Microwave cooking packaged frozen food

Abstract

To provide a microwave cooking packaged frozen food that can easily perform microwave heating and hardly causes oozing of a content to the outside.SOLUTION: A steam releasing part 6 for discharging water vapor inside a packaging bag 4 to an outside is arranged at at least one of a pair of short side edge parts 42, 42 of the packaging bag 4. The steam releasing part 6 is closed in a state where a packaged frozen food 1 is unheated, but is automatically opened due to an inner pressure increase of the packaging bag 4 that is generated when the moisture releasing part is subjected to microwave heating. When the maximum length in a direction parallel to long side edge parts 41 of the packaging bag 4 in a tray 3 is represented by L1, and the maximum height of the tray 3 is represented by H, and the maximum length in a direction parallel to the long side edge parts 41 of a storage part 40 in a state where a stored object is taken out from the storage part 40, and the packaging bag 4 is folded is represented by L2, a ratio (L2 occupancy ratio) of L2 to a total of L1 and H is 107 to 117%.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a packaged frozen food for microwave cooking, which includes a cooked frozen food and a packaging bag enclosing the food, and which is heated in microwaves together with the packaging bag when used. [Background technology]

[0002] With the increasing popularity of microwave ovens, pre-cooked frozen foods that can be easily heated with microwaves to achieve an authentic taste are now commercially available. These types of frozen foods are typically sold sealed in a vapor-impermeable packaging container. When such packaged frozen foods are heated in a microwave-resistant container, gases such as water vapor generated by the frozen food during heating accumulate inside the container without escaping to the outside, causing an increase in the internal pressure of the container and potentially resulting in problems such as the container bursting or the contents of the frozen food scattering. Therefore, it has been common practice to open the packaging bag, remove the frozen food, cover the frozen food with plastic wrap, and then microwave-heat the food. However, these pre-heating steps are tedious, and improvements in the convenience of packaged frozen foods are desired.

[0003] Patent Documents 1 to 4 disclose packaging containers equipped with a desteaming section that releases internal steam to the outside, as a technology that enables microwave heating of the contents of the packaging container without causing inconveniences such as rupture of the packaging container. Specifically, Patent Document 1 discloses a food container for microwave heating that has a steam adjustment hole that releases steam when the internal pressure exceeds a certain value. Patent Document 2 discloses a container for microwave heating that has a 0.5 to 4 mm ventilation hole formed in the lid of the container and is sealed with an easily peelable sealing member. Patent Documents 3 and 4 disclose pillow packaging bags in which part of the heat seal peels off to release steam when the internal pressure rises during microwave heating. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 62-282556 [Patent Document 2] Japanese Patent Application Publication No. 173028 / 1983 [Patent Document 3] Japanese Patent Application Laid-Open No. 2002-302165 [Patent Document 4] Japanese Patent Application Laid-Open No. 2007-217050 Summary of the Invention [Problem to be solved by the invention]

[0005] The food container described in Patent Document 1 has a steam adjustment hole that is always open, which causes problems with the shelf life of the contents, such as the contents leaking from the steam adjustment hole during distribution or foreign matter being mixed in through the steam adjustment hole during storage. Furthermore, solving this problem requires a separate packaging container to house the food container, which is disadvantageous in terms of manufacturing costs. The container described in Patent Document 2 also has problems with the shelf life of the contents, and requires a separate packaging container to house the container. Additionally, the container described in Patent Document 2 requires the vent hole to be covered with a special sealing member, which is disadvantageous in terms of manufacturing costs.

[0006] Furthermore, the present inventors conducted extensive research on packaged frozen foods using packaging bags (flexible packaging containers) with a desteaming section and found that such packaged frozen foods have unique problems. Specifically, when such packaged frozen foods are heated in microwaves, water vapor is generated from the frozen food, which increases the internal pressure of the packaging bag, causing the bag to expand. However, the water vapor is expelled through the desteaming section of the packaging bag, ultimately causing the expanded packaging bag to contract. If the frozen food contained in the packaging bag is placed in a tray with an open top, the desteaming section of the contracted packaging bag may come into contact with the tray and become closed, creating a vacuum inside the packaging bag. If liquid components, such as water or sauce, seep out of the frozen food in the tray, capillary action can cause the liquid components to seep out of the packaging bag from the desteaming section and adhere to the area around the packaged frozen food (e.g., the interior of a microwave oven used to microwave the packaged frozen food), contaminating the surrounding area. Furthermore, if the liquid components seeping out of the desteaming section are hot, there is a risk of burns to the user. Patent Documents 1 to 4 do not mention the issue of seeping out of the contents from the desteaming section after microwave heating, which is a problem specific to frozen foods packaged using a packaging bag having such a desteaming section.

