A method for rapidly evaluating the heat stability of high-protein beverages

Abstract

The application discloses a method for rapidly evaluating the thermal stability of high-protein beverages and belongs to the technical field of dairy products. It is found that the calcium ion activity in a protein solution system can be used as the effective concentration of calcium ions which react under high-temperature conditions to serve as calcium bridges between casein micelles to cause flocculation, so the calcium ion activity is selected as an index for evaluating the thermal stability. Through fitting the calcium ion activity and the thermal flocculation time, a prediction equation is obtained, the thermal stability of concentrated milk protein raw materials under a high-protein system can be accurately judged, and whether the concentrated milk protein raw materials are suitable for being used for thermal processing production can be determined.

Description

Technical Field

[0001] This invention relates to a method for rapidly evaluating the thermal stability of high-protein beverages, belonging to the field of dairy technology. Background Technology

[0002] Protein is an essential macronutrient for the human body. High-quality dietary protein can promote the synthesis of muscle protein, improve the adaptability of skeletal muscle to exercise, optimize the body's motor function, enhance immunity, and maintain overall health. Milk protein concentrate (MPC) is a high-quality protein source, mainly composed of casein. It is characterized by high protein, low fat, and low lactose content, and has wide applications in food processing.

[0003] While both milk protein concentrate (MPC) and whey protein concentrate (WPC) are common protein supplements in dairy products, they differ significantly in their raw material sources and physical properties. MPC is typically made from skim milk through ultrafiltration and other processing steps, and its protein content can vary between 42% and 92%, including casein and a small amount of whey protein. WPC, on the other hand, is mainly obtained through processing whey after casein removal. The two differ considerably in protein composition and applications.

[0004] Meanwhile, the stability of milk protein concentrate (MPC) and whey protein concentrate (WPC) differs significantly at high protein concentrations. WPC, when heated in high-protein beverage systems (protein concentration >6% (g / 100mL)), easily forms protein aggregates and gel-like structures, leading to precipitation and decreased product stability, limiting its application in high-protein beverages. Conversely, MPC maintains good stability even at a protein concentration of 8% (g / 100mL), exhibiting minimal gelation and precipitation, giving it a unique advantage in high-protein beverages. However, the thermal stability of MPC varies considerably depending on its source, origin, and processing methods, specifically manifesting as gelation and flocculation during storage after heating, which negatively impacts product quality. Accurately predicting the thermal stability of MPC raw materials is crucial for industrial applications, effectively preventing product quality problems.

[0005] From an industrial production perspective, predicting the thermal flocculation time of MPC (micro-coagulation) is a complex process involving various physical and chemical properties of proteins. Unlike simple parameter prediction, predicting thermal flocculation time requires considering factors such as protein thermal stability, the influence of shear forces, and enhanced protein-protein interactions. In actual production, the interactions of these factors make prediction extremely difficult, requiring in-depth process understanding and precise control techniques. Therefore, the choice between MPC and WPC should be determined based on the application requirements and desired characteristics of the final product. The high stability of MPC makes it more advantageous in liquid high-performance food and nutritional products.

[0006] The thermal stability of milk protein solutions refers to their ability to withstand high temperatures without flocculation or precipitation during heating, a crucial issue in the high-temperature sterilization process of high-protein sports drinks. Li Yan et al. studied the effect of calcium ions on the thermal stability of 3.5% whey protein concentrate (WPC), but the protein compositions of WPC and MPC differ significantly; WPC cannot be used in high-protein beverages, therefore, the thermal stability of WPC cannot be used to evaluate the thermal stability of MPC. Current scientific research mainly focuses on the thermal stability of milk, but the thermal stability of milk is not entirely consistent with that of high-protein beverages, exhibiting considerable differences. Firstly, the protein content differs significantly; milk contains approximately 3% protein, while high-protein beverages generally contain over 6% (g / 100mL). Secondly, their protein compositions are not entirely identical. Finally, the pH values ​​and mineral ion compositions of the two systems are different, therefore, the thermal stability of milk cannot be used to accurately assess the thermal stability of high-protein beverages.

