Method for extracting centella asiatica total glycosides by using nanoscale wall breaking technology

Abstract

The invention discloses a method for extracting asiaticoside by applying a nanoscale wall breaking technology, which comprises the following steps: step 1, naturally drying plant fiber traditional Chinese medicinal materials in the sun or baking, and keeping the water content at 4-5% to obtain a material A; 2, the obtained material A is placed in a grinding machine to be subjected to coarse grinding, the particle size of medicine powder is smaller than 2 mm, the medicine powder is sieved through a 10-mesh sieve after coarse grinding, and a material B is obtained; 3, the obtained material B is finely ground, so that the particle size of the medicine powder is smaller than 0.1 mm; step 4, performing secondary drying on the fiber particles which are not sieved by the 10-mesh sieve in the step 2, keeping the water content at 2-3%, and then performing fine grinding to enable the D90 of the fiber particles to be less than 0.1 mm; the herba centellae is subjected to drying, coarse grinding, screening, secondary drying, fine grinding, mixing and ultrafine grinding to obtain the traditional Chinese medicine powder of 400-800 nm. The powder obtained by grinding through the method is uniform in particle size, narrow in particle size distribution, high in wall breaking rate, high in effective substance dissolution amount, high in dissolution speed and more convenient to store.

Description

Technical Field

[0001] The invention relates to the technical field of extraction of total glycosides of Centella asiatica, and in particular to a method for extracting total glycosides of Centella asiatica by applying nano-scale wall-breaking technology. Background Art

[0002] The effective ingredients of Centella asiatica are mainly distributed in cells and intercellular matrix, and mainly in cells. Therefore, in order to improve the release rate and absorption rate of the effective ingredients, the existing Centella asiatica extraction process, the first is through high-temperature cooking, but the total glycosides of Centella asiatica in high-temperature cooking have a low dissolution rate, high energy consumption, large wastewater, damage to the environment, and high temperature is easy to destroy the total glycosides of Centella asiatica, the second is the leaching method, usually the medicinal materials are crushed and ground to improve the cell wall breaking rate, so that the effective ingredients can be quickly and in large quantities without passing through the cell wall and cell membrane, thereby improving the utilization rate of the medicinal materials and increasing the extraction rate. However, for plant-based Chinese medicinal materials with more fibers, they have strong toughness, and are easily deformed and not easily broken after being subjected to external mechanical forces, and their strong cohesive force can offset part of the external mechanical force, which will also increase the difficulty of crushing; thus, when crushing and grinding this type of Chinese medicinal materials, the shear force is too small to be fully crushed, and the shear force is too large to cause greater damage to the mechanical equipment, so the crushing and grinding parameters are difficult to determine. In addition, the control of the moisture content of Chinese medicinal materials before crushing and grinding directly determines the quality of grinding and dispersion. If the moisture content is too high, it is difficult to break and the particle size is uneven. If the moisture content is too low, it is easy to agglomerate and difficult to disperse. Therefore, it is urgent to design a nano-wall breaking technology with high wall breaking rate and uniform crushing. Summary of the invention

[0003] In view of the defects of the prior art, the purpose of the present invention is to provide a method for extracting total glycosides of Centella asiatica using nano-scale wall-breaking technology to solve the problems raised in the above-mentioned background technology.

[0004] The present invention solves the technical problem by adopting the following technical solution:

[0005] The present invention provides a method for extracting total glycosides of Centella asiatica using nano-scale wall-breaking technology, comprising the following steps:

[0006] Step 1: Naturally sun-dry or oven-dry the plant fiber Chinese medicinal materials to maintain a moisture content of 4-5% to obtain material A;

[0007] Step 2: Place the obtained material A in a grinder for coarse grinding to make the particle size of the powder less than 2 mm, and pass through a 10-mesh sieve after coarse grinding to obtain material B;

[0008] Step 3: Finely grind the obtained material B to make the particle size of the powder less than 0.1 mm;

[0009] Step 4: Dry the fiber particles that have not passed the 10-mesh sieve in step 2 for a second time to keep the moisture content at 2-3%, and then grind them to make the D90 of the fiber particles less than 0.1 mm;

[0010] Step 5: Evenly mix the powders obtained in step 3 and step 4, and then grind them in an ultrafine grinder to make the powder particle size 400-800nm.

