JP2007075096A - Method for thawing and/or preserving frozen food - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means giving effective thawing and/or preservation to frozen food without lowering freshness. <P>SOLUTION: This method for effectively thawing/preserving frozen food comprises introducing improved electric field conditions, warming means and preserving means for thawing/preserving the frozen food. The method for thawing the frozen food comprises setting, when thawing the frozen food, preservation conditions in a closed storage to such conditions that a current value of a primary side is 0.9 mA-5 mA per m<SP>2</SP>electrode, and 10V-30,000V alternating or direct current voltage is applied to electrode of a secondary side to bring to electric field atmosphere, controlling elevation of food temperature to ≤+3°C, bringing one electrode of the secondary side to one edge earth system, setting resistance on the other electrode of the secondary side, controlling a current condition of electric current, and additionally performing 10-40°C external warming. The method for preserving the frozen/thawed food comprises keeping a storage in a controlled water vapor pressure condition. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an improvement of a method for thawing and / or storing frozen food. Furthermore, it relates to an improvement in thawing and / or storage of frozen foods in an electric field atmosphere.

  The development of frozen food has brought about the prosperity of today's food culture. Freezing has enabled long-term storage and long-distance transportation of all foods. On the other hand, thawing of frozen foods has problems of thawing time and loss of freshness, and various means for thawing have been devised so far.

Means for subjecting food to electric field treatment are known, and there are reports of an increase in fermentation of food and antiseptic effect by this treatment (Patent Document 1) (Patent Document 2). In addition, there is a technique in which frozen food is thawed by applying a high-voltage negative electron under a condition that excludes a current flow to the frozen food (Patent Document 3). However, this thawing method requires a minimum of 8 hours and is far from practical use. Therefore, practically, quick thawing was performed with a microwave oven or the like, ignoring deterioration of food.
Japanese Patent Publication No. 38-6106 JP-A-61-58544 Patent No. 1940591

  An object of the present invention is to provide a means for efficiently thawing frozen foods and / or a storage method after thawing without reducing the freshness.

  As a result of intensive studies to solve the above problems, the present inventors have introduced improved electric field conditions, heating means and storage means for thawing frozen foods, A storage method after thawing was achieved and the present invention was completed.

That is, this invention consists of the following.
1. Upon thawing and storing frozen food, the storage condition in the storage chamber, at a current value 0.9mA~5mA per electrode 1 m ^2, and applying an AC or DC voltage of 10V~30000V the electrode and the electric field atmosphere, food temperature Is controlled to + 3 ° C or less, one pole of the secondary voltage side is grounded at one end, a resistor is provided at the other pole, the state of current flow is controlled, and 10-40 ° C external heating is added A method for thawing and / or storing frozen food.
2. The method for thawing and / or storing frozen food as described in 1 above, wherein external heating is performed when the surface temperature (or core temperature) of the frozen food reaches -5 to 0 ° C.
3. 3. The method for thawing and / or storing frozen food according to item 1 or 2, wherein the inside is adjusted to a controlled water vapor state.

  By the method of the present invention with improved electric field conditions and heating means, frozen foods achieved thawing of about 1000 g of beef pieces in 2-4 hours without loss of freshness, and preservation after thawing was achieved. .

  The thawing and / or storage used in the present invention is completely insulated from the inside and the outside, and there is a shelf made of a conductor in the cabinet, and food for thawing is placed on the shelf. . The interior has a distribution port connected to a cooler, and the cooler is also connected to a hitter for hot air. When food for thawing is placed on the shelf and thawing is started, warm air of 10 to 40 ° C., preferably 15 to 35 ° C. is developed in the cabinet by the hitter in the early stage of thawing. . Warm air circulates in the chamber, and the warm air spreads uniformly in the chamber. Hot air contacts frozen food from the surface and thaws the food. In food, protein denaturation by hot air is controlled, and the temperature of the sample is controlled to rise to + 3 ° C. or higher. The standard temperature is preferably controlled so that the temperature at the center of the standard is 3 ° C. or less. Control is performed by measuring the temperature at the surface of the standard and / or the center of the standard with a standard sensor. When the temperature reaches ℃, the sensor is activated and the inside of the cabinet is cooled by a cooler. When the sensor reaches around 0 ° C., the cooling is stopped, and the air is circulated in the cabinet only by the fan. An air flow is introduced from the upper part or the rear part by a fan from the cooler through the blower part.

