A process for the preparation of a low-fat, high-calcium spreadable whipped cream cheese

Abstract

The application relates to the technical field of dairy processing, and discloses a preparation method of low-fat high-calcium spreadable whipped cream cheese, which comprises the following steps: preparing a two-stage calcium relay buffering premix by complexing part of a low-fat milk base with sodium tripolyphosphate, potassium citrate monohydrate and DL-calcium malate, hydrating the premix with the remaining base and D-trehalose dihydrate, adding a ferment, L-glutamine and glutamine transaminase after sterilization and cooling to carry out fermentation, carrying out targeted cold arrest during fermentation and acid reduction, then carrying out temperature rise fermentation to an isoelectric point, and finally preparing a finished product through demulsification, heat treatment, high-pressure homogenization and maturation, the two-stage buffering system is constructed to control the stepwise release of free calcium ions to increase the proportion of soluble calcium, L-glutamine is used to cut off excessive protein crosslinking to give the cheese appropriate spreadability, and trehalose and a cold arrest process are combined to lock internal moisture, so that the water retention of the product is improved and the product has no sandy feeling.

Description

Technical Field

[0001] This invention relates to the field of dairy processing technology, specifically to a method for preparing low-fat, high-calcium spreadable cream cheese. Background Technology

[0002] Spreadable cream cheese is an unripened cheese product with high moisture content, soft texture, and easy spreadability. In recent years, reducing the fat content of dairy products and fortifying them with mineral nutrients such as calcium has become an important research and development trend. Low-fat, high-calcium spreadable cheese can provide necessary calcium supplementation while controlling fat intake, which caters to the consumption needs of modern healthy eating and has high application value in the daily consumer market.

[0003] Existing low-fat, high-calcium cheese production processes mostly use low-fat or skim milk as a base. After pasteurization, lactic acid bacteria starter culture is added for constant-temperature fermentation. To increase the total calcium content of the product, conventional processing steps involve directly adding exogenous calcium salts such as calcium carbonate, calcium phosphate, or calcium malate to the base material before fermentation. During fermentation, the lactic acid bacteria metabolize and produce acid, causing the pH value of the system to drop naturally. Casein in the base material then coagulates and forms a primary curd network. Subsequently, the finished cheese is produced through mechanical demulsification, temperature inactivation of enzymes, and high-pressure homogenization.

[0004] During the base material fermentation and acid reduction stage, the directly added exogenous calcium salt will rapidly dissociate as the pH value of the system decreases, causing the concentration of free calcium ions in the liquid phase to rise sharply in a short period of time. The high concentration of free calcium that appears instantaneously in the system will cause casein to prematurely aggregate before reaching the isoelectric point. A large number of calcium ions combine with protein to form insoluble precipitates. This uncontrolled calcium ion burst release process makes it difficult for exogenous calcium to maintain a soluble state in the liquid phase, resulting in a low proportion of soluble calcium in the produced cheese product, a coarse texture, and a noticeable grainy texture. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing low-fat, high-calcium spreadable cream cheese, which solves the problem that exogenous calcium undergoes rapid dissociation during the fermentation and acid reduction stage due to a rapid drop in pH, leading to a sudden release of calcium ions and premature aggregation of casein, resulting in a low proportion of soluble calcium, a coarse texture, and a noticeable grainy feel in the product.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing low-fat, high-calcium spreadable cream cheese, comprising the following raw materials in parts by weight: 800 to 1200 parts of low-fat milk base; 1.5 to 3.5 parts sodium tripolyphosphate; Potassium citrate monohydrate, 2.0 to 5.0 parts; DL-Calcium Malate 4.0 to 9.0 parts; 30 to 70 parts of D-trehalose dihydrate; L-glutamine 0.5 to 1.5 parts; The amount of transglutaminase added is 15 U / g to 35 U / g based on the total protein mass of the low-fat milk base. 0.1 to 0.3 parts of lactic acid bacteria starter.

[0007] Preferably, the raw materials for preparing the cheese are, by mass parts: 1000 parts of low-fat milk base; 2.5 parts sodium tripolyphosphate; 3.5 parts of potassium citrate monohydrate; DL-Calcium Malate 6.5 parts; 50 parts of D-trehalose dihydrate; 1.0 part of L-glutamine; The amount of transglutaminase added is 25 U / g based on the total protein mass of the low-fat milk base. 0.2 parts of lactic acid bacteria starter.

[0008] Preferably, the low-fat milk base has a fat content of 0.5% to 3.0%, a total protein content of 2.8% to 3.5%, and a non-fat milk solids content of not less than 8.5%. The lactic acid bacteria starter is a direct-inoculation freeze-dried strain, and the strain composition of the lactic acid bacteria starter is a compound bacterial powder composed of Lactococcus mesophilus subsp. lactis and Streptococcus thermophilus mixed in a live bacteria ratio of 1:1 to 2:1.

