Method for detecting the particle size of lactose crystals in whey crystallization solution and application thereof

Abstract

The present application relates to the product processing technical field, specifically disclose a kind of detection method of lactose crystal particle size in whey crystallization liquid and its application.The detection method of the present application uses lactose aqueous solution as dispersing agent to detect the particle size of lactose crystal in whey crystallization liquid with laser particle size analyzer wet module;The temperature of whey crystallization liquid is 5-40 DEG C, total solid content is 48-70%, and lactose accounts for 65-90% of total solid mass;The temperature of lactose aqueous solution is the temperature of whey crystallization liquid±1 DEG C, and the concentration is 0.75×e (0.028×T+2.389) 0.85×e (0.028×T+2.389) G lactose / 100g water, and T is the temperature of whey crystallization liquid.The detection method of the present application can directly detect the particle size of lactose crystal in whey crystallization liquid at different temperatures without filtering and drying the sample;It is fast, stable and accurate, and can guide the industrial production of whey powder.

Description

Technical Field

[0001] This invention relates to the field of product processing technology, and more specifically, to a method for detecting the particle size of lactose crystals in whey crystallizer and its application. Background Technology

[0002] Whey is a byproduct of cheese or casein processing, containing lactose, whey protein, milk mineral salts, vitamins, and other nutrients. After desalting (or not desalting), concentration, crystallization, and drying, it is produced as sweet whey powder and desalted whey powder with varying degrees of desalination, widely used in baking, confectionery, and infant formula. In the production of whey powder, the crystallization stage is crucial. The crystallization rate affects the powder's moisture resistance during storage and the whey thermoplastic temperature during spray drying, thus impacting the spray drying effect. Crystal particle size affects spray drying efficiency, powder flowability, and solubility. For example, excessively large crystal particles can clog nozzles and cause production interruptions, while excessively small particles result in excessively high whey viscosity, affecting spray drying dispersion and drying efficiency. Real-time monitoring of lactose crystal particle size during whey crystallization allows for adjustments to crystallization process parameters, which is essential for producing high-quality whey powder.

[0003] There are few reports on methods for monitoring the particle size of lactose crystals during whey crystallization. Generally, existing methods involve first filtering the whey crystallizer using vacuum filtration, rinsing the resulting crystals with a small amount of cold water, and then drying them in a vacuum oven at 45°C. The dried sample is then analyzed using a laser particle size analyzer (such as a Malvern particle size analyzer) dry method module. However, this method of determining the particle size of lactose crystals in whey during crystallization involves a long vacuum oven drying time, making it difficult to adjust the crystallization process in a timely manner.

[0004] Therefore, further research is still needed on how to quickly, in real-time, and accurately detect the particle size of lactose crystals in whey crystallizer. Summary of the Invention

[0005] One of the objectives of this invention is to provide a method for rapidly, in real-time, and accurately detecting the particle size of lactose crystals in whey crystallizer during the whey crystallization process.

[0006] This invention provides a method for detecting the particle size of lactose crystals in whey crystallization solution, which uses an aqueous lactose solution as a dispersant and employs a laser particle size analyzer wet method module to detect the particle size of lactose crystals in whey crystallization solution;

[0007] The whey crystallization solution is prepared at a temperature of 5-40°C and has a total solids content of 48-70%, of which lactose accounts for 65-90% of the total solids content.

[0008] The temperature of the lactose aqueous solution is within ±1℃ of the temperature of the whey crystallizing solution;

[0009] The concentration of the lactose aqueous solution is 0.75 × e (0.028×T+2.389) up to 0.85×e (0.028×T+2.389) g lactose / 100g water (mass of lactose added per 100g of water, in g), where e is the base of the natural logarithm (its decimal part is infinite and non-repeating, approximately equal to 2.71828), and T is the temperature of the whey crystallization solution (the time at which the crystal size is monitored).

[0010] This invention reveals that existing methods for detecting lactose crystal size in whey crystallizers often require prolonged drying before testing, resulting in lengthy testing times (often several hours). This fails to reflect the real-time results of the ongoing crystallization process during whey powder preparation, making it impossible to promptly determine the lactose crystal size (which is directly related to product yield, flowability, solubility, and hygroscopicity), and thus cannot provide timely guidance for adjusting crystallization conditions. While focused beam reflectance measurement (FBRM) can achieve this, such equipment is expensive, and the results are presented as the percentage of crystals within a certain size range, which differs from commonly used particle size assessment standards like D10, D50, and D90, making it unsuitable for directly guiding industrial production.

