JPH07253265A - Defreezing method and defreezing device for frozen food - Google Patents

Abstract

PURPOSE:To provide a defreezing method for a frozen food in which a degree of freshness of the food can be kept high and a rapid defreezing can be carried out. CONSTITUTION:A refrigeration temperature of a food including a minus temperature range is set as an inter-refrigerator set temperature, an upper limit temperature and a lower limit temperature are set across the set temperature, and at the same time a frozen food is stored within the refrigerator and when the temperature within the refrigerator is decreased down to the lower limit temperature due to a cooling action obtained from the frozen food, a heating heater 42 is operated and when the temperature within the refrigerator is increased up to the upper limit temperature under an operation of this heating heater 42, the heating heater 42 is stopped in its operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for thawing frozen food such as frozen fish meat and meat.

[0002]

2. Description of the Related Art Conventionally, when thawing fish meat such as frozen tuna or frozen meat such as frozen pork blocks brought into a hotel or restaurant, it has been left at room temperature or thawed under running water. According to the report, the thawing time is short, but a large amount of drip (juicy juice) from food flows out.
There was a problem that the weight was lost. There are also microwave ovens for rapid thawing,
Due to the rapid temperature rise, the temperature distribution in the food is inevitably non-uniform, and it is partially overheated and the deterioration progresses,
There were inconveniences such as discoloration of meat, discoloration, and poor morphology.

Therefore, Japanese Patent Application No. 4-
In No. 167535, the refrigerating temperature is set as the temperature inside the refrigerator, the upper limit temperature and the lower limit temperature are set above and below the set temperature, the heater is caused to generate heat at the lower limit temperature, and the cooling device is stopped to set the upper limit temperature. The heating of the heater is stopped and the cooling device is operated in reverse to thaw the frozen food at the refrigerating temperature.

According to such thawing, since the thawing is performed in the refrigerating temperature zone, it is possible to prevent the drip from flowing out of the food due to the thawing and to keep the food fresh by uniformly thawing. However, it becomes possible to suppress discoloration and fading.

[0005]

However, in the above-mentioned thawing process, the food is cooled by the cooling device while the heater stops generating heat, so that the maximum ice crystal production zone of the food is -1 ° C to It has a drawback that it takes a long time to pass -5 ° C and a relatively long time is required to complete the thawing.
In particular, in a restaurant or hotel where food is thawed and then cooked in a short period of time or immediately, the work efficiency is deteriorated by the time required for thawing, which is not suitable.

[0006] Further, if the thawing takes too long, there is a problem that the methification of the food (determined by the methification rate of myoglobin (Mb) as an index of the degree of fading of browning) progresses during the thawing. It was

Further, conventionally, when thawing is finished, the user actually touches it by hand to judge the thawing condition, or by measuring the food temperature using an expensive device such as an infrared sensor. Therefore, it has been desired to develop an inexpensive and reliable automatic thawing determination means.

The present invention has been made in order to solve the above-mentioned conventional technical problems, and can quickly thaw while keeping the freshness of food high, and further, the thaw is automatically terminated to continue the freshness. It is an object of the present invention to provide a method and an apparatus for thawing frozen food that can be well preserved.

[0009]

According to the method for thawing frozen food of the present invention, the refrigerating temperature of the food including the minus temperature zone is set as the set temperature in the refrigerator, and the upper and lower limits are set above and below the set temperature. While setting the lower limit temperature, the frozen food is stored in the refrigerator, and when the temperature inside the refrigerator decreases to the lower limit temperature due to the cooling action from the frozen food, the heating means is operated, and the inside temperature is kept by the operation of this heating means. When the temperature rises to the upper limit temperature, the heating means is stopped.

In the method for thawing frozen food according to the second aspect of the present invention, the refrigerating temperature of the food including the minus temperature zone is set as the set temperature in the refrigerator, and the upper and lower limits are set above and below the set temperature. Along with setting, store the frozen food in the refrigerator, and when the temperature inside the refrigerator decreases to the lower limit temperature due to the cooling action from the frozen food, the heating means is operated, and the temperature inside the refrigerator reaches the upper limit temperature by the operation of this heating means. When the temperature rises, the heating means is stopped and the frozen food is thawed, and the thawing end time is predicted based on the heating time from the start of thawing until the heating means stops operating, and after the thawing end time elapses, the cooling means is used. The inside temperature is maintained between the upper limit temperature and the lower limit temperature.

