A soothing stomach-fortifying freeze-dried millet porridge and a preparation method thereof

Abstract

The present application belongs to the technical field of food processing, and particularly relates to a kind of dried millet porridge for nourishing the heart and stomach and a preparation method thereof. The present application utilizes the compounding effect between raw materials to make the millet porridge have the effect of nourishing the heart and stomach. At the same time, the millet porridge is prepared into a microcapsule form by using an embedding agent to overcome the problem of no fragrance. Pre-gelatinized starch is added at an appropriate time to overcome the problems of poor reconstitution, non-uniformity after reconstitution, and poor taste.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology, specifically relating to a soothing and stomach-nourishing freeze-dried millet porridge and its preparation method. Background Technology

[0002] Millet, also known as foxtail millet, is the hulled product of the foxtail millet plant (Setaria viridis), a member of the Poaceae family. Originating in the Yellow River basin of my country, it is one of the oldest crops. Millet is rich in various vitamins, minerals, dietary fiber, and high levels of protein. It is a gluten-free, nutritious whole grain food and also a high-quality grain with both medicinal and edible properties. In China, people usually like to cook millet into porridge and eat it as a type of porridge.

[0003] With the fast pace of modern life, freshly cooked millet porridge can no longer meet the needs of young people who pursue a fast-paced lifestyle. Furthermore, this fast-paced lifestyle leads to stomach problems and insomnia for many young people, who also have a greater need for the health benefits of porridge. Therefore, frozen millet porridge has begun to appear on the market, offering the advantages of convenience and quick preparation. However, frozen millet porridge currently on the market often has the following drawbacks: 1. Due to freezing, instant porridge often lacks aroma and the fragrance of freshly cooked traditional millet porridge; 2. Existing instant porridges often suffer from uneven mixing, poor reconstitution properties, and unpleasant taste, making them difficult to compare with freshly cooked millet porridge; 3. Few instant porridges offer stomach-nourishing or calming effects.

[0004] Therefore, how to improve the aroma and taste of instant millet porridge, enhance its reconstitution properties after preparation, and make instant millet porridge have the effects of calming the nerves and nourishing the stomach to meet the needs of modern people has become an urgent problem to be solved in this field. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a soothing and stomach-nourishing freeze-dried millet porridge and its preparation method. By utilizing the compounding effect between various raw materials, the millet porridge acquires the effect of soothing the nerves and nourishing the stomach. Simultaneously, the millet porridge is prepared into microcapsules using an encapsulation agent to overcome the problem of its lack of aroma. Furthermore, pregelatinized starch is added at an appropriate time to overcome the problems of poor restitution, uneven mixing after reconstitution, and poor taste.

[0006] The technical solution of the present invention is as follows:

[0007] In a first aspect of the present invention, a soothing and stomach-nourishing freeze-dried millet porridge is provided, comprising the following ingredients by weight:

[0008] 80-100 parts millet, 3-5 parts Hericium erinaceus powder, 3-5 parts Poria cocos powder, 3-5 parts Ziziphus jujuba seed powder, 0.5-1 part baking soda, 1.5-2.5 parts hydroxypropyl-β-cyclodextrin, 6-10 parts maltodextrin, and 15-20 parts pregelatinized starch.

[0009] Furthermore, by weight, the soothing and stomach-nourishing freeze-dried millet porridge comprises the following ingredients:

[0010] 100 parts millet, 5 parts Hericium erinaceus powder, 5 parts Poria cocos powder, 5 parts Ziziphus jujuba seed powder, 0.5 parts baking soda, 2.5 parts hydroxypropyl-β-cyclodextrin, 10 parts maltodextrin, and 20 parts pregelatinized starch.

[0011] Hericium erinaceus, or monkey head mushroom, is a higher fungus belonging to the genus Hericium in the family Myricaceae. It is named for its resemblance to a monkey's head. Hericium erinaceus is delicious and nutritious. Its fruiting body, mycelium, and fermentation broth are rich in various bioactive compounds, including hericium polysaccharides, hericium ketones, sterols, and polypeptides. Traditional Chinese medicine considers hericium erinaceus to be sweet and neutral in nature, possessing the functions of "benefiting the five internal organs and aiding digestion." It has been found, particularly in daily life and clinical practice, to be remarkably effective in treating gastrointestinal mucosal diseases.

