Adsorbent for pudding made from liquids other than beer

Abstract

To provide a purine body adsorbent for liquid other than beer that is made of an acid-treated product of dioctahedral type smectite-based clay, and has excellent adsorption properties for purine bodies and a small amount of iron ion elution.SOLUTION: The present invention relates to a purine body adsorbent for liquid other than beer that is made of an acid-treated product of dioctahedral type smectite-based clay, in which the ratio of BET specific surface area (A) measured by water vapor adsorption method to BET specific surface area (B) measured by nitrogen adsorption method, (A) / (B), is in the range of 0.90 to 5.00, and the amount of exchangeable iron ions is 0.25 mmol / 100 g or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an adsorbent for purines in liquids other than beer that can adsorb purines such as xanthine compounds represented by caffeine and compounds containing adenine or guanine compounds represented by adenine and guanine as constituent components.

Background Art

[0002] Currently, from the perspective of health consciousness and the like, caffeine-free beverages are commercially available. This caffeine-free beverage is a beverage obtained by removing caffeine from tea, coffee, and the like.

[0003] By the way, caffeine, adenine, guanine, etc. are all compounds having a purine skeleton (collectively referred to as purines). As adsorbents for removing these from beverages, zeolites, dioctahedral smectite-based clays (acidic clay), etc. are known (Patent Document 1).

[0004] However, zeolites have poor selectivity for purines and adsorb even the active ingredients contained in beverages, so they are not used industrially.

[0005] In addition, although clays such as acidic clay have the advantages of high selective adsorption for purines and low cost, they have the problem of low filterability. That is, a part of this type of clay is colloidal-dispersed in water, causing clogging of the filter during filtration. To avoid this, if centrifugation is performed instead of filtration, loss of active ingredients also occurs, and the processing cost becomes high.

[0006] Furthermore, Patent Document 1 discloses that activated clay obtained by acid-treating acidic clay has excellent adsorbability for caffeine (xanthine compound). For example, in its examples, activated clay (Galeon Earth NF-2, Galeonite No. 251, manufactured by Mizusawa Chemical Industry Co., Ltd.) manufactured and sold by the present applicant shows high adsorbability for caffeine.

[0007] However, the adsorbability for caffeine in Patent Document 1 was evaluated by dissolving 40 mg of green tea extract powder (caffeine-containing substance) in 5 mL of water and adding 1 g (20 parts by mass per 100 parts by mass of water) of an adsorbent such as activated clay to the resulting aqueous solution. That is, this experiment was conducted by adding a large amount of adsorbent to a paste containing a large amount of caffeine-containing powder, and it is difficult to say that the adsorbability for caffeine was properly evaluated. In fact, it is not cost-effective to add such a large amount of adsorbent to a beverage to remove caffeine. Also, it is a problem from the viewpoint of separating the adsorbent after treatment. Moreover, when the applicant conducted an adsorption test by adding 0.1 g of activated clay (Galerion Earth NF-2, Galenite No. 251) to 30 g of an aqueous caffeine solution with a concentration of 0.2 g / L according to the actual adsorption treatment, it was found that the caffeine adsorbability of these activated clays (Galerion Earth NF-2, Galenite No. 251) was significantly inferior to that of acid clay.

[0008] Therefore, the present inventors conducted many experiments and studies on the adsorption performance of an acid-treated product obtained by acid-treating dioctahedral smectite-based clay. As a result, without performing acid treatment up to the region called activated clay used in various applications, but acid-treating at a weaker level (hereinafter referred to as weakly acid-treated clay), it shows superior adsorption performance compared to non-acid-treated clay (acid clay), and moreover, it has excellent filterability and can be easily separated from the solution after the adsorption treatment. The inventors found such a finding (Patent Document 2).

[0009] However, the solution after the adsorption treatment when using the above-mentioned weakly acid-treated clay, although the purine substance was removed, sometimes felt a metallic taste that was not felt before the adsorption treatment. When investigating the cause, it was considered that the iron content contained in the acid clay before the acid treatment eluted during the acid treatment and was semi-fixed as an exchangeable cation in the clay, and eluted as iron ions into the solution during the adsorption treatment of the purine substance.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0011] An object of the present invention is to provide an adsorbent for purine bodies in liquids other than beers, which is made of an acid-treated product of dioctahedral smectite-based clay, has excellent adsorbability to purine bodies, and has a low iron ion elution amount. Note that the use of the adsorbent is limited to purine bodies in liquids other than beers because an invention of an adsorbent for purine bodies in beers was filed on the same day as the present invention, in order to distinguish it from the said invention. Here, the beers are not limited to beers under the Liquor Tax Law, but include all liquids generally considered to be similar to beers, such as so-called low-malt beers, third beers, non-alcoholic beers, and beer-taste beverages.

Means for Solving the Problems

[0012] The present inventors conducted and examined many experiments on the elution amount of iron ions in weakly acid-treated clay. As a result, when the elution amount of iron ions in the weakly acid-treated clay itself is below a specific value, it was found that these clays have excellent adsorbability to purine bodies and can reduce the addition of metallic taste, and the present invention was completed. Here, although the iron ions may be divalent or trivalent, in the present invention, they are simply referred to as iron ions without particularly distinguishing between the two.

