JP2001163377A - Frozen food container and frozen food able to be evenly heated by microwave oven - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a container with which dense watery frozen food such as stew or soup can be heated evenly in a microwave oven. SOLUTION: This is a heat resistant tray shaped plastic container for frozen food having a roughly square outer edge and a food storage part in its center. The plane projection of the food storage part is roughly 2N square shape when N is an integer of 4 or 6 and the volume of stored food is 0.15 or more times of the smallest diameter of the storage part. Water contained in the frozen food stored in the tray shaped container is 70% or more, and apparent specific gravity when the food is frozen is 0.92 or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-resistant plastic tray-shaped container for frozen food which can be served on a table only by heating and cooking in a microwave oven, and a frozen cooked food stored in the container.

[0002]

2. Description of the Related Art With the spread of microwave ovens, frozen cooked foods compatible with microwave cooking have become widespread.
However, conventional frozen cooked food in a container is particularly difficult to cook in a microwave oven, especially for frozen cooked food such as gratin, doria, curry, and stew, which has a large amount of water and is tightly packed in a container. It was difficult to heat, and it was often found that even though a part of the food after heating was heated to such a degree as to cause burns, the other part remained cold and in extreme cases was in a frozen state.

[0003] It is understood that such non-uniform heating occurs by the following mechanism. That is, in microwave heating of frozen cooked foods, the dielectric loss of the food itself is significantly different between the frozen and thawed parts, and the dielectric loss in the thawed part is large, so that the heating is remarkably accelerated. The defrosted portion caused by the wave focus effect is heated to a significantly higher temperature, unlike the portion far from the focus, resulting in non-uniform heating. Since the microwave penetrates almost perpendicularly from the surface of the container, the focusing effect is considered to be derived only from the shape of the side wall portion in a container having a wide opening and a shallow space such as a tray-shaped container.

Some inventions have been made for the purpose of reducing such uneven heating. Frisco Juandu SA
(Japanese Patent Publication No. 59-6789) proposes a tray in which the side and rim of the tray are covered with microwave impermeable material, and the bottom is made of microwave transparent material or the tray can be removed. By controlling the microwave penetration of
It was pointed out that the contents could be heated uniformly by microwave heating. However, if the microwave impermeable material covering the side and the rim is a conductive material such as a commonly used metal foil, depending on its shape, there is a risk of sparking when heated in a microwave oven, In addition, the step of coating the portion of the tray becomes complicated, and it has been difficult to provide an economical container.

[0005] Toyo Seikan Co., Ltd. (Patent Registration No. 2522355) provides a spherical projection at the center of the bottom of a cylindrical container so as to protrude below the container, and concentrates microwaves on the projection to generate a heating point. In addition, a proposal has been made to make it possible to uniformly raise the temperature of the contents by a method of canceling the microwave focusing effect derived from the side wall portion. However, the container of the present invention is limited to a cup-like deep container, and it is difficult to apply the present invention to a tray-like shallow container.

[0006]

The problem to be solved by the present invention is to heat the food in a microwave oven even for dense frozen food such as gratin, doria, curry, stew and soup. The present invention is to realize by selecting a container capable of uniform heating from a specific shape.

[Means to solve the problem]

[0007] The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have limited the ratio between the specific polygonal shape of the food storage part and the bulk of the stored food and the minimum diameter of the container food storage part. It has been found that excellent uniform heating is possible in heating cooking in a microwave oven, and the present invention has been completed. That is, the present invention relates to a heat-resistant plastic container having a substantially rectangular outer edge portion and a food container disposed in the center, wherein the food container has a substantially 2N square planar projection shape, where N is an integer of 4 to 6. Characterized in that the bulk of the contained food is at least 0.15 times the shortest distance across the plane projection shape, referred to as the minimum diameter of the container food container of the present invention, furthermore, a tray-shaped container for frozen food, The planar projection shape of the housing portion is substantially a 2N polygon, and the angle between each side constituting the polygon is 13
2. The tray-shaped container for frozen food according to claim 1, wherein the upper portion is at 0 degrees or more, and furthermore, an upper portion selected from an elliptical shape, an elliptical shape, and a shape in which both ends of an opposing semicircular arc are connected by two straight lines at the center of the container. 3. A frozen food tray-shaped container according to claim 1, further comprising a structure, and a food storage portion provided at a lower portion thereof, and wherein the water content of the frozen food tray-shaped container is 70%. This is a frozen cooked food having an apparent specific gravity of 0.92 or more when frozen.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

