Lactoferrin lyophilized powder and method for its preparation

Abstract

The application discloses a lactoferrin freeze-dried powder and a preparation method thereof, and relates to the technical field of food processing and biological products. The preparation method comprises the following steps: placing a lactoferrin solution in a freeze-drying device, supercooling the lactoferrin solution to obtain a supercooled sample; starting a forced freezing program to cool the supercooled sample to below-35 DEG C, and rapidly freezing the supercooled sample for 1-3 hours to obtain a rapidly frozen sample; and sequentially performing sublimation drying and resolution drying on the rapidly frozen sample under vacuum conditions. In the application, supercooling is performed before freezing, the freezing process can be actively and accurately controlled, and the flowability of the lactoferrin freeze-dried powder can be significantly improved by inducing the formation of small and uniform ice crystals; and the method is safe and efficient without the need of adding a flow agent.

Description

Technical Field

[0001] This invention relates to the field of food processing and biological products technology, and more specifically, to a lactoferrin freeze-dried powder and its preparation method. Background Technology

[0002] Lactoferrin is an important functional protein, often freeze-dried into powder for easier storage and transportation. However, traditional freeze-drying processes have a significant drawback: during the conventional freezing stage, ice crystals grow slowly and directionally, easily forming large, vertical columnar ice crystals. After sublimation drying, this ice crystal morphology leaves behind a porous framework with low structural strength and uneven pore size, resulting in a final product that is brittle, has severe interparticle adhesion, and poor flowability, seriously affecting the product's application performance (such as reconstitution properties and accurate quantitative packaging).

[0003] Currently, methods to improve powder flowability mostly focus on adding anti-caking agents or optimizing lyophilization protectant formulations. These methods are "post-natal remedies," which may introduce foreign components and have limited effectiveness. Therefore, improving the quality of the final product by actively controlling the microstructure of ice crystals during the freezing stage is a technical problem that urgently needs to be solved.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a lactoferrin freeze-dried powder and its preparation method, which can actively and precisely control the freezing process and significantly improve the flowability of the lactoferrin freeze-dried powder by inducing the formation of fine and uniform ice crystals. This method does not require the addition of flow aids and is safe and efficient.

[0006] This invention is implemented as follows:

[0007] In a first aspect, the present invention provides a method for preparing lyophilized lactoferrin powder, comprising:

[0008] A lactoferrin solution with a mass-volume percentage concentration of 15-25% was placed in a freeze-drying device and supercooled to -2℃ to -12℃ and held for 10-60 minutes. The lactoferrin solution was supercooled at a cooling rate of 0.5-5℃ / min to obtain a supercooled sample.

[0009] Start the forced quick-freezing program to cool the supercooled sample to below -35°C within 3-8 minutes, and quick-freeze for 1-3 hours to obtain the quick-frozen sample;

[0010] The quick-frozen sample was subjected to sublimation drying and desorption drying under vacuum conditions in sequence.

[0011] In an optional embodiment, before cooling the supercooled sample to below -35°C, the supercooled sample is subjected to a momentary physical stimulus to trigger nucleation.

[0012] In an optional implementation, the transient physical stimulation includes one or more of ultrasonic treatment, mechanical vibration, and electrical pulse treatment.

[0013] In an optional embodiment, the ultrasonic frequency during ultrasonic treatment is 25-35kHz, and the treatment time is 1-5s.

[0014] And / or, the mechanical vibration includes striking the freeze-drying equipment with a leather hammer for 3-7 seconds;

[0015] And / or, the pulse frequency of the electrical pulse is 15-25 kHz, and the processing time is 3-7 s.

[0016] In an optional embodiment, before the sublimation drying, a vacuum is first drawn to a vacuum level of 8-12 Pa;

[0017] And / or, the sublimation drying includes sublimation drying for 15-25 hours under a vacuum of 30-50 Pa and a temperature of 8-12 °C;

[0018] And / or, the analytical drying includes first performing analytical drying at a vacuum of 30-50 Pa and a temperature of 30-40°C for 4-6 hours, followed by analytical drying at a vacuum of 1-2 Pa and a temperature of 30-40°C for 5-7 hours. In an optional embodiment, after analytical drying, the material is further discharged, pulverized, and then sieved.