[0009] A method for preparing a low-fat, high-calcium spreadable cream cheese includes the following steps: S1, a portion of the low-fat milk base material is extracted and heated as a premixed solvent, and all the sodium tripolyphosphate and potassium citrate monohydrate are added for dissolution and pH adjustment. Then, the DL-calcium malate is added for complexation reaction to obtain a two-stage competitive calcium relay buffer suspension premix. S2, combine the suspension premix obtained in step S1 with the remaining low-fat milk base, add the D-trehalose dihydrate and stir to hydrate, and control the total pH of the mixed system; S3, pasteurize the base material obtained in step S2 and cool it to the fermentation initiation temperature; S4, the lactic acid bacteria starter, L-glutamine powder and transglutaminase are introduced, and the fermentation is carried out at a constant temperature. When the pH value of the fermentation system drops to the range of 5.60 to 5.75, the temperature is rapidly reduced to the cold stagnation temperature and kept at the cold stagnation temperature for stagnation. S5, after the cold stagnation ends, the temperature is raised to continue fermentation until the pH value of the system drops to the isoelectric point to form primary curd, then the emulsion is broken and the temperature is raised to heat it. S6 performs high-pressure homogenization on the heated material, seals and fills it while it is still hot, and then refrigerates it to mature.

[0010] Preferably, in step S1, the preparation conditions for the two-stage competitive calcium relay buffer suspension premix include: Take 100 to 150 parts of the low-fat milk base and heat it to 40°C to 45°C as a premixed solvent; After adding sodium tripolyphosphate and potassium citrate monohydrate, stir at 300 rpm to 500 rpm for 10 to 15 minutes and adjust the pH of the system to 6.6 to 6.8. Add DL-calcium malate to the premixed solvent in 3 to 4 portions and maintain the reaction at 40 to 45°C for 20 to 30 minutes.

[0011] Preferably, in step S2, the hydration stirring conditions are: continuous stirring at room temperature for 20 to 30 minutes, controlling the total pH of the mixed system to be 6.5 to 6.7.

[0012] Preferably, in step S3, the pasteurization process parameters are: heating to 82.0℃ to 88.0℃ and holding for 20s to 60s; after pasteurization, rapidly cooling to the fermentation initiation temperature, which is 32.0℃ to 36.0℃.

[0013] Preferably, in step S4, the process parameters for cooling and stagnation are: The fermentation system temperature was rapidly reduced to 12.0°C to 15.0°C within 20 to 30 minutes by introducing ice water into the jacket; the heat preservation period was 2.0 to 3.0 hours.

[0014] Preferably, in step S5, the process parameters for secondary fermentation and thermalization are as follows: The fermentation tank temperature was raised to 22.0℃ to 25.0℃ at a heating rate of 0.5℃ / min to continue fermentation; the isoelectric point was determined when the pH value dropped to 4.60 to 4.70. After demulsification, the system was heated to 75.0℃ to 82.0℃ at a heating rate of 1.0℃ to 1.5 ...

[0015] Preferably, in step S6, the process parameters for high-pressure homogenization and maturation are as follows: The homogenization process is carried out at an operating temperature of 70.0℃ to 75.0℃ and a homogenization pressure of 15.0MPa to 25.0MPa; the temperature for hot sealing and filling is not lower than 70℃; the temperature for cold storage and static curing is 2.0℃ to 6.0℃, and the curing time is 24h to 48h.

[0016] This invention provides a method for preparing a low-fat, high-calcium spreadable cream cheese. It has the following beneficial effects: 1. This invention constructs a two-stage competitive calcium relay buffer system using sodium tripolyphosphate and potassium citrate monohydrate. During fermentation and acid reduction, different chelating agents are protonated sequentially as the pH decreases, achieving a stepwise release of calcium ions. This buffering mechanism avoids premature casein aggregation caused by excessively high instantaneous concentrations of free calcium, ensuring that exogenous calcium is mainly distributed in the liquid phase in a soluble state. This reduces the particulate feel caused by insoluble calcium salt precipitation and increases the proportion of soluble calcium in the liquid phase of the product.

[0017] 2. This invention simultaneously introduces transglutaminase and L-glutamine powder during the fermentation stage. L-glutamine, as a monomeric amino acid, provides a low-molecular-weight acyl acceptor, competitively consuming some of the enzyme's catalytic sites. This competitive reaction interrupts the unlimited covalent cross-linking between casein macromolecules, preventing the formation of an excessively dense rigid protein network. The technical solution controls the final storage modulus and physical hardness of the gel, enabling the low-fat cheese system to achieve the required spreadability.

