Pre-concentrated cheese and preparation method thereof

Abstract

The preparation method comprises the following steps: (1) concentrating milk by using an ultrafiltration membrane, setting the concentration multiple, stopping ultrafiltration when the total solid content is reached, and collecting ultrafiltration milk; (2) performing falling film concentration on the ultra-filtered milk, setting the concentration multiple, stopping falling film concentration when the total solid content is reached, and collecting concentrated milk; (3) mixing the concentrated milk with the single cream, sterilizing and cooling; (4) inoculating a leavening agent and chymosin, uniformly stirring, and fermenting to obtain curd; and (5) maturing the fermented curds. The method omits a whey discharging step, simplifies the operation process, reduces the loss of nutritional ingredients, and is suitable for industrial continuous production.

Description

Technical Field

[0001] This invention patent belongs to the field of dairy product technology, specifically relating to a pre-concentrated cheese and its preparation method. Background Technology

[0002] Cheese is a solid product made by coagulating milk proteins with rennet, adding fermentation starters, and fermenting the cheese through processes such as removing or not removing whey. Cheese is often called "milk gold" because it contains essential nutrients such as protein, fat, vitamins, and minerals, as well as various bioactive substances, playing an important role in meeting the body's nutritional needs.

[0003] One of the core steps in traditional cheese production is "whey removal," which involves separating the curd from the large amount of liquid whey after the milk has coagulated. While this traditional process is mature, modern industrial production and consumer demands have revealed several drawbacks: First, significant nutrient loss occurs. Whey is not "wastewater"; it is rich in easily absorbed whey protein, vitamins, and minerals. The whey removal process directly leads to the loss of these valuable nutrients, reducing the final nutritional value and yield of the cheese. Whey protein is the second largest protein in milk and has beneficial functions such as improving gut health, enhancing immunity, and promoting brain development. Second, many dairy companies in China currently lack efficient and economical whey deep-processing measures. Large quantities of whey are directly discharged or discarded as byproducts, not only causing significant waste of raw materials and increasing production costs but also generating high-concentration organic wastewater, placing enormous pressure on the environment. This makes it difficult to scale up the production of whole fresh cheese in China, limiting it to manual or small-batch production. Ultrafiltration, as a membrane concentration process, can retain large molecules such as whey protein and casein through a semi-permeable membrane before curdling, and reduce lactose content, in contrast to traditional processes that drain whey after curdling. To avoid draining whey, the industry has explored various methods. For example, directly adding milk protein powder (MPC) often results in a powdery texture that fails to replicate the rich flavor of natural milk protein and is difficult to mix evenly at high solids levels. Using ultrafiltration equipment alone is typically limited by membrane flux and concentration limits, only able to concentrate total solids to a certain range. Using falling membrane concentration equipment alone increases the concentration of lactose and minerals in milk, thus reducing the protein content, increasing heat consumption during evaporation, and raising production costs. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a pre-concentrated cheese and its preparation method. The method utilizes a combination of ultrafiltration and falling membrane concentration equipment for pre-concentration. First, proteins are selectively concentrated, while unwanted lactose, minerals, and water are removed. Subsequently, falling membrane concentration equipment is used to evaporate the water, resulting in cheese that maintains a smooth texture while increasing its total solids content. This cheese preparation method is simple, omitting the whey removal step, simplifying the operation process, reducing nutrient loss, and is suitable for continuous production.

[0005] To achieve the above objectives, the present invention is specifically implemented through the following technical solutions:

[0006] In its first aspect, this application provides a method for preparing pre-concentrated cheese, comprising the following steps:

[0007] (1) The milk is concentrated by ultrafiltration to a total solids content of 12%-15% to obtain ultrafiltered milk;

[0008] (2) The ultrafiltration milk is evaporated and concentrated to a total solids content of 30%-60% to obtain concentrated milk.

[0009] On the other hand, this application provides cheese, which is obtained from pre-concentrated cheese prepared by any of the preparation methods described above or from the pre-concentrated cheese described above.

[0010] On the other hand, this application provides a food product containing pre-concentrated cheese prepared by any of the above-described preparation methods, the aforementioned pre-concentrated cheese, or the aforementioned cheese.

[0011] Beneficial effects:

[0012] The method described in this application produces cheese that retains its smooth texture while increasing its total solids content. Furthermore, the preparation method is simple, omitting the whey removal step, simplifying the operation process, reducing nutrient loss, and making it suitable for continuous production. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of Example 1.

