Method for preparing a protein-standardized milk and products thereof

Abstract

The present application relates to the field of food technology, and provide a kind of protein standardization method for preparing milk and its product, the method comprises: the raw milk after impurity removal is sequentially subjected to one homogenization, pasteurization, protein index adjustment, second homogenization, protein maintenance and ultra high temperature sterilization;Protein index adjustment includes: using the ultrafiltration membrane system comprising two-stage ultrafiltration membrane connected in series to filter skim milk to obtain ultrafiltration permeate with protein content of 0 and lactose content of 4.5-5.5g / 100g;Add the ultrafiltration permeate to the pasteurized milk obtained by pasteurization to obtain milk with protein content of 2.9-3.8g / 100g;The ratio of the addition amount of ultrafiltration permeate to the mass of the pasteurized milk is 1-20:100.The method of the present application can achieve protein standardization while avoiding problems such as unqualified physicochemical indicators, inconsistent taste, non-compliant calcium content, etc., and can ensure the stability of the obtained milk product within the shelf life.

Description

Technical Field

[0001] This invention relates to the field of food technology, and in particular to a method for protein standardization in the preparation of milk and its products. Background Technology

[0002] Raw milk, also known as raw milk, has physicochemical properties that fluctuate significantly due to factors such as dairy cow breed, region, and season. This objective phenomenon poses a challenge to the consistency of physicochemical properties and taste when raw milk is used as a raw material to prepare products.

[0003] When the protein content of raw milk is lower than that of the target product, protein standardization of the final product can be achieved through concentration. However, when the protein content of raw milk is higher than that of the target product, it is necessary to perform "downward" standardization of the high-protein raw milk's protein content. Methods for achieving this type of protein standardization are less common. According to the "General Rules for Labeling of Prepackaged Foods" in the National Food Safety Standard, if the protein content of a product is standardized by adding water to high-protein milk, this must be indicated in the product's ingredient list. Furthermore, adding water may result in a product with a significantly different taste from the standard product and a risk of failing to meet calcium content standards.

[0004] Therefore, when the protein content of raw milk is higher than that of the target product, there is an urgent need to provide a method that does not involve adding water to high-protein milk to achieve protein standardization, and can avoid problems such as unqualified physicochemical indicators and taste. Summary of the Invention

[0005] This invention provides a protein standardization method and product for preparing milk, addressing the shortcomings of existing technologies that standardize protein indicators by adding water to high-protein milk, resulting in significant differences in taste compared to the standard product and substandard calcium content. By adding a specifically obtained permeate and controlling its proportion, a "downward" standardization process is achieved from high-protein raw milk. The process flow and parameters are optimized to ensure protein standardization while avoiding issues such as substandard physicochemical indicators, inconsistent taste, and non-compliant calcium content.

[0006] This invention provides a method for protein standardization in milk preparation, comprising: subjecting purified raw milk to a first homogenization, pasteurization, protein index adjustment, a second homogenization, protein retention, and ultra-high temperature sterilization in sequence;

[0007] The protein index adjustment includes: filtering skim milk using an ultrafiltration membrane system comprising two interconnected ultrafiltration membranes to obtain an ultrafiltration permeate with a protein content of 0 and a lactose content of 4.5~5.5g / 100g; adding the ultrafiltration permeate to pasteurized milk to make the protein content of the resulting milk 2.9~3.8g / 100g; the ratio of the amount of ultrafiltration permeate added to the mass of the pasteurized milk is 1~20:100.

[0008] Studies have found that when using ultrafiltration permeate with a lactose content maintained in the range of 4.5~5.5g / 100g as a dilution medium for the "downward" standardization of high-protein raw milk, in order to ensure that the final product has no significant difference in taste from the standard sample, its addition must be strictly controlled to not exceed 20%.

[0009] In this invention, the lactose content is 4.5~5.5g / 100g, for example, it can be any value or a range of any values ​​among 4.5g / 100g, 4.6g / 100g, 4.7g / 100g, 4.8g / 100g, 4.9g / 100g, 5.0g / 100g, 5.1g / 100g, 5.2g / 100g, 5.3g / 100g, 5.4g / 100g and 5.5g / 100g.

[0010] In this invention, the protein content in the obtained milk is 2.9~3.8g / 100g, for example, it can be any value or a range of any values ​​from 2.9g / 100g, 3.0g / 100g, 3.1g / 100g, 3.2g / 100g, 3.3g / 100g, 3.4g / 100g, 3.5g / 100g, 3.6g / 100g, 3.7g / 100g to 3.8g / 100g.

[0011] In this invention, the ratio of the amount of ultrafiltration permeate added to the mass of pasteurized milk is 1 to 20:100, for example, it can be any value or a range of any values ​​among 1:100, 3:100, 5:100, 7:100, 9:100, 11:100, 13:100, 15:100, 17:100, 19:100 and 20:100.

[0012] According to the protein standardization method for preparing milk provided by the present invention, the first homogenization includes: homogenizing the purified raw milk under a secondary pressure of 25-35 bar.