[0011] Therefore, through extensive research, this invention has discovered that the selection of dispersant is crucial when directly detecting the particle size of lactose crystals in whey crystallization liquid using a laser particle size analyzer wet process module. However, the composition of whey crystallization liquid produced during whey powder production is complex, and its components such as proteins and oligosaccharides can affect the accuracy of detection, making it difficult to find a suitable dispersant. Ultimately, this invention found that using lactose solution as a dispersant, with specific control over its concentration and temperature, yields stable and accurate detection results. Excessive or insufficient dispersant concentration, or excessively high or low temperature, will affect the stability of the detection. Furthermore, this invention's method has a short detection time, allowing real-time monitoring of the ongoing crystallization process. It can be used to determine whether the target particle size has been obtained and to guide timely adjustments to crystallization process parameters based on the detection results, which is of great significance for the industrial production of whey powder.

[0012] In the whey crystallization solution detected by the method of the present invention, there must already be formed crystals. Generally speaking, the temperature is 5-40℃, the total solids content is 48-70%, and lactose crystals have begun to precipitate in the whey crystallization solution in which lactose accounts for 65-90% of the total solids.

[0013] In the method for detecting the particle size of lactose crystals of the present invention, the volume ratio of the dispersant to the whey crystallizer is 1:(300-1800), preferably 1:(520-875), and more preferably 1:(535-540).

[0014] By constructing the detection system according to the volume ratio of dispersant and whey crystallizer specified in this invention, effective and accurate detection can be achieved within the detection range of the wet method module of the laser particle size analyzer.

[0015] During testing, it is preferable to add the dispersant first, and then add the whey crystallizer to be tested dropwise into the dispersant. At the same time, the change in occlusion can be observed to determine whether the occlusion reaches the detection range (10~40%).

[0016] The method of this invention uses a laser particle size analyzer equipped with a wet detection module, which can effectively determine the particle size distribution of lactose crystals in whey crystallization solution with only a small amount of the solution to be tested.

[0017] Preferably, in the method for detecting the particle size of lactose crystals of the present invention, the temperature of the lactose aqueous solution is equal to the temperature of the whey crystallizing solution, so as to obtain more stable and accurate detection results.

[0018] Preferably, in the method for detecting the particle size of lactose crystals of the present invention, the concentration of the lactose aqueous solution is 0.8 × e (0.028×T+2.389) To obtain more stable and accurate test results, use 1 g lactose / 100g water.

[0019] In the method for detecting the particle size of lactose crystals of the present invention, the particle size of lactose crystals is expressed as D10 / D50 / D90. The present invention can also be used for testing D20 / D50 / D80 or other target particle size representations.

[0020] D10 represents the particle size at which the cumulative volume (number / surface area) of the particles being tested reaches 10% of the total volume (total number / total surface area) of the particles in the dispersant when the particles are arranged in ascending order. In other words, particles smaller than this size account for 10% (volume / surface area / number percentage). D50 represents the particle size (median diameter or median particle size) at which the cumulative volume (number / surface area) of the particles reaches 50%. It is usually used to represent the average particle size of crystals. D90 represents the particle size at which the cumulative volume (number / surface area) of the particles reaches 90%. In other words, particles smaller than this size account for 90%.

[0021] In the method for detecting the particle size of lactose crystals of the present invention, the whey crystallizing solution comes from the crystallization stage in the whey powder preparation process.

[0022] The preparation process of whey powder in this invention is a method known in the art. The specific target product can be desalted whey or non-desalted whey, or acidic whey or sweet whey. The raw materials can be animal milk, cheese, casein, yogurt, and other milk and dairy product by-products.

[0023] The present invention also provides the application of the above-mentioned method for detecting the particle size of lactose crystals in the preparation of whey powder.

[0024] The detection method of this invention targets lactose crystals during the crystallization process of whey liquid, rather than lactose crystals after filtration and drying. It can detect samples at different temperatures during the crystallization process of whey liquid, and can monitor the progress of the crystallization stage in real time during the preparation of whey powder, thereby helping to determine whether it can proceed to the next critical drying stage and providing production guidance for the target product.

