JP7267082B2 - Trigonelline adsorbent and trigonelline adsorption method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel trigonelline adsorbent and a trigonelline adsorption method.

Trigonelline is contained in coffee beans, some fish and shellfish, etc., is a type of alkaloid having a pyridine ring, and is a compound represented by the following formula.

Trigonelline is known as a component that imparts bitterness and harshness to coffee. In addition, nicotinic acid, which is produced by thermal decomposition of trigonelline, is also known as a component that exhibits bitterness and harshness (Patent Document 1). Therefore, from the viewpoint of reducing bitterness and harshness, it is desirable to separate and remove trigonelline.

As a method for separating trigonelline from a coffee extract, etc., a method using hot water (Patent Document 2), a method using chromatography (Patent Document 3), a method using an ion exchange resin, etc. are known. is.
In addition, methods using chromatography and ion exchange resins are extremely costly to implement industrially, so there is a demand for inexpensive mineral adsorbents that adsorb trigonelline. The fact is that it has hardly been considered.

Japanese Patent Application Laid-Open No. 2010-119386 JP 2018-191543 JP 2013-242284 A

The present inventors have investigated trigonelline adsorbents and found that acid-treated dioctahedral smectite clay obtained by adjusting the degree of acid treatment can effectively adsorb trigonelline from an aqueous solution of trigonelline. I got some surprising knowledge.

Accordingly, an object of the present invention is to provide a trigonelline adsorbent capable of effectively adsorbing trigonelline from an aqueous solution of trigonelline.

According to the present invention, there is provided a trigonelline adsorbent comprising an acid-treated dioctahedral smectite clay, wherein the acid-treated product has a BET specific surface area (A) measured by a water vapor adsorption method and a BET specific surface area (A) measured by a nitrogen adsorption method. The ratio of the BET specific surface area (B), (A) / (B) is in the range of 0.60 to 5.00, and the solid acid amount of Ho ≤ -3.0 is 0.10 to 0.70 mmol /g-dry clay range. In this specification, "mmol/g-dry clay" refers to the amount of solid acid per 1 g of anhydrous adsorbent.

In the trigonelline adsorbent of the present invention,
(1) 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;
(2) (A)/(B) is in the range of 0.90 to 2.80;
is preferred.

Further, according to the present invention, there is provided a method for adsorbing trigonelline, characterized by adding the adsorbent according to any one of claims 1 to 3 to an aqueous trigonelline-containing aqueous solution to adsorb trigonelline.

In the trigonelline adsorption method of the present invention, it is preferable to add the adsorbent in an amount of 0.01 parts by mass or more per 1 part by mass of trigonelline contained in the aqueous solution.

In the present invention, the acid-treated dioctahedral-type smectite clay used as a trigonelline adsorbent is not acid-treated to the extent of conventionally known activated clay used in various applications, and is at a weaker level than that. It is acid treated. That is, as described in JP-A-2008-266144, dioctahedral-type smectite clay (acidic clay) that has not been acid-treated and activated clay that has been acid-treated to a certain level or higher are trigonelline adsorbents. Although it does not have excellent functionality, in the present invention, as a result of adjusting the degree of acid treatment below a certain level, trigonelline can be effectively adsorbed from an aqueous solution of trigonelline.

Therefore, by adding the trigonelline adsorbent of the present invention to an aqueous coffee bean component extraction solution or an aqueous solution containing trigonelline obtained by a synthetic reaction using an enzyme or the like, trigonelline can be adsorbed from these solutions. be able to.

In addition, the trigonelline adsorbent of the present invention has higher filterability than acid clay, is easily separated from the solution after the adsorption treatment, and trigonelline is easily recovered by releasing trigonelline from the used adsorbent. can do.

4 is an X-ray diffraction chart derived from the surface index (06) of the adsorbent of the present invention used in Example 1. FIG.