[0019] Secondly, the present invention provides a lactoferrin freeze-dried powder, which is prepared by the method for preparing lactoferrin freeze-dried powder as described in any of the foregoing embodiments.

[0020] The present invention has the following beneficial effects:

[0021] The method for preparing lyophilized lactoferrin powder provided by this invention involves first supercooling the lactoferrin solution, followed by rapid freezing to below -35°C. In this invention, the first supercooling puts the lactoferrin solution into a "metastable liquid state," also known as the "supercooled state" (temperature below freezing point but not yet frozen). This allows the molecules sufficient time for conformational adjustment, reducing mechanical damage during ice crystal formation. Subsequent rapid freezing quickly fixes the adjusted stable conformation, reducing the risk of thermal denaturation. Simultaneously, after supercooling, a small number of "crystal nuclei" form in the solution. Subsequent rapid freezing allows uniform, loose ice crystal structures to grow around these nuclei. The pores left by the sublimation of the ice crystals after freeze-drying are more regular and have better connectivity. The combination of pre-cooling followed by quick-freezing allows for proactive and precise control of the freezing process. By inducing the formation of fine, uniform ice crystals, it avoids the damage caused by large ice crystals formed during slow freezing and solves the problem of uneven ice crystal distribution caused by direct quick-freezing. This achieves the ideal state of "fine and uniform ice crystals," transforming the vertical crystals of conventional freeze-drying into granular crystals. Subsequent drying and pulverization significantly improve powder flowability. This method requires no flow aids and is safe and efficient. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 The images show products obtained by different freeze-drying processes of the present invention, wherein, from left to right, they are product images of Comparative Example 1, Example 1, and Example 4, respectively.

[0024] Figure 2 The product diagram provided is for Comparative Example 3 of this invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0026] This invention provides a method for preparing lyophilized lactoferrin powder, comprising: placing a lactoferrin solution in a lyophilizing device and supercooling the lactoferrin solution to obtain a supercooled sample; starting a forced quick-freezing program to cool the supercooled sample to below -35°C and quick-freezing for 1-3 hours to obtain a quick-frozen sample; and subjecting the quick-frozen sample to sublimation drying and desorption drying under vacuum conditions.

[0027] "Supercooling" is a concept in thermodynamics, referring to the phenomenon where the temperature of a substance drops below its equilibrium phase transition temperature, but it still retains its original phase state (without undergoing a phase transition). It is commonly seen in the phase transition process from liquid to solid.

[0028] This invention achieves a uniform supercooling state within the supercooled sample by supercooling the lactoferrin solution before quick-freezing, thereby accumulating nucleation potential.

[0029] Because conventional freeze-drying involves directly freezing to below -35°C, the sudden drop in solution temperature during direct freezing causes a large number of small, vertical ice crystals to form rapidly, resulting in poor flowability after subsequent drying and pulverization.

[0030] In this invention, supercooling is performed first, placing the lactoferrin solution in a "supercooled state" (temperature below freezing point but not yet frozen). This allows the molecules sufficient time for conformational adjustment, reducing mechanical damage during ice crystal formation. Subsequent forced quick-freezing rapidly fixes the adjusted, stable conformation, reducing the risk of thermal denaturation. Simultaneously, supercooling creates a small number of "crystal nuclei" in the solution, which, upon subsequent quick-freezing, allow for the growth of uniform, loose ice crystal structures around these nuclei. The pores left by the sublimation of the ice crystals after freeze-drying are more regular and interconnected. Stepwise cooling controls the ice crystal growth rate: the combination of supercooling followed by quick-freezing avoids the damage caused by slow freezing leading to large ice crystals and solves the problem of uneven ice crystal distribution caused by direct quick-freezing, achieving the ideal state of "small and uniform ice crystals." This transforms the ice crystals from the vertical crystals of conventional freeze-drying into granular crystals, significantly improving powder flowability after subsequent drying and pulverization.