[0007] An object of the present invention is to provide a packaged frozen food for microwave cooking that can be easily heated by microwaves and that is less likely to cause the contents to leak out. [Means for solving the problem]

[0008] The present invention provides a packaged frozen food for microwave cooking, comprising a cooked frozen food, a tray for accommodating the cooked frozen food, and a steam-impermeable packaging bag containing a storage section for accommodating the cooked frozen food and the tray in a sealed state, The tray has a bottom wall and a peripheral wall extending from the peripheral edge of the bottom wall, The packaging bag has a rectangular shape in a plan view, and has a pair of long side edges extending in a longitudinal direction and a pair of short side edges extending in a width direction perpendicular to the longitudinal direction, and the storage section is located between one and the other of the pair of short side edges, a desteaming section for discharging water vapor from inside the packaging bag to the outside is disposed on at least one of the pair of short side edges, the desteaming section being closed when the packaged frozen food is in an unheated state, but being automatically opened by an increase in internal pressure of the packaging bag that occurs when the packaged frozen food is heated by microwaves; This is a packaged frozen food for microwave cooking, in which L1 is the maximum length of the tray in a direction parallel to the long side edge of the packaging bag, H is the maximum height of the tray, and L2 is the maximum length of the storage section in a direction parallel to the long side edge of the storage section when the contained item is removed from the storage section and the packaging bag is folded, and the ratio of L2 to the sum of L1 and H is 107 to 117%. [Effects of the Invention]

[0009] According to the present invention, a packaged frozen food for microwave cooking is provided which can be easily heated by microwave and in which the contents are less likely to leak out. The packaged frozen food for microwave cooking of the present invention has a packaging bag provided with a desteaming section that automatically changes from a closed state to an open state when the internal pressure of the packaging bag increases due to microwave heating, so that problems such as the packaging bag bursting are unlikely to occur even when the contents of the packaging bag (cooked frozen food) are heated in the microwave together with the packaging bag. Therefore, the cooked frozen food contents can be brought to an edible state by simply heating the packaged frozen food for microwave cooking in a microwave oven. Furthermore, because the dimensions of each part of the storage section of the packaging bag are adjusted to a specific range, the contents are unlikely to seep out of the desteaming section after microwave heating, as mentioned above. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic perspective view of one embodiment of a packaged frozen food for microwave cooking of the present invention. [Figure 2] FIG. 2 is a cross-sectional view schematically showing a cross section taken along line II in FIG. 1 (a cross section along the longitudinal and thickness directions of the packaged frozen food). [Figure 3]FIG. 3 is a diagram showing a cooked frozen food and a tray that constitute the packaged frozen food shown in FIG. 1, and is a perspective view that schematically shows the cooked frozen food contained in the tray. [Figure 4] FIG. 4 is a diagram showing a packaging bag constituting the packaged frozen food shown in FIG. 1, and is a plan view schematically showing the back side of the packaging bag in a folded state. DETAILED DESCRIPTION OF THE INVENTION

[0011] 1 and 2 show a packaged frozen food 1, which is one embodiment of the packaged frozen food for microwave cooking of the present invention. Packaged frozen food 1 includes a frozen food 2, a tray 3 for containing frozen food 2, and a vapor-impermeable packaging bag 4 that contains a storage section 40 and hermetically stores frozen food 2 and tray 3 in storage section 40.

[0012] Since the frozen food 2 is contained inside the packaging bag 4 while being contained on the tray 3, the frozen food 2 can be more easily removed from the packaging bag 4 than when the frozen food 2 is contained inside the packaging bag 4 without the tray 3, and if liquid components such as water seep out from the microwave-heated frozen food 2, the inconvenience of the liquid components adhering to the surrounding area when the frozen food 2 is removed from the packaging bag 4 is prevented.

[0013] Frozen food 2 is a frozen product of cooked food. Frozen food 2 is thawed and made edible by microwave heating using a microwave cooking appliance such as a microwave oven. The food that constitutes frozen food 2 is not particularly limited as long as it is a food that can be microwaved, and may be, for example, noodles, rice dishes, main dishes, or side dishes. Examples of types of noodles include pasta (e.g., spaghetti, macaroni, penne, ravioli, etc.), udon, soba, and Chinese noodles. Frozen food 2 may be a frozen product of one type of food, or two or more types of food. A specific example of the latter is a one-plate frozen food consisting of a staple food (noodles, rice dishes, etc.) and a side dish.

[0014] In this embodiment, the frozen food 2 is cooked frozen noodles. Specifically, the frozen food 2 is frozen spaghetti as shown in Figures 2 and 3, and is composed of a frozen cooked spaghetti and a frozen cooked pasta sauce placed on top of the cooked spaghetti, with the two frozen products being integrated together.

[0015] The amount of frozen food 2 to be placed in packaging bag 4 is not particularly limited, and may be, for example, an amount for a small number of people, such as one to two meals, or an amount for a large number of people, such as three or more meals. The amount of frozen food 2 to be placed in packaging bag 4 may be 1 kg or more. For example, in the present embodiment, when the cooked frozen food is a frozen dish that uses noodles, the weight of a small portion of cooked frozen food is typically about 150 to 400 g.

[0016] The tray 3 has a bottom wall 30 and a peripheral wall 31 erected from the peripheral edge of the bottom wall 30. In the present invention, the shape of the bottom wall 30 in a plan view is not particularly limited, and examples thereof include shapes that are elongated in one direction (anisotropic shapes) such as a rectangle or an ellipse; and isotropic shapes such as a square or a circle.