Furthermore, in the thaw apparatus for frozen foods according to the third aspect of the present invention, there is provided a cooling means for cooling the inside of the refrigerator, a heating means for heating the inside of the refrigerator, a temperature detecting means for detecting the temperature inside the refrigerator, and this temperature detection. The cooling means and the heating means are controlled on the basis of the temperature inside the refrigerator output by the means, and the control means is provided with a control means for executing the thawing operation and the cooling operation. Set the upper limit temperature and the lower limit temperature, operate the cooling means at the upper limit temperature during the cooling operation, stop the cooling means at the lower limit temperature, prohibit the operation of the cooling means during the defrosting operation, and heat at the lower limit temperature. The means is operated, and the heating means is stopped at the upper limit temperature.

The frozen food defrosting apparatus according to the invention of claim 4 is
In the above, the control means integrates the heating time from the start of the thawing operation until the heating means stops operating, predicts the thawing end time based on this heating time, and ends the thawing operation at this thawing end time. After that, it is characterized by shifting to the cooling operation.

[0013]

In the present invention, the frozen food is thawed at the refrigerating temperature of the food containing the minus temperature zone, so that the drip outflow from the food due to the thawing can be minimized, and
By uniformly thawing, discoloration and fading can be suppressed while maintaining the freshness of food.

In particular, the heating means is operated at the lower limit temperature and stopped at the upper limit temperature, and the temperature inside the refrigerator is lowered from the upper limit temperature by the cooling action of the frozen food itself. The time during which the food passes through the maximum ice crystal formation zone of -1 ° C to -5 ° C can be shortened as compared with the case where the inside of the refrigerator is cooled by the cooling means during the stop. Therefore, it is possible to shorten the time required for thawing the food and improve the work efficiency thereafter, and it is also possible to suppress the methation of the food during thawing.

On the other hand, in the method according to claim 1 or the apparatus according to claim 3, when the frozen food is thawed and its temperature rises, the internal temperature does not reach the lower limit temperature at a certain point, and thereafter, The heating means are deactivated. There is a certain proportional relationship between the heating time from the start of the thawing operation until the heating means is stopped and the time until the thawing ends, and is not related to the food weight.

Therefore, in the inventions of claims 2 and 4, in addition to the above inventions, the defrosting end time is predicted based on the heating time, and the defrosting is finished at this defrosting end time, and then cooled. Since it shifts to cooling operation in the same temperature zone by means, without using an infrared sensor or the like,
It is possible to automatically end the thawing operation accurately. Therefore, the labor of the user can be remarkably improved without causing a cost increase.

In particular, after thawing, since the food is stored in the same temperature zone, the freshness of the food can be kept high until cooking is started.

[0018]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a vertical cross-sectional side view of a thawing device 1 for realizing the frozen food thawing method of the present invention, and FIG. 2 is a block diagram of an electric circuit of a control device 41 thereof.

In FIG. 1, the defrosting device 1 is installed in a kitchen of a restaurant, for example, and is a heat conductive box that opens forward at a predetermined interval inside the main body of a heat insulating box 2 that opens forward. A storage box 3 is housed and arranged.
The storage box 3 is formed by fixing a heat conduction plate such as a stainless steel plate with a screw and sealing the joint surface with a sealing material.
The inside of the storage box 3 is divided into upper and lower parts by a partition part 4, and an upper storage chamber 5 is formed above and a lower storage chamber 6 is formed below. The space between the storage box 3 and the heat insulating box 2 and the interior of the partition section 4 form a series of ducts 8. The duct 8 is divided by a dividing plate 9 into a discharge side duct 8A and a return side duct 8B.

A vertical strut 10 is attached to the front opening of the heat insulating box 2, and the front opening of the upper and lower storage chambers 5 and 6 partitioned by the partition 4 and the strut 10 has a pair of upper and lower double-sided heat insulation. The doors 11 and 12 are closed so that they can be opened and closed.

