JP2024021914A - Freshness preserving method for fruits and vegetables - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preserving freshness of fruits and vegetables, for which the preserving bags are easier to make than conventional ones, and low cost can be realized.

SOLUTION: The present invention relates to a freshness preserving method for fruits and vegetables, in which fruits and vegetables are inserted into a fruits and vegetables freshness-preserving storage bag which is made of biaxially oriented polypropylene film that has at least one layer containing polyethylene resin, of which the opening part is twisted and the twisted part is fixed with a fixing device or fixing tape; the squeezing degree that is determined by the formula (1) below is 7 to 35%. Squeezing degree=[Film cross-sectional area (bottom length of freshness-preserving bag (mm)×2×freshness-preserving bag thickness (mm)]/cross-sectional area of twisted part (mm²)×100(%)....(1).

SELECTED DRAWING: Figure 3

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a storage bag for preserving the freshness of fruits and vegetables made of a synthetic resin film.

Fruits and vegetables such as leafy vegetables, fruit vegetables, root vegetables, fruits, and mushrooms continue to have a respiratory effect even after being harvested. Since energy is consumed by this respiration, the freshness of fruits and vegetables is significantly reduced during storage, distribution, etc. after harvest.

In recent years, fruits and vegetables are often packaged in film when selling them, partly with the intention of suppressing deterioration in freshness. When packaging fruits and vegetables with a film, a material for preserving the freshness of fruits and vegetables that not only wraps but also seals and provides an MA (Modified Atomosphere) effect is used as the film. This method of packaging fruits and vegetables is called MA packaging.

MA packaging involves packaging fruits and vegetables in bags that control the amount of gas permeation, and creating a low oxygen concentration and high carbon dioxide concentration inside the package by balancing the amount of respiration of the packaged fruits and vegetables with the amount of gas permeation through the packaging bag. It suppresses the respiration of fruits and vegetables to maintain their freshness.

For MA packaging, for example, in the techniques described in Patent Documents 1 to 5, a method is adopted in which the amount of gas permeation is controlled by perforating the film, and this has become the mainstream technology of MA packaging. There is a problem in that the cost of the synthetic resin film used in storage bags for preserving the freshness of fruits and vegetables is high because it is necessary to perform hole punching.

As a method for solving the above problem, in Patent Document 6, a non-perforated film is inserted through an opening into which root vegetables are inserted on one side, and a bag sealing member is tied to the insertion opening. A method for preserving the freshness of root vegetables is disclosed, in which the above-mentioned MA packaging effect improves the freshness preservation of root vegetables by closing the opening. However, this method uses an ethylene-vinyl alcohol copolymer as the non-perforated film, making the film expensive, and has the problem that fruits and vegetables are limited to root vegetables.

On the other hand, in Patent Document 7, in a fruit and vegetable package in which the opening of a synthetic resin film is bound using a binding material, the gas permeability of the package is controlled by the tightness of the binding material, and the MA packaging effect improves the freshness of the fruit and vegetables. A retention package technique is disclosed. This method uses a biaxially oriented polypropylene film, which is an inexpensive film, so the problem in Patent Document 6 is improved, but it is expensive because a polycarbonate caulking tool is used as the binding material. However, even if other binding materials are used, there is a problem in that the tightness of the binding material must be changed depending on the type of binding material, which is complicated.

Furthermore, Patent Document 8 discloses a technology for individually wrapping fresh plants in which the whole fresh plant is individually wrapped with a plastic film having specific characteristics and MA-wrapped in an unsealed state by folding or twist-wrapping. has been done. However, this method uses a styrene-butadiene block copolymer as the plastic film, is expensive, and has the problem that it is necessary to control the oxygen concentration within the package to 2 to 10%.