[0017] In this embodiment, the bottom wall 30 has a rectangular shape in plan view and, as shown in Fig. 3, has a pair of long side edges extending in the longitudinal direction X3 and a pair of short side edges extending in the width direction Y3 perpendicular to the longitudinal direction X3. The peripheral wall 31 extending from the periphery of the rectangular bottom wall 30 in plan view includes, as shown in Figs. 2 and 3, a pair of long side walls 310 extending from the pair of long side edges of the bottom wall 30 and a pair of short side walls 311 extending from the pair of short side edges of the bottom wall 30. The long side walls 310 of the peripheral wall 31 extend in the longitudinal direction X3 of the bottom wall 30, and the short side walls 311 of the peripheral wall 31 extend in the width direction Y3.

[0018] In tray 3, the space surrounded by bottom wall 30 and peripheral wall 31 functions as a storage area for the item (frozen food 2). The upper part of bottom wall 30 is defined by the upper end of peripheral wall 31 (the end opposite bottom wall 30), and forms an upper opening with an opening area equal to or larger than the area of ​​bottom wall 30. Items can be placed in and removed from the space through this upper opening. The upper opening of tray 3 also functions as an outlet for steam generated by microwave heating of frozen food 2 placed in the space.

[0019] In this embodiment, the tray 3 includes, in addition to the bottom wall 30 and the peripheral wall 31, a flange portion 32 connected to the upper end of the peripheral wall 31. The flange portion 32 contributes to improving the strength of the tray 3 and also functions as a handle when the tray 3 is held with the fingers, thereby contributing to improving the handleability of the tray 3.

[0020] There are no particular restrictions on the material of tray 3, and examples include paper, resin, or a composite material combining these. When microwave heating of packaged frozen food 1 increases the internal pressure of packaging bag 4, causing packaging bag 4 to expand, which may cause tray 3 to bend or deform. However, if tray 3 is made of paper, there is an advantage that tray 3 is less likely to break even if it is deformed.

[0021] The qualities required of tray 3 include the ability to not impede microwave heating of the contents (frozen food 2) (microwave transparency), the ability to withstand the high temperatures that may be caused by microwave heating when the contents are heated (heat resistance), and water resistance. If tray 3 is water-resistant, even if microwave heating causes a portion of the contents to melt and liquid components such as water to seep out of the contents, the liquid components can be prevented from diffusing to the surrounding area. The material of tray 3 is preferably selected to satisfy these required qualities.

[0022] As described above, tray 3 is an open container that has an upper opening and communicates with the inside and outside of tray 3 through said upper opening, and therefore is vapor permeable regardless of whether the material of tray 3 is vapor permeable or not. Therefore, tray 3 does not substantially restrict the movement of water vapor generated from frozen food 2 by microwave heating in storage section 40, or the increase in internal pressure of packaging bag 4 caused by storage section 40 being filled with said water vapor.

[0023] This type of packaged frozen food may use a non-open bag-like container called an "inner bag" instead of an open container such as tray 3, with the frozen food placed in the inner bag, and the inner bag then being placed in another non-open bag-like container called an "outer bag," but tray 3 is different from such an inner bag. The packaged frozen food for microwave cooking of the present invention, represented by packaged frozen food 1, has a packaging bag equivalent to the outer bag, but does not have the inner bag.

[0024] Fig. 1 shows the front side of the packaging bag 4, and Fig. 4 shows the back side of the packaging bag 4. The packaging bag 4 has a rectangular shape in a plan view and has a pair of long side edges 41, 41 extending in the longitudinal direction X4 and a pair of short side edges 42, 42 extending in a width direction Y4 perpendicular to the longitudinal direction X4. The long side edges 41 are the side edges (long side edges) along the longitudinal direction X4 in a plan view of the packaging bag 4 and their vicinity, and the short side edges 42 are the side edges (short side edges) along the width direction Y4 in the same plan view and their vicinity. A storage section 40 in which the frozen food 2 and tray 3 to be stored are accommodated is located between one and the other of the pair of short side edges 42, 42. The storage section 40 also has a rectangular shape in a plan view.

[0025] As the packaging bag 4, any bag that can be used as a packaging bag for this type of frozen food can be used without any particular restrictions, provided that it does not impede the manifestation of the effects of the present invention. The packaging bag 4 may be made by molding a single sheet material into a bag shape, or by overlapping two sheets of material and sealing the edges, or by having two opposing sides connected by a gusset or gusset portion. Specific examples of the packaging bag 4 include side-sealed bags, three-side-sealed bags, four-side-sealed bags, pillow bags, gusset bags, and pouch bags.

[0026] In this embodiment, the packaging bag 4 is a pillow bag formed from a single sheet material 5. The pillow bag packaging bag 4 can be produced by joining both ends of a single sheet material 5 in one direction to form a back seal portion 43, thereby forming the sheet material 5 into a cylindrical body, and then sealing the openings at both ends of the cylindrical body in a direction perpendicular to the one direction to form a pair of short side edges 42, 42. Pillow bags are suitable as packaging bags 4 because they are easy to handle when storing items.

[0027] 4, the spine seal portion 43 is located in the center of the width direction Y4 on the back surface of the packaging bag 4 and extends in the longitudinal direction X4 of the packaging bag 4 over the entire length of the packaging bag 4. In the spine seal portion 43, both ends of one sheet material 5 constituting the packaging bag 4 are joined together in a palm-on-palm manner.