A rectangular window hole 1 is formed in the ceiling wall 2A of the heat insulating box 2.
4 is opened, and a mounting base 15 is attached so as to close the window hole 14 from above. A compressor 17, a condenser 18, and a condenser fan 19 which constitute a refrigerating device 16 as a cooling means are installed on the upper surface of the mounting base 15, and the front of these is concealed by a grill 21 having a control panel or the like. Has been done.

On the lower surface of the mounting base 15, the refrigeration system 16 is provided.
The cooler 22 constituting the above is attached to face the inside of the duct 8 above the storage box 3, and the duct 8 in front of the cooler 22 corresponds to a fan cover portion (not shown) formed in the drain pan 23 below the cooler 22. A cooling fan 24 is attached inside. A defrost heater 25 is provided below the cooler 22.

When the cooling fan 24 is operated, the cooler 2
The cool air cooled in 2 is blown out to the discharge side duct 8A of the duct 8 as shown by the arrow in FIG. 1, flows down from the upper surface of the storage box 3 to the back and side, flows into the partition section 4, and then makes a U-turn. The lower part of the storage box 3 flows downward, flows under the bottom surface of the storage box 3, flows into the return duct 8B, rises the return duct 8B, and returns to the suction side of the cooler 22.

The wall surface of the storage box 3 is cooled by the cold air circulation, and the insides of the upper and lower storage chambers 5 and 6 are indirectly cooled from the wall surface of the storage box 3. In this way, the upper and lower storage chambers 5 and 6 are connected to the storage box 3
The interior is configured to be maintained at a high humidity of, for example, 70% to 98% due to the indirect cooling effect from the wall surface, the evaporation of water from the food etc. stored inside, and the moisture entering from the outside. There is.

A dew receiving plate 31 which is slanted rearward is arranged in the upper part of the lower storage chamber 6, and the partitioning part 4 communicates with the upper and lower storage chambers 5 and 6 to open above the dew receiving plate 31. Tube 3
2 is attached. Further, the storage box 3 at the bottom of the lower storage chamber 6 is provided with a drainage path 33 for discharging drain water in the upper and lower storage chambers 5, 6 and the duct 8. Further, reference numeral 34 is a shelf for placing food on the upper and lower storage chambers 5 and 6.

The top wall 3A of the storage box 3 in the upper storage room 5
An upper duct member 36 is attached to the lower side with a space, and a rear end of the upper duct member 36 is spaced downward from the upper wall of the upper storage chamber 5 with a space from the rear wall 3B of the storage box 3. A rear duct member 37 having an excellent thermal conductivity is attached.
Thus, an internal duct 38 that descends from the ceiling of the upper storage chamber 5 to the back is formed in the space between the duct members 36 and 37 and the storage box 3. An internal circulation fan 41 and a heater 42 as a heating means are provided in the internal duct 38 located on the ceiling, a suction port 43 is provided at the front end of the upper duct member 36, and a rear duct member is provided. A discharge port 44 is formed at the lower end of 37.

A temperature sensor 46 in the refrigerator is provided at the suction port 43.
Is provided. Also, for example, in a suitable place on the outer surface of the storage box 3,
An outside air temperature sensor 47 for detecting the outside air temperature is also provided.

Next, in FIG. 2, the control device 51 comprises a general-purpose microcomputer 52. The outputs of the inside temperature sensor 46 and the outside air temperature sensor 47 are input to the microcomputer 52, and the output of the microcomputer 52 is the compressor 17, the cooling fan 24, the defrost heater 25, and the inside circulation fan 41. And the heater 42 is connected.

A method of thawing frozen food by the operation of the thawing apparatus 1 of the present invention having the above-mentioned configuration will be described with reference to FIGS. 3 and 4. The microcomputer 52 has an upper storage room 5
Set temperature (internal temperature TR) = 0 ° C. As a result, the microcomputer 52 has its upper and lower ± 0.
Set the upper and lower temperature limits to 5 ° C. Then, frozen foods F such as frozen tuna and frozen pork blocks are stored in the upper storage chamber 5, placed on the shelf 34, and the thawing operation is started.

