Process for preparing porous milk powder by combining freeze drying and foaming methods

Abstract

The invention belongs to the technical field of milk powder production and processing, and discloses a process for preparing porous milk powder by combining freeze drying and foaming methods, which comprises the following steps: preparing a liquid milk solution meeting the requirements of fluidity and stability; cO2 bubbles are injected into the liquid milk solution; a bubble structure in the liquid milk solution is locked in a quick freezing mode; and freeze-drying to retain a porous structure. Food-grade CO2 bubbles are injected into a liquid milk solution, a bubble structure is locked in a rapid freezing process, and a porous structure is reserved through freeze drying, so that the porosity, the solubility and the physical stability of the milk powder are remarkably improved, specifically, the porosity of the porous milk powder prepared according to the process can reach 70%-90%, the solubility of the milk powder can reach 70%-90%, and the physical stability of the milk powder can reach 70%-90%. Compared with traditional milk powder, the dissolving time is shortened by at least 50% or above, and milk powder particles have high mechanical strength and structural stability in storage and transportation by optimizing bubble stability and freeze-drying conditions.

Description

Technical Field

[0001] The present invention belongs to the technical field of milk powder production and processing, and particularly relates to a process for preparing porous milk powder by combining freeze-drying and foaming method. Background Art

[0002] The surface of the particles of porous milk powder has multiple tiny pores. This porous structure helps to improve the solubility and dispersibility of milk powder, enabling it to dissolve faster in liquid and reducing caking.

[0003] The existing milk powder preparation processes mainly include: 1. Spray drying process and 2. Freeze-drying process. In the spray drying process, it is easy for milk powder to lose some nutrients, and the porosity is relatively low, which is not conducive to improving the dissolution performance; in the freeze-drying process, although more nutrients can be retained, the porous structure of the produced milk powder is relatively single, and the solubility and physical properties of the milk powder cannot be fully optimized. Therefore, both of these production processes have certain limitations in terms of the solubility, porous structure, and product performance of milk powder.

[0004] Therefore, a process for preparing porous milk powder by combining freeze-drying and foaming method is provided to solve the technical problems that the existing production processes cannot meet the requirements of milk powder in terms of solubility, porous structure, and product performance. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a process for preparing porous milk powder by combining freeze-drying and foaming method.

[0006] To achieve the above technical purpose, the technical solution adopted by the present invention is as follows:

[0007] In the first aspect, the present invention provides a process for preparing porous milk powder by combining freeze-drying and foaming method, including

[0008] (Ⅰ) Preparing a liquid milk solution that meets fluidity and stability;

[0009] (Ⅱ) Injecting CO 2 bubbles into the liquid milk solution;

[0010] (Ⅲ) Locking the bubble structure in the liquid milk solution by means of rapid freezing;

[0011] (Ⅳ) Freeze-drying to retain the porous structure.

[0012] The present invention injects CO 2 bubbles into the liquid milk solution, locks the bubble structure during the rapid freezing process, and retains its porous structure through freeze-drying, thereby significantly improving the porosity, solubility, and physical stability of the milk powder. In addition, since the porous milk powder is for edible use, the CO 2The bubbles should be food-grade gas to ensure cleanliness and hygiene and meet food safety requirements.

[0013] As a preferred technical solution of the present invention, in step (Ⅰ), the concentration of the liquid milk solution is 10% - 20%, for example, it can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable. In step (Ⅱ), the 2 The injection amount of the bubbles is 10% - 30% of the volume of the liquid milk solution, for example, it can be 10%, 15%, 20%, 21%, 22%, 25%, 28.5%, 29%, 30%, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0014] The present invention particularly limits the concentration of the liquid milk solution to 10% - 20%, and the 2 injection amount of the CO 2 bubbles is 10% - 30% of the volume of the liquid milk solution because the liquid milk solution with a concentration of 10% - 20% has appropriate fluidity and stability during the subsequent injection of CO 2 bubbles and the process of rapid freezing; and the injection amount of the CO

[0015] As a preferred technical solution of the present invention, in step (Ⅱ), the 2 CO 2 bubbles are directly generated in the liquid milk solution by ultrasonic waves, and the

[0016] CO 2 bubbles have a particle size of 1μm - 50μm. 2 The present invention particularly limits the generation method of the CO

[0017] As a preferred technical solution of the present invention, in step (Ⅱ), the 2 CO 2 bubbles are generated by the method of swirl shearing. Specifically, the superficial gas velocity is 5m / s - 50m / s, and the CO 2 gas is injected into the high-speed rotating liquid milk solution through a rotating shearing device, and the generated

[0018] CO 2The generation method of the bubbles is the swirl shear method because the CO generated by this method 2 The bubble diameter is 1μm - 30μm. According to the actual needs of product quality, production convenience, and cost, this bubble generation method can be selected.