[0028] In this embodiment, the pair of short side edges 42, 42 each have a sheet material joint 50 where the sheet materials 5 constituting the packaging bag 4 are overlapped and the opposing sheet materials 5, 5 are joined together. As described above, in this embodiment, the packaging bag 4 is a pillow bag formed from a single sheet material 5, and the sheet material joint 50 is formed by sealing the openings at both ends of the tubular body during the process of making the pillow bag, i.e., by joining both ends of opposing sheets of sheet material 5 that define the openings. The sheet material joint 50 extends in the same direction in the width direction Y4 over the entire length of the short side edge 42. The method for joining the sheet materials 5 at the sheet material joint portion 50 is not particularly limited, and examples thereof include fusion bonding and adhesive bonding. Typically, fusion bonding is performed by heat sealing, ultrasonic sealing, or the like. The width of the sheet material joint 50 (the length in the direction perpendicular to the extending direction of the sheet material joint 50) is not particularly limited, but is preferably 4 to 30 mm.

[0029] In this embodiment, the short side edge 42 of the packaging bag 4 has a sheet material joint portion 50, but the long side edge 41 of the packaging bag 4 does not have a sheet material joint portion 50. At the long side edge 41, the opposing sheet materials 5, 5 are not joined to each other.

[0030] Packaging bag 4 is vapor-impermeable, and is designed to prevent gases such as water vapor from moving between the inside and outside of packaging bag 4. Therefore, when packaged frozen food 1 is heated with microwaves, gases such as water vapor generated from frozen food 2 by the heating do not escape to the outside of packaging bag 4 but accumulate inside (storage section 40), causing an increase in the internal pressure of packaging bag 4. In this embodiment, packaging bag 4 is formed from sheet material 5, and this sheet material 5 is vapor-impermeable.

[0031] The packaging bag 4 (sheet material 5) is required to have microwave transparency, heat resistance, and water resistance. Materials that satisfy these required properties are preferred for the packaging bag 4 (sheet material 5), and examples include heat-resistant plastics such as nylon, polyethylene terephthalate, crystallized polyethylene terephthalate, polypropylene, polyethylene, and polystyrene; paper that is partially or entirely coated with a heat-resistant and water-resistant coating; and composite materials that combine two or more of these.

[0032] One of the main features of the packaged frozen food for microwave cooking of the present invention is that a desteaming section 6 that discharges water vapor from inside the packaging bag 4 to the outside is disposed on at least one of the pair of short side edges 42, 42. In this embodiment, as shown in Fig. 1, a desteaming section 6 is disposed on both of the pair of short side edges 42, 42.

[0033] The desteaming section 6 is closed when the packaged frozen food 1 is in an unheated state (unused state), but is designed to open automatically due to an increase in the internal pressure of the packaging bag 4 that occurs when the packaged frozen food 1 is microwave heated. "Automatically opens" here means that the desteaming section 6 opens without any manual operation. In other words, the inside and outside of the packaged frozen food 1 are not always in communication via the desteaming section 6; rather, the inside and outside only become in communication via the desteaming section 6 when the packaged frozen food 1 is microwave heated.

[0034] As mentioned above, the desteaming section 6 is closed when the packaged frozen food 1 is in an unheated state, and "closed" here includes a state in which, when the packaged frozen food 1 is in an unheated state, communication between the inside and outside of the packaging bag 4 in the desteaming section 6 is completely blocked (a completely closed state), and a state in which the inside and outside of the packaging bag 4 are in communication in the desteaming section 6 but water vapor cannot be discharged to the outside via the desteaming section 6 (an incompletely closed state). An example of the incompletely closed state is a state in which an opening has a very small diameter that allows gases such as oxygen to pass through but prevents water vapor from passing through. When the packaged frozen food 1 is microwave-heated and the internal pressure of the packaging bag 4 increases, the desteaming section 6 in the incompletely closed state "automatically opens" as the surrounding sheet material 5 that defines the opening tears starting from the opening. A packaging bag 4 having a devaporation section 6 in an incompletely closed state is susceptible to problems such as breakage originating from the devaporation section 6 during transportation and storage, or the introduction of foreign matter into the packaging bag 4 through the devaporation section 6. Therefore, in order to eliminate such concerns, a devaporation section 6 in a completely closed state is preferred.

[0035] As described above, in this embodiment, the short side edge 42 has a sheet material joint 50 where the sheet materials 5 are overlapped and the opposing sheet materials 5, 5 are joined together, and the interlayer bond strength at the sheet material joint 50 in the desteaming section 6 is lower than in the non-positioning portion of the desteaming section 6 in the short side edge 42. Therefore, when the packaged frozen food 1 is microwave-heated and the internal pressure of the packaging bag 4 increases, the short side edge 42 automatically opens as the bond between the sheet materials 5 at the sheet material joint 50 is released in the desteaming section 6, which has a relatively low interlayer bond strength, but the bond between the sheet materials 5 at the sheet material joint 50 is not released in the non-positioning portion of the desteaming section 6, which has a higher interlayer bond strength than the desteaming section 6.

