JPS6256158B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for extracting and purifying stevioside from stevioside-containing plants. Stevioside is derived from Stevia rebaudiana Bertoni, a perennial plant of the Asteraceae family that grows primarily in Paraguay and parts of Brazil in South America.
Rebaudiana Bertoni) is a sweetening ingredient contained in
It is a white crystal with a molecular weight of 804.9 and a melting point of 198°C. It is soluble in hot water and easily soluble in various organic solvents, and its sweetness is said to be about 100 to 300 times that of sugar. It has advantages not found in sugars, such as a mild sweet taste, low calorie, non-fermentability, and non-viscosity, making it an excellent sweetener for food processing. Conventionally, the method for extracting and purifying stevioside from stevia leaves is to take advantage of the fact that stevioside is easily soluble in water and polar organic solvents, and extract it with hot water or hydrous alcohol to remove impurities and coloration in the extract. A known method is to remove a substance using an ion exchange resin or lead acetate and hydrogen sulfide, concentrate it, and then crystallize it using a solvent such as methanol. However, with this method, the extract from Stevio leaves has a dark brown color, and the solid content in the extract is about 280 g per 1 kg of dried leaves, of which only about 80 g is stevioside. Furthermore, the purity of stevioside obtained by this method is about 80%. As described above, it is not industrially easy to efficiently separate stevioside from other components and obtain highly pure stevioside, and the cost of purification inevitably increases as a proportion of the product cost. In addition, it is difficult to obtain highly pure crystals, so although it is expected to be a new sweetener, market development is currently delayed. In view of these circumstances, the present inventors conducted intensive research and found that activated carbon with specific pore characteristics adsorbs stevioside well from a stevioside-containing liquid. The present inventors have discovered that the present invention can be desorbed and purified, and based on this knowledge, they have completed the present invention. That is, the present invention extracts a stevioside-containing plant by (1) extracting it with water or hydrous alcohol, (2) contacting the extract with activated carbon having the following pore characteristics, and reducing the total pore volume of pores with a diameter of 15μ or less to 1c. Total pore volume of pores with a diameter of .c./g or more and a diameter of 300Å or less 0.6cc/
Average pore diameter of pores with a diameter of 300 Å or more
This is a stevioside purification method characterized by (3) eluting stevioside adsorbed on activated carbon with a hydrophilic organic solvent, and (4) concentrating and crystallizing the eluate if necessary. In the present invention, stevioside-containing plants are first extracted with water or hydrous alcohol. Stevioside-containing plants include, for example, Stevia Rebaudiana Bertoni.
Bertoni), etc. This stevioside is contained in any part of a stevioside-containing plant, such as leaves, petioles, buds, and stems. Particularly preferred are leaves and petioles. The leaves and petioles can be either dry or moist. Hydrous alcohols include, for example, hydrous methanol with a water content of at least 20% (V/V);
Examples include hydrous ethanol. The amount of water or water-containing alcohol to be used is preferably about 5 to 20 times by weight per 1 part of the stevioside-containing plant. The extraction temperature is room temperature to 100°C, preferably room temperature to 70°C. It can also be extracted with water or hydroalcohol with an alkaline pH. The extracted liquid is subjected to known treatment operations such as adding slaked lime or diatomaceous earth, if necessary, to remove colloidal particles in the extracted liquid. Next, this extract is brought into contact with activated carbon having the following pore characteristics. Total pore volume of pores with a diameter of 15 μ or less: 1 c.c./g or more, total pore volume of pores with a diameter of 300 Å or less: 0.6 cc/g
Average pore diameter of pores with a diameter of 25 Å or more, and a diameter of 300 Å or less
Of the above pore characteristics, the total pore volume of pores with a diameter of 15μ or less can be determined, for example, by mercury intrusion method, nitrogen gas adsorption method (Tominaga Kei: Adsorption, pp. 95-113 (1967), Kyoritsu Shuppan) It is measured by methods such as Diameter 300
The total pore volume of pores of Å or less is measured, for example, by a method such as a nitrogen gas adsorption method (method described in the above-mentioned document). Also, the diameter is 300Å
The average pore diameter of the pores below is calculated by the BET formula (method described in the above literature) from the pore volume and nitrogen gas adsorption isotherm, assuming that the pores with a diameter of 300 Å or less are cylindrical. This value is calculated from the specific surface area by the following formula. Average pore diameter = 4 x pore volume/specific surface area (Note) The pore volume in this case refers to the total pore volume of pores with a diameter of 300 Å or less. Activated carbon with the specific pore characteristics described above can be produced by soaking wood materials such as wood chips, sawdust, and fruit shells in chemicals such as zinc chloride, phosphoric acid, and calcium chloride at approximately 600 to 700°C. After firing, it is obtained by removing added chemicals and washing with an acid such as hydrochloric acid. The activated carbon produced in this manner has a large ability to adsorb stevioside, and the adsorbed stevioside has the property of being easily desorbed by an organic solvent such as methanol. The activated carbon may be in the form of powder or granules, but granules are preferred for efficient adsorption and elution. Examples of the means for contacting with activated carbon include known means such as catalytic filtration, fixed bed adsorption, moving bed adsorption, and fluidized bed adsorption. Next, the stevioside adsorbed on the activated carbon is eluted with a hydrophilic organic solvent. Examples of the hydrophilic organic solvent include alcohols such as methanol, ethanol, and propanol, with methanol and ethanol being particularly preferred. The elution temperature is preferably room temperature to 80°C. The amount of the hydrophilic organic solvent is preferably about 2 to 10 times the volume of activated carbon. The eluate obtained in this way has a pale yellow color, but by the above procedure, the color in the extract is about 95%
