JP2006136231A - Thawing method using vacuum microwave - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thawing method using vacuum microwaves by which a frozen material such as Daifuku rice cake (rice cake stuffed with sweetened bean jam) is thawed without causing spill of ingredients. <P>SOLUTION: The thawing method using vacuum microwaves comprises a preliminary drying process (I) and a thawing process (II)sequentially carried out. The preliminary drying process (I) comprises reducing the pressure in a thawing chamber to have a vacuum condition for the preliminary drying while the microwaves are not irradiated so that frost adhering to the surface of the Daifuku rice cake is sublimated in this process (I). The thawing process (II) comprises irradiating the microwaves into the thawing chamber while recovering the condition in the thawing chamber from the vacuum condition for the preliminary drying to vacuum condition close to that under atmospheric pressure so as to finish the process while keeping the thawing chamber have the vacuum condition close to that under the atmospheric pressure. According to the process, reliability in discharge of the air in the chamber is reduced because the pressure in the thawing chamber does not get reduced depending on the softened condition of the coating dough of the rice cake and the temperature rising condition of the contained air, so that the coating dough of the rice cake hardly generates cuts and thereby the ingredients are prevented from being spilled out. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a vacuum microwave thawing method for thawing a frozen material stored in a thawing chamber based on irradiation of microwaves in the thawing chamber.

In the vacuum microwave thawing method, it has been proposed to suppress the stress applied to the frozen cells based on the fusion of microwave heating and vacuum sublimation cooling. This microwave heating is performed over the time of decompressing the decompression chamber in the vacuum state and the decompression decompressing the vacuum chamber, and the vacuum sublimation cooling is performed when the decompression chamber is decompressed in the vacuum state. This is done by stopping on the way. This thawing method is suitable for thawing a uniform material such as tuna, and the uniform material such as tuna can be thawed from outside to inside with low stress based on repeated microwave heating and vacuum sublimation cooling.
JP 2003-61635 A

  In the above conventional method, when thawing frozen products such as Daifuku rice cake, the scab becomes soft based on being heated by microwaves, and the temperature of the candy is raised together with the contained air based on being heated by microwaves. When depressurizing in a vacuum state, air may break through the scab and be released. For this reason, since a wound arises in a crust, a wrinkle may spill from a wound.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a vacuum microwave thawing method capable of thawing a frozen material without spilling the contents.

The vacuum microwave thawing method of the present invention is characterized in that 1) a preliminary drying step and 2) a thawing step are sequentially performed.
1) The preliminary drying step is a step in which the thawing chamber is depressurized to a vacuum state for preliminary drying in a non-microwave irradiation state.
2) The thawing process is a process in which a decompression operation for restoring the pressure in the thawing chamber from a vacuum state for preliminary drying to a vacuum state near atmospheric pressure and a heating operation for irradiating microwaves in the thawing chamber are combined. The process is terminated while substantially maintaining a vacuum state near atmospheric pressure. Here, the “vacuum state near atmospheric pressure” means a vacuum state near atmospheric pressure compared to the vacuum state for preliminary drying, and “substantially hold in a vacuum state near atmospheric pressure” means near vacuum pressure. It includes reducing the pressure from the vacuum state to the extent that it does not adversely affect the frozen state of the frozen product.

  A pre-drying step is performed in which the inside of the thawing chamber is depressurized to a vacuum state for pre-drying in a non-irradiated state of microwaves, and frost attached to the surface of a frozen material such as Daifuku is sublimated. After the preliminary drying process is completed, a decompression operation is performed to restore the pressure in the thawing chamber from a vacuum state for preliminary drying to a vacuum state near atmospheric pressure. During this decompression operation, the crust and cocoon are thawed based on the microwave irradiation in the thawing chamber, and the thawing is completed while the thawing chamber is substantially maintained in a vacuum state near atmospheric pressure. For this reason, since the decompression chamber is not detrimentally depressurized in the softened state of the scab and the temperature rise of the contained air, the probability that the contained air breaks the scab and is released is reduced. Accordingly, since it is difficult for the wound to be generated in the scab, the spill is prevented from spilling from the wound.

1. Configuration of Vacuum Microwave Defroster As shown in FIG. 1, the cabinet 1 has a rectangular box shape with an open front, and the caster 2 is mounted on the lower surface of the cabinet 1 at four corners. . In the cabinet 1, as shown in FIG. 2, a chamber 3 corresponding to an inner box and a pressure vessel is fixed. The chamber 3 has a rectangular box shape with an open front, and a thawing chamber 4 is formed in the chamber 3. The thawing chamber 4 stores a frozen material that is an object of vacuum microwave thawing, and corresponds to a decompression chamber.

