A composition containing 7 probiotics and a preparation method of a drinkable yogurt thereof

Abstract

The application discloses a kind of 7 kinds of composition containing probiotic and its preparation method of drinkable yoghurt, belong to microbial fermentation technical field.Composition includes the combination of 2 kinds of lactic acid bacteria and 7 kinds of probiotic, lactic acid bacteria is the combination of lactococcus lactis subsp cremoris and lactococcus lactis subsp lactis;Probiotic is the combination of lactobacillus bulgaricus, streptococcus thermophilus, bifidobacterium lactis, lactobacillus acidophilus, paracasei, lactobacillus rhamnosus and bifidobacterium infantis.The composition can provide the required probiotic for children, young people, old people respectively, and in the new preparation method developed additionally, through the combination of lactic acid bacteria and probiotic, lactase pretreatment and two-step inoculation fermentation process in fermentation stage, twice post-ripening process can effectively guarantee the acidity of composition fermentation moderate, improve the stability of composition system and taste.The overall additive of the obtained product is zero addition and the flavor is excellent and high stability.

Description

TECHNICAL FIELD

[0001] The present application relates to a composition containing 7 probiotics and a preparation method of drinkable yogurt thereof, and belongs to the technical field of microbial fermentation. BACKGROUND

[0002] Probiotics refer to live microorganisms that have a health effect on the host when reaching a certain amount. To exert the probiotic effect of probiotics, it is necessary to ensure the intake of a sufficient number of active bacteria every day. Yogurt is an excellent carrier of probiotics, and drinkable yogurt is one of the more common intake methods.

[0003] Yogurt is a product prepared by inoculating lactic acid bacteria into milk or dairy products after homogenization and sterilization, and then fermenting and cooling. It not only contains active probiotics, but also contains rich nutrients such as protein, calcium, and vitamins. Drinkable yogurt has the outstanding characteristics of refreshing taste and convenient drinking. The texture of drinkable yogurt is of great significance to the dairy industry and consumers. However, there are quality defects such as whey separation and fat floating during its processing and cold storage. Whey separation can lead to the loss of water-soluble nutrients and the generation of undesirable sensory properties, affecting the acceptance of consumers. Therefore, how to improve the quality and stability of drinkable yogurt is a technical problem in yogurt production.

[0004] At present, in addition to controlling the composition and quality of raw milk, the type and activity of fermentation agents, and processing technology, the quality and stability of drinkable yogurt can also be improved by adding food stabilizers. Among them, many dairy companies such as Yili, Mengniu, Guangming, Xinwangxing, and Junlebao use a variety of additives such as hydroxypropyl distarch phosphate, agar, pectin, gelatin, acetylated distarch phosphate, glycerol monostearate, and sodium alginate to improve the system stability of their products. However, food additives are now a turn-off for consumers, and natural additive-free diet has become a consumer trend. Therefore, starting from factors such as raw milk quality, fermentation agent type, and processing technology, it is of great market prospect to develop a zero-additive, high-stability, excellent-flavor drinkable yogurt containing 7 probiotics. SUMMARY

[0005] In view of the above problems, the present application provides a composition containing 7 probiotics, and a preparation method of drinkable yogurt is developed. Through specific fermentation conditions, the effect of controlling whey separation and ensuring system stability under zero-additive conditions is achieved. The specific scheme is as follows:

[0006] Firstly, the present application provides a composition containing 7 probiotics, which comprises a combination of 2 lactic acid bacteria and 7 probiotics.

[0007] Preferably, the lactic acid bacteria are a combination of Lactococcus lactis subsp. cremoris and Lactococcus lactis subsp. lactis.

[0008] Preferably, the probiotic bacteria are a combination of Lactobacillus bulgaricus, Streptococcus thermophilus, Bifidobacterium lactis, Lactobacillus acidophilus, Lactobacillus paracasei, Lactobacillus rhamnosus and Bifidobacterium infantis.

[0009] Preferably, the ratio of the viable counts of Lactococcus lactis subsp. cremoris, Lactococcus lactis subsp. lactis and probiotic Streptococcus thermophilus is (18-22):(22-27):(51-60), and the total amount of addition is 0.3-0.9 x 10 7 CFU / g.

[0010] Preferably, the ratio of the viable counts of the probiotic bacteria Lactobacillus bulgaricus, Bifidobacterium lactis, Lactobacillus acidophilus, Lactobacillus paracasei, Lactobacillus rhamnosus and Bifidobacterium infantis is (16-18):(20-22):(16-18):(16-18):(12-14):(10-20), and the total amount of addition is 0.1-0.5 x 10 8 CFU / g.

[0011] Secondly, the present application also provides a method for preparing the above-mentioned drinkable yoghurt containing seven probiotic bacteria, comprising the following steps:

[0012] The raw milk is pretreated, sterilized, and the above-mentioned two lactic acid bacteria and seven probiotic bacteria are added to the feed liquid in proportion for inoculation and fermentation, and the obtained fermented milk is post-treated to obtain drinkable yoghurt.

[0013] Preferably, the pretreatment comprises adding lactase, stirring and then standing for enzymolysis, and inactivating the lactase.

[0014] Preferably, the enzymolysis has a lactase addition amount of 0.1‰-0.5‰wt, a stirring time of 5-10 min, an enzymolysis time of 1-1.5 h, and an enzymolysis temperature of 35-39℃.

[0015] Preferably, the inactivation specifically comprises heating the feed liquid to 72-77℃ and stirring for 5-10 min.

[0016] Preferably, after the pretreatment, one or both of white granulated sugar or desalted whey powder can be added to the feed liquid and mixed uniformly; the addition amounts are 0-8%wt and 0-2%wt, respectively.

[0017] Preferably, before sterilization, the feed liquid is subjected to homogenization treatment, and the homogenization pressure is 20-40 bar for the second stage and 150-200 bar for the first stage.

[0018] Preferably, the sterilization comprises pasteurization, and the sterilization temperature is 93-99℃ and the sterilization time is 250-350 s.

[0019] Preferably, the inoculation fermentation comprises twice inoculation fermentation, once inoculation fermentation, inoculation of Lactococcus lactis subsp. lactis, Lactococcus lactis subsp. lactis and Streptococcus thermophilus for fermentation, twice inoculation fermentation, inoculation of Lactobacillus bulgaricus, Bifidobacterium lactis, Lactobacillus acidophilus, Paracasei lactis, Lactobacillus rhamnosus and Bifidobacterium infantis for fermentation.

[0020] Preferably, the post-treatment comprises demulsification stirring of the fermented milk, the stirring speed is 15-30 rpm, and the stirring time is 3-5 min.

[0021] Preferably, the post-treatment comprises homogenization of the demulsified fermented milk, the homogenization pressure is: 0-5 bar for the secondary pressure and 10-40 bar for the primary pressure.

[0022] Preferably, the post-treatment comprises cooling and standing of the fermented milk for post-ripening, the post-ripening temperature is 15-20℃, and the time is 15-20 h.

[0023] Preferably, the post-treatment further comprises secondary post-ripening of the fermented milk, the post-ripening temperature is 2-6℃, and the time is 20-24 h.