[0007] With the rise of national fitness campaigns and increased health awareness among residents, the market for high-protein liquid beverages is growing rapidly. Before producing high-protein beverages, it is essential to assess the thermal stability of the concentrated milk protein solution system. Otherwise, scaling or even blockage of pipelines during high-temperature sterilization can lead to economic losses. In laboratory conditions, thermal stability is primarily evaluated by visually observing the concentrated milk protein solution at 140°C and recording the time to the start of flocculation (HCT). This method is subjective, destructive to the sample, and the high temperature poses a safety risk to laboratory personnel.

[0008] The aforementioned technical solutions, whether predicting thermal stability through calcium ion concentration or relying on visual observation to detect the thermal stability of protein solutions, are inaccurate. Therefore, there is an urgent need to develop a method for accurately predicting the thermal stability of high-protein solution systems, which would have extremely high practical and economic value. Summary of the Invention

[0009] To address the aforementioned issues, this invention discovers that calcium ion activity in high-protein solution systems can serve as the effective concentration of calcium ions acting as calcium bridges between casein micelles, leading to flocculation under high-temperature conditions. Therefore, calcium ion activity is chosen as an indicator for evaluating thermal stability. This invention obtains a predictive equation by fitting calcium ion activity and thermal flocculation time, which can accurately determine the thermal stability of concentrated milk protein raw materials in high-protein systems, thereby determining their suitability for thermal processing and providing guidance for material selection in actual production.

[0010] The first objective of this invention is to provide a method for rapidly predicting the thermal flocculation time of concentrated milk protein based on calcium ion activity, comprising the steps of:

[0011] (1) By detecting the calcium ion activity and thermal flocculation time of concentrated milk protein solutions with different calcium ion concentrations, the calcium ion activity and thermal flocculation time were fitted to obtain the prediction equation; the prediction equation is:

[0012] When x is less than or equal to 1.86, y = -18.51x + 36.51;

[0013] When x is greater than 1.86, y = 14.86e -x / 0.83 + 0.18;

[0014] Where x is calcium ion activity, mM; y is thermal flocculation time, min;

[0015] (2) Take the concentrated milk protein to be tested, prepare the concentrated milk protein test solution, detect the calcium ion activity of the concentrated milk protein test solution, substitute the calcium ion activity into the prediction equation, and obtain the thermal flocculation time.

[0016] In one implementation, calcium ion activity can be expressed by formula a. Ca =γ Ca ×c Ca Calculated; where a Ca (mM) represents calcium ion activity; c Ca (mM) represents the concentration of free calcium ions; γ Ca This represents the activity coefficient of calcium ions.

[0017] In one implementation, the concentration of free calcium ions can be expressed by the formula Ec. Ca =a×ln(c Ca The result is obtained by calculating E + b; where E Ca (mV) is the potential value; a and b are constants related to the ionic strength, which can be calculated from the ionic strength.

[0018] In one embodiment, the method for preparing concentrated milk protein solutions with different calcium ion concentrations in step (1) is as follows:

[0019] Concentrated milk protein and water were mixed, homogenized, and refrigerated to obtain a concentrated milk protein solution; different concentrations of calcium ions were added to obtain concentrated milk protein solutions with different calcium ion concentrations.

[0020] In one embodiment, concentrated milk protein and water are mixed at a ratio of 6-8 g: 100 mL.

[0021] In one embodiment, mixing is performed by stirring at 30–50°C and 300–300 rpm for 0.5–2 hours.

[0022] In one embodiment, homogenization is performed at 20–30°C and 25–35 MPa for 3–5 times.

[0023] In one implementation, refrigeration involves placing the item at 2–8°C for more than 12 hours.

