Protein standardization method for preparing milk and product thereof

Abstract

The invention relates to the technical field of food, and provides a protein standardization method for preparing milk and a product thereof, and the method comprises the following steps: carrying out primary homogenization, pasteurization, protein index adjustment, secondary homogenization, protein maintenance and ultra-high temperature sterilization on impurity-removed raw milk in sequence; the protein index adjustment comprises the following steps: filtering the skimmed milk by adopting an ultrafiltration membrane system comprising two stages of ultrafiltration membranes which are connected in series to obtain ultrafiltration penetrating fluid with the protein content of 0 and the lactose content of 4.5-5.5 g / 100g; the ultrafiltration penetrating fluid is added into pasteurized pasteurized milk, so that the protein content in the obtained milk is 2.9-3.8 g / 100g; the ratio of the addition amount of the ultrafiltration penetrating fluid to the mass of the pasteurized milk is (1-20): 100. According to the method disclosed by the invention, the problems of unqualified physicochemical indexes, non-uniform taste, non-compliant calcium content and the like of the product are avoided while protein standardization is realized, and the stability of the system of the obtained milk product in the shelf life can be ensured.

Description

Technical Field

[0001] The invention relates to the technical field of food, and in particular to a protein standardization method for preparing milk and a product thereof. Background Art

[0002] Raw milk, also known as raw milk, has physical and chemical indicators that fluctuate greatly due to factors such as dairy cow breed, region, and season. When raw milk is used as raw material to prepare products, this objective phenomenon poses a challenge to the consistency of the product's physical and chemical indicators and the uniformity of its taste.

[0003] When the protein index of raw milk is lower than that of the target product, protein standardization of the final product can be achieved by concentration; however, when the protein index of raw milk is higher than that of the target product, the index of high-protein raw milk needs to be standardized "downward", and there are few such methods to achieve protein standardization. According to the "National Food Safety Standard General Rules for Pre-packaged Food Labeling", if the protein index of the product is standardized by adding water to high-protein milk, it needs to be marked in the product ingredient list, and after adding water, the resulting product has the risk of a large difference in taste from the standard product and unqualified calcium content index.

[0004] Therefore, when the protein index of raw milk is higher than that of the target product, it is urgent to provide a method for achieving protein standardization without adding water to high-protein milk, and to avoid problems such as unqualified physical and chemical indicators and taste of the product. Summary of the invention

[0005] The present invention provides a protein standardization method for preparing milk and a product thereof, which are used to solve the defects of adding water to high-protein cow's milk in the prior art to standardize the protein index of the product, such as the taste of the obtained product is greatly different from that of the standard product, and the calcium content index of the product is unqualified. By adding a permeate obtained in a specific way and controlling its addition ratio to perform "downward" standardization of high-protein raw milk, and optimizing the process flow and parameters of protein standardization, it is achieved that while standardizing the protein, the physical and chemical indexes of the product are unqualified, the taste is not uniform, the calcium content of the product is not compliant, and other problems are avoided.

[0006] The present invention provides a protein standardization method for preparing milk, comprising: subjecting the impurity-removed raw milk to primary homogenization, pasteurization, protein index adjustment, secondary homogenization, protein retention and ultra-high temperature sterilization in sequence; The protein index adjustment comprises: using an ultrafiltration membrane system including two-stage ultrafiltration membranes connected in series to filter skimmed milk to obtain an ultrafiltration permeate having a protein content of 0 and a lactose content of 4.5-5.5 g / 100 g; adding the ultrafiltration permeate to the pasteurized milk obtained by pasteurization to make the protein content in the obtained milk 2.9-3.8 g / 100 g; and the ratio of the amount of the ultrafiltration permeate added to the mass of the pasteurized milk is 1-20:100.

[0007] The study found that when using ultrafiltration permeate with a lactose content 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 amount must be strictly controlled to not exceed 20%.

[0008] In the present invention, the lactose content is 4.5~5.5g / 100g, for example, it can be any value 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, or a range consisting of any values.

[0009] In the present invention, the protein content in the obtained milk is 2.9~3.8g / 100g, for example, it can be any value between 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 or a range of any values.

[0010] In the present invention, the mass ratio of the added amount of the ultrafiltration permeate to the pasteurized milk is 1-20:100, for example, it can be any value of 1:100, 3:100, 5:100, 7:100, 9:100, 11:100, 13:100, 15:100, 17:100, 19:100 and 20:100, or a range of any values.

[0011] According to the protein standardization method for preparing milk provided by the present invention, the primary homogenization comprises: homogenizing the raw milk after impurities removal at a secondary pressure of 25-35 bar.

[0012] It was found in the experiment that the use of a secondary pressure of 25~35 bar during primary homogenization can achieve the best homogenization effect and effectively ensure the stability of the product system.