[0024] Some embodiments of the present application specifically comprise the following steps:

[0025] S1. Preparation of raw materials: the obtained raw milk is immediately cooled to 2-6℃, filtered by using a 80-150 mesh filter screen to obtain a liquid;

[0026] S2. Primary sterilization: the liquid treated by S1 is heated to 70-75℃, kept for 15-20 s for primary sterilization treatment, and then cooled to 35-39℃;

[0027] S3. Enzymolysis: lactase 0.1‰-0.5‰ wt (the added enzyme activity is: 5200-5700 NLU / g) is added to the liquid treated by S2, stirred for 5-10 min, and then subjected to static enzymolysis, the enzymolysis time is 1-1.5 h, and the temperature is 35-39℃, to obtain an enzymolysis liquid;

[0028] S4. Heating and mixing: the enzymolysis liquid treated by S3 is heated to 72-77℃, white granulated sugar 0-8% wt and desalted whey powder 0-2% wt are added, stirred for 5-10 min to inactivate the lactase, and at the same time, the white granulated sugar and / or desalted whey powder are fully dissolved;

[0029] S5. Degassing: the liquid treated by S4 is subjected to degassing treatment by a vacuum degassing tank, the degassing pressure is -0.5--0.8 bar;

[0030] S6. Homogenization: the material liquid treated by S5 is homogenized by a homogenizer, the homogenization pressure is: secondary pressure 20-40 bar, primary pressure 150-200 bar;

[0031] S7. Pasteurization: the material liquid treated by S6 is pasteurized, the pasteurization temperature is 93-99℃, the pasteurization time is 250-350s;

[0032] S8. Cooling: the material liquid treated by S7 is cooled to 38-42℃;

[0033] S9. Primary inoculation fermentation: the material liquid treated by S8 is inoculated with Lactococcus lactis subsp. cremoris, Lactococcus lactis subsp. lactis and Streptococcus thermophilus according to the above preferred ratio, stirred for 5-10 min, and then fermented for 1-1.5h at 38-42℃;

[0034] S10. Secondary inoculation fermentation: the material liquid treated by S9 is inoculated with Lactobacillus bulgaricus, Bifidobacterium lactis, Lactobacillus acidophilus, Paracaseicola casei, Lactobacillus rhamnosus and Bifidobacterium infantis according to the above preferred ratio, stirred for 5-10 min, and then fermented for 4-8h at 38-42℃, the final fermentation acidity is 70-80 O T;

[0035] S11. Demulsification: the fermented milk treated by S10 is demulsified and stirred, the stirring speed is 15-30 rpm, and the stirring time is 3-5 min;

[0036] S12. Homogenization: the fermented milk treated by S11 is homogenized, the homogenization pressure is: secondary pressure 0-5 bar, primary pressure 10-40 bar;

[0037] S13. Primary post-ripening: the material liquid treated by S12 is immediately cooled to 15-20℃, stirred for 5-10 min, and then subjected to post-ripening treatment for 15-20h, which is the primary post-ripening;

[0038] S14. Filling and packaging: the material liquid treated by S13 is filled and packaged to obtain a semi-finished product;

[0039] S15. Secondary post-ripening: the semi-finished product treated by S14 is subjected to secondary post-ripening in a cold storage, the cold storage temperature is 2-6℃, and the holding time is 20-24h, and then the product is obtained.

[0040] Beneficial effects

[0041] The present application provides a composition containing 7 probiotics and 2 lactic acid bacteria, which can provide the required probiotics for children, young people and the elderly respectively. In addition, in the newly developed preparation method, the step of sterilizing heat treatment of raw milk can inactivate enzymes in raw milk and effectively kill various pathogenic bacteria in raw milk, thereby avoiding quality problems such as off-flavor of raw milk and proliferation of miscellaneous bacteria caused by enzyme hydrolysis process due to the presence of enzymes and miscellaneous bacteria. At the same time, through the combination of lactic acid bacteria and probiotics, lactase pretreatment, and two-step inoculation fermentation process and twice post-ripening process in the fermentation stage, the acidity of the composition can be effectively ensured to be moderate, and the system and taste stability of the composition can be improved. The obtained product has zero additive and excellent flavor stability. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 : Process flow chart of the composition containing 7 probiotics and the preparation process of the drinkable yogurt thereof.

[0043] Figure 2 : Product stability test results (supernatant height).

[0044] Figure 3 : Product stability test results (precipitation rate).

[0045] Figure 4 : Consumer preference test results of the product (week 0).

[0046] Figure 5 : Consumer preference test results of the product (week 1).

[0047] Figure 6 : Consumer preference test results of the product (week 2).

[0048] Figure 7 : Consumer preference test results of the product (week 3).

[0049] Figure 8 : Consumer preference test results of the product (week 4).

[0050] Figure 9 : Chromatogram of volatile flavor substances of the product prepared according to Example 1.

[0051] Figure 10 : Chromatogram of volatile flavor substances of the product prepared according to Comparative Example 1.

[0052] Figure 11 : Chromatogram of volatile flavor substances of the product prepared according to Comparative Example 6.

[0053] Figure 12 : Chromatogram of volatile flavor substances of the product prepared according to Comparative Example 8. DETAILED DESCRIPTION

[0054] The advantages and effects of the present application can be easily understood by those skilled in the art from the description. The present application can also be implemented or applied by different specific embodiments, and various modifications or changes can be made based on different views and applications without departing from the spirit of the present application. Unless otherwise specified, the following examples and comparative examples are parallel tests, using the same processing steps and parameters.

[0055] Lactococcus lactis subsp. cremoris LLc46 and Lactococcus lactis subsp. lactis LLa61 involved in the following examples are purchased from Weikang Probiotics (Suzhou) Co., Ltd.

[0056] Streptococcus thermophilus involved in the following examples is a strain owned by Kaisi Yogurt (Suzhou) Co., Ltd., and was deposited at Guangdong Microbial Culture Collection Center on October 27, 2023, with the accession number GDMCC NO: 63936 and the address of the depositary being No. 59 Building, 5th Floor, 100, Martyrs' Avenue, Guangzhou.

[0057] Lactobacillus bulgaricus LB-G40 and Bifidobacterium infantis BI-G201 involved in the following examples are purchased from Junyao Runying Biological Technology (Shanghai) Co., Ltd.; Lactobacillus bifidus BB-12, Lactobacillus paracasei L.casei 431 and Lactobacillus rhamnosus LGG involved in the following examples are purchased from Chr. Hansen; Lactobacillus acidophilus NCFM involved in the following examples is purchased from Danisco.

[0058] Lactase involved in the following examples is purchased from DSM.

[0059] Example 1: Preparation method of composition containing 7 probiotics and drinkable yogurt thereof

[0060] The composition used in this example comprises a combination of 2 lactic acid bacteria and 7 probiotics; the combination of 2 lactic acid bacteria comprises Lactococcus lactis subsp. cremoris and Lactococcus lactis subsp. lactis; the combination of 7 probiotics comprises Lactobacillus bulgaricus, Streptococcus thermophilus, Lactobacillus bifidus, Lactobacillus acidophilus, Lactobacillus paracasei, Lactobacillus rhamnosus and Bifidobacterium infantis; the preparation method comprises the following steps:

[0061] S1. Preparation of raw materials: the raw cow milk obtained was immediately cooled to 4℃, filtered with a 120-mesh filter screen to obtain a feed liquid;

[0062] S2. Primary sterilization: the feed liquid treated in S1 was heated to 72℃ and maintained for 17s for primary sterilization, and then cooled to 37℃.

