Milk product for controlling carbohydrates and preparation method thereof

Abstract

The invention relates to the technical field of dairy product processing, in particular to a dairy product capable of controlling carbohydrates and a preparation method thereof, the preparation method comprises the following steps: 1) separating raw milk to obtain skimmed milk and single cream; 2) diverting the skimmed milk into a first skimmed milk stream and a second skimmed milk stream; 3) performing ultrafiltration concentration on the first skimmed milk flow to obtain ultrafiltration concentrated skimmed milk; 4) performing nanofiltration concentration on the second skimmed milk flow to obtain nanofiltration concentrated skimmed milk; and 5) mixing the ultra-filtered and concentrated skimmed milk obtained in the step 3) and the nano-filtered and concentrated skimmed milk obtained in the step 4) to obtain the dairy product for controlling carbohydrates. According to the invention, no processing aid is used, and the low-sodium high-calcium dairy product can be prepared on the premise of controlling carbohydrates only through combined use of processes, so that the health demand and the taste demand of consumers are both considered.

Description

Technical Field

[0001] This invention relates to the field of dairy processing technology, and in particular to a dairy product with controlled carbohydrate content and its preparation method. Background Technology

[0002] With increasing consumer demand for nutrition and health, high-protein milk is gradually becoming a market trend. Various companies are employing different concentration methods to increase the protein, calcium, and other nutrient content of milk. Commonly used milk concentration methods in current technology include evaporation concentration, falling membrane concentration, and the increasingly popular reverse osmosis (RO) concentration. However, when using these full concentration processes, when the milk is concentrated to a protein content of ≥4.5% or higher, a noticeable salty taste begins to appear. Although this improves nutritional value, the excessive saltiness may make it unacceptable to consumers. This is because protein concentration increases the content of sodium and potassium ions in the milk, and the increased salt content has a negative impact on both taste and consumer health.

[0003] Sodium is an essential mineral for the human body, helping to maintain fluid balance, nerve conduction, and muscle contraction. However, excessive sodium intake can have adverse health effects, such as increasing the risk of high blood pressure and cardiovascular disease. Therefore, sodium intake needs to be controlled appropriately. Calcium is also an essential nutrient for the human body. It is well known that calcium plays a crucial role in bone health and muscle strength, and calcium has become the first ingredient that people look for when purchasing dairy products.

[0004] Nanofiltration (NF) technology can concentrate dairy products while allowing monovalent salt ions to pass through the membrane and retaining divalent salt ions, thereby reducing the sodium content and increasing the calcium content of the concentrated milk. Ultrafiltration (UF) technology can concentrate milk protein components, retaining protein micelles and allowing lactose and monovalent salt ions to pass through the membrane, thereby concentrating protein and calcium and slightly reducing the lactose and sodium content of the concentrated milk.

[0005] Most milk on the market is currently produced using either concentrated or unconcentrated milk (UF) methods. The disadvantages of these methods include significant susceptibility to seasonal fluctuations in raw milk prices and the inability to standardize the control of salt ions and lactose. Concentrated milk typically has a high sodium content, which is detrimental to health in the long term. UF milk reduces carbohydrates and concentrates protein, offering almost no improvement in taste or consumer experience.

[0006] Therefore, there is a need to develop a milk product that can both improve the taste for consumers and benefit their health. Summary of the Invention

[0007] In view of the shortcomings of the prior art described above, in order to solve the problem that it is difficult to balance the health requirements of low sodium and high calcium with the retention of an appropriate amount of carbohydrates to improve the taste in the current dairy product processing, the purpose of this application is to provide a method for preparing dairy products with controlled carbohydrates, so as to solve the problems in the prior art.

[0008] To achieve the above and other related objectives, this application first provides a method for preparing dairy products with controlled carbohydrate content, comprising the following steps:

[0009] 1) Separate the raw milk to obtain skim milk and light cream;

[0010] 2) Divide the skim milk into a first skim milk stream and a second skim milk stream;

[0011] 3) The first skim milk stream is concentrated by ultrafiltration to obtain ultrafiltration concentrated skim milk;

[0012] 4) The second skim milk stream is concentrated by nanofiltration to obtain nanofiltration concentrated skim milk;

[0013] 5) Mix the ultrafiltration concentrated skim milk obtained in step 3) and the nanofiltration concentrated skim milk obtained in step 4) to obtain a dairy product with controlled carbohydrates.

[0014] This application further provides a dairy product with controlled carbohydrates prepared by the above-described method.

[0015] Compared with the prior art, the beneficial effects of this application are as follows:

[0016] 1) The preparation method provided by the present invention allows factories to adjust the mixing ratio of nanofiltration concentrated milk and ultrafiltration concentrated milk to prepare dairy products with different carbohydrate contents, the carbohydrate content of which can be controlled in the range of 5.0~6.8 g / 100g.