About % has been removed. Furthermore, about 20 to 50% of the solid content in the eluate is stevioside. If necessary, the eluate is concentrated and then crystallized at a low temperature to obtain white, highly pure stevioside crystals.
The crystallization mother liquor contains about 6 to 9% of stevioside and about 12 to 19% of rebaudioside as a solid content, and when it is dried and powdered, it can be used as a sweetener. The activated carbon from which stevioside has been removed by the hydrophilic organic solvent is again subjected to adsorption of stevioside. Activated carbon whose adsorption or desorption ability has decreased due to repeated use can be adsorbed or eluted by washing with an alkaline substance such as caustic soda or aqueous ammonia, or an alkali-containing solvent such as alkaline methanol. Its ability is restored and it can be used to purify Stevioside again. In this way, activated carbon can be used repeatedly, so the unit consumption for the product is small, and manufacturing costs can be reduced. According to the present invention, an extract containing stevioside can be purified through a simple process, and highly purified stevioside can be obtained efficiently and at low cost. EXAMPLES The present invention will be specifically explained below with reference to Examples. Example 1 After extracting 1000 g of dried Stevia leaves with hot water at 60°C, 35 g of calcium hydroxide was added to the extract, and the resulting precipitate was separated. Hydrochloric acid was added to the liquid to make the pH of the liquid weakly acidic. A dark brown calcium-treated extract 15 was obtained. The solids content was 1.7% by weight. Activated carbon 50 with the pore characteristics described below
The liquid is passed through a column consisting of 50 g to adsorb stevioside. When the flow rate reached 3.3, stevioside started flowing out into the effluent from the column.
The fluid flow was stopped. After removing the liquid in the column, the adsorbate was eluted using methanol 2. After the elution, the calcium-treated extract was passed through the column again to adsorb stevioside, and the column was eluted as described above. Extract 15 was processed by repeating adsorption and elution in this manner. The average amount of fluid passed before stevioside begins to flow into the effluent is 1.5
(30ml/g activated carbon). The liquids flowing out from the column were combined and evaporated to dryness to obtain 120 g of solid content. It did not contain stevioside. The methanol eluates were combined and concentrated under reduced pressure to 200 ml. When this concentrated solution was left in a cold place (5° C.) overnight, 52 g of white crystals containing 96.6% by weight of stevioside were obtained. The crystallization mother liquor was evaporated to dryness to obtain 67 g of a tan solid. This is the stevioside content
It was 7.3% by weight. The pore characteristics of the activated carbon used are as follows. Total pore volume of pores with a diameter of 15 μ or less 1.81 cc/g Total pore volume of pores with a diameter of 300 Å or less 1.02 cc/g Average pore diameter of pores with a diameter of 300 Å or less 31 Å Note that the specific surface area of activated carbon (N ₂ BET method) is 1320
m ² /g. Example 2 After extracting 1000 g of dried Stevia leaves with hot water at 60° C., 30 g of diatomaceous earth was added to the extract, and the extract was filtered by suction to obtain a dark green-brown extract 15. Solid content is 1.78
It was in weight%. When this liquid was passed through a column made of activated carbon having pore characteristics described below and treated in the same manner as in Example 1, the following results were obtained. Average processing liquid volume per cycle
1 (20ml/g activated carbon) Column effluent solid content 73g Crystals 54g (stevioside content 96.8% by weight) Crystallization mother liquor solid content
84g (stevioside content: 7.3% by weight) The pore characteristics of the activated carbon used are as follows. Total pore volume of pores with a diameter of 15 μ or less 1.38 cc/g Total pore volume of pores with a diameter of 300 Å or less 0.69 cc/g Average pore diameter of pores with a diameter of 300 Å or less 26 Å The specific surface area of the activated carbon ( N ₂ BET method) is
It was 1055m ² /g. Comparative examples 1 and 2

[Table] When the specific surface area (N ₂ BET method) of the above activated carbon was measured, it was 1320 m ² /g in Comparative Example 1.
was 1060 m ² /g, and Comparative Example 2 was 1200 m ² /g. When activated carbon having the above-mentioned pore characteristics was treated in the same manner as in Example 1, the following results were obtained.

【table】

Claims (1)

[Scope of Claims] 1. Stevioside-containing plants are (1) extracted with water or hydrous alcohol, (2) the extract is brought into contact with activated carbon having the following pore characteristics, and all pores with a diameter of 15 μm or less are extracted. Total pore volume of pores with a volume of 1 c.c./g or more and a diameter of 300 Å or less 0.6 cc/
Average pore diameter of pores with a diameter of 300 Å or more
25 Å or more (3) A method for purifying stevioside, which is characterized by eluting stevioside adsorbed on activated carbon with a hydrophilic organic solvent, and (4) concentrating and crystallizing the eluate if necessary.