[0063] S3. Enzymatic hydrolysis: lactase 0.2 ‰wt was added to the solution after S2, after stirring for 8 min, the solution was subjected to static enzymatic hydrolysis, the hydrolysis time was 1.2 h, the temperature was 37℃, and the enzymatic hydrolysis solution was obtained;

[0064] S4. Temperature mixing: the enzymatic hydrolysis solution obtained in S3 was heated to 75℃, and white sugar 4%wt and desalted whey powder 1%wt were added, stirred for 8 min to inactivate lactase, and at the same time, the white sugar and desalted whey powder were fully dissolved;

[0065] S5. Degassing: the solution after S4 was subjected to degassing treatment by a vacuum degassing tank, and the degassing pressure was -0.7 bar;

[0066] S6. Homogenization: the solution after S5 was subjected to homogenization by a homogenizer, and the homogenization pressure was: secondary pressure 30 bar, primary pressure 170 bar;

[0067] S7. Pasteurization: the solution after S6 was subjected to pasteurization, the pasteurization temperature was 97℃, and the pasteurization time was 300 s;

[0068] S8. Cooling: the solution after S7 was cooled to 40℃;

[0069] S9. Primary inoculation fermentation: Lactococcus lactis subsp. cremoris, Lactococcus lactis subsp. lactis and Streptococcus thermophilus were inoculated in the solution after S8, the ratio of inoculated viable bacteria was about 22:22:56, and the total viable bacteria count was 0.6×10 7 CFU / g, after stirring for 8 min, the solution was subjected to static fermentation for 1.2 h, and the fermentation temperature was 40℃;

[0070] S10. Secondary inoculation fermentation: Lactobacillus bulgaricus, Bifidobacterium lactis, Lactobacillus acidophilus, Paracaseicola casei, Lactobacillus rhamnosus and Bifidobacterium infantis were inoculated in the solution after S9, the ratio of inoculated viable bacteria was about 18:21:17:17:13:14, and the total viable bacteria count was 0.3×10 8 CFU / g, after stirring for 10 min, the solution was subjected to static fermentation for about 6 h, the fermentation temperature was 38℃, and the fermentation acidity was monitored, and when the fermentation acidity was 75 O T, the fermentation was terminated;

[0071] S11. Demulsification: the fermented milk after S10 was subjected to demulsification stirring, the stirring speed was 26 rpm, and the stirring time was 4 min;

[0072] S12. Homogenization: the fermented milk after S11 was subjected to homogenization, and the homogenization pressure was: secondary pressure 3 bar, primary pressure 30 bar;

[0073] S13. Primary post-ripening: The material liquid treated by S12 is immediately cooled to 15℃, and after stirring for 10 min, it is placed for post-ripening treatment for 20 h, which is the primary post-ripening;

[0074] S14. Filling and packaging: The material liquid treated by S13 is filled and packaged to obtain a semi-finished product;

[0075] S15. Secondary post-ripening: The semi-finished product treated by S14 is placed in a cold storage for secondary post-ripening, the temperature of the cold storage is 6℃, and the holding time is 22 h, and then it is a finished product.

[0076] Example 2: Preparation of a composition containing 7 probiotics and a drinking type yogurt thereof

[0077] The composition used in this example is the same as that in Example 1; the preparation method comprises the following steps:

[0078] S1. Preparation of raw materials: The raw cow milk obtained is immediately cooled to 2℃, filtered by using an 80-mesh filter screen to obtain a material liquid;

[0079] S2. Primary sterilization: The material liquid treated by S1 is warmed to 72℃, and held for 15 s for primary sterilization treatment, and then cooled to 35℃;

[0080] S3. Enzymolysis: Lactase 0.1‰wt (the added enzyme activity is: 5200 NLU / g) is added to the material liquid treated by S2, stirred for 5 min, and then placed for enzyme hydrolysis, the enzyme hydrolysis time is 1 h, and the temperature is 35℃, to obtain an enzyme hydrolysis liquid;

[0081] S4. Warming and mixing: The enzyme hydrolysis liquid obtained by S3 is warmed to 72℃, and white granulated sugar or desalted whey powder is not added, and stirred for 5 min to inactivate the lactase;

[0082] S5. Degassing: The material liquid treated by S4 is subjected to degassing treatment by a vacuum degassing tank, and the degassing pressure is -0.5 bar;

[0083] S6. Homogenization: The material liquid treated by S5 is subjected to homogenization by a homogenizer, and the homogenization pressure is: secondary pressure 20 bar, and primary pressure 150 bar;

[0084] S7. Pasteurization: The material liquid treated by S6 is subjected to pasteurization, the pasteurization temperature is 93℃, and the pasteurization time is 250 s;

[0085] S8. Cooling: The material liquid treated by S7 is cooled to 38℃;

[0086] S9. Primary inoculation and fermentation: Lactococcus lactis subsp. cremoris, Lactococcus lactis subsp. lactis and Streptococcus thermophilus are inoculated into the material liquid treated by S8, the inoculation ratio of viable bacteria is about 18:22:60, and the total viable bacteria number is 0.3x107 CFU / g, stirring for 5 min and then standing for fermentation for 1 h, fermentation temperature 38℃;

[0087] S10. Secondary inoculation fermentation: inoculating Lactobacillus bulgaricus, Bifidobacterium lactis, Lactobacillus acidophilus, Lactobacillus paracasei, Lactobacillus rhamnosus and Bifidobacterium infantis in the material liquid treated in S9, the ratio of the number of live bacteria being about 16:20:16:16:12:20, and the total number of live bacteria being 0.1 x 10 8 CFU / g, stirring for 5 min and then standing for fermentation for about 4 h, fermentation temperature 38℃, and monitoring the fermentation acidity, the fermentation acidity being controlled at 75 O T Stop the fermentation;

[0088] S11. Demulsification: demulsifying and stirring the fermented milk treated in S10, stirring speed 15 rpm, and stirring time 3 min;

[0089] S12. Homogenization: homogenizing the fermented milk treated in S11, the homogenization pressure being: secondary pressure 0 bar and primary pressure 10 bar;

[0090] S13. Primary post-ripening: immediately cooling the material liquid treated in S12 to 15℃, stirring for 5 min and then standing for post-ripening treatment for 15 h, which is the primary post-ripening;

[0091] S14. Filling and packaging: filling and packaging the material liquid treated in S13 to obtain a semi-finished product;

[0092] S15. Secondary post-ripening: putting the semi-finished product treated in S14 into a cold storage for secondary post-ripening, the cold storage temperature being 2℃, and the holding time being 20 h, and then the product is obtained.

[0093] Example 3: Preparation of a composition containing 7 probiotics and a drinking type yogurt thereof

[0094] The composition used in this example is the same as that in Example 1; the preparation method comprises the following steps:

[0095] S1. Preparation of raw materials: immediately cooling the obtained raw cow milk to 6℃, filtering the raw cow milk using a 150-mesh filter to obtain a material liquid;

[0096] S2. Primary sterilization: warming the material liquid treated in S1 to 75℃, maintaining for 20 s for primary sterilization treatment, and then cooling to 39℃;

[0097] S3. Enzymolysis: adding lactase 0.5‰wt (the added enzyme activity is: 5700 NLU / g) to the material liquid treated in S2, stirring for 10 min and then standing for enzyme hydrolysis, the enzyme hydrolysis time being 1.5 h, and the temperature being 39℃, to obtain an enzyme hydrolysis liquid;

[0098] S4. Temperature rising mixing: white sugar and desalted whey powder addition: the enzyme solution obtained from S3 was heated to 75℃, 8%wt white sugar and 2%wt desalted whey powder were added, and the lactase was inactivated by stirring for 10 min, while the white sugar and desalted whey powder were fully dissolved;

[0099] S5. Degassing: the material liquid treated by S4 was subjected to degassing treatment by a vacuum degassing tank, and the degassing pressure was -0.8 bar;

[0100] S6. Homogenization: the material liquid treated by S5 was subjected to homogenization by a homogenizer, and the homogenization pressure was: secondary pressure 40 bar, primary pressure 200 bar;

[0101] S7. Pasteurization: the material liquid treated by S6 was subjected to pasteurization, and the pasteurization temperature was 99℃, and the pasteurization time was 350 s;

