Method for preparing licorice protein from licorice residues

Abstract

The invention discloses a method for preparing licorice protein from licorice residues. Comprising the steps of licorice protein crude product separation, extraction, refining, decoloration and purification. The liquorice protein is prepared from the liquorice residues, and the method has the advantages of being simple in extraction process and high in operability; and the used solvent and raw materials are easy to buy and have small influence on the environment. The glycyrrhiza uralensis residues are used for preparing the glycyrrhiza uralensis protein to the greatest extent, the prepared glycyrrhiza uralensis protein with the content of 55%-70% meets the requirement of the market for feed protein, and the glycyrrhiza uralensis residues have extremely high market prospects.

Description

Technical Field

[0001] The invention belongs to the field of plant extraction, and particularly relates to a method for preparing liquorice protein from liquorice residue. Background Art

[0002] Licorice, also known as Guolao, sweet grass, Ural licorice, and sweet root, is the dried root and rhizome of Glycyrrhiza uralensis Fisch., Glycyrrhiza inflata Bat., or Glycyrrhiza glabra L. of the leguminous plants. Licorice is distributed in the provinces and regions of Northeast China, North China, and Northwest China. Licorice has extremely high medicinal value and has the effects of tonifying the spleen and replenishing qi, clearing away heat and detoxifying, removing phlegm and relieving cough, relieving pain, and harmonizing various medicines. It is often used for weak spleen and stomach, fatigue, palpitations and shortness of breath, cough and sputum, acute pain in the abdomen and limbs, carbuncle, sore, and relieve drug toxicity and potency. Licorice was listed as a national second-level protected plant in the "National Key Protected Wild Plant List" in 2021.

[0003] Licorice protein is a natural plant protein with high nutritional value and anti-stress, detoxification and immune health functions. Licorice protein is often used as feed protein to promote animal growth and improve the quality of meat, eggs and dairy products. The protein content in licorice is about 4.9%, containing more than a dozen essential amino acids for farmed animals.

[0004] However, the current processing of licorice is mainly to extract glycyrrhizic acid, and the residue is discarded. The licorice residue after extracting glycyrrhizic acid also contains a large amount of useful substances. And discarding it with the residue is undoubtedly a huge waste of licorice material resources. Since licorice is currently listed as a national second-level protected plant, licorice protein has broad market prospects. Therefore, it is urgent to invent a method for preparing licorice protein from licorice residue, which can not only meet the market demand for feed protein, but also maximize the use of licorice material resources. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing liquorice protein from liquorice residue, so as to maximize the use of liquorice material resources.

[0006] In order to achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing licorice protein from licorice residue comprises the following steps: 1) Isolation of crude licorice protein: add 3-5 times amount of purified water to licorice residue and heat to extract, heat to 70-80°C, stir for 3-5 hours; repeat 2-4 times, combine all purified water, centrifuge, and collect supernatant; under room temperature, add 1.5-2.5 times amount of 93-95% ethanol to the supernatant, stir, let stand, filter to remove the filtrate, dry at 60-70°C and crush to obtain licorice protein isolate; 2) Extraction of crude licorice protein: add 8-10 times the amount of 93-95% ethanol to the licorice protein isolate and heat and stir to 60-75°C for 2-3 hours; after stirring, centrifuge to remove the ethanol solution, dry and crush the wet material at 70-85°C to obtain crude licorice protein material 1; 3) Purification of crude licorice protein: add 13-15 times amount of purified water and 0.20-0.30 times amount of sodium hydroxide to crude licorice protein material 1, heat and stir, heat to 85-95°C, and stir for 1-2 hours; after stirring, centrifuge to remove alkali solution, wash the wet material with 5-8 times amount of purified water, dry and crush at 70-85°C to obtain crude licorice protein material 2; 4) Decolorization and purification of licorice protein: add 8-10 times of water to the crude licorice protein material 2, and add glacial acetic acid or hydrochloric acid to the material to adjust the pH to 6-7, and stir and dissolve at 50℃-60℃ for 0.5-2 hours to form a mixed solution; then add 0.10-0.20 times of activated carbon, stir at 50℃-60℃ for 0.5-1 hour, and then cool to 25℃-30℃; after removing the filtrate, dry and crush at 50℃-70℃ to obtain the finished licorice protein.

