JP2005291525A - Food freezing device and food thawing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To store food in a frozen state in a good state by applying a magnetic field so that it can be thawed.
A freezing device 21 performs a freezing process in which a food is frozen at a predetermined freezing temperature with respect to the food to make the food a frozen food. At this time, an alternating magnetic field is applied to the food from at least a part of the freezing process from the magnetic field generating coil 21e. The storage freezer 22 performs a storage process in which the frozen food is stored frozen at a predetermined storage temperature with respect to the frozen food. Then, an alternating magnetic field is selectively applied to the frozen food during the storage process according to the type of the frozen food from the magnetic field generating coil 22e.
[Selection] Figure 1

Description

  In the present invention, when freezing food such as fresh food, the food is frozen in a good state in the presence of a magnetic field, and frozen food (hereinafter referred to as frozen food) is stored in a good state. The present invention relates to a food frozen storage system for thawing frozen food as necessary.

  In general, when food such as fresh food is stored frozen, it is necessary to prevent the freshness and flavor of the food from being impaired by freezing. That is, foods such as fresh foods contain a large amount of moisture, and when such foods are frozen, a crystal structure is formed by hydrogen bonding. Most of the moisture contained in the food freezes at 0 ° C. to −5 ° C., although the freezing point slightly decreases due to the influence of bound water and electrolyte.

  At this time, if large ice crystals are generated inside the food, the separation and movement of moisture occurs, and the food tissue is destroyed. When such frozen food is thawed, the freshness and flavor of the food itself will be impaired.

  In order to prevent such problems, quick freezing is used to pass the maximum ice crystal generation temperature zone in a short time to suppress ice crystal formation and minimize tissue destruction. However, when the food is quickly frozen, the surface layer of the food freezes first, and the water inside the food is sucked up by the ice core near the surface layer, resulting in a structure due to the separation and movement of the water. May be destroyed.

  For this reason, for example, by generating a magnetic field or electric field that fluctuates with time in the internal space of the freezer, the water molecules and ions in the water contained in the food located in the internal space are vibrated to freeze the water. There is one in which the food is supercooled below the normal freezing temperature and the generation or fluctuation of the magnetic field or electric field is stopped and the food is immediately frozen at a low temperature.

  Furthermore, as a refrigeration system that prevents deterioration in food quality, the water clusters contained in the food are subdivided to dehumidify the low-temperature gas generated by the heat exchanger, and the low-temperature gas is circulated within the main body of the refrigeration system. On the other hand, there is one in which a magnetic field is applied to a food containing moisture and the strength of the magnetic field is changed over time (see Patent Document 2).

JP 2001-86967 A (paragraph (0009) to paragraph (0029), FIGS. 1 to 5) JP 2004-53243 A (paragraph (0082) to paragraph (0155), FIGS. 1 to 3)

  By the way, in the refrigeration apparatus described in Patent Document 1, an electric field that fluctuates with time is generated, and vibrations are imparted to water molecules and ions in water contained in the food located in the internal space. While suppressing freezing, after supercooling the food below the normal freezing temperature, the generation or fluctuation of the electric field is stopped, and then the food is instantly frozen at a low temperature, that is, while applying the electric field, After the food is supercooled below the freezing temperature, the generation of the electric field is stopped and the food is instantly frozen (rapid freezing). After stopping the generation, the tissue may be destroyed due to the separation and movement of moisture due to the rapid freezing.

  On the other hand, in the refrigeration apparatus described in Patent Document 2, the magnetic field strength is changed with time while circulating the low-temperature gas to freeze the food. The time from the start to the completion is extremely short, that is, quick freezing is performed, and as a result, the tissue may be destroyed due to the separation and movement of moisture.

  In any case, the conventional refrigeration apparatus has a problem that the food cannot always be frozen and stored in a good state, and further, there is a problem that the frozen food cannot be thawed well. That is, in the conventional refrigeration apparatus, the food is supercooled to a normal freezing temperature or lower and rapidly frozen, and thus there is a problem that it is difficult to store the food in a good state in a frozen state.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a food frozen storage system capable of applying a magnetic field and freezing and thawing food in a good state at all times.