[0012] Poria cocos is the dried sclerotium of the fungus Poria cocos, belonging to the Polyporaceae family. It often parasitizes the roots of Pinus massoniana or Pinus tabuliformis. It resembles a sweet potato in shape, with a dark brown outer skin and a white or pink interior. It mainly contains two types of compounds: triterpenoids and polysaccharides. The Shennong's Classic of Materia Medica notes that Poria cocos, "when taken for a long time, calms the soul, nourishes the spirit, prevents hunger, and prolongs life."

[0013] Sour jujube seed is the dried, mature seed of a deciduous shrub or small tree belonging to the Rhamnaceae family. It is neutral in nature, sweet and sour in taste, and enters the liver, gallbladder, and heart meridians. It has the effects of nourishing the heart and liver, astringing sweat, and promoting body fluid production. Modern pharmacological studies have shown that sour jujube seed possesses biological activities such as anticonvulsant, sedative-hypnotic, anti-anxiety, cognitive function improvement, immune function enhancement, anti-atherosclerosis, anti-inflammation, and cardioprotective effects. Its main chemical components include triterpenes, flavonoids, alkaloids, and polysaccharides. When used in combination with Poria cocos, it can enhance the sedative-hypnotic, calming, and tranquilizing effects.

[0014] Pregelatinized starch, also known as α-starch, is a modified starch that has been gelatinized by heating it using a certain method.

[0015] In a second aspect of the present invention, a method for preparing the above-mentioned soothing and stomach-nourishing freeze-dried millet porridge is provided, the method comprising the following steps:

[0016] (1) Preparation of embedding agent: Hydroxypropyl-β-cyclodextrin and maltodextrin were added to distilled water and heated in a water bath to mix evenly, so as to obtain a mixed solution of hydroxypropyl-β-cyclodextrin and maltodextrin.

[0017] (2) Cooking: Put millet into a pot, rinse quickly, drain the water, add the following weight proportions of Hericium erinaceus powder, Poria cocos powder, Ziziphus jujuba seed powder, baking soda, and the mixed solution of hydroxypropyl-β-cyclodextrin and maltodextrin obtained in (1), then add drinking water, cover the pot, bring to a boil, remove the pot lid, adjust the heat, and continue cooking for 10 minutes to obtain the cooked millet porridge sample;

[0018] (3) Freeze-drying: After the millet porridge sample obtained in (2) is placed at room temperature, it is poured into a petri dish and placed in a refrigerator to freeze until the sample is completely frozen. After freezing, the sample is taken out, covered with a layer of plastic wrap, and vent holes are left on the plastic wrap. The sample is then placed in a vacuum freeze dryer for freeze-drying.

[0019] (4) Preparation: After the millet porridge sample in (3) is completely freeze-dried, take it out, put it in a container, add the pregelatinized starch in the weight proportions of the freeze-dried millet porridge, and brew it with warm water to obtain the brewed millet porridge.

[0020] Furthermore, in (1), the weight ratio of hydroxypropyl-β-cyclodextrin to maltodextrin is 1:2 to 1:5; the weight of distilled water added is 4 times the sum of the weights of hydroxypropyl-β-cyclodextrin and maltodextrin.

[0021] Furthermore, in (1), the water bath temperature is 68-72℃, and even further, it is 70℃.

[0022] Furthermore, in (2), the weight ratio of the mixed solution of hydroxypropyl-β-cyclodextrin and maltodextrin obtained in (1) to the weight ratio of millet is 100:62.5.

[0023] Furthermore, in (2), drinking water is added at a ratio of 1:10 between the weight of millet and the weight of drinking water.

[0024] Furthermore, in (3), the temperature of the refrigerator is -38.6°C;

[0025] Furthermore, in (3), the freeze-drying process is as follows: after the temperature reaches -40°C, a vacuum is drawn, the temperature is lowered to below 10Pa, and then the temperature is raised to -2°C for freeze-drying for 48 hours.

[0026] Furthermore, in (4), warm water refers to drinking water at 45-50℃.