[0024] The second objective of this invention is to provide a method for rapidly predicting the thermal flocculation time of high-concentration milk protein beverages based on calcium ion activity:

[0025] (1) By detecting the calcium ion activity and thermal flocculation time of concentrated milk protein solutions with different calcium ion concentrations, the calcium ion activity and thermal flocculation time were fitted to obtain the prediction equation; the prediction equation is:

[0026] When x is less than or equal to 1.86, y = -18.51x + 36.51;

[0027] When x is greater than 1.86, y = 14.86e -x / 0.83 + 0.18;

[0028] Where x is the calcium ion activity (mM) and y is the thermal flocculation time (min);

[0029] (2) Take the high-concentration milk protein beverage to be tested, detect the calcium ion activity in the high-concentration milk protein beverage, and substitute the calcium ion activity into the prediction equation to obtain the thermal flocculation time.

[0030] In one embodiment, the protein concentration of the high-concentration milk protein beverage is 6-8% (g / 100mL).

[0031] In one embodiment, the above method can be used to predict the heat sterilization time of high-concentration milk protein beverages to ensure that the proteins in the high-concentration milk protein beverages do not denature or precipitate during the heat sterilization process.

[0032] In one embodiment, the method for preparing concentrated milk protein solutions with different calcium ion concentrations in step (1) is as follows:

[0033] Concentrated milk protein and water were mixed, homogenized, and refrigerated to obtain a concentrated milk protein solution; different concentrations of calcium ions were added to obtain concentrated milk protein solutions with different calcium ion concentrations.

[0034] In one embodiment, concentrated milk protein and water are mixed at a ratio of 6-8 g: 100 mL.

[0035] In one embodiment, mixing is performed by stirring at 30–50°C and 300–500 rpm for 0.5–2 hours.

[0036] In one embodiment, homogenization is performed at 20–30°C and 25–35 MPa for 3–5 times.

[0037] In one implementation, refrigeration involves placing the item at 2–8°C for more than 12 hours.

[0038] The third objective of this invention is to provide a method for evaluating the thermal stability of high-protein beverages based on calcium ion activity, comprising the following steps:

[0039] (1) The calcium ion activity of the high-protein beverage was detected, and the calcium ion activity was substituted into the prediction equation to obtain the thermal flocculation time; the prediction equation is:

[0040] When x is less than or equal to 1.86, y = -18.51x + 36.51;

[0041] When x is greater than 1.86, y = 14.86e -x / 0.83 + 0.18;

[0042] Where x is the calcium ion activity (mM) and y is the thermal flocculation time (min);

[0043] (2) If the thermal flocculation time is greater than 2 min, the high-protein beverage is considered to have good thermal stability; if the thermal flocculation time is greater than or equal to 1 min and less than or equal to 2 min, the high-protein beverage is considered to have average thermal stability; if the thermal flocculation time is less than 1 min, the high-protein beverage is considered to have poor thermal stability.

[0044] High-concentration milk protein beverages have a protein concentration of 6-8% (g / 100mL).

[0045] The beneficial effects of this invention are:

[0046] This invention provides a standardized method for preparing concentrated milk protein solutions under laboratory conditions, minimizing the differences in thermal stability caused by variations in solution preparation methods during thermal stability evaluation. Furthermore, this invention offers a method for evaluating concentrated milk protein solutions based on calcium ion activity. The predictive model established by this method has good accuracy, and the thermal flocculation time can be calculated quickly and easily by measuring calcium ion activity without damaging the sample. This allows for rapid and accurate screening of suitable concentrated milk protein raw materials for processing, helping to improve product quality and stability, meet market demand for high-protein sports supplements, and provide practical guidance for the processing of milk protein beverages in high-protein systems. Attached Figure Description

[0047] Figure 1 The fitted curve of the prediction equation in Example 1;

[0048] Figure 2 The fitted curve for the prediction equation in Comparative Example 1;

[0049] Figure 3 The fitted curve for the prediction equation in Comparative Example 2;

[0050] Figure 4 The fitted curve for the prediction equation in Comparative Example 3;

[0051] Figure 5 This is the fitted curve of the prediction equation for Comparative Example 4. Detailed Implementation

[0052] The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0053] raw material

[0054] The concentrated milk protein was purchased from Fonterra, and was a standard type of concentrated milk protein (hereinafter referred to as concentrated milk protein in the examples).