First, the heat-resistant plastic container of the present invention will be described. The material constituting the heat-resistant plastic container of the present invention is a plastic having heat resistance that does not cause deformation or elution of components of the material at a temperature of 100 ° C. or higher. As the polyolefin material, heat-resistant plastics such as linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, polypropylene, and polymethylpentene are preferable. Polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polycarbonate; Fluorinated resins such as nylon (polyamide resin), polyvinylidene fluoride, polytetrafluoroethylene and polytrifluoride are also exemplified as preferred heat-resistant plastics. The heat-resistant plastic is also excellent in heat resistance, mechanical strength, texture, etc.
It is preferably selected.

[0010] In the present invention, the tray-shaped container refers to a container having a shallow container shape in which the depth of the food container is equal to or less than half the minimum diameter of the food container, and the minimum diameter is defined as the diameter of the food container. It refers to the delivery in the direction that is the smallest of the deliverys. However, in the heat-resistant plastic tray-shaped container in which the food storage portion of the present invention is disposed at the center, the food storage portion has a planar projection shape of approximately 2N square, where N is It is an integer of 4 to 6 and the bulk of the contained food is selected to be at least 0.15 times the minimum diameter of the container food container.

According to the present invention, the bulk of the stored food is selected to be at least 0.15 times the minimum diameter of the container food container, but if the bulk is at most 0.13 times the minimum diameter of the container, the container is stored. The food has a shallow shape and the side wall of the housing has a smaller relative area than the upper surface of the housing, so that the food is easily heated uniformly. On the other hand, since the food is stored in a very thin form, for example, gratin, doria, curry, stew, soup, etc. In such cooked foods, not only the contents become unstable in the storage part, but also it becomes extremely difficult to eat.

Conversely, when the volume of the stored food is 0.13 times or more the minimum diameter of the container food storage portion, the container is stable and the container is easy to eat. Since the relative area is larger than that of the upper surface, non-uniform heating is likely to occur because the microwaves entering from the side walls focus. The bulk of the contained food is generally the depth of the food
Never more than double.

The present inventors have examined various container side wall shapes. As a result, when the side wall portion is substantially flat, the microwaves entering from the side wall portion are less likely to form a clear focal point, and uniform heating is performed. Found that it is possible. Although the food storage portion formed by the substantially flat side wall portion has a polygonal planar projection shape, when the planar projection shape is a quadrangle to a heptagon, the angle formed by the side wall surfaces sandwiching the corner becomes small, When the angle is less than 130 degrees, the microwave tends to focus slightly but clearly. In the case of a planar projection shape of a polygon having an angle of 130 degrees or more and an octagon or more, the tendency to focus is clearly reduced.

The polygon of the planar projection shape selected in the present invention is approximately 2
An N-square shape is preferred. This is because symmetry is more easily obtained in the case of the even-numbered square shape than in the case of the odd-numbered square shape. Since the container is used as tableware containing frozen cooked food, a shape having at least one or more line symmetry is preferable in that it gives a sense of stability to the appearance, and a shape having two orthogonal line symmetries is further preferable. preferable.

[0015] In the 2N polygonal shape, N is preferably 4 to 6, and when N is 2 to 3 or less, the microwave tends to focus slightly but clearly for the above-mentioned reason, which is not preferable. On the other hand, when N exceeds 6, each side wall surface is divided into a small area, which is substantially close to a curved surface, and conversely, a clear focus is easily formed by the lens effect.

