Heat treatment packaging

Abstract

To provide a package for thermal processing allowed to suppress the pressure change within a package due to water vapor within the package or thermal expansion of internal air and prevent a chuck seal unit from being unsealed upon a rise of internal pressure, so as to thermally process a content such as a food material efficiently.SOLUTION: A package for thermal processing in the present invention comprises a bag body made up with a package film, a chuck seal unit that hermetically seal a content inputted into the bag body, and a principal-raftered seal unit for releasing the internal pressure raised when the content is thermally processed. One of male and female chucks of the chuck seal unit has a non-joined region not contacting with the bag body at from an end on a bag-interior side of a contact face contacting with the bag body toward an exterior of the bag body. In a predetermined position of the bag body, a crease is formed nearly in parallel with the chuck seal unit and having a valley fold on a side the non-joined region is formed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a package for heat-treating the contents. [Background technology]

[0002] Conventionally, packaged foods have been available on the market in which cooked or semi-cooked food is packed into a heat-resistant plastic package and cooked in a microwave oven just before eating. However, when such packaged foods are heated in a microwave oven, the internal pressure increases due to the thermal expansion of the water vapor and air inside the package, which can cause the package to burst, scattering the contents and contaminating the inside of the microwave oven.

[0003] A method of preventing the package from bursting is to pierce the package before cooking in a microwave oven to prevent the internal pressure from increasing. However, this method causes the generated steam to immediately escape from the package, which not only reduces the steaming effect of the steam but also causes the food inside the package to dry out, resulting in a deterioration in taste. Therefore, a package with an easy-peel section that allows steam to pass through and release pressure when the internal pressure of the package increases is known.

[0004] Patent Document 1 describes a package for heat treatment in which the same sides of plastic films are abutted against each other and a first joint is provided that is joined in a gabled shape with a heat seal of a specified width, and the contents to be heat-treated are sealed and packaged inside. The first joint is positioned to one side of the package, and is an easy-to-open seal that allows pressure to escape when the internal pressure of the package increases due to heating.

[0005] Patent Document 2 describes a packaging bag for heating in a microwave oven, which is made by using a composite film having at least one surface made of a sealant layer to form a lower member with the sealant side as the upper surface and wing sections with the sealant sides facing each other and sealing at least the sides, and then overlapping an upper member with the sealant side as the lower surface and sealing the peripheral edges to form a main sealed section, in which a point sealed section is formed in the central region of the wing section, connected to the upper edge seal section or the folded section of the wing section, and at least one or more vapor-permeable means is provided within this point sealed section.

[0006] Patent Document 3 describes a package for heat-treating contents, the package having a seam seal portion formed to protrude outward from above the package, a steam-passing region formed in the center of the seam seal portion through which steam passes when the contents are heat-treated and internal pressure increases, the steam-passing region having a first non-sealed region opening on the outer side of the seam seal portion, the first non-sealed region having a first region with a constant opening width toward the inner side of the package of the seam seal portion, and a second region formed continuous with the first region and whose opening width gradually decreases toward the inner side of the package, the opening width of the first region being 20 to 40 mm. One side of this package for heat treatment has a zipper seal portion, allowing consumers to insert contents such as foodstuffs through the zipper seal portion and seal it.

[0007] Consumers can purchase these pre-packaged foods, which are sold in a state where the contents are filled in the package, and simply heat them, which is very convenient. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 9-150864 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-182779 [Patent Document 3] Patent Publication No. 2021-104813 Summary of the Invention [Problem to be solved by the invention]

[0009] The packages in Patent Documents 1 and 2 are designed to be filled with contents and sealed by the manufacturer, and consumers cannot fill the packages with contents themselves. Some consumers want to reduce the burden of cooking but still want to cook by hand, so providing the package with a zip-seal portion (zipper) has been considered, and packages such as those in Patent Document 3 are actually available commercially. However, it was necessary to prevent the zip-seal from opening first when the internal pressure increases, thereby reducing the steaming effect of the food.

