JP2003106726A - Freezer and method of freezing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To freeze a foodstuff while keeping its raw texture and components so that the thawed and cooked foodstuff can taste almost like the original foodstuff. SOLUTION: The freezer comprises a freezer compartment 3, a cooling device 4 for cooling the inside of the freezer compartment 3, a foodstuff selecting means for inputting the kind of a foodstuff 2 set in the freezer compartment 3, and a cooling speed control device 7 for controlling the speed of cooling the foodstuff 2 based on the inputted kind of the foodstuff.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a refrigerator and a freezing method for freezing food materials.

[0002]

2. Description of the Related Art When a food material is frozen, the temperature of the tissue of the food material is rapidly lowered, the water in the tissue reaches a freezing point, and a freezing period of 0 ° C. to -5 ° C. (maximum ice crystal forming zone, freezing). While there is a slight temperature difference depending on the type of food, 70 to 80% of the water inside the tissue freezes. After the freezing of the food reaches the center, the temperature of the tissue falls again and reaches the ambient temperature of the freezing room in which the food is installed.

When freezing foodstuffs, it is important that the entire foodstuff reaches the target storage temperature as quickly as possible. When the freezing period becomes long, ice crystals grow and the tissue itself is destroyed, and water, umami, etc. flow out as a drip during thawing, and the quality is significantly impaired compared to before freezing. Therefore, the freezing period is shortened and the growth of ice crystals is suppressed by lowering the atmospheric temperature inside the freezing chamber.

FIG. 8 shows a change with time in the temperature inside the meat when the meat is frozen by the conventional freezing method. In the illustrated freezing method 1, cooling was performed in a freezing chamber having an ambient temperature of -20 ° C, in freezing method 2, cooling was performed in a freezing chamber having an ambient temperature of -40 ° C, and in freezing method 3, cooling was performed in a freezing chamber having an ambient temperature of -80 ° C. The freezing period in the meat is 50 minutes (in the figure) according to the freezing method 1, 15 minutes (in the figure) according to the freezing method 2, and 2.5 minutes (in the figure) according to the freezing method 3. Medium), and the lower the ambient temperature, the shorter the freezing period can be.

[0005]

However, lowering the ambient temperature and shortening the freezing period is not sufficient to maintain the quality of food. Table 1 shows the freezing period of the foodstuffs (meat) by the above-mentioned freezing methods 1, 2, and 3, the tissue state and component concentration after freezing and thawing, and the sensory evaluation after cooking. The evaluation of the tissue state is ○ when the tissue of the frozen food material is hardly destroyed as compared with the raw food material before freezing, × when the destruction is less than 1/2 of the area of the tissue, and 1/2 when the destruction is caused. In the above case, it was marked as XX. The component concentration was evaluated as ◯ when almost no component of the frozen food was flowed out, as × when the component flowed out was less than 1/2 of the component before freezing, and as XX when it was 1/2 or more. In the sensory evaluation, the raw state before freezing was set to 1.5 points, and the closer to this value, the closer to the taste before freezing. A difference of 1 point clearly identifies the difference in taste.

[0006]

[Table 1] According to Table 1, in the frozen product obtained by the freezing method 1 (atmosphere temperature −20 ° C.), both the tissue state and the component concentration after thawing are poor, and the sensory evaluation after cooking is as low as 0 point. When the texture state of the frozen product according to this Freezing Method 1 during freezing is observed in the photograph shown in FIG. 9, pores (cavities) presumed to contain ice crystals are observed on the sample surface. This hole has the same size as the muscle fiber of the raw tissue before freezing observed in the photograph shown in FIG. From this, during the freezing period of 50 minutes, ice crystals of the same size as muscle fibers are generated and the tissue is destroyed,
As a result, it is presumed that, as described above, the tissue condition at the time of thawing is deteriorated, the components flow out from the food material along with the moisture to the outside, and the concentration of the components is deteriorated, and the sensory evaluation after thawing and cooking is lowered.

In the case of a frozen product according to the freezing method 2, the freezing method 1
Compared with, the tissue condition after thawing and the component concentration were better. This is because by lowering the ambient temperature to -40 ℃,
It is presumed that the freezing period was shortened to 15 minutes, which suppressed the growth of ice crystals and reduced the tissue destruction due to ice crystals. However, the sensory evaluation after thawing and cooking was 0.5
There is a difference of 1 point between the point and raw, and it is clearly recognized that the taste is bad.