[0013] According to the present invention, there is provided an adsorbent for purines in liquids other than beers, which is composed of an acid-treated product of dioctahedral smectite-based clay and has a ratio (A) / (B) of the BET specific surface area (A) measured by the water vapor adsorption method to the BET specific surface area (B) measured by the nitrogen adsorption method in the range of 0.90 to 5.00 and an exchangeable iron ion amount of 0.25 mmol / 100 g or less. Here, the exchangeable iron ion amount is the number of moles of exchangeable iron ions contained in 100 g of the dioctahedral smectite-based clay.

[0014] In the adsorbent of the present invention, (1) the acid-treated product of the dioctahedral smectite-based clay has been further subjected to a treatment for reducing the iron ion content; (2) the amount of interlayer water specific to the dioctahedral smectite-based clay is 30 mg or less per gram of the adsorbent excluding adsorbed water and interlayer water; (3) the amount of solid acid with Ho ≦ -3.0 is in the range of 0.10 to 0.70 mmol / g-dry clay; (4) the value of the BET specific surface area measured by the nitrogen adsorption method is in the range of 65 to 400 m 2 / g; (5) (A) / (B) is in the range of 0.90 to 2.80; (6) the purine is a xanthine compound; (7) the xanthine compound is caffeine; (8) the purine is an adenine or guanine compound are preferable.

[0015] Further, according to the present invention, there is provided a method for removing purines from liquids other than beers, which comprises adding the adsorbent to a liquid other than beers containing purines to adsorb and remove the purines.

Effects of the Invention

[0016] As shown in the examples described later, the adsorbent of the present invention can remove a large amount of purine bodies from a purine body-containing solution equivalent to or more than acidic clay by using a small amount, and in addition, can reduce the addition of metallic taste.

[0017] In addition, since the adsorbent of the present invention is composed of clay that has been subjected to weak acid treatment, it has higher filterability than acidic clay and can be easily removed from the solution after the adsorption treatment.

[0018] Therefore, the adsorbent of the present invention has high adsorbability for purine bodies and can be suitably applied to the production of caffeine-free beverages by removing caffeine from beverages such as tea and coffee. And since the adsorbent of the present invention is composed of an acid-treated product of dioctahedral smectite-based clay, compared with smectite-based clay that has not been subjected to a conventionally known acid treatment, the contained leachable Na ions and Ca ions are kept low, suppressing the generation of precipitates such as Ca oxalate, and furthermore, since the elution amount of iron ions can be reduced, the influence on the color, flavor, and aroma of the beverage can be suppressed.

Mode for Carrying Out the Invention

[0019] <Weak acid-treated low iron ion clay> The adsorbent of the present invention is an adsorbent for purine bodies in liquids other than beers, which is composed of an acid-treated product of dioctahedral smectite-based clay and has an exchangeable iron ion amount of 0.25 mmol / 100 g or less, or when the exchangeable iron ion amount of the acid-treated product exceeds 0.25 mmol / 100 g, the acid-treated product is further subjected to an iron ion content reduction treatment to make the iron ion elution amount 0.25 mmol / 100 g or less, and is obtained by performing a weaker acid treatment than that generally called activated clay, or by further performing an iron ion content reduction treatment. Therefore, hereinafter, the acid treatment used as an adsorbent for purine bodies in liquids other than beers, or the product after further iron ion content reduction treatment may be referred to as "weak acid-treated low iron ion clay".

[0020] Regarding the treatment of weak acid treatment and reduction of iron ion content, basically, by performing weak acid treatment, the purpose is to obtain clay with excellent adsorption performance for purine substances and excellent filterability. When only the weak acid treatment is carried out, when the amount of exchangeable iron ions exceeds 0.25 mmol / 100 g, the purpose is to reduce the iron ion elution amount by further performing a treatment for reducing the iron ion content of the acid-treated product.

[0021] Regarding the weak acid treatment, in Japanese Patent Laid-Open No. 2009-072759 by the applicant of the present application, it is disclosed that an acid-treated product called semi-active clay obtained by acid-treating dioctahedral clay is used as a catalyst for depolymerizing polylactic acid. However, the weak acid treatment used in the present invention is a weaker acid treatment than this acid treatment.

[0022] Generally, the iron ion elution amount of the clay after acid treatment increases. This is presumably because part of the iron in the iron-containing compound contained as iron in the clay skeleton before acid treatment or as an impurity is dissolved by the acid treatment, and part of it is semi-fixed as an exchangeable cation between the clay layers. Furthermore, this semi-fixed iron ion cannot be completely removed by washing after acid treatment, and it is considered that it elutes into the beverage due to the action of organic acids contained in the beverage during the purine substance adsorption treatment of the beverage, and this eluted iron ion is considered to be the cause of the metallic taste in the beverage. The iron ion elution amount depends on the quality of the clay before acid treatment (iron content in the clay, types and amounts of impurities, etc.) and the conditions of acid treatment.

[0023] When the amount of exchangeable iron ions in the clay itself after weak acid treatment is 0.25 mmol / 100 g or less, it is not necessary to perform the treatment for reducing the iron ion content by the cation treatment described below. When the amount of exchangeable iron ions exceeds 0.25 mmol / 100 g, since the solution after the adsorption treatment shows a metallic taste, the treatment for reducing the iron ion content by the cation treatment described below is performed. Here, it is preferable that the amount of exchangeable iron ions is 0.15 mmol / 100 g or less.

