Casein gel strength enhancing method based on tripolyphosphate concentration gradient regulation

Abstract

The invention discloses a method for regulating and controlling the strength of casein gel based on tripolyphosphate concentration gradient, belongs to the technical field of food processing and colloidal materials, and is particularly suitable for precise texture regulation and control of high-protein gel in dairy products. In order to solve the problems of poor strength adjustment flexibility and insufficient network structure compactness of casein gel in the prior art, the concentration gradient (0-60mEq / L, and adjacent concentration difference greater than or equal to 5mEq / L) of tripolyphosphate is designed, and the dissociation degree of casein micelles is regulated, so that the integral number of micelle suspension and the proportion of hydrophobic groups are synchronously increased, and the stability of the casein micelle is improved. Finally, directional enhancement of the gel strength and the network compactness is realized. The method specifically comprises the following steps: mixing tripolyphosphate solutions with at least three concentration gradients with casein micelle powder, fully dispersing, adjusting the pH value to be neutral, adding 0.5-3% of an acidifying agent (such as gluconic acid-delta-lactone), and carrying out constant-temperature treatment at 35-40 DEG C to form gel. Dynamic rheology and texture analysis show that the maximum storage modulus of the gel can reach 2596-28000 Pa, the hardness reaches 179.88-2349.19 N, and the performance parameters are in positive correlation with the concentration gradient of tripolyphosphate. The method has the innovativeness that 1) the micelle dissociation degree is controlled through concentration gradient design, and the limitation of single concentration regulation and control is broken through; and 2) the crosslinking density of the gel network is enhanced through double improvement of the volume fraction of dissociated micelles and the proportion of hydrophobic groups.

Description

Technical Field

[0001] The present invention relates to a protein gel modification method in the field of food processing technology, and in particular to a technology for regulating casein gel strength based on a tripolyphosphate concentration gradient. Specifically, the present invention changes the degree of dissociation, suspension volume fraction and hydrophobic group ratio of casein micelles by regulating the tripolyphosphate concentration gradient, thereby achieving directional enhancement of the density and mechanical strength of the gel network structure.

[0002] The present invention is particularly suitable for the field of dairy product processing, and can accurately regulate the texture characteristics of high-protein dairy products, such as cheese, yogurt, and protein-based meal replacement foods, to solve problems such as insufficient gel strength and loose structure caused by the traditional uniform concentration method, and provide technical support for the development of functional dairy products. Background Art

[0003] Casein is the highest-proportioned protein in dairy products (accounting for about 80% of the total protein in cow's milk). Its gel network structure directly affects the texture properties (such as hardness and elasticity), water retention and sensory quality of products such as cheese, yogurt, and protein-based meal replacement foods. In recent years, with the rapid growth of consumer demand for high-protein, low-additive, and functional dairy products, how to accurately control the strength of casein gel to adapt to different application scenarios has become one of the core technical challenges of the food industry.

[0004] Phosphates have shown good potential in regulating the texture of gel samples based on casein micelles. Phosphates have been shown to significantly enhance the hydration and solubility of casein micelle powders, laying the foundation for their application in food. In addition, the presence of phosphates can lead to a series of changes in the physical and chemical properties of MCC suspensions, affecting the microstructure, acidification rate and gel pH of acid-induced gels. The most interesting property of phosphates is that phosphates can directly interact with casein micelles. The incorporation of calcium chelate salts into high-concentration casein micelle systems helps to dissociate individual caseins from micelles, increasing the volume fraction and steric hindrance, which further affects the formation of rigid structures in casein gels. In addition, the hydrophobic regions of caseins bind to each other in a water-soluble state to form porous micelles, which are affected by phosphates. Phosphates promote micelle dissociation and change the balance of hydrophobic and hydrophilic groups within micelles and systems, thereby affecting the formation of three-dimensional gel networks and their water retention capacity. In view of their functional properties, polyphosphates may be considered as potential candidates for manipulating the texture of MCC gels. Summary of the invention

