JPH02175140A - Film for preserving freshness of vegetable and fruit - Google Patents

Abstract

PURPOSE:To suppress respiratory metabolism of the vegetables and fruits and also to prevent formation of water by dew condensation by interposing a water absorptive layer between a synthetic resin film and a porous synthetic resin film having specified maximum pore diameter. CONSTITUTION:A film for holding freshness of the vegetables and fruits is constituted of a laminated film obtained by interposing a water absorptive layer between a synthetic resin film and a porous synthetic resin film. The porous synthetic resin film is regulated to <=30mum maximum pore diameter and water-vapor permeability is regulated to >=100g/m<2>/24hr. Hydrophilic treatment is performed for the porous synthetic resin film by an imparting agent of hydrophilic property. Further the water absorptive layer is partially interposed and the transparency of oxygen of the film for holding freshness of the vegetables and the fruits is regulated to 2,000 - 20,000ml/m<2>/24hr/atm. By the above-mentioned constitution, control of humidity in a package is performed between the vegerables and the fruits and the water absorptive layer via the porous synthetic resin film and formation of water by dew condensation is prevented. On the other hand, respiration of the vegetables and fruits is controlled and respiratory metabolism thereof is inhibited by controlling the concn. of carbon dioxide in the package, especially the concn. of oxygen by the combination of the synthetic resin film and the water absorptive layer.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention relates to a freshness-preserving film for fruits and vegetables that is used as a packaging material for fruits and vegetables and controls the respiration of the fruits and vegetables. This invention relates to a freshness-preserving film for fruits and vegetables that maintains the freshness of fruits and vegetables for a long period of time by controlling carbon dioxide gas concentration.

(b) Conventional technology Fruits and vegetables such as vegetables and fruits have a limited harvest period, and their value as food gradually declines over time from when they are harvested in the field until they are consumed. .

In fact, fruits and vegetables respire for a while after being harvested, and over time they become exhausted due to respiration, and as a result of this respiration, metabolites such as water and carbon dioxide accumulate, and as time passes, they become overheated and microorganisms begin to grow. This self-generated carbon dioxide also reduces the vitality of fruits and vegetables.

In particular, this phenomenon appears on green-skinned fruits such as Sudachi and Kabosu, as well as fruits that are painful and have a short shelf life such as peaches, loquats, and strawberries.

In addition, when vegetables are separated from the plant, such as leafy vegetables,
There are some vegetables that suffer from "wilting" phenomenon, and there are also vegetables such as spinach, cucumbers, and tomatoes that suffer quickly after being harvested and have a short shelf life.

For this reason, attempts have been made to preserve the harvested fruits and vegetables for as long as possible while maintaining their freshness at the time of harvest.

For example, fresh fruits and vegetables are stored at low temperatures to maintain their freshness, or they are quickly frozen and then stored in that state.It is thought that the practical application of freshness preservation technology will further develop as the cold chain is established. Ru. In other words, in this case, by lowering the temperature and suppressing wicking, the metabolism is suppressed and the freshness is maintained for a long period of time.

In addition, recently, new technologies have been put into practical use, such as fruit and vegetable storage, CA storage that increases the carbon dioxide concentration in the packaging, and suppresses respiration by lowering the oxygen concentration, which can extend the shelf life of fruits and vegetables. has become possible.

(c) Problems to be Solved by the Invention When fruits and vegetables are stored at low temperatures, their respiration is suppressed and their freshness can be maintained for a longer period of time. In other words, in general, for agricultural foods such as fruits and vegetables, the amount of respiration increases by 2.5 degrees for every 10°C rise in temperature.
It is said that the effect of transpiration is doubled, and the lower the humidity and the higher the temperature, the more significant the transpiration effect becomes. For this reason, efforts are being made to maintain the freshness of fruits and vegetables over a long period of time by storing them at low temperatures.

However, low-temperature or frozen storage seriously damages the structure of agricultural foods, and therefore, even when stored at low temperatures or frozen, the color and taste deteriorate, and the quality after storage is considerably inferior and completely different from when it was fresh. It may have a stale texture. In addition, such a state will significantly affect the subsequent storage stability and accelerate discoloration and generation of off-flavors. Furthermore, some vegetables can suffer from low-temperature damage if the temperature is low, so care must be taken.Moreover, vegetables, like fruits, undergo water evaporation during storage, which often reduces food value.

In addition, in CA storage, there is a problem of carbon dioxide disturbance depending on the case, and it cannot be used easily.

Furthermore, conventional preservation methods are not only large-scale and expensive, but also cannot be adequately applied to food distribution processes or long-term storage of food in ordinary households.

