Preparation method of high-stability beta-glucan yoghourt

Abstract

The invention discloses a preparation method of high-stability beta-glucan yoghourt. Mixing the sterilized fresh milk with a composite strain consisting of lactobacillus delbrueckii subsp. Bulgaricus, streptococcus salivarius subsp. Thermophilus, bifidobacterium animalis subsp. Lactis, plant lactobacillus, bifidobacterium breve, lactobacillus paracasei, lactobacillus helveticus, lactobacillus rhamnosus and bifidobacterium longum subsp. Longum, and fermenting; and adding beta-glucan into the fermented yoghourt to obtain the high-stability beta-glucan yoghourt. Before beta-glucan is added, the compound bacterial strain is added into the milk, protein in the milk can be gathered under the action of the compound bacterial strain to form a three-dimensional curd network, so that the flowability of a system is reduced, then glucan is added, and the glucan can be uniformly dispersed in curd gaps, so that the glucan is prevented from being excessively combined with the protein in the milk; the stability of a yoghourt system is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of food fermentation, and in particular to a preparation method of high-stability beta-glucan yogurt. BACKGROUND

[0002] Beta-glucan, as an important water-soluble dietary fiber, is widely present in natural sources such as oats, barley, yeast, etc. It has been widely proven to have significant physiological activities, including regulating immunity, reducing cholesterol, improving intestinal health, controlling blood sugar, etc. With the improvement of consumers' health awareness, the market demand for healthy foods rich in functional ingredients (such as beta-glucan), especially protein beverages and fermented dairy products (such as yogurt), is increasing.

[0003] However, studies have found that beta-glucan molecules are prone to interact with proteins (such as casein and whey protein in milk), destroying the secondary structure (such as alpha-helix and beta-sheet) and high-level structure stability of the proteins. Therefore, it is a major technical obstacle to effectively integrate beta-glucan into protein-containing beverage systems.

[0004] Yogurt, as a popular fermented dairy product, its preparation process involves lactic acid bacteria fermentation to produce acid, resulting in a decrease in the pH value of the system to the isoelectric point of casein (about pH 4.6). In this sensitive acidic environment, the destructive effect of beta-glucan on milk protein structure is significantly amplified. Yogurt products directly added with beta-glucan often have serious problems such as uneven texture, obvious layering, graininess, rough mouthfeel, and poor storage stability, which seriously affect the sensory quality, commercial value and consumer acceptance of the products.

[0005] To improve the stability of yogurt containing beta-glucan, the existing technology usually adopts the following methods: first, adding a large amount of stabilizers / thickeners such as gum, CMC, xanthan gum, etc. This method can improve the texture and stability to some extent, but may bring unnatural sticky mouthfeel, mask the refreshing flavor of yogurt itself, increase cost and ingredient complexity, and may not fundamentally solve the deep instability problem caused by protein structure destruction; second, pretreatment (such as enzymatic hydrolysis, shearing, etc.) of beta-glucan or protein. These methods may be high in cost and complex in process, and may affect the biological activity of beta-glucan or the natural properties of the product; in addition, some studies also try to use the extracellular polysaccharide (EPS) of specific lactic acid bacteria to improve the texture. However, the EPS produced by a single strain is limited in terms of type, yield and function, and its stabilizing effect is often insufficient when facing the challenge of high beta-glucan addition.

[0006] Therefore, it is urgent to develop a new preparation method for yogurt containing beta-glucan, which should effectively overcome the damage of beta-glucan to the secondary structure of milk protein and the overall stability, produce high-quality products with delicate taste, uniform texture, no whey separation, shelf stability, and maximum retention of the physiological activity of beta-glucan and the inherent flavor of yogurt without excessive dependence on exogenous stabilizers or complex pretreatment. SUMMARY

[0007] In view of the above problems, the purpose of the present application is to provide a preparation method of high-stability beta-glucan yogurt to solve the problems of poor stability of existing yogurt containing beta-glucan.

