Preparation method for improving stability of high-protein and high-fat neutral milk

Abstract

The invention discloses a preparation method for improving the stability of high-protein and high-fat neutral milk, and relates to the technical field of improvement of the stability of a protein-containing emulsion. The problems of layering and precipitation of the high-protein and high-fat neutral milk in the processing and storage processes are effectively solved, the defects of whey separation, pasty or granular sensation and the like are avoided, and the stable state of the product in the shelf life is prolonged. By optimizing the process, the fat globules are smaller in average particle size and more uniform in distribution, meanwhile, the protein denaturation rate is reduced, a more stable emulsification system is constructed, and the microstructure stability of the product is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of improving the stability of protein-containing emulsions, specifically to a preparation method for improving the stability of high-protein and high-fat neutral emulsions. Background Technology

[0002] In the dairy processing industry, neutral dairy products (pH 6.4-7.0) with high protein and high fat content are increasingly favored by the market due to their rich nutrition and smooth taste. However, such products face severe stability challenges in industrial production, especially in ultra-high temperature (UHT) sterilization processes: First, high protein content (typically ≥4.3g / 100g) easily leads to excessive aggregation of casein micelles during heat treatment, forming irreversible gels or precipitation; second, high fat content (typically ≥12.5g / 100g) significantly increases the probability of fat globule collisions, causing fat to float and separate during sterilization and storage; third, interfacial competitive adsorption between the protein and fat phases weakens the homogeneity of the emulsion system, further exacerbating the risk of phase separation.

[0003] Existing technologies generally employ the addition of emulsifiers (such as monoglycerides) and stabilizers (such as CMC-Na and carrageenan) to delay stratification. However, traditional processes have significant limitations: when directly mixing high-proportion fat raw materials (such as anhydrous butter and light cream), the emulsifier struggles to quickly coat the newly exposed fat globule surface, leading to incomplete local emulsification; conventional homogenization processes (single-stage or pressure ≤250 bar) lack sufficient particle size control for high-solids (≈38%) systems, failing to effectively inhibit fat globule flocculation; the high-temperature shearing during UHT sterilization disrupts the already formed emulsion structure, and the thermodynamic changes in the subsequent cooling stage are more likely to induce protein-fat complex precipitation. Furthermore, the increased system viscosity due to high solids content hinders the uniform breakup efficiency within the homogenizing valve, further reducing process stability.

[0004] Market feedback indicates that existing high-protein, high-fat neutral emulsion products commonly exhibit defects such as whey separation, paste-like consistency, or graininess during their shelf life, severely hindering product quality and consumer experience. Therefore, there is an urgent need to develop a targeted preparation method that optimizes the emulsion structure construction path, improves homogenization efficiency, and reduces thermal processing damage through process innovation, thereby achieving long-term physical stability of the product at the microstructural level. Summary of the Invention

[0005] The purpose of this invention is to address the problems existing in the prior art by providing a method to improve the stability of high-protein (4.3-5.0g / 100g) and high-fat (12.5-14.5g / 100g) neutral milk during processing and storage. This method utilizes a staged emulsification process, two-stage homogenization control, and specific UHT sterilization parameters to achieve synergistic effects and solve the problems of water separation and stratification. To achieve the above objectives, the technical solution adopted by the present invention is: a method for preparing high-protein and high-fat neutral milk with improved stability, characterized by comprising the following steps: (1) Add raw milk to the reactor, control the temperature at 65-70℃, add skim milk powder, white sugar, emulsifier and stabilizer in sequence, and perform high-speed shear mixing to obtain material A; (2) Add anhydrous butter, light cream and sweetened condensed milk to material A in sequence, and mix them by high-speed shearing to obtain material B; (3) Add water to the material B to make up to the target weight, stir and mix, sieve, perform pre-homogenization, UHT sterilization, post-homogenization, cool and fill to obtain the finished thick milk. The finished thick milk contains 4.3-5.0g of protein and 12.5-14.5g of fat, and has a pH of 6.4-7.0.

[0006] Furthermore, the mass ratio of the skim milk powder, white sugar, emulsifier, and stabilizer is 6%, 10%, 0.45%, and 0.32%, respectively. Furthermore, the mass ratio of the anhydrous butter, light cream, and sweetened condensed milk is 7:4:10. Furthermore, the temperature of the pre-homogenization and post-homogenization in step (3) is controlled at 70-75℃.

[0007] Furthermore, the pressure of the pre-homogenization in step (3) is 40 / 200 bar, with an allowable deviation of ±10 bar.

