FUNCTIONAL FILM, FUNCTIONAL CONTAINER, AND METHOD FOR RETAINING FRESHNESS

Abstract

Provided are a functional film capable of efficiently adsorbing and decomposing ethylene, a functional container, and a method for retaining freshness of a plant or a food.

The functional film of the present invention is obtained in the following manner: a substance having a catalytic capability of decomposing ethylene is added in a plastic film material having an ethylene adsorption effect, or applied to or deposited on a surface of the plastic film material. The functional container of the present invention is obtained in the following manner: a substance having a catalytic capability of decomposing ethylene is added in a plastic material having an ethylene adsorption effect, or applied to or deposited on a surface of the plastic material. Alternatively, the functional container of the present invention is obtained in the following manner: a substance having a catalytic capability of decomposing ethylene is added in a plastic material having an ethylene adsorption effect, and the mixture is molded into a predetermined shape, or the plastic material is molded into a predetermined shape, and the substance is then applied to or deposited on a surface of the plastic material. The method for retaining freshness according to the present invention includes the step of adsorbing and decomposing or/and discharging ethylene generated from a plant or the like using the functional film or the functional container.

Claims

1. A functional film which is a sheet-like plastic film capable of adsorbing ethylene to a surface thereof, wherein a substance having a catalytic function capable of decomposing the ethylene into carbon dioxide and water or/and discharging the ethylene from one surface to other surface of the functional film is contained in at least ppm order or ppb order, or applied to or deposited on the surface.

2. The functional file of claim 1 wherein said film is formed into a container including at least one of a bag-like structure, a cylindrical structure, a tunnel structure, a layered structure, and a nested structure.

3. (canceled)

4. A method for retaining freshness of a plant or a food, the method comprising: an application step of applying the functional film according to claim 1 at a site where the plant or the food is preserved; and an adsorption step of adsorbing the ethylene, which is generated from the plant or the food in a vicinity of the plant or the food, to the functional film according to claim 1.

5. The method for retaining freshness according to claim 4, further comprising the step of maintaining the carbon dioxide and the water, which are obtained by decomposing the ethylene adsorbed in the adsorption step, on a surface of the functional film according to claim 1.

6. The method of claim 4 further comprising: a discharge step of discharging the ethylene, which is generated from the plant or the food in a vicinity of the plant or the food, outside the functional film according to claim 1.

7. The method of claim 4 further comprising the step of forming a container from said film and surrounding or enclosing the plant or the food in a vicinity of a surface of the plant or the food by the functional film.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0031] FIG. 1 is a diagram for illustrating the effect of attenuating ethylene by 30 ppm and 100 ppm for a 0.02 mm freshness retaining bag (masterbatch content: 0.6% (mass ratio)) in an example according to the present invention.

[0032] FIG. 2 is a diagram for illustrating the effect of attenuating ethylene by 30 ppm and 100 ppm for a 0.006 mm freshness retaining bag (masterbatch content: 0.6% (mass ratio)) in an example according to the present invention.

[0033] FIG. 3 is a diagram for illustrating the effect of attenuating ethylene by 100 ppm for a 0.01 mm freshness retaining bag (masterbatch content: 1.0% (mass ratio)) in an example according to the present invention.

[0034] FIG. 4 is a diagram for illustrating the effect of discharging ethylene by 100 ppm for a 0.01 mm freshness retaining bag (masterbatch content: 1.0% (mass ratio)) in an example according to the present invention.

[0035] FIG. 5 is a diagram showing the result of comparing measurement data for a standard ethylene gas in a control bag and a freshness retaining bag in an example according to the present invention.

[0036] FIG. 6 is a diagram showing a state of a decomposition process from ethylene to carbon dioxide in an example according to the present invention.

[0037] FIG. 7 is a diagram showing a state of an ethylene adsorption process of a low-density polyethylene bag (non-processed) in an example according to the present invention.