  As shown in FIG. 1, a door 5 is mounted on the cabinet 1 so as to be rotatable about a vertical axis on the right side, and the front surface of the thawing chamber 4 is airtight based on the rotation operation of the door 5. Opened and closed to state. A handle 6 is mounted on the left side of the door 5 so as to be rotatable about a shaft 7 extending in the front-rear direction. A lock plate is fixed to the handle 6, and when the handle 6 is rotated in the closed state of the door 5, the lock plate rotates integrally with the handle 6, so that the lock plate in the cabinet 1 is moved. The door 5 is locked in the closed state by the engaging force between the lock plate and the lock hole.

  A through hole-like excitation port is formed in the rear plate of the chamber 3. This excitation port is sealed in an airtight state by a pressure plate wall (not shown) made of a glass plate, and the rear plate of the chamber 3 is located at the periphery of the excitation port as shown in FIG. Thus, the front end of the waveguide 8 is fixed. A magnetron 9 corresponding to a microwave generator is fixed to the rear end portion of the waveguide 8, and when the magnetron 9 oscillates, microwaves enter the thawing chamber 4 from the magnetron 9 through the waveguide 8 and the excitation port. Irradiated.

  A machine room is formed in the cabinet 1 below the thawing room 4, and a control circuit 10 is accommodated in the machine room as shown in FIG. The control circuit 10 is mainly composed of a microcomputer and has a CPU 11, a ROM 12 and a RAM 13. This control circuit 10 corresponds to an operation control means, and controls the oscillation state of the magnetron 9 based on driving control of the inverter circuit 14.

  As shown in FIG. 2, a table motor 15 is fixed in the cabinet 1 below the chamber 3, and the control circuit 10 drives and controls the motor drive circuit 16 (see FIG. 3). The rotation state of the table motor 15 is controlled. As shown in FIG. 2, a circular dish-shaped turntable 17 is mounted on the rotating shaft of the table motor 15 at the bottom of the thawing chamber 4. The turntable 17 has a frozen object placed thereon, and the control circuit 10 rotates the table motor 15 in a constant direction at a constant speed while the magnetron 9 is oscillating. Are uniformly irradiated with microwaves.

  As shown in FIG. 2, a vacuum pump 18 corresponding to a decompressor is fixed in the cabinet 1, and a suction port of the vacuum pump 18 is connected to the thawing chamber 4 through a pipe 19. The vacuum pump 18 uses a pump motor 20 (see FIG. 3) as a drive source, and the control circuit 10 controls the rotation state of the pump motor 20 based on the drive control of the motor drive circuit 21, and the thawing chamber. The air in 4 is discharged from the pipe 19. As shown in FIG. 2, a check valve 22 is interposed in the pipe 19. This check valve 22 stops the air flow flowing into the thawing chamber 4 through the pipe 19 and allows the air flow discharged from the thawing chamber 4 through the pipe 19.

  The chamber 3 is equipped with an atmosphere release valve 23 and a pressure regulating valve 24 corresponding to a pressure regulator. The air release valve 23 and the pressure regulating valve 24 completely shut off the air flow in the closed state, and the thawing chamber 4 is air in a state where all of the door 5, the air open valve 23, and the pressure regulating valve 24 are closed. Is reduced to the target pressure based on the suction. The atmospheric release valve 23 and the pressure regulating valve 24 are driven by an open valve solenoid 25 (see FIG. 3) and a pressure regulating solenoid 26 (see FIG. 3), and the control circuit 10 has an open valve solenoid 25 and a pressure regulating solenoid. The air release valve 23 and the pressure regulating valve 24 are opened and closed based on turning on and off 26 through the solenoid drive circuit 27 and the solenoid drive circuit 28. The opening degree of the pressure regulating valve 24 is mechanically adjustable, and the opening degree of the pressure regulating valve 24 is set so that the flow rate is smaller than that of the atmosphere opening valve 23.

  A pressure sensor 29 is attached to the chamber 3 as shown in FIG. The pressure sensor 29 outputs an electrical signal at a level corresponding to the internal pressure of the thawing chamber 4, and the control circuit 10 detects the internal pressure of the thawing chamber 4 based on the output signal from the pressure sensor 29. The chamber 3 is provided with a door switch 30 (see FIG. 3). The door switch 30 is turned on and off mechanically in conjunction with the opening and closing of the door 5, and the control circuit 10 detects the opening and closing of the door 5 based on the on and off of the door switch 30.