That is, fruits and vegetables are generally packaged in small portions during the wide-area distribution process or packaged before being displayed at supermarkets. The packaging material used in this packaging prevents foreign substances from entering the fruits and vegetables from the outside, prevents them from drying out, and enables more hygienic handling. In addition, by packaging fruits and vegetables, it is possible to not only improve the appearance and increase the product value, but also to display the contents, and packaging has become indispensable.

By the way, this packaging material is generally made of paper such as paper or paperboard, various plastic films, or a laminate film of the plastic film and paper or metal foil. Very little consideration has been given to preventing the generation of water, maintaining the freshness of fruits and vegetables, and suppressing deterioration, alteration, and discoloration of the fruits and vegetables themselves, such as loss of flavor, and it is extremely inadequate.

In other words, this type of packaging material has almost no function to control the respiration of fruits and vegetables, and therefore cannot control the carbon dioxide concentration by changing the humidity or oxygen concentration of fruits and vegetables in the packaging, and thus prolonging the freshness of fruits and vegetables. They cannot be held together over a period of time. Therefore, when fruits and vegetables are packaged and stored using the above-mentioned packaging material, the inside of the package becomes highly humid due to the moisture generated by the fruits and vegetables breathing and the water vapor inside the package. The condensed water produced by this overhumidity causes fruits and vegetables to become damaged and the fruit's sugar content to drop, which can lead to rotting from the condensed water.

For this reason, studies have recently been conducted on (1) using synthetic wood Wi films with controlled oxygen and carbon dioxide concentrations, and (2) using water-absorbing polymers.

Among these, in the case of (1) above, consideration has been made to obtain the CA effect by packaging [1], but since the packaging is sealed, evaporation of moisture causes
Conversely, the inside of the package becomes highly humid. This overhumidity and the resulting condensed water cause damage to the fruits and vegetables, particularly a decrease in the sugar content of the fruits, and furthermore, the condensed water often accumulates, leading to rotting of the fruits and vegetables.

In addition, methods for (2) above include: (1) forming a water-absorbing polymer into a bead shape, a bead shape, a sheet, etc. and placing it in a paper bag; (2) forming a water-absorbing polymer into a synthetic resin film and paper. Alternatively, methods include inserting a multilayer film sandwiched between nonwoven fabrics into a package, or using the multi-MIi film as a package, and (ii) mixing a water-absorbing polymer into a synthetic resin film and using it as a package. .

However, when paper is used as shown in ■ and ■, when the water-absorbing polymer absorbs water, the paper or non-woven fabric absorbs moisture and retains moisture, resulting in dew condensation on the surface, and furthermore, the paper and synthetic resin There is a problem that the adhesive force with the film or the adhesive force between the nonwoven fabric and the synthetic resin film becomes very weak, and eventually they peel off and the water-absorbing polymer leaks out.

Furthermore, since the maximum pore diameter of the paper or nonwoven fabric is large, there is a problem in that the water-absorbing polymer used oozes out from its surface, staining fruits and vegetables and lowering their commercial value.

Also, in the case of ■, synthesis! Since a water-absorbing polymer is mixed into the lubricant film, there is very little contact with water.
There are problems such as low water absorption, moisture absorption, and moisture release rates, insufficient humidity control, and the inability to prevent dew condensation and the "wilting phenomenon."

In this way, for freshness-keeping films for fruits and vegetables, we use synthetic wood 1ffi film that specifies oxygen and carbon dioxide concentrations, and we use water-absorbing polymers as a means to prevent condensation water that occurs as a result of being placed in high humidity environments. A method of using water-absorbing polymers to provide water-absorbing functions or storing them inside the packaging is being considered, but neither method is completely effective and has problems such as leakage of water-absorbing polymers and low water-absorbing capacity. There is.

The present invention relates to this kind of packaging film for fruits and vegetables,
A synthetic resin film and a specific porous synthetic O (a water-absorbing layer is interposed between the fat film to express sufficient water-absorbing function,
Furthermore, by specifying the type and thickness of the synthetic resin film, it is possible to control not only humidity but also certain oxygen and carbon dioxide concentrations suitable for fruits and vegetables.

Furthermore, by using a specific porous synthetic resin film, various functions described below are exhibited.

That is, (1) Preventing the water-absorbing polymer from seeping out.

■Excellent heat sealability.

■It does not peel off even after water absorption and prevents the water-absorbing polymer from leaking out, preventing direct contact between fruits and vegetables and the water-absorbing polymer, and as a result, staining of the fruits and vegetables is prevented.

■When dew condenses on the film surface, it absorbs water quickly, so it has sufficient water absorption and moisture absorption effect even at high humidity, and as a result,
Condensation is prevented.

■Since no water droplets form on the film, the surface acts as saran and does not wet fruits and vegetables.