[0005] The present invention first solves the problem that casein gel has poor water holding capacity and loose texture. The casein micelle powder is dispersed by phosphate solution and hydrated overnight, which can greatly improve the hydration characteristics of casein micelles, and also make the casein micelles fully contact with phosphate. The casein micelle destruction effect of phosphate makes the hydrophobic groups in the casein micelles partially break free from the constraints of the micelles, increase the proportion of hydrophobic groups in the casein suspension, increase the interaction between caseins, promote the generation of a dense three-dimensional network structure of cross-linking in the gel, increase the content of fixed water in the gel, and significantly improve water holding capacity. In addition, phosphate promotes the dissociation of individual proteins from casein micelles, significantly improves the volume fraction of casein suspension, increases the interaction of caseins, promotes the generation of more hydrogen bonds and disulfide bonds in the gel, and obtains a casein gel with significantly improved gel strength.

[0006] In addition, the specific phosphate (tripolyphosphate) proposed in the present invention has the effect of improving the strength of casein gel depending on the regularity of tripolyphosphate concentration, and the indexes of gel strength including maximum storage modulus, hardness, water holding capacity, microstructure voids, and bound water content all show a high degree of consistency. Gel strength can present an ideal linear fit with the concentration of tripolyphosphate, so the method provided by the present invention can accurately, quickly and flexibly meet the diverse demands for gel strength in different application scenarios.

[0007] The objective of the present invention is achieved through the following technical solutions: A method for regulating casein gel strength by adding tripolyphosphate and its application, the steps are as follows: (1) Preparation of tripolyphosphate solutions of different concentrations: Prepare a tripolyphosphate mother solution with a concentration of 60 mEq / L and dilute it with distilled water to 30, 20, 10, and 10 in sequence to obtain tripolyphosphate solutions with a concentration range of 0-60 mEq / L; (2) Preparation of casein suspensions containing different concentrations of tripolyphosphate: casein micelle powder was dispersed in the tripolyphosphate suspension prepared in (1), sheared at a low speed (500 rpm) for 5 h in a 50°C water bath, and then placed in a 4°C refrigerator overnight for hydration to obtain a casein micelle suspension containing 0-60 mEq / L tripolyphosphate; (3) Fully mixing the casein suspension and GDL: The MCC suspension prepared in (2) was restored to room temperature in a 37°C water bath, the pH was adjusted to 7 with 1M HCI or 1M NaOH, 1.5% GDL (w / w) was added, and the mixture was mixed at 300 rpm for 3 min to obtain a casein suspension fully mixed with GDL; (4) GDL-induced gel formation: The MCC suspension thoroughly mixed with GDL in step (3) was placed in a 37°C incubator for 3 h to obtain a series of acid-induced casein gels. (5) partially placing the casein suspension thoroughly mixed with GDL in step 3 on a rheometer, measuring the storage modulus (G') at 37°C in a time scan mode at a frequency of 0.1 Hz and a low amplitude (0.5% strain), and recording the process for 180 minutes; (6) Using TA.XT Plus to texture the casein gel obtained in step (4) to determine its texture properties; (7) using a HAAKE MARS 40 rheometer to measure the rheological properties of the casein gel obtained in step (4); (8) Take 24 mL of the casein suspension mixed with GDL in step (3) and transfer it to 24 1.5 mL centrifuge tubes and place them in a constant temperature incubator at 37°C to form a gel. Take out one centrifuge tube every 15 minutes and centrifuge it at 1000g for 5 minutes. Record the weight of the precipitated water and calculate the water holding capacity using the following formula: W1 is the weight of the centrifugal supernatant (9) Water distribution and binding state in gel: The water distribution of the casein gel obtained in step (4) was measured using a low-field nuclear magnetic resonance (LF-NMR) analyzer. (10) Preparation of freeze-dried gel sample: The casein gel obtained in step (4) was quickly frozen with dry ice, and then freeze-dried at -80°C to obtain a freeze-dried gel sample. (11) Characterization of microstructure in gel: The frozen casein gel obtained in step (9) was coated with platinum to improve the conductivity and examined using a tungsten scanning electron microscope (SEM, SU3800, Hitachi Limited, Japan). Images were taken at magnifications of 100 μm and 50 μm, with an accelerating voltage of 5 kV. (12) The casein gel obtained in step (4) was photographed to record the effect of different concentrations of tripolyphosphate on the gel appearance. (13) Infrared spectroscopy analysis of gel samples: The frozen cheese protein gel obtained in step (9) was thoroughly mixed with KBr at a ratio of 1:100 and compressed into pellets for Fourier transform infrared spectroscopy analysis. 1 The spectral data were collected within a wavenumber range of 256 scans with a spectral resolution of 4 cm 1 The acquired data were further analyzed using OPUS software. (14) Determination of thiol (SH) content of gel sample: The frozen casein gel (50 mg) obtained in step (9) was dispersed in 7.5 mL Tris-glycine buffer (containing 0.086 M Tris, 0.09 M glycine, 0.04 M EDTA and 8 M urea, pH 8.0). In order to determine the free thiol (SH_free) content, 50 μL of 10 mM 5,5'-dithiobis-[2-nitrobenzoic acid (Ellman's reagent) was introduced into the mixture. Fresh Tris-glycine buffer was used as a blank reference, and the absorbance was measured at 412 nm. Where A represents the absorbance measured at 412 nm, C represents the sample concentration (mg / mL), and D represents the dilution factor. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is the appearance of the gel formed after GDL induced casein micelle suspension sample for 3 hours, and the microstructure shown by SEM;

