A combination of fermented milk starter agents with good fermentation characteristics and its application

Abstract

The present invention discloses a fermented milk starter combination with good fermentation characteristics and its application, wherein the starter combination is composed of thermophilic Streptococcus IMAU20229 and Lactobacillus delbrueckii subspecies bulgaricus IMAU20762. The fermented milk starter combination provided by the present invention comprises two new lactic acid bacteria strains, can provide a new fermented milk flavor; has the characteristics of fast fermentation speed and weak post-acidification ability, can improve the production efficiency of fermented milk, and is expected to extend the shelf life of fermented milk; has a good viscoelastic change curve, good fermentation characteristics, and is expected to reduce the use of stabilizers and thickeners in fermented milk.

Description

Technical Field

[0001] The invention relates to the technical field of fermentation agents, in particular to a group of fermented milk fermentation agent combinations with good fermentation characteristics and applications thereof. Background Art

[0002] Fermented dairy products are nutritionally comprehensive and have a unique flavor. They are more easily absorbed and utilized by the human body than fresh cow's milk and / or goat's milk. Domestic and foreign studies have shown that lactic acid bacteria (LAB) can produce a large amount of lactic acid, other organic acids, amino acids, B vitamins and enzymes during the fermentation process, thereby giving fermented milk a variety of prebiotic functions.

[0003] The fermentation process of fermented milk requires the selection of suitable lactic acid bacteria. Commonly used ones are Lactobacillus, Streptococcus lactis, and Lactobacillus lactis. Different lactic acid bacteria have different effects on the fermentation speed, acidity, taste, flavor, nutrition, etc. of milk under different conditions.

[0004] Since fermented milk contains active lactic acid bacteria, it will continue to ferment during storage, which will further increase the acidity and affect the taste and quality of the fermented milk. In addition, manufacturers often add some auxiliary materials to improve the quality and taste of yogurt during the production process of fermented milk. For example, in order to increase the consistency and taste of fermented milk, some manufacturers will add some stabilizers and thickeners. The addition of these auxiliary materials will change the molecular structure and chemical properties of fermented milk, making it more susceptible to bacterial infection and shortening the shelf life.

[0005] Therefore, it is particularly important to actively develop new strains with good fermentation characteristics in order to increase the fermentation speed and nutritional value of fermented milk, enrich and improve the taste and flavor of fermented milk, extend the shelf life of fermented milk, reduce the use of additives, and meet consumers' ever-increasing quality requirements for fermented dairy products. Summary of the invention

[0006] The purpose of the present invention is to provide a group of fermented milk starter combinations with good fermentation characteristics and applications thereof, and to provide a new starter strain combination to increase the fermentation speed and the nutritional value of fermented milk, enrich and improve the taste and flavor of fermented milk, extend the shelf life of fermented milk, reduce the use of additives, and meet consumers' ever-increasing quality requirements for fermented milk products.

[0007] To achieve the above object, the present invention provides a group of fermented milk starter combinations with good fermentation characteristics and applications thereof, wherein the starter combination consists of thermophilic Streptococcus IMAU20229 and Lactobacillus delbrueckii subspecies bulgaricus IMAU20762. Both thermophilic Streptococcus IMAU20229 and Lactobacillus delbrueckii subspecies bulgaricus IMAU20762 were deposited in China Center for Type Culture Collection (CCTC C, address: Wuhan University, Wuhan, China) on July 12, 2023, and the classification names of the deposited strains are Streptococcust hermophilusIMAU20229 and LactobacillusbulgaricusIMAU20762, and the deposit numbers are CCTCCNO: M20231266 and CCTCCNO: M20231267, respectively.

[0008] Preferably, the starter combination can also be compounded with other conventional starter agents to prepare a composite starter agent for fermentation of dairy products. The dosage of each strain in the starter combination can be adjusted while ensuring the smooth progress of the fermentation reaction.

[0009] Preferably, the conventional starter includes one or more of Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus thermophilus, Lactobacillus acidophilus, Bifidobacterium, Lactobacillus casei and Lactobacillus mucosus rhamnosus.

[0010] A group of fermented milk starter combinations with good fermentation characteristics as described above are used in the preparation of fermented dairy products and dairy starter combinations.

[0011] A fermented dairy product prepared from the above starter combination.

[0012] A method for preparing fermented dairy products with the starter combination as described above comprises the following steps: adding the starter combination to sterilized dairy products in a certain proportion, shaking for 30 to 50 seconds, placing the dairy product-starter combination mixed system in a constant temperature incubator, and reacting at a certain temperature for a certain period of time in an oxygen-insulated insulation.

[0013] Preferably, the addition amounts of the thermophilic Streptococcus IMAU20229 and the Lactobacillus delbrueckii subspecies bulgaricus IMAU20762 are 1×10 6 CFU / mL and 1×10 3 CFU / mL; the temperature of the constant temperature incubator is 40-44°C; the insulation time is 6-9h.