In the freezing method 3, the atmospheric temperature is lowered to −80 ° C., which is lower than that in the freezing method 2, so that the point of such sensory evaluation approaches to the raw value of 1.5, and the freezing period is 2.
It was shortened to 5 minutes. It was estimated that this would further reduce the tissue destruction due to ice crystals.
The actual texture state, component concentration, and sensory evaluation of the frozen product were worse than those of Freezing Method 2.

Observation of the microstructure of the frozen material (freezing period 2.5 minutes, cooling rate 2 ° C./min) by the freezing method 3 during freezing is shown in the photograph shown in FIG. The cavity is shown in FIG. 9 (freezing method 1; freezing period 5) described above.
It is smaller than the hole at 0 minutes and a cooling rate of 0.1 ° C./min). However, since pores presumed to have ice crystals smaller than the muscle fibers of the raw tissue observed in FIG. 10 described above are observed, ice crystals are generated inside the muscle fibers to damage the myofibrils. It is presumed that, by this, the tissue state and component concentration after thawing became worse, and the sensory evaluation after thawing and cooking became lower.

As described above, it is not possible to reduce the damage to the tissue of the foodstuff by simply increasing the cooling rate during the freezing period,
When thawing, it is difficult to reproduce the original taste of the food. The present invention solves the above problems, and an object of the present invention is to provide a freezing method and a freezer that can freeze a food material while preserving its raw tissue and components, and bring it closer to the original taste of the food material after thawing and cooking. It is a thing.

[0011]

In order to solve the above-mentioned problems, the present invention according to claim 1 provides a refrigerator, a freezer compartment, cooling means for cooling the freezer compartment, and food materials installed in the freezer compartment. And a cooling rate control means for controlling the cooling rate of the foodstuff based on the inputted foodstuff type.

[0012] With this, by setting an appropriate cooling rate for each food material, it becomes possible to obtain a good frozen product in which the texture state of the food material is maintained. According to a second aspect of the present invention, in the refrigerator according to the first aspect, there is provided temperature detection means for detecting the temperature of at least one of the food in the freezing chamber and the heat transfer medium that transfers heat to the food, and cooling speed control is provided. The means stores in advance the optimum cooling rate determined for each type of food, extracts the optimum cooling rate for the food according to the food type information from the food selection means, and detects the temperature information detected by the temperature detection means. While the central temperature of the foodstuff in the freezing room obtained more directly or indirectly is in the maximum ice crystal formation zone, the cooling speed of the foodstuff in the freezing room is transferred to the extracted optimum cooling speed by the cooling means. It is characterized in that it is configured to be controlled via a heat medium.

As described above, by controlling the cooling rate in the maximum ice crystal production zone for freezing foodstuffs to the optimum cooling rate predetermined for each type of foodstuffs, ice crystals produced inside the tissue are It is possible to suppress the size of the tissue so as not to be damaged. Therefore, it is possible to obtain a good frozen product that retains the textured state of the food product before freezing, and when the frozen product is thawed and cooked, the outflow of the components is small, and the original taste of the food product can be realized. The heat transfer medium is air, brine, or the like that transfers heat by contacting food materials.

According to a third aspect of the present invention, in the refrigerator according to the second aspect, the temperature detecting means detects the surface temperature of the food material, and the cooling speed control means detects the surface temperature of the food material for each type of food material. Correlation information of the central part temperature is stored in advance, and the central part temperature of the foodstuff in the freezer compartment is estimated by using the value of the surface temperature of the foodstuff detected by the temperature detecting means. .