[0014] Figure 2 This is a schematic diagram for Comparative Example 2. Detailed Implementation

[0015] The specific embodiments of this application will be further described in detail below with reference to the accompanying drawings. These embodiments are only for illustrating this application and are not intended to limit the scope of the invention.

[0016] In the description of this invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The invention is further illustrated below by way of embodiments, but this does not limit the invention to the scope of the described embodiments.

[0017] Unless otherwise specified, experimental methods in the following examples were performed using conventional methods and conditions, or according to the product instructions. All raw materials and reagents used in the following examples were commercially available.

[0018] Based on the existing technical problems, this application provides a method for preparing concentrated milk. The prepared concentrated milk can be used for the fermentation of pre-concentrated cheese, which can improve the taste of pre-concentrated cheese, reduce the graininess and powdery texture, and is inexpensive and easy to operate.

[0019] In its first aspect, this application provides a method for preparing pre-concentrated cheese, comprising the following steps:

[0020] (1) Milk is concentrated by ultrafiltration to obtain ultrafiltered milk, wherein the total solids content of the ultrafiltered milk is 12%-15% by mass.

[0021] (2) The ultrafiltration milk is evaporated and concentrated to obtain concentrated milk. The total solids in the concentrated milk are 30%-60% by mass based on the total mass of the concentrated milk.

[0022] In a specific embodiment, the pore size of the ultrafiltration concentration is 5-100 nm.

[0023] In a specific embodiment, the milk is skim milk. In a specific embodiment, the milk contains protein, and the protein content is 3.3-3.6% by weight of the total milk mass. In a specific embodiment, the milk contains lactose, and the lactose content is 4.5-5.0% by weight of the total milk mass.

[0024] Compared with existing technologies, this application optimizes the concentration method by first using ultrafiltration concentration followed by evaporation concentration, and optimizes the concentration factor to ensure sufficient total solids content in the intermediate product. Furthermore, compared to omitting the falling film concentration step or using a concentration factor lower than the scope of this invention, it increases the total solids content of the intermediate product, balances the evaporation load of the subsequent falling film concentration process, significantly improves production efficiency, and consequently enhances its flavor intensity, texture fullness, and stability.

[0025] As used in this application, "ultrafiltration concentration" refers to a method that, under pressure, utilizes a membrane with a specific pore size as a selective barrier, allowing solvents (usually water) and small-molecule solutes to permeate through the membrane while retaining large-molecule solutes, thereby concentrating the latter in solution. In practice, ultrafiltration membranes with pore sizes of 1–100 nm are typically used as the separation medium. Under a transmembrane pressure difference of 0.1–0.5 MPa, water and small molecules (salts, solvents, etc.) permeate through the membrane pores, while retaining large molecules (proteins, enzymes, colloids, polysaccharides, etc.) with molecular weights of 1–300 kDa. This membrane concentration method achieves the purpose of "dehydration-concentration" under ambient temperature and no phase change conditions. It can include dead-end ultrafiltration concentration, cross-flow ultrafiltration concentration, batch concentration, fed-batch / diafiltration-concentration, diafiltration + concentration, and multi-stage concentration.

[0026] As used in this application, "evaporation concentration" refers to a unit operation that uses heating to vaporize part of the solvent (usually water) in a solution, thereby increasing the solute concentration. The concentration methods mainly include falling film evaporation concentration (the same as falling film concentration in this application), rising film evaporation concentration, forced circulation evaporation concentration, scraped film evaporation concentration, single-effect evaporation concentration, multi-effect evaporation concentration, heat pump evaporation concentration, and spray evaporation / drying concentration. In a specific embodiment, the evaporation concentration is falling film evaporation (falling film concentration), and the other evaporation concentration methods mentioned above are all alternative means.

[0027] In a specific embodiment, the method further includes: (3) mixing the concentrated milk with light cream to obtain a mixture, sterilizing it, and cooling it.

[0028] In a specific embodiment, the method further includes: (4) inoculating with a fermenting agent and rennet, stirring evenly, and fermenting under suitable conditions to obtain curd.

[0029] In a specific embodiment, the method further includes: (5) maturing the fermented curd to obtain pre-concentrated cheese.

[0030] In a specific embodiment, in step (1), the concentration factor is 3.1-3.7.

[0031] Furthermore, controlling the concentration factor and total solids content range in the above steps can effectively balance membrane separation efficiency and equipment operational stability: too low a concentration will affect the efficiency of subsequent processes, while too high a concentration can easily lead to increased membrane fouling and decreased membrane flux, which is not conducive to continuous and stable production. At the same time, this total solids content also provides a suitable material basis for the subsequent falling membrane concentration process, helping to control the final concentration ratio of lactose and minerals while optimizing energy consumption, which is crucial for the flavor and texture formation of the finished cheese. The total solids content was measured using a moisture analyzer and calculated using the difference method.

