Carbohydrate-free dairy product and preparation method thereof

Abstract

The invention discloses a preparation method of a zero-carbohydrate dairy product, which comprises the following steps: S1, performing purification treatment on raw milk, degreasing, and separating to obtain cream and skimmed milk; s2, feeding the skimmed milk into membrane separation equipment through a pump, and performing circular treatment for 10-60 minutes to obtain a concentrated solution; s3, adding an eluent at 60-70 DEG C into the concentrated solution in the step S3, and continuously circulating for 20-40 minutes; s4, sampling and detecting the contents of lactose and total carbohydrates in the concentrated solution, backfilling cream, and homogenizing; and S5, circulating the homogenized material at 60-70 DEG C for 20-40 minutes to complete pasteurization, and performing hot filling to obtain the carbohydrate-free dairy product. According to the preparation method of the zero-carbohydrate milk product, lactose and various oligosaccharides in skimmed milk can be thoroughly stripped, the carbohydrate content of the final product is less than or equal to 0.5 g / 100g, the zero-carbohydrate standard is really achieved, the strict requirements of ketogenic diet, diabetic patients and sugar-controlled people are completely met, and the market prospect is wide. And blood sugar fluctuation and metabolic burden caused by sugar intake are avoided from the source.

Description

Technical Field

[0001] This invention relates to the field of dairy processing technology, specifically to a zero-carbohydrate dairy product and its preparation method. Background Technology

[0002] Dairy products, as an important source of high-quality protein, calcium, and various bioactive substances (such as lactoferrin and immunoglobulins), occupy an important position in the daily diet and are favored by people of all ages. However, lactose, which is naturally present in conventional dairy products, is the main source of carbohydrates. Every 100g of regular milk contains approximately 4.5-5.0g of lactose. This characteristic makes it difficult to meet the dietary needs of certain groups: for those who follow a ketogenic diet, a low-carb diet, or are fitness enthusiasts controlling their blood sugar, lactose intake can affect blood sugar stability and the achievement of metabolic goals; for approximately 70% of the global population who are lactose intolerant, lactose cannot be completely digested and absorbed, easily causing gastrointestinal discomfort such as bloating and diarrhea; for people with chronic diseases such as diabetes, the glucose produced from lactose metabolism can directly cause blood sugar fluctuations, increasing the difficulty of disease control.

[0003] To address the aforementioned issues, various existing technologies have been developed to reduce the lactose content in dairy products. The most common method involves adding lactase to enzymatically hydrolyze lactose. However, this method only breaks down lactose into glucose and galactose, failing to achieve the "zero-carbohydrate" goal and still placing a burden on those controlling their sugar intake. Some solutions employ membrane filtration technology to separate lactose, such as the multi-stage filtration method disclosed in patent CN116998555A, which uses 10-20KD and 800-1000D molecular weight cutoff membranes. While this method can separate lactose, the membrane pore size design is not specifically targeted, easily leading to adsorption loss or incomplete separation of active proteins in the milk. Furthermore, it requires multiple filtration steps and subsequent separate sterilization processes, making the process complex and potentially damaging the product's flavor. In addition, some processes reduce lactose content through dilution, sugar removal, and concentration. However, this can lead to an imbalance in the proportions of core nutrients such as protein and calcium in dairy products, or the inactivation of active substances such as lactoferrin and lactoperoxidase due to high-temperature processing, severely impacting the product's nutritional value and drinking experience.

