CN101367847A - A kind of crystallization preparation method of high-purity raffinose - Google Patents

Abstract

The invention discloses a crystallization preparation method of high-purity raffinose, which adopts an aqueous solution of C1-C3 alcohol as a crystallization solvent, uses small-grain raffinose as a crystal seed to induce crystallization, grows crystals for 2-24 hours, and then filters and dries Obtain high purity raffinose. The purity of the obtained raffinose product can reach more than 99%, and the crystallization yield can reach more than 80%. The method has the advantages of simple process, low production cost and easy industrial production.

Description

A kind of crystallization preparation method of high-purity raffinose

technical field

The invention relates to a method for preparing high-purity raffinose by crystallization of crude raffinose, belonging to the technical field of industrial crystallization.

Background technique

Raffinose, also known as Melitriose, is composed of galactose, glucose and fructose. It is an oligosaccharide and a non-reducing sugar. Its structural formula is as follows:

Raffinose is widely found in beet, cottonseed, honey, cabbage, yeast, potato, grape, wheat, corn and the seeds of legumes. It is the most widely distributed oligosaccharide in plants except sucrose. One of the main components of polysaccharides. Among them, the content of raffinose is the highest in cottonseed, about 4-9%, about 1.0% in sugar beet, and about 1.3% in soybean. These raw materials are all important sources for extracting raffinose. Because the human digestive enzyme system lacks α-galactosidase that can decompose raffinose, raffinose can pass through the stomach and intestinal tract smoothly without being directly decomposed and absorbed by the human body. Research has found that raffinose is an excellent nutrient source for beneficial bacteria such as Bifidobacterium and Lactobacillus acidophilus in the human intestinal tract, which can promote their proliferation, thereby inhibiting the growth of spoilage bacteria in the intestinal tract and reducing the formation of toxic fermentation products . Bifidobacteria ferment raffinose to produce a large amount of short-chain fatty acids, which can stimulate intestinal peristalsis, increase stool moisture and maintain a certain osmotic pressure, thereby preventing constipation. In addition, raffinose can improve the digestive function of the human body, promote the absorption of calcium by the human body, thereby enhancing the immunity of the human body, and has obvious effects on disease prevention and anti-aging. Raffinose can also be used as the main component of protective delivery fluid for human and animal living organ transplantation and as a synergist for prolonging the survival period of living bacteria at normal temperature. Raffinose has good acid resistance and heat resistance, and it will not absorb moisture and agglomerate at a relative humidity of 90%. It can be used as a food additive to improve the processing characteristics of food, prevent product browning, improve product quality, and prolong product life. shelf life. Because of its excellent physical and chemical properties and physiological activity, raffinose has been widely used in food, medicine and cosmetics industries.

Raffinose is widely distributed in nature and is the most widely distributed oligosaccharide in plants except sucrose. It is widely found in beet, cottonseed, honey, cabbage, yeast, potato, grape, wheat, corn and legumes Among the seeds, the content in cottonseed is the highest, about 4 to 9%. After the cottonseed kernel is extracted from cottonseed oil, a large amount of by-products—defatted cottonseed meal is produced. The content of raffinose in the defatted cottonseed meal remains basically unchanged. Therefore, the defatted cottonseed meal cake is an excellent raw material for industrial production of raffinose.

In the prior art, the production of raffinose from defatted cottonseed meal is usually obtained by directly concentrating and crystallizing the extract of raffinose without pigment and then recrystallizing it multiple times. Such as Zhang Dayu et al. (Research on extracting raffinose from non-glandular cottonseed, China Oils and Fats, 1996, 5, 7-9) disclosed technology for extracting raffinose from non-glandular cottonseed, the extraction rate of raffinose is 58.8% %, the product purity is more than 97%. Chinese patent application 200710014172.4 discloses a method for extracting raffinose from cottonseed meal, and the yield of raffinose product is also very low. Since defatted cottonseed meal includes raffinose, protein, salt, gossypol pigment, monosaccharide and sucrose, etc., after solvent extraction, impurities such as protein, salt, gossypol pigment and other monosaccharide or sucrose still exist, and these The presence of impurities will lead to difficulties in the crystallization of raffinose. If these impurities are not removed before the raffinose is crystallized and refined, high-purity raffinose must be obtained through multiple recrystallizations, which will inevitably lead to a lower yield of raffinose. Even the extraction rate of extracting raffinose from non-glandular absorbent cotton (without decolorization treatment) is lower than 60%. The production process of this method has serious material waste and cannot be used for industrial scale production.

