JPH0228311B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is directed to the use of vegetables, root vegetables, fruits, flowers, flowering plants, mushrooms, etc. (hereinafter referred to as fruits and vegetables in a broad sense in this specification), which have strong physiological effects even after harvest. This paper deals with a method for maintaining the freshness of fruits and vegetables at the time of harvest for a long period of time. [Conventional technology] In recent years, many fruits and vegetables such as fresh vegetables, fruits, fresh flowers, and mushrooms have been transitioned from open-field cultivation to planned multiplex and diversified cultivation using horticultural facility cultivation. It is often necessary to harvest and package large quantities of fruits and vegetables within a country. In addition, since the harvest period for fruits and vegetables that are mainly grown in open fields is fixed, a large amount of the harvest must be packaged and shipped within a short period of time. The biggest problem in the distribution process up to the point of crossing the border is how best to maintain freshness at the time of harvest. In order to meet these demands, research is actively underway to improve packaging bags with a focus on preserving freshness, and the present applicant has also proposed several improved packaging films and packaging bags. By the way, fruits and vegetables such as those mentioned above do not immediately lose their physiological effects after being harvested, but especially for a while after being harvested, they continue to maintain their physiological effects to the extent that they are almost the same as before harvest. Furthermore, if they are kept under appropriate storage conditions, their physiological effects will continue for a longer period of time, and as long as they maintain their physiological effects, fruits and vegetables will maintain good freshness. In other words, if it is not stored in a good condition, it will lose its sustained physiological function and will deteriorate prematurely. It is known that the physiological effects of fruits and vegetables in a packaged state include a decrease in moisture due to transpiration, consumption of atmospheric oxygen and generation of carbon dioxide due to respiration, and temperature rise due to generation of carbon dioxide and heat generation. As the oxygen concentration decreases, the carbon dioxide concentration increases, and since heat is not dissipated, the internal temperature of the package rises. The respiration process becomes more active above a certain temperature, and at high temperatures it becomes more susceptible to decomposition due to the stuffiness phenomenon. In addition, the transpiration effect becomes greater in an atmosphere of high temperature or low humidity, and as a result, it becomes more likely to rot in the high temperature and high humidity environment. Therefore, in order to improve the freshness retention effect during storage by taking into account the physiological effects mentioned above, ventilation is improved by making holes of an appropriate size in the packaging bag or cutting the bottom of the bag. Attempts have been made to increase the temperature, prevent a decrease in oxygen concentration, prevent an increase in carbon dioxide concentration, and suppress temperature rise. However, these are only temporary measures, and do not necessarily equalize the temperature distribution and gas composition inside the packaging bag, leading to localized decay, especially in areas that cannot be seen from the outside. This can have the unintended consequence of deceiving consumers. Moreover, in the packaging bags for fruits and vegetables that use packaging films that are currently in practical use, the moisture produced by the transpiration of fruits and vegetables or the evaporation of adhering moisture adheres to the inner surface of the packaging bag, causing cloudiness and clouding of the contents. In addition to the problem that things become difficult to see from the outside, there is also the problem that when fruits and vegetables come into direct contact with moisture condensed in the cloudy area, so-called water rot occurs. From this point of view, it is possible to maintain the conditions inside the bag at a temperature and gas composition suitable for the physiological effects of fruits and vegetables, and to exhibit excellent antifogging properties, without having to make holes or cut the bag. Although it has been desired to develop a packaging bag that is suitable for packaging fruits and vegetables that have strong physiological effects, it has not yet been developed. For example, although polyethylene film has a moderate water vapor permeability, it lacks oxygen and carbon dioxide gas permeability, which causes fruit and vegetables to suffocate during short-term storage, resulting in loss of freshness. It has an oxygen and carbon dioxide gas permeability of , and the respiration effect of fruits and vegetables can be