[0024] The iron ion content reduction treatment in the present invention is not particularly limited as long as the amount of iron ion eluted from the clay after weak acid treatment can be reduced to a desired concentration. For example, it can be carried out by contacting the above-mentioned clay with an aqueous solution containing cations other than iron ions and then separating and washing. By the above iron ion content reduction treatment, all or part of the iron ions in the clay are replaced with cations other than iron, and as a result, an iron ion content reduction treated clay with a reduced amount of iron ion elution in the clay can be obtained.

[0025] Cations other than iron ions are not particularly limited as long as they are acceptable as food and drink. For example, sodium ions, potassium ions, magnesium ions, calcium ions, aluminum ions, etc. can be mentioned. Among these, sodium ions and potassium ions are preferred. In the cation treatment, one or more cations other than iron ions can be used.

[0026] In the cation treatment, the above-mentioned cations can be added to the above-mentioned clay in the form of salts so that the iron ions in the above-mentioned clay are replaced with cations. The salt formed by the cation may be either an inorganic salt or an organic salt. For example, sulfates, chlorides, gluconates, ascorbates, citrates, lactates, etc. can be mentioned, and sulfates are preferred. In the cation treatment, one or more inorganic salts and organic salts can be used.

[0027] In the iron ion content reduction treatment, it is desirable that the cation contacted with the above-mentioned clay is in the form of an aqueous solution. The concentration of the cation is not particularly limited as long as the amount of exchangeable iron ions in the above-mentioned clay can be reduced to 0.25 mmol / 100 g or less. Preferably, it is 0.01 to 1000 milliequivalents (hereinafter referred to as "mEq / L"), more preferably 0.1 to 1000 mEq / L, and even more preferably 1 to 1000 mEq / L. When using two or more kinds of cations or salts, the concentration of the cation is preferably such that the sum of the concentrations of each cation is the above concentration.

[0028] In the iron ion content reduction treatment, it is preferable to add an acidic substance so that the pH becomes 5.0 or less. From the viewpoint of the efficiency of reducing the iron ion content, the acidic substance is preferably added so that the pH is 3.0 or less, particularly preferably 2.0 or less. When the pH is greater than 5.0, the efficiency of reducing the iron ion content deteriorates, and sufficient reduction of the iron ion content may not be achieved. The acidic substance to be added is not particularly limited, but it is generally preferable to use an aqueous sulfuric acid solution used for the acid treatment of clay.

[0029] In the iron ion content reduction treatment, the contact time and contact temperature between the above-mentioned clay and the cation are not particularly limited as long as the iron ion content in the clay can be reduced to a desired concentration. The contact time is preferably 1 to 48 hours, more preferably 1 to 24 hours, and the contact temperature is preferably 4 to 50 ° C, more preferably 10 to 30 ° C. The weakly acid-treated low-iron ion clay of the present invention has the characteristics of the weakly acid-treated clay described later (for example, the ratio (A) / (B) of the BET specific surface area (A) measured by the water vapor adsorption method to the BET specific surface area (B) measured by the nitrogen adsorption method is 0.90 to 5.00), and the iron ion content reduction treatment is appropriately controlled in terms of contact time and contact temperature so as not to be a stronger acid treatment than such a weakly acid treatment.

[0030] In the iron ion content reduction treatment, it is desirable to subject the mixture of the above-mentioned clay and the cation to solid-liquid separation treatment to remove the iron ions that have been eluted by being released from the clay and the cations that have not been replaced by the iron ions in the clay, and then wash. Examples of the solid-liquid separation treatment include centrifugation and filtration. The washing is not particularly limited as long as it can remove the eluted iron ions and the cations that have not been replaced by the iron ions in the clay, but it is preferable to wash 2 to 3 times with pure water.

[0031] Such weakly acid-treated low-iron ion clay has a very low acid treatment level for dioctahedral smectite-based clay, and thus the ratio (A) / (B) of the BET specific surface area (A) measured by the water vapor adsorption method to the BET specific surface area (B) measured by the nitrogen adsorption method is 0.90 or more. From the viewpoint of adsorption performance, it is preferably 1.10 or more, particularly preferably 1.20 or more. Also, it is 5.00 or less, and from the viewpoint of filterability, it is preferably 4.20 or less, particularly preferably 3.30 or less, and most preferably 2.80 or less.