[0025] The present invention also provides the application of the above-mentioned method for detecting lactose crystal size in real-time monitoring of lactose crystal size in whey crystallizer.

[0026] The present invention also provides the application of the above-mentioned method for detecting the particle size of lactose crystals in determining the crystallization endpoint of whey crystallization solution.

[0027] The present invention also provides the application of the above-mentioned method for detecting the particle size of lactose crystals in adjusting the crystallization conditions during the preparation of whey powder.

[0028] In whey powder preparation, the particle size distribution in the crystallization solution is related to product yield, flowability, solubility, and hygroscopicity. It can also be used to determine whether the crystallization solution will clog nozzles or affect drying efficiency in subsequent drying stages. The detection method of this invention can determine whether to terminate the crystallization process or guide adjustments to crystallization conditions by detecting whether the particle size distribution of lactose crystals in the whey crystallization solution meets the target requirements. If the existing crystallization process cannot obtain the target product, the process parameters can be adjusted based on the current particle size distribution and known crystal morphology adjustment methods. Furthermore, during the adjustment process, continuous testing of changes in the particle size distribution in the crystallization solution helps to explore and obtain better production parameters.

[0029] The beneficial effects of this invention are at least as follows:

[0030] The detection method of this invention does not require filtration and drying of the sample. It can directly detect the particle size of lactose crystals in the crystallization solution at different temperatures during the whey crystallization process. The detection speed is fast, the results are stable and accurate, and it can realize real-time monitoring of the crystallization results. It can determine the crystallization endpoint and make timely feedback and adjustment to the process based on the detection results, which is of great significance to the industrial production of whey powder. Detailed Implementation

[0031] The preferred embodiments of the present invention will now be described in detail with reference to specific examples. It should be understood that the following examples are given for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications and substitutions to the present invention without departing from its spirit and essence.

[0032] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples are commercially available or prepared according to conventional methods in the art.

[0033] Example 1

[0034] This embodiment provides a method for testing the particle size of lactose crystals in whey crystallization solution during the preparation of whey powder, as detailed below:

[0035] 1. Obtaining whey crystallization solution during whey powder preparation:

[0036] Sweet whey (pH=6.2) was used as raw material and defatted at 50℃ and 7800 rpm. The fat content of the defatted whey was 0.065 g / 100g. The whey was then sterilized by heating to 75℃ and holding for 20 seconds. Subsequently, a double-effect falling film evaporator was used to concentrate the whey. The preheating temperature was 72℃, the vacuum degree of the first-effect evaporator was -57 kPa (gauge pressure), and the vacuum degree of the second-effect evaporator was -68 kPa (gauge pressure). The discharge temperature was 65℃. After evaporation, the total solids of the whey reached 55.82 g / 100g, of which lactose accounted for 66.2%. The whey was immediately flash-cooled (flash-cooling system vacuum degree -95 kPa (gauge pressure)) to 35℃ after evaporation, and then cooled at a temperature gradient of 1.5℃ / h. The particle size of lactose crystals in the whey crystallization solution during the cooling process was analyzed.

[0037] 2. Determination of lactose crystal size in whey crystallization solution:

[0038] A sweet whey crystallization solution with a crystallization temperature of 15℃, a total solids content of 55.82%, and lactose accounting for 66.2% of the total solids was taken, and the particle size distribution of lactose crystals in it was determined as follows:

[0039] (1) Based on the temperature of the whey crystallizer T=15, according to 0.8×e (0.028×T+2.389) Calculate and prepare a lactose aqueous solution of the corresponding concentration (approximately 13.3 g / 100g water) using g / 100g water, and adjust the temperature to 15℃, the same as that of whey crystallization solution, as a dispersant for detection by a Malvern particle size analyzer (laser particle size analyzer).

[0040] (2) Transfer 350 mL of dispersant into the sample cell of the Malvern particle size analyzer;

[0041] (3) Add 0.65 mL of the whey crystallization solution to the sample cell (to achieve 22% light occlusion) and begin the test. Read the particle size distribution data D10, D50, and D90. During the test, the Malvern particle size analyzer performs a data measurement every 20 seconds, and the average of the three D10, D50, and D90 data measurements is taken as the final result. The stability of the test can be evaluated by the standard deviation of the three D50 data measurement results (20-second intervals).