[0036] In this way, making the interlayer bond strength partially different at the sheet material joint 50 (short side edge 42) can be achieved by appropriately adjusting the conditions that affect the interlayer bond strength depending on the method of forming the sheet material joint 50 (the method of joining the sheet materials 5 together). For example, when forming the sheet material joint 50 by heat sealing, methods that can be used include shortening the heating time, lowering the heating temperature, shortening the seal width (the length in the direction perpendicular to the extension direction of the sheet material joint 50) for the portion where the desteaming portion 6 is to be formed, compared to the portion where the desteaming portion 6 is not to be formed, or using a sheet material with lower seal strength.

[0037] The ratio of the interlayer bonding strength in the closed state of the desteaming section 6 to the interlayer bonding strength in the non-placed portion of the desteaming section 6 in the short side edge 42 is preferably 15 to 33%, more preferably 20 to 30%. The interlayer bonding strength of the devaporation section 6 in the closed state is preferably 3 to 8N, and more preferably 4 to 6.5N. The interlayer bonding strength can be measured by a method in accordance with JIS Z 1707 "General rules for food-grade plastic films" 7.4 "Heat seal strength test".

[0038] According to packaged frozen food 1, packaging bag 4 is provided with desteaming section 6, which allows for easy microwave heating of frozen food 2. Specifically, due to the presence of desteaming section 6, even if gases such as water vapor are generated from frozen food 2 due to microwave heating of packaged frozen food 1, the gases are discharged to the outside of packaging bag 4 via desteaming section 6. In particular, in packaged frozen food 1, desteaming section 6 is located in short side edge 42, which is the area where the expansion force is most concentrated when packaging bag 4 expands in response to an increase in the internal pressure of packaging bag 4 (containing section 40), which has a rectangular shape in plan view. Therefore, an increase in the internal pressure of packaging bag 4 triggers a smooth change of desteaming section 6 from a closed state to an open state, and the inconvenience of the sheet materials 5 being released from the joint in the area where desteaming section 6 is not located is prevented. Therefore, when heating the frozen food 2 in the microwave, there is no need to open the packaging bag 4 and remove the frozen food 2; the entire packaged frozen food 1 can be heated in the microwave with the packaging bag 4 remaining unopened, and the frozen food 2 can be easily brought to a state where it can be eaten without causing inconveniences such as the packaging bag 4 bursting or the frozen food 2 scattering. In addition, by providing the desteaming section 6 in the packaging bag 4, an inner bag with a desteaming function used to package the frozen food 2 inside the packaging bag 4 is no longer necessary, thereby reducing the manufacturing cost of the packaged frozen food 1.

[0039] In particular, in this embodiment, since a devastation section 6 is arranged on both of the pair of short side edge sections 42, 42, even if one of the devastation sections 6 does not automatically open due to an increase in the internal pressure of the packaging bag 4 for some reason (for example, a manufacturing defect, physical blockage of the devastation section 6 by the contents of the packaging bag 4, etc.), there is a high probability that the other devastation section 6 will function normally, and water vapor from within the packaging bag 4 can be discharged more stably.

[0040] In this embodiment, as shown in FIG. 1 , one desteaming section 6 is arranged in the center in the direction in which the short side edge 42 extends (the width direction Y of the packaging bag 4). In the present invention, the number and arrangement of desteaming sections 6 are not particularly limited, and can be adjusted appropriately as long as the effects of the present invention are not hindered. For example, multiple desteaming sections 6 may be arranged intermittently in the direction in which the short side edge 42 extends. Furthermore, when desteaming sections 6 are arranged in both of a pair of short side edges 42, 42, the arrangement pattern of the desteaming sections 6 (the number and positions of the desteaming sections 6) may be the same or different between one short side edge 42 and the other short side edge 42, as in this embodiment.

[0041] In Figure 1, the desteaming section 6 is shown with a pattern consisting of multiple diagonal lines to clearly indicate its position, but in actual packaged frozen foods for microwave cooking, the desteaming section may not necessarily have a pattern. In the present invention, the desteaming section 6 may be patterned or colored to make it possible to visually distinguish the desteaming section 6 from the surrounding area. This makes it possible to appeal to the user of the packaged frozen food 1 about the presence of the desteaming section 6, and to provide the user with information that is useful when handling the packaged frozen food 1.

[0042] The packaged frozen food for microwave cooking of the present invention is characterized in that the dimensions of each part of the packaging bag 4 are adjusted to fall within a specific range. That is, if L1 (see FIG. 2) is the "maximum length of tray 3 in a direction parallel to long edge 41 of packaging bag 4," H (see FIG. 2) is the "maximum height of tray 3," and L2 (see FIG. 4) is the "maximum length of storage section 40 in a direction parallel to long edge 41 of storage section 40 in a state in which the contents (frozen food 2 and tray 3) have been removed from storage section 40 and packaging bag 4 has been folded," then the ratio of L2 to the sum of L1 and H (hereinafter also referred to as the "L2 occupancy rate"), i.e., the value calculated by the following formula, is 107 to 117%, and preferably 108 to 115%. L2 occupancy rate (%)={L2 / (L1+H)}×100