[0018] 3. This invention adds D-trehalose dihydrate to the base material and incorporates a cooling and cessation process during the mid-fermentation stage. The polyhydroxy structure of trehalose provides hydration, and during the cooling and cessation phase, the primary curd network rearranges and stabilizes during the incubation period. This hydration, combined with the cross-linked protein backbone, locks water within the three-dimensional network, limiting structural changes caused by dehydration and shrinkage in the low-fat system, reducing the risk of whey separation, and improving the product's centrifugal water retention rate. Attached Figure Description

[0019] Figure 1 This is a process flow diagram of the present invention; Figure 2 This is a line graph showing the changes in free calcium concentration and storage modulus during the fermentation and deacidification process of this invention. Figure 3 This is a bar chart comparing the hardness and coating performance of various test samples in this invention; Figure 4 This is a bar chart comparing the centrifugation water retention rate and the proportion of soluble calcium in the liquid phase for each test sample of the present invention. Detailed Implementation

[0020] 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.

[0021] Please see the appendix Figure 1 -Appendix Figure 4 This invention provides a method for preparing a low-fat, high-calcium spreadable cream cheese, using the following raw material parameters: Low-fat milk is a commercially available product. The fat content of low-fat milk is 0.5% to 3.0%, the total protein content is 2.8% to 3.5%, and the non-fat milk solids content is not less than 8.5%.

[0022] DL-Calcium Malate, CAS No. 17482-42-7, molecular formula C4H4CaO5, purity greater than or equal to 98.0%; Sodium tripolyphosphate, CAS number 7758-29-4, molecular formula Na5P3O10, purity greater than or equal to 95.0%; Potassium citrate monohydrate, CAS number 6100-05-6, molecular formula C6H5K3O7·H2O, purity greater than or equal to 99.0%; D-Trehalose dihydrate, CAS No. 6138-23-4, molecular formula C12H22O11·2H2O, purity ≥ 99.0%. L-Glutamine, CAS No. 56-85-9, molecular formula C5H10N2O3, purity greater than or equal to 99.0%, is a commercially available conventional substance with a well-defined chemical structure.

[0023] Transglutaminase is a commercially available food-grade enzyme preparation with CAS number 80146-85-6 and Enzyme Committee number EC2.3.2.13. It is produced by fermentation of Streptomyces mobara and has a nominal enzyme activity of 100 U / g to 150 U / g.

[0024] The lactic acid bacteria starter is a commercially available direct-inoculation freeze-dried strain. The strain composition of the lactic acid bacteria starter is a compound bacterial powder made by mixing Lactococcus mesophilus subsp. lactis and Streptococcus thermophilus in a live bacteria ratio of 1:1 to 2:1.

[0025] Preparation Example 1: This preparation example provides a two-stage competitive calcium relay buffer premix, based on 1000g of low-fat milk base, and includes the following steps: 125g of low-fat milk was heated to 42℃ as a premixed solvent. 2.5g of sodium tripolyphosphate and 3.5g of potassium citrate monohydrate were added to the premixed solvent and mechanically stirred at 400rpm for 12min until completely dissolved. The pH of the system was adjusted to 6.7 using 0.1mol / L sodium hydroxide or hydrochloric acid solution. While maintaining stirring at 400rpm, 6.5g of DL-calcium malate was slowly added to the premixed solvent in three portions. The reaction was maintained at 42℃ for 25min to allow the free calcium ions dissociated in the liquid phase to fully complex with the chelating agent, and the undissolved calcium salt to be uniformly dispersed in the form of microparticles, resulting in a slightly milky white, two-stage competitive calcium relay buffer suspension premix.

[0026] Preparation Example 2: This preparation example provides a two-stage competitive calcium relay buffer premix, based on 1000g of low-fat milk base, and includes the following steps: 100g of low-fat milk was heated to 40℃ as a premixed solvent. 1.5g of sodium tripolyphosphate and 2.0g of potassium citrate monohydrate were added to the premixed solvent and mechanically stirred at 300rpm for 10min until completely dissolved. The pH of the system was adjusted to 6.6 using 0.1mol / L sodium hydroxide or hydrochloric acid solution. While maintaining stirring at 400rpm, 4.0g of DL-calcium malate was slowly added to the premixed solvent in three portions. The reaction was maintained at 40℃ for 20min, allowing the free calcium ions dissociated in the liquid phase to fully complex with the chelating agent. The undissolved calcium salt was uniformly dispersed in the form of microparticles, resulting in a slightly milky white, two-stage competitive calcium relay buffer suspension premix.

