JP2011225234A - Method for packaging food, and film for packaging food - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for packaging a food which quickly discharges moisture at the initial high moisture activation time so as not to deteriorate texture of the inner food, and has water vapor permeation to the extent that the moisture activity is maintained until at least the expiration date after the moisture activity for the proper texture is achieved.SOLUTION: The film used for packaging the food has moisture permeation showing moisture dependence represented by (1) A=1.1±0.1 and (2) B≥0.14 at a temperature of 23°C under relative humidity RH of 60% of the storage surrounding atmosphere, and shows (3) moisture permeation of 500 to 1,000/(mday) at 40°C under RH of 90% of the surrounding atmosphere for the 30 μm thick film wherein the coefficient k is defined by weight of moisture permeating the film/(moisture permeation of film×surface area of film×use days×difference of relative humidity between the inside of the packaging bag and the surrounding atmosphere/90), and the value of k is represented by k=A×e, x being the relative humidity of the inside of the packaging bag. The film is obtained by kneading a polyurethane resin and SBS and forming them into a film or laminating them by heat-bonding.

Description

  The present invention relates to a food packaging method and a food packaging film.

  Conventionally, foods such as bread have been sold in paper bags or olefin plastic film bags. Here, with respect to paper bags, the danger of contamination by microorganisms, dust, and foreign matters has always been a problem. On the other hand, with respect to olefin-based bags, there is a problem that the flavor or texture of bread inside is significantly impaired. In particular, in the case of foods characterized by a hard texture such as French bread, the water activity representing the ratio of free water excluding bound water in the water immediately after baking is 0.95 (sealed atmosphere) The water activity that gives an appropriate texture is 0.90 to 0.85, and it must be packaged after leaving and drying until such water activity is achieved. If the total moisture content in the packaging system is large, the hard texture is impaired. If the bread is packaged with an olefin plastic bag before it dries enough to reduce the water activity, the bread will soften rapidly due to the high moisture resistance of the packaging bag (because of its low moisture permeability) The texture is impaired. On the other hand, when packaging with a paper bag often used for packaging French bread, the moisture permeability of the paper is too high, and the moisture in the bag is excessively reduced to 0.85 or less, which is an appropriate water activity. Since it falls, the bread | bread in inside will become hard in 2 to 3 days before a expiration date, and a texture will also be impaired in this case.

  Therefore, up to a water activity of 0.90, which is the upper limit of the appropriate texture, a water vapor permeability is high and water is quickly evaporated outside the system, and thereafter, a packaging film in which water is not evaporated as much as possible is an ideal packaging material. At least after the water activity reaches 0.90, a film having a water vapor transmission rate low enough to keep the water activity at 0.85 or more until 3 days after the expiration date is suitable as a packaging material for bread. Will be.

In the case of packaging with an olefin-based plastic film bag, in order to solve the above-described problem that the moisture permeability is too low, a bag having many holes with a diameter of about 0.5 mm to 3 mm has been used. However, by making many such holes, the risk of intrusion of dust from the outside of the bag and contamination by microorganisms has increased. Recently, crimes that mix needles and the like in packaging bags are increasing, and packaging that prevents mischief (Tamper Resist Packaging) has been demanded. However, since the holes are opened, it is difficult to distinguish between contamination during manufacture and mischief in the store, resulting in a problem that crime and mischief cannot be prevented. This is also described in Patent Document 1, for example.
JP 2002-370320 A

Currently, there are many foods sold in a sealed state in a packaging bag, but the flavor and texture of the original food may be significantly impaired as described above. For this reason, packaging bags made of materials that do not impair the flavor and texture of foods have been devised. For example, a polyurethane resin widely used in the medical and industrial fields generally has a high moisture permeability for foods, and is 1300-1500 g / (m ² · day) at a thickness of 30 μm. Since it reached 6000 g / (m ² · day) at 30 μm, it was not used even in the field of food. In addition, the polyurethane resin is soft and difficult to process because it is sticky, and is usually processed with a release paper (separator) and then peeled off from the release paper after processing.