Japanese Patent Application Publication No. 4-53445 Japanese Unexamined Patent Publication No. 7-170907 Japanese Patent Application Publication No. 63-44837 Japanese Unexamined Patent Publication No. 61-259982 Japanese Patent Application Publication No. 2003-199490 Japanese Patent Application Publication No. 2018-172146 Japanese Patent Application Publication No. 2003-180242 Japanese Patent Application Publication No. 8-48382

The present invention has been made against the background of such conventional problems. That is, an object of the present invention is to provide a freshness-keeping packaging method for fruits and vegetables that can improve the freshness-keeping effect of fruits and vegetables with the MA packaging effect using an inexpensive transparent film made of inexpensive polyolefin resin and processed without holes. It is in.

As a result of intensive studies to solve the above problem, the present inventors inserted fruits and vegetables into the storage bag made of the above-mentioned inexpensive transparent film, twisted the opening of the storage bag, and fixed the twisted part with fixing tape or the like to a specific area. They discovered that this can be achieved by fixing the cross-sectional area, and completed the present invention.

That is, the present invention consists of the following configuration.
[1] Fruits and vegetables are inserted into a freshness-keeping storage bag for fruits and vegetables made of a biaxially oriented polypropylene film having at least one layer containing a polyethylene resin, the opening is twisted, and the twisted part is fixed. A method for preserving the freshness of fruits and vegetables, characterized in that the degree of squeezing determined by the following formula (1) is 7 to 35%.
Squeezing degree...[Film cross-sectional area (bottom length of freshness-keeping bag (mm) x 2 x freshness-keeping bag thickness (mm)] ÷ twisted section cross-sectional area (mm2) x 100 (%) (1)
[2] The method for preserving the freshness of fruits and vegetables according to [1], wherein the content of the polyethylene resin in the base layer of the biaxially stretched polypropylene film is 5 to 15% by weight.
[3] The method for preserving the freshness of fruits and vegetables according to [1] or [2], wherein the biaxially stretched polypropylene film is a non-perforated film.
[4] The method for preserving the freshness of fruits and vegetables according to any one of [1] to [3], wherein the fixing tape for the twisted portion is a back sealing tape.
[5] The method for preserving the freshness of fruits and vegetables according to any one of [1] to [4], wherein the polyethylene is biomass-derived polyethylene.

The method for preserving the freshness of fruits and vegetables according to the present invention uses an inexpensive synthetic resin film, and there is no need to uniformly provide multiple fine holes or slits in the synthetic resin film during film manufacturing or bag making process. In addition, the freshness-keeping effect of fruits and vegetables can be expressed by an inexpensive and simple method of twisting the opening after inserting the fruits and vegetables and fixing the twisted part, which is excellent in economical efficiency. Furthermore, by adjusting the ratio of the cross-sectional area of the film included in the cross-sectional area of the twisted portion, the MA packaging characteristics of the storage bag for preserving the freshness of fruits and vegetables can be controlled, making it effective for many types of fruits and vegetables. It is possible to ensure a freshness retaining effect.

This figure shows a cut surface of a packaging bag fixed with back sealing tape. It is a diagram when 12 points are specified on the inside of the sealing surface in order to measure the cross-sectional area of the twisted part surrounded by the back sealing tape. It is a correlation diagram showing the relationship between the squeezing degree and the freshness retention evaluation results using the results of Examples and Comparative Examples.

{Materials and composition of storage bags for keeping fruits and vegetables fresh}
The storage bag for preserving the freshness of fruits and vegetables according to the present invention is preferably a biaxially oriented polypropylene film having at least one layer containing a polyethylene polymer.

The above-mentioned biaxially stretched polypropylene film may be of a single layer type, but it is more preferably a multilayer type consisting of at least two layers.

For example, in the case of a two-layer type, it is preferably composed of a base layer (A) and a sealing layer (B), and in the case of a three-layer type, a surface layer (C) is provided on the opposite side of the sealing layer of the two-layer type. It is preferable that these are laminated.

{Base material layer (A)}
It is preferable that the base material layer (A) mainly consists of polypropylene resin. Examples of the polypropylene resin include polypropylene homopolymers and crystalline polypropylene resins. Crystalline polypropylene resin is preferred. The crystalline polypropylene resin preferably has a melting point of 155°C to 165°C.

