JP2876225B2 - How to keep horticultural crops fresh - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for maintaining freshness of horticultural crops, and more particularly to a method for suppressing ripening, aging and discoloration of horticultural crops.

(Prior Art) Horticultural crops are known to cause physiological disorders due to growth-promoting substances such as ethylene generated during storage and accelerate ripening, aging and discoloration.

On the other hand, it is known that ozone rapidly oxidatively decomposes unsaturated hydrocarbon compounds such as ethylene, and is also effective for disinfecting microorganisms. Foods utilizing this ethylene decomposing action and disinfecting effect are known. (“Packaging of Food”, Vol. 17, No. 1-29, 1986).

However, in general, when ozone is contained in an atmosphere gas containing ethylene at a high concentration of 100 ppm or more, the decomposition of ethylene proceeds rapidly, and although the bactericidal effect is large, when the ozone concentration is less than 100 ppm, the oxidation reaction occurs. , The ethylene removal effect is reduced and the bactericidal effect is also reduced. Further, when the concentration of ethylene in the atmosphere is several to several tens ppm or less, the ethylene removing effect is further reduced.

However, in practice, if ethylene cannot be rapidly removed at a stage where the ethylene concentration in the atmospheric gas is several to several tens of ppm or less, ripening, aging, discoloration, and the like of horticultural crops cannot be prevented.

Therefore, there has been a demand for a method for efficiently removing a low concentration of a growth promoting compound such as ethylene.

(Problems to be Solved by the Invention) An object of the present invention is to provide a horticultural crop which can efficiently remove horticultural crop growth promoting substances such as ethylene at a low concentration, which is practically problematic, and has an excellent bactericidal effect. Another object of the present invention is to provide a method for maintaining freshness.

The present inventors have conducted intensive studies to achieve this object, and as a result, when the atmospheric gas of a horticultural crop is brought into contact with a specific semiconductor under ultraviolet irradiation in the presence of ozone, the growth of ethylene and the like is promoted. The inventors have found that the substance is rapidly degraded, and have completed the present invention based on this finding.

(Means for Solving the Problems) Thus, according to the present invention, the atmospheric gas of the horticultural crop is
0.5 to 5 eV under UV irradiation in the presence of ozone
A method for maintaining freshness of a horticultural crop, comprising contacting a semiconductor having a forbidden band width with a semiconductor.

In the present invention, it is necessary to irradiate the atmospheric gas of the horticultural crop with ultraviolet light in the presence of ozone. In order for the atmospheric gas of the horticultural crop to coexist with ozone, ozone may be generated from the atmospheric gas, or ozone separately generated may be mixed with the atmospheric gas. The location and timing of generating ozone are not particularly limited. For example, an ozone generator may be installed inside a reactor in which a semiconductor layer and an ultraviolet lamp are installed, or may be generated at another place outside the reactor and introduced into the reactor by piping.

As a method for generating ozone, a conventionally known method can be employed. Specifically, a dielectric is inserted between a pair of electrodes, and an alternating high voltage (several kV to several kV) is applied between the electrodes.
10kV), air or oxygen is passed through this discharge space, and a thin wire discharge electrode group is placed on the surface of a flat or cylindrical high-purity alumina ceramic, a plate-like dielectric electrode is placed inside, It is formed using electrodes and a suitable high-frequency voltage is applied between the two electrodes to allow air or oxygen to pass through. An ultraviolet lamp system or the like that irradiates air or oxygen passing therethrough is preferable, but electrolysis, chemical reaction, α-ray,
It may be generated by other methods such as a cathode ray or heat.

In the method of the present invention, the concentration of ozone is not particularly limited, but may be 100 ppm or less. Above 100 ppm, the rate of decomposition of the growth-promoting substances increases, but the harmfulness of ozone causes problems in the horticultural crop itself and in the emission of atmospheric gases after treatment.

The ultraviolet light used in the present invention has a wavelength of 400 to 2
Near ultraviolet rays of 00 nm are preferable, but vacuum ultraviolet rays of 200 nm or less may be included. These ultraviolet rays can be generated by using an ultra-high-pressure mercury lamp, a xenon lamp, or a low-pressure mercury lamp alone or in combination, but the mercury and a third component other than the rare gas, such as gallium and thallium, coexist in the discharge tube to meet the purpose. Light sources modified to have wavelength distribution characteristics may be used. Of course, light rays other than ultraviolet rays, for example, visible light rays may be included.

The semiconductor used in the present invention needs to have a band gap of 0.5 to 5 eV, preferably 1 to 3 eV.