  Further, as materials other than polyurethane resin, non-woven fabric with high moisture permeability, rayon paper, cellophane, perforated film, polylactic acid film, and styrene film having a thickness of 30 μm or less can be considered. Since it has a sealing property, it can be processed into a bag shape, whereas a non-woven fabric or the like has a problem that it does not have a heat seal property, and it cannot be processed into a bag shape by itself.

  Furthermore, if the water activity of the food immediately after packaging is high, the water content of the food is quickly evaporated due to high moisture permeability, and after the food is reduced to an appropriate water activity, the food is not overlooked so as not to impair the food texture. It is desirable to have a packaging bag of material that can maintain the proper water activity of the food for a predetermined period of time. That is, a packaging bag made of a material having a humidity dependency of a condition of moisture permeability is suitable for packaging foods that obtain an appropriate texture in such a range of water activity.

  Cellophane, which is a hydrophilic film, can be cited as a film having such a characteristic that moisture permeability depends on humidity. Cellophane has a large decrease in strength when wet, and cannot obtain sufficient strength. Moreover, moisture-proof cellophane with heat sealability has low moisture permeability.

  In view of the problems as described above, the present invention has a high water vapor permeability up to the water activity which is the upper limit of an appropriate texture, and quickly evaporates the water out of the system. It is an object to provide a food packaging method and a food packaging film that can maintain water activity above the water activity that is the lower limit of the feeling.

In order to solve the above-mentioned problems, the food packaging method according to the present invention is characterized in that the coefficient k is expressed as follows: Permeable moisture weight of film / (moisture permeability of film × film surface area × number of days of use × relative humidity difference between packaging bag and ambient atmosphere / 90) and the value of k is expressed as k = A · e ^Bx , where x is the relative humidity in the packaging bag, and the storage ambient atmosphere (outside the packaging bag) is at a temperature of 23 ° C. and a relative humidity of 60 When% RH, (1) A = 1.1 ± 0.1, (2) B ≧ 0.14 has a moisture permeability having a humidity dependency, and (3) 40 ° C./90% RH A film having a characteristic of moisture permeability of 500 to 1000 / (m ² · day) at an ambient atmosphere of 30 μm in thickness is used.

Further, in order to solve the above-mentioned problems, the film for food packaging or the film for bread packaging according to the present invention has a coefficient k, the weight permeated moisture of the film / (the moisture permeability of the film × the surface area of the film × the number of days used × the inside of the packaging bag) And relative ambient humidity difference / 90), and the value of k is k = A · e ^Bx , where x is the relative humidity inside the packaging bag, and the storage ambient atmosphere (outside the packaging bag) Has a moisture permeability that has a humidity dependency of (1) A = 1.1 ± 0.1, (2) B ≧ 0.14, 3) It has a characteristic of moisture permeability of 500 to 1000 / (m ² · day) at an ambient atmosphere of 40 ° C. and 90% RH and a thickness of 30 μm.

  The food packaging film of one embodiment can be formed by kneading polyurethane resin and SBS at a predetermined mixing ratio and forming a film, or by heat bonding.

  In addition, in order to solve the above-mentioned problems, a laminated film for food packaging according to the present invention is formed by laminating a food packaging film comprising a polyurethane resin and SBS on at least one side of a permeable substrate. Is done.

  Furthermore, in the laminated film for food packaging having the above-described configuration, it is preferable that the permeable substrate is any one of a nonwoven fabric, rayon paper, cellophane, a perforated film, a polylactic acid film, and a styrene film having a thickness of 30 μm or less.

  Moreover, in order to solve the said subject, the food packaging bag which concerns on this invention forms the laminated | multilayer film for food packaging in a cylinder shape or a bag shape.

  Further, in the food packaging film having the above-described structure, it is preferable to apply the film to bread, vegetables, fruits, meats, seafood, salads, and prepared dishes.

  Moreover, in the food packaging method having the above-described structure, it is preferable to apply the film to bread, vegetables, fruits, meats, seafood, salads, and prepared dishes.

  According to the food packaging method and the food packaging film of the present invention, a film having a characteristic that the moisture permeability changes appropriately according to the change in the relative humidity of the food in the package within a predetermined range is used. That is, if the relative humidity of the food immediately after packaging is high, the moisture of the food is quickly evaporated due to the high moisture permeability of the film, and the food texture is not impaired after the food has fallen to an appropriate relative humidity. The film may have a characteristic that can maintain an appropriate relative humidity of the food for a predetermined period of time displayed at the store.

