Method for preparing membrane concentrated liquid dairy product

Abstract

The present invention relates to the technical field of dairy product production, and in particular to a method for preparing a membrane-concentrated liquid dairy product. The preparation method comprises: sterilizing, inactivating proteases and performing protein concentration processes on skimmed milk, and then backfilling fat to obtain semi-finished milk; the protein concentration process comprises: performing protein concentration by reverse osmosis membrane concentration and / or ultrafiltration membrane concentration so that the ratio of protein and lactose in the concentrated milk reaches a certain condition after backfilling fat. The present invention focuses on the problem that dairy products may lose small molecules and the like during the concentration process, resulting in a decrease in taste. An additional sterilization and enzyme inactivation process is added before protein concentration, and the concentration process is controlled to effectively increase the content of 2.3-pentanedione flavoring substances after concentration, thereby having a better creamy aroma and higher system stability.

Description

Technical Field

[0001] The present invention relates to the technical field of dairy product production, in particular to a method for preparing a membrane concentrated liquid dairy product. Background Art

[0002] Concentrated milk is a dairy product made by partially removing the water from milk. It contains higher levels of protein and fat than regular cow's milk. Due to its high protein content, it is often used in the preparation of various foods, especially dairy products.

[0003] Membrane concentration technology is currently widely used in the production of concentrated dairy products. However, existing concentrated dairy products suffer from various issues, such as flavor and stability. The loss of small molecules during the concentration process can lead to a decrease in product taste. Many products using direct pasteurization have a short shelf life and are prone to bitterness. Furthermore, most concentrated dairy products use a single membrane, which is relatively simple, resulting in low concentration efficiency and difficulty in producing concentrated milk with high stability and flavor. Summary of the Invention

[0004] To address the problems of the prior art, the present invention provides a method for preparing a membrane-concentrated liquid dairy product. By combining multiple sterilization and concentration processes, concentrated milk with a high content of 2,3-pentanedione flavoring substances is obtained.

[0005] In a first aspect, the present invention provides a method for preparing a membrane concentrated liquid dairy product, comprising:

[0006] After the skim milk is sterilized, protease is inactivated and protein is concentrated, fat is backfilled to obtain semi-finished milk;

[0007] The protein concentration process includes:

[0008] Protein concentration is achieved by reverse osmosis membrane concentration and / or ultrafiltration membrane concentration so that the concentrated milk meets the following conditions after fat backfilling:

[0009] When the protein concentration in the semi-finished milk is less than 4.5 g / 100 g, the ratio of protein to lactose is 1:(1.21-1.50);

[0010] When the protein concentration in the semi-finished milk is ≥4.5g / 100g, the ratio of protein to lactose is 1:(0.8-1.20).

[0011] The present invention has discovered that heat treatment of milk under different conditions produces varying degrees of Maillard reaction, resulting in differences in the flavor compounds produced. The composition of milk's aroma compounds is complex, and during heating, milk undergoes varying degrees of flavor change. Sulfur compounds contribute significantly to the steamed flavor of milk. The present invention has discovered that by optimizing the protein concentration process and controlling the ratio of protein to lactose after concentration through reverse osmosis membrane concentration and ultrafiltration membrane concentration, the ketone content of milk after sterilization can be effectively regulated. Within a specific range, a higher content of ketone compounds (such as the flavor compound 2,3-pentanedione) can be achieved.

[0012] Furthermore, the inactivation of protease is to reduce the protease in the milk to 700U / 100ml.

[0013] Furthermore, the inactivation of the protease comprises: inactivating the enzyme at a low temperature of 65 to 85° C. for 30 to 360 seconds.

[0014] The content of protease will significantly affect the protein content of the product, and further affect the proportion of each component in the milk product. The removal of protease in the present invention is equivalent to indirectly regulating the proportion of protein components in the milk product, which also has a significant impact on the content of flavor substances in the subsequent concentration process.

[0015] Furthermore, the reverse osmosis membrane concentration is 1.01 to 1.40 times at 1 to 10° C., and the ultrafiltration membrane concentration is 1.01 to 2.0 times at 1 to 10° C.

[0016] Furthermore, the sterilization is performed by passing the milk through a 0.05-1.5 μm MF membrane at 4-10° C.

