Adsorbents and methods for preserving fruits and vegetables

Abstract

This invention provides an adsorbent with a longer lifespan compared to conventional technologies, and a method for preserving fruits and vegetables using this adsorbent. [Solution] The solution comprises zeolite, an oxidizing agent in an amount of 2.0 parts by mass to 7.5 parts by mass per 100 parts by mass of zeolite, and an anionic surfactant in an amount of 0.035 parts by mass to 0.175 parts by mass per 100 parts by mass of zeolite.

Description

[Technical Field]

[0001] This invention relates to an adsorbent and a method for preserving fresh produce. [Background technology]

[0002] When preserving fresh produce, deterioration caused by substances secreted by the produce itself can be a problem. For example, ethylene secreted by fresh produce is known to promote aging and maturation, and this effect can lead to deterioration of the produce.

[0003] Therefore, various attempts have been reported to extend the shelf life of fruits and vegetables by preventing them from acting on them by adsorbing and capturing target substances such as ethylene. For example, Japanese Patent Publication No. 2004-322005 (Patent Document 1) discloses an ethylene gas adsorbent characterized by comprising a porous coordination polymer complex containing copper. Also, Japanese Patent Publication No. 2022-1357 (Patent Document 2) discloses an ethylene gas adsorbent characterized by comprising a porous metal complex or a metal-supported inorganic porous body. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2004-322005 [Patent Document 2] Japanese Patent Publication No. 2022-1357 [Overview of the project] [Problems that the invention aims to solve]

[0005] While the inventions described in Patent Documents 1 and 2 have considered the adsorption of ethylene gas, they have not sufficiently considered how to maintain the performance of adsorbing ethylene gas, and there was room for improvement in this respect.

[0006] Therefore, there is a need to realize an adsorbent with a longer lifespan compared to conventional technologies, and a method for preserving fruits and vegetables using this adsorbent. [Means for solving the problem]

[0007] The adsorbent according to the present invention is characterized by comprising a zeolite, an oxidizing agent in an amount of 2.0 parts by mass to 7.5 parts by mass per 100 parts by mass of the zeolite, and an anionic surfactant in an amount of 0.035 parts by mass to 0.175 parts by mass per 100 parts by mass of the zeolite.

[0008] The present invention relates to a method for preserving fresh produce, characterized by preserving fresh produce together with an adsorbent containing zeolite, an oxidizing agent in an amount of 2.0 parts by mass to 7.5 parts by mass per 100 parts by mass of zeolite, and an anionic surfactant in an amount of 0.035 parts by mass to 0.175 parts by mass per 100 parts by mass of zeolite.

[0009] With these configurations, the zeolite and oxidizing agent work cooperatively to achieve adsorption and decomposition of the target substance, while the anionic surfactant suppresses the reduction of the oxidizing agent's decomposition effect. As a result, an adsorbent with a longer lifespan compared to conventional technologies can be realized.

[0010] Preferred embodiments of the present invention will be described below. However, the scope of the present invention is not limited by the examples of preferred embodiments described below.

[0011] In one embodiment, the adsorbent according to the present invention preferably contains potassium permanganate as the oxidizing agent.

[0012] This configuration makes it possible to create an adsorbent with particularly high performance in decomposing target objects.

[0013] In one embodiment, the adsorbent according to the present invention preferably contains an anionic surfactant which is a compound having an unsaturated alkyl group and a sulfo group in its molecule.

[0014] According to this configuration, an adsorbent with a particularly long service life can be realized.

[0015] Further features and advantages of the present invention will become clearer from the following description of illustrative and non-limiting embodiments described herein. DESCRIPTION OF EMBODIMENTS FOR CARRYING OUT THE INVENTION

[0016] With regard to the embodiments of the present invention, an example in which the present invention is applied to an adsorbent used for preserving fruits and vegetables and a method for preserving fruits and vegetables using the same will be described.

[0017] [Configuration of Adsorbent] The adsorbent according to the present embodiment includes zeolite, an oxidizing agent, and an anionic surfactant. The content of each component is 2.0 parts by mass or more and 7.5 parts by mass or less for the oxidizing agent, and 0.035 parts by mass or more and 0.175 parts by mass or less for the anionic surfactant, relative to 100 parts by mass of zeolite.

