2) Production of synthetic resin films and packaging bags Example 1 First, a synthetic resin film was prepared according to the following procedure. A commercially available polypropylene resin (homopolymer), an ethylene-propylene copolymer (random copolymer, ethylene content 3%), and an anti-fog agent were co-extruded from a T-die (multi-die) at a temperature of 230°C so as to obtain the "layer structure" shown in Table 1 below, and the extrusion was cooled for 2 seconds with a roll set at 20°C, and then taken up with a roll at room temperature (not particularly temperature-adjusted) to obtain a synthetic resin film.

[0065] Next, two sheets of the obtained synthetic resin film were stacked together with the inner layer facing outwards, and heat-sealed on three sides using an impulse sealer (manufactured by Fuji Impulse Co., Ltd., FI-400Y-10PK) to form a 10 mm wide heat-sealed area at 160°C for a sealing time of 1 second, to produce packaging bags with the bag size (inner dimensions) shown in Table 1.

[0066] <Example 2> Packaging bags were produced in the same manner as in Example 1, except that the layer structure (thickness) was changed as shown in Table 1.

[0067] Example 3 A packaging bag was produced in the same manner as in Example 2, except that one punch hole having a hole diameter of 5 mm was made in the packaging bag obtained in Example 2.

[0068] Example 4 Packaging bags were produced in the same manner as in Example 1, except that the bag thickness and layer structure (thickness) were changed to those shown in Table 1 and extrusion was used instead of co-extrusion.

[0069] <Example 5> Packaging bags were produced in the same manner as in Example 1, except that the bag thickness and layer structure (thickness) were changed to those shown in Table 1 and extrusion was used instead of co-extrusion.

[0070] <Comparative Example 1> Packaging bags were produced in the same manner as in Example 1, except that the bag thickness and layer structure (thickness) were changed to those shown in Table 1 and extrusion was used instead of co-extrusion.

[0071] <Comparative Example 2> Packaging bags were produced in the same manner as in Example 1, except that the bag thickness and layer structure (thickness) were changed to those shown in Table 1 and extrusion was used instead of co-extrusion.

[0072] <Comparative Example 3> The melt extruded at 230°C was stretched 5 times vertically and 9 times horizontally, cooled for 2 seconds with a roll set to 20°C, and then taken up with a roll at room temperature (no particular temperature adjustment) to obtain a synthetic resin film. Using this synthetic resin film, a packaging bag was produced in the same manner as in Example 1.

[0073] (3) Evaluation [Freshness preservation, anti-fogging] First, fruits and vegetables were placed in each packaging bag and stored under the following conditions. 1 kg of fresh shredded cabbage was placed in each of the packaging bags obtained in Example 1 and Comparative Example 3, and the packaging bag was sealed to prepare a package containing fruits and vegetables, which was then stored at 10°C for 3 days. 500 g of fresh potatoes were placed in each of the packaging bags obtained in Examples 2 to 5 and Comparative Examples 1 and 2, and the packaging bags were sealed to prepare packages containing fruits and vegetables, which were then stored at 20°C under lighting for 7 days. Next, the fruits and vegetables inside were visually inspected from the outside, and the anti-fogging ability was evaluated according to the following criteria: The fruits and vegetables were then removed, and changes in appearance were observed, and the freshness retention was evaluated according to the following criteria. · Freshness retention (standard) ◎: No loss of freshness 〇: Slight decrease in freshness △: Clear decrease in freshness ×: Significant decrease in freshness Anti-fogging (standard) ◎: No condensation occurs. The contents are clearly visible. 〇: A small amount of condensation occurs. The contents are slightly difficult to see. △: Condensation is evident. Contents are difficult to see. ×: Significant condensation occurred. The contents were barely visible.

[0074] [Bag strength] The package stored for the above freshness retention was shaken up and down 10 times so that the fruits and vegetables inside were vigorously moved, and then the strength of the packaging bag was evaluated according to the following criteria. ·Bag strength (standard) ◎: No tear or deformation of the bag. Good: No tear in the bag. Slight deformation of the bag. △: There is a small tear in the bag. ×: There is a clear tear in the bag.

[0075] [Table 1]

Claims

1. A freshness-keeping bag for fruits and vegetables made of a synthetic resin film, The synthetic resin film includes polyethylene and polypropylene, When the contact angle of the inner surface of the fruit and vegetable freshness-keeping bag is αi and the contact angle of the outer surface is αo, αo / αi is 1.1 to 4.0, A fruit and vegetable freshness-keeping bag having a tensile elongation of 200 to 500% as measured by the following procedure 1. Step 1: Prepare a No. 1 dumbbell test piece according to JIS K 7127 so that the machine direction of the synthetic resin film is the test direction. Pull the dumbbell test piece in the test direction at 23°C and a tensile speed of 500 mm / min. Measure the length L (mm) between the gauge lines just before breakage, starting from a point 40 mm between the gauge lines. The tensile elongation (%) is calculated as {(L - 40) / 40} x 100 (%).

2. The fruit and vegetable freshness-keeping bag according to claim 1, Furthermore, the fruit and vegetable freshness-keeping bag has a tear strength of 1000 to 2500 N / cm as measured by the following procedure 2. Step 2: A rectangular tear test piece as specified in JIS K 7128-3 and JIS K 6252 is prepared so that the MD direction of the synthetic resin film is the test direction, and the rectangular tear test piece is pulled in the test direction at 23°C and a pulling rate of 200 mm / min. The maximum load required to tear the rectangular tear test piece is defined as the tear strength (N / cm).

3. The fruit and vegetable freshness-keeping bag according to claim 1 or 2, The freshness-keeping bag for fruits and vegetables, wherein αi is 10° to 45°.

4. The fruit and vegetable freshness-keeping bag according to claim 1 or 2, The synthetic resin film has a multi-layer structure.

5. The fruit and vegetable freshness-keeping bag according to claim 1 or 2, The fruit and vegetable freshness-keeping bag has an inner surface made of a layer of polypropylene.

6. The fruit and vegetable freshness-keeping bag according to claim 1 or 2, The freshness-keeping bag for fruits and vegetables, wherein the synthetic resin film contains an anti-fogging agent.

7. The fruit and vegetable freshness-keeping bag according to claim 1 or 2, The fruit and vegetable freshness-keeping bag has through holes with a diameter of 4 mm or more.

8. A package containing fruits and vegetables, in which fruits and vegetables are housed in the fruit and vegetable freshness-keeping bag according to claim 1 or 2.

9. A method for preserving the freshness of fruits and vegetables, comprising the step of storing fruits and vegetables in the fruit and vegetable freshness-preserving bag according to claim 1 or 2.

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