JP2001055276A - Foodstuff container for microwave oven and foodstuff package for microwave oven - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a foodstuff container for a microwave oven and a foodstuff package using the foodstuff container which serves to uniformly heat foodstuffs to be cooked and to reduce a heating time by a method wherein steam generated from the surface of the foodstuffs when heated by the microwave oven is utilized for a temperature rise at a portion of the foodstuffs, which is positioned at a bottom of the container. SOLUTION: This microwave-transmittable container is used for heating foodstuffs to be cooked by a microwave oven. The container is composed of a bottom plate 10, a side wall 20 extending upward from a circumferential edge of the bottom plate 10, and a lid for closing the container by joining to an upper edge of the side wall 20. At least a portion of the side wall 20 is constituted double, thereby forming a flow passage 70 for causing steam generated from the surface of the foodstuffs to be cooked when heated by the microwave oven to flow down toward the underface of the bottom plate 10, and an air port 30 communicating with the flow passage 70 to introduce the steam is provided at an upper part of the container.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method of filling cooked foods such as gratin, lasagna, curry and rice (hereinafter collectively referred to as "cooked foods" unless otherwise specified) and storing them at room temperature, refrigerated, or frozen. The present invention relates to a food container to be stored and heated by microwaves at the time of use, and to a food package using the food container. In particular, the food container and the food package of the present invention can be uniformly heated when the filled cooked food is heated in a microwave oven, thereby enabling uniform heating and shortening the heating time. Things.

[0002]

2. Description of the Related Art Heretofore, packaged foods have been marketed which can be used simply by filling cooked foods into containers, storing them in a frozen state, and heating the foods as they are in a microwave oven. The container used for the packaged food is usually made of a microwave transmitting material. When the packaged food is heated in a microwave oven, the temperature of the cooked food located near the surface layer of the cooked food and the side wall of the container rises quickly, but the temperature of the cooked food near the bottom plate of the container, especially near the center of the bottom plate, increases. There is a problem that the rise is slow and uneven heating occurs as a whole.

[0003] This uneven heating is particularly noticeable when the frozen food is heated in a microwave oven. The cause is said to be due to the characteristics of microwaves emitted from the magnetron of the microwave oven. That is, frozen food is -18 ° C
It is generally stored at the following temperature, and the water content is in the form of ice. The dielectric constant of microwaves with respect to ice is much lower than that of water, and it takes considerable energy to melt to water. However, once melted into water, the dielectric constant of microwaves is said to rise sharply, making it easier to raise the temperature by about 400 times than ice. For this reason, when the frozen food filled in the container is heated in a microwave oven, the ice located near the surface layer and the side wall which is likely to be irradiated with microwaves melts first and becomes a water state, and only that part is melted. Heating is selectively promoted. On the other hand, ice located near the center of the bottom plate does not easily melt. As a result, a hot portion and a cold portion are generated, and uneven heating occurs. Then, when the whole is heated to a required temperature, the previously melted portion becomes overheated, and the cooked food becomes undesirable in terms of flavor and organization.

[0004] Under such circumstances, various containers have been developed to minimize uneven heating when cooking food is heated in a microwave oven. For example, in order to accelerate the temperature rise in a portion where the temperature rises slowly, particularly a portion located near the center of the bottom plate of the container, a structure in which the portion is raised to the bottom, or a peripheral wall surface (side wall) of the container or at least the A food package in which the inner surface (inner surface), rim (flange), corners, etc. are covered with a microwave reflecting material or an impermeable material, and the bottom surface (bottom plate) is formed of a microwave transmitting material (Japanese Patent Publication No. 59-6789) ) Is disclosed.

Further, a vent (exhaust port) or a discharge valve is provided at the top of the lid of the container to discharge water vapor generated from the surface layer of the cooked food, which has a rapid temperature rise, so that the upper layer can be removed. Food containers for microwave ovens that prevent overheating and contribute to uniform heating (Japanese Patent Application Laid-Open Nos. 61-173028 and 8-324465) have also been proposed.