[0009] Figure 2 This is the change of storage modulus over time in casein micelle suspension induced by 1.5% (W / W) GDL within 3 hours;

[0010] Figure 3 This is the rheological-frequency scanning diagram of the gel formed after GDL induced casein micelle suspension sample for 3 hours;

[0011] Figure 4 This is the rheological-stress scanning diagram of the gel formed after GDL induced casein micelle suspension sample for 3 hours.

[0012] Figure 5 This is the texture analysis-hardness diagram of the gel formed after GDL-induced casein micelle suspension sample for 3 hours;

[0013] Figure 6 This is the graph showing the change in water holding capacity of the gel formed by the GDL-induced casein micelle suspension sample within 5 hours;

[0014] Figure 7 This is the water distribution diagram of the gel formed after GDL induced casein micelle suspension sample for 3 hours;

[0015] Figure 8 This is the Fourier infrared image of the freeze-dried sample of the GDL-induced casein micelle suspension sample 3 hours later;

[0016] Fig. 9 This is the free thiol content of the freeze-dried sample of the casein micelle suspension sample 3 hours after GDL induction. DETAILED DESCRIPTION The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0018] Example 1 A method for preparing casein gel in this embodiment comprises the following steps:

[0019] 10 g of casein micelle powder was dispersed in 90 g of distilled water and 90 g of a 10 mEq / L tripolyphosphate solution, and sheared at a low speed (500 rpm) for 5 h in a 50°C water bath, and then placed in a 4°C refrigerator overnight for hydration to obtain a casein micelle suspension that did not contain phosphate and had a concentration of 10 mEq / L;

[0020] 50 g of each of the casein micelle suspensions containing no phosphate and having a concentration of 10 mEq / L were taken and restored to room temperature in a 37°C water bath, and then the pH was adjusted to 7 with 1 M HCI or 1 M NaOH, and then 750 mg of GDL was added and mixed thoroughly to obtain a casein micelle suspension containing no phosphate and having a concentration of 10 mEq / L that was fully mixed with GDL;

[0021] The casein micelle suspension containing no phosphate and having a concentration of 10 mEq / L and fully mixed with GDL was placed in a 37°C incubator for 3 h to obtain an acid-induced casein gel containing no phosphate and a casein gel containing 10 mEq / L tripolyphosphate;

[0022] Part of the casein suspension sample thoroughly mixed with GDL in step 2 was placed on the rheometer, and the storage modulus (G') at 37°C was measured in a time scan mode at a frequency of 0.1 Hz and a low amplitude (0.5% strain), and the process was recorded for 180 minutes;

[0023] The casein gel sample obtained in step (3) was subjected to a TA.XT Plus texture test to determine its texture characteristics;

[0024] The casein gel sample obtained in step (3) was used to measure the rheological properties of the gel using a HAAKE MARS 40 rheometer;

[0025] Take 24 mL of the casein micelle suspension mixed with GDL in step (3) and transfer it to 24 1.5 mL centrifuge tubes and place them in a constant temperature incubator at 37°C to form a gel. Take out one centrifuge tube every 15 minutes and centrifuge it at 1000g for 5 minutes. Record the weight of the precipitated water and calculate the water holding capacity using the following formula: W1 is the weight of the centrifugal supernatant

[0026] Water distribution and binding state in the gel: The water distribution of the casein gel sample obtained in step (4) was measured using a low-field nuclear magnetic resonance (LF-NMR) analyzer.