[0027] The beneficial effects of this invention are as follows:

[0028] (1) This invention uses hydroxypropyl-β-cyclodextrin and maltodextrin as encapsulation agents and adopts "microencapsulation" encapsulation technology. When millet porridge is cooked, it is added and adsorbed on the surface of the rice grains. After the rice grains are gelatinized, it plays a role in protecting the aroma of millet porridge and greatly improves the aroma of frozen millet porridge. At the same time, it prevents the formation of hydrogen bonds between starch molecules and starch aging, improves rehydration, viscosity of rice porridge, overall uniformity and stability, and improves the reconstitution of instant porridge products.

[0029] (2) In view of the problems of uneven preparation, poor reconstitution and poor taste of instant porridge products, the present invention adds pregelatinized starch after freeze-drying, which improves its reconstitution and taste after preparation, so that people with swallowing and chewing difficulties can also eat it.

[0030] (3) The freeze-dried millet porridge provided by the present invention uses millet as a base, supplemented with pregelatinized starch, and adds extracts of Chinese medicinal herbs such as Hericium erinaceus, Ziziphus jujuba var. spinosa, and Poria cocos. After cooking, it is made into a compound millet porridge that can be brewed and eaten immediately, which improves the flavor of millet porridge and has the health benefits of calming the nerves and nourishing the stomach. Attached Figure Description

[0031] Figure 1 Image of a freeze-dried millet porridge sample from Example 1;

[0032] Figure 2 The image shows the millet porridge prepared in Example 1 after mixing.

[0033] Figure 3 Image of the millet porridge prepared in Comparative Example 2 after mixing;

[0034] Figure 4 Image of the millet porridge prepared in Comparative Example 3 after mixing;

[0035] Figure 5 Image of the millet porridge prepared in Comparative Example 4 after mixing;

[0036] Figure 6 This is a picture of the millet porridge prepared in Comparative Example 5 after mixing. Detailed Implementation

[0037] To enable those skilled in the art to better understand the present invention, the present invention will now be further described in conjunction with specific embodiments.

[0038] Example 1

[0039] A type of freeze-dried millet porridge for calming the nerves and nourishing the stomach, comprising the following ingredients by weight:

[0040] 100 parts millet, 5 parts Hericium erinaceus powder, 5 parts Poria cocos powder, 5 parts Ziziphus jujuba seed powder, 0.5 parts baking soda, 2.5 parts hydroxypropyl-β-cyclodextrin, 10 parts maltodextrin, and 20 parts pregelatinized starch.

[0041] The preparation method of the above-mentioned millet porridge for calming the nerves and nourishing the stomach includes the following steps:

[0042] (1) Preparation of encapsulating agent: 2.5 parts of hydroxypropyl-β-cyclodextrin and 10 parts of maltodextrin were added to 50 parts of distilled water at a weight ratio of 1:4 and heated in a water bath at 70°C to mix evenly to obtain a mixed solution of hydroxypropyl-β-cyclodextrin and maltodextrin.

[0043] (2) Cooking: Weigh 100 parts of millet using a balance and put them into a 24cm diameter flat-bottomed pot with a lid. Rinse the millet twice quickly with tap water, drain the water, add 5 parts of Hericium erinaceus powder, 5 parts of Poria cocos powder, 5 parts of Ziziphus jujuba seed powder, 0.5 parts of baking soda, the mixed solution of hydroxypropyl-β-cyclodextrin and maltodextrin obtained in (1) and 1000 parts of pre-boiled drinking water, cover the pot and boil it at 2100W on an induction cooker; remove the pot lid, adjust the power of the induction cooker to 1400W, and continue cooking for 10 minutes, stirring several times during the process to prevent the sample from boiling over. After cooking, the millet porridge sample is obtained.

[0044] (3) Freeze-drying: After the millet porridge sample obtained in (2) is placed at room temperature, it is poured into a glass petri dish and placed in a refrigerator at -38.6℃ until the sample is completely frozen. After the sample is taken out, it is covered with a layer of plastic wrap and a certain number of vent holes are left on the plastic wrap. It is then placed in a vacuum freeze dryer for freeze-drying. Specifically, after the temperature reaches -40℃, a vacuum is drawn and the temperature is lowered to below 10Pa. Then, the temperature is raised to -2℃ and freeze-dried for 48 hours.

[0045] (4) Preparation: After the sample is completely freeze-dried, take it out, put it in a bowl, add 20 parts of pregelatinized starch, and brew it with warm water at about 45°C to obtain compound instant millet porridge.

[0046] The photo of the resulting freeze-dried millet porridge is as follows Figure 1 As shown in the picture, the millet porridge after preparation is as follows. Figure 2 As shown.