[0013] Experiments have shown that using a two-stage pressure of 25-35 bar during the first homogenization stage yields the best homogenization effect, effectively ensuring the stability of the product system.

[0014] According to the protein standardization method for preparing milk provided by the present invention, the secondary homogenization includes: homogenizing the milk with the adjusted protein index under a secondary pressure of 25-35 bar.

[0015] Experiments have shown that using a secondary pressure of 25-35 bar during the second homogenization process yields the best homogenization effect, effectively ensuring the stability of the product system.

[0016] According to the protein standardization method for preparing milk provided by the present invention, the protein retention includes: retaining the protein in the milk after secondary homogenization at 85~95°C for 60~120s.

[0017] Studies have found that when using ultrafiltration permeate with a lactose content maintained in the range of 4.5~5.5g / 100g as a dilution medium for the "downward" standardization of high-protein raw milk, the protein retention process needs to be carried out at 85~95℃ for 60~120s to avoid the formation of white particles in the product.

[0018] According to the protein standardization method for preparing milk provided by the present invention, the ultra-high temperature sterilization includes sterilizing the milk after protein preservation at 136-138°C. Experiments have shown that when using an ultrafiltration permeate with a lactose content maintained in the range of 4.5-5.5 g / 100 g as a dilution medium for the "downward" standardization of high-protein raw milk, the high-temperature sterilization process needs to be carried out at 136-138°C to avoid product instability.

[0019] According to the protein standardization method for preparing milk provided by the present invention, in the two-stage ultrafiltration membrane, the molecular weight cutoff of the first-stage ultrafiltration membrane is 1000~10000 Da, and the molecular weight cutoff of the second-stage ultrafiltration membrane is 1000~5000 Da.

[0020] According to the protein standardization method for preparing milk provided by the present invention, the method for preparing the ultrafiltration permeate includes:

[0021] Raw milk is purified at a temperature of 45~55℃.

[0022] The purified raw milk is subjected to fat separation at a temperature of 45~55℃ to obtain cream and skim milk; the fat content of the cream is 38~42%; the cream is supplied to downstream processing enterprises as raw material.

[0023] Preferably, a milk separator is used to achieve the removal of impurities and the separation of fats.

[0024] This invention employs a milk separator that combines milk separation and fat separation capabilities, which can solve the separation of milk and fat in one stop, reducing processing steps; in particular, the separation of milk and fat is carried out at a temperature of 45~55℃, which can reduce the loss of slag discharged from the separator.

[0025] The skim milk is cooled to 2-6°C. The ultrafiltration membrane system is sensitive to microbial contamination. This invention has found that cooling the skim milk to 2-6°C before it enters the ultrafiltration membrane system can prevent cross-contamination caused by microbial proliferation during subsequent ultrafiltration, thus ensuring the food safety of the final product.

[0026] The cooled skim milk is filtered using an ultrafiltration membrane system to obtain a protein concentrate and an ultrafiltration permeate; the protein concentrate has a protein content of 10-15% and is supplied to downstream processing enterprises; the ultrafiltration permeate has a non-protein nitrogen content of 0.18-0.22%.

[0027] The ultrafiltration membrane system includes two ultrafiltration membranes connected in series. The molecular weight cutoff of the first ultrafiltration membrane is 1000~10000 Da, and the molecular weight cutoff of the second ultrafiltration membrane is 1000~5000 Da.

[0028] Generally, ultrafiltration membrane systems can effectively separate components from raw milk. In the "downward" standardization research of high-protein raw milk in this invention, it was found that adding a permeate to the high-protein raw milk is an option to achieve protein standardization while avoiding substandard physicochemical indicators and taste issues. Based on this, after extensive experimental comparisons, this invention found that when the ultrafiltration membrane system uses the above parameters, a protein concentrate with a protein content of 10-15% and an ultrafiltration permeate with a lactose content maintained within the range of 4.5-5.5 g / 100g can be obtained. Adding the permeate obtained by this method to high-protein raw milk is one of the important factors in ensuring that the final product has no significant difference in taste from the standard sample. At the same time, the protein concentrate can meet the requirements of downstream processing.

[0029] According to the protein standardization method for preparing milk provided by the present invention, the protein standardization method for preparing milk includes the following steps:

[0030] Impurity removal: The raw milk is cleaned of impurities.

[0031] First homogenization: The purified raw milk is homogenized under a total pressure of 100-120 bar and a secondary pressure.

[0032] Pasteurization: Pasteurize the raw milk after one homogenization to obtain pasteurized milk; the parameters of pasteurization include: temperature 75℃, time 15s.

[0033] Protein index adjustment: Add the ultrafiltration permeate to the pasteurized milk.

[0034] Secondary homogenization: The milk with the protein index adjusted is homogenized at a total pressure of 200~250 bar, secondary pressure, and a temperature of 70~80℃.

[0035] Protein retention: The milk after the second homogenization is subjected to protein retention.

[0036] Ultra-high temperature sterilization: Sterilize the milk after the protein is preserved for 4-6 seconds.

[0037] Aseptic filling: Products are filled using aseptic filling machines.