sustained for a long period of time, but because the water vapor permeability is too high, the water evaporation effect becomes significant, causing discoloration or wilting of fruits and vegetables in a short period of time. However, it is not possible to maintain good freshness over a long period of time. Moreover, all of the above-mentioned films have poor antifogging properties, which not only lowers the commercial value in terms of appearance, but also causes so-called water rot when fruits and vegetables come into direct contact with moisture condensed in the cloudy areas. [Problems to be Solved by the Invention] The present inventors have focused on the above-mentioned circumstances, and have developed a packaging bag that has water vapor permeability, oxygen and carbon dioxide properties that are suitable for the physiological effects of fruits and vegetables without opening or cutting the packaging bag. We conducted research to develop a multilayer film that exhibits gas permeability of 100% and does not cause clouding on the inner surface. As a result, if the water vapor permeability, oxygen permeability, and carbon dioxide permeability of the multilayer film are specified within appropriate ranges, and an appropriate amount of antifogging agent is blended into the multilayer film constituent materials, it is possible to solve the above problems. After confirming that the problem had been resolved, we filed a patent application based on this knowledge. However, as further research progressed, the following facts became clear. That is, when using a bag made of the multilayer film according to the prior invention,
The purpose of preserving freshness is effectively achieved for fruits and vegetables that have relatively mild physiological effects after harvest, but fruits and vegetables that have strong physiological effects even after harvest (e.g. yellow cucumber, edamame, enokidake, kidney beans, etc.) When used for packaging, the oxygen concentration, carbon dioxide concentration, or humidity within the bag will fluctuate significantly.
Ordinary packaging methods sometimes have difficulty keeping up with such rapid fluctuations, making it impossible to maintain a gas atmosphere suitable for the intense physiological effects of the fruits and vegetables, making it impossible to fully achieve the purpose of preserving freshness. I found out. Moreover, when there is a sudden temperature change between day and night or when the food is put in and taken out of the refrigerator, the water vapor inside the bag condenses and water accumulates inside the packaging bag, causing the problem of water rot in the fruits and vegetables. It's coming. The present invention was developed as a result of further research focusing on such problems, and its purpose is to target fruits and vegetables that have strong physiological effects, and to maintain the same effect even when the fruits and vegetables are subjected to rapid temperature changes. Not only can the packaging bag atmosphere be maintained suitably for the physiological effects of fruits and vegetables, but it also eliminates the problem of water rot due to condensed water.
The purpose is to provide a method that can maintain excellent freshness of fruits and vegetables for a long period of time. [Means for solving the problems] The configuration of the method of the present invention specified as requirements for achieving the above objectives is as follows: water vapor permeability is 15 to 200 g/m ² / 24 hr / 40°C; oxygen permeability is 3000～35000c.c./m ²・24hr・
ATM・20℃・90%RH、Carbon dioxide permeability 12000~130000c.c./ ^m2・
24 hours, ATM, 20℃, 90%RH, and an antifogging agent is present on at least one surface layer, and the surface layer exhibits antifogging properties during repeated temperature changes between 040℃ and , using a multilayer film that exhibits a fusing seal strength of 3.0 Kg-cm/15 mm or more when fusing-sealed at 270°C, and formed into a bag shape with at least three sides closed so that the surface layer is on the inside, In addition, 0.02% of the total surface area of the film surface of the bag is applied to a part or the entire surface of the film surface of the bag.
The gist is that fruits and vegetables are stored in a packaging bag provided with one or more openings having a total opening area of ~3.5%. [Function] The multilayer film constituting the packaging bag used in the present invention first specifies the water vapor permeability, oxygen permeability, and carbon dioxide permeability as the first condition, and also has a Since it is characterized by the presence of an antifogging agent in the surface layer on the contacting side, the reasons for determining each of the above characteristics will be explained below. Water vapor permeability: 15 to 200 g/m ² , 24 hr, 40°C It is an important characteristic in preventing the phenomenon of rot and suppressing rot, as well as in preventing fruits and vegetables from wilting, discoloration (yellowing or browning), softening, loss of elasticity, etc. due to lack of humidity.
