CN1861638A - Process for preparing pectin and heavy metallic ion adsorber by soybean peel combined production - Google Patents

Abstract

The invention relates to a method for preparing pectin and a heavy metal ion adsorbent through joint production of soybean seed coats. Including (1) Preparation of pectin: (1) Soybean seed coat is selected, removed and washed with water; (2) Soybean pectin extraction: using a complexing agent for one extraction and two extractions; (3) Decolorization Two methods: activated carbon adsorption decolorization and cold alkali decolorization; (4) pectin precipitation: use 6 mol/raise to adjust the pH value to 1.5-3.0 by acid precipitation; (5) solid-liquid separation: deacidification by suction filtration water; (6) solvent treatment: the solvent adopts pectin insoluble in its water-miscible organic solvent, and it is precipitated from the concentrated solution to reclaim pectin; (7) precipitate is recovered: adopt suction filtration and further solvent Eluting and dehydration to remove impurities; (8) Product acquisition: solvent removal, drying and pulverization. (2) Preparation of heavy metal ion adsorbent: use soybean seed coat or dried soybean skin after extracting pectin as raw material, pretreat with metal chelating agent and dilute alkali, and then treat with organic acid, inorganic weak acid and surfactant Finally, the residual acid is removed by rinsing with water, dried and pulverized to obtain a powdery heavy metal ion adsorbent. The invention has the advantages that the soybean seed coat is used as a raw material, the price is cheap, and the technology is mature.

Description

Method for preparing pectin and heavy metal ion adsorbent by co-production of soybean seed coat

One, technical field: the present invention relates to a kind of method for preparing pectin and heavy metal ion adsorbent, especially take soybean seed coat as main raw material, extract the method for pectin and heavy metal ion adsorbent by deep processing.

2. Background technology: soybean oil and various soybean proteins are the main products of domestic and foreign soybean processing industries at present. In the process of soybean processing, it is first necessary to carry out selection and sorting preprocessing such as dehulling and degerming to ensure the quality and yield of soybean oil and various soybean proteins. Soybean seed coat is the largest by-product produced during soybean deep processing, accounting for about 8-10% of soybean weight. The nutritional value of soybean seed coat is low (crude protein content 11%, crude fiber content 36%, crude fat content 1%), it is not easy to be digested and absorbed by animals, and it contains a large amount of anti-nutritional factor - phytic acid, even if it is barely used as cattle Feeds for ruminants such as sheep and sheep have low utilization value. Pectin has good gelation, emulsification and adsorption functions, and is widely used in the fields of food, medicine, cosmetics production and water treatment.

At present, the raw materials for extracting pectin at home and abroad are mainly citrus peel, apple pomace, sugar beet pomace and other materials. In the process, the pectin is insoluble in ethanol, acetone and other water-miscible organic solvents or is extracted by flocculation and precipitation in the presence of some metal salt ions. The process flow is: raw material pretreatment→acid hydrolysis→filtration→decolorization→ash removal→concentration→precipitation→drying→crushing→standardized treatment→finished product. The key points in the pectin production process are the two steps of extraction and separation.

In recent years, foreign countries have begun to use soybean seed coats as raw materials to carry out research and development of extracting pectin. The representative method for preparing pectin from soybean seed coats is: (1) Raw material pretreatment: soybean seed coats (through sieving and wind selected) as raw material, stirred with water 12 times the weight of soybean skin for 1 hour, after flotation and washing, poured out the floating part, rinsed and drained and used to remove impurities such as silt. (2) Soybean seed coat hydrolysis: acid and heat hydrolysis, one extraction and two extractions of slag extraction. The concentration of inorganic acid is expressed in moles, diluted with a solution with a concentration of 6 moles/liter, and then fine-tuned to the rated pH value under the monitoring of the acidity meter, stirred, hydrolyzed and leached for a certain period of time under a certain bath ratio; Monitor pH changes during extraction. (3) Neutralization: Use 4 mol/L NaOH solution to adjust the pH value to reduce the acidity, so as not to stay in a strong acid environment for a long time, resulting in excessive hydrolysis and affecting the pectin yield and product quality. (4) Solid-liquid separation: Suction filtration is carried out in a Buchner funnel, and a vacuum pump provides negative pressure. (5) Decolorization: Activated carbon adsorption decolorization. The solution is preheated to 82° C., the pH is adjusted to 2.5, 2 to 5% (weight/volume) of the solution is added with activated carbon, the mixture is kept under stirring for 30 minutes, and the activated carbon is removed by suction filtration in a Buchner funnel. (6) Concentration: Atmospheric pressure, reduced pressure (65° C.) and ultrafiltration concentration were carried out respectively. (7) Solvent precipitation: Solvent precipitation is one of the effective methods for separating pectin substances. With methanol, ethanol and acetone, the effects of flocculation and sedimentation are similar. (8) Sediment recovery: adopt suction filtration method, then rinse with water-containing ethanol, and dehydrate with concentrated ethanol to remove impurities. (9) Obtaining the product: pulverize after precipitation and drying, and pass through a 100-mesh standard sieve. This method theoretically solves the technical feasibility of extracting pectin from soybean seed coat, but in the actual application process, there are problems of low output efficiency and high difficulty in process control.