[0038] The protein standardization method for preparing milk provided by the present invention, such as... Figure 1 As shown, the protein standardization method for preparing milk includes the following steps:

[0039] (1) Preparation of ultrafiltration permeate

[0040] (1.1) Milk separation: The raw milk is purified and separated from fat at a temperature of 45~55℃ to obtain cream and skim milk; the fat content of the cream is 38~42%; the fat content of the skim milk is less than 0.05%.

[0041] Preferably, a milk separator is used to achieve the removal of impurities and separation of fat in one step.

[0042] (1.2) UF ultrafiltration: Skim milk cooled to 2~6℃ is filtered using an ultrafiltration membrane system to obtain protein concentrate and ultrafiltration permeate; the protein concentrate has a protein content of 10~15%; the ultrafiltration permeate has a non-protein nitrogen content of 0.18~0.22%.

[0043] The ultrafiltration membrane system includes two ultrafiltration membranes connected in series. The molecular weight cutoff of the first ultrafiltration membrane is 1000~10000 Da, and the molecular weight cutoff of the second ultrafiltration membrane is 1000~5000 Da.

[0044] (2) Cleaning milk: removing impurities from raw milk.

[0045] (3) First homogenization: The raw milk after impurity removal is homogenized under a total pressure of 100~120 bar and a secondary pressure.

[0046] (4) Pasteurization: Pasteurize the raw milk after one homogenization to obtain pasteurized milk. The parameters for pasteurization include: temperature 75℃ and time 15s.

[0047] (5) Protein index adjustment: Add the ultrafiltration permeate to the pasteurized milk.

[0048] (6) Secondary homogenization: The milk with the protein index adjusted is homogenized at a total pressure of 200~250 bar, secondary pressure, and a temperature of 70~80℃.

[0049] (7) Protein retention: The milk after the second homogenization is subjected to protein retention.

[0050] (8) Ultra-high temperature sterilization: Sterilize the milk after the protein is preserved for 4~6 seconds.

[0051] (9) Aseptic filling: Aseptic filling machine is used for product filling.

[0052] The present invention also provides milk prepared by the protein standardization method described above for preparing milk.

[0053] According to the milk provided by the present invention, the protein content of the milk is 2.9~3.8g / 100g, and the deviation of the protein content of the milk from the target protein content is 1%.

[0054] When the protein index of raw milk differs from that of the target product, protein standardization is required. In this invention, the target protein content refers to the protein content of the target product.

[0055] This invention provides a protein standardization method and product for preparing milk. It achieves "downward" standardization of high-protein raw milk by adding a permeate obtained through a specific method and controlling its addition ratio. The method also optimizes the protein standardization process and parameters, ensuring that while achieving protein standardization, it avoids problems such as substandard physicochemical indicators, inconsistent taste, and non-compliant calcium content in the product. The method of this invention ensures that the resulting milk product maintains system stability during its shelf life and that its calcium content complies with GB 28050 "General Rules for Nutrition Labelling of Prepackaged Foods (National Food Safety Standard)". Attached Figure Description

[0056] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0057] Figure 1 This is one of the flowcharts of the protein standardization method for preparing milk provided by the present invention. Detailed Implementation

[0058] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0059] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field, or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels.

[0060] All raw milk used in this invention has been inspected and approved according to the standard GB 19301 National Food Safety Standard for Raw Milk, and is used only after passing the inspection. However, the calcium content of the raw milk used in different embodiments and comparative examples varies.

[0061] The equipment used in this invention includes: a milk purifying machine, a milk purifying separator with fat separation capability, a two-stage combined ultrafiltration membrane filtration device, a homogenizer, a pasteurizer, an ultra-high temperature sterilizer, and an aseptic filling machine, all of which are sourced from the market.

[0062] Preparation Example 1: Ultrafiltration Permeate

[0063] This preparation example provides an ultrafiltration permeate, the specific preparation steps of which are as follows:

[0064] (1) Raw milk was purified and fat was separated using a milk separator at a temperature of 45°C to obtain cream and skim milk;

[0065] Whipping cream has a fat content of 38%, while skim milk has a fat content of 0.05%. Whipping cream is supplied to downstream processing companies as a raw material.

[0066] (2) Cool the skim milk to 2°C;

[0067] (3) The cooled skim milk is filtered using an ultrafiltration membrane system to obtain protein concentrate and ultrafiltration permeate; wherein the ultrafiltration membrane system includes two ultrafiltration membranes connected in series, the molecular weight cutoff of the first ultrafiltration membrane is 1000~10000 Da, and the molecular weight cutoff of the second ultrafiltration membrane is 1000~5000 Da.

[0068] The resulting protein concentrate has a protein content of 10% and is supplied to downstream processing companies.

[0069] The obtained ultrafiltration permeate had a non-protein nitrogen content of 0.18%, a protein content of 0, and a lactose content of 4.5 g / 100 g.

