Yogurt rich in immunoglobulin and preparation method thereof

Abstract

The present invention belongs to the technical field of dairy product processing, and specifically relates to a yogurt rich in immunoglobulins and a preparation method thereof. The present invention first performs a defatting treatment on raw milk, heats and sterilizes the cream without immunoglobulins, and performs low-temperature microfiltration sterilization on the skimmed milk containing a large amount of immunoglobulins, which can maximize the retention of the immunoglobulin content in the raw milk on the basis of ensuring the sterilization effect; and through fermentation with a specific lactic acid bacteria composition, the problems of low viscosity, poor formability, and poor overall sensory perception of yogurt caused by the unheated denaturation of whey protein can be avoided, and the prepared yogurt is rich in immunoglobulins and has a fine texture and stable sensory perception.

Description

Technical Field

[0001] The invention belongs to the technical field of dairy product processing, and more specifically, relates to a yogurt rich in immunoglobulin and a preparation method thereof. Background Art

[0002] Yogurt is known for its nutrition and delicious taste. It is made from raw milk (cow or sheep, etc.) or milk powder, sterilized, inoculated with lactic acid bacteria and fermented. It is a healthy food that is deeply loved by consumers. Raw milk itself contains a variety of nutrients needed by the human body and precious immunoglobulin IgG. However, in order to eliminate the impact of the original microorganisms in raw milk on the safety, quality and shelf life of yogurt, and to give yogurt a better gel structure through the thermal denaturation of whey protein, the yogurt production process must first be heat sterilized. Currently, the most common sterilization method in the world is heating at 95°C for 300 seconds; however, under high temperature conditions of 95°C, most of the active ingredients in raw milk, such as immunoglobulins, have been inactivated. Therefore, the yogurt produced by this method basically does not contain active ingredients such as immunoglobulins.

[0003] In order to improve the active ingredients of yogurt, Chinese patent application CN101554186A discloses a stomach-protecting yogurt, which improves the nutritional value and added value of yogurt by adding a large amount of active immune protein IgG and lactoferrin LF; however, after adding active immune protein IgG and lactoferrin LF, the yogurt is still sterilized under the conditions of 95-100°C and 300s, and the added active immune protein IgG and lactoferrin LF are destroyed in structure and lose their activity, and the effective content cannot be maintained in the yogurt obtained after production. In order to avoid the influence of long-term high-temperature heating sterilization on the active ingredients, Chinese patent application CN110214812A discloses a yogurt, which adopts steam immersion sterilization treatment, flash degassing for 0.09-0.5s at 130-157°C, and can effectively kill microorganisms under the premise of minimizing the loss of nutrients; however, after this sterilization process, although the high-temperature sterilization time is shortened, the loss rate of active immune protein IgG>90% cannot be avoided. Summary of the invention

[0004] The technical problem to be solved by the present invention is to increase the immunoglobulin content of raw milk raw materials, overcome the defects and shortcomings of the existing yogurt preparation process that easily causes the inactivation of active ingredients such as immunoglobulins, solve the poor sensory properties of yogurt under non-thermal sterilization technology, and provide a method for preparing yogurt that is rich in immunoglobulins and has a fine texture and stable sensory organs.

[0005] The purpose of the invention is to provide a yogurt rich in immunoglobulin prepared by the method.

[0006] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0007] A method for preparing immunoglobulin-rich yogurt specifically comprises the following steps:

[0008] S1, skimming raw milk to obtain cream and skimmed milk;

[0009] S2, adding ingredients to the skim milk obtained in step S1 and fully dissolving them to obtain liquid A;

[0010] S3, after heating and sterilizing the cream obtained in step S1 (the protein content in the cream is very low, and this high temperature sterilization has little effect on the IgG content of the subsequent product), immediately cool it to obtain liquid B;

[0011] S4, using a microfiltration membrane to sterilize the feed liquid A obtained in step S2, the pore size of the microfiltration membrane is 0.8-1.4 μm, to obtain feed liquid C;

[0012] S5, mixing the liquid B obtained in step S3 with the liquid C obtained in step S4, heating and homogenizing;

[0013] S6. After homogenization, the mixture is cooled and lactic acid bacteria are added. The lactic acid bacteria include Lactobacillus delbrueckii subspecies bulgaricus and Streptococcus thermophilus 210202 strain. The CFU activity ratio of the two is 1:1 to 1:10. The total inoculation amount is (0.5 to 5)×10 7 CFU / g, after stirring evenly, standing and fermenting until the pH value drops to 4.6 to obtain fermented milk;

[0014] S7, stirring the fermented milk obtained in step S6 to break the emulsion, cooling, filling, packaging, and refrigerating. When it passes the test, it is a finished product.

