JPH0461882B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field] The present invention relates to a method for insolubilizing acidic polysaccharides. Acidic polysaccharides refer to polysaccharides having acidic substituents such as carboxyl groups, sulfate groups, and phosphate groups.
Generally, it is dissolved in water and used as a food thickener or gelling agent, but in recent years, insolubilized products such as fibrous, film, and spherical shapes have been produced from aqueous solutions of acidic polysaccharides to be used in food and pharmaceutical products. It has come to be used in a wide range of fields, including agricultural chemicals. Among these, spherical objects are used for various purposes such as imitation foods, aromatics, sustained-release medicines and agricultural chemicals, chromatography fillers, and immobilization of enzymes and yeast cells. [Prior art] Polysaccharide spheres are produced by dropping an aqueous solution of a polysaccharide with gelling ability through a nozzle of an appropriate shape and size and contacting the polysaccharide with an aqueous solution containing a gelling agent. Manufactured in An example of gelling a polysaccharide with metal ions is disclosed in Japanese Patent Publication No. 18867/1983. Carrageenan, sodium alginate, and pectin are used as polysaccharides, but since carrageenan forms a strong gel, there is a particular demand for insolubilized products using carrageenan. In addition, fluidity of the aqueous solution is required when extruding the polysaccharide from a nozzle or die in order to form it into a desired form, and sodium-type carrageenan with sodium as a counter cation is used as the carrageenan. Sodium-type carrageenan can be gelled by contacting it with an aqueous solution of water-soluble salts such as potassium, calcium, ammonium, aluminum, etc., but when gelled with salts such as potassium, calcium, ammonium, etc., the amount is about 50 times the amount. When stirred in water, it dissolves, causing problems when used as an insolubilized enzyme base material or a sustained release agent. On the other hand, gelling with aluminum salt does not cause this problem, and aluminum salt has the characteristic that it can insolubilize not only carrageenan but also various acidic polysaccharides such as sodium alginate and pectin. However, all aqueous solutions of water-soluble aluminum salts exhibit strong acidity with a pH of 2 to 3, and therefore, gelling polysaccharides with water-soluble aluminum salts has the disadvantage that the polysaccharides deteriorate and the strength of the insoluble product decreases. . Furthermore, in practical use, many spherical substances have added flavoring ingredients, flavoring ingredients, medicinal ingredients, enzymes, bacterial cells, etc., but some of these substances may deteriorate in performance in such a strong acidic atmosphere. There are many things that bring about something, or things that become inactive and become useless. On the other hand, to avoid this
If the pH is 4 or higher, aluminum ions precipitate as aluminum hydroxide, making it impossible to insolubilize acidic polysaccharides efficiently. Although insolubilization of polysaccharides using aluminum salts is a simple and excellent method, it has not been widely put into practical use due to the above-mentioned drawbacks. Although spherical products have been described above, the same situation applies not only to spherical products but also to the production of fibers and films from acidic polysaccharides. Fibers and films made of acidic polysaccharides are used for clothing, materials, food, and as base materials for immobilizing enzymes, bacteria, and medicinal ingredients.Aluminum salts are used for insolubilization, but when insolubilized, they are strongly acidic. It also has the above-mentioned drawbacks to which it is exposed. [Object of the Invention] That is, the object of the present invention is to provide a method for insolubilizing acidic polysaccharides without the above-mentioned disadvantages while retaining the advantages of conventional insolubilization using aluminum salts.
The object of the present invention is to provide a method for insolubilizing acidic polysaccharides in the range of 1 to 10. [Structure of the Invention] The gist of the present invention is a method for insolubilizing acidic polysaccharides, which is characterized by bringing an aqueous acidic polysaccharide solution into contact with an aqueous solution with a pH of 4 to 10 containing an aluminum salt and a solubilizing reagent for the aluminum salt. . Acidic polysaccharides used in the present invention include carrageenan, furceleran, agar, sodium alginate, pectin, gum arabic, xanthan gum, chondroitin sulfate, heparin, carboxymethylated cellulose, carboxymethylated starch, carboxymethylated guar, and sulfated cellulose. Examples include polysaccharides into which acidic groups have been chemically introduced, such as sulfated starch, sulfated agar, phosphorylated cellulose, and phosphorylated starch. Among these, it is preferable to use carrageenan because the strength of the insolubilized product is excellent. Among carrageenans, sodium-type carrageenan having sodium as a counter cation is preferred because it has excellent fluidity in aqueous solution. The concentration of acidic polysaccharide in aqueous solution is 2 to 10%.