In the present invention, by combining a polyurethane resin and SBS, it becomes possible to use a polyurethane resin that has not been suitable as a material for food packaging films. That is, it is possible to make up for the point that the moisture permeability is too high and the point that it is too soft and difficult to form a film on the release paper by combining with SBS. Such a combined film has a moisture permeability of 500 to 1000 g / (m ² · day), and when the relative humidity of the food immediately after packaging is high, the film has a high moisture permeability. After the food has evaporated and the food has fallen to the proper relative humidity, you can maintain the proper relative humidity of the food for a certain period of time that is displayed in the store so as not to damage the food texture, It is especially suitable for food packaging such as bread.

  Cellophane, polylactic acid film, and styrene film other than polyurethane resin do not have heat-sealability and are not suitable for food packaging, whereas polyurethane resin has high heat-sealability and is better when wet than cellophane. It is possible to obtain a food packaging film that does not have a significant decrease in strength, and that has appropriate moisture permeability characteristics and is easy to process in combination with SBS. And since it has moderate moisture permeability, even if it seals, it can prevent impairing the food texture of the foodstuffs of the packaging bag. In addition, since it is not necessary to make a hole, it is possible to prevent contamination by microorganisms, dust, foreign matter, and mischief, and to provide a safer product for consumers. In addition, since there are no holes, even if the food surface is coated with fluid seasonings such as butter, cream, jam, sauce, mustard, ketchup, mayonnaise, etc. There is no chance of getting dirty, and the purchaser's hands are not stained or clothes are not stained.

  Moreover, the film for food packaging of this invention can be applied not only to bread but also to vegetables, fruits, meats, and seafood as food. When applied to vegetables and fruits, it is possible to significantly delay the deterioration of food by reducing condensation inside the packaging bag due to the evaporation of water vapor. When applied to meats, seafood, salads, and prepared dishes, it is possible to prevent contamination from the outside by not having a hole, and to prevent the growth of microorganisms by preventing the inside from condensing.

FIG. 1 shows a method for testing changes in food over time, taking bread as an example for testing the effect of the packaging bag according to the present invention, and FIG. 1 (a) shows a method for applying a load to the bottom of the bread. FIG. 1 (b) shows a method of applying a load to the inside of the pan.

  Hereinafter, preferred embodiments of a film for food packaging, a laminated film for food packaging, and a food packaging bag using the same according to the present invention will be described.

The laminated film for food packaging according to the present invention is formed by laminating a synthetic resin film composed of polyurethane resin and SBS on at least one side of a permeable base material by thermal bonding without using an adhesive. . This synthetic resin film is a film used as a material for food packaging bags, and is made of polyurethane resin and SBS (styrene / butadiene / styrene), and has a moisture permeability of 500 to 1000 g · 30 μm / (m ² · day, 40 ° C. · 90. % RH). The synthetic resin film is produced by kneading polyurethane resin and SBS at a predetermined mixing ratio to form a film, or by thermally laminating both thin films without providing an adhesive layer between them. . The mixing ratio of the polyurethane resin and SBS is preferably 8: 2 by weight, but is not limited to such a ratio, and SBS is mixed at a weight percentage ranging from 5% to 40%. The In addition, as long as the characteristics of the present invention are not impaired, the synthetic resin film has a known heat stabilizer, antioxidant, crystal nucleating agent, slip agent, antistatic agent, light stabilizer, light shielding agent, A freshness retaining agent or the like may be added.

  The permeable substrate is preferably a nonwoven fabric, rayon paper, cellophane, a perforated film, a polylactic acid film, a styrene film having a thickness of 30 μm or less, and the like. This permeable substrate complements the tensile strength, tear strength, puncture strength, etc. of the synthetic resin film, absorbs and occludes water vapor and moisture in the bag, controls moisture in the bag, and as a cushioning material for the contents In addition, when making a bag, it can be used as a heat-sealing layer, and it can be expected to give fashion.

