JPS6120339B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to oxygen scavengers. Furthermore, the present invention relates to an oxygen absorber suitable for preserving various foods.

It has been reported that when foods containing oil, such as oil sweets, potato chips, and peanuts, are exposed to air, they produce oxides and peroxides, which not only impair flavor but also sometimes become poisonous. Furthermore, if fruits are left in the air after harvesting, they will overheat in a short period of time due to respiration, significantly reducing their commercial value. Mold and rot occur in vegetables and fish during storage. Furthermore, fur and clothing are often eaten by insects or damaged by mold during storage.

To protect stored items from these damages, freezing methods, refrigeration methods, vacuum packing methods, inert gas substitution methods,
Methods using insect repellents, fungicides, etc. are used, and food additives such as antioxidants are also used. However, measures such as freezing methods require large-scale equipment and complicated operations, and have the drawback of being expensive. In addition, insect repellents and fungicides are often harmful to the human body, and the effects of antioxidants used as food additives on the human body are also being debated.
The trend is for its use to be regulated.

In order to prevent oils from oxidizing, to prevent the survival and proliferation of mold, bacteria, and even higher organisms such as insects, and to suppress overheating of fruits, it is necessary to remove oxygen from the atmosphere inside containers and bags that store food. In this method, carbon dioxide gas is introduced in an amount not less than the amount of oxygen gas removed, and the inside of the container or bag is maintained in a somewhat pressurized state, and the carbon dioxide gas suppresses the growth of fungi and prevents the fruit from overheating. is the appropriate method.

After examining various oxygen scavengers suitable for this purpose, we discovered that ferrous carbonate has both an oxygen removing effect and a carbon dioxide gas generating function.

Ferrous carbonate is a hexagonal crystal that occurs naturally as siderite, and is usually produced by adding alkali carbonate to a solution of ferrous salt in the absence of air to form a precipitate.
Obtained by heating to 150℃. This material gradually decomposes in humid air to form ferric hydroxide.

However, these commonly obtained ferrous carbonates are too slow to decompose for use as oxygen scavengers, and therefore their oxygen scavenging rate is slow, making them unsuitable for general use as oxygen scavengers.

In order to develop a highly practical oxygen scavenger, we the inventors further investigated various aspects and discovered that there is a correlation between the surface area of ferrous carbonate and its oxygen scavenging ability.
The inventors have further discovered that ferrous carbonate needs to have a specific specific surface area, and have arrived at the present invention.

That is, the present invention has a specific surface area of at least 20
m ² /g of ferrous carbonate as a main component.

The present invention will be explained in more detail below.

Ferrous carbonate, which is the main component of the oxygen scavenger according to the present invention, is produced by dissolving a ferrous salt such as ferrous sulfate in water, removing air, and adding an alkali carbonate such as soda carbonate. Ferrous iron is produced, a coagulant is added as appropriate to coagulate the precipitate, and the product is separated and dried in an air-free state.

To use ferrous carbonate as an oxygen scavenger, a certain amount of water is required, and the amount is 5wt% or more relative to ferrous carbonate, but if it exceeds 15wt%, the deoxidation rate will not increase. It becomes less. However, on the other hand, the rate of carbon dioxide gas generation increases.

Ferrous carbonate having a specific surface area of 20 m ² /g or more is suitable, and one with a specific surface area of 50 m ² /g or more is more practical. Further, when examining the crystallites, crystallites with a diameter of 400 Å or less show favorable characteristics.

When ferrous carbonate is used as an oxygen scavenger, other components may be used in combination as necessary. For example, a desiccant such as silica gel or another oxygen scavenger such as iron powder may be used in combination.

To form ferrous carbonate as an oxygen scavenger,
First, the required amount of ferrous carbonate is weighed, filled into a small gas-permeable bag, and the opening is sealed. Store this in a high gas barrier container to remove moisture. To use it, take it out, adjust the moisture content, and insert it into a high gas barrier container together with an object that does not want the presence of oxygen, such as food. Moisture is insufficient in the amount contained in normal air, so if the object to be treated does not contain sufficient moisture, it is necessary to replenish it into ferrous carbonate. By doing so, the ferrous carbonate gradually reacts with oxygen and moisture in the air surrounding the object, releases carbon dioxide gas, and protects the object from oxygen.

When using the product, the amount of ferrous carbonate and amount of water to be added should be determined after careful consideration of the type and amount of the object and the conditions under which it will be stored, especially the temperature, amount of moisture, and amount of carbon dioxide gas generated. be.

As is clear from the above explanation, the oxygen scavenger of the present invention not only has a high oxygen removal ability, but also contains metal halides, such as when reduced iron is used, and compounds with crystallized water for supplying water. It has a wide range of compatibility and does not require the coexistence of auxiliary agents, and since carbon dioxide gas is generated when oxygen is absorbed, food storage containers do not have reduced pressure, and the carbon dioxide generation prevents the growth of aerobic bacteria and fruits. It also has desirable properties as an oxygen scavenger, such as its ability to suppress overheating.

