JPH01269449A - Freshness preservation of plant and device used to carry out the same preservation - Google Patents

Abstract

PURPOSE:To eliminate water stuck to a catalyst and to stably maintain freshness of fruits, vegetables, etc., for many hours, by bringing air in a storage chamber into contact with an ethylene oxidizing catalyst while intermittently heating the air and circulating the air. CONSTITUTION:A case 1 having an air inlet 2 and an air outlet 3 is equipped with a filter 4, a fan 5 and a heater 6 and packed with a catalyst (e.g., iron manganese-based catalyst) 7 to oxidize ethylene and to produce water. The case is connected to a storage chamber preserving fruits, vegetables, flowers, etc., and freshness of the aimed plants are maintained by, for example, intermittent operation wherein the heater 6 is worked for three minutes and then suspended for 20 minutes.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention maintains the freshness of fruits and vegetables such as fruits and vegetables stored in a storage room, as well as flowers and trees, thereby making it possible to preserve the fruits and vegetables for a long period of time. The present invention relates to a method for maintaining the freshness of food and a device used to carry out the method.

[Prior art] Conventional techniques for preserving fruits and vegetables for a long period of time include methods of lowering the temperature of fruits and vegetables, methods of lowering the oxygen concentration of atmospheric gas, and methods of increasing the C○2 concentration of atmospheric gas. This is a common method of hibernating.

Recently, it has been found that the shelf life of fruits and vegetables can be extended by removing ethylene gas, a spoilage hormone that promotes the ripening and decomposition of fruits and vegetables, from around the fruits and vegetables in storage. .

The mechanism by which fruits and vegetables rot is thought to be that as fruits and vegetables ripen, putrefaction hormones mainly composed of ethylene are generated, and this putrefaction hormone acts as an inducer to further promote ripening. For this reason, especially for fruits and vegetables that have been stored in large quantities, in order to prevent the production of spoilage hormones as much as possible, measures such as lowering the internal temperature as described above should be taken, and the produced spoilage hormones should be removed from around the fruits and vegetables. It is effective for long-term preservation of fruits and vegetables. Therefore, we provide ventilation to prevent ethylene gas from accumulating around fruits and vegetables, and install activated carbon or an adsorbent such as Crystomurai 1 to adsorb ethylene gas, which is a spoilage hormone, in the storage room to absorb the air inside the storage room. A technique has been proposed for removing ethylene gas by circulating it through a chemical agent (Japanese Unexamined Patent Publication No. 118144/1983).

[Problem to be Solved by the Invention] However, in storages where large amounts of fruits and vegetables need to be stored, large amounts of spoilage hormones are continuously generated. For this reason, it is difficult to remove ethylene gas over a long period of time and at low cost by conventionally removing ethylene gas using an adsorbent.

Furthermore, in the method of removing ethylene gas only by ventilation, it is not possible to leave fruits and vegetables in an atmosphere with a low ethylene gas concentration for a long period of time in a closed space such as in a storage warehouse.

The present invention has been made in view of such problems, and includes:
To provide a method for maintaining the freshness of plants, which can stably remove spoilage hormones generated in large quantities over a long period of time and at low cost, and facilitate the long-term preservation of plants such as fruits and vegetables, and a device used for carrying out the method. I take that as a priority.

[Means for Solving the Problems] The method for maintaining the freshness of plants according to the first invention of the present application includes a catalyst that oxidizes ethylene to produce at least moisture, a gas containing ethylene emitted by plants in a storage, and heating. It is characterized by forcibly feeding regeneration gas at an elevated temperature alternately.

The plant freshness maintaining device according to the second invention of the present application includes a case provided with a gas inlet and an outlet, and a fan and a heater arranged in the case and arranged in a direction from the inlet to the outlet. and a catalyst, and control means for turning on and off the heater, respectively, each time a predetermined off time and a predetermined on time elapse, and the catalyst oxidizes ethylene to produce moisture. A gas containing ethylene released by plants in the storage is introduced into the case through the inlet by the fan, and after passing through a catalyst, is supplied into the storage from the outlet. .

The plant freshness maintaining device according to the third invention of the present application includes a catalyst that oxidizes ethylene to produce water, a drive means that rotates the catalyst around its central axis, and a part of the area where the catalyst is present. A storage air supply means for supplying the gas in the product storage to the provided processing zone and returning the gas inside the storage through the catalyst portion of the processing zone, and the remainder of the area where the catalyst is present. an outside air supply means for supplying gas from outside the storage to a regeneration zone provided in the storage, and discharging the outside gas to the outside of the storage after passing through a catalyst portion of a regeneration zone; It is characterized by having a heating means for heating the air outside the refrigerator.