[0008] To achieve the above purpose, the present application first provides a preparation method of high-stability beta-glucan yogurt, comprising the following steps:

[0009] S1: weigh fresh milk, sterilize and cool to 35-42℃ in ice water bath;

[0010] S2: take the cooled milk of step S1, add a composite strain to it, stir thoroughly until completely mixed and evenly distributed, to ensure uniform dispersion of the strain, to obtain a strain milk solution;

[0011] S3: pour the pre-mixed strain milk solution of S2 back into S1, stir thoroughly again to ensure uniform distribution of the strain in the entire milk;

[0012] S4: pour the milk solution with mixed strain in S3 into a sterilized fermentation container, and ferment under sealed conditions;

[0013] S5: add beta-glucan to the fermented yogurt of step S4, stir evenly, then package, seal, and sterilize the prepared yogurt to obtain high-stability beta-glucan yogurt;

[0014] Wherein, the high-stability beta-glucan yogurt contains 100-200 parts of fresh milk, 1-5 parts of beta-glucan, and 1-3 parts of a composite strain, and the composite strain is composed of Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus salivarius subsp. thermophilus, Bifidobacterium animalis lactis, Lactobacillus plantarum, Bifidobacterium breve, Paracaseicoccus casei, Lactobacillus helveticus, Lactobacillus rhamnosus, and Bifidobacterium longum longum subsp.

[0015] In one embodiment of the present application, in step S1, the sterilization is pasteurization, the heating method is water bath heating, the water bath temperature is 80℃, and the time is 5min.

[0016] In an embodiment of the present application, in step S2, the mass ratio of Streptococcus thermophilus, Bifidobacterium animalis lactis, Lactobacillus plantarum, Bifidobacterium breve, Paracaseicobacter casei, Lactobacillus helveticus, Lactobacillus rhamnosus and Bifidobacterium longum longum to Lactobacillus delbrueckii subsp. bulgaricus in the compound bacterial strain is 1:1-2, preferably 1:1, based on Lactobacillus delbrueckii subsp. bulgaricus.

[0017] In an embodiment of the present application, in step S2, the stirring speed is 350-500 rpm, and the stirring time is 3-8 min.

[0018] In an embodiment of the present application, in step S4, the fermentation temperature is 50-55℃, and the fermentation time is 8-12 h.

[0019] In an embodiment of the present application, in step S5, the sterilization is pasteurization, the heating mode is water bath heating, the water bath temperature is 80℃, and the time is 5 min.

[0020] The present application also discloses a high-stability beta-glucan yogurt prepared by the preparation method.

[0021] In an embodiment of the present application, the high-stability beta-glucan yogurt comprises 100-200 parts of fresh milk, 1-2 parts of beta-glucan and 1-3 parts of the compound bacterial strain, based on weight, and the compound bacterial strain comprises Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus thermophilus, Bifidobacterium animalis lactis, Lactobacillus plantarum, Bifidobacterium breve, Paracaseicobacter casei, Lactobacillus helveticus, Lactobacillus rhamnosus and Bifidobacterium longum longum, wherein the mass ratio of Streptococcus thermophilus, Bifidobacterium animalis lactis, Lactobacillus plantarum, Bifidobacterium breve, Paracaseicobacter casei, Lactobacillus helveticus, Lactobacillus rhamnosus and Bifidobacterium longum longum to Lactobacillus delbrueckii subsp. bulgaricus in the compound bacterial strain is 1:1-2.

[0022] Beneficial effects:

[0023] 1. In the present application, the compound bacterial strain is used to ferment the sterilized milk, and then beta-glucan is added to the fermented yogurt. During the fermentation of the yogurt, the proteins in the milk are gathered to form a three-dimensional curd network under the action of the compound bacterial strain, so that the flowability of the system is reduced. At this time, the beta-glucan is uniformly dispersed in the curd gap, avoiding excessive combination with the proteins in the milk, and improving the stability of the yogurt system.

[0024] 2、The present application is compounded by selecting nine strains of Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus salivarius subsp. thermophilus, Bifidobacterium animalis lactis, Lactiplantibacillus plantarum, Bifidobacterium breve, Paracaseicola caseica, Lactobacillus helveticus, Lactobacillus rhamnosus and Bifidobacterium longum subsp. longum, under the action of which casein aggregates to form a dense, stable and uniform curd network, and after the addition of glucan, the glucan can be better dispersed in the curd interstice and will not cause the network structure to collapse due to interaction with the protein, further improving the stability of the yogurt system.

