Method for preparing amorphous rebaudioside M

Abstract

The invention discloses a method for preparing amorphous rebaudioside M. The preparation method of the amorphous rebaudioside M, disclosed by the invention, comprises the following steps: carrying out instantaneous cooling on a high-temperature rebaudioside M aqueous solution to obtain the amorphous rebaudioside M, the instantaneous cooling comprises a step of adding a high-temperature rebaudioside M aqueous solution into a low-temperature polar protic solvent; wherein the temperature of the high-temperature rebaudioside M water solution is 90-100 DEG C, and the temperature of the low-temperature polar protic solvent is 1-8 DEG C. The preparation method of the amorphous rebaudioside M, disclosed by the invention, has one or more of the following advantages: high yield, low energy consumption, mild reaction conditions, simplicity in operation, low cost and suitability for industrial production.

Description

Technical Field

[0001] The present invention relates to a method for preparing amorphous rebaudioside M. Background Art

[0002] Stevioside is a natural, low-calorie, high-intensity sweetener extracted from the leaves of Stevia rebaudiana Bertoni, a small shrub of the Asteraceae family native to northeastern Paraguay in South America. Currently, over 60 types of steviol glycosides have been isolated from stevia, including stevioside, rebaudioside A (Reb A), rebaudioside D (Reb D), rebaudioside M (Reb M, RM), and steviolbioside. Furthermore, steviol glycosides have received Generally Recognized as Safe (GRAS) certification as a food additive from the U.S. Food and Drug Administration (FDA) and have been approved by the Food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (WHO).

[0003] Among them, RM was first isolated and purified by Prakash et al. from the leaves of Stevia cultivar AKH L1, and its molecular formula is C 56 H 90 O 33 , the structural formula is shown in Formula 1 below.

[0004]

[0005] RM has far fewer calories than sucrose, yet is many times sweeter, making it an excellent choice for many patients with diabetes and hypertension. RM can exist in crystalline, polymorphic, or amorphous forms. Amorphous RM offers greater advantages in solubility and other aspects when used as a food additive, thus attracting a broader market.

[0006] CN105407738A discloses a method for preparing amorphous RM (also known as rebaudioside X), which comprises mixing 100g of a sample having an RM content of 97.4% with 300g of water, increasing the temperature to 121°C at a rate of 1°C per minute, maintaining for 1h, and then lowering the temperature to room temperature (25°C) at a rate of 1°C per minute to obtain a concentrated solution of RM. 100g of the concentrated solution was dried using a spray dryer operating at an inlet temperature of 175°C and an outlet temperature of 100°C to obtain 20g of amorphous RM powder. This method requires a programmed heating and cooling process and the use of a spray dryer to dry the product. The operating steps are relatively complicated, and the aqueous solution of RM needs to be heated to above 100°C, which consumes a lot of energy and has a high cost. Moreover, only 20g of product was obtained from 100g of sample, and the yield was low.

[0007] Given the importance of RM, there is an urgent need to develop a preparation method for RM that is suitable for industrial production and has high yield, low energy consumption, mild reaction conditions, simple operation and low cost. Summary of the Invention

[0008] The technical problem to be solved by the present invention is that the existing methods for preparing amorphous rebaudioside M suffer from low yield, high energy consumption, cumbersome operation, and high cost. To this end, the present invention provides a method for preparing amorphous rebaudioside M, which has one or more of the following advantages: high yield, low energy consumption, mild reaction conditions, simple operation, low cost, and suitability for industrial production.

[0009] The present invention solves the above technical problems through the following technical solutions:

[0010] The present invention provides a method for preparing amorphous rebaudioside M, which comprises the following steps:

[0011] The high-temperature aqueous solution of rebaudioside M is instantaneously cooled to obtain the amorphous rebaudioside M; the instantaneous cooling includes the step of adding the high-temperature aqueous solution of rebaudioside M to a low-temperature polar protic solvent; wherein the temperature of the high-temperature aqueous solution of rebaudioside M is 90°C-100°C, and the temperature of the low-temperature polar protic solvent is 1°C-8°C.