[0004] Therefore, there is an urgent need to develop a preparation technology that can effectively remove carbohydrates while preserving the original quality of dairy products. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing zero-carbohydrate dairy products. Through the design of membrane separation equipment and the use of a 60-70℃ hot water circulation elution process, lactose and various oligosaccharides in skim milk can be completely removed. The final product has a carbohydrate content of ≤0.5g / 100g, truly achieving the "zero-carbohydrate" standard. This fully meets the strict requirements of ketogenic diets, diabetic patients, and people controlling their blood sugar, and avoids blood sugar fluctuations and metabolic burden caused by sugar intake from the root.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: The first aspect of this invention provides a method for preparing zero-carbohydrate dairy products, comprising the following steps: S1. Raw milk is purified, then defatted, and separated to obtain cream and skim milk; S2. Skim milk is pumped into a membrane separation device and circulated for 10-60 minutes to obtain a concentrate; the membrane element of the membrane separation device has a pore size of 400-2000 Daltons and a flow channel size of 0.2-0.6 mil; S3. Add 60-70℃ eluent to the concentrate from step S3 and continue circulating for 20-40 minutes; S4. Sample and test the lactose and total carbohydrate content in the concentrate. Once the carbohydrate content is confirmed to be ≤0.5g / 100g, backfill the separated cream from step S1 and perform homogenization. S5. The homogenized material is pasteurized at 60-70℃ for 20-40 minutes. After the microbial indicators of the material are found to be qualified, it is hot-filled to obtain the zero-carbohydrate dairy product.

[0007] Preferably, in step S1, the raw milk can be any mammalian milk, including but not limited to one or more of cow's milk, goat's milk, and camel's milk.

[0008] Preferably, in step S1, the milk purification process employs centrifugation or filtration. This purification process removes impurities and somatic cells from the raw milk.

[0009] Preferably, in step S2, the membrane separation equipment consists of a pump, membrane tubing, a washing tank, a concentrate return pipe, a filtrate return pipe, a pressure gauge, a flow meter, and membrane elements, wherein the membrane elements are ceramic membranes or polyethersulfone membranes.

[0010] In step S2 of this invention, the membrane element of the membrane separation device has a pore size of 400-2000 Daltons and a flow channel size of 0.2-0.6 mil. This size is suitable for the precise retention of lactose molecules and at the same time reduces protein adsorption loss.

[0011] Preferably, in step S2, the pressure inside the membrane separation equipment is controlled at 0.3-0.8 MPa and the flow rate at 5-15 m³ / h, and the skim milk is circulated for 10-60 minutes to separate byproducts containing low protein, low fat, oligosaccharides, and dietary fiber. The separated byproducts, after concentration and drying, can be used to prepare functional feeds or food additives.

[0012] Preferably, in step S3, the volume ratio of the eluent to the concentrate is 2:1 to 4:1.

[0013] Preferably, in step S3, the eluent is hot water.

[0014] In step S3 of this invention, hot water is used as the eluent for cyclic elution, which can thoroughly remove residual lactose from the concentrate and improve purity. Secondly, a temperature of 60-70°C can reduce the viscosity of the milk without damaging the spatial structure of lactoferrin, thus improving membrane separation efficiency. Furthermore, at a relatively low pressure of 0.3-0.8 MPa, the reduction in material viscosity due to temperature achieves the lactose removal effect that would otherwise require ultra-high pressure nanofiltration, reducing energy consumption and minimizing shear damage to the protein.

[0015] Conventional sugar removal processes often lead to an imbalance in the calcium-to-phosphorus ratio. However, this invention, through a membrane with a specific pore size and a specific elution temperature (60-70°C), achieves an extraordinary retention ratio of active substances such as calcium and lactoferrin while thoroughly removing carbohydrates.

[0016] Preferably, in step S3, the eluent is a mineral conditioning solution; in a preferred embodiment, the mineral conditioning solution contains 0.05-0.15% by mass of soluble calcium salt and 0.02-0.08% by mass of phosphate.

[0017] In another preferred embodiment, the mineral conditioning solution comprises a permeate obtained by separating the byproducts separated in step S2 via a nanofiltration membrane.

[0018] Using hot water for cyclic elution removes a significant amount of soluble minerals such as calcium, magnesium, and phosphorus along with lactose. Therefore, in a preferred embodiment, the byproducts separated in step S2 are separated via nanofiltration to obtain a permeate rich in mineral ions and small-molecule minerals. By refluxing the permeate containing the byproducts, residual lactose in the eluent can be removed while maintaining osmotic pressure balance across the membrane, reducing the loss of minerals from the protein micelles, and thus ensuring a final product calcium content ≥220 mg / 100 g.