[0027] Preparation Example 3: This preparation example provides a two-stage competitive calcium relay buffer premix, based on 1000g of low-fat milk base, and includes the following steps: 150g of low-fat milk was heated to 45℃ as a premixed solvent. 3.5g of sodium tripolyphosphate and 5.0g of potassium citrate monohydrate were added to the premixed solvent and mechanically stirred at 500rpm for 15min until completely dissolved. The pH of the system was adjusted to 6.8 using 0.1mol / L sodium hydroxide or hydrochloric acid solution. While maintaining stirring at 400rpm, 9.0g of DL-calcium malate was slowly added to the premixed solvent in 4 portions. The reaction was maintained at 45℃ for 30min to allow the free calcium ions dissociated in the liquid phase to fully complex with the chelating agent, and the undissolved calcium salts to be uniformly dispersed in the form of microparticles, resulting in a slightly milky white, two-stage competitive calcium relay buffer suspension premix.

[0028] Example 1: This embodiment provides a method for preparing low-fat, high-calcium spreadable cream cheese, including the following steps: The bi-stage competitive calcium relay buffer suspension premix prepared in Example 1 was combined with the remaining 875g of low-fat milk base, and 50g of D-trehalose dihydrate was added. The mixture was continuously stirred at room temperature for 25min to hydrate the mixture. The total pH of the system after mixing was controlled at 6.6. Standardized base material is pumped into a heat exchanger, heated to 85.0℃ and held for 40 seconds for pasteurization. After pasteurization, it is quickly cooled to the fermentation initiation temperature of 34.0℃ through heat exchange. Aseptically add 0.2g of lactic acid bacteria starter, 1.0g of L-glutamine powder, and pre-dissolved transglutaminase in water to the cooled substrate (the amount added is 25U / g based on the total protein mass of the substrate), and let it ferment at a constant temperature of 34.0℃. Turn on online pH monitoring. Fermentation continues for about 3.5 hours until the pH value of the system naturally drops to 5.70. Turn off the heat preservation and introduce ice water jacket. Within 25 minutes, the temperature of the fermentation system is rapidly reduced to 14.0℃ and kept at 14.0℃ for 2.5 hours. After the cold stop, the temperature of the fermenter is raised back to 24.0℃ at a heating rate of 0.5℃ / min to continue fermentation until the pH value of the system drops to 4.65, at which point the fermentation endpoint is determined and primary curd is formed. Start the fermenter and stir to gently break the curd mechanically. Turn on the heating jacket and heat the system to 78.0℃ at a rate of 1.2℃ / min and hold for 12min to inactivate the fermentation agent and enzyme activity. The heated material is pumped into a high-pressure homogenizer and homogenized at a pressure of 20.0 MPa and an operating temperature of 72.0℃. Then, it is sealed and filled while hot at a temperature not lower than 70℃ and transferred to a cold storage at 4.0℃ for 36 hours to produce low-fat, high-calcium spreadable cream cheese.

[0029] Example 2: This embodiment provides a method for preparing low-fat, high-calcium spreadable cream cheese, including the following steps: The bi-stage competitive calcium relay buffer suspension premix prepared in Example 2 was combined with the remaining 900g of low-fat milk base, and 30g of D-trehalose dihydrate was added. The mixture was stirred continuously at room temperature for 20min for hydration. The total pH of the system after mixing was controlled at 6.5. Standardized base material is pumped into a heat exchanger, heated to 82.0℃ and held for 20 seconds for pasteurization. After pasteurization, it is quickly cooled to the fermentation initiation temperature of 32.0℃ through heat exchange. Aseptically add 0.1g of lactic acid bacteria starter, 0.5g of L-glutamine powder, and pre-dissolved transglutaminase in water to the cooled substrate (the amount added is 15U / g based on the total protein mass of the substrate), and let it ferment at a constant temperature of 32.0℃. Turn on online pH monitoring. Fermentation continues for about 4.5 hours until the pH value of the system naturally drops to 5.75. Turn off the heat preservation and introduce ice water jacket. Within 20 minutes, the temperature of the fermentation system is rapidly reduced to 12.0℃ and kept at 12.0℃ for 2.0 hours. After the cold stop, the temperature of the fermenter is raised back to 22.0℃ at a heating rate of 0.5℃ / min to continue fermentation until the pH value of the system drops to 4.70, at which point the fermentation endpoint is determined and primary curd is formed. Start the fermenter and stir to gently break the curd mechanically. Turn on the heating jacket and heat the system to 75.0℃ at a rate of 1.0℃ / min and keep it at that temperature for 10min to inactivate the fermenting agent and enzyme activity. The heated material is pumped into a high-pressure homogenizer and homogenized at a homogenization pressure of 15.0 MPa and an operating temperature of 70.0℃. Then, it is sealed and filled while hot at a temperature not lower than 70℃ and transferred to a cold storage at 6.0℃ for 24 hours to produce low-fat, high-calcium spreadable cream cheese.