[0047] Example 2

[0048] The difference from Example 1 is that, by weight, the calming and stomach-nourishing millet freeze-dried porridge includes the following ingredients:

[0049] 80 parts millet, 3 parts monkey head mushroom powder, 3 parts poria cocos powder, 3 parts jujube seed powder, 0.5 parts baking soda, 1.5 parts hydroxypropyl-β-cyclodextrin, 6 parts maltodextrin, and 20 parts pregelatinized starch.

[0050] The preparation method is the same as in Example 1.

[0051] Example 3

[0052] The difference from Example 1 is that in (1), the weight ratio of hydroxypropyl-β-cyclodextrin to maltodextrin is 1:2.

[0053] Example 4

[0054] The difference from Example 1 is that in (1), the weight ratio of hydroxypropyl-β-cyclodextrin to maltodextrin is 1:5.

[0055] Comparative Example 1

[0056] The difference from Example 1 is that, by weight, the calming and stomach-nourishing millet freeze-dried porridge includes the following ingredients:

[0057] 100 parts millet, 5 parts monkey head mushroom powder, 5 parts poria cocos powder, 5 parts jujube seed powder, 0.5 parts baking soda, and 20 parts pregelatinized starch.

[0058] This comparative example did not use an embedding agent to embed the millet porridge, that is, it did not include step (1) in Example 1, and the mixed solution of hydroxypropyl-β-cyclodextrin and maltodextrin obtained in (1) was not added in step (2). The other preparation methods were the same as in Example 1.

[0059] Comparative Example 2

[0060] The difference from Example 1 is that no pregelatinized starch was added to the raw materials, that is, in step (4), the freeze-dried millet porridge was directly prepared without adding pregelatinized starch.

[0061] The photo of the prepared millet porridge is as follows Figure 3 As shown.

[0062] Comparative Example 3

[0063] The difference from Example 1 is that pregelatinized starch is added before freeze-drying, specifically:

[0064] (1) Preparation of encapsulating agent: Hydroxypropyl-β-cyclodextrin and maltodextrin were added to 50 parts of distilled water at a weight ratio of 1:4 and heated in a water bath at 70°C to mix evenly to obtain a mixed solution of hydroxypropyl-β-cyclodextrin and maltodextrin.

[0065] (2) Cooking: Weigh 100 parts of millet using a balance and put them into a 24cm diameter flat-bottomed pot with a lid. Rinse the millet quickly twice with tap water, drain the water, add 5 parts of Hericium erinaceus powder, 5 parts of Poria cocos powder, 5 parts of Ziziphus jujuba seed powder, 0.5 parts of baking soda, 20 parts of pregelatinized starch, the mixed solution of hydroxypropyl-β-cyclodextrin and maltodextrin obtained in (1) and 1000 parts of pre-boiled drinking water, cover the pot and boil it at 2100W on an induction cooker; remove the pot lid, adjust the power of the induction cooker to 1400W, and continue cooking for 10 minutes, stirring several times during the process to prevent the sample from boiling over. After cooking, the millet porridge sample is obtained.

[0066] (3) Freeze-drying: After the millet porridge sample obtained in (2) is placed at room temperature, it is poured into a glass petri dish and placed in a refrigerator at -38.6℃ until the sample is completely frozen. After the sample is taken out, it is covered with a layer of plastic wrap and a certain number of vent holes are left on the plastic wrap. It is then placed in a vacuum freeze dryer for freeze-drying. Specifically, after the temperature reaches -40℃, a vacuum is drawn and the temperature is lowered to below 10Pa. Then, the temperature is raised to -2℃ and freeze-dried for 48 hours.

[0067] (4) Preparation: After the sample is completely freeze-dried, take it out, put it in a bowl, and brew it with warm water at about 45°C to obtain compound instant millet porridge.

[0068] The photo of the prepared millet porridge is as follows Figure 4 As shown.

[0069] Comparative Example 4

[0070] The difference from Example 1 is that the pregelatinized starch is in the form of 10 parts by weight, and the resulting millet porridge is shown in the picture below. Figure 5 As shown, when there is too little pregelatinized starch, the mixing effect is not good.

