Low post-acid direct vat set yogurt starter and preparation method

Abstract

The application belongs to the field of food fermentation, and particularly relates to a low post-acid direct-vat yogurt starter and a preparation method. The application provides a low post-acid direct-vat yogurt starter, which comprises Streptococcus thermophilus NJ21 and Lactobacillus helveticus LH-08B; the preservation number of the Streptococcus thermophilus NJ21 is CCTCC NO.M2014250, and the preservation number of the Lactobacillus helveticus LH-08B is CCTCC NO.M2019013. The two bacteria are compounded according to a certain proportion to prepare the direct-vat yogurt starter, which is used for preparing yogurt as a starter, has a fast fermentation speed, and has weak post-acid and good quality.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of food fermentation, and particularly relates to a low-post-acid direct-vat yogurt starter and a preparation method. BACKGROUND

[0002] Yogurt is a kind of sweet and sour milk drink, which is prepared by adding beneficial bacteria (starter) into milk after pasteurization, and then cooling and filling. Yogurt products on the market are mostly of the coagulation type, stirring type and fruit type with the addition of various fruit juice and jam. The longer yogurt is stored, the more sour the taste will be, but the activity of lactic acid bacteria will decrease. This phenomenon is yogurt post-acidification, which refers to the phenomenon that the residual lactic acid bacteria in yogurt continue to produce acid using lactose during storage and transportation, thus deteriorating the taste of yogurt. Yogurt post-acidification is the slow fermentation of residual lactose by bacteria during storage, transportation and sales, thus continuously producing lactic acid and increasing the acidity of yogurt. When the accumulation reaches a certain level, the over-acid taste makes consumers unacceptable, thus losing the value as a commodity.

[0003] In view of this problem, many scholars have proposed different measures to inhibit post-acidification, including cold storage, use of additives, heat treatment and change of the composition of yogurt starter. The two methods of rapid cooling after fermentation and low-temperature storage have been widely recognized, which to some extent solves the problem of yogurt post-acidification in actual production. Rapid cooling after fermentation is to inhibit the growth of strains, rapidly reduce the activity and acid production, thus slowing down the post-acidification of yogurt. Low-temperature storage is the same, which is one of the most key factors to ensure the weak post-acidification of yogurt. However, these measures only change the production process, and cannot solve the problem of post-acidification from the source and increase the production cost.

[0004] Chinese patent CN 115948290 A relates to a normal temperature weak post-acidification Lactobacillus fermentum grx501 and its application. Lactobacillus fermentum grx501 was preserved in China General Microbiological Culture Collection Center on July 20, 2022, and was classified and named as Lactobacillus fermentum, with the preservation number being CGMCC NO. 25349. The Lactobacillus fermentum grx501 is isolated from traditional fermented pickles. Through the present application, Lactobacillus with weak growth ability in milk environment and storage resistance is screened from non-dairy product environment (pickle). After identification of the strain, it is added to sterilized yogurt, so that the product still has weak post-acidification under normal temperature conditions on the premise of maintaining a high number of viable bacteria. After sterilizing the yogurt, the Lactobacillus fermentum grx501 is added, and the sample pH is reduced by 0.02-4.08 and 0.03-4.10 respectively under storage conditions of 4℃ and 25℃ for 21d, and the acidity is increased by 18.98°T-103.19°T and 20.33°T-103.06°T respectively. It still has weak post-acidification under normal temperature. It can be applied to the production of normal temperature weak post-acidification live type fermented milk.

