A composite cheese dairy product and process for its preparation

Abstract

The present application relates to the technical field of dairy processing, and discloses a compound cheese dairy product and a preparation process thereof.The product is prepared from purified water, rennet casein, anhydrous butter, compound molten salt, alginate propylene glycol ester and trehalose premixed solid phase powder, low-methoxyl pectin aqueous solution and a proper amount of lactic acid solution.The preparation process comprises the following steps: the basic raw materials are heated and stirred in an emulsification reactor, the premixed powder is added to form an interface adsorption layer through high-shear emulsification;the temperature is lowered, and lactic acid solution is added dropwise to promote the release of calcium ions, and the free calcium is uniformly distributed through isothermal mechanical shearing;then, the pectin aqueous solution is added to crosslink with the free calcium under low shear to build a three-dimensional gel skeleton;finally, hot filling and cooling and shaping are performed.The present application reduces the fat bleeding rate of cheese when heated, slows down the texture hardening during low-temperature storage, and solves the defects of agglomeration and sanding during processing.

Description

Technical Field

[0001] This invention relates to the field of dairy processing technology, specifically to a compound cheese dairy product and its preparation process. Background Technology

[0002] Compound cheese is a product made by adding emulsified salt, water, fat and other ingredients to cheese as the main raw material, and then heating and mixing them to emulsify them. Due to its adjustable flavor and specific processing characteristics, it is widely used in baking, catering and other fields.

[0003] In practical downstream cooking or baking applications, compound cheeses usually need to undergo secondary high-temperature heat processing. Under heat, the internal emulsified structure of existing compound cheeses is often difficult to maintain stability. Dispersed liquid fat globules will collide and aggregate, thereby destroying the original multiphase system, causing severe phase separation and free fat leakage. This directly affects the appearance and eating experience of the food. During long-term low-temperature refrigeration or cold chain circulation, due to the limited ability of the existing product matrix to bind water, free water will migrate internally and cause the protein skeleton to shrink. Macroscopically, this manifests as the cheese texture gradually hardening and drying out, losing its original elasticity and smoothness.

[0004] To improve the heat stability and water retention capacity of compound cheese, the conventional method is to introduce hydrophilic polymer materials into the formula for structural thickening. However, in actual large-scale production, when dry powdered polymer materials are directly added to an aqueous system, the powder surface will quickly hydrate and form a dense film. This film hinders the further dissolution of the internal powder, resulting in the formation of hard agglomerates that are difficult to disperse in the system. At the same time, cheese systems naturally contain calcium ions. When the ingredients contain colloidal macromolecules that can react with calcium ions, the free calcium ions in the initial stage of material mixing are often unevenly distributed, causing disordered cross-linking of colloids in areas with high concentrations of calcium ions. This uneven micro-cross-linking reaction will produce tiny hard gel particles in the matrix, resulting in a grainy texture in the final product, which is difficult to meet the production requirements of high-quality dairy products. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a compound cheese dairy product and its preparation process, which solves the problems of fat seepage during heat processing, hardening of texture during low-temperature storage, and agglomeration and sanding of polymer ingredients during processing in existing compound cheese products.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] In a first aspect, the present invention provides a compound cheese dairy product comprising the following raw materials in parts by weight: 41.2 to 64.2 parts purified water; 12 to 18 parts rennet casein; 20 to 30 parts anhydrous butter; 1.0 to 2.0 parts compound molten salt; 1.2 to 2.5 parts propylene glycol alginate and trehalose premixed solid powder, wherein the propylene glycol alginate and trehalose premixed solid powder utilizes trehalose to physically occupy and pull apart the polymer chains in the system to prevent aggregation, and forms an adsorption layer with steric hindrance at the oil-water interface; 1.6 to 6.3 parts low-methoxyl pectin aqueous solution, wherein the low-methoxyl pectin aqueous solution coordinates and crosslinks with free calcium ions released in the system to form a macroscopic continuous three-dimensional network structure that physically traps fat-protein complexes; and a lactic acid solution, wherein the amount of lactic acid solution added is an appropriate amount required to adjust the pH of the preparation system to 5.5 to 5.6.

[0008] By adopting the above technical solution, the present invention constructs an anti-physical migration network inside the composite cheese matrix. In terms of its specific formation process, when the raw materials begin to disperse, the trehalose crystals in the premixed solid phase use their own physical volume to pull apart the molecular chains of propylene glycol alginate. When the powder enters the aqueous phase, the dissolving effect of the trehalose crystals changes the surface dissolution kinetics of the propylene glycol alginate dry powder, preventing the dry powder surface from prematurely hydrating to form a dense gel film. This directly avoids the internal powder from being encapsulated and forming irreversible hard agglomerates. As the system enters the emulsification process, the free propylene glycol alginate molecules migrate to the contact interface between the anhydrous butter and the aqueous phase and undergo physical adsorption, forming an interface protective layer with steric hindrance effect.

[0009] The interface protective layer can reduce the probability of collisions and aggregation of internal liquid free fat globules under high temperature conditions, thereby inhibiting the formation of continuous oil phase. To construct a stable cross-linking network, the system uses lactic acid to lower the pH value of the environment to near the isoelectric point, breaking the original chelation state of calcium ions inside rennet casein by the composite molten salt, so that the free calcium ions are released and enter the continuous aqueous phase. Subsequently, in the low methoxy pectin aqueous solution, the galacturonic acid units on the low methoxy pectin molecular chain coordinate cross-link with the free calcium ions, spontaneously constructing a three-dimensional gel skeleton in the continuous phase.

[0010] The three-dimensional gel framework spatially traps dispersed fat-protein complexes. When subjected to high-temperature heat processing, the steric hindrance of the micro-interface and the trapping network work together to limit the physical deformation and extrusion migration path of the heat-expanded fat, reducing the fat leakage rate of the finished product. When the product is stored at low temperature for a long time, the pores of the three-dimensional gel framework can bind the free water inside the system, increase the fluid diffusion resistance, slow down the rate of free water migration and contraction to the protein surface, and maintain the stable texture, elasticity and mechanical state of the finished product.