[0017] 2) This invention separates raw milk into skim milk and cream, and pre-processes them separately. Subsequently, cream can be added back as needed according to the required fat content in the product to prepare milk products with different fat contents.

[0018] 3) The preparation method provided by this invention uses a combined nanofiltration and ultrafiltration process to prepare concentrated skim milk. After standardizing the backfill of light cream, it is finally homogenized and sterilized to prepare dairy products with controlled carbohydrates. Compared with ordinary high-protein, high-calcium milk, the milk prepared by this invention has a sodium content ≤50 mg / 100g, and compared with milk of the same high protein concentration, the sodium content is 25% or more lower, while the calcium content can reach more than 135 mg / 100g. Attached Figure Description

[0019] Figure 1This is a flowchart illustrating the process for preparing dairy products with controlled carbohydrates according to the present invention. Detailed Implementation

[0020] To make the inventive objectives, technical solutions, and beneficial effects of this application clearer, the following description, in conjunction with embodiments, further illustrates this application. It should be understood that the embodiments described are for illustrative purposes only and are not intended to limit the scope of the application. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this description.

[0021] Through extensive research and experimentation, the inventors of this invention discovered that by separating raw milk to obtain skim milk and cream, the skim milk is concentrated through nanofiltration and ultrafiltration, then mixed in proportion, and then mixed with cream for standardization before homogenization and sterilization. This process yields dairy products with controlled carbohydrate content, where the sodium content is lower than that of other high-calcium milk products with the same level of concentration. The carbohydrate content can be adjusted and controlled each time production is carried out based on the internal control requirements at that time.

[0022] This invention employs a technology that combines ultrafiltration and nanofiltration concentration. While concentrating protein and calcium, it filters out a portion of sodium and precisely controls the carbohydrate content. This solves the problems of concentrated milk having a salty taste and its indicators being greatly affected by seasonal fluctuations. It also addresses the issue of ultrafiltration milk having little difference in taste from regular milk and failing to meet consumers' demands for a rich and flavorful milk with high-quality indicators. Based on these findings, this invention was completed.

[0023] The first aspect of this application provides a method for preparing dairy products with controlled carbohydrate content, comprising the following steps:

[0024] 1) Separate the raw milk to obtain skim milk and light cream;

[0025] 2) Divide the skim milk into a first skim milk stream and a second skim milk stream;

[0026] 3) The first skim milk stream is concentrated by ultrafiltration to obtain ultrafiltration concentrated skim milk;

[0027] 4) The second skim milk stream is concentrated by nanofiltration to obtain nanofiltration concentrated skim milk;

[0028] 5) Mix the ultrafiltration concentrated skim milk obtained in step 3) and the nanofiltration concentrated skim milk obtained in step 4) to obtain a dairy product with controlled carbohydrates.

[0029] In this application, the term "ultrafiltration concentration" refers to the process of sieving a skim milk stream under pressure using an ultrafiltration membrane with a specific pore size or molecular weight cutoff. The principle is based on separation through differences in molecular size. This process selectively retains protein micelles and most divalent ions such as calcium, while allowing small molecules such as lactose and sodium, as well as some monovalent salt ions, to permeate through the membrane. Therefore, ultrafiltration concentration can significantly increase the concentration of protein and calcium in the concentrated product, while simultaneously reducing the content of lactose and sodium in the product.

[0030] In this application, the term "nanofiltration concentration" refers to the separation process of skim milk streams under pressure using nanofiltration membranes with nanoscale micropores and charged membrane surfaces. Its separation principle combines molecular size sieving and charge effect. This process can selectively retain lactose, protein, and divalent salt ions such as calcium, while allowing more monovalent salt ions such as water and sodium to permeate through the membrane. Therefore, nanofiltration concentration can effectively reduce the sodium content in the product while concentrating lactose, protein, and calcium in the skim milk stream.

[0031] In some specific embodiments, in step 1), the raw milk is raw cow's milk, with a protein content of 2.9~4.2 wt% and a carbohydrate content of 4.5~5.5 wt%.

[0032] In some specific embodiments, in step 1), the raw milk separation is carried out by centrifugal separation.

[0033] Preferably, the centrifugal separation conditions are: temperature 40~60℃, rotation speed 4000~5000rpm.

[0034] More preferably, the centrifugal separation conditions are: temperature of 50~55℃ and rotation speed of 4500~5000rpm.

[0035] In some specific embodiments, in step 2), the fat content of the skim milk is ≤0.05 wt%.