[0019] Preferably, in step S4, the homogenization temperature is 45-55℃, and the homogenization is performed 1-2 times.

[0020] A second aspect of the present invention provides a zero-carbohydrate dairy product prepared by the aforementioned method, wherein the dairy product has a dry matter content of 10-18 g / 100 g, a fat content of 0.01-9 g / 100 g, carbohydrates ≤0.5 g / 100 g, protein ≥5.5 g / 100 g, calcium ≥220 mg / 100 g, lactoferrin ≥18 mg / 100 g, immunoglobulins ≥30 mg / 100 g, and lactoperoxidase ≥180 IU / 100 g.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention, through the design of membrane separation equipment and the combination of a 60-70℃ circulating elution process, can completely remove lactose and various oligosaccharides from skim milk. The final product has a carbohydrate content of ≤0.5g / 100g, truly achieving the "zero-carbohydrate" standard. This fully meets the strict requirements of ketogenic diets, diabetic patients, and people controlling their blood sugar, and avoids blood sugar fluctuations and metabolic burden caused by sugar intake from the root.

[0022] 2. This invention adopts an integrated separation-sterilization process using membrane separation equipment. Under mild pasteurization conditions of 60-70℃, lactose separation and sterilization are completed simultaneously. Compared with the existing enzymatic hydrolysis method that destroys nutrients and the traditional multi-step process that leads to the inactivation of active ingredients, this invention can efficiently retain high-quality protein (≥5.5g / 100g), calcium (≥220mg / 100g), and bioactive substances such as lactoferrin and immunoglobulins in milk. Moreover, the product flavor is highly consistent with natural pasteurized milk, without any off-flavors or nutritional imbalances.

[0023] 3. The zero-carbohydrate dairy product prepared by this invention has a dry matter content of 10-18g / 100g, carbohydrates ≤0.5g / 100g, protein ≥5.5g / 100g, fat 0.01-9g / 100g, calcium ≥220mg / 100g, lactoferrin ≥18mg / 100g, immunoglobulins ≥30mg / 100g, and lactoperoxidase ≥180IU / 100g. People with lactose intolerance can drink it normally. This product is also suitable for patients with hyperglycemia, diabetes, and other chronic diseases, as well as those who need to control their blood sugar. Detailed Implementation

[0024] The present invention will be further described below with reference to specific embodiments, so that those skilled in the art can better understand and implement the present invention, but the embodiments are not intended to limit the present invention.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0026] Unless otherwise specified, the experimental methods used in the following examples and comparative examples are conventional methods, and the materials and reagents used are commercially available unless otherwise specified. Example

[0027] This embodiment provides a method for preparing zero-carbohydrate dairy products, including the following steps: 1. Raw material preparation: Fresh milk was selected as raw milk. Its physicochemical indicators were tested and found to be 3.2g / 100g protein, 3.5g / 100g fat, and 110mg / 100g calcium. The microbiological indicators met the requirements of GB 25190-2010 and there were no adulteration items.

[0028] 2. Milk purification process: The raw milk is centrifuged using a disc centrifuge to remove impurities and somatic cells, resulting in clean raw milk.

[0029] 3. Defatting process: The clean raw milk is defatted using a defatting separator to separate the cream (refrigerated for later use) and skim milk.

[0030] 4. Membrane separation treatment: Skim milk is fed into the membrane separation equipment by a booster pump. The membrane element has a pore size of 800 Da and a flow channel of 0.4 mil. The pressure inside the equipment is controlled at 0.5 MPa and the flow rate is 10 m³ / h. The equipment is circulated for 30 minutes to separate the by-products.

[0031] 5. Hot water elution: Add sterile hot water at 65°C (hot water to concentrate volume ratio 2:1) to the concentrate and continue circulation for 30 minutes.

[0032] 6. Testing and Adjustment: The carbohydrate content of the sample was found to be 0.3g / 100g. The sample was then backfilled with refrigerated cream and homogenized once at 50℃ and 25MPa pressure.

