A method for decolorizing and deodorizing high-transparency tamarind polysaccharide gum

Abstract

This invention discloses a method for preparing high-transparency tamarind polysaccharide gum through decolorization and deodorization. A combined purification process of enzymatic hydrolysis-sedimentation-chemical degradation-solvent washing-ultrafiltration is employed. Enzymatic hydrolysis degrades large molecules of proteins and fats in the extract into smaller molecules. Sodium hypochlorite is used for chemical degradation, oxidizing aldehydes and ketones in the extract into carboxylic acids. Finally, organic solvent washing and ultrafiltration purification remove impurities generated during enzymatic hydrolysis and chemical degradation, ultimately yielding high-transparency, odorless tamarind polysaccharide gum. The final product is white, with a transmittance of up to 95.4% at a 1% concentration, and is completely odorless, significantly improving product quality. This preparation process is simple, operates under mild conditions, and is suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of natural polysaccharide extraction and purification technology, specifically to a method for efficiently decolorizing and deodorizing tamarind polysaccharide gum to obtain a product with high transparency. Background Technology

[0002] Tamarind polysaccharide gum is a natural plant polysaccharide extracted from tamarind seeds. It possesses excellent thickening, stabilizing, gelling, and water-retaining properties, and is widely used in food, pharmaceuticals, and cosmetics. However, the raw gum extracted directly from tamarind seeds is usually dark in color (brownish or yellowish-brown) and has a pronounced beany and astringent taste, which severely limits its application in high-end, transparent products or products with strict flavor requirements. Tamarind seeds contain 65-73% non-fiber carbohydrates, 6-8% fat, 3-5% fiber, 2.5-3.2% ash, and 15-20% protein. Fat and protein are the two most abundant substances in tamarind seeds besides non-fiber carbohydrates. In the processing of tamarind polysaccharide gum (such as extraction and drying), amino acids and reducing sugars undergo Maillard reaction under heating conditions. This reaction not only produces pigments (leading to a darker color), but its side reaction, Streck degradation, generates some small molecules with off-flavors, such as pyrazines, furans, and sulfur-containing compounds, contributing to the "beany" and "roasted" tastes.

[0003] In existing technologies, decolorization of tamarind gum often employs oxidants such as activated carbon and hydrogen peroxide, or methods using ion exchange resins. The final product is typically brown to brownish-gray and often has a pronounced beany odor. For example, while activated carbon decolorization has some effect, its poor adsorption selectivity easily leads to polysaccharide loss, and its effectiveness in removing odor-causing substances is limited. Decolorization with strong oxidants like hydrogen peroxide, while highly efficient, may cause polysaccharide chain degradation, affecting its colloidal properties, and carries the risk of chemical residues, which does not align with the consumer trend towards clean labeling. Ion exchange resin methods have high equipment investment and operating costs, and the resin is easily contaminated. For deodorization, enzymatic hydrolysis or masking methods are commonly used, but these often suffer from high costs or incomplete results.

[0004] Therefore, developing a high-efficiency, mild, safe preparation method that can simultaneously achieve deep decolorization and deodorization while maximizing the preservation of the functional properties of tamarind polysaccharide gum is of great significance for enhancing its product value and expanding its application areas. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to overcome the shortcomings of the prior art and provide a simple, mild, transparent, and odorless method for preparing tamarind polysaccharide gum for decolorization and deodorization. Technical solution

[0006] A method for decolorizing and deodorizing high-transparency tamarind polysaccharide gum includes the following steps: a. Extraction: Add tamarind kernel powder to purified water at a ratio of 30-50 times by weight, heat and extract, cool the extract to room temperature, let it stand, separate the solid and liquid, remove water-insoluble impurities, collect the liquid phase, and obtain crude tamarind polysaccharide extract. b. Enzymatic hydrolysis: Add a complex enzyme to the crude extract prepared in step a for enzymatic hydrolysis. The complex enzyme contains lipase and protease. After enzymatic hydrolysis, the enzyme is inactivated to degrade water-soluble proteins and fats into small molecules. The solid and liquid phases are separated, and the liquid phase is collected to obtain the enzymatic hydrolysate. c. Sedimentation: Add citric acid to the enzymatic hydrolysate prepared in step b, adjust the pH of the system to 3-5, separate the solid and liquid phases, collect the liquid phase, add a strong base to the liquid phase, adjust the pH of the system to 11-12, stir the reaction for 1-2 hours, and obtain purified solution 1. d. Chemical degradation: Cool the purified liquid 1 prepared in step c to 0-10℃, add sodium hypochlorite solution with 10% available chlorine content, stir and react until the system decolorizes, oxidize the aldehydes and ketones in the extract into carboxylic acids, and obtain purified liquid 2. e. Solvent washing: Add an organic solvent to the purified solution 2 prepared in step d, stir for 0.5-2 hours, wash to remove fatty acid substances, let stand to separate the layers, collect the aqueous phase, and obtain purified solution 3. f. Ultrafiltration: The purified liquid 3 prepared in step e is purified and concentrated by ultrafiltration to remove impurities after chemical degradation and inorganic salt impurities, to obtain purified liquid 4; g. Crystallization: Add a low alcohol solvent to the purified liquid 4 prepared in step f, cool to 0-5℃, precipitate solid, filter, collect the filter cake, wash and vacuum dry, and pulverize to obtain the high transparency tamarind polysaccharide gum.