  Therefore, in order to solve such problems, the present invention performs a freezing process in which the food is frozen at a predetermined freezing temperature with respect to the food in a food frozen storage system apparatus used when the food is frozen and stored. Freezing means that uses the food as frozen food, first alternating magnetic field applying means that applies an alternating magnetic field to the food during at least a part of the freezing process, and the frozen food is predetermined for the frozen food. And a second alternating magnetic field applying means for selectively applying an alternating magnetic field to the frozen food in accordance with the type of the frozen food during the storage process. It is characterized by having.

  In the present invention, the frequency of the alternating magnetic field applied to the food during the freezing process is different from the frequency of the alternating magnetic field applied to the frozen food during the storage process, and is further applied to the food during the freezing process. The frequency of the alternating magnetic field may be changed according to the type of food.

  In the present invention, the alternating magnetic field may be applied to the food in the vicinity of the maximum ice crystal generation temperature range of the food during the freezing process. In addition, it is desirable to apply the alternating magnetic field to the food in the presence of cold air.

  In the present invention, in the freezing process, an alternating magnetic field including a frequency component obtained based on the impedance characteristic of the food is applied to the food. Moreover, it is desirable to apply a rectangular wave-like alternating magnetic field as the alternating magnetic field. Furthermore, the alternating magnetic field may be one in which a plurality of different alternating magnetic fields are superimposed.

  In the present invention, the frequency of the alternating magnetic field is in the range of 0 (not including 0) to 10 MHz, and the intensity is 0.1 Tesla or less. Furthermore, the alternating magnetic field may be superimposed on a non-alternating magnetic field.

  In the present invention, for example, the freezing means includes a transport conveyor formed in a spiral shape to transport the food, a non-magnetic cylindrical body in which the transport conveyor is housed, and a cooling means for cooling the cylindrical body. And the first alternating magnetic field applying means includes a magnetic field generating coil disposed on a partial circumferential surface of the cylindrical body. Furthermore, a thawing means for performing a thawing process for thawing the frozen food at a thawing temperature determined for the frozen food, and a third alternating magnetic field applying means for applying an alternating magnetic field to the frozen food in the thawing process. You may make it have.

  As described above, the food freezing apparatus of the present invention freezes food, applies an alternating magnetic field, freezes the food, and freezes the frozen food while applying an alternating magnetic field according to the type of food. As a result, large ice crystals are not generated inside the food, and there is an effect that the food can always be frozen and stored well using an alternating magnetic field.

  In the present invention, when frozen food is thawed, it is thawed while applying an alternating magnetic field, so that the frozen food can be thawed well, and the freshness and flavor of the food are not impaired. .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this embodiment are not intended to limit the scope of the present invention only to the description unless otherwise specified. It is just an example.

  FIG. 1 is a block diagram schematically showing an example of a food frozen storage system having a food freezing device and a food thawing device according to the present invention. The illustrated food freezing / thawing system includes a food freezing device 11 and a food thawing device 12. The food freezing device 11 has a freezing device 21 and a storage freezer 22.

  The freezing device 21 has an insulated freezing device main body 21a, and in the freezing device main body 21a, a cooling device 21b, a blower fan 21c, an object placement portion 21d, and a magnetic field generating coil (air core coil). ) 21e is disposed, and in the illustrated example, the magnetic field generating coil 21e is disposed so as to sandwich the object placement portion 21d from above and below and from the left and right. A food 31 that is an object to be cooled is placed on the object to be cooled 21d, and the low-temperature air cooled by the cooling device 21b is circulated in the cabinet as indicated by a thick arrow in the drawing by the blower fan 21c.

  The freezing apparatus main body 21a shown in the drawing extends from the front side to the back side of the paper surface in FIG. 1, for example, and the cooled object placement unit 21d is, for example, a transport conveyor. The food is cooled while being transported by the transport conveyor. At this time, an alternating magnetic field (dynamic magnetic field) is applied to the food 31 from the magnetic field generating coil 21e as described later.