[0031] Specifically, the temperature is supercooled to -2℃ to -12℃ and held for 10-60 minutes. This invention strictly controls the supercooling temperature and holding time to ensure that lactoferrin molecules adapt to the low-temperature environment in advance without freezing, creating conditions for the subsequent formation of ideal ice crystal structures. This allows the lactoferrin molecules to undergo sufficient conformational adjustment and crystal nucleation preparation at the supercooled temperature. If the precooling holding time is too short, the conformational adjustment time of the molecules will be reduced, increasing the mechanical damage during ice crystal formation and preventing the effective formation of ideal ice crystal structures. However, if the precooling holding time is too long, the conformational adjustment time will be excessive, resulting in ice crystals that are half vertical and half granular, which also reduces their fluidity.

[0032] Furthermore, this invention specifies that the lactoferrin solution is cooled to -2°C to -12°C at a cooling rate of 0.5~5°C / min. By limiting the supercooling rate, the lactoferrin solution can be cooled to a supercooled state slowly. Slow cooling allows lactoferrin molecules sufficient time to adapt to the low temperature, avoiding activity loss due to conformational mutation, while gradually forming uniform crystal nuclei, laying the foundation for subsequent quick-freezing. Using medium or rapid cooling rates above 5°C / min during the supercooling stage will skip the molecular adaptation process and directly induce rapid ice crystal growth, thus damaging the lactoferrin structure.

[0033] During the supercooling stage, lactoferrin molecules complete conformational adjustments at low temperatures, reaching a more stable state. This is followed by rapid freezing. In this invention, the supercooled sample is cooled to below -35°C within 3-8 minutes. This rapid cooling quickly "fixes" this stable conformation, preventing thermal denaturation or conformational disorder caused by prolonged exposure to low temperatures, while also reducing mechanical damage to the protein structure from ice crystal growth. The small number of uniform crystal nuclei formed during the supercooling stage allow ice crystals to grow rapidly along these nuclei during rapid freezing, resulting in uniform size and regular shape, thus enabling controllable ice crystal growth.

[0034] The lactoferrin solution targeted in this invention has a mass-volume percentage concentration of 15-25%. The concentration of the lactoferrin solution also has a certain impact on its supercooling temperature. In order to achieve supercooling quickly, during the test, the lactoferrin solution (taking 500ml as an example) is spread evenly in the freeze-drying tray, maintaining a certain material thickness of 8-15mm, so that it can be quickly supercooled and frozen.

[0035] In some embodiments, before cooling the supercooled sample to below -35°C, a transient physical stimulus is applied to the supercooled sample to trigger nucleation. The transient physical stimulus in this invention is an optional solution. Even without transient physical stimulus, the crystal morphology can still be directionally reconstructed by "supercooling" + "rapid freezing," changing "vertical crystallization" to "granular crystallization," which significantly improves powder flowability.

[0036] In this context, instantaneous physical stimulation can precisely trigger uniform nucleation in supercooled samples, avoiding the randomness of spontaneous nucleation. Specifically, supercooled samples (-2℃ to -12℃) are in a "supercooled metastable state," where, although not frozen, their energy is higher than the equilibrium state, resulting in a low and uncontrollable probability of spontaneous nucleation (it may only occur randomly during the rapid freezing stage). Spontaneous nucleation easily leads to a small number of crystal nuclei and uneven distribution, and subsequent rapid freezing can result in large ice crystals or localized dense ice crystals, damaging the protein structure.

[0037] Instantaneous physical stimulation inputs energy through external force, breaks the metastable equilibrium, and actively triggers the aggregation of water molecules in the solution to form crystal nuclei. It can precisely control the nucleation sites, so that a large number of uniformly distributed micro crystal nuclei are formed inside the sample, providing a unified "template" for ice crystal growth in the quick-freezing stage and solving the problem of randomness in spontaneous nucleation.

