JP2020179366A - Trigonelline adsorbent and trigonelline adsorption method - Google Patents

Abstract

To provide a trigonelline adsorbent that can effectively adsorb trigonelline from aqueous solution of trigonelline.SOLUTION: A trigonelline adsorbent comprises an acid treated product of dioctahedral smectite clay, wherein, the ratio between a BET specific surface area (A) measured by water vapor adsorption and a BET specific surface area (B) measured by nitrogen adsorption, (A)/(B), is 0.60-5.00, and a solid acid amount of Ho≤-3.0 is 0.10-0.70 mmol/g-dry clay.SELECTED DRAWING: None

Description

The present invention relates to a novel trigonelline adsorbent and a method for adsorbing trigonelline.

Trigonelline is a kind of alkaloid having a pyridine ring contained in coffee beans and some seafood, and is a compound represented by the following formula.

Trigonelline is known as a component that exhibits the bitterness and harshness of coffee. In addition, nicotinic acid produced by decomposition of trigonelline by heat is also known as a component exhibiting 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 coffee extract or the like, a method using hot water or the like (Patent Document 2), a method using chromatography (Patent Document 3), a method using an ion exchange resin, etc. are known. Is.
In addition, since chromatography and methods using ion exchange resins are extremely costly to carry out industrially, inexpensive mineral-based adsorbents that adsorb trigonelline are required. The reality is that little consideration has been given.

JP-A-2010-119386 JP-A-2018-191543 JP 2013-242284

As a result of examining an adsorbent for trigonelline, the present inventors have found that an acid-treated product of dioctahedral smectite-based clay obtained by adjusting the degree of acid treatment can effectively adsorb trigonelline from an aqueous solution of trigonelline. I got a surprising finding.

Therefore, 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, it is a trigonerin adsorbent composed of an acid-treated product of dioctahedral type smectite clay, and the acid-treated product is measured by the BET specific surface area (A) measured by the steam adsorption method and the nitrogen adsorption method. BET specific surface area (B), (A) / (B) is in the range of 0.60 to 5.00, and the amount of solid acid with Ho ≦ -3.0 is 0.10 to 0.70 mmol. A trigonerin adsorbent is provided, which is characterized by being in the range of / g-dry clay. The term "mmol / g-dry clay" as used herein refers to the amount of solid acid per 1 g of the 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 0.99 to 2.80,
Is preferable.

Further, according to the present invention, there is provided 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.

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

In the present invention, the acid-treated product of dioctahedral type smectite clay used as a trigonelline adsorbent does not undergo acid treatment up to a conventionally known region called activated clay, which is used for various purposes, and at a weaker level. It is acid-treated. That is, as described in Japanese Patent Application Laid-Open No. 2008-266144, dioctahedral-type smectite clay (acidic clay) that has not been acid-treated and activated clay that has been acid-treated above a certain level can be used as a trigonelline adsorbent. Although it does not have excellent functionality, in the present invention, as a result of adjusting the degree of acid treatment to a certain level or less, trigonelline can be effectively adsorbed from an aqueous solution of trigonelline.

Therefore, by adding the trigonelline adsorbent of the present invention to an aqueous solution containing coffee bean components or an aqueous solution containing trigonelline obtained by a synthetic reaction using an enzyme or the like, trigonelline is 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 easily recovers trigonelline by releasing trigonelline from the used adsorbent. can do.

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

<Trigonelline adsorbent>
[Weak acid treated white clay]
The trigonelline adsorbent of the present invention is composed of an acid-treated product of dioctahedral type smectite clay, but it is obtained by a weak acid treatment as compared with what is generally called activated clay, and should be called a weak acid-treated clay. It is a thing. Therefore, hereinafter, the acid-treated product used as a trigonelline adsorbent may be referred to as "weak acid-treated white 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 weak acid-treated clay used in the present invention is obtained by a weaker acid treatment than this semi-activated clay.
That is, the above-mentioned weak acid-treated white clay used as a trigonelline adsorbent in the present invention shows a peculiar X-ray diffraction peak derived from the crystal structure of dioctahedral type smectite clay, and for example, in X-ray diffraction measurement, the plane index (06). It has a diffraction peak derived from 2θ = 62 degrees (d = 1.49 to 1.50 Å).