  As shown in FIG. 1, an operation panel 31 is fixed to the cabinet 1 above the door 5. The operation panel 31 is provided with an on switch 32 and an off switch 33, and the main power is turned on based on the operation of the on switch 32 and shut off based on the operation of the off switch 33. The operation panel 31 is provided with a fish shell switch 34, a meat switch 35, and a confectionery switch 36. When the control circuit 10 detects that either the fish shell switch 34 or the meat switch 35 is operated, it is standard. When the thawing mode is set and it is detected that the confectionery switch 36 is operated, the non-standard thawing mode is set. That is, the fish shell switch 34 to the confectionery switch 36 correspond to a thawing mode designation means for designating the thawing mode.

  As shown in FIG. 1, an up switch 37 and a down switch 38 are attached to the operation panel 31. The up switch 37 and the down switch 38 correspond to mass input means, and the control circuit 10 sets the mass of the frozen material based on the operation contents of the up switch 37 and the down switch 38. As shown in FIG. 1, a mass indicator 39 is attached to the operation panel 31. This mass indicator 39 is composed of an LED indicator, and the control circuit 10 controls the LED drive circuit 40 (see FIG. 3) based on the mass setting result, and the mass indicator 39 displays the mass setting result. Display numerically.

As shown in FIG. 1, a start switch 41 and a stop switch 42 are attached to the operation panel 31. The start switch 41 and the stop switch 42 correspond to operation start means and operation stop means for instructing operation start and operation stop, and the control circuit 10 operates based on detecting an effective operation of the start switch 41. The operation is stopped halfway based on detecting the effective operation of the stop switch 42. As shown in FIG. 1, a time indicator 43 is attached to the operation panel 31. This time indicator 43 is composed of an LED indicator, and the control circuit 10 drives and controls the LED drive circuit 44 (see FIG. 3) based on the progress of the operation. Displays operation time information as a numerical value.
2. Outline of operation 2-1. Explanation of standard thawing mode As shown in FIG. 4, in the standard thawing mode, a pre-drying step (I) in which the inside of the thawing chamber 4 is depressurized in a microwave non-irradiation state and the microwave in the thawing chamber 4 is irradiated in a vacuum state. A thawing step (II) and an end step (III) for returning the pressure in the thawing chamber 4 to atmospheric pressure. In the preliminary drying step (I), frost adhering to the surface of the frozen material is preliminarily removed based on vacuum sublimation cooling of the frozen material in the thawing chamber 4, and the degree of vacuum G is reduced to the vacuum equilibrium value Go. Finish based on descending. The degree of decompression G refers to the amount of change per unit time of the internal pressure P in the thawing chamber 4, and the internal pressure P when “decompression degree G ≦ the decompression equilibrium value Go” is detected is referred to as the equilibrium pressure Po.

  The thawing step (II) is cyclically repeated until the operation end condition is satisfied. In each thawing step (II), the decompression chamber 4 is restored from the equilibrium pressure Po to the decompression upper limit Pu, and then restored. The pressure is reduced again from the pressure upper limit Pu to the equilibrium pressure Po. This return pressure upper limit Pu is mechanically set as the opening degree of the pressure regulating valve 24 in the open state, and the microwave heating is a lower limit at which the inside of the thawing chamber 4 does not induce a vacuum discharge as shown by a thick line. When the pressure is equal to or higher than Px, the process is performed at the time of decompression and decompression, and stops halfway at the time of decompression. After the microwave heating is stopped halfway, the frozen material is subjected to vacuum sublimation cooling based on the fact that the inside of the thawing chamber 4 is depressurized without being irradiated with microwaves. That is, each thawing step (II) is a combination of microwave heating and vacuum sublimation cooling, and the frozen material is thawed with low stress based on the repeated thawing step (II).

  The equilibrium pressure Po varies depending on the temperature and mass of the frozen material. That is, in the thawing chamber 4, the frozen matter is vaporized as the frozen matter is thawed, and the amount of the frozen matter varies depending on the temperature and mass of the frozen matter. On the other hand, the pump motor 20 is rotationally driven at a constant torque and a constant speed, and the pressure reduction capability of the vacuum pump 18 is constant. Therefore, the pressure reduction capacity of the vacuum pump 18 and the internal pressure P of the thawing chamber 4 are balanced at an equilibrium pressure Po corresponding to the temperature and mass of the frozen material.