  The frozen food frozen by the freezing device 21 is transported to the storage freezer 22 by the transport conveyor. The storage freezer 22 has an insulated storage freezer main body 22a, and a cooling device 22b, a blower fan 22c, a frozen body storage space 22d, and a magnetic field generating coil 22e are arranged in the storage freezer main body 22a. In the illustrated example, the magnetic field generating coil 22e is disposed so as to sandwich the frozen storage space 22d from above and below and from the left and right. The frozen food storage space 22d stores the frozen food 32, and the low-temperature air cooled by the cooling device 22b is circulated through the interior of the refrigerator as indicated by the bold arrows in the figure by the blower fan 22c. Then, an alternating magnetic field is applied to the frozen food 32 from the magnetic field generating coil 22e.

  The frozen food 32 stored in the storage freezer 22 is thawed as necessary. When thawing, the frozen food 32 is transported to the food thawing device 12 and thawed. The food thawing device 12 has an insulated thawing device main body 12a, and a heating / humidity adjusting device 12b, a blower fan 12c, a conveyor 12d, and a magnetic field generating coil 12e are arranged in the thawing device main body 12a. In the illustrated example, the magnetic field generating coil 12e is arranged so as to sandwich the conveyor 12d from above and below and from the left and right. The frozen food 32 is placed on the conveyor 12d, and the air heated by the heating / humidifying device 12b is circulated through the inside of the cabinet as indicated by the thick arrow in the figure, and the frozen food 32 is thawed. The At this time, an alternating magnetic field is applied to the frozen food 32 from the magnetic field generating coil 12e.

  In addition, you may make it use what is shown with the code | symbol 23 in FIG. In this freezing apparatus, the magnetic field generating coil 21e is disposed so as to sandwich the conveyor 21d from the diagonally lower side and the diagonally upper side. Moreover, you may make it use what is shown by the code | symbol 24 in FIG. In this food thawing device 24, a thawing chamber (thawing chamber) 24a is defined instead of the conveyor 12d, and a magnetic field generating coil 12e is arranged so as to surround the thawing chamber 24a from above and below and from the left and right.

  Referring also to FIG. 2, when paying attention to the freezing device 21, a dynamic magnetic field generating device 41 is connected to a magnetic field generating coil 21e (not shown in FIG. 2) arranged in the freezing device main body 21a. A waveform generator (function generator) 42 is connected to the generator power supply 41. As will be described later, various waveforms (for example, a pulse waveform or a sine wave) generated by the waveform generator 42 are supplied to the dynamic magnetic field generator power supply 41, and the dynamic magnetic field generator power supply 41 is supplied from the waveform generator 42. In response to the signal waveform, a current is passed through the magnetic field generating coil 21e, and a dynamic magnetic field (alternating magnetic field) is generated by the magnetic field generating coil 21e.

  Here, with reference to FIG. 3, now the sweet potato is used as the food (unfrozen food) 31, and the relative permittivity and the relative dielectric loss factor of the sweet potato before and after freezing are measured by an impedance meter, and the absorbed energy and The relationship with the dynamic magnetic field frequency was measured (measured electrical characteristics of the article to be frozen: step S1). The results are shown in FIGS. 4 to 6, curves A1 to E1 indicate dynamic magnetic field frequencies (f) -relative permittivity when cooled at 5 ° C., 0 ° C., −2.5 ° C., −5 ° C., and −20 ° C., respectively. (Ε ′), dynamic magnetic field frequency (f) −relative dielectric loss factor (ε ″), and dynamic magnetic field frequency (f) −absorbed energy (f · ε ″).

As shown in FIG. 4, at a cooling temperature of 5 ° C., 0 ° C., and −2.5 ° C., the relative dielectric constant is almost flat at a dynamic magnetic field frequency of about 1 kHz to 100 kHz, whereas FIG. Thus, the relative dielectric loss factor decreases as the dynamic magnetic field frequency increases regardless of the temperature. Further, as shown in FIG. 6, the absorbed energy (f · ε ″ × 10 ⁻⁶ ) is a cooling temperature of 5 ° C. (A1), 0 ° C. (B1), −2.5 ° C. (C1), and −5. At ° C (D1), the dynamic magnetic field frequency became maximum near 1 MHz.

