KR100490475B1 - Combined absorbent for maintaining the agricultural freshness - Google Patents

Abstract

The present invention Disclosed is a composite adsorbent for freshness maintenance of a crop consisting of calcined natural zeolite, silver-supported natural zeolite, calcium chloride-supported natural zeolite and activated carbon.

If the composite adsorbent of the present invention is placed in the packaging container of the crop, the freshness of the crop can be maintained for a long time.

Description

Composite adsorbent for maintaining crop freshness {COMBINED ABSORBENT FOR MAINTAINING THE AGRICULTURAL FRESHNESS}

The present invention relates to a composite adsorbent for maintaining the freshness of the crop. More specifically, the present invention relates to a composite adsorbent which mixes calcined natural zeolites, silver-supported natural zeolites, calcium chloride-supported natural zeolites, and activated carbon and puts them together in a packaging container to maintain the freshness of the crops for a long time.

Fruits and vegetables that are sufficiently mature while attached to the mother are best in terms of taste and nutrition, but most crops are harvested slightly under ripened, taking into account the time it takes to travel from the place of origin to the consumer. Therefore, the harvested crops are still ripened during storage and transport, and if the storage conditions are poor, deterioration and decay also occur. The stress separated from the mother weakens the crop's resistance, and the ethylene produced at the separated site or at the wound site during harvesting or migration promotes ripening and alteration. In addition, mold and microbial invasion also accelerate the decay of crops.

Since crops should be provided to consumers in fresh condition, ripening or alteration after harvesting should be restrained as much as possible. Substances that promote ripening or alteration of crops include oxygen and moisture required for metabolism and ethylene, a growth hormone. In addition, there are claims that carbon dioxide also promotes the deterioration of crops, but no objective verification has been made. In addition, microorganisms and fungi also have a great effect on the decay and deterioration of crops. In addition to these substances and organisms, temperature and humidity also affect the metabolism and decay of crops. Aging or decay is also a physiological activity of living things, because the proper temperature and humidity is fast. The substances and factors listed above contribute to the ripening and decay independently, but there is also an interaction between them, and their effects on the ripening and decay of crops are very complicated.

Therefore, in order to maintain the freshness by suppressing the ripening and decay of crops, it is necessary to remove the above-mentioned substances or to maintain the temperature and humidity properly. In order to eliminate the oxygen required for metabolism and to prevent ripening or decay at the source, nitrogen or argon is injected into the packaging of the crop to exclude oxygen. The removal of water slows down the metabolism of crops, inhibits the growth of microorganisms and molds, and can keep crop fresh for a long time. At the same time, when the temperature is lowered, the physiological activity of the crop is lowered, so that ripening or deterioration is delayed, and thus, low temperature storage is widely used as a method of maintaining freshness. In addition, by removing ethylene, a growth hormone of crops, it is possible to delay ripening and maintain freshness. Although the rate of ethylene generation and susceptibility to ethylene vary depending on the crops, it is known that sweet persimmons, tangerines, pears, plums, etc. generate a lot of ethylene and have high susceptibility. Some argue that removal of carbon dioxide also contributes to maintaining crop freshness, but it is not clear.

Storage of harvested crops at low temperature is the most widely used as a leading maintenance method. It not only delays physiological activity and delays ripening and deterioration, but also suppresses the growth of microorganisms and molds, and can be used widely regardless of the type of crop. However, storing crops at too low a temperature can also cause irreversible damage, which limits the freshness of the freshness alone. In addition, it is expensive to maintain the low temperature, so the cost should be taken into account. Therefore, the low temperature storage method is difficult to apply for short-term storage of crops packaged in small units due to the facility investment cost for cooling, but is suitable for large storage facilities for long-term storage.

The removal of oxygen by replacing the air in containers or storage facilities with crops with nitrogen or argon is also effective in maintaining freshness. This method can be applied to large-scale installations and to small-scale packaged crops, but is not very effective and is not widely used due to the high risk of corruption due to water saturation.