If it is less than 2%, the shape retention during insolubilization will be insufficient, and if it exceeds 10%, the fluidity of the aqueous solution will be poor, which is not preferable. Particularly when manufacturing spherical objects, the content is preferably 3 to 10% in order to improve the spherical shape. A hydrophilic organic solvent such as methanol, ethanol, isopropanol, or acetone may be added to the aqueous solution as long as it does not insolubilize the acidic polysaccharide, and flavor components and flavoring agents may be added depending on the use of the insolubilized material. Components, medicinal ingredients, enzymes, or bacterial cells may be dissolved or dispersed. Although heating the acidic polysaccharide aqueous solution is effective in increasing fluidity, care must be taken to prevent deterioration, alteration, deactivation, and escape of the acidic polysaccharide and additive substances. In order to insolubilize the acidic polysaccharide in a desired form, it is first dripped or extruded through an appropriately shaped nozzle or die to contact with an aqueous solution containing an aluminum salt and a solubilizing reagent for the aluminum salt. For example, in order to obtain a composite spherical material in which the outer layer and the inner layer have different compositions, a composite nozzle may be used to drop them. As the aluminum salt used in the present invention, water-soluble aluminum salts such as aluminum chloride, aluminum sulfate, and aluminum nitrate are preferably used, but even aluminum that is difficult to dissolve in water alone can be dissolved in the presence of a solubilizing reagent. For example, aluminum hydroxide can also be used. Moreover, a plurality of the above aluminum salts can be used in combination. The concentration of the aluminum salt in the aqueous solution is 0.05 to 2 mol/ml. 0.05
If the amount is less than 2 mol/mol, the gelling effect is insufficient and it is difficult to obtain a good insolubilized product, and if it exceeds 2 mol/mol/mol, not only is no improvement in the gelling effect seen, but a larger amount of solubilizing reagent is required. Therefore, it is economically disadvantageous. As a solubilizing reagent, any solubilizing reagent that can substantially dissolve aluminum ions in water or maintain a dissolved state in the pH range of 4 to 10 can be used, but hydroxypolycarboxylic acids and their salts are toxic. It is preferable in that it has less. Among them, citric acid, tartaric acid, malic acid and their sodium or potassium salts are more preferably used. A combination of a plurality of these may be used. When carrageenan is used as the acidic polysaccharide, the use of potassium salt of hydroxypolycarboxylic acid as the solubilizing reagent has the advantage of increasing the strength of the insolubilized product. The solubilizing reagent may be added in an amount necessary to keep coexisting aluminum ions in a dissolved state in the pH range of 4 to 10. For example, if citrate is used as the solubilizing reagent, 1 citrate ion per 1 mole of aluminum ions is added. It may be used in an amount of 5 to 5 moles. If it is less than 1 mol, the dissolution of aluminum ions will be insufficient, and if it is used in excess of 5 mol, no further effect can be expected. When aluminum salt and solubilizing reagent are added to water in the above formulation and stirred, the aluminum salt alone will precipitate as aluminum hydroxide (pH 4-10).
Even in this region, the aluminum ion and the solubilizing reagent form a complex, resulting in a stable aqueous solution. When an aqueous polysaccharide solution is formed into a desired shape and brought into contact with the aqueous solution, the polysaccharide gels in that shape and can be taken out. However, in this state, it will dissolve if it comes into contact with a large amount of water. In other words, when a solubilizing reagent coexists, aluminum ions form a stable complex with the solubilizing reagent, and even when brought into contact with an aqueous acidic polysaccharide solution, they become free aluminum ions and cannot react with the acidic polysaccharide, causing the acidic polysaccharide to gel. This shows that it cannot be made insolubilized even if Next, this gelled acidic polysaccharide is brought into contact with an aqueous solution of a water-soluble calcium salt. Water-soluble calcium salts include calcium chloride,
Examples include calcium nitrate, calcium acetate, and calcium lactate. Further, these salts may be used in combination. When brought into contact with such a water-soluble calcium salt aqueous solution, the complex between the aluminum ion and the solubilizing reagent is destroyed, and the aluminum ion is liberated and at the same time reacts with the acidic polysaccharide, making the acidic polysaccharide insolubilized. Although the calcium ion concentration varies depending on the amount of solubilizing reagent used, it is usually 0.005 to 5 mol/concentration. If the concentration is less than 0.005 mol/mol, the complex between the aluminum ion and the solubilizing reagent is insufficiently destroyed, and even if the concentration exceeds 5 mol/mol/mol, no further improvement in the insolubilizing effect is observed. It is preferable to adjust the pH of the calcium aqueous solution to a range of 4 to 10. [Example] The present invention will be specifically explained below with reference to Examples. In the examples, the solubility is 100 spherical particles (approximately 0.5
After dispersing g) in 100 ml of room temperature distilled water and stirring for 1 hour, the state of dissolution was checked, and those in which none of the 100 particles had dissolved or lost their shape were judged to be insoluble, and the others were judged to be dissolved. Furthermore, the pH of this dispersion was measured. The stress required to break the spherical object was determined by placing the spherical object on the platform of a rheometer and pushing the platform up 6 cm/min to determine the stress required to break the spherical object. Example 1 Pectin, sodium alginate, and katsupa carrageenan containing sodium as a countercation were separately dissolved to prepare 4% aqueous solutions of each. Next, prepare a 4.8% (0.2 mol/) aqueous solution (PH2.5) of aluminum chloride hexahydrate, and add 17.6% (0.6 mol/) trisodium citrate diwater to this.