<Trigonelline adsorbent>
[Weak acid treated clay]
The trigonelline adsorbent of the present invention is made of an acid-treated dioctahedral smectite clay, which is obtained by a weak acid treatment compared to what is generally called activated clay, and should be called a weakly acid-treated clay. It is. Therefore, hereinafter, the acid-treated material used as the trigonelline adsorbent is sometimes referred to as "weakly acid-treated clay".
For example, Japanese Patent Application Laid-Open No. 2009-072759 by the present applicant discloses that an acid-treated product called semi-activated clay obtained by acid-treating dioctahedral clay is used as a catalyst for polylactic acid depolymerization. , the weakly acid-treated clay used in the present invention is obtained by a weaker acid treatment than this semi-activated clay.
That is, the weakly acid-treated clay used as the trigonelline adsorbent in the present invention exhibits a unique X-ray diffraction peak derived from the crystal structure of the dioctahedral smectite clay. has a diffraction peak derived from 2θ=62 degrees (d=1.49 to 1.50 Å).

Such weak acid-treated clay has a very low acid treatment level of dioctahedral smectite clay, so the BET specific surface area (A) measured by the water vapor adsorption method and the BET specific surface area (B) measured by the nitrogen adsorption method are different. The ratio (A)/(B) is 0.60 or more, preferably 0.90 or more, particularly preferably 1.10 or more, and most preferably 1.20 or more from the viewpoint of adsorptivity. In addition, it is 5.00 or less, preferably 4.20 or less, particularly preferably 3.30 or less, and most preferably 2.80 or less from the viewpoint of filterability.

In the present invention, the BET specific surface area ratio (A/B) in the above range of the weakly acid-treated clay is presumed to be one of the reasons why it exhibits excellent adsorption performance for trigonelline.
That is, as a method for measuring the BET specific surface area, a method using nitrogen (nitrogen method) is generally used, but there is also a method using water vapor (steam method). According to Clay Handbook (3rd edition), in the nitrogen method, the total external surface area including the end face per unit mass is measured. Only the external surface area is measured since there is no penetration between the layers at temperature. On the other hand, in the steam method using a polar adsorbate such as steam, the internal surface is measured because such adsorbate penetrates well between the layers of the clay. Therefore, the fact that A/B is within the above range means that the very weak acid treatment increases the micropores and expands the inter-layer spacing of the basic three layers of the smectite clay. Increased micropores improve adsorption for relatively small molecules such as trigonelline.
That is, in the adsorbent (weakly acid-treated clay) of the present invention having the above A/B value, moderate expansion between the basic three layers and formation of micropores within the layers occur in a well-balanced manner in the acid treatment step. It is believed to exhibit adsorptive properties for small molecules such as trigonelline.
For example, in conventionally known activated clay and semi-activated clay obtained by treatment with a strong acid, the expansion between the basic three layers becomes large, and moreover, the micropores formed between the layers are collapsed. Therefore, the value of A/B becomes small, and almost no adsorptivity to trigonelline is exhibited.

In addition, since the weakly acid-treated clay used as an adsorbent in the present invention is acid-treated, albeit weakly, the BET specific surface area by the nitrogen method is improved compared to smectite clay that is not acid-treated. preferably in the range of 65-400 m ² /g, particularly preferably in the range of 100-400 m ² /g.

Furthermore, the weak acid treated clay used as an adsorbent in the present invention is obtained by weak acid treatment compared to what is generally called activated clay, so the Na content covering Al and Mg acting as solid acid sites and Ca are removed, and furthermore, the decrease in the amount of solid acid caused by the elution of Al and Mg as the acid treatment progresses is suppressed. As a result, it exhibits a solid acid content equal to or greater than that of what is generally called activated clay obtained by conventional acid treatment or acid clay not subjected to acid treatment. For example, the solid acid amount of Ho ≤ -3.0 is in the range of 0.10 to 0.70 mmol/g-dry clay, preferably in the range of 0.3 to 0.7 mmol/g-dry clay, and a relatively strong solid acid contains a lot of
The fact that the above-mentioned weakly acid-treated clay contains a large amount of such a strong solid acid is also considered to be a factor in exhibiting excellent adsorption to trigonelline.