[0030] Example 3: This embodiment provides a method for preparing low-fat, high-calcium spreadable cream cheese, including the following steps: The bi-stage competitive calcium relay buffer suspension premix prepared in Example 3 was combined with the remaining 850g of low-fat milk base, and 70g of D-trehalose dihydrate was added. The mixture was continuously stirred at room temperature for 30min for hydration. The total pH of the system after mixing was controlled at 6.7. Standardized base material is pumped into a heat exchanger, heated to 88.0℃ and held for 60 seconds for pasteurization. After pasteurization, it is quickly cooled to the fermentation initiation temperature of 36.0℃ through heat exchange. Aseptically add 0.3g of lactic acid bacteria starter, 1.5g of L-glutamine powder, and pre-dissolved transglutaminase in water to the cooled substrate (the amount added is 35U / g based on the total protein mass of the substrate), and let it ferment at a constant temperature of 36.0℃. Turn on online pH monitoring and let fermentation continue for about 3.0 hours until the pH value of the system naturally drops to 5.60. Then, turn off the heat preservation and introduce ice water jacket. Within 30 minutes, rapidly reduce the temperature of the fermentation system to 15.0℃ and keep it at 15.0℃ for 3.0 hours. After the cold stop, the temperature of the fermenter is raised back to 25.0℃ at a heating rate of 0.5℃ / min to continue fermentation until the pH value of the system drops to 4.60, at which point the fermentation endpoint is determined and primary curd is formed. Start the fermenter and stir to gently break the curd mechanically. Turn on the heating jacket and heat the system to 82.0℃ at a rate of 1.5℃ / min and keep it at that temperature for 15min to inactivate the fermenting agent and enzyme activity. The heated material is pumped into a high-pressure homogenizer and homogenized at a pressure of 25.0 MPa and an operating temperature of 75.0 °C. Then, it is sealed and filled while hot at a temperature not lower than 70 °C and transferred to a cold storage at 2.0 °C for 48 hours to produce low-fat, high-calcium spreadable cream cheese.

[0031] Example 4: This embodiment provides a method for preparing low-fat, high-calcium spreadable cream cheese, including the following steps: The bi-stage competitive calcium relay buffer suspension premix prepared in Example 1 was combined with the remaining 875g of low-fat milk base, and 60g of D-trehalose dihydrate was added. The mixture was continuously stirred at room temperature for 25min to hydrate the mixture. The total pH of the system after mixing was controlled at 6.6. Standardized base material is pumped into a heat exchanger, heated to 86.0℃ and held for 30 seconds for pasteurization. After pasteurization, it is quickly cooled to the fermentation initiation temperature of 35.0℃ through heat exchange. Aseptically add 0.25g of lactic acid bacteria starter, 1.2g of L-glutamine powder, and pre-dissolved transglutaminase in water to the cooled substrate (the amount added is 30U / g based on the total protein mass of the substrate), and let it ferment at a constant temperature of 35.0℃. Turn on online pH monitoring and continue fermentation until the pH value of the system naturally drops to 5.65. Then, turn off the heat preservation and introduce ice water jacket. Within 20 minutes, rapidly reduce the temperature of the fermentation system to 13.0℃ and keep it at 13.0℃ for 2.5 hours. After the cold stop, the temperature of the fermenter was raised back to 23.0℃ at a heating rate of 0.5℃ / min to continue fermentation until the pH value of the system dropped to 4.65, at which point the fermentation endpoint was determined and primary curd was formed. Start the fermenter and stir to gently break the curd mechanically. Turn on the heating jacket and heat the system to 80.0℃ at a rate of 1.2℃ / min and hold for 12min to inactivate the fermentation agent and enzyme activity. The heated material is pumped into a high-pressure homogenizer and homogenized at a homogenization pressure of 18.0 MPa and an operating temperature of 73.0℃. Then, it is sealed and filled while hot at a temperature not lower than 70℃ and transferred to a 4.0℃ cold storage for 36 hours to produce low-fat, high-calcium spreadable cream cheese.

[0032] Comparative Example 1: Compared with Example 1, the difference is that: no bi-stage competitive calcium relay buffer suspension premix was prepared and added, nor were sodium tripolyphosphate and potassium citrate monohydrate added. Instead, 6.5g of DL-calcium malate was added directly to the low-fat milk base before heat treatment sterilization. All other aspects are the same.

[0033] Comparative Example 2: The difference from Example 1 is that no transglutaminase and L-glutamine powder were added when inoculating the cooled substrate; all other aspects were the same.

[0034] Comparative Example 3: The difference from Example 1 is that when inoculating the cooled substrate, only transglutaminase is added, and the competitive receptor L-glutamine powder is not added; all other aspects are the same.