[0071] Comparative Example 5

[0072] The difference from Example 1 is that the pregelatinized starch was used in 50 parts by weight, and the resulting millet porridge was shown in the picture. Figure 6 As shown, when there is too much pregelatinized starch, the viscosity of the millet porridge becomes too high, resulting in clumping.

[0073] Comparative Example 6

[0074] The difference from Example 1 is that the weight parts of hydroxypropyl-β-cyclodextrin are 2.5 parts, the weight parts of maltodextrin are 2.5 parts, and the weight ratio of hydroxypropyl-β-cyclodextrin to maltodextrin is 1:1.

[0075] Comparative Example 7

[0076] The difference from Example 1 is that the weight parts of hydroxypropyl-β-cyclodextrin are 2 parts, the weight parts of maltodextrin are 0.5 parts, and the weight ratio of hydroxypropyl-β-cyclodextrin to maltodextrin is 4:1.

[0077] Comparative Example 8

[0078] The difference from Example 1 is that hydroxypropyl-β-cyclodextrin was not used as the embedding agent; only maltodextrin was used, and the amount of maltodextrin used was 12.5 parts.

[0079] Comparative Example 9

[0080] The difference from Example 1 is that maltodextrin was not used as the embedding agent; only hydroxypropyl-β-cyclodextrin was used, and the amount of hydroxypropyl-β-cyclodextrin used was 12.5 parts.

[0081] Experimental Example 1

[0082] The freeze-dried millet porridge obtained in Examples 1-4 and Comparative Examples 1-9 was prepared by mixing. After the prepared millet porridge was cooled, it was wrapped in gauze and filtered. An appropriate amount of filtrate was taken for aroma component analysis by gas chromatography-mass spectrometry, and volatile substances were analyzed by GC-O-MS (Trace 1310 / TSQ 9000 Thermo Fisher Scientific Inc., Massachusetts, USA).

[0083] Weigh 2g of sample and place it in a headspace vial. Next, add 10μL of 2mol / L 2-methyl-3-heptanone (dissolved in methanol) as an internal standard, and immediately seal the vial with a headspace cap fitted with a PTFE silicone gasket. For the extraction process, use a 50 / 30μm DVB / CAR / PDMS fiber tip, age it at 250℃ for 30 min, equilibrate the sample at 50℃ for 30 min, and then insert the extraction tip into the headspace vial for 40 min. Finally, pull out the extraction tip and desorb it in the inlet at 240℃ for 2 min.

[0084] GC conditions: DB-WAX column (30m×0.18mm×0.18μm), splitless injection; temperature program: injection port temperature 240℃, initial column temperature 40℃, hold for 3 minutes, increase to 120℃ at a rate of 5℃ / min, increase to 230℃ at a rate of 10℃ / min, hold for 10 minutes.

[0085] MS conditions: ion source temperature 200℃, transfer line temperature 250℃, electron energy 70eV. Signal acquisition was performed in full scan mode, with a scan range of 35–500 m / z.

[0086] Qualitative analysis: MS results were compared with the database of the National Institute of Standards and Technology (NIST) in the United States. The results showed that the match of volatile flavors was greater than 80, with a maximum match of 100.

[0087] Quantitative analysis: Based on the known concentration and peak area of ​​the internal standard 2-methyl-3-heptanone, the content of the flavor compound to be tested relative to the internal standard was calculated using the internal standard method.

[0088] The results are shown in Table 1:

[0089] Table 1. Characteristic compounds obtained from the detection of examples and comparative examples.

[0090]

[0091] Table 1 shows that when millet porridge is not encapsulated, the content of flavor compounds (characteristic compounds) is very low, and the porridge has little aroma. When the weight ratio of hydroxypropyl-β-cyclodextrin to maltodextrin in the encapsulating agent is not within 1:2 to 1:5, the content of flavor compounds in the millet porridge is relatively low, and the aroma is not obvious. Although the content of flavor compounds is higher than that of unencapsulated millet porridge, the improvement is not significant. When no pregelatinized starch is added, the millet porridge after reconstitution separates into rice and water, and its reconstitution is very poor. When the amount of pregelatinized starch added is small, the separation of rice and water in the millet porridge after reconstitution is improved, but it still cannot restore the viscous state of fresh millet porridge. When the amount of pregelatinized starch added is large, the viscosity of the millet porridge after reconstitution is too high, the fluidity is too poor, and the reconstitution is also poor. When pregelatinized starch is added before freeze-drying, the millet porridge is very sticky when cooked, the aroma cannot be fully released, and it is not easy to reconstitute after reconstitution.

