JPH0576482B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention is a method for recovering acidic polysaccharides from an aqueous solution of acidic polysaccharides obtained by extraction from substances containing acidic polysaccharides or by introducing acidic groups. Regarding how to. [Prior Art] Acidic polysaccharides have unique physical properties such as developing high viscosity or gelation when dissolved in water, and are used in a wide range of fields such as foods, textiles, paper manufacturing, cosmetics, and pharmaceuticals. Polysaccharides, including acidic polysaccharides, are generally recovered from the extraction filtrate obtained by extracting the polysaccharides from raw materials containing the polysaccharides into water using an appropriate method, and filtering the extraction residue as necessary. It becomes a product.
Recovery methods include (1) a method of directly removing water from the extraction filtrate, such as spray drying or drum drying; (2)
A method in which a water-miscible organic solvent is added to the extraction filtrate to precipitate the polysaccharide, and then the polysaccharide is separated and dried.(3) A certain cation is added to the extraction filtrate to precipitate the polysaccharide, and then the polysaccharide is precipitated again with acid or alkali. A method of dissolving and re-precipitating, for example with a water-miscible organic solvent, and separating and drying this, (4)
There is a method in which polysaccharides are precipitated by adding certain cations to the extraction filtrate, and aluminum is removed by washing with a water-miscible organic solvent containing acid or alkali. Method (1) is not only economically disadvantageous as it requires a large amount of latent heat to evaporate dozens of times more water than the recovered polysaccharide, but also leaves water-soluble impurities remaining in the polysaccharide. Therefore, it has the disadvantage of low product purity. Method (2) can solve the drawbacks of method (1) to some extent, but it requires several tens of times more water-miscible organic solvent than the polysaccharide, and it requires a recovery process to recover this organic solvent. This method has the disadvantage that the costs associated with equipment and recovered heat are large. The polysaccharides that can be applied to method (3) are limited to acidic polysaccharides; however, acidic polysaccharides precipitate with extremely high selectivity, resulting in high quality products; Even if an organic solvent is used in combination, the amount of water-miscible organic solvent used is significantly reduced, so it is also economically advantageous. In particular, aluminum ions are excellent as cations because they are non-toxic.
However, in this method, the acid or alkali used must have a concentration of 1 to 6 normal;
Acidic polysaccharides deteriorate significantly due to such a strongly acidic or strongly alkaline atmosphere. Additionally, a neutralization step is required to obtain the final product. Recovery of acidic polysaccharides for handling strong acids or strong alkalis,
Furthermore, it has the disadvantage that recovery operations for water-miscible organic solvents are difficult, and despite being an excellent method as mentioned above, it has only been put into practical use in very few cases. be. Method (4) has the same advantages as (3), and is also superior in that acidic polysaccharides can be solubilized simply by washing without dissolving and reprecipitating; however, like (3), It is necessary that the acid or alkali used has a concentration of 1 to 6 normal, and such a strongly acidic or strongly alkaline atmosphere causes significant deterioration of the acidic polysaccharide. Additionally, a neutralization step is required to obtain the final product. There is a drawback that recovery of acidic polysaccharides and further recovery of water-miscible organic solvents becomes difficult due to the handling of strong acids or strong alkalis. [Object of the invention] In view of the current situation, the above method using aluminum
The object of the present invention is to provide a method for recovering polysaccharides which is superior in quality and economy by eliminating the drawbacks while retaining the advantages of the recovery method (4). [Structure of the Invention] That is, the gist of the present invention is to add a water-soluble aluminum salt to an aqueous solution of an acidic polysaccharide, and then convert the precipitate formed by using one or more aluminum solubilizing reagents selected from polyphosphates, hydroxypolycarboxylic acids, or salts thereof. A method for recovering acidic polysaccharides, which comprises washing with a mixed solution of an aqueous solution and a water-miscible organic solvent. That is, the present invention provides (1) When an aluminum solubilizing reagent is added to a dispersion of aluminum hydroxide