The removal of moisture from storage containers or facilities containing crops is also effective in maintaining freshness of crops. Appropriate removal of water reduces the physiological activity of crops and inhibits the growth of microorganisms and fungi. Excessive moisture removal, however, impairs the taste and aroma of the crops and results in a change in surface condition, resulting in a loss of commodity value.

The method of removing ethylene, which is a growth hormone of plants, is also effective in maintaining freshness of crops, and various methods for removing ethylene generated from crops being stored or transported have been proposed and applied. Small-scale sealed packaging crops contain a dehumidifying agent containing potassium permanganate to provide activated oxygen. The ethylene is completely oxidized and removed with carbon dioxide and water. Potassium permanganate is an effective removal of ethylene, but its potent oxidizer, potassium permanganate, is itself a very toxic substance and is therefore strictly regulated in situations where contact with crops is a concern. Activated carbon, which selectively adsorbs organic matter, may be packaged together with the crops to remove ethylene by adsorbing. Under low humidity conditions, ethylene is adsorbed on activated carbon in large quantities, so ethylene can be safely removed. However, in most crops, water evaporates, so the sealed container is saturated with water vapor. In this state, water is adsorbed on activated carbon, so that ethylene is desorbed, thereby eliminating ethylene removal of activated carbon. In addition, a photocatalyst is used to oxidize and remove ethylene with oxygen in the air. In addition to the power required for the light source, it does not require any additional cost or reactants and is very effective because it can be used stably for a long time. However, photocatalysts are not applicable to small-packaged crops due to facility investment costs and the cost of photocatalysts themselves, and are suitable for removing ethylene from large storage facilities. Combustion catalysts can also be used to completely remove low concentrations of ethylene at low temperatures. Ethylene can be removed very quickly and reliably, but fuel costs and stability are burdensome.

In order to maintain freshness, it is necessary to suppress the growth of microorganisms and molds, but the application of pesticides to storage crops is strictly regulated due to the toxicity of residual pesticides. Although the crops are packaged with antimicrobial packaging, their contribution to maintaining freshness has not been quantitatively verified.

Although various methods are used to maintain the freshness of these harvested crops, it is very difficult to quantitatively verify the freshness maintenance effect. Even if they are of the same type, the conditions of the crops vary considerably depending on the place and time of harvest. Although seemingly the same, the degree of aging or deterioration varies greatly from individual to individual, making it difficult to objectively demonstrate the function of the freshener. In addition, since several factors are involved in aging or deterioration at the same time, it is not easy to quantitatively estimate the function of the leading oil.

Despite these uncertainties, leading freshness during storage and transportation of crops is crucial to maintaining the value of the crops. In large facilities, ethylene and water are removed using adsorbents and photocatalysts while being stored at low temperatures to slow down the metabolism of harvested crops and suppress the growth of mold and microorganisms. Small-scale crops may use adsorbents mixed with synthetic zeolite A and activated carbon for dehumidification and ethylene removal. Since ethylene and water promote ripening and deterioration of crops, the addition of these fresheners helps to maintain the freshness of the packaged crops. However, in the sealed packaging state, the moisture is evaporated from the crops and the internal humidity may be increased, leading to a saturation step. As the water is adsorbed on the activated carbon, all of the adsorbed ethylene is desorbed.

Taken together, it can be concluded that a complex adsorbent that can adsorb a lot of water and ethylene to keep the humidity and ethylene concentration low, while suppressing the growth of mold and microorganisms, is effective in maintaining the freshness of crops.

Crops should be provided to consumers in a fresh state with minimal loss of nutrition and taste during distribution. Therefore, maintaining the freshness of crops is very important nationally in that it can use the crops produced and reduce the losses from disposal, in addition to the primary effect of increasing farm income. However, it is difficult to develop an effective freshness maintenance method applicable to all crops because the rate of ripening and decay varies greatly according to the type and condition of crops, and the sensitivity to surrounding conditions is also different. Moreover, it is difficult to generalize all cases because the proper freshness maintenance method depends on the size and duration of the crop to be stored. The present invention has devised a method for producing a leading oil and fat that can contribute to maintaining the freshness of vegetables or fruits that are packaged and sold in units of 10 kg or smaller.

