JPH0771423B2 - Reduced pressure storage method and apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reduced pressure storage method for storing a stored material in a reduced pressure state and an improvement of the apparatus.

[0002]

2. Description of the Related Art Conventionally, a differential pressure type reduced pressure storage method has been known as a reduced pressure storage method for storing a stored product such as an agricultural product in a storage chamber which is maintained at a reduced pressure of less than 1 atm.

By the way, the harvested fruits and vegetables are independent living foods until they are processed, and have a respiratory action to maintain life. Then, by this respiratory action, oxygen is absorbed and carbon dioxide gas is released, so that metabolic activity is carried out to consume nutrients such as sugar and acid in the body.

Therefore, in order to store for a long period of time, it is necessary to reduce the respiratory action to suppress metabolic activity and suppress the consumption of nutrients in the body.

[0005] As one method for suppressing this respiratory action, a storage method (Controlled Atmosph) for controlling the air structure in a storage as a storage environment.
ere Storage; abbreviated as CA storage), and there is a reduced pressure storage method performed under reduced pressure as one of the methods for satisfying this CA condition.

At this time, the CA conditions for controlling the air composition in the storage as a storage environment for fruits and vegetables are different depending on the fruits and vegetables, but horticultural materials (all horticultural science [use department, Haginuma], 1973. Hort Review No.
2C. A. B. , [Fidler et al., 1972]), the oxygen gas concentration is about 3% and the carbon dioxide concentration is about 5% in the refrigerating region where the internal temperature is 0 to 4 ° C., and these gas concentrations can be maintained together. It is important for maintaining the freshness of fruits and vegetables.

[0007] Increasing the concentration of carbon dioxide has the effect of suppressing the aging and maturation of fruits and vegetables and maintaining the freshness because it suppresses the generation of ethylene gas, but conversely,
If the carbon dioxide concentration is too high, the fruits and vegetables cause a kind of physiological disorder to accelerate the damage of the stored products, resulting in a shortened storage period.

In the differential pressure type reduced pressure storage method, two pressures having different predetermined widths are set, and the pressure fluctuates with time while reciprocating within the range of the two pressures.
It has an intake solenoid valve and a vacuum pump that are installed in a vacuum tank for storage, and the vacuum pump operation that accompanies the opening and closing of the intake solenoid valve introduces air into the vacuum tank and the gas in the vacuum tank. The pressure in the vacuum tank is fluctuated by repeating the exhaust region for discharging the gas to the outside of the vacuum tank.

The pressure fluctuation in the vacuum tank in this case is shown in FIG.

Fruits and vegetables harvested from fields and stored in vacuum tanks absorb oxygen gas by breathing action and release carbon dioxide gas instead, and the concentration of carbon dioxide gas in the intake region is the outside air (air) introduction. The concentration of carbon dioxide gas in the vacuum tank increases over time because it is diluted by.

When the inside of the vacuum tank reaches the set pressure which is the upper limit value of the carbon dioxide concentration, this time it moves to the exhaust region and the pressure inside the vacuum tank is exhausted to the set pressure which is the lower limit value of the oxygen gas concentration. Carbon dioxide concentration decreases.

[0012]

However, in such a differential pressure type reduced pressure storage method, low pressure and low oxygen gas concentration (for example, {100/760} × 21% = 2.76).
%) Was easy, but since the increase in carbon dioxide concentration was slow, it took time, and the concentration between the low concentration point and the high concentration point fluctuated almost linearly and was repeated. However, there is a problem that the difference in concentration becomes relatively large, and it is difficult to increase the concentration of carbon dioxide gas as fast as the CA condition is satisfied (for example, 4%) and maintain it for a long time.

Further, the pressure is constant (for example, 100 mmH
g) and continuously ventilating (constant pressure type: Japanese Patent Publication No. 57)
However, in this case, there is a problem that not only the water content is depleted from the stored material, but also the vacuum pump provided in the storage device requires a large capacity and the operating time becomes long.