[0007] In a preferred embodiment, step 1) is repeated 3 times. In step 1), ethanol is added to the supernatant in an amount twice that of the supernatant. In step 3), sodium hydroxide is added in an amount of 0.25 times. In step 4), activated carbon is added in an amount of 0.15 times that of the supernatant.

[0008] In a preferred embodiment, in step 1), 3-5 times of purified water is added to the licorice residue to heat and extract, where times refers to the mass multiple; 1.5-2.5 times of ethanol is added to the supernatant, where times refers to the volume multiple. In step 2), 8-10 times of ethanol is added to the licorice protein isolate and heated and stirred, where times refers to the mass multiple. In step 3), 13-15 times of purified water and 0.20-0.30 times of sodium hydroxide are added to the licorice protein crude material 1 and heated and stirred, and the wet material is washed with 5-8 times of purified water, where times refers to the mass multiple. In step 4), 8-10 times of water is added to the licorice protein crude material 2, where times refers to the mass multiple. In step 4), adding 0.10-0.20 times of activated carbon means: the mass of the activated carbon added is 0.10-0.20 times the mass of the mixed solution.

[0009] Among them, step 1) is used to separate a mixture of glycyrrhizic acid, glycyrrhizic acid, polysaccharides, pigments, flavonoids, etc. from the licorice residue. Step 2) is used to remove most of the glycyrrhizic acid and polysaccharides. Step 3) is used to remove flavonoids and polysaccharides. Step 4) is used to remove pigments and a small amount of sugar. The above steps are used in sequence to gradually purify the material, glycyrrhizic acid and polysaccharides can be removed together, and decolorization and purification can be performed together to save time.

[0010] Each step is carried out under certain extraction reagents, processes and parameters to ensure higher extraction and purification effects.

[0011] After adding sodium hydroxide in step 3), the material is black and the aqueous solution is alkaline. Therefore, the purpose of step 4) activated carbon decolorization is to reduce licorice polysaccharides and pigments. Experiments have found that adjusting the pH to 6-7 with glacial acetic acid or hydrochloric acid has better reaction efficiency.

[0012] The benefits of the present invention are as follows: the present invention prepares licorice protein from licorice residue, which has the advantages of simple extraction process and strong operability; the solvents and raw materials (ethanol, sodium hydroxide, glacial acetic acid, etc.) used are easy to purchase and have little impact on the environment. Compared with using licorice as a raw material, it is more difficult to prepare high-purity licorice protein using licorice residue as a raw material. The preparation of licorice protein from licorice residue maximizes the use of licorice material resources, and no amylase or polysaccharide enzyme treatment is required during the preparation process. The licorice protein with a content of 55%-70% prepared by the present invention meets the market demand for feed protein and has a very high market prospect. DETAILED DESCRIPTION

[0013] The present invention is described in detail below with reference to specific embodiments.

[0014] Embodiment 1: A method for preparing liquorice protein from liquorice residue, comprising the following steps: 1. Isolation of crude licorice protein: Add 5 times the amount of purified water to the licorice residue and heat it up to 70°C for extraction, stirring for 5 hours. Repeat 3 times (referring to the operation: "Add 5 times the amount of purified water to the licorice residue and heat it up to 70°C for extraction, stirring for 5 hours" for a total of 3 times), combine all the purified water, centrifuge at 4000 rpm for 15 minutes, and collect the supernatant. Under normal temperature conditions, add 2 times the amount of 95% ethanol to the supernatant, stir for 0.5 hours, then let it stand for 8 hours, filter and remove the filtrate, dry and crush at 60°C to obtain licorice protein isolate.