[0036] In this application, the raw milk is separated and defat is removed so that the fat content in the milk is ≤0.05 wt% in order to prevent the fat from contaminating and interfering with the ultrafiltration and nanofiltration membranes, and to ensure that the subsequent membrane separation process can efficiently separate and concentrate the protein, lactose, calcium and sodium as designed.

[0037] In some specific embodiments, in step 3), the ultrafiltration concentration uses an ultrafiltration membrane with a pore size of 5~100 nm.

[0038] Preferably, the ultrafiltration concentration uses an ultrafiltration membrane with a pore size of 5~20nm.

[0039] In some specific embodiments, in step 3), the ultrafiltration concentration uses an ultrafiltration membrane made of polyamide film composite material.

[0040] In some specific embodiments, in step 3), the temperature of ultrafiltration concentration is 4~10 ℃.

[0041] In some specific embodiments, in step 3), the feed pressure during ultrafiltration concentration is 1~5 bar.

[0042] Preferably, the feed pressure during ultrafiltration concentration is 3 to 5 bar; for example, the feed pressure can be 3 bar, 4 bar, or 5 bar.

[0043] More preferably, the feed pressure during ultrafiltration concentration is 4 bar.

[0044] In some specific embodiments, in step 3), the concentration ratio during ultrafiltration concentration is 1.0 to 3.3. Preferably, the concentration ratio during ultrafiltration concentration is 1.35 to 1.60.

[0045] In some specific embodiments, in step 3), the ultrafiltration concentrated skim milk has a protein content of 4.0~5.5 wt% and a carbohydrate content of 4.0~5.0 wt%.

[0046] In some specific embodiments, in step 4), the nanofiltration concentration uses a nanofiltration membrane with a pore size of 0.5~2 nm.

[0047] Preferably, the nanofiltration concentration uses a nanofiltration membrane with a pore size of 0.5~1 nm.

[0048] In some specific embodiments, in step 4), the nanofiltration concentration uses a nanofiltration membrane made of polyamide film composite material.

[0049] In some specific embodiments, in step 4), the temperature of nanofiltration concentration is 4~10 °C.

[0050] In some specific embodiments, in step 4), the feed pressure during nanofiltration concentration is 10~20 bar.

[0051] Preferably, the feed pressure during nanofiltration concentration is 15-17 bar; for example, the feed pressure can be 15 bar, 16 bar, or 17 bar.

[0052] More preferably, the feed pressure during nanofiltration concentration is 15 bar.

[0053] In some specific embodiments, in step 4), the concentration ratio during nanofiltration concentration is 1.0 to 3.3. Preferably, the concentration ratio during nanofiltration concentration is 1.35 to 1.60.

[0054] In some specific embodiments, in step 4), the nanofiltration concentrated skim milk has a protein content of 4.0-5.5 wt% and a carbohydrate content of 5.5-7.6 wt%.

[0055] In some specific embodiments, in step 5), the mixing mass ratio Y of the ultrafiltration concentrated skim milk and the nanofiltration concentrated skim milk conforms to the following formula:

[0056]

[0057] Wherein, A is the expected mass percentage concentration of carbohydrates in the dairy product; B is the mass percentage concentration of carbohydrates in the ultrafiltration concentrated skim milk; and C is the mass percentage concentration of carbohydrates in the nanofiltration concentrated skim milk.

[0058] The mass percentage concentration of carbohydrates in ultrafiltration concentrated skim milk and nanofiltration concentrated skim milk can be obtained by detection after steps 3) and 4), respectively.

[0059] In some specific embodiments, in step 5), the temperature of the nanofiltration concentrated skim milk and the ultrafiltration concentrated skim milk is 4~10℃.

[0060] In some specific embodiments, in step 5), the protein content in the dairy product with controlled carbohydrates is 4.0~5.4 wt%, and the carbohydrate content is 5.0~6.8 wt%.

[0061] In some specific implementations, after step 5), the addition of heavy cream to a dairy product with controlled carbohydrates is also included.

[0062] In some specific implementations, after step 5), the dairy product containing controlled carbohydrates is further homogenized and sterilized.

[0063] Preferably, the homogenization temperature is 50~65°C. More preferably, the homogenization temperature is 55~65°C.

[0064] Preferably, the homogenization pressure is 150-200 bar. More preferably, the homogenization pressure is 180-200 bar.

[0065] Preferably, the sterilization is selected from pasteurization, high-temperature sterilization, and direct steam injection sterilization.

[0066] More preferably, the pasteurization temperature is 72~76 ℃ and the holding time is 15-30s.

[0067] More preferably, the sterilization temperature of the high-temperature sterilization is 120~127 ℃, and the holding time is 15-60s.

[0068] More preferably, the sterilization temperature of the direct steam injection sterilization is 142~157 ℃, and the holding time is 0.09~6s.