[0016] In the approximately 2N polygon of the planar projection shape selected in the present invention, each side length may be different, but it is a length that forms line symmetry at a point that gives a sense of stability to the eye. It is preferable to set a pair of side length and angle.

[0017] In the approximately 2N polygon of the planar projection shape selected in the present invention, the vertices formed by the sides may be rounded. The roundness is preferable in that it maintains the impact resistance of the food container, and is also easy to scoop the contents when eating the content food with a spoon or the like, but the radius of curvature is larger than the bulk of the frozen cooked food filled in the container. Is also preferably small.

The heat-resistant plastic tray-like container of the present invention is selected to have a substantially square outer edge. The term “substantially rectangular” means that two sides facing each other at the outer edge are parallel to each other and have a linear portion of a sufficient length. Although a so-called rectangular shape is also included, a sharp outer edge is not preferable from the viewpoint of impact resistance, and a shape in which a sharp corner is rounded is preferable.

A container having a substantially square outer edge has good stability with little damage to the soft packaging material due to sufficient contact between the straight portion of the container and the soft packaging when the container is wrapped with the soft packaging material. Not only is it preferable in that packaging is possible, but it has a shape excellent in impact resistance when the container is dropped, for example, when the container is dropped in the corrugated cardboard case because the contact portion increases when the container is accommodated in the outer case of the cardboard case.

[0020] The four substantially rectangular corners of the outer edge of the container constitute a sufficiently wide flat portion between the container and the food storage portion arranged in the center, and carry the frozen cooked food stored in the container after heating. Since it becomes a handle at the time, danger such as burns can be reduced.

The heat-resistant plastic tray-shaped container of the present invention comprises:
A food container having a planar projection shape of approximately 2N square (where N is an integer of 4 to 6) is disposed at the center, and an elliptical shape, an elliptical shape, and both semicircular arcs are formed on the upper portion of the food container. It is possible to arrange a superstructure selected from rectangles having the same. The upper structure is preferable in that when the container is viewed from above, the shape of the upper structure is first seen and is recognized as a shape with less discomfort as tableware.

[0022] The frozen cooked food contained in the heat-resistant plastic tray-shaped container of the present invention has a water content of 70% or more,
Foods having an apparent specific gravity of 0.92 or more when frozen are more preferably selected. In such a high-moisture, high-density frozen cooked food, the frozen water is uniformly and densely distributed as ice crystals. Since the ice crystal has a large latent heat of melting and a very small dielectric loss as compared with the thawed state, it is liable to generate remarkably non-uniform heating as compared with other frozen cooked foods.

That is, in the high-moisture, high-density frozen cooked food of the present invention, the focusing effect of the microwaves penetrating from the side wall portion is extremely large, so that uneven heating is likely to occur. The projected shape is approximately 2N square (N
Is an integer of 4 to 6), whereby an effect of clearly preventing uneven heating can be obtained as compared with other low-moisture or low-density frozen cooked foods.

In the medium / low moisture frozen cooked food having a water content of less than 70% and the medium / low specific gravity frozen cooked food having an apparent specific gravity of 0.91 or less, the water content distribution in the frozen state becomes uneven and low density. Therefore, the influence of the container shape is reduced,
Non-uniform heating is relatively reduced.

[0025] Examples of the high-moisture, high-density frozen cooked food of the present invention include gratin, doria, curry, beef struganov, risotto, porridge, stew, and soup. Even cooked food,
If the food has a water content of 70% or more and an apparent specific gravity of 0.92 or more when frozen, the container of the present invention can be effectively used. In the present invention, the water content of the frozen cooked food is less than 98.5%, and the apparent specific gravity at the time of freezing is 1.45.
Is less than.

Hereinafter, the present invention will be described with reference to examples, but the contents of the present invention are not limited to only the examples.