[0033] 7. Integrated sterilization: Maintain 65℃ and circulate for 30 minutes in the membrane separation equipment to complete pasteurization.

[0034] 8. Filling and Packaging: Hot filling at 80℃, followed by sealing and packaging after cooling to 4℃. Example

[0035] This embodiment provides a method for preparing zero-carbohydrate dairy products, including the following steps: 1. Raw material preparation: Goat milk and camel milk were mixed in a 1:1 ratio as raw milk. The physicochemical indicators were tested and found to be 3.1g / 100g protein, 3.3g / 100g fat, and 105mg / 100g calcium. The microbiological indicators met the requirements of GB 25190-2010 and there were no adulteration items.

[0036] 2. Milk purification process: Raw milk is purified using a filtration process to remove impurities and somatic cells.

[0037] 3. Defatting process: Defatting is performed using a defatting separator to separate cream (for refrigeration) and skim milk.

[0038] 4. Membrane separation treatment: Skim milk is fed into a membrane separation device with a membrane element pore size of 1500 Da and a flow channel of 0.3 mil. The pressure is controlled at 0.6 MPa and the flow rate at 8 m³ / h. The process is circulated for 40 min to separate the byproducts.

[0039] 5. Hot water elution: Add sterile hot water at 62℃ (hot water to concentrate volume ratio 3:1) and continue circulation for 35 minutes.

[0040] 6. Testing and Adjustment: The carbohydrate content of the sample was found to be 0.4g / 100g. The butter was then backfilled and homogenized twice at 48℃ and 22MPa pressure.

[0041] 7. Integrated sterilization: Maintain 62℃ and circulate for 35 minutes in the membrane separation equipment to complete pasteurization.

[0042] 8. Filling and Packaging: Hot filling at 78℃, followed by sealing and packaging after cooling to 4℃. Example

[0043] This embodiment provides a method for producing zero-carbohydrate dairy products, including the following steps: 1. Raw material preparation: Pure camel milk was selected as raw milk. Its physicochemical indicators were tested and found to be 3.3g / 100g protein, 3.6g / 100g fat, and 115mg / 100g calcium. The microbiological indicators met the requirements of GB 25190-2010 and there were no adulteration items.

[0044] 2. Milk purification process: Milk is purified by centrifugation using a disc centrifuge.

[0045] 3. Defatting process: Defatting separator separates cream (refrigerated) and skim milk.

[0046] 4. Membrane separation treatment: Skim milk is fed into a membrane separation device with a membrane element pore size of 500 Da, a flow channel of 0.5 mil, a pressure of 0.4 MPa, a flow rate of 12 m³ / h, and a circulation treatment of 25 min to separate the by-products.

[0047] 5. Hot water elution: Add sterile hot water at 68℃ (hot water to concentrate volume ratio 4:1) and circulate for 25 minutes.

[0048] 6. Testing and adjustment: Carbohydrate content 0.2g / 100g, backfill with butter, homogenize once at 52℃ and 28MPa.

[0049] 7. Integrated sterilization: Maintain 68℃ for 25 minutes in the membrane separation equipment to complete pasteurization.

[0050] 8. Filling and Packaging: Hot filling at 82℃, then cooling to 3℃ and sealing for packaging. Example

[0051] This embodiment provides a method for preparing zero-carbohydrate dairy products, including the following steps: 1. Raw material preparation: Fresh milk was selected as raw milk. Its physicochemical indicators were tested and found to be 3.2g / 100g protein, 3.5g / 100g fat, and 110mg / 100g calcium. The microbiological indicators met the requirements of GB 25190-2010 and there were no adulteration items.

[0052] 2. Milk purification process: The raw milk is centrifuged using a disc centrifuge to remove impurities and somatic cells, resulting in clean raw milk.

[0053] 3. Defatting process: The clean raw milk is defatted using a defatting separator to separate the cream (refrigerated for later use) and skim milk.