  A non-woven fabric that can be used as a permeable substrate is made by forming synthetic fibers, natural fibers, or the like into mats or thin cotton by an appropriate method, and bonding the fibers together with the adhesive or the heat of the fibers themselves. Here, acrylic fibers, acetate fibers, triacetate fibers, nylon fibers, rayon fibers, vinylon fibers, polyester fibers, polyethylene fibers, polypropylene fibers and the like are suitable as synthetic fibers. On the other hand, as natural fibers, long fibers and short fibers such as cotton fibers and hemp fibers are suitable.

  As described above, the laminated film for food packaging according to the present invention is formed by forming a synthetic resin film made of polyurethane resin and SBS on at least one side of a permeable substrate. The manufacturing method includes a manufacturing method in which a synthetic resin is extrusion coated onto a permeable substrate at a temperature of 190 to 220 ° C. by a T die of a film extruder. Moreover, you may manufacture by heat-bonding the film and permeable base material which were obtained by extruding a synthetic resin with the T die of a film extruder at the temperature of 190-220 degreeC, and cooling.

  The food packaging bag using the laminated film for food packaging according to the present invention is produced as follows. That is, it is manufactured in a bag shape by cutting a laminated film for food packaging into a shape such as a triangle, a quadrangle, a rectangle, etc., and heat-bonding the periphery with the food input port left in a state where two sheets are stacked. As another manufacturing method, the laminated film for food packaging is formed into a tube shape, and the palm portion is thermally bonded, and then the tube is flattened and a flat tube in the transverse direction perpendicular to the longitudinal direction is heat bonded. And the food which one end is opening by cutting the middle position of the part which carried out heat bonding, the next part which carried out heat bonding, and the middle position of heat bonding part itself in the direction perpendicular to the longitudinal direction of a bag A packaging bag is completed. The filling of the food bag into the bag may be carried out through the opening of the bag made as described above, and the opening may be heat-bonded, or the food is first laminated in the bag manufacturing process. You may heat-bond the peripheral part of a bag, after putting between films, and cut | disconnecting the laminated | multilayer film for food packaging after that, or not cut | disconnecting.

  In addition, the food packaging bag according to the present invention is not limited to the case where the food packaging bag is composed of a permeable base material and a synthetic resin film made of polyurethane resin and SBS, but only the synthetic resin film produced as described above is used for food packaging. You may comprise a bag.

  Hereinafter, various test results using a bread packaging bag as an example will be described in detail.

  Here, the temporal change of bread when French bread was put in a food packaging bag was measured. Six types of food packaging bags were used including the food packaging bags produced using the laminated film for food packaging according to the present invention.

The test implementation method is as follows.
Food: 145g of French bread
Size of packaging bag: 160 mm × 350 mm (1120 cm ² )
Test conditions (ambient atmosphere): Temperature 23 ° C Humidity 60% RH
Packaging bag material:
1. 1. Laminated film comprising 50 g of nonwoven fabric 17 g / (polyurethane resin 80% SBS 20%) having a moisture permeability of 700 g / (m ² · day, 40 ° C. · 90% RH). ^2. Laminated film composed of 30 g of nonwoven fabric 17 g / (polyurethane resin 80% SBS 20%) having a moisture permeability of 1000 g / (m ² · day, 40 ° C., 90% RH). ^3. Laminated film composed of 50 g of nonwoven fabric 17 g / (polyurethane resin) having a moisture permeability of 1500 g / (m ² · day, 40 ° C. · 90% RH). 4. Laminated film composed of 30 g of nonwoven fabric 17 g / (polyurethane resin) having a moisture permeability of 2000 g / (m ² · day, 40 ° C. · 90% RH) 5. OPP (stretched polypropylene) film having a thickness of 35 μm and a moisture permeability of 4.3 g / (m ² · day, 40 ° C. · 90% RH) Copy paper weighing 50g (control)

  The test methods were as follows: 1 day after putting in the packaging bag immediately after cooking, 3 days later, 7 days later, the bread was taken out of the bag and the bottom of the bread was 3 mm in diameter as shown in FIG. When the probe is pushed by a cylindrical stainless steel probe, the load when the probe breaks through the pan; as shown in FIG. 2, the cross-section of the pan is cut with a 10 mm diameter cylindrical aluminum probe. Two types of measurement were performed: load at the time when 10 mm was pushed toward the inside. The probe pushing speed is 1 mm / s in all tests.

