Preparation method of polyphenol substances in sugarcane byproducts

Abstract

The invention discloses a preparation method of polyphenol substances in sugarcane byproducts. The preparation method comprises the following steps: (1) adding ethanol into a sugarcane byproduct solution, extracting, filtering, and concentrating filtrate to prepare an aqueous solution; (2) filtering the aqueous solution through a nanofiltration membrane, collecting membrane filtrate, and drying to obtain sugarcane polyphenol; the molecular weight of the nanofiltration membrane is 100 to 5000D; the aqueous solution is filtered by a nanofiltration membrane at least twice. The process disclosed by the invention is simple to operate, high in process unit continuity, cost-saving, easy to industrialize, capable of improving the production efficiency and relatively good in economic benefit; according to the method disclosed by the invention, the sugarcane polyphenol can be extracted under the condition that toxic and harmful organic solvents and / or macroporous resins are not adopted for purification, so that the safety of the product is ensured, the production cost is reduced, and the harm to the environment is reduced; cheap and easily available cane molasses can be used as a raw material, and the additional value of by-products in the sugar industry is improved.

Description

Technical Field

[0001] The invention relates to a method for preparing polyphenols in sugarcane by-products. Background Art

[0002] Polyphenols are a class of secondary metabolites commonly found in plants, primarily in their roots, leaves, bark, and fruits. Their antioxidant, antibacterial, anti-inflammatory, antiviral, and hypoglycemic, hypolipidemic, and antihypertensive properties have made them a research hotspot in the pharmaceutical and food industries. The content and structure of polyphenols vary significantly in different foods, with sugarcane boasting a high polyphenol content and possessing potent free radical scavenging and antioxidant activity.

[0003] Sugarcane (Saccharum officinarum L.), a member of the genus Saccharum, is a temperate and tropical crop used as a raw material for sucrose production. Widely cultivated in Guangxi, Guangdong, and Yunnan provinces of my country, it is a highly renewable plant. Sugarcane is sweet, neutral, and non-toxic, and has benefits such as promoting salivation, clearing heat, and relieving dryness and hangover.

[0004] Domestic and foreign scholars have conducted in-depth research on the extraction of polyphenolic compounds from sugarcane and its byproducts. For example, CN106177555A discloses a method for extracting sugarcane polyphenols from sugarcane scum, CN112715937A discloses a method for preparing a sugarcane polyphenol extract from sugarcane, CN106890273A discloses a method for preparing polyphenols from sugarcane bagasse, CN104306758A discloses a method for extracting polyphenols from sugarcane peel, and CN113197975A discloses a method for preparing sugarcane leaf polyphenols. However, traditional extraction methods, on the one hand, mostly use large amounts of organic solvents (such as ethyl acetate, acetone, methanol, etc.) for extraction, extraction, and purification. The large amount of organic solvents used can cause solvent residues in the product, affecting food safety. On the other hand, the purification process often uses macroporous resins, which generate large amounts of acidic and alkaline wastewater during use, increasing the cost of industrial wastewater treatment for enterprises and causing serious harm to the environment.

[0005] Sugarcane molasses is a byproduct of the sugar industry. It is a brownish-yellow viscous liquid whose main components are sugars, proteins, amino acids, and minerals. The sugarcane sugar industry produces large quantities of sugarcane molasses, making it readily available and inexpensive. Sugarcane molasses contains a large amount of fermentable sugars, making it an excellent fermentation raw material. It can be used as a substrate for fermentation products such as yeast and monosodium glutamate, and can also be used as animal feed. Compared to byproducts such as sugarcane husks, bagasse, and sugarcane leaves, sugarcane molasses is easier to store and transport and less prone to spoilage. However, little research has been conducted on the extraction of sugarcane polyphenols from sugarcane molasses.