[0007] Preferably, in step a, the heating and extraction temperature is 60-100℃.

[0008] Preferably, in step b, the amount of the compound enzyme added is 0.1-0.5% of the mass of the crude extract; the enzymatic hydrolysis conditions are: pH 4.5-5.5, temperature 45-55℃, and time 1-2 hours.

[0009] Preferably, in step c, the strong alkali is one or a combination of sodium hydroxide, potassium hydroxide, and lithium hydroxide.

[0010] Preferably, in step d, the amount of sodium hypochlorite solution used is 10-30% of the tamarind kernel powder.

[0011] Preferably, in step e, the organic solvent is one of ethyl acetate, isopropyl acetate, and dichloromethane.

[0012] Preferably, in step f, the ultrafiltration purification membrane has a molecular weight cutoff of 50 kDa.

[0013] Preferably, in step g, the lower alcohol is food-grade ethanol or isopropanol, and the amount used is 3-6 times the volume of the purified liquid 4, and the washing solvent is a 70% ethanol solution.

[0014] Preferably, the vacuum drying temperature is 50-70℃ and the drying time is more than 12 hours.

[0015] Beneficial effects:

[0016] (1) This method uses an enzymatic hydrolysis purification process to degrade large protein and fat molecules in the extract into smaller molecules. A sodium hypochlorite chemical degradation purification process is then used to oxidize aldehydes and ketones in the extract into carboxylic acids. Finally, an organic solvent washing process and ultrafiltration purification process are used to remove impurities generated during enzymatic hydrolysis and chemical degradation purification, ultimately producing a highly transparent, odorless tamarind polysaccharide gum. The final product is white, with a transmittance of up to 95.4% at a 1% concentration, and has no odor, resulting in a high-quality product.

[0017] (2) The process is simple and easy to scale up: The method described in this invention has clear steps, mild operating conditions, and low equipment requirements. Compared with traditional chromatographic column purification processes, it has a significant cost advantage and is suitable for large-scale industrial production. Attached Figure Description

[0018] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Figure 1 Infrared spectrum of tamarind polysaccharide gum prepared in step 1; Figure 2 Photograph of the tamarind polysaccharide gum prepared for implementation 1. Detailed Implementation

[0019] The present invention will be described in detail below with reference to embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of this application can be combined with each other.

[0020] Example 1

[0021] Add 100g of tamarind seed kernel powder to 4000g of purified water, heat to 70℃ and extract for 70min. Cool the extract to room temperature, let stand for 1h, then centrifuge and collect the crude extract. Add 0.3g of lipase (Novozymes) to the crude extract. ®677 BG) and 0.5 g of protease (Flavourzyme 500L) were added, and the system was maintained at pH 4.5-5.5 and temperature 45-55℃ for 2 h of enzymatic hydrolysis. The temperature was then raised to 85℃ and maintained for 15 minutes to inactivate the enzyme. The mixture was centrifuged, and the liquid hydrolysate was collected. Citric acid was added to the hydrolysate to adjust the pH to 4, and the mixture was centrifuged again. The liquid phase was collected, and sodium hydroxide was added to adjust the pH to 11-12. The mixture was stirred for 2 h. The reaction solution was cooled to 5℃, and 20 g of sodium hypochlorite solution with 10% available chlorine content was added. The mixture was stirred until the system decolorized. 20 ml of ethyl acetate was added to the reaction solution, and the mixture was stirred for 1 h. After standing and separation, the aqueous phase was collected. The aqueous phase was heated to 40℃ and purified by ultrafiltration. The ultrafiltration membrane had a molecular weight cutoff of 50 kDa, and the pressure was 0.3 MPa. After purification, the solution was concentrated to one-third of its original volume. Add 4 times the volume of food-grade ethanol to the concentrate, cool the system to 3°C, allow crystallization for 6 hours, filter, and wash the filter cake twice with a 70% ethanol solution. Dry under vacuum at 60°C for 14 hours, then pulverize at a vacuum of -0.095 MPa to obtain white tamarind polysaccharide gum with an extraction rate of 25.4%.