Therefore, in order to realize the industrialized production of high-purity raffinose from defatted cottonseed meal, it is necessary to reduce costs, increase yield, and simplify the process, which can be considered from the following aspects: (1) leaching from defatted cottonseed meal with organic solvents In the process of obtaining the raffinose extract, the method of low production cost and high raffinose extraction rate is adopted; (2) before the raffinose crystallization is refined, the raffinose extract is purified, that is, the raffinose extract is decolorized, Deproteinization, desalination, and removal of monosaccharides and sucrose, etc., and adopt optimized purification processes as much as possible; (3) Adopt optimized raffinose refining processes.

In the prior art, the extraction methods for obtaining raffinose from defatted cottonseed meal mainly include water extraction, aqueous organic solvent extraction, and enzymatic hydrolysis-alcoholic solution extraction. At present, the most commonly used method for extracting raffinose from defatted cottonseed meal is to use alcohol solution as the extraction solvent, and to extract the defatted cottonseed meal by static leaching. People such as Wang Xingguo (Research on the Extraction Method of Raffinose in Defatted Cottonseed Meal, China Oils and Oils, 2005, 3, 57-60) disclosed a process for extracting raffinose in cottonseed meal, using ethanol solution as the extraction solvent, at a certain temperature After extraction with stirring, the extraction solution is separated. After multiple extractions, the extraction solutions are combined and filtered to obtain a raffinose extract. The amount of solvent used in this static leaching method is large, which causes difficulties in solvent recovery and causes solvent waste. At the same time, the utilization rate of the solvent is low, and the active ingredient is not completely leached. Extraction leads to an increase in the content of impurities in the extract, and the composition becomes complex, making subsequent separation and purification difficult, and it is difficult to prepare high-purity products. Therefore, using the existing common technology, high extraction rate and low cost cannot be taken into account, especially the solvent consumption is huge, and the cost of solvent recovery also increases accordingly.

In the prior art, the relevant reports on the purification of the raffinose extract are mainly reports on a single method for removing certain types of impurities. Such as: (1) Pigment removal: The decolorization method of raffinose extract is mainly to use powdered activated carbon for decolorization. Liang Lixin et al. (Decolorization of raffinose extract in methanol phase of cottonseed two-liquid phase extraction process, Food and Fermentation Industry, 2007, 4, 73-76) and Jin Qingzhe et al. (Decolorization of raffinose extract and removal of gossypol , China Oils and Fats, 2005, 4, 47-49) discloses a method of adding powdered activated carbon to a tank reactor equipped with a raffinose extract for static decolorization, and after the decolorization is completed, the activated carbon is separated from the solution to obtain a decolorization solution; (2) Removal of salt: desalination mainly adopts ion exchange resin and nanofiltration desalination (Luo Tienan et al., Application of ion exchange resin in sugar juice desalination, China Beet Sugar Industry, 2000, 1, 3-5; Wang Xiaolin et al., Application Experimental research on nanofiltration membrane separation of sugar and salt, Membrane Science and Technology, 2001, 1, 44-48); (3) remove protein: mainly adopt ultrafiltration membrane separation, such as Liang Lixin et al. (Cottonseed two-liquid phase extraction process Decolorization of raffinose extract in methanol phase, Food and Fermentation Industry, 2007, 4, 73-76) reported a method of denaturing and precipitating protein by adding lead acetate, and then using ultrafiltration membrane separation to complete the decolorization of raffinose extract. (4) The usual process of removing monosaccharides and sucrose is accomplished simultaneously during the crystallization process. These methods can only remove a single impurity, and there are such and such problems in themselves, mainly including: as (1), a large amount of powdered activated carbon needs to be used to achieve a satisfactory decolorization effect, and powdered activated carbon cannot be reused at the same time, and it is easy to remain in After decolorization, it is difficult to complete the removal in the solution; (2) a large amount of waste acid and waste alkali will be produced when the ion exchange resin column resin in (2) is regenerated, causing environmental pollution, and the equipment investment used for nanofiltration membrane separation is large, and the separation membrane is easy to pollute the service life short; (3) the use of lead acetate will bring heavy metal residues, the equipment used for ultrafiltration membrane separation has a large investment, and the separation membrane is easy to pollute and has a short life; (4) removing monosaccharides and sucrose in the crystallization means that high purity is finally obtained Raffinose must be realized through multiple recrystallizations, resulting in a low yield of raffinose. Therefore, if only a series of procedures such as removing pigment, salt, protein, monosaccharide and sucrose in the prior art are simply combined to purify raffinose Extraction solution, still can not obtain ideal raffinose yield. The raffinose purification process needs further optimization and simplification.