[0069] More preferably, when the sterilization is selected from steam direct injection sterilization, the homogenization step should be placed after the sterilization process and should be homogenization in a sterile environment.

[0070] Preferably, after sterilization, the dairy products containing controlled carbohydrates are cooled to 2-6°C.

[0071] The second aspect of this application provides a dairy product with controlled carbohydrates prepared by the method described in the first aspect.

[0072] In some specific embodiments, based on the total mass of the dairy product containing controlled carbohydrates, the protein content of the dairy product containing controlled carbohydrates is 4.0~5.4 g / 100g. Preferably, the protein content of the dairy product containing controlled carbohydrates is 4.0~5.0 g / 100g.

[0073] In some specific embodiments, based on the total mass of the dairy product with controlled carbohydrates, the carbohydrate content of the dairy product with controlled carbohydrates is 5.0~6.8 g / 100g. Preferably, the carbohydrate content of the dairy product with controlled carbohydrates is 5.2~6.5 g / 100g.

[0074] In some specific embodiments, based on the total mass of the dairy product with controlled carbohydrates, the calcium content of the dairy product with controlled carbohydrates is ≥135 mg / 100g. Preferably, the calcium content of the dairy product with controlled carbohydrates is 140~180 mg / 100g.

[0075] In some specific embodiments, based on the total mass of the dairy product containing controlled carbohydrates, the sodium content of the dairy product containing controlled carbohydrates is ≤50 mg / 100g. Preferably, the sodium content of the dairy product containing controlled carbohydrates is 35~50 mg / 100g.

[0076] The present invention will be further illustrated by the following examples, but these examples do not limit the scope of the invention.

[0077] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. All reagents or instruments whose manufacturers are not specified are conventional products that can be purchased commercially. In addition to the specific methods, equipment, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description of this invention, any prior art methods, equipment, and materials similar to or equivalent to those described, used, and materials in the embodiments of this invention may be used to implement this invention.

[0078] Example 1

[0079] This embodiment 1 provides a method for preparing low-sodium, high-calcium milk with controlled carbohydrate content, comprising the following steps:

[0080] 1) Raw milk separation: The raw milk is heated to about 52 ℃ and separated into skim milk and cream using a centrifuge. The fat content of the skim milk is 0.05 wt%.

[0081] 2) Ultrafiltration Concentration: Part of the skim milk is concentrated by ultrafiltration. The ultrafiltration membrane is made of polyamide membrane composite material with a pore size of 10nm. The feed pressure during ultrafiltration concentration is 4 bar, the temperature is 4℃, and the concentration ratio is 1.60. After concentration, the skim milk has a protein content of 5.2wt% and a carbohydrate content of 4.8wt%.

[0082] 3) Nanofiltration Concentration: The remaining skim milk is concentrated by nanofiltration. The nanofiltration membrane is made of polyamide film composite material with a pore size of 1 nm. The feed pressure during nanofiltration concentration is 15 bar, the temperature is 4℃, and the concentration ratio is 1.60. After concentration, the skim milk contains 5.2 wt% protein and 7.6 wt% carbohydrates.

[0083] 4) Standardization: Mix ultrafiltration concentrated skim milk and nanofiltration concentrated skim milk at a ratio of 4:6 to obtain concentrated skim milk with a carbohydrate content of 6.5%, and then add light cream until the fat content is 4.0 wt%.

[0084] 5) Homogenization and sterilization: Standardized milk is heated to 55 ℃ for homogenization at a pressure of 180 bar and then pasteurized at a temperature of 72 ℃ for 25 s to obtain a low-sodium, high-calcium milk with controlled carbohydrates.

[0085] Example 2

[0086] In this embodiment 2, the carbohydrate content in the milk was adjusted by further adjusting the addition ratio of the two concentrated skim milks during standardization. The specific steps are as follows:

[0087] 1) Raw milk separation: The raw milk is heated to about 52 ℃ and separated into skim milk and cream using a centrifuge. The fat content of the skim milk is 0.05 wt%.

[0088] 2) Ultrafiltration Concentration: Part of the skim milk is concentrated by ultrafiltration. The ultrafiltration membrane is made of polyamide membrane composite material with a pore size of 10nm. The feed pressure during ultrafiltration concentration is 4 bar, the temperature is 4℃, and the concentration ratio is 1.60. After concentration, the skim milk has a protein content of 5.2wt% and a carbohydrate content of 4.8wt%.

[0089] 3) Nanofiltration Concentration: The remaining skim milk is concentrated by nanofiltration. The nanofiltration membrane is made of polyamide film composite material with a pore size of 1 nm. The feed pressure during nanofiltration concentration is 15 bar, the temperature is 4℃, and the concentration ratio is 1.60. After concentration, the protein content of the ultrafiltration concentrated skim milk is 5.2 wt% and the carbohydrate content is 7.6 wt%.