[0038] The supercooling stage allows lactoferrin molecules to complete conformational adjustments. After nucleation is triggered by instantaneous physical stimulation, the process can immediately enter the quick-freezing stage, preventing excessive crystal growth (forming large ice crystals). Active nucleation reduces the "ice crystal growth time lag" in the quick-freezing stage, ensuring uniform ice crystal growth during rapid cooling and maximizing the synergistic effect of "supercooling + quick-freezing." Ultimately, this improves the activity retention rate, product consistency, production stability, and flowability of the lactoferrin freeze-dried powder.

[0039] Instantaneous physical stimulation includes, but is not limited to, one or more of ultrasonic processing, mechanical vibration, and electrical pulse processing.

[0040] Among them, the ultrasonic frequency during ultrasonic treatment is 25-35 kHz, and the treatment time is 1-5 s; and / or, mechanical vibration includes striking the freeze-drying equipment with a leather hammer for 3-7 s; and / or, the pulse frequency of the electrical pulse is 15-25 kHz, and the treatment time is 3-7 s.

[0041] When two or three instantaneous physical stimuli are used simultaneously, the operating conditions described above should be followed. Multiple instantaneous physical stimuli can simultaneously trigger instantaneous uniform nucleation of the entire sample.

[0042] The quick-frozen samples were subjected to sublimation drying and desorption drying under vacuum conditions. Before sublimation drying, a vacuum of 8-12 Pa was applied. Sublimation drying was carried out for 15-25 hours under a vacuum of 30-50 Pa and a temperature of 8-12℃. Desorption drying involved first desorption drying for 4-6 hours under a vacuum of 30-50 Pa and a temperature of 30-40℃, followed by desorption drying for 5-7 hours under a vacuum of 1-2 Pa and a temperature of 30-40℃. After desorption drying, the material was discharged, pulverized, and sieved through an R028 sieve to obtain a lyophilized lactoferrin powder with significantly improved flowability.

[0043] The lactoferrin lyophilized powder prepared by the above-described method has good flowability.

[0044] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0045] Example 1

[0046] This embodiment provides a lactoferrin lyophilized powder, the preparation method of which includes:

[0047] S1. Spread 500ml of 18% w / v lactoferrin solution evenly on a freeze-drying tray, place it in a freeze-drying device, cool it to -5℃ at a rate of 5℃ / min, and maintain it for 30 minutes.

[0048] S2. Start the quick-freezing program to lower the sample center temperature to -40℃ within 5 minutes and freeze-dry for 1.5 hours;

[0049] S3. Evacuate to a vacuum degree of 10 Pa, then perform sublimation drying at a vacuum degree of 35 Pa and a temperature of 10 °C for 18 h; perform desorption drying at a vacuum degree of 35 Pa and a temperature of 35 °C for 5 h, and then continue desorption drying at a vacuum degree of 1 Pa and a temperature of 35 °C for 6 h.

[0050] S4. Discharge and crush using a crusher, with screen specification R028.

[0051] Example 2

[0052] This embodiment provides a lactoferrin lyophilized powder, the preparation method of which includes:

[0053] S1. Spread 500ml of 15% w / v lactoferrin solution evenly on a freeze-drying tray, place it in a freeze-drying device, cool it to -10℃ at a rate of 5℃ / min, and maintain it for 15 minutes.

[0054] S2. Start the quick-freeze program to lower the center temperature of the sample to -35°C within 5 minutes and freeze-dry for 2 hours.

[0055] S3. Evacuate to a vacuum degree of 10 Pa, then perform sublimation drying at a vacuum degree of 35 Pa and a temperature of 10 °C for 18 h; perform desorption drying at a vacuum degree of 35 Pa and a temperature of 35 °C for 5 h, and then continue desorption drying at a vacuum degree of 1 Pa and a temperature of 35 °C for 6 h.