[0032] It is presumed that such weakly acid-treated low-iron ion clay can exhibit excellent adsorption performance for purine substances by having a BET specific surface area ratio (A / B) within the above range. That is, as a method for measuring the BET specific surface area, a method using nitrogen (nitrogen method) is common, but there is also a method using water vapor for measurement (water vapor method). According to the Clay Handbook (Third Edition), in the nitrogen method, the total external surface area including the end faces per unit mass is measured. For those having a three-layer structure such as dioctahedral smectite-based clay, since nitrogen molecules do not penetrate into the interlayer at liquid nitrogen temperature, only the external surface area is measured. On the other hand, in the water vapor method using a polar adsorbate such as water vapor, since such an adsorbate sufficiently penetrates into the interlayer of the clay, the internal surface is measured. Therefore, the fact that A / B is within the above range means that micropores are increased by a very weak acid treatment, and the interlayer of the basic three-layer of smectite-based clay is expanded. The increase in micropores improves the selective adsorption for purine substances (especially xanthine compounds such as caffeine), and the expansion of the interlayer of the basic three-layer brings about appropriate surface hydrophilicity and enhances the adsorption of purine substances in aqueous and alcohol solutions. The adsorbent (weakly acid-treated low-iron ion clay) of the present invention having the above A / B value is believed to exhibit extremely high selective adsorption for purine substances because an appropriate expansion of the interlayer of the basic three-layer and the formation of micropores within the interlayer occur in a well-balanced manner in the acid treatment process. For example, in the case of conventionally known activated clay and semi-activated clay obtained by treatment with a strong acid, the expansion between the basic triple layers becomes large, and moreover, the micropores formed between the layers are crushed. Therefore, the value of A / B becomes small, and thus, the purine body adsorption characteristics become extremely low.

[0033] Furthermore, it is presumed that such weakly acid-treated low-iron ion clay has excellent filterability because it has been subjected to acid treatment. Smectite-based clay (acidic clay) that has not been subjected to acid treatment has a large interlayer containing cations such as Na between the basic layers, and thus shows high swelling property with respect to water, and it is considered that the filterability is poor due to microdispersion by swelling. In the case of such weakly acid-treated low-iron ion clay, a part of the basic components in the smectite-based clay reacts with the acid and becomes a binder insoluble in water or alcohol, etc., to bond between particles, so that the microdispersion in the solution is suppressed and excellent filterability is shown. Therefore, the weaker the degree of acid treatment, the larger A / B becomes, and there is a risk that the filterability will be impaired.

[0034] The water held in clay minerals is classified into adsorbed water adsorbed on the particle surface, interlayer water present in the interlayer region, and structural water indicating hydroxyl groups inside the crystal structure. As a result of examining the interlayer water of the weakly acid-treated low-iron ion clay, the present inventors have found that when the amount of interlayer water is in a specific range, the adsorptivity to purine bodies is improved. Here, it is known that the adsorbed water is desorbed from the clay mineral at 60 to 80°C, and the interlayer water is desorbed at 90 to 150°C. Therefore, the present inventors measured the weight loss on drying at 80°C (indicating the amount of adsorbed water) and the weight loss on drying at 150°C (indicating the amount of adsorbed water + interlayer water) as in the examples described later, and used the difference between them as the amount of interlayer water. The amount of interlayer water is shown as the amount (mg / g) per 1 g of the adsorbent excluding the adsorbed water and the interlayer water.

[0035] The weakly acid-treated low-iron ion clay used as the adsorbent in the present invention has an interlayer water amount of 30 mg / g or less, preferably 20 mg / g or less, and more preferably 15 mg / g or less. Also, the amount of interlayer water is preferably 3 mg / g or more, particularly 5 mg / g or more. This is because, in order to make the amount of interlayer water fall below the above value, it is inevitably necessary to perform treatment at a high temperature. If this is done, the micropores formed between the layers will collapse, and the adsorptivity for purine bodies will be impaired.

[0036] The mechanism by which the adsorptivity improves when the amount of interlayer water is within a specific range is not yet clear. However, it is considered that the water molecules covering the purine body adsorption sites from the micropores between the layers and within the layers are removed, making it easier for the purine bodies to be adsorbed.

[0037] Also, even if the adsorbent of the present invention with a reduced amount of adsorbed water absorbs moisture again, the absorbed water is retained as adsorbed water, so interlayer water is not newly retained and the adsorption performance is not impaired.

[0038] The weakly acid-treated low-iron ion bentonite used as the adsorbent in the present invention is obtained by a weaker acid treatment compared to what is generally referred to as activated bentonite. Therefore, the Na and Ca components covering Al and Mg that act as solid acid sites are removed, and furthermore, the decrease in the amount of solid acid caused by the elution of Al and Mg components as the acid treatment progresses is suppressed. As a result, it shows an amount of solid acid equal to or greater than that of what is generally referred to as activated bentonite obtained by a conventional acid treatment, or acidic bentonite that has not undergone an acid treatment. The weakly acid-treated low-iron ion bentonite preferably has an amount of solid acid of Ho ≦ -3.0 in the range of 0.10 to 0.70 mmol / g-dry clay, which means it contains a relatively large amount of relatively strong solid acids. That is, the chemical adsorption performance by the solid acid for purine bodies is enhanced, and as shown in the examples described later, by using a small amount, more purine bodies can be removed from a purine body-containing solution than conventional known activated bentonite or acidic bentonite, or at least as much.

[0039] In addition, the weakly acid-treated low-iron ion bentonite used as an adsorbent in the present invention has been acid-treated, albeit weakly. Therefore, its BET specific surface area by the nitrogen method is improved compared to smectite-based clay that has not been acid-treated, and is preferably 65 to 400 m 2 / g, particularly preferably in the range of 100 to 400 m 2 / g. However, such weakly acid-treated low-iron ion bentonite has a lower BET specific surface area ratio (A / B) compared to smectite-based clay that has not been acid-treated, but is considered to exhibit high adsorptivity.

