JP2003334050A - Method for thawing frozen food and thawing apparatus used for the method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for thawing a frozen food, by which the quality of the pre-frozen food can be restored, when the frozen food is thawed. <P>SOLUTION: Frozen foods are received in the thawing device, and air in the thawing apparatus is circulated with a blower 15. Each frozen food is thawed with a heating heat exchanger 14 according to a temperature pattern prescribed for each frozen food. When the thawing is finished, a damper 16 is opened to guide the outer air into the thawing apparatus and simultaneously discharge the gas in the thawing apparatus. Thereby, the temperature of the air in the thawing apparatus is approximately balanced with the temperature of the outside. When the frozen food is packaged with a packaging material and thawed, the air in the thawing apparatus is heated so that the temperature of the air in the thawing apparatus is higher than the temperature of the packaging material and the surface temperature of the frozen food. After the thawing is finished, the temperature of the air in the thawing apparatus is approximately balanced with the temperature of the outside, while the temperature of the air in the thawing apparatus is maintained higher than the temperature of the packaging material and the surface temperature of the frozen food. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for thawing frozen food and a thawing apparatus used for this thawing method.
The present invention relates to a method for preventing condensation and drying that occur when thawing a frozen food.

[0002]

2. Description of the Related Art Generally, when thawing frozen foods, in particular, cooked frozen foods that do not require processing or cooking after thawing, such as bento boxes, sushi, side dishes, confectionery, breads, etc. Is difficult to accurately control the temperature and relative humidity during thawing, and if the time-series changes in these temperature and relative humidity are not properly controlled, in unpacked frozen foods, so-called naked frozen foods, thawing In many cases, defects such as discoloration, discoloration, dryness, and swelling (fog) occur on the surface layer of foods due to drying or dew condensation. When such defects occur, the appearance, taste, texture and the like of the food are significantly deteriorated, and the commercial value is lowered. In extreme cases, the product value will be lost.

On the other hand, when packed frozen food (including frozen food in a container) is thawed, volatile substances such as acetic acid, alcohol, and flavors, which are contained substances, are contained in the inner wall of the package (container) in addition to water. May be condensed. Then, when extracting the thawed food from the thaw during or after the thaw, as described above, condensed water and other volatile substances fall or penetrate into the surface layer of the food, discoloring and fading the food. , Topping flow, and swelling may occur.

Further, during thawing, not only water and other volatile components generated from frozen foods are condensed, but also water vapor in the air present in the thawing device is condensed to form a package (including a container). If all or part of the material is hygroscopic, not only the packaging material or container is deformed due to moisture absorption, but also a so-called flow occurs in printing on the packaging material or container, which reduces the commercial value. It may end up. And in extreme cases, the commercial value is lost.

[0005] For example, when packed rice balls sold at convenience stores and bento stores are thawed in a microwave oven, the surface layer of the seaweed and rice becomes sticky, and the value of the rice balls is greatly reduced. become. On the other hand, when the bento in a container is thawed in a microwave oven, the food in contact with the container, especially the upper surface of the food, the condensed water and other volatile substances penetrate into the surface layer of the food, causing the food to discolor, sauce, etc. Flow of topping and discoloration occur.

In the commonly used defrosting method using air as the heat medium, when the defrosted food is taken out from the apparatus after the defrosting, the air temperature and the humidity (air dew point temperature) of the taken out place are inadequate. Therefore, not only dew condensation occurs in the package but also dew condensation occurs on the outer surface of the package, which causes damage to the food and the packaging material as in the case of thawing in a microwave oven. When damaged or altered or deformed,
It loses its commercial value as it becomes a different food that loses the properties of the original food.

[0007]

For this reason, in recent years, so-called chilled or normal temperature distribution has been used when providing ready-made meals to consumers. Therefore, we manufacture foods such as prepared meals,
It took a long time for the food to reach the consumer,
Considering not only the taste is deteriorated but also the normal temperature distribution, microorganisms may proliferate. In order to prevent such a problem, a food improving material, a bacteriostatic agent, or the like is used to deliver 3 to 4 flights per day. With such a delivery system, the manufacturer, the deliverer, and the store have to operate 365 days a day, 24 hours a day, and
When the unsold product or the like is generated, since the product is distributed at room temperature, it is necessary to discard the food, and the loss due to the food discard is inevitably generated.

[0008] In order to prevent such problems in chilled or normal temperature distribution, freezing of prepared meals has been attempted, but the product value is deteriorated / decreased due to the above-mentioned problems caused by thawing. At this point, very limited products such as curry and pilaf that are reheated at the same time as thawing are frozen.

The object of the present invention is to prevent the evaporation and condensation of water and other volatile substances generated when thawing frozen foods, and to prevent the foods from drying, thereby reproducing the frozen foods to the quality before freezing. It is to provide a method for thawing frozen foods that can be done.

Another object of the present invention is to provide a method for thawing frozen foods, which is safe and can maintain the quality of freshly made foods.

Still another object of the present invention is to provide a thawing device capable of reproducing frozen food to the quality before freezing.

[0012]

According to the present invention, in a thawing method used when thawing the frozen food using a thawing device for thawing the frozen food, the frozen food is stored in the thawing device. A defrosting step of storing and thawing the air in the defrosting device to defrost the frozen food according to a temperature pattern determined for each frozen food to obtain a defrosted product, and before taking out the defrosted product from the defrosting device. To approximately equilibrate the air temperature in the defroster to the temperature at the location where the defroster is installed, or approximately equalize the air dew point temperature in the defroster to the air dew point temperature at the location where the defroster is installed. A method for thawing a frozen food product is provided, which comprises an equilibration step.

As described above, during thawing, thawing is performed while circulating the air inside the thawing device, and before the thawing product is taken out from the thawing device, the temperature of the air inside the thawing device is set at the location where the said thawing device is installed. When the temperature is almost equilibrium, the defrosted product can be reproduced to the quality before freezing (that is, the freshly made quality can be retained) without dew condensation or drying. Instead, the frozen food is thawed to obtain a thawed product, so that it is possible to ensure the safety of the propagation of bacteria and the like as compared with chilled or normal temperature distribution. Before removing the defrosted product from the defrosting device, if the humidity inside the defrosting device is also adjusted to be approximately in equilibrium with the humidity at the place where the defrosting device is installed, dew condensation can be prevented more effectively, and even better. The thawed product after thawing can be reproduced to the quality before freezing.