[0012] In the preparation method, the step of adding the high-temperature aqueous solution of rebaudioside M to the low-temperature polar protic solvent is to dropwise add the high-temperature aqueous solution of rebaudioside M to the low-temperature polar protic solvent.

[0013] The dripping is preferably performed drop by drop; preferably, the mass of the high-temperature rebaudioside M aqueous solution dripped per minute accounts for 1%-5% of the mass of the low-temperature polar protic solvent, such as 1.8%-2.7%.

[0014] In the preparation method, the high-temperature rebaudioside M aqueous solution is preferably prepared by the following steps: mixing rebaudioside M crystals and water, and heating to obtain the high-temperature rebaudioside M aqueous solution.

[0015] Wherein, preferably, the X-ray powder diffraction pattern of the rebaudioside M crystal expressed in 2θ angles has diffraction peaks at one or more of the following 2θ angles: 3.5645°±0.2000°, 4.3457°±0.2000°, 5.3081°±0.2000°, 6.6031°±0.2000°, 8.0747°±0.2000°, 8.4723°±0.2000°, 9.0367°±0.2000°, 9.6254°±0.2000°, 10.9001°±0.2000°, 11.3171°±0.2000°, 12. 2000°, 11.9128°±0.2000°, 12.8578°±0.2000°, 13.4339°±0.2000°, 13.9888°±0.2000°, 14.6015°±0.2000°, 15.0635°±0.2000°, 16.0931°±0.2000°, 16.3534°±0.2000°, 17.6024°±0.2000°, 18.3673°±0.2000°, 19.1458°±0.2000°, 19.7629°±0.20 00°, 20.2799°±0.2000°, 20.9073°±0.2000°, 21.5337°±0.2000°, 22.1568°±0.2000°, 22.5692°±0.2000°, 23.2536°±0.2000°, 23.5661°±0.2000°, 23.7384°±0.2000°, 24.2613°±0.2000°, 24.6821°±0.2000°, 25.3416°±0.2000°, 26.0580°±0.2000 °, 26.9184°±0.2000°, 27.4549°±0.2000°, 28.6047°±0.2000°, 29.9133°±0.2000°, 34.8416°±0.2000°, 35.4380°±0.2000°, 36.5483°±0.2000°, 39.0707°±0.2000°, 40.6692°±0.2000°, 41.6507°±0.2000°, 45.4843°±0.2000° and 50.0970°±0.2000°;

[0016] Alternatively, the X-ray powder diffraction pattern of the rebaudioside M crystal expressed in 2θ angles is substantially as follows Figure 1 shown.

[0017] In the preparation method, the polar protic solvent is preferably water, more preferably purified water.

[0018] In the preparation method, the mass fraction of rebaudioside M in the high-temperature rebaudioside M aqueous solution is preferably 5%-10%, more preferably 6%-8%.

[0019] In the preparation method, the temperature of the high-temperature rebaudioside M aqueous solution is preferably 90°C-98°C, for example 92°C.

[0020] In the preparation method, the mass ratio of the solvent contained in the high-temperature rebaudioside M aqueous solution to the low-temperature polar protic solvent is preferably (1.0-1.8):1, more preferably (1.5-1.6):1.

[0021] In the preparation method, the temperature of the low-temperature polar protic solvent is preferably 1°C-5°C, such as 1°C, 2°C, 3°C, 4°C or 5°C.

[0022] In the preparation method, the temperature difference between the high-temperature rebaudioside M aqueous solution and the low-temperature polar protic solvent is preferably 82°C-99°C, more preferably 85°C-97°C, and even more preferably 90°C-97°C.

[0023] In the preparation method, during the process of adding the high-temperature rebaudioside M aqueous solution to the low-temperature polar protic solvent, the temperature of the mixed system is preferably maintained at 1°C-8°C; more preferably, the temperature of the mixed system is maintained at 1°C-5°C, for example, 1°C, 2°C, 3°C, 4°C or 5°C.