The equilibrium pressure Po when the thawing step (II) is completed is higher than the equilibrium pressure Po when the thawing step (II) is started. That is, in the thawing step (II), the frozen material is heated by microwaves, and the thawing of the frozen material proceeds according to the mass. Accordingly, when the thawing step (II) is completed, a larger amount of ice is vaporized than when the thawing step (II) is started, so that the decompression capacity of the vacuum pump 18 and the internal pressure P of the thawing chamber 4 are increased. Balance is performed at a higher equilibrium pressure Po than the equilibrium pressure Po when the thawing step (II) is started.
2-2. Description of Non-Standard Thawing Mode As shown in FIG. 5, the non-standard thawing mode has a preliminary drying step (I), a thawing step (II), and an end step (III). In the pre-drying step (I), the inside of the thawing chamber 4 is depressurized in a non-microwave irradiation state, and the frost adhering to the surface of the frozen material is cooled by sublimation cooling of the frozen material in the thawing chamber 4. This is done for the purpose of preliminary removal. This pre-drying step (I) does not end under the condition of the degree of reduced pressure G, but ends when the reduced pressure time Td reaches the set value. The depressurization time Td refers to the elapsed time from when the internal pressure P of the thawing chamber 4 reaches the lower limit pressure Px that does not induce vacuum discharge, and is a variable value set based on the input result of the mass Wg. . The depressurized state in the thawing chamber 4 when the depressurization time Td has elapsed is referred to as a predrying vacuum state.

  The thawing step (II) is a combination of a decompression operation for returning the inside of the thawing chamber 4 from a vacuum state for preliminary drying to a vacuum state near atmospheric pressure, and a heating operation for irradiating the inside of the thawing chamber 4 with microwaves. . The return pressure operation is performed by opening the air release valve 23 in a vacuum state for preliminary drying. During this pressure recovery operation, the vacuum pump 18 is continuously operated from the preliminary drying step (I), and the internal pressure P of the thawing chamber 4 rapidly increases in conjunction with the opening of the air release valve 23. Later, when the pressure reduction capability of the vacuum pump 18 and the air supply capability of the air release valve 23 are balanced, the vacuum pump 18 is stabilized. A state in which the internal pressure P of the thawing chamber 4 is stable is referred to as a vacuum state near atmospheric pressure.

The heating operation is to irradiate microwaves into the thawing chamber 4 with the air release valve 23 opened as shown by a thick line. Microwave irradiation is performed after the internal pressure P of the thawing chamber 4 exceeds the lower limit pressure Px. It is started and continued until the thawing step (II) is completed. This microwave irradiation is performed in the operation state of the vacuum pump 18, and the vaporized component released from the frozen material is discharged through the pipe 19 by the exhaust flow generated by the vacuum pump 18. The microwave irradiation time Tm and the microwave output W are variable values set based on the input result of the mass Wg, and the thawing step (II) is performed by turning off the vacuum pump 18 when the microwave irradiation time Tm has elapsed. finish. That is, the thawing step (II) is continued while the inside of the thawing chamber 4 is maintained in a vacuum state close to the atmospheric pressure, and ends without performing a decompression operation for depressurizing the inside of the thawing chamber 4.
3. Details of Operation Contents Operation control data and an operation control program are recorded in the ROM 12 of the control circuit 10, and the CPU 11 of the control circuit 10 includes a magnetron 9, a table motor 15, a pump motor 20, an opening valve solenoid 25, and a pressure regulating valve solenoid 26. The above-described operation is executed by controlling the drive based on the operation control program. Hereinafter, the control contents of the control circuit 10 will be described in detail.

  The CPU 11 of the control circuit 10 determines the operation state of the seafood switch 34 in step S1 of FIG. 6, determines the operation state of the meat switch 35 in step S2, and determines the operation state of the confectionery switch 36 in step S3. For example, when it is detected in step S1 or step S2 that the seafood switch 34 or meat switch 35 has been operated, the process proceeds to step S4, and the thawing mode is set to the standard thawing mode. If it is detected in step S3 that the confectionery switch 36 has been operated, the process proceeds to step S5, and the thawing mode is set to the non-standard thawing mode.

  When the CPU 11 sets the thawing mode, the initial value is set to the mass Wg in step S6, and the operation state of the up switch 37 is determined in step S7. When the operation of the up switch 37 is detected here, the process proceeds to step S8, and the unit mass ΔWg is added to the current value of the mass Wg.

  When proceeding to step S9, the CPU 11 determines the operation state of the down switch 38. When the operation of the down switch 38 is detected here, the process proceeds to step S10, and the unit mass ΔWg is subtracted from the current value of the mass Wg.