[0018] Zeolite is a substance having a large number of fine pores, and has a function of taking in a target substance to be adsorbed into the pores and adsorbing the substance. In the adsorbent according to the present embodiment, the function of zeolite is utilized to capture the target substance to be adsorbed. The oxidizing agent plays a role of oxidizing and decomposing the target substance captured by the function of zeolite. The anionic surfactant serves to prevent decomposition of the oxidizing agent by hindering contact between the oxidizing agent and moisture in the air, and to facilitate sustaining the action of the oxidizing agent.

[0019] When the content of the oxidizing agent in the adsorbent is 2.0 parts by mass or more relative to 100 parts by mass of zeolite, the effect of oxidizing and decomposing the adsorbed target substance can be significantly obtained. The upper limit of the content of the oxidizing agent in the adsorbent is not particularly limited, but a content of 7.5 parts by mass or less relative to 100 parts by mass of zeolite is advantageous in terms of economic efficiency when producing the adsorbent.

[0020] When the anionic surfactant content in the adsorbent is 0.035 parts by mass or more per 100 parts by mass of zeolite, a significant protective effect against the oxidizing agent is obtained. When the anionic surfactant content in the adsorbent is 0.175 parts by mass or less per 100 parts by mass of zeolite, the preparation of the adsorbent by impregnating the zeolite with an aqueous solution containing anionic surfactant becomes easier.

[0021] Any known zeolite can be used without particular restriction. Therefore, the zeolite may be naturally occurring (generally referred to as natural zeolite), artificially produced (referred to as synthetic zeolite, artificial zeolite, etc.), or a mixture thereof. The crystal structure of the zeolite is also not particularly limited and may be mordenite, ferrielite, ZSM-5, beta, etc., or a mixture of zeolites with different crystal structures. The silica-alumina ratio of the zeolite is also not particularly limited and any zeolite with any silica-alumina ratio can be used. However, a silica-alumina ratio of 5 or higher is advantageous in terms of adsorption performance of the adsorbed material.

[0022] The form of the zeolite is not particularly limited, and powder, beads, pellets, granules, etc., can be used as desired. The particle size of the zeolite is not particularly limited, but for example, the number-average particle size (equivalent spherical diameter) may be between 100 nm and 10 mm. The specific surface area of ​​the zeolite is not particularly limited, but for example, 150 m² 2 / g or more 400m 2 It may be less than / g.

[0023] The oxidizing agent is not limited as long as it is a substance that can oxidize the adsorbed substance, and may include potassium permanganate, sodium permanganate, palladium chloride, titanium dioxide, zinc oxide, tungsten oxide, etc. The oxidizing agent may be a single compound or a mixture of several compounds. The oxidizing agent plays a role in oxidative decomposition of the adsorbed substance captured by the function of the zeolite. For example, potassium permanganate is a relatively strong oxidizing agent and is one of the suitable oxidizing agents. Potassium permanganate has a sufficient decomposition effect on substances such as ethylene, xylene, geosmin, and 2-methylisoborneol. For example, in ethylene, the double bond is cleaved by the action of the oxidizing agent, producing carbon dioxide. The oxidizing agent may be a single compound or a mixture of several compounds.

[0024] The anionic surfactant can be any known anionic surfactant without particular limitation. The anionic surfactant may be a single compound or a mixture of several compounds. The anionic surfactant is present in the adsorbent with its hydrophilic group facing the oxidizing agent and its hydrophobic group facing outward, preventing moisture from the air from coming into contact with the oxidizing agent. This suppresses the consumption of the oxidizing agent in the reaction to oxidize water, thereby extending the lifespan of the oxidizing agent. It is preferable that the anionic surfactant contains compounds having an unsaturated alkyl group and a sulfo group in the molecule, as this provides better protection for the oxidizing agent. It is even more preferable that the anionic surfactant contains a compound having the structure shown in the following formula (1), where R represents a substituted or unsubstituted unsaturated alkyl group. R-SO3Na (1)

[0025] Compounds represented by general formula (1) include sodium tetradecenesulfonate (R=C 14 H 27 ), sodium hexadecene sulfonate (R=C 16 H 31 ), sodium hydroxyhexadecyl sulfonate (R=HO-C 16 H 32 Examples include, but are not limited to, these.

[0026] The adsorbent according to this embodiment may include other substances such as zeolite, oxidizing agents, and anionic surfactants. Examples of such other substances include, but are not limited to, silica, silica gel, activated carbon, and aluminosilicates.