[0006] The quality requirements for sugarcane molasses in the Light Industry Standard QB / T2684-2005 of the People's Republic of China are shown in Table 1 below:

[0007] Table 1

[0008] project Require Detection method Appearance Dark brown viscous liquid sensory odor No odor sensory Total sugar (sucrose + reducing sugar) / % ≥48.0 QB / T2684-2005 Purity (total sugar / refractive index) / % ≥60.0 QB / T2684-2005 acidity ≤15 QB / T2684-2005 Total ash (sulfated ash) / % ≤12.0 QB / T2684-2005 Copper (Cu) / (mg / kg) ≤10.0 QB / T2684-2005 Total colony count / (cfu / g) <![CDATA[≤5.0×10 5 ]]> QB / T2684-2005

[0009] It can be seen from the standards that the presence of polyphenols in sugarcane molasses lowers the standards of sugarcane molasses. Therefore, if sugarcane polyphenols can be extracted from sugarcane molasses, not only can the quality standards of sugarcane molasses be improved, but also high value-added polyphenols can be obtained. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a method for preparing polyphenols from sugarcane by-products. The process of the present invention is simple to operate, has strong continuity of process units, is cost-effective, is easy to industrialize, improves production efficiency, and has good economic benefits. The present invention can extract sugarcane polyphenols without using toxic and harmful organic solvents and / or macroporous resins for purification, thereby ensuring product safety, reducing production costs, and minimizing environmental harm. The method can use inexpensive and readily available sugarcane molasses as a raw material, thereby increasing the added value of sugar industry by-products.

[0011] The present invention solves the above technical problems through the following technical solutions.

[0012] The present invention provides a method for preparing polyphenols from sugarcane by-products, comprising the following steps:

[0013] (1) adding ethanol to the sugarcane byproduct solution for extraction, filtering, and concentrating the filtrate to prepare an aqueous solution;

[0014] (2) The aqueous solution is filtered through a nanofiltration membrane, and the membrane filtrate is collected and dried to obtain sugarcane polyphenols; the molecular weight of the nanofiltration membrane is 100-5000D; the aqueous solution is filtered through the nanofiltration membrane at least twice.

[0015] In the present invention, preferably, the preparation method does not require the use of organic solvents other than ethanol, especially toxic and harmful organic solvents such as ethyl acetate, acetone or methanol.

[0016] In the present invention, preferably, the preparation method can extract and obtain sugarcane polyphenols without using a macroporous resin for purification.

[0017] In step (1), the sugarcane by-product can be selected from one or more of sugarcane molasses, sugarcane peel, sugarcane bagasse and sugarcane leaves, preferably sugarcane molasses.

[0018] In step (1), the sugarcane by-product solution can be obtained by diluting the sugarcane by-product with water.

[0019] Wherein, the water may be pure water.

[0020] The amount of water used may be 3-10 times the mass of the sugarcane by-product, such as 3 times, 4 times, 5 times or 10 times, preferably 4-5 times.

[0021] In step (1), the concentration of ethanol can be conventional in the art, for example, 95%. The ethanol used in the present invention can be food grade alcohol.

[0022] In step (1), the amount of ethanol used can be controlled so that the ethanol concentration in the solution reaches 50-90°, such as 50°, 70°, 80° or 90°, preferably 70-80°. Preferably, the ethanol is added in batches.

[0023] In step (1), the amount of ethanol used can be 3-120 times the mass of the sugarcane by-product, for example, 4 times, 12 times, 22 times or 120 times.

[0024] In step (1), preferably, ethanol is added with stirring.

[0025] The stirring time may be 0.5-1 h, for example 0.5 h.

[0026] In step (1), preferably, after adding the ethanol, the process may further include a standing operation.

[0027] The standing time may be 0.5-1 h, for example 0.5 h.

[0028] In step (1), the filtration can be carried out by vacuum filtration.

[0029] In step (1), the filtration process may further include the operation of spreading red soil to aid filtration.

[0030] In step (1), the concentration can be carried out by a reduced pressure concentration method. In the present invention, the concentration operation can remove ethanol from the solution to obtain an aqueous solution.

[0031] In step (1), the concentration equipment can be conventional in the art, such as a rotary evaporator.

[0032] In step (2), the molecular weight of the nanofiltration membrane may be 100D, 500D, 3000D or 5000D, preferably 500-3000D.

[0033] In step (2), preferably, the aqueous solution is filtered twice through a nanofiltration membrane, first through a nanofiltration membrane with a molecular weight of 3000-5000D, and then through a nanofiltration membrane with a molecular weight of 100-500D. The aqueous solution is first filtered through a high molecular weight filter to remove macromolecular impurities such as proteins; and then filtered through a low molecular weight filter to remove small molecular impurities such as inorganic salts.

