Preparation method of licorice extract and preservative

Abstract

The preparation method comprises the following steps: crushing licorice roots, adding ethanol with the concentration of 50-70%, carrying out first alcohol extraction, and collecting a first extracting solution; adding ethanol which contains 0.3-0.8% of ammonia and has the concentration of 50-70% into the precipitate, carrying out second alcohol extraction, and collecting a second extracting solution, wherein the addition amount of the ethanol is 3-10 times of the mass of the liquorice; the pH value of the acidic ethanol is 2-4, the concentration of the acidic ethanol is 50-70%, the addition amount of the acidic ethanol is 3-10 times of the mass of the licorice roots, third alcohol extraction is carried out, and a third extracting solution is collected; and combining the first extracting solution, the second extracting solution and the third extracting solution, evaporating and concentrating to obtain the liquorice extract. The glycyrrhizic acid content can reach 12% or above, the liquiritin content can reach 1.5% or above, and the glycyrrhizic acid and liquiritin compound has a good antibacterial effect, is natural and safe when being used as a food preservative, and can prolong the shelf life of food.

Description

Technical Field

[0001] The present invention belongs to the technical field of preservatives, and particularly relates to a preparation method of licorice extract and a preservative comprising the licorice extract prepared by this method. Background Art

[0002] Licorice is a perennial plant of the legume family, with a sweet taste and a neutral nature, and has a long medicinal history. Licorice is both a food and a drug resource and is a safe and non-toxic substance. Licorice extract is an additive with various functions such as antibacterial, anti-inflammatory, detoxifying, and deodorizing. The main active substances of licorice extract include glycyrrhizic acid, glycyrrhetinic acid, liquiritin, liquiritin apioside, isoliquiritin apioside, isoliquiritigenin, glycyrrhizinate, etc.

[0003] Traditional licorice extraction techniques include water extraction method and solvent extraction method. Among them, the water extraction method has a higher extraction rate, but there are more impurity components obtained; currently, the solvent extraction method is more common and can extract the main active substances of licorice extract. In the prior art, licorice extract is mainly used in the pharmaceutical field for drugs such as cough relief, anti-inflammatory, and liver protection, in the cosmetic field for cosmetics such as whitening, sunscreen, and moisturizing, and in the food field for enhancing the taste and fragrance of food, improving the quality and stability of food, and the utilization of its antibacterial effect is relatively less. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method of licorice extract applicable to food preservatives, and the obtained licorice extract has high contents of glycyrrhizic acid and liquiritin, has good antibacterial activity, is used as a food preservative, is natural and safe, and can effectively extend the shelf life of food.

[0005] The present invention provides a preparation method of licorice extract, comprising:

[0006] S1: After crushing licorice, sieve it through a 10 - 40 mesh sieve;

[0007] S2: Add ethanol with a concentration of 50 - 70% to the obtained licorice powder, and the addition amount of ethanol is 5 - 12 times the mass of licorice, perform the first alcohol extraction, and collect the first extraction solution;

[0008] S3: Add ethanol with a concentration of 50 - 70% containing 0.3 - 0.8% ammonia to the precipitate after extraction, and the addition amount of ethanol is 3 - 10 times the mass of licorice, perform the second alcohol extraction, and collect the second extraction solution;

[0009] S4: Add acidic ethanol with a concentration of 50 - 70% and a pH value of 2 - 4 to the precipitate after extraction, and the addition amount of acidic ethanol is 3 - 10 times the mass of licorice, perform the third alcohol extraction, and collect the third extraction solution;

[0010] S5: Combine the first extract, the second extract and the third extract, evaporate and concentrate to obtain the licorice extract.

[0011] With the above solution, different ethanol solvents are used to extract licorice successively. Most of the active ingredients are extracted in the first ethanol extraction process, glycyrrhizic acid is further extracted in the second ethanol extraction, liquiritin is further extracted in the third ethanol extraction. The content of glycyrrhizic acid in the finally obtained licorice extract can reach more than 12%, and the content of liquiritin can reach more than 1.5%. It has good antibacterial effects, is natural and safe as a food preservative, and can extend the shelf life of food.