[0011] Preferably, the composite molten salt is composed of sodium hexametaphosphate and trisodium citrate, and the weight ratio of sodium hexametaphosphate to trisodium citrate is 1.5:1 to 2.5:1.

[0012] By adopting the above technical solution, sodium hexametaphosphate provides strong dissociation and chelation capabilities, while trisodium citrate provides the thermodynamic buffering effect of the system. When the two are combined in this ratio, the casein micelle structure can be quickly broken in the initial heating stage to promote fat emulsification, and the buffering capacity of the system can be maintained in the subsequent acidification and pH reduction stage to ensure the stable dissociation and release of calcium ions.

[0013] Preferably, the propylene glycol alginate and trehalose premixed solid powder is prepared by mechanically dry mixing propylene glycol alginate and crystalline trehalose at room temperature, and the weight ratio of the two is 1:4 to 1:5.

[0014] By adopting the above technical solution, this ratio is set so that the total volume of crystalline trehalose can basically physically isolate the propylene glycol alginate powder particles, ensuring that when the premix enters the aqueous phase, no hydration dead zone will be generated due to excessively high local polymer concentration, thereby improving the overall uniformity of material dispersion.

[0015] Preferably, the low-methoxyl pectin aqueous solution is prepared by dissolving low-methoxyl pectin and purified water under heating and stirring conditions, and the weight ratio of the two is 1:15 to 1:20.

[0016] By adopting the above technical solution, the low-methoxyl pectin is pre-converted into a homogeneous solution of a specific concentration, eliminating the physical entanglement of macromolecular chain segments in the dry state. This pre-dissolved state can avoid the rapid and disordered surface cross-linking caused by direct contact between polymer dry powder and free calcium ions, ensuring the smooth progress of the network construction process.

[0017] Secondly, the present invention provides a preparation process for a compound cheese dairy product, comprising the following steps: S1. Add purified water, rennet casein, anhydrous butter and compound molten salt into the emulsification reactor, turn on the outer wall scraper and turn on the heating source to make the material in the reactor rise to a constant temperature. S2. Under constant temperature conditions, the premixed solid powder of propylene glycol alginate and trehalose is uniformly added into the emulsification reactor, and the inner high-shear homogenizing head is turned on simultaneously to carry out a continuous shear reaction. S3. Close the inner high-shear homogenizer head, control the material in the reactor to cool down to the set temperature, and dynamically add lactic acid solution until the pH of the system is stably adjusted down and maintained in the target range, then stop adding solution. S4. Maintain the isothermal state inside the vessel, increase the stirring speed of the outer wall scraper, and continuously perform constant mechanical shearing. This isothermal shearing delay operation overcomes the mass transfer resistance of the aqueous phase and smooths out the local concentration gradient of free calcium ions. S5. Pump the low-methoxyl pectin aqueous solution into the emulsification reactor and reduce the stirring speed of the outer wall scraper to allow the pectin to continuously react and crosslink with the homogeneously distributed free calcium. S6. Use the pump to pump the material out of the kettle to complete the hot filling of the mold, and then quickly cool down and shape it to obtain the compound cheese dairy product.

[0018] By adopting the above technical solution, this process achieves the stable generation of an anti-migration physical network by controlling the timing of material addition and the stirring method. The raw materials initially establish a primary emulsion structure under the action of heating and bidirectional shearing. At this time, propylene glycol alginate is uniformly dispersed in the strong shear flow field and completes interfacial adsorption arrangement. As the process progresses, the cooling operation increases the viscosity of the fluid system matrix, and the addition of lactic acid makes the acidity approach the isoelectric point of the protein, forcing calcium ions to dissociate.

[0019] To ensure a uniform distribution of the released calcium ions, the system undergoes an isothermal shear-delayed operation. During this stage, no cross-linking reactants are introduced. Instead, the mechanical energy input from the outer wall scraping and stirring is used to continuously drive the fluid through physical displacement in the high-viscosity aqueous phase. This overcomes mass transfer resistance and uniformly disperses the locally high concentration of free calcium ions throughout the entire reaction system. After the aforementioned treatment, low-methoxyl pectin is introduced into the system where a uniform distribution of free calcium has been achieved. At the same time, the stirring speed is reduced to provide a low-stress flow field environment, allowing the pectin macromolecules to undergo gentle coordination cross-linking under a uniform ion concentration. This prevents local calcium ion excess from causing disordered reactions that produce hard sand particles, reduces the sand-forming rate of the finished product, and ensures the consistency of the texture.

[0020] Preferably, in S1, the temperature of the material inside the vessel is controlled to be constant at 80 to 88°C, and the rotation speed of the outer wall scraper is maintained at 20 to 50 r / min; in S2, the rotation speed of the inner high-shear homogenizer is set to 2000 to 3500 r / min, and the shear reaction time is 10 to 20 minutes.

[0021] By employing the above technical solution, the established isothermal range allows the protein and cream to fully melt and reduces their apparent viscosity. The inner layer utilizes high-speed shearing to tear large fat globules, combined with the outer layer's low-speed scraping and stirring to maintain material flow and renewal. This allows the solid powder to rapidly hydrate in a strong flow field, accelerating its migration and adsorption to the fat interface.

[0022] Preferably, in S3, during the process of closing the inner high-shear homogenizing head, controlling the cooling of the material in the reactor and dynamically adding lactic acid solution, the temperature of the material in the reactor is controlled to drop to 70 to 74°C at a cooling rate of 1.5 to 2.5°C / min, and the mass fraction of the added lactic acid solution is 10%.

[0023] By adopting the above technical solution, a gradual cooling rate is set to avoid the generation of rapid thermal crystallization shrinkage stress inside the fat. A lactic acid concentration of 10% can meet the acidification requirements without introducing too much external moisture, and also limit the instantaneous drop in local acidity, providing reaction time for the stable dissociation of calcium ions.