[0025] 3、The present application can add more than 2% of beta-glucan in the yogurt, which greatly improves the nutritional value of the yogurt while improving the stability of the yogurt. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The picture is the appearance of the yogurt prepared in Example 1 and Comparative Examples 1-2. DETAILED DESCRIPTION

[0027] The technical solutions in the examples of the present application will be described clearly and completely below, obviously, the described examples are only a part of the examples of the present application, not all the examples. Based on the examples in the present application, all other examples obtained by those skilled in the art without creative labor belong to the scope of protection of the present application.

[0028] The strains involved in the examples and comparative examples of the present application are all purchased strain powders on the market.

[0029] Example 1

[0030] Raw material composition:

[0031] 1 part of complex strains, the complex strains are composed of Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus salivarius subsp. thermophilus, Bifidobacterium animalis lactis, Lactiplantibacillus plantarum, Bifidobacterium breve, Paracaseicola caseica, Lactobacillus helveticus, Lactobacillus rhamnosus and Bifidobacterium longum subsp. longum in a ratio of 1:1:1:1:1:1:1:1:1, 100 parts of fresh milk, 1 part of beta-glucan

[0032] Preparation steps:

[0033] S1: weigh 100 parts of fresh milk, sterilize the milk by heating in a water bath to 80℃ for 5 min;

[0034] S2: cool the heated milk in S1 in an ice water bath to 42℃;

[0035] S3: take 1 part of the milk in S2, add the complex strains into it, stir thoroughly until completely mixed and uniform, and ensure that the strains are uniformly dispersed;

[0036] S4: Pour the pre-mixed bacteria milk liquid in S3 back into S2, and stir thoroughly again to ensure that the bacteria are evenly distributed throughout the milk;

[0037] S5: Pour the bacteria-mixed milk liquid in S4 into a sterilized fermentation container, cover the container, and place it in a constant temperature device set at a constant temperature of 50°C for 8h of fermentation;

[0038] S6: Weigh the β-glucan and add it to the fermented yogurt in S5, and mix it evenly using a stirrer under the condition of 200 revolutions per minute for 15 minutes;

[0039] S7: Package and seal the yogurt in S6, and perform pasteurization again under the condition of water bath heating at 80°C for 5 minutes.

[0040] Example 2

[0041] Raw material composition:

[0042] 1 part of composite strains, which are composed of Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus salivarius subsp. thermophilus, Bifidobacterium animalis lactis, Lactiplantibacillus plantarum, Bifidobacterium breve, Paracaseicoccus caseicombabovis, Lactobacillus helveticus, Lactobacillus rhamnosus, and Bifidobacterium longum subsp. longum at a ratio of 1:1:1:1:1:1:1:1:1, 100 parts of fresh milk, and 2 parts of β-glucan

[0043] Preparation steps:

[0044] S1: Weigh 100 parts of fresh milk and perform sterilization under the condition of water bath heating to 80°C for 5 minutes;

[0045] S2: Cool the heated milk in S1 in an ice water bath to 42°C;

[0046] S3: Take 1 part of the milk in S2, add the composite bacteria to it, and stir thoroughly until completely mixed and evenly distributed;

[0047] S4: Pour the pre-mixed bacteria milk liquid in S3 back into S2, and stir thoroughly again to ensure that the bacteria are evenly distributed throughout the milk;

[0048] S5: Pour the bacteria-mixed milk liquid in S4 into a sterilized fermentation container, cover the container, and place it in a constant temperature device set at a constant temperature of 50°C for 8h of fermentation;

[0049] S6: Weigh the β-glucan and add it to the fermented yogurt in S5, and mix it evenly using a stirrer under the condition of 200 revolutions per minute for 15 minutes;

[0050] S7: The yogurt in S6 is divided into portions, sealed, and pasteurized again, with the condition being water bath heating at 80°C for 5 min.

[0051] Comparative Example 1

[0052] The difference between Comparative Example 1 and Example 1 is that the order of adding β-glucan is different. In Comparative Example 1, fresh milk is mixed with β-glucan first, and then fermented.