[0055] Methods for calculating calcium ion activity:

[0056] Following the method of Crowley et al. (Heat stability of reconstituted milk proteinconcentrate powders; doi.org / 10.1016 / j.idairyj.2014.03.005), a series of standard solutions were prepared using potassium chloride and calcium chloride, with total ionic strengths of 5, 10, 20, 40, 60, or 80 mM, and c under each ionic strength was specified. Ca =0, 0.25, 0.50, 1, 2, 3 mM, the potential values ​​E of the standard solutions were measured using a calcium ion selective electrode and a conductivity meter, respectively. Ca (mV) and conductivity value κ (ms·cm) -1 ).

[0057] (1) Establish the relationship between ionic strength I (mM) and conductivity κ (ms·cm) -1 The standard curve of () is given by the following formula:

[0058] κ=0.1339I+0.3385 Formula (1)

[0059] The ionic strength can be calculated by measuring the conductivity of the sample using formula (1).

[0060] (2) Potential value E Ca (mV) and free calcium ion concentration c Ca (mM)

[0061] The potential value E of the standard solution (i.e., a series of standard solutions prepared from potassium chloride and calcium chloride as described above) was established using a calcium ion-selective electrode. Ca (mV) and free calcium ion concentration c Ca The relationship between (mM) is expressed by the formula:

[0062] Ec Ca =a×ln(c Ca Formula (2) + b

[0063] Where a and b are constants related to ionic strength, and their relationship is as follows:

[0064] a=-0.73×ln(I)+16.30 Formula (3)

[0065] b = -3.72 × ln(I) - 16.61 Formula (4)

[0066] The concentration of free calcium ions c in the sample can be calculated using the formulas (1) to (4) above. Ca (mM).

[0067] (3) Calcium ion activity a Ca (mM) and free calcium ion concentration c Ca (mM)

[0068] Calcium ion activity coefficient γ Ca The result is obtained using the Debye-Hückel limit formula, as follows:

[0069]

[0070] In formula (5), Z is Ca 2+ The charge number, Z = 2; I is the ionic strength (mM);

[0071] Calcium ion activity a Ca (mM) can be obtained through a Ca =γ Ca ×c Ca The formula is used for calculation.

[0072] Method for detecting thermal flocculation time

[0073] Take 2 mL of sample and put it into an ampoule. After heat sealing, place it in an oil bath at 140°C. Shake the ampoule at a constant speed of 8 times per minute. Record the time when flocculation first appears by visual observation. This is the thermal flocculation time.

[0074] Centrifugation sedimentation rate was used as another indicator to measure the concentrated milk protein solution. 2 mL of samples with different calcium additions were put into ampoules. The reconstituted solution after heat treatment at 140℃ was immediately cooled to room temperature under running cool water, centrifuged at 3000g for 30 min, and then the precipitate was dried at 105℃ for 7 h until it reached equilibrium weight. The percentage of the weight of the dried precipitate to the weight of the corresponding uncentrifuged reconstituted solution after drying was taken as the centrifugation sedimentation rate.

[0075] Unless otherwise specified, the concentration % in this article means g / 100mL.

[0076] Example 1: Segmented Fitting of Calcium Ion Activity and Thermal Flocculation Time Curves

[0077] 1. Prepare concentrated milk protein solution, following these steps:

[0078] (1) Mix concentrated milk protein and water at a ratio of 8:100 (8g / 100mL) and stir at 50℃ and 300rpm for 1h;

[0079] (2) After stirring, the mixture was homogenized three times at 25°C and 30MPa, and then refrigerated at 4°C to obtain a concentrated milk protein solution with good homogeneity and a solubility of 97.8%.