[0102] S8. Cooling: the material liquid treated by S7 was cooled to 42℃;

[0103] S9. Primary inoculation fermentation: Lactococcus lactis subsp. cremoris, Lactococcus lactis subsp. lactis and Streptococcus thermophilus were inoculated in the material liquid treated by S8, and the inoculation viable cell number ratio was about 22:27:51, and the total viable cell number was 0.9x10 7 CFU / g, and after stirring for 10 min, the fermentation was carried out for 1.5 h at 42℃;

[0104] S10. Secondary inoculation fermentation: Lactobacillus bulgaricus, Bifidobacterium lactis, Lactobacillus acidophilus, Paracaseicola casei, Lactobacillus rhamnosus and Bifidobacterium infantis were inoculated in the material liquid treated by S9, and the inoculation viable cell number ratio was about 18:22:18:17:14:11, and the total viable cell number was 0.5x10 8 CFU / g, and after stirring for 10 min, the fermentation was carried out for about 8 h at 42℃, and the fermentation acidity was monitored, and when the fermentation acidity reached 80 O T, the fermentation was terminated;

[0105] S11. Demulsification: the fermented milk treated by S10 was subjected to demulsification stirring, and the stirring speed was 30 rpm, and the stirring time was 5 min;

[0106] S12. Homogenization: the fermented milk treated by S11 was subjected to homogenization, and the homogenization pressure was: secondary pressure 5 bar, primary pressure 40 bar;

[0107] S13. Primary post-ripening: the material liquid treated by S12 was immediately cooled to 20℃, and after stirring for 10 min, the post-ripening treatment was carried out for 20 h, which was the primary post-ripening;

[0108] S14. Filling and packaging: the material liquid treated by S13 was subjected to filling and packaging, and the semi-finished product was obtained;

[0109] S15. Secondary post-ripening: The semi-finished product after S14 is placed in a cold storage for a second post-ripening at a temperature of 6°C for 24 hours. After that, it becomes the finished product.

[0110] Comparative Example 1: (Different compositions, preparation method is the same as in Example 1 except that it is changed to a single inoculation fermentation)

[0111] The composition used in this comparative example includes Lactobacillus bulgaricus, Streptococcus thermophilus, and Bifidobacterium lactis as described above; the preparation method includes the following steps:

[0112] S1. Preparation of raw materials: The obtained raw milk is immediately cooled to 4°C and filtered through a 120-mesh filter to obtain the liquid.

[0113] S2. First sterilization: The liquid treated by S1 is heated to 72°C and held for 17 seconds for first sterilization, and then cooled to 37°C.

[0114] S3. Enzymatic hydrolysis: Add 0.2‰wt of lactase (enzyme activity: 5500 NLU / g) to the solution after S2 treatment, stir for 8 min and then let it stand for enzymatic hydrolysis for 1.2 h at 37℃ to obtain the enzymatic hydrolysate.

[0115] S4. Heating and mixing: Heating the enzymatic hydrolysate obtained in S3 to 75°C, adding 4%wt of white sugar and 1%wt of desalted whey powder, stirring for 8 minutes to inactivate lactase, and at the same time to fully dissolve the white sugar and desalted whey powder;

[0116] S5. Degassing: The liquid material treated by S4 is degassed in a vacuum degassing tank at a degassing pressure of -0.7 bar.

[0117] S6. Homogenization: The liquid treated in S5 is homogenized by a homogenizer. The homogenization pressure is: 30 bar for the second stage and 170 bar for the first stage.

[0118] S7. Pasteurization: Pasteurize the liquid after S6 treatment at a temperature of 97℃ for 300 seconds.

[0119] S8. Cooling: Cool the liquid material treated in S7 to 40°C;

[0120] S9. Inoculation and Fermentation: Lactobacillus bulgaricus, Streptococcus thermophilus, and Bifidobacterium lactis are inoculated into the feed liquid after S8 treatment, with a viable count ratio of approximately 20:50:30, and a total viable count of 0.3 × 10⁻⁶. 8 CFU / g, stirred for 10 minutes, then allowed to ferment for about 6 hours at a fermentation temperature of 38℃, with an acidity of 75 at the end of fermentation. O T;

[0121] S10. Breaking emulsion: the fermented milk treated in S9 was stirred for breaking emulsion, stirring speed 26 rpm, stirring time 4 min;

[0122] S11. Homogenization: the fermented milk treated in S10 was homogenized, homogenization pressure: secondary pressure 3 bar, primary pressure 30 bar;

[0123] S12. Primary post-ripening: the material liquid treated in S11 was immediately cooled to 15℃, after stirring for 10 min, it was placed for post-ripening treatment for 20 h, which was primary post-ripening;

[0124] S13. Filling and packaging: the material liquid treated in S12 was filled and packaged to obtain semi-finished products;

[0125] S14. Secondary post-ripening: the material liquid treated in S13 was placed in a cold storage for secondary post-ripening, cold storage temperature 6℃, holding time 22 h, and then it was a finished product.

[0126] Comparative Example 2: (different composition, the preparation method was changed to one-time inoculation fermentation, and other processes were the same as Example 1)

[0127] The composition used in the present comparative example included Lactococcus lactis subsp. cremoris, Lactococcus lactis subsp. lactis, Lactobacillus bulgaricus, Streptococcus thermophilus and Lactobacillus rhamnosus as described above.

[0128] The preparation method included the following steps:

[0129] S1. Preparation of raw materials: the raw milk obtained was immediately cooled to 4℃, filtered by a 120 mesh filter screen to obtain a material liquid;

[0130] S2. Primary sterilization: the material liquid treated in S1 was heated to 72℃ and maintained for 17 s for primary sterilization treatment, and then cooled to 37℃;

[0131] S3. Enzymolysis: lactase 0.2‰wt was added to the material liquid treated in S2 (the added enzyme activity was 5500 NLU / g), stirred for 8 min, and then placed for enzyme hydrolysis, the enzyme hydrolysis time was 1.2 h, and the temperature was 37℃;

[0132] S4. Heating and mixing: the material liquid treated in S3 was heated to 75℃, white granulated sugar 4%wt and desalted whey powder 1%wt were added, stirred for 8 min to inactivate lactase, and at the same time, the white granulated sugar and desalted whey powder were fully dissolved;

[0133] S5. Degassing: the material liquid treated in S4 was subjected to degassing treatment by a vacuum degassing tank, and the degassing pressure was -0.7 bar;

[0134] S6. Homogenization: The material liquid treated by S5 is homogenized by a homogenizer, and the homogenization pressure is: secondary pressure 30 bar, primary pressure 170 bar;

[0135] S7. Pasteurization: The material liquid treated by S6 is subjected to pasteurization, and the pasteurization temperature is 97°C, and the pasteurization time is 300s;

[0136] S8. Cooling: The material liquid treated by S7 is cooled to 40°C;

[0137] S9. Inoculation and fermentation: Lactococcus lactis subsp. cremoris, Lactococcus lactis subsp. lactis, Lactobacillus bulgaricus, Streptococcus thermophilus and Lactobacillus rhamnosus are inoculated in the material liquid treated by S8, and the ratio of inoculated viable bacteria is about 20:20:10:40:10, and the total viable bacteria is 0.3x10 8 CFU / g, after stirring for 10 min, the fermentation is carried out for about 6h, the fermentation temperature is 38°C, and the fermentation termination acidity is 75 O T;

[0138] S10. Demulsification: The fermented milk treated by S9 is subjected to demulsification stirring, and the stirring speed is 26 rpm, and the stirring time is 4 min;

[0139] S11. Homogenization: The fermented milk treated by S10 is subjected to homogenization, and the homogenization pressure is: secondary pressure 3 bar, primary pressure 30 bar;

[0140] S12. First post-ripening: The material liquid treated by S11 is immediately cooled to 15°C, stirred for 10 min, and then subjected to post-ripening treatment for 20h, which is the first post-ripening;

[0141] S13. Filling and packaging: The material liquid treated by S12 is subjected to filling and packaging to obtain a semi-finished product;

[0142] S14. Second post-ripening: The material liquid treated by S13 is subjected to second post-ripening in a cold storage, and the cold storage temperature is 6°C, and the holding time is 22h, and then the product is obtained.