[0015] 2. Extraction of crude licorice protein: Add 8 times the amount of 95% ethanol to the licorice protein isolate and stir at a temperature of 70°C for 2 hours. After stirring, centrifuge to remove the ethanol solution, dry and crush the wet material at 70°C to obtain crude licorice protein material 1.

[0016] 3. Purification of crude licorice protein: Add 13 times the amount of purified water and 0.25 times the amount of sodium hydroxide to the crude licorice protein material 1, heat and stir, heat to 85°C, and stir for 2 hours. After stirring, centrifuge to remove the alkalized liquid (i.e., lye), wash the wet material with 5 times the amount of purified water, dry and crush at 85°C, and obtain the crude licorice protein material 2.

[0017] 4. Licorice protein decolorization and purification: Add 10 times water to the crude licorice protein material 2, and add glacial acetic acid or hydrochloric acid to the material to adjust the pH to 7, and stir and dissolve at 55°C for 1 hour. Then add 0.15 times the amount of activated carbon, stir at 50°C-60°C for 1 hour and then cool to 25°C. After removing the filtrate, dry and crush at 60°C to obtain licorice protein. The licorice protein content is 67% (mass fraction, the same below). The yield is 10 kg of licorice residue (licorice protein content is 4.0%). According to this process step, 0.26 kg of licorice protein with a content of 67% can be obtained.

[0018] Embodiment 2: A method for preparing liquorice protein from liquorice residue, comprising the following steps: 1. Isolation of crude licorice protein: Add 3 times the amount of purified water to the licorice residue and heat it up for extraction, raise the temperature to 70°C, and stir for 3 hours. Repeat 3 times, combine all the purified water, centrifuge at 4000 rpm for 15 minutes, and collect the supernatant. Under normal temperature conditions, add 2 times the amount of 95% ethanol to the supernatant, stir for 0.5 hours, then let it stand for 8 hours, filter and remove the filtrate, dry and crush at 60°C to obtain licorice protein isolate.

[0019] 2. Extraction of crude licorice protein: Add 8 times the amount of 95% ethanol to the licorice protein isolate and stir at a temperature of 60°C for 2 hours. After stirring, centrifuge to remove the ethanol solution, dry and crush the wet material at 70°C to obtain crude licorice protein material 1.

[0020] 3. Refining of crude licorice protein: Add 13 times the amount of purified water and 0.25 times the amount of sodium hydroxide to the crude licorice protein material 1, heat and stir, heat to 85°C, and stir for 1 hour. After stirring, centrifuge to remove the alkalized liquid, wash the wet material with 5-8 times the amount of purified water, dry and crush at 70°C to obtain the crude licorice protein material 2.

[0021] 4. Licorice protein decolorization and purification: Add 8 times water to the crude licorice protein material 2, and add glacial acetic acid or hydrochloric acid to the material to adjust the pH to 7, and stir and dissolve at 60°C for 2 hours. Then add 0.15 times the amount of activated carbon, stir at 50°C for 0.5 hours and then cool to 25°C. After removing the filtrate, dry and crush at 50°C to obtain licorice protein. The licorice protein content is 60%. The yield is 10 kg of licorice residue (licorice protein content is 4.0%). According to this process step, 0.28 kg of licorice protein with a content of 60% can be obtained.

[0022] Comparative Example 1 The method is basically the same as Example 1, except that step 2 is omitted. The content of licorice protein is 10%, and the yield is 3.5 kg of licorice protein with a content of about 10% can be obtained from 10 kg of licorice residue (the content of licorice protein is 4.0%).

[0023] Comparative Example 2 The method is basically the same as Example 1, except that step 3 is omitted. The content of licorice protein is 30%, and the yield is 0.95 kg of licorice protein with a content of about 30% can be obtained from 10 kg of licorice residue (the content of licorice protein is 4.0%).

[0024] Comparative Example 3 The method is basically the same as Example 1, except that step 4 is omitted. The content of licorice protein is about 40%, and the yield is 0.45 kg of licorice protein with a content of about 40% can be obtained from 10 kg of licorice residue (the content of licorice protein is 4.0%).