[0008] Furthermore, the pre-homogenization is intended to initially reduce the size of fat globules, preparing for UHT sterilization.

[0009] Furthermore, the post-homogenization pressure in step (3) is 30 / 150 bar, with an allowable deviation of ±10 bar.

[0010] Furthermore, the post-homogenization further refines the particle size and repairs structural damage during the sterilization process.

[0011] Furthermore, the high-speed shearing rate in step (1) is 10,000 rpm, and the duration is 15 minutes; The high-speed shearing rate in step (2) is 10,000 rpm, and the duration is 10 minutes.

[0012] Furthermore, the sieving in step (3) uses an 80-mesh sieve.

[0013] Furthermore, the UHT sterilization in step (3) adopts a direct spray sterilization mode with a temperature of 141±1℃ and a time of 4 seconds.

[0014] Furthermore, the water addition and volume adjustment in step (3) includes calculating the amount of water to be added based on the total solids content: Water replenishment = (Total solids content of semi-finished product × Actual liquid level / Target total solids content) - Actual liquid level; The target total solids content is 38.0%; stir for 600 seconds after adding water.

[0015] Furthermore, the emulsifier includes mono- and diglyceride fatty acid esters, phospholipids, and sucrose fatty acid esters.

[0016] Furthermore, the mass ratio of the mono- and diglyceride fatty acid esters, phospholipids, and sucrose fatty acid esters is 0.25%, 0.07%, and 0.13%, respectively. Furthermore, the stabilizer includes microcrystalline cellulose, sodium carboxymethyl cellulose, carrageenan, and disodium hydrogen phosphate.

[0017] Furthermore, the mass ratio of the microcrystalline cellulose, sodium carboxymethyl cellulose, carrageenan, and disodium hydrogen phosphate is 0.1%, 0.1%, 0.02%, and 0.1%, respectively. Furthermore, in step (3), the cooling control liquid temperature is set to 23±2℃, and the cooling time does not exceed 8 hours; the filling adopts aseptic filling, and the aseptic tank pressure is ≥1.0 bar.

[0018] The core innovations of this technical solution are: ① Staged emulsification: Prioritizing the processing of proteins and emulsifiers before introducing fat raw materials optimizes interfacial adsorption kinetics. ② Optimized two-stage homogenization pressure: Initial homogenization uses higher pressure (40 / 200 bar) to initially break down fat globules, while subsequent homogenization uses lower pressure (30 / 150 bar) to refine and stabilize the system, avoiding excessive shearing that could lead to protein denaturation. ③ Parameter synergy: Combining specific UHT sterilization (141±1℃ / 4s) and cooling control reduces the risk of thermodynamic instability.

[0019] Compared with the prior art, the beneficial effects of the present invention are: 1. Significantly improved stability: Effectively solves the problems of layering and sedimentation in high-protein, high-fat neutral milk during processing and storage, avoids defects such as whey separation, paste formation or graininess, and extends the product's stable state during its shelf life.

[0020] 2. Superior System Structure: By optimizing the process, the average particle size of fat globules is made smaller and more uniformly distributed, while reducing the protein denaturation rate, thus building a more stable emulsion system and ensuring the stability of the product's microstructure.

[0021] 3. High process reliability: It can still stably produce high-quality products under different implementation conditions (such as different raw material ratios and fluctuations in process parameters), with good repeatability and robustness, making it suitable for industrial mass production. Detailed Implementation

[0022] The technical solution of the present invention will be clearly and completely described below in conjunction with the inventive content. 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.