[0143] Comparative Example 3: (different fermentation inoculation sequence, and the others are the same as Example 1)

[0144] The composition used in this comparative example is the same as that of Example 1.

[0145] The preparation method comprises the following steps:

[0146] S1. Preparation of raw materials: The raw milk obtained is immediately cooled to 4°C, filtered by a 120-mesh filter screen to obtain a material liquid;

[0147] S2. First sterilization: The material liquid treated by S1 is warmed to 72°C and maintained for 17s for first sterilization treatment, and then cooled to 37°C;

[0148] S3. Enzymatic hydrolysis: Add 0.2‰wt of lactase (enzyme activity: 5500 NLU / g) to the solution after S2 treatment, stir for 8 min and then let it stand for enzymatic hydrolysis for 1.2 h at 37℃ to obtain the enzymatic hydrolysate.

[0149] S4. Heating and mixing: Heating the enzymatic hydrolysate obtained in S3 to 75°C, adding 4%wt of white sugar and 1%wt of desalted whey powder, stirring for 8 minutes to inactivate lactase, and at the same time to fully dissolve the white sugar and desalted whey powder;

[0150] S5. Degassing: The liquid material treated by S4 is degassed in a vacuum degassing tank at a degassing pressure of -0.7 bar.

[0151] S6. Homogenization: The liquid treated in S5 is homogenized by a homogenizer. The homogenization pressure is: 30 bar for the second stage and 170 bar for the first stage.

[0152] S7. Pasteurization: Pasteurize the liquid after S6 treatment at a temperature of 97℃ for 300 seconds.

[0153] S8. Cooling: Cool the liquid material treated in S7 to 40°C;

[0154] S9. Single-stage inoculation fermentation: Lactobacillus bulgaricus, Bifidobacterium lactis, Lactobacillus acidophilus, Lactobacillus paracasei, Lactobacillus rhamnosus, and Bifidobacterium infantis were inoculated into the substrate after S8 treatment. The ratio of viable bacteria was approximately 18:21:17:17:13:14, with a total viable bacteria count of 0.3 × 10⁻⁶. 8 CFU / g, stirred for 8 minutes and then allowed to stand for 1.2 hours for fermentation at 40℃;

[0155] S10. Secondary inoculation and fermentation: *Lactococcus lactis* subsp. *milk fat*, *Lactococcus lactis* subsp. *lactolaccos*, and *Streptococcus thermophilus* were inoculated into the substrate after S9 treatment. The ratio of viable cells was approximately 22:22:56, with a total viable cell count of 0.6 × 10⁻⁶. 7 CFU / g, stirred for 10 minutes, then allowed to ferment for about 6 hours at a fermentation temperature of 38℃. The fermentation acidity was monitored and maintained at 75℃. O T terminates fermentation;

[0156] S11. Demulsification: The fermented milk treated by S10 is demulsified and stirred at a speed of 26 rpm for 4 min.

[0157] S12. Homogenization: Homogenize the fermented milk after S11 treatment. The homogenization pressure is: 3 bar for secondary pressure and 30 bar for primary pressure.

[0158] S13. Primary post-ripening: The material liquid treated by S12 was immediately cooled to 15℃, and after stirring for 10 min, it was placed for post-ripening treatment for 20 h, which was the primary post-ripening;

[0159] S14. Filling and packaging: The material liquid treated by S13 was filled and packaged to obtain a semi-finished product;

[0160] S15. Secondary post-ripening: The semi-finished product treated by S14 was placed in a cold storage for secondary post-ripening, the temperature of the cold storage was 6℃, and the holding time was 22 h, and then it was a finished product.

[0161] Comparative Example 4: (without lactase treatment, and the others were the same as Example 1)

[0162] The composition used in the present comparative example was the same as that in Example 1.

[0163] The preparation method included the following steps:

[0164] S1. Preparation of raw materials: The raw milk obtained was immediately cooled to 4℃, and filtered by using a 120-mesh filter screen to obtain a material liquid;

[0165] S2. Primary sterilization: The material liquid treated by S1 was warmed to 75℃, and held for 17 s for primary sterilization treatment, and then cooled to 37℃;

[0166] S3. Warming and mixing: The material liquid treated by S2 was added with 4%wt of white granulated sugar and 1%wt of desalted whey powder, and stirred for 8 min to fully dissolve the white granulated sugar and desalted whey powder;

[0167] S4. Degassing: The material liquid treated by S3 was subjected to degassing treatment by a vacuum degassing tank, and the degassing pressure was -0.7 bar;

[0168] S5. Homogenization: The material liquid treated by S4 was subjected to homogenization by a homogenizer, and the homogenization pressure was: 30 bar for the second stage, and 170 bar for the first stage;

[0169] S6. Pasteurization: The material liquid treated by S5 was subjected to pasteurization, and the pasteurization temperature was 97℃, and the pasteurization time was 300 s;

[0170] S7. Cooling: The material liquid treated by S6 was cooled to 40℃;

[0171] S8. Primary inoculation and fermentation: Lactococcus lactis subsp. cremoris, Lactococcus lactis subsp. lactis and Streptococcus thermophilus were inoculated into the material liquid treated by S7, and the ratio of the live bacteria number was about 22:22:56, and the total live bacteria number was 0.6×10 7 CFU / g, and after stirring for 8 min, it was placed for fermentation for 1.2 h, and the fermentation temperature was 40℃;

[0172] S9. Secondary inoculation fermentation: inoculate Lactobacillus bulgaricus, Bifidobacterium lactis, Lactobacillus acidophilus, Lactobacillus paracasei, Lactobacillus rhamnosus and Bifidobacterium infantis in the material liquid treated by S8, the ratio of inoculated viable bacteria is about 18:21:17:17:13:14, and the total viable bacteria is 0.3x10 8 CFU / g, after stirring for 10 min, the fermentation is carried out for about 6 h, the fermentation temperature is 38℃, and the fermentation termination acidity is 75 O T;

[0173] S10. Demulsification: demulsification stirring is carried out on the fermented milk treated by S9, the stirring speed is 26 rpm, and the stirring time is 4 min;

[0174] S11. Homogenization: the fermented milk treated by S10 is subjected to homogenization, and the homogenization pressure is: secondary pressure 3 bar and primary pressure 30 bar;

[0175] S12. Primary post-ripening: the material liquid treated by S11 is immediately cooled to 15℃, after stirring for 10 min, post-ripening treatment is carried out for 20 h, which is primary post-ripening;

[0176] S13. Filling and packaging: the material liquid treated by S12 is subjected to filling and packaging, and a semi-finished product is obtained;

[0177] S14. Secondary post-ripening: the material liquid treated by S13 is subjected to secondary post-ripening in a cold storage, the cold storage temperature is 6℃, and the holding time is 22 h, and then a finished product is obtained.

[0178] Comparative Example 5: (without secondary inoculation fermentation, and other processes are the same as those in Example 1)

[0179] The composition used in the present comparative example is the same as that in Example 1.