Aging and decay of crops are also biological reactions, so cold storage and oxygen removal are effective. However, there is a limit to the continuous storage of crops at low temperatures during distribution. Moreover, when stored in a sealed state for oxygen removal, the decay can be promoted by rising humidity, so the effect of the oxygen removal method is also unclear. In this case, it is preferable to put the adsorbent which can remove water and ethylene at the same time with the crop to suppress the corruption and deterioration of the crop. Adsorbents are preferably adsorbed a lot of ethylene under low humidity conditions and irreversibly adsorbs ethylene even under high humidity conditions, so that part of the ethylene is not desorbed even when saturated with water vapor.

To this end, an adsorbent capable of adsorbing a large amount of moisture even in a small amount can maintain a low humidity. This adsorbent should also adsorb a lot of ethylene. In particular, it is effective to adsorb as much ethylene as possible even in high humidity conditions. However, except for a few crops that are kept in a completely sealed state such as sweet persimmon, most crops are packaged for ventilation, so that they do not reach saturated humidity except during the rainy season or special conditions. Therefore, the use of an adsorbent capable of adsorbing a large amount of water can increase the dehumidification capacity and express the ethylene removal function. The method of dehumidifying a lot of water so that the packaged crops do not reach saturated humidity is very important for maintaining freshness as it can maintain water removal as well as water removal.

Some crops, like strawberries, are easily rotted by microorganisms or fungi. These crops contain a lot of water, so it is difficult to maintain freshness by dehumidification methods, and is easily deteriorated by microorganisms or molds introduced from the outside. Therefore, the freshness must be maintained to suppress their reproduction. The addition of antimicrobial activity against fungi and microorganisms to the adsorbent can greatly improve the performance as a leading maintenance agent for crops.

In order to solve the above problems, the present inventor can not only strongly adsorb a lot of water and ethylene, but also use a composite adsorbent having antimicrobial ability to harvested fruits or vegetables, so that the freshness of the fruits or vegetables is maintained for a long time. It has been found that the present invention can be completed.

In the present invention, a method for producing a composite adsorbent that can remove moisture and ethylene while simultaneously maintaining antibacterial activity is designed to maintain the freshness of the crop. To increase the adsorption amount of natural or synthetic zeolite loaded with silver or copper with strong antibacterial ability while adsorbing a lot of ethylene, and natural zeolite ethylene loaded with calcium chloride to adsorb a lot of moisture and to delay ethylene desorption by water. The composite adsorbent prepared by mixing a certain ratio of activated carbon carrying silver to neutralize or to provide antibacterial function was effective as a leading oil retainer of crops.

After the natural zeolite is evacuated at 200 ° C. to remove moisture, ethylene is hardly adsorbed at room temperature even when exposed to ethylene. However, supporting silver significantly increases the adsorption amount of ethylene. The increase in ethylene adsorption due to silver loading is also evident when silver is supported on clay. [1] When exposed to water vapor, zeolites are hydrophilic, so that water adsorbs and ethylene is desorbed. However, at relative humidity below 70%, 40% of adsorbed ethylene remains undesorbed. Even when the relative humidity reaches around 90%, the adsorption of ethylene is enhanced by the support of silver so that about 15% of the adsorbed ethylene remains. The supported amount of silver nitrate of the natural zeolite carrying silver used in the present invention is preferably 0.5% by weight to 2.0% by weight. When the amount of silver nitrate is increased, the dispersion of silver is lowered. Even though silver nitrate is supported at 2.0 wt% or more, the amount of ethylene adsorption, which is a supporting effect of silver, is not significantly increased, but is less than 0.5 wt%, compared to the sample supporting silver nitrate at 0.5 wt%. In the case of natural zeolite, the adsorption amount of ethylene may remarkably fall at room temperature.