[0040] Furthermore, the above-mentioned weakly acid-treated low-iron ion bentonite exhibits specific X-ray diffraction peaks derived from the crystal structure of dioctahedral smectite-based clay. For example, in X-ray diffraction measurement, it has a diffraction peak derived from the plane index (06) near 2θ = 62° (d = 1.49 to 1.50 Å).

[0041] <Production of Weakly Acid-Treated Low-Iron Ion Bentonite> The weakly acid-treated low-iron ion bentonite having the above characteristics is produced by crushing and kneading dioctahedral smectite-based clay and then performing acid treatment under predetermined conditions using an acid aqueous solution of a predetermined concentration. That is, this weakly acid-treated low-iron ion bentonite is obtained in the same manner as semi-activated bentonite, but is obtained by acid treatment under milder conditions compared to semi-activated bentonite.

[0042] The dioctahedral smectite-based clay used as the raw material clay is considered to be a product of the alteration of volcanic rocks, lava, etc. under the influence of seawater. The main component, dioctahedral smectite, consists of a SiO4 tetrahedral layer - AlO6 octahedral layer - SiO4 tetrahedral layer, and has a three-layer structure in which these tetrahedral and octahedral layers are partially isomorphously substituted with different metals as the basic structure (unit layer). Between the stacked layers of such a three-layer structure, there are cations such as Ca, K, Na, etc., hydrogen ions, and water molecules coordinated with them. Also, since a part of Al in the octahedral layer of the basic three-layer structure is substituted with Mg or Fe(II), and a part of Si in the tetrahedral layer is substituted with Al, the crystal lattice has a negative charge, and this negative charge is neutralized by the metal cations or hydrogen ions present between the basic layers. Such smectite-based clays include acid clay, bentonite, fuller's earth, etc., and they exhibit different characteristics depending on the type and amount of metal cations present between the basic layers, the amount of hydrogen ions, etc. For example, in bentonite, the amount of Na ions present between the basic layers is large. Therefore, the pH of the dispersion suspended in water is high, generally on the high-alkali side, and it also shows high swelling property in water, and further shows the property of gelling and solidifying. On the other hand, in acid clay, the amount of hydrogen ions present between the basic layers is large. Therefore, the pH of the dispersion suspended in water is low, generally on the acidic side, and although it shows swelling property in water, compared with bentonite, its swelling property is generally lower and it does not reach gelation.

[0043] In the present invention, the dioctahedral smectite-based clay used for the production of weakly acid-treated low-iron ion clay is not particularly limited, and any of the various types described above can be used. Also, although such raw material clay varies depending on the origin of the clay, the production area, and the burial location (face) even in the same production area, generally, it has the following composition in terms of oxide conversion. SiO2; 50 - 75 mass% Al2O3; 11 - 25 mass% Fe2O3; 2 - 20 mass% MgO; 2 - 7 mass% CaO; 0.1 - 3 mass% Na2O; 0.1 to 3 mass% K2O; 0.1 to 3 mass% Other oxides (such as TiO2); 2 mass% or less Ig-loss (1050 °C); 5 to 11 mass%

[0044] Also, depending on the origin and other factors, the raw material clay may contain a large amount of impurities such as quartz. Therefore, it is advisable to subject the above dioctahedral smectite-based clay to purification operations such as stone sand separation, flotation, magnetic separation, elutriation, and winnowing as necessary to remove impurities as much as possible, and then perform acid treatment. After such treatment, by performing acid treatment under mild conditions described below, a weakly acid-treated clay with A / B within the above range can be obtained.

[0045] The acid treatment is carried out by charging the raw material clay into an aqueous acid solution and mixing and stirring. The aqueous acid solution used for the acid treatment is not particularly limited, but an aqueous sulfuric acid solution is generally used from the viewpoints of cost, environmental impact, etc.

[0046] Also, as described above, such acid treatment is carried out under mild conditions compared to the acid treatment in the production of conventionally known activated clay and semi-activated clay. For example, when using an aqueous sulfuric acid solution, the amount of the aqueous sulfuric acid solution calculated assuming that the moisture contained in the raw material clay also constitutes the aqueous sulfuric acid solution is 250 to 800 mass parts per 100 mass parts of the raw material clay (as a dried product at 110 °C), and the concentration of the aqueous sulfuric acid solution at that time is about 1 to 15 mass%. The acid treatment may be carried out under conditions such that heating can be performed to about 25 to 95 °C if necessary. In this way, depending on the composition of the raw material, the acid concentration of the aqueous acid solution used, the treatment temperature, etc., the acid treatment may be carried out for a time (about 0.5 to 12 hours, preferably about 0.5 to 8 hours, particularly preferably about 0.5 to 4 hours) such that the specific surface area ratio (A / B) falls within a predetermined range.

[0047] When the amount of exchangeable iron ions in the clay itself after weak acid treatment is 0.25 mmol / 100 g or less, it is not necessary to perform the iron ion content reduction treatment by cation treatment. When the amount of the exchangeable iron ions exceeds 0.25 mmol / 100 g, the iron ion content reduction treatment by cation treatment is performed.

[0048] The iron ion content reduction treatment is carried out by putting the clay after acid treatment into an aqueous sulfate solution containing cations such as sodium sulfate, and mixing and stirring, so that the iron ions are replaced by cations such as sodium. Further, it can also be carried out by putting the clay after acid treatment into an acidic aqueous solution such as sulfuric acid or citric acid, and mixing and stirring to elute the iron ions into the acidic aqueous solution.