[0027]

Example 1 A 500 μm thick polypropylene sheet filled with 30% by weight of talc was placed in a tray-like container 1 having the shape shown in FIGS. 1 and 2 (outer peripheral shape: 177 mm long, horizontal) using a vacuum forming machine.
121 mm, depth: 32 mm). The tray-shaped container contained 250 g of macaroni gratin, and was rapidly frozen at -30 ° C. The bulk of frozen macaroni gratin is 18.4 mm
(Ratio to minimum diameter: 0.167), moisture content is 75%,
The apparent specific gravity was 1.03. Commercial microwave oven (output 50
After heating for 5 minutes using 0W), the temperature measuring device shown in FIGS. 10 and 11 was inserted to a position where the tip of the temperature measuring terminal enters the 10 mm gratin, and the temperature of each measurement point of the gratin was measured. The results are shown in Table 1.

[0028]

[Example 2] A tray-shaped container having the shape shown in Fig. 3 and Fig. 4 was formed from a polypropylene sheet having a thickness of 600 µm using a vacuum forming machine.
2 (peripheral shape: 177 mm long, 121 mm wide, depth: 32 mm)
Processed to. The tray-shaped container contained 250 g of evidria and was rapidly frozen at -30 ° C. The volume of evidria in the frozen state was 17.3 mm (ratio to the minimum diameter: 0.157), the water content was 71%, and the apparent specific gravity was 0.99. After heating in a microwave oven as in Example 1, the temperature of each measurement point of the gratin was measured. The results are shown in Table 1.

[0029]

EXAMPLE 3 A 600 μm thick polypropylene sheet filled with 30% by weight of talc was placed in a tray-like container 3 (outer peripheral shape: 177 mm long, horizontal) having a shape shown in FIGS.
121 mm, depth: 32 mm). The tray-shaped container contained 250 g of beef stew and was rapidly frozen at -30 ° C. The bulk of the beef stew in a frozen state was 17.2 mm (ratio to the minimum diameter: 0.164), the water content was 81%, and the apparent specific gravity was 1.04. Commercial microwave oven (output 600
After heating for 4 minutes using W), the temperature of each measurement point of the beef stew was measured in the same manner as in Example 1. The results are shown in Table 1.

[0030]

[Comparative Example 1] Using a vacuum molding machine, a polypropylene sheet having a thickness of 600 µm was placed in comparative tray containers 1 to 3 having the shapes shown in Figs. 7, 8, and 9 (outer peripheral shape: 177 mm long, 121 mm wide,
(Depth: 32 mm). Each comparative tray container has 250g of macaroni gratin, 250g of evidria and
After storing 250 g of beef stew in the same manner as in Examples 1 to 3 and rapidly freezing at −30 ° C., heating it for 5 minutes using a commercially available microwave oven (output 500 W), heating the food in the same manner as in Example 1 The temperature at each measurement point was measured. The results are shown in Table 1.

[0031]

[Table 1] Comparison of uniformity of microwave oven heating by container shape (Part 1)

[0032] As is clear from Table 1, it was confirmed that the frozen cooked food contained in the container having the shape according to the present invention was heated more clearly and uniformly by microwave heating as compared with containers having other shapes.

[0033]

Example 4 110 g of hard fried noodles were placed in the container of Example 2 (FIGS. 3 and 4), and 140 g of hard fried noodles were placed in the upper part thereof in a frozen state. Moisture content of hard fried noodles and ingredients is 62%,
The apparent specific gravity was 0.62. The container of Example 3 (see FIG.
5, FIG. 6) was filled with 150 g of frozen cooked rice, and 100 g of frozen oyakodon ingredients were placed thereon. The frozen rice and frozen oyakodon ingredients have a moisture content of 72% and an apparent specific gravity of 0.
It was 85. These frozen cooked foods in the container were heated in a commercially available microwave oven (output: 500 W) for 5 minutes, and the temperature at each measurement point was measured in the same manner as in Example 1. The results are shown in Table 2.

[0034]

[Comparative Example 1] In the comparative tray container 3 (Fig. 11), the hard fried noodles and the ingredients of Example 4, the frozen rice and the ingredients of the frozen oyakodon were respectively stored. The temperature at the measurement point was measured. The results are shown in Table 2.

