Method for detecting whey protein content in a goat milk-based infant formula

Abstract

The application discloses a method for detecting the content of whey protein in goat milk-based infant formula food, wherein the method comprises the following steps: preparing samples and determining the theoretical proportion of whey protein in each sample; determining the peak area ratio of the measured whey protein to total protein in each sample, and the measured peak area of whey protein and the measured peak area of casein protein in the target goat milk-based infant formula food; determining the undetermined coefficient of each sample according to the theoretical proportion of whey protein in each sample and the corresponding measured peak area ratio of whey protein to whey protein and casein protein, and determining the correction coefficient according to all the undetermined coefficients; determining the total whey protein correction peak area of the target goat milk-based infant formula food according to the measured peak area of whey protein in the target goat milk-based infant formula food and the correction coefficient; and determining the proportion of whey protein in the target goat milk-based infant formula food according to the total whey protein correction peak area and the measured peak area of total whey protein in the target goat milk-based infant formula food. The application aims to improve the accuracy of measuring whey protein in goat milk-based infant formula.

Description

Technical Field

[0001] This invention relates to the field of food technology, and in particular to a method for detecting the whey protein content in sheep milk-based infant formula. Background Technology

[0002] Currently, according to national standards for infant formula, the whey protein content in milk-based infant formula should be ≥60%, and the whey protein content in milk-based follow-up formula should be ≥40%. The existing whey protein testing standard, GB / T5413.2-1997, for the determination of whey protein in infant formula and milk powder, mainly involves SDS-PAGE electrophoresis of the sample, followed by the measurement of the casein and whey protein bands separated in molecular weight order using an optical densitometer to determine the casein-to-whey protein ratio. However, SDS-PAGE operation is easily affected by factors such as operator technique, resulting in low accuracy of this method.

[0003] Meanwhile, other literature reports methods for detecting whey protein content in dairy products, including high-performance liquid chromatography (HPLC) and gel permeation chromatography (GPC). Each method has its advantages and disadvantages depending on its application. For example, HPLC offers good recovery and precision, reproducibility, and simple operation, but sample pretreatment is cumbersome and costly. Furthermore, since whey protein is composed of multiple proteins, detecting the total whey protein requires standards for each protein, some of which are difficult to obtain, leading to inaccurate results that do not represent the overall whey protein content. GPC, on the other hand, is stable, accurate, low-cost, and simple to operate, but its applicability is limited, and its effectiveness in separating and detecting goat whey protein is highly uncertain. Therefore, given the shortcomings of existing technologies, there is an urgent need to develop a new method for detecting whey protein content in milk-based infant formula. Summary of the Invention

[0004] The main objective of this invention is to provide a method for detecting whey protein content in goat milk-based infant formula, aiming to solve the technical problem of low accuracy in existing methods for detecting whey protein content in goat milk-based infant formula.

[0005] To achieve the above objectives, the present invention provides a method for detecting the whey protein content in goat milk-based infant formula, characterized in that the method includes the following steps;

[0006] Step 1: Prepare samples and determine the theoretical value R of whey protein as a percentage of total protein in each sample. 2i ;

[0007] Step 2: Determine the percentage (R) of whey protein in the peak area of ​​whey protein and casein in each sample using capillary gel electrophoresis.1i And the measured peak area A of whey protein in the target goat milk-based infant formula was determined by capillary gel electrophoresis. w And the measured peak area A of casein cn ;

[0008] Step 3, based on the theoretical value R of whey protein as a percentage of total protein for each sample. 2i The corresponding measured percentage of whey protein in the peak area of ​​whey protein and casein (R) 1i Determine the undetermined coefficients Q for each sample i and all undetermined coefficients Q i Mean averaging yields the correction coefficient k;

[0009] Step 4, based on the measured peak area A of whey protein in the target goat milk-based infant formula... w The correction peak area A of total whey protein in the target goat milk-based infant formula was determined using the correction factor k. cw ;

[0010] Step 5: Correct the peak area A based on the total whey protein in the target goat milk-based infant formula. cw Compared with the measured peak area A of total whey protein cn Determine the whey protein content in the target sheep milk-based infant formula.