[0027] Preparation of freeze-dried gel sample: The casein gel sample obtained in step (4) was quickly frozen with dry ice, and then freeze-dried at -80°C to obtain a freeze-dried gel sample.

[0028] Characterization of microstructure in gel: The frozen casein gel sample obtained in step (5) was coated with platinum to improve the conductivity and examined using a tungsten scanning electron microscope (SEM, SU3800, Hitachi Limited, Japan). Images were taken at magnifications of 100 μm and 50 μm, with an accelerating voltage of 5 kV.

[0029] The casein gel sample obtained in step 4 is photographed to obtain the appearance of the gel.

[0030] Infrared spectroscopy analysis of gel samples: The frozen cheese protein gel sample obtained in step (7) was fully mixed with KBr at a ratio of 1:100 and compressed into pellets for Fourier transform infrared spectroscopy analysis. 1 The spectral data were collected within a wavenumber range of 256 scans with a spectral resolution of 4 cm 1 The acquired data were further analyzed using OPUS software.

[0031] Determination of the sulfhydryl (SH) content of the gel sample: The frozen casein gel sample (50 mg) obtained in step (7) was dispersed in 7.5 mL Tris-glycine buffer (containing 0.086 M Tris, 0.09 M glycine, 0.04 M EDTA and 8 M urea, pH 8.0). In order to determine the free sulfhydryl (SH_free) content, 50 μL of 10 mM 5,5'-dithiobis-[2-nitrobenzoic acid (Ellman's reagent) was introduced into the mixture. Fresh Tris-glycine buffer was used as a blank reference and the absorbance was measured at 412 nm. Where A represents the absorbance measured at 412 nm, C represents the sample concentration (mg / mL), and D represents the dilution factor.

[0032] In this embodiment, Figure 1As shown in the figure, the casein gel formed without phosphate is soft and has obvious water precipitation. The microstructure shows a coarse network structure and the gel voids are large. The casein gel containing 10mEq / L phosphate is moist, but there is no obvious water precipitation. Compared with the casein gel without phosphate, the microstructure has a significantly smaller pore size and the three-dimensional network is densely cross-linked.

[0033] In this embodiment, Figure 2-4 As shown, the maximum storage modulus of the casein gel formed without phosphate and the gel with a concentration of 10mEq / L are 2596Pa and 3466Pa, respectively, which is increased by 33.52%; Figure 5 As shown, the hardness is 179.88N and 192.9N respectively, an increase of 7.24%; Figure 6 As shown in the figure, after 3 h of gelation, the water holding capacity decreased from 100% to 20% and 38%, respectively, and increased by 90%. Figure 7 The retention time T23 in the LF-NMR analysis decreased from 178.34 to 135.09 ms, and T21 decreased from 7.31 to 1.12 ms, indicating a significant decrease in free water and an increase in bound water in the gel.

[0034] In this embodiment, Figure 8 As shown, the gel formed without phosphate and with a concentration of 10 mEq / L tripolyphosphate has a wavelength of 3200-3600 cm representing the -OH bond. -1 The tensile vibration absorption peaks are 3304.77 and 3303.79 cm –1 , indicating the formation of more hydrogen bonds; Fig. 9 The concentration of free thiol groups increased from 4.56 μmol g –1 decreased to 4.12 μmol g –1 , indicating the formation of more disulfide bonds.