[0012] According to another specific embodiment of the present invention, in the preparation method of the licorice extract disclosed by the present invention, in step S4, add acidic ethanol with a concentration of 60% and a pH value of 3 to the precipitate. The addition amount of the acidic ethanol is 6 times the mass of the licorice, and reflux at 90 °C for 60 min.

[0013] With the above solution, due to two extractions, the content of the remaining active substances in the precipitate decreases, and the extraction efficiency is greatly reduced. Therefore, the heating reflux method is selected to extract as many remaining active substances as possible at a high temperature.

[0014] According to another specific embodiment of the present invention, in the preparation method of the licorice extract disclosed by the present invention, in step S3, add ethanol with a concentration of 60% containing 0.8% ammonia to the precipitate. The addition amount of the ethanol is 8 times the mass of the licorice, and perform ultrasonic-assisted extraction. The power of the ultrasonic extraction is 500 W, and the extraction time is 60 min.

[0015] With the above solution, ultrasonic-assisted extraction is used without heating, reducing the loss of ammonia in the solution, and greatly shortening the extraction time and improving the extraction efficiency.

[0016] According to another specific embodiment of the present invention, in the preparation method of the licorice extract disclosed by the present invention, in step S2, add ethanol with a concentration of 70% which is 10 times the mass of the licorice to the licorice powder, and perform ultrasonic-assisted extraction for 90 min; then add ethanol with a concentration of 70% which is 6 times the mass of the licorice, and perform ultrasonic-assisted extraction for 60 min; the power of the ultrasonic extraction is 400 W.

[0017] With the above solution, ultrasonic-assisted extraction is used without heating, the temperature during the extraction process is relatively low, reducing the loss of volatile components, and greatly shortening the extraction time and improving the extraction efficiency.

[0018] According to another specific embodiment of the present invention, the preparation method of the licorice extract disclosed by the present invention further includes: S6: In the licorice extract obtained in step S5, add ethanol with a concentration of 50% for dissolution, and the addition amount of ethanol is 8 times the mass of the licorice extract. Then add activated carbon accounting for 12% of the mass of the licorice extract, heat to 60 °C, keep warm and stir for 90 min, filter to obtain a filtrate, and evaporate and concentrate it.

[0019] Adopting the above solution, the licorice extract is decolorized, and when the obtained licorice extract is added to food as a preservative, it will not affect the original color of the food.

[0020] The present invention also provides a preservative for use in food, which includes a licorice extract prepared by the preparation method of the licorice extract provided by the present invention.

[0021] Adopting the above solution, the licorice extract has an antibacterial effect when used in food, can inhibit the growth of microorganisms therein, can be used as a preservative to extend the shelf life of food. Moreover, the licorice extract has effects such as protecting the liver and immunomodulation. After being added, it can increase the health care effect of food, and the unique sweet taste of the licorice extract can adjust the taste of food.

[0022] According to another specific embodiment of the present invention, the disclosed preservative further includes at least one of aloe extract, honeysuckle extract, and dandelion extract.

[0023] Adopting the above solution, aloe extract, honeysuckle extract, and dandelion extract are all extraction components of natural foods or medicines and have antibacterial and bactericidal effects. On the basis of adding the licorice extract, these components are further added to the preservative to further improve the antibacterial effect.

[0024] According to another specific embodiment of the present invention, the disclosed preservative is added and used in food; the addition amount of the licorice extract is 0.5 - 3‰, and the addition amounts of aloe extract, honeysuckle extract, and dandelion extract are 0.5 - 1.5‰, 0.2 - 0.8‰, and 1 - 1.8‰ respectively.

[0025] According to another specific embodiment of the present invention, the disclosed preservative is used by coating the surface of food; the preservative is formulated into an aqueous solution to obtain a fresh-keeping solution, and the fresh-keeping solution includes licorice extract with a concentration of 3.5 - 5.5 g / L, and at least one of aloe extract with a concentration of 8 - 11 g / L, honeysuckle extract with a concentration of 0.5 - 1.2 g / L, and dandelion extract with a concentration of 10 - 15 g / L; the food is soaked in the fresh-keeping solution or the fresh-keeping solution is sprayed on the surface of the food.