[0024] In the preparation method, preferably, the instantaneous cooling step further includes a standing and heat preservation step; more preferably, the standing and heat preservation step further includes a filtration step; further preferably, the filtration step further includes a drying step.

[0025] The temperature of the standing and heat preservation step is preferably 1°C-8°C, more preferably 1°C-5°C, such as 1°C, 2°C, 3°C, 4°C or 5°C; the time of the standing and heat preservation step is preferably 0.5-2h, such as 1h.

[0026] The temperature of the drying step is preferably 60-70°C, more preferably 63-67°C, for example 65°C; the time of the drying step is preferably 20-30h, for example 24h; the drying method of the drying step is preferably oven drying.

[0027] In the preparation method, preferably, the X-ray powder diffraction pattern of the amorphous rebaudioside M expressed in 2θ angles is substantially as follows Figure 2 shown.

[0028] In one embodiment of the present invention, in the preparation method, the materials used are composed of a rebaudioside M aqueous solution and a polar protic solvent.

[0029] Explanation of terms:

[0030] The "solution" described in the present invention, unless otherwise specified, refers to a clear solution.

[0031] Unless otherwise specified, the "RM" mentioned in the present invention stands for rebaudioside M.

[0032] Without violating the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain preferred embodiments of the present invention.

[0033] The reagents and raw materials used in the present invention are commercially available.

[0034] The positive progress of the present invention is that the preparation method of amorphous RM provided by the present invention has one or more of the following advantages: no programmed heating and slow cooling processes are required, high yield, low energy consumption, mild reaction conditions, simple operation, low cost and suitability for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is the X-ray powder diffraction pattern of RM crystal collected under Cu-Kα radiation;

[0036] Figure 2 is the X-ray powder diffraction pattern of amorphous RM collected under Cu-Kα radiation. DETAILED DESCRIPTION

[0037] 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.

[0038] The X-ray powder diffraction (XRPD) data and patterns in this application were measured under the following conditions:

[0039] The measuring instrument was manufactured by Bruker, model D8ADVANCA25. The test conditions were: Target: Cu; 40 kV, 40 mA; scanning range 3-60°, scanning speed 4° / min, step size 0.026°, measuring temperature 25°C; K-Alpha 1 K-Alpha2 is K-Beta is

[0040] The preparation method of the amorphous RM of the present invention comprises the following steps:

[0041] (1) Take a four-necked flask ①, add RM crystals and purified water into the four-necked flask ①, and heat to 90-100°C to dissolve the RM crystals and make them clear, thereby obtaining an RM aqueous solution;

[0042] (2) Take four-necked flask ② and add purified water to it, maintaining the initial temperature of the purified water in the four-necked flask ② at 1-5°C;

[0043] (3) Slowly drip the RM aqueous solution obtained in step (1) into the purified water in the four-necked flask ②, and keep the temperature of the purified water in the four-necked flask ② between 1-8°C during the dripping process until all the RM aqueous solution is dripped;

[0044] (4) After all the RM aqueous solution has been dripped into the four-necked flask ②, the temperature of the liquid in the four-necked flask ② is adjusted to 1-5°C and maintained for 1-2 hours. Then, the liquid in the four-necked flask ② is filtered and the precipitate is collected.

[0045] (5) The precipitate is dried in an oven to obtain amorphous RM powder.

[0046] In step (1), after adding RM crystals and purified water into the four-necked flask ①, the temperature is raised to 90-100°C, preferably 90-98°C, for example 92°C.

[0047] High temperatures facilitate the dissolution of RM, resulting in a high RM concentration and a high yield of amorphous RM when the solution is clear. However, if the temperature is too low, the RM concentration is low when the solution is clear, and the yield of amorphous RM is reduced. Therefore, a temperature of 90-100°C is recommended.

[0048] In step (1), the mass fraction of RM in the RM aqueous solution is 5%-10%, preferably 6%-8%. If the amount of purified water added to prepare the RM aqueous solution is too small, some RM crystals will be difficult to dissolve and clarify, affecting the yield of amorphous RM. If the amount of purified water added to prepare the RM aqueous solution is too large, the mass fraction of RM will be relatively reduced, the amount of precipitation will be reduced, and the yield of amorphous RM will also be affected.