[Function] In the present invention, ethylene, which is a spoilage hormone, is stably oxidized and decomposed over a long period of time using a catalyst at room temperature or at low temperature.

In general, iron-manganese-based, copper-manganese-based, or copper-zinc-based catalysts are known as room-temperature reaction type catalysts for hydrocarbon gases such as ethylene. When reacted in air balance, it decomposes into water and carbon dioxide. Part of the water generated here is adsorbed by the catalyst and blocks the active groups of the catalyst, resulting in water deactivation of the catalyst. For this reason, from the viewpoint of catalyst life, use in the normal temperature range has been restricted.

The inventors of the present application have solved the sailor activation phenomenon of the catalyst by heating the catalyst itself or by circulating high-temperature gas.
It was discovered that by removing the adsorbed water, the original catalytic reaction could be restored, and based on this perspective, the catalyst was designed to be able to be used continuously for a long time.

That is, ethylene is oxidized and decomposed by supplying room-temperature or low-temperature air containing ethylene to a predetermined catalyst layer, and after a certain period of time, water, which is a reaction product, is adsorbed to the catalyst, reducing the catalytic effect. Before the catalyst is heated, heated air is supplied to the catalyst for a predetermined period of time, and this high-temperature gas removes moisture adhering to the catalyst. In this way, after the catalytic action is restored, ethylene-containing gas is again fed to the catalyst to decompose ethylene. At least locally, by alternately passing such an ethylene-containing gas and the regenerated warm gas through the catalyst portion, it is possible to continuously control the concentration of ethylene gas to a low level over a long period of time.

According to the apparatus according to the second aspect of the present invention, such removal of ethylene gas is achieved by forming a flow of air in the case from the air inlet of the case to the air outlet via the catalyst, and turning on the heater. This can be done by controlling on/off. That is, when the control means first turns off the heater for a predetermined period and allows air containing ethylene gas to pass through the catalyst, the ethylene gas is decomposed by the catalyst and water is produced. Next, as the adhesion of moisture progresses, the resolution of ethylene gas begins to decline, so after a certain period of time has elapsed, the heater is turned on by the control means to heat the air from the air inlet and then pass it through the catalyst. Removes adhering moisture from the catalyst. In this way, by repeatedly turning the heater on and off, the catalyst can be operated continuously and stably over a long period of time to decompose the ethylene gas in the internal gas.

On the other hand, in the apparatus according to the third invention of the present application, while rotating the catalyst around its central axis, the ethylene-containing gas in the storage is fed to the processing soak, and the heated regeneration gas is fed to the regeneration soak. supply. Thereby, the catalyst portion that has passed through the processing zone and has been subjected to ethylene decomposition is dehydrated by the hot gas while passing through the regeneration soak. In this manner, the present apparatus can continuously process the gas within the refrigerator.

[Examples] Examples of the present invention will be described below with reference to the accompanying drawings.

In the method according to the embodiment of the present invention, ethylene-containing gas in a storage where fruits, vegetables, or flowers are stored is passed through a catalyst at room temperature without heating to decompose ethylene.

Conventionally, a technique is known in which ethylene-based gas containing putrefactive hormones is heated to several hundred degrees and then passed through a catalyst to decompose ethylene. However, this technology cannot be directly applied to maintaining the freshness of fruits and vegetables. As mentioned above, when preserving fruits and vegetables, it is important to prevent the production of spoilage hormones from the fruits and vegetables, and it is necessary to both suppress the generation of ethylene gas itself and remove the generated ethylene gas. This prevents fruits and vegetables from rotting and allows them to be preserved for a long time. For this reason, it is necessary to preserve fruits and vegetables in a low temperature range, and it is extremely difficult to raise the ethylene-containing gas to a high temperature and cause it to react with the catalyst from the viewpoint of processing costs and system configuration.

Therefore, in the method of this embodiment, the ethylene-containing gas in the storage is passed through the catalyst at room temperature. In this case, a part of the gas generated by the decomposition of ethylene gas turns into water, and this water adheres to the catalyst, deteriorating the decomposition performance of ethylene gas. Therefore, even if ethylene-containing gas at room temperature is passed through the catalyst continuously, it is difficult to stably process a large amount of gas over a long period of time.