[0042] To verify the accuracy of the method of the present invention, the whey crystallization solution to be tested was also taken, washed and dried according to conventional methods in the art, and its particle size distribution data D10, D50, and D90 were tested. Specifically, the whey crystallization solution was filtered through a 0.4 μm filter membrane, rinsed with isopropanol, and dried in a vacuum oven at 45°C. The dried lactose crystals were then transferred to a Malvern particle size analyzer and detected using the dry method module.

[0043] Example 2

[0044] This embodiment provides a method for testing the particle size of lactose crystals in whey crystallization solution during the preparation of whey powder, as detailed below:

[0045] 1. Obtaining whey crystallization solution during whey powder preparation:

[0046] Using sweet cheese whey (pH=6.2) as raw material, defatting was performed at 7800 rpm, resulting in a whey fat content of 0.088 g / 100g. Pasteurization was then carried out at 72℃ for 15 seconds. The pasteurized whey was then passed through a cation exchange resin (30℃, flow rate 3 BV / h), followed by nanofiltration (25 bar, 30℃), electrodialysis (1.5 V / membrane, 30℃), and finally anion exchange resin (30℃, flow rate 3 BV / h) to obtain a desalted whey solution with a total solids content of 22.73% and an ash content of 0.22 g / 100g. The desalted whey was then concentrated using a double-effect evaporation process to achieve a total solids content of 68.79 g / 100g, with lactose accounting for 74.33% of the total solids. The preheating temperature for the double-effect falling film evaporation was 70℃, and the vacuum degree for the first-effect evaporation was -59°C. kPa (gauge pressure); the vacuum degree of the double-effect evaporator is -62 kPa (gauge pressure), and the discharge temperature is 60.2℃. After evaporation, the material is immediately flash-cooled to 42℃, and the vacuum degree of the flash-cooling system is -95 kPa (gauge pressure). Then, the temperature is reduced in a gradient of 2℃ / h. During the cooling process, the particle size of lactose crystals in the desalted whey crystallizer is to be tested.

[0047] 2. Determination of lactose crystal size in whey crystallization solution:

[0048] A desalted whey crystallizer with a crystallization temperature of 40℃, a total solids content of 68.79%, and lactose accounting for 74.33% of the total solids was used to analyze the lactose crystal size distribution. The details are as follows:

[0049] (1) Based on the temperature of the whey crystallizer T=40, according to 0.85×e (0.028×T+2.389) Calculate and prepare a lactose aqueous solution of the corresponding concentration (approximately 28.4 g / 100 g water) using g / 100 g water, and adjust the temperature to 39°C, to be used as a dispersant for Malvern particle size analyzer testing;

[0050] (2) Transfer 350 mL of dispersant into the sample cell of the Malvern particle size analyzer;

[0051] (3) Take the above-mentioned whey crystallization solution to be tested and drop it into the sample cell. After a total of 0.2 mL is added (the light-blocking degree reaches 10%), start the detection and read the particle size distribution data D10, D50 and D90. During the detection, the Malvern particle size analyzer performs a data detection every 20 seconds, and the average value of the three data detections of D10, D50 and D90 is used as the final result.

[0052] To verify the accuracy of the test method of the present invention, the whey crystallization solution to be tested was also taken, washed and dried according to the method described in Example 1, and its particle size distribution data D10, D50 and D90 were tested.

[0053] Example 3

[0054] This embodiment provides a method for testing the particle size of lactose crystals in whey crystallization solution during the preparation of whey powder, as detailed below:

[0055] 1. Obtaining whey crystallization solution during whey powder preparation:

[0056] Using skim milk (fat content 0.06%) as raw material, the skim milk was separated using a ceramic membrane with a pore size of 0.14 μm to obtain natural whey. The natural whey was then sequentially passed through nanofiltration (pressure 30 mbar, temperature 25℃) and electrodialysis (voltage 1.5V / membrane, temperature 25℃) to obtain a desalted whey solution with a total solids content of 18.86 g / 100g and an ash content of 1.08 g / 100g. The desalted whey solution was concentrated by double-effect falling membrane evaporation until the total solids content reached 48.10%, of which lactose accounted for 89.45%. The preheating temperature of the double-effect falling membrane evaporation was 70℃, the vacuum degree of the first-effect evaporation was -58 kPa (gauge pressure), the vacuum degree of the second-effect evaporation was -61 kPa (gauge pressure), and the discharge temperature was 59.5℃. Flash-cool to 20°C with a vacuum of -99 kPa (gauge pressure) in the flash-cooling system, and then cool down at a temperature gradient of 2°C / h. During the cooling process, the particle size of lactose crystals in the desalted whey crystallizer is to be tested.