[0035] Example 2 A method for preparing casein gel in this embodiment comprises the following steps:

[0036] 10 g of casein micelle powder was dispersed in 90 g of distilled water and 90 g of tripolyphosphate solution with a concentration of 20 mEq / L, and sheared at a low speed (500 rpm) for 5 h in a 50°C water bath, and then placed in a 4°C refrigerator overnight for hydration to obtain a casein micelle suspension without phosphate and with a concentration of 20 mEq / L;

[0037] 50 g of each of the casein micelle suspensions containing no phosphate and having a concentration of 20 mEq / L were taken and restored to room temperature in a 37°C water bath, and then the pH was adjusted to 7 with 1 M HCI or 1 M NaOH, and then 750 mg of GDL was added and mixed thoroughly to obtain a casein micelle suspension containing no phosphate and having a concentration of 20 mEq / L that was fully mixed with GDL;

[0038] The casein micelle suspension containing no phosphate and having a concentration of 20 mEq / L and fully mixed with GDL was placed in a 37°C incubator for 3 h to obtain an acid-induced casein gel containing no phosphate and a casein gel containing 20 mEq / L tripolyphosphate;

[0039] Determination of storage modulus and water holding capacity changes during the acidification process; rheological texture analysis of the formed gel; surface and microstructural analysis; Fourier transform infrared spectroscopy analysis of freeze-dried gel samples and determination of free thiol groups.

[0040] In this embodiment, Figure 1 As shown in the figure, the casein gel formed without phosphate is soft and has obvious water precipitation. The microstructure shows a coarse network structure and the gel voids are large. The apparent softness of the casein gel containing 20mEq / L phosphate is greatly improved. The microstructure has a significantly smaller pore size than the casein gel without phosphate, and the three-dimensional network is densely cross-linked.

[0041] In this embodiment, Figure 2-4 As shown, the maximum storage modulus of casein gel without phosphate and gel with a concentration of 20 mEq / L were 2596 Pa and 4003 Pa, respectively, an increase of 54.20%; Figure 5 The hardnesses shown are 179.88N and 225.39N, respectively, an increase of 25.30%; Figure 6 As shown in Figure 3, 3 hours after gelation, the water holding capacity of the gel decreased from 100% to 20% and 47%, respectively, an increase of 135%; Figure 7 As shown, the retention time T23 in LF-NMR analysis decreased from 178.34 to 126.08 ms, T22 decreased from 7.31 to 0 ms, and T21 decreased from 0.32 to 0.3 ms, indicating a significant decrease in free water and an increase in bound water in the gel.

[0042] In this embodiment, Figure 8 As shown, the gel formed without phosphate and with a concentration of 10 mEq / L tripolyphosphate has a wavelength of 3200-3600 cm representing the -OH bond. -1 The tensile vibration absorption peaks are 3304.77 and 3303.29 cm –1 , indicating the formation of more hydrogen bonds; Fig. 9As shown in Figure 2, the concentration of free thiol groups increased from 4.56 μmol g –1 decreased to 3.84 μmol g –1 , indicating the formation of more disulfide bonds.

[0043] Example 3 The preparation method of a casein gel in this embodiment comprises the following steps:

[0044] 10 g of casein micelle powder was dispersed in 90 g of distilled water and 90 g of a 30 mEq / L tripolyphosphate solution, and sheared at a low speed (500 rpm) for 5 h in a 50°C water bath, and then placed in a 4°C refrigerator overnight for hydration to obtain a casein micelle suspension that did not contain phosphate and had a concentration of 30 mEq / L;

[0045] 50 g of each of the casein micelle suspensions containing no phosphate and having a concentration of 30 mEq / L are taken and restored to room temperature in a 37°C water bath, and then the pH is adjusted to 7 with 1 M HCI or 1 M NaOH, and then 750 mg of GDL is added and mixed thoroughly to obtain a casein micelle suspension containing no phosphate and having a concentration of 30 mEq / L that is fully mixed with GDL;

[0046] The casein micelle suspension containing no phosphate and having a concentration of 30 mEq / L and fully mixed with GDL was placed in a 37°C incubator for 3 h to obtain an acid-induced casein gel containing no phosphate and a casein gel containing 30 mEq / L tripolyphosphate;

[0047] Determination of storage modulus and water holding capacity changes during the acidification process; rheological texture analysis of the formed gel; surface and microstructural analysis; Fourier transform infrared spectroscopy analysis of freeze-dried gel samples and determination of free thiol groups.