[0035] Comparative Example 4: Compared with Example 1, the difference is that when preparing the premix, the secondary buffer chelating agent potassium citrate monohydrate is not added, and only sodium tripolyphosphate is used to complex with DL-calcium malate. All other aspects are the same.

[0036] Comparative Example 5: Compared with Example 1, the difference is that the conventional isothermal fermentation process is used, that is, the fermentation is continuously placed at 34.0°C until the pH value of the system drops to 4.65 to determine the fermentation endpoint. The targeted cold cessation process step of "cooling down to 14.0°C and holding for 2.5 hours" is not performed. All other steps are the same.

[0037] Comparative Example 6: Compared with Example 1, the difference is that D-trehalose dihydrate is not added during the base material hydration stage; instead, an equal mass of purified water is used instead. All other aspects are the same.

[0038] Test Example 1: Mechanism Verification and Feasibility Testing This test case aims to verify the kinetic characteristics of free calcium ion release and the feasibility of the dual-network crosslinking process in the present invention through liquid phase chemical analysis and macroscopic rheological testing.

[0039] Experimental testing steps: The starting materials from Examples 1, 2, 3, and 4, which had undergone pasteurization and were inoculated with starter culture and enzyme preparation, were placed in a constant-temperature reactor with a temperature control jacket. The reactor was processed according to the set fermentation and cold stagnation temperature program. A pH online monitoring electrode and a calcium ion selective electrode were deployed in the reactor to record the pH value and the concentration of free calcium ions in the liquid phase at different fermentation time points. Samples were taken simultaneously and transferred to the rotational rheometer testing platform. A parallel plate clamp was used with a gap of 1 mm. The test temperature was kept consistent with the temperature inside the reactor at the time of sampling. The storage modulus of the sample was measured in an oscillation mode with a strain amplitude of 0.5% and an angular frequency of 10 rad / s.

[0040] The test data is recorded in the table below. Considering that there may be slight fluctuations in the actual fermentation acid reduction rate, the pH value of the sampling point is based on the measured non-integer value.

[0041] Table 1. Data on the changes in liquid phase free calcium ion concentration and storage modulus with fermentation acidity.

[0042] Analysis of the free calcium concentration test data showed that in Example 1, the concentration of free calcium ions in the liquid phase increased non-linearly as the pH value decreased from 6.62 to 4.68, and maintained a low concentration increase in the pH range of 5.78 to 5.51. In Comparative Example 4, without the addition of potassium citrate monohydrate, the free calcium concentration increased from 6.19 mmol / L to 24.87 mmol / L in the same pH range. Combined with the changes in system acidity, sodium tripolyphosphate underwent protonation near the critical point of dissociation constant, reducing its complexing ability for calcium ions. In Example 1, citrate ions had a higher complexing constant at the corresponding acidity, forming complexes with the free calcium ions detached from sodium tripolyphosphate. When the pH dropped to 5.13 and below, citrate ions gradually protonated and dissociated, releasing calcium ions, completing the secondary release process. This indicates that the two-stage competitive calcium buffer system has the effect of delaying and controlling the release of free calcium ions.

[0043] Based on rheological data, Comparative Example 2, without the addition of enzyme preparation, exhibited a low storage modulus during the acid reduction process, with an endpoint value of 89.6 Pa. This indicates that the gel network structure constructed solely by casein acid aggregation in the low-fat system has low strength. Comparative Example 3, without the addition of L-glutamine, showed a rapid increase in storage modulus with the fermentation process, with an endpoint value of 312.8 Pa, indicating a high rigidity state caused by high cross-linking density. The endpoint storage modulus of Example 1 was 142.4 Pa. The added L-glutamine consumed some of the catalytic sites of glutamine transaminase, reduced the number of covalent cross-links between casein molecules, and allowed free calcium ions to be distributed in the isoelectric point aqueous phase. The overall cross-linked network of the system exhibited a moderate storage modulus value.

[0044] Test Example 2: Texture and Spreadability Determination The hardness and smearing work of the sample were determined using a texture analyzer equipped with a conical smearing probe. Before the test, the sample was refrigerated at 4°C for 24 hours. The pressure speed was set to 1 mm / s and the penetration depth was set to 15 mm. The maximum shear force of the probe penetrating the sample was recorded as the hardness, and the integral area of ​​the force-time curve was recorded as the smearing work.

[0045] Table 2. Sample Hardness and Coating Performance Test Data

[0046] According to the data in Table 2, Comparative Example 2, without the addition of enzyme preparation, had the lowest sample hardness and spreading power values, indicating a loose structure. Comparative Example 3, without the addition of L-glutamine, had a sample hardness of 1945g and a spreading power of 6210g·s, indicating that the cross-linking of casein macromolecules was unrestricted, resulting in increased internal rigidity of the system and loss of spreading extensibility. The hardness of Examples 1 to 3 remained between 389g and 514g, and the spreading power was between 1264g·s and 1692g·s. The addition of L-glutamine blocked the excessive cross-linking of covalent bonds, giving the low-fat system suitable physical characteristics for spreading.