[0011] Optionally, step 1 specifically includes: preparing samples with various ratios of whey protein to casein, measuring the protein concentration of each sample, and calculating the theoretical value R of whey protein as a percentage of total protein for each sample. 2i .

[0012] Optionally, in step 2, the migration time of the protein internal standard is 12.8 min ± 0.5 min, and the migration time of the internal standard peak is 12.8 min ± 0.5 min.

[0013] Optionally, in step 2, the percentage R of whey protein in the peak area of ​​whey protein and casein in each sample is determined by capillary gel electrophoresis. 1i The steps include:

[0014] Capillary gel electrophoresis was used to determine the peak areas of small-molecule whey protein, large-molecule whey protein, and casein in each sample. The peak areas of small-molecule whey protein and large-molecule whey protein in each sample were summed and divided by the sum of the peak areas of small-molecule whey protein, large-molecule whey protein, and casein to obtain the percentage R of the peak area of ​​whey protein in each sample relative to the total peak area of ​​whey protein and casein. 1i .

[0015] Optionally, in step 3, the step of basing the whey protein content of each sample on the theoretical value R of the total protein content is... 2i The corresponding measured percentage of whey protein in the peak area of ​​whey protein and casein (R) 1i Determine the undetermined coefficient Q for each sample. i The calculation formula is as follows:

[0016] Q i =R 2i *(1-R 1i ) / [R 1i *(1-R 2i )];

[0017] Where R 1i R represents the percentage of whey protein in the peak area of ​​whey protein and casein for each sample. 2i is the theoretical value of whey protein as a percentage of total protein in each sample, and i is the corresponding sample number.

[0018] Optionally, in step 2, the measured peak area A of whey protein in the target goat milk-based infant formula is determined using capillary gel electrophoresis. w And the measured peak area A of casein cn The steps include:

[0019] The peak areas of small whey protein, large whey protein, and total casein in the target sheep milk-based infant formula were determined by capillary gel electrophoresis. The peak areas of small whey protein and large whey protein were then summed to obtain the corrected peak area of ​​total whey protein.

[0020] Optionally, step 4 specifically includes:

[0021] The measured peak area A of whey protein in the target sheep milk-based infant formula was determined. w Multiplying by the correction factor k, we obtain the corrected peak area A of total whey protein in the target goat milk-based infant formula. cw The specific formula is: A cw =k×A w .

[0022] Optionally, step 5 specifically includes: adjusting the corrected peak area A of the total whey protein in the target goat milk-based infant formula. cw Divide by the measured peak area A of total whey protein cn Corrected peak area A with total whey protein cw The sum of these values ​​yields the whey protein percentage in the target goat milk-based infant formula. The specific formula is: Whey protein content = [A...] cw / (A cw +Acn )]*100%.

[0023] Optionally, the protein concentration of each sample was determined using a BCA protein quantification kit.

[0024] Beneficial effects:

[0025] This invention discloses a method for detecting whey protein content in milk-based infant formula. Step 1 involves preparing samples and determining the theoretical value R of whey protein as a percentage of total protein in each sample. 2i Step 2: Determine the percentage (R) of whey protein in the peak area of ​​whey protein and casein in each sample using capillary gel electrophoresis. 1i And the measured peak area A of whey protein in the target goat milk-based infant formula was determined by capillary gel electrophoresis. w And the measured peak area A of casein cn Step 3: Based on the theoretical value R of whey protein as a percentage of total protein for each sample. 2i The corresponding measured percentage of whey protein in the peak area of ​​whey protein and casein (R) 1i Determine the undetermined coefficients Q for each sample i and all undetermined coefficients Q i The mean value was used to obtain the correction coefficient k; Step 4, based on the measured peak area A of whey protein in the target goat milk-based infant formula... w The correction peak area A of total whey protein in the target goat milk-based infant formula was determined using the correction factor k. cw Step 5: Correct the peak area A based on the total whey protein in the target goat milk-based infant formula. cw Compared with the measured peak area A of total whey protein cn This method determines the whey protein content in target goat milk-based infant formula. It demonstrates that this method can determine the whey protein content in goat milk-based formulas with uncertain detailed components. It can also be used to further verify whether the whey protein content error in goat milk-based formulas with known components is controlled within the standard range. The entire determination process is simple, convenient, and low-cost, and possesses corresponding stability, reproducibility, and accuracy, thus facilitating its widespread application. Attached Figure Description