[0025] The above embodiments are only used to illustrate the technical solutions of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any form, and any technical solutions obtained by equivalent replacement or equivalent transformation shall fall within the protection scope of the present invention.

Claims

1. A method for preparing glycyrrhizin from glycyrrhizic acid residue, characterized in that: The steps include: 1) Isolation of crude licorice protein: add 3-5 times amount of purified water to licorice residue and heat to extract, heat to 70-80°C, stir for 3-5 hours; repeat 2-4 times, combine all purified water, centrifuge, and collect supernatant; under normal temperature, add 1.5-2.5 times amount of ethanol to the supernatant, stir, let stand, filter to remove the filtrate, dry at 60-70°C and crush to obtain licorice protein isolate; 2) Extraction of crude licorice protein: add 8-10 times the amount of ethanol to the licorice protein isolate and heat it to 60-75°C with stirring for 2-3 hours; after stirring, centrifuge to remove the ethanol solution, dry and crush the wet material at 70-85°C to obtain a crude licorice protein material 1; 3) Purification of crude licorice protein: add 13-15 times amount of purified water and 0.20-0.30 times amount of sodium hydroxide to the crude licorice protein material 1, heat and stir, raise the temperature to 85-95°C, and stir for 1-2 hours; After the stirring is completed, the alkali solution is removed by centrifugation, and the wet material is washed with 5-8 times amount of purified water, and then dried and crushed at 70-85°C to obtain a crude licorice protein material 2; 4) Decolorization and purification of licorice protein: add 8-10 times of water to the crude licorice protein material 2, and add glacial acetic acid or hydrochloric acid to the material to adjust the pH to 6-7, and stir and dissolve at 50℃-60℃ for 0.5-2 hours to form a mixed solution; then add 0.10-0.20 times of activated carbon, stir at 50℃-60℃ for 0.5-1 hour, and then cool to 25℃-30℃; after removing the filtrate, dry and crush at 50℃-70℃ to obtain the finished licorice protein.

2. The method for preparing glycyrrhizin from glycyrrhizin residue according to claim 1, characterized in that: In step 1), repeat 3 times.

3. The method for preparing glycyrrhizin from glycyrrhizin residue according to claim 1, characterized in that: In step 1), add ethanol twice the amount of the supernatant to the supernatant.

4. The method for preparing glycyrrhizin from glycyrrhizic acid residue according to claim 1, characterized in that: In step 3), add 0.25 times the amount of sodium hydroxide.

5. The method for preparing glycyrrhizin from glycyrrhizic acid residue according to claim 1, characterized in that: In step 4), add 0.15 times the amount of activated carbon.

6. The method for preparing glycyrrhizin from glycyrrhizic residue according to claim 1, characterized in that: In step 1), 3-5 times amount of purified water is added to the liquorice residue to extract by heating, wherein times refers to the mass multiple; 1.5-2.5 times amount of ethanol is added to the supernatant, wherein times refers to the volume multiple.

7. The method for preparing glycyrrhizin from glycyrrhizin residue according to claim 1, characterized in that: In step 2), 8-10 times amount of ethanol is added to the licorice protein isolate, and the mixture is heated and stirred, wherein times refers to the mass multiple.

8. The method for preparing glycyrrhizin from glycyrrhizic residue according to claim 1, characterized in that: In step 3), 13-15 times amount of purified water and 0.20-0.30 times amount of sodium hydroxide are added to the crude licorice protein material 1, and the mixture is heated and stirred. The wet material is washed with 5-8 times amount of purified water, where times refers to mass multiples.

9. The method for preparing glycyrrhizin from glycyrrhizic residue according to claim 1, characterized in that: In step 4), add 8-10 times of water to the crude liquorice protein material 2, where times refers to the mass multiple.

10. The method for preparing glycyrrhizin from glycyrrhizic residue according to claim 1, characterized in that: In step 4), adding 0.10-0.20 times the amount of activated carbon means that the mass of the activated carbon added is 0.10-0.20 times the mass of the mixed solution.