[0032] In specific embodiments, the concentration factor is 3.1, 3.3, 3.5, or 3.7.

[0033] In a specific embodiment, in step (2), the concentration factor is 2.5-4.0;

[0034] In specific embodiments, the concentration factor is 2.5, 3.1, 3.6, or 4.0.

[0035] In a specific embodiment, in step (2), the temperature of the falling film concentration is 55-65℃;

[0036] In specific embodiments, the falling film concentration temperature is 55°C, 60°C, 62°C, or 65°C.

[0037] Furthermore, the concentration factor in step (2) is 2.5-4.0, the total solids content of the concentrated material is 30%-60%, and the falling film concentration temperature is 55-65℃. After this process, the lactose content of the concentrated milk is controlled at 1-5%, and the protein content is controlled at 20-60%. Limiting the concentration factor and total solids content in this step can prevent excessive evaporation load or reduced efficiency due to excessively high solids content. Controlling the lactose content within this range provides a suitable carbon source for subsequent fermentation processes, ensuring the normal formation of microbial fermentation activity and flavor. On the other hand, it prevents excessively high lactose content from causing excessively high osmotic pressure in the material, which is not conducive to microbial growth and affects the flavor of the final product. Controlling the protein content can effectively control the viscosity of the concentrated material, preventing excessive scaling on the inner walls of transmission pipelines and equipment, thereby ensuring the continuity and efficiency of production.

[0038] In a specific embodiment, in step (3), the concentrated milk and light cream are mixed to make the mass ratio of fat to protein 0.6-1.2:1;

[0039] In specific embodiments, the mass ratio of fat to protein in the mixture is 1.2:1, 1:1, 0.8:1, or 0.6:1.

[0040] In a specific embodiment, the sterilization in step (3) includes pasteurization; in a specific embodiment, the sterilization temperature is 63-90℃, and preferably, the sterilization time is 5s-30min;

[0041] In specific embodiments, the sterilization temperature is 63°C, 72°C, 85°C, or 90°C.

[0042] In specific embodiments, the sterilization time is 30 min, 20 s, 15 s, or 5 s.

[0043] In a specific embodiment, in step (4), the ratio of the fermenting agent to the mixture is 46 mg: 1 kg. In a specific embodiment, the fermenting agent includes one or more of lactic acid bacteria fermenting agents and CH21.31 fermenting agents. In a specific embodiment, the mass ratio of the lactic acid bacteria fermenting agent to the CH21.31 fermenting agent is 16-30 mg: kg.

[0044] In a specific embodiment, the lactic acid bacteria starter is STA IDC 604 lactic acid bacteria starter, which was purchased from Beijing Duoate Biotechnology Co., Ltd.

[0045] In a specific embodiment, the CH21.31 fermentation agent was purchased from Tianjin Yu'ao Trading Co., Ltd.

[0046] In a specific embodiment, in step (4), the ratio of the rennet to the mixture is 25 mg: 1 kg.

[0047] In a specific embodiment, in step (4), the fermentation temperature is 30-35℃ and the fermentation time is 18-24h;

[0048] In specific embodiments, the fermentation temperature is 30°C, 32°C, 34°C, or 35°C.

[0049] In specific embodiments, the fermentation time is 18h, 20h, 22h, or 24h.

[0050] In a specific embodiment, in step (5), the maturation temperature is 12-15℃ and the time is 7-14 days.

[0051] In specific embodiments, the maturation temperature is 12℃, 13℃, 14℃, or 15℃.

[0052] In specific embodiments, the maturation time is 7 days, 10 days, 12 days, or 14 days.

[0053] For example, the protein content is 3.3%; in step (1), the ultrafiltration concentration factor is 3.1, and the total solids content reaches 12%; in step (2), the falling membrane concentration factor is 2.5, the concentration temperature is 55°C, and the total solids content reaches 30%.

[0054] For example, the protein content is 3.4%; in step (1), the ultrafiltration concentration factor is 3.3, and the total solids content reaches 13%; in step (2), the falling membrane concentration factor is 3.1, the concentration temperature is 60°C, and the total solids content reaches 40%.

[0055] For example, the protein content is 3.5%; in step (1), the ultrafiltration concentration factor is 3.5, and the total solids content reaches 14%; in step (2), the falling membrane concentration factor is 3.6, the concentration temperature is 62°C, and the total solids content reaches 50%.