[0013] According to the protein standardization method for preparing milk provided by the present invention, the secondary homogenization includes: homogenizing the milk after the protein index is adjusted at a secondary pressure of 25-35 bar.

[0014] It was found in the experiment that the use of a secondary pressure of 25~35bar during secondary homogenization can achieve the best homogenization effect and effectively ensure the stability of the product system.

[0015] According to the protein standardization method for preparing milk provided by the present invention, the protein preservation comprises: preserving the protein of the milk after the secondary homogenization at 85-95° C. for 60-120 s.

[0016] The study found that when ultrafiltration permeate with lactose content maintained in the range of 4.5~5.5g / 100g is used as the dilution medium for the "downward" standardization of high-protein raw milk, in order to avoid the production of white particles in the product, the protein retention process needs to be carried out at 85~95℃ and 60~120s.

[0017] According to the protein standardization method for preparing milk provided by the present invention, the ultra-high temperature sterilization includes: sterilizing the milk after the protein is maintained at 136-138° C. Experiments have found that when the ultrafiltration permeate with a lactose content maintained in the range of 4.5-5.5 g / 100 g is used as a dilution medium, in order to avoid product instability during the "downward" standardization of high-protein raw milk, the high-temperature sterilization process needs to be carried out at 136-138° C.

[0018] 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 1000-10000Da, and the molecular weight cutoff of the second-stage ultrafiltration membrane is 1000-5000Da.

[0019] According to the protein standardization method for preparing milk provided by the present invention, the method for preparing the ultrafiltration permeate comprises: The raw milk is cleaned at a temperature of 45-55°C.

[0020] The raw milk after impurities removal is subjected to fat separation at a temperature of 45-55° C. to obtain cream and skimmed milk; the fat content of the cream is 38-42%; and the cream is supplied to downstream processing enterprises as raw materials.

[0021] Preferably, a milk separator is used to achieve the impurity removal and fat separation.

[0022] The present invention adopts a milk purifying separator with the ability to separate milk and fat, which can solve the separation of milk and fat in one stop and reduce the processing procedures; wherein, the milk purifying and fat separation is carried out at a temperature of 45-55°C, which can reduce the slag loss of the separator.

[0023] The skimmed milk is cooled to 2-6°C; the ultrafiltration membrane system is sensitive to microbial contamination. The present invention has found that cooling the skimmed milk to 2-6°C before entering the ultrafiltration membrane system can avoid cross contamination caused by microbial proliferation during subsequent ultrafiltration membrane filtration, thereby ensuring the food safety of the final product.

[0024] The cooled skimmed 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 companies; the non-protein nitrogen content of the ultrafiltration permeate is 0.18-0.22%.

[0025] The ultrafiltration membrane system comprises two stages of ultrafiltration membranes connected in series, the molecular weight cutoff of the first stage ultrafiltration membrane is 1000-10000Da, and the molecular weight cutoff of the second stage ultrafiltration membrane is 1000-5000Da.

[0026] In general, the ultrafiltration membrane system can better separate the components in the milk raw material. When the present invention studies the "downward" standardization of high-protein raw milk, it is found that in order to achieve protein standardization, while avoiding the problems of unqualified physical and chemical indicators and taste of the product, adding permeate to the high-protein raw milk is an optional method. Based on this, after a large number of experimental comparisons, the present invention finds that when the ultrafiltration membrane system adopts the above parameters, a protein concentrate with a protein content of 10-15% and an ultrafiltration permeate with a lactose content of 4.5-5.5g / 100g can be obtained. The permeate obtained by this method is added to the high-protein raw milk, which is one of the important factors to ensure 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.

[0027] According to the protein standardization method for preparing milk provided by the present invention, the protein standardization method for preparing milk comprises the following steps: Removing impurities: Remove impurities from the raw milk.

[0028] Primary homogenization: homogenizing the cleaned raw milk at a total pressure of 100-120 bar and a secondary pressure.

[0029] Pasteurization: pasteurize the raw milk after the primary homogenization to obtain pasteurized milk; the pasteurization parameters include: temperature 75° C., time 15 s.

[0030] Protein index adjustment: adding the ultrafiltration permeate into the pasteurized milk.

[0031] Secondary homogenization: homogenize the milk after adjusting the protein index at a total pressure of 200-250 bar, a secondary pressure, and a temperature of 70-80° C.

[0032] Protein preservation: the milk after the secondary homogenization is subjected to protein preservation.

[0033] Ultra-high temperature sterilization: sterilize the milk after the protein is retained for 4 to 6 seconds.

[0034] Aseptic filling: Use aseptic filling machine to fill the product.

[0035] According to the protein standardization method for preparing milk provided by the present invention, Figure 1 As shown, the protein standardization method for preparing milk comprises the following steps: (1) Preparation of ultrafiltration permeate (1.1) Clean milk separation: The raw milk is subjected to impurity removal and fat separation at a temperature of 45-55°C to obtain cream and skimmed milk; the fat content of the cream is 38-42%; the fat content of the skimmed milk is less than 0.05%.