  The experimental results are shown below. Table 1 shows the results of experiments conducted on the bottom surface of the bread. On the other hand, Table 2 shows a suitable load range and an upper limit and a lower limit of the load range for the bottom surface of the bread with respect to the texture of the bread. If it is in the range, it indicates that it is an edible range. Table 3 is a graph showing the relationship between elapsed days and load. As shown in Tables 1 and 3, in the case of paper, the preferred load range was 800 g weight to 1671 g weight range from cooking until after the lapse of one day. After 3 days, the load greatly exceeded the suitable load range, and the result was not suitable for food.

In the case of the OPP film, the weight was less than 800 g in any case, and the result was already too soft when one day had passed. On the other hand, when a packaging bag having a moisture permeability of 700 g (hereinafter, the unit of g / (m ² · day, 40 ° C. · 90% RH) is omitted as appropriate) of the present invention is used, it is suitable when 7 days have passed. Although it exceeded the load range, it was found to be less than 1672 g weight until 3 days later, and good until 3 days later. When the packaging bag having a moisture permeability of 1000 g according to the present invention was used, the load range exceeded a suitable load range after 3 days, but the weight was 2164 g in the edible range. When a packaging bag with a moisture permeability of 1500 g and a packaging bag of 2000 g were used, it was found that both exceeded the suitable load range significantly after 3 days, and became too hard after 3 days.

  Next, the results of experiments conducted on the inside of the bread will be shown. Table 4 shows the results of experiments conducted on the inside of the bread. Table 5 shows the preferred load range and the upper and lower limits of the load range for the inside of the pan, which is good when in the preferred load range and acceptable when in the upper or lower range. Indicates that it is in the range of meals. Table 6 is a graph showing the relationship between elapsed days and load. As shown in Tables 4 and 6, in the case of paper, the preferred load range was 79 g to 256 g. After 3 days, the load greatly exceeded the preferred load range, and the result was too hard.

  In the case of the OPP film, the load range was suitable even after 7 days. On the other hand, when the packaging bag of 700 g of moisture permeability according to the present invention is used, it exceeds the suitable load range when 3 days have passed, but it is within the upper limit of the load and is within the edible range until after 3 days. I understood. The same applies to the case of using the packaging bag having a moisture permeability of 1000 g and the packaging bag having a moisture permeability of 1500 g according to the present invention, and it was found that the edible range was maintained after 3 days. On the other hand, when a packaging bag having a moisture permeability of 2000 g was used, it was found that the suitable load range was greatly exceeded after 3 days, and it became too hard after 3 days.

The above results are summarized in Table 7 below. Here, the numerical values in Table 7 are 50 points when the load is within the above suitable load range, 25 points when the load is at the upper limit or lower limit of the load, It is the numerical value that added together. Here, the case of 100 points is close to freshly made, the case of 75 points is good, the case of 50 points is a limit of what can be provided as a product, and the case of 25 points cannot be provided as a product. Usually, the shelf life of bread is 2 to 3 days, so when comparing the test results in the column after the passage of 3 days in Table 7, the total score is 75 points when the packaging bag of 700 g of moisture permeability of the present invention is used. The moisture permeability was most suitable for bread packaging. That is, it was found that the quality of the food inside during the best-before date was the best when the packaging bag having a moisture permeability of 700 g of the present invention was used. Next, the total score is higher when the packaging bag with a moisture permeability of 1000 g according to the present invention is used (50 points). From these facts, the moisture permeability suitable for packaging bread is one day after the moisture permeability of 700 g. since There is at least 50 points of edible limit at 75 points, the present invention 500g / ^{(m 2} · day, 40 ℃ · 90% RH) ~1000g / (m 2 · day, 40 ℃ · 90% RH) It can be said. Moreover, when the film which has moisture permeability other than the above was used, the favorable quality was not obtained within the expiration date. In addition, it is estimated that suitable moisture permeability changes with the surface area of the film to be used, and the quantity of bread | pan put in.