[0010] Therefore, the present invention aims to provide a heat-processing package that can suppress fluctuations in pressure inside the package due to water vapor inside the package or thermal expansion of the internal air, and can prevent the zipper seal from opening when the internal pressure rises, thereby enabling the contents, such as food ingredients, to be efficiently heat-processed. [Means for solving the problem]

[0011] The heat treatment package according to the present invention is a package for heat treating contents, The bag includes a bag body made of a packaging film, a zipper seal part that seals the contents when the contents are placed inside the bag body, and a joint seal part that releases pressure when the internal pressure increases due to heat treatment of the contents, the zipper seal portion has a male zipper and a female zipper joined to the bag body, one of the male zipper and the female zipper has a non-bonded region that is not bonded to the bag body from an end of a contact surface that contacts the bag body on the bag body inner side toward an outside of the bag body, the bag Front and back ofWhen viewed from a direction perpendicular to the front and rear surfaces of the bag body, the non-bonded region is disposed along an end portion of the non-bonded region on the inner side of the bag body, or from an end portion of the non-bonded region on the inner side of the bag body. 15 A fold line is formed at a distance not exceeding 1 / 2 mm, which is approximately parallel to the zipper seal portion, The fold is a valley fold on the side where the non-bonded region is formed. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a heat-processing package that can suppress fluctuations in pressure inside the package due to water vapor inside the package or thermal expansion of the internal air, and can prevent the zipper seal from opening when the internal pressure rises, thereby enabling the contents, such as food ingredients, to be efficiently heat-processed. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic diagram showing an example of the configuration of a package for heat treatment according to the present invention. [Figure 2] 2 is a schematic cross-sectional view showing an example of the configuration of the vicinity of the zipper seal of the package for heat treatment shown in FIG. 1. FIG. [Figure 3] 2 is a schematic diagram showing the state of the zipper seal portion when the package for heat treatment shown in FIG. 1 is expanded. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] One embodiment of a package for heat treatment according to the present invention will be described with reference to the drawings. The package for heat treatment according to the present invention is suitable for use when heat-treating contents in a microwave oven, and is also suitable for use when heat-treating food ingredients.

[0015] Figure 1 shows an example of the configuration of a package for heat treatment according to the present invention. The package for heat treatment 1 shown in Figure 1 is composed of a bag 2, a zipper seal portion 10 provided on one side of the bag 2, and a joint seal portion 20 that releases internal pressure when the contents are heated and the pressure increases. With this configuration, consumers can insert contents such as food ingredients through the zipper seal portion and seal the bag. The bag 2 is composed of, for example, two sheets of packaging film 22, and has a peripheral seal portion 5 where three sides of the two sheets of packaging film 22 are sealed.

[0016] Considering that the packaging film 22 will be heated in a microwave oven, it is preferable that it be made of a plastic material that is heat-resistant to microwave heating. Specific examples of such plastic materials include polyolefins such as polyethylene and polypropylene; halogenated polyolefins such as polyvinylidene chloride and polyvinylidene fluoride; polyvinyl alcohol; polyamides such as nylon 6, nylon 6,6, and polymetaxylylene adipamide; polyesters such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and polybutylene naphthalate; polyacrylic acid esters such as polymethyl(meth)acrylate, polyethyl(meth)acrylate, and polybutyl(meth)acrylate; and copolymers of monomers that form these. Note that "(meth)acrylic" refers to either methacrylic or acrylic.

[0017] Specific examples of polyethylene include linear low-density polyethylene, high-pressure low-density polyethylene, high-density polyethylene, metallocene polyethylene, etc. Specific examples of polypropylene include propylene homopolymer, random or block copolymer of propylene with ethylene or 1-butene, etc.

[0018] The packaging film 22 may be a single layer, or may be laminated with two or more layers by coextrusion, etc. For example, the packaging film 22 preferably comprises a base layer and a sealant layer, and may further have another layer between the base layer and the sealant layer.

[0019] For example, polyamides such as nylon 6, nylon 6,6, and polymetaxylylene adipamide, and polyesters such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and polybutylene naphthalate can be used as the base layer of the packaging film 22. For example, polyolefins such as polyethylene and polypropylene can be used as the sealant layer. Furthermore, for example, the above-mentioned polyamides and polyesters can be used as the intermediate layer provided between the base layer and the sealant layer.

[0020] When the packaging film 22 is made up of multiple layers, at least one of the layers is preferably made of polyester, and more preferably made of polybutylene terephthalate, which makes it easier to make the packaging bag film 22 have an appropriate hardness while improving its heat resistance.

[0021] The packaging film 22 may also be a gas-barrier composite film provided with a thin inorganic oxide film such as aluminum oxide or silicon oxide. This composite film can be obtained by heating and vaporizing aluminum oxide or silicon oxide alone or in a mixture under vacuum and depositing the vapor on the surface of the above-mentioned film. Furthermore, the packaging film 22 may have an adhesive layer with gas-barrier properties, such as one based on polyepoxy resin, or a layer with gas-barrier properties, such as a polyvinyl alcohol-based polymer resin, cellulose, or urethane-based resin.

