Casein-gellan gum double gel and its preparation method and application

Abstract

The present invention belongs to the technical field of protein gel preparation, and specifically relates to a casein-gellan gum double gel and its preparation method and application. The double gel raw materials include casein and / or casein sodium salt, gellan gum, calcium ion chelating agent and acidified sustained release agent. The double gel is based on calcium ion chelating agent so that casein and / or casein sodium salt and gellan gum are interspersed with each other to form a double network structure, with high hardness, strong water holding capacity and stable structure; compared with gellan gum-casein sodium bicontinuous phase gel without calcium ion sustained release, the hardness is increased by about 187%, the water holding capacity is increased by about 64%, and the structural stability is significantly improved; compared with casein sodium-calcium ion gel without gellan gum, the hardness is increased by about 645%, the water holding capacity is increased by about 233%, and the structural stability is significantly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of protein gel preparation, and in particular relates to a casein-gellan gum double gel and a preparation method and application thereof. Background Art

[0002] Casein or its sodium salt is a protein derived from cow's milk with rich nutritional value and special functions. It is composed of four casein monomers, α, β, γ, and κ, and contains various amino acids necessary for the human body. Moreover, casein or its sodium salt has the functions of stabilizing properties, strengthening protein, thickening and foaming. After being hydrolyzed and absorbed by the body, it can participate in the normal metabolism of the body. It is a high-quality protein source and can be added to various foods as a high-protein nutritional enhancer. In addition, casein or its sodium salt also has good gelling properties, which can improve food utilization and stability, improve taste, embed flavor substances and probiotics, etc., so it is currently widely used in the field of dairy processing.

[0003] However, casein or its sodium salt gel has the defects of soft structure and easy whey separation, which limits the application of casein or its sodium salt gel as flavor substances or probiotic embedding materials. Therefore, how to prepare casein or its sodium salt gel with excellent mechanical properties and without changing its original properties has always been a research hotspot at home and abroad. The existing methods for improving the structure of casein or its sodium salt gel mainly include TG enzyme covalent cross-linking, blending casein or its sodium salt with high and low acyl gellan gum and agar, or using chemical modification methods. These methods have the defects of poor water holding capacity, soft structure and poor stability of the prepared gel, and the chemical modification method also has the defect of changing the original properties of casein or its sodium salt gel.

[0004] Therefore, a different method is now needed to modify casein or its sodium salt to obtain a casein or its sodium salt gel with good water holding capacity, compact structure and good stability. Summary of the invention

[0005] In view of the above problems, one of the purposes of the present invention is to provide a casein-gellan gum double gel, which is prepared by combining casein or its sodium salt with gellan gum. Under the action of a calcium ion chelating agent to slowly release calcium ions, casein and / or casein sodium salt and gellan gum are interspersed with each other to form a double network structure, and at the same time, under the action of a pH slow-release agent to slowly acidify, the reaction system is formed by acidifying to the isoelectric point of casein. The prepared casein-gellan gum double gel has excellent water holding capacity, high hardness and stable structure.

[0006] In order to achieve the above object, the present invention can adopt the following technical solutions:

[0007] The present invention provides a casein-gellan gum double gel, the raw materials of which include casein and / or casein sodium salt, gellan gum, a calcium ion chelating agent and an acidifying sustained-release agent.

[0008] Another aspect of the present invention provides a method for preparing the above-mentioned casein-gellan gum double gel, comprising: mixing a casein and / or casein sodium salt solution with a gellan gum solution to obtain a mixed solution; mixing the mixed solution with a calcium ion chelating agent and an acidifying sustained-release agent to react until the pH reaches 3.5-4.6 to obtain the casein-gellan gum double gel.

[0009] Another aspect of the present invention provides a use of the casein-gellan gum double gel in the preparation of fermented milk.

[0010] The beneficial effects of the present invention include at least:

[0011] (1) The casein-gellan gum double gel provided by the present invention is based on a calcium ion chelating agent so that casein and / or casein sodium salt and gellan gum are interlaced with each other to form a double network structure, which has high hardness, strong water holding capacity and stable structure; compared with the gellan gum-sodium casein double continuous phase gel under the condition of sustained release without calcium ions, the hardness is increased by about 187%, the water holding capacity is increased by about 64%, and the structural stability is significantly improved; compared with the casein sodium-calcium ion gel under the condition of not containing gellan gum, the hardness is increased by about 645%, the water holding capacity is increased by about 233%, and the structural stability is significantly improved.

[0012] (2) The preparation method of the casein-gellan gum double gel provided by the present invention is simple, the conditions are mild, and it is conducive to industrial production.

[0013] (3) The fermented milk, especially the yogurt, prepared based on the casein-gellan gum double gel system provided by the present invention has a tighter structure, a smoother surface, basically no bubbles, and basically no whey precipitation compared with the yogurt prepared without gellan gum and calcium ion chelating agent; the water holding capacity can be increased by more than 7% compared with the yogurt prepared without calcium ion chelating agent; the water holding capacity can be increased by 68% compared with the yogurt prepared without gellan gum; the texture can be increased by 678% in thickness, 583% in viscosity, 1430% in firmness, and 905% in cohesion compared with the yogurt prepared without gellan gum; the texture can be increased by 178% in viscosity, with little difference in firmness, and 316% in cohesion compared with the yogurt prepared without calcium ion chelating agent. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Example 1 (0.05% LA-CN / Ca 2+ ) Gel appearance picture;

[0015] Figure 2 Example 2 (0.2% LA-CN / Ca2+ ) Gel appearance picture;

[0016] Figure 3 Example 3 (0.5% LA-CN / Ca 2+ ) Gel appearance picture;

[0017] Figure 4 This is the appearance of the gel of Comparative Example 1 (0.5% LA-CN);

[0018] Figure 5 For comparative example 2 (CN / Ca 2+ ) Gel appearance picture;

[0019] Figure 6 For comparative example 3 (0.4% LA-CN / Ca 2+ ) Gel appearance picture;

[0020] Figure 7 For comparative example 4 (0.6% LA-CN / Ca 2+ ) Gel appearance picture;

[0021] Figure 8 It is a graph showing the pH value changes during the gel fermentation process in the examples and comparative examples;

[0022] Fig. 9 It is a comparison chart of the water holding capacity of gels in the embodiment and the comparative example;

[0023] Fig.10 It is a comparison diagram of gel hardness between the embodiment and the comparative example;

[0024] Fig.11 This is a schematic diagram of the yogurt preparation process;