The flow chart of FIG. 4 shows a control program of the microcomputer 52. When the defrosting operation is started, the microcomputer 52 first prohibits the operation of the compressor 17 and the cooling fan 24. Here, the internal circulation fan 41 is continuously operated. Next, in step S1 of FIG. 4, the inside temperature TR of the upper storage chamber 5 detected by the inside temperature sensor 46 is the lower limit temperature (−0.5).
C)) or less.

Frozen food F is stored in the upper storage room 5,
Cooling from the food itself lowers the internal temperature TR. Then, when the temperature becomes equal to or lower than the lower limit temperature, the microcomputer 52 proceeds to step S3 to energize (operate / ON) the heater 42 to generate heat.

The air heated by the heat generated by the heating heater 42 is accelerated by the internal circulation fan 41, passes through the internal duct 38 and descends, and eventually the rear duct member 3 is formed.
7 is discharged from the discharge port 44 at the lower end to the lower part inside the upper storage chamber 5. Then, it is circulated in the upper storage chamber 5 and returned from the suction port 43 to the internal duct 38 (forced convection shown by a white arrow in FIG. 1).

When the internal temperature TR rises due to the heat generated by the heating heater 42 and becomes equal to or higher than the upper limit temperature (+ 0.5 ° C.), the microcomputer 52 proceeds from step S1 to step S2 to step S4, and the heating heater 42 Is de-energized (stop / OFF).

By such cooling from the food F and heating of the heater 42, the inside of the upper storage chamber 5 is kept at the high humidity as described above and at the set temperature of 0 ± 0.5 ° C. Then, the temperature of the frozen food F stored in the upper storage chamber 5 gradually rises and is thawed. That is, since frozen foods are thawed in the vicinity of the freezing point, the foods are uniformly thawed without partial overheating, drip outflow is suppressed, and discoloration and fading are suppressed to a low level. Therefore,
The increase in the K value as a freshness index of food and the increase in the rate of methemoglobin are suppressed, and the freshness of food is kept high.

When the food F is thawed and its temperature rises, the effect of cooling the inside of the upper storage chamber 5 decreases, so that the inside temperature TR eventually stops heating the heating heater 42 (OF
Even after F), the temperature does not fall to the lower limit temperature of -0.5 ° C, and the food continues to thaw due to the natural temperature rise.

The microcomputer 52 executes step S
It is determined at 5 whether or not the heating heater 42 is continuously turned off for, for example, one hour (Hr) or more. Due to the temperature increase of the food, the heating heater 42 is turned off at time t1 in FIG. When the time is one hour or more, the microcomputer 52 proceeds from step S5 to step S6 and reads the time (hereinafter referred to as heating time) from the start of the thawing operation to the time t1 (this time is the function of the microcomputer 52). Accumulated by a timer. The same applies below.)

Here, the heating time and the thawing time from the start of the thawing operation until the central temperature of the food F rises to, for example, -3 ° C. (the temperature at which a kitchen knife can be inserted) (the time when the thawing of the food ends) Table 1 shows the relationship measured by the experiment. Table 1 shows that a JIS test package having a center temperature of -25 ° C (starting temperature) is stored in the upper storage chamber 5 as a refrigerating load under the condition of the outside temperature + 25 ° C, and the weight of the refrigerating load is 40%.
The heating time and the thawing time (the time until the central temperature of the refrigerating load reaches −3 ° C. (end temperature)) were measured while changing them to kg, 20 kg, 10 kg, and 1 kg.

[0038]

[Table 1]

As is clear from Table 1, there is a substantially constant proportional relationship between the heating time and the thawing time, which is independent of the weight of the refrigeration load. And
From the proportional relationship, the thawing end time can be predicted by the formula shown in the middle part of Table 2. That is, the outside temperature is +25
In the case of ℃, the estimated end time of thawing is (heating time + 1) × 4.
It is obtained as 0 and is approximately approximated to the actual thawing time shown in Table 1.

[0040]

[Table 2]

The estimated defrosting time is affected by the outside temperature. That is, according to the experiment, when the outside air temperature is + 30 ° C, the coefficient put in the parentheses in the above formula is 3.5 as shown in the upper part of Table 2 above, and when the outside air temperature is + 20 ° C,
It was confirmed to be 4.5 as shown in the lower part of Table 2.