[0022] The shape of the package for heat treatment 1 is not important as long as it can be configured so that the contents can be placed inside and sealed. That is, the bag body 2 can be in the form of a three-sided seal as shown in Fig. 1, a four-sided seal, a stick, a pillow, a gusset, an envelope seal, a standing seal, a glove seal, etc. The shape of the outer edge of the package for heat treatment 1 can be a polygon such as a triangle, a rectangle, or a pentagon, a circle, an ellipse, or a combination of these, but is generally a rectangle.

[0023] The seal width of the peripheral seal 5 formed on the sides and bottom of the package for heat treatment 1 (bag 2) is preferably 3 to 15 mm, more preferably 5 to 12 mm, and even more preferably 7 to 10 mm. The peripheral seal 5 may be formed in a V-shape, with the seal formed on the sides sloping inward toward the bottom, or in a U-shape, with the seal formed at the corners of the sides and bottom being rounded. A V- or U-shape can effectively prevent the seal formed at the bottom from receding or coming off when filling the package for heat treatment 1 with contents such as foodstuffs, and also makes it less likely for the contents to remain at the corners of the sides and bottom, preventing the contents from burning when heated.

[0024] The peripheral seal 5 may be completely sealed at room temperature and in an atmosphere at 90°C, or may be easily opened as long as it has a stronger seal strength than the zipper seal 10 and the gable seal 20. When the peripheral seal 5 is easily opened, the seal strength at room temperature and in an atmosphere at 90°C is preferably 10 to 50 N / 15 mm, and more preferably 12 to 45 N / 15 mm. The seal strength at room temperature and in an atmosphere at 90°C is a value measured at room temperature and in an atmosphere at 90°C, respectively, in accordance with JIS Z0238 "Test method for hermetically sealed flexible packaging bags."

[0025] The zipper seal portion 10 has a male zipper 11 and a female zipper 12, an example of which is shown in Figure 2. The male zipper 11 and female zipper 12 are each joined to the bag body 2 (packaging film 22), and can be sealed (hermetically sealed) by fitting the convex portion of the male zipper 11 into the concave portion of the female zipper 12. There may be multiple male zippers and multiple female zippers as long as they fit together.

[0026] In this embodiment, the male zipper 11 is heat-sealed at two locations on the contact surface 13 that comes into contact with the bag body 2: one on the inside side of the bag body 2 (the lower side in Fig. 1, the right side in Fig. 2) and one on the outside side of the bag body 2 (the upper side in Fig. 1, the left side in Fig. 2), to form a joint 15. Note that the joint 15 may be formed on the entire contact surface 13.

[0027] In contrast, the female zipper 12 has a joint 16 formed by heat sealing at only one location on the outer side of the bag body 2 (upper side in Fig. 1, left side in Fig. 2) of the contact surface 14 that comes into contact with the bag body 2. That is, a non-joined region 17 that is not joined to the bag body 2 is formed from the end of the contact surface 14 that comes into contact with the bag body 2 on the inner side of the bag body 2 (lower side in Fig. 1, right side in Fig. 2) toward the outside of the bag body.

[0028] The bag body 2 has a fold 3 formed therein that is approximately parallel to the zipper seal portion 10. As shown in FIG. 2, this fold 3 has a valley fold on the side where the non-bonded region 17 is formed. With this configuration, when the package for heat treatment 1 expands, the internal pressure is concentrated at the bonded portion 16 on the side where the non-bonded region 17 is formed, as shown by the arrow in FIG. 3. As a result, it is possible to prevent the expansion pressure from concentrating on the mating portion of the male zipper 11 and the female zipper 12. Note that "approximately parallel" does not only mean that the two are completely parallel, but also includes cases where one is slightly inclined relative to the other as long as the purpose is achieved, and includes cases where the inclination of one relative to the other is, for example, -10° to +10°.