[0006]

As described above, various containers for uniformly heating cooked foods in a microwave oven have been developed. However, in the case of the container in which the center portion of the bottom plate is raised, the raised bottom is used. Part of the cooked food becomes less bulky. Therefore, the temperature rise of the raised bottom part is accelerated to some extent, but from the viewpoint of uniform heating, heating unevenness is still not eliminated, and the filling amount of cooked food is reduced,
There is also a problem that the container is bulky.

In the container disclosed in Japanese Patent Publication No. 59-6789, the side wall or flange and the corner of the container are simply covered with a microwave impervious material. Although an extreme rise in temperature of the food is suppressed, overheating of the surface layer of the cooked food cannot be prevented. In addition, since the action of the microwave on the central portion of the container, particularly the portion located near the center of the bottom plate, is still small, there is a problem that the whole cannot be uniformly heated to obtain cooked food without uneven heating.

Further, the containers disclosed in the above-mentioned Japanese Patent Application Laid-Open Nos. 61-173028 and 8-324465 disclose water vapor generated from the surface of cooked food through an exhaust port provided at the top of a lid. Due to the discharge, extreme overheating of the upper part is avoided, but overheating of the cooked food located near the side wall of the container is not avoided. In addition, it takes a long time to heat the whole to a required temperature, and it still does not eliminate the uneven heating. As described above, the conventional food containers for microwave ovens have a problem in that the cooked foods uniformly stored in the containers cannot be uniformly heated without any difference in the range, so that the usage mode is limited. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to promote the heating of cooked food filled in the bottom of a container so as to achieve uniform heating as a whole. It is. That is, the present invention contributes to uniform heating and shortening of the heating time by effectively utilizing the steam generated from the surface of the cooked food when heating the cooked food in the microwave oven to raise the temperature of the cooked food at the bottom of the container. Microwave food containers,
Another object is to provide a food package using the food container.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a food container for a microwave oven as described below and a food package using the food container for a microwave oven. That is, the food container for microwave oven of the present invention,
A microwave permeable container for heating cooked food in a microwave oven, comprising a bottom plate, a side wall extending upward from a peripheral edge of the bottom plate, and a lid joined to an upper edge of the side wall to close the container. Then, at least a part of the side wall is formed as a double, and a steam generated from the surface when the cooked food is heated by the microwave oven forms a flow path for flowing down to the lower surface of the bottom plate, and communicates with the flow path. A vent hole for taking in the steam by means of an upper portion of the container. The food package for microwave oven of the present invention, when filling the food container for microwave oven with cooked food and heating with a microwave oven, takes in steam generated from the surface of the cooked food from the vent hole and flows down the flow path. Then, it is guided to the lower surface of the bottom plate to promote the heating of the cooked food filled in the bottom of the container. Here, the food package for a microwave oven may be covered with a synthetic resin film, and an exhaust hole for discharging steam may be provided in the synthetic resin film at a position substantially corresponding to the center of the bottom surface of the container.

[0011]

Embodiments of the present invention will be described below in detail. The present invention relates to a microwave-permeable food container for a microwave oven and a food package filled with cooked food and heated by a microwave oven during use. The container is made of a microwave-transmitting material such as a composite material of glass, pottery, paper or the like as a main component and coated with a synthetic resin, or a synthetic resin. However, a container made of a synthetic resin is particularly preferable in consideration of economy. Suitable synthetic resins include thermoplastic synthetic resins such as polyethylene, polypropylene, polystyrene, polyethylene terephthalate, polyvinyl chloride, and polyacrylonitrile-butadiene-styrene. After these resins are formed into a sheet, a container is formed by vacuum forming, pressure forming, compression molding, or by injection molding after melting the resin.