The crystalline polypropylene resin is a copolymer of propylene and other α-olefins. Examples of α-olefins other than propylene include α-olefins other than propylene having 2 to 10 carbon atoms, such as ethylene, 1-butene, 1-pentene, 1-hexene, etc. α-olefins can be mentioned. Furthermore, carbon atoms having 2 to 4 carbon atoms, such as ethylene and 1-butene, are preferable, and ethylene is particularly preferable. These α-olefins other than propylene may be used alone or in combination of two or more. The content of α-olefins other than propylene is suitably 1.3% by weight or less, and 0.5% by weight or less. It is preferably 5% by weight or less.

{Blending polyethylene resin into base layer (A)}
In the present invention, it is preferable that the base material layer (A) contains a polyethylene resin.

The melting point of the polyethylene resin is preferably 100°C to 135°C, more preferably 105°C to 130°C. Further, the density is measured according to JIS K7113, and is preferably 0.90 g/cm ³ or more and 0.94 g/cm ³ or less, more preferably 0.91 g/cm ³ or more and 0.93 g/cm ³ or less.
Examples of the polyethylene resin include random or block copolymers of 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, etc., or mixtures thereof. Moreover, it is more preferable to use an environmentally friendly biomass-derived ethylene resin. Examples of the environmentally friendly biomass-derived ethylene polymer include those using plant-derived ethylene obtained from plants such as sugar cane, potato, and corn.

By blending the above-mentioned polyethylene resin, the twisted portion can be easily returned, and even if the twisted portion is fixed, a preferable MA packaging effect can be ensured. The polyethylene resin may also be blended into the seal layer (B) and surface layer (C), which will be described later.

It is preferable to add an antifogging agent to the resin forming the base layer (A). If an antifogging agent is not added, the inside of the fruit or vegetables will become cloudy when packaged, and spoilage will progress more easily, resulting in a decrease in product value. The mechanism of the antifogging property of the polypropylene resin multilayer film of the present invention is that by adding an antifogging agent to the resin forming the base layer (A), the film can be manufactured and stored after film formation. The antifogging agent migrates to the sealing layer (B), and the surface of the sealing layer (B) becomes in a state having antifogging properties. This effect can be demonstrated when packaging fruits and vegetables, which are characterized by their continued physiological effects even after harvest. In order to maintain excellent anti-fog properties over the long term during the distribution process, it is necessary to take into account temperature changes during storage and distribution, even in environments where the temperature repeatedly changes between 5 and 40 degrees Celsius. It is preferable to select an antifogging agent that exhibits antifogging properties.

Examples of antifogging agents added to the resin forming the base layer (A) include fatty acid esters of polyhydric alcohols, amines of higher fatty acids, amides of higher fatty acids, and amines and amides of higher fatty acids. Typical examples include ethylene oxide adducts. The amount of antifogging agent present in the film is preferably 0.1 to 10% by weight, particularly 0.2 to 5% by weight based on the total layer.

In addition, various additives may be added to improve quality such as slipperiness and antistatic properties, as long as they do not impair the effects of the present invention. For example, lubricants such as wax and metal soap, plastic It is also possible to incorporate known heat stabilizers, antioxidants, antistatic agents, ultraviolet absorbers, etc., which are usually added to polypropylene films.

{Seal layer (B)}
The sealing layer (B) in the present invention preferably has excellent heat-sealing properties since it is made by a heat-sealing method when forming the freshness-keeping storage bag for fruits and vegetables of the present invention. Furthermore, in the present invention, it is preferable to use a non-perforated film from the point of view of economy, and therefore it is preferable to use a resin with excellent gas permeability.

The resin constituting the seal layer (B) is not limited as long as it is a polypropylene resin, but it is preferably a copolymer of propylene with a melting point of 120 to 140° C. and an α-olefin other than propylene. Examples of α-olefins other than propylene include α-olefins other than propylene having 2 to 20 carbon atoms, such as ethylene, 1-butene, 1-pentene, 1-hexene, 4-Methyl-1-pentene, 3-methyl-1-pentene, 1-octene, 3-methyl-1-butene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1- Eicosene, cyclopentene, cycloheptene, norbornene, 5-ethyl-2-norbornene, tetracyclododecene, 2-ethyl-1,4,5,8-dimethano-1,2,3,4,4a,5,8,8a - Octahydronaphthalene and the like. Among these, those having 2 to 4 carbon atoms, such as ethylene and butene, are preferred, and ethylene is more preferred. These α-olefins other than propylene may be used alone or in combination of two or more.