[0024] Preferably, in S4, while maintaining the isothermal state inside the vessel and increasing the stirring speed of the outer wall scraper while continuously performing constant mechanical shearing, after the pH is stabilized and lowered, the system is maintained at an isothermal temperature of 70 to 74°C, and the stirring speed of the outer wall scraper is increased to 50 to 80 r / min. Under this condition, constant mechanical shearing is performed for 8 to 15 minutes.

[0025] By adopting the above technical solution, the increased rotation speed expands the range of shear influence, and the constant temperature mechanical work within the set time fully eliminates the internal ion concentration difference caused by acid addition and pH reduction, so as to promote the stable retention and distribution of released calcium ions in the protein interstitial space, thus constructing highly uniform subsequent cross-linking reaction conditions.

[0026] Preferably, in step S5, the step of pumping the low-methoxyl pectin aqueous solution into the emulsification reactor and reducing the stirring speed of the outer wall scraper is carried out while maintaining a constant temperature of 70 to 74°C inside the reactor and reducing the stirring speed of the outer wall scraper to 20 to 40 r / min, and continuing the reaction for 8 to 12 minutes.

[0027] By adopting the above technical solution, the rotation speed is reduced to decrease the physical damage to the newly formed macromolecular gel skeleton caused by mechanical shearing. Within the set time and temperature conditions, pectin molecules obtain sufficient physical space to complete the assembly of coordination bonds and generate a highly elastic network structure.

[0028] Preferably, in step S6, during the process of pumping the material out of the vessel using the pump body to complete the hot filling and rapid cooling and shaping of the mold, the hot filling of the mold is completed at 70 to 74°C, and then the material is sent into the cooling tunnel to be rapidly cooled to 2 to 6°C.

[0029] By adopting the above technical solution, maintaining the filling temperature can preserve the plasticity and flowability of the fluid matrix. The subsequent rapid cooling and shaping causes the internal liquid free fat to solidify instantly, fixing the relative spatial positions of the multiphase components and completing the final shaping of the physical network structure.

[0030] This invention provides a compound cheese dairy product and its preparation process. It has the following beneficial effects: 1. This invention reduces the fat leakage rate of compound cheese during heat processing. The propylene glycol alginate molecules in the system are adsorbed at the interface between anhydrous butter and the aqueous phase, forming an adsorption layer with steric hindrance effect, reducing the probability of collision and aggregation of liquid fat globules. At the same time, low-methoxyl pectin coordinates and crosslinks with the free calcium ions released in the system to construct a continuous three-dimensional gel framework, which physically traps the fat-protein complex. These two aspects together limit the physical deformation and extrusion path of the heat-expanded fat, preventing phase separation.

[0031] 2. This invention improves the problem of texture hardening of finished products during long-term low-temperature storage. The three-dimensional gel framework formed by cross-linking of low-methoxyl pectin and free calcium ions can bind the free water inside the system and increase the diffusion resistance of fluid inside the matrix. This structure slows down the rate of free water migration to the protein surface and causes shrinkage, so that the product can maintain a stable moisture distribution and texture during low-temperature storage.

[0032] 3. This invention solves the problems of agglomeration and localized sanding defects in polymer ingredients during processing. It utilizes the physical occupancy of trehalose to isolate propylene glycol alginate powder, avoiding the phenomenon of excessively rapid surface hydration of the powder when it is added to water, which would result in a dense film encapsulating the internal dry powder. Combined with the isothermal shearing operation after cooling and acidification in the preparation process, the free calcium ions are evenly dispersed in the matrix. Then, pre-dissolved pectin is added for low-speed cross-linking, preventing disordered reactions caused by excessively high local calcium ion concentrations and ensuring the smoothness of the matrix texture. Attached Figure Description

[0033] Figure 1 This is a comparison chart of solid-phase dispersion hydration and slag retention rate in Examples 1-4 and Comparative Examples 1-7 of the present invention; Figure 2 This is a comparison chart of the anti-local condensation sanding rate test results of Examples 1-4 and Comparative Examples 1-7 of the present invention; Figure 3 This is a comparison chart of the semi-interpenetrating polymer network energy storage modulus measurement results of Examples 1-4 and Comparative Examples 1-7 of the present invention; Figure 4 This is a comparison chart showing the measurement results of the loss tangent of the semi-interpenetrating polymer network in Examples 1-4 and Comparative Examples 1-7 of the present invention; Figure 5 The graphs show the determination of free fat exudation rate during high-temperature baking in Examples 1-4 of this invention. Figure 6 The graphs show the determination of free fat exudation rate during high-temperature baking in Comparative Examples 1-7 of this invention. Figure 7 The graphs show the changes in texture and hardness during long-term refrigeration in Examples 1-4 of this invention. Detailed Implementation

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0036] Rennet casein: Food grade, with a dry protein content of not less than 88%; Anhydrous butter: food grade, fat content not less than 99.8%; Sodium hexametaphosphate: food grade, CAS number 10124-56-8; Trisodium citrate (dihydrate): food grade, CAS number 6132-04-3; Crystalline trehalose: food grade, purity not less than 99.0%, CAS number 6138-23-4; Propylene glycol alginate: food grade, CAS number 9005-37-2; Pectin: Food grade, CAS number 9000-69-5, low methoxyl pectin; Lactic acid: food grade, purity not less than 85%, CAS number 50-21-5, prepared with purified water to a mass fraction of 10% before use.

[0037] In this invention, the units of measurement for all materials and solvents are uniformly referred to as parts by weight.

[0038] Preparation Example 1: This preparation example provides a method for preparing a premixed solid powder of propylene glycol alginate and trehalose, including the following steps: 0.35 parts by weight of propylene glycol alginate and 1.5 parts by weight of crystalline trehalose were placed in a three-dimensional mixer and mechanically dry-mixed at room temperature for 5.5 minutes to obtain propylene glycol alginate and trehalose premixed solid powder A.