Since trigonelline has a pyridine ring and a carboxylic acid group, cations, zwitterions and anions are in equilibrium in an aqueous solution, and equilibrium migration occurs according to pH changes in the aqueous solution.
For example, under high pH (basic) conditions, the carboxylic acid becomes an anion, so the equilibrium is tilted towards the anion side. Here, when the adsorbent of the present invention containing a strong solid acid (weak acid-treated clay) is added to the aqueous solution, the pH decreases, the pyridine ring becomes a cation, and the equilibrium of trigonelline shifts to the cation side. do. Therefore, the cations of trigonelline are captured by the negative charges between the layers of the weakly acid-treated clay, and as a result, the adsorptivity of trigonelline develops. Thus, it is presumed that the fact that the weakly acid-treated clay has a strong solid acid is also a factor in the development of the adsorptivity to trigonelline.
In the present invention, the pH of such weak acid-treated clay is usually 6.0 or less, preferably 5.5 or less, and particularly preferably 4.5 or less.

Furthermore, the weakly acid-treated clay has excellent filterability due to the acid treatment.
Smectite clay that has not been acid-treated (acidic clay) has large interlayers containing cations such as Na between the basic layers, so it exhibits high swelling properties in water and finely disperses due to swelling. Filterability is thought to be poor due to oxidization. However, in the case of the weakly acid-treated clay used in the present invention, part of the base component in the smectite clay reacts with the acid to form a binder that is insoluble in water, alcohol, etc., and binds particles together. In addition, fine dispersion in the solution is suppressed, and it is thought that excellent filterability is exhibited.
Therefore, the weaker the degree of acid treatment, the greater the A/B ratio, which may impair the filterability.

[Production of weak acid-treated clay]
The weakly acid-treated clay having the properties as described above is produced by coarsely pulverizing and kneading the dioctahedral smectite clay and subjecting it to acid treatment under predetermined conditions using an acid aqueous solution of a predetermined concentration. That is, this weakly acid-treated clay is obtained in the same manner as the semi-activated clay, but is obtained by acid treatment under milder conditions than the semi-activated clay.

The _dioctahedral -type smectite-based clay used _as raw material clay is thought to have been metamorphosed from volcanic rock, lava, etc. under the influence of seawater. The basic structure (unit layer) is a three-layer structure (unit layer) consisting of _SiO4 tetrahedral layers, and these tetrahedral layers and octahedral layers are partially isomorphically substituted with dissimilar metals. Between the layers, cations such as Ca, K, Na, etc., hydrogen ions, and water molecules coordinated thereto are present. In addition, Mg and Fe (II) are substituted for part of Al in the octahedral layer of the basic three-layer structure, and Al is substituted for part of Si in the tetrahedral layer, so the crystal lattice is negative. It has an electric charge, and this negative electric charge is neutralized by metal cations and hydrogen ions existing between the basic layers. Such smectite clays include acid clay, bentonite, fuller's earth, etc., and exhibit different characteristics depending on the type and amount of metal cations present between the basic layers, the amount of hydrogen ions, and the like. For example, bentonite has a large amount of Na ions existing between the basic layers, and therefore, the pH of the dispersion dispersed in water is high, and is generally on the high alkaline side. Furthermore, it exhibits the property of gelling and consolidating. On the other hand, in acidic clay, the amount of hydrogen ions present between the basic layers is large, so the pH of the dispersion dispersed in water is low, generally on the acidic side, and exhibits swelling in water. However, compared with bentonite, its swelling property is generally low and gelation does not occur.