If the water vapor permeability is less than 15 g/m ² / 24 hr / 40°C, fruits and vegetables are likely to rot due to swelling caused by excessive humidity, while if it exceeds 200 g / m ² / 24 hr / 40°C, there may be insufficient humidity inside the packaging bag. Fruits and vegetables tend to wilt, change color, etc., and in either case, a satisfactory freshness-keeping effect cannot be obtained. A more preferable water vapor permeability range is 20 to 150 g/m ² , 24 hr, and 40° C. in order to ensure a good freshness-keeping effect. Oxygen permeability: ^{3000-35000c.c./m2}・24hr・
ATM・20℃・90%RH Oxygen permeability is an extremely important characteristic for sustaining physiological effects by compensating for the decrease in oxygen concentration due to respiration by permeation of external air. .c.／ ^m2・24hr・atm・20℃・90%RH
If the amount is less than 100%, the amount of internal oxygen will be insufficient when packaging fruits and vegetables, which have a significant respiration effect (high oxygen consumption), resulting in suffocation, and a sufficient freshness-keeping effect will not be exhibited. On the other hand, 35000c.c./m ²・24hr・atm・20
If the temperature exceeds ℃ and 90% RH, there is no risk of oxygen depletion, but the freshness-keeping effect of fruits and vegetables that develop mold due to the invasion of bacteria from the outside may actually decrease. A more preferable range of oxygen permeability is 4000 to 20000
cc/ ^m2・24hr・atm・20℃・90%RH. Carbon dioxide permeability: ^{12000-130000c.c./m2}・
24hr/ATM/20℃/90%RH Carbon dioxide gas permeability maintains the appropriate gas composition within the packaging bag, guarantees the respiration of fruits and vegetables, avoids carbon dioxide damage, and prevents bacterial invasion and proliferation. This property is also effective in preventing spoilage due to the permeability of ^12000c.c./m2 , 24hr, ATM, 20℃, 90%.
If the RH is less than RH, the carbon dioxide concentration in the packaging bag becomes too high, which inhibits the respiration of fruits and vegetables, leading to a rapid decline in freshness and taste. On the other hand, 130000c.c./m ² , 24hr, atm, 20℃, 90%
When the RH is exceeded, the CO ₂ concentration inside the packaging bag becomes too low, and the anti-corrosion and deterioration suppressing effects are no longer effectively exhibited. A more preferable range of carbon dioxide permeability is 15,000~
^{100000c.c./m2}・24hr・ATM・20℃・90%RH. Furthermore, the surface layer of the multilayer film used in the present invention on the side that comes into contact with fruits and vegetables must contain an antifogging agent that exhibits antifogging properties during storage and distribution. That is, in the present invention, the antifogging effect is extremely important not only to prevent the inner surface of the packaging bag from becoming cloudy and thereby increasing the product value, but also to prevent the contents from being spoiled by water droplets that are formed as clouding progresses. In addition, in order to maintain excellent anti-fogging properties over the long term during the distribution process, it is necessary to take into account temperature changes during storage and distribution, and to continue to maintain the temperature during storage and distribution. An antifogging agent that exhibits antifogging properties must be present in the surface layer. As mentioned above, the present invention is intended for packaging fruits and vegetables that continue to have strong physiological effects even after harvest, and it is preferable to store them at room temperature rather than freezing them, but it is important to take into account the temperature difference between indoors and outdoors in winter. Therefore, when setting the antifogging property in the present invention, it is preferable to determine it based on "antifogging durability when the temperature is repeatedly changed between 040°C", which is determined by the method described below, for example. In the present invention, it is desired that the antifogging property be maintained for one day or more as measured by the following measurement method. (Anti-fog property evaluation method) Fill a 200 c.c. beaker with 150 c.c. of 40°C warm water, and place the sample over the beaker with the anti-fog side facing inside. After that, it was kept at 0℃ for 6 hours, and then kept at 40℃ for 6 hours.
This temperature change is repeated twice (total of 24 hours), and judgment is made based on whether the contents of the container can be clearly observed through the film surface. The type of antifogging agent to be present in the surface layer is not particularly limited, and in addition to conventionally known antifogging agents, all substances that can exhibit antifogging properties such as antistatic agents and lubricating agents may be used. If necessary, two or more types can be used in combination. These antifogging agents can be directly mixed into the surface layer constituent materials, or they can be mixed only into the base layer constituent materials and diffused and transferred to the surface layer after lamination, thereby imparting antifogging properties to the surface layer. is also possible. The amount of antifogging agent present in the surface layer varies depending on the type of antifogging agent, so it is not appropriate to specify it uniformly, but it is preferably in the range of 0.3 to 3% by weight.