Further, a preset pressure P1 (for example, 10
To stop the operation of the vacuum pump was lowered with a vacuum pump to a 0 mmHg), supplemented with air (oxygen O ₂₎ in the leak adjustment device such as a vacuum tank, the pressure P ₂ (e.g. 300mmH
g), the vacuum pump is operated to ventilate and the pressure is adjusted to P ₁
And then stop the vacuum pump. There is also a method of repeating this operation (differential pressure type: refer to Japanese Patent Publication No. 53-24347), but in this case, since the ventilation must be performed within an extremely short time, the exhaust capacity of the vacuum pump increases and the device There was also a problem that it became expensive.

The present invention has been made in view of the above problems, and an object thereof is to reduce the carbon dioxide concentration in a relatively short time by a low-cost device using a small-sized and small-capacity decompression means. It is an object of the present invention to provide a reduced pressure storage method and an apparatus thereof which can be increased to the extent that the CA condition is satisfied and can be kept in that state for a long time.

[0016]

In order to achieve the above object, a reduced pressure storage method according to the present invention is a reduced pressure storage method for storing a stored material in a plurality of storage chambers which are held at a reduced pressure of 1 atm or less. In the above, each storage chamber is
Then, the pressure is sequentially reduced, and each storage chamber is set to a first pressure in a low pressure state, and then a low pressure holding region is provided to hold the first pressure for a certain period by sealing the inside of each storage chamber, Varying from the low pressure holding region to the second pressure in the low pressure state,
Further, the second pressure is changed to the first pressure, and continuous pressure fluctuation from the low pressure holding region to the first pressure via the second pressure is repeatedly performed for each storage chamber. There is.

Further, vacuum storage device according to the present invention, in a vacuum storage device having a plurality of storage chamber which is vacuum held to the low pressure of less than one atmosphere for storing the reservoir, vacuum the storage rooms state Pressure reducing means, the exhausting means for individually causing the decompressing means to function in the storage chamber, and the intake means for each of the storage chambers, and controlling the exhausting means and the intake means to control the pressure in the low pressure state. After being set to one pressure, a low pressure holding region for keeping the inside of the storage chamber in a closed state to hold the first pressure for a certain period is provided, and the pressure is changed from the low pressure holding region to the second pressure in the low pressure state. Providing control means for varying from the second pressure to the first pressure,
Continuous pressure fluctuation from the low pressure holding region to the first pressure through the second pressure is repeatedly performed, and each storage
It is characterized in that the chambers are sequentially decompressed by the decompression means .

[0018]

In the decompression storage device having the above structure, after setting each storage chamber to the first pressure in the low pressure state, the inside of each storage chamber is hermetically closed and the first pressure is maintained for a certain period of time. A holding area is provided, and it is changed from the low pressure holding area to the second pressure in the low pressure state, and further from the second pressure to the first pressure, and continuously from the low pressure holding area to the second pressure through the first pressure. The pressure fluctuation for changing the pressure is repeatedly performed for each storage chamber .

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a reduced pressure storage device according to the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the reduced pressure storage device 10 includes
A vacuum tank 11 as a storage chamber, a vacuum pump 12 as a pressure reducing means, a pressure gauge 13, a solenoid valve 14 and a flow rate control valve 19 as an intake means, a solenoid valve 15 as an exhaust means, and a refrigerator 16. Have

The solenoid valve 14 is a control timer (not shown).
The opening / closing is controlled by the output signal from.

A refrigerator 17 is attached to the refrigerator 16, and cold air produced by the refrigerator 17 is agitated by a fan 17a and sent into the refrigerator 16.

In the refrigerator 16, four vacuum tanks 11A having a thin wall thickness (for example, 2 mm),
11B, 11C, 11D are stored, and a humidifier 18 is further installed.

Each vacuum tank 11 includes
A vacuum pump 12 installed outside the refrigerator 16 is connected via an electromagnetic valve 15 provided for each, and individually,
A pressure gauge 13, an electromagnetic valve 14 and a flow rate control valve 19, a pressure switch 20 as a control means, and a manual valve 21 for breaking the vacuum are respectively mounted.

The vacuum pump 12 is connected to the solenoid valve 15 via a check valve 22.

Next, the operation of the reduced pressure storage device having the above structure will be described.

FIG. 2 shows the operation of the vacuum storage device 10.
The pressure fluctuation and the carbon dioxide concentration change in the vacuum tank 11A are shown.