[0027] [Method for manufacturing adsorbents] The adsorbent according to this embodiment can be manufactured by known methods, as long as the zeolite, oxidizing agent, anionic surfactant, and any other components that may be added are uniformly mixed. For example, an aqueous solution containing an oxidizing agent and anionic surfactant is prepared, the zeolite is immersed in the aqueous solution, and then the water is removed by heating and drying to obtain an adsorbent containing zeolite, an oxidizing agent, and anionic surfactant. In this method, as long as the heating and drying is performed at a temperature lower than the boiling point or decomposition temperature of the zeolite, oxidizing agent, and anionic surfactant, and higher than the boiling point of water (100°C), the masses of the zeolite, oxidizing agent, and anionic surfactant used as raw materials are substantially retained. Therefore, the raw materials can be weighed according to the desired adsorbent formulation and mixed by the method described above.

[0028] If the oxidizing agent content in the adsorbent is 7.5 parts by mass or less per 100 parts by mass of zeolite, the amount of water that needs to be removed by heating and drying when manufacturing the adsorbent using the method exemplified above can be suppressed, thereby reducing the time and energy required for such heating and drying. Therefore, having the oxidizing agent content within the above range is economically advantageous when manufacturing the adsorbent.

[0029] [Structure of methods for preserving fruits and vegetables] The method for preserving fruits and vegetables according to this embodiment includes preserving the fruits and vegetables together with the above-mentioned adsorbent.

[0030] The above adsorbent has a function of adsorbing and decomposing substances that are adsorption targets. When fruits and vegetables are stored together with this adsorbent, substances that may cause deterioration of the fruits and vegetables can be adsorbed and decomposed, so that the freshness of the stored fruits and vegetables can be easily maintained. For example, ethylene secreted by fruits and vegetables has the effect of promoting aging and ripening of the fruits and vegetables themselves, and this effect leads to deterioration of the fruits and vegetables, but the deterioration of the fruits and vegetables can be prevented by adsorbing and decomposing ethylene.

[0031] When the adsorbent is applied to the storage of fruits and vegetables, the adsorbent can be housed in a container such as a vessel or a packaging material. Such a housing can be made of a gas-permeable material (for example, paper, nonwoven fabric, film, etc.). The material constituting the housing is preferably a water-impermeable material, and a moisture-permeable waterproof film, a moisture-permeable waterproof nonwoven fabric and the like are preferable examples.

[0032] [Other Embodiments] It should be understood that, with regard to other configurations, the embodiments disclosed in the present specification are illustrative in all respects, and the scope of the present invention is not limited by them. A person skilled in the art will readily understand that appropriate modifications can be made without departing from the spirit of the present invention. Accordingly, other embodiments modified without departing from the spirit of the present invention are naturally included in the scope of the present invention. [Examples]

[0033] Hereinafter, the present invention will be further described with reference to Examples. However, the following Examples do not limit the present invention.

[0034] [Reagents] The following substances were used as reagents in producing the adsorbents according to Examples and Comparative Examples.

[0035] As the zeolite, granular natural zeolite having a mordenite crystal structure was used. The silica-alumina ratio of the zeolite was 60, the particle size was 3.3 to 1.9 mm (those remaining on a 6 to 10 mesh sieve), and the specific surface area was 250 m 2 / g.

[0036] Potassium permanganate of general reagent grade was used as the oxidizing agent.

[0037] As the anionic surfactant, general reagent-grade sodium tetradecenesulfonate was used. To improve handling during the preparation of the adsorbent, sodium tetradecenesulfonate was dissolved in pure water to prepare an aqueous solution with a solid content of 35%.

[0038] [Preparation of adsorbent] (Example 1) Potassium permanganate, an aqueous solution of sodium tetradecenesulfonate, and pure water were weighed and mixed to obtain an aqueous solution containing 2.0 parts by mass of potassium permanganate and 0.0875 parts by mass of sodium tetradecenesulfonate per 100 parts by mass of pure water. 100 parts by mass of zeolite was immersed in this aqueous solution, and then heated and dried at 120°C for 3 hours to obtain the adsorbent of Example 1.