[0049] The mass ratio of the purified water in the four-necked flask ① of step (1) to the purified water in the four-necked flask ② of step (2) can be (1.0-1.8):1, or can be (1.5-1.6):1. If the amount of purified water added to the four-necked flask ② is too much, the amount of RM dissolved in the water will increase, thereby reducing the final yield of amorphous RM. For example, the mass of the purified water in the four-necked flask ① is 360 g, and the mass of the purified water in the four-necked flask ② is 240-360 g.

[0050] In step (2), the initial temperature of the purified water in the four-necked flask ② is 1-5°C, preferably 2-3°C, for example 3°C.

[0051] In step (3), when the RM aqueous solution is added dropwise, the temperature of the liquid in the four-necked flask ② is maintained between 1-8°C, preferably 1-5°C, for example, 1°C, 2°C, 3°C, 4°C, 5°C, 6°C, 7°C, 8°C.

[0052] When the hot RM aqueous solution in four-necked flask ① is dripped dropwise into the cooler liquid in four-necked flask ②, the hot RM aqueous solution experiences a transient cooling, causing the RM to precipitate in an amorphous form. To achieve this transient cooling, a certain temperature difference between the RM aqueous solution and the purified water in four-necked flask ② is required. This temperature difference can be between 82 and 99°C, preferably between 85 and 97°C, and more preferably between 90 and 97°C.

[0053] Furthermore, to ensure instantaneous cooling of the high-temperature RM aqueous solution, the mass of RM aqueous solution added to four-necked flask ② must be kept small. If the mass of RM aqueous solution added each time is too large, the temperature rise in four-necked flask ② will increase significantly after each addition, making it difficult to achieve the required temperature difference for instantaneous cooling of the RM aqueous solution, thus affecting the final yield and purity of the amorphous RM. Maintaining the temperature in four-necked flask ② will also require a longer time, making it uneconomical for industrial production. Therefore, not only must the RM aqueous solution be added dropwise, but the amount added each time must also be controlled within an appropriate range.

[0054] After each drop of the aqueous solution, the temperature inside the four-necked flask ② will rise slightly. However, it is important to ensure that the temperature inside the flask returns to between 1-8°C (preferably 1-5°C) before the next drop of the RM aqueous solution. This means that the addition rate (or the time interval between the addition of two drops of the RM aqueous solution) must be controlled. If the addition rate is too fast and the temperature inside the four-necked flask ② exceeds the above range, it will be difficult to achieve an instantaneous cooling effect on the newly added aqueous solution, affecting the yield and purity of the amorphous RM.

[0055] In addition, during the dropwise addition process, the maintenance temperature of the liquid in the four-necked flask ② can be between 1-8°C. However, as the maintenance temperature increases from 1°C to 8°C, the temperature difference between the RM aqueous solution and the liquid in the four-necked flask ② decreases, and the solubility of RM increases, the amount of precipitated amorphous RM tends to decrease.

[0056] In step (3), the time from the start of dripping the RM aqueous solution into the four-necked flask ② to the completion of the dripping of the RM aqueous solution is related to the total mass of the RM aqueous solution and the dripping rate of the RM aqueous solution. The dripping rate of the RM aqueous solution is also related to the time required for the liquid in the four-necked flask ② to return to the maintenance temperature (1-8°C) after the dripping.

[0057] In step (5), the temperature for drying the precipitate is 60-70° C., preferably 63-67° C., for example 65° C. The drying temperature should not be too high or too low. If it is too low, the drying time will be too long, which will extend the production time of the amorphous RM and increase the production cost.

