JPH0698990B2 - Preservation method of perishables - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention suppresses the decay and mold generation of an object to be preserved and preserves the color of a preserved object when preserving a sample such as a fresh food or a collected animal or plant. The present invention relates to an excellent storage method with little discoloration or discoloration.

[Prior Art] Conventionally, when storing, storing or storing fresh food such as fresh vegetables and fruits from supermarkets and grocery stores to general households, polyvinylidene chloride wraps and polyethylene are used. The method of preserving the freshness by wrapping it with plastic films such as that has already been put into practical use.

When these are stored, preserved, or stored by these methods, they have some effects in the sense of preventing contamination from the outside, reducing the commercial value, and suppressing the evaporation of water of the preservation object itself. However, these methods merely prevent evaporation of water and stains, and have no effect of suppressing germ cells such as bacteria and fungi that propagate in the preservation target. If left unattended, the object to be stored will become moldy. In addition, fresh vegetables and fruits are discolored brown, and the color of the objects to be preserved is significantly fading or changing. In other words, there has been a limit to the improvement of the conventional method of storing or preserving or wrapping with film (including wrap).

[Problems to be Solved by the Invention] The present inventors have arrived at the present invention as a result of extensive studies on a method of storing an object to be stored that does not have the above-mentioned drawbacks.

INDUSTRIAL APPLICABILITY The present invention is for a long period of time from the distribution process such as storage, transportation, and storage of fresh foods such as fresh vegetables, fruits, and raw fish, and specimens such as collected animals and plants, to storage after being handed to consumers. It has the effect of suppressing decay over a long period of time, and retains freshness well. In particular, it suppresses the reproduction of germ cells such as bacteria and fungi by the electrical action of electret sheet-like products, and also the fading of the color of stored objects. An object of the present invention is to provide an excellent method for preserving an object to be preserved, which is less discolored and does not impair the change in appearance.

[Means for Solving Problems] The present invention has the following configurations.

That is, carbon dioxide permeability is 500 to 350,000 cc / m ² · 24hr ·
Atm, oxygen permeability is 100 to 35000cc / m ² · 24hr · atm, moisture permeability is 5 to 700g / m ² · 24hr The storage target is characterized by packaging the storage target with a electret sheet made of polyolefin This is a method of storing fresh food.

Hereinafter, the present invention will be described in detail.

As a material constituting the electret sheet-like material used in the present invention, any material having an electrical resistivity of 10 ¹³ · Ω · cm or more can be processed as an electret, and examples thereof include a polyolefin-based material and a polyester-based material. , Fluorine-containing, PVC, polyamide, polyacrylic, etc. Of these, polyolefins have good electretization performance, and in the present invention, particularly polyolefins are used to obtain higher effects by the electret.

As the form of such a sheet-like material, a film-like sheet, a paper-like sheet, a non-woven fabric-like sheet or the like can be used, but a film-like sheet is preferred in the sense that evaporation of water in the object to be stored is suppressed.

In addition, when the object to be preserved is freshly breathing such as fresh vegetables and fruits, when the sheet-like object is opened, transpiration, atrophy, and dryness caused by transpiration associated with respiration occur, resulting in a marked decrease in freshness. The commercial value is lost. On the other hand, in the completely sealed package, carbon dioxide concentration becomes abnormally high and oxygen concentration decreases due to the gas breathed by itself. That is, things such as fresh vegetables and fruits that are highly respirable cannot normally breathe, and the vaporized water vapor condenses to promote the growth of microorganisms.

Therefore, the property required for packaging materials such as fresh vegetables and fruits is the selective permeability of carbon dioxide and oxygen. This gas permeability differs depending on the type of storage object, but in the case of fresh vegetables and fruits, the carbon dioxide gas permeability is 500 to 350,000c.
c / m ² · 24hr · atm is preferable, more preferably 25000 to 25
It is 0000cc / m ² · 24hr · atm. Also, the oxygen permeability is 100
~ 35000cc / m ² · 24hr · atm is preferred, more preferably 3
It is 000 ~ 30000cc / m ² · 24hr · atm.