  Next, the French bread put together with various weights of silica gel in a packaging bag using a film in which polyurethane resin and SBS are mixed is dried for a predetermined time, and then the bottom surface of the bread is pushed with a probe as described above. (Fig. 1 (a)), a test was performed to measure the load when the probe broke through the pan. The test results are shown in Table 8 below. In addition, the weight of the silica gel put into the packaging bag is 0 g (sample 0), 9.35 g (sample 1), 21.43 g (sample 2), and 37.44 g (sample 3).

  As shown in Table 8, the bread ERH (equilibrium relative humidity, 100 times the water activity) is highest in the sample without the silica gel (sample 0), and the ERH value increases as the weight of the silica gel increases. It decreased and became the lowest value in the sample 3. The water content of the bread was also highest for sample 0, and decreased as the weight of silica gel increased, and sample 3 was the lowest. On the other hand, the load strength of the bread was lowest for sample 0, about 240 g weight, and increased as the weight of silica gel increased, and for sample 3, it exceeded 3000 g weight.

  Table 9 below shows the results of graphing the ERH, moisture, and load strength of bread based on the data in Table 8. In Table 9, the horizontal axis represents ERH (%), the left vertical axis represents bread moisture (%), and the right vertical axis represents bread load strength (g weight). Each curve in the graph is an approximate curve obtained based on the values of four points. Here, as shown in Table 2, when an appropriate load strength is about 690 to 2160 g, the water activity (1/100 of ERH) in that case is 0.82 to 0 from the curve regarding the load strength in Table 9. It is estimated to be about .91. Further, the moisture content of the bread at that time is estimated to be about 18.5% to 25.8% from the moisture-related curve in Table 9. In this way, it is possible to estimate the preferred water activity and moisture of the bread.

  In addition, it is thought that the water | moisture content of a fresh bread is about 31.0% when the silica gel of Table 8 is not put. Also, assuming that the load strength after 1 day from baking is about 630 g weight from the value after 1 day of OPP in Table 1, even after 1 day from baking, the moisture content is 26.0% from Table 9. It is estimated that this is the case.

  After baking, the bread removes moisture while taking rough heat, cools it to an arbitrary temperature, and conveys it to a subsequent process (slicing, packaging). Insufficient cooling or removal of moisture causes mold generation due to condensation of moisture on the surface of the product after packaging, caving due to softening of the product, or poor slicing. On the other hand, in the case of overcooling, water loss during cooling increases, which greatly affects the texture such as surface hardening. Since bread is generally sold for about 3 days after it is displayed in stores, the film used as the material for bread packaging bags is from 31.0% freshly baked to 25.8% after cooling. It is preferable to have a characteristic of maintaining 18.5% for at least 3 days thereafter. Further, from Table 9, in the case of freshly baked water having a moisture content of 31.0%, the relative humidity is 90% RH or higher, so that a film having a large moisture weight to be transmitted at a relative humidity of 90% RH or higher is preferable.

In consideration of such conditions, a film suitable for bread packaging specifically has a coefficient k, the weight of permeated moisture of the film / (the moisture permeability of the film × the surface area of the film × the number of days used × the inside and the surroundings of the packaging bag) Relative humidity difference with the atmosphere / 90), and the value of k is
k = A · e ^Bx where x is the relative humidity in the packaging bag, when the ambient atmosphere (outside the packaging bag) is 23 ° C. and the relative humidity is 60% RH, (1) A = 1. 1 ± 0.1, (2) having a moisture permeability having a humidity dependency of B ≧ 0.14, and (3) an ambient atmosphere of 40 ° C. and 90%, a moisture permeability at a thickness of 30 μm of 500 to It is a film having a characteristic of 1000 / (m ² · day). Thus, a film suitable for bread wrapping has a coefficient k (or moisture permeability) defined as described above having humidity dependency (the moisture permeability is high under high humidity).

