JP7562948B2 - Potato packaging, method for preserving potato freshness, and method for inhibiting mold growth - Google Patents

Description

The present invention relates to a freshness-preserving packaging container for potatoes, a potato package, a method for preserving the freshness of potatoes, and a method for inhibiting mold growth.

Fruits and vegetables continue to breathe even after harvesting, and the more active their respiration, the more likely they are to deteriorate. Respiration of fruits and vegetables is suppressed in an environment with moderate oxygen and carbon dioxide, which differs from the composition of the atmosphere. When fruits and vegetables are stored under such conditions, deterioration and ripening of the fruits and vegetables are suppressed. For this reason, in recent years, a method of packaging fruits and vegetables that preserves the freshness of the fruits and vegetables using a technology called MA (Modified Atmosphere) packaging has been used. This MA packaging technology achieves an oxygen and carbon dioxide environment that is more suitable for preserving fruits and vegetables than the atmosphere by adjusting the balance between the respiration rate of the fruits and vegetables packaged in a packaging container and the gas permeation rate of the packaging container (Patent Documents 1 to 3, etc.).

Japanese Patent Application Publication No. 2-85181 Japanese Patent Application Publication No. 9-252718 JP 2007-186248 A

In general, among fruits and vegetables, root vegetables such as potatoes are sometimes stored in a refrigerator and sometimes stored at room temperature. The present inventor has found a new problem that the freshness of potatoes may not be sufficiently maintained when the potatoes are stored in a refrigerator using a conventional freshness preservation technology called MA packaging.
Specifically, root vegetables such as potatoes, which grow underground, tend to respire more when exposed to light during storage, distribution, or preservation after harvest, unlike fruits and other fresh produce that grow under light. When root vegetables such as potatoes are stored in a refrigerator, the occurrence of sprouts is reduced, but mold occurs and the vegetables are unable to maintain a stable and sufficient freshness.

The inventors therefore conducted extensive research with a view to solving this new problem, and discovered that having an MA packaging container that meets a specific water vapor permeability is effective in solving the problem. In other words, the present invention is based on the new finding that when an MA packaging container meets a specific water vapor permeability, it is possible to distinguish between cases in which the freshness of potatoes is adequately maintained and cases in which it is not, and uses the specific water vapor permeability as an indicator.

According to the present invention,
A freshness-preserving packaging container for potatoes made of a synthetic resin film,
The present invention provides a freshness-maintaining packaging container for potatoes, which has a water vapor transmission rate of 1.1 g/day·atm or more and 3.3 g/day·atm or less per 100 g of potatoes at 40° C. and 90% RH when potatoes are stored in the freshness-maintaining packaging container for potatoes.

The present invention also provides a potato package in which potatoes are contained in the potato freshness-preserving packaging container.

The present invention also provides a method for preserving the freshness of potatoes, which comprises storing potatoes in the potato freshness-preserving packaging container and storing them in an environment of 10°C±2°C.

The present invention also provides a method for inhibiting mold growth, in which potatoes are placed in the potato freshness-preserving packaging container and stored in an environment of 10°C±2°C.

The present invention provides a technology that can preserve the freshness of potatoes for a longer period of time.

The following is a detailed description of an embodiment of the present invention. In this specification, the term "approximately" means that the range includes consideration of manufacturing tolerances and assembly variations, unless otherwise specified. In this specification, the expression "a to b" in the explanation of a numerical range means a to b, unless otherwise specified. For example, "1 to 5% by mass" means "1% by mass to 5% by mass."