[0015] The microfiltration sterilization technology can achieve a good sterilization effect and fully retain the active substances in raw milk. However, if the raw milk is not subjected to heat denaturation treatment of whey protein, the yogurt formed after fermentation has low viscosity, poor formability, and poor overall sensory properties. In order to solve the above problems, the present application adjusts the ingredients and uses Lactobacillus delbrueckii subspecies bulgaricus and Streptococcus thermophilus 210202 as lactic acid bacteria for fermentation. It is unexpectedly found that the finished product can have a delicate texture and good sensory properties without heat denaturation treatment of whey protein.

[0016] Furthermore, in step S1, the raw milk is concentrated before being defatted, and the concentration process is organic membrane reverse osmosis concentration, the concentration temperature is 2 to 10° C., and the concentration multiple is 1.1 to 2.0 times. This technology can be used to perform reverse osmosis concentration under low temperature conditions to increase the immunoglobulin content in the raw material.

[0017] Preferably, in step S1, the degreasing temperature is 50-60°C.

[0018] Furthermore, in step S2, the dissolving temperature is 40-50°C.

[0019] Furthermore, in step S2, the ingredients include, by total mass, 0-8% white sugar, 0-0.5% bovine colostrum powder, and 0-2% whey protein powder.

[0020] Furthermore, in step S3, the heat sterilization is sterilized at 120-125°C for 4-15 seconds; and the cooling temperature is 55-65°C.

[0021] Furthermore, in step S5, the heating temperature is 60-70° C., and the homogenization pressure is 15-20 MPa.

[0022] Furthermore, in step S6, the mixture is cooled to 40-45° C. after homogenization.

[0023] Further, in step S6, the depository unit of the Streptococcus thermophilus 210202 strain is: China General Microbiological Culture Collection Center (CGMCC, No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing), the deposit date is October 15, 2018, and the deposit number is CGMCC No. 16585.

[0024] Furthermore, in step S7, the stirring speed is 15 to 35 rpm, and the stirring time is 2 to 10 min.

[0025] Furthermore, in step S7, the cooling is to 15-25°C, and the refrigeration is to 2-6°C.

[0026] In addition, the present invention also provides a yogurt rich in immunoglobulin prepared by the preparation method.

[0027] The present invention has the following beneficial effects:

[0028] The invention firstly performs defatting treatment on raw milk, heats and sterilizes the cream without immunoglobulin, and performs low-temperature microfiltration sterilization on the skimmed milk containing a large amount of immunoglobulin, so that the immunoglobulin content in the raw milk can be retained to the maximum extent on the basis of ensuring the sterilization effect; and through fermentation with a specific lactic acid bacteria composition, the problems of low viscosity of yogurt, poor formability, poor overall sensory perception, etc. caused by the whey protein not being thermally denatured can be avoided, and the prepared yogurt is rich in immunoglobulin, has a fine texture, and is sensory stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The present invention is a flowchart of a method for preparing an immunoglobulin-rich yogurt according to Example 1. DETAILED DESCRIPTION

[0030] The present invention is further described below in conjunction with the accompanying drawings and specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0031] The Streptococcus thermophilus 210202 strain used therein is deposited at the General Microbiology Center of China Microorganism Culture Collection Administration (CGMCC, No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing), deposited on October 15, 2018, with a deposit number of CGMCC No. 16585; it has been disclosed in Chinese patent application CN110218675A.