Zeolite adsorbs a large amount of water by itself, but supporting calcium chloride greatly improves the dehumidification capacity. However, the calcium chloride must be supported in the pores of the zeolite so that even if the humidity is very high, the surface will not get wet, so that it will not contaminate the crops and thus can be used safely. Improved dehumidification capacity with calcium chloride support reduces the amount of zeolite needed to remove water, which can reduce the amount of lead oil used and lower the price. The supported amount of calcium chloride in the present invention is 5% by weight to 30% by weight, more preferably 5% by weight to 20% by weight. The amount of calcium chloride depends on the purpose of use of the dehumidifying agent.In the case of removing a large amount of water in a relatively dry condition, about 40% by weight may be used in natural zeolite, but if it is more than 30% by weight, the humidity is very high. Prolonged exposure may cause the surface to get wet due to deliquescent of calcium chloride. Therefore, if the amount of calcium chloride supported is large, the dehumidification effect is increased, but the state of the target food to maintain freshness due to the surface wet phenomenon may be lowered, more preferably 20% by weight or less. If less than 5% by weight, the dehumidification effect when calcium chloride is supported is not suitable for freshness maintenance.

Silver is well known for its antimicrobial properties. [2] Finely divided silver is used as an antibacterial agent for various purposes because it has strong sterilization function and is not harmful to the human body at all. Carrying silver on activated carbon can suppress the influx of microorganisms and mold from the outside and contribute to freshness. The supported amount of silver nitrate of the activated carbon carrying silver used in the present invention is preferably 0.5% by weight to 2.0% by weight. When the amount of silver nitrate is increased, the dispersion of silver becomes low, and even though silver nitrate is supported by 2.0 wt% or more, there is no significant difference in freshness compared to the sample carrying silver nitrate by 0.5% by weight. The present invention may be inferior. The present invention provides a natural zeolite supported by silver which is capable of adsorbing a lot of ethylene while having strong antibacterial properties, a natural zeolite supported by calcium chloride to adsorb a large amount of water, and activated carbon from 20 to 40: 30 to 30 A composite adsorbent prepared by mixing at a weight ratio of 50:20 to 40 is most preferable because it has the greatest effect as a freshness maintaining agent of crops.

Hereinafter, an Example is given and this invention is demonstrated further more concretely.

Example 1.

Natural zeolites mined near Yeongil Bay in Gyeongsangbuk-do usually contain significant amounts of zeolite components such as mordenite and clinol tyrolite. The content varies depending on the place of origin and the location of mining, but it is generally estimated to be 40-60%. When the natural zeolite having a surface area of 30 m ² / g and a particle size of 1.7 to 2.8 mm is calcined at 200 ° C. for about 4 hours, most of the adsorbed water is removed and some of the mixed carbonate is decomposed.

After firing, calcium chloride was supported on the cooled natural zeolite to drastically enhance the dehumidifying ability of the natural zeolite. 1 g of a solution prepared by dissolving 100 g of calcium chloride in 1 l of water was sprayed onto 1 kg of calcined natural zeolite and dried at 100 ° C. for 2 hours. Subsequently, calcining was carried out at 200 to 400 ° C. for 2 to 4 hours to prepare a natural zeolite loaded with calcium chloride.

1 shows a comparison of the effect of improving the dehumidification capacity of natural zeolite due to calcium chloride loading.

This is the result of measuring the degree of mass increase as water is adsorbed at equilibrium steam pressure of 25 ° C saturated ammonium chloride solution. The water adsorption amount per 1 g of natural zeolite is 0.08 g when exposed to water vapor for 2 days, but the water adsorption amount of natural zeolite loaded with 10% by weight of calcium chloride is 0.2 g, which greatly increases the water adsorption amount on calcium chloride. The amount of water adsorption of the natural zeolite calcined at 200 ° C. is 0.35 g, but it is difficult to use it as a freshness maintaining agent of crops because the surface is wet and calcium chloride may elute. On the other hand, if the temperature is raised and fired at 400 ° C., the adsorption amount is small but the surface is not wet. If the amount of calcium chloride supported is very large or the firing temperature is low, the surface wetting phenomenon is severe. In particular, when calcium chloride is supported on the surface of the zeolite rather than the pores, the moisture absorption rate is high and the adsorption amount is high, but the surface wetting phenomenon is very severe. Therefore, the amount of calcium chloride supported and the firing temperature should be determined in consideration of the stability in use with the improvement of dehumidification performance. In order to prevent the surface wetting phenomenon, natural zeolite was loaded with 10% by weight of calcium chloride in a weight ratio, and when calcined at 300 ° C. or higher, the adsorption amount of water increased by three times and the wetness did not appear even in a humidity state. It can be used as a leading maintainer of crops while reducing requirements by one third.