[0058] Example 1 Preparation of RM amorphous material

[0059] (1) Take a 1000 mL four-necked flask ①, add 30 g of RM crystals and 360 g of purified water into the four-necked flask ①, and heat to 92°C to dissolve the RM crystals to a clear state, thereby obtaining a RM solution. The RM crystals were prepared according to the preparation method of Example 1 in CN106866757A, and their XRPD pattern is as follows: Figure 1As shown, the X-ray powder diffraction pattern expressed in 2θ angles has diffraction peaks at the following 2θ angles: 3.5645°±0.2000°, 4.3457°±0.2000°, 5.3081°±0.2000°, 6.6031°±0.2000°, 8.0747°±0.2000°, 8.4723°±0.2000°, 9.0367°±0.2000°, 9.6254°±0.2000°, 10.9001°±0.2000°, 11.3171°±0.2000°, 11.9128°±0. 0.2000°、12.8578°±0.2000°、13.4339°±0.2000°、13.9888°±0.2000°、14.6015°±0.2000°、15.0635°±0.2000°、16.0931°±0.2000°、16.3534°±0.2000°、17.6024°±0.2000°、18.3673°±0.2000°、19.1458°±0.2000°、19.7629°±0.2000°、20.279 9°±0.2000°, 20.9073°±0.2000°, 21.5337°±0.2000°, 22.1568°±0.2000°, 22.5692°±0.2000°, 23.2536°±0.2000°, 23.5661°±0.2000°, 23.7384°±0.2000°, 24.2613°±0.2000°, 24.6821°±0.2000°, 25.3416°±0.2000°, 26.0580°±0.2000°, 26. 9184°±0.2000°, 27.4549°±0.2000°, 28.6047°±0.2000°, 29.9133°±0.2000°, 34.8416°±0.2000°, 35.4380°±0.2000°, 36.5483°±0.2000°, 39.0707°±0.2000°, 40.6692°±0.2000°, 41.6507°±0.2000°, 45.4843°±0.2000° and 50.0970°±0.2000°.

[0060] (2) Take a 1000 mL four-necked flask ② and add 240 g of purified water into the flask. Maintain the temperature of the purified water in the flask at 3°C.

[0061] (3) The RM solution obtained in step (1) was slowly dripped into the purified water in the four-necked flask ②. During the addition process, the temperature of the purified water in the four-necked flask ② was maintained between 1-5°C until all the RM solution was added (this embodiment takes about 1 hour).

[0062] (4) After all the RM solution has been dripped into the four-necked flask ②, adjust the temperature of the liquid in the four-necked flask ② to 3°C and keep it warm for 1 hour. Then filter the liquid in the four-necked flask ② and collect the precipitate.

[0063] (5) Drying: The precipitate was dried in an oven at 65 °C for 24 h to obtain 28.2 g of RM powder.

[0064] The obtained RM powder was measured using an X-ray diffractometer. The X-ray diffraction pattern (2θ) of the RM powder is as follows: Figure 2 As shown. Figure 2 It can be seen that the RM powder obtained in Example 1 is amorphous RM.

[0065] Example 2 Preparation of RM amorphous material

[0066] (1) Add 30 g of RM crystals and 360 g of purified water to a 1000 mL four-necked flask (1), and heat to 92° C. to dissolve and clarify the RM crystals, thereby obtaining a clear RM solution. RM crystals were prepared according to the preparation method of Example 1 in CN106866757A , and their XRPD pattern and diffraction peaks were the same as those of the RM crystals used in Example 1 of the present invention.

[0067] (2) Take a 1000 mL four-necked flask ② and add 360 g of purified water into the flask ②. Maintain the temperature of the purified water in the flask ② at 2°C.

[0068] (3) The RM solution obtained in step (1) was slowly dripped into the purified water in the four-necked flask ②. During the addition process, the temperature of the purified water in the four-necked flask ② was maintained between 5-8°C until all the RM solution was added (this embodiment took about 1 hour).

[0069] (4) After all the RM solution has been dripped into the four-necked flask ②, adjust the temperature of the liquid in the four-necked flask ② to 2°C and keep it warm for 1 hour. Then filter the liquid in the four-necked flask ② and collect the precipitate.

[0070] (5) Drying: The precipitate was dried in an oven at 65°C for 24 h to obtain 27.6 g of RM powder. X-ray diffractometer analysis showed that the RM powder was amorphous RM.