[0011] Preferably, the drying temperature in step 1 is 50-60°C.

[0012] Preferably, the drying temperature in step 4 is 50-60°C.

[0013] Preferably, the coarse grinding speed in step 2 is 1000-1500 r / min.

[0014] Preferably, the fine grinding speed in step three is 1000-1500r / min.

[0015] Preferably, the fine grinding speed in step 4 is 1500-2000r / min.

[0016] Preferably, the ultrafine grinding speed in step 5 is 15000-28000 r / min.

[0017] Preferably, the coarse grinding in step 2 is performed multiple times in a short time, each grinding time does not exceed 1 minute, and the added amount is 1 / 3-1 / 2 of the total capacity.

[0018] Preferably, the plant fiber Chinese medicinal material is Centella asiatica.

[0019] Preferably, in the multiple grindings in a short time, the grinding is stopped for 20-30 seconds after each grinding, and cold air with a temperature of minus 5-0° C. is introduced into the bottom of the grinder to cool it down during the interval of stopping the grinding, and the material in the grinder is continuously turned over.

[0020] The nanometer-scale wall-breaking technology prepared by the present invention is applied to the method for extracting total glycosides of Centella asiatica, and is aimed at plant-based Chinese medicinal materials with a high fiber content, such as the nanometer wall-breaking technology for Centella asiatica. The Chinese medicinal powder with a diameter of 400-800 nm is obtained by drying, coarse grinding, screening, secondary drying, fine grinding, mixing, and ultra-fine grinding of the Centella asiatica. The powder ground by the method has a uniform particle size, a narrow particle size distribution, a high wall-breaking rate, a high dissolution amount of effective substances, a fast dissolution speed, and is more convenient to store.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention adopts a circulation method to reduce the temperature during the coarse grinding process of Centella asiatica. During the multiple grinding processes in a short time, the grinding is stopped for 20-30 seconds after each grinding. In the interval of stopping the grinding, cold air with a temperature of minus 5-0°C is introduced into the bottom of the grinder for cooling, and the material in the grinder is continuously turned over, thereby reducing the temperature rise of the Centella asiatica and the grinding head during the grinding process, reducing the loss of effective ingredients in the material under high temperature conditions, and at the same time improving the grinding effect, making the particle size distribution after grinding more uniform, and thus improving the dissolution rate of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the present invention using methanol to soak Centella asiatica powder, shaking and mixing for 10 minutes and then performing high performance liquid chromatography detection;

[0024] Figure 2 This is a schematic diagram of the high performance liquid chromatography detection after 20 minutes of methanol extraction using vibration in the present invention. DETAILED DESCRIPTION

[0025] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] The present invention of this embodiment provides a method for extracting total glycosides of Centella asiatica using nano-scale wall-breaking technology, comprising the following steps:

[0027] Step 1: Naturally sun-dry or oven-dry the plant fiber Chinese medicinal materials to maintain a moisture content of 4-5% to obtain material A. In this step, the moisture content of the medicinal materials can be reasonably controlled. Too high a moisture content after drying is not conducive to the crushing of the Centella asiatica medicinal materials, and too low a moisture content will cause the Centella asiatica powder with small particle size to agglomerate, reducing the dispersibility of the powder;

[0028] Step 2: Place the obtained material A in a grinder for coarse grinding to make the particle size D50 of the powder less than 2 mm, and pass it through a 10-mesh sieve after coarse grinding to obtain material B. This screening can separate the fiber Centella asiatica particles from the powder with a small particle size, so as to facilitate the secondary drying of the fiber particles;

[0029] Step 3: Finely grind the obtained material B to make the particle size D90 of the powder less than 0.1 mm;

[0030] Step 4: Dry the fiber particles that have not passed the 10-mesh sieve in step 2 for a second time to keep the moisture content at 2-3%, and then grind them to make the D90 of the fiber particles less than 0.1 mm;

[0031] Step 5. Evenly mix the powders obtained in step 3 and step 4, and then grind them in an ultrafine grinder to a powder particle size of 400-800 nm. In this step, the powder particle size is reasonably controlled. If the particle size of Centella asiatica powder is too small, the hygroscopicity and adsorption of the powder will be increased, and the difficulty of storage will be increased. If the particle size of Centella asiatica powder is too large, the amount and rate of dissolution of the effective substance will be reduced.