[0053] Raw material composition:

[0054] 1 part of complex strains, which are composed of Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus salivarius subsp. thermophilus, Bifidobacterium animalis lactis, Lactobacillus plantarum, Bifidobacterium breve, Paracaseicola casei, Lactobacillus helveticus, Lactobacillus rhamnosus, and Bifidobacterium longum subsp. longum in a mass ratio of 1:1:1:1:1:1:1:1:1, 100 parts of fresh milk, and 1 part of β-glucan

[0055] Preparation steps:

[0056] S1: 100 parts of fresh milk and 1 part of β-glucan are weighed and mixed uniformly, and then sterilized, with the condition being water bath heating to 80°C for 5 min;

[0057] S2: The milk heated in S1 is cooled in an ice water bath to 42°C;

[0058] S3: 1 part of the milk in S2 is taken, and an appropriate amount of strain is weighed and added, stirred thoroughly until completely mixed uniformly, and the strain is uniformly dispersed;

[0059] S4: The strain milk liquid in S3 is poured back into S2, and stirred again to ensure that the strain is uniformly distributed in the whole milk;

[0060] S5: The milk liquid mixed with the strain in S4 is poured into a sterilized fermentation container, the lid is covered, the container is placed in a constant temperature device, the constant temperature is set to 50°C, and the fermentation time is 8 h;

[0061] S6: The yogurt in S6 is divided into portions, sealed, and pasteurized again, with the condition being water bath heating at 80°C for 5 min.

[0062] Comparative Example 2

[0063] The difference between Comparative Example 1 and Example 1 is that the complex strain is composed of Streptococcus salivarius subsp. thermophilus, Lactobacillus delbrueckii subsp. bulgaricus, Lactococcus lactis subsp. lactis, and Lactococcus cremoris in a mass ratio of 1:1:1:1.

[0064] Raw material composition:

[0065] Compound strain 1 part, the compound strain is composed of Streptococcus salivarius subsp. thermophilus, Lactobacillus delbrueckii subsp. bulgaricus, Lactococcus lactis subsp. lactis, Lactococcus cremoris, fresh milk 100 parts, β-glucan 1 part.

[0066] Preparation steps:

[0067] S1: weigh the fresh milk and β-glucan, mix well, and then sterilize, the condition is water bath heating to 80℃, maintain 5 min;

[0068] S2: cool the heated milk mixture of S1 in an ice water bath to 42℃;

[0069] S3: take 1 part of the milk mixture in S2, weigh the compound strain and add it, stir well until completely mixed and evenly distributed;

[0070] S4: pour the pre-mixed strain milk liquid of S3 back into S2, stir again to ensure uniform distribution of the strain in the milk;

[0071] S5: pour the milk liquid mixed with the strain in S4 into a sterilized fermentation container, cover the lid, and place the container in a constant temperature device, set the constant temperature to 25℃, and ferment for 12 h;

[0072] S6: weigh β-glucan and add it to the fermented yogurt in S5, mix well with a stirrer, stirring condition is 200 revolutions, 15 min;

[0073] S7: package and seal the yogurt in S6.

[0074] Comparative Example 3

[0075] The difference between Comparative Example 3 and Example 1 is that Bifidobacterium breve is replaced by Bifidobacterium bifidum.

[0076] Raw material composition:

[0077] Compound strain 1 part, the compound strain is composed of Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus salivarius subsp. thermophilus, Bifidobacterium animalis lactis subsp. lactis, Lactobacillus plantarum, Bifidobacterium bifidum, Paracaseicola casei, Lactobacillus helveticus, Lactobacillus rhamnosus, Bifidobacterium longum subsp. longum according to 1:1:1:1:1:1:1:1:1, fresh milk 100 parts, β-glucan 1 part.

[0078] Preparation steps:

[0079] S1: weigh 100 parts of fresh milk, sterilize, the condition is water bath heating to 80℃, maintain 5 min;

[0080] S2: cool the heated milk of S1 in an ice water bath to 42℃;

[0081] S3: Take 1 part of the milk in S2, weigh the compound strain and add it, stir thoroughly until completely mixed and evenly distributed, ensuring uniform distribution of the strain;

[0082] S4: Pour the pre-mixed strain milk liquid in S3 back into S2, stir thoroughly again to ensure uniform distribution of the strain throughout the milk;

[0083] S5: Pour the mixed strain milk liquid in S4 into a sterilized fermentation container, cover it with a lid, and place it in a constant temperature device, set the constant temperature to 50°C, and ferment for 8 hours;

[0084] S6: Weigh the beta-glucan and add it to the fermented yogurt in S5, mix it evenly using a stirrer, and stir at 200 rpm for 15 minutes;

[0085] S7: Package and seal the yogurt in S6, and perform pasteurization again, with the condition being water bath heating at 80°C for 5 minutes.