[0056] For example, the protein content is 3.6%; in step (1), the ultrafiltration concentration factor is 3.7, and the total solids content reaches 15%; in step (2), the falling membrane concentration factor is 4.0, the concentration temperature is 65°C, and the total solids content reaches 60%.

[0057] For example, in step (3), the concentrated milk is mixed with light cream to achieve a fat-to-protein mass ratio of 1.2:1, and the sterilization is performed at 63°C for 30 minutes.

[0058] On the other hand, this application provides pre-concentrated cheese prepared by any of the preparation methods described above.

[0059] The pre-concentrated cheese prepared in the above manner, compared with pre-concentrated cheese produced by adding milk protein powder, does not have a noticeable grainy or powdery texture, and it does not have a protein powder taste, possessing a natural milky aroma. Therefore, the concentrated milk prepared in the above manner is a preferred raw material for preparing pre-concentrated cheese.

[0060] In a specific implementation, the pre-concentrated cheese contains protein, and the protein mass percentage is ≥14.5% based on the total mass of the pre-concentrated milk. In a specific implementation, the protein mass percentage is ≥18.6%. In a specific implementation, the protein mass percentage is ≥23.4%. In a specific embodiment, the protein mass percentage is ≤29.6%.

[0061] In a specific implementation, the pre-concentrated cheese contains fat, and the mass percentage of the fat is ≥17.4% based on the total mass of the pre-concentrated milk. In a specific implementation, the mass percentage of the fat is ≥17.8%. In a specific implementation, the mass percentage of the fat is ≥18.6%. In a specific embodiment, the mass percentage of the fat is ≤18.7%.

[0062] In specific implementation, the pre-concentrated cheese has one or more functions selected from the following:

[0063] (1) Under normal field of vision, there is no obvious graininess or powdery feel;

[0064] (2) Sensory score ≥ 33.0; preferably, the sensory score is based on a 10-point scale: the higher the score, the better the indicator, and the indicator includes product color, texture, overall aroma, and overall taste;

[0065] The color rating is as follows: 7-10 points for a uniform, milky white color; 4-6 points for a moderate, somewhat dull color; and 1-3 points for an uneven, noticeably different color.

[0066] The specific scores for tissue condition are as follows: 7-10 points for a uniform texture, smooth and delicate surface with no graininess; 4-6 points for a relatively uniform texture with slightly loose small particles on the surface; and 1-3 points for a rough, loose, and brittle texture.

[0067] The overall aroma rating is as follows: 7-10 points for a rich, creamy aroma with a pleasant sourness and good flavor; 4-6 points for a fairly strong, pleasant, and relatively good aroma with no unpleasant odors and a slight sourness; and 1-3 points for a strong, unpleasant aroma with no creamy aroma and a noticeable off-odor.

[0068] In a specific embodiment, the conventional field of view is taken at twice the distance between the human eye and the cheese sample (15-20cm) or the distance between the mobile phone and the cheese sample (10-20cm).

[0069] Compared with the traditional whey removal process, the pre-concentrated cheese prepared in this application not only has a similar overall sensory score to the example, but also retains its nutritional components, which proves that the process of this application is more advantageous than the traditional process.

[0070] On the other hand, this application provides cheese, which is obtained from pre-concentrated cheese prepared by any of the preparation methods described above or from the pre-concentrated cheese described above.

[0071] On the other hand, this application provides a food product containing pre-concentrated cheese prepared by any of the above-described preparation methods, the aforementioned pre-concentrated cheese, or the aforementioned cheese.

[0072] Without violating common sense in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0073] The cheese and its preparation method provided by this invention have the following technical advantages: The combination of ultrafiltration and falling membrane concentration equipment allows for efficient overall efficiency, with ultrafiltration responsible for concentrating whey protein in the early stages to reduce nutrient loss, and falling membrane concentration responsible for increasing total solids in the later stages. This method eliminates the powdery texture caused by artificial blending and omits the whey removal step, simplifying the operation process and facilitating its integration into automated production lines.

[0074] The milk used in this example was pasteurized skim milk with a pH of 6.75 or higher. By weight, the lactose content was 4.5-5.0%, and the protein content was 3.3-3.6%. The starter cultures used in this example included STA IDC 604 lactic acid bacteria starter culture and CH21.31 starter culture, in a mass ratio of 16:30. STA IDC 604 lactic acid bacteria starter culture was purchased from Beijing Duoate Biotechnology Co., Ltd., and CH21.31 starter culture was purchased from Tianjin Yu'ao Trading Co., Ltd.