[0032] Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0033] Example 1 Preparation method of immunoglobulin-rich yogurt

[0034] The preparation method of the immunoglobulin-rich yogurt specifically comprises the following steps:

[0035] S1. Raw milk is concentrated by organic membrane reverse osmosis, the concentration temperature is 2°C, and the concentration multiple is 2.0 times;

[0036] S2, heating the concentrated raw milk obtained in step S1 to 55° C., performing a milk purification and skimming process to obtain cream and skimmed milk;

[0037] S3, adding ingredients to the skim milk obtained in step S2 and fully dissolving them at 40° C., the ingredients being 8% white sugar, 0.5% bovine colostrum powder, and 1.0% whey protein powder based on the total mass, to obtain liquid A;

[0038] S4, sterilizing the cream obtained in step S2 at 120° C. for 4 seconds, and then immediately cooling to 55° C. (the protein content in the cream is very low, and this high-temperature sterilization has little effect on the IgG content of the subsequent product), to obtain liquid B;

[0039] S5, using a microfiltration membrane to sterilize the feed liquid A obtained in step S3, the pore size of the microfiltration membrane is 0.8 μm, and the feed liquid C is obtained;

[0040] S6, mixing the liquid B obtained in step S4 with the liquid C obtained in step S5, heating to 60°C, and homogenizing at a homogenization pressure of 20 MPa;

[0041] S7, after homogenization, cool to 42°C, take samples to detect the total colony count, the result is <1 CFU / mL, add lactic acid bacteria, the lactic acid bacteria contain Lactobacillus delbrueckii subspecies bulgaricus and Streptococcus thermophilus 210202 strain, the CFU activity ratio of the two is 1:5, the inoculation amount is 0.5×10 7 CFU / g, after stirring evenly, standing and fermenting until the pH value drops to 4.6 to obtain fermented milk;

[0042] S8. Stir the fermented milk obtained in step S7 to break the emulsion at a stirring speed of 15 rpm and a stirring time of 5 min. After stirring and breaking the emulsion, cool to 15° C., fill and package, and refrigerate in an environment of 2 to 6° C. When the temperature drops to ambient temperature and the test is qualified, it is a finished product.

[0043] For detailed procedures, see Figure 1 .

[0044] Example 2 Preparation method of a yogurt rich in immunoglobulin

[0045] The preparation method of the immunoglobulin-rich yogurt specifically comprises the following steps:

[0046] S1. Raw milk is concentrated by organic membrane reverse osmosis at a temperature of 6°C and a concentration multiple of 2.0 times;

[0047] S2, heating the concentrated raw milk obtained in step S1 to 60° C., performing a milk purification and skimming process to obtain cream and skimmed milk;

[0048] S3, adding ingredients to the skim milk obtained in step S2 and fully dissolving them at 45° C., wherein the ingredients are 8% white sugar, 0.0% bovine colostrum powder, and 0.5% whey protein powder based on the total mass, to obtain liquid A;

[0049] S4, sterilizing the cream obtained in step S2 at 122° C. for 4 seconds, and then immediately cooling to 55° C. (the protein content in the cream is very low, and this high-temperature sterilization has little effect on the IgG content of the subsequent product), to obtain liquid B;

[0050] S5, using a microfiltration membrane to sterilize the feed liquid A obtained in step S3, the pore size of the microfiltration membrane is 1.4 μm, to obtain feed liquid C;

[0051] S6, mixing the liquid B obtained in step S4 with the liquid C obtained in step S5, heating to 65°C, and homogenizing at a homogenization pressure of 20 MPa;

[0052] S7, after homogenization, cool to 40°C, take samples to detect the total colony count, the result is <1 CFU / mL, add lactic acid bacteria, the lactic acid bacteria contain Lactobacillus delbrueckii subspecies bulgaricus and Streptococcus thermophilus 210202 strain, the CFU activity ratio of the two is 1:10, the inoculation amount is 0.5×10 7 CFU / g, after stirring evenly, standing and fermenting until the pH value drops to 4.6 to obtain fermented milk;

[0053] S8. Stir the fermented milk obtained in step S7 to break the emulsion at a stirring speed of 15 rpm and a stirring time of 5 min. After stirring and breaking the emulsion, cool to 15° C., fill and package, and refrigerate in an environment of 2 to 6° C. When the temperature drops to ambient temperature and the test is qualified, it is a finished product.