[0026] With the above-mentioned solution, the preservative ingredient has an antibacterial effect. When the preservative is applied to the surface of food, it forms an antibacterial protective film on the food surface, preventing the food from spoiling and extending the shelf life of the food.

[0027] According to another specific embodiment of the present invention, the preservative and the fresh-keeping liquid disclosed in the present invention further include modified starch with a concentration of 0.5-1.5 g / L, and the modified starch includes at least one of hydroxypropyl starch, carboxymethyl starch, cyclodextrin, and octenyl succinic anhydride starch ester.

[0028] With the above-mentioned solution, adding hydroxypropyl starch and / or carboxymethyl starch to the fresh-keeping liquid increases the film-forming property of the fresh-keeping liquid components, which is beneficial to the fresh-keeping liquid components covering the food surface to form a thin film, improving the wrapping effect and utilization rate of the fresh-keeping liquid components, and is beneficial to extending the shelf life; and the formed thin film is also beneficial to maintaining the moisture in the food and preventing water loss. Adding cyclodextrin and / or octenyl succinic anhydride starch ester to the fresh-keeping liquid can form microcapsules of the active ingredients in the fresh-keeping liquid, forming a slow-release effect, extending the effective time of the fresh-keeping liquid components, and being beneficial to extending the food shelf life. Specific Embodiments

[0029] Traditional licorice extraction techniques include water extraction method and solvent extraction method. Among them, the water extraction method has a higher extraction rate, but there are more impurity components obtained; currently, the solvent extraction method is more common and can extract the main active substances of licorice extract. The main active substances of licorice extract include glycyrrhizic acid, glycyrrhetinic acid, liquiritin, liquiritin apioside, isoliquiritin, isoliquiritigenin, glycyrrhizinate, etc. If the antibacterial activity of licorice extract can be improved, it is beneficial to utilize its antibacterial effect.

[0030] To solve the above problems, the present invention provides a preparation method of licorice extract and a preservative for food, including the licorice extract prepared by this preparation method. Among them, the present invention provides a preparation method of licorice extract to prepare licorice extract, and successively uses different ethanol solvents to extract licorice. In the first alcohol extraction process, most of the effective components are extracted, in the second alcohol extraction, glycyrrhizic acid is further extracted, in the third alcohol extraction, liquiritin apioside is further extracted, and the obtained licorice extract can have a glycyrrhizic acid content of more than 12% and a liquiritin apioside content of more than 1.5%, having good antibacterial effects, being natural and safe as a food preservative, and being able to extend the food shelf life.

[0031] In the following, the present invention will be described in detail through specific examples. However, the present invention is not limited to these examples.

[0032] Example 1

[0033] Provide a preparation method of licorice extract, including the following steps S1-S5.

[0034] S1: Weigh the licorice raw materials. After cleaning, crush the licorice and sieve it through a 10 - 40 mesh sieve, preferably a 20 - mesh sieve.

[0035] S2: Add ethanol with a concentration of 50 - 70% to the obtained licorice powder. The addition amount of ethanol is 5 - 12 times the mass of the licorice. After soaking for a period of time, perform the first ethanol extraction and collect the first extract. Specifically, the first ethanol extraction can be room - temperature extraction (such as room - temperature extraction for 7 - 15 h), heating extraction (such as extraction at 60 - 80 °C for 5 - 8 h), heating reflux extraction (such as reflux extraction at 90 °C for 2 - 4 h), ultrasonic - assisted extraction, etc. The first ethanol extraction can add ethanol in portions for 1 - 3 extractions. For example, in the case of heating reflux extraction, first add 70% ethanol with a mass 10 times that of the licorice, reflux extract for 2 h, then add 70% ethanol with a mass 8 times that of the licorice and reflux extract for 1 h.