In the prior art, the refining process of raffinose is usually realized by crystallization or precipitation. Because the precipitation method will introduce new impurities, it is usually refined by crystallization or multiple recrystallization. U.S. Patent No. 6,224,684 discloses a method and device for crystallizing raffinose in a crystallizer with a circulation device using pure water as a crystallization solvent. In this invention, pure water is used as the crystallization solvent, and the mass percentage concentration of the initial raffinose is 60%. Decline, only cooling time just needs as much as 50 hours, and the yield of final raffinose is also lower simultaneously.

In general, under the existing technical conditions, in order to realize the industrialization (low cost, high yield, simple process) of producing high-purity raffinose from defatted cottonseed meal, it is necessary to separately or overall improve the extraction method of raffinose, raffinose The extraction liquid purification process and the raffinose refining process are improved, and the improvement of the raffinose refining process has a direct impact on the yield and purity of the raffinose in the final product. In the existing refining technology, although cyclic crystallization and multiple recrystallization can ensure the purity of raffinose in the final product, the yield of raffinose is very low, which is not suitable for industrial production.

Contents of the invention

The invention provides a method for refining raffinose and obtaining high-yield and high-purity raffinose in the presence of crystal seeds in an aqueous alcohol solution. The purity of the raffinose obtained by the method can reach more than 99%, and the yield can reach Up to 80% or more.

A crystallization preparation method of high-purity raffinose, comprising the steps of:

(1) Mixing the crude raffinose product with an aqueous solution of C ₁ -C ₃ alcohol with a concentration of 60-80% by volume, and raising the temperature of the obtained mixed system to 50-85° C. to dissolve the crude raffinose product;

(2) When cooling the mixed system to 30-50°C, adding raffinose grains to induce crystallization;

(3) After the crystals are precipitated, the temperature of the system is cooled to 5-30°C and the crystals are grown for 2-24 hours;

(4) The crystal obtained by filtering out is vacuum-dried at 30～40° C.;

The crude raffinose is obtained through the following processes: extracting a raffinose extract from defatted cottonseed meal with an alcohol solution; removing gossypol and decolorizing the raffinose extract; desalting, deproteinizing, and sugar-removing the decolorized liquid, and then removing the solvent.

The process of preparing crude raffinose from defatted cottonseed meal, including each step, can be realized by using the prior art. The present invention specifically provides a method for preparing crude raffinose from defatted cottonseed meal, the detailed steps are as follows:

(a) percolation extraction:

Fill the raw material defatted cottonseed meal into the percolation column, add extraction solvent into the percolation column, soak at 50-70°C for 30-60 minutes, the volume of the added extraction solvent is 0.6-1 times of the accumulated volume of the defatted cottonseed meal. Under the condition of heat preservation, percolation operation is carried out in the percolation column, and the extraction solvent is continuously added to the percolation column while collecting the percolation liquid, until the volume of the collected percolation liquid is 3-3% of the accumulated volume of defatted cottonseed meal. 5 times.