[0023] Example 1: Preparation of a high-protein, high-fat neutral milk: (1) Add 600 kg of raw milk to the reactor, turn on the temperature control system, and stabilize the temperature of the material in the reactor at 68℃; then add 60 kg of skim milk powder (6% of the total mass of the finished product), 100 kg of white sugar (10% of the total mass of the finished product), 4.5 kg of emulsifier (0.45% of the total mass of the finished product, including 2.5 kg of mono- and diglycerides of fatty acids, 0.7 kg of phospholipids, and 1.3 kg of sucrose fatty acids) and 3.2 kg of stabilizer (0.32% of the total mass of the finished product, including 1.0 kg of microcrystalline cellulose, 1.0 kg of sodium carboxymethyl cellulose, 0.2 kg of carrageenan, and 1.0 kg of disodium hydrogen phosphate) in sequence; start the high-speed shearing equipment and mix continuously at a shearing rate of 10,000 rpm for 15 minutes to ensure that all raw materials are fully dissolved and evenly dispersed to form a stable pre-emulsified system, thus obtaining material A; (2) Keep the temperature of the reactor stable at 68℃, and add 70kg of anhydrous butter (7% of the total mass of the finished product), 40kg of light cream (4% of the total mass of the finished product), and 100kg of sweetened condensed milk (10% of the total mass of the finished product) to the above material A in sequence. The mass ratio of anhydrous butter, light cream, and sweetened condensed milk meets the process requirement of 7:4:10. Continue to mix at a shear rate of 10000rpm for 10 minutes to fully integrate the fat raw materials with material A, achieve the initial coating of fat globules, and obtain a uniformly emulsified material B. (3) First, the total solids content of material B is tested. Based on the target total solids content of 38.0%, 22.3 kg of purified water is added. The purified water is added to the reactor to bring the total volume to 1000 kg, and then the mixture is stirred continuously at a normal stirring rate for 600 seconds. The material after volume adjustment is filtered through an 80-mesh sieve. The filtered material is sent to a homogenizer, and the homogenization temperature is controlled at 72℃ for pre-homogenization treatment. The pre-homogenization pressure is set to 40 / 200 bar. The material after pre-homogenization enters U. The HT sterilization system uses a direct injection sterilization mode, controlling the sterilization temperature at 141℃ and the sterilization time at 4 seconds. After sterilization, the material immediately enters the post-homogenization process, maintaining the homogenization temperature at 72℃ and the post-homogenization pressure at 30 / 150 bar. The post-homogenized material is then sent to the cooling system, where the liquid temperature is cooled to 23℃ within 6 hours. Finally, aseptic filling equipment is used to fill the cooled material, controlling the aseptic tank pressure at 1.2 bar, resulting in a finished product: a high-protein, high-fat neutral milk.

[0024] Example 2, Preparation of a high-protein, high-fat neutral milk: (1) Add 580 kg of raw milk to the reactor, start the temperature control module, and precisely adjust the temperature of the material in the reactor to 66℃; according to the raw material addition order set in the process, add 60 kg of skim milk powder (accounting for 6% of the total mass of the finished product), 100 kg of white sugar (accounting for 10% of the total mass of the finished product), 4.5 kg of emulsifier (accounting for 0.45% of the total mass of the finished product, including 2.5 kg of mono- and diglycerides of fatty acids, 0.7 kg of phospholipids, and 1.3 kg of sucrose fatty acids), and 3.2 kg of stabilizer (accounting for 0.32% of the total mass of the finished product, including 1.0 kg of microcrystalline cellulose, 1.0 kg of sodium carboxymethyl cellulose, 0.2 kg of carrageenan, and 1.0 kg of disodium hydrogen phosphate); turn on the high-speed shear device and continuously mix at a constant shear rate of 10,000 rpm for 15 minutes to ensure that all components are completely dissolved and form a uniform pre-emulsified matrix to obtain material A; (2) Maintain the reactor temperature at 66℃, and add 70kg of anhydrous butter (7% of the total mass of the finished product), 40kg of light butter (4% of the total mass of the finished product), and 100kg of sweetened condensed milk (10% of the total mass of the finished product) to material A in sequence. The mass ratio of the three materials meets the process ratio of 7:4:10. Continue to mix at a shear rate of 10000rpm for 10 minutes to fully integrate the fat raw materials with material A and obtain a uniformly emulsified material B. (3) Test the total solids content of material B and add 42.5 kg of purified water; add purified water to the reactor to make up to a total mass of 1000 kg, and then stir continuously at a conventional stirring rate for 600 seconds; filter the material after making up to a fixed volume through an 80-mesh sieve; the filtered material is sent to a homogenizing device, the homogenization temperature is controlled at 74℃, and pre-homogenization is performed, with the pre-homogenization pressure set at 40 / 200 bar; the material after pre-homogenization enters the UHT sterilization system, adopts the direct injection sterilization mode, controls the sterilization temperature at 142℃, and the sterilization time is 4 seconds; after sterilization, the material immediately enters the post-homogenization process, maintaining the homogenization temperature at 74℃, and the post-homogenization pressure is set at 30 / 150 bar; the material after post-homogenization is sent to the cooling system, and the liquid temperature is cooled to 25℃ within 5 hours. Finally, the cooled material is filled using aseptic filling equipment, and the aseptic tank pressure is controlled at 1.1 bar (≥1.0 bar process requirement), thus obtaining a high-protein, high-fat neutral milk product.