[0025] Fig.12 This is an appearance diagram of the yogurt prepared in Example 4;

[0026] Fig.13 This is the appearance of the yogurt prepared in Comparative Example 5;

[0027] Fig.14 This is the appearance of the yogurt prepared in Comparative Example 6;

[0028] Fig.15 A comparison chart of the acidity of yogurt prepared in different groups;

[0029] Fig.16 Comparison of water holding capacity of yogurt prepared in different groups;

[0030] Fig.17 This is a comparison chart of the consistency of yogurt prepared in different groups;

[0031] Fig.18 Comparison of the viscosity of yogurt prepared in different groups;

[0032] Fig.19 Comparison of the firmness of yogurt prepared in different groups;

[0033] Fig. 20 Comparison of the cohesion of yogurt prepared in different groups;

[0034] Fig.21 This is the principal component analysis diagram of yogurt electronic tongue;

[0035] In the figure, 0.05% LA-CN / Ca 2+ Example 1 gel; 0.2% LA-CN / Ca 2+ Example 2 gel; 0.5% LA-CN / Ca 2+ The gel of Example 3; 0.5% LA-CN is the gel of Comparative Example 1; CN / Ca 2+ Comparative Example 2 gel; 0.4% LA-CN / Ca 2+ This is the gel of Comparative Example 3; 0.6% LA-CN is the gel of Comparative Example 4. DETAILED DESCRIPTION

[0036] The examples are provided to better illustrate the present invention, but the present invention is not limited to the examples. Therefore, those skilled in the art may make non-essential improvements and adjustments to the implementation scheme according to the above invention content, which still fall within the protection scope of the present invention.

[0037] The terms used herein are only used to describe specific embodiments and are not intended to limit the present disclosure. Unless the context has a significantly different meaning, expressions in the singular include expressions in the plural. As used herein, it should be understood that terms such as "include", "have", "include" and the like are intended to indicate the presence of features, numbers, operating materials or combinations. The terms of the present invention are disclosed in the specification, and are not intended to exclude the possibility that one or more other features, numbers, operations, materials or combinations thereof may exist or may be added. As used herein, " / " may be interpreted as "and" or "or", depending on the circumstances.

[0038] In the present invention, the term "calcium ion chelating agent" refers to a chelate that can slowly release calcium ions; the term "acidification slow-release agent" refers to a substance that can slowly acidify the system.

[0039] The embodiment of the present invention provides a casein-gellan gum double gel, the raw materials of which include casein and / or casein sodium salt, gellan gum, a calcium ion chelating agent and an acidifying sustained-release agent.

[0040] It should be noted that in the present invention, a calcium ion chelating agent is used as a calcium sustained-release agent. While the acidified sustained-release agent induces the sodium caseinate-gellan gum dispersion system to slowly acidify to the isoelectric point of casein to form a casein gel, the calcium ion chelating agent induces the release of calcium ions in calcium citrate and cross-links with the anionic sites of the gellan gum, thereby forming a casein-gellan gum interpenetrating double network gel during the acidification process.

[0041] It should also be noted that in recent years, the properties of casein gel have been greatly improved by inducing the mixing of gellan gum and casein to form a composite gel by acid induction; however, in the composite gel, gellan gum only acts as a polymer and electrostatically combines with casein to play a role. In the present invention, by combining the physical properties of gellan gum and protein (casein or its sodium salt), a multi-level or layered binary system mixed gel microstructure is produced. The binary system mixed gel can form a three-dimensional network structure independently based on two polymers, and finally form an interpenetrating network gel. The interpenetrating network gel has more excellent gel properties such as gel strength, toughness and hardness; adding an appropriate second polymer network (calcium ion chelator) can achieve a balance between strength and toughness by adjusting the interaction and structure within the two networks, thereby improving the overall mechanical properties of the gel again.

[0042] As is known to all, gellan gum is an anionic linear extracellular polysaccharide, the main chain of which is a linear tetrasaccharide repeating unit, which is composed of (1,3)-β-D-glucose, (1,4)-β-D-glucuronic acid, (1,4)-β-D-glucose and (1,4)-α-L-rhamnose, thereby inducing casein to form a firm gel. Therefore, when gellan gum is blended with casein, while casein forms a gel, calcium ions cross-link with anionic sites of gellan gum such as carboxyl or carboxyl salt groups to form a gel, and the casein-gellan gum double gel formed in this way has better gel properties than the casein-gellan gum composite gel.

[0043] The above shows that in the absence of Ca 2+ In the case of sustained release, sodium caseinate and gellan gum have electrostatic repulsion, and sodium caseinate and gellan gum have poor compatibility during the fermentation process, resulting in poor water holding capacity of the gel and poor stability; in the absence of gellan gum, the stability of the casein gel is relatively poor; that is, the casein gel in the present invention is under the action of calcium ion sustained release, casein or its sodium salt and gellan gum will intersperse with each other to form a double network structure, thereby improving the water holding capacity and stability of the sodium caseinate gel. In some specific embodiments, compared with the gellan gum-sodium caseinate bicontinuous phase gel under the condition of calcium ion sustained release, the hardness is increased by about 187%, the water holding capacity is increased by about 64%, and the structural stability is significantly improved; compared with the casein sodium-calcium ion gel under the condition of gellan gum free, the hardness is increased by about 645%, the water holding capacity is increased by about 233%, and the structural stability is significantly improved.

[0044] In addition, it should be emphasized that the calcium ion chelating agent selected in the present invention is not calcium ion. If an inorganic calcium salt, such as calcium chloride, is selected, due to CaCl 2 The solubility in water is high. 2 The moment the solution comes into contact with the mixed solution of casein or its sodium salt and gellan gum, precipitation can be rapidly generated, affecting the formation of gel. Therefore, it is necessary to select a calcium ion chelator to achieve the controlled release of calcium ions during the reaction process with casein or its sodium salt or gellan gum, thereby slowing down the gelation rate.

[0045] It should be understood that the raw materials of the above-mentioned casein gel may include casein, gellan gum, calcium ion chelating agent and acidifying slow-release agent; may also include casein sodium salt, gellan gum, calcium ion chelating agent and acidifying slow-release agent; may also include casein, casein sodium salt, gellan gum, calcium ion chelating agent and acidifying slow-release agent.