[0026] Figure 1 This is a schematic flowchart of a method for detecting whey protein content in goat milk-based infant formula according to an embodiment of the present invention.

[0027] Figure 2 Capillary gel electrophoresis patterns of sheep whey protein powder and sheep casein powder;

[0028] Figure 3Capillary gel electrophoresis patterns of stage 1, stage 2, and stage 3 goat milk-based infant formula milk powder, liquid goat milk, whole goat milk powder, and skimmed goat milk powder;

[0029] Figure 4 Capillary electrophoresis refinement of protein from six consecutive injections of target goat milk infant formula milk powder;

[0030] Figure 5 The linear correlation between the measured whey protein value and the theoretical whey protein value in the sample after adding a preset amount of milk powder is shown in the graph. Detailed Implementation

[0031] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings.

[0032] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0033] like Figure 1 As shown, this invention discloses an embodiment of a method for detecting whey protein content in goat milk-based infant formula, the method comprising the following steps;

[0034] Step S1: Prepare samples and determine the theoretical value R of whey protein as a percentage of total protein in each sample. 2i Specifically, samples with various ratios of whey protein to casein are prepared, and the specific sample processing steps include:

[0035] Step S1.1 Prepare samples with different ratios. Weigh 500mg of samples with different ratios of whey protein to casein powder and place them in 10mL centrifuge tubes. Add water to the 5mL mark, vortex until fully dissolved and mixed evenly (containing approximately 15mg / mL protein).

[0036] Step S1.2 Preparation of reaction solution: Use a pipette to transfer 10 μL of the prepared sample solution into a 2.0 mL centrifuge tube, then add 85 μL of capillary electrophoresis analysis preparation solution and 5 μL of β-mercaptoethanol, mix and vortex, and tighten the cap.

[0037] Step S1.3 Boiling water bath: Heat the sample in a 100°C water bath for 5 minutes, cool the sample to room temperature, and centrifuge quickly to allow the liquid to collect at the bottom of the tube.

[0038] Step S1.4: Load the sample, vortex, and use a pipette to transfer 90 μL of sample to the bottom of a 200 μL PCR tube, taking care to avoid air bubbles. Insert the microsample tube into a universal sample vial, and tighten the universal cap.

[0039] Step S1.5 Sample detection time limit: Generally, the sample can remain stable within 24 hours.

[0040] The samples mentioned above are those with known whey protein content, mainly including stage 1, stage 2, and stage 3 goat milk-based infant formula (SPL1, SPL2, SPL3), liquid goat milk (SPL4), goat whey protein powder (SPL5), goat casein powder (SPL6), whole goat milk powder (SPL7), skimmed goat milk powder (SPL8), and stage 1 infant formula 2 (SPL9), etc. Generally, the protein concentration of each sample is determined using a BCA protein quantification kit. The same sample can be repeated three times, and the readings are taken at 560 nm on a microplate reader to create a standard curve. Then, the corresponding protein concentration of each sample can be calculated, thus obtaining the theoretical value R of whey protein as a percentage of total protein for each sample. 2i .

[0041] Step S2: The percentage of whey protein in the peak area of ​​whey protein and casein in each sample was determined by capillary gel electrophoresis. 1i And the measured peak area A of whey protein in the target goat milk-based infant formula was determined by capillary gel electrophoresis. w And the measured peak area A of casein cn .