The content of α-olefin other than propylene in the propylene copolymer is preferably 14% by weight or less, more preferably 10% by weight or less.

Furthermore, since the sealing layer (B) comes into contact with fruits and vegetables, an appropriate amount of a deodorant or an antibacterial agent can be added to the sealing layer. In addition, the combination of the deodorant and antibacterial agent is effective in suppressing foreign odors. The deodorant may be blended into the sealing layer in an amount of, for example, 1 to 6 parts by weight based on 100 parts by weight of the resin composing the layer, and the antibacterial agent may be blended with the resin composing the sealing layer. For example, it is preferable to mix the amount in the range of 0.1 to 1 part by weight per 100 parts by weight.

The antifogging agent blended in the base layer (A) is transferred (bleeded out) to the sealing layer (B) even if the antifogging agent is not blended, and the antifogging property of the sealing surface of the sealing layer is is expressed. By incorporating the above-mentioned antifogging agent into the sealing layer as well, the antifogging properties of the sealing layer (B) surface are further stabilized. The type of antifogging agent blended into the seal layer (B) may be the same as or different from the antifogging agent blended into the base layer (A).

{Surface layer (C)}
The surface layer (C) of the present invention may be the same as the seal layer (B) or may be different. It is preferable to use a copolymer resin with a melting point of 130 to 140° C. that has a slightly lower content of α-olefins other than propylene in the propylene copolymer used for the sealing layer (B).

In a preferred embodiment, an antifogging agent is also blended into the surface layer (C). When packaging fruits and vegetables and displaying them in supermarkets, etc., the surface will be improved due to dew condensation, etc.

The type of antifogging agent blended into the surface layer (C) may be the same as or different from the antifogging agent blended into the base layer (A).

{Blend of anti-blocking agent}
The outer surfaces of the sealing layer (B) and the surface layer (C) are smooth, and the films are in close contact with each other, resulting in poor sliding properties between the films and poor handling properties. Therefore, in order to prevent this problem, an anti-blocking agent or a lubricant may be included to the extent that the effects of the present invention are not impaired. Examples of such anti-blocking agents include commonly used inorganic silica, kaolin, zeolite, etc., and organic crosslinked acrylic beads. Furthermore, examples of the lubricant include calcium stearate. The anti-blocking agent and the lubricant may be used alone or in combination of two or more.

The amount of the anti-blocking agent or lubricant added may be adjusted appropriately depending on the type of resin, etc., and is preferably 0.3 to 3.0 parts by weight based on 100 parts by weight of the resin constituting the layer. is 0.5 to 2.0 parts by weight.

{Shape of storage bag for preserving freshness}
The shape of the freshness-keeping storage bag according to the present invention is not particularly limited. Shapes such as three-sided bags made by heat-sealing the edges and bottom, two-sided bags made by folding a synthetic resin film in half and then heat-sealing the edges, and gassho bags made by folding the left and right sides of the film and heat-sealing them on the back. It is possible to implement it by

{Size of storage bag for keeping fruits and vegetables fresh}
The size of the freshness-keeping storage bag according to the present invention is not limited. The size can be appropriately selected depending on the type of fruits and vegetables to be packaged, the weight of the fruits and vegetables to be stored, etc.

{Back sealing tape}
It is preferable to use a polyester adhesive binding tape with an adhesive layer laminated on one side. However, the type and material of the back sealing tape are not limited.