[0054] 4. Membrane separation treatment: Skim milk is fed into the membrane separation equipment by a booster pump. The membrane element has a pore size of 800 Da and a flow channel of 0.4 mil. The pressure inside the equipment is controlled at 0.5 MPa and the flow rate is 10 m³ / h. The equipment is circulated for 30 minutes to separate the by-products.

[0055] 5. Mineral conditioning solution elution: Collect the byproducts, filter them through a nanofiltration membrane to obtain the permeate, heat it to 65°C and add it to the concentrate (permeate to concentrate volume ratio 2:1), and continue to circulate for 30 min.

[0056] 6. Testing and Adjustment: The carbohydrate content of the sample was found to be 0.3g / 100g. The sample was then backfilled with refrigerated cream and homogenized once at 50℃ and 25MPa pressure.

[0057] 7. Integrated sterilization: Maintain 65℃ and circulate for 30 minutes in the membrane separation equipment to complete pasteurization.

[0058] 8. Filling and Packaging: Hot filling at 80℃, followed by sealing and packaging after cooling to 4℃.

[0059] Comparative Example 1: Traditional Enzymatic Hydrolysis Fresh milk, the same as in Example 1, was selected, lactase (0.5%) was added, and the milk was enzymatically hydrolyzed at 40°C for 2 hours. It was then pasteurized (65°C for 30 minutes), homogenized, and then filled and packaged.

[0060] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that Comparative Example 2 does not include a hot water rinsing step.

[0061] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that the membrane element pore size is 10 kDa.

[0062] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that Comparative Example 4 uses warm water at 25°C during the elution process.

[0063] The components of the dairy products prepared in the test examples and comparative examples were obtained, and the results are shown in Table 2.

[0064] Table 1 shows the sensory rating criteria.

[0065] Table 1 Evaluation Dimensions Weight Scoring Description (Standard Score Range) Color 10 points Uniform color, milky white or slightly yellow (8-10 points); uneven color or dull color (0-7 points). taste 40 points It has the inherent milky aroma of dairy products, a sweet and pure taste, and no off-flavors (32-40 points); the taste is mild, with a slight salty or bitter taste (0-31 points). odor 20 points It has a pure milky aroma, without any boiled, oxidized, or off-odors (16-20 points); a faint milky aroma or an off-odor (0-15 points). Organizational status 30 points It is a uniform liquid, smooth and mellow, without lumps, sediment, or residue adhering to the walls (24-30 points); or it is thin or has a noticeable grainy texture (0-23 points). Table 2 Group Carbohydrates (g / 100g) Protein (g / 100g) Calcium (g / 100g) Lactoferrin (g / 100g) Immunoglobulins (g / 100g) Sensory rating (out of 100) Example 1 0.32 5.8 228 19.5 32.8 92 Example 2 0.41 5.6 222 18.8 31.5 90 Example 3 0.21 6.2 235 20.4 36.2 93 Example 4 0.20 5.9 256 21.2 38.5 96 Comparative Example 1 4.85 3.2 112 5.4 8.2 85 Comparative Example 2 1.75 5.7 215 18.5 30.1 78 Comparative Example 3 0.62 4.1 182 8.6 14.5 75 Comparative Example 4 2.12 5.5 2081 17.2 28.6 70 Comparing the data from Example 1 and Comparative Example 2, it can be seen that without the elution step, the carbohydrate content is as high as 1.75g / 100g, failing to meet the "zero carbohydrate" standard. This demonstrates that the cyclic elution step described in this invention plays a crucial role in thoroughly removing residual lactose encapsulated around the protein micelles.

[0066] Comparing the data from Example 1 and Comparative Example 3, it can be seen that when the membrane pore size is increased to 10 kDa (a commonly used ultrafiltration pore size in the industry), the protein content drops sharply from 5.8 g to 4.1 g, and more than half of the small molecule active proteins such as lactoferrin and immunoglobulins are lost. This proves that the present invention achieves an unexpectedly precise balance between retaining active proteins and permeating lactose by selecting a pore size of 400-2000 Da.