First, the agricultural product a is stored in the vacuum tank 11 in the refrigerator 16. The stored agricultural product a passes through the thin wall of the vacuum tank 11 at a temperature immediately after harvest (for example, 25
C) to a storage temperature (eg 2 C).

After accommodating the agricultural product a in the vacuum tank 11A, the vacuum pump 12 is operated and the electromagnetic valve 15 is opened to evacuate.

By this evacuation, a decompression region T ₁ is formed in the vacuum tank 11A to decompress the interior of the vacuum tank 11A to a low pressure state of 1 atm or less (after the time t ₀ from the start of decompression, see FIG. 2).

At this time, each solenoid valve 14, each manual valve 21,
In addition, the respective solenoid valves 15 of the remaining vacuum tanks 11B, 11C and 11D are closed.

The vacuum pump 12 is continuously operated while exhausting, and when the inside of the vacuum tank 11A reaches the pressure P ₁ (first pressure, for example, 200 mmHg) which is the set value of the pressure switch 20 ( Time t from decompression start
After ₀ , refer to FIG. 2), the solenoid valve 15 is automatically closed.

After that, the above operation is carried out in the vacuum tanks 11B, 1B.
The steps 1C and 11D are also performed (in any order), and the vacuum pump 12 is automatically stopped when all the vacuum tanks 11 reach the pressure P ₁ .

When the vacuum pump 12 is stopped, a low pressure holding region T ₂ in which the pressure P ₁ is held for a certain period is formed in the vacuum tank 11 which is in a sealed state.

In the control panel (not shown ) after the low-pressure holding region is held for a certain period (time t ₁ from the start of depressurization, see FIG. 2)
In advance by the below condition from the control timer placed
The solenoid valve 14 is opened by the programmed output signal.

When the electromagnetic valve 14 is opened, the amount of cold air in the refrigerator 16 set by the flow control valve 19 is introduced into the vacuum tank 11.

The pressure in the vacuum tank 11 rises due to the introduction of cold air (oxygen O ₂ ), and the pressure P ₂ (second pressure, eg, 300 mmHg) in the vacuum tank 11A after a certain time.
Pressure rising region T ₃ (when time t _{2 has} elapsed since the start of pressure reduction,
(See) is formed.

The temperature and humidity inside the refrigerator 16 at this time are controlled by stirring the cool air produced by the refrigerator 17 with the fan 17a and then humidifying the required amount with the humidifier 18.

By the way, the time t ₁ from the start of depressurization to the opening of the solenoid valve 14 (the total time of the depressurization area T ₁ and the low pressure holding area T ₂ ) depends on the breathing action at the storage temperature (eg, 2 ° C.) of the agricultural product a. By the time the amount of carbon dioxide CO2 discharged into the vacuum tank 11 reaches the pressure P ₁ (e.g., equivalent to 5.5% of oxygen O _{2 under} 200 mmHg and CA conditions), the volume ratio is 4%.
The pressure switch 20 and the control timer are set in advance by a calculated value and an experiment so as to satisfy (CA condition).

The pressure in the vacuum tank 11 is the pressure P.
_When it reaches ₂ , the solenoid valve 14 is closed by the output signal from the pressure switch 20, at the same time, the vacuum pump 12 is activated and the solenoid valve 15 is opened, and the pressure P in the vacuum tank 11 is increased.
An exhaust region T ₄ that is exhausted to ₁ is formed.

Hereinafter, the pressure fluctuation for continuously varying the pressure from the low pressure holding region to the first pressure through the second pressure is repeated.

When inspecting during storage or carrying out after storage, the manual valve 21 is opened to introduce the cold air in the refrigerator 16 into the vacuum tank 11, and the pressure of the pressure gauge 13 is 760 m.
After confirming that the pressure is mHg, the door of the vacuum tank 11 is opened.

In this way, the vacuum tank 11 is hermetically closed and the low pressure holding region for holding the pressure P ₁ which is the base pressure,
By opening the electromagnetic valve 14 for intake, the intake region where the pressure changes from P ₁ to P ₂ and by closing the electromagnetic valve 14 for intake and operating the vacuum pump 12, the pressure P ₂ is restored to the pressure P ₁ . A series of operations in the exhaust area is repeated.