Further, as described above, appropriate moisture permeability is also required in order to prevent condensation of water vapor evaporated on the inner surface of the packaging material and dew condensation. The moisture permeability also differs depending on the type of storage object,
The moisture vapor transmission rate is preferably 5 to 700 g / m ² · 24 hr. Water vapor transmission rate is 5g / m ²
・ If it is less than 24 hours, it may cause discoloration or discoloration.
If it exceeds m ² · 24hr, withering, atrophy, and dryness may occur, resulting in a marked decrease in freshness. More preferably 20-500g
/ m ² · 24hr. With this, the freshness of fresh vegetables and fruits can be maintained for a longer period of time. Therefore, according to the knowledge of the present inventors, in order to obtain a good preservation effect, it is important that the three characteristics of carbon dioxide permeability, oxygen permeability, and moisture permeability are well balanced, and particularly, Carbon dioxide permeability
^{500~35000cc / m 2 · 24hr · atm} , an oxygen permeability from 100 to 35,000
It is preferable to use an electret sheet having a cc / m ² · 24 hr · atm and a moisture permeability of 5 to 700 g / m ² · 24 hr. The important point that the above three characteristics of carbon dioxide permeability, oxygen permeability, and moisture permeability are well-balanced is from the viewpoint of preservation of perishables having a respiratory action.

The gas permeability of the fiber sheet is generally too large, and it is difficult to satisfy the above three characteristics in a well-balanced manner.

If the object to be preserved is meat or the like, appropriate permeability of oxygen is required. Its permeability is 5-200cc / m ² · 24hr · atm
Is preferred. If the oxygen permeability is less than 5 cc / m ² , 24 hr ・ atm, it may cause discoloration or discoloration, and 200 cc / m ² , 24 hr ・ atm.
If it exceeds, there is a possibility that it may be oxidized and promote the growth of microorganisms. Therefore, it is more preferably 20 to 100 cc / m ² · 24 hr · atm.

The carbon dioxide permeability, oxygen permeability, and water vapor transmission rate are
It is based on the S standard.

Carbon dioxide permeability: JIS Z 1707 method (20 ° C 90% RH) Oxygen permeability: JIS Z 1707 method (20 ° C 90% RH) Moisture vapor transmission rate: JIS Z 0208 method (40 ° C 90% RH) ， In particular, meat and the like accelerates discoloration and oxidation when exposed to ultraviolet rays, so in order to block infrared rays, the sheet-like material itself is colored or printed in reddish-blue color, etc.
Alternatively, when combined with another colored sheet, it is effective in maintaining the freshness by suppressing discoloration or oxidation of the object to be stored.

Further, the sheet-like material used in the present invention is highly flexible and is preferably applied to various purposes. Of course, a non-woven fabric, a sponge-like material, or paper or a metal sheet may be compounded on the outer surface to prevent physical external damage.

The thickness of the sheet-like material is preferably about 4 μm to 300 μm from the viewpoint of adhesion to the object to be stored. If it is less than 4 μm, it may be broken by an external force, and if it exceeds 300 μm, the packaging performance is deteriorated. More preferably 6 μm to 100 μm, and particularly preferably 10 μm to 50 μm.
μm.

The electret sheet material used in the present invention is described in
It can be easily obtained by the electret processing method disclosed in Japanese Unexamined Patent Publication No. 282471 or Japanese Unexamined Patent Publication No. 61-289177.

Since the charge amount applied to the electret sheet-like product is poor if it is too weak, the surface charge density retained on the surface of the electret sheet-like product is 1 × 10 ⁻¹¹ clones / cm ² or more, and more preferably, 1 x 10 ^-10 clones / cm
² or more, particularly preferably 1 × 10 ⁻⁹ clone / cm ² or more is desirable.

The surface charge density is calculated as follows. FIG. 1 is a schematic diagram showing a method for measuring the surface charge density. The measurement procedure is as follows: A sample 3 (area 100 cm ² ) is sandwiched between a grounded metal box 1 (material: true casting) and a metal plate electrode 2 (area 100 cm ² , material: true casting), and the charge generated by electrostatic induction is inserted. High-performance electrometer 5 (Takeda Riken TR85
Measure the potential in step 62). From the measured potential, the surface charge density on the surface of the sample 3 is calculated by the following calculation formula.