[0180] The preparation method comprises the following steps:

[0181] S1. Preparation of raw materials: the obtained raw milk is immediately cooled to 4℃, filtered by using a 120-mesh filter screen, and a material liquid is obtained;

[0182] S2. Primary sterilization: the material liquid treated by S1 is warmed to 72℃, subjected to primary sterilization treatment for 17 s, and then cooled to 37℃;

[0183] S3. Enzymolysis: lactase 0.2‰wt (the added enzyme activity is: 5500 NLU / g) is added to the material liquid treated by S2, stirring is carried out for 8 min, and then static enzymolysis is carried out, the enzymolysis time is 1.2 h, and the temperature is 37℃;

[0184] S4. Temperature rising mixing: the material liquid treated by S3 is heated to 75℃, 4%wt of white granulated sugar and 1%wt of desalted whey powder are added, and the mixture is stirred for 8 min to inactivate lactase and dissolve the white granulated sugar and desalted whey powder;

[0185] S5. Degassing: the material liquid treated by S4 is subjected to degassing treatment by a vacuum degassing tank, and the degassing pressure is -0.7 bar;

[0186] S6. Homogenization: the material liquid treated by S5 is subjected to homogenization by a homogenizer, and the homogenization pressure is: 30 bar for the second stage and 170 bar for the first stage;

[0187] S7. Pasteurization: the material liquid treated by S6 is subjected to pasteurization, and the pasteurization temperature is 97℃ and the pasteurization time is 300 s;

[0188] S8. Cooling: the material liquid treated by S7 is cooled to 40℃;

[0189] S9. Inoculation and fermentation: Lactococcus lactis subsp. cremoris, Lactococcus lactis subsp. lactis, Streptococcus thermophilus, Lactobacillus bulgaricus, Bifidobacterium lactis, Lactobacillus acidophilus, Paracaseicola casei, Lactobacillus rhamnosus and Bifidobacterium infantis are inoculated into the material liquid treated by S8, and the ratio of the number of live bacteria is about 5:5:8:13:17:13:13:8:18, and the total number of live bacteria is 0.3×10 8 CFU / g. After stirring for 10 min, the fermentation is carried out for about 6 h at a fermentation temperature of 38℃, and the final fermentation acidity is 75 O T;

[0190] S10. Demulsification: the fermented milk treated by S9 is subjected to demulsification stirring, and the stirring speed is 26 rpm and the stirring time is 4 min;

[0191] S11. Homogenization: the fermented milk treated by S10 is subjected to homogenization, and the homogenization pressure is: 3 bar for the second stage and 30 bar for the first stage;

[0192] S12. First post-ripening: the material liquid treated by S11 is immediately cooled to 15℃, stirred for 10 min, and then subjected to post-ripening treatment for 20 h, which is the first post-ripening;

[0193] S13. Filling and packaging: the material liquid treated by S13 is subjected to filling and packaging to obtain a semi-finished product;

[0194] S14. Second post-ripening: the material liquid treated by S13 is subjected to second post-ripening in a cold storage, and the cold storage temperature is 6℃ and the holding time is 22 h, and then the product is obtained.

[0195] Comparative Example 6: (without two post-ripenings, and the other processes are the same as those in Example 1)

[0196] The composition used in this comparative example is the same as in Example 1.

[0197] The preparation method comprises the following steps:

[0198] S1. Preparation of raw materials: The raw milk obtained was immediately cooled to 4°C, filtered using a 120-mesh filter screen, and a liquid was obtained;

[0199] S2. Primary sterilization: The liquid treated in S1 was heated to 72°C, maintained for 17 s for primary sterilization, and then cooled to 37°C;

[0200] S3. Enzymolysis: Lactase 0.2‰ wt (enzyme activity added: 5500 NLU / g) was added to the liquid treated in S2, stirred for 8 min, and then allowed to stand for enzyme hydrolysis, with a hydrolysis time of 1.2 h and a temperature of 37°C;

[0201] S4. Temperature increase and mixing: The liquid treated in S3 was heated to 75°C, and white granulated sugar 4% wt and desalted whey powder 1% wt were added, stirred for 8 min to inactivate the lactase, and at the same time, the white granulated sugar and desalted whey powder were fully dissolved;

[0202] S5. Degassing: The liquid treated in S4 was subjected to degassing treatment by a vacuum degassing tank, with a degassing pressure of -0.7 bar;

[0203] S6. Homogenization: The liquid treated in S5 was subjected to homogenization by a homogenizer, with a homogenization pressure of 30 bar for the second stage and 170 bar for the first stage;

[0204] S7. Pasteurization: The liquid treated in S6 was subjected to pasteurization, with a pasteurization temperature of 97°C and a pasteurization time of 300 s;

[0205] S8. Cooling: The liquid treated in S7 was cooled to 40°C;

[0206] S9. Primary inoculation and fermentation: Lactococcus lactis subsp. cremoris, Lactococcus lactis subsp. lactis, and Streptococcus thermophilus were inoculated into the liquid treated in S8, with a ratio of inoculated viable bacteria of about 22:22:56, and a total viable bacteria count of 0.6×10 7 CFU / g, stirred for 8 min, and then allowed to stand for fermentation for 1.2 h at a fermentation temperature of 40°C;

[0207] S10. Secondary inoculation and fermentation: Lactobacillus bulgaricus, Bifidobacterium lactis, Lactobacillus acidophilus, Paracaseicola casei, Lactobacillus rhamnosus, and Bifidobacterium infantis were inoculated into the liquid treated in S9, with a ratio of inoculated viable bacteria of about 18:21:17:17:13:14, and a total viable bacteria count of 0.3×10 8 CFU / g, stirred for 10 min, and then allowed to stand for fermentation for about 6 h at a fermentation temperature of 38°C, with a final fermentation acidity of 75O T;

[0208] S11. Demulsification: The fermented milk treated by S10 is demulsified and stirred at a speed of 26 rpm for 4 min.

[0209] S12. Homogenization: Homogenize the fermented milk after S11 treatment. The homogenization pressure is: 3 bar for secondary pressure and 30 bar for primary pressure.

[0210] S13. Post-curing: The liquid treated by S12 is immediately cooled to 15°C, stirred for 10 minutes, and then allowed to stand for 42 hours for post-curing. This is post-curing.

[0211] S14. Filling and Packaging: The liquid material treated by S13 is immediately cooled to 6°C, and then filled and packaged to become the finished product.

[0212] Comparative Example 7: (Pectin was added after fermentation, using conventional fermentation techniques)

[0213] The composition used in this comparative example is Lactobacillus bulgaricus and Streptococcus thermophilus as described above.

[0214] The preparation method includes the following steps:

[0215] S1. Preparation of raw materials: The obtained raw milk is immediately cooled to 4°C and filtered through a 120-mesh filter to obtain the liquid.

[0216] S2. Heating and mixing: Heating the liquid treated by S1 to 75°C, adding 4%wt of white sugar and 1%wt of desalted whey powder, stirring for 8 minutes to fully dissolve the white sugar and desalted whey powder;

[0217] S3. Degassing: The liquid material treated by S2 is degassed in a vacuum degassing tank at a degassing pressure of -0.7 bar.

[0218] S4. Homogenization: The liquid treated in S3 is homogenized by a homogenizer. The homogenization pressure is: 30 bar for the second stage and 170 bar for the first stage.

[0219] S5. Pasteurization: Pasteurize the liquid after S4 treatment at a temperature of 97℃ for 300 seconds.