[0005] Chinese patent CN 116694539 A discloses a direct injection type starter Lactobacillus plantarum J26 and its preparation method and application. The preparation method comprises the following steps: activating Lactobacillus plantarum J26, inoculating it into 100mL optimized carbon and nitrogen source medium at an inoculation amount of 4%, and performing high-density fermentation for 24h at 33℃ and pH 5.6 using a 5L fermenter, with constant-speed feeding at 4-24h and a feeding rate of 15mL / h, and the feeding medium is optimized carbon source: optimized nitrogen source = 5:2. After high-density fermentation is completed, the bacterial liquid is harvested and freeze-dried to obtain freeze-dried bacterial powder. The combination of the compound prebiotic and the direct injection type starter Lactobacillus plantarum J26 can promote the fermentation of soy milk, significantly increase the viable count of fermented soy milk, and slow down the post-acidification of fermented milk.

[0006] In order to meet the increasing quality needs of yogurt and dairy products, it is necessary to develop more low-post-acid direct injection type yogurt starters, simplify the yogurt fermentation steps, improve the production efficiency, control the production cost, and make the yogurt taste better and the probiotic content higher. SUMMARY

[0007] In order to solve the above problems, the present application provides a low-post-acid direct injection type yogurt starter, which comprises Streptococcus thermophilus NJ21 and Lactobacillus helveticus LH-08B, and the viable count ratio of the Streptococcus thermophilus NJ21 and the Lactobacillus helveticus LH-08B is 5-14:15-6.

[0008] In one aspect, the present application provides a low post-acid direct vat yogurt starter, comprising Streptococcus thermophilus NJ21 and Lactobacillus helveticus LH-08B; the Streptococcus thermophilus NJ21 has a preservation number of CCTCC NO. M2014250; and the Lactobacillus helveticus LH-08B has a preservation number of CCTCC NO. M2019013.

[0009] Specifically, the ratio of the viable cell number of the Streptococcus thermophilus NJ21 to the Lactobacillus helveticus LH-08B is 5-14:15-6.

[0010] In one embodiment, the ratio of the viable cell number of the Streptococcus thermophilus NJ21 to the Lactobacillus helveticus LH-08B is 5:15.

[0011] In another embodiment, the ratio of the viable cell number of the Streptococcus thermophilus NJ21 to the Lactobacillus helveticus LH-08B is 1:1.

[0012] In another embodiment, the ratio of the viable cell number of the Streptococcus thermophilus NJ21 to the Lactobacillus helveticus LH-08B is 14:6.

[0013] Specifically, the total number of the viable cells of the Streptococcus thermophilus NJ21 and the Lactobacillus helveticus LH-08B added can be 10 5 -10 6 cfu / mL.

[0014] In another aspect, the present application provides a method for preparing the low post-acid direct vat yogurt starter as described above, comprising the following steps:

[0015] (1) culturing the Streptococcus thermophilus NJ21 and the Lactobacillus helveticus LH-08B respectively to obtain seed liquids;

[0016] (2) inoculating the seed liquids of step (2) into a fermentation tank respectively at an inoculation amount of 5-10% to obtain fermentation liquids;

[0017] (3) centrifuging the fermentation liquids of step (2) respectively to obtain bacterial muds;

[0018] (4) mixing the bacterial muds of step (3) with freeze-drying protectants respectively, freezing and drying to obtain freeze-dried powders;

[0019] (5) mixing the freeze-dried powders of step (4) to obtain the low post-acid direct vat yogurt starter.

[0020] Specifically, the freeze-drying protectants of step (3) are: trehalose 5-15%, skim milk powder 10-15%, lactose 4-8%, inulin 4-8%, glycerol 2-5%, mannose 2-5%, sodium glutamate 3-6%, polyethylene glycol 1-3%, and the balance is water.

[0021] Preferably, the freeze-drying protectant of step (3) is: trehalose 10%, skimmed milk powder 15%, lactose 4%, inulin 6%, glycerol 2%, mannose 5%, sodium glutamate 6%, polyethylene glycol 3%, and the balance is water.

[0022] Specifically, the slurry of step (3) is mixed with the protectant solution at a mass ratio of 1:3-1:5.