Surface charge density (clone / cm ² = C × V / S) C: Capacitor capacity (farad) V: Potential (volt) S: Sample area (cm ² ) Further, the electret sheet used in the present invention has an internal charge of It is characterized in that it is highly oriented and polarized, and the surface and the back surface have different polarities, that is, if the surface is positively charged and positive, the back surface is negatively charged and negative. Therefore, it is possible to exert an electrical action on the outside of the sheet-shaped material and stabilize the electret performance for a long period of time.

The greatest feature of the present invention is to use such an electret sheet as a packaging material. In case of packaging with these, even if it is used alone (wrapping one sheet), the excellent effect is exhibited, but by stacking the electret sheet-like materials in a plurality of layers and packing, the preservation object has a longer life and can be used under external conditions. Also, durability, chemical resistance, heat resistance, and cold resistance are improved. For example, FIG. 2 shows a part of the cross section of the laminated sheet, but as shown in the figure, three electret sheet-like materials are laminated and packaged so that the orientations of polarization charges are in the same direction. This improves the above-mentioned durability and the like.

Such a laminated body may be integrated by various resin adhesives or mechanical bonding such as embossing or ultrasonic bonding so as not to lose electret performance. However, it is desirable to maintain the carbon dioxide permeability, oxygen permeability, and moisture permeability of the laminated sheet itself as described above.

The packing method may be either an electret sheet directly or indirectly by being combined with a non-woven fabric, a woven or knitted material, a paper sheet, etc., but it should be packed so that the surface of the object to be preserved is electrically operated. Preferably.

In the case of wrapping with an electret sheet, the polarity of the surface on the side of the object to be stored should be such that an electrical stimulus is given to the surface of the object to be stored, so that either positive or negative surface can be used. In particular, when the object to be stored is a plant, the larger the electric field formed by the electret sheet-like object, the more the storage performance thereof increases. To explain this effect, it is known that injured plants are charged with a negative charge due to the action of promoting self-repair and recovery, and also with an electrical stimulus. . Therefore, electrical stimulation of the electret sheet-like material allows the plant's repairing action to continue for a long period of time. It is presumed that this effect improves the storage stability of freshness and less color fading and discoloration, thus improving storage performance.

The inventors of the present invention have a plant leaf as a storage object, and compare the non-electretized film and the surface of the electret film on the storage object side by changing the polarity of the leaves to compare their color fading and discoloration with others. As a result, it was found that the film using the film, which is clearly electretized, was good, and it was preferable that the polarity of the object to be stored was negative. However, the polarity of the surface on the side of the storage target differs depending on the type of storage target.

Further, the air existing between the storage object and the electret sheet-like material is removed as much as possible, and if possible, the higher the degree of vacuum is, the more effective it is in suppressing the reproduction of germ cells such as bacteria and mold.

The storage place is not particularly limited, but the charge trapped in the electret sheet-like material may be attenuated in a place with high temperature and high humidity, and it may promote the reproduction of germ cells such as bacteria and fungi, so it is cool and dark. A good place is desirable.

[Action] In the present invention, the electrical action of the electret sheet-like product brings about an improvement that the reproduction of germ cells such as bacteria and mold is suppressed, and brings an improvement that the number of days until the storage object is damaged is prolonged. Moreover, it is unlikely that the color of the object to be preserved will fade or discolor, and will not damage the appearance.

Hereinafter, the present invention will be described more specifically and in detail with reference to Examples and Comparative Examples.

[Example] Example 1 The charge densities of the front and back surfaces of the electret sheet-like material were +9 x 10 ^-9 coulombs / cm ² and -1 x 10 ^-8 coulombs / cm ² , respectively.
² , the sheet-like material itself has a carbon dioxide permeability of 30,000 to 40,000 c
c / m ² .24hr.atm, oxygen permeability 7200-11800cc / m ² .24hr.at
Two sheets were laminated using a polypropylene electret film having a thickness of m and a moisture permeability of 27 to 29 g / m ² .24 hr and a thickness of 12 μm so that the electric field directions were the same. The laminated sheet was packaged so that the negative surface of the laminated sheet closely adhered to the surface of the fruit, Unshu mandarin orange, and left in a room at room temperature of 20 ° C ± 2 ° C and humidity of 65% ± 2%. The number of samples was set to 20, and the preservation rate was calculated over time.