[0034] In some preferred embodiments, the aqueous solution is first filtered through a nanofiltration membrane with a molecular weight of 5000D, and then filtered through a nanofiltration membrane with a molecular weight of 100D.

[0035] In some preferred embodiments, the aqueous solution is first filtered through a nanofiltration membrane with a molecular weight of 5000D, and then filtered through a nanofiltration membrane with a molecular weight of 500D.

[0036] In some preferred embodiments, the aqueous solution is first filtered through a nanofiltration membrane with a molecular weight of 3000D, and then filtered through a nanofiltration membrane with a molecular weight of 500D.

[0037] In step (2), the drying method can be spray drying or freeze drying.

[0038] The inlet air temperature of the spray drying may be 160-200°C, for example 180°C.

[0039] The outlet air temperature of the spray drying can be 80-100°C, for example 90°C.

[0040] The fan speed of the spray drying can be 40-60 Hz, for example 50 Hz.

[0041] The impact time of the spray drying may be 3-5 s, for example 4 s.

[0042] The striker interval of the spray drying may be 10-15 s, for example 13 s.

[0043] The pre-freezing temperature of the freeze-drying process may be (-50)-(-30)°C, for example -40°C.

[0044] The pre-freezing time of the freeze-drying process may be 3-5 hours, for example 4 hours.

[0045] The freezing temperature of the freeze-drying process may be (-60)-(-40)°C, for example -50°C.

[0046] The vacuum degree of the freeze-drying process may be less than 80 Pa, for example, less than 60 Pa.

[0047] On the basis of conforming to the common sense in this field, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0048] The reagents and raw materials used in the present invention are commercially available.

[0049] The positive progress effect of the present invention is:

[0050] (1) The process of the present invention can extract sugarcane polyphenols without using toxic and harmful organic solvents, avoiding the use of toxic and harmful reagents, using only food-grade alcohol, and recycling and removing it during the process, further ensuring the safety of the product and facilitating its development in the food field.

[0051] (2) The process of the present invention is simple to operate, has strong process unit continuity, is cost-effective, is easy to industrialize, improves production efficiency, and has good economic benefits. The present invention does not require the use of macroporous resin purification methods, does not generate a large amount of industrial wastewater, reduces production costs, and reduces environmental damage.

[0052] (3) The present invention can use cheap and easily available sugarcane molasses as raw material, not only obtaining high-value-added polyphenols therein, but also improving the quality standard of sugarcane molasses; it can increase the efficiency of enterprises and reduce the risk of raw material deterioration and corruption during production; it can reduce resource waste, increase the added value of sugar industry by-products, turn waste into treasure, extend the traditional sugar industry chain, increase farmers' income, achieve efficiency improvement for enterprises, and have important significance for sustainable development. DETAILED DESCRIPTION

[0053] The present invention is further illustrated by way of examples below, but the present invention is not limited to the scope of the examples. Experimental methods in the following examples where specific conditions are not specified were performed according to conventional methods and conditions, or selected according to the product specifications.

[0054] In the examples and comparative examples of the present invention, the sugarcane molasses was sourced from Guangxi Fengtang Biochemical Co., Ltd.

[0055] Example 1

[0056] A method for extracting sugarcane polyphenols from sugarcane molasses, comprising the following steps:

[0057] (1) Take 100g of sugarcane molasses paste, add 300g of pure water and stir to dissolve. Stir for 1h until completely dissolved to obtain a brown liquid;

[0058] (2) Add 400 g of 95% ethanol solution to the liquid of step (1), take a small amount of liquid to measure the alcohol content to be 50°, stir for 0.5 h, a large amount of precipitation appears, and let it stand for 0.5 h;

[0059] (3) The feed solution of step (2) is filtered under reduced pressure and covered with red clay to obtain a brown clear solution;

[0060] (4) The solution in step (3) was concentrated under reduced pressure using a rotary evaporator to obtain 300 g of concentrated solution;

[0061] (5) The concentrated solution in step (4) was passed through a nanofiltration membrane with a molecular weight of 5000D, and the permeate side liquid was collected. The permeate side liquid was passed through a nanofiltration membrane with a molecular weight of 100D again, and the concentrated side liquid and the product liquid were collected;

[0062] (6) The product liquid in step (5) was spray-dried (inlet air temperature 180°C, outlet air temperature 90°C, fan speed 50 Hz, striker time 4 s, striker interval 13 s) to obtain sugarcane polyphenols, which were brown solid powders with a bitter aroma of tannins.