precipitates formed when an aqueous solution containing aluminum ions is brought to a pH of 4 to 11, the aluminum hydroxide precipitates are dissolved regardless of the pH range. (2) When an acidic polysaccharide precipitated with aluminum ions is washed with a mixture of an aqueous solution of an aluminum solubilizing reagent and a water-miscible organic solvent, aluminum is removed from the precipitate and the acidic polysaccharide becomes soluble. They discovered this phenomenon and applied it to a method for recovering acidic polysaccharides, which involves washing the precipitate formed by adding a water-soluble aluminum salt to an aqueous acidic polysaccharide solution. The acidic polysaccharide used in the present invention is a polysaccharide containing an acidic substituent in its chemical structure, and examples of the acidic substituent include a carboxyl group, a sulfate group, and a phosphate group. In the present invention, the acidic polysaccharides include agar, furcerelan,
Carrageenan, sodium alginate, pectin, gum arabic, xanthan gum, or chondroitin sulfate, mucopolysaccharides such as heparin, and polysaccharides chemically introduced with acidic substituents, such as carboxymethylated cellulose, carboxymethylated starch, carboxymethylated starch, etc. Mention may be made of methylated guar, sulfated cellulose, sulfated starch, sulfated agar, phosphorylated cellulose, and phosphorylated starch. As the water-soluble aluminum salt used in the present invention, aluminum chloride, aluminum sulfate, or aluminum potassium sulfate is used. Moreover, the aluminum solubilizing reagent means a reagent that does not precipitate aluminum ions as aluminum oxide in any pH range. In other words, aluminum ions become aluminum oxide and precipitate in the neutral pH range of 4 to 11, but it refers to a reagent that prevents this from precipitating. Such reagents include polyphosphates, hydroxypolycarboxylic acids, or salts thereof. Examples of polyphosphates include water-soluble salts of hexametaphosphoric acid, tetrametaphosphoric acid, and pyrophosphoric acid, such as sodium salts and potassium salts.
Alternatively, as the hydroxypolycarboxylic acid or its salt, citric acid, tartaric acid, malic acid, or a water-soluble salt thereof such as sodium salt or potassium salt can be used. As the aluminum solubilizing reagent, two or more of these can also be used in combination. The concentration of the reagent in the aluminum solubilizing reagent aqueous solution is often 0.5 to 30% by weight; polysaccharides are not sufficiently dissolved at concentrations lower than this range, and even if the concentration exceeds 30% by weight, there is no improvement in the effect. It is difficult to see and is economically disadvantageous. Examples of the water-miscible organic solvent used in the present invention include methanol, ethanol, isopropanol, acetone, and tetrahydrofuran, and a combination of these may also be used. As the mixed solution of the aluminum solubilizing reagent aqueous solution and the water-miscible organic solvent, a mixture containing a water-miscible organic solvent in an amount of 10 to 300% of the volume of the aluminum solubilizing reagent aqueous solution is preferably used. If it is less than 10%, there is no re-dissolution prevention effect, and if it is more than 300%, it becomes difficult to remove aluminum and it is also economically disadvantageous. The amount of the mixed liquid used for washing is preferably 1 to 10 times the amount of precipitation. If the amount is less than 1 times, a sufficient cleaning effect cannot be obtained, and if the amount exceeds 10 times, no significant improvement in the effect will be observed. Note that it is effective to divide the mixed solution into several parts and repeat the cleaning several times. The stable PH range of acidic polysaccharides differs depending on the type, but in the method of the present invention, the pH of the aqueous solution when redissolving the acidic polysaccharides precipitated with aluminum can be set completely arbitrarily. Its solubilization effect is not affected by pH, and there is no need for a subsequent neutralization step, so it has the characteristics of being able to prevent deterioration of acidic polysaccharides. [Examples] The present invention will be described in more detail below with reference to Examples. In the Examples, the viscosity was measured using a B-type viscometer at 30 rpm, and the breaking strength of the gel was measured using a Neocard meter. Example 1 Add 2000 parts of water to 100 parts of Yukiyuma cotoni
60 parts of aluminum chloride hexahydrate was added to 2,050 parts of Katupa carrageenan solution obtained by heating and extraction at 95°C and filtration to obtain 170 parts of carrageenan precipitate. Of this, 10 parts are 70% by volume of an 8% aqueous solution of dipotassium citrate adjusted to pH 8 and 30% by volume of isopropanol.