<Freshness-preserving packaging container for potatoes>
The freshness-preserving packaging container for potatoes of this embodiment (hereinafter also simply referred to as the "packaging container") satisfies the following criteria.
Index: When potatoes are stored in a potato freshness-keeping packaging container, the water vapor transmission rate per 100 g of potatoes at 40° C. and 90% RH is 1.1 g/day·atm or more and 3.3 g/day·atm or less.
According to the packaging container of the present embodiment, by setting the water vapor transmission rate to be equal to or more than the above-mentioned lower limit, respiration and transpiration of the potatoes can be maintained at a suitable level, and weight loss can be suppressed to preserve freshness, while the respiration and transpiration of the potatoes can be suppressed from increasing humidity inside the packaging container, which would facilitate mold growth.
On the other hand, while the humidity around the packaging container is likely to be high during refrigerated storage, the packaging container of the present embodiment can prevent humid air from entering the packaging container and causing condensation inside the packaging container by setting the water vapor transmission rate to the above upper limit or less. As a result, mold growth can be suppressed. Furthermore, if the water vapor transmission rate is set to the above upper limit or less, the potatoes can be kept breathing at a moderate level, weight loss can be suppressed, and freshness can be maintained.
Furthermore, when potatoes are stored in the potato freshness-keeping packaging container of this embodiment, the water vapor transmission rate per 100 g of potatoes at 40° C. and 90% RH is preferably not less than 1.2 g/day atm and not more than 3.0 g/day atm, more preferably not less than 1.5 g/day atm and not more than 2.8 g/day atm, and even more preferably not less than 1.8 g/day atm and not more than 2.60 g/day atm.
By setting the water vapor transmission rate to be equal to or higher than the above lower limit, mold growth can be further suppressed, whereas by setting the water vapor transmission rate to be equal to or lower than the above upper limit, mold growth can be suppressed while maintaining the weight residual rate.

The water vapor permeability can be measured using a method conforming to JIS Z0208 (cup method).

The water vapor transmission rate of the packaging container can be adjusted by controlling the selection of the material of the synthetic resin film described below, the manufacturing method of the synthetic resin film, the layer structure of the synthetic resin film, the presence or absence of through holes, and the average diameter and number of through holes.

[Synthetic resin film]
The synthetic resin film is preferably transparent or semi-transparent, more preferably transparent, so that the potatoes can be visually recognized from the outside. Furthermore, the synthetic resin film may be printed with information for the purpose of identifying the potatoes, etc.

The synthetic resin constituting the synthetic resin film is not particularly limited as long as it can be used for packaging potatoes, and any known synthetic resin can be used.
Examples include various polyethylenes and ethylene copolymers, polypropylene, polyvinyl chloride, polystyrene, acrylic resins, polyester resins such as polyethylene terephthalate and polylactic acid, and polyamide resins such as nylon 6. These may be homopolymers, copolymers of two or more kinds, or blends containing two or more kinds of these homopolymers or copolymers.
Specific examples of the various polyethylenes and ethylene copolymers include ethylene-vinyl alcohol copolymers, high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene, metallocene-linear low density polyethylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-propylene copolymer, ethylene-α-olefin copolymer, and other copolymers or ionomers. These may be used alone or in combination of two or more, or may be mixed with other resins.

Among them, from the viewpoint of appropriately controlling the amount of water vapor permeation, polyester resins such as polyethylene, ethylene-vinyl alcohol copolymer, polypropylene, polystyrene, and polylactic acid, and polyamide resins such as nylon are preferable, and ethylene-vinyl alcohol copolymer, polystyrene, polylactic acid, and nylon are more preferable.

From the standpoint of cost and physical properties, it is preferable to use heat-sealable anti-fog stretched polypropylene film, low-density polyethylene film, linear low-density polyethylene film, or metallocene-catalyzed polyethylene.

The molding method of the synthetic resin film is not particularly limited, but may be extrusion, inflation, calendering, etc. When molding the synthetic resin film, additives such as an anti-fogging agent may be kneaded, or two or more types of resins may be blended, if necessary.
The synthetic resin film may be stretched or annealed, or may have a sealant layer. In particular, the synthetic resin film may be stretched to improve its rigidity, pinhole resistance, water vapor and oxygen barrier properties, and appearance. For example, stretched nylon, stretched polylactic acid, and stretched polystyrene are preferred.

The synthetic resin film may be used as a single layer or as a multi-layer structure of two or more layers.

For example, from the viewpoint of obtaining sufficient strength for packaging potatoes, it is preferable to use a multilayer film made of polyethylene by dry lamination, extrusion lamination, or coextrusion in addition to films such as unstretched polypropylene, oriented polypropylene, unstretched nylon, oriented nylon, and oriented polyester.