[0025] Example 3, Preparation of a high-protein, high-fat neutral milk: (1) Add 590 kg of raw milk to the reactor and start the temperature control system to precisely stabilize the temperature of the material in the reactor at 65℃. According to the raw material addition order set in the patent, add 60 kg of skim milk powder (accounting for 6% of the total mass of the finished product), 100 kg of white sugar (accounting for 10% of the total mass of the finished product), 4.5 kg of emulsifier (accounting for 0.45% of the total mass of the finished product, including 2.5 kg of mono- and diglycerides of fatty acids, 0.7 kg of phospholipids, and 1.3 kg of sucrose fatty acid esters), and 3.2 kg of stabilizer (accounting for 0.32% of the total mass of the finished product, including 1.0 kg of microcrystalline cellulose, 1.0 kg of sodium carboxymethyl cellulose, 0.2 kg of carrageenan, and 1.0 kg of disodium hydrogen phosphate). Turn on the high-speed shearing equipment and continuously mix at a constant shear rate of 10,000 rpm for 15 minutes to ensure that all raw materials are completely dissolved and evenly dispersed to form a stable pre-emulsified system, thus obtaining material A. (2) Maintain the reactor temperature at 65℃, and add 70kg of anhydrous butter (7% of the total mass of the finished product), 40kg of light butter (4% of the total mass of the finished product), and 100kg of sweetened condensed milk (10% of the total mass of the finished product) to material A in sequence. The mass ratio of the three materials must strictly meet the process ratio of 7:4:10. Continue to mix at a high speed of 10000rpm for 10 minutes to fully integrate the fat raw materials with material A and obtain a uniformly emulsified material B. (3) To test the total solids content of material B, 30.6 kg of purified water needs to be added. Add purified water to the reactor to bring the total volume to 1000 kg, then stir continuously at a normal stirring rate for 600 seconds to avoid uneven solids distribution. Filter the material after volume adjustment through an 80-mesh sieve. The filtered material is then transported to a homogenizer, and the homogenization temperature is controlled at 70℃ for pre-homogenization treatment. The pre-homogenization pressure is set to 40 / 200 bar (allowable deviation ±10 bar). The pre-homogenized material then enters U... The HT sterilization system employs a patented direct-injection sterilization mode, controlling the sterilization temperature at 140℃ and the sterilization time at 4 seconds. After sterilization, the material immediately enters the post-homogenization process, maintaining the homogenization temperature at 70℃ and setting the post-homogenization pressure at 30 / 150 bar. The post-homogenized material is then sent to a cooling system, where the liquid temperature is cooled to 21℃ within 7 hours. Finally, aseptic filling equipment is used to fill the cooled material, controlling the aseptic tank pressure at 1.3 bar, resulting in a high-protein, high-fat neutral milk product.

[0026] Comparative Example 1: This comparative example uses a conventional single-stage emulsification process and homogenization parameters, but does not implement the staged emulsification and two-stage homogenization optimization strategy of this invention. The specific steps are as follows: (1) Add 600 kg of raw milk to the reactor, heat to 68°C, and add all raw materials at once: 60 kg (6%) of skim milk powder, 100 kg (10%) of white sugar, 5 kg of emulsifier (2.5 kg of mono- and diglycerides of fatty acids + 0.7 kg of phospholipids + 1.8 kg of sucrose fatty acids), 3 kg of stabilizer (1 kg of microcrystalline cellulose + 1 kg of sodium carboxymethyl cellulose + 0.2 kg of carrageenan + 0.8 kg of disodium hydrogen phosphate), 70 kg (7%) of anhydrous butter, 40 kg (4%) of light butter, and 100 kg (10%) of sweetened condensed milk. Shear at 10,000 rpm for 25 minutes to obtain a mixture. (2) Add water to a final volume of 1,000 kg, stir for 600 seconds (10 minutes), and pass through an 80-mesh sieve; (3) At 70℃, single-stage homogenization (pressure 180 bar, no secondary pressure) is adopted, with an allowable deviation of ±10 bar; direct injection sterilization mode is adopted, temperature 143±1℃, time 6 seconds; directly cooled to 22℃ (≤6 hours), aseptic filling (aseptic tank pressure 1.2 bar) to obtain high protein and high fat neutral milk.

[0027] Performance testing: 1. The high-protein, high-fat neutral milk prepared in the examples and comparative examples was observed to show whether there was stratification after standing at 4°C for 30 days and at 25°C for 60 days. The data are shown in Table 1.