However, if it is less than 0.3% by weight, the antifogging performance will be insufficient, making it difficult to satisfy the required characteristics of the present invention;
If it exceeds % by weight, not only will the surface layer become white and the transparency will decrease, but also the water that adheres to the inner surface of the bag due to evaporation of fruits and vegetables will cause cloudiness, which will significantly reduce the product value. will also occur. It is also possible to use the surface tension of the surface layer as a simple method to evaluate the antifogging property of the film before bag making, and the inventors have confirmed that the surface tension is 38 dyne/ It has become clear that by adjusting the amount of antifogging agent present so that it is at least cm, it is possible to ensure antifogging durability that meets the objective. Next, the packaging bag used in the present invention is made by stacking the above-mentioned multilayer film so that the layer containing the antifogging agent is on the inside and melt-sealing it on three sides, or by sealing the two sides perpendicular to the folded side. It is made into a bag shape with at least three sides closed by means such as melt-cutting and sealing, and can prevent the seal from peeling off and being opened during filling or distribution of fruits and vegetables. It must have sufficient sealing strength,
The fusing seal strength when fusing and sealing at 270℃
3.0Kg-cm/15mm or more is required, and if the fusing seal strength is insufficient, there is a risk that the seal portion will peel off during filling or handling of fruits and vegetables. The fusing seal temperature was determined based on the general fusing sealing temperature currently in practical use, but as long as it can exhibit fusing sealing strength equal to or higher than the above set value under the above fusing sealing conditions, This does not preclude the adoption of a fusing seal temperature outside the range of . Multilayer films with the above characteristics are
Although they can be manufactured by coextrusion of synthetic resins that meet the respective required characteristics, in-line lamination method, etc., the most preferable base layer constituent materials and surface layer constituent materials are given in consideration of the relationship with the above-mentioned required properties. The explanation is as follows. First, the base layer not only ensures the minimum mechanical strength required for the film, but also has the greatest effect on the permeability of water vapor, oxygen, and carbon dioxide, and should be made of the following materials: A base layer can be obtained which fulfills the above-mentioned purpose. That is, the base layer constituent materials include one or more α-olefin copolymers having 2 to 10 carbon atoms and one or more monomer units consisting of vinyl acetate, acrylic acid, and styrene. A mixture with one or more copolymers accounting for 5 to 80% by weight of
Preferably, the mixture ratio is 30 to 90% by weight for the former and 10 to 70% by weight for the latter. Specific examples of the above-mentioned α-olefin having 2 to 10 carbon atoms include ethylene, propylene, butene, hexene, heptene, etc., but ethylene, propylene, and butene are more common. If a random copolymer or block copolymer of two or more of the above α-olefins is used, a base layer satisfying all of the above permeability values can be obtained more easily.
The copolymerization ratio in this case may be arbitrarily determined depending on the type of α-olefin to be combined. In addition, the copolymers constituting the above include vinyl acetate,
A copolymer containing 5 to 80% by weight of monomer units consisting of acrylic acid and styrene in the total constituents of the copolymer is preferred, and the monomers to be combined with these monomers include any copolymerizable monomer. Particularly preferred are α-olefins such as ethylene and propylene, acrylic esters, methacrylic esters, and butadiene. If the weight of the monomer units consisting of vinyl acetate, acrylic acid, and styrene in the copolymer is less than 5% or more than 80%, it will be difficult to satisfy all of the above-mentioned permeability requirements. If it exceeds %, the haze of the base film tends to deteriorate, and problems such as a decrease in the sealing properties of the weld and the formation of whiskers at the weld are likely to occur. The mixing ratio of the above and above is preferably in the range of 30 to 90% by weight of the former and 10 to 70% by weight of the latter,