[0042] Specifically, when using capillary gel electrophoresis on the target goat milk-based infant formula, sample preparation is required. The sample preparation steps are basically similar to the aforementioned sample processing steps, except that in this step, the target goat milk-based infant formula does not require the preparation of samples in different proportions. The specific capillary gel electrophoresis method includes the following:

[0043] Electrophoresis parameters: uncoated quartz capillary: 50μm×30cm (effective length: 20cm); detector: ultraviolet detector (UV), detection wavelength: 220nm; operating voltage: -15kV (484V / cm); capillary temperature control: 20℃±2℃; sample temperature control: 20℃±2℃; electro-injection: 5kV, 20s; window slits: 2 (100μm×200μm).

[0044] Equilibration procedure: wash with 0.1 mol / L NaOH at 30 psi for 10 min, acid wash with 0.1 mol / L HCl at 30 psi for 5 min, rinse with deionized water at 30 psi for 5 min, perfuse SDS gel at 50 psi for 10 min, and separate at 5.0 kV for 10 min. The detector used was an ultraviolet (UV) detector, and the operation was carried out at 4 °C.

[0045] Electrophoresis procedure: wash with 0.1 mol / L NaOH at 70 psi for 5 min, acid wash with 0.1 mol / L HCl at 40 psi for 2 min, rinse with deionized water at 40 psi for 2 min, perfuse SDS gel at 70 psi for 10 min, load sample at 5.0 kV for 20 s, separate at 5.0 kV for 30 min, use a UV detector, and detect at 4℃ to acquire data.

[0046] For quality control, the migration time of the protein internal standard should be 12.8 min ± 0.5 min; the acceptable standard for single-needle operation is that the migration time of the internal standard peak should be 12.8 min ± 0.5 min.

[0047] Furthermore, the percentage R of whey protein in the peak area of ​​whey protein and casein in each sample was determined using capillary gel electrophoresis. 1i The steps include:

[0048] Capillary gel electrophoresis was used to determine the peak areas of small-molecule whey protein, large-molecule whey protein, and casein in each sample. The peak areas of small-molecule whey protein and large-molecule whey protein in each sample were summed and divided by the sum of the peak areas of small-molecule whey protein, large-molecule whey protein, and casein to obtain the percentage R of the peak area of ​​whey protein in each sample relative to the total peak area of ​​whey protein and casein. 1i Both small-molecule whey protein and large-molecule whey protein belong to the whey protein family.

[0049] Furthermore, the measured peak area A of whey protein in the target goat milk-based infant formula was determined using capillary gel electrophoresis. w And the measured peak area A of casein cn The steps include:

[0050] The peak areas of small whey protein, large whey protein, and total casein in the target sheep milk-based infant formula were determined by capillary gel electrophoresis. The peak areas of small whey protein and large whey protein were then summed to obtain the corrected peak area of ​​total whey protein.

[0051] Specifically, the capillary gel electrophoresis patterns of sheep whey protein powder and sheep casein protein powder are shown in the following figures. Figure 2 As shown, the capillary gel electrophoresis patterns of other samples and the target goat milk-based infant formula are as follows: Figure 3 As shown in Table 1, the peak area integrals of whey protein and casein are listed, taking stage 1 and stage 2 infant formula milk powder (SPL1, SPL2) as examples.

[0052] Table 1. Peak areas of whey protein and casein in stage 1 and stage 2 infant formula milk powders.

[0053]

[0054]

[0055] Step 3, based on the theoretical value R of whey protein as a percentage of total protein for each sample. 2i The corresponding measured percentage of whey protein in the peak area of ​​whey protein and casein (R) 1i Determine the undetermined coefficients Q for each sample i and all undetermined coefficients Q i The correction coefficient k is obtained by mean averaging.