[0056] S4. Discharge and crush using a crusher, with screen specification R028.

[0057] Example 3

[0058] This embodiment provides a lactoferrin lyophilized powder, the preparation method of which includes:

[0059] S1. Spread 500ml of 25% w / v lactoferrin solution evenly on a freeze-drying tray, place it in a freeze-drying device, cool it to -5℃ at a rate of 5℃ / min, and maintain it for 45 minutes.

[0060] S2. Apply ultrasonic treatment at a frequency of 28kHz for 2s, and simultaneously start the quick-freezing program to lower the sample center temperature to -40℃ within 5 minutes and freeze-dry for 1.5h.

[0061] S3. Evacuate to a vacuum degree of 10 Pa, then perform sublimation drying at a vacuum degree of 35 Pa and a temperature of 10 °C for 18 h; perform desorption drying at a vacuum degree of 35 Pa and a temperature of 35 °C for 5 h, and then continue desorption drying at a vacuum degree of 1 Pa and a temperature of 35 °C for 6 h.

[0062] S4. Discharge and crush using a crusher, with screen specification R028.

[0063] Example 4

[0064] This embodiment provides a lactoferrin lyophilized powder, the preparation method of which includes:

[0065] S1. Spread 500ml of 20% w / v lactoferrin solution evenly on a freeze-drying tray, place it in a freeze-drying device, cool it to -10℃ at a rate of 5℃ / min, and maintain it for 20 minutes.

[0066] S2. Use a rubber mallet to tap the freeze-drying equipment for 5 seconds; at the same time, start the quick-freeze program to lower the center temperature of the sample to -35℃ within 5 minutes and freeze-dry for 2 hours.

[0067] S3. Evacuate to a vacuum degree of 10 Pa, then perform sublimation drying at a vacuum degree of 35 Pa and a temperature of 10 °C for 18 h; perform desorption drying at a vacuum degree of 50 Pa and a temperature of 35 °C for 5 h, and then continue desorption drying at a vacuum degree of 1 Pa and a temperature of 35 °C for 6 h.

[0068] S4. Discharge and crush using a crusher, with screen specification R028.

[0069] Example 5

[0070] This embodiment provides a lactoferrin lyophilized powder, the preparation method of which includes:

[0071] S1. Spread 500ml of 20% w / v lactoferrin solution evenly on a freeze-drying tray, place it in a freeze-drying device, cool it to -3℃ at a rate of 5℃ / min, and maintain it for 10 minutes.

[0072] S2. Apply an electrical pulse at a frequency of 20kHz for 5 seconds, and simultaneously start the quick-freezing program to lower the sample center temperature to -45℃ within 5 minutes and freeze-dry for 1 hour.

[0073] S3. Evacuate to a vacuum degree of 10 Pa, then perform sublimation drying at a vacuum degree of 35 Pa and a temperature of 10 °C for 18 h; perform desorption drying at a vacuum degree of 35 Pa and a temperature of 35 °C for 5 h, and then continue desorption drying at a vacuum degree of 1 Pa and a temperature of 35 °C for 6 h.

[0074] S4. Discharge and crush using a crusher, with screen specification R028.

[0075] Comparative Example 1

[0076] This comparative example provides a lyophilized lactoferrin powder, the preparation method of which includes:

[0077] S1. Spread 500ml of 20% w / v lactoferrin solution evenly on a freeze-drying tray and place it in a freeze-drying device.

[0078] S2. Cool to -40°C at a rate of 2°C / min and freeze-dry for 1.5 hours.

[0079] S3. Evacuate to a vacuum degree of 10 Pa, then perform sublimation drying at a vacuum degree of 35 Pa and a temperature of 10 °C for 18 h; perform desorption drying at a vacuum degree of 35 Pa and a temperature of 35 °C for 5 h, and then continue desorption drying at a vacuum degree of 1 Pa and a temperature of 35 °C for 6 h.