[0036] Preferably, a milk separator is used to achieve the impurity removal and fat separation at one time.

[0037] (1.2) UF ultrafiltration: The skimmed milk cooled to 2-6°C 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%; the ultrafiltration permeate has a non-protein nitrogen content of 0.18-0.22%.

[0038] The ultrafiltration membrane system comprises two stages of ultrafiltration membranes connected in series, the molecular weight cutoff of the first stage ultrafiltration membrane is 1000-10000Da, and the molecular weight cutoff of the second stage ultrafiltration membrane is 1000-5000Da.

[0039] (2) Purifying milk: removing impurities from raw milk.

[0040] (3) Primary homogenization: homogenizing the raw milk after impurity removal at a total pressure of 100-120 bar and a secondary pressure.

[0041] (4) Pasteurization: pasteurize the raw milk after the primary homogenization to obtain pasteurized milk. The pasteurization parameters include: temperature 75° C., time 15 s.

[0042] (5) Adjusting protein index: adding the ultrafiltration permeate to the pasteurized milk.

[0043] (6) Secondary homogenization: homogenize the milk after adjusting the protein index at a total pressure of 200-250 bar, a secondary pressure, and a temperature of 70-80° C.

[0044] (7) Protein preservation: The milk after the secondary homogenization is subjected to protein preservation.

[0045] (8) Ultra-high temperature sterilization: sterilize the milk after the protein is retained for 4 to 6 seconds.

[0046] (9) Aseptic filling: Use aseptic filling machines to fill products.

[0047] The present invention also provides milk obtained by the protein standardization method for preparing milk as described above.

[0048] According to the milk provided by the present invention, the protein content of the milk is 2.9-3.8 g / 100 g, and the deviation between the protein content of the milk and the target protein content is 1%.

[0049] When the protein index of raw milk is different from that of the target product, protein standardization is required. In the present invention, the target protein content refers to the protein content of the target product.

[0050] The protein standardization method and product for preparing milk provided by the present invention perform "downward" standardization of high-protein raw milk by adding a permeate obtained in a specific manner and controlling the addition ratio thereof, and optimize the process flow and parameters of protein standardization, thereby achieving protein standardization while avoiding problems such as unqualified physical and chemical indicators, inconsistent taste, and non-compliant calcium content in the product. The method of the present invention can ensure that the obtained milk product has a stable system during the shelf life and that the calcium content index complies with GB 28050 "General Rules for Nutrition Labeling of Prepackaged Foods, National Food Safety Standard". BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0052] Figure 1 This is one of the schematic diagrams of the process for preparing protein standardization of milk provided by the present invention. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0054] If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the field or the product instructions are used. If no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased through regular channels.

[0055] The raw milk used in the present invention is all inspected and accepted according to the standard "GB 19301 National Food Safety Standard Raw Milk" and used after passing the inspection. However, the calcium content of the raw milk used in different embodiments and comparative examples fluctuates.

[0056] The equipment used in the present invention includes: a milk purifier, a milk purifier 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.

[0057] Preparation Example 1 Ultrafiltration Permeate This preparation example provides an ultrafiltration permeate, and the specific preparation steps are as follows: (1) Using a milk separator to remove impurities and separate fat from raw milk at 45°C to obtain cream and skimmed milk; The fat content of light cream is 38%, and the fat content of skimmed milk is 0.05%. Light cream is supplied to downstream processing companies as raw materials.

[0058] (2) Cool skim milk to 2°C; (3) The cooled skimmed milk is filtered using an ultrafiltration membrane system to obtain a protein concentrate and an ultrafiltration permeate; wherein the ultrafiltration membrane system comprises two stages of ultrafiltration membranes connected in series, the molecular weight cutoff of the first stage ultrafiltration membrane is 1000-10000Da, and the molecular weight cutoff of the second stage ultrafiltration membrane is 1000-5000Da.

[0059] The protein content of the obtained protein concentrate is 10%, and the protein concentrate is supplied to downstream processing companies for use.

[0060] The non-protein nitrogen content of the obtained ultrafiltration permeate was 0.18%, the protein content was 0, and the lactose content was 4.5 g / 100 g.

[0061] Preparation Example 2 Ultrafiltration Permeate This preparation example provides an ultrafiltration permeate, and the specific preparation steps are as follows: (1) Using a milk separator to remove impurities and separate fat from raw milk at 50°C to obtain cream and skimmed milk; The fat content of light cream is 40%, and the fat content of skimmed milk is 0.03%. Light cream is supplied to downstream processing companies as raw materials.