The portion in which the cooked food is stored includes a bottom plate and side walls extending upward from the periphery of the bottom plate. The bottom plate or the side wall is provided with legs having a height of about 3 to 10 mm extending downward as necessary. The legs may extend downward from the lower surface of the bottom plate, or may extend continuously from the side walls. With the legs, the bottom plate is placed away from the bottom of the microwave oven, so in addition to guiding steam, it is also possible to guide microwaves reflected upward from the bottom of the microwave oven to the bottom surface of the bottom plate Become. A lid made of a microwave transmitting material is joined to the upper edge of the side wall, and the container is closed. A flange (flange) that extends horizontally (parallel to the bottom plate) may be provided at the upper end of the side wall as necessary, and a lid may be attached to this flange after cooking food is filled, or before or after freezing. .

In the present invention, at least a part of the side wall of the container formed into an appropriate shape as described above is doubled to form a flow path for flowing down the steam. This channel, as described later, is for guiding the steam generated from the surface of the cooked food when heated in a microwave oven to the lower surface of the bottom plate, and may be provided over the entire side wall or at a required width. It may be provided partially. When the flow path is provided in the entire side wall area, the second side wall is continuously extended downward from the entire circumference of the flange to form a double side wall. When the flow path is provided in a part of the side wall, the second side wall is formed outside the side wall. It is provided so as to protrude with an appropriate width over the top and bottom. In any case, the flow path may be extended to below the bottom of the container to cover the bottom plate to form a double bottom. In the case of a double bottom covering the entire bottom plate, an exhaust port for discharging steam is provided at the bottom.

At the upper portion of the container provided with the flow path for allowing the steam to flow down on the side wall as described above, a ventilation hole for taking in the steam is provided in an arbitrary size so as to communicate with the flow path.

In the present invention, the above-mentioned container is filled with the cooked food, and then a lid made of a microwave transmitting material is covered to obtain a food package. The filling height of the cooked food is set to a position slightly below the ventilation hole. When this food package is heated in a microwave oven, the temperature of the upper layer portion of the filled cooked food rises quickly, so that steam, particularly steam, is generated from the surface of the food. After the vapor fills the head space of the container, it is taken in from the vent and flows down the flow channel to reach the bottom plate bottom surface,
It promotes the heating of the cooked food filled in the container bottom together with the microwave. In this manner, the heating of the cooked food at the bottom of the container is promoted by the effective use of steam, so that uniform heating can be achieved as a whole and the heating time can be shortened.

In the present invention, the whole food package is covered with a synthetic resin film, and an exhaust hole for discharging steam is provided in the synthetic resin film at a position substantially corresponding to the center of the bottom surface of the container. It can be a food package. When this food package is heated in a microwave oven, the steam generated from the surface of the cooked food is taken in from the ventilation hole, and is intensively discharged from the exhaust hole via the flow path. As a result, a lot of high temperature steam contacts the center of the container bottom plate,
Heating of the cooked food located near the center of the bottom of the container is particularly facilitated, and enables uniform heating in a shorter time.

[0017]

EXAMPLES Hereinafter, four examples of a food container for a microwave oven according to the present invention and a food package using the food container will be described with reference to the drawings, and the results of comparative tests with comparative examples will be described. .

Embodiment 1 FIG. 1A is a perspective view showing a first embodiment of a food container for a microwave oven according to the present invention.
FIG. 1B is a cross-sectional view taken along the line XX ′ in FIG. With respect to the oval bottom plate (10), its periphery (10
A side wall (20) extends upward from d). Bottom plate (1
0) The inner surface (10a) has a major axis of 125 mm x a minor axis of 115 mm,
The height of the inner surface (20a) of the side wall (20) is 20 mm and its effective volume is 220 ml. The upper end of the side wall (20) is continuous with the second side wall (40) via the flange (22). The second side wall (40) extends downward from the entire periphery of the flange (22) to form a double side wall, and extends to a position lower than the bottom plate (10). For this reason, this container has a lower leg (4) which is lower than the bottom plate (10) of the second side wall (40).
Stand in step 1). The height of the leg (41) is preferably about 3 to 10 mm.