[0092] Experiment Example 2 Sensory Evaluation

[0093] Ten quality inspectors were selected to evaluate the texture, aroma, and acceptability of the millet porridge obtained in each example and comparative example after preparation. The evaluation criteria are as follows:

[0094] The millet porridge was scored as follows: thick (10 points), moderately thick (6 points), and thin (1 point); it had a distinct aroma (10 points), a faint aroma (6 points), and virtually no aroma (1 point); it was rated as "very likable" (9 points) and "very unlikable" (1 point). The results are shown in Table 2.

[0095] Table 2 Sensory evaluation of the examples and comparative examples

[0096]

[0097]

[0098] As can be seen from the data in the table above, the products in Examples 1-4 scored approximately 9.53-9.68 in texture, 9.59-9.72 in aroma, and 9.31-9.43 in acceptability. Compared with the products in Comparative Examples 1-9, the products in the examples scored higher. This indicates that the porridge prepared by the method of the present invention has a thick texture and a distinct aroma. This is because the porridge of the present invention uses an encapsulating agent, resulting in a rich aroma.

Claims

1. A method for preparing a soothing and stomach-nourishing freeze-dried millet porridge, characterized in that, By weight, the freeze-dried millet porridge comprises the following ingredients: The ingredients are: 80-100 parts millet, 3-5 parts Hericium erinaceus powder, 3-5 parts Poria cocos powder, 3-5 parts Ziziphus jujuba seed powder, 0.5-1 part baking soda, 1.5-2.5 parts hydroxypropyl-β-cyclodextrin, 6-10 parts maltodextrin, and 15-20 parts pregelatinized starch, wherein the weight ratio of hydroxypropyl-β-cyclodextrin to maltodextrin is 1:2-5. The preparation method includes the following steps: (1) Preparation of encapsulating agent: Hydroxypropyl-β-cyclodextrin and maltodextrin were added to distilled water and heated in a water bath to mix evenly, so as to obtain a mixed solution of hydroxypropyl-β-cyclodextrin and maltodextrin; (2) Cooking: Put millet into a pot, rinse quickly, drain the water, add the above weight proportions of Hericium erinaceus powder, Poria cocos powder, Ziziphus jujuba seed powder, baking soda, the mixed solution of hydroxypropyl-β-cyclodextrin and maltodextrin obtained in (1), add drinking water, cover the pot, bring to a boil, remove the pot lid, adjust the heat, and continue cooking for 10 minutes to obtain the cooked millet porridge sample; (3) Freeze-drying: After the millet porridge sample obtained in (2) is placed at room temperature, it is poured into a petri dish and placed in a refrigerator to freeze until the sample is completely frozen. After freezing, the sample is taken out, covered with a layer of plastic wrap, and vent holes are left on the plastic wrap. The sample is then placed in a vacuum freeze dryer for freeze-drying. (4) Preparation: After the millet porridge sample in (3) is completely freeze-dried, take it out, put it in a container, add pregelatinized starch, and brew it with warm water to obtain the brewed millet porridge.

2. The preparation method according to claim 1, characterized in that, In (1), the weight of distilled water added is 4 times the sum of the weights of hydroxypropyl-β-cyclodextrin and maltodextrin.

3. The preparation method according to claim 1, characterized in that, (1) The water bath temperature is 68~72℃.

4. The preparation method according to claim 1, characterized in that, In (2), the weight ratio of the mixed solution of hydroxypropyl-β-cyclodextrin and maltodextrin obtained in (1) to the weight of millet added is 100:62.

5.

5. The preparation method according to claim 1, characterized in that, (2) Add drinking water at a ratio of 1:10 between the weight of millet and the weight of drinking water.

6. The preparation method according to claim 1, characterized in that, (3) The temperature of the refrigerator is -38.6℃.

7. The preparation method according to claim 1, characterized in that, (3) The freeze-drying process is as follows: after the temperature reaches -40℃, a vacuum is drawn, the temperature is lowered to below 10Pa, and then the temperature is raised to -2℃ for freeze-drying for 48 h.

8. The preparation method according to claim 1, characterized in that, (4) Warm water refers to drinking water at 45~50℃.

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