[0036] In a specific embodiment, for the first ethanol extraction with ultrasonic - assisted extraction, first add 70% ethanol with a mass 10 times that of the licorice to the licorice powder, and perform ultrasonic - assisted extraction for 90 min; add 70% ethanol with a mass 6 times that of the licorice to the precipitate, and perform ultrasonic - assisted extraction for 60 min; the ultrasonic extraction power is 400 W.

[0037] By using ethanol extraction, the effective components of licorice can be extracted. And with ultrasonic - assisted extraction, there is no need for heating, the temperature during the extraction process is relatively low, reducing the loss of volatile components, and greatly shortening the extraction time and improving the extraction efficiency.

[0038] S3: Add ethanol with a concentration of 50 - 70% containing 0.3 - 0.8% ammonia to the precipitate after extraction. The addition amount of ethanol is 3 - 10 times the mass of the licorice, and perform the second ethanol extraction, then collect the second extract. Specifically, the second ethanol extraction can be room - temperature extraction (such as room - temperature extraction for 4 - 10 h), heating extraction (such as extraction at 60 - 80 °C for 3 - 5 h), heating reflux extraction (such as reflux extraction at 90 °C for 1 - 3 h), ultrasonic - assisted extraction, etc. The third ethanol extraction can add ethanol in portions for 1 - 3 extractions.

[0039] In a specific embodiment, for the second ethanol extraction, add 60% ethanol containing 0.8% ammonia to the precipitate. The addition amount of ethanol is 8 times the mass of the licorice, perform ultrasonic - assisted extraction, the ultrasonic extraction power is 500 W, and the extraction time is 60 min.

[0040] The remaining precipitate after the first ethanol extraction is extracted with ethanol containing ammonia, which can further extract glycyrrhizic acid therein, increase the glycyrrhizic acid content of the licorice extract, and enhance the antibacterial activity of the licorice extract. And ultrasonic-assisted extraction is adopted, without heating, reducing the loss of ammonia in the solution, and greatly shortening the extraction time and improving the extraction efficiency; moreover, since the first ethanol extraction has been carried out, the content of active substances in the precipitate decreases, and the extraction effect will be reduced, so the ultrasonic power is increased.

[0041] S4: Add acidic ethanol with a concentration of 50 - 70% and a pH value of 2 - 4 to the precipitate after extraction. The addition amount of the acidic ethanol is 3 - 10 times the mass of the licorice, and perform the third ethanol extraction, and collect the third extraction solution. Specifically, the third ethanol extraction can be methods such as normal temperature leaching, heating leaching, heating reflux leaching, ultrasonic-assisted leaching, etc. The third ethanol extraction can be carried out by adding the acidic ethanol in portions for 1 - 3 extractions.

[0042] In a specific embodiment, add acidic ethanol with a concentration of 60% and a pH value of 3 to the precipitate. The addition amount of the acidic ethanol is 6 times the mass of the licorice, and reflux at 90°C for 60 min.

[0043] Specifically, the acidic ethanol can be prepared by adding one of hydrochloric acid, sulfuric acid, and acetic acid solution to ethanol. Preferably, the acidic ethanol prepared with acetic acid solution is used. Acetic acid is relatively safe, and the third extraction solution obtained by extraction contains acetic acid. After subsequent mixing with the second extraction solution containing ammonia water, a small amount of ammonium acetate can be produced, and it also has an antiseptic effect and can be used in food.

[0044] The remaining precipitate after the second ethanol extraction is extracted with acidic ethanol, which can further extract liquiritin therein, increase the liquiritin content of the licorice extract, and enhance the antibacterial activity of the licorice extract. Since two extractions have been carried out, the content of the remaining active substances in the precipitate decreases, and the extraction efficiency is greatly reduced. Therefore, the heating reflux method is selected to extract as many remaining effective substances as possible at a high temperature.

[0045] S5: Combine the first extraction solution, the second extraction solution, and the third extraction solution, evaporate and concentrate to obtain the licorice extract.