[0070] Preparation Example 2: Ultrafiltration Permeate

[0071] This preparation example provides an ultrafiltration permeate, the specific preparation steps of which are as follows:

[0072] (1) Raw milk was purified and fat was separated using a milk separator at a temperature of 50°C to obtain cream and skim milk;

[0073] Whipping cream has a fat content of 40%, while skim milk has a fat content of 0.03%. Whipping cream is supplied to downstream processing companies as a raw material.

[0074] (2) Cool the skim milk to 3°C;

[0075] (3) The cooled skim milk is filtered using an ultrafiltration membrane system to obtain protein concentrate and ultrafiltration permeate; wherein the ultrafiltration membrane system includes two ultrafiltration membranes connected in series, the molecular weight cutoff of the first ultrafiltration membrane is 1000~10000 Da, and the molecular weight cutoff of the second ultrafiltration membrane is 1000~5000 Da.

[0076] The resulting protein concentrate has a protein content of 13%, and is supplied to downstream processing companies.

[0077] The obtained ultrafiltration permeate had a non-protein nitrogen content of 0.18%, a protein content of 0, and a lactose content of 5 g / 100 g.

[0078] Preparation Example 3: Ultrafiltration Permeate

[0079] This preparation example provides an ultrafiltration permeate, the specific preparation steps of which are as follows:

[0080] (1) Raw milk was purified and fat was separated using a milk separator at a temperature of 55°C to obtain cream and skim milk;

[0081] Whipping cream has a fat content of 42%, while skim milk has a fat content of 0.02%. Whipping cream is supplied to downstream processing companies as a raw material.

[0082] (2) Cool the skim milk to 4°C;

[0083] (3) The cooled skim milk is filtered using an ultrafiltration membrane system to obtain protein concentrate and ultrafiltration permeate; wherein the ultrafiltration membrane system includes two ultrafiltration membranes connected in series, the molecular weight cutoff of the first ultrafiltration membrane is 1000~10000 Da, and the molecular weight cutoff of the second ultrafiltration membrane is 1000~5000 Da.

[0084] The resulting protein concentrate has a protein content of 15% and is supplied to downstream processing companies.

[0085] The obtained ultrafiltration permeate had a non-protein nitrogen content of 0.19%, a protein content of 0%, and a lactose content of 5.5 g / 100 g.

[0086] Preparation Example 4: Ultrafiltration Permeate

[0087] The preparation method is basically the same as in Example 1, except that the protein content of the resulting protein concentrate is 15%.

[0088] Preparation Example 5: Ultrafiltration Permeate

[0089] The preparation method is basically the same as in Example 3, except that the skim milk is cooled to 5°C.

[0090] Example 1: Standardization Method

[0091] This embodiment provides a method for protein standardization in milk preparation, the specific steps of which are as follows:

[0092] (1) Milk purification: Raw milk with a protein content of 2.93g / 100g is purified at a temperature of 1℃;

[0093] (2) First homogenization: The raw milk after impurity removal is homogenized at a total pressure of 100 bar and a secondary pressure of 25 bar;

[0094] (3) Pasteurization: Pasteurize the raw milk after one homogenization to obtain pasteurized milk; the parameters for pasteurization include: temperature 75℃, time 15s; after the pasteurized milk is cooled to 1℃, proceed to the next step.

[0095] (4) Protein index adjustment: The ultrafiltration permeate added to pasteurized milk was added to pasteurized milk at a ratio of 1:100, so that the protein content of the milk was the target protein content. The milk was stored at 1°C for the next step.

[0096] (5) Secondary homogenization: The milk with adjusted protein content was homogenized at a total pressure of 200 bar, a secondary pressure of 25 bar, and a temperature of 70°C.

[0097] (6) Protein retention: The milk after the second homogenization was subjected to protein retention at 85°C for 60 seconds;

[0098] (7) Ultra-high temperature sterilization: The milk after the protein is preserved is sterilized at 136°C for 5 seconds; the milk after ultra-high temperature sterilization is cooled to 15°C before proceeding to the next step.

[0099] (8) Aseptic filling: The product is filled using Tetra Pak's aseptic filling machine.

[0100] Example 2 Standardization Method

[0101] This embodiment provides a method for protein standardization in milk preparation, the specific steps of which are as follows:

[0102] (1) Milk purification: Raw milk with a protein content of 3.72g / 100g is purified at a temperature of 3℃;

[0103] (2) First homogenization: The raw milk after impurity removal is homogenized at a total pressure of 110 bar and a secondary pressure of 30 bar;

[0104] (3) Pasteurization: Pasteurize the raw milk after one homogenization to obtain pasteurized milk; the parameters for pasteurization include: temperature 75℃, time 15s; after the pasteurized milk is cooled to 4℃, proceed to the next step.

[0105] (4) Protein index adjustment: The ultrafiltration permeate added to the pasteurized milk was added according to the ratio of the amount of ultrafiltration permeate added to the mass of pasteurized milk of 10:100, so that the protein content of the milk was the target protein content. The milk was stored at 4°C for the next step.

[0106] (5) Secondary homogenization: The milk with adjusted protein content was homogenized at a total pressure of 235 bar, a secondary pressure of 30 bar, and a temperature of 75°C.