According to a fourth aspect of the present invention, in the refrigerator according to the second aspect, there is provided physical characteristic information input means for inputting physical characteristic information such as dimensions and thermal conductivity for each kind of food material installed in the freezing chamber. The temperature detecting means detects the surface temperature of the food material, and the cooling rate control means stores in advance an arithmetic expression for calculating the central temperature of the food material from the surface temperature of the food material and the physical characteristic information. The temperature of the foodstuff in the freezer compartment is calculated by using the value of the surface temperature of the foodstuff detected in step 4, the physical property information from the physical property information input means, and the arithmetic expression. And

According to a fifth aspect of the present invention, in the refrigerator according to the second aspect, the temperature detecting means detects the temperature of the heat transfer medium which is a liquid, and the cooling speed control means, for each type of food, Correlation information between the temperature of the central portion of the food and the temperature of the liquid, and the information of the predetermined optimum liquid temperature of the liquid that can realize the optimum cooling rate is stored in advance, and the liquid detected by the temperature detecting means. The temperature of the liquid is estimated by the cooling means until the center temperature of the food in the freezing chamber is estimated from the temperature information of the temperature until the temperature of the estimated center of the food reaches the lower limit temperature of the maximum ice crystal formation zone. It is characterized in that it is configured to adjust.

According to a sixth aspect of the present invention, the temperature of the center of the food is detected when the food is frozen, and the food is cooled while the temperature of the center of the food is in the maximum ice crystal formation zone. It is characterized in that the speed is controlled to an optimum cooling speed that is predetermined for the type of food.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 is a sectional view showing a schematic configuration of a refrigerator according to Embodiment 1 of the present invention.

The refrigerator main body 1 includes a freezing room 3 in which a food material 2 or other object to be frozen is installed, and a cooling device for cooling air inside the freezing room 3, that is, as a heat transfer medium for transmitting heat to the food material 2. 4, a room temperature sensor 5 that detects the internal temperature (upper temperature) of the freezer compartment 3, an article temperature sensor 6 that detects the internal temperature of the food material 2 (the temperature at the central portion), a room temperature sensor 5, and an article temperature sensor 6 And a cooling rate control means 7 for controlling the cooling rate of the foodstuffs by driving the cooling device 4 on the basis of the information of 1. The cooling rate control means 7 stores the optimum cooling rate for each type of food as shown in Table 2 below.

[0020]

[Table 2] The cooling device 4 forms a refrigeration cycle by sequentially connecting a compressor 8, a condenser 9, a capillary tube 10 arranged outside the freezing chamber 3 and a direct-cooling evaporator 11 arranged inside the freezing chamber 3 in an annular shape. The inside of the freezer compartment 3 is directly cooled by the direct cooling type evaporator 11. In that case, freezer 3
At least one of the evaporation temperature of the refrigerant in the evaporator 11 and the capacity of the compressor 8 is controlled by using the internal temperature of the controller as a control value.

A control panel 12 as shown in FIG. 2 is provided on the outer surface of the refrigerator main body 1. The control panel 12 has a menu key 13 for selecting the type of food material 2 to be frozen, a setting key 14 for setting the storage temperature of the food material 2, an enter button 15 for confirming the set temperature by the setting key 14, A temperature display panel 16 for displaying the set temperature and the temperature in the freezer compartment 3, a start button 17 for starting and stopping the freezing operation, and a storage lamp 18 for notifying the end of freezing are provided.

A method of freezing the foodstuff 2 in the above refrigerator will be described by taking livestock meat (hereinafter referred to as meat) as the foodstuff 2 as an example. First, in the control panel 12, the temperature setting key 14 is used to set the temperature inside the freezer compartment −20 ° C.
Thereby, the set temperature displayed on the temperature display panel 16 is confirmed for several seconds, and then the temperature determination button 15 is pressed to fix the temperature. Next, "meat" is selected with the menu key 13, the food material 2 which is meat is set on the product temperature sensor 4 in the freezer compartment 3, and the start button 17 is pressed to start cooling the food material 2.

As a result, the direct-cooling type evaporator 11 of the cooling device 4 directly cools the inside of the freezer compartment 3, and the room temperature sensor 5,
The product temperature sensors 6 detect the temperatures inside the freezer compartment 3 and the food 2 respectively, and sequentially output them to the temperature control device 7.