The flange (22) has a flange slope (23) whose diameter increases from the upper end of the side wall (20) toward the flange upper surface (24). The flange slope (23)
Is partially recessed in the major axis direction and the flange slope recess (23)
a) is formed. Then, the flange slope recess (23)
In (a), a circular ventilation hole (30) penetrates. In the figure, two flange slope recesses (23a) are provided on the major axis and one ventilation hole (30) is provided, but the number of flange slope recesses (23a) and the number of ventilation holes (30) are arbitrary. Yes, and the ventilation holes (30) may be installed in the upper part of the flange slope (23) or the side wall (20). This container is suitable for production by sheet molding.

After filling the container having the above structure with 200 g of gratin, the container was sealed with a lid (not shown) and frozen at -18 ° C. to obtain a food package. Further, the entire surface of the food package is covered with a synthetic resin film (not shown), and a steam exhaust hole having a diameter of about 10 mm is formed in the synthetic resin film at a position corresponding to the center (10c) of the bottom plate (10). To provide an exhaust port (80).

As described above, in the container of the first embodiment, the vent hole (3) is formed in the concave portion (23a) of the flange slope which is the upper portion of the container.
0), a double side wall is formed by the second side wall (40), and the second side wall (40) stands on the leg (41).
The bottom plate (10) communicates from the upper surface (10a) to the lower surface (10b). Therefore, steam generated from the surface of the cooked food heated by the microwave passes through the ventilation hole (30), and the outer surface (20b) of the side wall (20), the outer surface (22a) of the flange (22), and the second surface. It flows down through the flow path (70) surrounded by the inner surface (40a) of the side wall (40), and is guided to the lower surface (10b) of the bottom plate (10). Thereby, the heating of the cooked food filled in the container bottom is promoted, and the cooked food is uniformly heated evenly and the heating time is shortened, as shown in a test example described later.

Embodiment 2 FIG. 2A is a perspective view showing a second embodiment of a food container for a microwave oven according to the present invention.
FIG. 2B is a cross-sectional view taken along the line XX ′ in FIG. Similar to the container of the first embodiment, the periphery of the bottom plate (10) (10
Extending upward from d) is a side wall (20) and a concave side wall (20 '). The bottom plate (10) is substantially elliptical with a recess in the major axis direction, and a recess side wall (20 ') extends from the recessed portion of the bottom plate (10). The upper end of the concave side wall (20 ') is provided with a second side wall step (4) extending parallel to the bottom plate (10).
Through 2), it continues to the second side wall (40). The second side wall (40) smoothly continues to the side wall (20) and has a bottom plate (1).
The smooth elliptical ring is formed by both (20) and (40) by compensating for the concave portion of (0). Sidewall (20) and second
At the upper end of the side wall (40), a flange (22) is provided on the bottom plate (1).
0), the side wall (20) and the second side wall (4).
The lower end of 0) extends to a position lower than the bottom plate (10) and forms legs (21) (41).

An air hole (30) is provided in the middle of the second side wall step (42). The vent hole (30) may enter the vent hole (30) depending on the content to be filled, and thus is formed in a horseshoe-shaped curved shape by the slit. The space surrounded by the outer surface (20'b) of the concave side wall (20 ') and the inner surface (40a) of the second side wall (40) is hollow and forms a flow path (70). The leg (21) of the side wall (20) at a position separated from the ventilation hole (30) is cut out to form an exhaust port (80). Although the figure shows an example in which the concave side wall (20 ') bulges inward of the side wall (20), the concave side wall (20') may bulge outward of the side wall (20). It may be made to hang from the bottom plate upper surface (10a) so as not to be continuous with the peripheral side wall (20). This container is suitable for production by injection molding.

After filling the container having the above structure with 200 g of gratin, the flange (22) was sealed with a sheet-like lid (60), and was frozen at -18 ° C to obtain a food package. The heating results of this food package are shown in the test examples described later.