[0017] Furthermore, after the protein concentration process, a sterilization process is also included, which includes: stabilizing the protein for 30 to 300 seconds at 76 to 95° C., and then directly steam sterilizing for 0.25 to 6 seconds at 140 to 154° C.

[0018] Furthermore, the direct steam sterilization is steam immersion sterilization or steam jet sterilization.

[0019] Furthermore, after the sterilization process, homogenization is also included under the conditions of 70-80° C. and 250-350 bar.

[0020] As a preferred embodiment, the present invention provides a method for increasing the content of 2,3-dipentanedione flavoring substances in milk, comprising:

[0021] (1) Raw cow milk is used as the raw milk, and most impurities and somatic cells are removed through filtration and centrifugation;

[0022] (2) performing fat standardization on the milk obtained in step (1): centrifuging and defatting the milk at 45-65° C. and 6000-6500 rpm;

[0023] (3) The milk treated in step (2) is passed through a 0.05-10 μm MF membrane at 4-10°C.

[0024] (4) Inactivate the enzyme in the milk treated in step (3) at a low temperature of 65 to 85° C. for 30 to 360 seconds.

[0025] (5) performing reverse osmosis membrane concentration and ultrafiltration membrane concentration on the milk treated in step (4);

[0026] Protein concentration is achieved by reverse osmosis membrane concentration and / or ultrafiltration membrane concentration so that the concentrated milk meets the following conditions after fat backfilling:

[0027] When the protein concentration in the semi-finished milk is less than 4.5 g / 100 g, the ratio of protein to lactose is 1:(1.21-1.50);

[0028] When the protein concentration in the semi-finished milk is ≥4.5g / 100g, the ratio of protein to lactose is 1:(0.8-1.20);

[0029] (6) The milk treated in step (5) is protein-stabilized at 76-95° C. for 30-300 seconds, and then directly sterilized by steam at 140-154° C. for 0.25-6 seconds.

[0030] The present invention has the following beneficial effects:

[0031] This invention combines multiple sterilization and concentration processes to produce concentrated milk with a high content of 2,3-pentanedione flavoring substances through a specific concentration method. Furthermore, through multi-step control of protein and fat content, the product achieves a balanced state, preventing precipitation and fat floating during storage.

[0032] The present invention provides condensed milk with a stable state and better flavor (richer cream flavor) by controlling the content of protein and fat, which is of great significance in the field of producing dairy products. DETAILED DESCRIPTION

[0033] The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0034] Example 1

[0035] Raw milk pretreatment: Raw cow milk is used as raw milk, which is filtered through a 60-mesh double filter to remove larger impurities or foreign matter, and then preheated to 50°C. The milk is centrifuged in a milk purifier (speed 5000rpm) to remove most impurities and somatic cells.

[0036] Fat standardization: The fat of the raw milk after milk purification is standardized and skimmed at a centrifugal speed of 6000 rpm and a temperature of 45°C.

[0037] MF membrane sterilization: The fat-standardized raw milk is sterilized and separated by MF membrane with a pore size of 1.4μm and a temperature below 10℃ to remove most spores and some bacteria.

[0038] Low temperature inactivation of enzymes: Inactivate enzymes in sterilized raw milk at 85°C for 30 seconds until the protease content is less than 700U / 100ml.

[0039] Membrane concentration: After standardization, the milk is directly concentrated, RO concentration (concentration conditions 1.19 times).

[0040] After fat is backfilled, the product is stirred for 10 minutes to a fixed volume to obtain a semi-finished product.

[0041] Steam immersion sterilization: protein stabilization: 76℃ / 60s, sterilization: 145℃ / 1s.

[0042] Sterile homogenization: The total homogenization pressure is 300 bar and the temperature is 75°C.

[0043] Aseptic filling: The cooled milk is aseptically filled.

[0044] Packaging: Aseptic packaging with dream cover.

[0045] Detection: Protein, fat and 2,3-pentanedione in raw milk, semi-finished products and finished products are detected by ultra-fast gas phase electronic nose. Protease content is detected by the enzyme activity detection method in protease preparations according to GB / T 23527.

[0046] Table 1 Changes in the content of each component before and after treatment

[0047]

[0048]

[0049] Example 2

[0050] Raw milk pretreatment: Raw cow milk is used as raw milk, which is filtered through a 60-mesh double filter to remove larger impurities or foreign matter, and then preheated to 50°C. The milk is centrifuged in a milk purifier (speed 5000rpm) to remove most impurities and somatic cells.