[0032] The drying temperature in step 1 of this embodiment is 50-60°C.

[0033] The drying temperature in step 4 of this embodiment is 50-60°C.

[0034] In step 2 of this embodiment, the coarse grinding speed is 1000-1500 r / min.

[0035] In step 3 of this embodiment, the fine grinding speed is 1000-1500r / min.

[0036] In step 4 of this embodiment, the fine grinding speed is 1500-2000r / min.

[0037] In step 5 of this embodiment, the ultra-fine grinding speed is 15000-28000 r / min.

[0038] In step 2 of this embodiment, the coarse grinding is performed multiple times in a short time, each grinding time does not exceed 1 minute, and the feeding amount is 1 / 3-1 / 2 of the total capacity. This setting is to prevent damage to the grinding equipment due to excessive grinding time and the temperature of the material, and to ensure sufficient and uniform grinding.

[0039] The plant fiber Chinese medicinal material in this embodiment is Centella asiatica.

[0040] In the short-time multiple grinding of the present embodiment, the grinding is stopped for 20-30 seconds after each grinding. In the interval of stopping the grinding, cold air with a temperature of minus 5-0°C is introduced into the bottom of the grinder for cooling, and the material in the grinder is continuously turned over. In this way, a circulation method is used for cooling during the coarse grinding of Centella asiatica, thereby reducing the temperature rise of Centella asiatica and the grinding head during the grinding process, reducing the loss of effective ingredients in the material under high temperature conditions, and at the same time improving the grinding effect and making the particle size distribution after grinding more uniform.

[0041] Example 1.

[0042] The present invention of this embodiment provides a method for extracting total glycosides of Centella asiatica using nano-scale wall-breaking technology, comprising the following steps:

[0043] Step 1: Naturally sun-dry or oven-dry the plant fiber Chinese medicinal materials to keep the moisture content at 4% to obtain material A. In this step, the moisture content of the medicinal materials can be reasonably controlled. Too high a moisture content after drying is not conducive to the crushing of the Centella asiatica medicinal materials, and too low a moisture content will cause the Centella asiatica powder with small particle size to agglomerate, reducing the dispersibility of the powder;

[0044] Step 2: Place the obtained material A in a grinder for coarse grinding to make the particle size D50 of the powder less than 2 mm, and pass it through a 10-mesh sieve after coarse grinding to obtain material B. This screening can separate the fiber Centella asiatica particles from the powder with a small particle size, so as to facilitate the secondary drying of the fiber particles;

[0045] Step 3: Finely grind the obtained material B to make the particle size D90 of the powder less than 0.1 mm;

[0046] Step 4: Dry the fiber particles that have not passed the 10-mesh sieve in step 2 for a second time to keep the moisture content at 2%, and then grind them to make the D90 of the fiber particles less than 0.1 mm;

[0047] Step 5. Evenly mix the powders obtained in step 3 and step 4, and then grind them in an ultrafine grinder to a particle size of 400 nm. In this step, the particle size of the powder is reasonably controlled. If the particle size of Centella asiatica powder is too small, the hygroscopicity and adsorption of the powder will be increased, and the difficulty of storage will be increased. If the particle size of Centella asiatica powder is too large, the dissolution amount and dissolution rate of the effective substance will be reduced.

[0048] The drying temperature in step 1 of this embodiment is 50°C.

[0049] The drying temperature in step 4 of this embodiment is 50°C.

[0050] In step 2 of this embodiment, the coarse grinding speed is 1000 r / min.

[0051] In step 3 of this embodiment, the fine grinding speed is 1000 r / min.

[0052] In step 4 of this embodiment, the fine grinding speed is 1500r / min.

[0053] In step 5 of this embodiment, the ultra-fine grinding speed is 15000 r / min.