[0046] In some specific embodiments, the mass ratio of casein and / or casein sodium salt to gellan gum can be 6:(0.05-0.5), and the mass fraction of gellan gum can be 0.05%-0.5%. It should be noted that the mass fraction of gellan gum refers to the mass percentage of the total solution system composed of casein and / or casein sodium salt solution, calcium ion chelating agent and gellan gum solution.

[0047] It should be understood that the raw materials of the casein-gellan gum double gel may be casein and gellan gum in a mass ratio of 6:(0.05-0.5); casein sodium salt and gellan gum in a mass ratio of 6:(0.05-0.5); or a combination of casein and casein sodium salt and gellan gum in a mass ratio of 6:(0.05-0.5); in some specific embodiments, casein and / or casein sodium salt and gellan gum in a mass ratio of 6:0.08, 6:0.1, 6:0.2 or 6:0.3, etc.; it should be noted that casein and / or casein sodium salt and gellan gum in a mass ratio of 6:0.08, 6:0.1, 6:0.2 or 6:0.3, etc. In the mass ratio of gellan gum, if the mass of casein and / or casein sodium salt is too much relative to gellan gum and exceeds the maximum mass ratio, the formed gel is a casein gel, not a double gel system, and the performance of the gel of the present invention cannot be reflected, and there are defects such as soft structure and whey separation. Similarly, in the mass ratio of casein and / or casein sodium salt to gellan gum, if the mass of gellan gum is less than that of casein and / or casein sodium salt and is lower than the minimum mass ratio, calcium ions will cross-link the anionic sites of the gellan gum polymer, and the relatively high concentration of calcium ions will form electrostatic repulsion in the gellan gum connection area, affecting the stability of the gel.

[0048] In some specific embodiments, the mass concentration of the gellan gum can be 0.08%, 0.1%, 0.3% or 0.4%, etc. It should be noted that the mass concentration of the gellan gum cannot be too low or too high. If the mass concentration of the gellan gum is too low, it cannot form a tight structure with casein and / or sodium caseinate, which affects the optimal stability of the casein-gellan gum double gel. If the mass concentration of the gellan gum is too high, the gellan gum and casein or its sodium salt will be phase separated, which will destroy the tightness of the two and also affect the stability of the casein-gellan gum double gel. Under the proportions of the embodiments of the present invention, the casein-gellan gum double gel has good stability and water holding capacity.

[0049] In some specific embodiments, in the casein-gellan gum double gel, when the mass concentration of casein or its sodium salt in the casein gel is 6% and the mass concentration of gellan gum is 0.5%, the prepared casein gel is better than the casein gel without Ca 2+ The water holding capacity of the gel under the conditions increased by about 64%, and the hardness increased by about 187%; compared with the gel under the conditions without gellan gum, the water holding capacity increased by about 233%, and the hardness increased by about 645%; compared with the gels prepared at other concentrations and mass ratios, the water holding capacity increased by at least 2%, and the hardness increased by at least 12%.

[0050] In some specific embodiments, the calcium ion chelating agent is a calcium salt chelated with a chelating agent, the calcium salt is selected from calcium chloride or calcium gluconate; the chelating agent is selected from sodium citrate, sodium acetate or sodium hexametaphosphate. It should be noted that the calcium salt can be selected from calcium salts known in the art that are easily soluble in water and have a neutral solution, such as calcium chloride or calcium gluconate; the chelating agent is selected from chelating agents known in the art, such as sodium citrate, sodium acetate or sodium hexametaphosphate, etc.; casein sodium salt is known in the art, such as sodium caseinate.

[0051] In some specific embodiments, the mass concentration of the calcium salt can be 3mmol / L-15mmol / L, such as 5mmol / L, 7mmol / L, 10mmol / L, 12mmol / L or 13mmol / L, etc.; the mass concentration of the chelating agent can be 3mmol / L-15mmol / L, such as 5mmol / L, 7mmol / L, 10mmol / L, 12mmol / L or 13mmol / L, etc. It should be noted that in the present invention, the role of calcium ions is: Ca 2+ Ca cross-links with the phosphate residues of serine on α-, s- and β-casein in casein or its sodium salt molecules. 2+ It cross-links with the -COO- of gellan gum, and then during the preparation process, as the pH of the solution changes, casein gradually releases some Ca 2+When the pH value is close to the casein isotope (pH = 4.6), gellan gum and casein are cross-linked at Ca 2+ Under the action of calcium ion, a denser double network gel is formed; however, the concentration of calcium ions should not be too high or too low. When it is too low, it will only cross-link with gellan gum and will not induce casein or its sodium salt to form a double network gel with gellan gum; when the concentration of calcium ions is too high, the ionic sites of gellan gum will be electrostatically repelled, destroying the ionic cross-linking between the anionic sites and calcium ions, affecting the stability of the gel. At the concentration of calcium ion chelating agent in the present invention, Ca 2+ It induces casein or its sodium salt to form a cohesive and strong gel.

[0052] In some specific embodiments, the mass concentration of the calcium salt is preferably 9mmol / L, and the mass concentration of the chelating agent is 15mmol / L. The water holding capacity of the gel prepared under this condition can be increased by more than 19% compared with the gel prepared by other proportions. In addition, when the mass concentration of the calcium salt is 30mmol / L, the water holding capacity of the gel prepared by the calcium salt with a mass concentration of 9mmol / L under the same conditions is significantly reduced. For example, when the mass fraction of sodium caseinate is 6%, the mass fraction of gellan gum is 0.5%, the concentration of sodium citrate is 15mmol / L, the concentration of calcium chloride is 9mmol / L, and the mass fraction of glucono-δ-lactone is 2.5%, the water holding capacity of the gel prepared is 97.53%; when the mass fraction of sodium caseinate is 6%, the mass fraction of gellan gum is 0.5%, the concentration of sodium citrate is 50mmol / L, the concentration of calcium chloride is 30mmol / L, and the mass fraction of glucono-δ-lactone is 2.5%, the water holding capacity of the gel prepared is 82.13%, which is a decrease of about 15.8%.

[0053] In some specific embodiments, the above-mentioned acidifying slow-release agent is selected from L-malic acid, glucono-δ-lactone or fermented strains. It should be noted that the acidifying slow-release agent in the present invention can be a known acidifying slow-release agent in the art (a substance that can slowly acidify the system), such as L-malic acid or glucono-δ-lactone. In addition, the acidifying slow-release agent is an analog of the fermented strain, which is consistent with the function of the fermented strain, that is, the acidifying slow-release agent can also be a fermented strain, and the fermented strain can be a strain known in the art, such as Lactobacillus bulgaricus or Streptococcus thermophilus.