[0029] The fold 3 is formed along the edge 18 of the non-bonded region 17 on the inner side of the bag body 2 when viewed from a direction perpendicular to the front and back surfaces of the bag body 2 (the front or back side in FIG. 1, the upper or lower side in FIG. 2). F =0 mm), or at a distance not exceeding 20 mm from the end 18 of the non-bonded region 17 on the inner side of the bag body 2 (D F≦20 mm). If the fold is too far from the end 18 of the non-bonded region 17 on the inner side of the bag body 2, the effect of forming the fold 3 is difficult to achieve. In FIGS. 1 to 3, the fold 3 is formed at a distance of not more than 20 mm from the end 18 of the non-bonded region 17 on the inner side of the bag body 2 in the direction opposite to the zipper seal portion 10. However, the fold 3 may be formed at a distance of not more than 20 mm from the end 18 of the non-bonded region 17 on the inner side of the bag body 2 in the direction opposite to the zipper seal portion 10. However, forming such a fold 3 makes the manufacturing process (particularly the process of forming the zipper seal portion 10) more difficult, so it is preferable that the fold 3 be formed at a distance of not more than 20 mm from the end 18 of the non-bonded region 17 on the inner side of the bag body 2 in the direction opposite to the zipper seal portion 10.

[0030] Furthermore, in this embodiment, as shown in Figures 2 and 3, it is preferable that the size of the contact surface 14 of the female zipper 12 provided with the non-bonding region 17 that comes into contact with the bag body 2 is longer toward the inside of the bag body 2 (the lower side in Figure 1) than the size of the contact surface 13 of the male zipper 11 that comes into contact with the bag body 2. This more effectively prevents the expansion pressure (internal pressure) from concentrating on the mating portion between the male zipper 11 and the female zipper 12. Note that the contact surface 13 and the contact surface 14 may be the same size. Also, it is sufficient that the size of the contact surface 14 of the female zipper 12 provided with the non-bonding region 17 that comes into contact with the bag body 2 is longer, at least in part, toward the inside of the bag body 2 (the lower side in Figure 1) than the size of the contact surface 13 of the male zipper 11 that comes into contact with the bag body 2.

[0031] In the above description, the non-bonding region 17 is provided on the female chuck 12 side, but the non-bonding region 17 may be provided on the male chuck 11 side.

[0032] In the present invention, one of the packaging films 22 constituting the bag 2 has a palm-seamed seal 20 formed by joining the inner surfaces of the films together with each other. This allows the pressure to be released through the palm-seamed seal 20 when the contents are heated and the internal pressure of the package for heat treatment 1 increases. The palm-seamed seal 20 is formed so as to protrude outward from the top of the package for heat treatment 1 (bag 2).

[0033] The palm-seamed seal portion 20 is formed so as to be positioned on the upper surface of the contents when the contents are heat-treated, and is formed to have easy-to-open properties that allow the pressure to escape when the internal pressure of the heat-treatment package 1 increases due to the heat treatment. The palm-seamed seal portion 20 can be formed by making the inner surfaces of the portions of the packaging film 22 that make up the palm-seamed seal portion 20 face each other and sandwiching an easy-to-open film (not shown) between them as needed.

[0034] It is important that the joint seal portion 20 has weaker easy-open properties in a 90°C atmosphere than the peripheral seal portion 5 and zipper seal portion 10. By doing so, when the contents are heat-treated and the internal pressure of the heat treatment package 1 increases, the joint seal portion 20 opens before the peripheral seal portion 5 and zipper seal portion 10 open, allowing the pressure to escape from the joint seal portion 20.

[0035] The heat seal strength of the palm-seamed seal portion 20 in a 90°C atmosphere is preferably 12 N / 15 mm or less, and more preferably 8 N / 15 mm or less. The heat seal strength of the palm-seamed seal portion 20 in a 90°C atmosphere may be 0 N / 15 mm, but is preferably 1 N / 15 mm or more. The palm-seamed seal portion 20 may be completely sealed at room temperature, or may have easy-open properties. When the palm-seamed seal portion 20 has easy-open properties, the seal strength at room temperature is preferably 0.5 to 30 N / 15 mm, and more preferably 1 to 25 N / 15 mm.

[0036] The palm-seamed seal portion 20, which is completely sealed at room temperature and has a heat seal strength of 12 N / 15 mm or less in an atmosphere of 90°C, can be achieved by using, as the easy-open film, polyolefin (for example, polyethylene with a melting point of 120°C or less (preferably 110°C or less), polypropylene with a melting point of 140°C or less (preferably 130°C or less), or a blend resin thereof. The melting point is a value measured in accordance with ASTM2117.