Example 2.

Under low humidity conditions, ethylene adsorbs well on activated carbon. However, when the humidity increases, the adsorbed ethylene desorbs as water is adsorbed at the polar adsorption point of activated carbon. Therefore, in order to improve the ethylene removal function of activated carbon, the polar adsorption point of activated carbon should be reduced. Residues of potassium hydroxide, which remain unremoved in the activation process or added to increase the surface area of the activated carbon, act as a polar activation point among the alkali materials in the activated carbon manufacturing raw material. The treatment eliminated the polar active site or supported the active carbon to shield the polar active site. Silver may be selectively supported at the polar adsorption point to suppress adsorption of water and become an antimicrobial function point. 30 mL of concentrated hydrochloric acid was dissolved in 1 L of water, and 1 L of hydrochloric acid solution was added to a container containing 1 kg of activated carbon and stirred for 2 to 4 hours. Subsequently, the activated carbon was washed with hot hydrochloric acid and washed with hot water to prepare activated carbon neutralized with acid. The activated carbon was sufficiently washed until the wash water became neutral and dried at 80 ° C. for 1 hour.

1 g of silver nitrate solution made by dissolving 8 g of silver nitrate in 1 l of water was sprayed onto activated carbon using a sprayer. The activated carbon was stirred well and the silver nitrate solution was evenly sprayed and then dried first at 80 ° C. for 2 to 4 hours. It was calcined at 300 ° C. in a nitrogen atmosphere to remove nitrogen oxide, and silver was reduced through a self-reduction reaction. After cooling with flowing nitrogen, the mixture was stabilized by carefully contacting with air at room temperature to prepare activated carbon having a weight ratio of 0.5% by weight.

Figure 2 shows the water adsorption properties of the activated carbon measured by the gravimetric adsorption apparatus equipped with a quartz spring. In untreated activated carbon, when the relative pressure of water reaches 0.5, the amount of adsorption of water rapidly increases. On the other hand, neutralization with hydrochloric acid shows that the relative pressure, which rapidly increases the amount of adsorption of water, increases to 0.6, indicating that the adsorption of water is suppressed. In the silver-supported activated carbon, the relative pressure of 0.6 was not only used to adsorb water but also to reduce the adsorption amount of water. If adsorption of water is suppressed, the desorption of ethylene can be delayed, so that the function as a leading retainer can be improved.

Example 3.

Since the adsorption of ethylene is linked to the adsorption of water, it is necessary to measure the adsorption properties of ethylene in the presence of moisture for functional evaluation as a leading maintenance agent. Therefore, the adsorption performance of ethylene was compared with different relative humidity. It is possible to measure the change in ethylene concentration according to the change in humidity, and predict the effect of ethylene removal under actual conditions. 2 to 10 g of the adsorbent prepared in the adsorbent packing tube was placed, and a heater was installed to exhaust the adsorbent from water and carbon dioxide for 2 hours at 200 ° C. After removing the heater, a temperature control tank connected to a circulating thermostat was installed to maintain a constant temperature of the adsorbent. The ethylene gas diluted with nitrogen is then supplied to fill the ethylene reservoir. When the initial condition is reached, the valve is opened to investigate the adsorption of ethylene on the adsorbent. By adjusting the temperature or by adjusting the partial pressure of ethylene, the adsorption amount of ethylene is calculated by measuring the change in concentration of ethylene. After the equilibrium of adsorption, water is injected into the syringe to control the humidity. Desorption of ethylene with water injection is investigated by measuring the change in concentration of ethylene with a directly connected gas chromatograph.