[0046] The preparation method of the licorice extract of the present invention can achieve a glycyrrhizic acid content of more than 12% and a liquiritin content of more than 1.5% in the prepared licorice extract. In particular, in step S2, first add ethanol with a concentration of 70% at 10 times the mass of the licorice, and assist in extraction with ultrasonic waves at a power of 400W for 90 minutes. Then add ethanol with a concentration of 70% at 6 times the mass of the licorice, and assist in extraction with ultrasonic waves at a power of 400W for 60 minutes; in step S3, add ethanol with a concentration of 60% containing 0.8% ammonia at 8 times the mass of the licorice to the precipitate, and assist in extraction with ultrasonic waves at a power of 500W for 60 minutes; in step S4, add acidic ethanol with a concentration of 60% and a pH value of 3 at 6 times the mass of the licorice to the precipitate, and reflux at 90°C for 60 minutes. The glycyrrhizic acid content in the prepared licorice extract can reach more than 18%, and the liquiritin content can reach more than 2.5%; it has good antibacterial activity and is suitable for use as a food preservative.

[0047] In a specific embodiment, the preparation method further includes S6: In the licorice extract obtained in step S5, add ethanol with a concentration of 50% for dissolution, and the addition amount of ethanol is 8 times the mass of the licorice extract. Then add activated carbon at 12% of the mass of the licorice extract, heat to 60°C, keep warm and stir for 90 minutes, filter to obtain a filtrate, and evaporate and concentrate. Using this method to decolorize the licorice extract, when the obtained licorice extract is added to food as a preservative, it will not affect the original color of the food.

[0048] Example 2

[0049] Provide a preservative. The preservative is used for food and includes a licorice extract, and the licorice extract is prepared by the preparation method of the licorice extract provided in Example 1.

[0050] The licorice extract has an antibacterial effect when used in food, can inhibit the growth of microorganisms therein, can be used as a preservative to extend the shelf life of food. And the licorice extract has effects such as protecting the liver and immunomodulation. After adding, it can increase the health care effect of food, and the unique sweet taste of the licorice extract can adjust the taste of food.

[0051] Specifically, the preservative is preferably used for wet powder. Wet powder foods refer to products mainly made from one or more of rice, wheat flour or other cereal flours, edible starches, with or without the addition of other auxiliary materials, and are generally made through production processes such as slurry preparation, forming, cooling, and packaging, including wet rice noodles, wet grain processed products, and wet starch products. The moisture content in wet powder is high, and it is easy to mildew, deteriorate and become sour at room temperature. Therefore, preservatives need to be added during the production of wet powder to inhibit the growth of microorganisms and extend the shelf life of wet powder. Among them, when using the preservative, it can be used after being mixed with the raw materials of the wet powder, or the preservative can be coated on the surface of the wet powder.

[0052] In a specific embodiment, the preservative further includes at least one of aloe extract, honeysuckle extract, and dandelion extract.

[0053] Aloe extract, honeysuckle extract, and dandelion extract are all extracted components of natural foods or medicines and have antibacterial and bactericidal effects. On the basis of adding licorice extract, these components are further added to the preservative to further improve the antibacterial effect.

[0054] In a specific embodiment, when the preservative is added and used in food, the addition amount of licorice extract is 0.5-3‰, and the addition amounts of aloe extract, honeysuckle extract, and dandelion extract are 0.5-1.5‰, 0.2-0.8‰, and 1-1.8‰ respectively.

[0055] Among them, adding and using the preservative in food means mixing the preservative with food raw materials, and the addition amount refers to the proportion in the main food raw materials. For example, when the preservative is used for wet powder, the preservative is mixed with the raw materials of the wet powder. Specifically, when preparing fresh wet rice noodles, the preservative is added to the rice slurry and then subsequent steps are carried out; when preparing fresh wet vermicelli, the preservative and starch are mixed and then the dough is prepared.