[0038] FIG. 8 is a diagram showing a state of a change in concentration of ethylene generated from a cherry tomato in a freshness retaining bag in an example according to the present invention. The blue bar indicates a non-processed low-density polyethylene bag, and the red bar indicates an ethylene concentration of a freshness retaining bag sample.

[0039] FIG. 9 is a diagram showing a state of a change in concentration of ethylene generated from spinach in a freshness retaining bag in an example according to the present invention.

[0040] FIG. 10 is a diagram showing a preserved state of a cherry tomato after a preservation test in an example according to the present invention.

DESCRIPTION OF EMBODIMENT

[0041] Hereinafter, an embodiment of the present invention will be described in detail.

[0042] A functional film and a functional container according to this embodiment are formed in the following manner: a granular compound (diameter: about 40 nm to 400 nm, preferably 100 nm to 200 nm) having the above-mentioned ethylene decomposition function is mixed with (added in) a predetermined film material at a volume ratio in at least ppm order or ppb order (about 1 ppb to 12 ppc (12%), preferably about 1 ppb to 5 ppc (5%)), or applied to or deposited on a surface of the film material. Specifically, it is possible to produce (1) a sheet-like functional film by performing film molding processing or inflation molding processing; (2) a multilayer functional film with an ethylene decomposition cycle, which is obtained by thermally depositing (heat-sealing) a functional film by T-die molding processing or lamination processing molding to bond the functional film to various films; and (3) a functional container obtained by processing the functional film in (1) or (2) into a bag-like structure, a cylindrical structure, a tunnel-like structure, a layered structure or a nested structure. Examples of the film material for use in this embodiment includes LDPE: low-density polyethylene, HDPE: high-density polyethylene, OPP: stretched polypropylene, CPP: unstretched polypropylene, ON: stretched nylon (polyamide), CN: unstretched nylon (polyamide), BDR: polybutadiene, PMP: polymethylbenzene, BOV: stretched vinylon, OV: PVDC-coated stretched vinylon, PET: polyethylene terephthalate, PVDC: polyvinyl chloride, KOP: polyvinyl chloride-coated OPP, KON: polyvinylidene chloride-coated ON, EVOH: ethylene-vinyl alcohol copolymer, EVA: ethylene-vinyl acetate copolymer, PS: polystyrene, PT: ordinary cellophane, and MST: polymer-type moisture-proof cellophane. When the compound having an ethylene decomposition function is mixed with the film material, the functional film and the functional container each have a thickness of, for example, 0.004 mm to 0.1 mm, and it is possible to absorb ethylene regardless of the thickness. The material of the functional film and the material of the functional container in this embodiment may be a mixture of two or more of the materials described above as examples. In addition, the film material for use in the embodiment of the present invention is not particularly limited as long as it is a material capable of adsorbing ethylene.

[0043] Here, a functional container according to another mode of this embodiment has a solid shape formed in, for example, a box-like shape with a lid by injection molding or the like, but the molding method is not limited as long as it is capable of forming a certain solid shape such as a box-like shape. In addition, the functional container according to another mode of this embodiment is formed in the following manner: a compound having the ethylene decomposition function is mixed (added), or formed into a solid boxy-like shape, and then applied to or deposited on the surface. Examples of the box-like shape here include a cube, a rectangular parallelepiped, a triangular prism, a cylinder, and a triangular pyramid, but the box-like shape is not limited as long as it can store an article therein. In addition, examples of the container material which is used for the functional container according to another mode and which adsorbs ethylene include low-density polyethylene (LDPE) (high-pressure method), linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE) (low-pressure method), ultra-high-molecular-weight polyethylene (UHMW-PE), crosslinked polyethylene, polyethylene terephthalate (PET), acrylonitrile-styrene (AS), polypropylene (PP), polystyrene (PS), polycyclohexanedimethylene terephthalate=highly-heat-resistance engineering plastic (PCT), saturated polyester resins, and polymethylpentene (TPX). The material of the functional container according to another mode may be a mixture of two or more of the materials described above as examples. In addition, the container material to be used in the functional container according to another mode is not particularly limited as long as it is a material capable of adsorbing ethylene.