[0220] S6. Cooling: Cool the liquid material treated by S5 to 40°C;

[0221] S7. Inoculation and Fermentation: Lactobacillus bulgaricus and Streptococcus thermophilus are inoculated into the feed liquid after S6 treatment, with a viable cell ratio of approximately 30:70, resulting in a total viable cell count of 0.6 × 10⁻⁶. 7CFU / g, stirring for 10 min and then standing for fermentation for about 6 h, fermentation temperature 38°C, fermentation termination acidity 80 O T;

[0222] S8. Adding high methoxyl pectin: 5% (w / w) sterile RO water is heated to 70°C, 2‰ high methoxyl pectin is added, and high-speed shearing is performed for 10 min. The formed pectin solution is added to the fermented milk after S7 treatment.

[0223] S9. Demulsification: the material liquid after S8 treatment is subjected to demulsification stirring, stirring speed 30 rpm, stirring time 10 min;

[0224] S10. Homogenization: the fermented milk after S9 treatment is subjected to homogenization, homogenization pressure: secondary pressure 20 bar, primary pressure 200 bar;

[0225] S11. Post-ripening: the material liquid after S10 treatment is immediately cooled to 15°C, stirred for 10 min, and then subjected to post-ripening treatment for 20 h, which is post-ripening;

[0226] S12. The material liquid after S11 treatment is subjected to filling and packaging, and then is the finished product.

[0227] Comparative Example 8: (without two post-ripening, the same as Example 1)

[0228] The composition used in this comparative example is the same as that in Example 1.

[0229] The preparation method comprises the following steps:

[0230] S1. Preparation of raw materials: the raw milk obtained is immediately cooled to 4°C, filtered using a 120-mesh filter screen, and the material liquid is obtained;

[0231] S2. Primary sterilization: the material liquid after S1 treatment is heated to 72°C, maintained for 17 s for primary sterilization treatment, and then cooled to 37°C;

[0232] S3. Enzymolysis: lactase 0.2‰ wt (the added enzyme activity is: 5500 NLU / g) is added to the material liquid after S2 treatment, stirred for 8 min, and then subjected to standing enzymolysis, enzymolysis time 1.2 h, temperature 37°C;

[0233] S4. Heating and mixing: the material liquid after S3 treatment is heated to 75°C, 4% wt of white granulated sugar and 1% wt of desalted whey powder are added, stirred for 8 min to inactivate lactase, and at the same time, the white granulated sugar and desalted whey powder are fully dissolved;

[0234] S5. Degassing: the material liquid after S4 treatment is subjected to degassing treatment by a vacuum degassing tank, degassing pressure -0.7 bar;

[0235] S6. Homogenization: The material liquid treated by S5 is homogenized by a homogenizer, and the homogenization pressure is: secondary pressure 30 bar, primary pressure 170 bar;

[0236] S7. Pasteurization: The material liquid treated by S6 is pasteurized, and the pasteurization temperature is 97℃, and the pasteurization time is 300s;

[0237] S8. Cooling: The material liquid treated by S7 is cooled to 40℃;

[0238] S9. Primary inoculation fermentation: Lactococcus lactis subsp. cremoris, Lactococcus lactis subsp. lactis and Streptococcus thermophilus are inoculated in the material liquid treated by S8, and the inoculation viable bacterial number ratio is about 22:22:56, and the total viable bacterial number is 0.6x10 7 CFU / g, and after stirring for 8 min, the fermentation is placed for 1.2 h, and the fermentation temperature is 40℃;

[0239] S10. Secondary inoculation fermentation: Lactobacillus bulgaricus, Bifidobacterium lactis, Lactobacillus acidophilus, Paracaseicola casei, Lactobacillus rhamnosus and Bifidobacterium infantis are inoculated in the material liquid treated by S9, and the inoculation viable bacterial number ratio is about 18:21:17:17:13:14, and the total viable bacterial number is 0.3x10 8 CFU / g, and after stirring for 10 min, the fermentation is placed for about 6 h, and the fermentation temperature is 38℃, and the fermentation termination acidity is 75 O T;

[0240] S11. Demulsification: The fermented milk treated by S10 is demulsified and stirred, and the stirring speed is 26 rpm, and the stirring time is 4 min;

[0241] S12. Homogenization: The fermented milk treated by S11 is homogenized, and the homogenization pressure is: secondary pressure 3 bar, primary pressure 30 bar;

[0242] S13. Post-ripening: The material liquid treated by S12 is immediately cooled to 6℃, and after stirring for 10 min, the post-ripening treatment is placed for 42 h, which is post-ripening;

[0243] S14. Filling and packaging: The material liquid treated by S13 is immediately cooled to 6℃, and after filling and packaging, it is the finished product.

[0244] Comparative Example 9: (fermentation after adding pectin, using conventional fermentation technology, adding enzyme hydrolysis step)

[0245] The composition used in this comparative example is the previously described Lactobacillus bulgaricus and Streptococcus thermophilus.

[0246] The preparation method comprises the following steps:

[0247] S1. Preparation of raw materials: The raw milk obtained was immediately cooled to 4°C, filtered with a 120-mesh filter screen, and a liquid was obtained;

[0248] S2. Enzymatic hydrolysis: The liquid treated in S1 was heated to 72°C, subjected to a sterilization treatment for 17 s, and then cooled to 37°C;

[0249] S3. Enzymatic hydrolysis: Lactase 0.2‰ wt (enzyme activity added: 5500 NLU / g) was added to the liquid treated in S2, and after stirring for 8 min, static enzymatic hydrolysis was performed, with a hydrolysis time of 1.2 h and a temperature of 37°C, to obtain an enzymatic hydrolysis liquid;

[0250] S4. Temperature increase and mixing: The enzymatic hydrolysis liquid obtained after S3 was heated to 75°C, and white granulated sugar 4% wt and desalted whey powder 1% wt were added, and stirred for 8 min to fully dissolve the white granulated sugar and desalted whey powder;

[0251] S5. Degassing: The liquid treated in S4 was subjected to a degassing treatment by a vacuum degassing tank, with a degassing pressure of -0.7 bar;

[0252] S6. Homogenization: The liquid treated in S5 was subjected to homogenization by a homogenizer, with a homogenization pressure of 30 bar for the second stage and 170 bar for the first stage;

[0253] S7. Pasteurization: The liquid treated in S6 was subjected to pasteurization, with a pasteurization temperature of 97°C and a pasteurization time of 300 s;

[0254] S8. Cooling: The liquid treated in S7 was cooled to 40°C;

[0255] S9. Inoculation and fermentation: Lactobacillus bulgaricus and Streptococcus thermophilus were inoculated into the liquid treated in S8, with a ratio of live bacteria of about 30:70, and a total live bacteria count of 0.6 x 10 7 CFU / g, stirred for 10 min, and then left to ferment for about 6 h, with a fermentation temperature of 38°C and a final fermentation acidity of 80 O T;

[0256] S10. Addition of high methoxyl pectin: 5% (w / w) sterile RO water was heated to 70°C, 2‰ high methoxyl pectin was added, and high-speed shearing was performed for 10 min. The pectin solution formed was added to the fermented milk treated in S9.

[0257] S11. Demulsification: The liquid treated in S10 was subjected to demulsification stirring, with a stirring speed of 30 rpm and a stirring time of 10 min;

[0258] S12. Homogenization: The fermented milk treated in S11 was subjected to homogenization, with a homogenization pressure of 20 bar for the second stage and 200 bar for the first stage;

[0259] S13. Post-ripening: the material liquid treated by S12 is immediately cooled to 15℃, and after stirring for 10 min, it is left to stand for post-ripening treatment for 20 h, which is post-ripening;

[0260] S14. Filling and packaging: the material liquid treated by S13 is filled and packaged, and then it is a finished product.