[0054] In some specific embodiments, the mass fraction of the acidifying sustained-release agent can be 2.0%-3.5%. It should be noted that the mass fraction of the acidifying sustained-release agent refers to the mass percentage of the total solution system composed of casein and / or casein sodium salt solution, calcium ion chelating agent, gellan gum solution and acidifying sustained-release agent solution.

[0055] It should be noted that the purpose of the acidifying sustained-release agent in the present invention is to induce the sodium caseinate dispersion system to slowly acidify to its PI point to form a gel state, so it is not possible to directly add an inorganic acid such as hydrochloric acid to reduce the pH value. If the pH is reduced too quickly, it is easy to cause rapid precipitation of the gel and precipitation of whey. In addition, since the pH value of the system cannot be too low (not less than 3.5), the amount of the acidifying sustained-release agent needs to be adjusted according to the initial pH value of the system; for example, when the initial pH is 6.6-7, the mass fraction of the acidifying sustained-release agent can be 2.0%-3.5%, such as 2.2%, 2.4%, 2.5% or 3.3%, etc., preferably 2.5%. At this concentration, the end point pH value of the system is about 4.0, which can achieve the best performance.

[0056] In addition, when glucono-δ-lactone is used as a protein coagulant for dairy products, glucono-δ-lactone is hydrolyzed in an aqueous solution to produce gluconic acid, and the pH value of the solution is reduced at a relatively slow rate, which can provide sufficient time for protein molecules to aggregate into a gel structure. It should also be noted that in some embodiments, in order to facilitate the control of the amount of the acidified sustained-release agent, an alkaline solution (such as a sodium hydroxide solution) can be added to the reaction system to adjust the pH to a fixed point, such as any pH point between 6.6 and 7.

[0057] Another embodiment of the present invention provides a method for preparing the above-mentioned casein-gellan gum double gel, comprising: mixing a casein and / or casein sodium salt solution with a gellan gum solution to obtain a mixed solution; mixing the mixed solution with a calcium ion chelating agent and an acidifying sustained-release agent to react until the pH reaches 3.5-4.6 to obtain a casein-gellan gum double gel.

[0058] It should be understood that in the above-mentioned method for preparing the casein-gellan gum double gel, the casein and / or casein sodium salt solution and the gellan gum solution are both aqueous solutions; in addition, the casein and / or casein sodium salt solution can be a casein solution, a casein sodium salt solution, or a combined solution of casein and casein sodium salt.

[0059] It should be noted that in the above-mentioned method for preparing the casein-gellan gum double gel, the calcium ion chelator can be obtained by direct reaction in the reaction system, or can be directly added to the calcium ion chelator; for example, in some specific embodiments, after the casein and / or casein sodium salt solution is mixed with the gellan gum solution, calcium chloride solution, sodium citrate solution and acidifying sustained-release agent can be added to the mixed solution to acidify the reaction system to obtain the casein-gellan gum double gel.

[0060] In some specific embodiments, in the preparation method of the above-mentioned casein-gellan gum double gel, fermentation is carried out at 40°C-50°C, such as 42°C, 45°C and 47°C. Specifically, the mixed system of all raw materials is fermented at a constant temperature of 40°C-50°C to obtain casein gel. It should be noted that the casein gel can be obtained by mixing the mixed solution with the calcium ion chelating agent, and then adding an acidifying sustained-release agent at 40°C-50°C for reaction; or the casein gel can be obtained by mixing the mixed solution, the calcium ion chelating agent and the acidifying sustained-release agent, and then reacting at 40°C-50°C.

[0061] In some specific embodiments, the method for preparing the casein-gellan gum double gel may include the following steps:

[0062] (1) dissolving sodium caseinate in deionized water at 70°C, stirring at a constant temperature of 70°C for 4 hours until the sodium caseinate is completely hydrated, thereby obtaining a sodium caseinate solution; dissolving gellan gum in deionized water at 80°C, stirring at a constant temperature of 80°C for 4 hours until the gellan gum is completely hydrated, thereby obtaining a gellan gum solution; (2) mixing the gellan gum solution and the sodium caseinate solution in the above-mentioned mass ratio, and adding deionized water to a certain mass, thereby preparing a gellan gum-sodium caseinate mixed solution; (3) adding the mixed emulsion in step (2) to a mixed solution of calcium chloride and sodium citrate, so that calcium ions cross-link gellan gum-sodium caseinate to form a double gel solution; (4) adding glucono-δ-lactone to the double gel solution obtained in step (3), stirring thoroughly for 20 seconds, thereby obtaining a sodium caseinate gel solution, and placing the solution in a constant temperature incubator at 42°C for fermentation for 4 hours, thereby obtaining a casein-gellan gum double gel.

[0063] Another embodiment of the present invention provides a use of the casein-gellan gum double gel in preparing fermented milk.

[0064] It should be noted that casein gel can be used as a material for sustained release of functional ingredients or flavor substances in dairy products to prevent the precipitation of fermented milk whey, and can also be used as an embedding material for probiotics. Based on the fact that the casein gel in the present invention has high hardness, strong water retention and a stable structure, it is applied in the preparation of fermented milk. Under the premise of ensuring the stability of the fermented milk, it can add rich functional ingredients, flavor substances or probiotics to the fermented milk, enriching the category of fermented milk. In addition, the phosphate residues of serine on α-casein and β-casein in sodium caseinate can be cross-linked with calcium ions to form a calcium supplement that is easily absorbed and utilized by the human body, which can enrich the nutritional elements of fermented milk.

[0065] In some specific embodiments, in addition to using the above-mentioned casein-gellan gum double gel as an embedding material for fermented milk, the casein-gellan gum double gel system can also be used to prepare fermented milk, for example, including: mixing an emulsion containing casein with a gellan gum solution to obtain a mixed solution a; mixing the mixed solution a with a calcium ion chelator, homogenizing, and sterilizing to obtain a mixed solution b; mixing the mixed solution b with an acidifying sustained-release agent, and fermenting to obtain fermented milk.

[0066] In addition, the fermented milk can be prepared by fermenting an emulsion containing casein as a yogurt matrix, adding gellan gum, a calcium ion chelator and an acidifying slow-release agent. In addition, the fermented milk in the present invention refers in particular to yogurt. In some embodiments, the yogurt prepared by the casein-gellan gum double gel system of the present invention has a tighter structure, a smoother surface, basically no bubbles, and basically no whey precipitation than the yogurt prepared without gellan gum and calcium ion chelator; the water holding capacity is increased by at least 7%, the consistency can be increased to 678%, the viscosity is increased to 583%, the firmness is increased to 1430%, and the cohesion is increased to 905%. That is, the yogurt prepared by the casein-gellan gum double gel system of the present invention can significantly improve the stability of the yogurt system.