The preservation rate was calculated as follows.

Storage rate K (%) = (N-n / N) x 100 N: Number of test samples n: Number of samples that were damaged by rotting, mold, drying, etc. As a result, the storage rate after one month was 100%. The preservation rate after 2 months was 70%, which was very good. Many of them did not impair the appearance.

Comparative Example 1 Two sheets of non-electretized polypropylene film having the same thickness as in Example 1 and having the same carbon dioxide permeability, oxygen permeability and moisture permeability of the sheet itself as in Example 1 were laminated. Then, Unshu mandarin orange, which is the same fruit as in Example 1, was packaged in the same manner. The same evaluation was performed by setting the number of samples and leaving conditions to be the same as in Example 1.

As a result, the preservation rate after 1 month was 60%, and the preservation rate after 2 months was only 5%, which caused mold and rot.

Comparative Example 2 Carbon dioxide gas permeability is 72 ~ 105cc / m ² .24hr.atm, oxygen permeability is
Example ² was carried out by laminating two commercially available vinylidene chloride wraps having a thickness of 32 to 40 cc / m ² .24 hr.atm, a moisture permeability of ^{2 to} 2.5 g / m ² .24 hr, and a thickness of 10 μ. Unshu mandarin orange, which is a fruit similar to the above, was similarly packaged. The same evaluation was performed by setting the number of samples and leaving conditions to be the same as in Example 1.

As a result, the preservation rate after 1 month was 30%, and the preservation rate after 2 months was 0%, and all samples were rotted and the original shape was not retained. This is because there is no electrical action due to electretization, and there is little gas permeability or moisture permeability, so the breathing action of the sample becomes impossible and decay is promoted.

Comparative Example 3 With the same thickness as in Example 1, the sheet-shaped material itself has a carbon dioxide gas permeability of 28000 to 36000 cc / m ² .24 hr.atm and an oxygen permeability of 9000.
〜10000cc / m ² .24hr.atm, moisture permeability 29〜31g / m ² .24hr Non-electretized polyethylene film 2 sheets are laminated to form Unshu mandarin fruit similar to Example 1. Packaged similarly. The same evaluation was performed by setting the number of samples and leaving conditions to be the same as in Example 1.

As a result, the preservation rate after 1 month was 40%, and the preservation rate after 2 months was 0%, and all the samples were moldy and decayed.

Comparative Example 4 The same fruit evaluation as in Example 1, Unshu mandarin orange, was not packaged in a film or wrap, and the same number of samples and all the standing conditions were the same as in Example 1 and the same evaluation was performed.

As a result, the preservation rate after 1 month was 10%, the preservation rate after 2 months was 0%, and all the samples were dried and shrunk and had no freshness.

The examples described below are Examples and Comparative Examples in which the fading and discoloration of the color of green plants were examined.

Example 2 The charge densities of the front and back surfaces of the electret sheet-like material were + 9 × 10 ⁻⁹ coulomb / cm ² and −9 × 10 ⁻⁹ coulomb / cm, respectively.
² , the carbon dioxide permeability of the sheet itself is 13000 to 20000c
c / m ² .24hr.atm, oxygen permeability 3400-6000cc / m ² .24hr.at
m, moisture permeability 14 ~ 16g / m ² .24hr, using a thickness of 24μ polypropylene electret film, sandwich the clover (Mitsuba) between the two films with their negative faces facing each other, A large number of pieces were created by melting and cutting with a heat cutter the area 5 cm away from the clover to prevent air from entering and exiting. Room temperature 20 ℃ ± 2 ℃,
The clover was allowed to stand in a room with a humidity of 65% ± 2% and evaluated for fading or discoloration of the color of the clover.

As a result, after 2 months, the appearance of the clover was slightly shrunk, but the leaf color remained dark green without fading or discoloration. There was no mold at all.