[0049] By the above acid treatment and iron ion content reduction treatment, the ratio A / B of the BET specific surface area by the nitrogen method to the BET specific surface area by the water vapor method, the amount of solid acid, and the value of the BET specific surface area by the nitrogen method are within the above ranges, and the adsorbent (weak acid-treated low iron ion clay) of the present invention having excellent adsorption performance for purine bodies can be obtained.

[0050] In addition, the weak acid-treated low iron ion clay obtained by the above acid treatment generally has the following chemical composition in terms of oxide conversion. SiO2; 50 - 85 mass% Al2O3; 8 - 23 mass% Fe2O3; 1 - 10 mass% MgO; 1 - 10 mass% CaO; 0.1 - 2 mass% Na2O; 0.1 - 3 mass% K2O; 0.1 - 5 mass% Other oxides (such as TiO2); 2 mass% or less Ig-loss (1050 °C); 4 - 9 mass%

[0051] After acid treatment or iron ion content reduction treatment, it is filtered and washed with water, and then a drying treatment is performed to adjust the amount of interlayer water. The drying treatment only needs to make the amount of interlayer water within a predetermined range, and can be carried out by any method such as heat drying in an oven, air drying, or microwave irradiation. The drying temperature varies depending on the drying method. For example, when static drying is carried out in an oven, in order to desorb the interlayer water from the clay mineral, it is preferable to set the oven temperature at 120°C or higher, and more preferably 140°C or higher. Also, in order not to crush the micropores formed between the layers, it is preferable to set the oven temperature below 200°C, and more preferably below 170°C. The drying time is not particularly limited as long as the amount of interlayer water falls within a predetermined range. However, when static drying is carried out in an oven, it is generally sufficient to carry out the drying for 2 hours or more.

[0052] <Purine body> In the present invention, the weak acid-treated low-iron ion clay described above exhibits excellent selective adsorption properties for purine bodies, that is, compounds having a purine skeleton.

[0053] The purine skeleton is represented by the following formula:

Chemical formula

[0054] One of the purine bodies is xanthine represented by the following formula:

Chemical formula

[0055] Furthermore, examples of compounds derived from xanthine include caffeine represented by the following formula:

Chemical formula

[0056] In addition, as purine substances, there are adenine and guanine. Examples of compounds derived from adenine or guanine include purine nucleosides (adenosine, guanosine) composed of adenine or guanine and ribose, and purine nucleotides (adenylic acid, guanylic acid) further containing phosphoric acid as a constituent. Other organic compounds derived from adenine or guanine include, but are not limited to, deoxyguanosine, deoxyguanosine triphosphate, nicotinamide adenine dinucleotide (NAD), flavin adenine dinucleotide (FAD), inosine, inosinic acid, etc. In this specification, the above-mentioned adenine or guanine and compounds derived from adenine or guanine are collectively referred to as adenine or guanine compounds. The adsorbent of the present invention exhibits selective adsorption properties for adenine and guanine, and therefore also exhibits excellent selective adsorption properties for adenine or guanine compounds, and is suitable as an adsorbent for such compounds.

[0057] <Use> The weakly acid-treated low-iron ion bentonite used as an adsorbent in the present invention not only has excellent selective adsorption properties for purine substances, but also has reduced elution of iron ions that can affect the flavor of beverages. Therefore, it is preferably used to remove caffeine from beverages such as tea and coffee to make them caffeine-free. For example, it is added and used in an amount of 0.001 to 10 parts by mass to a solution in which the above-mentioned purine substances are dissolved. To remove caffeine and the like from these beverages, the weakly acidic treated low-iron ion clay described above may be adjusted to a powder form with an appropriate average particle size (for example, about 10 to 300 μm), and this may be mixed with the beverage. The adsorbent for purine substances of the present invention can be used not only for the above beverages but also in solid-liquid separation (filtration) during the production process of various foods including various seasonings and supplements, or various chemicals used in industry and agriculture. It can be applied to beverages without any limitation by a method of appropriately adjusting the particle size to a suitable size in the process of use or a method of processing into a column or filter and passing a liquid through it. In addition, the adsorbent of the present invention can also be applied to the field of medicine such as drug discovery and pharmaceutical manufacturing by taking advantage of the selective adsorption property and filtration property of adenine or guanine compounds. The adsorbent of the present invention is particularly preferably applied to the fields of beverages and foods.

[0058] The weakly acidic treated low-iron ion clay used as the adsorbent in the present invention has the characteristics that the BET specific surface area increases by acid treatment and contains a relatively large amount of relatively strong solid acid. Therefore, like the conventional activated clay, the adsorbent of the present invention can be used without any limitation for the decolorization of oils and fats and mineral oils, and as a catalyst or a catalyst carrier.

Examples

[0059] The excellent effects of the present invention will be described by the following examples.

[0060] (1) BET specific surface area (B) by nitrogen adsorption method Measurement was carried out by the nitrogen adsorption method using TriStar 3000 manufactured by Micromeritics and calculated by the BET method. The pretreatment was carried out at 150 °C for 2 hours.