[0044] A case where the functional film in this embodiment is used as a freshness retaining film will now be described. As a method for applying the freshness retaining film, for example, the freshness retaining film is processed into a bag-like shape or a container to obtain a freshness retaining bag or a freshness retaining container, and a plant or food such as a fruit or vegetable is encapsulated therein; a plant or food such as a fruit or vegetable is covered with the freshness retaining film to bring the freshness retaining film into direct contact with the plant or food such as a fruit or vegetable; or the functional film is directly attached to an inner surface of a corrugated board, a container or the like for preserving a plant or food such as a fruit or vegetable, or attached to an inner surface of equipment such as a storage warehouse for preserving a plant or food such as a fruit or vegetable. In addition, for example, the functional film may be attached to a ventilation device or an air suction device in a storage warehouse for a plant or food such as a fruit or vegetable, etc.

[0045] The fruit or vegetable to be preserved using the freshness retaining bag and the freshness retaining container in this embodiment should be appropriately determined according to the type of a plant, the method for growing a plant, the climate, and the like.

[0046] The compound having an ethylene decomposition function (catalytic substance) is capable of removing not only ethylene generated from a plant or food such as a fruit or vegetable, but also a corrosive gas, such as aldehyde, which causes corrosion. By performing a corrosive gas decomposition treatment while removing ethylene after preservation, the freshness retaining effect is improved. As a condition for retaining freshness, ethylene decomposition is performed in a dark place almost as well as under a light condition. In addition, even when the gas component is changed under a humidity retaining condition which is an important factor in the preservation of a plant or food such as a fruit or vegetable, ethylene decomposition performance is exhibited as well as under a low-humidity condition. Specifically, humidification of the inside of an individual packaging or adjustment of a gas partial pressure is preferable for retaining freshness, and particularly, it is more preferable that the freshness retaining sheet is applied so as to be disposed in the vicinity of the surface of a plant or food (e.g. the surface of a fruit part of a fruit or vegetable).

[0047] Here, the freshness retaining bag has a hollow structure having a high porosity and specific surface area, or a ventilation function, and therefore by decomposition of ethylene, the minimum amount of oxygen given for respiration of a plant can be supplied, and carbon dioxide that further suppresses respiration can be provided. Accordingly, freshness is easily retained via suppression of respiration of a plant or food such as a fruit or vegetable, so that the storable duration can be increased. The freshness retaining bag and the freshness retaining container have a high water adsorbing power (power of adsorbing water) on the surface, and can impart water retainability and moisture retainability to a plant or food such as a fruit or vegetable.

[0048] Thus, when the freshness retaining bag or freshness retaining container is applied in preservation of a plant or food such as a fruit or vegetable, ethylene is effectively decomposed, and ethylene of the functional film is infectiously decomposed into carbon dioxide and water, so that retention of freshness can be eventually promoted by suppressing respiration of the plant or food such as a fruit or vegetable, and imparting humidity to the plant or food such as a fruit or vegetable.

Examples

[0049] Hereinafter, the present invention will be described more in detail by way of examples.

[0050] An ethylene gas decomposition test was conducted using low-density polyethylene as the freshness retaining bag. Here, as a material of the low-density polyethylene bag, one obtained by mixing an AP-MO masterbatch dispersion liquid (hereinafter, sometimes referred to simply as a masterbatch) from Nissho Chemical Co., Ltd. with low-density polyethylene and high-density polyethylene at a mass ratio of 0.1% to 10% was used.