In order to solve this problem, in the method of this embodiment, heated gas is applied to the catalyst just before the decomposition performance of the catalyst deteriorates due to moisture adsorption on the catalyst, and the adsorbed moisture is released from the catalyst. Regenerate the catalyst. After the catalyst is regenerated, the putrefactive hormone-containing gas in the storage is passed through the catalyst again to decompose the ethylene gas in the storage. By alternately passing the putrefactive hormone-containing gas and passing the heated regeneration gas over a predetermined period,
The catalyst maintains stable decomposition performance over a long period of time, the ethylene concentration of the gas in the storage chamber is maintained at an extremely low value, and the gas can be stored without applying a large heat load to the storage chamber stored at room temperature or at a low temperature. becomes possible.

As mentioned above, as a means for alternately passing the putrefactive hormone-containing gas to be treated and the regenerated heating gas through specific parts of the catalyst, the method is to intermittently and alternately treat the stationary catalyst. Gas and regeneration gas may be supplied, or the catalyst may be alternately moved to the processing gas supply area and the regeneration gas supply area.

The catalyst to be used is one that has excellent ethylene decomposition performance at room temperature and has stable performance during cycles including the regeneration process. Such catalysts include copper, mankan, oxides thereof, or mixtures of one or more thereof. This type of catalyst has extremely superior decomposition performance at room temperature and regeneration performance by moisture desorption, etc., over other known catalysts such as iron-based or zinc-based catalysts.

Furthermore, the effect of ethylene gas increases as the amount of catalyst used increases.

Furthermore, whether the ethylene-containing gas that is forcibly fed to the catalyst is preferable because it increases the amount of decomposition of spoilage hormones, or if this air volume is too large compared to the internal volume of the refrigerator,
It is necessary to keep the air volume at an appropriate level depending on the variety of fruits and vegetables, since this can accelerate the surface drying of fruits and vegetables, and conversely deteriorate the quality of the fruits and vegetables.

Next, the apparatus used to carry out the method of the present invention will be specifically explained.

FIG. 1 is a schematic cross-sectional view of a freshness maintaining device showing an embodiment in which the present invention is applied to maintaining the freshness of fruits and vegetables stored in a small storage.

In this device, an air (gas) intake port 2 and an air discharge port 3 in the storage are formed at both ends of a case 1.
A filter 4 is installed in the case 1 near the intake port 2, and a catalyst 7 is installed in the case 1 near the discharge port 3'. A fan 5 and a heater are connected between the filter 4 and the catalyst 7. This freshness maintaining device is connected to a commercial frequency power outlet (AC100V) to receive power, and the fan 5 is continuously operated after the power is turned on. For example, 6'Om7. An air flow is formed inside the kaiso with an air volume of /hour. The heater 6 is catalyzed by a timer (not shown)? Example 1, in which the active force, i, does not decrease by 1, is driven intermittently, such as 20 minutes of rest and 3 minutes of operation. The capacity of this heater is, for example, 8' OOW, and the air passing through it at the above-mentioned air volume is heated to a temperature of about 80°C.

The catalyst 7 is usually used in the form of pellets, but in order to treat a large amount of gas with high efficiency as in the present invention, it is necessary to use a catalyst with small pressure loss and a good catalytic reaction with the flowing gas. It is preferable to form it into a honeycomb shape. For example, if the catalyst 7 is formed into a honeycomb shape having approximately 500 through holes per square inch, the pressure loss will be 1/10 or less of that in the case of a pellet-shaped catalyst. Therefore, the fan 5 can blow air with low power. Further, the catalyst 7 has a total content of copper, manganese, and their oxides of 70% by weight.
The remainder is bainter components and impurities. Note that the size of the catalyst 7 is, for example, 60'mm in width and 12'mm in length.
0'mm, height is 50mm, and volume is 360cc.

In the freshness maintaining device configured as described above, the device is inserted into a storage where fruits and vegetables are stored and is cooled by a cooling device, and the power is turned on to start the fan 5. Then, the air inside the storage chamber is taken into the case through the intake port 2, and this air inside the storage chamber is filtered to remove dirt and dust by the filter 2, passes through the heater 6 and the catalyst 7, and then passes through the discharge port. 3, it is released into the warehouse and returned. In this way, the fan 5 forces the air inside the refrigerator to circulate through the filter 4, heater 6, and catalyst 7. The heater 6 is on standby for, for example, 20 minutes, and during this time the air inside the refrigerator is acted upon by the catalyst 7, and ethylene gas, which is a putrefactive hormone contained in the air, is decomposed into moisture. This moisture gradually adheres to the catalyst.