By specifying such a blending ratio range, it is possible to ensure well-balanced performance in all of the mechanical properties such as strength, transparency, fusing sealability, and each of the above-mentioned permeability. By the way, if the blending ratio of the copolymer is less than 30% by weight,
The transparency of the base film becomes low. On the other hand, if the copolymer content exceeds 90% by weight, it becomes difficult to keep the gas permeation performance within the range defined by the present invention. for example,
Even if the oxygen permeability and carbon dioxide gas permeability fall within the set ranges, problems arise when the water vapor permeability falls outside the set ranges, and in this case, it becomes difficult to obtain a packaging atmosphere suitable for the physiological effects of fruits and vegetables. In addition, when blending the above, 230℃
The melt index of the formulation in
100/10min, more preferably 2~50g/10min
It is preferable to select the above formulation so that: Next, the surface layer constituent material is required to have properties that can maintain excellent antifogging properties over a long period of time due to the presence of an antifogging agent, and it is also necessary to have excellent melt sealing properties. The surface layer constituent material to meet the requirements can be obtained by using two or more types selected from α-olefin monomers having 2 to 10 carbon atoms (ethylene, propylene, butene, pentene, hexene, octene, decene, etc.). Random copolymers or block copolymers are preferred, and these copolymers may be used alone or in combination. A particularly preferable surface layer constituent material for improving the melt sealing property is a polymer whose main component is an α-olefin homopolymer, copolymer, or a mixture of two or more thereof with a melting point of 80 to 150°C. It is. Methods for making the antifogging agent present in the surface layer constituent film include a method in which the antifogging agent is mixed into the surface layer constituent material itself, and a method in which an appropriate amount of the antifogging agent is included in the base layer film. It is also possible to adopt a method in which the antifogging agent is transferred into the film constituting the surface layer portion by diffusion after lamination. In this case, the amount of antifogging agent mixed into the base layer film is preferably 0.3 to 3% by weight, more preferably 0.4 to 2.2% by weight, and if it is less than 0.3% by weight, the amount of diffusion and transfer toward the surface layer film is insufficient. If the amount exceeds 3% by weight, the antifogging property of the surface layer side may be sufficiently increased, but the surface layer film may cause a whitening phenomenon. Product value deteriorates. However, when the base layer film contains 0.3 to 3% by weight of an antifogging agent and the surface layer film is laminated, the antifogging agent in the base layer film gradually diffuses and migrates toward the surface layer film, resulting in long-term problems. Good anti-fogging properties will be maintained throughout the period. The means for forming the composite film from the base layer constituent material and the surface layer constituent material is not particularly limited, and as mentioned above, it may be carried out by a well-known method such as coextrusion method or in-line lamination method. There are also no particular restrictions on the thickness of the base layer and surface layer, but the most common ones considering economic efficiency and physical properties are: base layer: about 4 to 200 μm, surface layer: about 0.3 to 200 μm.
It is about 8 μm. Also, the thickness ratio between the base layer and the surface layer (total thickness when both outer surfaces are surface layers) is
99.5-60: 0.5-40 is common. The most basic composite form of the film of the present invention is one in which a surface layer and a base layer are laminated, but surface layers are laminated on both sides of this base layer to provide antifogging and heat sealing properties on both sides. or printing on one side of the base layer (the side opposite to the surface layer laminated surface, however, if both surface layers have antifogging properties or heat sealing properties, one of the surface layers) Of course, it is also possible to perform processing, and all of these are included in the technical scope of the present invention. In addition, the films constituting the base layer and the surface layer may contain lubricants, anti-blocking agents, etc. as necessary.