The average thickness of the synthetic resin film is preferably 10 μm or more and 150 μm or less, more preferably 15 μm or more and 100 μm or less, and even more preferably 20 μm or more and 50 μm or less.
By making the average thickness of the synthetic resin film equal to or greater than the lower limit, it becomes easier to control the oxygen permeability and water vapor permeability to a higher degree, and the strength of the packaging container can be increased. On the other hand, by making the average thickness of the synthetic resin film equal to or less than the upper limit, the handling property of the packaging container can be improved, appropriate water vapor permeability and oxygen permeability can be imparted, and the production cost can be reduced.

[Through hole]
The packaging container of the present embodiment may have through holes. This allows the amount of water vapor passing through to be stably adjusted. Also, the freshness of the potatoes can be effectively maintained.

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

The average diameter of the through holes is preferably 30 μm to 1100 μm, more preferably 40 μm to 500 μm, and even more preferably 50 μm to 200 μm.
By making the average diameter of the through holes equal to or greater than the lower limit, the water vapor permeability and oxygen permeability are improved, and the occurrence of mold is suppressed while the freshness is easily maintained. On the other hand, by making the average diameter of the through holes equal to or less than the upper limit, the intrusion of humid outside air, which is likely to cause mold, can be suppressed. In addition, the packaging container of this embodiment can take in an appropriate amount of oxygen while minimizing the effect on the specific water vapor permeability.
The average diameter of the through holes is calculated from the opening area of the through holes, assuming that the through holes are perfect circles.

The number of through holes is adjusted appropriately depending on the size of the through holes and the amount of water vapor permeating through them. From the viewpoint of obtaining a stable amount of water vapor permeating through them, the number of through holes is preferably 1 to 150, more preferably 2 to 80, and even more preferably 3 to 50 per 1000 ^cm2 of the inner area of the packaging container.

The above-mentioned through holes may be formed in the synthetic resin film in advance when manufacturing the packaging container, or may be formed after the synthetic resin film is formed into a container, or may be formed before or after the synthetic resin film is formed into a container.
The through holes can be formed by any known method, such as a processing method using a hot needle, a method of perforating with a laser beam, or a method using a mold such as a roll cutter.

The oxygen permeability of the packaging container at 23°C and 60% RH is, from the viewpoint of maintaining the respiration of the potatoes and retaining their freshness, preferably not less than 2 cc/ ^m2 day atm, more preferably not less than 5 cc/ ^m2 day atm, and even more preferably not less than 300 cc/ ^m2 day atm.
On the other hand, the oxygen transmission rate of the packaging container at 23°C and 60% RH is preferably not more than 50,000 cc/ ^m2 day atm, more preferably not more than 10,000 cc/ ^m2 day atm, and even more preferably not more than 7,500 cc/ ^m2 day atm, from the viewpoint of preserving the quality and freshness of the potatoes.

The oxygen permeability of the packaging container can be adjusted by controlling the selection of the material for the synthetic resin film described above, the manufacturing method for the synthetic resin film, the layer structure of the synthetic resin film, the presence or absence of through holes, and the average diameter and number of through holes.

[Inner area]
The inner area of the packaging container in this embodiment is preferably 50 ^cm2 to 1000 ^cm2 per 100 g of potatoes, more preferably 70 ^cm2 to 500 ^cm2 , and more preferably 90 ^cm2 to 200 ^cm2 . By setting the inner area of the packaging container within the above numerical range, weight loss of the potatoes is suppressed to maintain freshness, while mold growth is easily suppressed.

[container]
Examples of the shape of the potato freshness-preserving packaging container include a bag-like shape and a self-supporting container. Among these, a bag-like shape is preferable because it can stably exert a freshness-preserving effect. As the bag, any bag known for containing potatoes can be used. In addition, the method for manufacturing the bag is not particularly limited, and examples thereof include a method of melt-cutting a synthetic resin film and sealing it, and a method of cutting a synthetic resin film and then heat-sealing it.