[0054] Example 3 Preparation method of yogurt rich in immunoglobulin

[0055] The preparation method of the immunoglobulin-rich yogurt specifically comprises the following steps:

[0056] S1. Raw milk is concentrated by organic membrane reverse osmosis at a temperature of 4°C and a concentration multiple of 1.1 times;

[0057] S2, heating the concentrated raw milk obtained in step S1 to 55° C., performing a milk purification and skimming process to obtain cream and skimmed milk;

[0058] S3, adding ingredients to the skim milk obtained in step S2 and fully dissolving them at 40° C., wherein the ingredients are 8% white sugar, 0.0% bovine colostrum powder, and 1.5% whey protein powder based on the total mass, to obtain liquid A;

[0059] S4, sterilizing the cream obtained in step S2 at 125° C. for 15 seconds, and then immediately cooling to 60° C. (the protein content in the cream is very low, and this high-temperature sterilization has little effect on the IgG content of the subsequent product), to obtain liquid B;

[0060] S5, using a microfiltration membrane to sterilize the feed liquid A obtained in step S3, the pore size of the microfiltration membrane is 0.8 μm, and the feed liquid C is obtained;

[0061] S6, mixing the liquid B obtained in step S4 with the liquid C obtained in step S5, heating to 60°C, and homogenizing at a homogenization pressure of 15 MPa;

[0062] S7, after homogenization, cool to 45°C, take samples to detect the total colony count, the result is <1 CFU / mL, add lactic acid bacteria, the lactic acid bacteria contain Lactobacillus delbrueckii subspecies bulgaricus and Streptococcus thermophilus 210202 strain, the CFU activity ratio of the two is 1:8, the inoculation amount is 0.5×107 CFU / g, after stirring evenly, standing and fermenting until the pH value drops to 4.6 to obtain fermented milk;

[0063] S8. Stir the fermented milk obtained in step S7 to break the emulsion at a stirring speed of 25 rpm and a stirring time of 2 min. After stirring and breaking the emulsion, cool to 20° C., fill and package, and refrigerate in an environment of 2 to 6° C. When the temperature drops to ambient temperature and the test is qualified, it is a finished product.

[0064] Comparative Example 1: A method for preparing yogurt

[0065] The preparation method of the yogurt specifically comprises the following steps:

[0066] S1. Raw milk is concentrated by organic membrane reverse osmosis, the concentration temperature is 2°C, and the concentration multiple is 2.0 times;

[0067] S2, adding ingredients to the concentrated milk obtained in step S1 and fully dissolving them at 40° C., wherein the ingredients are 8% white sugar, 0.5% bovine colostrum powder, and 1.0% whey protein powder based on the total mass, to obtain liquid A;

[0068] S3, heating the liquid A obtained in step S2 to 65°C for homogenization at a homogenization pressure of 20 MPa to obtain liquid B;

[0069] S4, sterilizing the liquid B obtained in step S3 at 95°C for 300 seconds, and then cooling to 40°C to obtain liquid C;

[0070] S5, adding lactic acid bacteria to the liquid C obtained in step S4, wherein the lactic acid bacteria contain Lactobacillus delbrueckii subspecies bulgaricus and Streptococcus thermophilus 210202 strain, the CFU activity ratio of the two is 1:5, and the inoculation amount is 0.5×10 7 CFU / g, after stirring evenly, standing and fermenting until the pH value drops to 4.6 to obtain fermented milk;

[0071] S6. Stir the fermented milk obtained in step S5 to break the emulsion at a stirring speed of 15 rpm and a stirring time of 5 min. After stirring and breaking the emulsion, cool to 15° C., fill and package, and place in a refrigerated environment at 2-6° C. When the temperature drops to ambient temperature, it is a finished product.

[0072] The difference from Example 1 is that the sterilization technology in the production process of this comparative example is changed to ordinary 95°C, 300 seconds sterilization, and the degreasing treatment is omitted.