[0067] It should also be noted that the above homogenization pressure can be 20 bar-200 bar; the sterilization method includes but is not limited to pasteurization.

[0068] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with specific examples, but the content of the present invention is not limited to the following examples.

[0069] 1. Sodium caseinate gel solution and gel preparation

[0070] Example 1 (0.05% LA-CN / Ca 2+ )gel

[0071] Weigh 9.60 g of sodium caseinate in 71 mL of deionized water, stir at 70° C. for 4 h until the sodium caseinate is completely hydrated, and add deionized water to 80 g to prepare a 12% (w / w) sodium caseinate solution;

[0072] Weigh 0.08 g of gellan gum in 40 mL of deionized water, stir at 80° C. for 4 h until the gellan gum is completely hydrated, and add deionized water to 40 g to prepare a 0.2% (w / w) gellan gum solution;

[0073] The gellan gum solution and the sodium caseinate solution were mixed, and the mixture was stirred at 70°C for 1 hour, and then deionized water was added to a system mass of 120 g. A mixed solution prepared by dissolving 0.716 g of sodium citrate dihydrate and 0.16 g of anhydrous calcium chloride in 10 mL of deionized water at 70°C was quickly added, and 1 mol / L of NaOH was added dropwise to adjust the pH value of the mixed system to 6.8.

[0074] 4.0 g of glucono-δ-lactone was weighed and dissolved in 25 mL of deionized water. After vortexing for 10 seconds, the mixture was immediately added to the above-mentioned mixed system and stirred for 20 seconds to obtain a gel solution.

[0075] The mass fraction of sodium caseinate in the gel system is 6%, the mass fraction of gellan gum is 0.05%, the concentration of sodium citrate is 15 mmol / L, the concentration of calcium chloride is 9 mmol / L, and the mass fraction of glucono-δ-lactone is 2.5%.

[0076] The pH of the gel solution was monitored; the gel solution was placed in a 42° C. constant temperature incubator and fermented for 4 hours to form a gel.

[0077] Example 2 (0.2% LA-CN / Ca 2+ )gel

[0078] Weigh 9.60 g of sodium caseinate in 71 mL of deionized water, stir at 70° C. for 4 h until the sodium caseinate is completely hydrated, and add deionized water to 80 g to prepare a 12% (w / w) sodium caseinate solution;

[0079] Weigh 0.32 g of gellan gum into 60 mL of deionized water, stir at 80° C. for 4 h until the gellan gum is completely hydrated, and add deionized water to 40 g to prepare a 0.8% (w / w) gellan gum solution;

[0080] The gellan gum solution and the sodium caseinate solution were mixed, and the mixture was stirred at 70°C for 1 hour, and then deionized water was added to a system mass of 120 g. A mixed solution prepared by dissolving 0.716 g of sodium citrate dihydrate and 0.16 g of anhydrous calcium chloride in 10 mL of deionized water at 70°C was quickly added, and 1 mol / L of NaOH was added dropwise to adjust the pH value of the mixed system to 6.8.

[0081] 4.0 g of glucono-δ-lactone was weighed and dissolved in 25 mL of deionized water. After vortexing for 10 seconds, the mixture was immediately added to the above-mentioned mixed system and stirred for 20 seconds to obtain a gel solution.

[0082] The mass fraction of sodium caseinate in the gel system is 6%, the mass fraction of gellan gum is 0.2%, the concentration of sodium citrate is 15 mmol / L, the concentration of calcium chloride is 9 mmol / L, and the mass fraction of glucono-δ-lactone is 2.5%.

[0083] The pH value of the gel solution was monitored; the gel solution was placed in a 42° C. constant temperature incubator to react for 4 hours to form a gel.

[0084] Example 3 (0.5% LA-CN / Ca 2+ )gel

[0085] Weigh 9.60 g of sodium caseinate in 71 mL of deionized water, stir at 70° C. for 4 h until the sodium caseinate is completely hydrated, and add deionized water to 75 g to prepare a 12.8% (w / w) sodium caseinate solution;

[0086] Weigh 0.80 g of gellan gum in 50 mL of deionized water, stir at 80° C. for 4 h until the gellan gum is completely hydrated, and add deionized water to 50 g to prepare a 1.6% (w / w) gellan gum solution;

[0087] The gellan gum solution and the sodium caseinate solution were mixed, and the mixture was stirred at 70°C for 1 hour, and then deionized water was added to a system mass of 125 g. A mixed solution prepared by dissolving 0.716 g of sodium citrate dihydrate and 0.16 g of anhydrous calcium chloride in 10 mL of deionized water at 70°C was quickly added, and 1 mol / L of NaOH was added dropwise to adjust the pH value of the mixed system to 6.8.

[0088] 4.0 g of glucono-δ-lactone was weighed and dissolved in 20 mL of deionized water. After vortexing for 10 seconds, the mixture was immediately added to the above-mentioned mixed system and stirred for 20 seconds to obtain a gel solution.

[0089] The mass fraction of sodium caseinate in the gel system is 6%, the mass fraction of gellan gum is 0.5%, the concentration of sodium citrate is 15 mmol / L, the concentration of calcium chloride is 9 mmol / L, and the mass fraction of glucono-δ-lactone is 2.5%.

[0090] The pH of the gel solution was monitored; the gel solution was placed in a 42°C constant temperature incubator to react for 4 hours to form a gel. Comparative Example 1 (0.5% LA-CN) Gel

[0091] Weigh 9.60 g of sodium caseinate in 71 mL of deionized water, stir at 70° C. for 4 h until the sodium caseinate is completely hydrated, and add deionized water to 75 g to prepare a 12.8% (w / w) sodium caseinate solution;

[0092] Weigh 0.80 g of gellan gum in 50 mL of deionized water, stir at 80° C. for 4 h until the gellan gum is completely hydrated, and add deionized water to 50 g to prepare a 1.6% (w / w) gellan gum solution;

[0093] The gellan gum solution and the sodium caseinate solution were mixed, and the mixture was stirred at 70°C for 1 hour, and then deionized water was added to a system mass of 125 g. 10 mL of deionized water was added at 70°C, and 1 mol / L of NaOH was added dropwise to adjust the pH value of the mixed system to 6.8.