[0086] Comparative Example 4 replaces the Paracaseicilus caseicilus with Caseicilus caseicilus based on Example 1

[0087] Comparative Example 4 differs from Example 1 in that Paracaseicilus caseicilus is replaced with Caseicilus caseicilus.

[0088] Raw material composition:

[0089] 1 part of compound strain, consisting of Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus salivarius subsp. thermophilus, Bifidobacterium animalis lactis, Lactiplantibacillus plantarum, Bifidobacterium breve, Caseicilus caseicilus, Lactobacillus helveticus, Lactobacillus rhamnosus, Bifidobacterium longum longum subsp. in a ratio of 1:1:1:1:1:1:1:1:1, 100 parts of fresh milk, and 1 part of beta-glucan.

[0090] Production steps:

[0091] S1: Weigh 100 parts of fresh milk and sterilize it by heating in a water bath to 80°C for 5 minutes;

[0092] S2: Cool the heated milk in S1 in an ice water bath to 42°C;

[0093] S3: Take 1 part of the milk in S2, weigh the compound strain and add it, stir thoroughly until completely mixed and evenly distributed, ensuring uniform distribution of the strain;

[0094] S4: Pour the pre-mixed strain milk liquid in S3 back into S2, stir thoroughly again to ensure uniform distribution of the strain throughout the milk;

[0095] S5: Pour the milk liquid mixed with the bacteria in S4 into the sterilized fermentation container, cover the lid, and place the container in the constant temperature device, set the constant temperature to 50℃, and ferment for 8h;

[0096] S6: Add β-glucan to the fermented yogurt in S5, mix evenly using a stirrer, and the stirring conditions are 200 revolutions and 15min;

[0097] S7: Package and seal the yogurt in S6, and perform pasteurization treatment again, with the condition being water bath heating at 80℃ for 5min.

[0098] Comparative Example 5

[0099] The difference between Comparative Example 5 and Example 1 is that Lactobacillus helveticus is replaced by Lactobacillus acidophilus.

[0100] Raw material composition:

[0101] 1 part of complex strains, which are composed of Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus salivarius subsp. thermophilus, Bifidobacterium animalis lactis, Lactiplantibacillus plantarum, Bifidobacterium breve, Paracaseicoccus caseicombabovis, Lactobacillus acidophilus, Lactobacillus rhamnosus, and Bifidobacterium longum subsp. longum at a ratio of 1:1:1:1:1:1:1:1:1, 100 parts of fresh milk, and 1 part of β-glucan.

[0102] Preparation steps:

[0103] S1: Weigh 100 parts of fresh milk and perform sterilization treatment, with the condition being water bath heating to 80℃ for 5min;

[0104] S2: Cool the heated milk in S1 in an ice water bath to 42℃;

[0105] S3: Take 1 part of the milk in S2, weigh the complex bacterial strain, and add it to the milk, stir thoroughly until completely mixed and evenly distributed;

[0106] S4: Pour the pre-mixed bacterial milk liquid in S3 back into S2, and stir again to ensure uniform distribution of the bacteria in the entire milk;

[0107] S5: Pour the milk liquid mixed with the bacteria in S4 into the sterilized fermentation container, cover the lid, and place the container in the constant temperature device, set the constant temperature to 50℃, and ferment for 8h;

[0108] S6: Add β-glucan to the fermented yogurt in S5, mix evenly using a stirrer, and the stirring conditions are 200 revolutions and 15min;

[0109] S7: The yogurt in S6 was divided, sealed, and pasteurized again, with the condition being water bath heating at 80°C for 5 min.

[0110] Comparative Example 6

[0111] Comparative Example 6 differs from Example 1 in that the proportions of the strains in the composite strain are different.