Examples of such a semiconductor include metal oxides such as tin dioxide, zinc oxide, tungsten trioxide, titanium dioxide, barium titanate, and ferric oxide, and mixed crystals thereof;
Chalcogen compounds such as zinc sulfide, cadmium sulfide, lead sulfide, zinc selenide, cadmium selenide and the like and mixed crystals thereof; Group IV elements such as silicon and germanium; Group IV compounds such as silicon carbide; gallium-phosphorus, gallium-
Group III-V compounds such as arsenic and indium-phosphorus and mixed crystals thereof; and organic semiconductors such as polyacetylene, polypyrrole, polythiophene, polyaniline, and polyvinylcarbazole can be given.

In addition, a semiconductor obtained by doping the above semiconductor with an impurity such as arsenic, phosphorus, aluminum, boron, sodium, or halogen can also be used.

Especially from a practical point of view, titanium dioxide, zinc oxide,
Metal oxides such as tungsten trioxide and cerium oxide and mixed crystals thereof are preferred.

Further, by supporting a noble metal such as gold, platinum or palladium on the surface of these semiconductors, the catalytic effect can be improved.

Further, an adsorbent such as activated carbon or oxidized clay may be used in combination.

The amount of semiconductor used depends on the type, composition, mixing ratio, concentration, concentration of ozone to be introduced, type of light source, amount of power used, and the like, but is not particularly limited.

In the present invention, the shape of the semiconductor is not particularly limited, and examples thereof include a method in which the semiconductor is supported on a suitable support by application, impregnation, or the like.

In the present invention, the method of irradiating the semiconductor with ultraviolet light also includes
There is no particular limitation, and it is carried on the surface of the light source or the reflector of the light source and irradiated, or around the light source,
A method of arranging and irradiating a support supporting a semiconductor and irradiating the support may be adopted, but the method is not limited thereto. The support provided around the light source is preferably manufactured by a filter from the viewpoint of reaction efficiency.

There is no particular limitation on the method for bringing the coexisting gas of the atmospheric gas of the horticultural crop and the ozone into contact with the semiconductor under ultraviolet irradiation. As a specific example, a method of introducing this gas into a batch system or a continuous system into a reactor equipped with an ozone generator and a semiconductor layer having a band gap of 0.5 to 5 eV and an ultraviolet lamp for irradiating the semiconductor can be shown. it can. Also,
It is of course possible to circulate the gas to be treated and repeatedly irradiate the ultraviolet rays. The reactor may be an open system or a closed system, or may be a ventilation system in which a fan is blown into the reactor.

The method of the present invention is effective even when sulfur oxides, nitrogen oxides, hydrocarbon compounds other than ethylene, and the like coexist in the atmospheric gas of a horticultural crop.

(Effect of the Invention) Thus, according to the present invention, a growth promoting compound such as ethylene can be efficiently decomposed. The method of the present invention can be used not only for maintaining the freshness of horticultural crops in the distribution process such as transportation and storage, which is the conventional use, but also for maintaining the freshness of horticultural crops in refrigerators in ordinary households.

(Examples) Hereinafter, the present invention will be described in more detail with reference to Examples.
The present invention is not limited to the following examples. In addition,
In this example, parts and percentages are by weight unless otherwise specified.

Example 1 A commercially available titanium dioxide powder (1.0 g) was introduced into a 300-ml Pyrex glass three-neck separable flask (hereinafter, simply referred to as a flask), and then introduced from a commercially available ozonizer (manufactured by Silver Seiko). The inside of the flask was replaced with air containing 46 ppm of ozone and sealed. Next, ethylene was injected with a syringe to obtain the initial concentration shown in Table 1, and an ultra-high pressure mercury lamp (illuminance: 10 cm) was installed at a distance of 20 cm from the flask.
mw / cm ² , dominant wavelength 365 nm).
The change over time in the concentration of ethylene after lighting was tracked by gas chromatography. The results are shown in Table 1.

Comparative Example 1 The same experiment as in Example 1 was performed except that the atmosphere in the flask was not replaced with air containing ozone. The results are shown in Table 1.

Comparative Example 2 The same experiment as in Example 1 was performed except that no ultraviolet irradiation was performed. The results are shown in Table 1.

Comparative Example 3 The same experiment as in Example 1 was performed except that titanium dioxide was not charged into the flask. The results are shown in Table 1.

Comparative Example 4 The same experiment as in Example 1 was performed except that titanium dioxide was not charged into the flask and ultraviolet irradiation was not performed. The results are shown in Table 1.