For example, in the equilibrium step, the air in the place where the defrosting device is installed is taken into the defrosting device so that the air temperature in the defrosting device is approximately equilibrated with the temperature in the place where the defrosting device is installed. Alternatively, the air dew point temperature in the defroster is approximately balanced with the air dew point temperature in the place where the defroster is installed. In the equilibrium step, the air inside the defroster is cooled to substantially equilibrate the temperature of the air inside the defroster to the temperature of the place where the thaw is installed, or the air inside the defroster is cooled and dehumidified. The temperature of the air dew point in the defroster may be approximately balanced with the temperature of the air dew point in the location where the defroster is installed. By doing so, it is possible to easily bring the air temperature in the defrosting apparatus to a substantially equilibrium state with the temperature of the place where the defrosting apparatus is installed, and further, to determine the air temperature and humidity in the defrosting apparatus. The temperature and humidity of the installed location can be approximately balanced.

Further, when the frozen food is packaged with a packaging material, in the thawing step, the air temperature inside the thawing device is controlled to be higher than the temperature of the packaging material and the surface temperature of the frozen food, In the equilibration step, the temperature of the air inside the thawing device is controlled to be higher than the temperature of the packaging material and the surface temperature of the thawing product. When the temperature control is performed in this manner, dew condensation does not occur on the inner and outer surfaces of the packaging material, and the quality does not deteriorate when the packaged frozen food is thawed. Further, even after thawing, no condensation occurs on the inner surface of the packaging material. Moreover, when the packaging material is hygroscopic, the flow of printing ink or the like and the deformation of the packaging material do not occur.

According to the present invention, in the equilibration step, the temperature of the place where the defrosting device is installed before the defrosted product is taken out from the defrosting device is approximately equilibrated with the air temperature in the defrosting device or the defrosting is performed. The air dew point temperature at the location where the device is installed may be approximately balanced with the air dew point temperature in the defrosting device. For example, if the thawing device is large and the space at the place where the thawing device is installed (the work space where the thawed product is taken out and then packed in a box or put into cosmetic packaging after the thawing is completed) is small, the air temperature inside the thawing device or the air dew point temperature is set to Rather than equilibrating to the air temperature or air dew point temperature of, the equilibrium state of the air temperature or air dew point temperature of the work place to the air temperature or the air dew point temperature of the defrosting device should be brought to the equilibrium state quickly. In addition to the above, it is possible to reduce the energy cost for achieving a substantially equilibrium state.

According to the present invention, there is provided a thawing device used for thawing frozen food, the housing housing the frozen food, and heating means for heating the inside of the housing.
A cooling means for cooling the inside of the housing, a circulating means for circulating the air in the housing, a heating means, the cooling means, and a control means for controlling the circulating means,
The control means controls the heating means in accordance with a temperature pattern defined for each frozen food and controls the circulation means to circulate the air inside the housing to defrost the frozen food, and to defrost the frozen food. When the above is finished, the cooling means is controlled to control the air temperature in the storage housing to a predetermined temperature, thereby obtaining a thawing device. The predetermined temperature is, for example, an external temperature at which the storage case is arranged.

As described above, when the defrosted product is taken out from the defrosting device, if the temperature of the air in the storage case is controlled to the outside temperature at which the storage case is installed, the defrosted product can be prevented from being condensed and dried. Not only can the thawed product be reproduced to the quality before freezing (that is, the freshly made quality can be retained), but also because frozen foods are thawed to obtain the thawed product, chilled or normal temperature distribution is possible. Compared with this, it is possible to ensure the safety of the reproduction of bacteria.

For example, the cooling means is a damper for selectively opening the housing case to the outside, and the control means drives and controls the damper to take in the external air into the housing case. At the same time, the air inside the housing is exhausted to the outside to control the temperature inside the storage housing to the predetermined temperature. With this configuration, it is possible to easily control the temperature of the air inside the housing to the outside temperature at which the housing is installed.

Further, a dehumidifying means for dehumidifying the inside of the storage housing is provided, and the control means controls the dehumidifying means to adjust the humidity inside the storage housing to the humidity outside the storage housing. You may do it. In this way, by controlling the humidity inside the housing, the quality of the defrosted product can be further improved.

Further, when the frozen food is packaged by a packaging material, the control means causes the air temperature in the housing to be the temperature of the packaging material and the surface temperature of the frozen food when the frozen food is thawed. The temperature of the air in the storage housing is controlled to be higher than that, and after the thawing is completed, the control means makes the air temperature in the storage housing higher than the temperature of the packaging material and the surface temperature of the defrosted product. When the temperature is controlled in this way, dew condensation does not occur on the inner surface of the packaging material, and the quality of the packaged frozen food does not deteriorate when it is thawed. Further, even after thawing, no condensation occurs on the inner surface of the packaging material. Moreover, when the packaging material is hygroscopic, the flow of printing ink or the like and the deformation of the packaging material do not occur.

[0022]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below with reference to the drawings. It should be noted that the dimensions, materials, shapes, relative arrangements, and the like of the components described in the illustrated examples are not intended to limit the scope of the present invention thereto unless otherwise specified, but are merely illustrative examples. Absent.

Referring to FIG. 1, the illustrated defrosting device includes a defrosting device housing 11, which is composed of a heat insulating outer plate. A storage shelf 12 for storing food to be thawed (that is, frozen food) in the defrosting device housing 11.
Are arranged. An air rectifying plate 13 is installed around the storage shelf 12 (side surface), and the air circulating in the defroster housing 11 is conditioned by the air rectifying plate 13. Storage shelf 1
A heating heat exchanger (heating means) 14 and a blower (circulation means) 15 are arranged above the unit 2. Then, the air inside the defrosting device housing 11 is circulated by the blower 15 as indicated by a thick arrow.

An opening is formed in the heat insulating outer plate (upper surface) of the thawing device housing 11, and this opening communicates with a room in which the thawing device is installed via a duct (not shown). . The damper 16 is installed in the opening, and the damper 16 is driven by a damper driving device (not shown),
The opening is opened and closed by the damper 16. A temperature sensor (not shown) is arranged in the defrosting device housing 11, and the control device (not shown) is connected to the heating heat exchanger 14 according to the temperature detected by the temperature sensor. The heat source medium (electricity, steam, hot water, hot brine, etc.) circuit is controlled, and the damper drive device and the blower 15 are controlled as described later.