[0107] (6) Protein retention: The milk after the second homogenization was subjected to protein retention at 90°C for 90 seconds;

[0108] (7) Ultra-high temperature sterilization: The milk after the protein is preserved is sterilized at 137°C for 5 seconds; the milk after ultra-high temperature sterilization is cooled to 25°C before proceeding to the next step.

[0109] (8) Aseptic filling: The product is filled using Tetra Pak's aseptic filling machine.

[0110] Example 3 Standardization Method

[0111] This embodiment provides a method for protein standardization in milk preparation, the specific steps of which are as follows:

[0112] (1) Milk purification: Raw milk with a protein content of 4.52g / 100g is purified at a temperature of 6℃;

[0113] (2) First homogenization: The raw milk after impurity removal is homogenized at a total pressure of 120 bar and a secondary pressure of 35 bar;

[0114] (3) Pasteurization: Pasteurize the raw milk after one homogenization to obtain pasteurized milk; the parameters for pasteurization include: temperature 75℃, time 15s; after the pasteurized milk is cooled to 7℃, proceed to the next step.

[0115] (4) Protein index adjustment: The ultrafiltration permeate added to the pasteurized milk was prepared in Example 3 at a ratio of 20:100 to the amount of ultrafiltration permeate added to the pasteurized milk so that the protein content of the milk was the target protein content. The milk was stored at 7°C for the next step.

[0116] (5) Secondary homogenization: The milk with adjusted protein content was homogenized at a total pressure of 250 bar, a secondary pressure of 35 bar, and a temperature of 80°C.

[0117] (6) Protein retention: The milk after the second homogenization was subjected to protein retention at 95°C for 120 seconds;

[0118] (7) Ultra-high temperature sterilization: The milk after the protein is preserved is sterilized at 138°C for 5 seconds; the milk after ultra-high temperature sterilization is cooled to 35°C before proceeding to the next step.

[0119] (8) Aseptic filling: The product is filled using Tetra Pak's aseptic filling machine.

[0120] Example 4 Standardization Method

[0121] This embodiment provides a method for protein standardization in milk preparation, the specific steps of which are as follows:

[0122] (1) Milk purification: Raw milk with a protein content of 3.24g / 100g is purified at a temperature of 1℃;

[0123] (2) First homogenization: The raw milk after impurity removal is homogenized at a total pressure of 100 bar and a secondary pressure of 25 bar;

[0124] (3) Pasteurization: Pasteurize the raw milk after one homogenization to obtain pasteurized milk; the parameters for pasteurization include: temperature 75℃, time 15s; after the pasteurized milk is cooled to 1℃, proceed to the next step.

[0125] (4) Protein index adjustment: The ultrafiltration permeate prepared in Preparation Example 4 was added to the pasteurized milk at a ratio of 20:100 to the amount of ultrafiltration permeate added to the pasteurized milk so that the protein content of the milk was the target protein content. The milk was stored at 1°C for the next step.

[0126] (5) Secondary homogenization: The milk with adjusted protein content was homogenized at a total pressure of 200 bar, a secondary pressure of 25 bar, and a temperature of 70°C.

[0127] (6) Protein retention: The milk after the second homogenization was subjected to protein retention at 85°C for 60 seconds;

[0128] (7) Ultra-high temperature sterilization: The milk after the protein is preserved is sterilized at 136°C for 5 seconds; the milk after ultra-high temperature sterilization is cooled to 15°C before proceeding to the next step.

[0129] (8) Aseptic filling: The product is filled using Tetra Pak's aseptic filling machine.

[0130] Example 5 Standardization Method

[0131] This embodiment provides a method for protein standardization in milk preparation, the specific steps of which are as follows:

[0132] (1) Milk purification: Raw milk with a protein content of 3.83g / 100g is purified at a temperature of 1℃;

[0133] (2) First homogenization: The raw milk after impurity removal is homogenized at a total pressure of 100 bar and a secondary pressure of 25 bar;

[0134] (3) Pasteurization: Pasteurize the raw milk after one homogenization to obtain pasteurized milk; the parameters for pasteurization include: temperature 75℃, time 15s; after the pasteurized milk is cooled to 1℃, proceed to the next step.

[0135] (4) Protein index adjustment: The ultrafiltration permeate added to pasteurized milk was added to pasteurized milk at a ratio of 1:100, so that the protein content of the milk was the target protein content. The milk was stored at 1°C for the next step.

[0136] (5) Secondary homogenization: The milk with adjusted protein content was homogenized at a total pressure of 200 bar, a secondary pressure of 25 bar, and a temperature of 70°C.

[0137] (6) Protein retention: The milk after the second homogenization was subjected to protein retention at 85°C for 60 seconds;

[0138] (7) Ultra-high temperature sterilization: The milk after the protein is preserved is sterilized at 136°C for 5 seconds; the milk after ultra-high temperature sterilization is cooled to 15°C before proceeding to the next step.

[0139] (8) Aseptic filling: The product is filled using Tetra Pak's aseptic filling machine.