[0080] 2. Investigating the effect of different calcium activities on the thermal flocculation time of concentrated milk protein solution.

[0081] Take the concentrated milk protein solution prepared in step 1, add different amounts of CaCl2, and adjust the pH to 6.8 to obtain samples with different calcium addition amounts. Calcium ion activity (α) is then detected and calculated. Ca (mM), thermal flocculation time (t, min), free calcium content (c) Ca , mM), particle size (D, nm) and zeta potential (ζ, mV).

[0082] The correlation coefficients (r) of the above indicators are shown in Table 1. If |r|≥0.8, the two factors can be considered to be significantly correlated. The results show that there is a significant correlation between pH, free calcium content, calcium ion activity and thermal flocculation time.

[0083] Table 1. Correlation coefficient results

[0084] The table shows r pH Free calcium content Zeta potential Average particle size calcium ion activity thermal flocculation time Total calcium content pH 1.00 -0.94 -0.47 0.34 -0.90 0.95 0.00 Free calcium content -0.94 1.00 0.65 -0.16 0.91 -0.95 0.29 Zeta potential -0.47 0.65 1.00 0.07 0.56 -0.54 0.70 Average particle size 0.34 -0.16 0.07 1.00 0.05 0.15 0.50 calcium ion activity -0.90 0.91 0.56 0.05 1.00 -0.95 0.27 thermal flocculation time 0.95 -0.95 -0.54 0.15 -0.95 1.00 -0.18 Total calcium content 0.00 0.29 0.70 0.50 0.27 -0.18 1.00

[0085] The relationship between calcium ion activity and thermal flocculation time in samples with different calcium addition amounts was found to be positive through linear and nonlinear fitting:

[0086] When the calcium ion activity is less than or equal to 1.86 and greater than 0.82, it shows a linear decreasing relationship with the thermal flocculation time (R0). 2 =0.99); when the calcium ion activity is greater than 1.86 and less than 5.22, it shows an exponential decreasing relationship with the thermal flocculation time (R = 0.99);2 =0.97), finally obtaining the piecewise function of calcium ion activity (mM) with respect to thermal flocculation time (min), the results are as follows: Figure 1 As shown.

[0087] That is, y = -18.51x + 36.51(0.82) <x≤1.86);y=14.86e -x / 0.83 + 0.18 (5.22 > x > 1.86).

[0088] 3. Protein thermal flocculation time and thermal stability

[0089] Table 2 shows the thermal flocculation time and corresponding centrifugal sedimentation rate of samples with different calcium addition amounts. The results show that as the amount of calcium added increases, the thermal flocculation time decreases while the centrifugal sedimentation rate increases. In addition, the increase of calcium makes the samples more susceptible to thermal instability, which is manifested by flocculation in a shorter time and more protein precipitation after heat treatment.

[0090] That is, if the thermal flocculation time (y) is greater than 2 minutes, the concentrated milk protein solution has better thermal stability; if the thermal flocculation time is greater than 1 minute and less than or equal to 2 minutes, the concentrated milk protein solution has moderate thermal stability; if the thermal flocculation time is less than or equal to 1 minute, the concentrated milk protein solution has poor thermal stability.

[0091] Table 2. Thermal flocculation time and centrifugal sedimentation rate under different calcium addition levels.

[0092] Calcium addition thermal flocculation time Centrifugal sedimentation rate 0 19.08 3.48％ 0.1 11.31 9.56％ 0.2 1.86 14.08％ 0.3 1.08 20.75％ 0.4 0.84 35.34％ 0.5 0.46 58.16％ 0.6 0.34 73.41％ 0.7 0.20 80.16％ 0.8 0.13 82.15％

[0093] Comparative Example 1: Direct Fitting of Calcium Ion Activity and Thermal Flocculation Time Curves

[0094] Based on Example 1, the fitting method was changed to nonlinear fitting, and the remaining steps were the same as in Example 1.