The thawing / preservation store of the present invention is provided with a sensor for interlocking the temperature in the store with the operation of the cooler. The sensor operates and stops the cooler in conjunction with the thermostat. The sensor is preferably inserted into the food product, but may be in contact with the food surface if desired.
After thawing, the food is stored in the main cabinet to prevent freshness loss during storage. The inside of the storage is maintained at −3 to 3 ° C., more preferably −3 to 3 ° C. The sensor works when the surface temperature (or core temperature) of the food reaches −5 ° C. or 3 ° C., and heating starts at −5 ° C., preferably −4 ° C., and cooling starts at 3 ° C. . The temperature management may be controlled by, for example, a timer (automatically repeats heating and cooling for a predetermined time), or may be managed by contacting food with a temperature sensor.

  Means for preventing drying of the surface of the food is introduced into the interior of the present invention. This prevents the food from deteriorating due to heat and air circulation during thawing and / or storage, for example, by external heating or the like. As a means for this, a steam supply tank is provided in a specific part of the warehouse, and the interior of the warehouse is brought into a controlled steam state corresponding to the interior temperature. The supply of steam may be a natural evaporation system from the tank, or the room air may be forcibly brought into a controlled steam state. For example, the management of the inflow of water vapor may be controlled by a timer (steam inflow for a certain time is automatically repeated), or the start and stop of the inflow may be managed by a water vapor sensor. It is also preferable to adjust the inside of the chamber to, for example, the control steam pressure. This adjustment can be performed by adjusting the inside of the cabinet to the control steam pressure in conjunction with the temperature and introducing a microcomputer control system for controlling the water and steam in the water supply tank in the cabinet. The control is a condition that prevents the surface of the food from being dried while preventing condensation in the cabinet, and is controlled from the saturated state to about 70% saturation.

  Inside the cabinet is a shelf for thawed food, which is made of a conductive material, such as metal. The conductive material may be, for example, a material coated with a known conductive material such as stainless steel, aluminum foil, conductive paint, conductive rubber, conductive tape, conductive ink, or the like. The food storage is in an electric field. When applied to the storage shelf, it becomes an electric field state. As a safety measure against this application, an insulating material (for example, a known insulating material such as polycarbonate, ABS resin, ceramic, Teflon (registered trademark), plastic, vinyl chloride resin, insulating glass, PBS, silicon, wood, paper, etc.) It may be a coated material or itself. Various means are known in order to make an electric field atmosphere for preservation of a standard food. For example, this can be achieved by simply placing an electrode plate in an insulated state on a specific part of a warehouse. Alternatively, this can be achieved by connecting the voltage generator to the shelf with a high voltage cable.

The thawing machine used for the thawing of the present invention has a current value of 0.9 mA to 5 mA per 1 m ^{2 of} electrode on the primary side and an AC or DC voltage of 10 V to 30000 V on the secondary side applied to the electrode to create an electric field atmosphere To do. At this time, one pole of the secondary side is grounded at one end, for example, grounding, and a resistance of about 1 to 10 MΩ is provided on the other secondary pole to control the state of current flow. The transformer detects the return current by returning one side of the secondary output to COMMON (safety device / overcurrent detection device), detects the overcurrent compared to the reference input, and a current exceeding the reference value flows. In this case, the safety device works (secondary high-voltage output stop). Since it is possible to control the current value of the secondary electrode (shelf), it is possible to output a high current value of 0.9 mA to 5.0 mA / m ² at normal times. In the present invention, by passing such an electric current, the freshness of the thawed food is more efficiently maintained, in particular, the effective aging effect of the food is achieved. For example, the amino acid increased by 120 to 300%, and the quality retention (lifetime) was 1.2 to 2 times as effective. Furthermore, the device of the present invention employs a static elimination transformer, and achieves a stable application with a balance of positive and negative ion balances that is neither negative nor positive. This application achieved more efficient thawing and freshness retention.

  The method of using the apparatus of the present invention is, for example, applied to an electrode with an AC or DC voltage of 10 V to 30000 V, preferably 1000 to 10000 V, more preferably 3000 to 7000 V with respect to a storage shelf as an electric field atmosphere. The food is preferably stored at -5 ° C to 3 ° C by sending warm air, for example, with external heating of 15 to 35 ° C.

  The thawing device of the present invention includes an inner layer portion formed of a heat insulating material and an outer wall formed of a protective material, and includes a door portion, an air circulation fan, a cooler including an evaporator and a compressor, and the like as constituent elements. . For example, a strength of about 1 to 5 m / s is sufficient for the air circulation fan.