[0140] Example 6 Standardization Method

[0141] This embodiment provides a method for protein standardization in milk preparation, the specific steps of which are as follows:

[0142] (1) Milk purification: Raw milk with a protein content of 3.24g / 100g is purified at a temperature of 6℃;

[0143] (2) First homogenization: The raw milk after impurity removal is homogenized at a total pressure of 120 bar and a secondary pressure of 35 bar;

[0144] (3) Pasteurization: Pasteurize the raw milk after one homogenization to obtain pasteurized milk; the parameters for pasteurization include: temperature 75℃, time 15s; after the pasteurized milk is cooled to 7℃, proceed to the next step.

[0145] (4) Protein index adjustment: The ultrafiltration permeate prepared in Preparation Example 5 was added to the pasteurized milk at a ratio of 20:100 to the amount of ultrafiltration permeate added to the pasteurized milk so that the protein content of the milk was the target protein content. The milk was stored at 7°C for the next step.

[0146] (5) Secondary homogenization: The milk with adjusted protein content was homogenized at a total pressure of 250 bar, a secondary pressure of 35 bar, and a temperature of 80°C.

[0147] (6) Protein retention: The milk after the second homogenization was subjected to protein retention at 95°C for 120 seconds;

[0148] (7) Ultra-high temperature sterilization: The milk after the protein is preserved is sterilized at 138°C for 5 seconds; the milk after ultra-high temperature sterilization is cooled to 35°C before proceeding to the next step.

[0149] (8) Aseptic filling: The product is filled using Tetra Pak's aseptic filling machine.

[0150] Example 7 Standardization Method

[0151] This embodiment provides a method for protein standardization in milk preparation, the specific steps of which are as follows:

[0152] (1) Milk purification: Raw milk with a protein content of 3.83g / 100g is purified at a temperature of 6℃;

[0153] (2) First homogenization: The raw milk after impurity removal is homogenized at a total pressure of 120 bar and a secondary pressure of 35 bar;

[0154] (3) Pasteurization: Pasteurize the raw milk after one homogenization to obtain pasteurized milk; the parameters for pasteurization include: temperature 75℃, time 15s; after the pasteurized milk is cooled to 7℃, proceed to the next step.

[0155] (4) Protein index adjustment: The ultrafiltration permeate prepared in Preparation Example 5 was added to the pasteurized milk at a ratio of 1:100 between the amount of ultrafiltration permeate added and the mass of pasteurized milk, so that the protein content in the resulting milk was the target protein content. The resulting milk was stored at 7°C for the next step.

[0156] (5) Secondary homogenization: The milk with adjusted protein content was homogenized at a total pressure of 250 bar, a secondary pressure of 35 bar, and a temperature of 80°C.

[0157] (6) Protein retention: The milk after the second homogenization was subjected to protein retention at 95°C for 120 seconds;

[0158] (7) Ultra-high temperature sterilization: The milk after the protein is preserved is sterilized at 138°C for 5 seconds; the milk after ultra-high temperature sterilization is cooled to 35°C before proceeding to the next step.

[0159] (8) Aseptic filling: The product is filled using Tetra Pak's aseptic filling machine.

[0160] Example 8

[0161] This is essentially the same as Example 2, except that the ultrafiltration permeate prepared in Example 2 is replaced with a permeate prepared by the following method:

[0162] The preparation method is basically the same as in Example 2, except for step (3):

[0163] (3) The cooled skim milk is filtered using an ultrafiltration membrane system to obtain protein concentrate and ultrafiltration permeate; wherein the ultrafiltration membrane system includes two ultrafiltration membranes connected in series, the molecular weight cutoff of the first ultrafiltration membrane is 1000~5000 Da, and the molecular weight cutoff of the second ultrafiltration membrane is 1000~5000 Da.

[0164] The resulting protein concentrate has a protein content of 15% and is supplied to downstream processing companies.

[0165] The obtained ultrafiltration permeate had a non-protein nitrogen content of 0.2%, a protein content of 0%, and a lactose content of 5 g / 100 g.

[0166] Comparative Example 1

[0167] It is basically the same as Example 1, except that the same mass of the ultrafiltration permeate obtained in Preparation Example 1 is replaced with pure water.

[0168] Accordingly, the ingredients and label of the resulting milk must include purified water.

[0169] Comparative Example 2

[0170] This is essentially the same as Example 2, except that the ultrafiltration permeate prepared in Example 2 is replaced with a permeate prepared by the following method:

[0171] The preparation method is basically the same as in Example 2, except for step (3):

[0172] (3) Use a 0.8 μm microfiltration membrane to filter the cooled skim milk to obtain permeate.

[0173] The lactose content of the obtained permeate was 5g / 100g.

[0174] Comparative Example 3

[0175] This is essentially the same as Example 2, except that the ultrafiltration permeate prepared in Example 2 is replaced with a permeate prepared by the following method:

[0176] The preparation method is basically the same as in Example 2, except for step (3):

[0177] (3) The cooled skim milk was filtered using a 0.01 μm nanofiltration membrane to obtain protein concentrate and permeate.

[0178] The protein concentration of the obtained protein concentrate is 15%.

