JPS5852999B2 - Stevioside Noseiseihou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves adsorbing a stevioside-containing hydroxyl solution extracted with water from Stevia raw leaves using a synthetic adsorbent that selectively adsorbs stevioside without using an ion exchange resin, and then using an organic medium. The present invention relates to a method for purifying stevioside, in which stevioside is desorbed using stevioside, and the organic acid medium is further treated with a weakly basic anion exchange resin.

Conventionally, the purification method for stevioside involves extracting Stevia leaves with water, which contains stevioside, and then performing a two-stage purification process using both a strongly acidic cation exchange resin and a weakly basic anion exchange resin to improve the purity of stevioside. A widely known method is to increase the amount of water to about 45-55%, then concentrate or dry up a large amount of water, and then crystallize as an organic enzyme solution such as methanol or dioxane to obtain crystals. .

However, although the purification method using the above-mentioned ion exchange resin is an excellent method with little loss of steposide, the following problems have not yet been solved in case of industrialization.

(1) When a stevioside-containing aqueous extract is passed through a cation exchange resin, sludge is generated, contaminates the cation exchange resin, and impairs liquid permeability.

(2) A two-stage purification process using a cation exchange resin and an anion exchange resin is required, which places a particularly heavy burden on the anion exchange resin.

(3) Since the two-stage purification treatment is performed, the amount of liquid after treatment becomes extremely large.

(4) When stevioside is crystallized from aqueous liquid, the crystallization rate is low, so in order to improve the crystallization rate, it is effective to convert the aqueous to an organic solvent system. It is necessary to condense a large amount of water and then convert it into an organic solvent acid solution.

Therefore, as a method for reducing the above-mentioned unresolved problems while maintaining the advantages of the ion exchange method, it is conceivable to extract Stevia raw leaves using an organic eluent or a water-containing organic solvent instead of extracting them with water.

In other words, by directly ion-exchanging the extract obtained by solvent extraction, the infusible substances generated when the liquid is passed through the cation exchange resin are removed during the extraction stage, so the operation to remove the insoluble substances is not necessary. Can be omitted.

In addition, since the processing liquid is an organic solvent, it requires less heat of evaporation, making it easier to concentrate than in the case of water extraction.However, in this case, the purification effect of the ion exchange resin is inferior to that of an aqueous system. In addition, since a large amount of organic solvent is used in the extraction process, it is necessary to recover the organic solvent, resulting in problems such as the process being more complicated than in the case of water extraction.

As a purification method for stevioside, a purification method using activated carbon in this pond can be considered, but since stevioside is extremely strongly adsorbed to activated carbon, it is difficult to desorb it, and the recovery rate of stevioside is low, so this method cannot be called a preferable method. .

As mentioned above, there is still room for investigation into the industrial purification method of stevioside, and in order to establish its position as a sweetener that is advantageous in terms of quality and price, it is necessary to find an effective purification method. Currently, there is a strong demand for this.

Therefore, as a result of intensive research and search for a highly selective adsorbent that can adsorb stevioside well and desorb it easily, we found a commercially available product called a synthetic adsorbent that is extremely suitable for this purpose. The present invention was achieved by discovering that this method is effective and also reduces the burden on the anion exchange resin in the subsequent stage.

The synthetic adsorbent referred to here is, for example, HP resin sold by Mitsubishi Chemical Industries, Ltd., which is a hard, insoluble, porous resin with a giant network structure produced by polymerizing styrene and divinylbenzene using a special method. This is a non-polar polymer with a characteristic Van de adsorption due to hydrophobic bonds, interactions between dipoles, hydrogen bonds, etc.
The r Waals force plays an important role, and since the adsorption force is generally small, it has the characteristic that adsorbed substances can be easily and quantitatively desorbed.

The invention will now be described.

That is, by passing an aqueous extract of Stevia leaves and a synthetic adsorbent as an aqueous suspension through a column packed to prevent air bubbles from entering, stevioside in the aqueous extract is synthesized along with some impurities. Adsorbed by adsorbent.

In this case, the conditions for processing the extract by synthetic adsorption are as follows:
The amount of synthetic adsorbent used per 1 g of extract solid content is 5 to 20 r.
IL11 liquid passing rate 5V is preferably in the range of 1 to 6.

The pH of the aqueous extract during passage is slightly acidic or around neutral (p
H5 to H8) is required.