[0051] First, a standard gas of ethylene in air in sample bags was diluted with dry air free from ethylene to prepare 1000 cc Tedlar bags (gas analysis sampling bags made of vinyl fluoride resin) containing gases with ethylene concentrations of 10 ppm, 30 ppm, 100 ppm, and 300 ppm, respectively, and a demonstration test on absorption and decomposition of ethylene was conducted using these bags. The standard ethylene gas was introduced into a freshness retaining bag sample (masterbatch content: 0.6% (mass ratio), thickness: 0.02 mm or 0.006 mm), and the absorption and decomposition amounts of ethylene was measured with a time-dependently change. In addition, for determining whether an ethylene gas was decomposed, the amount of emission of CO.sub.2 in the Tedlar bag was measured using a detection tube. As a measurement time, the amount was measured after 0, 3, 12, and 24 hours.

[0052] Similarly, the standard ethylene gas was introduced in an amount of 100 ppm into a freshness retaining bag sample (masterbatch content: 1.0% (mass ratio), thickness: 0.01 mm or 0.02 mm), and the absorption and decomposition amounts of ethylene was measured with a time-dependently change. In addition, for determining whether an ethylene gas was decomposed and discharged, the amount of emission of CO.sub.2 in the Tedlar bag was measured using a detection tube. As a measurement time, the amount was measured after 0, 3, 6, 12, 18, and 24 hours.

[0053] Further, a freshness retaining bag sample (masterbatch content: 0.6% (mass ratio), thickness: 0.01 mm or 0.02 mm, 150 mm (length)150 mm (width)) containing 100 cc of the 100 ppm standard ethylene gas was put in a 1000 cc Tedlar bag (gas analysis sampling bag made of vinyl fluoride resin), and the amount of ethylene discharged from the sample bag into the Tedlar bag was measured with a time-dependently change. As a measurement time, the amount was measured after 0, 3, 6, 12, 18, and 24 hours. FIG. 4 indicates that about 40% of ethylene is discharged from the sample bag 24 hours after the start of the test.

[0054] As shown in FIGS. 1 to 6, the effect of attenuating the ethylene standard gas was measured until 48 hours after the start of the test. It was evident that the standard ethylene gas was decomposed or/and discharged after 24 hours in the freshness retaining bag.

[0055] The results in FIGS. 1 and 2 showed that both the 30 ppm and 100 ppm standard ethylene gases were decomposed regardless of the difference in thicknesses of the freshness retaining bag (0.02 mm and 0.006 mm). Detailed comparison between the thickness of the freshness retaining bag and the ethylene decomposition effect showed that the thinner freshness retaining bag (masterbatch content: 0.6% (mass ratio), thickness: 0.006 mm) had higher efficiency, and the freshness retaining bag (masterbatch content: 1.0% (mass ratio), thickness: 0.01 mm) decomposed ethylene in a larger amount. In addition, the results in FIG. 5 showed that as compared to the control bag, the freshness retaining bag (sample bag) according to the present invention more efficiently decomposed even a high-concentration ethylene gas with a concentration of standard ethylene (300 ppm) as well as low-concentration ethylene (10 ppm, 30 ppm and 100 ppm). Thus, the freshness retaining bag was confirmed to contribute to retention of freshness of a plant.

[0056] The results in FIG. 6 showed that 600 ppm of carbon dioxide was generated from 300 ppm of ethylene, and therefore it was revealed that in this example, one ethylene molecule was decomposed into two carbon dioxide molecules.

[0057] The results in FIG. 7 show that the untreated low-density polyethylene bag adsorbs ethylene. 1 liter of 300 ppm ethylene was encapsulated in a 0.05 mm-thick low-density polyethylene bag, and how much ethylene was adsorbed was examined. The result showed that about 30% of ethylene was adsorbed in twenty and several hours. The result of measuring the concentration of carbon dioxide in the bag showed that the carbon dioxide concentration was not so high, and this indicated that even if ethylene was not decomposed, the ethylene was adsorbed and desorbed with its high affinity for the film material.