[0080] S4. Discharge and crush using a crusher, with screen specification R028.

[0081] Comparative Example 2

[0082] This comparative example is basically the same as Comparative Example 1, except that in this comparative example, step S2 involves cooling to -35°C at a rate of 5°C / min and freeze-drying for 2 hours.

[0083] Comparative Example 3

[0084] This comparative example is basically the same as Comparative Example 1, except that in this comparative example, step S1 involves cooling to -6°C at a rate of 5°C / min and holding for 75 minutes.

[0085] Experimental Example

[0086] The lactoferrin lyophilized powders prepared in Examples 1-5 and Comparative Examples 1-3 were subjected to flowability tests. The test parameters included: angle of repose, bulk density, dispersibility, and flow rate. The testing instrument was a Dandong Baite BT-1001. Specific parameter definitions and test methods are as follows:

[0087] (1) Angle of repose:

[0088] In a static equilibrium state, the acute angle between the free surface of the accumulated powder and the horizontal plane is called the angle of repose. It is measured after the powder has fallen naturally onto a specific platform in a specific manner, forming a cone. The testing instrument is the Dandong Baite BT-1001.

[0089] (2) Loose packing density:

[0090] The loose density is the ratio of the mass to the volume of powder after it has filled a standard container and been leveled, under the specified falling distance or conditions. It reflects the weight of powder contained in a unit volume container under normal conditions. The density is measured after the powder falls onto a specific platform and forms a cone. The testing instrument is the Dandong Baite BT-1001.

[0091] (3) Dispersion:

[0092] The percentage of powder that drifts outside the receiving tray after a certain amount of powder is dropped from a certain height. Dispersion is the degree to which powder disperses in the air, and it is related to the powder's dispersibility, drift, and splashing properties. The testing instrument is the Dandong Baite BT-1001.

[0093] (4) Outflow velocity: refers to the ratio of the "mass or volume" of powder flowing freely from the outlet of a standard funnel to the "time" under specific conditions (fixed funnel specifications, no external disturbance). Refer to the Hall flow meter method (GB / T 1482-2010).

[0094] Please refer to Table 1 for the test results.

[0095] Table 1. Statistical table of flowability test results for different examples of lactoferrin lyophilized powder.

[0096]