[0037] In the present invention, as shown in Fig. 1, it is preferable that a steam-passing area 21, through which steam passes when the contents are heated and the internal pressure increases, is formed in the center of the grommet-sealed portion 20. This results in a package for heat treatment 1 that is pressure-relieved so that it will not burst even when the internal pressure increases.

[0038] 1, the seam seal portion 20 is preferably formed approximately parallel to one side of the package for heat treatment 1, and the zipper seal portion 10 is preferably formed approximately parallel between the seam seal portion 20 and one side of the package for heat treatment 1. The distance H (see FIG. 1, the length of the package for heat treatment 1) from one side of the package for heat treatment 1 where the zipper seal portion 10 and the seam seal portion 20 are formed in parallel to the opposite side is preferably 100 to 500 mm, more preferably 125 to 400 mm, and even more preferably 150 to 300 mm.

[0039] The distance H between one side of the package for heat treatment 1 and the joint seal portion 20 P (see FIG. 1) is preferably 10 to 60% of the distance H from one side to the opposite side of the package for heat treatment 1, more preferably 25 to 50%, and even more preferably 30 to 40%. Within this range, the burst strength of the package for heat treatment 1 is low, and steam can easily pass through even with a weak force.

[0040] The distance H between one side of the heat treatment package 1 and the zipper seal portion 10 J (See FIG. 1) is the distance H between one side of the package for heat treatment 1 and the joint seal portion 20. PIt is preferably 10 to 80%, more preferably 20 to 60%, and even more preferably 40 to 50%.

[0041] With such a heat treatment package 1, consumers can fill the contents, such as foodstuffs, through the zipper seal portion 10 and seal it. The sealed contents can then be efficiently heated in a microwave oven or the like. Furthermore, by providing the gable seal portion 20, fluctuations in the pressure inside the package due to water vapor inside the package or thermal expansion of the internal air can be suppressed. Furthermore, by configuring the zipper seal portion 10 as described above and forming the specified fold 3, it is possible to effectively prevent the zipper seal portion 10 from opening when the internal pressure increases.

[0042] After the heat treatment is complete, the consumer can remove the contents by, for example, opening the joint seal 20. The opening may be at the zipper seal 10, or by tearing the heat treatment package 1 from the peripheral seal 5. A tear notch may be formed in the peripheral seal 5 to make the heat treatment package 1 easier to tear.

[0043] Although the preferred embodiments of the package for heat treatment of the present invention have been described above, the present invention is not limited to these. [Example]

[0044] Example 1 A heat treatment package (235 mm long x 200 mm wide) was prepared as shown in Figure 1. The package film used was made of polyethylene terephthalate (PET#12) / nylon (Ny#15) / non-oriented polypropylene (CPP#50). The palm seal was formed by inserting a PP-based easy-open tape and heat sealing it (H p =80mm, H J2, the size of the contact surface 14 of the female zipper 12 with the bag body 2 on the back side in FIG. 1 (the side on which the joint seal portion is not formed) is longer toward the inside of the bag body 2 than the contact surface 13 of the opposing male zipper 11 with the bag body 2, and a non-bonded region 17 is formed on the contact surface 14 side. In addition, the bag body 2 has a non-bonded region 17 along an end 18 on the inside side of the bag body 2 of the non-bonded region 17 (D F =0 mm), a fold 3 was formed parallel to the zipper seal portion 10, with the side where the non-bonded region 17 was formed (the back side in FIG. 1) being a valley fold.

[0045] <Example 2> The position where the fold 3 was formed was set to a position 5 mm away from the end of the non-bonded region 17 on the inner side of the bag body 2 (D F A package for heat treatment was produced in the same manner as in Example 1, except for the thickness (mm) of the outer periphery of the outer periphery (mm).

[0046] Example 3 The position where the fold 3 was formed was set to a position 10 mm away from the end of the non-bonded region 17 on the inner side of the bag body 2 (D F A package for heat treatment was produced in the same manner as in Example 1, except for the thickness (mm) of the outer periphery of the outer periphery (mm).

[0047] Example 4 The position where the fold 3 was formed was set to a position 15 mm away from the end of the non-bonded region 17 on the inner side of the bag body 2 (D F A package for heat treatment was produced in the same manner as in Example 1, except for the thickness (mm) of the outer periphery of the outer periphery (=15 mm).

[0048] <Comparative Example 1> A package for heat treatment was produced in the same manner as in Example 1, except that the fold 3 was not formed.