[0022] Example 2

[0023] Add 100g of tamarind seed kernel powder to 5000g of purified water, heat to 60℃ and extract for 70min. Cool the extract to room temperature, allow it to stand, centrifuge, and collect the crude extract. Add lipase (Novozymes) to the crude extract. ® 0.5g of 677 BG and 0.5g of proteinase (Flavourzyme 500L) were added, and the system was maintained at pH 4.5-5.5 and temperature 45-55℃ for 1 hour of enzymatic hydrolysis. The temperature was then raised to 85℃ and maintained for 15 minutes to inactivate the enzyme. The mixture was centrifuged, and the liquid hydrolysate was collected. Citric acid was added to the hydrolysate to adjust the pH to 3, and the mixture was centrifuged again. The liquid phase was collected, and potassium hydroxide was added to adjust the pH to 12. The mixture was stirred for 1 hour. The reaction solution was cooled to 10℃, and 30g of sodium hypochlorite solution with 10% available chlorine content was added. The mixture was stirred until the system decolorized. 20ml of isopropyl acetate was added to the reaction solution, and the mixture was stirred for 2 hours. After separation, the aqueous phase was collected. The aqueous phase was heated to 40℃ and purified by ultrafiltration. The ultrafiltration membrane had a molecular weight cutoff of 50 kDa, and the pressure was 0.3 MPa. After purification, the solution was concentrated to one-third of its original volume. Add 6 times the volume of food-grade isopropanol to the concentrate, cool the system to 5°C, filter, and wash the filter cake twice with 70% ethanol solution. Dry under vacuum at 50°C for 16 hours (vacuum degree -0.095 MPa), and pulverize to obtain white tamarind polysaccharide gum with an extraction rate of 22.6%.

[0024] Example 3

[0025] Add 100g of tamarind seed kernel powder to 3000g of purified water, heat to 100℃ and extract for 70min. Cool the extract to room temperature, allow it to stand, centrifuge, and collect the crude extract. Add lipase (Novozymes) to the crude extract. ® 0.1 g of 677 BG and 0.2 g of proteinase (Flavourzyme 500L) were added, and the system was maintained at pH 4.5-5.5 and temperature 45-55℃ for 2 hours for enzymatic hydrolysis. The temperature was then raised to 85℃ and maintained for 15 minutes to inactivate the enzyme. The mixture was centrifuged, and the liquid phase of the hydrolysate was collected. Citric acid was added to the hydrolysate to adjust the pH to 5, and the mixture was centrifuged again. The liquid phase was collected, and lithium hydroxide was added to adjust the pH to 12. The mixture was stirred for 1 hour. The reaction solution was cooled to 0℃, and 10 g of sodium hypochlorite solution with 10% available chlorine content was added. The mixture was stirred until the system decolorized. 20 ml of dichloromethane was added to the reaction solution, and the mixture was stirred for 2 hours. After separation, the aqueous phase was collected. The aqueous phase was heated to 40℃ and purified by ultrafiltration. The ultrafiltration membrane had a molecular weight cutoff of 50 kDa, and the pressure was 0.3 MPa. After purification, the solution was concentrated to one-third of its original volume. Add 3 times the volume of food-grade ethanol to the concentrate, cool the system to 5°C, filter, and wash the filter cake twice with a 70% ethanol solution. Dry under vacuum at 70°C for 12 hours (vacuum degree -0.095 MPa), and pulverize to obtain white tamarind polysaccharide gum with an extraction rate of 21.2%.