When the frozen food is thawed using the above-mentioned thaw device, first, after storing the frozen food in the storage rack 12,
When the thawing start switch is activated, the frozen food is thawed. At this time, the control device controls the damper drive device to close the opening by the damper 16 and drives the blower 15 to circulate the air inside the defroster housing 11. The temperature inside the defrosting device housing is set in advance as a temperature pattern (a pattern showing the relationship between the passage of time and temperature) for each type of frozen food, and the controller heats up based on this temperature pattern and the detected temperature. The amount of heat generated by the heat exchanger 14 is controlled. That is, the control device controls the heating heat exchanger 1 so that the detected temperature becomes the temperature indicated by the temperature pattern.
4 controls the amount of heat generated.

When the temperature inside the thawing device housing is controlled according to the above-mentioned temperature pattern and a predetermined time has elapsed (that is, when thawing is completed), the control device causes the heating heat exchanger 14 to heat the heating. While stopping, the damper drive device is controlled to drive the damper 16 and open the opening (the blower 15 is driven). As a result, outside air flows into the defroster housing 11 through the opening,
Air, moisture, and other volatile components inside the defrosting device housing 11 are discharged to the outside of the defrosting device housing 11, and the temperature inside the defrosting device housing 11 and the outside (indoor) temperature of the defrosting device housing 11 are substantially balanced. It will be.

More specifically, here, Edomae sushi packaged in a film is selected as a frozen food whose taste, texture, appearance and aroma easily change due to dew condensation upon thawing. When thawed, the results shown in FIG. 2 were obtained. In FIG. 2, is the room temperature in which the defroster is installed, is the temperature inside the defroster, is the central temperature of Edomae sushi fish, is the surface temperature of Edomae sushi fish,
Represents the surface temperature of the packaging material.

As shown in FIG. 2, the room temperature is about 30 ° C.
The temperature inside the defroster is set to about 50 ° C,
Thawed for minutes. Thereafter, as described above, the outside air was introduced and the air inside the defroster was discharged. Until the end of thawing, the fish core temperature gradually rises, but the fish surface temperature and the packaging material surface temperature rise sharply in the initial stage and then gradually rise. And after introducing the outside air, about 10
Minutes, room temperature, defroster temperature, fish surface temperature,
And the surface temperature of the packaging material became almost equilibrium. The surface temperature of the packaging material was always higher than the surface temperature of the fish.

When the Edomae sushi was thawed in this way, the temperature inside the thaw and the room temperature were made to equilibrate by introducing the outside air at the stage of the equilibration step.
No moisture or other volatile substances derived from Edomae-sushi were condensed in the package, and no condensation occurred, and no change in the quality of Edomae-sushi was observed.

Further, the frozen food (hereinafter referred to as "Ohagi in a hygroscopic cosmetic box") in which a rice ball stored in a plastic tray is put in a paper (hygroscopic) container (cosmetic box) was thawed. As a result, the results shown in FIG. 3 were obtained.
In Figure 3, is the room temperature where the defroster is installed,
Is the temperature inside the thawing device, is the central temperature of the ohagi, and is the surface temperature of the outer bottom surface of the cosmetic case.

As shown in FIG. 3, the room temperature is about 20 ° C.
After increasing the temperature inside the defroster from about 20 ° C to about 70 ° C, once lower the temperature inside the thaw (about 45 ° C).
Then, the temperature inside the defroster was raised again (about 55 ° C).
C). After the thawing was completed, the outside air was introduced and the air inside the thawing device was exhausted as described above. Until the end of thawing, both the central temperature of the ohagi and the surface temperature of the outer bottom surface gradually rise, and in about 20 minutes after the introduction of the outside air, the indoor temperature, the temperature inside the defroster, the central temperature of the ohagi surface, and the outer bottom surface temperature are in an equilibrium state. Became. The surface temperature of the outer bottom surface was always higher than the central temperature of the ohagi.

When the ohagi was thawed in this way, the temperature inside the thaw apparatus and the room temperature were equilibrated by introducing the outside air in the equilibration step.
There was no condensation or dew condensation of moisture or other volatile substances generated during thawing on the inner surface of the package, and there was no deterioration of the quality of the ohagi. Furthermore, since the temperature inside the thawing device is once lowered and then raised again (the portion indicated by A in FIG. 3), the moisture adhering to the outer bottom surface of the paper box is condensed to cause deformation of the box and printing ink. It didn't flow. In other words, if the temperature control shown by A in FIG. 3 is not performed, not only the box will be deformed due to moisture absorption of the paper box, but also the printing ink flow phenomenon will occur and the value as a product will be significantly reduced. It was Further, as shown by B in FIG. 3, since temperature control (exhaust temperature control) is performed, moisture and the like in the thawing device are exhausted together with air, and when the box is taken out, dew condensation inside the box is prevented. I was able to.

By the way, when thawing a large amount of frozen food at a time, the thawing apparatus shown in FIG. 4 is used instead of the thawing apparatus shown in FIG. The defrosting device shown in FIG.
The thawing chamber 21 is composed of a heat insulating outer plate. An air conditioning plate 13 is installed in the thawing chamber 21, and the air circulated in the thawing chamber 21 is conditioned by the air conditioning plate 13. In the example shown in the figure, two heating heat exchangers 22 and 2 are provided in the upper portion of the defroster 21 at a predetermined interval.
3 is arranged and the heat exchangers 22 and 23 for heating are arranged.
An air blower (air blower) 24 is arranged between them.

Openings are formed at two locations (both ends of the upper surface in the illustrated example) on the heat insulating outer plate (upper surface) of the thawing chamber 21, and the intake duct 25 and the exhaust duct 26 are formed in these openings. It is connected. A damper 27 is installed in each opening, and the damper 27 is driven by a damper driving device (not shown) to open and close the opening. A temperature sensor (not shown) is arranged in the defroster 21, and the control device (not shown) is connected to the heating heat exchangers 22 and 23 according to the detected temperature detected by the temperature sensor. The heat source medium (electricity, steam, hot water, hot brine, etc.) circuit is controlled, and the damper drive device and the blower 24 are controlled as described later. When thawing with the thawing device shown in FIG.
A storage shelf 28 with casters is housed in 1. Frozen food is stored in these storage shelves 28.