[0261] Application Example

[0262] Firstly, the products prepared according to the examples and the comparative examples of the present application are stored in a refrigerator at 4℃ for 4 weeks, and the comparison and detection evaluation are carried out in terms of product stability and consumer preference test at the 0th week, the 1st week, the 2nd week, the 3rd week and the 4th week, respectively.

[0263] Detection Method

[0264] 1. Stability detection: after the sample is shaken, 50 g is weighed into a centrifugal tube, centrifugal treatment is carried out at 2000 rpm for 5 min, then the supernatant height is measured by a vernier caliper, the centrifugal precipitate is weighed by an electronic balance, and the precipitation rate is calculated, and the results are shown in Tables 1-2, Figures 2-3 .

[0265] 2. Consumer preference test of the product: the scheme design is carried out according to the Sensory Evaluation of Milk and Dairy Products (Shengqinghai, Light Industry Press, 2009, P160), 200 consumers are selected according to the previous questionnaire survey results, and the nine-point preference scale is used for consumer preference test, and the results are shown in Tables 3-7, Figures 4-8 .

[0266] Secondly, the products prepared according to Example 1 and Comparative Examples 1, 6 and 8 of the present application are detected for volatile flavor substance composition by using a gas chromatograph mass spectrometer (GCMS-QP2020NX; Shimadzu Corporation, Japan) and a DB-WAX capillary column (30 m x 0.25 mm, 0.25 μm; Agilent Technologies, USA), and the detection procedure is as follows: gas phase conditions: the initial temperature is 40℃ and maintained for 3 min, then increased to 170℃ at a rate of 4℃ / min and maintained for 3 min, and then increased to 230℃ at a rate of 10℃ / min and maintained for 3 min. The injection port temperature is 250℃; helium gas with a flow rate of 1 mL / min is used as the carrier gas, and the sample is injected without splitting. Mass spectrometry conditions: the ion source is electron impact, the ionization energy is 70 eV, the ion source temperature is 230℃, the interface temperature is 250℃, and the quadrupole rod temperature is 150℃; the SCAN mode is used for scanning, and the scanning range is 30-450 m / z. The results are shown in Table 8 and Figures 9-12 .

[0267] Table 1 Product stability detection results (supernatant height)

[0268]

[0269]

[0270] Table 2 Product stability test results (precipitation rate)

[0271]

[0272] From Table 1 to Table 2, Figures 2-3 It can be seen that the stability test results of the products prepared according to Examples 1 to 3 are obviously superior to those of Comparative Examples 1 to 6 and 8, and are similar to those of Comparative Examples 7 and 9 (additional pectin as stabilizer). From Comparative Examples 3 and 5, it can be seen that the secondary inoculation fermentation and the inoculation fermentation sequence have a significant influence on stability. In combination with Comparative Examples 1 and 2, it can be seen that the selection of strains also has a certain influence on stability. From Comparative Example 4, it can be seen that the lactase treatment has a significant influence on stability in the scheme of the present application, but in combination with Comparative Example 9, the treatment of lactase has no influence on stability in the conventional fermentation process. The possible reason is that the treatment of lactase and the other steps of the present application synergistically or the combination of the strain combination of the present application, which produces such a significant influence. From Comparative Examples 6 and 8, it can be seen that the post-ripening step has some influence on stability, but not significant.

[0273] Table 3 Consumer preference test results of the product (week 0)

[0274]

[0275]

[0276] Table 4 Consumer preference test results of the product (week 1)

[0277]

[0278] Table 5 Consumer preference test results of the product (week 2)

[0279]

[0280] Table 6 Consumer preference test results of the product (week 3)

[0281]

[0282]

[0283] Table 7 Consumer preference test results of the product (week 4)

[0284]

[0285] From Table 3 to Table 7, Figures 4-8It can be seen that the results of the consumer preference test of the product tracking process prepared according to Examples 1-3 are obviously better than those of Comparative Examples 1-6 and 8 and are similar to those of Comparative Examples 7 and 9, but the number of people who determine the product prepared according to Examples 1-3 as "extremely like" and "very like" is obviously more than that of Comparative Examples 7 and 9.

[0286] Table 8 Main volatile flavor substances of the product and their concentrations

[0287]

[0288]

[0289] Note: ND means not detected

[0290] From Table 8, Figures 9-12 It can be seen that the product prepared according to Example 1 has obviously more main volatile flavor substances than Comparative Examples 1, 6 and 8, and according to the specific analysis, the product prepared according to Example 1 obviously reduces the content of 2,3-butanedione with butter and cake flavors, increases the content of 2-nonanone, acetone, 2-methyl-2-propanol and diisobutyl ketone with fruit flavors, and increases the content of hexanoic acid, pentanoic acid, octanoic acid and acetic acid with cheese flavor, thereby improving the flavor richness and the coordination of the mouthfeel of the product, the secondary ripening process has a significant influence on the flavor substances of the product, and in the prior art, the commonly used ripening process is 4-10℃, and the secondary ripening process used in the present application is 15℃ combined with 6℃, which has a significant improvement compared with the secondary ripening process using a single temperature.

[0291] In summary, the composition containing 7 kinds of probiotics and the preparation method of the drinkable yogurt thereof can provide daily required probiotics, and the product prepared according to the examples has no addition, high system stability, high consumer preference and rich volatile flavor substance composition.

[0292] Although the present application has been disclosed with the preferred embodiments as above, it is not intended to limit the present application, and anyone skilled in the art can make various modifications and modifications without departing from the spirit and scope of the present application, therefore the protection scope of the present application should be defined by the claims.

Claims

1. A method for preparing a drinkable yogurt containing 7 probiotic strains, characterized in that: Includes the following steps: Raw milk is pretreated and sterilized. A bacterial strain composition is added to the feed solution for inoculation and fermentation according to a specified ratio. The resulting fermented milk is then post-treated to obtain drinking yogurt. The pretreatment includes adding lactase, stirring, allowing it to stand for enzymatic hydrolysis, and then inactivating the lactase. The inoculation and fermentation process includes two inoculation fermentations: a first inoculation fermentation, inoculating the feed solution with *Lactococcus lactis* subsp. *fatty acid*, *Lactococcus lactis* subsp. *lactoacidus*, and *Streptococcus thermophilus*, with a viable count ratio of (18-22):(22-27):(51-60); and a second inoculation fermentation, inoculating the feed solution after the first inoculation fermentation with *Propionibacterium brevicaulis*. Fermentation is carried out using Lactobacillus bulgaricus, Bifidobacterium lactis, Lactobacillus acidophilus, Lactobacillus paracasei, Lactobacillus rhamnosus, and Bifidobacterium infantis, wherein the viable count ratio of Lactobacillus bulgaricus, Bifidobacterium lactis, Lactobacillus acidophilus, Lactobacillus paracasei, Lactobacillus rhamnosus, and Bifidobacterium infantis is (16~18):(20~22):(16~18):(16~18):(12~14):(10~20); the post-processing includes cooling the fermented milk and allowing it to stand for post-ripening, wherein the post-ripening includes primary post-ripening and secondary post-ripening, wherein the temperature of the primary post-ripening is 15~20℃ and the time is 15~20h, and the temperature of the secondary post-ripening is 2~6℃ and the time is 20~24h.

2. The method for preparing drinkable yogurt containing 7 kinds of probiotics according to claim 1, characterized in that: The enzymatic hydrolysis involves adding lactase at a rate of 0.1‰ to 0.5‰ wt, stirring for 5 to 10 minutes, hydrolysis for 1 to 1.5 hours, and hydrolysis at a temperature of 35 to 39°C.

3. The method for preparing drinkable yogurt containing 7 kinds of probiotics according to claim 1, characterized in that: The inactivation process specifically involves heating the liquid to 72-77°C and stirring for 5-10 minutes.

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