[0023] Specifically, the freeze-dried powder of step (4) is mixed at a ratio of 5-14:15-6 of the viable cell number of Streptococcus thermophilus NJ21 and Lactobacillus helveticus LH-08B.

[0024] In one embodiment, the viable cell number ratio of Streptococcus thermophilus NJ21 and Lactobacillus helveticus LH-08B is 5:15.

[0025] In another embodiment, the viable cell number ratio of Streptococcus thermophilus NJ21 and Lactobacillus helveticus LH-08B is 1:1.

[0026] In another embodiment, the viable cell number ratio of Streptococcus thermophilus NJ21 and Lactobacillus helveticus LH-08B is 14:6.

[0027] In another aspect, the present application provides a yogurt making method, comprising using the low post-acid direct-vat yogurt starter as described above.

[0028] Specifically, the total number of added viable cells of the low post-acid direct-vat yogurt starter is 10 5 -10 6 cfu / mL.

[0029] Specifically, the fermentation temperature is 35-40℃, and the fermentation time is 8-15h.

[0030] Preferably, the fermentation temperature is 37℃, and the fermentation time is 10h.

[0031] Specifically, it further comprises a fermentation base, a sweetener and / or a stabilizer.

[0032] Specifically, the sweetener includes but is not limited to one or more of white granulated sugar B, glucose, fructose, fructose-glucose syrup, erythritol, mannitol, maltitol, xylitol, isomaltitol, isomaltulose, lactitol, sorbitol, galactooligosaccharide, isomaltooligosaccharide, polydextrose, fructooligosaccharide, xylooligosaccharide, soybean oligosaccharide, aspartame, acesulfame, sucralose, steviol glycoside, monk fruit extract and thaumatin.

[0033] Specifically, the stabilizer includes but is not limited to one or more of starch, pectin, soybean polysaccharide, gelatin and agar, etc.

[0034] In yet another aspect, the present application provides use of the aforementioned low post-acid direct vat yogurt starter in the production of fermented dairy products.

[0035] Specifically, the fermented dairy products include, but are not limited to, soy milk, normal-temperature yogurt, low-temperature yogurt, stirred yogurt, set yogurt, drinkable yogurt, cheese or lactic acid bacteria beverage.

[0036] Technical effects achieved by the present application:

[0037] (1) High number of viable lactic acid bacteria in yogurt, with a viable count of 10 6 or more after 21 days of refrigeration.

[0038] (2) Weak post-acidification, the direct vat yogurt starter of the present application can effectively inhibit post-acidification of yogurt, so that the acidity of yogurt does not change much within 21 days of refrigeration, and is always maintained within 119 °T. DETAILED DESCRIPTION

[0039] The present application will be further described below in conjunction with specific examples, which are not intended to limit the present application, but merely serve to illustrate the present application. Unless otherwise specified, the experimental methods used in the following examples are in accordance with conventional conditions. Unless otherwise specified, the materials, reagents, etc. used in the following examples can be obtained from commercial sources.

[0040] As used herein, the terms "comprises" or "comprising" means "including, but not limited to". This term is intended to be open-ended, to designate any stated feature, element, integer, step, or component, but does not foreclose the addition of one or more other features, elements, integers, steps, components, or groups thereof. Therefore, the term "comprising" includes the more restrictive terms "consisting of" and "consisting essentially of". In one embodiment, the term "comprising" as used throughout the application, and in particular in the claims, can be replaced by the term "consisting of".

[0041] As used herein, the terms "optional", "any", "any" or "any" mean that the event or environment described later can but does not necessarily occur, and the description includes both cases where the event or environment occurs or does not occur. For example, "optionally comprising an antibody heavy chain variable region" means that the antibody heavy chain variable region of a specific sequence can but does not necessarily exist.

[0042] As used herein, the term "and / or" should be understood to mean any one of the options or a combination of any two or more of the options.