[0073] Comparative Example 2: A method for preparing yogurt

[0074] The preparation method of the yogurt specifically comprises the following steps:

[0075] S1. Raw milk is concentrated by organic membrane reverse osmosis, the concentration temperature is 2°C, and the concentration multiple is 2.0 times;

[0076] S2, heating the concentrated raw milk obtained in step S1 to 55° C., performing a milk purification and skimming process to obtain cream and skimmed milk;

[0077] S3, adding ingredients to the skim milk obtained in step S2 and fully dissolving them at 40° C., the ingredients being 8% white sugar, 0.5% bovine colostrum powder, and 1.0% whey protein powder based on the total mass, to obtain liquid A;

[0078] S4, sterilizing the cream obtained in step S2 at 120° C. for 4 seconds, and then immediately cooling to 55° C. (the protein content in the cream is very low, and this high-temperature sterilization has little effect on the IgG content of the subsequent product), to obtain liquid B;

[0079] S5, using a microfiltration membrane to sterilize the feed liquid A obtained in step S3, the pore size of the microfiltration membrane is 0.8 μm, and the feed liquid C is obtained;

[0080] S6, mixing the liquid B obtained in step S4 with the liquid C obtained in step S5, heating to 60°C, and homogenizing at a homogenization pressure of 20 MPa;

[0081] S7, after homogenization, cool to 40°C, add lactic acid bacteria, the lactic acid bacteria contain Lactobacillus delbrueckii subspecies bulgaricus and Streptococcus thermophilus (lactic acid bacteria are strains from Chr. Hansen of Denmark, the CFU activity ratio of the two is 1:5, wherein the Streptococcus thermophilus and the Streptococcus thermophilus 210202 strain of the present invention are different strains), stir evenly, and ferment until the pH value drops to 4.6 to obtain fermented milk;

[0082] S8, stirring the fermented milk obtained in step S7 to break the emulsion, the stirring speed is 15 rpm, the stirring time is 5 min, and after stirring and breaking the emulsion, it is cooled to 15°C, filled and packaged, and refrigerated in an environment of 2-6°C. When the temperature drops to ambient temperature, it is a finished product.

[0083] The difference from Example 1 is that this comparative example uses other strains for fermentation.

[0084] Comparative Example 3: A method for preparing yogurt

[0085] The preparation method of the yogurt specifically comprises the following steps:

[0086] S1. Buy commercially available cow milk produced by steam immersion sterilization process, and gently heat it to 40° C. to obtain liquid A;

[0087] S2, adding lactic acid bacteria to the liquid A obtained in S1, wherein the lactic acid bacteria include Lactobacillus delbrueckii subspecies bulgaricus and Streptococcus thermophilus (the lactic acid bacteria are strains from Chr. Hansen of Denmark, with a CFU activity ratio of 1:5, wherein the Streptococcus thermophilus and the Streptococcus thermophilus 210202 strain of the present invention are different strains), stirring evenly, and standing and fermenting until the pH value drops to 4.6 to obtain fermented milk;

[0088] S3. Stir the fermented milk obtained in step S2 to break the emulsion at a stirring speed of 15 rpm and a stirring time of 5 min. After stirring and breaking the emulsion, cool to 15° C., fill and package, and refrigerate in an environment of 2 to 6° C. When the temperature drops to ambient temperature, it is a finished product.

[0089] The difference from Comparative Example 2 is that in this comparative example, milk produced by the steam immersion sterilization process is directly fermented to produce yogurt.

[0090] Test Example 1 Determination of IgG Content in Yogurt

[0091] The content of active ingredient (immunoglobulin IgG) in raw milk, yogurt prepared in the examples and comparative examples, and commercially available yogurt was determined.

[0092] 1. Test method:

[0093] Refer to the T / SSFS 0002-2021 method to determine the immunoglobulin IgG content, and change the centrifugation parameters to: 4°C, 2000rpm, 10min.

[0094] 2. Test results:

[0095] Table 1 Determination results of active ingredients in yogurt

[0096]

[0097] As can be seen from the table, the yogurt prepared by the patented method is rich in immunoglobulin IgG, and its content is basically the same as that of the raw material. Concentrating or adding colostrum to the ingredients can increase the content of immunoglobulin IgG; when high-temperature sterilization is used, the activity of immunoglobulin IgG will be directly destroyed, resulting in no detection in the finished product. IgG is detected in the raw materials and yogurt treated by steam immersion sterilization process, but the content is very low.