[0062] (2) Cool skim milk to 3°C; (3) The cooled skimmed milk is filtered using an ultrafiltration membrane system to obtain a protein concentrate and an ultrafiltration permeate; wherein the ultrafiltration membrane system comprises two stages of ultrafiltration membranes connected in series, the molecular weight cutoff of the first stage ultrafiltration membrane is 1000-10000Da, and the molecular weight cutoff of the second stage ultrafiltration membrane is 1000-5000Da.

[0063] The protein content of the obtained protein concentrate is 13%, and the protein concentrate is supplied to downstream processing companies for use.

[0064] 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.

[0065] Preparation Example 3 Ultrafiltration Permeate This preparation example provides an ultrafiltration permeate, and the specific preparation steps are as follows: (1) Using a milk separator at 55°C to remove impurities and separate fat from raw milk to obtain cream and skimmed milk; The fat content of light cream is 42%, and the fat content of skimmed milk is 0.02%. Light cream is supplied to downstream processing companies as raw materials.

[0066] (2) Cool skim milk to 4°C; (3) The cooled skimmed milk is filtered using an ultrafiltration membrane system to obtain a protein concentrate and an ultrafiltration permeate; wherein the ultrafiltration membrane system comprises two stages of ultrafiltration membranes connected in series, the molecular weight cutoff of the first stage ultrafiltration membrane is 1000-10000Da, and the molecular weight cutoff of the second stage ultrafiltration membrane is 1000-5000Da.

[0067] The protein content of the obtained protein concentrate is 15%, and the protein concentrate is supplied to downstream processing companies for use.

[0068] The non-protein nitrogen content of the obtained ultrafiltration permeate was 0.19%, the protein content was 0, and the lactose content was 5.5 g / 100 g.

[0069] Preparation Example 4 Ultrafiltration Permeate The method is basically the same as Preparation Example 1, except that the protein content of the obtained protein concentrate is 15%.

[0070] Preparation Example 5 Ultrafiltration Permeate The method is basically the same as Preparation Example 3, except that the skimmed milk is cooled to 5°C.

[0071] Example 1 Standardization method This embodiment provides a protein standardization method for preparing milk, and the specific steps are as follows: (1) Purified milk: remove impurities from raw milk with a protein content of 2.93 g / 100 g at a temperature of 1°C; (2) Primary homogenization: homogenize the cleaned raw milk at a total pressure of 100 bar and a secondary pressure of 25 bar; (3) Pasteurization: The raw milk after homogenization is pasteurized to obtain pasteurized milk; the pasteurization parameters include: temperature 75°C, time 15s; the pasteurized milk is cooled to 1°C before proceeding to the next step.

[0072] (4) Adjustment of protein index: The ultrafiltration permeate prepared in Preparation Example 1 was added to the pasteurized milk at a ratio of 1:100 to the mass of the pasteurized milk, so that the protein content in the resulting milk reached the target protein content. The resulting milk was stored at 1°C for the next step.

[0073] (5) Secondary homogenization: homogenize the milk after adjusting the protein index at a total pressure of 200 bar, a secondary pressure of 25 bar, and a temperature of 70°C; (6) Protein retention: The milk after secondary homogenization is kept at 85°C for 60 seconds for protein retention; (7) Ultra-high temperature sterilization: sterilize the milk after the protein is retained at 136° C. for 5 seconds; after the ultra-high temperature sterilized milk is cooled to 15° C., proceed to the next step.

[0074] (8) Aseptic filling: Use Tetra Pak’s aseptic filling machine to fill the product.

[0075] Example 2 Standardization Method This embodiment provides a protein standardization method for preparing milk, and the specific steps are as follows: (1) Purified milk: remove impurities from raw milk with a protein content of 3.72 g / 100 g at 3°C; (2) Primary homogenization: homogenize the cleaned raw milk at a total pressure of 110 bar and a secondary pressure of 30 bar; (3) Pasteurization: The raw milk after homogenization is pasteurized to obtain pasteurized milk; the pasteurization parameters include: temperature 75°C, time 15s; the pasteurized milk is cooled to 4°C before proceeding to the next step.

[0076] (4) Adjustment of protein index: The ultrafiltration permeate prepared in Preparation Example 2 was added to the pasteurized milk at a mass ratio of 10:100, so that the protein content in the obtained milk reached the target protein content. The obtained milk was stored at 4°C for the next step.

[0077] (5) Secondary homogenization: homogenize the milk after adjusting the protein index at a total pressure of 235 bar, a secondary pressure of 30 bar, and a temperature of 75°C; (6) Protein preservation: The milk after secondary homogenization is kept at 90°C for 90 seconds for protein preservation; (7) Ultra-high temperature sterilization: sterilize the milk after the protein is retained at 137° C. for 5 seconds; after the ultra-high temperature sterilized milk is cooled to 25° C., proceed to the next step.

[0078] (8) Aseptic filling: Use Tetra Pak’s aseptic filling machine to fill the product.