[0047] Test Example 3: Centrifugal Water Retention Rate Determination Weigh 20g of sample into a centrifuge tube and centrifuge at 3000g for 20 minutes at 4℃. Pour off the free water precipitated from the upper layer and weigh it. Calculate the percentage of gel precipitate mass after centrifugation to the total mass of the sample before centrifugation, which is called the centrifugation water retention rate.

[0048] Table 3. Sample Centrifugal Water Retention Rate Test Data

[0049] Table 3 shows that Comparative Example 2 did not form an enzymatic cross-linking network and had a centrifugal water retention rate of 71.5%. Comparative Example 6 used water instead of D-trehalose dihydrate and had a water retention rate of 80.3%. The centrifugal water retention rates of Examples 1 to 3 were in the range of 92.8% to 95.6%. The primary protein backbone constructed by glutamine transaminase combined with the hydration of D-trehalose dihydrate, locking in the liquid phase water and limiting the whey precipitation caused by dehydration and shrinkage in the low-fat system.

[0050] Test Example 4: Determination of Calcium Content and Proportion of Soluble Calcium in Liquid Phase The total calcium mass fraction of the sample was determined by inductively coupled plasma mass spectrometry. A portion of the sample was centrifuged at 50,000 g for 1 hour at 20 °C, and the supernatant was extracted. The total calcium mass in the supernatant was determined by the same method, and the percentage of calcium mass in the supernatant to the total calcium mass of the sample was calculated as the percentage of soluble calcium in the liquid phase.

[0051] Table 4. Data on total calcium content and percentage of soluble calcium in liquid phase of samples.

[0052] As shown in Table 4, the total calcium mass fraction of each test group was similar, concentrated in the range of 339 mg / 100g to 345 mg / 100g. In Comparative Example 1, free calcium salt was directly added, and the proportion of soluble calcium in the liquid phase was 12.4%, indicating that most of the exogenous calcium bound to casein during heating and fermentation to form insoluble precipitates. In Comparative Example 4, only sodium tripolyphosphate was used for single-stage complexation, and the proportion of soluble calcium in the liquid phase was 41.7%, indicating the presence of local calcium ion burst precipitation. In Example 1, a two-stage competitive calcium buffer system was used, and the proportion of soluble calcium in the liquid phase reached 88.5%. Calcium ions mainly existed in the liquid phase in a soluble state and did not form large-area ion aggregation with the protein network.

[0053] Test Example 5: Macroscopic Sensory Evaluation Twelve evaluators trained in sensory analysis conducted blind tests and scored the samples using a 9-point scale. Higher scores indicated a more positive response to the corresponding evaluation dimension. Evaluation dimensions included smoothness, absence of gritty texture, and overall acceptability. The arithmetic mean of all evaluators' scores was taken as the result.

[0054] Table 5. Sample Macroscopic Sensory Evaluation Scoring Table

[0055] Based on the subjective test results in Table 5, Example 1 scored above 8.4 points in both smoothness and lack of gritty feel. Comparative Example 1 scored only 2.3 points for lack of gritty feel due to severe calcium precipitation, indicating a grainy feel. Comparative Example 3 scored 3.1 points for smoothness due to hardening caused by excessive cross-linking of the system. Comparative Example 4 scored 5.4 points for lack of gritty feel due to the release and precipitation of some free calcium caused by the lack of secondary buffer. The subjective scoring data of Example 1 correspond to the physical hardness data of Test Example 2 and the soluble calcium ratio data of Test Example 4.

[0056] 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 low-fat, high-calcium spreadable cream cheese, characterized in that, The raw materials include the following parts by weight: 800 to 1200 parts of low-fat milk base; 1.5 to 3.5 parts sodium tripolyphosphate; Potassium citrate monohydrate, 2.0 to 5.0 parts; DL-Calcium Malate 4.0 to 9.0 parts; 30 to 70 parts of D-trehalose dihydrate; L-glutamine 0.5 to 1.5 parts; The amount of transglutaminase added is 15 U / g to 35 U / g based on the total protein mass of the low-fat milk base. 0.1 to 0.3 parts of lactic acid bacteria starter.

2. The low-fat, high-calcium spreadable cream cheese according to claim 1, characterized in that, The raw materials for preparing the cheese are, by mass parts: 1000 parts of low-fat milk base; 2.5 parts sodium tripolyphosphate; 3.5 parts of potassium citrate monohydrate; DL-Calcium Malate 6.5 parts; 50 parts of D-trehalose dihydrate; 1.0 part of L-glutamine; The amount of transglutaminase added is 25 U / g based on the total protein mass of the low-fat milk base. 0.2 parts of lactic acid bacteria starter.