After repeating the operation of adding 25 parts of a mixed solution consisting of
Got 2.82 copies. The aluminum content of the carrageenan is 450 ppm, and the viscosity of its 1.5% aqueous solution is
It was 108 centipoise at 75°C. Moreover, the breaking strength of the gel was 440 g/cm ² . Comparative Example 1 Using 10 parts of the carrageenan precipitate obtained in Example 1, the operation of adding it to 25 parts of a mixed solution consisting of 70% by volume of a 2N hydrochloric acid solution and 30% by volume of isopropanol and stirring and washing was repeated three times. After that, it was neutralized with isopropanol containing 1% caustic potash and dried to obtain 2.76 parts of Katupa carrageenan. The aluminum content of the carrageenan is 1740 ppm, and the viscosity of its 1.5% aqueous solution at 75°C is
3.8 centipoise, and the breaking strength of the gel is 30
g/ ^cm2 . Example 2 350 g of dried squeezed fruit peel of a summer mandarin orange was added to 0.02 N hydrochloric acid aqueous solution 4, stirred at room temperature for 30 minutes, and filtered. The procedure was repeated twice, and then washed with water.
water, adjust the pH to 2.0 with hydrochloric acid, stir at 90℃ for 30 minutes to extract pectin, filter out the undissolved residue, add 0.5% of diatomaceous earth filter aid to this extract, mix and perform microfiltration. I did it. 0.5% aluminum chloride hexahydrate was dissolved and added to the obtained clear filtrate to obtain 500 g of pectin precipitate. to the precipitate
Add 12% sodium hexametaphosphate to 500ml of 60% isopropanol aqueous solution and pectin, stir and wash for 10 minutes, adjust to pH 3.8 with ammonia water, filter, press dry and crush to obtain powdered pectin 50%.
I got g. The pectin contained 520 ppm aluminum. Example 3 47 g of powdered pectin was obtained in the same manner as in Example 2, except that disodium citrate dihydrate was used instead of sodium hexametaphosphate. The aluminum content of the pectin was 590 ppm. Comparative Example 2 Pectin precipitate was obtained by repeating the operation of Example 2.
To the precipitate was added 500 ml of 60% isopropanol aqueous solution, washed with stirring for 10 minutes, adjusted to pH 3.8 with aqueous ammonia, filtered, compressed, dried and pulverized to obtain 52 g of powdered pectin. The pectin contained 7300 ppm aluminum. The quality of the pectin obtained in Examples 2 and 3 and Comparative Example 2 is shown in the table. 【table】

Claims (1)

[Scope of Claims] 1. A precipitate formed by adding a water-soluble aluminum salt to an aqueous solution of an acidic polysaccharide, 1 selected from polyphosphates, hydroxypolycarboxylic acids, or salts thereof.
A method for recovering acidic polysaccharides, which comprises washing with a mixed solution of an aqueous solution of at least one aluminum solubilizing reagent and a water-miscible organic solvent. 2. The method for recovering polysaccharides according to claim 1, wherein the polyphosphate is a water-soluble salt of an acid selected from the group consisting of hexametaphosphoric acid, tetrametaphosphoric acid, and pyrophosphoric acid. 3. Recovery of the acidic polysaccharide according to claim 1, wherein the hydroxypolycarboxylic acid or its salt is a sodium salt or potassium salt of an acid selected from the group consisting of citric acid, tartaric acid, and malic acid. Method. 4. The method for recovering acidic polysaccharides according to claim 1, wherein the water-miscible organic solvent is methanol, ethanol, isopropanol, acetone, or tetrahydrofuran.