{How to package fruits and vegetables using storage bags to maintain freshness}
Fruits and vegetables are inserted through the opening of the storage bag for preserving shape freshness, and any part between the opening and the vegetable storage section is twisted, and the twisted section is fixed. The fixing member is not particularly limited, but it is preferable to use back sealing tape, string, rubber bands, etc., which are more flexible than metals or clips, in order to take advantage of the good return of the twisted part. is preferred. In particular, it is preferable to bind using a back sealing tape and a back sealer device. Although the fixing location is not limited, it is preferable to place it in the middle between the opening and the vegetable storage section. Although the type and material of the back sealing tape are not limited, it is preferable to use a polyester binding adhesive tape with an adhesive layer laminated on one side. It is also possible to enclose an ethylene adsorbent, an oxygen scavenger, etc. together with the fruits and vegetables at the time of packaging.

{Aperture degree}
The degree of aperture can be determined by the following equation (1).
{Degree of squeezing} = [Film cross-sectional area (bottom length of freshness-preserving bag (mm) x 2 x freshness-preserving bag thickness (mm)] ÷ twisted section cross-sectional area (mm ² ) x 100 (%)... 1)

The cross-sectional area of the twisted portion refers to the portion surrounded by the fixing member. For example, if it is fixed with back sealing tape, cut the center of the part fixed with back sealing tape, and refer to the cut surface inside the sealing surface surrounded by back sealing tape (Figure 1). If it is fixed with a binding material other than back sealing tape, cut along the binding material and measure the cut surface of the part fixed with the binding material. The cross-sectional area of the film refers to the cross-sectional area of the part that is included in the cross-sectional area of the twisting part and that squeezes and fixes both the front and back sides of the bag.

The method for measuring the cross-sectional area of the twisted portion is to photograph the area of the twisted portion with a camera and measure the area using image processing software. The image processing software may be any software that can calculate the area by specifying the range of the photographed image. Since it is necessary to include a scale that shows the length in the photographed image, it is desirable to take the photograph with a ruler or the like. The area of the twisted part shown below in the text was photographed using "Tough TG-6" manufactured by OM Digital Solutions Co., Ltd., and was surrounded with back sealing tape using the image processing software "AreaQ" manufactured by Estech Co., Ltd. By specifying 12 points at equal intervals on the inside of the sealed seal surface (Figure 2), the cross-sectional area of the twisted portion was specified and measured. In the fruit and vegetable packaging method of the present invention, the degree of squeezing is preferably 7% or more and 35% or less. More preferably, it is 9% or more and 32% or less. Furthermore, it is most preferably 14% or more and 27% or less.

In the method for preserving the freshness of fruits and vegetables of the present invention, the degree of twisting changes the gas permeability within the package and changes the MA packaging effect. It is preferable to set the ratio within a specific range. When the degree of constriction is less than 9%, gas permeability decreases, anaerobic respiration is likely to occur, and problems such as odor are likely to occur. On the other hand, if it exceeds 32%, gas permeability increases too much, and discoloration due to excessive breathing is likely to occur.

Further, the thickness of the synthetic resin film that is the forming material of the storage bag for preserving the freshness of fruits and vegetables of the present invention is not particularly limited, but it is preferably in the range of 10 to 70 μm, and more preferably in the range of 15 to 40 μm. If the thickness is less than 10 μm, it is undesirable because the film loses its "stiffness" and the twisted part becomes difficult to return. On the other hand, if it exceeds 70 μm, the film becomes too rigid and it is difficult to fix the opening. This is not desirable.

{Applicable types of fruits and vegetables}
Furthermore, any type of fruits and vegetables that can be applied to the method for preserving the freshness of fruits and vegetables according to the present invention may be packaged. For example, various fruits and vegetables such as leaf vegetables, root vegetables, fruit vegetables, and mushrooms can be packaged. Yes, but not limited. The freshness-preserving effect is particularly likely to be exerted on leafy vegetables and mushrooms.

{Non-drilled film}
The freshness-keeping packaging method for fruits and vegetables of the present invention is a method for improving the freshness-keeping properties of fruits and vegetables by imparting the MA effect by optimizing the degree of squeezing as described above. For the film, a non-perforated film may be used from the point of view of economy. As the non-perforated film, a film with non-penetrating holes or grooves may be used. In addition, the freshness-keeping packaging bag according to the present invention can have minute through-holes formed at arbitrary positions in order to improve the freshness-keeping function.