[0051] Fat standardization: The fat of the raw milk after milk purification is standardized, and the rotation speed of the centrifugal separation is 5500 rpm.

[0052] MF membrane sterilization: The fat-standardized raw milk is sterilized by passing it through an MF membrane with a pore size of 1.4 μm and a temperature below 10°C to remove most spores and some bacteria.

[0053] Low temperature inactivation: sterilize the raw milk at 76°C for 300 seconds. Use for rapid protease detection (protease < 700U / 100ml).

[0054] Membrane concentration: After standardization, the milk is directly concentrated, and the RO concentration ratio is set to 1.14 times.

[0055] After fat is backfilled, the product is stirred for 10 minutes to a fixed volume to obtain a semi-finished product.

[0056] Steam immersion sterilization: protein stabilization: 76℃ / 300s, sterilization: 140℃ / 6s.

[0057] Sterile homogenization: The total homogenization pressure is 300 bar and the temperature is 75°C.

[0058] Aseptic filling: The cooled milk is aseptically filled.

[0059] Packaging: Aseptic packaging with dream cover.

[0060] Table 2 Changes in the content of each component before and after treatment

[0061] index Raw milk test value Semi-finished products Finished product test value Protein, g / 100g 3.48 4.0 3.98 Fat, g / 100g 3.5 3.45 3.45 Lactose, g / 100g 4.86 5.56 5.55 2.3-Pentanedione, ng / ml 758 Protease, U / 100ml 486 125

[0062] Example 3

[0063] Raw milk pretreatment: Raw cow milk is used as raw milk, which is filtered through a 60-mesh double filter to remove larger impurities or foreign matter, and then preheated to 50°C. The milk is centrifuged in a milk purifier (speed 5000rpm) to remove most impurities and somatic cells.

[0064] Fat standardization: The fat of the raw milk after milk purification is standardized, and the rotation speed of the centrifugal separation is 5500 rpm.

[0065] MF membrane sterilization: The fat-standardized raw milk is sterilized and separated by MF membrane with a pore size of 1.4μm and a temperature below 10℃ to remove most spores and some bacteria.

[0066] Low temperature inactivation: sterilize the raw milk at 76°C for 360 seconds. Use for rapid protease detection (protease < 700U / 100ml).

[0067] Membrane concentration: After standardization, the milk is directly concentrated, RO concentration (concentration ratio 1.19) and then UF concentration (concentration ratio: 1.38).

[0068] After fat is backfilled, the product is stirred for 10 minutes to a fixed volume to obtain a semi-finished product.

[0069] Tubular sterilization: Sterilization: 137℃ / 4s.

[0070] Sterile homogenization: The total homogenization pressure is 300 bar and the temperature is 75°C.

[0071] Aseptic filling: The cooled milk is aseptically filled.

[0072] Packaging: Aseptic packaging with dream cover.

[0073] Table 3 Changes in the content of each component before and after treatment

[0074] index Raw milk test value Semi-finished products Finished product test value Protein, g / 100g 2.9 4.75 4.75 Fat, g / 100g 3.9 4 4 Lactose, g / 100g 4.0 4.76 4.75 2.3-Pentanedione, ng / ml 865 Protease, U / 100ml 498 50

[0075] Example 4

[0076] Raw milk pretreatment: Raw cow milk is used as raw milk, which is filtered through a 60-mesh double filter to remove larger impurities or foreign matter, and then preheated to 50°C. The milk is centrifuged in a milk purifier (speed 5000rpm) to remove most impurities and somatic cells.

[0077] Fat standardization: The fat of the raw milk after milk purification is standardized, and the rotation speed of the centrifugal separation is 5500 rpm.

[0078] MF membrane sterilization: The fat-standardized raw milk is sterilized and separated by MF membrane with a pore size of 1.4μm and a temperature below 10℃ to remove most spores and some bacteria.

[0079] Low temperature inactivation: sterilize the raw milk at 65℃ for 200s. Use for rapid protease detection (protease < 700U / 100ml).

[0080] Membrane concentration: After standardization, the milk is directly concentrated, first RO concentration (concentration ratio: 1.1) and UF concentration (concentration ratio: 1.71).