■If the inside of the package is kept in an overhumidity state, water vapor evaporated from the fruits and vegetables and attached to the film surface as water droplets will be quickly absorbed.On the other hand, if the humidity is lower than the required level, that is, in a dry state, water will be absorbed quickly. 1g to release moisture from the layer, immediately transition to the humidity environment necessary to maintain the freshness of fruits and vegetables, and maintain that environment! The present invention is based on synthetic resin film and porous synthesis! j (By interposing a water absorption layer between the fat films, the porous synthetic 0 (by interposing the water absorption layer between the fat films, the humidity within the package is controlled between the fruits and vegetables and the water absorption layer via the fat film to prevent the formation of dew water) On the other hand, the combination of the synthetic resin film and the water absorption layer controls the oxygen concentration, charcoal, and fs concentration within the packaging, thereby controlling the respiration of fruits and vegetables and suppressing their metabolism. The purpose of the present invention is to provide a freshness-preserving film for fruits and vegetables that maintains their freshness for a long period of time.With this, the film can be used to preserve the freshness of fruits and vegetables after harvesting, during the distribution period of fruits and vegetables, and during the storage of fruits and vegetables at home. This suppresses the deterioration of its freshness.

(d) Means for solving the problem In order to achieve the above object, the fruit and vegetable freshness preservation film of the present invention takes the following technical measures.

That is, the freshness-keeping film for fruits and vegetables in the present invention is a laminated film in which a water-absorbing layer is interposed between a synthetic resin film and a porous synthetic resin film, and the porous synthetic resin film has a maximum pore diameter of 30 μm or less. That is.

That is, in the freshness-keeping film for fruits and vegetables of the present invention, the combination of the synthetic resin film and the water-absorbing layer specifies the oxygen concentration and charcoal-Pa2 concentration in the package, and the combination of the water-absorbing layer and the porous synthetic resin film This prevents the formation of dew condensation water by controlling the humidity inside the packaging, and the porous synthetic resin film prevents direct contact between the fruits and vegetables and the water absorbing layer, thereby preventing staining of the fruits and vegetables.

The synthetic 1fllW film used in the present invention is not particularly limited as long as it is made of synthetic resin, and it does not matter whether it is a single layer film or a composite film with two or more layers. Synthetic (fat film) is selected and used depending on the type and amount of fruits and vegetables, but in combination with the water absorbing layer described below, the carbon dioxide concentration in the package (bag) will be 0.5 to 10%, and the oxygen concentration will be lowered. The purpose is to control the amount so that the amount is 18% or less, preferably 2 to 15%.

In this way, in order to control the carbonate density and oxygen a degree of a synthetic resin film, generally, at a temperature of 25°C, the carbonate permeability is 5000ml/m'/24h.
r/at 11 or more, preferably 5000-20000
0 ml/m'/24br/atm, particularly preferably 5000-100000 so 1/m2/241
+r/atm, Wll elementary passage rate, 3000 me/
m”/241+r/ata+ or more, preferably 3
500-250000@n/m'/24hr/ateS
Particularly preferably 4000-20000ml/m'/
The synthetic resin for producing this film, which is preferably a 24 hr/atlm film, is not particularly limited, and includes, for example, polyethylene, polypropylene, polystyrene, cellophane, polyvinyl chloride, polyester, polyamide, polyvinyl alcohol,
Examples include vinylidene chloride and ethylene-vinyl acetate copolymer.

In this case, the permeability of carbon dioxide and oxygen is 2000-1
In the range of 5000I*l, /n2/24hr/atm, one film was used, and the values were measured using a mixed gas permeability tester GPM-200 model manufactured by LYSSY Co., Ltd., and using a scromatograph type 7 isobaric method.

Also, 15000 me/II+2/24hr/a
If the thickness exceeds tm, change the thickness or overlap two or more films to adjust the thickness to the above range,
The transmittance of one film is the value obtained by multiplying the obtained value by the number of films.

However, for products such as spinach whose deterioration is significantly accelerated by sealing, in other words, when it is desirable to keep the oxygen concentration in the packaging slightly lower than the oxygen concentration in the air, this synthetic (It is preferable to use a porous synthetic resin film as the fat film.

The thickness of the synthetic resin film is not particularly limited, but from the viewpoint of carbon dioxide and oxygen permeability, strength, processability such as heat fusion, and handleability, the thickness is 5 to 50 μm.
In particular, it is preferable to set it as a 20-40 micron cocoon.

The water-absorbing layer used in the present invention is a water-absorbing layer formed of a water-absorbing polymer alone or a water-absorbing composition consisting of a water-absorbing polymer and an inorganic water-absorbing agent. The thickness of this water absorption layer is not particularly limited, but from the viewpoint of water absorption and permeability of carbon dioxide and oxygen, the basis weight is I.
ll/m2 to 150 g/m2, especially 5 g/Wa2-
It is desirable to set it to 100 g/m'.