[0112] Raw material composition:

[0113] 1 part of the composite strain, which is composed of Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus salivarius subsp. thermophilus, Bifidobacterium animalis lactis, Lactobacillus plantarum, Bifidobacterium breve, Paracaseicobacter casei, Lactobacillus helveticus, Lactobacillus rhamnosus, and Bifidobacterium longum subsp. longum in a ratio of 1:0.5:1:2:1:1:2:1:3, 100 parts of fresh milk, and 1 part of β-glucan

[0114] Preparation steps:

[0115] S1: 100 parts of fresh milk were weighed and sterilized, with the condition being water bath heating to 80°C for 5 min;

[0116] S2: The milk heated in S1 was cooled in an ice water bath to 42°C;

[0117] S3: 1 part of the milk in S2 was taken, and the composite strain was weighed and added, and stirred thoroughly until completely mixed and uniform, to ensure uniform distribution of the strain;

[0118] S4: The strain milk liquid in S3 was poured back into S2, and stirred again to ensure uniform distribution of the strain in the entire milk;

[0119] S5: The milk liquid with the mixed strain in S4 was poured into a sterilized fermentation container, and the container was placed in a constant temperature device, with the constant temperature being set to 50°C, and the fermentation time being 8 h;

[0120] S6: β-glucan was weighed and added to the fermented yogurt in S5, and a stirrer was used to mix it uniformly, with the stirring condition being 200 revolutions for 15 min;

[0121] S7: The yogurt in S6 was divided, sealed, and pasteurized again, with the condition being water bath heating at 80°C for 5 min.

[0122] Figure 1 Pictures of the yogurt prepared in Example 1 and Comparative Examples 1-2 after being stored at -4°C for 12 h, from Figure 1It can be seen that the yogurt prepared in Example 1 can be stored for 12 h under acidic conditions without separation, coagulation and other phenomena, indicating that the yogurt has good storage stability. The comparative examples 1 and 2 both show deterioration after storage, indicating that the storage stability is significantly decreased, which may be due to the addition of glucan leading to the interaction between glucan and protein. In Example 1, before adding β-glucan, complex strains are added to the milk, and the proteins in the milk will be aggregated to form a three-dimensional coagulation network under the action of the complex strains, resulting in a decrease in the flowability of the system. At this time, the addition of glucan can uniformly disperse in the coagulation gap, avoiding excessive combination with the protein in the milk, and improving the stability of the yogurt system.

[0123] Tables 1-3 show the changes in viscosity, centrifugal precipitation rate and centrifugal suspension ratio of the yogurt with and without the addition of glucan in the examples and comparative examples. It can be seen from the table that after the addition of 1% glucan based on the mass of the milk, the viscosity of Example 1 slightly increases, the centrifugal precipitation rate increases, and the centrifugal suspension ratio slightly decreases, indicating that the stability slightly decreases after the addition of 1% glucan based on the mass of the milk, but the decrease is not large, and the stability is basically similar to that of the yogurt without the addition of glucan. With the further increase of the amount of glucan, when the glucan accounts for 2% of the mass of the milk, the stability of the yogurt decreases significantly, but it is still within an acceptable level.

[0124] In the comparative examples, after the addition of glucan, the viscosity, centrifugal precipitation rate and centrifugal suspension ratio of the yogurt all decrease significantly. The main reason for the poor acid stability of Comparative Example 1 is that the glucan is mixed with the milk before the preparation of the yogurt, resulting in the interaction between the protein in the milk and the glucan. In this case, the stability of the yogurt cannot be further improved after fermentation. Comparative Example 2 changes the type of the strain on the basis of Comparative Example 1, and the coagulation network structure formed in the late stage of fermentation of the yogurt is not dense and stable enough, resulting in relatively poor stability of the yogurt. Comparative Examples 3-6 change the type and ratio of the strain on the basis of the examples, which also leads to the decrease in the stability of the yogurt. After the addition of glucan, the glucan will still react with the milk protein, resulting in a significant decrease in the performance of the yogurt.

[0125] Table 1 Influence of glucan on the viscosity of different yogurts (cp)

[0126] Sample name No addition of dextran Addition of dextran Example 1 1008.50 1011.40 Example 2 1008.50 1467.21 Comparative Example 1 1008.50 117.32 Comparative Example 2 627.70 127.41 Comparative Example 3 921.45 570.31 Comparative Example 4 931.78 667.40 Comparative Example 5 1000.11 149.31 Comparative Example 6 1142.45 699.43

[0127] Table 2 Influence of glucan on the centrifugal precipitation rate of different yogurts (%)

[0128] Sample name No addition of dextran Addition of dextran Example 1 39.93±2.71 47.22±0.38 Example 2 39.93±2.71 97.89±0.11 Comparative Example 1 39.33±1.05 3.40±0.01 Comparative Example 2 42.26±1.42 1.42±0.01 Comparative Example 3 31.41±0.16 2.11±0.67 Comparative Example 4 27.09±1.21 3.46±9.81 Comparative Example 5 46.32±1.35 15.09±1.12 Comparative Example 6 33.98±1.78 20.62±1.20

[0129] Table 3 Influence of glucan on the centrifugal suspension ratio of different yogurts

[0130]

[0131]

[0132] The above examples are not intended to limit the scope of the present application, nor are the described steps intended to limit the order in which they are performed. Modifications to the present application, which fall within the scope of the claims, will be apparent to those skilled in the art with the benefit of this disclosure.