From the results in Table 1, it can be seen that ethylene can be efficiently removed by the method of the present invention.

Example 2 The same experiment as in Example 2 was conducted except that acetaldehyde having the initial concentration shown in Table 2 was used instead of ethylene.
The results are shown in Table 2.

The results in Table 2 show that the method of the present invention is also effective for removing acetaldehyde.

Example 3 The same experiment as in Example 1 was performed except that various semiconductors shown in Table 3 were used instead of titanium dioxide. The results are shown in Table 3.

From the results in Table 3, it can be seen that ethylene can be efficiently removed by the method of the present invention.

Example 4 A commercially available titanium dioxide powder (1.0 g) was charged into a flask.
Then, air containing ethylene having a concentration shown in Table 4 into which ozone generated by a commercially available ozonizer (manufactured by Silver Seiko) was added to a concentration shown in Table 4 was introduced into the flask from one port. And let it flow out of the other port, and irradiate it with an ultra-high pressure mercury lamp (illuminance 10mw / cm ² , main wavelength 365nm) installed at a distance of 20cm from the flask, and change the ethylene concentration at the inlet and outlet. Was measured by gas chromatography. The change in the concentration of ozone at the inlet and the outlet was measured with a gas detector manufactured by Gastech. The results are shown in Table 4.

Comparative Example 5 The same experiment as in Example 4 was performed except that titanium dioxide was not charged into the flask. The results are shown in Table 4.

Example 5 After putting 1.0 g of commercially available titanium dioxide powder into a flask, a commercially available low-pressure mercury lamp for ozone generation (illuminance: 4 mW / cm ² , main wavelength: 254 nm) installed inside the flask was turned on. Then, while air containing ethylene having the concentration shown in Table 4 was introduced into the flask from one port and discharged from the other port, the change in ethylene concentration at the inlet and outlet was measured by gas chromatography. did. In this case, the ozone concentration was not measured.

 The results are shown in Table 4.

From the results in Table 4, it can be seen that ethylene can be efficiently removed and the ozone concentration can be reduced by almost half by the method of the present invention.

Example 6 and Comparative Example 6 Ten fruit kiwis were put in a desiccator having an internal volume of 12 placed in a low-temperature thermostat, and then, an ozonizer (manufactured by Silver Seiko) and 1.0 g of commercially available titanium dioxide powder were put therein. The flask and the diaphragm type air pump were connected by a tube in this order. The parts other than the desiccator were installed outside the low-temperature constant temperature bath. Next, the desiccator was kept at a temperature of 15 ° C. and a humidity of 90% or more, and the air inside was circulated by a diaphragm type air pump. At this time, neither ethylene nor acetaldehyde was detected. In this state, an ultra-high pressure mercury lamp (illuminance: 10 mw / cm ² , dominant wavelength: 365 nm) with the flask placed at a distance of 20 cm therefrom
10 minutes per hour while constantly irradiating with UV light,
Irradiation was performed intermittently with an ozonizer (Example of the present invention, Experiment A). Further, for comparison, a similar experiment was carried out without any of the addition of titanium oxide, irradiation with an ozonizer, and ultraviolet irradiation (Comparative Example, Experiment B).

Two weeks later, when the concentrations of ethylene and acetaldehyde in the desiccator were measured by gas chromatography, it was not possible to detect ethylene and acetaldehyde in Experiment A, whereas in Experiment B, 10 ppm of ethylene and 6 ppm of acetaldehyde were detected. was detected.

In addition, when the sugar content of the kiwi was examined with a refractometer (manufactured by Atago Co., Ltd.), the sugar content was 16 in Experiment A, which was almost the same as the sugar content (17) before the experiment.
It decreased from (before the experiment) to 13 (after the experiment). Furthermore, in Experiment B, the kiwi was softer than in Experiment A.

From these results, it is clear that the method of the present invention is effective in maintaining the freshness of horticultural crops.

Example 7 The same experiment as in Example 6 and Comparative Example 6 was performed for two melons. As a result, there was no change in the appearance of the melon when the method of the present invention was used.
Each of the individuals developed white mold on part of the skin.

From these results, it is clear that the method of the present invention is effective in maintaining the freshness of horticultural crops.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-252244 (JP, A) JP-A-64-56684 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) A23B 7/00-9/34 A01F 25/00 A01N 3/00

Claims (1)

(57) [Claims] 1. A method for maintaining freshness of a horticultural crop, comprising bringing an atmospheric gas of the horticultural crop into contact with a semiconductor having a band gap of 0.5 to 5 eV under ultraviolet irradiation in the presence of ozone.