[0179] The lactose content of the obtained permeate was 0 g / 100 g.

[0180] Comparative Example 4

[0181] This is essentially the same as Example 2, except that the ultrafiltration permeate prepared in Example 2 is replaced with a permeate prepared by the following method:

[0182] The preparation method is basically the same as in Example 2, except for step (3):

[0183] (3) The cooled skim milk was filtered using a 0.001 μm reverse osmosis membrane to obtain protein concentrate and permeate.

[0184] The protein concentration of the obtained protein concentrate is 15%.

[0185] The lactose content of the obtained permeate was 0 g / 100 g.

[0186] Comparative Example 5

[0187] This is essentially the same as Example 2, except that the ultrafiltration permeate prepared in Example 2 is replaced with a permeate prepared by the following method:

[0188] The preparation method is basically the same as in Example 2, except for step (3):

[0189] (3) The cooled skim milk is filtered using an ultrafiltration membrane system to obtain protein concentrate and ultrafiltration permeate; wherein the ultrafiltration membrane system includes a primary ultrafiltration membrane with a molecular weight cutoff of 1000~10000 Da.

[0190] The resulting protein concentrate has a protein content of 6%, and cannot be supplied to downstream processing companies.

[0191] The resulting ultrafiltration permeate had a non-protein nitrogen content of 0.0%, a protein content of 0%, and a lactose content of 5 g / 100 g.

[0192] Comparative Example 6

[0193] This is essentially the same as Example 2, except that the ultrafiltration permeate prepared in Example 2 is replaced with a permeate prepared by the following method:

[0194] The preparation method is basically the same as in Example 2, except for step (3):

[0195] (3) The cooled skim milk is filtered using an ultrafiltration membrane system to obtain protein concentrate and ultrafiltration permeate; wherein the ultrafiltration membrane system includes two ultrafiltration membranes connected in series, the molecular weight cutoff of the first ultrafiltration membrane is 1000~10000 Da, and the molecular weight cutoff of the second ultrafiltration membrane is 1000~10000 Da.

[0196] The resulting protein concentrate has a protein content of 8%, and cannot be supplied to downstream processing companies.

[0197] The obtained ultrafiltration permeate had a non-protein nitrogen content of 0.18%, a protein content of 0, and a lactose content of 5 g / 100 g.

[0198] Comparative Example 7

[0199] This comparative example provides a protein standardization method for preparing milk, the specific steps of which are as follows:

[0200] (1) Impurity removal: Raw milk with a protein content of 3.25g / 100g was purified at a temperature of 1℃;

[0201] (2) First homogenization: The raw milk after impurity removal is homogenized at a total pressure of 100 bar and a secondary pressure of 25 bar;

[0202] (3) Pasteurization: Pasteurize the raw milk after one homogenization to obtain pasteurized milk; the parameters for pasteurization include: temperature 75℃, time 15s; after the pasteurized milk is cooled to 1℃, proceed to the next step.

[0203] (4) Protein index adjustment: The ultrafiltration permeate added to the pasteurized milk was added according to the ratio of the amount of ultrafiltration permeate added to the mass of pasteurized milk of 21:100, so that the protein content of the milk was the target protein content. The milk was stored at 1°C for the next step.

[0204] (5) Secondary homogenization: The milk with adjusted protein content was homogenized at a total pressure of 200 bar, a secondary pressure of 25 bar, and a temperature of 70°C.

[0205] (6) Protein retention: The milk after the second homogenization was subjected to protein retention at 85°C for 60 seconds;

[0206] (7) Ultra-high temperature sterilization: The milk after the protein is preserved is sterilized at 136°C for 5 seconds; the milk after ultra-high temperature sterilization is cooled to 15°C before proceeding to the next step.

[0207] (8) Aseptic filling: The product is filled using Tetra Pak's aseptic filling machine.

[0208] Comparative Example 8

[0209] The process is basically the same as Example 3, except that in the protein index adjustment process, the ratio of the amount of ultrafiltration permeate added to the mass of pasteurized milk is 21:100.

[0210] Comparative Example 9

[0211] It is basically the same as Example 5, except that the secondary pressure in the first homogenization is 24 bar.

[0212] Comparative Example 10

[0213] It is basically the same as Example 5, except that the secondary pressure in the first homogenization is 36 bar.

[0214] Comparative Example 11

[0215] It is basically the same as Example 5, except that the secondary pressure in the secondary homogenization is 24 bar.

[0216] Comparative Example 12

[0217] It is basically the same as Example 5, except that the secondary pressure in the secondary homogenization is 36 bar.

[0218] Comparative Example 13

[0219] It is basically the same as Example 2, except that the temperature in the protein holding process is 84°C and the time is 60s.

[0220] Comparative Example 14

[0221] It is basically the same as Example 2, except that the temperature in the protein holding process is 96°C and the time is 120s.

[0222] Comparative Example 15

[0223] It is basically the same as Example 2, except that the temperature in the protein holding process is 85°C and the time is 30 seconds.

[0224] Comparative Example 16

[0225] It is basically the same as Example 2, except that the temperature in the protein holding process is 95°C and the time is 150s.