The table 2 is stored in the memory table of the microcomputer 51. After the heating time is read in step S6, the outside air temperature is read by the outside air temperature sensor 47 in step S7, and these data are read in step S8. From Table 2 above, the estimated thawing end time is calculated. Here, for example, assuming that 8 hours (Hr) is predicted, the microcomputer 51 determines in step S9 whether or not 8 hours of this predicted time has elapsed from the start of thawing.

Then, at time t2 when the estimated time of 8 hours has elapsed from the start of the thawing operation, the microcomputer 52 finishes the thawing operation, proceeds from step S9 to step S11, and shifts to the cooling operation. In this cooling operation, the microcomputer 52 causes the set temperature (0
C) and the internal temperature TR of the upper storage chamber 5 detected by the internal temperature sensor 46, the internal temperature TR rises to + 0.5 ° C. which is the upper limit temperature, and the compressor 17 is operated (ON). . Note that the heater 42 is energized and the internal circulation fan 41 is
Operation is prohibited, and the cooling fan 24 operates continuously (ON)
Becomes

While the compressor 17 is in operation, the refrigerant evaporates in the cooler 22 to exert a cooling effect, and the cool air exchanged with the cooler 22 and cooled is circulated in the duct 8 as described above. The insides of the upper and lower storage chambers 5 and 6 are indirectly cooled via the wall surface of the storage box 3. That is, since the food F is stored in the upper storage chamber 5 in the minus temperature zone under the same conditions of 0 ± 0.5 ° C. even after the thawing is finished, keep the freshness of the food high until cooking is started. Is possible.

Here, for example, under the same conditions of a set temperature of 0 ± 0.5 ° C., the food is thawed only by cooling by the cooling device 16 as described above, and when the food is heated and cooled by the heater 42 as described in the conventional example. Each value of the thawing time (experimental value under the same refrigeration load) when the food is thawed by alternately performing cooling with the device 16 and when the food is thawed only by the heating heater 42 as in the present invention is shown. 3 shows.

[0046]

[Table 3]

It can be seen from Table 3 that the thawing time according to the present invention is obviously shortened. In particular, when the thawing time in the case of only cooling is taken as a reference (0%), the thawing time is reduced by about 39% as shown in the lower part of Table 3. In the case of the present invention, since the cooling by the cooling device 16 is prohibited during the thawing, the temperature of the food is in the maximum ice crystal formation zone (-1 ° C to
This is because the time to pass through (-5 ° C) is shortened.

As described above, according to the present invention, it becomes possible to complete the thawing of food in a shorter period of time than the conventional thawing, so that it is possible to improve the work efficiency such as subsequent cooking. Become. Further, as shown in Table 4, it is possible to suppress the formation of meteorite in the food during thawing. Table 4 compares the case where the same frozen food (for example, tuna) is alternately heated and cooled as described above with the case of the present invention.

[0049]

[Table 4]

As is clear from Table 4, when heating and cooling are alternately repeated, the thawing time becomes long (11 hours),
The methation rate increased from 21.58% at the start to 28.11%, whereas the thawing time was shortened (8 hours) when only the heating according to the present invention was used. However, it has only increased slightly from 23.22% at the start to 25.19%.

By the time the estimated thawing time elapses,
When the internal temperature TR has risen to a high temperature of + 10 ° C., for example, the microcomputer 52 determines in step S
The procedure proceeds from step 9 to step S10 to judge this, and the procedure proceeds from step S10 to step S11 to shift to the cooling operation without waiting for the elapse of the estimated thawing time. Further, the lower storage room 6 is used to store other foods or foods after thawing. Furthermore, in the embodiment, the outside air temperature sensor 47 is used to automatically set the outside air temperature, but the present invention is not limited to this, and the present invention is effective even if the user measures and sets the outside air temperature at the start of thawing. Furthermore, the set temperature is not limited to 0 ° C. in the embodiment, but may be a refrigerating temperature of food including a minus temperature zone (about −3 ° C. to 0 ° C.).

[0052]

As described above in detail, according to the present invention, since frozen food is thawed at the refrigerating temperature of the food including the minus temperature zone, the drip outflow from the food accompanying the thawing can be minimized. In addition, by thawing uniformly, discoloration and fading can be suppressed while maintaining the freshness of food.