At this time, the components that are not adsorbed by the synthetic adsorbent are discharged into the water effluent, but the sweetness of stevioside is hardly felt in the water effluent. Since the presence of stevioside was not recognized from the analysis results, it can be seen that almost all of the stevioside in the aqueous extract was adsorbed by the synthetic adsorbent.

When extracting stevioside from stevia leaves with water, it is necessary to extract at around neutrality in order to suppress the extraction of impurities as much as possible.

Next, when this extract is passed through a synthetic adsorbent column, the pH is preferably around neutral considering the treatment of the effluent after stevioside adsorption.

In other words, this effluent is unnecessary as wastewater, but since it contains perishable organic substances, it cannot be discharged and discarded without treatment for environmental conservation reasons.For example, after decomposition and concentration through biological treatment, solid It is necessary to carry out some kind of treatment such as oxidation or combustion.

Particularly when concentrating, it is desirable to reduce the amount of effluent as much as possible in order to reduce concentration operations and costs.

For this purpose, the effluent is reused for the next extraction of Stevia leaves, but in this case, if the pH of the extract is below 5, not only will the extraction rate of stevioside drop significantly, but the synthetic adsorbent column will pass through. The liquid properties are also poor.

Generally, the pH of the effluent tends to drop economically, so when it is used for the next extraction, it is desirable to neutralize it to pH 7-8 before use.

On the other hand, if the pH of the effluent is 8 or higher, the next extraction will be carried out in an alkaline state, which is undesirable because unnecessary impurities will be unnecessarily extracted.

Furthermore, even if it is permissible to discard the effluent without treatment, it must be neutralized to at least the pH specified in the wastewater standards.

For the reasons mentioned above, it is necessary to perform the extraction of Stevia raw leaves and the passage of the extract through the synthetic adsorbent at a pH within the range of 5 to 8.

Incidentally, if the permeability of the extract to the column is not good, this can be easily solved by mixing and dispersing an appropriate amount of p-superior into the extract and passing the liquid through the column.

After passing the aqueous extract, the column is washed with water to remove non-adsorbed components remaining in the column.

Next, when an organic solvent capable of fermenting stevioside such as methanol or dioxane is used as a desorption solvent and the liquid is passed through the column, most of the components adsorbed on the synthetic adsorbent are easily desorbed and recovered.

Stevioside can be recovered almost quantitatively through this adsorption and desorption process.

Although some adsorbed components remain in the synthetic adsorbent that has been subjected to desorption and recovery treatment using an organic solvent, it can be regenerated with a dilute aqueous alkaline solution and can be used repeatedly.

When the above treatment is performed, the amount of stevioside water extract adsorbed onto the synthetic adsorbent, the amount of solid content desorbed and recovered by the desorption solvent, and the stevioside purity at this time are determined by the stevioside purity in the water extract and the treated water. Although it varies depending on the ratio of extract and synthetic adsorbent, the type and amount of organic solvent used for desorption, etc., an example is as follows.

Synthetic adsorbent HP-i manufactured by Mitsubishi Chemical Industries, Ltd.

150 g and 200 g of water extract solid content (stevioside purity 16%) were treated with respect to a filling volume of 11, and desorbed and recovered with methanol, and the following results were obtained.

As is clear from the table above, when a water extract with a stevioside purity of 16% is adsorbed onto a synthetic adsorbent and methanol is used as the desorption solvent, stevioside is purified to a purity of about 40-50% with a recovery rate of 90% or more. It turns out that it is possible.

Although the column method has been described here, it is not necessarily limited to the column method, and it is of course possible to carry out the method of the present invention by a batch method.

If the stevioside-containing water solution is only treated with a synthetic adsorbent, the purity of the stevioside is still low, not only when it is used as a sweetener, but also when obtaining highly purified stevioside by methods such as crystallization, the product yield is low. Also, since the quality of the sweetener is not sufficient, it is necessary to further treat it with an anion exchange resin.

In this case, the solution desorbed and recovered from the synthetic adsorbent using an organic adsorbent such as methanol can be directly passed through the weakly basic anion exchange resin without being concentrated to dryness, which simplifies the process and reduces the loss of stevioside. has few advantages.

By performing such a treatment, the crystallization of stevioside can be made easier, and the amount of heat required for concentrating the solvent can be reduced.

It was previously stated that when an organic solvent such as methanol is passed through both a cation exchange resin and an anion exchange resin, the purification effect is inferior to that when an aqueous solution is passed, but the method of the present invention When a synthetic adsorbent treatment is performed and then an anion exchange resin treatment is performed, it is easy to purify even a methanol solution to the same level as the positive and anion exchange resin method (aqueous solution passage).