Since the acid treatment level of the dioctahedral smectite clay is very low in such weak acid-treated white clay, the BET specific surface area (A) measured by the steam adsorption method and the BET specific surface area (B) measured by the nitrogen adsorption method 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. Further, 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, it is presumed that the weak acid-treated white clay having a BET specific surface area ratio (A / B) in the above range is one of the reasons for exhibiting excellent adsorption performance for trigonelline.
That is, as a method of measuring the BET specific surface area, a method using nitrogen (nitrogen method) is common, but there is also a method of measuring using water vapor (steam method). According to the Clay Handbook (3rd edition), the nitrogen method measures the total external surface area including the end face per unit mass, and in the case of dioctahedral smectite-based clay having a three-layer structure, the nitrogen molecule is liquid nitrogen. Only the external surface area is measured as it does not penetrate between layers at temperature. On the other hand, in the water vapor method using a polar adsorbent such as water vapor, the adsorbent sufficiently penetrates between the layers of the clay, so that the internal surface is measured. Therefore, the fact that the A / B is within the above range means that the micropores are increased by the very weak acid treatment, and the layers of the basic three layers of the smectite clay are expanded. The increase in micropores improves the adsorptivity to relatively small molecules such as trigonelline.
That is, the adsorbent of the present invention (weak acid-treated white clay) having the above A / B value causes an appropriate expansion between the layers of the basic three layers and the formation of micropores within the layers in a well-balanced manner in the acid treatment step. It is believed to be adsorptive to small molecules such as trigonelline.
For example, in the conventionally known activated clay or semi-active clay obtained by treating with a strong acid, the spread between the layers of the basic three layers becomes large, and the micropores formed between the layers are crushed. Therefore, the value of A / B becomes small, and the adsorptivity to trigonelline is hardly shown.

Further, since the above-mentioned weak acid-treated clay used as an adsorbent in the present invention is weakly acid-treated, the BET specific surface area by the nitrogen method is improved as compared with the smectite-based clay not subjected to the acid treatment. It is preferably in the range of 65 to 400 m ² / g, and particularly preferably in the range of 100 to 400 m ² / g.

Further, since the weak acid-treated clay used as an adsorbent in the present invention is obtained by a weak acid treatment as compared with what is generally called activated clay, the Na content covering Al and Mg acting as solid acid points. And Ca are removed, and the decrease in the amount of solid acid due to the elution of Al and Mg as the acid treatment progresses is suppressed. As a result, the amount of solid acid is equal to or higher than that of what is generally called activated clay obtained by conventional acid treatment or acidic clay not subjected to acid treatment. For example, the amount of solid acid with Ho ≦ -3.0 is in the range of 0.10 to 0.70 mmol / g-dry clay, preferably 0.3 to 0.7 mmol / g-dry clay, and a relatively strong solid acid. Contains a lot.
The fact that the above-mentioned weak acid-treated white clay contains a large amount of such a strong solid acid is also considered to be a factor showing excellent adsorptivity to trigonelline.

Since trigonelline has a pyridine ring and a carboxylic acid group, cations, zwitterions and anions are in equilibrium in the aqueous solution, and equilibrium shift occurs according to the pH change in the aqueous solution.
For example, under high pH (basic) conditions, the carboxylic acid becomes an anion, so the equilibrium is inclined toward the anion. When the adsorbent of the present invention (weak acid-treated white clay) containing a strong solid acid is added to the aqueous solution, the pH drops, the pyridine ring becomes a cation, and the trigonelline equilibrium shifts to the cation side. To do. Therefore, the cations of trigonelline are captured by the negative charge between the layers of the weak acid-treated white clay, and as a result, the adsorptivity of trigonelline is exhibited. As described above, it is presumed that the weak acid-treated white clay having a strong solid acid is also a factor in expressing the adsorptivity to trigonelline.
In the present invention, the pH of the weak acid-treated white clay is usually 6.0 or less, preferably 5.5 or less, and particularly preferably 4.5 or less.

Further, the weak acid-treated white clay has excellent filterability because it has been subjected to the acid treatment.
Smectite clay (acid clay) that has not been treated with acid has a large layer containing cations such as Na between the basic layers, so it exhibits high swelling property with respect to water and is finely dispersed by swelling. It is considered that the filterability is poor due to the conversion. However, in the case of the weak acid-treated clay used in the present invention, a part of the base component in the smectite clay reacts with the acid and becomes a kind of insoluble binder for water, alcohol, etc. to bond the particles. In addition, it is considered that microdispersion in the solution is suppressed and excellent filterability is exhibited.
Therefore, the weaker the degree of acid treatment, the larger the A / B, which may impair the filterability.

[Manufacture of weak acid-treated white clay]
The weak acid-treated clay having the above-mentioned characteristics is produced by coarsely crushing and kneading dioctahedral type smectite clay and acid-treating it with an acid aqueous solution having a predetermined concentration under predetermined conditions. That is, this weak acid-treated clay is obtained in the same manner as the semi-activated clay, but is obtained by acid treatment under mild conditions as compared with the semi-activated clay.