  When proceeding to step S11, the CPU 11 determines the operation state of the start switch 41. Here, when the operation of the start switch 41 is detected, the mass Wg is determined at the current value, and the opening / closing of the door 5 is determined in step S12. Whether the door 5 is opened or closed is determined based on the state of the door switch 30. When the CPU 11 detects that the door 5 is closed in step S12, the process proceeds to step S13.

  When the CPU 11 proceeds to step S13, the air release valve 23 is closed. Then, the pressure regulating valve 24 is closed in step S14, the pressure in the thawing chamber 4 is reduced based on driving the vacuum pump 18 in step S15, and the process proceeds to step S16. The vacuum pump 18 is driven at a constant speed, a constant direction, and a constant torque. The vacuum pump 18 is continuously driven with a constant capacity until the end of the operation. That is, the CPU 11 depressurizes the inside of the thawing chamber 4 in a non-microwave irradiation state based on executing Steps S13 to S15, and preliminarily dries the frozen material based on vacuum sublimation cooling.

In step S16, the CPU 11 detects the setting result of the decompression mode. If it is detected that the decompression mode is set to the standard decompression mode, the process proceeds to the standard decompression process in step S17. If it is detected that the decompression mode is set to the nonstandard decompression mode, the nonstandard process in step S18 is performed. Move to decompression process.
3-1. Standard thawing process When the CPU 11 shifts to the standard thawing process, the internal pressure P in the thawing chamber 4 is detected every time the unit time ΔT (specifically, 30 seconds) elapses in step S21 in FIG. A differential pressure ΔP between the result and the current detection result is calculated. Then, “ΔP / ΔT” is calculated as the degree of decompression G, and the process proceeds to step S22.

  In step S22, the CPU 11 compares the calculation result of the degree of decompression G with the decompression equilibrium value Go (specifically, 13.3 Pa, 0.1 Torr). Here, when “G ≦ Go” is detected, it is determined that the inside of the thawing chamber 4 has reached the decompression equilibrium region, and the process proceeds to step S23. That is, the pre-drying step (I) in FIG. 4 is to depressurize the inside of the thawing chamber 4 in a microwave non-irradiated state, and sublimation of icing is performed compared to the thawing step (II) in which the pressure is reduced in the microwave irradiated state. The amount is small. Therefore, the pressure reduction capacity of the vacuum pump 18 and the internal pressure P of the thawing chamber 4 are balanced at the lowest equilibrium pressure Po.

  When proceeding to step S23 in FIG. 7, the CPU 11 compares the equilibrium pressure Po with the operation end value Pd (specifically, 453 Pa, 3.4 Torr). This equilibrium pressure Po refers to the internal pressure P of the thawing chamber 4 when it is determined in step S22 that the inside of the thawing chamber 4 has reached the decompression equilibrium region, and the CPU 11 ends the operation of the equilibrium pressure Po in step S23. When it is detected that the value Pd has not been reached, the process proceeds to step S24.

  When the CPU 11 proceeds to step S24, the pressure in the thawing chamber 4 is restored from the equilibrium pressure Po based on opening the pressure regulating valve 24, and the thawing step (II) in FIG. 4 is started. In step S25 of FIG. 7, the internal pressure P of the thawing chamber 4 is detected, and the detection result of the internal pressure P is compared with the heating start pressure Ps. The heating start pressure Ps is set higher than the lower limit pressure Px. When the CPU 11 detects that the internal pressure P of the thawing chamber 4 has reached the heating start pressure Ps in step S25, the process proceeds to step S26.

  In the ROM 12 of the control circuit 10, as shown in FIG. 9, the relationship between the mass Wg of the frozen material and the heating output W is recorded as operation control data, and the CPU 11 of the control circuit 10 proceeds to step S26 in FIG. Then, the heating output W corresponding to the determination result of the mass Wg is detected from the ROM 12, and the microwave output of the magnetron 9 is set as the detection result of the heating output W. For example, when the determination result of the mass Wg is “1500 grams”, the microwave output W is set to “460 W”.

  When the CPU 11 sets the microwave output W in step S26, the CPU 11 drives the table motor 15 in a constant direction at a constant speed in step S27. In step S28, the magnetron 9 is driven with the setting result of the microwave output W, and the frozen object is irradiated with the microwave with the microwave output W. Next, in step S29, the internal pressure P in the thawing chamber 4 is detected, and the detection result of the internal pressure P is compared with the return pressure upper limit Pu. Here, when it is detected that the detection result of the internal pressure P has reached the return pressure upper limit Pu, the process proceeds to step S30, and the decompression of the thawing chamber 4 is resumed based on closing the pressure regulating valve 24. In the driving state of the magnetron 9, the frozen material is irradiated with microwaves, and the frozen material is thawed based on the microwave heating.