3. Summary of the invention: the object of the present invention is to provide a method for preparing pectin and heavy metal ion adsorbent through coproduction of soybean seed coats for the defects of the prior art. The method for extracting pectin is based on the fact that the soybean seed coat contains pectin substances in a state of combining with calcium and magnesium ions, and thus cannot be dissolved in water. The complexing agent can compete with calcium and magnesium ions to combine with calcium and magnesium ions, so that the pectin in the state of binding to calcium and magnesium ions is free and becomes soluble in water, so that the pectin enters the extraction solution to achieve the purpose of extracting pectin. At the same time, the heavy metal ion adsorbent was directly prepared by using the soybean dregs separated after extraction.

Its technical solutions include:

(1) The method for preparing pectin:

(1) Preparation and pretreatment of raw materials: Soybean seed coat needs to be selected and removed, then add 10-20 times of normal temperature water, adjust the pH value to 11, stir for 20-40 minutes, wash and purify;

(2) Soybean pectin extraction: take the method of extracting once and twice by complexing agent; the amount of complexing agent is 0.5%-2.0% according to the concentration of making a certain solution, pH value 7.5-11.0, stirring for 50-70 minutes , and monitor the change of pH value at a temperature of 65°C to 95°C;

(3) Decolorization of extract: two methods of activated carbon adsorption decolorization and cold alkali decolorization;

(4) Pectin precipitation: adjust the pH value to 1.5-4.5, acid precipitation for 15-25 minutes;

(5) Solid-liquid separation: deacidified water by filter press;

(6) Pickling after press filtration: pickling for 10-25 minutes at a pH value of 1.5 to 4.5;

(7) Washing with alcohol/ammonia solution: After pectin is precipitated with an organic alcohol solvent with a concentration of 40-60%, the pH value is adjusted to 8.0-9.0 with ammonia water for 30 minutes;

(8) Separation and recovery of precipitates: the pectin obtained by solvent precipitation is rinsed with 60%, 70% and 95% to 98% aqueous solvents successively;

(9) Obtaining the product: desolvation, drying and pulverization.

The complexing agents used to extract soybean pectin include sodium hexametaphosphate and EDTA; the choice of organic alcohol solvents includes several solvents such as methanol, ethanol, propanol, isopropanol, acetone, etc., and food grade ethanol is suitable.

(2) The method for preparing heavy metal ion adsorbent:

Use soybean seed coats or dried soybean skins after extracting pectin as raw materials, pretreat with metal chelating agents and dilute alkali, and then treat with organic acids, inorganic weak acids and surfactants, and then soak with water to remove residual acids. After drying and crushing, a powdery heavy metal ion adsorbent is obtained.

The organic acid for preparing the heavy metal ion adsorbent is citric acid, the weak inorganic acid is phosphoric acid, and the drying temperature is between 70-95°C. (Please check if this part is correct)

On the basis of the above scheme, comparative research and experiments are carried out on the relevant technical parameters, and the following specific measures for improving the yield and quality of the product are proposed.

1. The impact of washing on the quality of pectin. Cleaning is conducive to improving product quality, and can effectively improve product color and reduce ash.

2. The particle size of bean curd affects the yield of pectin. Considering various factors comprehensively, the soybean seed coat raw material that is not crushed is used directly.

3. The influence of the type of complexing agent used to extract soybean pectin on the yield and product quality: Sodium hexametaphosphate, EDTA and other complexing agents are used to combine with calcium and magnesium ions in soybean seed coats. Comprehensive consideration of factors such as environmental protection, price, source, and effect has certain advantages for EDTA to be used as a complexing agent. It is also found in the experiment that the extraction yield can be improved by properly adjusting the pH value of the extract.

4. The influence of the complexing agent concentration in the extract on the yield: Soy pectin was extracted with different concentrations of complexing agent solutions, and it was found that the concentration of the complexing agent was lower than 0.2, the effect was not obvious, and the yield was low. The concentration is high, and the yield is stable, but the concentration is higher than 0.8 and no longer shows an upward trend.