[0094] 4.0 g of glucono-δ-lactone was weighed and dissolved in 20 mL of deionized water. After vortexing for 10 seconds, the mixture was immediately added to the above-mentioned mixed system and stirred for 20 seconds to obtain a gel solution.

[0095] The mass fraction of sodium caseinate in the gel system is 6%, the mass fraction of gellan gum is 0.5%, and the mass fraction of glucono-delta-lactone is 2.5%.

[0096] The pH of the gel solution was monitored; the gel solution was placed in a 42°C constant temperature incubator for 4 hours to react and form a gel. 2+ )gel

[0097] Weigh 9.60 g of sodium caseinate in 71 mL of deionized water, stir at 70° C. for 4 h until the sodium caseinate is completely hydrated, and add deionized water to 80 g to prepare a 12% (w / w) sodium caseinate solution;

[0098] The mass of the sodium caseinate solution was supplemented to 120 g, and the mixture was stirred at 70°C for 1 hour. Then, 10 mL of deionized water was quickly added to dissolve 0.716 g of sodium citrate dihydrate and 0.16 g of anhydrous calcium chloride at 70°C to prepare a mixed solution, and 1 mol / L of NaOH was added dropwise to adjust the pH value of the mixed system to 6.8.

[0099] 4.0 g of glucono-δ-lactone was weighed and dissolved in 20 mL of deionized water. After vortexing for 10 seconds, the mixture was immediately added to the above-mentioned mixed system and stirred for 20 seconds to obtain a gel solution.

[0100] In the gel system, the mass fraction of sodium caseinate is 6%, the concentration of sodium citrate is 15 mmol / L, the concentration of calcium chloride is 9 mmol / L, and the mass fraction of glucono-δ-lactone is 2.5%.

[0101] The pH of the gel solution was monitored; the gel solution was placed in a 42°C constant temperature incubator for 4 hours to react and form a gel. 2+ )gel

[0102] Weigh 9.60 g of sodium caseinate in 71 mL of deionized water, stir at 70° C. for 4 h until the sodium caseinate is completely hydrated, and add deionized water to 80 g to prepare a 12% (w / w) sodium caseinate solution;

[0103] Weigh 0.64 g of gellan gum in 60 mL of deionized water, stir at 70° C. for 4 h until the gellan gum is completely hydrated, and add deionized water to 50 g to prepare a 1.0% (w / w) gellan gum solution;

[0104] The gellan gum solution and the sodium caseinate solution were mixed, and the mixture was stirred at 70°C for 1 hour, and then deionized water was added to a system mass of 130 g. A mixed solution prepared by dissolving 0.716 g of sodium citrate dihydrate and 0.16 g of anhydrous calcium chloride in 10 mL of deionized water at 70°C was quickly added, and 1 mol / L of NaOH was added dropwise to adjust the pH value of the mixed system to 6.8.

[0105] 4.0 g of glucono-δ-lactone was weighed and dissolved in 20 mL of deionized water. After vortexing for 10 seconds, the mixture was immediately added to the above-mentioned mixed system and stirred for 20 seconds to obtain a gel solution.

[0106] The mass fraction of sodium caseinate in the gel system is 6%, the mass fraction of gellan gum is 0.4%, the concentration of sodium citrate is 9 mmol / L, the concentration of calcium chloride is 15 mmol / L, and the mass fraction of glucono-δ-lactone is 2.5%.

[0107] The pH of the gel solution was monitored; the gel solution was placed in a 42°C constant temperature incubator for 4 hours to react and form a gel. 2+ )gel

[0108] Weigh 9.60 g of sodium caseinate in 55 mL of deionized water, stir at 70° C. for 4 h until the sodium caseinate is completely hydrated, and add deionized water to 64 g to prepare a 15% (w / w) sodium caseinate solution;

[0109] Weigh 0.96 g of gellan gum into 60 mL of deionized water, stir at 70° C. for 4 h until the gellan gum is completely hydrated, and add deionized water to 80 g to prepare a 1.2% (w / w) gellan gum solution;

[0110] The gellan gum solution and the sodium caseinate solution were mixed, and the mixture was stirred at 70°C for 1 hour, and then deionized water was added to a system mass of 130 g. A mixed solution prepared by dissolving 0.716 g of sodium citrate dihydrate and 0.16 g of anhydrous calcium chloride in 10 mL of deionized water at 70°C was quickly added, and 1 mol / L of NaOH was added dropwise to adjust the pH value of the mixed system to 6.8.

[0111] 4.0 g of glucono-δ-lactone was weighed and dissolved in 20 mL of deionized water. After vortexing for 10 seconds, the mixture was immediately added to the above-mentioned mixed system and stirred for 20 seconds to obtain a gel solution.

[0112] The mass fraction of sodium caseinate in the gel system is 6%, the mass fraction of gellan gum is 0.6%, the concentration of sodium citrate is 9 mmol / L, the concentration of calcium chloride is 15 mmol / L, and the mass fraction of glucono-δ-lactone is 2.5%.

[0113] The pH of the gel solution was monitored; the gel solution was placed in a 42°C constant temperature incubator for 4 hours to react and form a gel.

[0114] For the convenience of comparison, the amounts of the components of the above Examples 1, 2 and 3 and Comparative Examples 1, 2, 3 and 4 are statistically organized as shown in Table 1 below.

[0115] Table 1 Components of Examples and Comparative Examples

[0116]

[0117] The gels prepared in the embodiments and comparative examples in Table 1 above were observed for appearance, statistically analyzed for pH changes, and statistically analyzed for water holding capacity and hardness, as shown below.

[0118] (1) Gel appearance

[0119] The appearance of the gels prepared in Examples 1 to 3 and the gels prepared in Comparative Examples 1 to 4 was recorded. The appearance of the gels prepared in Examples 1 to 3 was as follows: Figure 1 , Figure 2 and Figure 3 As shown, the appearance of the gels prepared in Comparative Examples 1 to 4 is as follows Figure 4 , Figure 5 , Figure 6 and Figure 7 The specific analysis is as follows:

[0120] In comparative example 1, see Figure 4 , in the absence of Ca 2+ Under such circumstances, there is electrostatic repulsion between sodium caseinate and gellan gum. During the fermentation process, sodium caseinate and gellan gum have poor compatibility, resulting in poor water holding capacity of the gel, which is manifested in phase separation and easy precipitation of water.