Antioxidants, ultraviolet absorbers, colorants, antistatic agents, etc. can also be added, and if desired, the multilayer film can be uniaxially or biaxially stretched to improve its physical properties. The multilayer film obtained in this way is made into a packaging bag by closing at least three sides with the layer containing the antifogging agent on the inner side, and fruits and vegetables with strong physiological effects are charged into this bag. If the fruit and vegetables are sealed tightly, the gas permeability of the film alone cannot adequately cope with the changes in internal gas composition and the increase in humidity caused by the intense physiological effects of fruits and vegetables, resulting in an oxygen-deficient state. When fruits and vegetables lose their physiological functions or undergo sudden temperature changes, the water vapor inside condenses and accumulates inside the bag, causing water rot. Therefore, in the present invention, openings of an appropriate size are provided in part or all of the film surface of the packaging bag so that changes in the gas composition within the packaging bag can be immediately averaged out by promoting ventilation inside and outside. . These holes eliminate the fluctuations in the gas inside the bag, which cannot be followed by the gas permeability of the multilayer film itself, due to the intense physiological effects of fruits and vegetables, as mentioned above, by promoting ventilation inside and outside. In addition to maintaining the physiological environment, it also prevents moisture from condensing due to sudden temperature changes, and even if a small amount of condensation occurs, the condensed water quickly flows out of the bag to prevent fruit and vegetables from rotting. In order to effectively exhibit these functions, it is necessary to ensure that the total open pore area is 0.02% or more of the surface area of the packaging film surface layer. Total open pore area
If it is less than 0.02%, the effect of promoting internal and external ventilation will be insufficient, and it will not only be difficult to cope with changes in the concentration of gas inside the bag due to intense physiological effects, but also prevent the generation of condensed water due to sudden changes in temperature. I can't. On the other hand, if the total open pore area is too large, especially when the humidity of the outside air is low, water evaporation becomes significant, which not only makes fruits and vegetables more likely to wilt or yellow, but also makes it easier for bacteria etc. to invade from the outside. Mold, etc. will occur. Furthermore, since the film strength becomes poor and the bag is torn during packaging or transportation, the total open pore area should be kept within 3.5% of the total bag area. The openings may be formed on both sides of the bag, or only on one side. By adjusting the size and number of openings to meet the above requirements, we can prevent the generation of condensed water due to the intense physiological effects of fruits and vegetables and sudden changes in outside temperature, without impairing the original function of the packaging bag. Even when viewed, the humidity and gas composition within the bag can be maintained at a suitable level, and the storage stability of fruits and vegetables can be further improved. Next, examples will be given to further clarify the present invention, but the present invention is not limited by the following examples. In the following examples, "%" means "% by weight" unless otherwise specified. The methods for measuring the permeability of water vapor, oxygen, and carbon dioxide defined in the present invention were as follows. Water vapor permeability: Measured in accordance with the moisture permeability test method for moisture-proof packaging materials specified by JIS-Z-0208 Method B. Oxygen permeability and carbon dioxide permeability: Measured according to the gas permeability test method in the "Test method for food-use plastic films" specified in JIS-Z-1707. However, each gas was not converted to standard temperature, but was calculated as the volume at 20°C, and as the amount of permeation per 24 hours. [Example] Example 1 An ethylene/propylene copolymer (ethylene content: 5%) and an ethylene/vinyl acetate copolymer with a vinyl acetate content of 28% were mixed into 65% of the former and 35% of the latter. The base layer constituent material is mixed in a ratio of 1:1 with propylene/butene-1 copolymer (butene-1 content: 18%) and butene/ethylene copolymer (ethylene content: 3.5%). A surface layer constituent material consisting of a mixed composition in a weight ratio (however, 6% higher fatty acid ester monoglyceride was mixed as an antifogging agent in the surface layer constituent material) was used, and a coextrusion method was used. Therefore, a multilayer film was prepared in which surface layers were laminated on both sides of the base layer (extrusion temperature: 260°C, cooling: 20°C), and then biaxial stretching was performed at a longitudinal stretching ratio of 3 times and a transverse stretching ratio of 8 times. A three-layer film having a base layer of 16 μm and a surface layer of 2 μm×2 (both sides) having a total thickness of 20 μm was obtained by applying a corona discharge treatment to both surfaces. The surface tension of one side (A) of this film is 42
dynes/cm, surface tension on the other side (B) is 38 dynes/cm
It was cm. Table 1 shows the properties of the multilayer film.

