JPH0613561B2 - Pectin purification method - Google Patents

Description

The present invention relates to a method for purifying pectin to obtain high quality pectin at low cost.

Pectin is a colloidal cell wall polysaccharide that is widely contained in the plant kingdom in general as a substance useful for packing between cells and supporting tissues, and is mainly α-of D-galacturonic acid.
It consists of 1,4 bonds. Particularly, citrus peels such as lemons, limes, oranges and grapefruits, apples and the like contain a considerable amount of high-quality pectin, and in the Western countries pectin is produced from these as raw materials, jams, marmalades, jelly confectionery, fruit juice drinks. Widely used in food industry as yogurt, soy milk, etc.

The general method for producing pectin is as follows. After treating lime-treated or untreated citrus peel with water or water containing mineral acid, pectin is extracted with mineral acid, and metal salts such as aluminum, copper and iron are added to this extract to form pectin as a metal salt. After being precipitated, or as it is or concentrated in the extract, a water-miscible organic solvent is added to precipitate pectin and the pectin is recovered. Particularly in the case of the metal salt precipitation method, it is necessary to subsequently wash the precipitate with an aqueous acid solution / water-miscible organic solvent to remove the metal content.

However, the pectin produced from citrus peels and the like by such a method is unsatisfactory in gelling power, water-soluble viscosity characteristics and the like.
In citrus peels and the like, pectin exists as protopectin in which it binds with cellulose, and it contains polyvalent metal ions such as calcium as well as galactan and araban, and many kinds other than pectin in the extract. This is because these substances are eluted and these impurities adversely affect the quality of pectin. Also, in the metal salt precipitation method, the residual metal used has a significant adverse effect on the properties of pectin. Therefore, in order to improve the quality of pectin, it is necessary to wash the pectin precipitate a large number of times with a large amount of acid aqueous solution-water miscible organic solvent. However, this method uses a large amount of water-miscible organic solvent, which increases the production cost of pectin. As another purification method, a method using a cation exchange resin is known (see Japanese Patent Laid-Open No. 50-148399). However, this method is also economically disadvantageous because the equipment cost is increased and the cation exchange resin must be regenerated. Therefore, although the production of citrus fruits is large in Japan, powdered pectin is not produced from the peel, and the powdered pectin used for each of the above-mentioned purposes is currently imported.

The present inventors have completed the present invention as a result of conducting research to obtain high-quality pectin at low cost.

The present invention is a pectin precipitate obtained by adding a metal salt selected from aluminum, copper and iron to a pectin solution,
It was obtained by washing with a mixed solution of a sulfuric acid aqueous solution / water-miscible organic solvent in a proportion that does not dissolve it, adding calcium hydroxide or / and barium hydroxide to the separated washing solution to neutralize, and removing the solid matter. A method for purifying pectin, which comprises adding sulfuric acid to a water-water-mixed organic solvent and reusing it for washing a pectin precipitate.

The metal salt precipitate of pectin used in the present invention is a method of extracting pectin from a pectin-containing plant peel using a mineral acid, preferably sulfuric acid, by a conventional method, and aluminum is added to this extract.
It is obtained by adding a salt of a metal such as copper or iron.

Water-miscible organic solvents include methanol, ethanol,
Alcohols such as isopropanol, acetone, methyl ethyl ketone, tetrahydrofuran, N, N-dimethylformamide and the like are used alone or as a mixture.

As a mixed solution of an aqueous sulfuric acid solution / water-miscible organic solvent in a ratio such that the pectin precipitate is not substantially dissolved, an aqueous sulfuric acid solution /
The volume ratio of the water-miscible organic solvent is preferably in the range of 1 / 0.65 to 1/20. Further, it is appropriate that the concentration of sulfuric acid at the time of washing the pectin precipitate is such that the pH in the washing system is 3.0 or less,
PH 0.8-1.8 for preventing pectin deterioration and cleaning efficiency.
Is particularly preferable.

In carrying out the present invention, first, the metal salt precipitate of pectin is washed with the above-mentioned mixed solution of aqueous sulfuric acid solution / water-miscible organic solvent (hereinafter referred to as a washing solution). The amount of the washing solution used is preferably 1 to 3 parts by weight with respect to 1 part by weight of the pectin precipitate. As the washing method, a method of adding a washing solution to the pectin precipitate and stirring is usually used. The washing can be performed at room temperature and is completed in 30 to 60 minutes. The washing may be divided into several times.

After the washing, the pectin precipitate and the washing liquid are separated, and calcium hydroxide and / or barium hydroxide are added to the separated liquid (hereinafter referred to as a washing waste liquid) to neutralize it, thereby forming an insoluble substance. This is separated by centrifugation, excess, etc., and sulfuric acid is added to this washing waste liquid to adjust the composition, and then reused for washing the pectin precipitate. Sulfuric acid may be added to the wash effluent or to the wash effluent and pectin precipitate slurry system. Rewashing and solid-liquid separation may be repeated several times.