When the frozen food is thawed by using the above-mentioned thaw device, first, the storage shelf 28 in which the frozen food is stored is stored in the thaw chamber 21 and then the thaw start switch is activated, whereby the frozen food is stored. Thawing is performed. At this time, the control device controls the damper driving device to close the opening by the damper 27 and drives the blower 24 to circulate the air in the defroster 21. At this time, air is circulated as indicated by the thick white arrow in the figure. Then, as described below with reference to FIG. 1, the control device controls the heating heat exchangers 22 and 2 so that the detected temperature becomes the temperature indicated by the temperature pattern.
The amount of heat generated by 3 is controlled.

When the thawing is completed, the control device stops the heating by the heat exchangers 22 and 23 for heating and controls the damper driving device to drive the damper 27 to open the opening. As a result, indoor air (outside air) is introduced into the defroster 21 through the intake duct 25, and
The air, moisture, and other volatile components in the defroster 21 are discharged to the outside of the refrigerator via the exhaust duct 26, so that the inside temperature and the outside air temperature are balanced. When introducing the outside air,
Intake and exhaust are performed as indicated by thick black arrows in the figure. By using such a thawing device, a large amount of frozen food can be thawed at a time while maintaining its quality. Although two heating heat exchangers 22 and 23 are arranged in the example shown in FIG. 4, the number of heating heat exchangers is appropriately changed according to the capacity of the defroster 21.

FIG. 5 is a diagram showing another example of the decompression device according to the present invention. In FIG. 5, the same components as those shown in FIG. 1 are designated by the same reference numerals. In the example shown in FIG. 5, the defrosting device housing 11 has an opening and a damper 16.
Is not provided, and instead, a heat exchanger for cooling (cooling means / dehumidifying means) 31 is arranged inside the defrosting device housing 11. The cooling heat exchanger 31 is controlled by the controller.

As described with reference to FIG. 1, the blower 15 is driven to circulate the air in the defroster housing 11, and
Heating is performed by the heating heat exchanger 14 to raise the air temperature in the defroster housing 11. Then, when the thawing is completed, the control device lowers the air temperature inside the thawing device housing 11 by the cooling heat exchanger 31 (for example, lowers the inside temperature of the housing 11 to the outside temperature). At this time, the water and the like in the housing 11 is discharged to the outside of the refrigerator by the cooling heat exchanger 31. That is, the cooling heat exchanger 31 adjusts the humidity inside the defroster housing 11.

In this way, after the thawing is completed, even if the temperature and humidity inside the thawing device housing 11 are controlled by using the cooling heat exchanger, the thawing is performed without deteriorating the quality of the frozen food. Furthermore, as a result of adjusting the humidity inside the defrosting device housing 11 (dehumidification), it is possible to more efficiently prevent the occurrence of dew condensation. The cooling heat exchanger 31 may be used to cool the inside of the defrosting device housing 11 to store the frozen food before defrosting in the defrosting device. In this way, from the frozen food storage to the thawing and the thawing food storage, the above-mentioned thawing device can be used.

FIG. 6 is a diagram showing still another example of the decompression device according to the present invention. In FIG. 6, the same components as those shown in FIG. 4 are designated by the same reference numerals. In the example shown in FIG. 6, the opening 11 and the damper 27 are not provided in the defroster housing 11, and instead the cooling heat exchangers 41 and 42 are arranged in the defroster 21. The cooling heat exchangers 41 and 42 are controlled by the controller.

As described with reference to FIG. 4, the blower 24 is driven to circulate the air in the defroster 21, and the heating heat exchangers 22 and 23 heat the air to defrost the refrigerator 2.
1 Increase the internal air temperature. Then, when the thawing is completed, the control device lowers the air temperature inside the thawing chamber 21 by the cooling heat exchangers 41 and 42 (for example, lowers the inside temperature to the outside temperature). At this time, the water and the like in the thawing chamber 21 are discharged to the outside by the cooling heat exchangers 41 and 42. That is, the cooling heat exchangers 41 and 4
The humidity inside the defroster 21 is adjusted by 2.

In this way, even after controlling the temperature and humidity inside the thawing chamber 21 by using the cooling heat exchanger after the thawing is completed, the thawing can be carried out without impairing the quality of the frozen food. Moreover, as a result of adjusting the humidity in the defroster 21 (dehumidification), it is possible to more efficiently prevent the occurrence of dew condensation. In addition, you may make it cool the inside of the defroster 21 using the heat exchangers 41 and 42 for cooling, and store frozen food before defrosting in a defrosting apparatus. Further, in the example shown in FIG. 6, two cooling heat exchangers 41 and 42 are arranged, but the number of cooling heat exchangers is the defroster 21.
It is appropriately changed according to the volume of the.

By the way, in the example shown in FIG. 4 or FIG. 6, the temperature of the air in the defrosting device is almost equilibrated to the temperature of the place where the defrosting device is installed before the defrosting product is taken out from the defrosting device. The air dew point temperature inside was set to approximately equilibrate with the air dew point temperature at the location where the defroster was installed. The air dew point temperature at the location where the defrosting device is installed may be approximately balanced to the air dew point temperature inside the defrosting device. For example, if the space of the defrosting device is large and the place where the defrosting device is installed (the work space where the defrosted product is taken out and then packed in a box or put in makeup packaging after the defrosting is completed) is smaller than the installation space of the defrosting device, the air inside the defrosting device is Rather than equilibrating the temperature or air dew point temperature to the air temperature or air dew point temperature in the workplace, it is quicker to equilibrate the air temperature or air dew point temperature in the workplace to the air temperature or air dew point temperature in the defroster. It is possible not only to achieve a substantially equilibrium state, but also to reduce the energy cost for achieving a substantially equilibrium state.

In other words, when the amount of heat including air at the place where the defroster is installed is equal to or less than the heat capacity of the defroster, air and the defroster in the defroster (specifically, the defroster is If the installation space of is larger than the space of the place (workplace) where the decompressor is placed,
The air temperature at the location where the defroster is installed is approximately balanced with the air temperature inside the defroster. Further, the air dew point temperature (air temperature and humidity) at the location where the defrosting device is installed may be set to be approximately in equilibrium with the air dew point temperature in the defrosting device.