Further, it is also possible to subject the fruit and vegetable freshness-preserving packaging bag of the present invention to a treatment such as material modification based on quantum theory.

The packaging bag for preserving freshness of the present invention will be explained in detail below using Examples and Comparative Examples. However, the packaging bag of the present invention is not limited to the contents of the Examples, and within the scope of the spirit of the present invention. It is possible to change it as appropriate.

(1) Freshness retention of fruits and vegetables (2)-1 Broccoli Place one broccoli plant (approximately 500 g) in a storage bag for preserving the freshness of fruits and vegetables with an opening and bottom width of 260 mm x length of 380 mm, and insert it through the opening. A 30 mm position was squeezed by hand and the twisted portion was fixed with back sealing tape.
The package was stored in an atmosphere of 20° C. and 60% RH for 120 hours (about 5 days). The state of the broccoli at that time was subjected to sensory evaluation in terms of color and odor in the following four stages.
4: No change in color or odor compared to before packaging 3: Items with partial discoloration or faint odor but can be sold 2: Items with discoloration or odor and cannot be sold 1: Items with discoloration or a faint odor that cannot be sold A rating of 4 is the most preferred, and a rating of 1 is the least preferred. A rating of 4 to 3 is preferred.

(2)-2 Shiitake Place shiitake mushrooms (approximately 200 g) in a fruit and vegetable freshness preservation storage bag with opening and bottom width of 200 mm x length of 250 mm, squeeze by hand 30 mm from the opening, and twist. The packaging bag, whose twisted portion was fixed with back sealing tape, was stored in an atmosphere of 20° C. and 60% RH for 120 hours (about 5 days). Sensory evaluation of the state of the shiitake mushrooms at that time was performed in the following four stages from the viewpoints of color, odor, and opening of the cap.
4: There is no change in color, odor, or opening of the umbrella compared to before packaging. 3: Partial discoloration, slight odor, or opening of the umbrella is observed, but it can be sold. 2: Discoloration, odor, or opening of the umbrella is acceptable. 1: Items with general discoloration, distinct odor, and cracks. A rating of 4 is the most preferred, and a rating of 1 is the least preferred. A rating of 4 to 3 is preferred.

(2)-3 Carrots Place about 250 g of carrots in a storage bag for preserving the freshness of fruits and vegetables with a size of 100 mm width x 250 mm height, and squeeze the twisted part by hand at a position 3 cm from the opening with back sealing tape on the twisted part. was fixed. It was stored for 120 hours (about 5 days) in an atmosphere of 20° C. and 60% RH. The state of the carrots at that time was evaluated in terms of color, odor, and bud elongation in the following four stages.
4: No change in color, odor, or growth of buds compared to before packaging 3: Partial discoloration, faint odor, or growth of buds, but can be sold 2: Partial discoloration, Or products that cannot be sold because of a slight off-odor or a difference in density. 1: An overall discoloration, a clear off-odor, or a change in density is observed. A rating of 4 is the most preferred, and a rating of 1 is the least preferred. A rating of 4 to 3 is preferred.

{Biaxially oriented polypropylene film A}
Evaluation was performed using a biaxially stretched polypropylene film having a thickness of 18 μm and having the following configuration.
(1) Base material layer (A)
Thickness: 16.9μm
Resin: Propylene/ethylene random copolymer (ethylene copolymerization amount: 0.6 mol%, melting point: 158 °C) / biomass-derived polyethylene (melting point: 126 °C, biobased degree: 84%) = 90/10 (mass ratio )
Additives: Total of 3 antifogging agents 1.0% by mass
(2) Seal layer (B)
Thickness: 0.5μm
Resin: Propylene/butene-1 copolymer (butene-1 copolymerization amount 25 mol%)
Additives: Contains one type of antifogging agent and an average particle size of 3.5 μm.
(3) Surface layer (C)
Thickness: 0.4μm
Random copolymer of propylene/ethylene/butene-1 = 90.5/2.5/7 (mol%)
Additive: Contains one type of anti-fog agent