[0056] Specifically, based on R obtained from Table 1 1i With R 2i Value, through formula

[0057] Q i =R 2i *(1-R 1i ) / [R 1i *(1-R 2i )];

[0058] Where R 1i R represents the percentage of whey protein in the peak area of ​​whey protein and casein for each sample. 2i Let _i_ represent the theoretical value of whey protein as a percentage of total protein in each sample, and _i_ represent the corresponding sample number. Then, the undetermined coefficients Q_ for each sample in Table 1 are obtained. i and obtain multiple Q i The mean value was calculated to obtain the correction coefficient k. In this embodiment, 12 batches of samples were used for the first and second stages, and the final k was approximately 1.5.

[0059] Step 4, based on the measured peak area A of whey protein in the target goat milk-based infant formula... w The correction peak area A of total whey protein in the target goat milk-based infant formula was determined using the correction factor k. cw .

[0060] Specifically, the measured peak area A of whey protein in the target goat milk-based infant formula was determined. w Multiplying by the correction factor k, we obtain the corrected peak area A of total whey protein in the target goat milk-based infant formula. cw The specific formula is: A cw. =k×A w .

[0061] In this embodiment, k is approximately 1.5, and therefore the above formula can be updated to A.cw. =1.5×A w .

[0062] Step 5: Correct the peak area A based on the total whey protein in the target goat milk-based infant formula. cw Compared with the measured peak area A of total whey protein cn Determine the whey protein content in the target sheep milk-based infant formula.

[0063] Specifically, the corrected peak area A of total whey protein in the target goat milk-based infant formula is... cw Divide by the measured peak area A of total whey protein cn Corrected peak area A with total whey protein cw The sum of these values ​​yields the whey protein percentage in the target goat milk-based infant formula. The specific formula is: Whey protein content = [A...] cw / (A cw +A cn )]*100%.

[0064] Furthermore, taking stage 1 and stage 2 infant formula milk powder as examples, the above-mentioned detection method for whey protein content in goat milk-based infant formula was verified. The determination data of stage 1 and stage 2 infant formula milk powder are shown in Table 2.

[0065] Table 2. Results of whey protein content determination in stage 1 and stage 2 infant formula milk powder

[0066]

[0067]

[0068] Further comparison of the whey protein content in Table 2 with the theoretical value of whey protein as a percentage of total protein in Table 1 shows that the detection results of stage 1 and stage 2 infant formula milk powder obtained according to the detection method of the present invention are close to the theoretical whey protein content results. This proves that the method can be used as a method for detecting the whey protein content of stage 1 and stage 2 infant formula milk powder, and meets the current standard requirements for detecting the whey protein content of infant formula and follow-up formula.

[0069] Furthermore, to better demonstrate the applicability of this invention for determining total whey protein in different goat milk-based infant formulas, further verification was conducted on the corresponding samples. Details are as follows:

[0070] Method stability testing

[0071] To examine the reproducibility of the established capillary electrophoresis method for protein component analysis, a single test was conducted with six consecutive injections of a stage 1 goat milk-based infant formula, yielding the following chromatograms: Figure 4As shown in Table 3, the migration time and relative standard deviation of each protein peak from the six injections are also presented. It can be seen that the relative standard deviation of the migration time for all 14 major protein peaks is less than 0.4%. Meanwhile, based on the peak area statistics of whey protein and casein in Table 4, the deviation of the final whey protein content determination result is 0.33%. This demonstrates that the whey protein content determination method of this invention exhibits a certain degree of stability.

[0072] Table 3 shows the migration time of each protein peak from six consecutive injections of a sheep milk-based infant formula.

[0073]

[0074] Table 4. Results of whey protein content determination from six consecutive injections of stage 1 goat milk-based infant formula.

[0075]

[0076] Method repeatability testing

[0077] The proteins were processed according to standard operating procedures. One sample of stage 1 goat milk infant formula was selected and six independent tests were conducted. Table 5 shows the migration time and relative standard deviation of each protein peak in the six injections. Table 6 shows the peak area statistics for whey protein and casein. The relative standard deviation of the migration time of all 14 major protein peaks was less than 1.9%. Table 6 also shows the peak area statistics for whey protein and casein. The results show that the relative standard deviation was 0.67%, which is basically within the error standard range. This indicates that the whey protein content determination method of this invention has a certain degree of repeatability.