The water-absorbing polymer is preferably one that is insoluble in water, and has a water-absorbing capacity of at least 15 times, preferably at least 20 times, its own weight.

Specifically, the starch-polyacrylonitrile copolymer disclosed in Japanese Patent Publication No. 49-43395;
Crosslinked polyalkylene oxide disclosed in Japanese Patent Publication No. 1-39672, saponified vinyl ester-ethylenically unsaturated carboxylic acid copolymer disclosed in Japanese Patent Publication No. 53-13495, and saponified product of vinyl ester-ethylenically unsaturated carboxylic acid copolymer disclosed in Japanese Patent Publication No. 54-30710. A self-crosslinking polyacrylate obtained by the disclosed reverse-phase suspension polymerization method, a reaction product of a polyvinyl alcohol polymer and a cyclic anhydride disclosed in JP-A-54-20093, JP-A-54-20093; Preferred are crosslinked polyacrylates disclosed in Japanese Patent Publication No. 55-84305.

This water-absorbing layer absorbs water vapor when the fruit or vegetables inside the package become overly humid due to breathing, preventing the generation of dew water and preventing the surface of the fruit or vegetables from getting abnormally wet.On the other hand, when the inside of the package becomes dry, This water-absorbing layer has the ability to absorb water and release the absorbed moisture, and by repeating the absorption and release of moisture within the package, it maintains an appropriate humidity level for fruits and vegetables. This is to prevent the sugar content from decreasing.

The water-absorbing layer used in the present invention includes the above-mentioned water-absorbing polymer and No.8! Examples include a layer formed of a water-absorbing composition made of a quality water-absorbing agent, etc., but the inorganic water-absorbing agent may especially be one that improves the moisture-absorbing ability of the water-absorbing layer or adsorbs ethylene, etc. Specific examples include, but are not limited to, activated carbon, zeolite, zeolite porous material, cristobalite, silica porous material, calcium silicate, activated alumina, and the like.

In addition, in order to further improve the freshness-keeping effect, this water-absorbing layer contains 1 to 30% by weight, preferably 3 to 15% by weight of antibacterial agents, deodorizing agents, fungicides, etc. based on the entire water-absorbing agent. ! @
It is desirable to contain it within a range.

In addition, in order to improve the adhesion between the synthetic resin film and the porous synthetic resin film described later, the water absorbing layer may be coated with a hydrophilic adhesive such as a polyurethane adhesive or a cellulose adhesive, if desired. It is desirable to add an adhesive of. In this case, the amount of adhesive added is 10
It is preferable to mix at most 500 parts by weight, preferably at most 250 parts by weight, relative to 0 parts by weight.

The porous synthetic resin film used in the present invention prevents direct contact between the water absorption layer and fruits and vegetables, controls humidity within the packaging via this film, and prevents condensation. The maximum pore diameter is 30 μm or less, especially 15 μm or less in the case of fruits and vegetables. Setting the maximum pore diameter to 15 μm or less is desirable because it prevents the water-absorbing polymer from seeping out from the water layer and improves the film strength.

If the maximum pore diameter of this porous synthetic υ1 fat film exceeds 30μ, the strength of the film will drop significantly and it may partially tear during handling, and when making bags using heat sealing etc. using this freshness preserving film, the sealing This is not preferable since the strength may decrease and peeling may occur, and the water-absorbing polymer may ooze out from the surface of the porous synthetic resin film.

In this case, the method for measuring the maximum pore diameter is Coulter
・Based on the bubble point method using a Coulter bolometer manufactured by Electronics.

In addition, the thickness of this porous synthetic resin film is not particularly limited, but from the viewpoint of film strength, processability such as heat fusion, and handleability, it should be 200μ or less, especially 20 to 80μ. It is preferable to do so.

The synthetic resin used to form this porous synthetic resin film is one that can be made into a film, and a film with a maximum pore diameter of 30μ or less can be made by various methods such as stretching, extraction of soluble substances after stretching, and extraction of soluble substances. It is not particularly limited as long as it can be obtained.

In addition, this synthetic resin is particularly suitable for hydrophilic synthetic resins and hydrophilic synthetic resins! L resin is desirable because it has good moisture and water vapor permeability.

The method for producing this porous synthetic tree 11w film is not particularly limited, but specifically includes the following methods.

That is, (a) after melting and stretching the polyolefin resin,
6 (b) A soluble liquid or solid is mixed into the synthetic resin to be heat treated and re-stretched, and after forming this into a film, the mixed liquid or solid is extracted.

(c) A synthetic resin film is formed and made porous by perforating it with a polar needle.