[0049] <Comparative Example 2> The position where the fold 3 was formed was set to a position 30 mm away from the end of the non-bonded region 17 on the inner side of the bag body 2 (D F A package for heat treatment was produced in the same manner as in Example 1, except for the thickness (mm) of the outer periphery of the outer periphery (=30 mm).

[0050] <Rating 1> Meat (250 g) and seasoning liquid (50 g) were placed into the zipper seal side of the heat treatment packages obtained in Example 1 and Comparative Example 1, and 85 samples of each were closed with the zipper seal. These samples were heated in a microwave oven and the presence or absence of openings in the zipper seal of each heat treatment package was examined. The results are shown in Table 1.

[0051] [Table 1]

[0052] In Comparative Example 1, in which the fold 3 was not formed, the zipper seal 10 opened in one sample. In contrast, in Example 1, in which the predetermined fold 3 was formed, steam passed through the steam passage area 21 of the joint seal portion 20 in all samples, and the zipper seal 10 did not open.

[0053] <Rating 2> 100 ml of water was poured into the zipper seal side of the heat treatment packages obtained in Examples 1 to 4 and Comparative Examples 1 and 2, and the zipper seals were closed to prepare samples (100 samples for Example 1 and Comparative Example 1, and 10 samples for Examples 2 to 4 and Comparative Example 2), which were then heated in a microwave oven and the presence or absence of openings in the zipper seal of each heat treatment package was checked. The results are shown in Table 2.

[0054] [Table 2]

[0055] In Comparative Example 1, in which the folds 3 were not formed, the zipper seals 10 opened in more than half (57 samples). This shows that the conditions in Evaluation 2 were more severe than those in Evaluation 1. Nevertheless, in Example 1, in which the specified folds 3 were formed, steam passed through the steam passage area 21 of the joint seal portion 20 in all samples, and the zipper seals 10 did not open.

[0056] On the other hand, in Example 2, in which the fold 3 was formed 5 mm from the end of the non-bonded region 17 on the inner side of the bag body 2, steam passed through the steam passage region 21 of the seam seal portion 20 in all samples, and the zipper seal 10 did not open. As the position in which the fold 3 was formed increased away from the end of the non-bonded region 17 on the inner side of the bag body 2, some samples had openings in the zipper seal 10, but when the distance was 20 mm or less (Examples 1 to 4), the non-opening rate was higher than in Comparative Example 1, and the effect of forming the fold 3 was evident. However, in Comparative Example 2, in which the fold 3 was formed 30 mm from the end of the non-bonded region 17 on the inner side of the bag body 2, the zipper seal 10 opened at a rate roughly equivalent to that of Comparative Example 1, in which the fold 3 was not formed. [Explanation of symbols]

[0057] 1. Heat treatment packaging 2 bags 3. Fold 5 Peripheral seal 10 Zipper seal 11 Male zipper 12 Female zipper 13 Contact surface 14 Contact surface 15 Joint 16 Joint 17 Non-bonded area 18 End 20. Joint seal 21 Vaporization area 22 Packaging film

Claims

1. A package for heat-treating contents, The bag includes a bag body made of a packaging film, a zipper seal part that seals the contents when the contents are placed inside the bag body, and a joint seal part that releases pressure when the internal pressure increases due to heat treatment of the contents, the zipper seal portion has a male zipper and a female zipper joined to the bag body, one of the male zipper and the female zipper has a non-bonded region that is not bonded to the bag body from an end of a contact surface that contacts the bag body on the bag body inner side toward an outside of the bag body, On the front and back surfaces of the bag body, when viewed from a direction perpendicular to the front and back surfaces of the bag body, a fold is formed along an edge of the non-bonded region on the bag body inner side, or at a distance not exceeding 15 mm from the edge of the non-bonded region on the bag body inner side, the fold being approximately parallel to the zipper seal portion; The fold is a valley fold on the side where the non-bonded region is formed. Packaging for heat treatment.

2. The size of each contact surface of the male zipper and the female zipper that contacts the bag body is such that the contact surface where the non-bonded region is provided is longer toward the inside of the bag body. The heat treatment package according to claim 1.

3. The joint seal portion is formed so as to protrude outward from above the bag body, A steam-passing area is formed in the center of the joint-sealed portion, through which steam passes when the contents are heated and the internal pressure increases. The heat treatment package according to claim 1 or 2.

4. The packaging film is composed of a plurality of layers, At least one of the layers is made of polybutylene terephthalate. The package for heat treatment according to any one of claims 1 to 3.

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