[0078] Table 5. Migration time of each protein peak in six independent replicate experiments of a stage 1 goat milk infant formula.

[0079] sample P1 P2 P3 P4 P5 P6 P7 P8 P9 P10 P11 P12 P13 P14 1 12.396 13.067 13.387 13.704 14.075 14.342 14.583 14.829 16.163 16.379 16.671 16.913 17.196 19.583 2 12.442 13.117 13.442 13.75 14.125 14.392 14.633 14.875 16.217 16.438 16.733 16.975 17.254 19.767 3 12.771 13.438 13.779 14.096 14.512 14.796 15.05 15.308 16.667 16.887 17.192 17.45 17.75 20.192 4 12.379 13.058 13.379 13.696 14.067 14.338 14.579 14.833 16.175 16.396 16.688 16.933 17.217 19.725 5 12.908 13.596 13.946 14.262 14.671 14.954 15.225 15.496 16.85 17.079 17.383 17.629 17.921 20.471 6 12.563 13.254 13.583 13.883 14.262 14.529 14.775 15.021 16.371 16.587 16.887 17.129 17.425 19.808 RSD 1.73％ 1.66％ 1.71％ 1.68％ 1.77％ 1.78％ 1.83％ 1.86％ 1.76％ 1.75％ 1.75％ 1.75％ 1.75％ 1.69％

[0080] Table 6. Results of whey protein content determination in six independent replicate experiments using stage 1 goat milk infant formula.

[0081]

[0082] Recovery rate determination

[0083] Whey protein powder was added to stage 3 goat milk-based infant formula in a specific ratio. A certain mass of the formula was taken, and the protein content was calculated according to the label. A 40 mg / mL whey protein solution was prepared using the whey protein powder, and the addition ratios are shown in Table 7. The whey protein content of each sample was determined by capillary gel electrophoresis. The recovery rates are shown in Table 8, ranging from 100.87% to 104.02%.

[0084] Table 7 Recovery rate determination, dosage of additive

[0085]

[0086] Table 8 Results of whey protein recovery rate

[0087]

[0088] Accuracy test

[0089] A curve was plotted with the theoretical whey addition amount on the x-axis and the actual measured value on the y-axis. The results are as follows: Figure 5 As shown, the obtained standard curve equation is y = 1.0154x + 0.0061, and the linear correlation coefficient R0 is... 2 The correlation coefficient is 0.9985, indicating a good linear correlation between the theoretical and measured values. This demonstrates that the whey protein content determination method of this invention possesses a certain degree of accuracy.

[0090] Commercially available sample testing

[0091] Two samples of stage 1 infant formula milk powder were purchased from the market and subjected to capillary electrophoresis according to the method established above. The results are shown in Table 9. The whey protein content of the two goat milk-based infant formula milk powder samples meets the requirements of the current standards.

[0092] Table 9 Results of whey protein content determination in commercially available samples

[0093] serial number Small molecule whey Casein macromolecular whey Total whey protein whey protein correction whey protein content 1 140211 128432 5286 145497 218245.5 62.95％ 2 132076 124096 6798 138874 208311 62.67％

[0094] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or system that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or system. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or system that includes that element.