In the present invention, the dioctahedral smectite clay used for producing the weakly acid-treated clay is not particularly limited, and any of the various types described above can be used. Further, such raw material clay differs depending on the origin of the clay, the place of production, and even in the same place of production, the burial place (face), etc., but in general, it has the following composition in terms of oxide.
SiO ₂ ; 50 to 75% by mass
Al ₂ O ₃ ; 11 to 25% by mass
Fe ₂ O ₃ ; 2 to 20% by mass
MgO; 2 to 7% by mass
CaO; 0.1 to 3% by mass
Na ₂ O; 0.1 to 3% by mass
K ₂ O; 0.1 to 3% by mass
Other oxides (TiO _2, etc.); 2% by mass or less Ig-loss (1050°C); 5 to 11% by mass

In addition, raw material clay may contain a large amount of impurities such as quartz depending on the place of production. Therefore, the dioctahedral smectite clay should be subjected to refining operations such as sand separation, buoyancy, magnetic beneficiation, elutriation, wind elutriation, etc., to remove impurities as much as possible, and then acid treatment. After such treatment, acid treatment under mild conditions described below can be performed to obtain weakly acid-treated clay having A/B within the above range.

The acid treatment is carried out by adding raw material clay to an acid aqueous 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 viewpoint of cost, environmental impact, and the like.

In addition, as already mentioned, such an acid treatment is carried out under milder conditions than the conventionally known acid treatment for producing activated clay or semi-activated clay. , the amount of sulfuric acid aqueous solution calculated assuming that the water contained in the raw material clay also constitutes the aqueous sulfuric acid solution is 250 to 800 parts by mass per 100 parts by mass of raw clay (as a dried product at 110 ° C.), and the concentration of the sulfuric acid aqueous solution at that time is 1. The acid treatment may be carried out under conditions such that the content becomes about 15% by mass. In the acid treatment, heating to about 25 to 95° C. can be carried out if necessary. In this way, depending on the composition of the raw material, the acid concentration of the acid aqueous solution used, the treatment temperature, etc., the time required for the specific surface area ratio (A / B) to be within a predetermined range (about 0.5 to 12 hours, preferably 0 0.5 to 8 hours, particularly preferably 0.5 to 4 hours).

By the acid treatment as described above, the ratio A / B of the BET specific surface area by the nitrogen method and the BET specific surface area by the steam method, the amount of solid acid, and the value of the BET specific surface area by the nitrogen method are in the above ranges, and the adsorption performance for trigonelline It is possible to obtain the adsorbent (weakly acid-treated clay) of the present invention which is excellent in

Further, the weakly acid-treated clay obtained by the acid treatment described above generally has the following chemical composition in terms of oxide.
SiO ₂ ; 50 to 85% by mass
Al ₂ O ₃ ; 8 to 23% by mass
Fe ₂ O ₃ : 1 to 10% by mass MgO: 1 to 5% by mass CaO: 0.1 to 2% by mass Na ₂ O: 0.1 to 1% by mass
K ₂ O; 0.1 to 1% by mass
Other oxides (TiO _2, etc.); 2% by mass or less Ig-loss (1050°C); 4 to 9% by mass

[Application]
The weakly acid-treated clay used as an adsorbent in the present invention can effectively adsorb trigonelline from an aqueous solution containing trigonelline. For example, by removing trigonelline from coffee beverages using the adsorbent of the present invention, the bitterness and harshness derived from trigonelline can be reduced.
In addition, the adsorbent of the present invention can be used without any limitation for solutions containing trigonelline compounds bound to various salts such as phosphates and hydrochlorides.

<Method of Adsorption of Trigonelline>
In the trigonelline adsorption method of the present invention, trigonelline is adsorbed by adding the trigonelline adsorbent (weak acid-treated clay) of the present invention to a trigonelline-containing aqueous solution. At this time, the adsorbent is 0.01 parts by mass or more, preferably 0.01 to 160 parts by mass, more preferably 0.01 to 320 parts by mass per 1 part by mass of trigonelline contained in the aqueous solution. . If the input amount is small, as a matter of course, the adsorption amount of trigonelline becomes insufficient. In addition, if the amount to be charged is larger than necessary, it is disadvantageous in terms of cost.