[0121] In Example 1, Example 3 and Comparative Example 2, see Figure 1 , Figure 3 and Figure 5Under the action of gellan gum, the water holding capacity of the gel is significantly improved, and it is not easy to precipitate water. In Example 1, Example 3 and Example 1, the specific Figure 1 , Figure 3 and Figure 4 Under the action of calcium ions, the water holding capacity of the gel is significantly improved and it is not easy to precipitate water.

[0122] In Example 1 to Example 3, see Figure 1 , Figure 2 and Figure 3 The calcium ions released by sodium citrate chelated calcium cross-link with the phosphate residues in sodium caseinate. When the acidified sustained-release agent induces the sodium caseinate-gellan gum dispersion system to slowly acidify to the isoelectric point of casein to form casein gel, casein gradually releases part of the Ca 2+ , can cross-link with the anionic sites of gellan gum, thus forming a casein-gellan gum interpenetrating double network gel during the acidification process, that is, when the pH value drops to 4.6, gellan gum and sodium caseinate in the presence of Ca 2+ Under the action of , a denser double network gel is formed.

[0123] In addition, when there is no gellan gum, sodium caseinate and CaCl 2 The gel formed by this system only has the cross-linking effect between calcium ions and sodium caseinate. Therefore, the hardness and water holding capacity of the gel in this system are not optimal (see Fig. 9 and Fig.10 ); Gellan gum is negatively charged. As the pH value decreases to the isoelectric point of sodium caseinate, sodium caseinate becomes partially positively charged. When the concentration of gellan gum in the system is too high, sodium caseinate and calcium ions cannot completely neutralize the negative charge of the gellan gum tape, resulting in a slight decrease in hardness and water holding capacity (see Fig. 9 and Fig.10 ).

[0124] (2) pH change of gel solution

[0125] The pH changes of the gel solutions prepared in Examples 1 to 3 and Comparative Examples 1 to 4 are as follows: Fig.13 As shown in the figure, after adding glucono-δ-lactone, as the fermentation proceeds, the gel systems of Examples 1 to 3 and Comparative Examples 1 to 4 can all reach the isoelectric point of sodium caseinate pH 4.6 or less, indicating that the gel system achieves the release of Ca from casein. 2+ conditions.

[0126] (3) Gel water holding capacity and hardness

[0127] The water holding capacity and hardness of the gels prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were tested. The water holding capacity test results are as follows: Fig. 9The hardness test results are shown in Fig.10 The specific analysis is as follows:

[0128] With the increase of gellan gum concentration, the water holding capacity and hardness of the gel first increased and then decreased. 2+ The group without Ca 2+ The water holding capacity and hardness of the group are higher. This is because gellan gum and sodium caseinate have the conditions to form a co-continuous phase, and Ca 2+ The formation of a double network structure of gellan gum and sodium caseinate gel was promoted; therefore, in the gel system prepared in Example 3, the gellan gum concentration was 0.5%, Ca 2+ When the concentration was 9 mmol / L, the gel showed the best water holding capacity and hardness. 2+ The water holding capacity of the gellan gum-sodium caseinate bicontinuous phase gel under the condition of gellan gum-sodium caseinate was increased by about 64%, and the hardness was increased by about 187%; the water holding capacity of the gel of Example 3 was increased by about 233% and the hardness was increased by about 645% compared with the caseinate sodium calcium ion gel under the condition of no gellan gum in Comparative Example 2, so Ca 2+ It has a synergistic effect with acidifying sustained-release agents.

[0129] 3. Application experiment of casein-gellan gum gel yogurt

[0130] (I) Preparation of casein-gellan gum gel yogurt

[0131] In the following embodiments, according to Fig.11 The preparation process shown uses casein-gellan gum gel to prepare yogurt, and the specific steps include: (1) dissolving an appropriate amount of whole milk powder in water and swelling it at 75°C for 1 hour to obtain an emulsion; (2) dissolving an appropriate amount of gellan gum in water and swelling it at 80°C for 1 hour to obtain a gellan gum solution; (3) mixing the emulsion and the gellan gum solution to obtain a mixed solution a; (4) adding an appropriate amount of calcium citrate solution to the mixed solution a to obtain a mixed solution b; (5) homogenizing the mixed solution b at 100 bar to obtain a mixed solution c; (6) taking 400 g of the mixed solution c for pasteurization, adding an appropriate amount of glucono-δ-lactone and fermenting it at 42°C.

[0132] In the following examples, due to the small amount of loss in homogenization or other steps during the preparation of yogurt, the calculated percentages have experimental errors, which are normal. In addition, the 80% casein percentage refers to the casein content in whole milk powder protein; the mass concentrations of calcium chloride and sodium citrate are calculated based on the entire solution system.

[0133] Example 4 Preparation of casein-gellan gum gel yogurt

[0134] Yogurt was prepared according to the above method, wherein the amounts of whole milk powder, gellan gum, calcium chloride, sodium citrate and GDL were as shown in Table 2 below.

[0135] Table 2 Ratios of raw materials for preparing yogurt in Example 4

[0136]

[0137] Comparative Example 5 Yogurt Preparation (without gellan gum)

[0138] Yogurt was prepared according to the above method without adding gellan gum, wherein the amounts of whole milk powder, calcium chloride, sodium citrate and GDL were as shown in Table 3 below.

[0139] Table 3 Ratios of raw materials for preparing yogurt in Comparative Example 5

[0140]

[0141] Comparative Example 6 Yogurt Preparation (without calcium chloride and sodium citrate)

[0142] Yogurt was prepared according to the above method without adding calcium chloride and sodium citrate, wherein the amounts of whole milk powder, gellan gum and GDL are shown in Table 4 below.

[0143] Table 4 Ratios of raw materials for preparing yogurt in Comparative Example 6

[0144]

[0145] (II) Performance verification of casein-gellan gum gel yogurt

[0146] For the convenience of comparison, the amounts of the components of the yogurts prepared in the above Example 4, Comparative Example 5 and Comparative Example 6 are statistically sorted, as shown in the following Table 5.

[0147] Table 5 Components of Examples and Comparative Examples

[0148]

[0149] In Table 5 above, the mass fractions or mass concentrations of casein, gellan gum, sodium citrate and calcium chloride in Example 4, Comparative Example 5 and Comparative Example 6 are obtained by converting the total solution system after the mixed solution is homogenized and the GDL solution is added.