[0039] Preparation Example 2: This preparation example provides a method for preparing a premixed solid powder of propylene glycol alginate and trehalose, including the following steps: 0.2 parts by weight of propylene glycol alginate and 1.0 parts by weight of crystalline trehalose were placed in a three-dimensional mixer and mechanically dry-mixed for 3 minutes at room temperature to obtain propylene glycol alginate and trehalose premixed solid powder B.

[0040] Preparation Example 3: This preparation example provides a method for preparing a premixed solid powder of propylene glycol alginate and trehalose, including the following steps: 0.5 parts by weight of propylene glycol alginate and 2.0 parts by weight of crystalline trehalose were placed in a three-dimensional mixer and mechanically dry-mixed for 8 minutes at room temperature to obtain propylene glycol alginate and trehalose premixed solid powder C.

[0041] Preparation Example 4: This preparation example provides a method for preparing a low-methoxyl pectin aqueous solution, including the following steps: 0.2 parts by weight of low-methoxyl pectin were added to 3.5 parts by weight of purified water at 72°C and stirred until completely dissolved to prepare a homogeneous low-methoxyl pectin aqueous solution A, which was then kept at 72°C for later use.

[0042] Preparation Example 5: This preparation example provides a method for preparing a low-methoxyl pectin aqueous solution, including the following steps: Add 0.1 parts by weight of low-methoxyl pectin to 1.5 parts by weight of purified water at 70°C, stir until completely dissolved, and prepare a homogeneous low-methoxyl pectin aqueous solution B, and keep it at 70°C for later use.

[0043] Preparation Example 6: This preparation example provides a method for preparing a low-methoxyl pectin aqueous solution, including the following steps: 0.3 parts by weight of low-methoxyl pectin were added to 6.0 parts by weight of purified water at 74°C and stirred until completely dissolved to prepare a homogeneous low-methoxyl pectin aqueous solution C, which was then kept at 74°C for later use.

[0044] Example 1: This embodiment provides a preparation process for a compound cheese dairy product, including the following steps: S1. Add 52.95 parts of purified water, 15.0 parts of rennet casein, 25.0 parts of anhydrous butter, and 1.5 parts of a composite molten salt consisting of 1.0 part of sodium hexametaphosphate and 0.5 parts of trisodium citrate to the emulsification reactor. Turn on the outer wall scraper and set the speed to 35 r / min. Introduce jacketed heating steam to raise the temperature of the material in the reactor to a constant 85°C. S2. Under constant temperature of 85℃, 1.85 parts by weight of propylene glycol alginate and trehalose premixed solid powder A are evenly sprinkled into the emulsification reactor. Simultaneously, the inner high-shear homogenizing head is turned on, and the speed is set to 2500 r / min. The outer wall scraping stirring speed is kept constant, and the shear reaction is continued for 15 minutes. S3. Close the inner high-shear homogenizing head, leaving only the outer wall scraping agitator. Switch the jacket to cooling circulating water and control the material temperature in the reactor to drop to 72℃ at a cooling rate of 2.0℃ / min. At 72℃, add 10% lactic acid solution dropwise into the reactor in a thin stream using a metering pump. Dynamically monitor the pH in the reactor. Stop adding the solution when the pH of the system stabilizes and remains at 5.5. S4. After the addition of lactic acid is completed and the pH stabilizes at 5.5, maintain the jacket temperature to keep the inside of the vessel at an isothermal state of 72°C. Increase the stirring speed of the outer wall scraper to 60 r / min. Under this condition, continue mechanical constant shearing for 10 minutes to complete the isothermal shearing delay operation. S5. Pump 3.7 parts by weight of low methoxy pectin aqueous solution A into the emulsification reactor, maintain the temperature inside the reactor at 72°C, reduce the stirring speed of the outer wall scraper to 30 r / min, and continue the reaction for 10 minutes. S6. Use a positive displacement pump to pump the material out of the kettle, complete the hot filling of the mold at 72°C, and after filling, send it into the cooling tunnel to quickly cool down to 4°C to obtain the compound cheese dairy product.

[0045] Example 2: This embodiment provides a preparation process for a compound cheese dairy product, including the following steps: S1. Add 64.2 parts of purified water, 12.0 parts of rennet casein, 20.0 parts of anhydrous butter, and 1.0 part of a composite molten salt consisting of 0.6 parts of sodium hexametaphosphate and 0.4 parts of trisodium citrate into the emulsification reactor. Turn on the outer wall scraper and set the speed to 20 r / min. Introduce jacketed heating steam to raise the temperature of the material in the reactor to a constant 80°C. S2. Under constant temperature of 80℃, 1.2 parts by weight of propylene glycol alginate and trehalose premixed solid powder B are evenly sprinkled into the emulsification reactor. The inner high shear homogenizer head is turned on at the same time, and the speed is set to 2000 r / min. The outer wall scraping stirring speed is kept constant, and the shear reaction is continued for 10 minutes. S3. Close the inner high-shear homogenizer head, leaving only the outer wall scraper agitator. Control the temperature of the material in the reactor to drop to 70℃ at a cooling rate of 1.5℃ / min. At 70℃, add 10% lactic acid solution dropwise into the reactor using a metering pump. Stop adding the solution when the pH of the system is steadily adjusted down and maintained at 5.6. S4. After the addition of lactic acid is completed and the pH stabilizes at 5.6, maintain the jacket temperature to keep the inside of the vessel at an isothermal state of 70°C. Increase the stirring speed of the outer wall scraper to 50 r / min. Under this state, continue mechanical constant shearing for 8 minutes to complete the isothermal shearing delay operation. S5. Pump 1.6 parts by weight of low methoxy pectin aqueous solution B into the emulsification reactor, maintain the temperature inside the reactor at 70°C, reduce the stirring speed of the outer wall scraper to 20 r / min, and continue the reaction for 8 minutes. S6. Use a positive displacement pump to pump the material out of the kettle, complete the hot filling of the mold at 70°C, and send it into the cooling tunnel to quickly cool down to 6°C to obtain the compound cheese dairy product.