The adsorbent of the present invention that has adsorbed trigonelline is separated and taken out by a known method such as centrifugation or filtration. Filtration is preferable as the separation method from the viewpoint of less loss of the active ingredient.

Trigonelline can also be released from an adsorbent that adsorbs and retains trigonelline by a solvent extraction method or the like. For example, an adsorbent in which trigonelline is adsorbed and retained is put into pure water, trigonelline is released by subjecting it to a stirring operation such as ultrasonic vibration, and trigonelline can be recovered by concentration or solvent removal. Pure water is preferably used as the solvent for desorption, but a part or all of it can be replaced with an aqueous solution of various salts or an organic solvent. The solvent used for desorption is used at 25° C. or lower, particularly at room temperature, but the heating temperature can be appropriately set to the extent that trigonelline is not denatured.

The excellent effects of the present invention will be explained by the following experimental examples.

(Example 1)
700 g of dioctahedral smectite clay pellets from Tainai City, Niigata Prefecture were put into 1000 ml of a 5% by mass sulfuric acid aqueous solution heated to 90°C. The mixture was stirred while maintaining the liquid temperature at 90° C., and acid treatment was performed for 30 minutes. After acid treatment, the pellets washed with water were dried at 110° C., pulverized and classified to obtain weakly acid-treated clay powder. Further, the obtained weakly acid-treated clay powder was measured by an XRD measuring device (RINT-Ultima IV (X-rays=CuKα rays) manufactured by Rigaku Corporation). An X-ray diffraction chart is shown in FIG.

(Comparative example 1)
Silica gel manufactured by Mizusawa Chemical Industry Co., Ltd.

(Comparative example 2)
Acid clay (A) manufactured by Mizusawa Chemical Industry Co., Ltd.

(Comparative Example 3)
Acid clay (B) manufactured by Mizusawa Chemical Industry Co., Ltd.

(1) BET specific surface area (B) by nitrogen adsorption method
It was measured by the nitrogen adsorption method using TriStar 3000 manufactured by Micromeritics, and calculated by the BET method. The pretreatment was performed at 150° C. for 2 hours. Table 1 shows the results.

(2) BET specific surface area (A) by water vapor adsorption method
BELSORP MAX manufactured by Nippon Bell Co., Ltd. was used for measurement by the water vapor adsorption method, and calculated by the BET method. The pretreatment was performed at 150° C. for 2 hours. Table 1 shows the results.

(3) pH
Adsorbent powder was added to ion-exchanged water so that the adsorbent concentration was 5% by mass, and after stirring for 30 minutes, the pH was measured with a pH meter HM-30R manufactured by DKK Toa. Table 1 shows the results.

(4) Solid acid content A solid acid content of Ho≤-3.0 was measured by n-butylamine titration method. The sample was dried at 150° C. for 3 hours in advance and measured {Reference: “Catalyst” Vol. 11, No. 6, P210-216 (1969)}. Table 1 shows the results.

(5) Trigonelline reduction test of commercial coffee beverage 1 g of adsorbent (anhydrous) was added to 30 g of commercial coffee beverage, and shaker (SA300 manufactured by Yamato Scientific Co., Ltd., shaking speed 5) was used. Shake for 5 hours. Next, the supernatant of the liquid was treated with a centrifugal separator (manufactured by Kubota Corporation, 5200) at a centrifugal acceleration of 3000 rpm for 15 minutes, and the supernatant was filtered through a filter for HPLC pretreatment (manufactured by Merck, filter pore size: 0.20 μm) to obtain a sample liquid. .
The obtained sample solution was analyzed by liquid chromatography (HPLC) under the following conditions.
Measuring device: Shimadzu high performance liquid chromatograph Prominece
Column: Shim-pack VP-ODS manufactured by Shimadzu Corporation
Detector: UV
Measurement wavelength: 270 nm
The amount of trigonelline in the sample solution was calculated using a previously prepared calibration curve showing the relationship between the trigonelline concentration and the peak area ratio of trigonelline in HPLC analysis. Table 2 shows the trigonelline content and reduction rate of the coffee beverage after the adsorption treatment.