Here, changes in carbon dioxide concentration and oxygen gas concentration in the vacuum tank 11 are examined.

The carbon dioxide concentration is initially a minute concentration, but in the low-pressure holding region, the agricultural product a such as fruits and vegetables performs a respiration action in a sealed state, whereby the carbon dioxide concentration gradually increases. The rate of increase is larger than that in the differential pressure formula in which outside air (oxygen O ₂ ) is introduced, and the set value of the carbon dioxide concentration under the CA condition is reached earlier in terms of time.

Thereafter, in the intake region, the increase in carbon dioxide concentration is very small due to the CA effect. Although it may decrease depending on the conditions, the carbon dioxide concentration can be substantially constant if the outside air introduction rate and the carbon dioxide concentration increase rate at that time are made equal.

In the exhaust region, the pressure in the vacuum tank 11 is exhausted to the pressure P ₁ which is the base pressure, and the carbon dioxide concentration starts to decrease and finally becomes a minute concentration.

From the above, the carbon dioxide concentration reaches the set target for the CA condition earlier than the differential pressure type, and the carbon dioxide concentration can be maintained for a long time.

On the other hand, the oxygen gas concentration changes between the oxygen gas concentrations of the pressure P ₁ and the pressure P ₂ substantially according to the pressure, if the oxygen consumption due to the breathing of the agricultural product a is neglected. Therefore, it is not much different from the differential pressure type. Specifically, in the T ₂ region, the oxygen gas concentration is fruit a
It is slightly reduced by the breathing action of the
The air leaks from the lube
It penetrates into the link 11 and becomes almost constant as a result. Well
Moreover, the pressure in the vacuum tank 11 also rises slightly.

As described above, the following effects can be obtained in the reduced pressure storage method according to the present invention.

1. Since the vacuum tank 11 operates by using the pressure P ₁ as the base pressure to change the pressure, the oxygen O ₂
Adjustment of the concentration is easier if it is set by the pressure P ₁ .

[0052] Moreover, except when the intake or exhaust operation during ventilation, since the vacuum tank 11 is maintained in a substantially sealed condition of constant pressure, it is possible to increase easily the carbon dioxide gas concentration, as environmental storage The CA condition can be obtained easily and inexpensively.

2. Intake or exhaust of the vacuum tank 11 is always performed with a pressure difference in a short time by fresh air whose temperature and humidity are controlled.

That is, since the flow of low-temperature air exists even inside the agricultural product a as a storage due to the pressure change in the vacuum tank 11, the fresh air is irrelevant regardless of the accumulation method or the packaging method of the stored agricultural product a. Replenishment and ventilation can be performed uniformly and easily.

Further, since ethylene gas or the like which accelerates the aging of the agricultural product a can be easily discharged from the vacuum tank 11, the freshness of fruits and vegetables can be maintained and the storability can be improved.

3. During operation in the low-pressure holding region, the agricultural product a is held in the vacuum tank 11 in a substantially sealed state, so that the humidity inside the vacuum tank 11 increases due to the breathing action of the agricultural product a.

In addition, during ventilation, since the moist air whose temperature and humidity have been previously adjusted to the fresh air is sucked into the tank, the vacuum tank 11 is always filled with the moist air. Therefore, compared with other storage methods such as refrigeration in which cold air is circulated and constant pressure decompression storage method in which fresh air is constantly taken in (see the conventional example), less water is evaporated from the surface of the agricultural product a and the loss is suppressed. It

4. Since a plurality of small-sized and small-capacity vacuum tanks are used, the vacuum pump 11 having a small exhaust capacity can evacuate the inside of the vacuum tank 11, and a low-cost device can be realized.

Moreover, the amount of electric power consumed by the vacuum pump 12 can be reduced as compared with the constant pressure type with a large ventilation amount and the differential pressure type with abrupt ventilation.

5. Since the vacuum tank 11 is installed in the refrigerator 16 which is a refrigerating facility, the degree of acceleration of drying and aging of the agricultural product a is reduced.