[0075] The rennet used in the examples is calf abomasal rennet from Beijing Duoate Biotechnology Co., Ltd.

[0076] Example 1

[0077] Milk with a protein content of 3.3% was concentrated using an ultrafiltration membrane with a pore size of 5 nm. The concentration factor was set to 3.1, and the total solids content reached 12%. Ultrafiltration was then stopped, and the ultrafiltered milk was collected. The ultrafiltered milk was then concentrated using a falling membrane at a temperature of 55℃. The concentration factor was set to 2.5, and the total solids content reached 30%. The falling membrane concentration was then stopped, and the concentrated milk was collected.

[0078] Concentrated milk and light cream were mixed to achieve a fat-to-protein ratio of 1.2:1, resulting in a concentrated milk and light cream mixture. The mixture was sterilized at 63°C for 30 minutes. A starter culture was added at a ratio of 46 mg / kg of starter culture to the concentrated milk and light cream mixture, and rennet was added at a ratio of 25 mg / kg of rennet to the mixture. The mixture was stirred at 20 rpm until homogeneous, and fermented at 30°C for 18 hours. The fermented curd was then aged at 12°C for 7 days to obtain pre-concentrated cheese.

[0079] Total solids content determination: Measured using a moisture analyzer, and calculated using the difference method: First, the moisture content is detected using a moisture analyzer; then, the total mass of the original sample is subtracted from the moisture content; the difference is the total solids content.

[0080] Protein content determination: Protein content was determined according to the Kjeldahl method in GB 5009.5—2025, "National Food Safety Standard - Determination of Protein in Food".

[0081] Fat content detection: The fat content was determined according to the alkaline hydrolysis method in GB 5009.6—2016 "National Food Safety Standard - Determination of Fat in Food".

[0082] The starter cultures used in this embodiment include STA IDC 604 lactic acid bacteria starter culture and CH21.31 starter culture, with a mass ratio of 16:30. STA IDC 604 lactic acid bacteria starter culture was purchased from Beijing Duoate Biotechnology Co., Ltd., and CH21.31 starter culture was purchased from Tianjin Yu'ao Trading Co., Ltd.

[0083] The rennet is a calf abomasal rennet from Beijing Duoate Biotechnology Co., Ltd.

[0084] Example 2

[0085] Milk with a protein content of 3.4% was concentrated using an ultrafiltration membrane with a pore size of 30 nm. The concentration factor was set to 3.3, and the total solids content reached 13%. Ultrafiltration was then stopped, and the ultrafiltered milk was collected. The ultrafiltered milk was then concentrated using a falling membrane at a temperature of 60℃. The concentration factor was set to 3.1, and the total solids content reached 40%. The falling membrane concentration was then stopped, and the concentrated milk was collected.

[0086] Concentrated milk and light cream were mixed to achieve a fat-to-protein mass ratio of 1:1, resulting in a concentrated milk and light cream mixture. The mixture was sterilized at 72°C for 20 seconds. A starter culture was added at a ratio of 46 mg / kg of the concentrated milk and light cream mixture, and rennet was added at a ratio of 25 mg / kg of the same mixture. The mixture was stirred at 20 rpm until homogeneous, fermented at 32°C for 20 hours, and then allowed to mature at 13°C for 10 days. This yielded pre-concentrated cheese. The methods for determining total solids, protein, and fat content, as well as the starter culture, are as described in Example 1.

[0087] Example 3

[0088] Milk with a protein content of 3.5% was concentrated using an ultrafiltration membrane with a pore size of 70 nm. The concentration factor was set to 3.5, and the total solids content reached 14%. Ultrafiltration was then stopped, and the ultrafiltered milk was collected. The ultrafiltered milk was then concentrated using a falling membrane at a temperature of 62℃. The concentration factor was set to 3.6, and the total solids content reached 50%. The falling membrane concentration was then stopped, and the concentrated milk was collected.

[0089] Concentrated milk and light cream were mixed to achieve a fat-to-protein mass ratio of 0.8:1, resulting in a concentrated milk and light cream mixture. The mixture was sterilized at 85°C for 15 seconds. A starter culture was added at a ratio of 46 mg / kg of the concentrated milk and light cream mixture, and rennet was added at a ratio of 25 mg / kg of the same mixture. The mixture was stirred at 30 rpm until homogeneous. Fermentation was carried out at 34°C for 22 hours. The fermented curd was then aged at 14°C for 12 days to obtain pre-concentrated cheese. The methods for determining the total solids content, protein content, and fat content, as well as the starter culture, are as described in Example 1.