Embodiment 3 FIG. 3A is a perspective view showing a third embodiment of a food container for a microwave oven according to the present invention.
FIG. 3B is a cross-sectional view taken along the line XX ′ in FIG. The container of the third embodiment has a double container structure. Similar to the container of the first embodiment, the inner container has a side wall (2) extending upward from the periphery (10d) of the oval bottom plate (10).
The flange upper surface (24) extends parallel to the bottom plate (10) at the upper end thereof, and the flange hanging portion (25) extends downward from the periphery thereof. Similarly, the outer container has a second side wall (40) extending upward from the periphery (50d) of the elliptical second bottom plate (50), and a second side wall flange (43) at the upper end thereof. Then, the second side wall flange (43) is fitted in a gap surrounded by the flange upper surface (24) and the flange hanging portion (25), and the inner container is stored and fixed in the outer container.

A ventilation hole (30) penetrates through the upper part of the side wall (20), and an exhaust port (80) penetrates through the lower part of the second side wall (40), so that a gap between the inner container and the outer container is formed. Channel (7
0).

After filling the container having the above structure with 200 g of gratin, the upper surface (24) of the flange was sealed with a lid (not shown) and frozen at -18 ° C to obtain a food package. The heating results of this food package are shown in the test examples described later.

Embodiment 4 FIG. 4 (a) is a perspective view showing a fourth embodiment of a food container for a microwave oven according to the present invention.
FIG. 4B is a sectional view taken along the line XX ′ in FIG. The container of the fourth embodiment includes a second side wall (40) and a second side wall (40).
The bottom plate (50) and the lid (60) are composed of one sheet. Similar to the container of the first embodiment, the bottom plate (1
0), the side wall (20) extends upward from the periphery (10d),
At its upper end, a flange (22) extends parallel to the bottom plate (10). When one sheet of synthetic paper or the like is folded and surrounded, the second side wall (40) bulges out of the side wall (20) to form a channel (70). Side wall (20)
The upper vent hole (30) and the vent hole (21a) cut out in the leg (21) are arranged vertically above and below the position facing the second side wall (40).

After filling the container having the above structure with 200 g of gratin, the container was frozen at -18 ° C to obtain a food package. The heating results of this food package are shown in the test examples described later. In any of the above embodiments, in order to increase the heat exchange in the bottom plate (10), fins for heat exchange may be provided on the bottom plate (10) or the area may be increased by providing irregularities. Further, a partition for guiding the steam introduced to the lower surface (10b) of the bottom plate (10) to the center (10c) thereof may be provided.

Test Example: In order to confirm the effects of the food containers for microwave ovens of Examples 1 to 4, the food package obtained in each of the examples was placed in a microwave oven (model: EMO- manufactured by Sanyo Electric Co., Ltd.).
Heating was performed for 5 minutes and 30 seconds at VA4), and the temperature change was measured. As a comparative example, FIG.
The conventional container shown in (b) was used. This container is shown in FIG.
(A) From the container of the second embodiment shown in (b), the vent hole (3
0) and the second side wall (40) are removed.
This was filled with 200 g of gratin, covered, and frozen at −18 ° C. to obtain a food package. Then, in order to prevent rupture, a hole having a diameter of 10 mm was formed in the lid (60), and the lid was heated in the same microwave oven for 6 minutes, and the temperature change was measured in the same manner. The measurement point of the temperature is inside the cooked food at the position shown in the plan view of FIG. 6, and the temperature after heating is as shown in Table 1.

[0031]

As is clear from Table 1, the food package obtained in each of the examples has a high temperature at the central portion (T1), a short-peripheral edge (T2) and a long-peripheral edge (T3). The temperature has risen to about the same degree as that of, and the whole is uniformly heated. In contrast, the food package of the comparative example was heated for 30 seconds longer than the heating time of the food package obtained in each example, but the central portion (T
It is clear that the temperature of 1) is low, and there is a large temperature difference between the peripheral portions (T2) and (T3), which causes uneven heating. In order to elevate the central part to a required temperature (about 60 ° C.), heating for about one minute is further required, during which the peripheral parts (T2) and (T3) are heated more than necessary, which is organizationally favorable. Is no longer.