On the other hand, the temperature control device 7 decreases the internal temperature at that time and the internal temperature at a certain time interval from when the internal temperature 0 ° C. (starting temperature of the freezing period) of the food 2 is detected. And the cooling rate is calculated. In addition, for each calculation, the calculated value was compared with the optimum cooling rate of 0.5 ℃ / min for "meat" shown in Table 1 above, and the calculated value was reduced to 0.5 ℃ / min. The temperature inside the freezer compartment 3 is controlled so as to approach. And the internal temperature of the foodstuff 2 −
After 5 ° C (end temperature of the freezing period) is detected, the temperature inside the freezer compartment 3 is controlled to -20 ° C. After that, when the internal temperature of the food material −20 ° C. is detected, the storage lamp 18 is turned on.

FIG. 3 shows changes in temperature inside the food material 2 and the freezer compartment 3 in the above refrigerator. At the start of the freezing operation, both the inside of the freezing room and the inside of the food (meat) are around 20 ° C., which is room temperature. After the start of the freezing operation, the inside of the freezing room is promptly -20
The inside of the food is cooled to 0 ℃
The temperature inside the freezer is controlled at -20 ° C until the temperature reaches. After the inside of the food reaches 0 ° C, the temperature inside the freezer is controlled so that the inside of the food is cooled at the above-mentioned 0.5 ° C / min, and the temperature inside the freezer reaches around -40 ° C. As a result, when the inside of the food reaches -5 ° C in about 10 minutes, the inside of the freezer is controlled again to -20 ° C, and the inside of the food is finally cooled to the temperature inside the freezer of -20 ° C.

FIG. 4 shows the relationship between the cooling rate of the meat during the freezing period of 0 to -5 ° C., the void ratio of myofibrils when thawed after freezing, and the sensory evaluation when thawed and cooked. Here, the void ratio of myofibrils is the ratio (percentage) of the voids of myofibrils to the cross-sectional area of the muscle fibers that make up the tissue of the meat. In the raw food material before freezing, almost no voids of myofibrils were observed, so the void ratio was set to 0%, and the sensory evaluation was 1.5.
It was a point.

When the cooling rate was 0.5 ° C./min, the void ratio of myofibrils was about 10%, the lowest, and the sensory evaluation was 1 point.
Closest to raw 1.5 points. When the cooling rate is 2 ° C / min or more, the void ratio of myofibrils becomes large, and the sensory evaluation is 0.
The point is clearly worse compared to raw. This is because, as described above for the conventional freezing method 3, when the cooling rate becomes 2 ° C./min or more, ice crystals with a small average particle size are generated inside the muscle fibers, and the ice crystals damage the myofibrils. Is presumed to give.

As is clear from this result, when the food material is meat, the tissue state after thawing is improved by controlling the cooling rate during the freezing period to 0.5 ° C./min, and the meat is most raw. It is possible to achieve a similar taste, that is, the original taste of the food.

As shown in Table 1 above, the optimum cooling rate for fish is 0.8 ° C / min and the optimum cooling rate for vegetables is 3 ° C / min. By controlling each optimum cooling rate during the freezing period, the original taste of the food can be realized after thawing.

In the above description, the article temperature sensor 6 is used to detect the internal temperature of the food 2. However, actually inserting the article temperature sensor 6 into the food 2 to detect the internal temperature impairs the appearance. Therefore, the correlation data between the surface temperature and the internal temperature of various foodstuffs is experimentally obtained in advance and stored in the product temperature sensor 6 itself or the temperature control device 7, and the surface of the foodstuff 2 is measured by the product temperature sensor 6. The internal temperature may be estimated by detecting the temperature.

As a method of controlling the cooling rate in the refrigerator constituted by the direct cooling type evaporator as described above, in addition to the method of setting the internal temperature of the freezing compartment 3 to the control value as described above,
There are a method of setting the evaporation temperature of the refrigerant of the evaporator 11 associated with the internal temperature of the freezer compartment 2 as a control value, a method of setting the capacity of the compressor 8 as a control value, and the like. (Embodiment 2) FIG. 5 is a sectional view showing a schematic configuration of a refrigerator according to Embodiment 2 of the present invention. This refrigerator is different from the refrigerator according to the first embodiment described above in the configuration of the cooling device 3 and the point that the article temperature sensor 6 detects the temperature of the surface of the food 2.