[0081] After fat is backfilled, the product is stirred for 10 minutes to a fixed volume to obtain a semi-finished product.

[0082] Steam immersion sterilization: protein stabilization: 95℃ / 35s sterilization: 154℃ / 0.25s.

[0083] Sterile homogenization: The total homogenization pressure is 300 bar and the temperature is 75°C.

[0084] Aseptic filling: The cooled milk is aseptically filled.

[0085] Packaging: Aseptic packaging with dream cover.

[0086] Table 4 Changes in the content of each component before and after treatment

[0087] index Raw milk test value Semi-finished products Finished product test value Protein, g / 100g 3.45 6.48 6.5 Fat, g / 100g 3.8 4 4 Lactose, g / 100g 4.90 5.40 5.41 2.3-Pentanedione, ng / ml 672 Protease, U / 100ml 412 56

[0088] Example 5

[0089] Raw milk pretreatment: Raw cow milk is used as raw milk, which is filtered through a 60-mesh double filter to remove larger impurities or foreign matter, and then preheated to 50°C. The milk is centrifuged in a milk purifier (speed 5000rpm) to remove most impurities and somatic cells.

[0090] Fat standardization: The fat of the raw milk after milk purification is standardized, and the rotation speed of the centrifugal separation is 5500 rpm.

[0091] MF membrane sterilization: The fat-standardized raw milk is sterilized and separated by MF membrane with a pore size of 1.4μm and a temperature below 10℃ to remove most spores and some bacteria.

[0092] Low temperature inactivation: sterilize the raw milk at 80℃ for 90 seconds. Use for rapid protease detection (protease < 700U / 100ml).

[0093] Membrane concentration: After standardization, the milk is directly concentrated, RO concentration (concentration ratio: 1.19).

[0094] After fat is backfilled, the product is stirred for 10 minutes to a fixed volume to obtain a semi-finished product.

[0095] Steam immersion sterilization: protein stabilization: 95℃ / 30s sterilization: 148℃ / 1s.

[0096] Sterile homogenization: The total homogenization pressure is 300 bar and the temperature is 75°C.

[0097] Aseptic filling: The cooled milk is aseptically filled.

[0098] Packaging: Aseptic packaging with dream cover.

[0099] Table 5 Changes in the content of each component before and after treatment

[0100] index Raw milk test value Semi-finished products Finished product test value Protein, g / 100g 3.78 4.5 4.50 Fat, g / 100g 3.95 4.6 4.6 Lactose, g / 100g 4.20 5.00 5.00 2.3-Pentanedione, ng / ml 777 Protease, U / 100ml 463 130

[0101] Test Example 1

[0102] This test example used a variety of concentration methods during the research process, which are specifically as follows to contrast with the technical solutions of Examples 1-5:

[0103] Control group 1

[0104] Raw milk pretreatment: Raw cow milk is used as raw milk, which is filtered through a 60-mesh double filter to remove larger impurities or foreign matter, and then preheated to 50°C. The milk is centrifuged in a milk purifier (speed 5000rpm) to remove most impurities and somatic cells.

[0105] Fat standardization: The fat of the raw milk after milk purification is standardized, and the rotation speed of the centrifugal separation is 5500 rpm.

[0106] Low temperature inactivation: sterilize the raw milk at 85℃ for 30 seconds. Use for rapid protease detection (protease < 700U / 100ml).

[0107] Membrane concentration: After standardization, the milk is directly concentrated, RO concentration (concentration ratio: 1.18).

[0108] After fat is backfilled, the product is stirred for 10 minutes to a fixed volume to obtain a semi-finished product.

[0109] Steam immersion sterilization: protein stabilization: 85℃ / 30s sterilization: 145℃ / 1s.

[0110] Sterile homogenization: The total homogenization pressure is 300 bar and the temperature is 75°C.

[0111] Aseptic filling: The cooled milk is aseptically filled.

[0112] Packaging: Aseptic packaging with dream cover.