(d) A filler is added to a synthetic resin, the resulting film is melted and formed into a film, and then stretched at least uniaxially, or after at least uniaxially stretched, the soluble filler is extracted using water, an acid, or an alkali.

Among these, polyolefin resins are preferred as synthetic resins, especially in the case of (d) above, since they have good productivity and are low in cost.

This polyolefin 111 resin includes polyethylene,
Homopolymers or copolymers such as polypropylene, polybutadiene, or blend polymers thereof may be mentioned, but in particular, polypropylene (PP), high density polyethylene (HDPE), linear low density polyethylene (L
-LDPE> is preferable from the above-mentioned viewpoint.

Inorganic and organic fillers are used as the above fillers, and the inorganic fillers include calcium carbonate, talc, clay kaolin, silica, diatomaceous earth, magnesium carbonate, barium carbonate, magnesium sulfate, barium sulfate, calcium sulfate, and hydroxide. Aluminum, zinc oxide, magnesium hydroxide, calcium oxide, magnesium oxide, titanium oxide, alumina, mica, asbestos powder, glass powder, shirasu balloon, zeolite, clay silicate, etc. are used, especially calcium carbonate, talc, clay, silica, diatomaceous earth,
Barium sulfate and the like are preferred.

On the other hand, examples of organic fillers include wood flour, bulb, melamine powder, silicone resin powder, and the like.

The above-mentioned filler has an average particle size of 10 μm or less, especially a total
ff (from the viewpoint of miscibility with fat and homogenization of the film, it is preferably in the range of 0.5 to 5μ), and the amount added is 50 to 300 parts by weight per 100 parts by weight of the synthetic resin.
11j1 part, preferably 100 to 2001ifi parts.

In the freshness-keeping film for fruits and vegetables of the present invention, the moisture permeability of the porous synthetic resin film is determined by the pore size and the degree of hydrophilicity of the film, and the moisture permeability is determined when the moisture permeability is 100 g.
/l/24 hr or more is desirable, and 100
If it is less than 24 hours, the moisture permeability is too low, and depending on the type 11 type of fruit or vegetable and the amount, the inside of the package may become overhumidified and dew water may form locally, which is not preferable.

By the way, this moisture permeability is measured according to JIS Z-0208.

In the freshness-keeping film for fruits and vegetables of the present invention, the porous synthetic bottom film that has been treated with a hydrophilic agent has an extremely high water absorption rate, and the freshness can be maintained even after washing with water and immediately draining the water before packaging. This is preferable because excess moisture on the surface is immediately absorbed and the humidity within the package is quickly controlled.

The above-mentioned hydrophilicity imparting agent is not limited to any one as long as it is provided on the surface of the film and improves the hydrophilicity of the film (glycerin, polyglycerin,
Examples include polyhydric alcohols such as ethylene glycol and polyethylene glycol, and various surfactants.

Methods for hydrophilizing the porous synthetic resin film using the hydrophilicity-imparting agent include a method in which the hydrophilicity-imparting agent is mixed into the porous synthetic resin film, and a method in which the surface of the porous synthetic resin film is hydrophilized. Examples include a method of applying a hydrophilicity imparting agent, dipping the film in an aqueous solution of a hydrophilicity imparting agent, and a method of spraying this aqueous solution onto the film.

In the freshness-keeping film for fruits and vegetables of the present invention, it is preferable to partially interpose a water-absorbing layer because the permeability of the water-absorbing layer, oxygen, and carbon dioxide gas can be adjusted.

In the fruit and vegetable freshness preservation film of the present invention, the oxygen permeability is 2000 ml/m2/24 hr/
At eyelids or more, preferably 2000 to 200000 eyelids 1/
m2/24 hr/arm, even 2000-15
000+++1/*'/24 hr/aLm is particularly desirable.

This oxygen permeability was measured by the method described above.

That is, the oxygen permeability is 2000 yen 1/Ig'/
If it is less than 24br/atw, due to the respiration of fruits and vegetables,
Depending on the type of fruits and vegetables, the carbon dioxide concentration inside the packaging may become high and cause serious carbon dioxide problems.
If it exceeds 000 val/m2/24 hr/arIa, the oxygen permeability is good and the respiration of fruits and vegetables cannot be suppressed sufficiently, which means that the metabolism cannot be suppressed, and the freshness of fruits and vegetables cannot be maintained for a long period of time. This is not desirable because there are cases where it cannot be done.

By the way, 1! For plants such as spinach whose oxygen concentration may be approximately equal to the oxygen concentration in the air and which are easily affected by carbon dioxide when sealed, synthetic υ (with a porous fat film and an oxygen permeability of 200,000 ml) is used. / m2/
It is possible to exceed 241+r/arm.