[0026] Comparative Example 1

[0027] Add 100g of tamarind seed kernel powder to 4000g of purified water, heat to 70℃ and extract for 70min. Cool the extract to room temperature, let stand for 1h, then centrifuge and collect the crude extract. Add 0.3g of lipase (Novozymes) to the crude extract. ® 677 BG) and 0.5 g of protease (Flavourzyme 500L) were added, and the system was maintained at pH 4.5-5.5 and temperature 45-55℃ for 2 h of enzymatic hydrolysis. The temperature was then raised to 85℃ and maintained for 15 minutes to inactivate the enzyme. The mixture was centrifuged, and the liquid hydrolysate was collected. Citric acid was added to the hydrolysate to adjust the pH to 4, and the mixture was centrifuged again. The liquid phase was collected, and sodium hydroxide was added to adjust the pH to 11-12. The mixture was stirred for 2 h. The reaction solution was cooled to 5℃, and 20 g of sodium hypochlorite solution with 10% available chlorine content was added. The mixture was stirred until the system decolorized. The reaction solution was heated to 40℃ and purified by ultrafiltration. The ultrafiltration membrane had a molecular weight cutoff of 50 kDa, and the pressure was 0.3 MPa. After purification, the solution was concentrated to one-third of its original volume. Four times the volume of food-grade ethanol was added to the concentrate, and the system was cooled to 3℃ for 6 h of crystallization. The mixture was filtered, and the filter cake was washed twice with 70% ethanol solution. Vacuum drying at 60℃ for 14 hours (vacuum degree -0.095MPa) followed by pulverization yielded white tamarind polysaccharide gum with an extraction rate of 25.7%.

[0028] Comparative Example 2

[0029] Add 100g of tamarind seed kernel powder to 4000g of purified water, heat to 70℃ and extract for 70min. Cool the extract to room temperature, let it stand for 1h, centrifuge, and collect the crude extract. Add citric acid to the crude extract to adjust the pH to 4, centrifuge, collect the liquid phase, add sodium hydroxide to the liquid phase to adjust the pH to 11-12, and stir for 2h. Cool the above reaction solution to 5℃, add 20g of sodium hypochlorite solution with 10% available chlorine content, and stir until the system decolorizes. Heat the reaction solution to 40℃ and purify by ultrafiltration. The ultrafiltration membrane has a molecular weight cutoff of 50 kDa and a pressure of 0.3MPa. After purification, concentrate to one-third of the original volume. Add 4 times the volume of food-grade ethanol to the concentrate, cool the system to 3℃, crystallize for 6h, filter, and wash the filter cake twice with 70% ethanol solution. Freeze-dry for 36 hours at a vacuum degree of -0.085 MPa, then pulverize to obtain gray tamarind polysaccharide gum with an extraction rate of 26.5%.

[0030] Comparative Example 3

[0031] Add 100g of tamarind seed kernel powder to 4000g of purified water, heat to 70℃ and extract for 70min. Cool the extract to room temperature, let stand for 1h, then centrifuge and collect the crude extract. Add 0.3g of lipase (Novozymes) to the crude extract. ® 677 BG) and 0.5 g of protease (Flavourzyme 500L) were added, and the system was maintained at pH 4.5-5.5 and temperature 45-55℃ for 2 h of enzymatic hydrolysis. The temperature was then raised to 85℃ and maintained for 15 minutes to inactivate the enzyme. The mixture was centrifuged, and the liquid hydrolysate was collected. Citric acid was added to the hydrolysate to adjust the pH to 4, and the mixture was centrifuged again. The liquid phase was collected, and sodium hydroxide was added to adjust the pH to 11-12. The mixture was stirred for 2 h. The reaction solution was cooled to 5℃, and 20 g of sodium hypochlorite solution with 10% available chlorine content was added. The mixture was stirred until the system decolorized. 20 ml of ethyl acetate was added to the reaction solution, and the mixture was stirred for 1 h. After standing and separating the layers, the aqueous phase was collected and concentrated under reduced pressure to one-third of its original volume. Four times the volume of food-grade ethanol was added to the concentrate, and the system was cooled to 3℃ for 6 h of crystallization. The crystals were filtered, and the filter cake was washed twice with 70% ethanol solution. Freeze-dry for 36 hours at a vacuum degree of -0.085 MPa, and after pulverization, a white tamarind polysaccharide gum was obtained with an extraction rate of 29.8%.

[0032] The physical properties and extraction yields of the samples prepared in each embodiment and comparative example are summarized in Table 1 below. Extraction yield = weight of tamarind polysaccharide gum / tamarind kernel powder × 100%.

[0033] Table 1: Summary Table of Properties and Extraction Yield

[0034] Analysis of the results in Table 1 shows that the yield of Example 3 was slightly lower than that of Examples 1 and 2, indicating that the extraction temperature was too high, which may have led to a small amount of degradation of the polysaccharide components and a decrease in the extraction yield. Comparative Example 3 had the highest extraction yield, and the ultrafiltration step in the surface purification process had the greatest impact on the yield.

[0035] Transmittance test: Instrument: Ultraviolet-Vis spectrophotometer Wavelength: 660nm Sample preparation: The products obtained in Examples 1-3 and Comparative Examples 1-3 were prepared into 1% aqueous solutions as test solutions; deionized water was used as a reference with 100% transmittance.