[0063] Example 2

[0064] A method for extracting sugarcane polyphenols from sugarcane molasses, comprising the following steps:

[0065] (1) Take 100g of sugarcane molasses paste, add 1000g of pure water and stir to dissolve. Stir for 1 hour until completely dissolved to obtain a brown liquid;

[0066] (2) Add 12000 g of 95% ethanol solution to the liquid of step (1), take a small amount of liquid to measure the alcohol content to be 90°, stir for 0.5 h, a large amount of precipitation appears, and let it stand for 1 h;

[0067] (3) The feed solution of step (2) is filtered under reduced pressure and covered with red clay to obtain a brown clear solution;

[0068] (4) The solution in step (3) was concentrated under reduced pressure using a rotary evaporator to obtain 800 g of concentrated solution;

[0069] (5) The concentrated solution in step (4) was passed through a nanofiltration membrane with a molecular weight of 5000D, and the permeate side liquid was collected. The permeate side liquid was passed through a nanofiltration membrane with a molecular weight of 500D again, and the concentrated side liquid and the product liquid were collected;

[0070] (6) The product liquid in step (5) was spray-dried (inlet air temperature 180°C, outlet air temperature 90°C, fan speed 50 Hz, striker time 4 s, striker interval 13 s) to obtain sugarcane polyphenols, which were brown solid powders with a bitter aroma of tannins.

[0071] Example 3

[0072] A method for extracting sugarcane polyphenols from sugarcane molasses, comprising the following steps:

[0073] (1) Take 100g of sugarcane molasses paste, add 500g of pure water and stir to dissolve. Stir for 1h until completely dissolved to obtain a brown liquid;

[0074] (2) Add 2200 g of 95% ethanol solution to the liquid of step (1), take a small amount of liquid to measure the alcohol content to be 80°, stir for 0.5 h, a large amount of precipitation appears, and let it stand for 0.5 h;

[0075] (3) The feed solution of step (2) is filtered under reduced pressure and covered with red clay to obtain a brown clear solution;

[0076] (4) The solution in step (3) was concentrated under reduced pressure using a rotary evaporator to obtain 400 g of concentrated solution;

[0077] (5) The concentrated solution in step (4) was passed through a nanofiltration membrane with a molecular weight of 3000D, and the permeate side liquid was collected. The permeate side liquid was passed through a nanofiltration membrane with a molecular weight of 500D again, and the concentrated side liquid and the product liquid were collected;

[0078] (6) The product liquid in step (5) was spray-dried (inlet air temperature 180°C, outlet air temperature 90°C, fan speed 50 Hz, striker time 4 s, striker interval 13 s) to obtain sugarcane polyphenols, which were brown solid powders with a bitter aroma of tannins.

[0079] Example 4

[0080] A method for extracting sugarcane polyphenols from sugarcane molasses, comprising the following steps:

[0081] (1) Take 100g of sugarcane molasses paste, add 400g of pure water and stir to dissolve. Stir for 1h until completely dissolved to obtain a brown liquid;

[0082] (2) Add 1200 g of 95% ethanol solution to the liquid of step (1), take a small amount of liquid to measure the alcohol content to 70°, stir for 0.5 h, a large amount of precipitation appears, and let it stand for 0.5 h;

[0083] (3) The feed solution of step (2) is filtered under reduced pressure and covered with red clay to obtain a brown clear solution;

[0084] (4) The solution in step (3) was concentrated under reduced pressure using a rotary evaporator to obtain 300 g of concentrated solution;

[0085] (5) The concentrated solution in step (4) was passed through a nanofiltration membrane with a molecular weight of 3000D, and the permeate side liquid was collected. The permeate side liquid was passed through a nanofiltration membrane with a molecular weight of 500D again, and the concentrated side liquid and the product liquid were collected;

[0086] (6) The product liquid in step (5) was spray-dried (inlet air temperature 180°C, outlet air temperature 90°C, fan speed 50 Hz, striker time 4 s, striker interval 13 s) to obtain sugarcane polyphenols, which were brown solid powders with a bitter aroma of tannins.