<Potato packaging>
The potato package of this embodiment is intended to mean the potato freshness-preserving packaging container described above in which potatoes are contained. The amount of potatoes contained is appropriately set according to the size and weight of the potatoes and the internal surface area of the packaging container.

The potato packaging of this embodiment is preferably sealed after the potatoes are placed inside, and the open area may be heat sealed or a back sealing tape, cable ties, rubber bands, crimps, or other materials may be used.

In order to stably maintain the freshness of the potatoes, it is preferable that the potatoes are washed with water after harvesting and the moisture is removed. Alternatively, in order to remove the effects of moisture on the potatoes as soon as possible, the moisture adhering to the potatoes may be removed by vacuum pre-cooling or the like.

In addition, the weight retention rate of the potato packaging in this embodiment is preferably 95% or more, more preferably 97% or more, and even more preferably 98% or more. By achieving such a value, the freshness retention effect of the potatoes can be improved.

<How to keep potatoes fresh>
The method for preserving the freshness of potatoes in this embodiment involves storing potatoes in the above-mentioned potato freshness-preserving packaging container and storing them in an environment of 10° C.±2° C. This makes it possible to inhibit mold growth and preserve the freshness of the potatoes.
An environment of 10°C ± 2°C is a temperature suitable for preserving the freshness of potatoes when using the potato freshness-preserving packaging container of this embodiment.

<Method to prevent mold growth>
The method for inhibiting mold growth in this embodiment involves storing potatoes in the above-mentioned potato freshness-preserving packaging container and storing them in an environment of 10° C.±2° C. This makes it possible to inhibit mold growth on the potatoes.

Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various configurations other than those described above can also be adopted.
Below, examples of reference forms are given.
1.
A freshness-preserving packaging container for potatoes made of a synthetic resin film,
A freshness-maintaining packaging container for potatoes, in which, when potatoes are stored in the freshness-maintaining packaging container for potatoes, the water vapor transmission rate per 100 g of potatoes at 40° C. and 90% RH is 1.1 g/day·atm or more and 3.3 g/day·atm or less.
2.
1. The potato freshness-preserving packaging container according to 1., wherein the thickness of the synthetic resin film is 10 μm or more and 150 μm or less.
3.
3. The freshness-maintaining packaging container for potatoes according to 1. or 2., wherein an inner area of the freshness-maintaining packaging container for potatoes per 100 g of the potatoes is 50 cm2 ^or more and 1000 ^cm2 or less.
4.
4. The potato freshness-maintaining packaging container according to any one of 1. to 3., wherein the potato freshness-maintaining packaging container has a through hole.
5.
5. The freshness-maintaining packaging container for potatoes according to 4., wherein the number of the through holes per 1000 ^cm2 of the inside area of the freshness-maintaining packaging container for potatoes is 1 or more and 150 or less.
6.
6. The freshness-preserving packaging container for potatoes according to 4. or 5., wherein the through holes have an average pore size of 30 μm or more and 1100 μm or less.
7.
A potato package comprising potatoes housed in the potato freshness-keeping packaging container according to any one of 1. to 6.
8.
A method for preserving the freshness of potatoes, comprising placing potatoes in the potato freshness-preserving packaging container according to any one of 1. to 6. and storing the potatoes in an environment of 10°C ± 2°C.
9.
A method for inhibiting mold growth, comprising storing potatoes in the potato freshness-preserving packaging container according to any one of 1. to 6. and storing the potatoes in an environment of 10°C ± 2°C.

Next, the present invention will be described in detail using examples, but the content of the present invention is not limited to the examples.

Example 1
1) Preparation of Synthetic Resin Film A Nylon 6 (UBE Nylon (registered trademark) 1022B, manufactured by Ube Industries, Ltd.) and ethylene-vinyl alcohol copolymer resin (EVOH: manufactured by Nippon Synthetic Chemical Industry Co., Ltd., product name: Soarnol 16DX) were fed into a T-die extruder and subjected to co-extrusion T-die method to prepare a two-layered synthetic resin film A. The thickness of the obtained synthetic resin film A was 30 μm.
2) Preparation of packaging bag The synthetic resin film A was cut into a cylindrical shape with the nylon 6 layer of the synthetic resin film A facing inward, and the bottom of the bag was melt-cut at 190° C. for 2 seconds to prepare a packaging bag. The size (inner dimensions) of the obtained packaging bag was 175 mm × 320 mm.
3) Preparation of Package Potatoes were placed in a packaging bag, and the bag was back-sealed (tied) at a position approximately 70 mm from the opening to obtain a package.