Claims

1. A method for preparing highly stable β-glucan yogurt, characterized in that, Includes the following steps: S1: Weigh fresh milk, sterilize it, and then cool it down to 35-42℃ in an ice water bath; S2: Take the milk cooled in step S1, add the compound bacteria, stir thoroughly until completely mixed, and ensure that the bacteria are evenly dispersed to obtain the inoculated milk liquid. S3: Pour the premixed milk with starter culture from S2 back into S1 and stir thoroughly again to ensure that the starter culture is evenly distributed throughout the milk. S4: Pour the milk liquid with the mixed bacteria from S3 into a sterilized fermentation container and ferment it under sealed conditions; S5: Add β-glucan to the fermented yogurt from step S4, stir well, then package, seal, and sterilize the prepared yogurt to obtain highly stable β-glucan yogurt. The high-stability β-glucan yogurt, by weight, contains 100-200 parts fresh milk, 1-5 parts β-glucan, and 1-3 parts compound bacteria. The compound bacteria consists of Lactobacillus de Germany subsp. bulgaricus, Streptococcus salivarius subsp. thermophilus, Bifidobacterium animalis subsp. lactis, Lactobacillus plantarum, Bifidobacterium breve, Lactobacillus paracasei, Lactobacillus helveticus, Lactobacillus rhamnosus, and Bifidobacterium longum subsp. longum.

2. The preparation method according to claim 1, characterized in that, In step S1, sterilization is performed by pasteurization, and the heating method is water bath heating at a temperature of 80°C for 5 minutes.

3. The preparation method according to claim 1, characterized in that, In step S2, using *Lactobacillus deutschlandiae* subsp. bulgaricus as a reference, the mass ratio of *Streptococcus salivarius* subsp. thermophilus, *Bifidobacterium animalis* subsp. lactis, *Lactobacillus plantarum*, *Bifidobacterium breve*, *Lactobacillus paracasei*, *Lactobacillus helveticus*, *Lactobacillus rhamnosus*, and *Bifidobacterium longum* subsp. bulgaricus to *Lactobacillus deutschlandiae* subsp. bulgaricus in the composite strain is 1:1 to 2.

4. The preparation method according to claim 1, characterized in that, In step S2, the stirring speed is 350-500 rpm and the stirring time is 3-8 min.

5. The preparation method according to claim 1, characterized in that, In step S4, the fermentation temperature is 50℃-55℃, and the fermentation time is 8h-12h.

6. The preparation method according to claim 1, characterized in that, In step S5, sterilization is performed by pasteurization, and the heating method is water bath heating at a temperature of 80°C for 5 minutes.

7. Highly stable β-glucan yogurt prepared by the preparation method according to any one of claims 1 to 6.

8. The high-stability β-glucan yogurt according to claim 7, characterized in that, Based on parts by weight, the high-stability β-glucan yogurt contains 100-200 parts of fresh milk, 1-2 parts of β-glucan, and 1-3 parts of a complex strain. The complex strain consists of Lactobacillus de Germany subsp. bulgaricus, Streptococcus salivarius subsp. thermophilus, Bifidobacterium animalis subsp. lactis, Lactobacillus plantarum, Bifidobacterium breve, Lactobacillus paracasei, Lactobacillus helveticus, Lactobacillus rhamnosus, and Bifidobacterium longum subsp. longum.

9. The high-stability β-glucan yogurt according to claim 7, characterized in that, In the complex strains, the mass ratio of Streptococcus salivarius thermophilus subsp., Bifidobacterium animalis lactis subsp., Lactobacillus plantarum, Bifidobacterium breve, Lactobacillus paracasei, Lactobacillus helveticus, Lactobacillus rhamnosus, and Bifidobacterium longis subsp. longis to Lactobacillus de Germany subsp. bulgaricus was 1:1 to 2.

Images