The extraction solvent is an aqueous methanol solution with a concentration of 70-85% by volume or an aqueous solution of ethanol with a concentration of 70-85%.

Bulk volume of defatted cottonseed meal: the volume of defatted cottonseed meal in a free accumulation state when the defatted cottonseed meal is packed into the percolation column, and its apparent density is the bulk density; the bulk density of the defatted cottonseed meal is about 0.77g/ml, that is, every The bulk volume of one kilogram of defatted cottonseed meal is about 1300ml.

(b) Decolorization:

Concentrate the percolation solution obtained in step (a), add water to form a solution with a solid content of 10%, adjust the pH value to 4-6, and obtain a prepared aqueous solution; Add the prepared aqueous solution into the fixed bed with adsorbent A at a flow rate of 3BV/h, and collect the effluent as the decolorization solution until the volume of the collected decolorization solution is 5-10BV.

In the described solution that is made into a solid content of 10% by adding water, the solid content refers to the percentage of the mass of the solution before drying when the solution is dried to a constant weight, which is the sum of the mass percentages of all solutes in the solution, Due to the complex components in the solution, suspension or precipitation may also occur. When calculating the total mass of the solution, it refers to the total mass of the mixed system, that is, it also includes the mass of suspended or precipitated impurities.

BV: bed volume, refers to the bed volume filled with adsorbent A in the fixed bed adsorption column;

BV/h: The volume of the mobile phase flowing through the bed filled with adsorbent A per hour is a multiple of the fixed bed volume BV;

The adsorbent A is granular activated carbon, nonpolar macroporous polystyrene adsorption resin, weakly polar macroporous polystyrene adsorption resin, nonpolar macroporous acrylic adsorption resin, weak polarity Macroporous acrylic resin, non-polar gel polystyrene resin, weak polar gel polystyrene resin, non-polar gel acrylic resin or weak polar gel type acrylic resin.

(c) Adsorption separation:

2～4B'V' of the decolorization solution obtained by step (b) is passed into the fixed bed equipped with adsorbent B at a flow rate of 0.5～3B'V'/h so that the raffinose is adsorbed by the adsorbent B, and then Rinse the fixed bed with deionized water at a flow rate of 0.5-3B'V'/h to recover the decolorization solution in the gap of the fixed bed, combine the obtained eluent and decolorization solution, and finally desorb with 2-4B'V' desorb the adsorbent B at a flow rate of 0.5-3B'V'/h to obtain an eluent containing raffinose, the temperature of the adsorption separation process is controlled at 40-80°C; the eluate is concentrated or dried to obtain a crude raffinose ;

The desorbing agent is an aqueous methanol solution with a volume percent concentration of 20-60% or an ethanol aqueous solution with a volume percent concentration of 20-60%.

B'V': bed volume, refers to the bed volume filled with adsorbent B in the fixed bed adsorption column;

B'V'/h: The volume of the mobile phase flowing through the bed filled with adsorbent B per hour is a multiple of the fixed bed volume B'V';

The adsorbent B is non-polar macroporous polystyrene adsorption resin, non-polar macroporous acrylic adsorption resin, non-polar gel polystyrene adsorption resin, non-polar gel type Acrylic adsorption resin, granular activated carbon, silica gel bonded with C ₁₈ or silica gel bonded with C ₃₀ ;

In the present invention, using the aqueous solution of C ₁ -C ₃ alcohols as the crystallization solvent can effectively accelerate the crystallization rate, and the raffinose can be completely precipitated within 24 hours; at the same time, the presence of lower alcohols in the aqueous solution of C ₁ -C ₃ alcohols, It can effectively reduce the solubility of raffinose in the mother liquor, thereby greatly increasing the yield of raffinose. The C ₁ -C ₃ alcohol is preferably methanol, ethanol or isopropanol.

In a more preferred solution, the volume concentration of the C ₁ -C ₃ alcohol in the aqueous solution of the C ₁ -C ₃ alcohol solution is 60-80%. The above-mentioned solvent has moderate boiling point, low toxicity, and the solubility of raffinose in it changes obviously with temperature, so it is a suitable crystallization solvent.