[0095] The fitted curve is as follows Figure 2 As shown, the results indicate that nonlinear fitting revealed an exponential decreasing relationship between calcium ion activity and thermal flocculation time (R0). 2 =0.96), thus obtaining the function y = 98.50e of calcium ion activity and thermal flocculation time. -x / 0.57-0.09;

[0096] When y > 2, the concentrated milk protein solution has better thermal stability; when 1 < y ≤ 2, the concentrated milk protein solution has moderate thermal stability; when y ≤ 1, the concentrated milk protein solution has poor thermal stability.

[0097] Comparative Example 2: Fitting the curves of calcium content and thermal flocculation time

[0098] The method for fitting the curves of calcium ion concentration and thermal flocculation time is as follows:

[0099] Based on Example 1, the calcium content and thermal flocculation time curves were fitted, and the fitting results are as follows. Figure 3 As shown, the results indicate that calcium content decreases with increasing thermal flocculation time (R0). 2 =0.99);

[0100] The function obtained by fitting Comparative Example 3: Fitting curves of free calcium concentration and thermal flocculation time

[0101] The simulated free calcium concentration and thermal flocculation time curves are obtained using the following method:

[0102] Based on Example 1, the curves of free calcium concentration and thermal flocculation time were fitted, and the fitting results are as follows. Figure 4 As shown, the results indicate that the concentration of free calcium decreases with increasing thermal flocculation time (R0). 2 =0.97);

[0103] The fitted function is y = 61.58e -x / 0.15 -0.46.

[0104] Comparative Example 4: Fitting pH value and thermal flocculation time curves

[0105] The method for fitting the pH and thermal flocculation time curves is as follows:

[0106] Concentrated milk protein solutions were prepared according to the method in Example 1. The pH was adjusted to 6.3 to 7.1 using 1 mol / L hydrochloric acid and sodium hydroxide solutions, and the thermal flocculation time was measured.

[0107] The pH and thermal flocculation time curves were obtained through nonlinear fitting, and the fitting results are as follows: Figure 5 As shown, the results indicate that pH and thermal flocculation time increase in an increasing manner (R0). 2 =0.99)

[0108] The function obtained by fitting Example 2: A method for rapidly evaluating the thermal stability of concentrated milk protein high-protein beverages

[0109] In the industrial production of high-protein beverages, the thermal stability is inconsistent and difficult to predict due to the different calcium content of concentrated milk protein from different sources and the different pH values ​​under different ingredient systems. Therefore, the pH and calcium content of high-protein beverages are adjusted to verify the accuracy of the prediction model.

[0110] A high-protein sports drink was prepared by referring to the ingredient list of commercially available high-protein sports drinks. The main raw materials were water, concentrated milk protein, fructooligosaccharides, whey protein powder, collagen peptides, and coconut oil. By weight, the components included: 100 parts water, 7.5 parts concentrated milk protein, 0.5 parts fructooligosaccharides, 0.5 parts whey protein, 0.5 parts collagen peptides, and 0.3 parts coconut oil. A homogeneous and stable solution was prepared according to the method in Example 1 and divided into 6 equal portions.

[0111] Three samples were adjusted to pH 6.5, 6.8, and 7.1 using 1 mol / L hydrochloric acid and sodium hydroxide solution, respectively. The other three samples were treated with calcium chloride to achieve calcium contents (mg / mL) of 1.95, 2.05, and 2.15, respectively, and their pH was adjusted to 6.8 using the same solution. The calcium ion activity of all six samples was then measured. Predicted values ​​for thermal flocculation time were calculated using different functions, and stability was assessed based on these predictions.