  And these measurement results were analyzed and the characteristic result (impedance characteristic) shown in FIG. 7 was obtained. In FIG. 7, the horizontal axis is the resistance value (Ω), the vertical axis is the reactance (Ω), and the maximum value P1 (in the respective curves L1 (20 ° C.), L2 (10 ° C.), and L3 (0 ° C.) 13 kHz), P2 (10 kHz), and frequencies corresponding to P3 (7 kHz) are extracted as singular frequencies (dielectric relaxation frequencies) (step S2). For example, in the case of sweet potato, the specific frequency at a temperature of 10 ° C. was 10 kHz. The specific frequency of the apple at a temperature of 10 ° C. was 1 kHz, and the specific frequency of the banana at a temperature of 10 ° C. was 28 kHz. The specific frequency of Toro at a temperature of 10 ° C. was 210 kHz.

  In consideration of the singular frequency described above, the waveform generation device 42 generates a synthesized wave (step S3), the waveform generation device 42 applies this synthesized wave to the dynamic magnetic field generator power supply 41, and the synthesized waveform from the magnetic field generation coil 21e. The dynamic magnetic field according to was applied to the sweet potato (step S4). Then, the sweet potato was frozen under application of a dynamic magnetic field (step S5).

  The average void area ratio of the sweet potato frozen in this way was examined. For comparison, the average void area ratio of fresh potatoes, quick-frozen potatoes and slow-frozen potatoes was also examined. The result is shown in FIG. In FIG. 8, the average void area ratio of fresh potatoes is 7.4%, whereas the average void area ratio of potatoes by quick freezing is 21.9%, and the average void area ratio of potatoes by slow freezing is 31. On the other hand, the potatoes frozen when irradiated with a magnetic field as described above had an average void area ratio of 10.1%, which is almost the same as the average void area ratio of raw potatoes. It was.

  After freezing in this way, it is stored frozen in a storage freezer (step S6) and thawed with a food thawing device (step S7), and it is confirmed that the freshness and flavor of the potato after thawing are almost the same as the raw potato. did it.

  With reference to FIG.1 and FIG.9, the temperature in the freezing apparatus 21 was controlled to -35 degreeC now, and the foodstuff 31 was frozen, conveying the foodstuff 31 with the conveyance conveyor 21d. At this time, a synthetic wave (for example, 7 kHz, 10 kHz, 13 kHz) having a specific frequency corresponding to the food 31 is generated by the waveform generation device 42 and supplied to the dynamic magnetic field generator power supply 41 to generate the magnetic field generation coil 21e. A dynamic magnetic field was applied to the food 31 by the above. As a result, the food 31 was lowered from a temperature of 20 ° C. to a temperature of −20 ° C., and the frozen food 32 was stored in the storage freezer 22 as the frozen food 32.

  The frozen food 32 was stored by controlling the temperature in the storage freezer 22 to −20 ° C. At this time, similarly to the case of freezing, a dynamic magnetic field corresponding to a specific frequency is applied to the frozen food 32 by the magnetic field generating coil 22e (for example, 600 Hz), and the frozen food 32 is stored frozen.

  When thawing the frozen food 32, the temperature in the food thawing apparatus 12 was controlled to 15 ° C., and the frozen food 32 was frozen while being transported by the transport conveyor 12d. At this time, as in the case of freezing, when a magnetic field having a specific frequency is applied to the frozen food 32 by the magnetic field generating coil 12e and thawed (for example, 7 kHz, 10 kHz, 13 kHz), the temperature of the frozen food 32 is increased. Rose from −20 ° C. to about 20 ° C., and thawing was completed. And when the freshness and flavor of the food after thawing were examined, there was almost no difference from the freshness and flavor before freezing.

  When freezing and thawing, the application of the dynamic magnetic field may be started before the maximum ice crystal generation temperature range shown in FIG. 9 is reached. The food can be frozen and thawed.

  Referring to FIG. 10, sweet potato was frozen and thawed using the food frozen storage system shown in FIG. 1, and the sensory test was performed. The result shown in FIG. 10 was obtained. For comparison, a sensory test was performed on raw potatoes, and a sensory test was also performed when thawing quick-frozen sweet potatoes without applying a magnetic field (hereinafter referred to as a conventional example).