[0054] In step 2 of this embodiment, the coarse grinding is performed multiple times in a short time, each grinding time does not exceed 1 minute, and the feeding amount is 1 / 3 of the total capacity. This setting is to prevent damage to the grinding equipment due to excessive grinding time and the temperature of the material, and to ensure sufficient and uniform grinding.

[0055] The plant fiber Chinese medicinal material in this embodiment is Centella asiatica.

[0056] In the short-time multiple grinding of this embodiment, the grinding is stopped for 20 seconds after each grinding. In the interval of stopping the grinding, cold air with a temperature of minus 5°C is introduced into the bottom of the grinder for cooling, and the material in the grinder is continuously turned over. In this way, a circulation method is used for cooling during the coarse grinding of Centella asiatica, thereby reducing the temperature rise of Centella asiatica and the grinding head during the grinding process, reducing the loss of effective ingredients in the material under high temperature conditions, and at the same time improving the grinding effect and making the particle size distribution after grinding more uniform.

[0057] Example 2.

[0058] The present invention of this embodiment provides a method for extracting total glycosides of Centella asiatica using nano-scale wall-breaking technology, comprising the following steps:

[0059] Step 1: Naturally sun-dry or oven-dry the plant fiber Chinese medicinal materials to maintain a moisture content of 4.5% to obtain material A. In this step, the moisture content of the medicinal materials can be reasonably controlled. Too high a moisture content after drying is not conducive to the crushing of the Centella asiatica medicinal materials, and too low a moisture content will cause the Centella asiatica powder with small particle size to agglomerate, reducing the dispersibility of the powder;

[0060] Step 2: Place the obtained material A in a grinder for coarse grinding to make the particle size D50 of the powder less than 2 mm, and pass it through a 10-mesh sieve after coarse grinding to obtain material B. This screening can separate the fiber Centella asiatica particles from the powder with a small particle size, so as to facilitate the secondary drying of the fiber particles;

[0061] Step 3: Finely grind the obtained material B to make the particle size D90 of the powder less than 0.1 mm;

[0062] Step 4: Dry the fiber particles that have not passed the 10-mesh sieve in step 2 for a second time to maintain a moisture content of 2.5%, and then grind them to make the D90 of the fiber particles less than 0.1 mm;

[0063] Step 5. Evenly mix the powders obtained in step 3 and step 4, and then grind them in an ultrafine grinder to a powder particle size of 600 nm. In this step, the powder particle size is reasonably controlled. If the particle size of Centella asiatica powder is too small, the hygroscopicity and adsorption of the powder will be increased, and the difficulty of storage will be increased. If the particle size of Centella asiatica powder is too large, the amount and rate of dissolution of the effective substance will be reduced.

[0064] The drying temperature in step 1 of this embodiment is 55°C.

[0065] The drying temperature in step 4 of this embodiment is 55°C.

[0066] In step 2 of this embodiment, the coarse grinding speed is 1200 r / min.

[0067] In step 3 of this embodiment, the fine grinding speed is 1200 r / min.

[0068] In step 4 of this embodiment, the fine grinding speed is 1700 r / min.

[0069] In step 5 of this embodiment, the ultra-fine grinding speed is 20000 r / min.

[0070] In step 2 of this embodiment, the coarse grinding is performed multiple times in a short time, each grinding time does not exceed 1 minute, and the feeding amount is 1 / 3 of the total capacity. This setting is to prevent damage to the grinding equipment due to excessive grinding time and the temperature of the material, and to ensure sufficient and uniform grinding.

[0071] The plant fiber Chinese medicinal material in this embodiment is Centella asiatica.

[0072] In the short-time multiple grinding of the present embodiment, the grinding is stopped for 25 seconds after each grinding. In the interval of stopping the grinding, cold air with a temperature of minus 3°C is introduced into the bottom of the grinder for cooling, and the material in the grinder is continuously turned over. In this way, a circulation method is used for cooling during the coarse grinding of Centella asiatica, thereby reducing the temperature rise of Centella asiatica and the grinding head during the grinding process, reducing the loss of effective ingredients in the material under high temperature conditions, and at the same time improving the grinding effect and making the particle size distribution after grinding more uniform.