[0061] (2) BET specific surface area (A) by water vapor adsorption method Measurement was carried out by the water vapor adsorption method using BELSORP MAX manufactured by Nippon Bell Co., Ltd. and calculated by the BET method. The pretreatment was carried out at 150 °C for 2 hours.

[0062] (3) Amount of interlayer water Weighed approximately 2 g of the adsorbent powder and allowed it to stand and dry in an oven at 80 °C for 2 hours. Then weighed it again to obtain the weight loss on drying at 80 °C based on the wet weight, W 80 (%). Weighed approximately 2 g of the adsorbent powder and allowed it to stand and dry in an oven at 150 °C for 2 hours. Then weighed it again to obtain the weight loss on drying at 150 °C based on the wet weight, W 150 (%). The following formula: W L =(W 150 -W 80 ) / (100-W 150 )×1000 was used to determine the amount of interlayer water per gram of the adsorbent, W L (mg / g), excluding adsorbed water and interlayer water.

[0063] (4) Amount of solid acid The amount of solid acid with Ho ≤ -3.0 was measured by the n-butylamine titration method. The measurement was performed on the sample that had been dried at 150 °C for 3 hours in advance {Reference: "Catalysis", Vol. 11, No. 6, P210 - 216 (1969)}.

[0064] (5) Caffeine adsorption test The caffeine adsorption capacity in this example was defined as the amount of caffeine (mg) that 1 g of the anhydrous adsorbent could adsorb from a 0.2 g / L caffeine aqueous solution, and was measured and calculated by the following method. First, anhydrous caffeine (special grade reagent, manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in ion-exchanged water to obtain a 0.2 g / L caffeine aqueous solution. Weighed 30 g of this 0.2 g / L caffeine aqueous solution into a centrifuge tube with a capacity of 50 mL, added 0.10 g of the adsorbent (0.3 mass% with respect to the liquid), and shaken it for 2.5 hours using a shaker (SA300 manufactured by Yamato Scientific Co., Ltd., shaking speed 5). Next, the supernatant of the liquid treated by a centrifuge (Kubota Corporation, model 5200) at a centrifugal acceleration of 3000 rpm for 15 minutes was diluted 10-fold with ion-exchanged water to obtain a liquid (sample liquid). The absorbance of the sample liquid at a wavelength of 273 nm was measured using a spectrophotometer (V-630 manufactured by JASCO Corporation). Then, the residual caffeine amount in the sample liquid was calculated using a calibration curve showing the relationship between the caffeine concentration and the absorbance of light at a wavelength of 273 nm prepared in advance, and the value obtained by subtracting this from the caffeine amount before the addition of the adsorbent was taken as the caffeine adsorption amount of the adsorbent.

[0065] (6) Exchangeable iron ion test In this example, the amount of exchangeable iron ions (exchangeable Fe amount) was measured and calculated by the following method. Weighed 35 mL of 1 N ammonium chloride aqueous solution into a 50 mL centrifuge tube, added 0.5 g of the adsorbent, and shaken it for 15 minutes using a shaker (SA300 manufactured by Yamato Scientific Co., Ltd., shaking speed 5). Next, it was treated by a centrifuge (Kubota Corporation, model 5200) at a centrifugal acceleration of 3000 rpm for 15 minutes, and the supernatant of the liquid in which exchangeable Fe ions had leached out was collected. The above operation was performed a total of 3 times on the adsorbent remaining in the centrifuge tube, and the total amount of the obtained supernatant liquid was made up to 250 ml with ion-exchanged water to obtain a sample liquid. The iron ion concentration in the sample liquid was measured using an ICP emission spectroscopic analyzer (iCAP6300 Duo manufactured by Thermo Fisher SCIENTIFIC), and the amount of exchangeable Fe ions was calculated.

[0066] (7) Iron ion elution test In this example, the amount of iron ion elution was defined as the amount (mg) of iron eluted from 1 g of the adsorbent (anhydrous) in green tea, and was measured and calculated by the following method. First, green tea (Kirin Beverage Co., Ltd.'s "Seicha" was filtered with filter paper No. 2C (manufactured by ADVANTEC), and the liquid obtained by removing precipitates such as matcha powder was used as the test liquid. Weighed 35 g of the same test liquid into a 50 mL centrifuge tube, added 0.35 g of the adsorbent, and shaken it at room temperature for 0.5 hour using a shaker (SA300 manufactured by Yamato Scientific Co., Ltd., shaking speed 5). Next, filtration was performed using filter paper No. 5C (manufactured by ADVANTEC), and the filtrate was collected. Further, re-filtration was performed using a membrane filter with a pore size of 0.2 μm to obtain a sample solution. The iron ion concentration in the sample solution was measured using an atomic absorption spectrophotometer (Z-2010 manufactured by Hitachi High-Technologies Corporation), and the iron elution amount was calculated.

[0067] Table 1 shows the physical properties and various adsorption test results for the adsorbent powders shown in the following Examples and Comparative Examples.