[0028] 2. The average particle size (nm) of fat globules was determined using a laser particle size analyzer, and the data are shown in Table 1.

[0029] 3. The protein denaturation rate was determined by SDS-PAGE electrophoresis, and the data are shown in Table 1.

[0030] Table 1.

[0031] Does it have layers? Is there any sediment? Average size of fat globules (nm) Protein denaturation rate Example 1 No layering No sediment 280 ＜10% Example 2 No layering No sediment 260 ＜10% Example 3 No layering No sediment 290 ＜10% Comparative Example 1 Slight stratification There is sediment 520 28% All examples showed a positive and consistent trend in terms of stratification, precipitation, fat globule size, and protein denaturation rate—namely, no stratification, no precipitation, smaller particle size, and lower denaturation rate. Conversely, Comparative Example 1 showed a negative trend across all metrics—stratification and precipitation occurred, larger particle size, and higher denaturation rate. This highlights the overall advantage of the present invention's preparation method (staged emulsification, two-stage homogenization, and specific UHT sterilization) in improving the stability of high-protein, high-fat neutral milk.

[0032] No significant differences were observed in the test results among the three examples, indicating that the preparation method of the present invention is reproducible under different implementation conditions (such as different raw material ratios or process parameters). Smaller fat globule particle size and lower protein denaturation rate are often associated with no stratification and no precipitation, supporting the theoretical basis of the core innovations of the present invention (such as optimized emulsification path and thermal processing control).

[0033] 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 method for preparing neutral milk with improved stability of high-protein and high-fat formulas, characterized in that, Includes the following steps: (1) Add raw milk to the reactor, control the temperature at 65-70℃, add skim milk powder, white sugar, emulsifier and stabilizer in sequence, and perform high-speed shear mixing to obtain material A; (2) Add anhydrous butter, light cream and sweetened condensed milk to material A in sequence, and mix them by high-speed shearing to obtain material B; (3) Add water to the material B to make up to the target weight, stir and mix, sieve, perform pre-homogenization, UHT sterilization, post-homogenization, cool and fill to obtain the finished thick milk. The finished thick milk contains 4.3-5.0g of protein and 12.5-14.5g of fat, and has a pH of 6.4-7.

0.

2. The preparation method for improving the stability of high-protein and high-fat neutral milk according to claim 1, characterized in that, The temperature of the pre-homogenization and post-homogenization in step (3) is controlled at 70-75℃.

3. The preparation method for improving the stability of high-protein and high-fat neutral milk according to claim 1, characterized in that, The pressure for pre-homogenization in step (3) is 40 / 200 bar, with an allowable deviation of ±10 bar.

4. The preparation method for improving the stability of high-protein and high-fat neutral milk according to claim 1, characterized in that, The pressure for post-homogenization in step (3) is 30 / 150 bar, with an allowable deviation of ±10 bar.

5. The preparation method for improving the stability of high-protein and high-fat neutral milk according to claim 1, characterized in that, The high-speed shearing rate in step (1) is 10,000 rpm and the duration is 15 minutes; The high-speed shearing rate in step (2) is 10,000 rpm, and the duration is 10 minutes.

6. The method for preparing a neutral milk with improved stability of high-protein and high-fat milk according to claim 1, characterized in that, The sieving in step (3) uses an 80-mesh sieve.

7. The preparation method for improving the stability of high-protein and high-fat neutral milk according to claim 1, characterized in that, The UHT sterilization in step (3) adopts the direct spray sterilization mode, with a temperature of 141±1℃ and a time of 4 seconds.

8. The preparation method for improving the stability of high-protein and high-fat neutral milk according to claim 1, characterized in that, The water addition and volume adjustment in step (3) includes calculating the amount of water to be added based on the total solids content: Water replenishment = (Total solids content of semi-finished product × Actual liquid level / Target total solids content) - Actual liquid level; The target total solids content is 38.0%; stir for 600 seconds after adding water.

9. The preparation method for improving the stability of high-protein and high-fat neutral milk according to claim 1, characterized in that, The emulsifiers include mono- and diglyceride fatty acid esters, phospholipids, and sucrose fatty acid esters; The stabilizers include microcrystalline cellulose, sodium carboxymethyl cellulose, carrageenan, and disodium hydrogen phosphate.

10. The preparation method for improving the stability of high-protein and high-fat neutral milk according to claim 1, characterized in that, In step (3), the cooling control liquid temperature is set to 23±2℃ and the cooling time does not exceed 8 hours; the filling adopts aseptic filling and the aseptic tank pressure is ≥1.0 bar.