In particular, the heating means is operated at the lower limit temperature and stopped at the upper limit temperature, and the temperature inside the refrigerator is lowered from the upper limit temperature by the cooling action of the frozen food itself. The time during which the food passes through the maximum ice crystal production zone can be shortened as compared with the case where the inside of the refrigerator is cooled by the cooling means during the stop. Therefore, it is possible to shorten the time required for thawing the food and improve the work efficiency thereafter, and it is also possible to suppress the methation of the food during thawing.

Further, in the inventions of claims 2 and 4,
In addition to the above inventions, the thawing end time is predicted based on the heating time until the heating means stops operating, and the thawing is completed at this thawing end time, and thereafter the cooling operation by the cooling means in the same temperature range. Therefore, it becomes possible to accurately and automatically terminate the thawing operation without using an infrared sensor or the like. Therefore, the labor of the user can be remarkably improved without causing a cost increase.

In particular, after thawing, since the food is stored in the same temperature zone, it is possible to keep the freshness of the food high until the cooking is started.

[Brief description of drawings]

FIG. 1 is a vertical side view of a frozen food defrosting device of the present invention.

FIG. 2 is a block diagram of an electric circuit of a control device of the decompression device of FIG.

FIG. 3 is a diagram showing a time transition of the temperature inside the refrigerator and the temperature of frozen food in the method for thawing frozen food of the present invention, and an operating state of each device of the thawing device in FIG. 1.

FIG. 4 is a flowchart showing a program of a microcomputer.

[Explanation of symbols]

 1 Defroster 2 Insulation Box 3 Storage Box 5 Upper Storage Room 16 Cooling Device 17 Compressor 22 Cooler 24 Cooling Fan 42 Heating Heater 46 Internal Temperature Sensor 47 Outside Air Temperature Sensor 51 Controller 52 Microcomputer

Claims (4)

[Claims] 1. A refrigerating temperature of food including a minus temperature zone is set as a set temperature in the refrigerator, and an upper limit temperature and a lower limit temperature are set above and below the set temperature, and frozen food is stored in the refrigerator. By operating the heating means when the temperature inside the refrigerator drops to the lower limit temperature due to the cooling action from the frozen food,
A method for thawing frozen food, wherein the heating means is stopped when the temperature inside the refrigerator rises to the upper limit temperature by the operation of the heating means. 2. A refrigerating temperature of food including a minus temperature zone is set as a set temperature in the refrigerator, an upper limit temperature and a lower limit temperature are set above and below the set temperature, and frozen food is stored in the refrigerator. By operating the heating means when the temperature inside the refrigerator drops to the lower limit temperature due to the cooling action from the frozen food,
When the internal temperature rises to the upper limit temperature by the operation of the heating means, the heating means is stopped to defrost the frozen food, and based on the heating time from the start of defrosting until the heating means is not operated. A method for thawing frozen foods, characterized by predicting a thawing end time and, after the thawing end time has elapsed, maintaining the inside temperature between the upper limit temperature and the lower limit temperature by a cooling means. 3. A cooling means for cooling the inside of the refrigerator, a heating means for heating the inside of the refrigerator, and a temperature detecting means for detecting the temperature inside the refrigerator.
In the defrosting device for frozen food, the defrosting device comprising: a control unit that performs a defrosting operation and a cooling operation by controlling the cooling unit and the heating unit based on the temperature inside the refrigerator output by the temperature detecting unit. The means sets an upper limit temperature and a lower limit temperature above and below the set temperature in the refrigerator, and during cooling operation, operates the cooling means at the upper limit temperature and stops the cooling means at the lower limit temperature, The frozen food defrosting device is characterized in that the operation of the cooling means is prohibited during the defrosting operation, the heating means is operated at the lower limit temperature, and the heating means is stopped at the upper limit temperature. 4. The control means integrates the heating time from the start of the thawing operation until the heating means stops operating, predicts the thawing end time based on the heating time, and the thawing at the thawing end time. The frozen food defrosting apparatus according to claim 3, wherein the operation is terminated and then the cooling operation is started.