[0046] Example 3: This embodiment provides a preparation process for a compound cheese dairy product, including the following steps: S1. Add 41.2 parts of purified water, 18.0 parts of rennet casein, 30.0 parts of anhydrous butter, and 2.0 parts of a composite molten salt consisting of 1.43 parts of sodium hexametaphosphate and 0.57 parts of trisodium citrate into the emulsification reactor. Turn on the outer wall scraper and set the speed to 50 r / min. Introduce jacketed heating steam to raise the temperature of the material in the reactor to a constant 88°C. S2. Under constant temperature of 88℃, 2.5 parts by weight of propylene glycol alginate and trehalose premixed solid powder C are evenly sprinkled into the emulsification reactor, and the inner high shear homogenizing head is turned on simultaneously. The rotation speed is set to 3500 r / min, and the shear reaction is continued for 20 minutes. S3. Close the inner high-shear homogenizer head and control the temperature of the material in the reactor to drop to 74℃ at a cooling rate of 2.5℃ / min. At 74℃, add 10% lactic acid solution to the reactor dropwise through a metering pump. Stop adding the solution when the pH of the system is steadily adjusted down and maintained at 5.5. S4. After the addition of lactic acid is completed and the pH stabilizes at 5.5, maintain the jacket temperature to keep the inside of the vessel at an isothermal state of 74°C, increase the stirring speed of the outer wall scraper to 80 r / min, and continue mechanical constant shearing for 15 minutes. S5. Pump 6.3 parts by weight of low methoxy pectin aqueous solution C into the emulsification reactor, maintain the temperature inside the reactor at 74°C, reduce the stirring speed of the outer wall scraper to 40 r / min, and continue the reaction for 12 minutes. S6. Use a positive displacement pump to pump the material out of the kettle, complete the hot filling of the mold at 74°C, and send it into the cooling tunnel to quickly cool down to 2°C to obtain the compound cheese dairy product.

[0047] Example 4: This embodiment provides a preparation process for a compound cheese dairy product, including the following steps: S1. According to the weight, add 48.65 parts of purified water, 16.0 parts of rennet casein, 28.0 parts of anhydrous butter, and 1.8 parts of composite molten salt composed of 1.2 parts of sodium hexametaphosphate and 0.6 parts of trisodium citrate into the emulsification reactor, turn on the outer wall scraper and stir at a speed of 40 r / min, and keep the temperature constant at 83℃. S2. Under constant temperature of 83℃, 1.85 parts by weight of propylene glycol alginate and trehalose premixed solid powder A are evenly sprinkled into the emulsification reactor, and the inner high shear homogenizing head is turned on simultaneously. The rotation speed is set to 3000 r / min, and the shear reaction is continued for 12 minutes. S3. Close the inner homogenizing head, control the temperature inside the reactor to drop to 72℃ at a cooling rate of 2.0℃ / min, and add 10% lactic acid solution dropwise into the reactor through a metering pump until the pH of the system is stably adjusted down and maintained at 5.55, then stop adding the solution. S4. Maintain an isothermal state of 72°C inside the vessel, increase the stirring speed of the outer wall scraper to 65 r / min, and continue mechanical constant shearing for 12 minutes. S5. Pump 3.7 parts by weight of low methoxy pectin aqueous solution A into the emulsification reactor, maintain the temperature inside the reactor at 72°C, reduce the stirring speed of the outer wall scraper to 25 r / min, and continue the reaction for 10 minutes. S6. Complete the hot filling of the mold at 72℃, and then quickly cool it down to 4℃ to obtain the compound cheese dairy product.

[0048] Comparative Example 1: Compared with Example 1, the difference is that: trehalose, propylene glycol alginate and low-methoxyl pectin are not added to the formula, and the corresponding weight parts are made up in purified water; S2, S4 and S5 are omitted in the process, and the rest are the same.

[0049] Comparative Example 2: Compared with Example 1, the differences are as follows: no crystalline trehalose is added to the formula, and the amount of purified water is increased by 1.5 parts by weight accordingly; in S2, solid-phase premixing is not performed, and 0.35 parts by weight of propylene glycol alginate powder is directly sprinkled into the reaction vessel, and the rest are the same.

[0050] Comparative Example 3: Compared with Example 1, the difference is that: propylene glycol alginate is not added to the formula, and the amount of purified water is increased by 0.35 parts by weight; in step S2, 1.5 parts by weight of crystalline trehalose is directly added to the reaction vessel, and the rest are the same.

[0051] Comparative Example 4: Compared with Example 1, the difference is that S4 is omitted, that is, after S3 is completed and the pH stabilizes at 5.5, S5 is immediately performed to add low methoxyl pectin aqueous solution, and the rest are the same.

[0052] Comparative Example 5: Compared with Example 1, the difference is that the feeding sequence is changed, and in S2, propylene glycol alginate, trehalose and low methoxyl pectin are all added to the reactor at once; and the subsequent S5 is omitted, while the rest are the same.

[0053] Comparative Example 6: Compared with Example 1, the difference is that: low-methoxyl pectin is not added to the formula, and the amount of purified water is increased by 0.2 parts by weight accordingly; S5 is omitted in the process, and the rest are the same.

[0054] Comparative Example 7: The difference from Example 1 is that 10% lactic acid solution is not added in S3 to maintain the system's natural pH at the initial dissociation state; all other aspects are the same.

[0055] Test Example 1: Intermediate fluids and the final composite cheese products collected during the preparation process of Examples 1 to 4 and Comparative Examples 1 to 7 were used as the experimental subjects for this test.