[0068] (Example 1) Octahedral smectite-based clay produced in Uchinada City, Niigata Prefecture was crushed, dried in an oven at 110 °C for 12 hours, pulverized, and classified to obtain clay powder. 220 mL of a 10% by mass sulfuric acid aqueous solution was placed in a beaker and heated to 90 °C. 30 g of the clay powder was added thereto, and stirring was carried out while maintaining the liquid temperature at 90 °C for 30 minutes for acid treatment. After completion of the acid treatment, the acid-treated product was filtered and washed with water, and the washed filter cake was left to dry in an oven at 150 °C for 12 hours, pulverized, and classified to obtain an acid-treated powder. Furthermore, 220 mL of a sodium sulfate aqueous solution with a concentration of 400 mEq / L adjusted to pH 1.0 by adding sulfuric acid was placed in a beaker, and the entire amount of the washed filter cake was added thereto, and iron ion content reduction treatment was carried out by stirring at room temperature for 24 hours. After completion of the iron ion content reduction treatment, the iron ion content reduction-treated product was filtered and washed with water, and the washed filter cake was left to dry in an oven at 150 °C for 12 hours, pulverized, and classified to obtain an adsorbent powder.

[0069] (Example 2) An adsorbent powder was obtained in the same manner as in Example 1 except that the operation of Example 1 was scaled up 90,000 times.

[0070] (Example 3) An adsorbent powder was obtained in the same manner as in Example 1 except that the 400 mEq / L sodium sulfate aqueous solution was changed to a 400 mEq / L potassium sulfate aqueous solution.

[0071] (Example 4) An adsorbent powder was obtained in the same manner as in Example 1, except that the 400 mEq / L sodium sulfate aqueous solution was changed to a 400 mEq / L magnesium sulfate aqueous solution.

[0072] (Example 5) An adsorbent powder was obtained in the same manner as in Example 1, except that the 400 mEq / L sodium sulfate aqueous solution was changed to a 40 mEq / L potassium aluminum sulfate aqueous solution.

[0073] (Example 6) An adsorbent powder was obtained in the same manner as in Example 1, except that the 400 mEq / L sodium sulfate aqueous solution was changed to a sulfuric acid aqueous solution.

[0074] (Example 7) An adsorbent powder was obtained in the same manner as in Example 1, except that the 400 mEq / L sodium sulfate aqueous solution was changed to a 1 mass% citric acid aqueous solution.

[0075] (Example 8) An adsorbent powder was obtained in the same manner as in Example 2, except that the sulfuric acid concentration was changed to 15 mass%, the weight of the added clay was increased to 1.5 times, and the sodium sulfate aqueous solution concentration was changed to 450 mEq / L.

[0076] (Comparative Example 1) An adsorbent powder was obtained in the same manner as in Example 1, except that the 400 mEq / L sodium sulfate aqueous solution adjusted to pH 1.0 was changed to distilled water.

[0077]

Table 1

[0078] In the adsorbents of Examples 1 to 8, (A) / (B) was in the range of 0.96 to 2.15, the adsorption amount of caffeine as a purine body was in the range of 37 to 49 mg / g, the amount of exchangeable iron ions was in the range of 0.05 to 0.23 mmol / 100 g, and the elution amount of iron ions in green tea was in the range of 0.02 to 0.09 mg / g. Further, the green tea from which the purine body was removed using the adsorbents of Examples 1 to 8 did not have a metallic taste. In the adsorbent of Comparative Example 1, (A) / (B) was 1.70, the adsorption amount of caffeine was 45 mg / g, the amount of exchangeable iron ions was 0.58 mmol / 100 g, and the elution amount of iron ions was 0.23 mg / g. Further, the green tea from which the purine body was removed using the adsorbent of Comparative Example 1 had a metallic taste.

Claims

1. It consists of an acid-treated product of dioctahedral smectite-based clay, and the ratio of the BET specific surface area (A) measured by the water vapor adsorption method to the BET specific surface area (B) measured by the nitrogen adsorption method, (A) / (B), is in the range of 0.90 to 5.00, and the adsorbent for purine bodies in liquids other than beers, characterized in that the amount of exchangeable iron ions is 0.25 mmol / 100 g or less.

2. The adsorbent according to Claim 1, wherein the acid-treated product of the dioctahedral smectite-based clay has further been subjected to a treatment for reducing the iron ion content.

3. The adsorbent according to Claim 1 or 2, wherein the amount of interlayer water specific to the dioctahedral smectite-based clay is 30 mg or less per 1 g of the adsorbent excluding adsorbed water and interlayer water.

4. The adsorbent according to Claims 1 to 3, wherein the amount of solid acid with Ho ≦ -3.0 is in the range of 0.10 to 0.70 mmol / g-dry clay.

5. The adsorbent according to any one of claims 1 to 4, wherein the value of the BET specific surface area measured by the nitrogen adsorption method is in the range of 65 to 400 m ２ / g.

6. The adsorbent according to any one of Claims 1 to 5, wherein (A) / (B) is in the range of 0.90 to 2.

80.

7. The adsorbent according to any one of Claims 1 to 6, wherein the purine body is a xanthine compound.

8. The adsorbent according to Claim 7, wherein the xanthine compound is caffeine.

9. The adsorbent according to any one of Claims 1 to 6, wherein the purine body is an adenine or guanine compound.

10. A method for removing a purine body from a liquid other than beers, characterized in that the adsorbent according to any one of Claims 1 to 9 is put into a liquid other than beers containing the purine body to adsorb and remove the purine body.

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