[0043] L1 and H are each obtained by leaving an unheated (unused) packaged frozen food 1 at rest and measuring tray 3 through packaging bag 4 with packaging bag 4 unopened. The state of packaged frozen food 1 when measuring L1 and H is equivalent to the state when packaged frozen food 1 is placed inside a microwave oven. Note that L1 and H may also be measured by opening packaging bag 4 and removing tray 3. In this embodiment, the bottom wall 30 of the tray 3 has a shape that is long in one direction (specifically, a rectangle) in a plan view, and the tray 3 is accommodated in the accommodation section 40 of the packaging bag 4 with its longitudinal direction X3 corresponding to the longitudinal direction X4 of the packaging bag 4 (a direction parallel to the long side edge 41). In addition, in this embodiment, the tray 3 has a flange portion 32 that extends outward (toward the opposite side from the upper opening) from the upper end of the peripheral wall 31. Therefore, in this embodiment, L1 is the maximum length of the tray 3 in the longitudinal direction X3, including the flange portion 32, as shown in FIG. 2. Furthermore, L2 is a value measured when the packaging bag 4 containing nothing is expanded so that the area of ​​its front (or back) surface is maximized, and is equal to the design dimension of the longitudinal direction X4 of the storage section 40.

[0044] Because the L2 occupancy rate is 107 to 117%, when water vapor is generated from the frozen food 2 by microwave heating and the packaging bag 4 expands, and then the packaging bag 4 shrinks as the water vapor is released from the devastation section 6, an appropriate gap is created between the shrunken packaging bag 4 and the tray 3, preventing the packaging bag 4 (devastation section 6) from coming into contact with the tray 3, and preventing the contents (liquid components derived from the frozen food 2, etc.) from seeping out from the devastation section 6 after microwave heating as described above.

[0045] In order to ensure that the effects of the present invention are more reliably achieved, it is preferable that the above L1, H, and L2 are adjusted to fall within the following ranges. The L1 is preferably 240 to 260 mm, and more preferably 245 to 255 mm. The above H is preferably 30 to 40 mm, more preferably 33 to 37 mm. The L2 is preferably 240 to 250 mm, and more preferably 243 to 247 mm.

[0046] The above L1 and L2 are the longitudinal lengths of the tray 3 or packaging bag 4, but in order to more reliably achieve the effects of the present invention, it is preferable to also adjust the widthwise lengths of the tray 3 and packaging bag 4 perpendicular to the longitudinal direction within an appropriate range. That is, the maximum length of the tray 3 in a direction parallel to the short side edge 42 of the packaging bag 4, in other words, the maximum length of the tray 3 (bottom wall 30) in the width direction Y3 in a plan view, is preferably 130 to 150 mm, more preferably 135 to 145 mm. Furthermore, when the contents (frozen food 2 and tray 3) are removed from the storage section 40 and the packaging bag 4 is folded, the maximum length in a direction parallel to the short side edge 42 of the storage section 40 is preferably 167 to 187 mm, more preferably 172 to 182 mm.

[0047] The ratio of the maximum expansion volume of the packaging bag 4 to the volume of the frozen food 2 (hereinafter also referred to as "maximum expansion volume occupancy"), that is, the value calculated by the following formula, is preferably 550 to 680%, more preferably 580 to 640%. Maximum expansion volume occupancy rate (%) = (maximum expansion volume of packaging bag / volume of cooked frozen food) x 100 The "maximum expansion volume of the packaging bag" referred to here refers to the volume of the packaging bag 4 just before the desteaming section 6 automatically opens due to the expansion of the packaging bag 4 caused by microwave heating of the packaged frozen food 1, and is equal to the volume of the storage section 40 just before the desteaming section 6 automatically opens. When the maximum expansion volume occupancy ratio is within the specified range, an appropriate amount of water vapor is likely to remain in storage section 40 during the time it takes for frozen food 2 to reach an edible state when packaged frozen food 1 is heated in the microwave, and the food that is finally obtained in an edible state (heated frozen food 2) is prevented from burning. In particular, when frozen food 2 contains large ingredients with a maximum diameter exceeding 10 mm, burning tends to occur easily, but by having the ratio within the specified range, this can be prevented. If the maximum expansion volume occupancy ratio is too small, the desteaming section 6 will open and steam will be released before the entire frozen food 2 has been sufficiently heated, and subsequent heating may cause some of the frozen food 2 to burn before the entire frozen food 2 has been sufficiently heated. If the maximum expansion volume occupancy ratio is too large, the desteaming section 6 will not open automatically even when the frozen food 2 is ready to eat, and the packaging bag 4 will remain expanded by steam, reducing the handleability of the packaged frozen food 1 and increasing the risk of burns to the user. In that case, if microwave heating is continued until the desteaming section 6 automatically opens, the frozen food 2 may burn due to overheating.

[0048] The maximum expansion volume of the packaging bag 4 is preferably 825 to 3400 cm 3 , more preferably 1650 to 1950 cm 3 is. The volume of the frozen food 2 is preferably 150 to 500 cm 3 , more preferably 200 to 400 cm 3 is.