Example 2
1) Preparation of synthetic resin film B A mixed material obtained by adding 2.5% by weight of an anti-fogging agent (glycerin laurate: decaglycerin laurate, 97 parts by weight: 3 parts by weight) to an ethylene-vinyl alcohol copolymer resin was applied to a biaxially oriented nylon film (manufactured by Unitika Ltd., product name "Emblem ONBC", thickness 25 μm) to obtain a synthetic resin film B at 800 mg/m ² (dry). Coating was performed by gravure coating (drying temperature 100° C., drying time 10 seconds). The thickness of the obtained synthetic resin film B was 25 μm.
2) Preparation of packaging bag The obtained synthetic resin film B was cut, and two synthetic resin films were stacked together with the layer containing the antifogging agent on the inside, and heat-sealed on three sides using an impulse sealer (manufactured by Fuji Impulse Co., Ltd., FI-400Y-10PK) to form a 10 mm wide heat-sealed portion at 190° C. for a sealing time of 1 second, thereby preparing a packaging bag. The bag size (inner dimensions) of the obtained packaging bag was 175 mm x 320 mm.
3) Preparation of Package Potatoes were placed in a packaging bag, and the bag was back-sealed (tied) at a position approximately 70 mm from the opening to obtain a package.

Example 3
1) Preparation of Synthetic Resin Film B Synthetic resin film B was prepared in the same manner as in Example 2.
2) Preparation of Packaging Bag A packaging bag was prepared in the same manner as in Example 2, except that the bag size (inner dimensions) of the packaging bag was set to 225 mm x 370 mm.
3) Preparation of Package Potatoes were placed in a packaging bag, and the bag was back-sealed (tied) at a position approximately 70 mm from the opening to obtain a package.

Example 4
1) Preparation of Synthetic Resin Film B Synthetic resin film B was prepared in the same manner as in Example 2.
2) Preparation of Packaging Bag A packaging bag was prepared in the same manner as in Example 2, and seven holes having a diameter of 60 μm were drilled by laser processing all over the obtained packaging bag.
3) Preparation of Package Potatoes were placed in a packaging bag, and the area approximately 70 mm from the opening was heat-sealed to obtain a package.

Example 5
1) Preparation of Synthetic Resin Film B Synthetic resin film B was prepared in the same manner as in Example 2.
2) Preparation of Packaging Bag A packaging bag was prepared in the same manner as in Example 2, and two holes having a diameter of 130 μm were punched by laser processing so as to be uniform throughout the obtained packaging bag.
3) Preparation of Package Potatoes were placed in a packaging bag, and the area approximately 70 mm from the opening was heat-sealed to obtain a package.

<Comparative Example 1>
1) Preparation of Synthetic Resin Film C Polypropylene resin (manufactured by Japan Polypropylene Corporation, product number WFW5T) was melted, extruded from a T-die at a temperature of 230° C., and stretched 5 times vertically and 9 times horizontally to obtain a biaxially stretched polypropylene film (synthetic resin film C). The thickness of the obtained synthetic resin film C was 25 μm.
2) Preparation of Packaging Bag A packaging bag was prepared in the same manner as in Example 2.
3) Preparation of Package Potatoes were placed in a packaging bag, and the bag was back-sealed (tied) at a position approximately 70 mm from the opening to obtain a package.

<Comparative Example 2>
1) Preparation of Synthetic Resin Film A Synthetic resin film A was prepared in the same manner as in Example 1.
2) Production of packaging bag A packaging bag was produced in the same manner as in Example 2. However, the thickness of the synthetic resin film A was set to 60 μm by doubling the amount of resin extruded per hour in the co-extrusion T-die method.
3) Preparation of Package Potatoes were placed in a packaging bag, and the bag was back-sealed (tied) at a position approximately 70 mm from the opening to obtain a package.