[0057] 2. Determination of lactose crystal size in whey crystallization solution:

[0058] A desalted whey crystallizer derived from membrane-separated whey, with a crystallization temperature of 5 ℃, a total solids content of 48.10%, and lactose accounting for 89.45% of the total solids, was used to determine the lactose crystal size distribution. The details are as follows:

[0059] (1) Based on the temperature of the whey crystallizer T=5℃, according to 0.75×e (0.028×T+2.389) Calculate and prepare a lactose aqueous solution of the corresponding concentration (approximately 9.41 g / 100g water) using g / 100g water, and adjust the temperature to 6℃, to be used as a dispersant for Malvern particle size analyzer detection;

[0060] (2) Transfer 400 mL of dispersant into the sample cell of the Malvern particle size analyzer;

[0061] (3) Take the above-mentioned whey crystallization solution to be tested and drop it into the sample cell. Add a total of 1.2 mL (the light-blocking degree reaches 38%) to start the test and read the particle size distribution data D10, D50 and D90. During the test, the Malvern particle size analyzer performs a data test every 20 seconds and takes the average value of the three data tests of D10, D50 and D90 as the final result.

[0062] To verify the accuracy of the test method of the present invention, the whey crystallization solution to be tested was also taken, washed and dried according to the method described in Example 1, and its particle size distribution data D10, D50 and D90 were tested.

[0063] Comparative Example 1

[0064] This comparative example provides a method for testing the particle size of lactose crystals in whey crystallization solution during the preparation of whey powder. The method is basically the same as that in Example 1, except that water at 15°C is used instead of the lactose aqueous solution as a dispersant for particle size testing.

[0065] Comparative Example 2

[0066] This comparative example provides a method for testing the particle size of lactose crystals in whey crystallization solution during the preparation of whey powder. The method is essentially the same as that in Example 1, except that it is changed to a concentration of 0.7×e at 15°C. (0.028×T+2.389) A lactose aqueous solution (concentration approximately 11.6 g / 100 g water) calculated and prepared was used as a dispersant for particle size testing.

[0067] Comparative Example 3

[0068] This comparative example provides a method for testing the particle size of lactose crystals in whey crystallization solution during the preparation of whey powder. The method is essentially the same as that in Example 1, except that it is changed to a concentration of 0.9 × e at 15°C.(0.028×T+2.389) A lactose aqueous solution (concentration approximately 14.9 g / 100 g water) calculated and prepared was used as a dispersant for particle size testing.

[0069] Comparative Example 4

[0070] This comparative example provides a method for testing the particle size of lactose crystals in whey crystallization solution during the preparation of whey powder. The method is essentially the same as that in Example 1, except that it is performed at a concentration of 1×e at 15°C. (0.028×T+2.389) A lactose aqueous solution (concentration approximately 16.6 g / 100 g) calculated and prepared by weighting 1 g / 100 g of water was used as a dispersant for particle size testing.

[0071] Comparative Example 5

[0072] This comparative example provides a method for testing the particle size of lactose crystals in whey crystallization solution during the preparation of whey powder. The method is basically the same as that in Example 1, except that a lactose aqueous solution at 12°C is used as a dispersant for particle size testing.

[0073] Comparative Example 6

[0074] This comparative example provides a method for testing the particle size of lactose crystals in whey crystallization solution during the preparation of whey powder. The method is basically the same as that in Example 1, except that a lactose aqueous solution at 18°C ​​is used as a dispersant for particle size testing.

[0075] Experimental results

[0076] The test results of the above embodiments and comparative examples are shown in Table 1.

[0077] Table 1

[0078]

[0079] As can be seen from the table, the method of the present invention has a smaller detection deviation compared to the comparative example, and the results are not much different from those of conventional drying and detection. However, it can significantly save detection time and realize real-time guidance for process production.