[0113] The changes in the content of each component before and after treatment of the control group 1 are shown in the following table:

[0114] Table 6 Changes in the content of each component before and after treatment

[0115] index Raw milk test value Semi-finished products Finished product test value Protein, g / 100g 3.2 3.8 3.8 Fat, g / 100g 3.7 3.5 3.5 Lactose, g / 100g 4.02 4.75 4.75 2.3-Pentanedione, ng / ml 707 Protease, U / 100ml 468 137

[0116] Control group 2

[0117] Raw milk pretreatment: Raw cow milk is used as raw milk, which is filtered through a 60-mesh double filter to remove larger impurities or foreign matter, and then preheated to 50°C. The milk is centrifuged in a milk purifier (speed 5000rpm) to remove most impurities and somatic cells.

[0118] Fat standardization: The fat of the raw milk after milk purification is standardized, and the rotation speed of the centrifugal separation is 5500 rpm.

[0119] MF membrane sterilization: The fat-standardized raw milk is sterilized and separated by MF membrane with a pore size of 1.4μm and a temperature below 10℃ to remove most spores and some bacteria.

[0120] Membrane concentration: After standardization, the milk is directly concentrated, RO concentration (concentration ratio: 1:1.18).

[0121] After fat is backfilled, the product is stirred for 10 minutes to a fixed volume to obtain a semi-finished product.

[0122] Steam immersion sterilization: protein stabilization: 85℃ / 30s sterilization: 145℃ / 1s.

[0123] Sterile homogenization: The total homogenization pressure is 300 bar and the temperature is 75°C.

[0124] Aseptic filling: The cooled milk is aseptically filled.

[0125] Packaging: Aseptic packaging with dream cover.

[0126] The changes in the content of each component before and after treatment of the control group 2 are shown in the following table:

[0127] Table 7 Changes in the content of each component before and after treatment

[0128]

[0129]

[0130] Control group 3

[0131] Raw milk pretreatment: Raw cow milk is used as raw milk, which is filtered through a 60-mesh double filter to remove larger impurities or foreign matter, and then preheated to 50°C. The milk is centrifuged in a milk purifier (speed 5000rpm) to remove most impurities and somatic cells.

[0132] Fat standardization: The fat of the raw milk after milk purification is standardized, and the rotation speed of the centrifugal separation is 5500 rpm.

[0133] MF membrane sterilization: The fat-standardized raw milk is sterilized and separated by MF membrane with a pore size of 0.05 micron to 10 micron and a temperature below 10°C to remove most spores and some bacteria.

[0134] Low temperature inactivation: sterilize the raw milk at 85℃ for 30 seconds. Use for rapid protease detection (protease < 700U / 100ml).

[0135] Membrane concentration: After standardization, the milk is directly concentrated, first through RO concentration (concentration ratio: 1.32) and UF concentration (concentration ratio: 1.08).

[0136] After fat is backfilled, the product is stirred for 10 minutes to a fixed volume to obtain a semi-finished product.

[0137] Steam immersion sterilization: protein stabilization: 85℃ / 30s sterilization: 145℃ / 1s.

[0138] Sterile homogenization: The total homogenization pressure is 300 bar and the temperature is 75°C.

[0139] Aseptic filling: The cooled milk is aseptically filled.

[0140] Packaging: Aseptic packaging with dream cover.

[0141] The changes in the content of each component in the control group 3 before and after treatment are shown in the following table:

[0142] Table 8 Changes in the content of each component before and after treatment

[0143]

[0144]

[0145] Control group 4

[0146] Raw milk pretreatment: Raw cow milk is used as raw milk, which is filtered through a 60-mesh double filter to remove larger impurities or foreign matter, and then preheated to 50°C. The milk is centrifuged in a milk purifier (speed 5000rpm) to remove most impurities and somatic cells.

[0147] Fat standardization: The fat of the raw milk after milk purification is standardized, and the rotation speed of the centrifugal separation is 5500 rpm.

[0148] MF membrane sterilization: The fat-standardized raw milk is sterilized by passing it through an MF membrane with a pore size of 1.4 microns and a temperature below 10°C to remove most spores and some bacteria.

[0149] Low temperature inactivation: sterilize the raw milk at 85℃ for 30 seconds. Use for rapid protease detection (protease < 700U / 100ml).

[0150] Membrane concentration: After standardization, the milk is directly concentrated, first through RO concentration (concentration ratio: 1.32) and UF concentration (concentration ratio: 1.08).