[0097] As can be seen from the table above, firstly, the angle of repose of Examples 1-5 is smaller than that of Comparative Examples 1-3. The size of the angle of repose directly reflects the flowability of lactoferrin powder; the smaller the angle, the better the flowability of the powder. Secondly, the loose bulk density reflects the weight of powder contained in a unit volume container under conventional conditions. The results show that the loose bulk density of Examples 1-5 is significantly higher than that of Comparative Examples 1-3, which is directly related to the state of the freeze-dried lactoferrin blocks. Figure 1The freeze-dried lactoferrin block products of Examples 1 and 4 and Comparative Example 1 also clearly show that Comparative Example 1, using a traditional freeze-drying process, produces crystals that are vertically fibrous, noticeably polished, and have low hardness. Examples 1 and 4, on the other hand, exhibit granular texture and high hardness. Example 4, by adding physical stimulation through hammering to Example 1, shows even better results than Example 1. The dispersibility of Comparative Examples 1-3 is significantly higher than that of Examples 1-5. Dispersibility characterizes the degree to which powder disperses in air and is related to the powder's dispersibility, dispersion, and splashing properties. If the dispersibility exceeds 50%, it indicates a strong tendency for dispersion. This characteristic directly affects its application in end products, such as when it is dry-mixed into emulsion base powder. If the dispersibility is too high, the amount added to the target product will be reduced. Finally, the outflow rate is another key indicator for evaluating the "flowability" of powder. The faster the outflow rate, the better the powder's flowability; conversely, the slower the outflow rate, the worse the flowability. The outflow rates of Examples 1-5 are also significantly higher than those of Comparative Examples 1-3. Typically, the outflow rate is less than 0.8 g / s, resulting in poor flowability, necessitating the addition of a main drying machine or further optimization of the drying process. Comparative Example 2 improved the cooling rate in step S2 of Comparative Example 1, but the effect remained unsatisfactory. Although pre-cooling was performed in Comparative Example 3, the excessively long pre-cooling holding time led to an excessively long conformational adjustment time, causing the ice crystals to exhibit... Figure 2 The half-vertical crystal and half-granular crystal configuration shown also leads to reduced fluidity. In summary, the method for preparing lactoferrin freeze-dried powder provided by this invention involves first supercooling the lactoferrin solution to -2℃ to -12℃ and holding for 10-60 minutes, followed by rapid freezing to below -35℃. In this invention, the first supercooling puts the lactoferrin solution in a "supercooled state" (temperature below freezing point but not yet frozen), allowing sufficient time for conformational adjustment and reducing mechanical damage during ice crystal formation. Subsequent forced rapid freezing quickly fixes the adjusted stable conformation, reducing the risk of thermal denaturation. Simultaneously, after supercooling, a small number of "crystal nuclei" form in the solution, and subsequent rapid freezing allows for the growth of uniform, loose ice crystal structures around these nuclei. The pores left by the sublimation of the ice crystals after freeze-drying are more regular and have better connectivity. The combination of pre-cooling followed by quick-freezing allows for proactive and precise control of the freezing process. By inducing the formation of fine, uniform ice crystals, it avoids the damage caused by large ice crystals formed during slow freezing and solves the problem of uneven ice crystal distribution caused by direct quick-freezing. This achieves the ideal state of "fine and uniform ice crystals," transforming the vertical crystals of conventional freeze-drying into granular crystals. Subsequent drying and pulverization significantly improve powder flowability. This method requires no flow aids and is safe and efficient.

[0098] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing lyophilized lactoferrin powder, characterized in that, It includes: A lactoferrin solution with a mass-volume percentage concentration of 15-25% was placed in a freeze-drying device and supercooled to -2℃ to -12℃ and held for 10-60 minutes. The lactoferrin solution was supercooled at a cooling rate of 0.5-5℃ / min to obtain a supercooled sample. First, the supercooled sample is subjected to a transient physical stimulus to trigger nucleation in the supercooled sample; Start the forced quick-freezing program to cool the supercooled sample to below -35°C within 3-8 minutes, and quick-freeze for 1-3 hours to obtain the quick-frozen sample; The quick-frozen sample was subjected to sublimation drying and desorption drying under vacuum conditions in sequence; After the analytical drying process, the material is discharged, crushed, and then sieved.

2. The method for preparing lactoferrin lyophilized powder according to claim 1, characterized in that, The instantaneous physical stimulation includes one or more of ultrasonic processing, mechanical vibration, and electrical pulse processing.

3. The method for preparing lactoferrin lyophilized powder according to claim 2, characterized in that, The ultrasonic frequency during ultrasonic treatment is 25-35kHz, and the treatment time is 1-5s. And / or, the mechanical vibration includes striking the freeze-drying equipment with a leather hammer for 3-7 seconds; And / or, the pulse frequency of the electrical pulse is 15-25 kHz, and the processing time is 3-7 s.

4. The method for preparing lactoferrin lyophilized powder according to any one of claims 1-3, characterized in that, Before the sublimation drying, a vacuum of 8-12 Pa is first applied; And / or, the sublimation drying includes sublimation drying for 15-25 hours under a vacuum of 30-50 Pa and a temperature of 8-12 °C; And / or, the analytical drying includes first performing analytical drying at a vacuum of 30-50 Pa and a temperature of 30-40 °C for 4-6 hours, followed by analytical drying at a vacuum of 1-2 Pa and a temperature of 30-40 °C for 5-7 hours.

5. A lyophilized lactoferrin powder, characterized in that, It is prepared by the method for preparing lactoferrin freeze-dried powder as described in any one of claims 1-4.

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