[0073] Example 3.

[0074] The present invention of this embodiment provides a method for extracting total glycosides of Centella asiatica using nano-scale wall-breaking technology, comprising the following steps:

[0075] Step 1: Naturally sun-dry or oven-dry the plant fiber Chinese medicinal materials to keep the moisture content at 5% to obtain material A. In this step, the moisture content of the medicinal materials can be reasonably controlled. Too high a moisture content after drying is not conducive to the crushing of the Centella asiatica medicinal materials, and too low a moisture content will cause the Centella asiatica powder with small particle size to agglomerate, reducing the dispersibility of the powder;

[0076] Step 2: Place the obtained material A in a grinder for coarse grinding to make the particle size D50 of the powder less than 2 mm, and pass it through a 10-mesh sieve after coarse grinding to obtain material B. This screening can separate the fiber Centella asiatica particles from the powder with a small particle size, so as to facilitate the secondary drying of the fiber particles;

[0077] Step 3: Finely grind the obtained material B to make the particle size D90 of the powder less than 0.1 mm;

[0078] Step 4: Dry the fiber particles that have not passed the 10-mesh sieve in step 2 for a second time to keep the moisture content at 3%, and then grind them to make the D90 of the fiber particles less than 0.1 mm;

[0079] Step 5. Evenly mix the powders obtained in step 3 and step 4, and then grind them in an ultrafine grinder to a powder particle size of 800 nm. In this step, the powder particle size is reasonably controlled. If the particle size of Centella asiatica powder is too small, the hygroscopicity and adsorption of the powder will be increased, and the difficulty of storage will be increased. If the particle size of Centella asiatica powder is too large, the amount and rate of dissolution of the effective substance will be reduced.

[0080] The drying temperature in step 1 of this embodiment is 60°C.

[0081] The drying temperature in step 4 of this embodiment is 60°C.

[0082] In step 2 of this embodiment, the coarse grinding speed is 1500 r / min.

[0083] In step 3 of this embodiment, the fine grinding speed is 1500r / min.

[0084] In step 4 of this embodiment, the fine grinding speed is 2000r / min.

[0085] In step 5 of this embodiment, the ultra-fine grinding speed is 28000 r / min.

[0086] In step 2 of this embodiment, the coarse grinding is performed multiple times in a short time, each grinding time does not exceed 1 minute, and the feeding amount is 1 / 2 of the total capacity. This setting is to prevent damage to the grinding equipment due to excessive grinding time and the temperature of the material, and to ensure sufficient and uniform grinding.

[0087] The plant fiber Chinese medicinal material in this embodiment is Centella asiatica.

[0088] In the short-time multiple grinding of this embodiment, the grinding is stopped for 30 seconds after each grinding. In the interval of stopping the grinding, cold air with a temperature of 0°C is introduced into the bottom of the grinder for cooling, and the material in the grinder is continuously turned over. In this way, a circulation method is used for cooling during the coarse grinding of Centella asiatica, thereby reducing the temperature rise of Centella asiatica and the grinding head during the grinding process, reducing the loss of effective ingredients in the material under high temperature conditions, and at the same time improving the grinding effect, making the particle size distribution after grinding more uniform.

[0089] The Centella asiatica powder obtained in Example 1-3 was subjected to a dissolution experiment of total Centella asiatica glycosides. The Centella asiatica powder was soaked in methanol, shaken and mixed for 10 minutes, and then subjected to high performance liquid chromatography detection. The detection results are as follows: Figure 1 The peak areas at 6, 8, and 16 min are shown;

[0090] The control group was made of the directly ground Centella asiatica powder without sieving and secondary drying. The powder was extracted with methanol for 20 minutes and then tested by HPLC. The test results were as follows: Figure 2 The peak areas at 6, 8 and 16 min are shown.

[0091] It can be seen from Examples 1-3 and the control group that the dissolution rate and dissolution amount of the total Centella asiatica glycosides in the Centella asiatica powder obtained by screening and secondary drying are significantly better than those in the control group, which shows that the nano-wall-breaking technology of the present invention has a good wall-breaking effect.