[0049] The ratio of the internal volume of the tray 3 to the volume of the frozen food 2 (hereinafter also referred to as "tray internal volume occupancy"), that is, the value calculated by the following formula, is preferably 150 to 250%, more preferably 170 to 220%. Tray internal volume occupancy rate (%) = (tray internal volume / cooked frozen food volume) x 100 If the tray internal volume occupancy rate is too small, and if part of the frozen food 2 falls off during transport of the packaged frozen food 1, the part of the frozen food 2 that falls off will likely fall outside of the tray 3 rather than inside the tray 3, and if the packaged frozen food 1 is heated in the microwave with part of the frozen food 2 outside of the tray 3, this part may melt and stain the inside of the tray 3 and the packaging bag 4. Furthermore, if the tray internal volume occupancy rate is too large, the frozen food 2 will be more likely to move around significantly within the tray 3 due to impacts during transport of the packaged frozen food 1, which may damage the frozen food 2. The internal volume of the tray 3 is preferably 225 to 1250 cm 3 , more preferably 450 to 750 cm3 is.

[0050] As described above, in this embodiment, frozen food 2 is cooked frozen noodles (frozen spaghetti), and it is preferable that frozen food 2 contains large ingredients with a maximum diameter length of preferably 10 to 100 mm, more preferably 15 to 40 mm. The "ingredients" mentioned above refer to ingredients other than noodles that are solid at room temperature and pressure in the cooked frozen noodles. As ingredients, ingredients that can be used in dishes using noodles can be used without any particular restrictions, and examples include meat, seafood, eggs, vegetables, and mushrooms, and these can be used alone or in combination of two or more. The "maximum diameter length" refers to the maximum value among the maximum diameter lengths of the projected image of an ingredient (large ingredient) in any one direction. In order to sufficiently heat the large ingredients contained in frozen food 2 by microwave heating packaged frozen food 1, it is necessary to adjust the heating conditions, such as setting the microwave heating output high or lengthening the heating time. However, with the packaged frozen food for microwave cooking of the present invention, an appropriate amount of water vapor is maintained in storage section 40 during microwave heating, so that even without adjusting the heating conditions, the noodles are prevented from burning, and the original desirable texture and flavor of the large ingredients and noodles can be enjoyed. [Example]

[0051] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0052] [Examples 1 to 5 and Comparative Examples 1 and 2] A cooked frozen food prepared by the method described below was placed in a tray, and the tray was then placed in a packaging bag and sealed to produce a packaged frozen food having the same basic configuration as packaged frozen food 1 shown in Figure 1. Specifically, both ends of a polypropylene film (sheet material) in one direction were joined by heat sealing to form a back seal portion, forming the film into a cylindrical body. A tray containing cooked frozen food was placed into an opening at one axial end of the cylindrical body, and then the openings at both axial ends of the cylindrical body were sealed by heat sealing to form a pair of short side edges consisting of the sheet material joint portion. In the process of forming such short side edges, sealing conditions such as heating temperature were appropriately changed to form one desteaming portion with relatively low interlayer bonding strength in the center of each of the pair of short side edges in the extension direction (width direction of the packaging bag), as in packaging bag 4 shown in Figure 4. In this way, packaged frozen foods were produced in polypropylene pouches that were vapor-impermeable. The interlayer bond strength of the short edge of the pouch was measured using the method described above, and the strength was 5 N in the desteaming section (closed state) and 20 N in the section where the desteaming section was not placed.

[0053] Examples 6 to 12 Using the packaged frozen food of Example 3 as a reference, the maximum expansion volume of the packaging bag was changed as appropriate by adjusting the length of the containing section of the packaging bag in the direction parallel to the short side edge (width direction of the packaging bag). Packaged frozen foods were produced in the same manner as in Example 3 except for the above points.

[0054] (Production of pre-cooked frozen foods) Cooked frozen spaghetti was produced as a cooked frozen food. Specifically, commercially available dried spaghetti was boiled to a boiling yield of 220 to 240% by mass, and then the boiled spaghetti was cooled by placing it in cold water. 190 g of the cooled boiled spaghetti was placed in a tray, and 40 g of peperoncino sauce was poured on top of the boiled spaghetti noodle block. After that, two pieces each of eggplant, okra, and bacon, each with a maximum diameter of 40 mm, were placed on top as solid ingredients to obtain cooked spaghetti (cooked food). The cooked spaghetti was quickly frozen together with the tray at -35°C, and then removed from the tray to produce the desired cooked frozen spaghetti (cooked frozen food). The volume of the produced cooked frozen food was 300 cm 3 The volume was calculated by placing the cooked frozen food in water and calculating the increase in the volume of the water.

[0055] [Evaluation Test 1] Examples 1 to 5 and Comparative Examples 1 and 2 were evaluated. The unopened packaged frozen foods to be evaluated were each heated in a microwave oven until the desteaming section opened. After such microwave heating, the packaged frozen foods were visually observed and evaluated for the presence or absence of liquid seeping out from the desteaming section. Ten samples were prepared for each type of packaged frozen food to be evaluated, and the number of samples in which liquid was observed to have seeped out from the desteaming section (the number of seeping samples) was counted. The fewer the number of seeping samples, the higher the evaluation. The evaluation results for the number of seeping samples are shown in Table 1 below, along with the dimensions of each part of the packaged frozen food.