【table】

[Table] A packaging bag measuring 280 mm long x 180 mm wide was prepared by melt-sealing the two sides of this composite film with the (A) side facing inside. As shown in Figure 1, 10 circular holes with a diameter of 2 mmφ are made on one side of the packaging bag (total opening area is 0.06% of the total surface area of the bag), and freshly harvested eggplants are inserted into these holes and the upper opening is opened. were fixed with tape (T) and examined for changes in freshness during storage. The respiration rate of eggplant is 20CO ₂ mg/Kg・hr at 15℃ and 110CO ₂ mg/Kg・hr at 25℃.
Kg/hr. The results are shown in Table 3 below. Example 2 Propylene-butene-1 copolymer (butene-1
content: 20%) and ethylene-styrene copolymer (styrene content: 40%), 90% of the former and 90% of the latter.
Base layer constituent material made by blending at a ratio of 10% (0.8% higher fatty acid ester monoglyceride as an antifogging agent)
% blend), propylene-butene-1 copolymer (butene-1 content: 18%) and propylene-butene-1 copolymer (butene-1 content: 30%), the former at 70% and the latter at 30%. A composite film with a three-layer structure was produced in the same manner as in Example 1 using the surface layer constituent materials blended at a ratio of
Cooling: 25℃). After that, the longitudinal stretching magnification was 2.5.
Biaxial stretching was performed at a transverse stretching ratio of 7.8 times and
A three-layer film with a total thickness of 23 μm was obtained, in which surface layers of 1.5 μm each were laminated on both sides of 20 μm. The surface tension of this film on one side (A) is 41 dynes/cm, and on the other side (B)
The surface tension of the side was 38 dynes/cm, and both sides showed good antifogging properties of the antifogging agent that had diffused from the base layer. The properties of the film are shown in Table 2.

【table】

[Table] This film was cut and sealed on two sides with the (A) side facing inside to produce a bag with a length of 320 mm and a width of 150 mm. This packaging bag has 3mmφ on one side of the top as shown in Figure 2.
Two holes of 4mmφ were opened on one side of the bottom (opening area ratio: 0.10%), and after charging freshly harvested cucumbers into these holes, the upper opening was fixed with tape (T). Changes in freshness during storage were investigated. Furthermore, the respiration rate of Yuuri is 25CO ₂ at 15℃.
mg/Kg・hr, 130CO ₂ mg/Kg・hr at 25°C. The results are shown in Table 4 below. Example 3 Edamame was sealed in the packaging bag obtained in Example 1, and changes in freshness during storage were examined in the same manner. The respiration rate of Edamame is 170 CO ₂ mg/Kg・hr at 15℃, 25
340 CO ₂ mg/Kg·hr at ℃. The results are shown in Table 5. For comparison, Tables 3, 4, and 5 show the case of no packaging, the case of sealed packaging with OPP film (biaxially stretched polypropylene film), PE film (polyethylene film), and the cases of notches in Examples 1 to 3 above. The results of each experiment using bags (comparative materials) obtained in exactly the same way except that the holes were omitted, as well as when using bags with a total open area ratio outside the specified range, are also listed. The evaluation criteria for the freshness retention test shown in Tables 3, 4, and 5 were as shown in Table 6.

【table】

【table】

【table】

【table】

【table】

【table】

[Table] Example 4 As shown in Table 7, propylene butene 1 (18%) was applied to both sides of the base layer constituent material made of various polymeric materials.
After laminating the surface layer constituent material made of a copolymer (each containing 1% higher aliphatic monoglyceride as an antifogging agent) by coextrusion, it was stretched biaxially to a size of 2.5 times in length and 7.5 times in width, and then stretched on both sides. A multilayer film was obtained by corona discharge treatment so that the surface tension of each film was 39 dynes/cm. Table 8 shows the water vapor permeability, oxygen permeability, carbon dioxide permeability, antifogging property, and fusing seal strength of each of the obtained multilayer films.

【table】

[Table] Using each of the multilayer films A to H obtained above,
A bag of mm x 180 mm was made, and 8 circular holes with a diameter of 2 mmφ were made on one side of the bag as shown in Figure 1 (the total opening area was 0.14% of the total surface area of the bag), and 70 g of peas were filled into the bags. Then, changes in freshness during storage were examined in the same manner as above. The storage conditions were 35°C x 70%RH. The results are summarized in Table 9, and the multilayer films (B, D,
Films using film A and film A had a good freshness retention effect overall.
Because water vapor permeability is too low, moisture dissipation does not occur, resulting in significant deterioration in terms of zulke and odor. On the other hand, since the water vapor permeability of Film C is too high, the interior becomes dehydrated, causing discoloration and softening. In addition, both films E and G have oxygen permeability and carbon dioxide permeability that are outside the specified range,
The discoloration caused by lack of breathing is particularly noticeable.