[0067] Comparing the data from Example 1 and Comparative Example 4, it can be seen that when eluting with 25°C warm water, the carbohydrate content reached as high as 2.12g. This is because the viscosity of the feed solution is high at low temperatures, the diffusion rate of lactose molecules is slow, and the membrane flux is extremely low. This invention uses elution at 60-70°C, utilizing thermodynamic principles to reduce viscosity and significantly improve desaccharification efficiency. Simultaneously, since this temperature falls within the pasteurization temperature range, it achieves integrated separation and sterilization.

[0068] Comparing the data from Examples 1 and 4, it can be seen that after elution with the byproduct nanofiltration permeate, the calcium content increased by approximately 12% (from 228 mg to 256 mg), resulting in the highest sensory score. This demonstrates that refilling with minerals not only prevents protein denaturation and loss but also locks in more active substances through osmotic pressure regulation, significantly enhancing the richness and flavor of the sugar-free milk.

[0069] The above-described embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. A method for preparing a zero-carbohydrate dairy product, characterized in that, Includes the following steps: S1. Raw milk is purified, then defatted, and separated to obtain cream and skim milk; S2. Skim milk is pumped into a membrane separation device and circulated for 10-60 minutes to obtain a concentrate; the membrane element of the membrane separation device has a pore size of 400-2000 Daltons and a flow channel size of 0.2-0.6 mil; S3. Add elution buffer at 60-70℃ to the concentrate from step S3 and continue circulating for 20-40 minutes; S4. Sample and test the lactose and total carbohydrate content in the concentrate. Once the carbohydrate content is confirmed to be ≤0.5g / 100g, backfill the separated cream from step S1 and perform homogenization. S5. The homogenized material is pasteurized at 60-70℃ for 20-40 minutes. After the microbial indicators of the material are found to be qualified, it is hot-filled to obtain the zero-carbohydrate dairy product.

2. The method for preparing a zero-carbohydrate dairy product according to claim 1, characterized in that, In step S1, the raw milk is selected from one or more of cow's milk, goat's milk, and camel's milk.

3. The method for preparing a zero-carbohydrate dairy product according to claim 2, characterized in that, In step S1, the milk purification process employs centrifugation or filtration.

4. The method for preparing a zero-carbohydrate dairy product according to claim 1, characterized in that, In step S2, the membrane separation equipment consists of a pump, membrane tubing, a washing tank, a concentrate return pipe, a filtrate return pipe, a pressure gauge, a flow meter, and membrane elements, wherein the membrane elements are ceramic membranes or polyethersulfone membranes.

5. The method for preparing a zero-carbohydrate dairy product according to claim 1, characterized in that, In step S2, the pressure inside the membrane separation equipment is controlled at 0.3-0.8 MPa and the flow rate is 5-15 m³ / h. Skim milk is circulated for 10-60 minutes to separate the byproducts.

6. The method for preparing a zero-carbohydrate dairy product according to claim 5, characterized in that, In step S2, the separated byproducts are concentrated and dried for use in the preparation of functional feeds or food additives.

7. The method for preparing a zero-carbohydrate dairy product according to claim 1, characterized in that, In step S3, the volume ratio of the eluent to the concentrate is 2:1 to 4:

1.

8. The method for preparing a zero-carbohydrate dairy product according to claim 7, characterized in that, In step S3, the eluent is hot water or a mineral conditioning solution; the mineral conditioning solution includes the permeate obtained by separating the byproducts separated in step S2 via a nanofiltration membrane.

9. The method for preparing a zero-carbohydrate dairy product according to claim 1, characterized in that, In step S4, the homogenization process is carried out at a temperature of 45-55°C and is performed 1-2 times.

10. A zero-carbohydrate dairy product prepared by any one of the preparation methods according to claims 1-9, characterized in that, The dairy product has a dry matter content of 10-18g / 100g, a fat content of 0.01-9g / 100g, a carbohydrate content of ≤0.5g / 100g, a protein content of ≥5.5g / 100g, a calcium content of ≥220mg / 100g, a lactoferrin content of ≥18mg / 100g, an immunoglobulin content of ≥30mg / 100g, and a lactoperoxidase content of ≥180IU / 100g.