[0036] The quality test results of the samples prepared in each embodiment and comparative example are summarized in Table 2 below.

[0037] Table 2: Quality Summary Table

[0038] Analysis of the results in Table 2 shows that the tamarind polysaccharide gum prepared by this method is all white and odorless, with a transmittance greater than 94%, indicating that the purification process of this invention can achieve the technical effects of decolorization and deodorization. The samples prepared in Comparative Examples 1-3 are all dark in color, and their solutions have poor transmittance. Comparative Example 1, without organic solvent washing, has the highest content of fatty acid impurities in its extract, indicating poor removal efficiency, suggesting that organic solvent washing can significantly reduce the fatty acid content in the product. Comparative Example 2, without enzymatic hydrolysis and organic solvent washing, has the highest protein residue in its final extract, reaching 4.56%, indicating that enzymatic hydrolysis can decompose the large protein molecules in the tamarind kernel powder, reducing their molecular weight. Combined with organic solvent washing and ultrafiltration, it can remove protein impurities from the extract. The chemical degradation purification process can oxidize the aldehydes and ketones that cause odor in the extract into carboxylic acids, which then form salts with sodium hydroxide, becoming water-soluble impurities, which are finally removed by ultrafiltration.

[0039] The above description is not intended to limit the present invention, nor is the present invention limited to the examples given above. Any changes, modifications, additions, or substitutions made by those skilled in the art within the scope of the present invention are also within the protection scope of the present invention.

Claims

1. A method for preparing high-transparency tamarind polysaccharide gum for decolorization and deodorization, characterized in that, Includes the following steps: a. Add tamarind kernel powder to purified water at a ratio of 30-50 times by weight, heat and extract, cool the extract to room temperature, let it stand, separate the solid and liquid, collect the liquid phase, and obtain crude tamarind polysaccharide extract; b. Add a complex enzyme to the crude extract prepared in step a for enzymatic hydrolysis. The complex enzyme contains lipase and protease. After enzymatic hydrolysis, the enzyme is inactivated, solid-liquid separation is performed, and the liquid phase is collected to obtain the enzymatic hydrolysate. c. Add citric acid to the enzymatic hydrolysate prepared in step b, adjust the pH of the system to 3-5, separate the solid and liquid phases, collect the liquid phase, add a strong base to the liquid phase, adjust the pH of the system to 11-12, stir the reaction for 1-2 hours, and obtain purified solution 1. d. Cool the purified solution 1 prepared in step c to 0-10℃, add a sodium hypochlorite solution with 10% available chlorine content, stir the reaction until the system decolorizes, and obtain purified solution 2; e. Add an organic solvent to the purified solution 2 prepared in step d, stir for 0.5-2 hours, allow to stand and separate into layers, collect the aqueous phase, and obtain purified solution 3; f. The purified solution 3 prepared in step e is purified by ultrafiltration and concentrated to obtain purified solution 4; g. Add a low alcohol solvent to the purified liquid 4 prepared in step f, cool to 0-5℃, precipitate solid, filter, collect the filter cake, wash and vacuum dry, and pulverize to obtain the high transparency tamarind polysaccharide gum.

2. The method according to claim 1, characterized in that, In step a, the extraction temperature is raised to 60-100℃.

3. The method according to claim 1, characterized in that, In step b, the amount of the compound enzyme added is 0.1-0.5% of the mass of the crude extract; the enzymatic hydrolysis conditions are: pH 4.5-5.5, temperature 45-55℃, and time 1-2 hours.

4. The method according to claim 1, characterized in that, In step c, the strong base is one or a combination of sodium hydroxide, potassium hydroxide, and lithium hydroxide.

5. The method according to claim 1, characterized in that, In step d, the amount of sodium hypochlorite solution used is 10-30% of the tamarind kernel powder.

6. The method according to claim 1, characterized in that, In step e, the organic solvent is one of ethyl acetate, isopropyl acetate, and dichloromethane.

7. The method according to claim 1, characterized in that, In step f, the ultrafiltration purification membrane has a molecular weight cutoff of 50 kDa.

8. The method according to claim 1, characterized in that, In step g, the lower alcohol is food-grade ethanol or isopropanol, and the amount used is 3-6 times the volume of the purified liquid 4. The washing solvent is a 70% ethanol solution.

9. A highly transparent tamarind polysaccharide gum prepared by the method according to any one of claims 1-8, characterized in that, Its 1% aqueous solution has a transmittance of ≥94% at a wavelength of 660nm and has no obvious fishy smell.

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