[0019] As a preferred technical solution of the present invention, in step (Ⅱ), the CO 2 bubbles are generated by the jet oscillation and microporous aeration methods. Specifically, the superficial gas velocity is 5m / s - 50m / s, driving the CO 2 gas to pass through the porous metal material, and the generated CO 2 bubble diameter is 50μm - 100μm.

[0020] The present invention particularly defines that the generation method of the CO 2 bubbles is the jet oscillation and microporous aeration methods because the CO 2 bubbles generated by this method have a diameter of 50μm - 100μm. According to the actual needs of product quality, production convenience, and cost, this bubble generation method can be selected.

[0021] As a preferred technical solution of the present invention, in step (Ⅲ), the temperature drop rate of rapid freezing is controlled above 10℃ / min, and the final temperature of rapid freezing is below -40℃.

[0022] The present invention particularly defines the cooling rate of rapid freezing because at a cooling rate of 10℃ / min, the bubble structure can be quickly locked to prevent bubble collapse or coalescence.

[0023] As a preferred technical solution of the present invention, in step (Ⅳ), the temperature condition for freeze-drying is -50℃ - -30℃, and the vacuum degree is 0.1Pa - 0.5Pa. Specifically, the liquid milk solution is quickly frozen and then freeze-dried by a vacuum freeze-dryer to remove moisture.

[0024] The present invention particularly defines the temperature condition and vacuum degree for freeze-drying because under these conditions, moisture can be removed while retaining the porous structure formed by the CO 2 bubbles.

[0025] In the second aspect, the present invention provides a porous milk powder prepared by using the process for preparing porous milk powder by combining freeze-drying and foaming method described in the first aspect. The porosity of the porous milk powder is between 70% and 90%, and the pore size distribution is between 10μm and 100μm.

[0026] Exemplarily, the present invention provides a process for preparing porous milk powder by combining freeze-drying and foaming method, including the following steps:

[0027] (1) Prepare a liquid milk solution with a concentration of 10% to 20%;

[0028] (2) Inject CO 2 bubbles into the liquid milk solution by ultrasonic oscillation method, swirl shear method or jet oscillation microporous aeration method. The injection volume of CO 2 bubbles is 10% to 30% of the volume of the liquid milk solution;

[0029] When using the ultrasonic oscillation method, CO 2 bubbles are directly generated in the liquid milk solution by ultrasonic waves. The particle size of CO 2 bubbles is 1 μm to 50 μm;

[0030] When using the swirl shear method, the superficial gas velocity is 5 m / s to 50 m / s. Inject CO 2 gas into the high-speed rotating liquid milk solution through a rotating shear device. The particle size of the generated CO 2 bubbles is 1 μm to 30 μm;

[0031] When using the jet oscillation microporous aeration method, the superficial gas velocity is 5 m / s to 50 m / s, driving CO 2 gas to pass through a porous metal material. The particle size of the generated CO 2 bubbles is 50 μm to 100 μm;

[0032] (3) Lock the bubble structure in the liquid milk solution by rapid freezing. The temperature drop rate of rapid freezing is controlled above 10 °C / min, and the final temperature of rapid freezing is below -40 °C;

[0033] (4) Freeze-dry the rapidly frozen liquid milk solution by a vacuum freeze dryer. The temperature condition is -50 °C to -30 °C, and the vacuum degree is 0.1 Pa to 0.5 Pa.