In a more preferred scheme, every kilogram of crude raffinose is mixed with 4-8 liters of aqueous solution of C ₁ -C ₃ alcohol. Under this optimized ratio, a raffinose solution with a sufficiently high supersaturation degree can be formed, and the raffinose can be crystallized quickly.

In a more preferred solution, the cooling described in step (2) and step (3) is carried out under slow stirring conditions, which is conducive to accelerating crystallization.

In a more preferred solution, the temperature-lowering cooling described in step (2) and step (3) has a cooling rate of 0.5-2° C./min, which is conducive to the formation of crystals with uniform particle size.

The particle size of the raffinose crystal grains is 170-200 meshes, and the dosage is 0.5-1.0% of the weight of the raw raffinose used. The addition of raffinose crystal grains as crystal seeds can make the obtained raffinose crystals larger in size and more uniform in particle size distribution.

In a more preferred solution, the mass percentage of raffinose in the crude raffinose product is 75% or higher. Take the crude raffinose as raw material, dissolve it in the aqueous solution of C ₁ -C ₃ alcohol, grow the crystal in the presence of seed crystals, and obtain the raffinose product after filtration as white needle-like crystals of raffinose pentahydrate. Its purity is greater than 99%, and its yield is greater than 80%.

Compared with prior art, the beneficial effect that the present invention has is:

The method has the advantages of simple process, high yield, low production cost and easy industrial production. The purity of the raffinose crystals prepared by the method is greater than 98%, and can be directly used as a food additive and added to various beverages, dairy products, health care products and other products.

Detailed ways

Hereinafter, the content of the present invention will be described in detail through examples, but the present invention is not limited thereto.

Embodiment 1: prepare raffinose crude product:

(a). Degreased cottonseed meal (wherein the mass percent content of raffinose is 3.9%) is sieved through a 1.8mm sieve, weighs 435 grams and puts it into a percolation column (Φ3.5cm×70cm), and fills After uniformity, its bulk volume is about 560 milliliters, then add 350 milliliters of volume percent concentration to the percolation column and be 75% ethanol aqueous solution, soak at 55 ℃ for 30 minutes to make the defatted cottonseed meal fully swell, open the percolation column outlet valve, and simultaneously Continuously add extraction solvent from the top of the percolation column, and control the flow rate to be 168 ml/hour until the volume of the percolation extract collected is 1900 ml. The percolating liquid is analyzed, and solid content (solid content refers to the percentage that the quality when solution is dried to constant weight accounts for the percentage of solution mass before drying, the same below) is 4.2%; The mass percentage of raffinose is 38.2% based on the mass of the solid, i.e. the mass sum of all solutes in the solution, the same below).

Finally, add deionized water from the top of the percolation column to replace the residual ethanol in the defatted cottonseed meal, control the flow rate to 560 ml/hour, collect the low-concentration ethanol at the outlet, and then recover the ethanol through concentration and rectification.

(b). The 1900 milliliters of percolation extract obtained in the previous step operation is concentrated to 1/10 of the original volume, added with water to prepare a solution (wherein, the solid content is 10%), and the hydrochloric acid with a mass percentage concentration of 5% is added to adjust the pH value to 5.

The granular activated carbon is loaded into an adsorption column with a size of Φ5.6cm×40cm, the column bed volume BV is 980mL, and about 230 grams of granular activated carbon (adsorbent A) is installed inside.

The above-mentioned pH-adjusted aqueous solution was passed through a fixed-bed adsorption column equipped with granular activated carbon at a flow rate of 1.0 BV/h, and the temperature was controlled at 40°C. Collect 10BV of the effluent (i.e. decolorized solution) of the loading process of the fixed bed adsorption column, which is lighter in color (color value is less than 10% of the color value of the sample aqueous solution). On a dry basis, the mass percentage of raffinose in the decolorizing solution is 50.6%. Rinse the adsorption column with 1.5BV deionized water at a flow rate of 1.0BV/h, and the collected washing liquid also contains a small amount of raffinose, which can continue to be recycled. During the whole process, the temperature of the adsorption column was controlled at 40°C. The decolorization solution flowing out during the sample loading process was analyzed by HPLC, and the recovery rate of raffinose was 95%.