[0039] (Examples 2-5 and Comparative Examples 1-3) Adsorbents for Examples 2-5 and Comparative Examples 1-3 were obtained in the same manner as in Example 1, except that the amounts of potassium permanganate and sodium tetradecenesulfonate per 100 parts by mass of zeolite, as well as the amount of pure water used and drying time during adsorbent preparation, were changed as shown in Table 1 below. In Table 1, potassium permanganate and sodium tetradecenesulfonate are listed as "oxidizing agent" and "surfactant," respectively. Furthermore, the amounts of sodium tetradecenesulfonate (surfactant) listed in Table 1 do not include the mass of pure water contained in the sodium tetradecenesulfonate aqueous solution.

[0040] In all examples, the tests were conducted assuming that each component was present in the adsorbent in the mass proportion used during preparation, and the quantitative analysis of each component in the prepared adsorbent was not performed. For example, in Example 1, it was assumed that an adsorbent containing 100 parts by mass of zeolite, 2.0 parts by mass of potassium permanganate, and 0.0875 parts by mass of sodium tetradecenesulfonate was obtained. It is obvious to those skilled in the art that this assumption does not cause any practical problems.

[0041] [Evaluation of adsorbents] Adsorption tests were conducted on each adsorbent in the examples and comparative examples, targeting three substances: ethylene, o-xylene, and a mold odor simulant. Durability tests were also performed on the adsorbent targeting ethylene.

[0042] (Ethylene adsorption test) A sampling bag containing 1 g of adsorbent was filled with ethylene-containing gas. As a control, a sampling bag was prepared without the adsorbent, filled with ethylene-containing gas. Both sampling bags had a total gas volume of 8 L and an ethylene concentration of 20 ppm. Both sampling bags were left to stand at 20°C for 6 hours. After standing, the ethylene concentration in the gas within each sampling bag was measured using a detector tube. The ethylene concentration of the sample with adsorbent (C) was measured. E (Unit: ppm) and the ethylene concentration C of the control sampling bag. E0 (Unit: ppm) and based on this, the ethylene concentration reduction rate R E The percentage was calculated using the following formula (2).

number

[0043] The calculated ethylene concentration reduction rate R E Based on the values, the following three levels were assigned. A: Ethylene concentration decrease rate R E over 70% B: Ethylene concentration decrease rate R E50% to less than 70% C: Ethylene concentration reduction rate R E less than 50%

[0044] (o-xylene adsorption test) A sampling bag containing 1 g of adsorbent was filled with gas containing o-xylene. As a control, a sampling bag containing gas with o-xylene but without adsorbent was prepared. Both sampling bags had a total gas volume of 8 L and an o-xylene concentration of 20 ppm. Both sampling bags were left to stand at 20°C for 24 hours. After standing, the o-xylene concentration in the gas in each sampling bag was measured using a detector tube. The o-xylene concentration C of the sample with adsorbent was measured. X (Unit: ppm) and the o-xylene concentration C of the control sampling bag. X0 (Unit: ppm) and based on this, the o-xylene concentration reduction rate R X The percentage was calculated using the following formula (3).

number

[0045] The calculated o-xylene concentration reduction rate R X Based on the values, the following three levels were assigned. A: o-xylene concentration reduction rate R X That was over 70%. B: R - Decrease rate of xylene concentration X The percentage was between 50% and 70%. C:o-Xylene concentration reduction rate R X The percentage was less than 50%.

[0046] (Adsorption test of mold odor simulating substances) An equal-mass mixture of geosmin and 2-methylisoborneol was used as a substance to simulate moldy odor. Both geosmin and 2-methylisoborneol are substances that cause moldy odor in tap water. For the adsorption experiment, gases containing 100 μg / L each of geosmin and 2-methylisoborneol were prepared as sample gases.

[0047] A sampling bag containing 1 g of adsorbent was filled with 2.5 L of sample gas. The sampling bag was left to stand at 28°C for 24 hours. After standing, the gas in the sampling bag was measured by GC-MS to check for the presence or absence of peaks attributed to geosmin and 2-methylisoborneol. Based on the presence or absence of peaks attributed to each substance, the samples were classified into the following three levels. A: No peaks for geosmin or 2-methylisoborneol were detected. B: One of the peaks, geosmin or 2-methylisoborneol, was detected. Peaks for both C: geosmin and 2-methylisoborneol were detected.