The cooling device 3 includes a cooler 19 having a compressor, a condenser and a capillary tube (not shown), a discharge duct 20 for introducing the cool air cooled by the cooler 19 into the freezer compartment 3, and a freezer. In the vicinity of the suction duct 21 for returning the cool air in the chamber 3 to the cooler 19, the blower 22 for forcedly ventilating the cool air by the cooler 19 into the freezing chamber 3 through the discharge duct 20, and the outlet 20a of the discharge duct 20. The damper thermo 23 is arranged to adjust the inflow amount of cold air. The damper thermo 23 is opened and closed by the driving force of the motor 24 according to an electric input from the temperature control device 7.

Further, as shown in FIG. 6, the control panel 12 is provided with a physical characteristic input key 25 for selecting a physical characteristic such as the width and thermal conductivity of the food material 2 to be frozen. Therefore, the setting key 14 sets not only the storage temperature of the food material but also the value of the physical characteristic selected by the physical characteristic input key 25, the decision button 15 confirms the setting value by the setting key 14, and the display panel 16 sets the setting key. The set value by 14 and the temperature in the freezer compartment 3 are displayed.

A method of freezing the food 2 in the above refrigerator will be described by taking fish as the food 2. First, in the control panel 12, the menu key 13 is used to select fish, the physical characteristic input key 25 is used to select a width, the setting key 14 is used to input a width value, and the enter button 15 is used to confirm the input value. Next, the thermal conductivity is selected with the physical property input key 25, the thermal conductivity value is input with the setting key 14, and the input value is confirmed with the enter button 15. Next, the setting key 14 is used to input the storage temperature of -20 ° C, and the enter button 15 is used to confirm the input value. Each input value is confirmed while confirming the value displayed on the display panel 16 for only a few seconds. After that, the food material 2, which is a fish, is placed on the product temperature sensor 4 in the freezer compartment 3, and the start button 17
Press to start cooling the food 2.

As a result, the cooling device 4 cools the inside of the freezer compartment 3, and the room temperature sensor 5 and the article temperature sensor 6 detect the internal temperature of the freezer compartment 3 and the surface temperature of the foodstuff 2 respectively, and successively control the temperature. Output to 7. On the other hand, the temperature control device 7 uses a pre-stored arithmetic expression based on the temperature information that is sequentially input and the width and thermal conductivity information that has been previously set and input, and uses the food ingredients that are fish. The internal temperature of 2 (center temperature) is calculated.

A relational expression of the amount of heat when the food material 2 is allowed to stand in low-temperature still air is expressed by, for example, the following expression. Here, the heat transfer coefficient h in still air is 5 W / m 2 · ° C,
The thermal conductivity λ is a value input from the control panel 12, and the heat transfer distance L is estimated from the width value input from the control panel 12, and the temperature Ta,
The temperature Tb of the food surface is a value detected by the temperature sensor 4. Therefore, the temperature Tc of the food center is calculated from the equation. Q is the amount of heat and S is the surface area.

Formula Q = h × (Tb−Ta) × S Formula Q = λ × ((Tc−Tb) / L) × S Formula = Formula From Formula h × (Tb−Ta) = λ × ((Tc− Tb) / L) Next, the temperature control device 7 performs the same internal temperature 0 ° C. (freezing period start temperature) of the food material 2 as in the first embodiment.
The cooling rate is calculated by checking the internal temperature at that time and the time required for the temperature to drop to the internal temperature at regular intervals from the time when is detected. In addition, each time the calculation is performed, the calculated value obtained is the optimum cooling rate of 0.8 for the "fish" shown in Table 1 above.
Compared to ℃ / min, the calculated value is cooling rate 0.8 ℃ / m
The temperature inside the freezer compartment 3 is controlled so as to approach in. Then, after the internal temperature of the food material −5 ° C. (end temperature of the freezing period) is detected, the temperature inside the freezer compartment 3 is controlled at −20 ° C. After that, when the internal temperature of the food material −20 ° C. is detected, the storage lamp 18 is turned on.

In this way, when the food material 2 is fish, by controlling the cooling rate during the freezing period to 0.8 ° C./min, the tissue state after thawing is improved, and the taste that is closest to the raw taste is obtained. Therefore, the original taste of food can be realized.