By adsorption and desorption of stevioside by the first stage synthetic adsorbent of the present invention, water, which is an extraction solvent, can be easily converted to an organic solvent, which is a crystallization fermentation medium, and there is no need to concentrate the aqueous solution. .

Therefore, a sufficient amount of water can be used to completely extract stevioside from stevia frozen vegetables.

As a result, if methanol is used as a desorption solvent, stevioside can be purified to a purity of about 40-50% with a recovery rate of 90% or more, which significantly simplifies the process compared to conventional purification methods. Is possible.

Immediately after this, the second stage anion exchange resin treatment is carried out to adsorb impurities that could not be removed in the first stage treatment to the ion exchange resin, while stevioside is not adsorbed at all and flows out together with the organic solvent. Impurities can be separated to increase yield and purity.

In this case, the amount of anion exchange resin used per 1 g of solid content in the solution to be treated is 5 to 20 rfL11 The flow rate is s
Each of the ranges from v-i to 6 is preferred.

In addition, in the method of the present invention, the desorption medium from the synthetic adsorbent and the transport medium for the anion exchange resin treatment are not limited to methanol and dioxane.

The advantage of this method is that recovery of the organic solvent only needs to be carried out on the ion-exchange resin treated solution, while the water effluent containing impurities is only from the first-stage synthetic adsorbent treatment; Even including the wastewater generated from the recycling process, the amount of liquid wastewater is significantly reduced.

Although the usefulness of the method of the present invention is clear from the above results, it will be further explained by showing comparative examples and examples.

Comparative Example 1500 cc of hot water extract of Stevia frozen vegetables (pH
5,7, solid content 78g 1 purity 15.4%, stevioside 12.0g) was packed in a column filled with a strongly acidic cation exchange resin (trade name, Amberlite IR-120H type) 11 and a weakly basic anion exchange resin ( When the liquid was sequentially passed through a column filled with Organo Clothing Amberlite IRA-930H type 11 at Sv of approximately 3, a phenomenon was observed in which insoluble matter was precipitated when the liquid was passed through the IR-12Q column, resulting in poor liquid permeability. After the two-stage treatment, the total liquid volume increased to 2500 cc (hydroxide solution), and a solid content of 22.8 g (purity 50.0%, stevioside 11.4 g) was obtained.

The recovery rate of stevioside at this stage was 95.0%.

After concentrating 2500 CC of hydroxyl solution to dryness, methanol 1
The mixture was fermented again to 00CC, impurities were removed, and crystallized at 5°C for 48 hours.

The results were 8.0 g of crystals (purity 85.5%, 6.84 g stevioside) and 13.6 g crystallization residue (purity 29%).
．． 8% stevioside (4.06 g) was obtained.

S
(2) The solution was passed through the solution at a temperature of about 5, and non-adsorbed components were removed by washing with water.

During this liquid passage, no precipitation of insoluble matter was observed, and the liquid permeability was good.

Next, in order to recover the adsorbed components, desorption was performed using methanol 11, but since the first liquid that flows out has a low methanol content and a high water content, this part was removed, and the liquid was removed after the methanol content became high. was recovered.

This methanol solution is saturated with methanol to create a weakly basic anion exchange resin (trade name: Amberlite RA-9).
SVVS2 was passed through a column packed with 30H type) 17.

Total liquid volume after two-stage treatment is 1500cc (methanol acid liquid)
and the solid content is 21. og (purity 53.3%, stevioside 11.2 g) was obtained.

The recovery rate of stevioside at this stage was 93.2%.

After concentrating 1500 cc of methanol solution to 100 cc, insoluble materials were removed and crystallization was performed at 5° C. for 48 hours.

As a result, 8.0 g of crystals (purity 87.9%, 7.03 g of stevioside) and 12.5 g of crystallization residue (purity 29%) were obtained.
．． 6% stevioside (3.7 g) was obtained.

Claims (1)

[Claims] 1. The extract obtained by contacting the dried leaves of Stevia rebaudiana Bertoni with water or hot water at pH 5,0 to 8.0 is brought into contact with a non-polar synthetic adsorbent at p) 15.0 to 8.0. After selectively adsorbing stevioside onto the adsorbent, the adsorbent is contacted with an organic solvent to desorb stevioside, and the stevioside-containing organic solvent is further contacted with a weakly basic anion exchange resin. Stevioside purification method characterized by process coupling.