Dioctahedral smectite clay used as starting clay is believed to volcanic rock and lava is modified under the influence of sea water, a major component dioctahedral smectite SiO ₄ tetrahedral layers -AlO ₆ octahedral layer - consists SiO ₄ tetrahedral layers, and has these tetrahedral layer and the octahedral layer is partially different metals in isomorphous-substituted three-layer structure the basic structure (unit layer), stacked in such a three-layer structure Between the layers, there are cations such as Ca, K, and Na, hydrogen ions, and water molecules coordinated thereto. Further, since Mg and Fe (II) are substituted in a part of Al in the octahedral layer of the basic three-layer structure and Al is substituted in a part of Si in the tetrahedral layer, the crystal lattice is negative. It has an electric charge, and this negative charge is neutralized by metal cations and hydrogen ions existing between the basic layers. Such smectite clays include acid clay, bentonite, fraze earth, etc., and exhibit different characteristics depending on the type and amount of metal cations existing between the basic layers, the amount of hydrogen ions, and the like. For example, in bentonite, the amount of Na ions present between the basic layers is large, so that the pH of the dispersion liquid suspended and dispersed in water is high, generally on the highly alkaline side, and has high swelling property with respect to water. In addition, it exhibits 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, and therefore the pH of the dispersion liquid suspended and dispersed in water is low, generally on the acidic side, and exhibits swelling property with respect to water. However, as compared with bentonite, its swelling property is generally low and gelation does not occur.

In the present invention, the dioctahedral type smectite clay used for producing the weak acid-treated white clay is not particularly limited, and any of the above-mentioned types can be used. Further, such raw material clay has the following composition in terms of oxide, although it differs depending on the origin of the clay, the place of origin and the place of burial (face) even in the same place of origin.
SiO ₂ ; 50 to 75% by mass
Al ₂ O ₃ ; 11-25% by mass
Fe ₂ O ₃ ; 2 to 20% by mass
MgO; 2-7% 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.); 5-11% by mass

In addition, the raw material clay may contain a large amount of impurities such as quartz depending on the production area and the like. Therefore, it is preferable to apply the above dioctahedral type smectite clay to refining operations such as stone sand separation, buoyancy beneficiation, magnetic beneficiation, elutriation, and elutriation to remove impurities as much as possible, and then perform acid treatment. After performing such a treatment, a weak acid-treated white clay having an A / B within the above range can be obtained by performing an acid treatment under the mild conditions described below.

The acid treatment is carried out by putting the raw material clay into the acid aqueous solution, mixing and stirring. The acid aqueous solution used for the acid treatment is not particularly limited, but a sulfuric acid aqueous solution is generally used from the viewpoint of cost, environmental impact and the like.

Further, as described above, the acid treatment is carried out under mild conditions as compared with the acid treatment for producing the conventionally known activated clay or semi-active clay, for example, when an aqueous sulfuric acid solution is used. The amount of sulfuric acid aqueous solution calculated assuming that the water content in the raw material clay also constitutes the sulfuric acid aqueous solution is 250 to 800 parts by mass per 100 parts by mass of the raw material 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 performed under conditions such that the content is about 15% by mass. In the acid treatment, it can be heated to about 25 to 95 ° C. if necessary. In this way, the specific surface area ratio (A / B) is within a predetermined range (about 0.5 to 12 hours, preferably 0) depending on the composition of the raw material, the acid concentration of the aqueous acid solution used, the treatment temperature, and the like. The acid treatment may be carried out for about 5 to 8 hours, particularly preferably about 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 to 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 within the above ranges, and the adsorption performance for trigonerin The adsorbent of the present invention (weak acid-treated white clay) having excellent surface area can be obtained.

Further, the weak acid-treated white clay obtained by the above-mentioned acid treatment generally has the following chemical composition in terms of oxide.
SiO ₂ ; 50 to 85% by mass
Al ₂ O ₃ ; 8-23% 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.); 4-9% by mass

[Usage]
The weak acid-treated white 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 a coffee beverage using the adsorbent of the present invention, bitterness and harshness derived from trigonelline can be reduced.
Further, the adsorbent of the present invention can be used without any limitation for a solution containing a trigonelline compound bound to various salts such as phosphate and hydrochloride.