[0090] 4) Standardization: Ultrafiltration concentrated skim milk and nanofiltration concentrated skim milk are mixed at a ratio of 6:4 to obtain concentrated skim milk with a carbohydrate content of 5.9 wt%, and then heavy cream is added back to bring the fat content to 4.0 wt%.

[0091] 5) Homogenization and sterilization: Standardized milk is heated to 55 ℃ for homogenization at a pressure of 200 bar and then pasteurized at a temperature of 75 ℃ for 15 s to obtain a low-sodium, high-calcium milk with controlled carbohydrates.

[0092] Example 3

[0093] In this embodiment 3, the protein and fat content in concentrated milk was adjusted by changing the concentration ratio and the amount of whipped cream added. The specific steps are as follows:

[0094] 1) Raw milk separation: The raw milk is heated to about 52 ℃ and separated into skim milk and cream using a centrifuge. The fat content of the skim milk is 0.05 wt%.

[0095] 2) Ultrafiltration Concentration: Part of the skim milk is concentrated by ultrafiltration. The ultrafiltration membrane is made of polyamide membrane composite material with a pore size of 10nm. The feed pressure during ultrafiltration concentration is 4 bar, the temperature is 4℃, and the concentration ratio is 1.35. After concentration, the skim milk contains 4.5wt% protein and 4.8wt% carbohydrates.

[0096] 3) Nanofiltration Concentration: The remaining skim milk is concentrated by nanofiltration. The nanofiltration membrane is made of polyamide film composite material with a pore size of 1 nm. The feed pressure during nanofiltration concentration is 15 bar, the temperature is 4℃, and the concentration ratio is 1.35. After concentration, the skim milk has a protein content of 4.5 wt% and a carbohydrate content of 6.5 wt%.

[0097] 4) Standardization: Ultrafiltration concentrated skim milk and nanofiltration concentrated skim milk are mixed at a ratio of 4:6 to obtain concentrated skim milk with a carbohydrate content of 5.8 wt%, and then heavy cream is added back to bring the fat content to 5.0 wt%.

[0098] 5) Homogenization and sterilization: Standardized milk is heated to 55 ℃ for homogenization at a pressure of 180 bar and then sterilized at 125 ℃ for 30 s to obtain a low-sodium, high-calcium milk with controlled carbohydrates.

[0099] Example 4

[0100] This Example 4, based on Example 3, adjusts the carbohydrate content of the milk by changing the ratio of the two concentrated skim milks added during standardization. The specific steps are as follows:

[0101] 1) Raw milk separation: The raw milk is heated to about 52 ℃ and separated into skim milk and cream using a centrifuge. The fat content of the skim milk is 0.05 wt%.

[0102] 2) Ultrafiltration Concentration: Part of the skim milk is concentrated by ultrafiltration. The ultrafiltration membrane is made of polyamide membrane composite material with a pore size of 10nm. The feed pressure during ultrafiltration concentration is 4 bar, the temperature is 4℃, and the concentration ratio is 1.35. After concentration, the skim milk contains 4.5wt% protein and 4.8wt% carbohydrates.

[0103] 3) Nanofiltration Concentration: The remaining skim milk is concentrated by nanofiltration. The nanofiltration membrane is made of polyamide film composite material with a pore size of 1 nm. The feed pressure during nanofiltration concentration is 15 bar, the temperature is 4℃, and the concentration ratio is 1.35. After concentration, the skim milk has a protein content of 4.5 wt% and a carbohydrate content of 6.5 wt%.

[0104] 4) Standardization: Mix ultrafiltration concentrated skim milk and nanofiltration concentrated skim milk at a ratio of 6:4 to obtain concentrated skim milk with a carbohydrate content of 5.5 wt%, and then add light cream until the fat content is 5.0 wt%.

[0105] 5) Homogenization and sterilization: Standardized milk is heated to 55 ℃ for homogenization at a pressure of 200 bar and then sterilized at 121 ℃ for 45 s to obtain a low-sodium, high-calcium milk with controlled carbohydrates.

[0106] Example 5

[0107] In Example 5, concentrated skim milk with different protein contents was obtained by using different concentration ratios of ultrafiltration and nanofiltration. After standardization, low-sodium, high-calcium milk with controlled carbohydrate content can still be obtained. However, this type of operation does not provide significant benefits for standardized production and is only an option. The specific steps are as follows:

[0108] 1) Raw milk separation: The raw milk is heated to about 52 ℃ and separated into skim milk and cream using a centrifuge. The fat content of the skim milk is 0.05 wt%.