The production of the fruit and vegetable freshness-keeping film of the present invention does not require any special Iji technique or equipment, and can be obtained by a conventional method. Specifically, for example, a coating liquid prepared by mixing a water-absorbing polymer or a water-absorbing agent or adhesive with the water-absorbing polymer is applied to the surface of either a synthetic resin film or a porous synthetic resin film using a gravure method. For example, after coating by a roll coating method or a silk screen method, the other film of either a synthetic resin film or a porous synthetic resin film is laminated together.

In this case, from the viewpoint of adhesive strength between the synthetic resin film and the porous synthetic resin film, water absorption amount, moisture absorption ability, etc., the water absorption layer may be provided on the entire surface or part of the film.

By packaging fruits and vegetables using the fruit and vegetable freshness-preserving film of the present invention, the freshness of the fruits and vegetables can be maintained for a long period of time for reasons described below.

(e) The freshness-keeping film for fruits and vegetables of the present invention has the above-mentioned structure, and has a synthetic υ (by interposing a water-absorbing layer between the fat film and the porous synthetic resin film, the porous synthetic resin film The moisture within the packaging is controlled between the fruits and vegetables and the water absorbing layer through the film to prevent the formation of condensation water, while the combination of the synthetic resin film and the water absorbing layer reduces the oxygen and carbon dioxide concentrations within the packaging, especially Control oxygen concentration,
This has the effect of controlling the respiration of fruits and vegetables and suppressing their metabolism.

In this way, by controlling the respiration of fruits and vegetables and suppressing their metabolism, it is possible to maintain the freshness of fruits and vegetables over a long period of time. It has the effect of suppressing the deterioration of freshness of fruits and vegetables during storage.

By the way, condensed water generally promotes deterioration and rot of fruits and vegetables. The reason for this is not clear, but as the fruits and vegetables breathe, the carbon dioxide concentration within the package increases, and this R acid gas dissolves in the condensed water, which increases the hydrogen ion concentration of the condensed water and protons. It is understood that (H+) promotes deterioration and decay of fruits and vegetables.

In other words, carbon dioxide produced by the respiration of fruits and vegetables dissolves in condensed water, and protons (H") are produced by this dissolution.
This is understood to be because it enters the interior of fruits and vegetables through the epidermis and lowers the internal pH, thereby promoting the growth of microorganisms such as yeast, particularly inside the fruits and vegetables, and promoting rot from within the fruits and vegetables.

However, by using the freshness-preserving film for fruits and vegetables of the present invention as a packaging material, the generation of dew water is prevented, and from this point of view as well, it is understood that the freshness of fruits and vegetables can be maintained for a long period of time.

(f) Examples Hereinafter, the present invention will be explained in detail based on Examples, but the present invention is not limited thereto.

In the following, the following materials were used for (a) synthetic resin film, (b) water absorbing layer material, and (c) porous synthetic resin film.

(,)Synthetic resin film density 0.927μlcm, MI=2.0. Thickness is 15
Polyethylene film of μ and 30μ, thickness of 1
0 μl of ethylene-vinyl acetate (vinyl acetate 28% by weight)
) A copolymer film was used.

The oxygen and carbon dioxide permeability of these films is as shown below.

Polyethylene film (thickness 15μ) oxygen permeability -1
4000 wj! / m2/ 24 hr/aLm Carbon dioxide permeability -33000ml/va2/ 24 hr
/ate polyethylene film (thickness fi30μ@) oxygen permeability -6600+1/m'/24 hr/a
tm carbon dioxide permeability -23000ml! / m2/ 2
4 hr/ate Vinyl acetate copolymer (thickness 10μ theory) M elementary permeability...-20000+al/Ia2/24
hr/atm carbon dioxide permeability -60000mj! /
m2/ 24 hr/ atm (b) Water-absorbing layer: Starch-polyacrylic acid graft copolymer used as water-absorbing polymer Sanyo Chemical Co., Ltd., Sunwet IM=300
) was used, and (EPS-75A) manufactured by Dainippon Ink Co., Ltd. was used as the urethane adhesive. Using this,
It was formed using a gravure roll described below.

(e) Porous synthetic resin film linear low density polyethylene (density 0.927μlcm",
MI=2.0) Average particle size 2°5μ per 100 parts by weight
150 parts by weight of barium sulfate was added and melted.
After forming one film, it is stretched to a thickness of 30μl, moisture permeability of 1400g/m2/24br, and maximum pore diameter of 7.5.
A μl film was obtained. Next, in order to improve the water absorption rate of this film, a 7enol-based surfactant (manufactured by Kyubishi Yuka Co., Ltd., MTN-Ff384) was applied to the film surface.
A 10% by weight isopropyl alcohol solution was applied by dipping to perform hydrophilic treatment. In this way, a porous synthetic resin film used in the present invention was obtained.