[0043] Example 1

[0044] 1.1 Strains

[0045] Streptococcus thermophilus NJ21, with the preservation number of CCTCC NO. M2014250;

[0046] Lactobacillus helveticus LH-08B, with the preservation number of CCTCC NO. M2019013;

[0047] Streptococcus thermophilus JMCC0033, with the preservation number of CGMCC NO. 22560;

[0048] Lactobacillus helveticus CCFM1034, with the preservation number of GDMCC No. 60451.

[0049] 1.2 Preparation of the direct-vat yogurt starter

[0050] (1) Cultivation of the strains. NJ21 and LH-08B were inoculated into liquid culture medium in a triangular flask respectively for cultivation at 35-40°C for 24-48h to obtain seed liquid, which was then inoculated into a fermentation tank at an inoculation amount of 5-10% for fermentation cultivation at 35-40°C for 24-48h.

[0051] The formula of the Streptococcus thermophilus culture medium is as follows: soybean peptone 5.0 g / L, proteose peptone 2.5 g / L, casein peptone 2.5 g / L, yeast extract 2.5 g / L, beef extract 5.0 g / L, lactose 5.0 g / L, sodium ascorbate 0.5 g / L, sodium B-glycerophosphate 19.0 g / L, magnesium sulfate 0.25 g / L, and pH 6.3.

[0052] The formula of the Lactobacillus helveticus culture medium is as follows: casein peptone 10 g / L, yeast extract 5 g / L, beef extract 10 g / L, glucose 20 g / L, diamine citrate 2 g / L, potassium phosphate dibasic 2 g / L, sodium acetate 5 g / L, MgSO4·7H2O 0.58 g / L, MnSO4·4H2O 0.25 g / L, Tween-80 1 mL / L, L-cysteine 0.5 g / L, and pH 7.0.

[0053] (2) Preparation of the freeze-dried powder. The fermentation liquid obtained in step (1) was centrifuged to obtain bacterial slurry; the bacterial slurry was mixed with freeze-drying protectant at a ratio of 1:1 (w / w) to obtain freeze-dried powder of NJ21 and LH-08B, and the viable cell count of each was detected.

[0054] The formula of the freeze-drying protectant is as follows: trehalose 10%, skimmed milk powder 15%, lactose 4%, inulin 6%, glycerol 2%, mannose 5%, sodium glutamate 6%, and polyethylene glycol 3%, with the balance being water.

[0055] (3) Preparation of the direct vat set yogurt starter. The two freeze-dried powders of step (2) were mixed in proportion, with the ratio of viable bacteria of NJ21 and LH-08B being 25:75.

[0056] 1.3 Yogurt fermentation process

[0057] Fresh milk was heated and sterilized at 95°C for 20 min or high-temperature heat sterilized at 140°C for 2 s, cooled to 30°C, and the direct vat set yogurt starter was added at an addition amount of 10 5 -10 6 cfu / mL (preferably 10 6 cfu / mL), fermented at 37°C for 8-15 h, and the fermentation was terminated when the pH reached 4.4. The fermented yogurt was refrigerated at 4°C.

[0058] Example 2

[0059] The difference from Example 1 is that the total number of viable bacteria of NJ21 and LH-08B is in the ratio of 50:50.

[0060] Example 3

[0061] The difference from Example 1 is that the total number of viable bacteria of NJ21 and LH-08B is in the ratio of 70:30.

[0062] Comparative Example 1

[0063] The difference from Example 1 is that NJ21 is replaced by JMCC0033.

[0064] Comparative Example 2

[0065] The difference from Example 1 is that LH-08B is replaced by CCFM1034.

[0066] Comparative Example 3

[0067] The difference from Example 1 is that only NJ21 freeze-dried powder is used.

[0068] Comparative Example 4

[0069] The difference from Example 1 is that only LH-08B freeze-dried powder is used.