[0109] 2) Ultrafiltration Concentration: Part of the skim milk is concentrated by ultrafiltration. The ultrafiltration membrane is made of polyamide membrane composite material with a pore size of 10nm. The feed pressure during ultrafiltration concentration is 4 bar, the temperature is 4℃, and the concentration ratio is 1.60. After concentration, the skim milk has a protein content of 5.2wt% and a carbohydrate content of 4.8wt%.

[0110] 3) Nanofiltration Concentration: The remaining skim milk is concentrated by nanofiltration. The nanofiltration membrane is made of polyamide film composite material with a pore size of 1 nm. The feed pressure during nanofiltration concentration is 15 bar, the temperature is 4℃, and the concentration ratio is 1.35. After concentration, the protein content of the ultrafiltration concentrated skim milk is 4.5 wt% and the carbohydrate content is 7.6 wt%.

[0111] 4) Standardization: Ultrafiltration concentrated skim milk and nanofiltration concentrated skim milk are mixed in a 5:5 ratio to obtain concentrated skim milk with 4.8 wt% protein and 6.2 wt% carbohydrates, and then light cream is added back to bring the fat content to 4.5 wt%.

[0112] 5) Homogenization and sterilization: Standardized milk is preheated and sprayed into an ultra-clean high-temperature steam chamber, rapidly heated to 157°C, held for 0.1 s, and then immediately cooled to 65°C by flash evaporation before aseptic homogenization at a pressure of 200 bar to obtain a low-sodium, high-calcium milk with controlled carbohydrates.

[0113] Comparative Example 1

[0114] The only difference between Comparative Example 1 and Example 1 is that only nanofiltration concentration is performed, and ultrafiltration concentration is not performed.

[0115] 1) Raw milk separation: The raw milk is heated to about 52 ℃ and separated into skim milk and cream using a centrifuge. The fat content of the skim milk is 0.05 wt%.

[0116] 2) Nanofiltration Concentration: Part of the skim milk is concentrated by nanofiltration. The nanofiltration membrane is made of polyamide film composite material with a pore size of 1 nm. The feed pressure during nanofiltration concentration is 15 bar, the temperature is 4℃, and the concentration ratio is 1.60. After concentration, the skim milk has a protein content of 5.2 wt% and a carbohydrate content of 7.6 wt%.

[0117] 3) Standardization: The whipped cream is refilled and mixed with nanofiltration concentrated skim milk until the fat content is 4.0 wt%.

[0118] 4) Homogenization and sterilization: Standardized milk is heated to 55 ℃ for homogenization at a pressure of 180 bar and then pasteurized at a temperature of 72 ℃ for 25 s to obtain a high-calcium milk.

[0119] Comparative Example 2

[0120] The only difference between Comparative Example 2 and Example 1 is that only ultrafiltration concentration is performed, without ultrafiltration concentration.

[0121] 1) Raw milk separation: The raw milk is heated to about 52 ℃ and separated into skim milk and cream using a centrifuge. The fat content of the skim milk is 0.05 wt%.

[0122] 2) Ultrafiltration concentration: Part of the skim milk is concentrated by nanofiltration. The ultrafiltration membrane is made of polyamide membrane composite material with a pore size of 10nm. The feed pressure during ultrafiltration concentration is 4 bar, the temperature is 4℃, the concentration ratio is 1.60, and the concentrated skim milk after ultrafiltration has a protein content of 5.2wt% and a carbohydrate content of 4.8wt%.

[0123] 3) Standardization: The whipped cream is refilled and mixed with nanofiltration concentrated skim milk until the fat content is 4.0 wt%.

[0124] 4) Homogenization and sterilization: Standardized milk is heated to 55 ℃ for homogenization at a pressure of 180 bar and then pasteurized at a temperature of 72 ℃ for 25 s to obtain a high-calcium milk.

[0125] Comparative Example 3

[0126] The only difference between Comparative Example 3 and Example 3 is that nanofiltration concentration in step 3) is replaced with reverse osmosis concentration (RO).

[0127] 1) Raw milk separation: The raw milk is heated to about 52 ℃ and separated into skim milk and cream using a centrifuge. The fat content of the skim milk is 0.05 wt%.

[0128] 2) Ultrafiltration Concentration: Part of the skim milk is concentrated by ultrafiltration. The ultrafiltration membrane is made of polyamide membrane composite material with a pore size of 10nm. The feed pressure during ultrafiltration concentration is 4 bar, the temperature is 4℃, and the concentration ratio is 1.35. After concentration, the skim milk contains 4.5wt% protein and 4.8wt% carbohydrates.

[0129] 3) Reverse osmosis concentration: The remaining skim milk is concentrated by reverse osmosis at a temperature of 4°C and a concentration ratio of 1.35. After concentration, the ultrafiltration concentrated skim milk has a protein content of 4.5 wt% and a carbohydrate content of 6.5 wt%.