[0226] Comparative Example 17

[0227] It is basically the same as Example 2, except that the temperature in the protein holding process is 95°C and the time is 120s, and the temperature in the ultra-high temperature sterilization process is 135°C.

[0228] Comparative Example 18

[0229] It is basically the same as Example 2, except that the temperature in the protein holding process is 95°C and the time is 120s, and the temperature in the ultra-high temperature sterilization process is 139°C.

[0230] The milk prepared in the above examples and comparative examples was tested using the following methods:

[0231] Protein content: Detected using FOSS FT120.

[0232] Calcium content: Tested according to GB 5009.92 "National Food Safety Standard - Determination of Calcium in Food"; according to GB28050 "National Food Safety Standard - General Rules for Nutrition Labelling of Prepackaged Foods", the calcium content should be ≥80% of the labeled value;

[0233] Taste test: The difference between the samples prepared for comparison and the standard samples was analyzed using the three-point test of sensory analysis method in GB / T12311-2012. Among them, the standard sample selection for taste analysis is as follows: Principle (1) Collect product data for the whole year, first summarize the product fat and protein data, generate a histogram through Minitab software, and select the sample with the most concentrated fat and protein detection values ​​as the standard sample; Principle (2) The protein labeling value of the standard sample and the control sample in the product nutrition facts table must be the same.

[0234] Sensory evaluation: The sensory requirements of GB25190—2010 "National Food Safety Standard for Sterilized Milk" were used to evaluate the samples after they were stored at room temperature for 180 days.

[0235] The test results are as follows:

[0236]

[0237] The test results above show that the present invention can effectively overcome the problem of inconsistent physicochemical indicators and inconsistent taste caused by raw milk protein index being higher than the target product index (target product protein content 2.9~3.8g / 100g). It can ensure that the product system is stable during the shelf life and that the calcium content index complies with GB 28050 "National Food Safety Standard General Rules for Nutrition Labelling of Prepackaged Foods".

[0238] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for protein standardization in milk preparation, characterized in that, include: The purified raw milk is subjected to a series of processes: homogenization, pasteurization, protein index adjustment, homogenization, protein retention, and ultra-high temperature sterilization. The protein index adjustment includes: filtering skim milk using an ultrafiltration membrane system comprising two interconnected ultrafiltration membranes to obtain an ultrafiltration permeate with a protein content of 0 and a lactose content of 4.5~5.5 g / 100 g; adding the ultrafiltration permeate to pasteurized milk to achieve a protein content of 2.9~3.8 g / 100 g in the resulting milk; the ratio of the amount of ultrafiltration permeate added to the mass of the pasteurized milk is 1~20:

100. The first homogenization includes: homogenizing the purified raw milk under a secondary pressure of 25-35 bar; The secondary homogenization includes: homogenizing the milk with the adjusted protein index at a secondary pressure of 25-35 bar; The protein retention includes: retaining the protein in the milk after the second homogenization at 85-95°C for 60-120 seconds. The ultra-high temperature sterilization includes sterilizing the milk after the protein has been preserved at 136~138℃.

2. The protein standardization method for preparing milk according to claim 1, characterized in that, The method for preparing the ultrafiltration permeate includes: Raw milk is purified at a temperature of 45~55℃; The purified raw milk is subjected to fat separation at a temperature of 45-55℃ to obtain cream and skim milk; the fat content of the cream is 38-42%. The skim milk is cooled to 2-6°C; The cooled skim milk was filtered using an ultrafiltration membrane system to obtain a protein concentrate and an ultrafiltration permeate; the protein concentrate had a protein content of 10-15%; and the ultrafiltration permeate had a non-protein nitrogen content of 0.18-0.22%. The ultrafiltration membrane system includes two ultrafiltration membranes connected in series. The molecular weight cutoff of the first ultrafiltration membrane is 1000~10000 Da, and the molecular weight cutoff of the second ultrafiltration membrane is 1000~5000 Da.

3. The protein standardization method for preparing milk according to claim 1, characterized in that, The protein standardization method for preparing milk includes the following steps: Impurity removal: The raw milk is then purified to remove impurities; First homogenization: The purified raw milk is homogenized under a total pressure of 100-120 bar and a secondary pressure. Pasteurization: Pasteurize the raw milk after one homogenization to obtain pasteurized milk; Protein index adjustment: Add the ultrafiltration permeate to the pasteurized milk; Secondary homogenization: The milk with the protein index adjusted is homogenized at a total pressure of 200-250 bar, secondary pressure, and a temperature of 70-80°C. Protein retention: The milk after the second homogenization is subjected to protein retention. Ultra-high temperature sterilization: Sterilize the milk after the protein is retained for 4-6 seconds; Aseptic filling: Products are filled using aseptic filling machines.

4. Milk prepared by the protein standardization method for preparing milk according to any one of claims 1 to 3.

5. The milk according to claim 4, characterized in that, The protein content of the milk is 2.9~3.8g / 100g, and the deviation between the protein content of the milk and the target protein content is 1%.

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