[0014] Therefore, the present invention provides a group of fermented milk starter combination with good fermentation characteristics and its application, and its specific technical effects are as follows:

[0015] (1) The starter combination provided by the present invention comprises two new lactic acid bacteria strains, which can provide a completely new fermented milk flavor;

[0016] (2) The starter combination provided by the present invention has the characteristics of fast fermentation speed and weak post-acidification ability, which can improve the production efficiency of fermented milk and is expected to extend the shelf life of fermented milk;

[0017] (3) The starter combination provided by the present invention has a good viscoelastic change curve and good fermentation characteristics, which is expected to reduce the use of stabilizers and thickeners in fermented milk.

[0018] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0020] Figure 1 The results are compared between the viscosity changes of the fermented milk prepared in Example 2 of the present invention and Comparative Example 1 during storage;

[0021] Figure 2 The comparison results of the acidity changes of the fermented milk prepared in Example 2 of the present invention and Comparative Example 1 during storage;

[0022] Figure 3 It is the comparison result of the change of microrheological parameters during the fermentation process of the fermented milk prepared in Example 2 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0024] In order to make the purpose, technical scheme and advantages of the present application clearer, more thorough and more complete, the technical scheme of the present invention is clearly and completely described below through the accompanying drawings and examples. The following detailed descriptions are all descriptions of the embodiments, and are intended to provide further detailed descriptions of the present invention. Unless otherwise specified, all technical terms used in the present invention have the same meaning as those generally understood by those skilled in the art to which the present application belongs.

[0025] The fresh raw milk in the following examples was purchased from Inner Mongolia Mengniu Dairy (Group) Co., Ltd.; the sealed bottles were purchased from Sichuan Shubo (Group) Co., Ltd.; the constant temperature incubator was produced by Shanghai Yiheng Scientific Instrument Co., Ltd., model PH-240; the pH meter was produced by Mettler-Toledo Group, model FE28-CN.

[0026] Embodiment 1

[0027] The activation of Streptococcus thermophilus IMAU20229 and Lactobacillus delbrueckii subspecies bulgaricus IMAU20762 strains is as follows:

[0028] Thermophilus Streptococcus IMAU20229 and Lactobacillus delbrueckii subsp. bulgaricus IMAU20762 were inoculated into M17 liquid medium and MRS liquid medium for first generation activation, respectively, and then cultured at 42°C for 24 hours and then subcultured at 2% of the inoculum amount. In this way, the strains were activated for three generations and used in fermentation experiments.

[0029] Embodiment 2

[0030] The fermented milk is prepared by using a starter combination consisting of thermophilic Streptococcus IMAU20229 and Lactobacillus delbrueckii subspecies bulgaricus IMAU20762, and the method is as follows:

[0031] Fresh milk was pasteurized at 95℃ for 5 min, and 1L of fresh milk was accurately measured and 1×10 9 CFU Streptococcus thermophilus IMAU20229 and 1 × 10 6 CFU Lactobacillus delbrueckii subspecies bulgaricus IMAU20762, after shaking for 30 seconds, the milk-starter mixture system was divided into 10 bottles with sealed lids and covered with sealed lids. These 10 bottles and lids were sterilized at 121°C for 30 minutes before and placed in a clean bench to cool to room temperature. The divided sealed bottles were placed in a 42°C constant temperature incubator for 7.5 hours.

[0032] Embodiment 3

[0033] The fermented milk was prepared using a starter culture of Streptococcus thermophilus IMAU20229 and Lactobacillus delbrueckii subsp. bulgaricus IMAU20762, in the same manner as in Example 2, except that the mixture was shaken for 40 seconds, the temperature of the constant temperature incubator was 40° C., and the incubation time was 9 hours.

[0034] Embodiment 4

[0035] The fermented milk was prepared using a starter culture combination of Streptococcus thermophilus IMAU20229 and Lactobacillus delbrueckii subsp. bulgaricus IMAU20762, and the method was exactly the same as that in Example 2, except that the mixture was shaken for 50 seconds, the constant temperature incubator was set at 44° C., and the incubation time was 6 hours.

[0036] Embodiment 5

[0037] The fermented milk was prepared by using a starter culture composed of Streptococcus thermophilus IMAU20229 and Lactobacillus delbrueckii subspecies bulgaricus IMAU20762. The method was exactly the same as that in Example 2, except that the starter culture also contained 1×10 9 CFU of Lactobacillus acidophilus.

[0038] Embodiment 6

[0039] The fermented milk was prepared by using a starter culture composed of Streptococcus thermophilus IMAU20229 and Lactobacillus delbrueckii subspecies bulgaricus IMAU20762. The method was exactly the same as that in Example 2, except that the starter culture also contained 1×10 10 CFU of Bifidobacterium.