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

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

In addition, trigonelline can be released from the adsorbent on which trigonelline is adsorbed and retained by a solvent extraction method or the like. For example, an adsorbent in which trigonelline is adsorbed and held in pure water is charged, and trigonelline is released by subjecting it to a stirring operation such as ultrasonic vibration, and trigonelline can be recovered by concentrating or removing the solvent. Pure water is preferably used as the solvent used for desorption, but a part or all of the solvent can be replaced with an aqueous solution of various salts or an organic solvent. The solvent used for desorption is 25 ° C. or lower, particularly at room temperature, but the heating temperature can be appropriately set so as not to denature trigonelline.

The excellent effect of the present invention will be described with reference to the following experimental examples.

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

(Comparative Example 1)
Silica gel manufactured by Mizusawa Industrial Chemicals Co., Ltd.

(Comparative Example 2)
Acid clay (A) manufactured by Mizusawa Industrial Chemicals Co., Ltd.

(Comparative Example 3)
Acid clay (B) manufactured by Mizusawa Industrial Chemicals Co., Ltd.

(1) BET specific surface area (B) by nitrogen adsorption method
The measurement was carried out by the nitrogen adsorption method using TriStar 3000 manufactured by Micromeritics, and the measurement was performed by the BET method. The pretreatment was carried out at 150 ° C. for 2 hours. The results are shown in Table 1.

(2) BET specific surface area (A) by water vapor adsorption method
The measurement was carried out by the steam 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. The results are shown in Table 1.

(3) pH
The adsorbent powder was added to the ion-exchanged water so that the adsorbent concentration was 5% by mass, and the mixture was stirred for 30 minutes, and then measured with a pH meter HM-30R manufactured by Toa DKK. The results are shown in Table 1.

(4) Amount of solid acid The amount of solid acid with Ho ≦ −3.0 was measured by the n-butylamine titration method. The sample was measured in advance on a sample dried at 150 ° C. for 3 hours. {Reference: "Catalyst" Vol. 11, No6, P210-216 (1969)}. The results are shown in Table 1.

(5) Trigonelline reduction test of commercially available coffee beverages 1 g of an adsorbent (anhydrous) is added to 30 g of commercially available coffee beverages, and a shaker (SA300 manufactured by Yamato Scientific Co., Ltd., shaking speed 5) is used. Shake for 5 hours. Next, the supernatant of the liquid treated with a centrifuge (5200 manufactured by Kubota Co., Ltd.) at a centrifugal acceleration of 3000 rpm for 15 minutes was filtered with an HPLC pretreatment filter (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: Shimadzu Shima-pack VP-ODS
Detector: UV
Measurement wavelength: 270 nm
The amount of trigonelline in the sample solution was calculated using a calibration curve showing the relationship between the trigonelline concentration prepared in advance and the peak area ratio of trigonelline in the HPLC analysis. Table 2 shows the trigonelline content and the reduction rate of the coffee beverage after the adsorption treatment.

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

(7) Trigonelline Adsorption Test The amount of trigonelline (mg / g-dry clay) capable of adsorbing 1 g of an adsorbent (anhydrous) from 30 g of an 800 ppm trigonelline aqueous solution was measured by the following method. The calculated values are shown in Table 4.
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 is weighed in a 50 ml volume centrifuge tube, 1 g of an adsorbent (3.3% by mass with respect to the liquid) is added, and a shaker (SA300 manufactured by Yamato Scientific Co., Ltd., shaking speed 5) is used. Shake for 2.5 hours.
Next, the supernatant of the liquid treated with a centrifuge (5200 manufactured by Kubota Co., Ltd.) at a centrifugal acceleration of 3000 rpm for 15 minutes was filtered with an HPLC pretreatment filter (Merck, filter pore size 0.20 μm) to obtain a sample liquid. .. Liquid chromatograph (HPLC) analysis was performed under the same conditions as the trigonelline reduction test for commercial coffee beverages. The residual amount of trigonelline in the sample solution was calculated, and the value subtracted from the amount of trigonelline before the addition of the adsorbent was taken as the amount of trigonelline adsorbed.

Claims (5)

A trigonelline adsorbent consisting of an acid-treated product of dioctahedral type smectite clay.
The acid-treated product has a ratio (A) / (B) of 0.60 to 5 between the BET specific surface area (A) measured by the steam adsorption method and the BET specific surface area (B) measured by the nitrogen adsorption method. A trigonerin adsorbent in the range of .00 and having a solid acid content of Ho ≤ -3.0 in the range of 0.10 to 0.70 mmol / g-dry cry. The trigonelline adsorbent according to claim 1, 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. The trigonelline adsorbent according to claim 1 or 2, wherein (A) / (B) is in the range of 0.99 to 2.80. A method for adsorbing trigonelline, which comprises adding the adsorbent according to any one of claims 1 to 3 to an aqueous solution containing trigonelline 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.