[0090] Example 4

[0091] Milk with a protein content of 3.6% was concentrated using an ultrafiltration membrane with a pore size of 100 nm. The concentration factor was set to 3.7, and the total solids content reached 15%. Ultrafiltration was then stopped, and the ultrafiltered milk was collected. The ultrafiltered milk was then concentrated using a falling membrane at a temperature of 65℃. The concentration factor was set to 4.0, and the total solids content reached 60%. The falling membrane concentration was then stopped, and the concentrated milk was collected.

[0092] Concentrated milk and light cream were mixed to achieve a fat-to-protein mass ratio of 0.6:1, resulting in a concentrated milk and light cream mixture. The mixture was sterilized at 90°C for 5 seconds. A starter culture was added at a ratio of 46 mg / kg of the concentrated milk and light cream mixture, and rennet was added at a ratio of 25 mg / kg of the concentrated milk and light cream mixture. The mixture was stirred at 50 rpm until homogeneous, fermented at 35°C for 24 hours, and then aged at 15°C for 14 days to obtain pre-concentrated cheese. The methods for determining the total solids content, protein content, and fat content, as well as the starter culture, are as described in Example 1.

[0093] Comparative Example 1

[0094] Milk protein powder (MPC60) filtered through a 70nm membrane, ultrapure water, and light cream were mixed to achieve a fat-to-protein mass ratio of 0.6:1, yielding a concentrated milk and light cream mixture. The mixture was sterilized at 90°C for 5 seconds. A starter culture was added at a ratio of 46 mg / kg of starter culture to the concentrated milk and light cream mixture. Rennet was added at a ratio of 25 mg / kg of rennet to the concentrated milk and light cream mixture. The mixture was stirred at 30 rpm until homogeneous. Fermentation was carried out at 35°C for 24 hours. The fermented curd was then matured at 15°C for 14 days to obtain cheese. The methods for determining total solids content, protein content, and fat content, as well as the starter culture, are as described in Example 1.

[0095] Comparative Example 2

[0096] Milk protein powder (MPC60) filtered through a 70nm membrane, ultrapure water, and light cream were mixed to achieve a fat-to-protein mass ratio of 1.2:1. The mixture was sterilized at 63°C for 30 minutes. A starter culture was added at a ratio of 46 mg / kg of the milk-to-cream mixture, and rennet was added at a ratio of 25 mg / kg of the milk-to-cream mixture. Fermentation was carried out at 30°C for 18 hours. The fermented curd was then matured at 12°C for 7 days to obtain cheese. The methods for determining total solids, protein, and fat content, and the starter culture were as described in Example 1.

[0097] Comparative Example 3

[0098] Skim milk was standardized to achieve a fat-to-protein weight ratio of 1.2:1 to obtain raw milk. The raw milk was pasteurized at 63°C for 30 minutes, then cooled to 30°C. A starter culture was added at a ratio of 46 mg / kg of starter culture to a mixture of concentrated milk and light cream, and rennet was added at a ratio of 100 mg / kg of rennet to a mixture of concentrated milk and light cream. The mixture was stirred at 30 rpm to obtain curd. The curd was cut into 2×2×2 cm cubes, stirred for 1 minute, and then allowed to stand for 30 minutes to obtain curd blocks. 82% of the total weight of whey was removed from the raw milk. The curd was then salted, dried, and matured at 12°C for 7 days to obtain cheese. The methods for determining the total solids content, protein content, and fat content, and the starter culture were as described in Example 1.

[0099] Comparative Example 4

[0100] Milk with a protein content of 3.6% was concentrated using a 70 nm ultrafiltration membrane. The concentration factor was set to 3.7, and the total solids content reached 15%. Ultrafiltration was then stopped, and the ultrafiltered milk was collected. The ultrafiltered milk was mixed with light cream to achieve a fat-to-protein mass ratio of 0.6:1, resulting in a concentrated milk-light cream mixture. The mixture was sterilized at 90°C for 5 seconds. A starter culture was added at a ratio of 46 mg / kg of starter culture to the concentrated milk-light cream mixture, and rennet was added at a ratio of 25 mg / kg of rennet to the concentrated milk-light cream mixture. The mixture was stirred at 30 rpm until homogeneous, fermented at 35°C for 24 hours, and then aged at 15°C for 14 days to obtain cheese. The methods for determining the total solids content, protein content, and fat content, as well as the starter culture, are as described in Example 1.