[0079] Example 3 Standardization Method This embodiment provides a protein standardization method for preparing milk, and the specific steps are as follows: (1) Purified milk: remove impurities from raw milk with a protein content of 4.52 g / 100 g at 6°C; (2) Primary homogenization: homogenize the cleaned raw milk at a total pressure of 120 bar and a secondary pressure of 35 bar; (3) Pasteurization: The raw milk after homogenization is pasteurized to obtain pasteurized milk; the pasteurization parameters include: temperature 75°C, time 15s; the pasteurized milk is cooled to 7°C before proceeding to the next step.

[0080] (4) Adjustment of protein index: The ultrafiltration permeate prepared in Preparation Example 3 was added to the pasteurized milk at a mass ratio of 20:100, so that the protein content in the obtained milk reached the target protein content. The obtained milk was stored at 7° C. for the next step.

[0081] (5) Secondary homogenization: homogenize the milk after adjusting the protein index at a total pressure of 250 bar, a secondary pressure of 35 bar, and a temperature of 80°C; (6) Protein preservation: The milk after secondary homogenization is kept at 95°C for 120 seconds for protein preservation; (7) Ultra-high temperature sterilization: sterilize the milk after the protein is retained at 138° C. for 5 seconds; after the ultra-high temperature sterilized milk is cooled to 35° C., proceed to the next step.

[0082] (8) Aseptic filling: Use Tetra Pak’s aseptic filling machine to fill the product.

[0083] Example 4 Standardization Method This embodiment provides a protein standardization method for preparing milk, and the specific steps are as follows: (1) Purified milk: remove impurities from raw milk with a protein content of 3.24 g / 100 g at 1°C; (2) Primary homogenization: homogenize the cleaned raw milk at a total pressure of 100 bar and a secondary pressure of 25 bar; (3) Pasteurization: The raw milk after homogenization is pasteurized to obtain pasteurized milk; the pasteurization parameters include: temperature 75°C, time 15s; the pasteurized milk is cooled to 1°C before proceeding to the next step.

[0084] (4) Adjustment of protein index: The ultrafiltration permeate prepared in Preparation Example 4 was added to the pasteurized milk at a mass ratio of 20:100, so that the protein content in the obtained milk reached the target protein content. The obtained milk was stored at 1°C for the next step.

[0085] (5) Secondary homogenization: homogenize the milk after adjusting the protein index at a total pressure of 200 bar, a secondary pressure of 25 bar, and a temperature of 70°C; (6) Protein retention: The milk after secondary homogenization is kept at 85°C for 60 seconds for protein retention; (7) Ultra-high temperature sterilization: sterilize the milk after the protein is retained at 136° C. for 5 seconds; after the ultra-high temperature sterilized milk is cooled to 15° C., proceed to the next step.

[0086] (8) Aseptic filling: Use Tetra Pak’s aseptic filling machine to fill the product.

[0087] Example 5 Standardization Method This embodiment provides a protein standardization method for preparing milk, and the specific steps are as follows: (1) Purified milk: remove impurities from raw milk with a protein content of 3.83 g / 100 g at 1°C; (2) Primary homogenization: homogenize the cleaned raw milk at a total pressure of 100 bar and a secondary pressure of 25 bar; (3) Pasteurization: The raw milk after homogenization is pasteurized to obtain pasteurized milk; the pasteurization parameters include: temperature 75°C, time 15s; the pasteurized milk is cooled to 1°C before proceeding to the next step.

[0088] (4) Adjustment of protein index: The ultrafiltration permeate prepared in Preparation Example 1 was added to the pasteurized milk at a ratio of 1:100 to the mass of the pasteurized milk, so that the protein content in the resulting milk reached the target protein content. The resulting milk was stored at 1°C for the next step.

[0089] (5) Secondary homogenization: homogenize the milk after adjusting the protein index at a total pressure of 200 bar, a secondary pressure of 25 bar, and a temperature of 70°C; (6) Protein retention: The milk after secondary homogenization is kept at 85°C for 60 seconds for protein retention; (7) Ultra-high temperature sterilization: sterilize the milk after the protein is retained at 136° C. for 5 seconds; after the ultra-high temperature sterilized milk is cooled to 15° C., proceed to the next step.

[0090] (8) Aseptic filling: Use Tetra Pak’s aseptic filling machine to fill the product.

[0091] Example 6 Standardization Method This embodiment provides a protein standardization method for preparing milk, and the specific steps are as follows: (1) Purified milk: remove impurities from raw milk with a protein content of 3.24 g / 100 g at 6°C; (2) Primary homogenization: homogenize the cleaned raw milk at a total pressure of 120 bar and a secondary pressure of 35 bar; (3) Pasteurization: The raw milk after homogenization is pasteurized to obtain pasteurized milk; the pasteurization parameters include: temperature 75°C, time 15s; the pasteurized milk is cooled to 7°C before proceeding to the next step.