[0056] In one specific embodiment, the preservative is used by coating the surface of the food. The preservative is formulated into an aqueous solution to obtain a fresh-keeping solution. The fresh-keeping solution includes licorice extract with a concentration of 3.5-5.5 g / L, and at least one of aloe extract with a concentration of 8-11 g / L, honeysuckle extract with a concentration of 0.5-1.2 g / L, and dandelion extract with a concentration of 10-15 g / L. Specifically, the food is soaked in the fresh-keeping solution or the fresh-keeping solution is sprayed on the surface of the food; specifically, when used for preparing fresh wet vermicelli, the cooked vermicelli is soaked in the fresh-keeping solution for 30-60 s.

[0057] The components of the preservative have antibacterial effects. When the preservative is used by coating the surface of the food, an antibacterial protective film is formed on the surface of the food to prevent the food from spoiling and extend the shelf life of the food.

[0058] In addition, the preservative can be used after being mixed with the raw materials of the food, and at the same time, the preservative is used by coating the surface of the food; in this way, the preservative is added both inside and outside the food. This combined method of internal addition and external addition ensures the antibacterial effect and extends the shelf life of the food.

[0059] In one specific embodiment, the preservative solution further includes modified starch with a concentration of 0.5 - 1.5 g / L. The modified starch includes at least one of hydroxypropyl starch, carboxymethyl starch, cyclodextrin, and octenyl succinic anhydride starch ester, and is fully mixed and stirred evenly, which is beneficial to extending the shelf life. Among them, adding hydroxypropyl starch and / or carboxymethyl starch to the preservative solution increases the film-forming property of the components of the preservative solution, which is beneficial for the components of the preservative solution to cover the surface of the food to form a thin film, improving the wrapping effect and utilization rate of the components of the preservative solution, and is beneficial to extending the shelf life; and the formed thin film is also beneficial to maintaining the moisture in the food and preventing water loss. Adding cyclodextrin and / or octenyl succinic anhydride starch ester to the preservative solution can form microcapsules with the active ingredients in the preservative solution, forming a slow-release effect and extending the effective time of the components of the preservative solution, which is beneficial to extending the shelf life of the food.

[0060] In a preferred embodiment, the preservative solution includes octenyl succinic anhydride starch ester with a concentration of 0.4 g / L and hydroxypropyl starch with a concentration of 0.6 g / L; this makes the preservative solution have both good film-forming property and slow-release property, and can significantly extend the shelf life of the food.

[0061] The preservative provided by the present invention is used in fresh wet noodles prepared from potato starch. After the fresh wet noodles are vacuum-packed, the total number of colonies (lg CFU / g) is detected after being stored at 4°C for different times. The results show that it can be stored for 2 - 3 months at 4°C. Compared with the fresh wet noodles without adding preservatives, which can only be stored for less than 7 days, the shelf life is significantly increased. It can be seen that the preservative of the present invention has an obvious antibacterial effect. And adding aloe extract, honeysuckle extract, dandelion extract and licorice extract for compound use can improve the antibacterial effect. Moreover, using part or all of licorice extract, aloe extract, honeysuckle extract or dandelion extract to prepare the preservative solution and coating it on the outside of the fresh wet noodles as an external preservative, so that the preservative is added both inside and outside the fresh wet noodles, can significantly improve the antibacterial effect and extend the shelf life. Further, adding modified starch with good film-forming property and microcapsule effect is beneficial to extending the antibacterial effect of the preservative solution and extending the shelf life.

[0062] It should be noted that, in addition to the embodiments of the present invention described in the above specific embodiments, those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Although the description of the present invention is introduced in combination with preferred embodiments, this does not mean that the features of this invention are limited to this embodiment. On the contrary, the purpose of introducing the invention in combination with the embodiment is to cover other alternatives or modifications that may be extended based on the claims of the present invention. In order to provide a deep understanding of the present invention, many specific details are included in the above description, and the present invention can also be implemented without using these details. In addition, in order to avoid confusion or obscuring the key points of the present invention, some specific details will be omitted in the description. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0063] Although the present invention has been described by referring to some preferred embodiments of the invention, those of ordinary skill in the art should understand that the above content is a further detailed description of the present invention in combination with specific embodiments, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions. Those skilled in the art can make various changes in form and details, including making several simple deductions or substitutions, without departing from the spirit and scope of the present invention.