[0087] Example 5

[0088] A method for extracting sugarcane polyphenols from sugarcane molasses, comprising the following steps:

[0089] (1) Take 100g of sugarcane molasses paste, add 400g of pure water and stir to dissolve. Stir for 1h until completely dissolved to obtain a brown liquid;

[0090] (2) Add 1200 g of 95% ethanol solution to the liquid of step (1), take a small amount of liquid to measure the alcohol content to 70°, stir for 0.5 h, a large amount of precipitation appears, and let it stand for 0.5 h;

[0091] (3) The feed solution of step (2) is filtered under reduced pressure and covered with red clay to obtain a brown clear solution;

[0092] (4) The solution in step (3) was concentrated under reduced pressure using a rotary evaporator to obtain 300 g of concentrated solution;

[0093] (5) The concentrated solution in step (4) was passed through a nanofiltration membrane with a molecular weight of 3000D, and the permeate side liquid was collected. The permeate side liquid was passed through a nanofiltration membrane with a molecular weight of 500D again, and the concentrated side liquid and the product liquid were collected;

[0094] (6) The product liquid in step (5) is freeze-dried (pre-freezing temperature: -40°C, pre-freezing time 4h, freezing temperature: -50°C, vacuum degree: <60Pa) to obtain sugarcane polyphenols, which are brown solid powders with a bitter aroma of tannins.

[0095] Comparative Example 1

[0096] A method for extracting sugarcane polyphenols from sugarcane molasses, comprising the following steps:

[0097] (1) Take 100g of sugarcane molasses paste, add 400g of pure water and stir to dissolve. Stir for 1h until completely dissolved to obtain a brown liquid;

[0098] (2) Add 1200 g of 95% ethanol solution to the liquid of step (1), take a small amount of liquid to measure the alcohol content to 70°, stir for 0.5 h, a large amount of precipitation appears, and let it stand for 0.5 h;

[0099] (3) The feed solution of step (2) is filtered under reduced pressure and covered with red clay to obtain a brown clear solution;

[0100] (4) The solution in step (3) was concentrated under reduced pressure using a rotary evaporator to obtain 300 g of concentrated solution;

[0101] (5) The concentrated solution in step (4) was passed through a nanofiltration membrane with a molecular weight of 10,000D, and the permeate side liquid was collected. The permeate side liquid was then passed through a nanofiltration membrane with a molecular weight of 500D, and the concentrated side liquid and the product liquid were collected;

[0102] (6) The product liquid in step (5) is freeze-dried (pre-freezing temperature: -40°C, pre-freezing time 4h, freezing temperature: -50°C, vacuum degree: <60Pa) to obtain sugarcane polyphenols, which are brown solid powders with a bitter aroma of tannins.

[0103] Comparative Example 2

[0104] A method for extracting sugarcane polyphenols from sugarcane molasses, comprising the following steps:

[0105] (1) Take 100g of sugarcane molasses paste, add 400g of pure water and stir to dissolve. Stir for 1h until completely dissolved to obtain a brown liquid;

[0106] (2) Add 1200 g of 95% ethanol solution to the liquid of step (1), take a small amount of liquid to measure the alcohol content to 70°, stir for 0.5 h, a large amount of precipitation appears, and let it stand for 0.5 h;

[0107] (3) The feed solution of step (2) is filtered under reduced pressure and covered with red clay to obtain a brown clear solution;

[0108] (4) The solution in step (3) was concentrated under reduced pressure using a rotary evaporator to obtain 300 g of concentrated solution;

[0109] (5) The concentrated solution in step (4) was passed through a nanofiltration membrane with a molecular weight of 10000D, and the permeate side liquid was collected. The permeate side liquid was passed through a nanofiltration membrane with a molecular weight of 100D again, and the concentrated side liquid and the product liquid were collected;

[0110] (6) The product liquid in step (5) is freeze-dried (pre-freezing temperature: -40°C, pre-freezing time 4h, freezing temperature: -50°C, vacuum degree: <60Pa) to obtain sugarcane polyphenols, which are brown solid powders with a bitter aroma of tannins.