For example, a heat exchanger for cooling, a heat exchanger for heating, and a blower are installed at a place (work place) where the defrosting device is installed (generally, these heat exchangers for cooling and heating are installed in the work place). Heat exchanger and blower are installed),
After the thawing is completed, the cooling heat exchanger and the heating heat exchanger are selectively operated, and the blower is driven to change the air temperature or the air dew point temperature of the work place into the air temperature or the air dew point temperature in the thawing device. And the equilibrium state.

Further, a stirring blower is installed in the work place,
After the thawing is completed, the stirring blower is driven to circulate the air inside the thawing device and the workplace air through the intake duct (intake port) and the exhaust duct (exhaust port), as described above, and the air in the workplace is circulated. The temperature or the air dew point temperature may be set to be substantially in equilibrium with the air temperature or the air dew point temperature in the defroster.

Here, the thawing device described in FIG. 1 and the thawing device with radiant heat transfer (hereinafter simply referred to as radiant heat transfer thawing device)
In the radiant heat transfer defroster, the thawing is performed by so-called surface heat transfer from air or other gas and radiant heat transfer such as far infrared rays or infrared rays. When the packaging material and the food have different heat energy absorption rates, and the packaging material has a lower absorption rate than the food itself, the temperature of the food surface layer may be higher than that of the packaging material. As a result, the water evaporated from the food,
Other volatile components are substantially cooled by the packaging material, and moisture or the like is condensed on the inner surface of the packaging material (that is, dew condensation occurs in the case of moisture). If such condensation occurs, it will have an unfavorable effect on the packaging material and the food.

On the other hand, in the thawing apparatus shown in FIG. 1, since the thawing atmosphere air is maintained at the temperature of the surface layer of the food or more, the inner surface of the packaging material is not necessarily condensed and the thawing is completed. After-exhaust is performed to substantially equilibrate the inside temperature with the outside temperature, so that food is not adversely affected. After the completion of thawing, when the temperature inside the refrigerator is approximately equilibrated with the outdoor temperature, the air temperature inside the refrigerator is made higher than the temperature of the packaging material and the surface temperature of the thawed product.

Now, referring to FIGS. 7 and 8, a concrete description will be given. Now, the frozen rice ball 51 packaged with the transparent resin film is stored in the heat radiation and heat transfer defroster 52 and thawed ( (Fig. 7). As shown in FIG. 7, this radiant heat transfer defroster 52 has a pair of heat radiating plates 52b and 52c arranged in a housing 52a, and a frozen rice ball 51 is arranged between the heat radiating plates 52b and 52c to thaw. I went. On this occasion,
The temperature (room temperature) in the room where the defrosting device 52 is placed is 23.6.
℃, the surface temperature of the heat sink 52b is 77 ℃, the heat sink 5
The surface temperature of 2c was 82 ° C. In this way, when the frozen rice ball 51 was thawed, when the air temperature of the thaw atmosphere was lower than the surface temperature of the rice ball 51, dew condensation occurred on the inner surface of the packaging material.

On the other hand, as shown in FIG. 8, a blower (fan) 53 is used to circulate the air in the defroster 52,
After thawing, the surface temperature of the heat dissipation plate 52b was 75.
The surface temperature of the heat dissipation plate 52c was 4 ° C and 80 ° C. Furthermore, when the air temperature inside the defroster, the surface temperature of the packaging material, and the surface temperature of the rice ball itself were measured, they were 47
C, 39.5 ° C to 46 ° C, and 37.5 ° C to 39 ° C. By circulating the air in this way, the surface temperature of the rice ball became lower than the air temperature in the refrigerator and the packaging material temperature, and dew condensation did not occur on the inner surface of the packaging material.

Further, the frozen food was thawed using a so-called microwave thawing (microwave oven). Now, the frozen packed rice ball 61 and the frozen packed triangular seaweed rice ball 62 (simple airtightly packed with two films so that the seaweed does not get wet) are stored in the microwave oven 63, and the microwave oven 63
These rice balls were thawed by the total thawing mode (see FIG. 9). At this time, the packaging material temperature, the surface temperature of the product to be defrosted, the air temperature in the microwave oven (in the defroster), and the air temperature outside the defroster were measured, and the results shown in FIGS. 10 and 11 were obtained.

As shown in FIG. 10, rice balls 61 and 6
In both cases, the surface temperature of the product to be defrosted> the temperature of the packaging material> the temperature of the air inside the defroster> the temperature of the air outside the defroster, and water-drop-like dew condensation occurred on the inner surface of the packaging material during thawing. Then, when the air temperature inside the defroster was equilibrated with the air temperature outside the defroster for about 20 minutes and the rice balls 61 and 62 were taken out from the microwave oven 63, the dew condensation that occurred during the thawing did not disappear. further,
Water droplets that had condensed on the inner surface of the packaging material adhered to part of the surface of the rice ball, and the rice grains were swollen. In addition, the seaweed became sticky, and the taste and texture were significantly deteriorated as compared with those before freezing.

Similarly, in FIG. 11, the surface temperature of the product to be defrosted> the packaging material temperature> the air temperature inside the defrosting device> the outside air temperature of the defrosting device. did. Then, when the air temperature inside the defroster was equilibrated with the air temperature outside the defroster for about 20 minutes and the rice balls 61 and 62 were taken out from the microwave oven 63, the dew condensation that occurred during the thawing did not disappear. Further, water droplets that had condensed on the inner surface of the packaging material adhered to a part of the surface of the rice ball, and the rice grains were swollen. In addition, the seaweed became sticky, and the taste and texture were significantly deteriorated as compared with those before freezing.

On the other hand, as shown in FIG.
Slits 64a and 64b facing each other were formed in the housing of No. 3, and one slit 64a was used as an intake port and the other slit 64b was used as an exhaust port. Then, the intake port 64a
A warm air generator (for example, a hair dryer) 65 was used to blow warm air into the microwave oven 63. On the other hand, the temperature sensor 66 is arranged at the exhaust port 64b, and the temperature sensor 66
Was connected to a temperature controller 67 as a control device. Then, the temperature controller 67 controls the warm air generator 65 to adjust the warm air temperature. At this time, the temperature controller 67 controls the warm air temperature according to the exhaust gas detection temperature detected by the temperature sensor 66. For example, the hot air temperature is controlled so that the exhaust gas detection temperature ≧ the surface temperature of the defrosted product.