That is, since the air sucked into the vacuum tank 11 is the air in the refrigerator 16 and there is no temperature difference with the inside of the vacuum tank 11 and sufficient humidity is secured, the agricultural products It is possible to prevent the drying of a and acceleration of aging.

6. Since the four vacuum tanks 11 can be controlled independently of each other, only the vacuum tanks 11 required for shipping can be opened and the vacuum tanks 11 can be shipped without affecting other vacuum tanks 11. Even if a disease occurs or a gas of an aging substance is exhausted, the vacuum tank 11 is always under a negative pressure, so that it can be managed individually.

7. When the amount of the agricultural product a stored in the vacuum tank 11 is small, it is difficult to increase the carbon dioxide concentration, but even at this time, the carbon dioxide concentration can be brought close to the set target by setting the low pressure holding region long. Reduced pressure storage is possible.

Therefore, by adjusting the oxygen gas concentration and the carbon dioxide concentration so as to obtain the optimum storage conditions, it is possible to suppress the excess energy that the stored products metabolize and to prevent the evaporation of water, so that further long-term storage is possible. Can be achieved.

Further, in order to make the concentration of carbon dioxide gas appropriate for the stored product, the time (t ₂ -t ₀ ) and the pressure P ₂ are adjusted and set. Further, the pressure P ₁ and the low pressure holding time are manually adjusted or automatically adjusted by a program according to the physiological condition, aging condition, etc. of the stored product which changes during the storage period.

[0066]

EFFECT OF THE INVENTION Vacuum storage according to claim 1 of the present invention
According to the method and the reduced pressure storage device according to claim 2, a small-sized storage device is provided.
A low-cost device using decompression means that does not have high performance
While providing the carbon dioxide concentration in a relatively short time,
High enough to satisfy the requirements, and keep that state for a long time
Wear.

[0067]

[0068]

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of a reduced pressure storage device according to the present invention.

FIG. 2 is an explanatory diagram showing a pressure fluctuation and a carbon dioxide gas concentration change in the reduced pressure storage device.

FIG. 3 is an explanatory diagram showing pressure fluctuations and carbon dioxide concentration changes in the differential pressure type reduced pressure storage device.

[Explanation of symbols]

 10 Decompression storage device 11 Vacuum tank (storage room) 12 Vacuum pump (decompression means) 13 Pressure gauge 14 Electromagnetic valve (intake means) 15 Electromagnetic valve (exhaust means) 19 Flow rate control valve (intake means) 20 Pressure switch (control means) a Agricultural product (storage)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Sadao Shogawa 1-9-3 Kamatahonmachi, Ota-ku, Tokyo Inside Niigata Iron Works Business Development Center (56) References JP-A-52-61555 (JP, A) )

Claims (2)

[Claims] The method according to claim 1] reservoir, the vacuum storage method of storing a plurality of storage chamber which is vacuum held to the low pressure below one atmosphere, the pressure was reduced in order the storage rooms by vacuum means, each
After setting the storage chamber to the first pressure in the low pressure state, the inside of each storage chamber is hermetically closed to provide a low pressure holding region for holding the first pressure for a certain period of time, and from the low pressure holding region to the first pressure in the low pressure state. To a second pressure, further from the second pressure to the first pressure, continuous pressure fluctuation from the low pressure holding region through the second pressure to the first pressure ,
A reduced pressure storage method characterized in that the storage chamber is repeatedly performed. 2. A decompression storage device having a plurality of storage chambers for decompressing and holding at a low pressure of 1 atm or less for storing a stored material, the decompression means for setting each of the storage chambers to a decompression state, and the decompression means. The storage means is individually provided with an exhaust means, and each storage room is provided with an intake means, and the exhaust means and the intake means are controlled to set the first pressure in the low pressure state, and then the storage is performed. A low-pressure holding region for holding the first pressure in a closed state for a certain period of time is provided by changing the inside of the chamber to a second pressure in the low-pressure state, and further from the second pressure to the first pressure. Control means for changing the pressure of the storage chamber from the low pressure holding region to the first pressure through the second pressure is repeatedly performed, and the storage chambers are sequentially operated by the pressure reducing means.
Vacuum storage apparatus characterized by reducing the pressure.