[0070] Example 5 Evaluation of the direct vat set yogurt starter for preparing yogurt

[0071] 5.1 Total number of viable bacteria of lactic acid bacteria in yogurt

[0072] The total number of viable bacteria of lactic acid bacteria in the yogurt of Examples 1-4 and Comparative Examples 1-4 was detected according to GB 4789.35-2010 Food Microbiological Examination Lactic Acid Bacteria Examination Standard, and the detection results are shown in Table 1.

[0073] Table 1

[0074]

[0075]

[0076] From Table 1, the total number of viable lactic acid bacteria of Examples 1-4 still maintained 10 6 The above meets the provisions of the national standard GB19302-2010; the total number of viable lactic acid bacteria of Comparative Examples 1-4 after 21d is lower than one order of magnitude of the national standard.

[0077] 5.2 Yogurt post-acidification detection

[0078] The yogurt of Examples 1-4 and Comparative Examples 1-4 was stored at 4℃ for 21d, and the change of acidity was recorded. The detection results are shown in Table 2.

[0079] Table 2

[0080]

[0081] From Table 2, the change of acidity of Examples 1-4 within 21d of refrigeration is not large, and is always maintained within 119°T, so that the yogurt maintains good taste, which indicates that the viable bacteria ratio of Streptococcus thermophilus NJ21 and Lactobacillus helveticus LH-08B in the examples can effectively inhibit the post-acidification phenomenon of yogurt when used for yogurt fermentation, significantly improve the shelf life and sensory characteristics of yogurt products, and improve the quality of yogurt products.

Claims

1. A low post-acid direct vat set yogurt starter, characterized in that, Streptococcus thermophilus NJ21, Lactobacillus helveticus LH-08B and a freeze-drying protective agent; the Streptococcus thermophilus NJ21 has a preservation number of CCTCC NO. M2014250, and the Lactobacillus helveticus LH-08B has a preservation number of CCTCC NO. M2019013; The live bacteria number ratio of the Streptococcus thermophilus NJ21 and the Lactobacillus helveticus LH-08B is 5-14:15-6. The freeze-drying protective agent is: 5-15% trehalose, 10-15% skimmed milk powder, 4-8% lactose, 4-8% inulin, 2-5% glycerol, 2-5% mannose, 3-6% sodium glutamate, 1-3% polyethylene glycol, and the rest is water.

2. The low-post acid direct vat acid yogurt starter according to claim 1, characterized in that, The live bacteria number ratio of the Streptococcus thermophilus NJ21 and the Lactobacillus helveticus LH-08B is 5:

15.

3. The low-post acid direct vat acid yogurt starter according to claim 1, characterized in that, The live bacteria number ratio of the Streptococcus thermophilus NJ21 and the Lactobacillus helveticus LH-08B is 1:

1.

4. The low-post acid direct vat acid yogurt starter according to claim 1, characterized in that, The live bacteria number ratio of the Streptococcus thermophilus NJ21 and the Lactobacillus helveticus LH-08B is 14:

6.

5. A method for preparing a low-postacid direct vat starter according to any one of claims 1 to 4, characterized in that, The method comprises the following steps: (1) culturing the Streptococcus thermophilus NJ21 and the Lactobacillus helveticus LH-08B respectively to obtain seed liquids; (2) inoculating the seed liquids of step (1) into a fermentation tank respectively at an inoculation amount of 5-10% to obtain fermentation liquids; (3) centrifuging the fermentation liquids of step (2) to obtain bacterial muds; (4) mixing the bacterial muds of step (3) with a freeze-drying protective agent respectively, freezing and drying to obtain freeze-dried powders; (5) mixing the freeze-dried powders of step (4) to obtain a low-post-acid direct-injection yogurt starter.

6. The method of claim 5, wherein, The bacterial mud of step (3) is mixed with the freeze-drying protective agent at a mass ratio of 1:3-1:

5.

7. A method of making a yogurt, characterized in that, The method comprises using the low-post-acid direct-injection yogurt starter of any one of claims 1-4.

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