  When the CPU 11 resumes decompression of the thawing chamber 4 in step S30, the process proceeds to step S31. Here, the internal pressure P in the thawing chamber 4 is detected, and the detection result of the internal pressure P is compared with the heating end pressure Pe. The heating end pressure Pe is set to be larger than the lower limit pressure Px and smaller than the heating start pressure Ps. When the CPU 11 detects that the detection result of the internal pressure P has decreased to the heating end pressure Pe in step S31, step S32 is performed. Then, the magnetron 9 is turned off, and the table motor 15 is turned off in step S33. When the magnetron 9 is in an off state, the inside of the thawing chamber 4 is depressurized without being irradiated with microwaves, and the frozen material is cooled by sublimation.

  When the CPU 11 turns off the table motor 15 in step S33, the pressure reduction degree G is detected in step S21, and the detection result of the pressure reduction degree G is compared with the pressure reduction equilibrium value Go in step S22. Here, when “G ≦ Go” is detected, it is determined that the inside of the thawing chamber 4 has reached the decompression equilibrium region, and the first thawing step (II) in FIG. 4 is finished. And it transfers to step S23 of FIG. 7, and the equilibrium pressure Po is compared with the operation completion value Pd. For example, when it is detected that the equilibrium pressure Po has not reached the operation end value Pd, the process proceeds to step S24, and the next thawing step (II) is performed based on repeating steps S24 to S33 and steps S21 to S23. Do.

  In the thawing step (II), as shown in FIG. 4, the microwave is irradiated to the frozen material for a variable microwave irradiation time Tx that spans during the decompression and decompression. This microwave irradiation is performed with a microwave output W corresponding to the mass Wg of the frozen material, and the thawing of the frozen material proceeds based on application of an amount of thawing energy corresponding to the mass Wg. Therefore, every time the thawing step (II) is repeated, the thawing of the frozen material proceeds, and the amount of sublimation of the icing is increased, so that the equilibrium pressure Po when the thawing step (II) is completed is repeated in the thawing step (II). And reaches the operation end value Pd at the end of thawing of the frozen material.

When the CPU 11 detects that the equilibrium pressure Po has reached the operation end value Pd in step S23 of FIG. 7, the CPU 11 turns off the vacuum pump 18 in step S34, and opens the atmosphere release valve 23 in step S35. In step S36, the pressure regulating valve 24 is opened, and the standard thawing process is completed.
3-2. Non-standard thawing process When the preliminary drying step (I) is started, the CPU 11 detects the internal pressure P in the thawing chamber 4 in step S41 of FIG. 8, and compares the detection result of the internal pressure P with the lower limit pressure Px. Here, when it is detected that the detection result of the internal pressure P has decreased to the lower limit pressure Px, the routine proceeds to step S42, where the timer T is started.

  As shown in FIG. 9, the ROM 12 of the control circuit 10 records the relationship between the mass Wg of the frozen material and the decompression time Td as operation control data. The CPU 11 of the control circuit 10 executes the timer in step S42 of FIG. When T is started, a depressurization time Td corresponding to the determination result of the mass Wg is selectively set from the ROM 12 in step S43, and the process proceeds to step S44. For example, when the determination result of the mass Wg is “1500 grams”, the decompression time Td is set to “170 seconds”.

  When proceeding to step S44, the CPU 11 compares the measurement result of the timer T with the setting result of the decompression time Td. Here, when it is detected that the measurement result of the timer T has reached the set result of the decompression time Td, the process proceeds to step S45 and the timer T is stopped. This decompression time Td is experimentally determined so that the contents do not spill from the surface of the frozen material such as Daifuku-an, and is set to such an extent that the frost adhering to the surface of the frozen material is sublimated. .

  When the CPU 11 stops the timer T in step S45, the timer T is reset in step S46, and the atmosphere release valve 23 is opened in step S47. Then, the inside of the thawing chamber 4 is connected to the outside air via the atmosphere release valve 23, and the internal pressure P of the thawing chamber 4 rises at a stretch. This internal pressure P is stable when the decompression capability of the vacuum pump 18 and the air supply capability of the air release valve 23 are balanced, and the subsequent thawing step (II) is an atmospheric pressure in which the internal pressure P of the thawing chamber 4 is stable. Proceeds with near vacuum.