Here, Table 10 shows the measured values when the coefficient k for the relative humidity x% RH in the packaging of the film is actually measured from the permeated moisture weight of the film in which the polyurethane resin and SBS are mixed. The horizontal axis of the graph of Table 10 is the relative humidity x (% RH) in the package, and the vertical axis indicates the value of the coefficient k defined as described above. The curve in the graph shows the storage ambient atmosphere (packaging bag) for the ambient atmosphere of 40 ° C. and 90% RH and the moisture permeability at a thickness of 30 μm is 700 g / (m ² · day) and 1000 g / (m ² · day). It is an approximated curve obtained by performing regression analysis from a total of six measurement values measured when the outside) is 23 degrees Celsius and the relative humidity is 60 RH.

This approximate curve is expressed by the equation k = A · e ^Bx . Here, A and B are constants, A = 1.1 ± 0.1, B ≧ 0.14, and e is the Euler number. This curve shows a high k value at a relative humidity of 90% RH or more, but the k value sharply decreases as the relative humidity decreases, and well represents the humidity dependence of the k value. In addition, the relative humidity is 92% RH, the k value is approximately 0.0045, the relative humidity is 87% RH, the k value is approximately 0.0030, the relative humidity is 82% RH, and the k value is approximately 0.0010. It is well suited to the above-mentioned conditions regarding the coefficient k. As a film for wrapping bread, it is preferable to use a film of a material having a k value as a characteristic as represented by the curve in the graph of Table 10, but k = A · e ^Bx as described above. When A = 1.1 ± 0.1 and B ≧ 0.14 when regression analysis is performed according to the equation, it is considered suitable for bread packaging.

  Examples of the film having high moisture permeability include films of styrene and soft vinyl chloride, but such a hydrophobic film does not have humidity dependency of moisture permeability. Among the hydrophilic films that have humidity dependency on moisture permeability, crystalline polymer nylon and EVOH (ethylene-vinyl alcohol copolymer resin) films do not have high moisture permeability under high humidity, and the moisture dependency of moisture permeability Does not have. Of the hydrophilic films, cellophane is highly dependent on moisture permeability, but the strength when wet is greatly reduced, and sufficient strength cannot be obtained. Further, the moisture-proof cellophane having heat sealability has low moisture permeability under high humidity.

  Therefore, from the results shown in Table 1, Table 9 and Table 10 above, a film suitable for bread packaging having high moisture permeability and temperature dependency on moisture permeability is hydrophobic to hydrophilic urethane resin. It is the film for food packaging which concerns on this invention which mixed the resin (SBS, EVA (ethylene vinyl acetate copolymer resin etc.)).

  In the above embodiment, (French) bread has been described as an example of food, but the food targeted by the present invention is not limited to bread, and other foods are possible. For example, even if the present invention is used for packaging vegetables and fruits, it is possible to prevent condensation inside the packaging bag due to evaporation of water vapor, and to quickly release water vapor generated from the packaged vegetables and fruits to the outside of the packaging bag. Thus, it is possible to greatly delay the deterioration of the food, and further prevent contamination by microorganisms. The same applies to the packaging of meat, seafood, salads, and side dishes. The absence of holes prevents contamination from the outside, and prevents condensation from occurring inside, thereby preventing the growth of microorganisms.

As mentioned above, although the suitable Example regarding the food packaging method of this invention and the film for food packaging was described, when the relative humidity of the food immediately after packaging is high, according to this invention, it is promptly by the high moisture permeability of a film. After the food has evaporated and the food has fallen to the proper relative humidity, it can maintain the proper relative humidity of the food for a certain period of time that is displayed at the store so as not to damage the food texture. It is possible to provide a film whose moisture permeability has an appropriate humidity dependency with respect to relative humidity. Further, by combining the polyurethane resin and SBS, it is possible to use a polyurethane resin that was not conventionally suitable as a material for food packaging films. That is, it is possible to compensate for the point that the moisture permeability is too high and the point that it is too soft and difficult to form a film on the release paper by combining with SBS. Such a film combining the two has a moisture permeability of 500 to 1000 g / (m ² · day) at 40 ° C. and 90% RH, and is particularly suitable for packaging food such as bread.