Production Example 1 100 parts by weight of the urethane adhesive described in (b) above and 1001 parts of the water-absorbing polymer were mixed at low speed in a homomixer, and this was mixed into a 15 μm thick polyethylene film ( Synthetic resin film) After coating the surface with a gravure roll to form a water-absorbing layer such that the amount of water-absorbing polymer is 88/2 as a result, apply the material described in (c) above on the water-absorbing layer. The freshness-preserving film for fruits and vegetables of the present invention was obtained by laminating the porous synthetic resin films prepared in the above manner.

The oxygen permeability of this fruit and vegetable freshness preservation film is 1300.
It was 0 vbl/m2/24 hr/atm.

Production Example 2 100 parts by weight of the turethane adhesive described in (b) above and 100 parts by weight of the water-absorbing polymer were mixed at low speed in a homomixer, and this was mixed into the 30 μl thick polyethylene film described in (a) above. (synthetic 4 fat film) surface,
After forming a water-absorbing layer by coating with a gravure roll so that the amount of water-absorbing polymer becomes 8 g/n' as a result, the porous synthetic resin film described in (c) above is laminated on the water-absorbing layer. In this way, the freshness-keeping film for fruits and vegetables of the present invention was obtained.

The oxygen permeability of this fruit and vegetable freshness preservation film is 4500.
Ifill/m2/24 hr/atm.

Production Example 3 100 parts by weight of the urethane adhesive described in (L,) above and 100 parts by weight of the water-absorbing polymer were mixed at low speed in a homomixer, and this was mixed into a membrane having a thickness of 10 as described in (a) above. As a result, the amount of water-absorbing polymer was 8 μl on the surface of the ethylene-vinyl acetate copolymer film (synthetic resin film).
After coating with a gravure roll to form a water-absorbing layer, the porous synthetic resin film described in (e) above is laminated on the water-absorbing layer, thereby improving the freshness of the fruits and vegetables of the present invention. A holding film was obtained.

The oxygen permeability of this fruit and vegetable freshness preservation film is 1.80
00 ul/m2/241+r/nLIrl.

Example 1 Freshness preservation film obtained in Production Example 1 and thickness 3 of the above (a)
0μm polyethylene film, each 40cm long
, cut it into a rectangle with a width of 30 cw, and place it on this freshness-keeping film piece, and (c) the porous synthetic resin film side and 30 μm.
A packaging bag with one end open was obtained by overlapping glossy polyethylene film pieces and heat sealing the three peripheral edges.

Kabosu 1' (5 kg) was placed in this packaging bag, stored at a temperature of 2°C, and changes over time were observed.

Health multiplier after 4 months and after 5 months, carbon dioxide concentration,
The oxygen concentration is shown in Table 1.

Example 2 Freshness preservation film obtained in Production Example 2 and thickness 3 of the above (a)
0μmfi polyethylene film, lengthwise 40mm
cm, width 300Ia, and on this freshness preservation film piece, (e) overlap the porous synthetic resin film side and the 30μω polyethylene film piece, and heat seal the three peripheral edges, one end. Got a packaging bag released.

1.5 pieces of Kabosu were placed in this packaging bag, stored at a temperature of 2'C, and changes over time were observed at +tq.

Health multiplier after 4 months and after 5 months, carbon dioxide concentration,
The oxygen concentration is shown in Table 1.

Example 3 Freshness preservation film obtained in Production Example 3 and thickness 3 of the above (a)
0μI polyethylene film, each 40cm long
, cut it into a rectangle with a width of 30 cm, and place it on this freshness-preserving film piece.
A packaging bag with one end open was obtained by overlapping m polyethylene film pieces and heat sealing the three peripheral edges.

1.5 kg of kabosu was placed in this packaging bag, stored at a temperature of 2"C, and changes over time were observed.

Health multiplier after 4 months and after 5 months, carbon dioxide concentration,
The oxygen gas concentration is shown in Table 1.

Comparative Example 1 A packaging bag was prepared using only the 30 μm thick polyethylene film (synthetic resin film) described in (a) above, and the same test as in Example 1 was conducted.

The results are shown in Table 1.

Comparative Example 2 A commercially available product/Ibaron (manufactured by Chiki Jushi Co., Ltd.) was placed in the packaging bag obtained in Comparative Example 1, and the same test as in Example 1 was conducted.

The results are shown in Table 1.

(Leaving space below) Example 4 Wash 128 g of spinach with water, simply shake it up and down to drain, wrap it in a lump shape with the freshness-preserving film obtained in Production Example 2, and store it at a temperature of 5°C for 10 days. When I saved it,
No dew condensation was observed, and no abnormalities such as wrinkles, wilting, chromaticity, dryness, etc. were observed.