3 shows a process in which ethylene is adsorbed on natural zeolite loaded with activated carbon and silver and ethylene is desorbed by water. As the ethylene is adsorbed onto activated carbon at 25 ° C., the ethylene concentration is lowered from 55 ppm to 25 ppm. This change in concentration means that 0.025 mg of ethylene is adsorbed per gram of natural zeolite. However, when water is added, relative humidity rapidly increases and ethylene desorbs. However, even when the relative humidity reaches 100% by weight, the ethylene concentration remains at 45 ppm and does not all desorb. The amount of adsorption of ethylene on the natural zeolite itself is not so high, but the support of silver increases the adsorption power of ethylene. Ethylene is adsorbed to the natural zeolite loaded with 0.5% by weight of silver, and all of the supplied ethylene is adsorbed at 25 ° C., resulting in ethylene concentration of 0 ppm. This change in concentration means that more than 0.055 mg of ethylene can be adsorbed onto 1 g of silver-supported natural zeolite. When water is added, ethylene desorbs up to 45 ppm, but some of the adsorbed ethylene remains undesorbed even when the relative humidity reaches 100% by weight. In other words, natural zeolite loaded with activated carbon and silver performs well as an ethylene remover even under saturated humidity conditions. In contrast, silver-free natural zeolites exhibit different behavior. A significant amount of ethylene is adsorbed to the natural zeolite exhausted at 100 ° C. Therefore, when water is added, almost all of the ethylene is desorbed as it is, the same as the initial concentration. Silver-free natural zeolites do not adsorb ethylene at all, even in the presence of water, which makes no sense as an ethylene remover. Supporting silver allows ethylene to be adsorbed even in the presence of water.

Example 4.

Activated charcoal, natural zeolite loaded with 0.5% by weight of silver, and natural zeolite loaded with 10% by weight of calcium chloride were mixed in a weight ratio of 30:30:40 to prepare a composite adsorbent. Since they are physically mixed, their respective performances remain the same, and the ethylene removal function with the dehumidification performance is shown as it is, and the performance as a leading retainer.

Strawberries are crops that are difficult to store freshly because they have high moisture content and weak skin. Fruits collected immediately from the field and sorted on the basis of size were purchased and packed in plastic containers to evaluate the function of the composite adsorbent as a leading oil retainer. For comparison, activated carbon, untreated natural zeolite, and natural zeolite loaded with 10% by weight of calcium chloride were tested in the same manner.

Six strawberries were placed in a well-sealed glass container, and the adsorbents to be evaluated were placed in a bowl made of filter paper with 2 g each. To verify test objectivity, two bowls of six strawberries were prepared. These containers were placed in a container maintained at 25 ° C. and stored together to investigate daily change of state. It was determined that black spots were formed on the outer surface of the strawberry or damaged when white molds bloomed. Table 1 also compared the results evaluated after 5 days.

Table 1. Leading oil application test for strawberries ^*

Applied freshener Sample sample (container) Number of damaged samples mold Remarks Do not put 12 (2) 4 + 4 - Juice is severe Calcium chloride supported natural zeolite 12 (2) 6 + 6 produce Juice flowed out Activated carbon 6 (1) 5 - Badly damaged Silver supported natural zeolite 6 (1) 4 - A little juice Composite adsorbent 12 (2) 3 + 1 - One side was very good

^* Sealed at 25 ℃ for 5 days

The rate of decay or deterioration was different depending on the condition of the strawberry, but there was no freshness retention function when only activated carbon or calcium chloride-supported natural zeolite with excellent dehumidification capacity was added. It was better than nothing, but after five days most of it was spoiled and juiced. On the other hand, in the adsorbents with dehumidification, ethylene removal and antibacterial activity, the freshness period was relatively long. After 5 days, some of the strawberry surface had black spots, but most of the berries were in good condition.

Example 5.

Unlike strawberries, the performance of fresh oil was evaluated in cherry tomatoes, which can be stored for one week at low temperature due to their outer skin. Silica, activated carbon, silver-supported activated carbon, and natural zeolite were also added with cherry tomatoes to investigate their effects on the decay of cherry tomatoes. The freshly harvested cherry tomatoes were placed in a sealed glass container in the same manner as strawberries, and 2 g of fresh oil was placed in the middle to investigate the change of state.