[0092] (4) Adjustment of protein index: The ultrafiltration permeate prepared in Preparation Example 5 was added to the pasteurized milk at a mass ratio of 20:100, so that the protein content in the obtained milk reached the target protein content. The obtained milk was stored at 7°C for the next step.

[0093] (5) Secondary homogenization: homogenize the milk after adjusting the protein index at a total pressure of 250 bar, a secondary pressure of 35 bar, and a temperature of 80°C; (6) Protein preservation: The milk after secondary homogenization is kept at 95°C for 120 seconds for protein preservation; (7) Ultra-high temperature sterilization: sterilize the milk after the protein is retained at 138° C. for 5 seconds; after the ultra-high temperature sterilized milk is cooled to 35° C., proceed to the next step.

[0094] (8) Aseptic filling: Use Tetra Pak’s aseptic filling machine to fill the product.

[0095] Example 7 Standardization Method This embodiment provides a protein standardization method for preparing milk, and the specific steps are as follows: (1) Purified milk: remove impurities from raw milk with a protein content of 3.83 g / 100 g at 6°C; (2) Primary homogenization: homogenize the cleaned raw milk at a total pressure of 120 bar and a secondary pressure of 35 bar; (3) Pasteurization: The raw milk after homogenization is pasteurized to obtain pasteurized milk; the pasteurization parameters include: temperature 75°C, time 15s; the pasteurized milk is cooled to 7°C before proceeding to the next step.

[0096] (4) Adjustment of protein index: The ultrafiltration permeate prepared in Preparation Example 5 was added to the pasteurized milk at a mass ratio of 1:100 to the mass ratio of the ultrafiltration permeate added to the pasteurized milk, so that the protein content in the obtained milk reached the target protein content. The obtained milk was stored at 7° C. for the next step.

[0097] (5) Secondary homogenization: homogenize the milk after adjusting the protein index at a total pressure of 250 bar, a secondary pressure of 35 bar, and a temperature of 80°C; (6) Protein preservation: The milk after secondary homogenization is kept at 95°C for 120 seconds for protein preservation; (7) Ultra-high temperature sterilization: sterilize the milk after the protein is retained at 138° C. for 5 seconds; after the ultra-high temperature sterilized milk is cooled to 35° C., proceed to the next step.

[0098] (8) Aseptic filling: Use Tetra Pak’s aseptic filling machine to fill the product.

[0099] Example 8 The method is basically the same as Example 2, except that the ultrafiltration permeate prepared in Preparation Example 2 is replaced by the permeate prepared by the following preparation method: The method is basically the same as Preparation Example 2, except for step (3): (3) The cooled skim milk is filtered using an ultrafiltration membrane system to obtain a protein concentrate and an ultrafiltration permeate; wherein the ultrafiltration membrane system comprises two stages of ultrafiltration membranes connected in series, the molecular weight cutoff of the first stage ultrafiltration membrane is 1000-5000Da, and the molecular weight cutoff of the second stage ultrafiltration membrane is 1000-5000Da.

[0100] The protein content of the obtained protein concentrate is 15%, and the protein concentrate is supplied to downstream processing companies for use.

[0101] 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.

[0102] Comparative Example 1 It is basically the same as Example 1, except that the mass of the ultrafiltration permeate obtained in Preparation Example 1 is replaced by pure water.

[0103] Accordingly, purified water needs to be indicated in the ingredients and labels of the resulting milk.

[0104] Comparative Example 2 The method is basically the same as Example 2, except that the ultrafiltration permeate prepared in Preparation Example 2 is replaced by the permeate prepared by the following preparation method: The method is basically the same as Preparation Example 2, except for step (3): (3) The cooled skim milk is filtered using a 0.8 μm microfiltration membrane to obtain the permeate.

[0105] The lactose content of the obtained permeate was 5 g / 100 g.

[0106] Comparative Example 3 The method is basically the same as Example 2, except that the ultrafiltration permeate prepared in Preparation Example 2 is replaced by the permeate prepared by the following preparation method: The method is basically the same as Preparation Example 2, except for step (3): (3) The cooled skim milk is filtered using a 0.01 μm nanofiltration membrane to obtain protein concentrate and permeate.

[0107] The protein content of the obtained protein concentrate was 15%.

[0108] The lactose content of the obtained permeate was 0 g / 100 g.

[0109] Comparative Example 4 The method is basically the same as Example 2, except that the ultrafiltration permeate prepared in Preparation Example 2 is replaced by the permeate prepared by the following preparation method: The method is basically the same as Preparation Example 2, except for step (3): (3) The cooled skim milk is filtered using a 0.001 μm reverse osmosis membrane to obtain protein concentrate and permeate.

[0110] The protein content of the obtained protein concentrate was 15%.