Comparative Example 5 Two sheets of polypropylene film having the same thickness as in Example 2 but having the same carbon dioxide permeability, oxygen permeability, and moisture vapor permeability of the sheet itself as in Example 2 but not electretized were prepared. A clover (mitsuba) similar to that of Example 2 was sandwiched between the films, and the periphery 5 cm away from the clover was melt-cut with a heat cutter to prepare a large number of air-tight air passages. The same evaluation was performed by using the same number of samples and leaving conditions as in Example 2.

As a result, in most of the samples, the leaf color faded after 3 weeks and turned brown by 1 month. Also, 1
Mold formation was confirmed in 40% of samples after a month.

Comparative Example 6 Carbon dioxide gas permeability is 72 ~ 105cc / m ² .24hr.atm, oxidation permeability is
32~40cc / m ² .24hr.atm, a moisture permeability of 2~2.5g / m ² .24hr, ² sheets of the film using the commercially available vinylidene chloride wrap has a 10μ thick (lap) between Clover (Mitsuba) similar to that used in Example 2, and 5c from the clover
A large number of pieces were created by welding and cutting the surroundings at a distance of m with a heat cutter to prevent air from entering and exiting. The same evaluation was performed by setting the number of samples and the conditions under which the samples were left as in Example 2.

As a result, in most of the samples, the discoloration of the leaf color progressed after 2 weeks, and after 3 weeks, it turned brown like Comparative Example 5. Mold formation was confirmed in 100% (all) samples after 1 month.

Comparative Example 7 With the same thickness as in Example 2, the sheet-shaped material itself has a carbon dioxide gas permeability of 12000 to 19000 cc / m ² .24 hr.atm and an oxygen permeability of 4000.
~ 5000cc / m ² .24hr.atm, moisture permeability 15 ~ 17g / m ² .24hr non-electretized polyethylene film was used between the two films clover (Mitsuba) similar to Example 2. A large number of scissors and clovers were created by melting and cutting the surroundings with a heat cutter at a distance of 5 cm to prevent air from entering and exiting. The same evaluation was performed by setting the number of samples and the conditions under which the samples were left as in Example 2.

As a result, in most of the samples, the leaf color faded after 2 weeks, and after 3 weeks, 50% of the samples turned yellow, 35% turned ocher, and 15% turned brown. Only 5% retained their green color. 1
Mold formation was confirmed in 25% of the samples a month later.

From the above examples and comparative examples, it can be seen that the long-term storage method of the present invention is excellent. In particular, Example 1 is suitable for a packaging material, and Example 2 is suitable for a sheet for specimens such as plants.

In addition, cucumber, cabbage, spinach for fresh vegetables, apple (Fuji) for fruits, flowers for plants and margarets and kogiku flowers sold at florists, stems and leaves were also evaluated in the same manner.

As a result, the number of days until decay depends on the type of the object to be preserved, but in any case, the preservation method according to the present invention was excellent.

[Effects of the Invention] (1) The effect of suppressing decay is excellent.

(2) The effect of suppressing the reproduction of germ cells such as bacteria and mold is excellent.

(3) The effect of suppressing fading or discoloration of the color of the object to be stored is excellent.

(4) It is excellent that there is little deformation or shrinkage of the object to be stored and the change in appearance is not impaired.

[Brief description of drawings]

FIG. 1 is a schematic sectional view for measuring the surface charge density. FIG. 2 is a schematic cross-sectional view showing the charge and the orientation direction of a laminate in which three electret sheet-like products are laminated. 1: Grounded metal box 2: Metal plate electrode (area 100 cm ² ) 3: Sample (area 100 cm ² ) 4: Capacitor 5: High-performance electrometer 6: Electret sheet

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-61-289177 (JP, A) JP-A-61-282471 (JP, A)

Claims (1)

[Claims] 1. The carbon dioxide gas permeability is 500 to 350,000 cc / m ² · 24hr.
· Atm, an oxygen permeability is stored object fresh vegetables, fruits or 5~200cc / m ² · 24hr · atm of meat such in 100~35000cc / m ² · 24hr · atm case of plants, the moisture permeability 5 700g / m ² · 24
A method for preserving fresh food to be preserved, characterized in that the object to be preserved is wrapped in an electret sheet made of polyolefin which is hr.