While sending warm air to the microwave oven 63 as described above, the frozen packaged rice ball 61 and the frozen packaged triangular seaweed rice ball 62 are housed in the microwave oven 63, and the microwave oven 6
These rice balls were thawed according to the total thawing mode of 3.
At this time, the packaging material temperature, the surface temperature of the defrosted product, the air temperature inside the defroster, and the air temperature outside the defroster were measured, and the results shown in FIGS. 13 and 14 were obtained. As shown in FIG.
Both of the rice balls 61 and 62 had an air temperature inside the defroster> a packaging material temperature and a surface temperature of the product to be defrosted, and fine frosted glass-like dew condensation occurred on the inner surface of the packaging material during the defrosting, but it disappeared soon. Then, after the thawing is finished, the air temperature inside the thawing device is equilibrated with the air temperature outside the thawing device in about 15 minutes, and the rice balls 61 and 62 are taken out from the microwave oven 63 and the packaging material is removed. There was no condensation on its own, and the appearance, taste and texture were similar to those of the onigiri before freezing.

Similarly, in FIG. 14, the temperature of the air inside the defroster is higher than the temperature of the packaging material and the surface temperature of the product to be defrosted. When the rice balls 61 and 62 were taken out from the microwave oven 63 in equilibrium with the temperature and the packaging material was removed, there was no dew condensation on the inner surface of the packaging material and the rice ball itself, and the appearance, taste, and texture were the same as those before freezing. It was equivalent.

Referring to FIG. 15, an air conditioner 72 is connected to the microwave oven 63 via a duct 71. The air conditioner 72 is provided with a heat exchanger for heating / cooling / dehumidification (hereinafter simply referred to as a heat exchanger) 72a, and is also provided with an agitator blower 72b, so that the inside of the microwave oven 63 is moved by the heat exchanger 72a. The air in the microwave oven 63 is agitated by the blower 72b while heating, cooling and dehumidifying.

In the microwave oven 63, the microwave irradiation unit 6
3a and a defrosting table (table) 63b are provided, and when defrosting frozen food, the frozen food is placed on the table 63b to operate the microwave oven 63 (in the example shown, frozen food As a result, the frozen food 74 stored in the packaging material is arranged). At this time, the blower 72b is driven so that the air in the microwave oven is
Air conditioner 72 and microwave oven 6 through duct 71
Cycle between 3 and. Then, the air in the microwave oven 63 is heated by the air conditioner 72. When the air in the microwave oven is heated in this way, the temperature of the air in the microwave oven 63 becomes higher than the surface temperature of the frozen food 74 as the product to be defrosted, as described above.

When the thawing is completed, the air conditioner 72 balances the temperature inside the microwave oven 63 with the room temperature,
It is cooled and dehumidified. In this way, after the temperature inside the microwave oven 63 is equilibrated with the room temperature, the thawed food is taken out from the microwave oven 63, and the packaging material is removed. There is no condensation on the inner surface of the packaging material and the food itself. ,appearance,
The taste and texture were similar to those of the food before freezing.

The air conditioner 72 may be provided with only the heat exchanger for heating. In this case, an opening is formed in the microwave oven and the damper 73 is attached to this opening. Further, a damper 71a is attached to the duct portion 71, and the duct portion 71 is selectively opened to the outside (indoor) by opening / closing the damper 71a. When the thawing is completed as described above, the blower 72b is driven and the dampers 73 and 71a are opened. As a result, the indoor air flows into the microwave oven 63, the air in the microwave oven 63 is exhausted, the inside of the microwave oven is dehumidified, and the temperature is equilibrated to the indoor temperature. Even in this case, dew condensation did not exist on the inner surface of the packaging material and the food itself, and the appearance, taste and texture were equivalent to those of the food before freezing.

The system shown in FIG. 15 is not limited to a decompressor using microwave heating such as a microwave oven, but also other high frequency heating, ultrasonic waves, electromagnetic waves, far infrared rays, infrared rays, etc. have energy absorption rates of packaging materials and frozen foods. It can be applied when it differs by itself (when the energy absorption rate of the frozen food itself is higher than that of the packaging material).

As is apparent from the above description, in the case of microwave heating (microwave thawing), microwaves are not absorbed by air, and resins other than special packaging materials such as metal foil films that reflect microwaves. In the case of film and paper packaging materials, there is almost no energy absorption in the packaging material and the temperature of the packaging material does not rise. Therefore, most of the microwave is absorbed in the surface layer of frozen food,
It becomes thermal energy and the frozen food is thawed. Therefore, when the surface layer portion is heated, water and other volatile components in the frozen food are evaporated and accumulated in the internal space of the packaging material. Since the temperature of the packaging material is lower than the temperature of the heated surface layer of the frozen food, water and the like accumulated in the internal space of the packaging material is condensed on the inner surface of the packaging material. After the thawing is completed, the condensed water or the like is partially reabsorbed on the surface of the food, and the thawed product cannot be reproduced in the state before freezing.

When thawing naked frozen food (frozen food not stored in the packaging material), volatile substances (for example, water, acetic acid, alcohols, and aroma substances contained in gas such as air) are thawed. ) And frozen food surface volatiles (eg,
Depending on the difference in vapor pressure between water, acetic acid, alcohols, and aroma substances, volatile substances evaporate from frozen foods and condense, thereby drying foods and adsorbing condensed components. And condensation will occur. The vapor pressure of volatile substances is a function of the dew point temperature, which is a function of the energy applied. Energy is given by heat transfer from the atmospheric gas (gas temperature, wind speed, wind direction), radiation of far infrared rays or infrared rays, vibration of ultrasonic waves, microwaves, high frequencies, electromagnetic waves, etc., and vapor of volatile substances. Since the pressure and the dew point temperature have a correlation, the condensation can be suppressed by controlling the temperature in the defrosting apparatus as described above when taking out the defrosted product after defrosting as described above.

On the other hand, in the case of packaged frozen food, condensation, adsorption and dew condensation of volatile substances on the inner and outer surfaces of the packaging material, further drying of the packaging material, drying of the frozen food and generation of the food itself. There is recondensation and adsorption of volatile substances on the food surface. In order to prevent condensation and dew condensation of the volatile substance in the defrosting atmosphere gas on the outer surface of the packaging material, the temperature of the packaging material may be maintained at the dew point temperature of the volatile substance in the atmosphere gas or higher. When the packaging material is a hygroscopic material (for example, paper or cellophane), the packaging material may be deformed or torn due to drying. It is desirable to retain.