Cherry tomatoes do not rot as easily as strawberries. The outer shell is so strong that even if the inside is decayed. Even if nothing was added, there was no change in appearance until about 4 days. However, after 5 to 7 days, the state of cherry tomato was different depending on the type of freshener. Table 2 summarizes the state of cherry tomatoes irradiated on 6 and 13 days.

Table 2. Application of Leading Oils to Cherry Tomato

Applied freshener Sample Sample condition Remarks 6 days 13th Do not put 12 Mold development Very severe High humidity causes mold to grow Silica 12 Mold development Severe Activated carbon 12 Mold development Severe Hydrogen Peroxide Soaked Silica 12 Mold development Very severe Natural zeolite 12 Status Corruption begins Silver supported natural zeolite 12 Status Corruption begins Composite adsorbent 12 Status Corruption begins

Cherry tomato decayed with mold. No juices or black spots were seen, but the decay was relatively rapid with no freshener or silica and activated carbon alone. On the other hand, it was confirmed that the lead holding ability was excellent in silver-supported natural zeolites having excellent dehumidification ability or antibacterial ability.

At higher relative humidity, natural zeolite, which adsorbed a lot of water at low relative humidity rather than silica having high adsorption, functioned better as a leading maintainer. Cherry tomatoes are hard to observe the process of decay inside because the outer shell is thick and mold occurs first around the nipples. However, although the dehumidifying ability and the antimicrobial ability contributed to maintaining the freshness of cherry tomatoes, the effect of activated carbon was not clear.

Activated charcoal or natural zeolite can also contribute to the freshness of the crop because it adsorbs ethylene and water on its own, but even if a large amount is used, the effect alone is insufficient. Even when a dehumidifying agent and an ethylene remover are used at the same time, when the humidity is kept at a very low level, the removal function of ethylene is expressed. Therefore, the lead retention function is remarkably improved when the activated carbon and natural zeolite are loaded with calcium chloride and silver. In particular, calcium chloride is supported on the natural zeolite to increase the dehumidification capacity, and silver is supported to improve the ethylene adsorption and removal ability of the natural zeolite. Thus, the synergistic action greatly improves the freshness retention function. Even if silver is supported on the activated carbon or neutralized with hydrochloric acid solution, the polar adsorption point is reduced and the desorption of ethylene is delayed, so the ethylene removal function is enhanced, which is effective as a freshness maintaining agent of crops. As shown in the results of the mixed adsorbent examples prepared by mixing, they easily contributed to maintaining freshness by delaying deterioration for a certain period of time, such as strawberries and cherry tomatoes.

1 is a diagram showing the water adsorption properties of natural zeolite loaded with calcium chloride.

2 is a diagram showing the water adsorption properties of silver-supported activated carbon measured by a gravimetric adsorption apparatus equipped with a quartz spring.

In FIG. 3, ethylene is adsorbed on activated zeolite and natural zeolite loaded with silver, and ethylene is desorbed by water.

Claims (5)

Composite adsorbent for fresh maintenance of crops consisting of silver-supported natural zeolite, calcium chloride-supported natural zeolite and activated carbon. The method of claim 1, wherein the silver-supported zeolite is a natural zeolite supported by 0.2-1.0% by weight of silver produced by spraying and spraying a 0.5-2.0% by weight solution of silver nitrate on a natural zeolite, and then calcining at 200-400 ° C. Composite adsorbent. The method of claim 1, characterized in that the natural zeolite carrying calcium chloride is a natural zeolite carrying 5-20% by weight of calcium chloride by firing at 250-450 ° C after spraying and spraying a saturated calcium chloride solution onto the natural zeolite. Composite adsorbent. 2. The activated carbon according to claim 1, wherein the activated carbon is a sprayed spray of 0.5 to 2.0% by weight of a solution of silver nitrate on the activated carbon, dried at 80 ° C, and calcined to 200 to 400 ° C in a nitrogen atmosphere, wherein the activated carbon is 0.2 to 1.0% by weight of activated carbon. Composite adsorbent. The composite adsorbent according to claim 1, wherein the silver-supported natural zeolite, the calcium chloride-supported natural zeolite, and the activated carbon are in a weight ratio of 20 to 40:30 to 50:20 to 40.