After the completion of rewashing, the pectin precipitate is recovered, preferably treated with aqueous ammonia, and then dried to obtain pectin having excellent gelling ability and aqueous solution viscosity characteristics.

According to the method of the present invention, the acid used for the pectin precipitate washing liquid is sulfuric acid, and the alkali used for neutralizing the washing waste liquid separated from the pectin precipitate is calcium hydroxide or / and barium hydroxide, whereby the pectin precipitate is obtained. The metal ions in the cleaning waste liquid separated from the product are metal hydroxides,
In addition, sulfate ions precipitate as calcium sulfate and / or barium sulfate, and the coexisting impurities in the cleaning liquid are adsorbed to these precipitates, so the impurities can be removed by simply removing these precipitates and reused. A wash solution from a water-water miscible organic solvent can be recovered. As a result, the amount of the cleaning liquid, especially the organic solvent used is reduced, and high-quality pectin can be manufactured at low cost. Other than sulfuric acid-calcium hydroxide or / and barium hydroxide system, such as hydrochloric acid-calcium hydroxide or / and barium hydroxide system,
In hydrochloric acid or sulfuric acid-ammonia system, etc., the metal ions in the cleaning waste liquid separated from the pectin precipitates are precipitated as metal hydroxides during neutralization, but chlorine ions or sulfate ions are water-soluble with the alkali metal for neutralization. Form a salt and remain as ions in the recovered washing solution, and gradually become concentrated in the process of reusing the washing solution, so a large amount of salt remains in the obtained pectin, resulting in a decrease in the gelling power of pectin. It is not preferable.

Example 0.03N sulfuric acid 4 was added to 350g of dried dried tangerine juice, and the mixture was stirred at room temperature for 30 minutes. After repeating this operation twice, the pericarp removed by washing with water to remove excess acid was added to water 8, the pH was adjusted to 2.0 with sulfuric acid, and the mixture was stirred at 90 ° C. for 30 minutes to extract pectin. Next, the undissolved residue is separated using a cloth, for example, gauze, and the diatomaceous earth aid is added to the separated liquid.
0.5% was added and precision filtration was performed. Aluminum sulfate 14-18 hydrate was dissolved and added to the obtained clear solution at a rate of 0.5% to precipitate and separate pectin. To this pectin precipitate, a double amount of isopropyl alcohol aqueous solution was added so that the concentration of isopropyl alcohol in the slurry system was 60%, and 1% of the slurry system was added.
After adding a volume of concentrated sulfuric acid and stirring for 30 minutes, a pectin precipitate and a washing waste liquid were separated using gauze.

Calcium hydroxide is added to the separated acid aqueous solution-isopropyl alcohol washing waste liquid to neutralize, the precipitate is removed by centrifugation, and the obtained clear liquid is added again to the separated pectin precipitate to form a slurry system. On the other hand, 1% by volume concentrated sulfuric acid was added, and after stirring for 30 minutes, a pectin precipitate and a washing waste liquid were separated using gauze. After repeating the above washing waste liquid recovery-precipitation washing operation, in order to remove excess acid,
The washing waste liquid recovery-precipitation washing operation was performed without adding sulfuric acid. Then, the washing waste liquid is collected, the collected washing liquid is added to the separated pectin precipitate, the pH is adjusted to 3.5 to 4.0 with aqueous ammonia, and then the pectin precipitate is fractionated and pressed and dried to obtain 49 g of powdered pectin. .

Comparative Example 1 51 g of powdered pectin was obtained in the same manner as in Example 1 except that ammonia water was used in place of calcium hydroxide in neutralizing the cleaning waste liquid.

Comparative Example 2 52 g of powdered pectin was obtained in the same manner as in Example 1 except that hydrochloric acid was used as the acid used for washing the skin, extraction and washing of the pectin precipitate.

Comparative Example 3 49 g of powdered pectin was obtained in the same manner as in Example 1 except that a fresh isopropyl alcohol aqueous solution was used instead of the isopropyl alcohol aqueous solution recovered by neutralization.

The amount of isopropyl alcohol used in the above Examples and Comparative Examples, the calcium and aluminum contents of the obtained powder pectin, the viscosity of the aqueous solution and the jelly grade are shown in the following table.

Claims (1)

[Claims] 1. A pectin precipitate obtained by adding a metal salt selected from aluminum, copper and iron to a pectin solution is a mixed solution of an aqueous sulfuric acid solution and a water-miscible organic solvent in a ratio that does not dissolve the pectin precipitate. After washing with water, calcium hydroxide and / or barium hydroxide is added to the separated washing solution to neutralize the solution, and sulfuric acid is added to the water-water mixed organic solvent obtained by removing the solid matter to wash the pectin precipitate. Characterized by being reused in
Pectin purification method.