[0056] [Table 1]

[0057] [Evaluation Test 2] Examples 6 to 12 were evaluated. The unopened packaged frozen foods to be evaluated were heated in a microwave oven at 500W for 5 minutes and 30 seconds, making the cooked frozen food inside edible. After such microwave heating, the packaging bags of the packaged frozen foods were visually inspected to evaluate whether or not there were any openings in the desteaming section. Ten samples were prepared for each type of packaged frozen food to be evaluated, and the number of samples in which openings in the desteaming section were found (number of samples with openings in the desteaming section) was counted. The higher the number of samples with openings in the desteaming section, the higher the evaluation. After microwave heating, the packaging bags of the packaged frozen foods were opened and the contents (cooked spaghetti in a tray) were removed and visually evaluated for the presence or absence of burnt noodle blocks. Ten samples were prepared for each type of packaged frozen food to be evaluated, and the number of samples in which burnt noodle blocks were observed (number of burnt noodle block samples) was counted. The fewer the number of burnt noodle block samples, the higher the evaluation. In addition, the microwave-heated cooked spaghetti was eaten by a panel of 10 experts, who evaluated the quality according to the following criteria. The average of the scores of the 10 experts was used as the evaluation result for the subject. The results of the above are shown in Table 2 below, along with the dimensions of each part of the packaged frozen food.

[0058] <Spaghetti quality evaluation criteria> 5 points: The noodles and ingredients have a good texture, are cooked evenly, and are extremely good. 4 points: The noodles and some of the ingredients have lost a little of their texture, but they are cooked fairly evenly and are good. 3 points: The noodles and some of the ingredients are slightly less chewy, or the texture and flavor are slightly reduced due to burning, making it slightly unsatisfactory. 2 points: The noodles and some of the ingredients have lost their chewiness, or the texture and flavor have deteriorated due to burning, making the product unsuitable. 1 point: The texture of the noodles and some of the ingredients has significantly decreased, or the texture and flavor have been significantly reduced due to burning, making the product extremely poor quality.

[0059] [Table 2]

[0060] As shown in Table 2, in Example 12, eight samples had holes in the desteaming section, and the remaining two samples had their desteaming sections not opened by microwave heating in Evaluation Test 2. One of the main reasons for this is that the maximum expansion volume occupancy rate of 730% was too high. The results in Table 2 show that the maximum expansion volume occupancy rate, i.e., the "ratio of the maximum expansion volume of the packaging bag to the volume of the cooked frozen food," is preferably around 550 to 680%, which is in the range of Examples 7 to 11. Two samples of Example 12 in which the desteaming section did not open were heated in a microwave oven until the desteaming section opened immediately after conducting Evaluation Test 2. The Reference Example in Table 2 is a re-microwave heating of Example 12, and the cooked spaghetti was found to have a deteriorated texture and flavor due to scorching. The results of this Reference Example show that in packaged frozen foods in which the maximum expansion volume occupancy rate is set too high, continuing microwave heating until the desteaming section of the packaging bag automatically opens may result in the cooked frozen food being overheated and scorched. [Explanation of symbols]

[0061] 1. Packaged frozen foods for microwave cooking 2. Pre-cooked frozen meals 3 trays 30 Bottom Wall 31 Peripheral wall 310 Long side wall 311 Short side wall 4 Packaging bag 40 Storage section 41 Long edge 42 Short edge 5 Sheet material 50 Sheet material joint 6 Devaporation section X3 Tray length direction Y3 Tray width direction X4 Longitudinal direction of packaging bag Y4 Width direction of packaging bag

Claims

1. A packaged frozen food for microwave cooking, comprising a cooked frozen food, a tray for accommodating the cooked frozen food, and a steam-impermeable packaging bag containing a storage section and for sealingly accommodating the cooked frozen food and the tray in the storage section, The tray has a bottom wall and a peripheral wall extending from the peripheral edge of the bottom wall, The packaging bag has a rectangular shape in a plan view, and has a pair of long side edges extending in a longitudinal direction and a pair of short side edges extending in a width direction perpendicular to the longitudinal direction, and the storage section is located between one and the other of the pair of short side edges, a desteaming section for discharging water vapor from inside the packaging bag to the outside is disposed on at least one of the pair of short side edges, the desteaming section being closed when the packaged frozen food is in an unheated state, but being automatically opened by an increase in internal pressure of the packaging bag that occurs when the packaged frozen food is heated by microwaves; A packaged frozen food for microwave cooking, wherein L1 is the maximum length of the tray in a direction parallel to the long side edge of the packaging bag, H is the maximum height of the tray, and L2 is the maximum length of the storage section in a direction parallel to the long side edge of the storage section when the contained item is removed from the storage section and the packaging bag is folded, and the ratio of L2 to the sum of L1 and H is 107 to 117%.

2. 2. The packaged frozen food for microwave cooking according to claim 1, wherein the ratio of the maximum expansion volume of the packaging bag to the volume of the cooked frozen food is 550 to 680%.

3. 3. The packaged frozen food for microwave cooking according to claim 1, wherein the cooked frozen food is cooked frozen noodles and includes a large ingredient having a maximum diameter of 10 to 100 mm.

4. The pair of short side edges each have a sheet material joint portion where sheet materials constituting the packaging bag are overlapped and the opposing sheet materials are joined to each other, 3. The packaged frozen food for microwave cooking according to claim 1, wherein the desteaming section has a lower interlayer bonding strength at the joint of the sheet material than a non-desteaming section in the short side edge portion.

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