5. The effect of extraction temperature on the yield of pectin: The pectin extraction experiments were carried out at room temperature 15°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 95°C, and 100°C, and the results found that : The temperature is low and the yield is low, but it is not high temperature, the yield is correspondingly high, extraction at 80 ℃ ~ 90 ℃, the recovery rate is similar, and the extraction rate above 95 ℃ decreases, and the compound The viscosity of the pectin aqueous solution that goes out also reduces to some extent. It may be that the leached pectin is further degraded under strong heat conditions, and the molecules become smaller and difficult to settle. When extracting pectin with EDTA, the influence of temperature on the yield is similar to that of acid extraction.

6. Effect of bath ratio on pectin yield and product quality: Other conditions were fixed, and the extraction experiment was carried out according to the conditions of bath ratio 5:1, 10:1, 15:1, 20:1, and 25:1, and the results found that: When the bath ratio is 5:1, the soybean seed coat cannot be completely soaked, and the bath ratio is more than 10:1 to completely soak through; Too high yield is also lower, and the viscosity of the obtained pectin solution is slightly worse. Further comparison between the more suitable bath ratios of 8:1 and 15:1 shows that 10:1 to 12:1 is the most suitable.

7. Effect of extraction time on pectin yield: other conditions are fixed, extraction time is a variable, and a series of comparative experiments are done. The result is: the time is too short, the pectin in the soybean seed coat is not completely hydrolyzed and extracted, and the yield is obviously low. If the time is too long, the pectin in the soybean hulls will be excessively hydrolyzed into small molecules, and after adding a solvent, it will be difficult to precipitate, and the yield will also decrease, and the obtained pectin will have poor water-soluble viscosity. The relationship between extraction time and pectin yield was consistent with the results and trends of the acid extraction test. Within 60 minutes, along with the increase of time, the yield rises, and 60 minutes is advisable, and prolonging time (90 minutes) yield drops slightly on the contrary.

8. The relationship between the pH value of acid precipitation and the yield of pectin: other conditions are fixed, the pH value of acid precipitation is variable, and a series of comparative experiments are done. The result is: the acid precipitation pH value is too low, the pectin precipitation in the soybean seed coat extract is not complete, the pectin substances are all lost with the liquid, and the yield is obviously low. It is better to have a pH value of 1.5 to 4.5.

9. The relationship between pickling pH value and pectin yield: Take the same amount of acid-precipitated pectin and wash it with acid water with different pH values. After comparing the cleaning effect, it is found that some pectin will dissolve in water if the pH is too low. The yield is low; the pH is too high, which is unfavorable to equipment and technology. It is better to wash with acidified water with a pH value similar to that of acid precipitation.

10. Selection of water-miscible organic solvents: Pectin is insoluble in water-miscible organic solvents such as ethanol, so it can be precipitated from the concentrate with such organic solvents. In the test, several solvents such as methanol, ethanol (absolute ethanol and industrial ethanol), propanol, isopropanol, and acetone were compared, and it was found that the precipitation effect was not much different. Considering comprehensive factors such as the toxicity of methanol, the source and price of propanol and isopropanol, the difficulty of recycling, and the specification requirements of food additives, it is better to choose food-grade ethanol produced by fermentation.

According to the new extraction conditions optimized by the laboratory, the improved new process route was used to carry out the scale-up and repeated experiments. The results of 7 batches of EDTA extraction pectin method stakeout experiments are shown in the following table:

Note: All batches of experiments only undergo one extraction, if the gel yield can reach 14-15% after two extractions batch 1 2 3 4 5 6 7 Sample weight (g) 200 200 400 400 400 400 400 Pectin weight (g) 22.375 23.087 47.048 44.091 46.016 44.16 47.03 Yield (%) 11.19 11.54 11.76 11.02 11.50 11.04 11.76

The present invention extracts pectin from soybean seed coat compared with the traditional method of extracting pectin from materials such as citrus peel, apple pomace, sugar beet pomace, at least has the following advantages: (1), soybean seed coat is used as the by-product of soybean processing enterprise , cheap and easy to collect; (2), soybean seed coats can be stored and transported without further processing; (3), forecasting the development trend of low-sugar, low-calorie health foods and functional foods and the increase in market demand, soybean seed coats The natural low-ester pectin (calcium gelation) obtained in the process will become a new type of pectin other than traditional pectin (high-ester pectin such as citrus pectin, apple pectin, high sugar gelation). In addition, in the scheme of the present invention, the heavy metal ion adsorbent can also be directly prepared by using the soybean dregs separated by extracting pectin. The technical scheme of the present invention has been proved through laboratory and pilot tests that the extraction and separation process is more mature and reasonable, and has a good application prospect.