[0111] The lactose content of the obtained permeate was 0 g / 100 g.

[0112] Comparative Example 5 The method is basically the same as Example 2, except that the ultrafiltration permeate prepared in Preparation Example 2 is replaced by the permeate prepared by the following preparation method: The method is basically the same as Preparation Example 2, except for step (3): (3) The cooled skim milk is filtered using an ultrafiltration membrane system to obtain a protein concentrate and an ultrafiltration permeate; wherein the ultrafiltration membrane system includes a first-stage ultrafiltration membrane with a molecular weight cutoff of 1000 to 10000 Da.

[0113] The protein content of the obtained protein concentrate is 6%, and the protein concentrate cannot be supplied to downstream processing companies for use.

[0114] The obtained 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.

[0115] Comparative Example 6 The method is basically the same as Example 2, except that the ultrafiltration permeate prepared in Preparation Example 2 is replaced by the permeate prepared by the following preparation method: The method is basically the same as Preparation Example 2, except for step (3): (3) The cooled skim milk is filtered using an ultrafiltration membrane system to obtain a protein concentrate and an ultrafiltration permeate; wherein the ultrafiltration membrane system comprises two stages of ultrafiltration membranes connected in series, the molecular weight cutoff of the first stage ultrafiltration membrane is 1000-10000Da, and the molecular weight cutoff of the second stage ultrafiltration membrane is 1000-10000Da.

[0116] The protein content of the obtained protein concentrate is 8%, and the protein concentrate cannot be supplied to downstream processing companies for use.

[0117] 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.

[0118] Comparative Example 7 This comparative example provides a protein standardization method for preparing milk, and the specific steps are as follows: (1) Impurity removal: impurities are removed from raw milk with a protein content of 3.25 g / 100 g at a temperature of 1°C; (2) Primary homogenization: homogenize the cleaned raw milk at a total pressure of 100 bar and a secondary pressure of 25 bar; (3) Pasteurization: The raw milk after homogenization is pasteurized to obtain pasteurized milk; the pasteurization parameters include: temperature 75°C, time 15s; the pasteurized milk is cooled to 1°C before proceeding to the next step.

[0119] (4) Adjustment of protein index: The ultrafiltration permeate prepared in Preparation Example 1 was added to the pasteurized milk at a mass ratio of 21:100, so that the protein content in the obtained milk reached the target protein content. The obtained milk was stored at 1°C for the next step.

[0120] (5) Secondary homogenization: homogenize the milk after adjusting the protein index at a total pressure of 200 bar, a secondary pressure of 25 bar, and a temperature of 70°C; (6) Protein retention: The milk after secondary homogenization is kept at 85°C for 60 seconds for protein retention; (7) Ultra-high temperature sterilization: sterilize the milk after the protein is retained at 136° C. for 5 seconds; after the ultra-high temperature sterilized milk is cooled to 15° C., proceed to the next step.

[0121] (8) Aseptic filling: Use Tetra Pak’s aseptic filling machine to fill the product.

[0122] Comparative Example 8 The method is basically the same as Example 3, except that in the protein index adjustment step, the mass ratio of the ultrafiltration permeate added to the pasteurized milk is 21:100.

[0123] Comparative Example 9 It is basically the same as Example 5, except that the secondary pressure in the first homogenization is 24 bar.

[0124] Comparative Example 10 It is basically the same as Example 5, except that the secondary pressure in the first homogenization is 36 bar.

[0125] Comparative Example 11 It is basically the same as Example 5, except that the secondary pressure in the secondary homogenization is 24 bar.

[0126] Comparative Example 12 It is basically the same as Example 5, except that the secondary pressure in the secondary homogenization is 36 bar.

[0127] Comparative Example 13 The method is basically the same as Example 2, except that the temperature in the protein holding step is 84° C. and the time is 60 seconds.

[0128] Comparative Example 14 The method is basically the same as Example 2, except that the temperature in the protein holding step is 96° C. and the time is 120 s.

[0129] Comparative Example 15 The method is basically the same as Example 2, except that the temperature in the protein holding step is 85° C. and the time is 30 seconds.

[0130] Comparative Example 16 The method is basically the same as Example 2, except that the temperature in the protein holding step is 95° C. and the time is 150 s.

[0131] Comparative Example 17 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.

[0132] Comparative Example 18 It is basically the same as Example 2, except that the temperature in the protein holding process is 95° C. and the time is 120 s, and the temperature in the ultra-high temperature sterilization process is 139° C.

[0133] The milk obtained in the above embodiment and comparative example was tested, and the testing method was as follows: Protein content: Detected by FOSS FT120.