Claims

1. A method for preparing a liquorice extract, characterized in that: include: S1: Grind the licorice and pass it through a 10-40 mesh sieve; S2: adding 50-70% ethanol to the obtained licorice powder, wherein the amount of ethanol added is 5-12 times the mass of the licorice, performing a first alcohol extraction, and collecting a first extract; S3: adding 50-70% ethanol containing 0.3-0.8% ammonia to the extracted precipitate, wherein the amount of ethanol added is 3-10 times the mass of the licorice, performing a second alcohol extraction, and collecting a second extract; S4: adding acidic ethanol with a pH value of 2-4 and a concentration of 50-70% to the extracted precipitate, wherein the amount of acidic ethanol added is 3-10 times the mass of the licorice, performing a third alcohol extraction, and collecting a third extract; S5: combining the first extract, the second extract and the third extract, evaporating and concentrating them to obtain the licorice extract.

2. The method for preparing the licorice extract according to claim 1, characterized in that: In step S4, 60% acidic ethanol with a pH value of 3 is added to the precipitate, the amount of the acidic ethanol added is 6 times the mass of the licorice, and the mixture is refluxed at 90° C. for 60 minutes.

3. The method for preparing the licorice extract according to claim 1, characterized in that: In step S3, 60% ethanol containing 0.8% ammonia is added to the precipitate, the amount of ethanol added is 8 times the mass of the licorice, and ultrasonic-assisted extraction is performed, the power of ultrasonic extraction is 500W, and the extraction time is 60 minutes.

4. The method for preparing the licorice extract according to claim 1, characterized in that: In step S2, 70% ethanol in a concentration of 10 times the mass of the licorice is added to the licorice powder, and ultrasonic-assisted extraction is performed for 90 minutes; then 70% ethanol in a concentration of 6 times the mass of the licorice is added, and ultrasonic-assisted extraction is performed for 60 minutes; wherein the power of the ultrasonic extraction is 400W.

5. The method for preparing the licorice extract according to any one of claims 1 to 4, characterized in that: The preparation method further comprises: S6: Add 50% ethanol to dissolve the licorice extract obtained in step S5, the amount of ethanol added is 8 times the mass of the licorice extract, and then add 12% activated carbon of the mass of the licorice extract, heat to 60°C and keep stirring for 90 minutes, filter, obtain the filtrate, and evaporate and concentrate.

6. A preservative, characterized in that The preservative is used for food and comprises a licorice extract, wherein the licorice extract is prepared by the preparation method of the licorice extract according to any one of claims 1 to 5.

7. The preservative according to claim 6, characterized in that The preservative further comprises at least one of aloe extract, honeysuckle extract and dandelion extract.

8. The preservative according to claim 7, characterized in that The preservative is added to food for use; The added amount of the licorice extract is 0.5-3‰, and the added amounts of the aloe extract, the honeysuckle extract, and the dandelion extract are 0.5-1.5‰, 0.2-0.8‰, and 1-1.8‰, respectively.

9. The preservative according to claim 7, characterized in that The preservative is applied on the surface of the food; wherein The preservative is prepared into an aqueous solution to obtain a fresh-keeping solution, wherein the fresh-keeping solution includes the licorice extract at a concentration of 3.5-5.5 g / L, and at least one of the aloe extract at a concentration of 8-11 g / L, the honeysuckle extract at a concentration of 0.5-1.2 g / L, and the dandelion extract at a concentration of 10-15 g / L; The food is immersed in the fresh-keeping liquid, or the fresh-keeping liquid is sprayed on the surface of the food.

10. The preservative according to claim 9, characterized in that The fresh-keeping solution also includes modified starch with a concentration of 0.5 to 1.5 g / L, and the modified starch includes at least one of hydroxypropyl starch, carboxymethyl starch, cyclodextrin, and octenyl succinate starch ester.