[0092] The innovation of the present invention is:

[0093] The present invention is aimed at plant-based Chinese medicinal materials with high fiber content, such as the nano-wall-breaking technology for Centella asiatica. The Chinese medicinal powder with a diameter of 400-800 nm is obtained by drying, coarse grinding, screening, secondary drying, fine grinding, mixing, and ultra-fine grinding of the Centella asiatica. The powder obtained by grinding using the method has uniform particle size, narrow particle size distribution, high wall-breaking rate, high effective substance dissolution amount, fast dissolution speed, and more convenient storage. In addition, a circulation method is used for cooling during the coarse grinding of the Centella asiatica. During multiple grinding processes in a short time, the grinding is stopped for 20-30 seconds after each grinding. In the interval of stopping the grinding, cold air with a temperature of minus 5-0°C is introduced into the bottom of the grinder for cooling, and the material in the grinder is continuously turned over, thereby reducing the temperature rise of the Centella asiatica and the grinding head during the grinding process, reducing the loss of effective ingredients in the material under high temperature conditions, and at the same time improving the grinding effect, making the particle size distribution after grinding more uniform, thereby improving the dissolution rate of the product.

[0094] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

[0095] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for extracting total glycosides of Centella asiatica using nano-scale wall-breaking technology, characterized in that: The following steps are involved: Step 1: Naturally sun-dry or oven-dry the plant fiber Chinese medicinal materials to maintain a moisture content of 4-5% to obtain material A; Step 2: Place the obtained material A in a grinder for coarse grinding to make the particle size of the powder less than 2 mm, and pass through a 10-mesh sieve after coarse grinding to obtain material B; Step 3: Finely grind the obtained material B to make the particle size of the powder less than 0.1 mm; Step 4: Dry the fiber particles that have not passed the 10-mesh sieve in step 2 for a second time to keep the moisture content at 2-3%, and then grind them to make the D90 of the fiber particles less than 0.1 mm; Step 5: Evenly mix the powders obtained in step 3 and step 4, and then grind them in an ultrafine grinder to make the powder particle size 400-800nm.

2. The method for extracting total glycosides of Centella asiatica using nano-scale wall-breaking technology according to claim 1, characterized in that: The drying temperature in step 1 is 50-60°C.

3. The method for extracting total glycosides of Centella asiatica using nano-scale wall-breaking technology according to claim 2, characterized in that: The drying temperature in step 4 is 50-60°C.

4. The method for extracting total glycosides of Centella asiatica using nano-scale wall-breaking technology according to claim 1, characterized in that: The coarse grinding speed in the step 2 is 1000-1500 r / min.

5. The method for extracting total glycosides of Centella asiatica using nano-scale wall-breaking technology according to claim 4, characterized in that: The fine grinding speed in step 3 is 1000-1500r / min.

6. The method for extracting total glycosides of Centella asiatica using nano-scale wall-breaking technology according to claim 5, characterized in that: The fine grinding speed in the step 4 is 1500-2000r / min.

7. The method for extracting total glycosides of Centella asiatica using nano-scale wall-breaking technology according to claim 6, characterized in that: The ultra-fine grinding speed in step 5 is 15000-28000 r / min.

8. The method for extracting total glycosides of Centella asiatica using nano-scale wall-breaking technology according to claim 1, characterized in that: The coarse grinding in step 2 is performed multiple times in a short time, each grinding time does not exceed 1 minute, and the added amount is 1 / 3-1 / 2 of the total capacity.

9. The method for extracting total glycosides of Centella asiatica using nano-scale wall-breaking technology according to claim 8, characterized in that: The plant fiber Chinese medicinal material is Centella asiatica.

10. The method for extracting total glycosides of Centella asiatica using nano-scale cell wall breaking technology according to claim 4, characterized in that: During the multiple grindings in a short time, the grinding is stopped for 20-30 seconds after each grinding. In the interval of stopping the grinding, cold air with a temperature of minus 5-0° C. is introduced into the bottom of the grinder to cool it down, and the material in the grinder is continuously turned over.

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