From Table 1 and the results of the observation, when the food for cooking, such as gratin, is filled in the microwave oven container of the present invention and heated in the microwave, about 3 minutes 30 seconds after the heating, the surface layer of the cooking food is obtained. The part is heated to generate steam from its surface, and the steam is taken in from the vent hole (30) and reaches the lower surface (10a) of the bottom plate (10) via the flow path (70). It is believed that the steam heats the bottom cooked food with microwaves for about the remaining two minutes, thereby accelerating the temperature rise, allowing for reduced heating time and uniform heating.

[0034]

The food container for a microwave oven according to the present invention has a steam vent at the top and a channel at the side wall, so that a food package using this container can be heated by a microwave oven. Vapor generated in the head space is taken in from the ventilation hole and guided to the lower surface of the bottom plate via the flow path.
Therefore, the steam is effectively used to promote the heating of the cooked food filled in the bottom of the container, thereby shortening the heating time and enabling uniform heating.

[Brief description of the drawings]

1 is a perspective view showing a first embodiment of a food container for a microwave oven according to the present invention.

FIG. 2 is a perspective view showing a second embodiment of the food container for a microwave oven according to the present invention.

3 is a perspective view showing a third embodiment of a food container for a microwave oven according to the present invention.

FIG. 4 (a) is a perspective view showing a fourth embodiment of the food container for a microwave oven according to the present invention.

5A is a perspective view showing a food container for a microwave oven of a comparative example. FIG.

FIG. 6 is an explanatory plan view showing temperature measurement points in the food package for a microwave oven.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Bottom plate 10a Upper surface of bottom plate 10b Lower surface of bottom plate 10c Center of bottom plate 10d Perimeter of bottom plate 20 Side wall 20 'Recess side wall 20a Inner surface of side wall 20b Outer surface of side wall 20'b Outer surface of concave side wall 21 Side wall leg 21a Side wall ventilation Mouth 22 Flange 22a Outer surface of flange 23 Flange slope 23a Flange slope recess 24 Flange upper surface 25 Flange hanging portion 30 Vent hole 40 Second side wall 40a Inner surface of second side wall 40b Outer surface of second side wall 41 Leg of second side wall 42 Second Side wall step 43 Second side wall flange 50 Second bottom plate 50d Peripheral edge of second bottom plate 60 Cover 70 Flow path 80 Exhaust port

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Keisuke Shimizu 1-6-2 Hanakoganei Minamicho, Kodaira-shi, Tokyo 510 Shatai-popo (72) Inventor Keisuke Sasaki 63 Aoyagi, Sayama-shi, Saitama 14-305F, Shin-Sayama Heights Term (reference) 4B035 LC12 LE11 LP16 LP45 LT16

Claims (3)

[Claims] 1. A microwave permeable container for heating cooked food in a microwave oven, wherein the container is closed by joining a bottom plate, a side wall extending upward from a peripheral edge of the bottom plate, and an upper edge of the side wall. A lid, wherein at least a part of the side wall is formed in a double form, and a channel for flowing steam generated from the surface of the cooked food by the microwave oven to the lower surface of the bottom plate is formed. A food container for a microwave oven, wherein a vent hole for taking in steam by communicating with a road is provided at an upper portion of the container. 2. A food container for a microwave oven according to claim 1, which is filled with cooked food and heated by a microwave oven, the steam generated from the surface of the cooked food is taken in from a vent hole to flow down a flow path. A food package for a microwave oven, wherein the food package is guided to a lower surface of a bottom plate to promote heating of cooked food filled in a container bottom. 3. The food package for a microwave oven according to claim 2, which is covered with a synthetic resin film, and an exhaust hole for discharging steam is formed in the synthetic resin film at a position corresponding to substantially the center of the bottom surface of the container. Food package for microwave oven provided.