  Cellophane, polylactic acid film, and styrene film other than polyurethane resin do not have heat-sealability and are not suitable for food packaging, whereas polyurethane resin has high heat-sealability and is better when wet than cellophane. The decrease in strength is not large, and further, in combination with SBS, it becomes possible to obtain a food packaging film having an appropriate moisture permeability and easy to process. And since it has moderate water vapor transmission rate, it is hard to condense a water | moisture content inside a packaging bag, and it can prevent impairing the food texture of the foodstuffs of a packaging bag. In addition, since it is not necessary to make a hole, it is possible to prevent contamination by microorganisms, dust, foreign matter, and mischief, and to provide a safer product for consumers. In addition, since there are no holes, even if the food surface is coated with fluid seasonings such as butter, cream, jam, sauce, mustard, ketchup, mayonnaise, etc. There is no chance of getting dirty, and the purchaser's hands are not stained or clothes are not stained.

  The film for food packaging, the laminated film for food packaging, and the food packaging bag using the same according to the present invention can be applied to food packaging such as bread.

Claims (9)

A food packaging method comprising:
The coefficient k is defined as the permeated moisture weight of the film / (the moisture permeability of the film × the surface area of the film × the number of days used × the relative humidity difference between the inside of the packaging bag and the ambient atmosphere / 90), and the value of k is defined as
k = A · e ^Bx where x is the relative humidity inside the packaging bag, when the storage ambient atmosphere (outside the packaging bag) is at a temperature of 23 ° C. and a relative humidity of 60% RH, (1) A = 1.1 ± 0.1, (2) having a moisture permeability having a humidity dependency of B ≧ 0.14, and (3) an ambient atmosphere of 40 ° C. and 90% RH, a moisture permeability of 500 μm at a thickness of 30 μm. A food packaging method using a film having a characteristic of 1000 / (m ² · day). A film for food packaging,
The coefficient k is defined as the permeated moisture weight of the film / (the moisture permeability of the film × the surface area of the film × the number of days used × the relative humidity difference between the inside of the packaging bag and the ambient atmosphere / 90), and the value of k is defined as
k = A · e ^Bx where x is the relative humidity inside the packaging bag, when the storage ambient atmosphere (outside the packaging bag) is at a temperature of 23 ° C. and a relative humidity of 60% RH, (1) A = 1.1 ± 0.1, (2) having a moisture permeability having a humidity dependency of B ≧ 0.14, and (3) an ambient atmosphere of 40 ° C. and 90% RH, a moisture permeability of 500 μm at a thickness of 30 μm. A food packaging film having a characteristic of 1000 / (m ² · day). A film for wrapping bread,
The coefficient k is defined as the permeated moisture weight of the film / (the moisture permeability of the film × the surface area of the film × the number of days used × the relative humidity difference between the inside of the packaging bag and the ambient atmosphere / 90), and the value of k is defined as
k = A · e ^Bx where x is the relative humidity inside the packaging bag, when the storage ambient atmosphere (outside the packaging bag) is at a temperature of 23 ° C. and a relative humidity of 60% RH, (1) A = 1.1 ± 0.1, (2) having a moisture permeability having a humidity dependency of B ≧ 0.14, and (3) an ambient atmosphere of 40 ° C. and 90% RH, a moisture permeability of 500 μm at a thickness of 30 μm. A film for bread packaging characterized by having a characteristic of 1000 / (m ² · day).   The food packaging film according to claim 2, wherein the film is formed by kneading polyurethane resin and SBS at a predetermined mixing ratio and forming a film, or by heat bonding.   A laminated film for food packaging, wherein the film for food packaging according to claim 4 is laminated by thermal bonding with the polyurethane resin and SBS on at least one side of a permeable substrate.   The laminate for food packaging according to claim 5, wherein the permeable substrate is any one of a nonwoven fabric, rayon paper, cellophane, a perforated film, a polylactic acid film, or a styrene film having a thickness of 30 µm or less. the film.   A food packaging bag, wherein the laminated film for food packaging according to claim 5 or 6 is formed in a cylindrical shape or a bag shape.   The food packaging film according to claim 2 or 4, which is applied to bread, vegetables, fruits, meats, seafood, salads, and prepared dishes.   The food packaging method according to claim 1, which is applied to bread, vegetables, fruits, meats, seafood, salads, and prepared dishes.