{Biaxially oriented polypropylene film B}
Evaluation was performed using a biaxially oriented polypropylene film with a thickness of 18 μm under the same conditions except that the mass ratio of the base layer (A) of the biaxially oriented polypropylene film A was changed to the following conditions.
Resin: Propylene/ethylene random copolymer (ethylene copolymerization amount: 0.6 mol%, melting point: 158 °C) / biomass-derived polyethylene (melting point: 126 °C, biobased degree: 84%) = 95/5 (mass ratio )
Additives: Total of 3 antifogging agents 1.0% by mass

{Biaxially oriented polypropylene film C}
Evaluation was performed using a biaxially oriented polypropylene film with a thickness of 18 μm under the same conditions except that the mass ratio of the base layer (A) of the biaxially oriented polypropylene film A was changed to the following conditions.
Resin: Propylene/ethylene random copolymer (ethylene copolymerization amount: 0.6 mol%, melting point: 158 °C) / biomass-derived polyethylene (melting point: 126 °C, biobased degree: 84%) = 85/15 (mass ratio )
Additives: Total of 3 antifogging agents 1.0% by mass

{Biaxially oriented polypropylene film D}
Evaluation was performed using a biaxially oriented polypropylene film with a thickness of 18 μm under the same conditions except that the mass ratio of the base layer (A) of the biaxially oriented polypropylene film A was changed to the following conditions.
Resin: Propylene/ethylene random copolymer (ethylene copolymerization amount: 0.6 mol%, melting point: 158 °C) / biomass-derived polyethylene (melting point: 126 °C, biobased degree: 84%) = 80/20 (mass ratio )
Additives: Total of 3 antifogging agents 1.0% by mass

{Biaxially oriented polypropylene film E}
Evaluation was made using Toyobo Co., Ltd. "P5562" with a thickness of 20 μm.

{Example 1}
Using the above-mentioned biaxially oriented polypropylene film A, place one broccoli plant (approx. The twisted portion was squeezed by hand, and the twisted portion was fixed with a back sealer device using a back sealing tape, and changes in the freshness of the broccoli were observed according to the above method for evaluating freshness retention of fruits and vegetables. The results are shown in Table 1.

{Example 2}
It was packaged under the same conditions as in Example 1, except that the biaxially oriented polypropylene film B was used, and changes in freshness were observed. The results are shown in Table 1.

{Example 3}
It was packaged under the same conditions as in Example 1, except that the biaxially oriented polypropylene film C was used, and changes in freshness were observed. The results are shown in Table 1.

{Comparative example 1}
It was packaged under the same conditions as in Example 1, except that the biaxially oriented polypropylene film D was used, and changes in freshness were observed. The results are shown in Table 1.

{Comparative example 2}
It was packaged under the same conditions as in Example 1, except that the biaxially stretched polypropylene film E was used, and changes in freshness were observed. The results are shown in Table 1.

{Example 4}
Using the above biaxially oriented polypropylene film A, put shiitake mushrooms (approximately 200 g) into a fruit and vegetable freshness preservation storage bag with an opening and bottom width of 200 mm x length of 250 mm, and place it at a position 30 mm from the opening. The broccoli was squeezed by hand, the twisted portion was fixed with a back sealing tape, and changes in the freshness of the broccoli were observed according to the above method for evaluating freshness retention of fruits and vegetables. The results are shown in Table 1.

{Example 5}
It was packaged under the same conditions as in Example 4, except that the biaxially oriented polypropylene film B was used, and changes in freshness were observed. The results are shown in Table 1.

{Example 6}
It was packaged under the same conditions as in Example 4, except that the biaxially oriented polypropylene film C was used, and changes in freshness were observed. The results are shown in Table 1.

{Comparative example 3}
It was packaged under the same conditions as in Example 4, except that the biaxially oriented polypropylene film D was used, and changes in freshness were observed. The results are shown in Table 1.

