JPH0379971B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a freshness-preserving agent for preserving the freshness of agricultural products after harvesting.

(b) Problems to be solved by conventional techniques and inventions In recent years, when it comes to fresh agricultural products, people are more attracted to aroma, color, freshness, etc. than nutritional components, and sensual aspects such as texture, flavor, taste, etc. Emphasis has begun to be placed on In other words, it is no exaggeration to say that the value of fresh agricultural products lies in their freshness. However, there have been cases where the freshness of agricultural products decreases during packaging and transportation from the production area to the consumption area after harvesting, resulting in a decrease in the commercial value of the fresh agricultural products.

A decrease in the freshness of fresh produce occurs due to various factors, but the most important factor is ethylene gas, which is also said to be an aging hormone, produced by fresh produce. That is, in the closed environment of packaging, the packaging container is filled with ethylene gas produced by fresh produce, which acts on the fresh produce and accelerates its aging.

In order to eliminate this factor, it is possible to put an ethylene adsorbent that adsorbs ethylene gas in the packaging container, or to coat or mix the ethylene adsorbent into the packaging material. However, even if the ethylene gas is once adsorbed by the ethylene adsorbent, it may be released to the outside again when the temperature of the outside air rises. This is because the movement of ethylene gas becomes more active as the temperature rises. The released ethylene gas fills the packaging container and acts on fresh agricultural products, accelerating their aging.

Therefore, the present invention aims to provide a freshness-preserving agent that does not release the ethylene gas once adsorbed, even if the temperature of the outside air rises, by blending an ethylene adsorbent with another specific substance. be.

(c) Means for solving the problems That is, the present invention provides a polymer complex in which copper chloride (2) and aluminum chloride are coordinated to cross-linked polystyrene, and a polymer complex in which silver chloride (2) and aluminum chloride are coordinated to cross-linked polystyrene. Polymer complex, a polymer complex in which copper chloride () is coordinated with an ion exchange resin,
Selected from the group consisting of an inorganic complex in which copper ( ) ions are coordinated to zeolite, an inorganic complex in which copper ( ) ions are coordinated to γ-alumina, and an inorganic complex in which copper nitrate is coordinated to activated carbon. an ethylene adsorbent, a superabsorbent resin, a salt of a polyvalent metal having a valence of at least 2 and which can have a valence of less than 2, and reducing the salt of the polyvalent metal in the presence of water. The present invention relates to a freshness-preserving agent characterized by containing sodium bisulfite, which is a metal salt with a reduced valence, as an essential component.

In the present invention, the ethylene adsorbent is a polymer complex made of cross-linked polystyrene coordinated with copper chloride (2) and aluminum chloride, a polymer complex made of cross-linked polystyrene coordinated with silver chloride (2) and aluminum chloride, and an ion exchange resin. A polymer complex in which copper () chloride is coordinated, an inorganic complex in which copper () ions are coordinated in zeolite, an inorganic complex in which copper () ions are coordinated in γ-alumina, and copper nitrate in activated carbon. The coordinated inorganic complexes may be used alone or in combination.

A polymer complex in which copper chloride and aluminum chloride are coordinated to crosslinked polystyrene can be obtained by the following method. First, styrene and divinylbenzene are mixed in an appropriate ratio and polymerized to obtain crosslinked polystyrene. When this crosslinked polystyrene is mixed with copper chloride (2) and aluminum chloride and heated, a polymer complex coordinated to the crosslinked polystyrene is obtained. It is thought that the coordination site of copper chloride (2) and aluminum chloride is the aromatic ring of crosslinked polystyrene. Other ethylene adsorbents can also be obtained in a similar manner.

The superabsorbent resin used in the present invention is a polymer that absorbs and retains water at least 10 times its own weight, preferably at least 100 times its own weight, such as starch-acrylonitrile graft polymer, starch-acrylic acid Examples include salt graft polymers, self-crosslinked polyacrylates, acrylic acid-acrylonitrile copolymers, and crosslinked polyacrylates.

Salts of polyvalent metals that have a valence of at least 2 and can have a valence of less than 2 for use in the present invention include ferric sulfate (Fe ₂ (SO ₄ ) ₃ ), ferric chloride (FeCl ₃ ), cupric sulfate (CuSO ₄ ), cupric chloride (CuCl ₂ ), chromic sulfate (Cr ₂ (SO ₄ ) ₃ ),
Chromium chloride (CrCl ₃ ) or the like is used. These polyvalent metal salts are reduced by reacting with sodium bisulfite in the presence of water, reducing the valence of the polyvalent metal and forming ferrous sulfate (FeSO ₄ ) and ferrous chloride (FeCl ₂ ), respectively. , cuprous sulfate (Cu ₂ SO ₄ ), cuprous chloride (CuCl), chromous sulfate (CrSO ₄ ), chromium chloride (CrCl ₂ ), etc. This reduction reaction of the polyvalent metal salt becomes an endothermic reaction that removes external heat and exerts a cooling effect.

Each substance used in the present invention is blended in a desired ratio depending on the state of the outside air. In other words, since the outside air is relatively hot in the summer, a salt of a polyvalent metal that has a valence of at least 2 and can have a valence of less than 2, which works together to exert a cooling effect, and It is preferable to blend a large amount of sodium bisulfite, which is a metal salt whose valence is reduced by reducing the salt of a valent metal in the presence of water, and a superabsorbent resin. Moreover, at that time, the superabsorbent resin may be made to contain water in advance. Since the outside air is relatively low in winter, it is better to mix in a smaller amount of substances other than the ethylene gas adsorbent, such as super absorbent resin.