[0048] (Durability test) In the durability test, repeated trials were conducted to adsorb ethylene onto the adsorbent, and the number of trials required for the adsorption performance of the adsorbent to fall below a certain level, as well as the total amount of ethylene adsorbed, were evaluated.

[0049] The test was conducted in the same manner as the ethylene adsorption test described above, except that the standing conditions for the sampling bag were changed to 20°C for 24 hours. The calculated ethylene concentration reduction rate was used as the first measurement value.

[0050] Furthermore, the amount of ethylene adsorbed (unit: mg / g) was calculated based on the measured values. The amount of ethylene adsorbed is the mass of ethylene adsorbed per gram of adsorbent (unit: mg). In the ideal gas law, the ethylene concentration C of the sample containing the adsorbent was calculated. E , the ethylene concentration C of the control sampling bag E0 The amount of ethylene adsorbed can be calculated by using the molecular weight of ethylene (28.05), the test temperature (20°C (293K)), the pressure during the test (atmospheric pressure of 1 atm), and the volume of gas filled in the sampling bag (8L) as variables.

[0051] After the first measurement, all the gas was drained from the sampling bag containing the adsorbent, and it was refilled with ethylene-containing gas (total gas volume 8L, ethylene 20ppm) in the same manner as the first measurement. This sampling bag was left standing at 20°C for 24 hours along with the control sampling bag, and the rate of decrease in ethylene concentration and the amount of ethylene adsorbed were calculated for the second measurement.

[0052] The following steps were repeated using the same procedure, involving gas exchange, storage, and calculation of the ethylene concentration decrease rate and ethylene adsorption amount. The test was terminated when the ethylene concentration decrease rate fell below 10%. The number of repetitions at the end of the test and the total amount of ethylene adsorbed up to the end of the test were used as the test results for each example. Furthermore, the total amount of ethylene adsorbed was classified into the following two levels. A: The total amount of ethylene adsorbed was 2.5 mg / g or more. C: The total amount of ethylene adsorbed was less than 2.5 mg / g.

[0053] 〔result〕 Table 1 shows the formulations and evaluation results for each example in the examples and comparative examples.

[0054] Table 1: Examples and Comparative Examples [Table 1]

[0055] Examples 1 to 5 all showed good results in adsorption and durability tests. On the other hand, the comparison between the examples and comparative examples indicates that there is a suitable range for the proportions of zeolite, oxidizing agent, and anionic surfactant when implementing the adsorbent according to the present invention. From the comparison between Comparative Example 1 and each example, it was found that the adsorbent exhibits good adsorption when it contains a certain amount or more of the oxidizing agent (potassium permanganate).

[0056] Furthermore, a comparison between Comparative Example 2 and each example revealed that the durability of the adsorbent improved when an anionic surfactant (sodium tetradecenesulfonate) was present. However, Comparative Example 3 showed that excessive use of anionic surfactants had a counterproductive effect. When preparing the adsorbent in Comparative Example 3, the viscosity of the aqueous solution containing potassium permanganate and sodium tetradecenesulfonate was higher than in the other examples, which is thought to have hindered the adsorption of potassium permanganate and sodium tetradecenesulfonate onto the zeolite. Since the viscosity of the aqueous solution is due to the anionic surfactant, it can be said that there is an upper limit to the amount of anionic surfactant used, considering its behavior when preparing the adsorbent. [Industrial applicability]

[0057] This invention can be applied to the preservation of fruits and vegetables.

Claims

1. Zeolite and, The oxidizing agent is present in an amount of 2.0 parts by mass or more and 7.5 parts by mass or less per 100 parts by mass of the zeolite, An adsorbent comprising 0.035 parts by mass or more and 0.175 parts by mass or less of an anionic surfactant per 100 parts by mass of the zeolite.

2. The adsorbent according to claim 1, wherein the oxidizing agent comprises potassium permanganate.

3. The adsorbent according to claim 1, wherein the anionic surfactant comprises a compound having an unsaturated alkyl group and a sulfo group in its molecule.

4. A method for preserving fresh produce, comprising preserving fresh produce together with an adsorbent containing zeolite, an oxidizing agent in an amount of 2.0 parts by mass to 7.5 parts by mass per 100 parts by mass of zeolite, and an anionic surfactant in an amount of 0.035 parts by mass to 0.175 parts by mass per 100 parts by mass of zeolite.

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