Furthermore, 15wt% (W,
Another great advantage is that moisture of the level B (wet base) cannot be easily dried by a desiccant, and therefore it can be used in combination with a desiccant such as _CaC2 silica gel.

Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples unless the gist thereof is exceeded.

Example 1 Dissolve 1 kg of ferrous sulfate heptahydrate in 6 parts of distilled water,
0.4 kg of sodium carbonate was added in a nitrogen atmosphere while stirring to obtain ferrous carbonate. PH after adding soda carbonate
was 7.5. After that, the flocculant Diamond Clear MA
-3000H was added at 5 ppm to the reaction solution to coagulate the ferrous carbonate precipitate. The filtration was carried out in a dry box purged with nitrogen, and the mixture was decanted three times with distilled water to remove adhering sodium sulfate. The ferrous carbonate residue was placed in a vacuum dryer purged with nitrogen and dried at 120° C. for about 3 hours under reduced pressure.

Dried products are divided into portions and weighed in a dry box.
It was used for moisture measurement, divalent iron ion analysis, and deoxidation experiments. The moisture content was determined to be 13.8% when the vaporizer was operated at 250°C and the vaporized gas was introduced into the Karl Fuschier reagent solution. Iron divalent ions accounted for 41% of the total sample. When the sample was added to a sulfuric acid solution and the amount of ferrous carbonate was determined from the carbon dioxide gas generated, the purity of ferrous carbonate in the sample was approximately 85%.
Crystal diffraction using X-rays revealed that most of the particles were small particles in the crystalline region. The specific surface area determined by the BET method was 70 m ² /g.

Weigh out 5.0g of the sample in a dry box and place it in a small polyvinyl chloride bag with gas barrier properties.
Hot sealed. First, put 5g of ferrous carbonate into a large bag with a high gas barrier rubber stopper sample opening.
After putting in the sachet with the inside and hot-sealing it, inject 500cc of air with a gas sampler. After being kept in a room at 20°C for a while, the sachet was broken and the ferrous carbonate was brought into contact with air. decrease in oxygen over time,
Figure 1 shows the increase in carbon dioxide gas.

In the figure, the ≦ line indicates a change in the residual amount of oxygen, and the ≦ line indicates a change in the amount of carbon dioxide gas generated.

Example 2 Using crushed ferrous carbonate as a seed crystal, 1% of the ferrous carbonate to be obtained was added, and the material was aged at 70°C for 1.5 hours using the same amounts of raw materials as described above. A precipitate of ferrous carbonate was obtained. After overdrying using the same procedure as in Example 1, the moisture content was 13.6%, and the ferrous ion content was 86% based on the total iron content.

The specific surface area determined by the BET method was 21 m ² /g.
Measurement of deoxidation and carbon dioxide generation rate was carried out in Example 1.
I went the same way. The results are shown in Figure 2.

Comparative Example 1 Siderite from West Germany was crushed to a size of about 0.1 to 1μ. The specific surface area of the crushed siderite was 7.3 m ² /g. Adding a hydrated shirasu balloon to this, the moisture content relative to siderite was 19% on a wet basis, and the deoxidation rate was measured in the same manner as in Example 1.
This is shown in FIG. 3 by line a. Figure 3 also shows sample b, which was obtained by further drying the sample of Example 1 and had a moisture content of 6.7%, and the b-line and c-line results when a hydrous Shirasu balloon was added to this sample to make the total moisture content 14% on a wet basis. Also listed in. As can be seen from the figure, there is no difference in the deoxidation rate when a hydrous Shirasu balloon is added or when pre-hydrated ferrous carbonate is used. From the above, it is understood that ferrous carbonate, which has a specific surface area of 20 m ² /g or more and contains moisture necessary for oxygen absorption, exhibits a practical oxygen removal rate. On the other hand, it is understood that ferrous carbonate having a small specific surface area or a water content less than the required water content has a low oxygen absorption rate and a slow carbon dioxide generation rate, and has low practical value as an oxygen scavenger.

In addition, the crystallite size obtained using the Sierer formula from the amplitude of the diffraction line at 2θ° (Fe) = 40.5° in the X-ray diffraction diagram is shown for the samples of Examples 1 and 2 and Comparative Example 1. It is as follows.

Sample name Crystallite size Example 1 150Å 2 800Å Comparative example 1 (siderite) 1700Å

[Brief explanation of the drawing]

1 and 2 are graphs showing changes over time in the amount of oxygen and carbon dioxide, respectively, and FIG. 3 is a graph showing changes over time in the amount of oxygen.

Claims (1)

[Claims] 1 Oxygen scavenger based on ferrous carbonate with a specific surface area of at least 20 m ² /g.