[0048] In this embodiment, Figure 1 As shown in the figure, the casein gel formed without phosphate is soft and has obvious water precipitation. The microstructure shows a coarse network structure and the gel voids are large. The apparent plasticity of the casein gel containing 30mEq / L phosphate is visibly enhanced. Compared with the casein gel without phosphate, the microstructure has a significantly smaller pore size and a significantly deeper three-dimensional network cross-linking density.

[0049] In this embodiment, Figure 2-4 As shown, the maximum storage modulus of casein gel without phosphate and gel with a concentration of 30 mEq / L were 2596 Pa and 17702 Pa, respectively, an increase of 582.05%; Figure 5 As shown, the hardness is 179.88N and 350.71N respectively, which is increased by 94.99%; Figure 6As shown, 3 h after gelation, the water holding capacity decreased from 100% to 20% and 83%, respectively, an increase of 315%; Figure 7 As shown, the retention time T23 in LF-NMR analysis decreased from 178.34 to 102.34 ms, T22 decreased from 7.31 to 0 ms, and T21 decreased from 0.32 to 0.26 ms, indicating a significant decrease in free water and an increase in bound water in the gel.

[0050] In this embodiment, Figure 8 As shown, the gel formed without phosphate and with a concentration of 10 mEq / L tripolyphosphate has a wavelength of 3200-3600 cm representing the -OH bond. -1 The tensile vibration absorption peaks are 3304.77 and 3300.28 cm –1 , indicating the formation of more hydrogen bonds; Fig. 9 As shown in Figure 2, the concentration of free thiol groups increased from 4.56 μmol g –1 decreased to 3.41 μmol g –1 , indicating the formation of more disulfide bonds.

[0051] Example 4 The preparation method of a casein gel in this embodiment comprises the following steps:

[0052] 10 g of casein micelle powder was dispersed in 90 g of distilled water and 90 g of a tripolyphosphate solution with a concentration of 60 mEq / L, and sheared at a low speed (500 rpm) for 5 h in a 50°C water bath, and then placed in a 4°C refrigerator overnight for hydration to obtain a casein micelle suspension without phosphate and with a concentration of 60 mEq / L;

[0053] 50 g of each of the casein micelle suspensions containing no phosphate and having a concentration of 60 mEq / L were taken and restored to room temperature in a 37°C water bath, and then the pH was adjusted to 7 with 1 M HCI or 1 M NaOH, and then 750 mg of GDL was added and mixed thoroughly to obtain a casein micelle suspension containing no phosphate and having a concentration of 60 mEq / L that was fully mixed with GDL;

[0054] The casein micelle suspension containing no phosphate and having a concentration of 60 mEq / L and fully mixed with GDL was placed in a 37°C incubator for 3 h to obtain an acid-induced casein gel containing no phosphate and a casein gel containing 60 mEq / L tripolyphosphate;

[0055] Determination of storage modulus and water holding capacity changes during the acidification process; rheological texture analysis of the formed gel; surface and microstructural analysis; Fourier transform infrared spectroscopy analysis of freeze-dried gel samples and determination of free thiol groups.

[0056] In this embodiment, Figure 1As shown, the casein gel formed without phosphate appears soft and has obvious water precipitation. The microstructure shows a coarse network structure and the gel voids are large. The apparent plasticity of the casein gel containing 60mEq / L phosphate is visibly enhanced. Compared with the casein gel without phosphate, the microstructure has a significantly reduced pore size and a significantly deepened three-dimensional network cross-linking density.

[0057] In this embodiment, Figure 2-4 As shown, the maximum storage modulus of casein gel without phosphate and gel with a concentration of 60mEq / L are 2596Pa and 28000Pa, respectively, an increase of 978.89%; Figure 5 As shown, the hardness is 179.88N and 2349.19N respectively, which is increased by 1206.02%; Figure 6 As shown in Figure 3, 3 h after gelation, the water holding capacity decreased from 100% to 20% and 92%, respectively, an increase of 360%; Figure 7 As shown, the retention time T23 in LF-NMR analysis decreased from 178.34 to 83.099 ms, T22 decreased from 7.31 to 0 ms, and T21 decreased from 0.32 to 0.16 ms, indicating a significant decrease in free water and an increase in bound water in the gel.