[0130] 4) Standardization: Mix ultrafiltration concentrated skim milk and nanofiltration concentrated skim milk at a ratio of 4:6 to obtain concentrated skim milk with a carbohydrate content of 5.8%, and then add light cream until the fat content is 5.0 wt%.

[0131] 5) Homogenization and sterilization: Standardized milk is heated to 55 ℃ for homogenization at a pressure of 180 bar and then sterilized at 125 ℃ for 30 s to obtain a high-calcium milk.

[0132] Comparative Example 4

[0133] The only difference between Comparative Example 4 and Example 3 is that the ultrafiltration concentration in step 2) is replaced with reverse osmosis concentration (RO).

[0134] 1) Raw milk separation: The raw milk is heated to about 52 ℃ and separated into skim milk and cream using a centrifuge. The fat content of the skim milk is 0.05 wt%.

[0135] 2) Reverse osmosis concentration: Part of the skim milk is concentrated by ultrafiltration at a temperature of 4°C and a concentration ratio of 1.35. After concentration, the protein content of the ultrafiltration-concentrated skim milk is 4.5 wt% and the carbohydrate content is 6.5 wt%.

[0136] 3) Nanofiltration Concentration: The remaining skim milk is concentrated by nanofiltration. The nanofiltration membrane is made of polyamide film composite material with a pore size of 1 nm. The feed pressure during nanofiltration concentration is 15 bar, the temperature is 4℃, and the concentration ratio is 1.35. After concentration, the skim milk has a protein content of 4.5 wt% and a carbohydrate content of 6.5 wt%.

[0137] 4) Standardization: Mix ultrafiltration concentrated skim milk and nanofiltration concentrated skim milk at a ratio of 4:6 to obtain concentrated skim milk with a carbohydrate content of 6.5%, and then add light cream until the fat content is 5.0 wt%.

[0138] 5) Homogenization and sterilization: Standardized milk is heated to 55 ℃ for homogenization at a pressure of 180 bar and then sterilized at 125 ℃ for 30 s to obtain a high-calcium milk.

[0139] Comparative Example 5

[0140] The only difference between Comparative Example 5 and Example 5 is that in step 5), aseptic homogenization is performed first, followed by direct steam injection sterilization.

[0141] 1) Raw milk separation: The raw milk is heated to about 52 ℃ and separated into skim milk and cream using a centrifuge. The fat content of the skim milk is 0.05 wt%.

[0142] 2) Ultrafiltration Concentration: Part of the skim milk is concentrated by ultrafiltration. The ultrafiltration membrane is made of polyamide membrane composite material with a pore size of 10nm. The feed pressure during ultrafiltration concentration is 4 bar, the temperature is 4℃, and the concentration ratio is 1.60. After concentration, the skim milk has a protein content of 5.2wt% and a carbohydrate content of 4.8wt%.

[0143] 3) Nanofiltration Concentration: The remaining skim milk is concentrated by nanofiltration. The nanofiltration membrane is made of polyamide film composite material with a pore size of 1 nm. The feed pressure during nanofiltration concentration is 15 bar, the temperature is 4℃, and the concentration ratio is 1.35. After concentration, the protein content of the ultrafiltration concentrated skim milk is 4.5 wt% and the carbohydrate content is 7.6 wt%.

[0144] 4) Standardization: Ultrafiltration concentrated skim milk and nanofiltration concentrated skim milk are mixed in a 5:5 ratio to obtain concentrated skim milk with 4.8 wt% protein and 6.2 wt% carbohydrates, and then light cream is added back to bring the fat content to 4.5%.

[0145] 5) Homogenization and sterilization: Standardized milk is preheated to 65°C for aseptic homogenization at a pressure of 200 bar. It is then sprayed into an ultra-clean high-temperature steam chamber, rapidly heated to 157°C, held for 0.1 s, and immediately cooled by flash evaporation to obtain a high-calcium milk.

[0146] The protein, carbohydrates, calcium, and sodium in the low-sodium, high-calcium milk with controlled carbohydrates obtained in Examples 1-5 and Comparative Examples 1-5, as well as the control high-calcium milk, were tested. The results are shown in Table 1.

[0147] Table 1

[0148]

[0149] Note: Protein and carbohydrates are measured in g / 100g, while calcium and sodium are measured in mg / 100g.

[0150] According to the results in Table 1:

[0151] 1) Both Comparative Examples 1 and 2 used either ultrafiltration or nanofiltration. After concentrating milk protein to 5.0%, the carbohydrate content could not be controlled between 5.0% and 6.8%. In other words, it was impossible to control the carbohydrate content of the concentrated high-calcium milk through different process combinations.