Claims

1. A method for preparing amorphous rebaudioside M, comprising the following steps: The high-temperature aqueous solution of rebaudioside M is instantaneously cooled to obtain the amorphous rebaudioside M; the instantaneous cooling comprises the step of adding the high-temperature aqueous solution of rebaudioside M to a low-temperature polar protic solvent; wherein, The temperature of the high-temperature rebaudioside M aqueous solution is 90°C-100°C, and the temperature of the low-temperature polar protic solvent is 1°C-8°C.

2. The preparation method according to claim 1, wherein adding the high-temperature rebaudioside M aqueous solution dropwise into the low-temperature polar protic solvent; Preferably, the dripping is dropwise addition; More preferably, the mass of the high-temperature rebaudioside M aqueous solution added dropwise per minute accounts for 1%-5%, such as 1.8%-2.7% of the mass of the low-temperature polar protic solvent.

3. The preparation method according to claim 1, wherein It meets one or more of the following conditions: (1) The high-temperature rebaudioside M aqueous solution is prepared by the following steps: mixing rebaudioside M crystals and water, and heating to obtain the high-temperature rebaudioside M aqueous solution; Preferably, the X-ray powder diffraction pattern of the rebaudioside M crystal expressed in 2θ angles has diffraction peaks at one or more of the following 2θ angles: 3.5645°±0.2000°, 4.3457°±0.2000°, 5.3081°±0.2000°, 6.6031°±0.2000°, 8.0747°±0.2000°, 8.4723°±0.2000°, 9.0367°±0.2000°, 9.6254°±0.2000°, 10.9001°±0.2000°, 11.3171°±0.2000°. 0°, 11.9128°±0.2000°, 12.8578°±0.2000°, 13.4339°±0.2000°, 13.9888°±0.2000°, 14.6015°±0.2000°, 15.0635°±0.2000°, 16.0931°±0.2000°, 16.3534°±0.2000°, 17.6024°±0.2000°, 18.3673°±0.2000°, 19.1458°±0.2000°, 19.7629°±0.2000 °, 20.2799°±0.2000°, 20.9073°±0.2000°, 21.5337°±0.2000°, 22.1568°±0.2000°, 22.5692°±0.2000°, 23.2536°±0.2000°, 23.5661°±0.2000°, 23.7384°±0.2000°, 24.2613°±0.2000°, 24.6821°±0.2000°, 25.3416°±0.2000°, 26.0580°±0.2000° , 26.9184°±0.2000°, 27.4549°±0.2000°, 28.6047°±0.2000°, 29.9133°±0.2000°, 34.8416°±0.2000°, 35.4380°±0.2000°, 36.5483°±0.2000°, 39.0707°±0.2000°, 40.6692°±0.2000°, 41.6507°±0.2000°, 45.4843°±0.2000° and 50.0970°±0.2000°; Alternatively, the X-ray powder diffraction pattern of the rebaudioside M crystal expressed at 2θ angles is substantially as shown in FIG1 ; (2) The polar protic solvent is water; preferably, purified water; (3) In the high-temperature rebaudioside M aqueous solution, the mass fraction of rebaudioside M is 5%-10%; (4) The mass ratio of the solvent contained in the high-temperature rebaudioside M aqueous solution to the low-temperature polar protic solvent is (1.0-1.8):1; (5) The temperature of the high-temperature rebaudioside M aqueous solution is 90° C.-98° C.; (6) The temperature of the low-temperature polar protic solvent is 1°C-5°C; (7) The temperature difference between the high-temperature rebaudioside M aqueous solution and the low-temperature polar protic solvent is 82° C.-99° C.; (8) During the process of adding the high-temperature rebaudioside M aqueous solution to the low-temperature polar protic solvent, the temperature of the mixed system is maintained at 1° C. to 8° C.; (9) The instantaneous cooling step further includes a static heat preservation step; Preferably, the step of standing and keeping warm further includes a filtering step; More preferably, the filtering step further comprises a drying step; (10) The X-ray powder diffraction pattern of the amorphous rebaudioside M expressed at 2θ angles is substantially as shown in FIG2 .