Considering the frozen food itself stored in the packaging material, when thawing, the vapor of the volatile substance derived from the frozen food is present in a substantially saturated state in the internal space of the packaging material. Depending on the thawing method and the progress of the thawing process, these volatile substances condense and condense on the inner surface of the packaging material, while the composition of the food itself changes due to the volatile substances escaping (for example, when water is lost). When it is scattered, it dries). Then, although some of the volatile substances that have once dissipated may be absorbed again by the food, they will not return to their original state. further,
Condensation formed on the inner surface of the packaging material adheres to the surface of the food, causing unfavorable phenomena such as swelling, discoloration, outflow of dye, and partial drying on the surface of the food.

Further, when the frozen food is thawed using radiation such as ultrasonic waves, microwaves, high frequency waves, electromagnetic waves, vibration energy such as far infrared rays, infrared rays and gas as a heat medium, as described above, the packaging material and the frozen foods are used. Since the energy absorption rate of and is different, the defrosting atmosphere gas temperature is the food to be defrosted (frozen food)
If the surface temperature of the frozen food becomes lower than that of the packaging material, the surface temperature of the frozen food becomes higher than that of the packaging material. As a result, food-derived volatile substances are condensed and condensed on the inner surface of the packaging material. Such a phenomenon also occurs when the temperature of the space in which the defrosted product is taken out is lower than the temperature of the packaged defrosted product when the defrosted product is taken out from the defrosting device after the completion of defrosting.

On the other hand, as described above, the temperature of the gas is raised above the surface temperature of the frozen food being thawed. Then, when the thawing process progresses and reaches the final stage of thawing, the thermal energy given to the gas is reduced and finally stopped. By doing so, the above-mentioned problems can be prevented. When thawing the packed frozen food, the ambient temperature is 30 to 8
It was found that when the temperature was 0 ° C., good results were obtained by lowering the temperature to 15 to 30 ° C. in 5 to 15 minutes. In addition, in the above description, the substantially equilibrium state means that the air temperature in the defroster is within ± 5 ° C. with respect to the external air temperature.

[0068]

As described above, according to the present invention,
During thawing, perform thawing while circulating the air inside the thawing device, and after thawing, before removing the thawed product from the thawing device, set the air temperature inside the thawing device to the temperature of the place where the thawing device is installed. Since the defrosted product is set in a substantially equilibrium state, defrosting and drying do not occur in the defrosted product, and it is possible to reproduce the defrosted product in the quality before freezing. Further, since the frozen food is thawed to obtain a thawed product, there is an effect that safety can be ensured with respect to the propagation of bacteria and the like as compared with chilled or normal temperature distribution. Furthermore, if the humidity inside the defrosting device is also adjusted to be approximately in equilibrium with the humidity at the place where the defrosting device is installed, it is possible to prevent condensation and the like better, and to improve the quality of the defrosted product. There is an effect that it can be in a state.

According to the present invention, after the thawing process is completed and before the thawing product is taken out from the thawing device, the air in the place where the thawing device is installed is taken into the thawing device so that the temperature of the air inside the thawing device is controlled by the thawing device. Since the temperature of the place where the defrosting device is installed is approximately balanced, the temperature of the air inside the defrosting device can be easily balanced to the temperature of the place where the defrosting device is installed. In addition, if the air in the place where the defrosting device is installed is taken into the defrosting device, the temperature and humidity of the air inside the defrosting device can be approximately balanced with the temperature and humidity where the defrosting device is installed. There is an effect that defrosting and drying of the product can be prevented, and the thawed product can be better reproduced by the quality before freezing.

According to the present invention, after the thawing process is completed and before the thawing product is taken out from the thawing device, the air inside the thawing device is cooled so that the temperature of the air inside the thawing device is approximately equilibrated with the temperature of the place where the thawing device is installed. Since it is set in the state, there is an effect that the temperature of the air in the defrosting device can be easily brought into a substantially equilibrium state with the temperature of the place where the defrosting device is installed. Furthermore, by dehumidifying the inside of the defroster so that the humidity inside the defroster is approximately in equilibrium with the humidity at the place where the defroster is installed, it is easy to prevent condensation and drying of the defrosted product, and Has the effect that it can be better reproduced by the quality before freezing.

According to the present invention, when the frozen food is packaged by the packaging material, the air temperature inside the defrosting device is controlled to be higher than the temperature of the packaging material and the surface temperature of the frozen food during thawing, Furthermore, after thawing, increase the air temperature inside the thawing device to higher than the temperature of the packaging material and the surface temperature of the thawing product, and then make the air temperature inside the thawing device approximately equilibrium with the temperature of the place where the thawing device is installed. Therefore, dew condensation does not occur on the inner surface of the packaging material, and the quality of the packaged frozen food does not deteriorate when it is thawed. Further, even after thawing, no condensation occurs on the inner surface of the packaging material. Moreover, when the packaging material is hygroscopic, there is an effect that the flow of printing ink and the like and the deformation of the packaging material do not occur.

In the present invention, the temperature of the place where the defrosting device is installed before the defrosted product is taken out from the defrosting device is approximately equilibrated with the air temperature in the defrosting device, or where the defrosting device is installed. Since the air dew point temperature of is approximately balanced with the air dew point temperature in the defroster,
When the thawing device is large and the space where the thawing device is installed is small, a substantially equilibrium state can be quickly achieved. Then, there is an effect that defrosting and drying do not occur in the thawed product, and the thawed product can be reproduced to the quality before freezing. Further, there is an effect that it is possible to reduce the energy cost for achieving a substantially balanced state.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a defrosting device according to the present invention.

FIG. 2 is a diagram showing the relationship between the external temperature when thawing Edomae sushi using the thawing apparatus shown in FIG. 1, the gas temperature in the thawing apparatus, the fish core temperature of Edomae sushi, the fish surface temperature of Edomae sushi, and the packaging material surface temperature. FIG.

FIG. 3 is an external temperature when defrosting a hygroscopic cosmetic box-containing ohagi using the defrosting apparatus shown in FIG. 1, a gas temperature in the defrosting apparatus,
It is a figure which shows the relationship of Ogi's center temperature and the outer bottom surface temperature of a cosmetic case.

FIG. 4 is a cross-sectional view showing another example of the defrosting device according to the present invention.

FIG. 5 is a sectional view showing still another example of the defrosting device according to the present invention.

FIG. 6 is a sectional view showing still another example of the defrosting device according to the present invention.