[0034] Advantages of the present invention: By injecting food-grade CO 2 bubbles into the liquid milk solution, locking the bubble structure during the rapid freezing process, and retaining its porous structure through freeze-drying, thereby significantly improving the porosity, solubility and physical stability of the milk powder. Specifically, for the porous milk powder prepared by the process of the present invention, its porosity can reach 70% to 90%, and the dissolution time is at least shortened by more than 50% compared with traditional milk powder. And by optimizing the bubble stability and freeze-drying conditions, the milk powder particles have high mechanical strength and structural stability during storage and transportation. Brief Description of the Drawings

[0035] The present invention can be further illustrated by the non-limiting embodiments given in the drawings;

[0036] Figure 1Process flow chart of the embodiment of the present invention; Detailed implementation manners

[0037] The technical solution of the present invention will be described in detail below in conjunction with specific embodiments and their accompanying drawings. The embodiments recorded herein are specific specific implementation manners of the present invention and are used to illustrate the concept of the present invention; these descriptions are all explanatory and exemplary and should not be construed as limiting the implementation manner of the present invention and the protection scope of the present invention. Except for the embodiments recorded herein, those skilled in the art can also adopt other obvious technical solutions based on the content disclosed in the claims and the specification of this application. These technical solutions include technical solutions that make any obvious substitutions and modifications to the embodiments recorded herein.

[0038] Example 1

[0039] As Figure 1 shown, this embodiment provides a process for preparing porous milk powder by combining freeze-drying and foaming method, including the following steps,

[0040] (1) Prepare a liquid milk solution with a concentration of 20%;

[0041] (2) Inject CO 2 bubbles into the liquid milk solution by ultrasonic oscillation method. The injection volume of CO 2 bubbles is 20% of the volume of the liquid milk solution, and the particle size of CO 2 bubbles is 10μm - 50μm;

[0042] (3) Lock the bubble structure in the liquid milk solution by rapid freezing. The temperature drop rate of rapid freezing is controlled above 10°C / min, and the final temperature of rapid freezing is below -40°C;

[0043] (4) Freeze-dry the rapidly frozen liquid milk solution by a vacuum freeze-dryer. The temperature condition is -50°C to -30°C, the vacuum degree is 0.1Pa to 0.5Pa, and the drying time is 24 hours.

[0044] Example 2

[0045] As Figure 1 shown, this embodiment provides a process for preparing porous milk powder by combining freeze-drying and foaming method, including the following steps,

[0046] (1) Prepare a liquid milk solution with a concentration of 15%;

[0047] (2) Inject CO 2 bubbles into the liquid milk solution by swirl shear method. 2The injection volume of the bubbles is 15% of the volume of the liquid milk solution. Specifically, the superficial gas velocity is 5 m / s to 50 m / s, and CO 2 gas is injected into the rapidly rotating liquid milk solution through a rotary shear device to generate CO 2 bubbles with a particle size of 5 μm to 30 μm;

[0048] (3) Lock the bubble structure in the liquid milk solution by rapid freezing. The temperature drop rate of rapid freezing is controlled above 10 °C / min, and the final temperature of rapid freezing is -50 °C;

[0049] (4) Freeze-dry the rapidly frozen liquid milk solution by a vacuum freeze dryer. The temperature condition is -50 °C, the vacuum degree is 0.2 Pa, and the drying time is 36 hours.

[0050] Example 3

[0051] As Figure 1 shown, this embodiment provides a process for preparing porous milk powder by combining freeze-drying and foaming method, including the following steps.

[0052] (1) Prepare a liquid milk solution with a concentration of 10%;

[0053] (2) Inject CO 2 bubbles into the liquid milk solution by the jet oscillation micropore aeration method. The injection volume of the CO 2 bubbles is 25% of the volume of the liquid milk solution. Specifically, the superficial gas velocity is 30 m / s, driving the CO 2 gas to pass through the porous metal material, and the generated CO 2 bubbles have a particle size of 50 μm to 100 μm;

[0054] (3) Lock the bubble structure in the liquid milk solution by rapid freezing. The temperature drop rate of rapid freezing is controlled above 10 °C / min, and the final temperature of rapid freezing is below -45 °C;

[0055] (4) Freeze-dry the rapidly frozen liquid milk solution by a vacuum freeze dryer. The temperature condition is -45 °C, the vacuum degree is 0.1 Pa, and the drying time is 48 hours.

[0056] Perform performance tests on the porous milk powder obtained in Examples 1 to 3. The test indexes include porosity, pore size distribution, and dissolution time (compared with traditional milk powder).