4. The preparation method according to claim 3, wherein It meets one or more of the following conditions: (1) In the high-temperature rebaudioside M aqueous solution, the mass fraction of rebaudioside M is 6%-8%; (2) The mass ratio of the solvent contained in the high-temperature rebaudioside M aqueous solution to the low-temperature polar protic solvent is (1.5-1.6):1; (3) The temperature of the high-temperature rebaudioside M aqueous solution is 92° C.; (4) The temperature of the low-temperature polar protic solvent is 1°C, 2°C, 3°C, 4°C or 5°C; (5) During the process of adding the high-temperature rebaudioside M aqueous solution to the low-temperature polar protic solvent, the temperature of the mixed system is maintained at 1°C to 5°C, for example, 1°C, 2°C, 3°C, 4°C or 5°C; (6) The temperature difference between the high-temperature rebaudioside M aqueous solution and the low-temperature polar protic solvent is 85°C-97°C, preferably 90°C-97°C.

5. The preparation method according to claim 3, wherein It meets one or more of the following conditions: (1) The temperature of the static insulation step is 1°C-8°C; (2) The time of the standing and heat preservation step is 0.5-2h; (3) The temperature of the drying step is 60°C-70°C; (4) The drying step takes 20-30 hours; (5) The drying step is carried out by oven drying.

6. The preparation method according to claim 3, wherein It meets one or more of the following conditions: (1) The temperature of the standing and heat preservation step is 1°C-5°C; (2) The time of the static insulation step is 1 hour; (3) The temperature of the drying step is 63°C-67°C; (4) The drying step is performed for 24 hours.

7. The preparation method according to claim 3, wherein It meets one or more of the following conditions: (1) The temperature of the standing and holding step is 1°C, 2°C, 3°C, 4°C or 5°C; (2) The temperature of the drying step is 65°C.

8. The preparation method according to claim 1, wherein In the high-temperature rebaudioside M aqueous solution, the mass fraction of rebaudioside M is 5%-10%; the temperature of the high-temperature rebaudioside M aqueous solution is 90°C-100°C; the mass ratio of the solvent contained in the high-temperature rebaudioside M aqueous solution to the low-temperature polar protic solvent is (1.0-1.8):1; the temperature of the low-temperature polar protic solvent is 1°C-8°C; the temperature difference between the high-temperature rebaudioside M aqueous solution and the low-temperature polar protic solvent is 82°C-99°C; in the process of adding the high-temperature rebaudioside M aqueous solution to the low-temperature polar protic solvent, the temperature of the mixed system is maintained at 1°C-8°C.

9. The preparation method according to claim 1, wherein The high-temperature rebaudioside M aqueous solution is prepared by the following steps: mixing rebaudioside M crystals and water, and heating to obtain the high-temperature rebaudioside M aqueous solution; the polar protic solvent is purified water; the mass fraction of rebaudioside M in the high-temperature rebaudioside M aqueous solution is 6%-8%; the temperature of the high-temperature rebaudioside M aqueous solution is 90°C-100°C; the high-temperature rebaudioside M aqueous solution is added dropwise to the low-temperature polar protic solvent; the dropping is dropwise addition; the mass of the high-temperature rebaudioside M aqueous solution added per minute accounts for 1% to 5%, for example, 1.8% to 2.7%; the mass ratio of the solvent contained in the high-temperature rebaudioside M aqueous solution to the low-temperature polar protic solvent is (1.5-1.6):1; the temperature of the low-temperature polar protic solvent is 1°C-8°C; the temperature difference between the high-temperature rebaudioside M aqueous solution and the low-temperature polar protic solvent is 90°C-97°C; in the process of adding the high-temperature rebaudioside M aqueous solution to the low-temperature polar protic solvent, the temperature of the mixed system is maintained at 1°C-5°C; the instantaneous cooling step further includes a standing and heat preservation step, a filtration step and a drying step.

10. The preparation method according to claim 1, wherein In the preparation method, the materials used are composed of a rebaudioside M aqueous solution and a polar protic solvent.

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