  When the CPU 11 opens the atmosphere release valve 23 in step S47, the timer T is started in step S48, and the measurement result of the timer T is compared with the heating standby value Tw in step S49. This heating standby value Tw refers to the time required for the internal pressure P of the thawing chamber 4 to rise to the heating start pressure Ps, and is set to a fixed value unrelated to the input result of the mass Wg.

  When the CPU 11 detects that the measurement result of the timer T has reached the heating standby value Tw in step S49, the CPU 11 determines that the internal pressure P of the thawing chamber 4 has increased to the heating start pressure Ps. In step S50, the timer T is stopped, and in step S51, the timer T is reset. Next, in step S52, the heating output W corresponding to the determination result of the mass Wg is detected from the ROM 12, and the microwave output of the magnetron 9 is set as the detection result of the heating output W.

  As shown in FIG. 9, a plurality of arithmetic expressions are recorded as operation control data in the ROM 12 of the control circuit 10, and the CPU 11 of the control circuit 10 determines the mass Wg from the ROM 12 when the process proceeds to step S <b> 53 in FIG. 8. An arithmetic expression corresponding to the result is detected, and a determination result of the mass Wg is input to the detection result of the arithmetic expression. Each of these arithmetic expressions uses K1 to K5 and C1 to C5 as constants, and the mass Wg and the microwave irradiation time Tw as variables. The CPU 11 determines the mass Wg as the detection result of the arithmetic expression in step S53 of FIG. The microwave irradiation time Tm is calculated based on the input of the result.

  After calculating the microwave irradiation time Tm in step S53, the CPU 11 drives the table motor 15 in a constant direction at a constant speed in step S54. In step S55, the magnetron 9 is driven with the setting result of the microwave output W, and the frozen object is irradiated with the microwave with the output W corresponding to the determination result of the mass Wg. In the driving state of the magnetron 9, the frozen material is irradiated with microwaves, and the frozen material is thawed based on the microwave heating.

  When starting the microwave irradiation in step S55, the CPU 11 compares the measurement result of the timer T with the setting result of the microwave irradiation time Tm in step S56. Here, when it is detected that the measurement result of the timer T has reached the setting result of the microwave irradiation time Tm, the process proceeds to step S57, and the microwave irradiation is ended based on turning off the magnetron 9. In step S58, the table motor 15 is turned off and the turntable 16 is stopped. Next, the exhaust operation is finished based on turning off the vacuum pump 18 in step S59, and the non-standard thawing process is finished based on opening the pressure regulating valve 24 in step S60.

  According to Example 1, the pre-drying step (I) was performed in which the inside of the thawing chamber 4 was depressurized to a pre-drying vacuum state in a non-microwave irradiation state when the non-standard thawing mode was set. For this reason, since the frost adhering to the surface of the frozen material such as Daifuku coffee sublimes, stickiness of the surface of the frozen material can be suppressed. Moreover, since the thawing step (II) is performed in which the microwave is irradiated into the thawing chamber 4 while the pressure in the thawing chamber 4 is restored from the vacuum state for preliminary drying to the vacuum state near atmospheric pressure when the non-standard thawing mode is set. It is possible to thaw frozen foods such as Daifuku coffee in a sticky deterrent state. Furthermore, the thawing step (II) was completed while the inside of the thawing chamber 4 was kept in a vacuum state near atmospheric pressure when the non-standard thawing mode was set. For this reason, since the inside of the thawing chamber 4 is not depressurized in the softened state of the scab and the temperature rise of the contained air, the probability that the contained air breaks the scab and is released is reduced. Accordingly, since it is difficult for a wound to occur in the scab, it is possible to prevent the spill from spilling from the wound.

  Since the decompression time Td of the pre-drying step (I) is adjusted according to the mass Wg of the frozen material when the non-standard thawing mode is set, the frozen material can be vacuum sublimated and cooled to an appropriate level according to the mass Wg. For this reason, since the degree of decompression in the thawing chamber 4 does not become excessive in the preliminary drying step (I), it is possible to prevent a wound from being generated in the crust due to a pressure difference between inside and outside.

  Since both the microwave irradiation time Tm in the thawing step (II) and the microwave output W in the thawing step (II) were adjusted according to the mass Wg of the frozen material when the non-standard thawing mode was set, An appropriate amount of thawing energy can be supplied. For this reason, since the thawing | frozen state of a frozen material does not become excessive and insufficient, a frozen material can be thawed | stable stably irrespective of the magnitude of mass Wg.