In the same manner as above, the optimum cooling rate for meat is 0.5 ° C / min and the optimum cooling rate for vegetables is 3 ° C / m.
By controlling to in during the freezing period, the original taste of the food can be realized after thawing.

As a method of controlling the cooling rate in the refrigerator constituted by the forced convection evaporator as described above, in addition to the method of using the temperature in the freezer compartment 3 as the control value as described above, There are a method of setting the temperature of the cold air cooled by the cooler 19 as a control value, a method of setting the amount of cold air flowing into the freezer compartment 3 by the damper thermo 23 as a control value, and a method of setting the air volume of the blower 22 as a control value. . (Embodiment 3) FIG. 7 is a sectional view showing a schematic configuration of a refrigerator according to Embodiment 3 of the present invention.

The refrigerator main body 1 has a brine 27 as a heat transfer medium for immersing and cooling the object to be frozen such as the food 2 inside the freezer tank 26, and a direct cooling type evaporation for cooling the brine 27. The container 11 is provided with a stirring screw 28 that stirs the brine 27, a liquid temperature sensor 29 that detects the temperature of the brine 27, and a basket 30 that houses the food material 2 and is immersed in the brine 27. The direct-cooling evaporator (cooling pipe) 11 constitutes a part of the refrigeration cycle (see FIG. 1) described in the first embodiment. A control panel 12 (see FIG. 2) similar to that of the first embodiment is provided on the outer surface of the refrigerator body 1 except that there is no storage lamp.

The temperature control device 7 stores optimum cooling rates of various food materials and experimentally obtained brine temperatures capable of realizing the optimum cooling rates as shown in Table 3 below. The temperature of the brine 27 is controlled via the direct cooling evaporator 11 based on the information.

[0043]

[Table 3] A method of freezing the food material 2 in the refrigerator described above will be described by taking vegetables as the food material 2 as an example. First, in the control panel 12, the temperature of the brine 27 is set to −40 ° C. with the setting key 14, the set temperature displayed on the display panel 16 for only a few seconds is confirmed, and the decision button 15 is pressed to confirm. After that, press “Menu” 13 to select “Vegetables”
Is selected, the basket 30 containing the foodstuff 2 that is a vegetable is directly immersed in the brine 27, and the start button 17 is pressed to start cooling the foodstuff 2.

As a result, the direct-cooling type evaporator 11 directly cools the brine 27 and quickly lowers the brine 27 to the above-mentioned predetermined brine temperature of -40 ° C., whereby
The inside of the food material 2, which is a vegetable, is controlled at a cooling rate of 3 ° C./min.

In this way, when the food material is vegetables, the optimum cooling rate can be controlled at 3 ° C./min during the freezing period by controlling the brine temperature at −40 ° C., and thus the thawing process can be performed. It is possible to improve the subsequent tissue state and achieve the taste that is the closest to the fresh taste and the original taste of the food.

In the same manner as above, by controlling the brine temperature at -20 ° C for meat, the optimum cooling rate can be controlled at 0.5 ° C / min during the freezing period, and for fish, the brine temperature can be controlled. By controlling the temperature to be -25 ° C, the optimum cooling rate can be controlled to 0.8 ° C / min during the freezing period, and the original taste of the food material can be realized after thawing.

As a method of controlling the cooling rate in the refrigerator using the brine 27, the brine 27 can be controlled by the brine temperature as described above.
Method using the flow rate (stirring speed) of the control value as a control value, the method using the evaporation temperature of the refrigerant of the evaporator 11 related to the brine temperature as the control value, and the capacity of the compressor as in the first embodiment described above. There is a method of setting the value.

[0048]

As described above, according to the present invention, by controlling the predetermined optimum cooling rate for each food in the freezing period (maximum ice crystal formation zone) for freezing food,
It becomes possible to obtain a good frozen product that retains the texture state of the food material before freezing, and when this frozen product is thawed and cooked,
The original taste of food can be realized with less outflow of ingredients.

[Brief description of drawings]

FIG. 1 is a sectional view showing a schematic configuration of a refrigerator according to a first embodiment of the present invention.

FIG. 2 is a front view of a control panel of the refrigerator shown in FIG.

FIG. 3 is a graph showing changes over time in the temperature inside the freezer and the food when the food is frozen by the freezing method using the refrigerator shown in FIG.