[Table] Comparative Example 4 Edamame was stored in the same manner as in Example 3 using a packaging bag obtained in exactly the same manner as in Example 1 except that no antifogging agent was added to the surface layer constituent material. I conducted a test. The results are shown in Table 11, and it was confirmed that water droplets were observed on the inner surface of the bag during short-term storage, and the freshness of the edamame rapidly decreased from the 4th day after the bag was sealed. Comparative Examples 5 and 6 A base layer having the same composition as that used in Example 1 (but containing 1% higher fatty acid ester monoglyceride as an antifogging agent) was used alone, and a 20 μm single layer was formed in the same manner as in Example 1. I got the film. The physical properties of the single layer film are shown in Table 10 below. Bags were prepared using this single-layer film, and the same edamame storage test as in Example 3 was conducted on bags with holes (Comparative Example 5) and bags without holes (Comparative Example 6). The results are shown in Table 11 below, and in all cases, water droplets were observed on the inside of the bag during short-term storage, and the freshness of the edamame decreased rapidly from the 4th day after packaging. confirmed. Comparative Example 7 Coextrusion was carried out using polypropylene (containing 1% higher fatty acid ester monoglyceride as an antifogging agent) as the base layer and ethylene-propylene copolymer (ethylene content 5% by weight) as the surface layer. After axial stretching, the surface layer was subjected to corona treatment (thickness, base layer/surface layer = 23/2 μm). Table 10 shows the physical properties of this multilayer film. A bag is made using the multilayer film obtained above,
A freshness retention test of green soybeans was conducted in the same manner as in Example 3. The results are shown in Table 11 below, and it was confirmed that water droplets were observed on the inner surface of the bag after short-term storage, and the freshness of the edamame rapidly decreased from the fourth day after being sealed.

【table】

【table】

【table】

[Table] [Effects of the Invention] The present invention is constructed as described above, and the multilayer film used not only has the permeability of water vapor, oxygen, and carbon dioxide appropriately adjusted, but also has a Since the appropriate size opening is formed,
Fruits and vegetables can maintain their strong physiological effects even after packaging, and their freshness can be significantly extended. In addition, this multilayer film has excellent anti-fog properties and long-lasting anti-fog properties, so it may become difficult to see the contents during the distribution process, lowering the product value, or moisture condensing in the cloudy areas may cause There is no risk of accelerated rotting of fruits and vegetables, and even if there is a sudden change in temperature, moisture condensation is unlikely to occur, and even if condensation does occur, this condensation water can quickly flow through the openings into the bag. Since it leaks outside, there is no risk of water rot, etc., and it is possible to prevent deterioration of the appearance and product image of fruits and vegetables, and to supply them to consumers in a fresh state.

[Brief explanation of drawings]

Figures 1 and 2 are diagrams showing packaging bags used in Examples.

Claims (1)

[Claims] 1. Water vapor permeability is 15 ^to 200 g/ ^m 2.24 hr. at 40°C. Oxygen permeability is 3000 to 35000 c.c./m 2.24 hr.
ATM・20℃・90%RH、Carbon dioxide permeability 12000~130000c.c./ ^m2・
24 hours, ATM, 20℃, 90%RH, and an antifogging agent is present in the surface layer of at least one side, and the surface layer exhibits antifogging properties during repeated temperature changes between 040℃ and A multilayer film is used that exhibits a sealing strength of 3.0 Kg-cm/15 mm or more when melt-sealed at 270°C, and is formed into a bag shape with at least three sides closed so that the surface layer is on the inside, and 0.02 to 0.02 to the total surface area of the film surface of the bag on a part or the entire surface of the film surface of the bag.
A method for preserving the freshness of fruits and vegetables, which comprises storing fruits and vegetables with strong physiological effects in a packaging bag provided with one or more openings having a total opening area of 3.5%. 2 The base layer constituent material of the multilayer film has a carbon number of 2 to 10
One or more α-olefin copolymers: 30 to 90
% by weight and one or more copolymers in which one or more monomer units consisting of vinyl acetate, acrylic acid and styrene account for 5 to 80% by weight of the total constituents: 10
70% by weight of the freshness preserving method according to claim 1. 3 The surface layer constituent material of the multilayer film has a carbon number of 2 to
10. The method for preserving freshness according to claim 1 or 2, which is an α-olefin copolymer of No. 10.