[0112] The results are shown in Table 3. The results show that only the predicted thermal stability of Example 1 is completely consistent with the actual thermal stability. Compared with Comparative Example 1, which is directly fitted, the error value of Example 1 predicted by piecewise fitting is smaller and the accuracy is higher. Comparative Example 2, which is fitted based on calcium content, has a higher accuracy when the pH is constant, but when the pH of the system changes, Comparative Example 2 cannot be used for prediction. Comparative Example 3, which is fitted based on pH, has a higher accuracy when the calcium content is constant, but when the calcium content of the system changes, Comparative Example 3 cannot be used for prediction.

[0113] In summary, only Example 1, which is based on calcium ion activity fitting, can ignore the effects of system pH and calcium content and accurately predict the thermal stability of concentrated milk protein solution.

[0114] Table 3 Prediction Effect Detection

[0115]

[0116]

[0117] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method for rapidly predicting the thermal flocculation time of concentrated milk protein based on calcium ion activity, characterized in that, Including the following steps: (1) By detecting the calcium ion activity and thermal flocculation time of concentrated milk protein solutions with different calcium ion concentrations, the calcium ion activity and thermal flocculation time were fitted to obtain the prediction equation. In the concentrated milk protein solution, concentrated milk protein and water are mixed at a ratio of 6-8 g: 100 mL. The prediction equation is: When x is less than or equal to 1.86, ; When x is greater than 1.86, ; Where x is calcium ion activity, mM; y is thermal flocculation time, min; (2) Take the concentrated milk protein to be tested, prepare the concentrated milk protein test solution, detect the calcium ion activity of the concentrated milk protein test solution, substitute the calcium ion activity into the prediction equation, and obtain the thermal flocculation time.

2. The method according to claim 1, characterized in that, The preparation method of concentrated milk protein solutions with different calcium ion concentrations in step (1) is as follows: Concentrated milk protein and water were mixed at a ratio of 6-8 g: 100 mL, homogenized, and refrigerated to obtain a concentrated milk protein solution; different concentrations of calcium ions were added to obtain concentrated milk protein solutions with different calcium ion concentrations.

3. The method according to claim 2, characterized in that, Mixing is done at 30-50℃ and 300-500 rpm for 0.5-2 hours; homogenization is done at 20-30℃ and 25-35 MPa for 3-5 times; refrigeration is done at 2-8℃ for more than 12 hours.

4. A method for rapidly predicting the thermal flocculation time of high-concentration milk protein beverages based on calcium ion activity, characterized in that, Including the following steps: (1) By detecting the calcium ion activity and thermal flocculation time of concentrated milk protein solutions with different calcium ion concentrations, the calcium ion activity and thermal flocculation time were fitted to obtain the prediction equation; the prediction equation is: When x is less than or equal to 1.86, ; When x is greater than 1.86, ; Where x is calcium ion activity, mM; y is thermal flocculation time, min; (2) Take the high-concentration milk protein beverage to be tested, detect the calcium ion activity in the high-concentration milk protein beverage, substitute the calcium ion activity into the prediction equation, and obtain the thermal flocculation time. Among them, the protein concentration of high-concentration milk protein beverages is 6-8%, and the concentration percentage is g / 100 mL.

5. The method according to claim 4, characterized in that, The preparation method of concentrated milk protein solutions with different calcium ion concentrations in step (1) is as follows: Concentrated milk protein and water were mixed at a ratio of 6-8 g: 100 mL, homogenized, and refrigerated to obtain a concentrated milk protein solution; different concentrations of calcium ions were added to obtain concentrated milk protein solutions with different calcium ion concentrations.

6. The method according to claim 5, characterized in that, Mix at 30~50℃ and 300~500 rpm for 0.5~2 hours.

7. The method according to claim 5, characterized in that, Homogenization is performed at 20-30℃ and 25-35 MPa for 3-5 times.

8. The method according to claim 5, characterized in that, Refrigeration involves placing the container at 2-8°C for at least 12 hours.

Images