[0056] After step S2 of each process group is completed, immediately take 200 grams of intermediate hot fluid from the reactor and slowly pour the fluid onto a preheated 80-mesh standard test sieve. Use 40°C warm purified water to rinse the sieve surface with a gentle flow of water. Stop rinsing once the sieve material no longer appears milky white and turbid. Collect the unhydrated polymer agglomerates and insoluble residues adhering to the sieve. Place the collected material in a vacuum oven at 105°C and dry it to a constant weight. Weigh and record the mass of the dried residue and calculate its percentage of the initial sampled fluid mass. Use this value as the sieve residue retention rate.

[0057] Weigh 500g of the compound cheese product after it has been refrigerated and shaped at 4℃, and place it in a jacketed mixing container with a constant temperature water bath. Slowly heat it to 75℃ to restore the system to a completely melted state. Add 2500ml of purified water preheated to 80℃ to the mixing cylinder, mix it with the melted cheese, and disperse it for 10 minutes at 500 rpm using a top-mounted stirrer. Pour all the dispersed diluted solution into a 100-mesh nylon filter for filtration. Use hot water to repeatedly wash away the fat droplets and free casein flocculents attached to the screen, and retain the hard, sandy granular coagulation on the screen. Dry the coagulation and weigh it, and calculate its mass percentage in the 500g finished product. This is used as the sanding rate index.

[0058] Table 1: Test data on slag retention rate and sand-forming rate of each embodiment and comparative example

[0059] According to Table 1 and Figure 1 and Figure 2 It can be seen that the slag retention rate of Examples 1 to 4 is maintained below 0.02%. In Comparative Example 2, after removing the premixed carrier of trehalose, propylene glycol alginate directly contacts the hot water phase, and the surface rapidly hydrates to form a dense local gel film. This surface effect encapsulates the internal dry powder and forms irreversible fish-eye agglomerates. The macroscopic retention rate increases accordingly to 0.841%. The comparative experiment shows that trehalose crystals physically occupy and pull apart the polymer chains in the solid phase. Combined with the hydration after entering the water, it changes the dissolution kinetics of the system and reduces the probability of polymer aggregation.

[0060] Regarding the sanding rate index, the test data reflects the engineering effect of the fluid dynamics shear delay period mechanism. In conventional processes, adding acid to lower the pH usually causes a sharp increase in local calcium ion concentration, leading to disordered cross-linking of pectin in the local microenvironment, forming hard sand particles. The sanding rate of Comparative Example 4, which did not set a delay period, reached 1.253%, confirming the tendency of a large amount of free calcium to coagulate under non-homogenized conditions. In the Example group, continuous mechanical work was performed by scraping and stirring under isothermal conditions. The macroscopic fluid kinetic energy was used to overcome the mass transfer resistance in the high-viscosity aqueous phase, so that the local free calcium was evenly distributed in the reactor. Subsequently, when low-methoxyl pectin was pumped in, the system already had a uniform low-concentration free calcium environment, and the cross-linking reaction proceeded slowly. The sanding rate of the finished product was stable at about 0.05%.

[0061] In Comparative Example 5, which uses a single-stage feeding method, the amount of slag and the sand-forming rate (1.682%) both showed a significant increase. This indicates that premature intervention of pectin at the high-temperature stage will interfere with the reconstruction of the lipoprotein interface and cause disordered reactions with the free phase, affecting the overall thermodynamic balance of the formulation. The cross-comparison of the above macroscopic parameters shows that this process is reproducible in actual preparation operations through the decoupling control of material components and step sequence.

[0062] Test Example 2: The composite cheese products prepared in Examples 1 to 4 and Comparative Examples 1 to 7 and refrigerated at 4°C for 24 hours were collected as test subjects. Round slices with a thickness of 2 mm and a diameter of 20 mm were cut from the center of each sample for later use.

[0063] The test was conducted using a dynamic rotational rheometer equipped with a Peltier temperature control system. A parallel plate rotor system with a diameter of 20 mm was selected, and the test gap was set to 1.8 mm. Before the formal test, a strain scanning test was performed on the sample to determine the linear viscoelastic region of the material. Based on the scanning results, the test strain was fixed at 0.5%.

[0064] The test temperature was kept constant at 4℃, and dynamic frequency scanning tests were performed in a non-destructive small amplitude oscillation shear mode. The scanning angular frequency range was set from 0.1 to 100 radians / second. The original test values ​​of the energy storage modulus and loss modulus of each group of samples at an angular frequency of 10 radians / second were extracted, and the corresponding loss tangent value was calculated.

[0065] Table 2: Dynamic rheological parameters of samples from each embodiment and comparative example

[0066] According to Table 2 and Figure 3 and Figure 4 It can be seen that rheological parameters directly reflect the construction state of the continuous phase network structure inside the composite system. The mechanical behavior of dairy product systems is often constrained by the entanglement mode of internal polymer chain segments. In conventional multiphase emulsion matrices, since the structure is mainly maintained by weak van der Waals forces and hydrophobic interactions between molecules, this physical stacking usually exhibits a low elastic modulus on a macroscopic scale. As the experimental data shows, the storage modulus of the example group is generally increased to above 46000 Pa, while the loss tangent value is reduced to below 0.24. From the perspective of rheological analysis, the combination of high modulus and low loss tangent confirms that a dense continuous three-dimensional gel skeleton has been formed inside the system.

[0067] By comparing the test data of each formulation group, it can be found that the cross-linking reaction of polysaccharide materials under specific thermodynamic conditions is the key factor. For example, in Comparative Example 6 without the addition of low-methoxyl pectin, even if there is interfacial adsorption of propylene glycol alginate in the early stage, the overall storage modulus falls back to the benchmark range of 23015.8 Pa due to the lack of long-chain molecules in the continuous aqueous phase that can build a macroscopic framework.