After 20 minutes have elapsed, the heater 6 is turned on by the timer operation, and the air passing through the case is heated to, for example, 80 to 90°C by the heater 6.

As this high temperature air passes through the catalyst, moisture adhering to the catalyst 7 is removed and the catalyst 7 is regenerated. Then, for example, after three minutes have elapsed, the heater 6 is de-energized. During this heater energization, high-temperature air is discharged from the discharge port 3 into the refrigerator, but the amount of air discharged into the refrigerator during this period is extremely small compared to the total volume of the refrigerator due to the short energization time of the heater 6. Therefore, the discharge of this high-temperature air does not increase the temperature inside the refrigerator, which is constantly cooled.

Next, during the next 20 minutes, the ethylene gas-containing air inside the storage chamber passes through the catalyst 7 at the internal temperature, and the ethylene gas contained therein is decomposed.

By repeatedly turning on and off the heater 6 in this way, the amount of ethylene gas in the refrigerator is reduced, or the ethylene gas concentration in the refrigerator is maintained at an extremely low value. Therefore, fruits and vegetables in the refrigerator are always kept fresh.

Actually, using the apparatus shown in Fig. 1 and setting specifications such as the operating conditions of the heater and the processing air volume of the fan as described above, approximately 6.
This apparatus was installed in a storage cabinet having an internal volume of 0.0 m and controlled at a temperature of 3°C by an appropriate cooling device. After introducing ethylene gas into the refrigerator until the concentration reached 100 ppm, the device was operated, and the ethylene gas concentration decreased to 20 ppm in about 1 hour, and after 5 hours, it was 0. The O content decreased to 5 ppm or less.

By the way, for example, apples are stored for a long time by being refrigerated at the production site and in a CO2 gas-rich atmosphere, and then sent to the site based on demand. The disadvantage of using shinari is that it rapidly matures during use, resulting in a high rate of spoilage. Therefore, when we tried to transport apples by loading the device of this example described above into a sealed normal (non-refrigerated) container car, we found that the rate of decomposition was below the permissible limit and that the apples could be used. Met. In addition, during normal transportation, the ethylene concentration ranges from several ppm to several tens of ppm.
The pm level was confirmed, and in the case of this example, the level was maintained below the detection limit of the detection tube, 0.2 ppm.

In this way, the economic benefits of not using refrigerated container cars are enormous.

Next, an embodiment in which the present invention is applied to maintaining the freshness of fruits and vegetables stored in a large storage room will be described with reference to FIG. In this example, the catalytic decomposition of spoilage hormones at room temperature and the release of adsorbed water are carried out in parallel.

That is, the cylindrical catalyst 10 fitted into the cylindrical casing has a honeycomb shape similar to the first embodiment, and the direction in which the through hole extends coincides with the central axis of the motor 1].
It is designed to be driven to rotate around its central axis. The size of this rotor-shaped catalyst 10 is, for example, 600 mm in diameter and 20111 mm in length! It is ll. A filter 12 is installed in the housing (not shown) of the device at an inlet for taking in air inside the refrigerator, and the air inside the refrigerator filtered by this filter 12 is passed through piping 14 by a blower 13 for air inside the refrigerator. is supplied to the processing zone 10a of the rotor-shaped catalyst 10, and after passing through the processing zone]Oa, is guided to the discharge port 15 provided in the housing,
It is supplied into the warehouse through this discharge port 15. Note that the amount of air circulation in the refrigerator by the blower 13 is, for example, 1200 m'
/It is time.

On the other hand, the air outside the storage filter 16 provided in the device housing is connected to an appropriate pipe (not shown) to collect air from outside the storage.
It is designed to be supplied via. Then, the outside air that has not been filtered by this filter 16 is passed through piping 18 by a blower 17 for outside air to a rotor-shaped catalyst 10.
is supplied to the regeneration sorter 10b. The amount of outside air circulation by the blower 17 is, for example, 200 m3/hour.

Piping] In the middle of 8 is a heater 19 with a capacity of, for example, 15 KW.
The heater 19 heats the outside air supplied to the regeneration sorter and Ob to raise the temperature to about 80°C.

The high temperature air that has passed through the regeneration zone 10b is guided to an outside air outlet 20 provided in the housing.
and is discharged to the outside of the storage via appropriate piping (not shown).