The freshness preserving agent according to the present invention may be used by uniformly mixing the above-mentioned four substances, and may be used, for example, by spraying it inside the packaging, or by applying it to the inner surface of the packaging material with an adhesive.

(d) Effect The ethylene adsorbent used in the present invention adsorbs ethylene gas, which is an aging hormone produced by fresh agricultural products. Super absorbent resins contain water that evaporates from fresh produce or water that is added manually. A salt of a polyvalent metal having a valence of at least 2 and which can have a valence of less than 2, and sodium bisulfite which is a metal salt with reduced valence by reducing the salt of the polyvalent metal in the presence of water. When the water contained in the superabsorbent resin evaporates, it comes into contact with the water and a reduction reaction occurs, exerting a cooling effect.

Therefore, when the temperature of the outside air rises, the water contained in the superabsorbent resin evaporates, and the salt of the polyvalent metal, which has a valence of at least 2 and can have a valence of less than 2, and the polyvalent metal evaporate. It exerts a cooling effect when it comes into contact with sodium bisulfite, which is a metal salt whose valence is reduced by reducing it in the presence of water. This cooling does not increase the ambient temperature of the ethylene adsorbent, making it difficult for the ethylene gas once adsorbed to be released.

(E) Examples Example 1 12.7 g of cross-linked polystyrene (8:2 copolymer of styrene and divinylbenzene, macroreticular type), 9.9 g of chloride (2), and 13.3 g of aluminum chloride were mixed in carbon disulfide. The mixture was heated and stirred at 50°C, and the solvent carbon disulfide was removed under reduced pressure to obtain a polymer complex in which copper chloride and aluminum chloride were coordinated to cross-linked polystyrene.

A freshness-preserving agent was obtained by uniformly mixing 10 g of this polymer complex, 7 g of super absorbent resin, 8 g of ferric sulfate, and 5 g of sodium sulfite.

Example 2 Crosslinked polystyrene (8:2 copolymer of styrene and vinylbenzene macroreticular type)
12.7g and silver chloride () 14.6g and aluminum chloride
After putting 13.3g of chloride into carbon disulfide and heating under reflux for 6 hours, the solvent carbon disulfide was removed under reduced pressure to form a polymer complex in which silver chloride and aluminum chloride were coordinated to cross-linked polystyrene. Obtained.

A freshness-preserving agent was obtained by uniformly mixing 10 g of this polymer complex, 10 g of super absorbent resin, 10.8 g of ferric chloride, and 8 g of sodium sulfite.

Comparative Example 1 The polymer complex obtained in Example 1 alone was used as a freshness-preserving agent.

Comparative Example 2 The polymer complex obtained in Example 2 alone was used as a freshness-preserving agent.

In order to evaluate the performance of the freshness preserving agents obtained in Examples 1 and 2 and Comparative Examples 1 and 2, the following tests were conducted. That is, cut persimmons were sealed in bags made of polyethylene film, and bags containing no freshness-preserving agent and those containing the freshness-preserving agents of Examples 1 and 2 and Comparative Examples 1 and 2 were prepared. Then, the time required for the cut part of the persimmon to turn black was measured. The temperature of the outside air at this time was maintained at 35°C. As a result, the product without the freshness preserving agent turned black after 45 minutes, the product in Example 1 turned black after 130 minutes, and the product in Example 2 turned black after 130 minutes.
After 65 minutes had elapsed for Comparative Example 1, and after 60 minutes for Comparative Example 2, it turned black. Therefore, it can be seen that the freshness preserving agents obtained in Examples 1 and 2 are effective in preserving freshness.

(F) Effects of the Invention As explained above, the ethylene adsorbent used in the present invention adsorbs ethylene gas, which is a aging hormone produced by fresh agricultural products. The water-containing superabsorbent resin evaporates water as the temperature of the outside air rises, and the water evaporates into a polyvalent metal salt whose valence is at least 2 and which can have a valence of less than 2. The polyvalent metal salt is reduced in the presence of water to produce a metal salt with reduced valence, which is sodium hydrogen sulfite, causing a reduction reaction and exerting a cooling effect. Due to this cooling effect, the ambient temperature of the ethylene adsorbent does not rise, making it difficult for the ethylene gas once adsorbed to be released.

Therefore, the packaging is less likely to be filled with ethylene gas, and the effect of ethylene gas, which is an aging hormone, on agricultural products is reduced. Therefore, the freshness of the fresh produce within the package can be maintained for a long period of time.

Claims (1)

[Claims] 1 Polymer complex in which copper chloride (2) and aluminum chloride are coordinated to cross-linked polystyrene, polymer complex in which silver chloride (2) and aluminum chloride are coordinated to cross-linked polystyrene, copper chloride (2) coordinated to ion exchange resin an inorganic complex in which copper ( ) ions are coordinated to zeolite, an inorganic complex in which copper ( ) ions are coordinated to γ-alumina, and an inorganic complex in which copper nitrate is coordinated to activated carbon. an ethylene adsorbent selected from the group consisting of; a superabsorbent resin; a salt of a polyvalent metal having a valence of at least 2 but capable of having a valence of less than 2; and a salt of the polyvalent metal selected from the group consisting of A freshness-preserving agent characterized by containing as an essential component sodium bisulfite, which is a metal salt whose valence has been reduced by reducing it in the presence of.