(6) Trigonelline reduction test of coffee bean extract 1 g of adsorbent (anhydrous) was added to 30 g of coffee bean extract, and a shaker (SA300 manufactured by Yamato Scientific Co., Ltd., shaking speed 5) was used. Shake for 5 hours. The coffee bean extract was prepared by a paper drip method using 650 ml of hot water at 85° C. for 60 g of medium-roasted, medium-fine ground Brazilian coffee beans.
Next, the supernatant of the liquid was treated with a centrifugal separator (manufactured by Kubota Corporation, 5200) at a centrifugal acceleration of 3000 rpm for 15 minutes, and the supernatant was filtered through a filter for HPLC pretreatment (manufactured by Merck, filter pore size: 0.20 μm) to obtain a sample liquid. . The resulting sample solution was analyzed by liquid chromatography (HPLC) under the same conditions as the trigonelline reduction test for commercially available coffee beverages. Table 3 shows the trigonelline content and reduction rate of the coffee bean extract after adsorption treatment.

(7) Trigonelline adsorption test The amount of trigonelline (mg/g-dry clay) that can be adsorbed by 1 g of adsorbent (anhydrous) from 30 g of trigonelline aqueous solution of 800 ppm was measured by the following method. Table 4 shows the calculated values.
First, trigonelline (manufactured by Cayman Chemical) was dissolved in distilled water to obtain an 800 ppm trigonelline aqueous solution. 30 g of this 800 ppm trigonelline aqueous solution was weighed into a 50 ml capacity centrifuge tube, 1 g of adsorbent (3.3% by mass relative to the liquid) was added, and a shaker (SA300 manufactured by Yamato Scientific Co., Ltd., shaking speed 5) was used. Shake for 2.5 hours.
Next, the supernatant of the liquid was treated with a centrifugal separator (manufactured by Kubota Corporation, 5200) at a centrifugal acceleration of 3000 rpm for 15 minutes, and the supernatant was filtered through a filter for HPLC pretreatment (manufactured by Merck, filter pore size: 0.20 μm) to obtain a sample liquid. . Liquid chromatography (HPLC) analysis was performed under the same conditions as the trigonelline reduction test for commercially available coffee beverages. The amount of trigonelline remaining in the sample solution was calculated, and the value obtained by subtracting the amount of trigonelline before addition of the adsorbent was used as the amount of trigonelline adsorbed.

Claims (5)

A trigonelline adsorbent comprising an acid-treated dioctahedral smectite clay,
In the acid-treated product, the ratio of the BET specific surface area (A) measured by the steam adsorption method to the BET specific surface area (B) measured by the nitrogen adsorption method, (A)/(B) is 0.60 to 5. 0.00 and a solid acid content of Ho≤-3.0 in the range of 0.10 to 0.70 mmol/g-dry clay. The trigonelline adsorbent according to claim 1, which has a BET specific surface area value in the range of 65 to 400 m ² /g as measured by a nitrogen adsorption method. Trigonelline adsorbent according to claim 1 or 2, wherein (A)/(B) is in the range of 0.90 to 2.80. A method for adsorbing trigonelline, which comprises adding the adsorbent according to any one of claims 1 to 3 to a trigonelline-containing aqueous solution to adsorb trigonelline. The trigonelline adsorption method according to claim 4, wherein the adsorbent is added in an amount of 0.01 parts by mass or more per 1 part by mass of trigonelline contained in the aqueous solution.

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