Note that the area ratio between the processing zone 10a and the regeneration sorter 10 in the rotor-shaped catalyst 10 is, for example, 6:1.

In the freshness maintaining device configured in this manner, the rotor-shaped catalyst 10 is constantly controlled by the morph 11, for example, at 6 rpm.
It is rotated in one direction at a rotation speed of h. After the air inside the refrigerator is filtered by the filter 12 through the floor 13, it is circulated and supplied to the treatment zone 10a of the catalyst 10 at a flow rate of, for example, 1200 m3/hour. When room temperature air inside the refrigerator passes through the catalyst 10 in the processing zone 10a, the ethylene gas contained therein is decomposed and moisture is generated. This moisture adheres to the catalyst [O], but due to the rotation of the rotor-shaped catalyst 10, the part where the moisture has adhered is the regeneration zone],
In the regeneration zone 1ob, moisture is removed from the catalyst 10 by the passage of high-temperature air. This high-temperature air is introduced into the device from outside the refrigerator through an intake port] 6, and is heated by a heater 19 to
After being heated to .degree. C., it is supplied to the regeneration zone 10b. As mentioned above, this high temperature air is used to regenerate the moisture-adhered catalyst portion in the processing zone 1.0a, and then
This relatively high-temperature air containing moisture is guided outside the refrigerator through the outlet 20 and is discharged outside the refrigerator.

In this embodiment, since the regenerated air is not discharged into the refrigerator but is discharged outside the refrigerator, the influence of the regenerated air on the temperature, humidity, etc. inside the refrigerator is extremely small. Furthermore, since decomposition of ethylene gas and water removal and regeneration are performed in parallel while rotating the catalyst 10, it is possible to decompose ethylene gas continuously.

As a result of purifying the inside of a refrigerated storage facility with an internal volume of 8,000 m3 for storing mandarin oranges using the freshness maintaining device shown in Figure 2 under the above-mentioned operating conditions, the spoilage rate of mandarin oranges was approximately 115% lower than in the conventional case. It declined to .

The catalyst used in the present invention may be any room-temperature oxidation type catalyst as described above, but copper mankan or its oxides or their oxides have been found to have the highest decomposition efficiency at room temperature and low humidity. It is one type or a mixture of two or more types.

[Effects of the Invention] According to the present invention, spoilage hormones mainly composed of ethylene generated in the storage of fruits and vegetables are decomposed under the action of a catalyst, and the generated moisture is removed from the catalyst using heated gas, so that the ethylene gas concentration can be reduced. can be maintained at an extremely low value, allowing fruits and vegetables to be stored stably for a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a freshness maintaining device according to a second embodiment of the present invention, and FIG. 2 is a perspective view showing a freshness maintaining device according to a second embodiment of the present invention. 4.12,16. Filter, 5; Fan, 6°19; Heater, 7, 10; Catalyst, 13.17. floor

Claims (3)

[Claims] (1) The feature is that ethylene-containing gas emitted by plants in the storage and regeneration gas heated to an elevated temperature are alternately and forcibly fed to the catalyst that oxidizes ethylene to produce at least moisture. How to maintain the freshness of plants. (2) A case provided with a gas inlet and an outlet;
A fan, a heater, and a catalyst are disposed inside the case and arranged in parallel in the direction from the inlet to the outlet, and each of the heaters is turned on and off every time a predetermined off time and a predetermined on time elapse, respectively. and a control means for turning off the catalyst, wherein the catalyst oxidizes ethylene to produce moisture, and the fan causes the ethylene-containing gas emitted by the plants in the storage to be transferred into the case through the inlet. A device for maintaining the freshness of plants, which is introduced into the refrigerator, passed through a catalyst, and then supplied into the refrigerator from an outlet. (3) a catalyst that oxidizes ethylene to produce water;
A driving means for rotationally driving this catalyst around its central axis, and a drive means for supplying gas in the plant storage to a treatment zone provided in a part of the area where the catalyst is present, and the gas in the storage to the catalyst part of the treatment zone. The gas from outside the storage is supplied to the regeneration zone provided in the remainder of the area where the catalyst is present, and the gas from outside the storage is transferred to the catalyst in the regeneration zone. 1. An apparatus for maintaining freshness of plants, comprising: an outside air supply means for discharging air outside the refrigerator through a part of the refrigerator, and a heating means for heating the outside air supplied to the regeneration zone.