Four, accompanying drawing description: accompanying drawing is process flow chart of the present invention.

Five, specific embodiment:

Referring to the accompanying drawings, specific embodiments of the present invention include:

(1) The scheme for preparing pectin is:

(1) Preparation and pretreatment of raw materials: Soybean seed coats need to be selected and removed, then add 15 times of normal temperature water, adjust the pH value to 11, stir for 30 minutes, wash and purify.

(2) Extraction of soybean pectin: take the method of one extraction and two extractions of the complexing agent. Sodium hexametaphosphate or EDTA is used as the complexing agent, the concentration of which is made into a certain solution is 1.0%, the pH value is 9.5, stirred for 60 minutes, and the change of the pH value is monitored at a temperature of 85°C.

(3) Decolorization of extract: two methods of activated carbon adsorption decolorization and cold alkali decolorization.

(4) Pectin precipitation: adjust the pH value to 2.5, acid precipitation for 20 minutes.

(5) Solid-liquid separation: deacidify water by suction filtration.

(6) Pickling after press filtration: pickling for 15 minutes at pH 2.5.

(7) Washing with alcohol/ammonia solution after pressure filtration again: after the pectin is precipitated with 50% ethanol solvent, the pH value is adjusted to 8.5 with ammonia water for 30 minutes;

(8) Separation and recovery of precipitates: the pectin obtained by solvent precipitation is rinsed with 60%, 70% and 95% aqueous solvents successively;

(9) The separated product is screw extruded, dried, pulverized and packaged to obtain a finished product.

(2) The scheme for preparing heavy metal ion adsorbent is:

Use soybean seed coats or dried soybean skins after extracting pectin as raw materials, pretreat with metal chelating agents and dilute alkali, and then treat with organic acids, inorganic weak acids and surfactants, and then soak with water to remove residual acids. After drying and crushing, a powdery heavy metal ion adsorbent is obtained. The organic acid for preparing the heavy metal ion adsorbent is citric acid, the weak inorganic acid is phosphoric acid, and the drying temperature is 90°C.

Claims (4)

1, a kind of method for preparing pectin and heavy metal ion adsorbent by coproduction of soybean seed coat, is characterized in that comprising: (1) The method for preparing pectin: (1) Preparation and pretreatment of raw materials: Soybean seed coat needs to be carefully selected, after removing impurities, add 10-20 times of normal temperature water, adjust the pH value to 11, stir for 20-40 minutes, wash and purify; (2) Soybean pectin extraction: take the method of one extraction and two extractions of the complexing agent, the dosage of the complexing agent is 0.5%-2.0% according to the concentration of a certain solution, the pH value is 7.5-11.0, and stirred for 50-70 minutes , and monitor the change of pH value at a temperature of 65°C-95°C; (3) Decolorization of extract: activated carbon adsorption decolorization and cold alkali decolorization methods: (4) Pectin precipitation: adjust the pH value to 1.5-4.5, acid precipitation for 15-25 minutes; (5) Solid-liquid separation: deacidified water by filter press; (6) pickling after press filtration: pickling for 10-25 minutes under the condition of pH value 1.5-4.5; (7) Washing with alcohol/ammonia solution: After the pectin is precipitated with an organic alcohol solvent with a concentration of 40-60%, the pH value is adjusted to 8.0-9.0 with ammonia water for 30 minutes; (8) Separation and recovery of precipitates: the pectin obtained by solvent precipitation is rinsed with 60%, 70% and 95% to 98% aqueous solvents successively; (9) Product acquisition: pulverization after precipitation and drying; (2) The method for preparing heavy metal ion adsorbent: Use soybean seed coats or dried soybean skins after extracting pectin as raw materials, pretreat with metal chelating agents and dilute alkali, and then treat with organic or inorganic weak acids and surfactants, then soak with water to remove residual acids. After drying and crushing, a powdery heavy metal ion adsorbent is obtained. 2. The method for preparing pectin and heavy metal ion adsorbents according to claim 1, characterized in that: the complexing agent used to extract soybean pectin comprises sodium hexametaphosphate, EDTA; organic alcohol solvent Choices include methanol, ethanol, propanol, isopropanol, acetone, and several solutions. 3. The method for preparing pectin and heavy metal ion adsorbents according to claim 1, characterized in that: the organic acid for preparing the heavy metal ion adsorbents is citric acid, the weak inorganic acid is phosphoric acid, and the drying temperature is 70 Between -95°C. 4. The method for preparing pectin from soybean seed coats according to claim 2, characterized in that: the choice of organic alcohol solvent is preferably food grade ethanol.

Images