[0058] In this embodiment, Figure 8 As shown, the gel formed without phosphate and with a concentration of 10 mEq / L tripolyphosphate has a wavelength of 3200-3600 cm representing the -OH bond. -1 The tensile vibration absorption peaks are 3304.77 and 3296.29 cm –1 , indicating the formation of more hydrogen bonds; Fig. 9 As shown in Figure 2, the concentration of free thiol groups increased from 4.56 μmol g –1 decreased to 2.88 μmol g –1 , indicating the formation of more disulfide bonds.

[0059] Combining implementation cases 1, 2, 3, and 4, we can get the following: Figure 2 When the tripolyphosphate concentrations were 0, 10, 20, 30, and 60 mEq / L, the maximum storage modulus of the casein gel induced by GDL were 2596 Pa, 3466 Pa, 4003 Pa, 17702 Pa, and 28000 Pa, respectively. The maximum storage modulus was linearly correlated with the concentration of tripolyphosphate, and a linear equation with phosphate concentration as X and maximum storage modulus as Y was obtained: Y=465.74X-24.396, R2=0.9014, indicating that when the casein micelle concentration was fixed, the maximum storage modulus of the gel could be precisely controlled according to the phosphate concentration.

[0060] Combining implementation cases 1, 2, 3, and 4, we can get the following: Figure 5 As shown, the hardness of the gel increases with the increase of the concentration of tripolyphosphate, and the hardness of the gel increases from 179.88N to 2349.19N. Using concentration as the independent variable and hardness as the dependent variable, a linear equation (R2=0.98) can be derived (equation: y=36.776x+36.361). This shows that when the concentration of casein micelles is fixed, the hardness of the gel can be precisely controlled according to the concentration of phosphate.

Claims

1. A method for enhancing casein gel strength based on tripolyphosphate concentration gradient regulation, characterized in that: The following steps are involved: (1) preparing tripolyphosphate solutions of different concentrations, wherein the concentration range is 0-60 mEq / L, and the difference between adjacent concentrations is ≥5 mEq / L; (2) mixing the tripolyphosphate solution prepared in step 1 with casein micelle powder, subjecting the mixture to shear treatment at 50-60° C., and then subjecting the mixture to low temperature hydration to obtain a hydrated casein micelle suspension; (3) adjusting the pH of the suspension to neutral, adding an acidifier and mixing well; (4) The mixed suspension is treated at a constant temperature of 35-40°C to form an acid-induced casein gel.

2. The method according to claim 1, characterized in that: The low-temperature hydration temperature in step (2) is 2-8°C, and the hydration time is 8-12 hours.

3. The method according to claim 1, characterized in that: The acidulant in step (3) is at least one of glucono-δ-lactone (GDL), L-malic acid or bacterial strains.

4. The method according to claim 3, characterized in that: The acidulant is added in an amount of 0.5-3% (w / w).

5. The method according to claim 1, characterized in that: The time of the constant temperature treatment in step (3) is 0.5-6 hours.

6. The method according to claim 1, characterized in that: The concentration of the casein micelle suspension is ≥8% (w / w).

7. The method according to claim 1, characterized in that: In the hydrated casein micelle suspension, the proportion of micelles with a particle size greater than 500 nm does not exceed 10%, as determined by dynamic light scattering.

8. The method according to claims 1-6, characterized in that: The maximum storage modulus of the casein gel is positively correlated with the concentration gradient of tripolyphosphate. When the casein concentration is 10% (w / w), the maximum storage modulus of the casein gel is 2596-28000 Pa, which is measured by a dynamic rheometer at a frequency of 1 Hz and a strain of 1%.

9. The method according to claims 1-6, characterized in that: The hardness of the casein gel is positively correlated with the concentration gradient of tripolyphosphate. When the casein concentration is 10% (w / w), the hardness of the casein gel is 179.88-2349.19N, which is measured by a texture analyzer probe P / 50 at a test speed of 1mm / s.

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