[0035]

[Table 2] Comparison of uniformity of microwave oven heating by container shape (Part 2)

As is clear from Table 2, the frozen cooked food contained in the container having the shape according to the present invention has a lower moisture content and apparent specific gravity than the food having a high moisture content and apparent specific gravity. Although uniform heating is unlikely to occur, it was confirmed that heating by microwave oven was clearly and uniformly heated compared to containers of other shapes.

[0037]

According to the present invention, there is provided a heat-resistant plastic container having a substantially rectangular outer edge portion and a food container disposed at the center, wherein the food container has a substantially 2N square planar projection shape, where N is an integer of 4 to 6. When the frozen cooked food is stored in a frozen food tray-shaped container, wherein the bulk of the stored food is 0.15 times or more the minimum diameter of the container food storage portion, The industrial significance is extremely large in that the non-uniformity of heating can be clearly reduced as compared with containers of other shapes.

[Brief description of the drawings]

1 to 9 are a plan view or a side view of a tray-shaped container formed by processing a polypropylene sheet or polypropylene sheet filled with talc into a tray having a peripheral shape of 177 mm in length, 121 mm in width and 32 mm in depth by a vacuum forming machine. is there.

FIG. 1 is a plan view of a tray container for frozen food of Example 1.

FIG. 2 is a side view of the tray container for frozen food of Example 1.

FIG. 3 is a plan view of a tray container for frozen food of Example 2.

FIG. 4 is a side view of the tray container for frozen food of the second embodiment.

FIG. 5 is a plan view of a tray container for frozen food of Example 3.

FIG. 6 is a side view of the tray container for frozen food of the third embodiment.

FIG. 7 is a plan view of a comparative tray container 1 of a comparative example.

FIG. 8 is a plan view of a comparative tray container 2 of a comparative example.

FIG. 9 is a plan view of a comparative tray container 3 of a comparative example.

FIG. 10 is a perspective view of a temperature measuring device of an example and a comparative example.

FIG. 11 is a plan view of a temperature measuring device of an example and a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Container outer periphery and mountain-shaped fold part 2 Valley-shaped fold part 3 Ridge part of container food storage bottom

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) A47J 27/00 107 A47J 27/00 107 (72) Inventor: Tsukasa Hayashi 1210 Yoshida, Oizumi-cho, Oizumi-cho, Oraku-gun, Gunma Prefecture No. 5 Inside Ajinomoto Fresh Foods Co., Ltd. (72) Inventor Ryosuke Shimizu 1210 Yoshida, Oizumi-machi, Ouraku-gun, Gunma Prefecture No. 5 Inside Ajinomoto Fresh Foods Co., Ltd. Address 5 F-term in Ajinomoto Fresh Foods Co., Ltd. (reference) 4B023 LC07 LE13 LK20 LP15 LP19 4B036 LE05 LF01 LF19 LP17 LP19 4B046 LB10 LC12 LE15 LE18 LP69 LP71 LQ05 4B055 AA10 BA22 CA01 CB01 DB15 FB34 FB35 FB36 FB36 FB36 FB36

Claims (4)

[Claims] 1. A heat-resistant plastic container having a substantially rectangular outer edge and a food container disposed at the center, wherein the food container has a substantially 2N square planar projection shape, where N is an integer of 4 to 6. A tray-shaped container for frozen food, wherein the volume of the stored food is at least 0.15 times the minimum diameter of the container food storage part. 2. The frozen food product according to claim 1, wherein a planar projection shape of the food container is substantially a 2N polygon, and an angle between sides forming the polygon is 130 degrees or more. Tray-shaped container. 3. An upper structure selected from an elliptical shape, an elliptical shape, and a shape in which both ends of an opposing semi-circular arc are connected by two straight lines at the center of the container, and a food container is disposed at a lower portion. The frozen food tray-like container according to claim 1 or 2, wherein 4. A frozen cooked food having a water content of 70% or more and an apparent specific gravity of 0.92 or more when frozen, which is contained in the frozen food tray-like container according to any one of claims 1 to 3.