[0101] Comparative Example 5

[0102] Milk with a protein content of 3.5% was concentrated using an ultrafiltration membrane with a pore size of 70 nm. The concentration factor was set to 2.5, and the total solids content was 10%. Ultrafiltration was then stopped, and the ultrafiltered milk was collected. The ultrafiltered milk was then concentrated using a falling membrane at a temperature of 62℃. The concentration factor was set to 2.0, and the total solids content was 20%. The falling membrane concentration was then stopped, and the concentrated milk was collected.

[0103] Concentrated milk and light cream were mixed to achieve a fat-to-protein mass ratio of 0.8:1, resulting in a concentrated milk and light cream mixture. The mixture was sterilized at 85°C for 15 seconds. A starter culture was added at 46 mg / kg of the concentrated milk and light cream mixture, and rennet was added at 25 mg / kg of the mixture. The mixture was stirred at 30 rpm until homogeneous. Fermentation was carried out at 34°C for 22 hours. The fermented curd was then aged at 14°C for 12 days to obtain cheese. The methods for determining the total solids content, protein content, and fat content, as well as the starter culture, are as described in Example 1.

[0104] Table 1. Physicochemical properties of cheese obtained from different embodiments.

[0105]

[0106] The sensory evaluation methods are as follows:

[0107] Professional descriptive testing evaluators: The evaluation team members are selected and trained R&D and product evaluators.

[0108] Participants: 10 people.

[0109] Descriptive testing: This requires evaluators to score and describe the various sensory characteristics of a product according to standards.

[0110] The tasting was conducted using a 10-point scale: the higher the score, the better the characteristic indicator. A professional tasting panel evaluated five product characteristics, including product color, texture, overall aroma, and overall taste, and scored each characteristic. The average score from 10 professionals was taken, and the results are shown in Table 2.

[0111] The color rating is as follows: Uniform color, milky white, very likable - 7-10 points. Average color, rather dull, somewhat likable - 4-6 points. Uneven color, obvious variations, disliked - 1-3 points.

[0112] The specific organizational condition ratings are as follows: Uniform texture, smooth and delicate surface, no graininess, very good - 7-10. Relatively uniform texture, with slightly loose small particles on the surface, somewhat good - 4-6. Coarse texture, loose, brittle, not good - 1-3.

[0113] The overall aroma ratings are as follows: Rich milky aroma with a pleasant sourness, good flavor, very much liked -7-10. Relatively rich milky aroma, no unpleasant odors, slightly sour, good flavor, somewhat liked -4-6. No milky aroma, noticeable off-odor, disliked -1-3.

[0114] The overall taste rating is as follows: Possesses its own unique flavor, moderate intensity, no bitterness, no irritation, very much liked -7-10. Possesses its own unique flavor, weak intensity, weak bitterness, somewhat liked -4-6. Poor taste, noticeable off-flavor, disliked -1-3.

[0115] Table 2 Sensory test results of cheeses obtained from different embodiments

[0116]

[0117] According to the sensory evaluation results in Table 2, the cheese prepared using the technical solution of this invention (Examples 1-4) has a significantly higher overall sensory score than all comparative examples, especially in terms of texture and flavor (e.g., Figure 1 , Figure 1 (The cheese prepared in Example 1).

[0118] Specifically, the cheeses produced in Comparative Example 1 and Comparative Example 2 (pre-added milk protein powder process) exhibit a noticeable grainy and powdery texture (e.g., ...). Figure 2 , Figure 2 The cheese prepared in Comparative Example 2 had a certain protein powder flavor and lacked the natural milk aroma of the product of this invention. This is a common defect when using traditional pre-addition processes. Although Comparative Example 3 (traditional whey removal process) was similar to the examples in terms of overall sensory score, its specific process defects led to the unexpected loss of nutrients, which proves that its process route is insufficient in maintaining the nutritional balance of the product.

[0119] More significantly, Comparative Example 4 (omitting the falling film concentration step) and Comparative Example 5 (using a concentration factor lower than that of this invention) directly resulted in insufficient total solids content in the intermediate products. In particular, the excessively low concentration factor in the membrane filtration concentration step of Comparative Example 5 led to an imbalance in the evaporation load of the subsequent falling film concentration process, significantly reducing production efficiency. This resulted in a low total solids content in the finished cheese, fundamentally negatively impacting its flavor intensity, texture fullness, and stability. This contrasts sharply with the richly flavored and firm-textured products achieved in Examples 1-4.

[0120] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing concentrated milk, characterized in that, Includes the following steps: (1) Milk is concentrated by ultrafiltration to obtain ultrafiltered milk, wherein the total solids content of the ultrafiltered milk is 12%-15% by mass. (2) The ultrafiltration milk is evaporated and concentrated to obtain concentrated milk. The total solids in the concentrated milk are 30%-60% by mass based on the total mass of the concentrated milk.