[0095] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0096] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural or procedural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A method for detecting whey protein content in goat milk-based infant formula, characterized in that, The method includes the following steps; Step 1: Prepare samples and determine the theoretical value R of whey protein as a percentage of total protein in each sample. 2i ; Step 2: Determine the percentage (R) of whey protein in the peak area of ​​whey protein and casein in each sample using capillary gel electrophoresis. 1i And the measured peak area A of whey protein in the target goat milk-based infant formula was determined by capillary gel electrophoresis. w And the measured peak area A of casein cn ; Step 3, based on the theoretical value R of whey protein as a percentage of total protein for each sample. 2i The corresponding measured percentage of whey protein in the peak area of ​​whey protein and casein (R) 1i Determine the undetermined coefficients Q for each sample i and all undetermined coefficients Q i Mean averaging yields the correction coefficient k; Step 4, based on the measured peak area A of whey protein in the target goat milk-based infant formula... w The correction peak area A of total whey protein in the target goat milk-based infant formula was determined using the correction factor k. cw ; Step 5: Correct the peak area A based on the total whey protein in the target goat milk-based infant formula. cw Compared with the measured peak area A of total whey protein cn Determine the whey protein content in the target sheep milk-based infant formula; In step 3, the theoretical value R of whey protein as a percentage of total protein for each sample is used. 2i The corresponding measured percentage of whey protein in the peak area of ​​whey protein and casein (R) 1i Determine the undetermined coefficient Q for each sample. i The calculation formula is as follows: Q i =R 2i *(1-R 1i ) / [R 1i *(1-R 2i )]; Where R 1i R represents the percentage of whey protein in the peak area of ​​whey protein and casein for each sample. 2i is the theoretical value of whey protein as a percentage of total protein in each sample, and i is the corresponding sample number.

2. The method for detecting whey protein content in milk-based infant formula according to claim 1, characterized in that, Step 1 specifically includes: preparing samples with various ratios of whey protein to casein, measuring the protein concentration of each sample, and calculating the theoretical value R of whey protein as a percentage of total protein for each sample. 2i .

3. The method for detecting whey protein content in milk-based infant formula according to claim 1, characterized in that, In step 2, the migration time of the protein internal standard is 12.8 min ± 0.5 min, and the migration time of the internal standard peak is 12.8 min ± 0.5 min.

4. The method for detecting whey protein content in milk-based infant formula according to claim 3, characterized in that, In step 2, capillary gel electrophoresis is used to determine the percentage R of whey protein in the peak area of ​​whey protein and casein in each sample. 1i The steps include: Capillary gel electrophoresis was used to determine the peak areas of small-molecule whey protein, large-molecule whey protein, and casein in each sample. The peak areas of small-molecule whey protein and large-molecule whey protein in each sample were summed and divided by the sum of the peak areas of small-molecule whey protein, large-molecule whey protein, and casein to obtain the percentage R of the peak area of ​​whey protein in each sample relative to the total peak area of ​​whey protein and casein. 1i .

5. The method for detecting whey protein content in milk-based infant formula according to claim 3, characterized in that, In step 2, the measured peak area A of whey protein in the target goat milk-based infant formula is determined using capillary gel electrophoresis. w And the measured peak area A of casein cn The steps include: The peak areas of small whey protein, large whey protein, and total casein in the target sheep milk-based infant formula were determined by capillary gel electrophoresis. The peak areas of small whey protein and large whey protein were then summed to obtain the corrected peak area of ​​total whey protein.

6. The method for detecting whey protein content in milk-based infant formula according to any one of claims 1 to 5, characterized in that, Step 4 specifically includes: The measured peak area A of whey protein in the target sheep milk-based infant formula was determined. w Multiplying by the correction factor k, we obtain the corrected peak area A of total whey protein in the target goat milk-based infant formula. cw The specific formula is: A cw =k×A w .

7. The method for detecting whey protein content in milk-based infant formula according to claim 6, characterized in that, Step 5 specifically includes: adjusting the corrected peak area A of the total whey protein in the target goat milk-based infant formula. cw Divide by the measured peak area A of total whey protein cn Corrected peak area A of total whey protein cw The sum of these values ​​yields the whey protein percentage in the target goat milk-based infant formula. The specific formula is: Whey protein content = [A...] cw / (A cw +A cn )]*100%.

8. The method for detecting whey protein content in milk-based infant formula according to claim 2, characterized in that, The protein concentration of each sample was determined using the BCA protein quantification kit.

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