[0068] The addition of components alone is insufficient to spontaneously form a stable cross-linked structure. The process parameters that regulate the release of free ions also limit the formation of the reaction network. For Comparative Example 7, since lactic acid was not added, the acidity of the system was not adjusted to near the isoelectric point of the protein. The chelation state of the molten salt on the internal calcium ions was not broken, and the microenvironment could not provide enough free calcium. The low-methoxyl pectin segments could only be scattered in the aqueous phase in a free coiled state, which could not trigger the rigid coordination structure formed by the galacturonic acid unit and the calcium ions. The test results also showed a low storage modulus (19842.5 Pa) and the highest loss characteristics (0.381). The embodiment releases calcium ions through precise acidity regulation and smooths out local concentration gradients through isothermal shearing, providing uniformly distributed crosslinking sites for pectin segments in the continuous phase. The formed network physically traps free fat and protein complexes in space. The construction of this semi-interpenetrating polymer network changes the stress transmission path inside the material, enabling the system to obtain excellent elastic response.

[0069] Test Example 3: The composite cheese products of Examples 1 to 4 and Comparative Examples 1 to 7 after being refrigerated and shaped at 4°C were selected as experimental subjects. Using stainless steel stamping molds, each sample was cut into round pieces with a diameter of 30 mm and a thickness of about 3 mm in a low-temperature environment.

[0070] Select quantitative glass fiber filter paper, place it in a 105℃ drying oven for constant weight treatment, weigh and record the initial mass of the filter paper, place the cut cheese slices flat in the center of the filter paper, weigh the total mass, and calculate the initial mass of each sample before the test by the difference.

[0071] Transfer the quantitative filter paper containing the sample to a preheated oven at 250°C and bake at a constant temperature for 6 minutes.

[0072] After baking, remove the sample and let it cool at room temperature for 2 minutes. Use a scraper to peel off and clean the cheese residue and caramelized matter from the surface of the filter paper. Weigh the filter paper after it has absorbed the leached oil, and divide the difference between the weight of the filter paper and the initial weight of the filter paper by the initial weight of the cheese sample to calculate the free fat leaching rate.

[0073] Table 3: Test data on free fat exudation rate of each embodiment and comparative example

[0074] According to Table 3 and Figure 5 and Figure 6 It can be seen that the free fat exudation rate of Examples 1 to 4 was maintained below 1.5%. In the daily thermal processing observation of dairy products, the free fat inside the matrix will undergo phase change and volume expansion as the temperature rises. The resulting internal free stress often causes the casein network that encapsulates the fat to deform or even break. As a basic blank group, Comparative Example 1 had an exudation rate of 22.45%, indicating that the traditional multiphase emulsion matrix is ​​difficult to maintain its original structure under the high temperature condition of 250°C, and obvious oil phase separation and migration occur.

[0075] In the face of thermal instability, regulating the physicochemical properties of the oil-water interface can affect the restriction of fat migration. Data comparison shows that the exudation rate of the control group 3 without the addition of propylene glycol alginate increased to 28.71%. Due to the lack of phase separation effect induced by trehalose, propylene glycol alginate could not form an adsorption layer with steric hindrance at the oil-water interface. When the system temperature exceeds the melting point of fat, the liquid fat globules that have lost steric hindrance protection collide and aggregate under the action of thermal motion to form a continuous oil phase. These large-volume oil phases will penetrate the heat-softened protein network, which is macroscopically manifested as an increase in the amount of oil phase precipitation.

[0076] Even if the interfacial adsorption of propylene glycol alginate is retained, the incompleteness of the macroscopic network structure will affect the overall retention effect. The exudation rate of Comparative Example 6, which did not add low-methoxyl pectin, and Comparative Example 7, which failed to crosslink due to the lack of lactic acid, was still around 10%. This reflects that the microscopic protective layer around the fat globules alone is not enough to completely resist thermal stress. If the aqueous phase lacks a semi-interpenetrating polymer network formed by the crosslinking of calcium ions and pectin, the deformation of the system will still cause free oil to be squeezed out.

[0077] The low exudation rate of the example group demonstrates that the combination of interfacial steric hindrance and macroscopic network structure is practically feasible in restricting fat migration. The propylene glycol alginate adsorption layer reduces the probability of thermal aggregation of fat globules at the microscale, while the continuous network formed by pectin and calcium ion coordination traps fat-protein complexes in the macroscopic space. This method of establishing physical structures at different scales reduces the degree of phase separation under high temperature conditions, enabling the composite system to maintain a relatively stable structure in a simulated baking environment.

[0078] Test Example 4: The finished compound cheese products prepared in Examples 1 to 4 and Comparative Examples 1 to 7 were transferred to a constant temperature cold storage room set at 4°C for long-term storage experiments.

[0079] The testing period was set, and longitudinal sampling was carried out on the 7th, 30th, 90th and 180th days after the samples were stored in the warehouse. The sampling operation was carried out in a low temperature environment. Each group of cheese was cut into cubic test blocks with a side length of 20 mm using a cutter. The cut samples were left to stand at 4°C for 1 hour to eliminate mechanical stress.

[0080] Texture profile analysis was performed using a physical property testing instrument equipped with a 50 kg load sensor. A cylindrical aluminum probe with a diameter of 36 mm was installed. The test mode was set to a two-cycle compression test. The probe's pre-test speed, test speed, and post-test speed were all set to 1 mm / s. The target compression deformation was set to 30% of the initial height of the sample. The interval between the two compression cycles was kept constant at 5 seconds.

[0081] The test was started and the software recorded the peak value of the maximum resistance experienced by the probe during the first compression cycle. The absolute value of this force was extracted as a hardness evaluation parameter. The test values ​​of each group of samples were recorded in different refrigeration cycles to observe the changes in their texture.

[0082] Table 4: Hardness test data of each embodiment and comparative example as a function of refrigeration time

[0083] According to Table 4 and Figure 7In long-term low-temperature storage tests, the hardness of the system increased to varying degrees over time. Free water in the dairy matrix tends to migrate to the protein surface, which leads to dehydration and shrinkage of the protein network, resulting in macroscopic hardening. The test results of Comparative Example 1 are consistent with this general phenomenon, with its hardness increasing from 512.4 grams on day 7 to 1845.6 grams on day 180. This indicates that the basic formula cannot avoid significant water migration and textural hardening during long-term storage.