Comparative Example 3 When the same test as in Example 4 was conducted using the polyethylene film with a thickness of 30 μm described above, it was found that after 7 days of storage, condensed water was generated in many places on the inner surface of the packaging material, and some parts It was observed that wilting and chromaticity occurred, and the commercial value was clearly reduced.

Example 5 After washing 673 g of carrots with water and draining the water by simply shaking the carrots up and down, 2.
When the sample was sealed in a No. 51 packaging bag and stored at a temperature of 20° C. for one month, no condensation water was observed, and no abnormalities such as chromaticity or dryness were observed.

Comparative Example 4 Using the polyethylene film with a thickness of 30 μm described above, the same test as in Example 5 was conducted.
After several months, condensation water will form in many places on the inside of the packaging bag.
It was observed that some of the carrots had something like mold growing on their necks, and some parts of the carrots had chromaticity, which clearly decreased their commercial value.

Example 6 The freshness-keeping film obtained in Production Example 2 was packed in a cardboard box (280
tamX 370mmX 118.5mm).

After washing 6 kg of green asparagus with water and simply shaking it up and down to drain the water, it was packed in a cardboard box lined with the above-mentioned freshness-preserving film and transported from Hokkaido to Tokyo at a temperature of 20°C. The transportation period was 2 days.

The results are shown in the Pt52 table.

Comparative Example 5 After washing 6 kg of green asparagus with water and draining it by simply shaking it up and down, a general cardboard box (280 mm
IsX118,51fim) and transported from Hokkaido to Tokyo at a temperature of 20°C. The transportation period was 2 days.

The results are shown in Table 2.

(Margins below) From the results shown in table f52, the freshness-keeping film for fruits and vegetables of the present invention can maintain a constant humidity inside the package, reduce oxygen concentration and carbon dioxide.
It is recognized that by controlling the gas concentration, the respiration of fruits and vegetables can be suppressed, and as a result, fruits and vegetables can be stored for a long period of time while maintaining their freshness.

(g) Effects of the Invention The freshness-keeping film for fruits and vegetables of the present invention has a water-absorbing layer interposed between the synthetic resin film and the porous synthetic resin film, so it prevents the formation of dew condensation water, while also preventing the formation of water-absorbing water between the synthetic resin film and the porous synthetic resin film. The combination of layers controls the concentration of oxygen and carbon dioxide in the package, especially the oxygen concentration, which not only controls the respiration of fruits and vegetables and suppresses their metabolism, but also prevents the formation of condensed water and reduces the amount of water inside the package. Humidity control is also carried out quickly, and the synergistic effect of these allows the freshness of fruits and vegetables to be maintained for a long period of time.

In addition, it is extremely useful because it can suppress deterioration in freshness of fruits and vegetables during storage after harvesting, during distribution of fruits and vegetables, and during storage of fruits and vegetables at home.

Furthermore, by using a porous synthetic film (fat film) with a maximum pore size of 30 μm or less, direct contact between fruits and vegetables and the water-absorbing layer is prevented, preventing staining of the fruits and vegetables, and also preventing the water-absorbing polymer from seeping out from the water-absorbing layer. This has the effect of preventing

Patent applicant Mitsui Toatsu Chemical Co., Ltd.

Claims (7)

[Claims] (1) In a packaging film used to maintain the freshness of fruits and vegetables, the packaging film is a laminated film in which a water-absorbing layer is interposed between a synthetic resin film and a porous synthetic resin film, and the above-mentioned porous A synthetic resin film for preserving the freshness of fruits and vegetables, characterized in that its maximum pore diameter is 30 μm or less. (2) The moisture permeability of the porous synthetic resin film is 100g/m
2. The freshness-keeping film for fruits and vegetables according to claim 1, which lasts for at least 2/24 hours. (3) The freshness-keeping film for fruits and vegetables according to claim 1 or 2, wherein the porous synthetic resin film has been subjected to hydrophilic treatment with a hydrophilicity imparting agent. (4) The fruit and vegetable freshness-keeping film according to any one of claims 1 to 3, wherein the water absorption layer is partially interposed. (5) In the freshness-keeping film for fruits and vegetables according to any one of claims 1 to 4, the oxygen permeability is 2000.
A film for preserving the freshness of fruits and vegetables with a rate of ml/m^2/24hr/atm or more. (6) In the freshness-keeping film for fruits and vegetables according to claim 5, the oxygen permeability is 2,000 to 200,000 ml.
/m^2/24hr/atm freshness preservation film for fruits and vegetables. (7) In the freshness-keeping film for fruits and vegetables according to any one of claims 1 to 4, the oxygen permeability is 2000.
A freshness-keeping film for fruits and vegetables with a yield of ~15000ml/m^2/24hr/atm.