  The seafood switch 34 to the confectionery switch 36 are mounted on the operation panel 31 and the standard thawing mode and the non-standard thawing mode are selectively executed according to the operation contents of the seafood switch 34 to the confectionery switch 36. For this reason, since the user can select the standard thawing mode and the non-standard thawing mode according to the type of the frozen material, convenience is improved.

  In Example 1 above, both the microwave irradiation time Tm and the microwave output W in the thawing step (II) were adjusted according to the mass Wg of the frozen material when the non-standard thawing mode was set, but this is limited to this. For example, one of the microwave irradiation time Tm and the microwave output W may be adjusted according to the mass Wg of the frozen material, and the other may be fixed regardless of the mass Wg of the frozen material.

  In the first embodiment, the magnetron 9 is turned on based on the internal pressure P of the thawing chamber 4 reaching the heating start pressure Ps in step S25 of the standard thawing process. However, the present invention is not limited to this. For example, the magnetron 9 may be turned on based on the elapsed time from opening the pressure regulating valve 24 in step S24 reaching the heating start value. This heating start value refers to a time obtained by experimentally determining the time required for the internal pressure P of the thawing chamber 4 to reach the heating start pressure Ps.

  In the first embodiment, the magnetron 9 is continuously turned on until the driving is stopped after the driving of the magnetron 9 is started in the thawing step (II) of the non-standard thawing process. A configuration may be adopted in which microwaves are intermittently applied to the frozen material based on intermittently turning on the magnetron 9. In the case of this configuration, since the heat of the surface of the frozen material penetrates into the inside when the microwave is not irradiated, the frozen material can be thawed uniformly from the surface to the inside.

  In the first embodiment, the non-standard thawing process is configured to open only the atmosphere release valve 23, but is not limited to this. For example, the pressure regulating valve 24 is configured to be opened together with the atmosphere release valve 23, Alternatively, a configuration may be adopted in which only the pressure regulating valve 24 is opened while the atmosphere opening valve 23 is closed.

  In the first embodiment, the magnetron 9 is turned on based on the measurement value of the timer T reaching the heating standby value Tw in step S49 of the non-standard thawing process. However, the present invention is not limited to this. For example, the magnetron 9 may be turned on based on the internal pressure P of the thawing chamber 4 reaching the heating start pressure Ps.

  In the first embodiment, the thawing step (II) of the non-standard thawing process is completed during the decompression period. However, the present invention is not limited to this. For example, the decompression in the thawing chamber 4 is performed after the decompression period ends. It may be terminated during the decompression period of the thawing chamber 4. This decompression is performed to such an extent that the contents do not spill out from the frozen material such as Daifuku-an, and the thawing step (II) is completed while the thawing chamber 4 is substantially maintained in a vacuum state near atmospheric pressure. include.

  In Example 1 above, the microwave irradiation was performed both at the time of decompression and decompression in the thawing step (II) of the standard thawing process. However, the present invention is not limited to this. Or it may be performed only at the time of decompression.

1 is a diagram showing an embodiment 1 of the present invention (a diagram showing the appearance of a vacuum microwave defroster). Diagram showing the internal configuration of the cabinet Block diagram showing electrical configuration Diagram for explaining the operation contents of standard decompression mode Diagram for explaining the operation details of non-standard decompression mode Flow chart showing control contents of control circuit Flow chart showing the control contents of the control circuit (showing the standard decompression process) Flow chart showing control contents of control circuit (figure showing non-standard decompression process) The figure which shows the record data of the control circuit

Explanation of symbols

4 is a thawing chamber, 9 is a magnetron (microwave generator), 10 is a control circuit (operation control means), 18 is a vacuum pump (decompressor), and 23 is an air release valve (pressure regulator).

Claims (3)

In the method of thawing the frozen material stored in the thawing chamber based on irradiating microwaves in the thawing chamber,
A pre-drying step of reducing the pressure in the thawing chamber to a vacuum for pre-drying in a non-irradiated state of microwaves;
The decompression process in which the decompression operation in which the decompression chamber is preliminarily dried from the vacuum state for pre-drying to the vacuum state near atmospheric pressure and the heating operation in which microwaves are irradiated into the decompression chamber are performed in order,
A vacuum microwave thawing method, wherein the thawing step is terminated while the thawing chamber is substantially maintained in a vacuum state near atmospheric pressure.   The vacuum microwave thawing method according to claim 1, wherein the time required for the preliminary drying step is adjusted according to the mass of the frozen material. 3. The vacuum microwave thawing according to claim 1, wherein at least one of the microwave irradiation time of the thawing step and the microwave output of the thawing step is adjusted according to the mass of the frozen material. Method.

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