[0058] In addition, as fruits, normally grown fruits having uniform sizes wherever possible were picked up and used. The fruits were put in the freshness retaining bags (sample bags) according to the present invention immediately after being taken, and the respiration amount and the ethylene production amount were measured for about 5 days. For the respiration amount, the amount of emission of CO2 was measured using a detection tube. Specifically, a polyethylene bag containing only a fruit as a positive control, and a freshness retaining bag (sample bag) containing an ethylene adsorbent were prepared, and ethylene production and removal effects were compared and examined. For the ethylene production amount, air in the sample bag was fully replaced by ethylene-free air immediately after measurement of the respiration amount, the fruit was then hermetically sealed in one Tedlar bag for a certain period of time, about 20 ml of air was taken from the head space of the bag, 1 ml of air was taken therefrom, the ethylene concentration was measured by gas chromatography, and the ethylene production/adsorption amount with the fruit was determined. The column used was packed column, the column temperature was 100 C., air was used as a carrier, and a FID detector was used. Ethylene was measured twice or more per sample, and the result is shown as an average value. The detection limit concentration of ethylene is 0.5 ppm. In the experiment, measurement was performed for 3 samples per product, and continuously for 5 days. FIG. 6 shows a change in ethylene concentration when a cherry tomato is encapsulated in the freshness retaining bag (sample bag) according to the present invention, and the freshness retaining effect was examined at a normal temperature of 25 C. for 5 days. In the non-processed low-density polyethylene bag, the ethylene concentration in the bag gradually increased, whereas in the freshness retaining bag (sample bag) according to the present invention, the ethylene concentration did not increase even with elapse of time. In addition, after 66 hours, the ethylene concentration was below the detection limit (0.1 ppm) in the freshness retaining bag (sample bag) according to the present invention, and thus measurement was difficult. These results show that the freshness retaining bag (sample bag) according to the present invention efficiently decomposes ethylene generated from the tomato, and as a result of the decomposition, an effect of improving freshness is exhibited. FIG. 8 shows a photograph of a preserved state of cherry tomatoes one week after the preservation test. In many of non-processed LDPE low-density polyethylene bags, dew condensation occurred on the surface of the fruit, softening of the fruit proceeded, so that the shape of the tomato was collapsed. On the other hand, it was revealed that when the freshness retaining bag (sample bag) according to the present invention was used, dew condensation did not occur on the surface of the tomato, the fruit was well shaped, and freshness was retained.

[0059] FIG. 9 shows a change in ethylene concentration when spinach is encapsulated in the freshness retaining bag (sample bag) according to the present invention, and the freshness retaining effect was examined at a normal temperature of 25 C. for 1 week. In the non-processed low-density polyethylene bag, an ethylene concentration of 0.2 ppm to 0.3 ppm was constantly observed, whereas in the freshness retaining bag (sample bag) according to the present invention, detection of ethylene was difficult for up to 92 hours. These results show that the freshness retaining bag (sample bag) according to the present invention efficiently decomposes ethylene generated from the spinach, and as a result of the decomposition, an effect of improving freshness is exhibited.

[0060] The above results showed that by mixing an ethylene decomposing catalytic substance with a film material having ethylene adsorption performance, ethylene was adsorbed and decomposed in a short time, and completely decomposed into carbon dioxide and water, or/and by discharging ethylene from the vicinity of a fruit or vegetable, the aging/ripeness effect of ethylene is reduced, respiration of the fruit or vegetable is suppressed, and transpiration from the surface of the fruit is suppressed. Thus, effects such as retention of freshness of a fruit or vegetable were obtained.

[0061] While the embodiment of the present invention has been described above, the specific configuration should not be construed to be limited to the embodiment. The scope of the present invention is given by claims rather than the description of the embodiment above, and includes meanings equivalent to claims, and all changes within the scope. For example, the present invention is effective for cultivation of not only of fruits and vegetables such as tomatoes but also root vegetables, cultivation of flowers such as orchids, cultivation of leaves in plant factories, and retention of freshness of mushrooms.