[0134] Calcium content: tested in accordance with GB 5009.92 "National Food Safety Standard Determination of Calcium in Foods"; according to GB28050 "National Food Safety Standard General Rules for Nutrition Labeling of Prepackaged Foods", the calcium content index should be ≥ 80% of the labeled value; Taste test: The difference analysis between the samples prepared by the comparative example and the standard samples was conducted using the "GB / T12311-2012 Sensory Analysis Method Three-Point Test". For taste analysis, the standard samples were selected as follows: Principle (1) Collect product data for the whole year, first summarize the product fat and protein data, generate a histogram using Minitab software, and then select the samples with the most concentrated fat and protein detection values ​​as standard samples; Principle (2) The protein label value in the product nutrition information table of the standard sample and the control sample must be the same.

[0135] Sensory test: After the samples were stored at room temperature for 180 days, the sensory requirements of GB25190-2010 "National Food Safety Standard Sterilized Milk" were used for evaluation.

[0136] The test results are as follows:

[0137] It can be seen from the above test results that the present invention can effectively overcome the problem of inconsistent physical and chemical indicators and inconsistent taste caused by the raw milk protein index being higher than the target product index (target product protein content 2.9~3.8g / 100g) through the above method, and can ensure that the product system is stable during the shelf life and the calcium content index complies with GB 28050 "National Food Safety Standard General Rules for Nutrition Labeling of Pre-packaged Foods".

[0138] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing protein standardization of milk, characterized in that include: The raw milk after impurities removal is subjected to primary homogenization, pasteurization, protein index adjustment, secondary homogenization, protein retention and ultra-high temperature sterilization in sequence; The protein index adjustment comprises: using an ultrafiltration membrane system including two-stage ultrafiltration membranes connected in series to filter skimmed milk to obtain an ultrafiltration permeate having a protein content of 0 and a lactose content of 4.5-5.5 g / 100 g; adding the ultrafiltration permeate to the pasteurized milk obtained by pasteurization to make the protein content in the obtained milk 2.9-3.8 g / 100 g; and the ratio of the amount of the ultrafiltration permeate added to the mass of the pasteurized milk is 1-20:

100.

2. The protein standardization method for preparing milk according to claim 1, characterized in that: The primary homogenization includes: homogenizing the raw milk after impurities removal at a secondary pressure of 25-35 bar.

3. The protein standardization method for preparing milk according to claim 1, characterized in that: The secondary homogenization includes: homogenizing the milk after the protein index is adjusted at a secondary pressure of 25-35 bar.

4. The protein standardization method for preparing milk according to claim 1, characterized in that: The protein preservation comprises: preserving the protein of the milk after the secondary homogenization at 85-95° C. for 60-120 seconds.

5. The protein standardization method for preparing milk according to claim 1, characterized in that: The ultra-high temperature sterilization comprises: sterilizing the milk after the protein is retained at a temperature of 136-138°C.

6. The protein standardization method for preparing milk according to claim 1, characterized in that: In the two-stage ultrafiltration membrane, the molecular weight cutoff of the first-stage ultrafiltration membrane is 1000-10000Da, and the molecular weight cutoff of the second-stage ultrafiltration membrane is 1000-5000Da.

7. The protein standardization method for preparing milk according to any one of claims 1 to 6, characterized in that: The preparation method of the ultrafiltration permeate comprises: Remove impurities from raw milk at a temperature of 45-55°C; The impurity-removed raw milk is subjected to fat separation at a temperature of 45-55° C. to obtain cream and skimmed milk; the fat content of the cream is 38-42%; The skimmed milk is cooled to 2-6°C; 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%; the ultrafiltration permeate has a non-protein nitrogen content of 0.18-0.22%; The ultrafiltration membrane system comprises two stages of ultrafiltration membranes connected in series, the molecular weight cutoff of the first stage ultrafiltration membrane is 1000-10000Da, and the molecular weight cutoff of the second stage ultrafiltration membrane is 1000-5000Da.

8. The protein standardization method for preparing milk according to any one of claims 1 to 6, characterized in that: The protein standardization method for preparing milk comprises the following steps: Remove impurities: remove impurities from raw milk; Primary homogenization: homogenizing the raw milk after impurity removal at a total pressure of 100-120 bar and a secondary pressure; Pasteurization: pasteurizing the raw milk after the primary homogenization to obtain pasteurized milk; Adjusting the protein index: adding the ultrafiltration permeate to the pasteurized milk; Secondary homogenization: homogenizing the milk after adjusting the protein index at a total pressure of 200-250 bar, a secondary pressure, and a temperature of 70-80° C.; Protein preservation: preserving the protein of the milk after the secondary homogenization; Ultra-high temperature sterilization: sterilizing the milk after the protein is retained for 4-6 seconds; Aseptic filling: Use aseptic filling machine to fill the product.

9. Milk obtained by the protein standardization method for preparing milk according to any one of claims 1 to 8.

10. The milk according to claim 9, characterized in that The protein content of the milk is 2.9-3.8 g / 100 g, and the deviation between the protein content of the milk and the target protein content is 1%.

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