  In FIG. 10, reference numeral N1 indicates the sweet potato frozen and stored according to the present invention, reference numeral N2 indicates the raw potato, and reference numeral N3 indicates the sensory test result of the conventional sweet potato. As shown in the figure, the sweet potato frozen and stored according to the present invention has almost no difference from raw potato, and its color, taste, fragrance, smoothness, and hardness (texture) are much higher than those of the conventional sweet potatoes. It turns out that it is favorable.

  FIG. 11 is a diagram illustrating another example of the freezing device 21. In the illustrated example, the transport conveyor 21d spirals in a cylindrical body 51 (for example, formed of a nonmagnetic material such as non-magnetic SUS). The food inlet is defined on the lower side of the cylindrical body 51, and the storage freezer 22 is positioned on the upper side. A partial peripheral surface of the cylindrical body 51 is defined by a magnetic field generating coil 21e. In the illustrated example, two magnetic field generating coils 21e are arranged to face each other.

  In the illustrated example, the magnetic field generating coils 21e are arranged apart from each other, so that the dynamic magnetic fields generated from the magnetic field generating coils 21e are independent from each other, and move as indicated by a two-dot chain line arrow in FIG. A magnetic field 52 is generated.

  Also in the example shown in FIG. 11, when the food 31 is transported on the transport conveyor 21d, the food 31 is cooled in the warehouse and affected by the dynamic magnetic field, and the other end portion from one end (lower end) of the transport conveyor 21d. As it moves to (upper end), it is frozen to become frozen food 32 and reaches the storage freezer 22.

  12 (a) and 12 (b), a plurality of magnetic field generating coils 21e are arranged coaxially with cylindrical body 51 at predetermined intervals in the axial direction, and cylindrical body 51 is magnetic field generating coil. It may be surrounded by 21e. In this way, a dynamic magnetic field 52 is formed along the axial direction of the cylindrical body 51 by the interaction, as shown by a two-dot chain line (FIG. 12A) and a dotted circle (FIG. 12B). A magnetic field having a substantially uniform intensity can be generated inside the cylindrical body 51.

  By the way, according to the experiments by the inventors, in FIGS. 4 and 5, the relative dielectric constant ε ′ and the relative dielectric loss factor ε ″, the temperature of the object to be cooled, and the dynamic magnetic field frequency have a function-function relationship with the latter as variables. I found out that From this, it can be seen that there exists a relative dielectric loss factor and a relative dielectric constant corresponding to the singular point of FIG. Furthermore, another singular point related to both is the maximum value of the curve group of FIG. It is clear from the results of the tissue test in FIG. 8 and the sensory test in FIG. 10 that food freezing using the conditions at the singular points in both figures has a good effect on the quality improvement of freezing and thawing. From these test results, it becomes possible to optimize the freezing / thawing quality of food by selecting an optimal dynamic magnetic field frequency corresponding to the temperature of the object to be cooled or by synthesizing a plurality of dynamic magnetic field frequencies.

  Furthermore, even when an alternating magnetic field in the ultra-low frequency region such as a frequency around 0 Hz, for example, a frequency of about 10 −6 Hz is applied, the food can be frozen well, and the alternating magnetic field ( It is easy to increase the strength of the dynamic magnetic field, and a high magnetic field of 1T (Tesla, 1T = 10000 Gauss) can be used by using a superconducting magnet or the like using a current high-temperature oxide. A magnetic field generator having a magnetic field strength of about 0.1 T or less is extremely practical. Furthermore, if the frequency of the alternating magnetic field is in the range of 0 Hz (not including 0) to 10 MHz, it has a positive effect on freezing of food.

  The specific heat of water contained in food is 4.22 kJ / kg ° C., the heat of melting of ice (coagulation heat) is 333.6 kJ / kg, and the freezing capacity of an actual freezing apparatus is such a content in a short time. It is powerful enough to freeze food. Compared to this, the electromagnetic wave energy used in the present invention may be considered as extremely small energy. Therefore, the weak magnetic field energy as in the present invention cannot have a macro effect on the degree of supercooling of the food, and the application of the alternating magnetic field is irrelevant to the degree of supercooling of the food. It is based on a completely different principle and effect.

  Since the frozen electromagnetic field is applied to the food while the food is frozen, the frozen food is frozen and the alternating magnetic field is selectively applied according to the type of food. As a result of always being able to store food in a frozen state, it can be applied when various foods are stored in a frozen state.