[0057] The performance test results of each example are shown in Table 1.

[0058] Table 1 Performance Test

[0059]

[0060] As can be seen from the test data in Table 1, in terms of dissolution time, the dissolution performance of the porous milk powders obtained in Examples 1 to 3 is significantly better than that of traditional milk powders. Compared with traditional milk powders, the dissolution time of the porous milk powders prepared according to the present invention is shortened by at least more than 50%. For some instant milk powder products, the adaptability is relatively high, which can greatly meet the needs of instant consumption; in terms of porosity, the porous milk powders obtained in Examples 1 to 3 maintain a high porosity of 70% to 90%, which is much higher than that of the milk powders prepared by the traditional freeze-drying process; in terms of pore size distribution, the porous milk powder prepared by Example 3 is mainly in the range of 50 μm to 100 μm, while the pore size distributions of the porous milk powders prepared by Examples 1 and 2 are relatively dispersed. According to the actual product requirements, the parameters and processes corresponding to different examples can be selected to produce suitable porous milk powders.

[0061] In summary, the present invention injects food-grade CO 2 bubbles into the liquid milk solution, locks the bubble structure by means of a rapid freezing process, and retains its porous structure by freeze-drying, thereby significantly improving the porosity, solubility and physical stability of the milk powder. Specifically, for the porous milk powder prepared according to the process of the present invention, its porosity can reach 70% to 90%, and the dissolution time is shortened by at least more than 50% compared with traditional milk powders. Moreover, by optimizing the bubble stability and freeze-drying conditions, the milk powder particles have high mechanical strength and structural stability during storage and transportation.

[0062] The above embodiments only exemplarily illustrate the principles and effects of the present invention, rather than limiting the present invention. Any person skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A process for preparing porous milk powder by combining freeze drying and foaming, characterized in that: include (I) preparing a liquid milk solution having satisfactory fluidity and stability; (II) injecting CO2 bubbles into the liquid milk solution; (III) Locking the bubble structure in the liquid milk solution by rapid freezing; (IV) Freeze drying to retain the porous structure.

2. The process for preparing porous milk powder by combining freeze drying and foaming method according to claim 1, characterized in that: In step (I), the concentration of the liquid milk solution is 10% to 20%.

3. The process for preparing porous milk powder by combining freeze drying and foaming method according to claim 2, characterized in that: In step (II), the injection amount of the CO2 bubbles is 10% to 30% of the volume of the liquid milk solution.

4. The process for preparing porous milk powder by combining freeze drying and foaming method according to claim 3, characterized in that: In step (II), the CO2 bubbles injected into the liquid milk solution are food grade CO2.

5. The process for preparing porous milk powder by combining freeze drying and foaming method according to claim 1, characterized in that: In step (II), the CO2 bubbles are directly generated in the liquid milk solution by ultrasound, and the particle size of the CO2 bubbles is 1 μm to 50 μm.

6. The process for preparing porous milk powder by combining freeze drying and foaming method according to claim 1, characterized in that: In step (II), the CO2 bubbles are generated by a swirl shearing method, and the particle size of the CO2 bubbles is 1 μm to 30 μm.

7. The process for preparing porous milk powder by combining freeze drying and foaming method according to claim 1, characterized in that: In step (II), the CO2 bubbles are generated by jet oscillation and microporous ventilation. Specifically, the CO2 gas is driven to pass through a porous metal material. The particle size of the CO2 bubbles is 50 μm to 100 μm.

8. The process for preparing porous milk powder by combining freeze drying and foaming method according to claim 1, characterized in that: In step (III), the temperature drop rate of rapid freezing is controlled to be above 10°C / min, and the final temperature of rapid freezing is below -40°C.

9. The process for preparing porous milk powder by combining freeze drying and foaming method according to claim 1, characterized in that: In step (IV), the freeze-drying temperature is -50°C to -30°C, and the vacuum degree is 0.1Pa to 0.5Pa.

10. A porous milk powder, characterized in that: According to the process for preparing porous milk powder by combining freeze drying and foaming method according to any one of claims 1-9, the porosity of the porous milk powder is between 70% and 90%, and the pore size distribution is between 10μm and 100μm.

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