FIG. 4 is a graph showing the relationship between the cooling rate when freezing meat and the tissue state and sensory evaluation.

FIG. 5 is a sectional view showing a schematic configuration of a refrigerator according to a second embodiment of the present invention.

6 is a front view of a control panel of the refrigerator shown in FIG.

FIG. 7 is a sectional view showing a schematic configuration of a refrigerator according to a third embodiment of the present invention.

FIG. 8 is a graph showing changes over time in the temperature inside foodstuffs when the foodstuffs are frozen by a conventional freezing method.

FIG. 9 is a photograph showing a tissue state after freezing raw meat by the conventional freezing method 1, showing pores after formation of ice crystals in muscle fibers.

FIG. 10 is a photograph showing the texture of raw meat.

FIG. 11 is a photograph showing a tissue state after freezing raw meat by the conventional freezing method 3, showing pores after formation of ice crystals in myofibrils.

[Explanation of symbols]

2 ingredients 3 freezer 4 Cooling device 5 Room temperature sensor 6 Product temperature sensor 7 Temperature control device 12 Control panel 26 Freezer 27 brine 29 Liquid temperature sensor

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Akihiro Jono             4-2-5 Takaidahondori, Higashi-Osaka City, Osaka Prefecture               Within Matsushita Cold Machinery Co., Ltd. F-term (reference) 3L045 AA02 LA12 MA01 MA02                 4B022 LB01 LF02 LN01 LT06

Claims (6)

[Claims] 1. A freezing compartment, a cooling means for cooling the freezing compartment, a food selection means for inputting the type of food installed in the freezing compartment, and a cooling rate of the food based on the input kind of food. A refrigerator comprising a cooling rate control means for controlling. 2. A temperature detecting means for detecting the temperature of at least one of the food in the freezing chamber and the heat transfer medium for transmitting heat to the food, and the cooling speed control means is the optimum cooling determined for each kind of food. The speed is stored in advance, the optimum cooling rate is extracted for the food according to the food type information from the food selection means, and the food in the freezer compartment is obtained directly or indirectly from the temperature information detected by the temperature detection means. While the center temperature of the is within the maximum ice crystal formation zone, the cooling rate of the food material in the freezing chamber is controlled to the extracted optimal cooling rate by the cooling means via the heat transfer medium. The refrigerator according to item 1. 3. The temperature detecting means detects the surface temperature of the food material, and the cooling speed control means stores in advance the correlation information between the surface temperature and the central temperature of the food material for each kind of food material, and the temperature detecting means uses the temperature detecting means. The refrigerator according to claim 2, which is configured to estimate the temperature of the central portion of the food in the freezer compartment by using the value of the detected surface temperature of the food. 4. A physical characteristic information input means for inputting physical characteristic information such as dimensions and thermal conductivity for each type of food material installed in the freezer compartment, wherein the temperature detecting means detects the surface temperature of the food material and the cooling rate. The control means stores in advance an arithmetic expression for calculating the central temperature of the food from the surface temperature of the food and the physical characteristic information, and inputs the value of the surface temperature of the food detected by the temperature detecting means and the physical characteristic information input. The refrigerator according to claim 2, wherein the refrigerator is configured to calculate the temperature of the central portion of the food in the freezer compartment by using the physical characteristic information from the means and the arithmetic expression. 5. The temperature detecting means detects the temperature of the heat transfer medium which is a liquid, and the cooling rate controlling means, for each type of food material, correlation information between the central temperature of the food material and the temperature of the liquid, Pre-stored with information of the optimum liquid temperature of the liquid which is predetermined that can realize the optimum cooling rate, and estimates the center temperature of the food in the freezer from the temperature information of the liquid detected by the temperature detecting means, The refrigerator according to claim 2, wherein the cooling means adjusts the temperature of the liquid to the optimum liquid temperature until the estimated central temperature of the food reaches the lower limit temperature of the maximum ice crystal formation zone. 6. The temperature of the center of the food is detected when the food is frozen, and the cooling rate of the food is determined by the type of the food while the temperature of the center of the food is in the maximum ice crystal formation zone. A refrigeration method in which the cooling rate is controlled to a predetermined optimum cooling rate.