It is a block diagram which shows roughly an example of the food frozen storage system by this invention. It is a block diagram for demonstrating the alternating magnetic field application in the freezing apparatus shown in FIG. It is a block diagram for demonstrating the freezing process, the storage process, and the thawing | decompression process in the food frozen preservation system shown in FIG. It is a figure which shows the relationship between a dynamic magnetic field frequency and the dielectric constant of a foodstuff. It is a figure which shows the relationship between a dynamic magnetic field frequency and the dielectric loss factor of a foodstuff. It is a figure which shows the relationship between a dynamic magnetic field frequency and the absorbed energy of a foodstuff. It is a figure which shows the impedance characteristic of foodstuffs (sweet potato). It is a figure which shows the average void | hole area ratio of the frozen foodstuff (sweet potato) compared with a prior art example. It is a figure which shows the food temperature change in the freezing process, the storage process, and the thawing | decompression process in the food frozen preservation system shown in FIG. It is a figure which shows the sensory test result at the time of defrosting the frozen food (sweet potato) compared with a prior art example. It is a figure which shows an example of the positional relationship of the conveyance conveyor and magnetic field generation coil in the freezing apparatus shown in FIG. It is a figure which shows the other example of the positional relationship of the conveyance conveyor and magnetic field generation coil in the freezing apparatus shown in FIG. 1, (a) is the figure seen from the side, (b) is the figure seen from upper direction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Food refrigeration apparatus 12 Food thawing apparatus 21 Freezing apparatus 22 Storage freezer 12e, 22e, 21e Magnetic field generation coil (air core coil)
41 Electromagnetic field generator 42 Waveform generator (function generator)

Claims (12)

In a food frozen storage system device used for freezing and storing food,
Freezing means for freezing the food product by performing a freezing process in which the food product is frozen at a predetermined freezing temperature;
First alternating magnetic field applying means for applying an alternating magnetic field to the food in at least part of the freezing process;
A frozen storage means for performing a storage process of storing the frozen food at a predetermined storage temperature for the frozen food;
A food frozen storage system, comprising: a second alternating magnetic field applying unit that selectively applies an alternating magnetic field to the frozen food during the storage process according to the type of the frozen food.   The food frozen storage system according to claim 1, wherein the frequency of the alternating magnetic field applied to the food in the freezing process is different from that of the alternating magnetic field applied to the frozen food in the storage process.   The food frozen storage system according to claim 1 or 2, wherein the frequency of the alternating magnetic field applied to the food is changed in accordance with the type of food in the freezing process.   The food frozen storage system according to any one of claims 1 to 3, wherein in the freezing process, the alternating magnetic field is applied to the food near a maximum ice crystal generation temperature range of the food.   The food frozen storage system according to any one of claims 1 to 4, wherein the alternating magnetic field is applied to the food in the presence of cold air.   The food freezing according to any one of claims 1 to 5, wherein an alternating magnetic field including a frequency component obtained based on impedance characteristics of the food is applied to the food in the freezing process. Preservation system.   The food frozen storage system according to any one of claims 1 to 5, wherein a rectangular wave-like alternating magnetic field is applied as the alternating magnetic field in the freezing process.   The food frozen storage system according to claim 7, wherein a plurality of different alternating magnetic fields are superimposed on the alternating magnetic field.   8. The food frozen storage system according to claim 7, wherein the frequency of the alternating magnetic field is in the range of 0 (not including 0) to 10 MHz, and the intensity thereof is 0.1 Tesla or less.   The food frozen storage system according to claim 7, wherein a non-alternating magnetic field is superimposed on the alternating magnetic field. The freezing means includes a transport conveyor formed in a spiral shape to transport the food, a non-magnetic cylindrical body in which the transport conveyor is housed, and a cooling means for cooling the cylindrical body,
The food storage system according to claim 1, wherein the first alternating magnetic field applying means includes a magnetic field generating coil disposed on a partial circumferential surface of the cylindrical body. Furthermore, a thawing means for performing a thawing process for thawing the frozen food at a thawing temperature determined for the frozen food,
The food frozen storage system according to claim 1, further comprising third alternating magnetic field applying means for applying an alternating magnetic field to the frozen food in the thawing process.

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