Finally, use 2BV volume percent concentration of 60% ethanol aqueous solution to wash the adsorption column with a flow rate of 1.0BV/h, and the eluent is dark red; then replace the ethanol in the adsorption column with deionized water, so that the adsorption column can be regenerated directly Enter the next decolorization operation.

(c). The pretreated HZ816 resin (adsorbent B) is packed into an adsorption column whose size is Φ5.6cm×97cm. The column bed volume B'V' is about 2400mL, and about 1700 grams of resin is housed therein. The sample loading liquid is the raffinose decolorization liquid obtained in step (b), wherein the solid content is 10%. Continuously feed the above-mentioned raffinose decolorization solution 2.5B'V' into the fixed bed adsorption column at a flow rate of 1.0B'V'/h, and the effluent collected during the sample loading process also contains a small amount of raffinose, which can be directly recycled . After loading the sample, wash the adsorption column with 2B'V' deionized water at a flow rate of 1.5B'V'/h to remove the decolorization solution remaining in the adsorbent gaps in the adsorption column, and the obtained washing solution can be recycled; then use 2B'V' The 'V' volume percentage concentration is 40% ethanol aqueous solution to wash the adsorption column at a flow rate of 1.0B'V'/h, desorb the HZ816 resin, elute the raffinose in the HZ816 resin, and collect the eluate containing raffinose. The temperature of the adsorption column was controlled at 60°C throughout the process. The eluate was spray-dried to obtain crude raffinose, and the mass percentage of raffinose was 80% by HPLC analysis.

Finally, the ethanol in the adsorption column was replaced with 2B'V' deionized water at a flow rate of 2B'V'/h to regenerate the HZ816 resin.

Embodiment 2: the preparation of high-purity raffinose

In a clean three-necked flask with a reflux condenser, add 100 grams of raffinose crude product with a purity of 80% and 500 milliliters of methanol aqueous solution with a volume concentration of 70% prepared by the method in Example 1, start stirring, and heat up to 65 ℃, after completely dissolving, first slowly cool down to 40°C at a rate of 0.5°C/min, add 0.5 g of 170-200 mesh raffinose (ie crystal seed) to induce crystallization, and then continue to slowly cool down to 10°C at the same speed , grow the crystal for 12 hours at this temperature. Then, the crystalline solid was filtered again, and the filter cake was washed with a small volume concentration of 70% methanol solution, and dried in a vacuum oven at 40°C for 6 hours to obtain 65.2 grams of white needle-shaped raffinose pentahydrate crystals, which were analyzed by HPLC. The purity is 98.7%, and the yield is 80.5%.

Embodiment 3: the preparation of high-purity raffinose

In a clean three-necked flask with a reflux condenser, add 100 grams of raffinose crude product with a purity of 80% and 400 milliliters of ethanol aqueous solution with a volume concentration of 60% obtained by the method in Example 1, start stirring, and heat up to 75 ℃, after it is completely dissolved, slowly cool down to 45°C at a speed of 1°C/min, add 0.6 g of 170-200 mesh raffinose (ie, seed crystal) to induce crystallization, and then continue to slowly cool down to 20°C at the same speed , grow crystals at this temperature for 24 hours. Finally, the crystalline solid was filtered, the filter cake was washed with a small amount of 70% ethanol solution, and dried in a vacuum oven at 40°C for 8 hours to obtain 63.8 grams of white needle-shaped raffinose pentahydrate crystals, which were analyzed by HPLC and had a purity of 98.2% , yield 78.4%.