[0151] Steam immersion sterilization: protein stabilization: 85℃ / 30s sterilization: 145℃ / 1s.

[0152] Sterile homogenization: The total homogenization pressure is 300 bar and the temperature is 75°C.

[0153] Aseptic filling: The cooled milk is aseptically filled.

[0154] Packaging: Aseptic packaging with dream cover.

[0155] The changes in the content of each component before and after treatment of the control group 4 are shown in the following table:

[0156] Table 8 Changes in the content of each component before and after treatment

[0157] index Raw milk test value Semi-finished products Finished product test value Protein, g / 100g 3.5 4.43 4.42 Fat, g / 100g 3.8 4 4 Lactose, g / 100g 4.4 4.4 4.43 2.3-Pentanedione, ng / ml 218 Protease, U / 100ml 532 190

[0158] 1. Stability analysis

[0159] The dairy products prepared in Examples 1 to 5 and Control Groups 1 and 2 were stored at room temperature for 45 days and observed with the naked eye for precipitation or fat floating. The results are shown in Table 1. The results show that the products of Examples 1 to 5 and Control Group 1 have good stability because the appropriate ratio of fat and casein can make the products uniform and consistent without precipitation.

[0160] There was no fat floating in Examples 1-5, but there was in Control Groups 1 and 2.

[0161] Table 10 Stability analysis of dairy products

[0162] Precipitation Fat floating Tasting evaluation Example 1 0.001mm sedimentation No fat floating 6.70 Example 2 No precipitation No fat floating 6.74 Example 3 No precipitation No fat floating 6.75 Example 4 No precipitation No fat floating 6.72 Example 5 No precipitation No fat floating 6.68 Control group 1 Bad Packet 0.002mm fat 6.56 Control group 2 Bitter bag sediment 3mm 0.02mm fat 5.43 Control group 3 No precipitation No fat floating 5.23 Control group 4 No precipitation No fat floating 4.96

[0163] Although the present invention has been described in detail above using general descriptions and specific embodiments, it will be apparent to those skilled in the art that modifications and improvements may be made based on the present invention. Therefore, such modifications and improvements, which do not depart from the spirit of the present invention, are intended to be within the scope of protection claimed herein.

Claims

1. A method for preparing a membrane concentrated liquid dairy product with increased 2,3-pentanedione flavoring substance content, characterized in that: include: After the skim milk is sterilized, protease is inactivated and protein is concentrated, fat is backfilled to obtain semi-finished milk; The protein concentration process includes: Protein concentration is achieved by reverse osmosis membrane concentration and / or ultrafiltration membrane concentration so that the concentrated milk meets the following conditions after fat backfilling: When the protein concentration in the semi-finished milk is less than 4.5 g / 100 g, the ratio of protein to lactose is 1:(1.21-1.50); When the protein concentration in the semi-finished milk is ≥4.5g / 100g, the ratio of protein to lactose is 1:(0.8-1.20); The reverse osmosis membrane concentration is 1.01 to 1.40 times at 1 to 10° C., and the ultrafiltration membrane concentration is 1.01 to 2.0 times at 1 to 10° C.

2. The preparation method according to claim 1, characterized in that The inactivation of protease is to reduce the protease in the milk to 700U / 100ml.

3. The preparation method according to claim 2, characterized in that The inactivation of the protease comprises: inactivating the enzyme at a low temperature of 65-85° C. for 30-360 seconds.

4. The preparation method according to claim 1, characterized in that The sterilization step is to pass the milk through a 0.05-1.5 μm MF membrane at 4-10° C.

5. The preparation method according to claim 1, characterized in that After the fat is backfilled, a sterilization process is also included, which includes: stabilizing the protein for 30 to 300 seconds at 76 to 95° C., and then sterilizing at 137 to 154° C. for 0.25 to 6 seconds.

6. The preparation method according to claim 5, characterized in that The sterilization is steam immersion sterilization, steam jet sterilization or tube sterilization.

7. The preparation method according to claim 6, characterized in that After the sterilization process, homogenization is further performed under conditions of 70-80° C. and 250-350 bar.

8. The preparation method according to claim 1, characterized in that Before sterilization, the process also includes: pre-treatment of raw milk by filtration and centrifugation, and fat standardization.

9. Concentrated milk prepared by the preparation method according to any one of claims 1 to 8.

Images