[0098] Test Example 2 Sensory Test of Yogurt

[0099] The sensory properties of the yogurts prepared in the examples and comparative examples were measured.

[0100] Fineness test: Use a small spoon to gently stir the sample, observe its texture against the light, take a spoonful to see if there are any particles, and then put it into your mouth to taste its fineness.

[0101] Viscosity detection: The viscosity of the samples of the embodiment and the comparative example was detected using a Brookfield rotational viscometer DV-I, using the same rotor and rotation speed.

[0102] Stability test: Refrigerate the sample at 2-6°C for 25 days, then take out the sample and observe the water separation.

[0103] 2. Test results:

[0104] Table 2 Yogurt sensory test results

[0105] Group Fineness Viscosity Stability during 25 days of refrigeration Example 1 Fine texture, no particles 5712 No precipitated water Example 2 Fine texture, no particles 5965 No precipitated water Example 3 Fine texture, no particles 2860 No precipitated water Comparative Example 1 There are a few particles, the fineness is average 8701 No precipitated water Comparative Example 2 Rough tissue 4012 Water separation about 10% Comparative Example 3 There are a few particles, the fineness is average 2010 Water extraction: about 1%

[0106] As can be seen from the table, the yogurt prepared by the patented method has a fine texture, moderate viscosity and good stability during the shelf life.

[0107] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing immunoglobulin-rich yogurt, characterized in that: The specific steps include: S1, skimming raw milk to obtain cream and skimmed milk; S2, adding ingredients to the skim milk obtained in step S1 and fully dissolving them to obtain liquid A; S3, heating and sterilizing the cream obtained in step S1, and then cooling it immediately to obtain liquid B; S4, using a microfiltration membrane to sterilize the feed liquid A obtained in step S2, the pore size of the microfiltration membrane is 0.8-1.4 μm, to obtain feed liquid C; S5, mixing the liquid B obtained in step S3 with the liquid C obtained in step S4, heating and homogenizing; S6. After homogenization, the mixture is cooled and lactic acid bacteria are added. The lactic acid bacteria include Lactobacillus delbrueckii subspecies bulgaricus and Streptococcus thermophilus 210202 strain. The CFU activity ratio of the two is 1:1 to 1:

10. The total inoculation amount is (0.5 to 5)×10 7 CFU / g, after stirring evenly, standing and fermenting until the pH value drops to 4.6 to obtain fermented milk; S7, stirring and demulsifying the fermented milk obtained in step S6, cooling, filling, packaging, and refrigerating. When the test is qualified, it is a finished product; The depository unit of the Streptococcus thermophilus 210202 strain is the General Microbiology Center of China Microorganism Culture Collection Administration, the deposit date is October 15, 2018, and the deposit number is CGMCC No.16585.

2. The preparation method according to claim 1, characterized in that: In step S1, the raw milk is concentrated before being defatted. The process used for the concentration is organic roll membrane reverse osmosis concentration. The concentration temperature is 2 to 10°C and the concentration multiple is 1.1 to 2.0 times.

3. The preparation method according to claim 1, characterized in that: In step S1, the degreasing temperature is 50-60°C.

4. The preparation method according to claim 1, characterized in that: In step S2, the dissolving temperature is 40-50°C.

5. The preparation method according to claim 1, characterized in that: In step S2, the ingredients include 0-8% white sugar, 0-0.5% bovine colostrum powder, and 0-2% whey protein powder, based on the total mass.

6. The preparation method according to claim 1, characterized in that: In step S3, the heating sterilization is sterilization at 120-125°C for 4-15 seconds; the cooling temperature is 55-65°C.

7. The preparation method according to claim 1, characterized in that: In step S5, the heating temperature is 60-70° C., and the homogenization pressure is 15-20 MPa.

8. The preparation method according to claim 1, characterized in that: In step S6, the mixture is cooled to 40-45° C. after homogenization.

9. A yogurt rich in immunoglobulin prepared by the preparation method according to any one of claims 1 to 8.

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