  EXAMPLES The present invention will be described below with reference to examples, but these show typical representative examples of the present invention, and the present invention is not limited thereto.

Example 1
FIG. 1 shows a wiring diagram of the thawing storage of the present invention. In the figure, A indicates the primary side and B indicates the secondary side. Reference numeral 1 denotes a fuse, which is set to 1A, for example. Reference numeral 2 denotes a style rack that adjusts the input voltage from 0V to 100V, for example. Reference numeral 3 denotes a leakage type transformer, which is a leaky type insulating transformer whose output current is limited to, for example, 20 mA even with the transformer alone. Reference numeral 4 denotes a transformer core that amplifies the input voltage by, for example, 60 to 80 times, preferably about 70 times. Reference numeral 5 denotes a high-voltage protection resistor, which uses a resistor of 1.5 MΩ, for example, and limits an instantaneous short-circuit current until the output protection circuit 6 operates to, for example, about 5 mA. An output protection circuit 6 includes an overcurrent detection PCB and a microcomputer-controlled safety device.

The electrical ratings of this device are organized as follows.
1) Continuous or short time: Continuous rating 2) Rated capacity (at maximum allowable output current): 20VA
3) Rated primary voltage: AC100V ± 10%, 50 / 60Hz
4) Rated output voltage: AC 0V to 7000V (can be set arbitrarily) 50 / 60Hz
5) Rated frequency: 50 / 60Hz
6) Rated primary current: 0.2A / 0.24A
7) Output short-circuit current: 2.1 mA (short-circuit protection circuit operating current value)
8) Protection circuit:
Fuse: Primary side short circuit protection Output short circuit protection circuit: Operates when the output current exceeds 2.1 mA, shuts down the output and at the same time, the abnormal indicator light (red) lights up, and a buzzer (electronic sound) warns. The warning is self-held until the power switch is turned off. Reaction time within 0.1 seconds. (Average value is 0.05 seconds)
High-voltage protection resistor: Insert a high-voltage resistor 1.5MΩ on the output side to limit the instantaneous short-circuit current to 5mA until the output protection circuit is activated.
Leakage type insulation transformer: The transformer adopts a leakage type, and the output current does not exceed 20mA even with the transformer alone.

The structural standard of this device is as follows.
1) Indoor use and outdoor use: Indoor use 2) Transformer structure: Leakage type insulation transformer 3) Installation method: Output side one end grounding method 4) Filling: Insulation compound (secondary winding, high voltage resistance part) (After PBT vacuum filling, the primary and secondary are filled with polyester + quartz sand under reduced pressure)
5) Output terminal: Glass-filled PBT resin 6) Cooling method: Natural cooling

The operating environment of this device is as follows.
1) Ambient temperature: 0 to 40 ° C
2) Ambient humidity: 20-100% (no condensation)

The following standards were used in the transformer unit test of this equipment.
1) Insulation resistance: 100MΩ or more between primary and ground at DC500V megger.
2) Dielectric withstand voltage: AC1500V is applied between primary and ground for 1 minute, and there is no abnormality.
3) Induction test: 1.5 times the rated primary voltage is applied for 1 minute and there is no abnormality.

(Example 2)
The thawing / preservation chamber is a thermostat linked to a temperature sensor that can be inserted into the center of the food set to operate at 3 ° C or higher and stop at 0 ° C or lower, for example, -4 ° C to 3 ° C. The storage shelf has an electric field atmosphere with a current value of 1 mA on the primary side and an AC voltage of about 3000 V on the secondary side. As a frozen food, 1000 g of beef (surface temperature −10 ° C.) was placed on a storage shelf, a warming machine was started, and warm air with an initial temperature of 35 ° C. was circulated in the cabinet at 3 m / s. For preservation, the door is opened and the specimen is placed on a storage shelf. The application is stopped by opening the door, and the application is restarted by closing the door. After storage for about 3 hours, the thawing was completed, the coliform group was negative, the number of viable bacteria was 1.3 × 10 ³ cells / cc, the drip amount was 0 g, and the weight loss rate was 0%. During this time, in the thawing / storage chamber, a water tank capable of spontaneously evaporating water vapor was placed in a place where it could come into contact with the air circulating in the chamber, and the interior of the chamber was adjusted to be in a controlled water vapor state (saturated). In addition, the freshness and taste of the sample were subjected to a sensory test with a microwave thawed product, but it was confirmed that 10 out of 10 samples were superior in the taste, flavor and color of the sample thawed by the method of the present invention. . In the amino acid detection test, the amount of amino acid was 1.9 times that of the food before freezing. In addition, the thawed food was tested from day 1 to day 7 under the same control using the present thaw / storage, and it was confirmed that sufficient quality retention was achieved.