Embodiment 4: the preparation of high-purity raffinose

In a clean three-necked flask with a reflux condenser, add 100 grams of raffinose crude product with a purity of 80% and 500 milliliters of isopropanol aqueous solution with a volume concentration of 70% prepared by the method in Example 1, start stirring, and heat up to 85°C. After completely dissolving, first slowly cool down to 25°C at a speed of 1.5°C/min, add 1.0 g of 170-200 mesh raffinose (ie, seed crystal) to induce crystallization, and then continue to slowly cool down to 5°C at the same speed. The crystal was grown for 24 hours at this temperature. Finally, the crystalline solid was filtered, the filter cake was washed with a small amount of pure water, and dried in a vacuum oven at 60° C. for 8 hours to obtain 60.5 grams of white needle-shaped raffinose pentahydrate crystals, which were analyzed by HPLC with a purity of 99.2%. rate of 75%.

Embodiment 5: the preparation of high-purity raffinose

In a clean three-necked flask with a reflux condenser, add 100 grams of raffinose crude product with a purity of 80% and 800 milliliters of methanol aqueous solution with a volume percentage concentration of 80% obtained by the process of Example 1, start stirring, and heat up to 65°C, after complete dissolution, slowly cool down to 30°C at a rate of 1.5°C/min, add 0.5 g of 170-200 mesh raffinose (seed crystal) to induce crystallization, and then continue to slowly cool down to 5°C, grow crystals at this temperature for 24 hours. Then, the crystalline solid was filtered again, and the filter cake was washed with a small amount of 80% methanol solution, and dried in a vacuum oven at 40°C for 6 hours to obtain 61.1 grams of white needle-shaped raffinose pentahydrate crystals, which were analyzed by HPLC with a purity of 99.3 %, yield 75.9%.

Embodiment 6: the preparation of high-purity raffinose

In a clean three-necked flask with a reflux condenser, add 100 grams of raffinose crude product with a purity of 80% and 400 milliliters of methanol aqueous solution with a volume percentage concentration of 60% obtained by the process of Example 1, start stirring, and heat up to 65°C, after it is completely dissolved, slowly cool down to 35°C at a rate of 1°C/min, add 1.0 g of 170-200 mesh raffinose (seed crystal) to induce crystallization, and then continue to slowly cool down to 10°C, grow crystals at this temperature for 12 hours. Then, the crystalline solid was filtered again, and the filter cake was washed with a small amount of 60% methanol solution, and dried in a vacuum oven at 40°C for 6 hours to obtain 57.4 grams of white needle-shaped raffinose pentahydrate crystals, which were analyzed by HPLC with a purity of 98.1 %, yield 70.4%.

Claims (7)

1. A crystallization preparation method of high-purity raffinose, comprising the steps of: (1) Mixing the crude raffinose product with an aqueous solution of C ₁ -C ₃ alcohol with a concentration of 60-80% by volume, and raising the temperature of the obtained mixed system to 50-85° C. to dissolve the crude raffinose product; (2) When cooling the mixed system to 30-50°C, adding raffinose grains to induce crystallization; (3) After the crystals are precipitated, the temperature of the system is cooled to 5-30°C and the crystals are grown for 2-24 hours; (4) The crystal obtained by filtering out is vacuum-dried at 30～40° C.; The crude raffinose is obtained through the following processes: extracting a raffinose extract from defatted cottonseed meal with an alcohol solution; removing gossypol and decolorizing the raffinose extract; desalting, deproteinizing, and sugar-removing the decolorized liquid, and then removing the solvent. 2. The crystal preparation method according to claim 1, characterized in that: the C1- _C3 alcohol is methanol, ethanol or isopropanol. 3. The crystallization preparation method according to claim 1, characterized in that: every kilogram of said crude raffinose is mixed with 4-8 liters of said C ₁ -C ₃ alcohol aqueous solution. 4. The crystallization preparation method according to claim 1, characterized in that: the cooling described in step (2) and step (3) is carried out under stirring conditions. 5 . The crystallization preparation method according to claim 1 , characterized in that the cooling rate in step (2) and step (3) is 0.5-2° C./min. 6. The crystallization preparation method according to claim 1, characterized in that: the particle size of the raffinose crystal grains is 170-200 mesh, and the dosage is 0.5-1.0 of the weight of the crude raffinose used in step (1). %. 7. The crystallization preparation method according to claim 2, characterized in that: the mass percentage of raffinose in the crude raffinose product is 75% or higher.