Add it so that it becomes
Adjusted to 7.5. The mixed aqueous solution was transparent.
This was divided into three equal parts, and the above three types of acidic polysaccharide aqueous solutions were dropped into each mixed aqueous solution through a capillary having a diameter of 0.8 mm to obtain spherical objects with a diameter of about 2 mm. Take some of these and 2.2% of calcium chloride
(0.2 mol/) aqueous solution (PH8.1) for 3 minutes and then taken out to obtain spheres according to the present invention. Table 1 shows the properties of the obtained spherical products. Comparative Example 1 A 4% aqueous solution of each of pectin, sodium alginate, and Katupa carrageenan containing sodium as a countercation was dropped into a 4.8% aqueous solution of aluminum chloride through a capillary with a diameter of 0.8 mm to obtain spherical objects each having a diameter of about 2 mm. . When 100 grains of each type of spherical material were dispersed in 100 ml of distilled water, it was found that they were insoluble in water but strongly acidic. Comparative Example 2 In Example 1, the spherical object was taken out before being immersed in a 2.2% aqueous solution of calcium chloride. When we investigated their solubility, we found that they were neutral but soluble in water.

[Table] Example 2 A spherical material was obtained in exactly the same manner as in Example 1 except that aluminum sulfate was used instead of aluminum chloride used in Example 1. Example 3 A coagulating solution containing 4.8% aluminum chloride (hexahydrate) and 17.6% trisodium citrate and having a pH adjusted to 7 with acetic acid was prepared by using a 7% sodium alginate aqueous solution through a nozzle with a pore size of 20 microns. The fibers were obtained by injecting the fiber into an aqueous solution containing 2.2% calcium chloride for 5 minutes. Such fibers were insoluble even in hot water at 75°C, and the pH of the liquid in which they were dispersed was 6.9. Example 4 A 5% carrageenan aqueous solution was cast onto a flat plate to a thickness of 0.5 mm, and then dried in a vacuum dryer at 95°C for 2 hours and peeled off to form a carrageenan film (A) with a thickness of 25 microns. Obtained. Film (A) is treated with aluminum chloride (hexahydrate).
A film (B) was obtained by immersion in a 4.8% (0.2 mol/) aqueous solution (PH2.5) for 2 minutes. Next, add Flume (A) to aluminum chloride (hexahydrate).
4.8% (0.2 mol/) and trisodium citrate
Contains 17.6% (0.6 mol/) and has a pH of 7.2 with acetic acid.
A film (C) was obtained by immersing the film in a solution prepared in 1 for 2 minutes. Furthermore, the film (C) was mixed with 2.2% (0.2%) of calcium chloride.
The film was immersed in an aqueous solution of mol/) for 5 minutes.
I got (D). Four types of films (A), (B), (C), and (D) were tested for solubility, dispersion pH, and tensile strength, and the results shown in Table 2 were obtained.

【table】

Claims (1)

[Claims] 1. An acidic polysaccharide aqueous solution containing an aluminum salt and a solubilizing reagent for the aluminum salt at pH 4 to 10.
1. A method for insolubilizing an acidic polysaccharide, which comprises contacting an aqueous solution of the acidic polysaccharide and then contacting the aqueous solution of a water-soluble calcium salt. 2. The solubilizing reagent can dissolve the aluminum salt at a pH of 4 to 10, and the aqueous solution containing the aluminum salt and the solubilizing reagent for the aluminum salt has a pH of 4 to 10.
10. The method for insolubilizing acidic polysaccharide according to claim 1, wherein the acidic polysaccharide is adjusted to 10%. 3. The method for insolubilizing an acidic polysaccharide according to claim 1 or 2, wherein the acidic polysaccharide is Katupa carrageenan containing sodium as a countercation. 4. Claim 1, wherein the aluminum salt is aluminum chloride, aluminum sulfate, aluminum nitrate, or a combination thereof.
3. The method for insolubilizing acidic polysaccharides according to item 1, 2 or 3. 5. The method for insolubilizing acidic polysaccharides according to claim 1, 2, or 3, wherein the solubilizing reagent is a hydroxypolycarboxylic acid or a salt thereof. 6. The method for insolubilizing acidic polysaccharides according to claim 5, wherein the hydroxypolycarboxylic acid or its salt is citric acid, tartaric acid, malic acid, or its potassium salt or sodium salt. 7. The method for insolubilizing acidic polysaccharides according to claim 1 or 3, wherein the water-soluble calcium salt is calcium chloride, calcium nitrate, calcium acetate, calcium lactate, or a combination thereof. 8. A method for insolubilizing an acidic polysaccharide according to claim 1, which comprises bringing the acidic polysaccharide in the form of droplets into contact with an aqueous solution containing an aluminum salt and a solubilizing reagent for the aluminum salt.