2. The method for preparing concentrated milk as described in claim 1, characterized in that, In step (1), the evaporation concentration is selected from falling film evaporation concentration, rising film evaporation concentration, forced circulation evaporation concentration, single-effect evaporation concentration, multi-effect evaporation concentration, heat pump evaporation concentration, and spray evaporation / drying concentration; preferably, the evaporation concentration is selected from falling film evaporation concentration. And / or, in step (1), the pore size of the ultrafiltration concentration is 5-100 nm; And / or, in step (1), the milk is skim milk; preferably, the milk contains protein, and the mass percentage of protein in the milk is 3.3-3.6% based on the total mass of the milk; preferably, the milk contains lactose, and the mass percentage of lactose in the milk is 4.5-5.0% based on the total mass of the milk; And / or, in step (1), the concentration factor is 3.1-3.7; And / or, in step (2), the concentration factor is 2.5-4.0; And / or, in step (2), the temperature of the falling film evaporation concentration is 55-65°C.

3. A method for preparing pre-concentrated cheese, characterized in that, include: The concentrated milk prepared by the method of any one of claims 1-2 is mixed with light cream to obtain a mixture, which is then sterilized and cooled.

4. The preparation method according to claim 3, characterized in that, The method further includes: inoculating the cooled mixture with a starter culture and rennet, stirring evenly, and fermenting under suitable conditions to obtain curd; preferably, the method further includes: maturing the curd to obtain pre-concentrated cheese.

5. The preparation method according to claim 3 or 4, characterized in that, The mixture contains fat and protein, wherein the mass ratio of fat to protein is 0.6-1.2:1; And / or, the sterilization includes pasteurization; preferably, the sterilization temperature is 63-90°C, and preferably, the sterilization time is 5s-30min; And / or, the starter culture is used for cheese fermentation; preferably, the ratio of the starter culture to the mixture is 46 mg: 1 kg; preferably, the starter culture includes one or more of lactic acid bacteria starter culture and CH21.31 starter culture; more preferably, the mass ratio of the lactic acid bacteria starter culture to the CH21.31 starter culture is 16:30; And / or, the ratio of the rennet to the mixture is 25 mg: 1 kg; And / or, the fermentation temperature is 30-35℃, and the fermentation time is 18-24h; And / or, the ripening temperature is 12-15℃, and the ripening time is 7-14 days.

6. Pre-concentrated cheese prepared by any one of the preparation methods according to claims 3-5.

7. The pre-concentrated cheese as described in claim 6, characterized in that, The pre-concentrated cheese contains protein, and the protein content in the pre-concentrated milk is ≥14.5% by mass based on the total mass of the pre-concentrated milk; preferably, the protein content is ≥18.6% by mass, and even more preferably, the protein content is ≥23.4% by mass. And / or, the pre-concentrated cheese contains fat, and the percentage of fat in the pre-concentrated milk is ≥17.4% by mass of the total mass of the pre-concentrated milk; preferably, the percentage of fat is ≥17.8% by mass, and more preferably, the percentage of fat is ≥18.6% by mass.

8. The pre-concentrated cheese as described in claim 6, characterized in that, The pre-concentrated cheese has one or more of the following: (1) Under normal visual conditions, there is no obvious graininess or powdery feel; (2) Sensory score ≥ 33.0; preferably, the sensory score is based on a 10-point scale: the higher the score, the better the indicator, and the indicator includes product color, texture, overall aroma, and overall taste; The color score is as follows: uniform color, milky white, scores 7-10 points; average color, rather dull, scores 4-6 points; uneven color, obvious changes, scores 1-3 points. The specific organizational condition score is as follows: 7-10 points for uniform texture, smooth and delicate surface, and no grainy texture; 4-6 points for relatively uniform texture with slightly loose small particles on the surface; and 1-3 points for rough, loose, and brittle texture. The overall aroma score is as follows: 7-10 points for a rich milky aroma with a pleasant sour taste and good flavor; 4-6 points for a relatively rich milky aroma with no unpleasant odors and a slightly sour taste and good flavor; and 1-3 points for no milky aroma and a noticeable off-odor.

9. Cheese, characterized in that, The cheese comprises the pre-concentrated cheese as described in any one of claims 6-8.

10. Food products, characterized in that, The food contains the pre-concentrated cheese as described in any one of claims 6-8, or the cheese as described in claim 9.

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