[0111] Effect embodiment

[0112] Sugarcane polyphenols are a new resource food. The "New Food Ingredients" have clear requirements for sugarcane polyphenols:

[0113] (1) Sensory indicators:

[0114] Table 2 Sensory requirements

[0115]

[0116] (2) Physical and chemical indicators:

[0117] Table 3 Physical and chemical indicators

[0118]

[0119]

[0120] The sugarcane polyphenols prepared in the above examples and comparative examples were tested, and the experimental results are shown in Table 4 below:

[0121] Table 4 Experimental results

[0122]

[0123] As can be seen from the above table, the processes of Examples 1-5 can all produce products that meet the requirements, while the use of nanofiltration process parameters other than those of the present invention cannot produce qualified products, and the total polyphenols and total flavonoids are both lower than the requirements for sugarcane polyphenols.

Claims

1. A method for preparing polyphenols from sugarcane by-products, characterized in that: The following steps are involved: (1) adding ethanol to the sugarcane byproduct solution for extraction, filtering, and concentrating the filtrate to obtain an aqueous solution; (2) The aqueous solution is filtered through a nanofiltration membrane, and the membrane filtrate is collected and dried to obtain sugarcane polyphenols; the molecular weight of the nanofiltration membrane is 100-5000D; and the aqueous solution is filtered through the nanofiltration membrane at least twice.

2. The method for preparing polyphenols from sugarcane by-products according to claim 1, characterized in that: The preparation method does not require the use of ethyl acetate, acetone or methanol; And / or, the preparation method does not require purification using a macroporous resin.

3. The method for preparing polyphenols from sugarcane by-products according to claim 1, characterized in that: In step (2), the molecular weight of the nanofiltration membrane is 100D, 500D, 3000D or 5000D.

4. The method for preparing polyphenols from sugarcane by-products according to claim 1, characterized in that: In step (2), the aqueous solution is filtered twice through a nanofiltration membrane, first through a nanofiltration membrane with a molecular weight of 3000-5000D, and then through a nanofiltration membrane with a molecular weight of 100-500D.

5. The method for preparing polyphenols from sugarcane by-products according to claim 4, characterized in that: In step (2), the aqueous solution is first filtered through a nanofiltration membrane with a molecular weight of 5000D, and then filtered through a nanofiltration membrane with a molecular weight of 100D; Alternatively, the aqueous solution is first filtered through a nanofiltration membrane with a molecular weight of 5000D, and then filtered through a nanofiltration membrane with a molecular weight of 500D; Alternatively, the aqueous solution is first filtered through a nanofiltration membrane with a molecular weight of 3000D, and then filtered through a nanofiltration membrane with a molecular weight of 500D.

6. The method for preparing polyphenols from sugarcane by-products according to claim 1, characterized in that: In step (1), the sugarcane by-product is selected from one or more of sugarcane molasses, sugarcane husk, bagasse and sugarcane leaves; And / or, in step (1), the sugarcane by-product solution is obtained by diluting the sugarcane by-product with water; the amount of water used is preferably 3-10 times the mass of the sugarcane by-product.

7. The method for preparing polyphenols from sugarcane by-products according to claim 1, characterized in that: In step (1), the sugarcane by-product is selected from sugarcane molasses.

8. The method for preparing polyphenols from sugarcane by-products according to claim 1, characterized in that: In step (1), the concentration of ethanol is 95%; And / or, in step (1), the amount of ethanol is controlled so that the ethanol concentration in the solution reaches 50-90°; And / or, in step (1), the amount of ethanol used is 3-120 times the mass of the sugarcane by-product; And / or, in step (1), after adding the ethanol, the step further comprises a standing operation; the standing time is preferably 0.5-1h.

9. The method for preparing polyphenols from sugarcane by-products according to claim 1, characterized in that: In step (1), the filtration is carried out by vacuum filtration; And / or, in step (1), the concentration is carried out by a reduced pressure concentration method; And / or, in step (2), the drying method is spray drying or freeze drying.

10. The method for preparing polyphenols from sugarcane by-products according to claim 9, characterized in that: The inlet air temperature of the spray drying is 160-200°C; And / or, the outlet air temperature of the spray drying is 80-100°C; And / or, the fan speed of the spray drying is 40-60 Hz; And / or, the impaction time of the spray drying is 3-5s; And / or, the spray drying needle interval is 10-15s; And / or, the pre-freezing temperature of the freeze-drying is (-50)-(-30)°C; And / or, the pre-freezing time of freeze drying is 3-5h; And / or, the freezing temperature of the freeze-drying is (-60)-(-40)°C; And / or, the vacuum degree of the freeze-drying is <80Pa.

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