FIG. 7 is a cross-sectional view showing a conventional example when thawing rice balls using a heat dissipation heat transfer thawing device.

FIG. 8 is a cross-sectional view showing an example of thawing a rice ball with a heat dissipation heat transfer thawing device using an example of the thawing method according to the present invention.

FIG. 9 is a cross-sectional view showing a conventional example when thawing rice balls using a microwave oven.

10 is a diagram showing an example of measurement results of a packaging material temperature, a surface temperature of a product to be defrosted, an air temperature in a defroster, and an air temperature outside the defroster in the defrosting shown in FIG.

11 is a diagram showing another example of the measurement results of the packaging material temperature, the surface temperature of the product to be defrosted, the air temperature in the defroster, and the air temperature outside the defroster in the defrosting shown in FIG.

FIG. 12 is a cross-sectional view showing an example of thawing rice balls in a microwave oven using an example of the thawing method according to the present invention.

13 is a diagram showing an example of measurement results of a packaging material temperature, a surface temperature of a product to be defrosted, an air temperature inside the defroster, and an air temperature outside the defroster in the thawing shown in FIG.

FIG. 14 is a diagram showing another example of the measurement results of the packaging material temperature, the surface temperature of the product to be defrosted, the air temperature in the defroster, and the air temperature outside the defroster in the defrosting shown in FIG.

FIG. 15 is a cross-sectional view showing an example of thawing rice balls in a microwave oven using another example of the thawing method according to the present invention.

[Explanation of symbols]

11 Defrosting device housing 12 storage shelves 13 Air conditioning board 14,22,23 Heating heat exchanger 15 blower 16,27 damper 21 Defroster 24 Blower (Blower) 25 Intake duct 26 Exhaust duct 28 Storage shelves 31, 41, 42 Cooling heat exchanger

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tsuneo Tsuna             2-13-1, Peony, Koto-ku, Tokyo Stock market             Shamaegawa Works (72) Inventor Masaharu Shigamatsu             2-13-1, Peony, Koto-ku, Tokyo Stock market             Shamaegawa Works (72) Inventor Daisuke Minato             2-13-1, Peony, Koto-ku, Tokyo Stock market             Shamaegawa Works (72) Inventor Hiroaki Yamaoka             2-13-1, Peony, Koto-ku, Tokyo Stock market             Shamaegawa Works (72) Inventor Hiroshi Matsuno             2-13-1, Peony, Koto-ku, Tokyo Stock market             Shamaegawa Works F term (reference) 4B022 LB01 LB02 LF01 LQ01 LQ07                       LT07

Claims (10)

[Claims] 1. A thawing method used when thawing the frozen food using a thawing device for thawing the frozen food, wherein the frozen food is stored in the thawing device and air inside the thawing device is circulated. While defrosting the frozen food according to the temperature pattern determined for each frozen food, and a defrosting step of defrosting the defrosted product, the air temperature in the defrosting device before taking out the defrosted product from the defrosting device. Or an equilibrium step of substantially equilibrating the air dew point temperature in the defrosting device to the air dew point temperature in the place where the defrosting device is installed. How to thaw frozen food. 2. In the equilibration step, the air in the place where the defrosting device is installed is taken into the defrosting device so that the air temperature in the defrosting device is approximately balanced with the temperature in the place where the defrosting device is installed. Alternatively, the method of thawing frozen food according to claim 1, wherein the air dew point temperature in the thawing device is made to approximately equilibrate with the air dew point temperature of the place where the thawing device is installed. 3. In the equilibrium step, the air inside the defrosting apparatus is cooled to substantially equilibrate the temperature of air inside the defrosting apparatus to the temperature of the place where the defrosting apparatus is installed, or the air inside the defrosting apparatus is cooled. 2. The defrosting method for frozen foods according to claim 1, wherein the defrosting is performed so that the air dew point temperature in the defrosting device is approximately balanced with the air dew point temperature in the place where the defrosting device is installed. 4. When the frozen food is packaged with a packaging material, in the thawing step, the air temperature inside the thawing device is controlled to be higher than the temperature of the packaging material and the surface temperature of the frozen food, The frozen food according to any one of claims 1 to 3, wherein in the equilibrium step, the air temperature in the defrosting device is controlled to be higher than the temperature of the packaging material and the surface temperature of the defrosted product. Thawing method. 5. A thawing method used when thawing the frozen food using a thawing device for thawing the frozen food, wherein the frozen food is stored in the thawing device and air inside the thawing device is circulated. While defrosting the frozen food according to the temperature pattern determined for each frozen food, and a defrosting step of defrosting the defrosted product, before the defrosting device is taken out from the defrosting device, where the defrosting device is installed. Or an equilibrium step of substantially equilibrating the temperature of the air in the defroster to the temperature of the air in the defroster. How to thaw frozen food. 6. A thawing device used when thawing frozen food, the housing housing storing the frozen food,
A heating unit that heats the inside of the housing, a cooling unit that cools the inside of the housing, a circulating unit that circulates the air inside the housing, and a control that controls the heating unit, the cooling unit, and the circulating unit. Means, the control means controls the heating means according to the temperature pattern specified for each frozen food and controls the circulation means to circulate the air in the storage housing to circulate the frozen food. A thawing device, wherein thawing is performed, and when the thawing is completed, the cooling means is controlled to control the air temperature in the housing case to a predetermined temperature. 7. The thawing apparatus according to claim 6, wherein the predetermined temperature is an external temperature in which the housing is arranged. 8. The cooling means is a damper for selectively opening the storage housing to the outside, and the control means drives and controls the damper to take in the external air into the storage housing. The thawing apparatus according to claim 6, wherein the inside air of the housing is exhausted to the outside to control the inside temperature of the housing to the predetermined temperature. 9. A dehumidifying means for dehumidifying the inside of the storage housing, wherein the control means controls the dehumidifying means to adjust the humidity inside the storage housing to the humidity outside the storage housing. The defrosting device according to claim 6, wherein 10. When the frozen food is packed in a packaging material, and when the frozen food is thawed, the control means determines the air temperature in the storage housing from the temperature of the packaging material and the surface temperature of the frozen food. The temperature is controlled so as to be higher, and after the thawing is finished, the control means is configured to make the air temperature in the storage housing higher than the temperature of the packaging material and the surface temperature of the thawed product. The defrosting device according to claim 6.