[0084] Comparative Example 6, lacking low-methoxyl pectin, reached a hardness of 1462.3 g on day 180. Although the formulation contained propylene glycol alginate, a gel skeleton failed to form in the aqueous phase, and the water in the system remained in a relatively free migration state. Comparative Example 7, which showed similar performance, failed to fully release calcium ions due to the absence of lactic acid during preparation. The pectin in the aqueous phase lacked the coordinating ions required for cross-linking, and thus could not restrict the transfer of water to the protein phase, ultimately leading to a significant increase in hardness.

[0085] In contrast, the hardness increase in the example group was smaller during the 180-day test period. Taking Example 1 as an example, the value ranged from 458.2 g to 582.1 g. In the formulation of the example, low-methoxyl pectin and homogenized free calcium ions formed a three-dimensional cross-linked network, and some free water was distributed in the network pores. This physical structure not only increases the fluid resistance in the system, but also reduces the rate of water diffusion. The above comparative data show that the continuous aqueous phase network constructed by specific components can weaken the internal migration tendency of free water, which helps the compound dairy products maintain stable textural characteristics under long-term refrigeration.

[0086] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A compound cheese dairy product, characterized in that, The compound cheese dairy product comprises the following ingredients in parts by weight: 41.2 to 64.2 parts purified water; 12 to 18 parts of rennet and casein; 20 to 30 portions of anhydrous butter; 1.0 to 2.0 parts of composite molten salt; 1.2 to 2.5 parts of propylene glycol alginate and trehalose premixed solid powder; 1.6 to 6.3 parts of low-methoxyl pectin aqueous solution; Lactic acid solution, the amount of which is added is the appropriate amount required to adjust the pH of the preparation system to 5.5 to 5.

6.

2. The compound cheese dairy product according to claim 1, characterized in that, The composite molten salt is composed of sodium hexametaphosphate and trisodium citrate, and the weight ratio of sodium hexametaphosphate to trisodium citrate is 1.5:1 to 2.5:

1.

3. The compound cheese dairy product according to claim 1, characterized in that, The premixed solid powder of propylene glycol alginate and trehalose is prepared by mechanical dry mixing of propylene glycol alginate and crystalline trehalose at room temperature, and the weight ratio of the two is 1:4 to 1:

5.

4. The compound cheese dairy product according to claim 1, characterized in that, The low-methoxyl pectin aqueous solution is prepared by dissolving low-methoxyl pectin and purified water under heating and stirring conditions, and the weight ratio of the two is 1:15 to 1:

20.

5. The preparation process of the compound cheese dairy product according to any one of claims 1 to 4, characterized in that, The preparation process includes the following steps: S1. Add purified water, rennet casein, anhydrous butter and compound molten salt into the emulsification reactor, turn on the outer wall scraper and turn on the heating source to make the material in the reactor rise to a constant temperature. S2. Under constant temperature conditions, the premixed solid powder of propylene glycol alginate and trehalose is uniformly added into the emulsification reactor, and the inner high-shear homogenizing head is turned on simultaneously to carry out a continuous shear reaction. S3. Close the inner high-shear homogenizer head, control the material in the reactor to cool down to the set temperature, and dynamically add lactic acid solution until the pH of the system is stably adjusted down and maintained in the target range, then stop adding solution. S4. Maintain the isothermal state inside the vessel, increase the stirring speed of the outer wall scraper, and continuously perform constant mechanical shearing. This isothermal shearing delay operation overcomes the mass transfer resistance of the aqueous phase and smooths out the local concentration gradient of free calcium ions. S5. Pump the low-methoxyl pectin aqueous solution into the emulsification reactor and reduce the stirring speed of the outer wall scraper to allow the pectin to continuously react and crosslink with the homogeneously distributed free calcium. S6. Use the pump to pump the material out of the kettle to complete the hot filling of the mold, and then quickly cool down and shape it to obtain the compound cheese dairy product.

6. The preparation process of the compound cheese dairy product according to claim 5, characterized in that, In S1, the temperature of the material inside the vessel is controlled to be kept constant at 80 to 88°C; the rotation speed of the outer wall scraper is maintained at 20 to 50 r / min. In S2, the rotational speed of the inner high-shear homogenizing head is set to 2000 to 3500 r / min, and the shearing reaction time is 10 to 20 minutes.

7. The preparation process of the compound cheese dairy product according to claim 5, characterized in that, In S3, during the process of closing the inner high-shear homogenizing head, controlling the cooling of the material in the reactor and dynamically adding lactic acid solution, the temperature of the material in the reactor is controlled to drop to 70 to 74°C at a cooling rate of 1.5 to 2.5°C / min, and the mass fraction of the added lactic acid solution is 10%.

8. The preparation process of the compound cheese dairy product according to claim 5, characterized in that, In S4, while maintaining the isothermal state inside the vessel and increasing the stirring speed of the outer wall scraper while continuously performing constant mechanical shearing, after the pH is stabilized and lowered, the system is maintained at an isothermal temperature of 70 to 74°C, and the stirring speed of the outer wall scraper is increased to 50 to 80 r / min. Under this condition, constant mechanical shearing is performed for 8 to 15 minutes.

9. The preparation process of the compound cheese dairy product according to claim 5, characterized in that, In step S5, the step of pumping the low-methoxyl pectin aqueous solution into the emulsification reactor and reducing the stirring speed of the outer wall scraper is to maintain a constant temperature of 70 to 74°C in the reactor, reduce the stirring speed of the outer wall scraper to 20 to 40 r / min, and continue the reaction for 8 to 12 minutes.

10. The preparation process of the compound cheese dairy product according to claim 5, characterized in that, In S6, during the process of pumping the material out of the vessel using the pump body to complete the hot filling and rapid cooling and shaping of the mold, the hot filling of the mold is completed at 70 to 74°C, and then it is sent into the cooling tunnel to be rapidly cooled to 2 to 6°C.

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