[0150] The yogurts prepared in the embodiments and comparative examples in Table 5 were observed for appearance, statistically analyzed for pH changes, and analyzed for water holding capacity and texture, as shown below.

[0151] (1) Appearance of yogurt

[0152] The appearance of the yogurt prepared in Example 4, Comparative Example 5 and Comparative Example 6 was recorded. Fig.12 As shown, the yogurt prepared in Comparative Examples 5 and 6 is shown in Fig.13 and Fig.14 The specific analysis is as follows:

[0153] In comparative example 5, see Fig.13 In the absence of gellan gum, the surface is rough, there are many bubbles, and whey precipitation is serious. Fig.14 In the case of adding only gellan gum, the yogurt surface is smooth, there are fewer bubbles, and whey precipitation is significantly reduced. Fig.12 Under the action of gellan gum and calcium ions, the yogurt has a tight structure, a smooth surface, basically no bubbles, and basically no whey precipitation.

[0154] (2) Yogurt acidity and water holding capacity

[0155] The acidity and water holding capacity of the yogurts prepared in Example 4, Comparative Example 5 and Comparative Example 6 are as follows: Fig.15 and Fig.16 The specific analysis is as follows: after adding glucono-δ-lactone, as the fermentation proceeds, the acidity of the yogurt prepared in Example 4 and Comparative Examples 5 and 6 can reach above 70°, meeting the requirements of fermented yogurt.

[0156] Compared with comparative example 6, the water holding capacity of example 4 is increased by 7%, which is due to the fact that some Ca contained in milk 2+ Promotes cross-linking of gellan gum and milk, but due to the Ca in milk 2+ The content of Ca 2+ The introduction of gellan gum forms more double network structures, which enhances the water holding capacity of yogurt. Compared with comparative example 5, the water holding capacity of Example 4 is increased by 68%. The reason is that with the optimization of the yogurt system by gellan gum, the texture of yogurt is enhanced, resulting in a significant increase in the water holding capacity of yogurt.

[0157] (3) Yogurt texture

[0158] The texture of the yogurt prepared in Example 4, Comparative Example 5 and Comparative Example 6 is as follows: Fig.17 , Fig.18 , Fig.19 and Fig. 20 The specific analysis is as follows:

[0159] With the addition of gellan gum and Ca 2+The introduction of gellan gum significantly enhances the texture of yogurt. Compared with comparative example 5, the consistency, viscosity, firmness and cohesion of example 4 are all greatly enhanced, among which the consistency is increased by 678%, the viscosity is increased by 583%, the firmness is increased by 1430%, and the cohesion is increased by 905%. The reason is that with the introduction of gellan gum, the concentration of the total polymer in the system is increased, the compatibility of each substance is good, and Ca 2+ It promotes the formation of a double network structure between gellan gum and protein.

[0160] Compared with comparative example 6, the texture of Example 4 is more optimized, in which the thickness is slightly reduced, the viscosity is increased by 178%, the firmness is not much different, and the cohesion is increased by 316%. The reason is that gellan gum strengthens the yogurt system mainly in terms of viscosity and cohesion, which proves that Ca 2+ It promotes the formation of a double network structure between gellan gum and protein, which can significantly improve the stability of the yogurt system.

[0161] (4) Yogurt sensory electronic tongue test

[0162] The texture of the yogurt prepared in Example 4, Comparative Example 5 and Comparative Example 6 is as follows: Fig.21 As shown. The specific analysis is as follows: The electronic tongue principal component analysis shows that the contribution rate of the first principal component PC1 reaches 99.38%, proving that the first principal component can basically represent the flavor value of the product. The flavor differences between the samples of Example 4 and Comparative Example 5 are smaller, and the flavor difference between Comparative Example 6 and the first two is greater. However, the horizontal and vertical axis distance unit (=0.5) value of the PCA graph is small, indicating that the difference in flavor between the samples of Example 4, Comparative Example 5 and Comparative Example 6 is not significant, that is, the yogurt prepared using the casein-gellan gum dual gel system of the present invention does not have a negative impact on the taste.

[0163] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be covered by the scope of the claims of the present invention.

Claims

1. A casein-gellan gum double gel, characterized in that: The raw materials include casein and / or casein sodium salt, gellan gum, calcium salt, chelating agent and acidifying sustained-release agent; the mass ratio of casein and / or casein sodium salt to gellan gum is 6:(0.05-0.5), the mass fraction of gellan gum is 0.05%-0.5%; the mass concentration of calcium salt is 3mmol / L-15mmol / L, and the mass concentration of chelating agent is 3mmol / L-15mmol / L; the pH of casein-gellan gum double gel is 3.5-4.6; and the chelating agent is used for chelating calcium ions.

2. The casein-gellan gum double gel according to claim 1, characterized in that: The calcium salt is selected from calcium chloride or calcium gluconate; the chelating agent is selected from sodium citrate, sodium acetate or sodium hexametaphosphate.

3. The casein-gellan gum double gel according to claim 1 or 2, characterized in that: The acidifying sustained-release agent is selected from L-malic acid, glucono-δ-lactone or fermentation bacteria.

4. The casein-gellan gum double gel according to claim 1 or 2, characterized in that: The mass fraction of the acidified sustained-release agent is 2.0%-3.5%.

5. The casein-gellan gum double gel according to claim 3, characterized in that: The mass fraction of the acidified sustained-release agent is 2.0%-3.5%.

6. The method for preparing the casein-gellan gum double gel according to any one of claims 1 to 5, characterized in that: include: The casein and / or casein sodium salt solution is mixed with the gellan gum solution to obtain a mixed solution; The mixed solution is mixed with a calcium ion chelating agent and an acidifying slow-release agent for fermentation at 40-50°C until the pH reaches 3.5-4.6 to obtain a casein-gellan gum double gel; the calcium ion chelating agent is formed by chelating calcium salt with a chelating agent.

7. Use of the casein-gellan gum double gel according to any one of claims 1 to 5 in the preparation of fermented milk.

8. The use of the casein-gellan gum double gel according to claim 7 in preparing fermented milk, comprising: Fermented milk is prepared by using casein-gellan gum double gel, wherein a casein-containing emulsion and a gellan gum solution are mixed to obtain a mixed solution a; The mixed solution a is mixed with the calcium ion chelating agent, homogenized, and sterilized to obtain the mixed solution b; the mixed solution b is mixed with the acidifying slow-release agent and fermented at 40-50° C. to obtain the fermented milk; the calcium ion chelating agent is formed by chelating the calcium salt with the chelating agent.

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