{Comparative example 4}
It was packaged under the same conditions as in Example 4, except that the biaxially oriented polypropylene film E was used, and changes in freshness were observed. The results are shown in Table 1.

{Example 7}
Using the above-mentioned biaxially oriented polypropylene film A, put about 250 g of carrots into a storage bag for preserving the freshness of fruits and vegetables with a size of 100 mm width x 250 mm height, and squeeze the twisted part by hand at a position 30 mm from the opening. The twisted portion was fixed with back sealing tape, and changes in the freshness of the carrots were observed according to the above method for evaluating freshness retention of fruits and vegetables. The results are shown in Table 1.

{Example 8}
It was packaged under the same conditions as in Example 7, except that the biaxially oriented polypropylene film B was used, and changes in freshness were observed. The results are shown in Table 1.

{Example 9}
It was packaged under the same conditions as in Example 7, except that the biaxially oriented polypropylene film C was used, and changes in freshness were observed. The results are shown in Table 1.

{Comparative example 5}
It was packaged under the same conditions as in Example 7, except that the above biaxially oriented polypropylene film D was used, and changes in freshness were observed. The results are shown in Table 1.

{Comparative example 6}
It was packaged under the same conditions as in Example 7, except that the biaxially oriented polypropylene film E was used, and changes in freshness were observed. The results are shown in Table 1.

〔表１〕

[Table 1]

From Table 1, it can be confirmed that the packaging bags of Examples 1 to 9 all have excellent freshness retention function. On the other hand, it can be confirmed that Comparative Examples 1 to 6, which do not meet the requirements, have poor freshness keeping function. By controlling the ratio of the cross-sectional area of the film included in the cross-sectional area of the twisted portion, it is possible to maintain freshness more easily than ever before.

Using the results of Examples 1 to 9 and Comparative Examples 1 to 6 in Table 1, the relationship between the ratio of the cross-sectional area of the film included in the cross-sectional area of the twisted portion and the freshness retention evaluation results is shown in FIG. It can be seen from FIG. 3 that the preferred range of the present invention is critical.

The method for preserving the freshness of fruits and vegetables according to the present invention uses an inexpensive synthetic resin film, and there is no need to uniformly provide multiple fine holes or slits in the synthetic resin film during film manufacturing or bag making process. This method is excellent in economical efficiency since it is possible to express the effect of preserving the freshness of fruits and vegetables by an inexpensive and simple method of inserting the fruits and vegetables therein, twisting the opening, and fixing the twisted part. Furthermore, by adjusting the degree of squeezing, it is possible to control the MA packaging characteristics of storage bags for preserving the freshness of fruits and vegetables, making it possible to effectively maintain the freshness of a wide variety of fruits and vegetables. It is a great contribution to the

1: Back sealing tape 2: Cross-sectional area of twisted part

Claims (5)

A vegetable or fruit product characterized by inserting the fruit or vegetable into a storage bag for preserving the freshness of fruits and vegetables made of a biaxially oriented polypropylene film having at least one layer containing a polyethylene resin, twisting the opening, and fixing the twisted part. A method for preserving the freshness of fruits and vegetables, characterized in that the squeezing degree determined by the following formula (1) is 7 to 35%.
Squeezing degree = [Film cross-sectional area (bottom length of freshness-preserving bag (mm) x 2 x freshness-preserving bag thickness (mm)] ÷ twisted section cross-sectional area (mm ² ) x 100 (%) ... (1) The method for preserving the freshness of fruits and vegetables according to claim 1, wherein the content of polyethylene resin in the base layer of the biaxially oriented polypropylene film is 5 to 15% by weight. The method for preserving the freshness of fruits and vegetables according to claim 1, wherein the biaxially stretched polypropylene film is a non-perforated film. The method for maintaining the freshness of fruits and vegetables according to claim 1, wherein the fixing tape for the twisted portion is a back sealing tape. The method for preserving the freshness of fruits and vegetables according to claim 1, wherein the polyethylene is biomass-derived polyethylene.

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