[0080] Example 4: Application Case

[0081] This embodiment applies the real-time testing method for lactose crystal size in whey crystallization solution of the present invention to guide whey powder production, as detailed below:

[0082] Whey powder was prepared according to the method in Example 2. During the gradient cooling stage of whey crystallization, a whey crystallizer with a temperature of 20°C and a total solids content of 68.79% was taken and its particle size distribution (D10, D50, and D90) was tested according to the method in Example 2. The results were: D10 = 12.277 μm; D50 = 36.530 μm; D90 = 68.322 μm. According to conventional knowledge in the art, it is ideal for D50 to be controlled within 25-30 μm and D90 to be controlled within 50 μm. In this test, the D50 and D90 results were too high, which may lead to nozzle clogging, poor atomization effect in spray drying, decreased powder flowability, and increased moisture absorption.

[0083] The desalted whey crystallizer was spray-dried at an inlet air temperature of 165℃ and an outlet air temperature of 90℃. The flowability index of the sprayed powder (flowability index test method refers to GB / T 31057.3) was 68, which is lower than that of commercially available products. The moisture absorption rate (the increase in mass of the powder after absorbing water after being placed in an environment with 75% relative humidity and 25℃ for 48 hours) was 4.82%, which is higher than that of commercially available products. Furthermore, three instances of nozzle clogging occurred during the spray drying process, consistent with the prediction.

[0084] Accordingly, the crystallization process was adjusted. After evaporation and concentration, 1‰ of seed crystals with a particle size of 3-5 μm were added. The flash cooling temperature and cooling rate remained unchanged. When the temperature dropped to 20℃, samples were taken and the lactose crystal particle size was tested according to the method in Example 2. The results were D10=8.277μm; D50=25.530μm; D90=46.322μm, and the lactose crystal size was controlled within the optimal range.

[0085] The desalted whey crystallizer was spray-dried at an inlet air temperature of 165°C and an outlet air temperature of 90°C. No nozzle clogging occurred during the entire spray-drying process. The flowability evaluation index of the sprayed powder was 75, which is comparable to commercially available products. The moisture absorption rate was 3.51%, which is also comparable to commercially available products, consistent with the above judgment.

[0086] In summary, by using the method of this invention to detect and obtain the particle size distribution D10, D50, and D90 of whey crystallizer in a timely manner, the adjustment of crystallization process conditions can be guided, the production process endpoint can be accurately determined, and an ideal product can be obtained.

[0087] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for detecting the particle size of lactose crystals in whey crystallization solution, characterized in that, Lactose aqueous solution was used as a dispersant for detecting the particle size of lactose crystals in whey crystallization solution using a laser particle size analyzer wet method module. The whey crystallization solution is prepared at a temperature of 5-40°C and has a total solids content of 48-70%, of which lactose accounts for 65-90% of the total solids content. The temperature of the lactose aqueous solution is within ±1℃ of the temperature of the whey crystallizing solution; The concentration of the lactose aqueous solution is 0.75 × e (0.028×T+2.389) up to 0.85×e (0.028×T+2.389) g lactose / 100g water, where e is the base of the natural logarithm and T is the temperature of the whey crystallization solution; During testing, the volume ratio of the dispersant to the whey crystallizer is 1:(300-1800).

2. The method for detecting lactose crystal size according to claim 1, characterized in that, The volume ratio of the dispersant to the whey crystallizer is 1:(520-875).

3. The method for detecting lactose crystal size according to claim 1, characterized in that, The temperature of the lactose aqueous solution is equal to the temperature of the whey crystallizing solution.

4. The method for detecting lactose crystal size according to claim 1, characterized in that, The concentration of the lactose aqueous solution is 0.8 × e (0.028×T+2.389) g lactose / 100g water.

5. The method for detecting the particle size of lactose crystals according to any one of claims 1-4, characterized in that, The whey crystallizer comes from the crystallization stage of the whey powder preparation process.

6. The application of the method for detecting the particle size of lactose crystals according to any one of claims 1-5 in the preparation of whey powder.

7. The application of the method for detecting lactose crystal size according to any one of claims 1-5 in real-time monitoring of lactose crystal size in whey crystallizer.

8. The application of the method for detecting the particle size of lactose crystals according to any one of claims 1-5 in determining the crystallization endpoint of whey crystallization solution.

9. The application of the method for detecting the particle size of lactose crystals according to any one of claims 1-5 in adjusting the crystallization conditions during the preparation of whey powder.

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