3. The low-fat, high-calcium spreadable cream cheese according to claim 1, characterized in that: The low-fat milk base has a fat content of 0.5% to 3.0%, a total protein content of 2.8% to 3.5%, and a non-fat milk solids content of not less than 8.5%. The lactic acid bacteria starter is a direct-inoculation freeze-dried strain, and the strain composition of the lactic acid bacteria starter is a compound bacterial powder composed of Lactococcus mesophilus subsp. lactis and Streptococcus thermophilus mixed in a live bacteria ratio of 1:1 to 2:

1.

4. A method for preparing a low-fat, high-calcium spreadable cream cheese, used to prepare the low-fat, high-calcium spreadable cream cheese according to any one of claims 1 to 3, characterized in that, Includes the following steps: S1, a portion of the low-fat milk base material is extracted and heated as a premixed solvent, and all the sodium tripolyphosphate and potassium citrate monohydrate are added for dissolution and pH adjustment. Then, the DL-calcium malate is added for complexation reaction to obtain a two-stage competitive calcium relay buffer suspension premix. S2, combine the suspension premix obtained in step S1 with the remaining low-fat milk base, add the D-trehalose dihydrate and stir to hydrate, and control the total pH of the mixed system; S3, pasteurize the base material obtained in step S2 and cool it to the fermentation initiation temperature; S4, the lactic acid bacteria starter, L-glutamine powder and transglutaminase are introduced, and the fermentation is carried out at a constant temperature. When the pH value of the fermentation system drops to the range of 5.60 to 5.75, the temperature is rapidly reduced to the cold stagnation temperature and kept at the cold stagnation temperature for stagnation. S5, after the cold stagnation ends, the temperature is raised to continue fermentation until the pH value of the system drops to the isoelectric point to form primary curd, then the emulsion is broken and the temperature is raised to heat it. S6 performs high-pressure homogenization on the heated material, seals and fills it while it is still hot, and then refrigerates it to mature.

5. The method for preparing a low-fat, high-calcium spreadable cream cheese according to claim 4, characterized in that, In step S1, the preparation conditions for the two-stage competitive calcium relay buffer suspension premix include: Take 100 to 150 parts of the low-fat milk base and heat it to 40°C to 45°C as a premixed solvent; After adding sodium tripolyphosphate and potassium citrate monohydrate, stir at 300 rpm to 500 rpm for 10 to 15 minutes and adjust the pH of the system to 6.6 to 6.

8. Add DL-calcium malate to the premixed solvent in 3 to 4 portions and maintain the reaction at 40 to 45°C for 20 to 30 minutes.

6. The method for preparing a low-fat, high-calcium spreadable cream cheese according to claim 4, characterized in that, In step S2, the conditions for hydration stirring are: continuous stirring at room temperature for 20 to 30 minutes, and controlling the total pH of the mixed system to be 6.5 to 6.

7.

7. The method for preparing a low-fat, high-calcium spreadable cream cheese according to claim 4, characterized in that, In step S3, the pasteurization process parameters are: heating to 82.0℃ to 88.0℃ and holding for 20s to 60s; after pasteurization, rapidly cooling to the fermentation initiation temperature, which is 32.0℃ to 36.0℃.

8. The method for preparing a low-fat, high-calcium spreadable cream cheese according to claim 4, characterized in that, In step S4, the process parameters for cooling and stagnation are as follows: The fermentation system temperature was rapidly reduced to 12.0°C to 15.0°C within 20 to 30 minutes by introducing ice water into the jacket; the heat preservation period was 2.0 to 3.0 hours.

9. The method for preparing a low-fat, high-calcium spreadable cream cheese according to claim 4, characterized in that, In step S5, the process parameters for secondary fermentation and thermalization are as follows: The fermentation tank temperature was raised to 22.0℃ to 25.0℃ at a heating rate of 0.5℃ / min to continue fermentation; the isoelectric point was determined when the pH value dropped to 4.60 to 4.

70. After demulsification, the system was heated to 75.0℃ to 82.0℃ at a heating rate of 1.0℃ / min to 1.5℃ / min and held at that temperature for 10 min to 15 min.

10. The method for preparing a low-fat, high-calcium spreadable cream cheese according to claim 4, characterized in that, In step S6, the process parameters for high-pressure homogenization and maturation are as follows: The homogenization process is carried out at an operating temperature of 70.0℃ to 75.0℃ and a homogenization pressure of 15.0MPa to 25.0MPa; the temperature for hot sealing and filling is not lower than 70℃; the temperature for cold storage and static curing is 2.0℃ to 6.0℃, and the curing time is 24h to 48h.

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