(Example 3)
Except for the current of 2 mA and 5000 V under the conditions of Example 2, substantially the same results were obtained by performing the thawing process and / or storing process in the same manner as in Example 2.

Example 4
Except for the current of 0.5 mA, 10000 V, and the controlled water vapor state of 80% saturation, thawing treatment and / or storage treatment were performed in the same manner as in Example 2 to obtain substantially the same results.

(Comparative Experimental Example 1)
The number of viable cells (CFU / g) was measured by calculating the number of colonies in the addition test using the standard agar medium pour method. The temperature, humidity, time, working time lag, etc. are the same in a commercially available existing thawing / storage container (manufactured by S Company) (1 mA, 500 V) and the device of the present invention (1 mA, 5000 V), and at 20 ° C. after thawing. The number of viable bacteria in the storage time (0, 24 hours, 48 hours) was compared. As a result, significant suppression of viable cell growth of the device of the present invention was confirmed in Daifuku, Mitarashi, Andango, Ohagi, Tofu (open state), and Tofu (sealed state) (Table 1).

(Comparative Experiment Example 2)
The number of staphylococci (CFU / g) was measured by calculating the number of colonies in the addition test according to the method of coating on egg yolk-added mannitol salt agar medium. The temperature, humidity, time, working time lag, etc. are the same in a commercially available existing thawing / storage container (manufactured by S Company) (1 mA, 500 V) and the device of the present invention (1 mA, 5000 V), and at 20 ° C. after thawing. The number of staphylococci at storage time (0, 24 hours, 48 hours) was compared. As a result, significant suppression of the growth of viable bacteria of the device of the present invention was confirmed in Daifuku, Mitarashi, Andango, Ohagi, Tofu (open state), and Tofu (sealed state) (Table 2).

(Comparative Experiment 3)
The viable cell count (CFU / g) was measured by counting the colonies by the standard agar medium pour method. The temperature, humidity, time, working time lag, etc. are the same in a commercially available existing thawing / storage container (manufactured by S Company) (1 mA, 500 V) and the device of the present invention (1 mA, 5000 V), and at 16 ° C. after thawing. The number of viable bacteria in the storage time (14 hours, 38 hours) was compared. As a result, in Daifuku, Mitarashi, and Ohagi, significant suppression of viable cell growth of the device of the present invention was confirmed (Table 3).

(Comparative Experimental Example 4)
The number of E. coli and Staphylococcus aureus were determined by counting the colonies in the addition test by the microcolony (MC) method (CFU / ml). With a commercially available existing thawing / preservation box (manufactured by S) (1 mA, 500 V) and the apparatus of the present invention (1 mA, 5000 V), the temperature, humidity, time, working time lag, etc. are the same, and the bacteria are sterilized phosphate buffer. The bacterial count was compared and examined by the MC method (6 to 16 hours) in storage time at 20 ° C. (0, 24 hours, 48 hours, 72 hours). As a result, significant suppression of viable cell growth of the device of the present invention was confirmed (Table 4).

  The method of the present invention can be used for efficient thawing and storage of frozen foods.

Electrical wiring diagram

Explanation of symbols

A: Primary side B: Secondary side 1: Fuse 2: Slitac 3: Leakage
4: Transformer core 5: High voltage protection resistor 6: Output protection circuit 7: Storage shelf 8: Earth

Claims (3)

Upon thawing and storing frozen food, the storage condition in the storage chamber, at a current value 0.9mA~5mA per electrode 1 m ^2, and applying an AC or DC voltage of 10V~30000V the electrode and the electric field atmosphere, food temperature Is controlled to + 3 ° C or less, one pole of the secondary voltage side is grounded at one end, a resistor is provided at the other pole, the state of current flow is controlled, and 10-40 ° C external heating is added A method for thawing and / or storing frozen food. The method for thawing and / or storing frozen food according to claim 1, wherein external heating is performed when the surface temperature (or core temperature) of the frozen food reaches -5 to 0 ° C. The method for thawing and / or storing frozen food according to claim 1 or 2, wherein the inside of the refrigerator is adjusted to a controlled water vapor state.

Images