[0152] 2) Comparative Examples 3 and 4 both used reverse osmosis instead of either ultrafiltration or nanofiltration. Reverse osmosis is a full concentration method that concentrates all monovalent salt ions, including sodium. Therefore, after standardization, the sodium content cannot reach ≤50 mg / 100g, meaning that low-sodium, high-calcium milk cannot be prepared by reverse osmosis concentration.

[0153] 3) Comparative Example 5 used a process of aseptic homogenization followed by direct steam sterilization. On the 5th day under low-temperature refrigeration, fat stratification and floating occurred. However, Example 5 used a process of direct steam sterilization followed by aseptic homogenization. After 20 days of low-temperature refrigeration, it remained homogeneous and no obvious fat floating was observed. This indicates that when using direct steam sterilization, the position of the aseptic homogenization process cannot be changed.

[0154] In summary, the method of this invention employs a combination of ultrafiltration and nanofiltration concentration techniques after separating the raw milk. This concentrates protein and calcium while filtering out a portion of sodium and accurately controlling the carbohydrate content. The cream is then refilled and standardized. Throughout the entire production process, no processing aids are used; the desired low-sodium, high-calcium dairy products can be prepared solely through the combination of these processes, while controlling carbohydrate content.

[0155] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit this application. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this application. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this invention should still be covered by the claims of this application.

Claims

1. A method for preparing a carbohydrate-controlled dairy product, comprising the following steps: 1) separating raw milk to obtain skim milk and cream; 2) splitting the skim milk into a first skim milk stream and a second skim milk stream; 3) subjecting the first skim milk stream to ultrafiltration concentration to obtain ultrafiltration concentrated skim milk; 4) subjecting the second skim milk stream to nanofiltration concentration to obtain nanofiltration concentrated skim milk; 5) mixing the ultrafiltration concentrated skim milk obtained in step 3) and the nanofiltration concentrated skim milk obtained in step 4) to obtain the carbohydrate-controlled dairy product.

2. The production method according to claim 1, wherein In step 2), the fat content in the skim milk is ≤0.05 wt %.

3. The production method according to claim 1, wherein In step 3), the ultrafiltration concentration uses an ultrafiltration membrane with a pore size of 5-100 nm; and / or, the ultrafiltration concentration uses an ultrafiltration membrane made of polyamide thin film composite material; and / or, the ultrafiltration concentration is performed at a temperature of 4-10 ℃; and / or, the ultrafiltration concentration is performed at a feed pressure of 1-5 bar; and / or, the ultrafiltration concentration is performed at a concentration ratio of 1.0-3.3; and / or, the ultrafiltration concentrated skim milk has a protein content of 4.0-5.5 wt % and a carbohydrate content of 4.0-5.0 wt %.

4. The production method according to claim 1, wherein In step 4), the nanofiltration concentration uses a nanofiltration membrane with a pore size of 0.5-2 nm; and / or, the nanofiltration concentration uses a nanofiltration membrane made of polyamide thin film composite material; and / or, the nanofiltration concentration is performed at a temperature of 4-10 ℃; and / or, the nanofiltration concentration is performed at a feed pressure of 10-20 bar; and / or, the nanofiltration concentration is performed at a concentration ratio of 1.0-3.3; and / or, the nanofiltration concentrated skim milk has a protein content of 4.0-5.5 wt % and a carbohydrate content of 5.5-7.6 wt %.

5. The production method according to claim 1, wherein In step 5), the mixing mass ratio Y of the ultrafiltration concentrated skim milk and the nanofiltration concentrated skim milk satisfies the following formula: wherein A is the expected mass percentage concentration of carbohydrates in the dairy product; B is the mass percentage concentration of carbohydrates in the ultrafiltration concentrated skim milk; and C is the mass percentage concentration of carbohydrates in the nanofiltration concentrated skim milk.

6. The production method according to claim 1, wherein After step 5), the method further comprises adding cream to the carbohydrate-controlled dairy product.

7. The production method according to claim 1, wherein After step 5), the method further comprises subjecting the carbohydrate-controlled dairy product to homogenization and sterilization.

8. The production method according to claim 7, wherein The homogenization is performed at a temperature of 50-65 ℃; and / or, the homogenization is performed at a pressure of 150-200 bar; and / or, the sterilization is selected from one of pasteurization, high-temperature sterilization, and steam direct injection sterilization.

9. The production method according to claim 8, wherein The pasteurization is performed at a sterilization temperature of 72-76 ℃ for a holding time of 15-30 s; The high-temperature sterilization is performed at a sterilization temperature of 120-127 ℃ for a holding time of 15-60 s; The steam direct injection sterilization is performed at a sterilization temperature of 142-157 ℃ for a holding time of 0.09-6 s. 10.A carbohydrate-controlled dairy product prepared by the method of any one of claims 1-9.

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