<Comparative Example 3>
1) Preparation of Synthetic Resin Film A Synthetic resin film A was prepared in the same manner as in Example 1.
2) Production of packaging bag A packaging bag was produced in the same manner as in Example 2. However, the thickness of the synthetic resin film A was set to 40 μm by increasing the amount of resin extruded per hour in the co-extrusion T-die method by 1.3 times.
3) Preparation of Package Potatoes were placed in a packaging bag, and the bag was back-sealed (tied) at a position approximately 70 mm from the opening to obtain a package.

<Comparative Example 4>
1) Preparation of Synthetic Resin Film B Synthetic resin film B was prepared in the same manner as in Example 2.
2) Preparation of packaging bag A packaging bag was prepared in the same manner as in Example 2. However, the bag size (inner dimensions) of the packaging bag was changed to 275 mm x 420 mm.
3) Preparation of Package Potatoes were placed in a packaging bag, and the bag was back-sealed (tied) at a position approximately 70 mm from the opening to obtain a package.

The following measurements and evaluations were carried out using the resulting package. The results are shown in Table 1.

<Measurement>
Measurement of water vapor transmission rate at 40°C and 90% RH Measurement was performed according to JIS Z0208 (cup method). The measurement conditions were set to 40°C and 90% RH. Weighing was performed under conditions of 23°C and 50% RH. The unit is g/(day·atm·100g of potatoes).
In addition, when the water vapor permeation rate of the synthetic resin film was too high to use the method based on JIS Z0208 (cup method), calcium chloride was heat-sealed and packaged in a bag of 50 mm x 100 mm (inner dimensions) instead of a cup, and the water vapor permeation rate was calculated from the change in weight of the bag over time. In this case, the storage period of the bag was set within a range in which calcium chloride would not completely absorb moisture.

Measurement of the average hole diameter (μm) of through holes The open hole area of the inner surface of the packaging bag was measured for five holes using a microscope (Keyence Corporation, VH-6300). Assuming that the open hole is a perfect circle, the diameter was calculated from the open hole area, and the average diameter was calculated.

<Evaluation>
Each of the potato-containing packages obtained above (each with a potato content in the range of 700 to 900 g) was stored for 23 days at 10° C. Thereafter, the potatoes were removed from the packages, and the "mold occurrence rate (%),""germination rate (%)," and "weight remaining rate (%)" were measured by the following methods.
Mold occurrence rate (%): The presence or absence of mold was visually observed, and the number of potatoes observed to have mold occurrence relative to the total number of potatoes was calculated to obtain the mold occurrence rate (%).
Germination rate (%): The presence or absence of germination was visually observed, and the number of potatoes observed to have sprouted out of the total number of potatoes was calculated to obtain the germination rate (%).
Weight residual rate (%): the ratio (%) of the weight (g) of the potatoes after storage to the weight (g) of the potatoes before storage was calculated.

Claims (5)

A potato package in which potatoes are contained in a potato freshness-preserving packaging bag made of a synthetic resin film,
The potato freshness-preserving packaging bag has no through-holes,
a water vapor transmission rate per 100 g of potato at 40° C. and 90% RH of 1.1 g/day atm or more and 3.3 g/day atm or less ;
The potato package has an inner area of the potato freshness-preserving packaging bag of 50 cm2 or more and 200 cm2 or less ^per 100 ^g of potatoes . The potato packaging according to claim 1, wherein the thickness of the synthetic resin film is 10 μm or more and 150 μm or less. 3. The potato packaging according to claim 1 or 2, wherein the synthetic resin film has a single layer or a multilayer structure and contains one or more resins selected from polyethylene, ethylene copolymer, polypropylene, polyvinyl chloride, polystyrene, acrylic resin, polyester resin, and polyamide resin. A method for preserving the freshness of potatoes, comprising storing the potato package according to any one of claims 1 to 3 in an environment of 10°C ± 2°C. A method for inhibiting mold growth, comprising storing the potato package according to any one of claims 1 to 3 in an environment of 10°C ± 2°C.