[0040] Embodiment 7

[0041] The fermented milk was prepared by using a starter culture composed of Streptococcus thermophilus IMAU20229 and Lactobacillus delbrueckii subspecies bulgaricus IMAU20762. The method was exactly the same as that in Example 2, except that the starter culture also contained 1×10 9 CFU of Lactobacillus casei.

[0042] Embodiment 8

[0043] The fermented milk was prepared by using a starter culture composed of Streptococcus thermophilus IMAU20229 and Lactobacillus delbrueckii subspecies bulgaricus IMAU20762. The method was exactly the same as that in Example 2, except that the starter culture also contained 1×10 5 CFU of Lactobacillus mucilaginosus.

[0044] Comparative Example 1

[0045] Fermented milk was prepared using a combination of starter cultures commonly used on the market. The direct-injection starter YF-L922 (produced by Chr. Hansen, Denmark) was selected. The preparation method was exactly the same as in Example 2, except that the bacteria contained therein were Lactobacillus bulgaricus and Streptococcus thermophilus, which were inoculated according to the mass ratio, and the inoculation amount was 0.03‰.

[0046] Effect Example 1

[0047] The viscosity-producing ability of the starter combination was investigated by:

[0048] When the pH value of the fermented milk was 4.6, it was recorded as the fermentation end point. The viscosity of the fermented milk prepared in Comparative Example 1 and Example 2 was measured at 1d, 7d, 14d and 21d after the fermentation end point using a Brookfield DV-2T viscometer. The conditions were as follows: the fermented milk was placed at room temperature (25°C) for 15min before measurement, and rotor No. 4 was used for measurement, with a torque of 64%, a time of 30s, and a speed of 100r / min. Each sample was measured three times in parallel. The results are shown in Table 1. Figure 1 .

[0049] Effect Example 2

[0050] The post-acidification ability of the fermentation agent combination was investigated by:

[0051] The fermented milk prepared in Example 2 and Comparative Example 1 at the end of fermentation was placed at 4°C for 12 hours. The acidity of the fermented milk prepared in Example 2 and Comparative Example 1 was measured on the 1st, 7th, 14th and 21st day of post-ripening. The fermented milk was stored at 4°C during non-measurement time. The results are shown in Table 1. Figure 2 .

[0052] Effect Example 3

[0053] The viscoelastic changes of fermented milk were investigated as follows:

[0054] An optical microrheometer was used to measure the rheological properties of the samples during the fermentation process. Microrheology can study the rheological properties of samples without damaging the samples, and can indicate the viscoelastic changes of the samples by tracking the movement of particles in the system. In the pre-sterilized matching microrheometer sample bottles, add the milk inoculated with the fermentation agent according to Example 2 and Comparative Example 1, respectively. Keep the walls of the sample bottles clean to prevent optical errors. Set the temperature of the rheometer to 42°C in advance and place the sample in the measuring tank. Measure every 5 minutes until the end of fermentation. According to the MSD curve, four factors reflecting the structural characteristics of the sample can be calculated, namely the solid-liquid balance factor (SLB), viscosity factor (Macroscopic viscosity index, MVI), elasticity factor (Elastic index, EI) and flowability factor (Fluidity index, FI). The results are shown in Table 1. Figure 3 , where (a) is the comparison result of the change of elasticity factor during yogurt fermentation; (b) is the comparison result of the change of solid-liquid equilibrium factor during yogurt fermentation; (c) is the comparison result of the change of flow factor during yogurt fermentation; (d) is the comparison result of the change of viscosity factor during yogurt fermentation.

[0055] Effect Example 4

[0056] The textural characteristics of fermented milk were investigated as follows:

[0057] The changes in consistency, firmness, viscosity index and cohesiveness of the fermented milk prepared in Example 2 and Comparative Example 1 during storage were measured using a TA.XTplus texture analyzer on the 1st, 7th, 14th and 21st days after the end of fermentation.

[0058] The sample to be tested was subjected to compression cycle test using a 5kg load cell. The probe was A / BE, the penetration depth was 30mm, the speed was fixed at 1mm / s, the sample to be tested was required to reach room temperature before the test, and each group was parallel to 3. The measurement results are shown in Table 1.

[0059] Table 1

[0060]

[0061] Results Analysis

[0062] Depend on Figure 1 It can be seen that during the storage of fermented milk at 4°C for 21 days, the viscosity trends of the fermented milk prepared in Example 2 and Comparative Example 1 both first increased and then decreased. Overall, the viscosity of Example 2 of the present invention was lower than that of Comparative Example 1, but it showed a good low viscosity characteristic, indicating that the starter combination we screened had a good viscosity characteristic.

[0063] Depend on Figure 2 It can be seen that after the fermented milk was stored at 4°C for 21 days, the pH of the fermented milk prepared in Example 2 of the present invention was 4.18, and the pH of the fermented milk prepared in Comparative Example 1 was 4.21. After storage for 21 days, the pH value of the starter used in the present invention was close to that of the commercial starter (P>0.05), indicating that the starter combination provided by the present invention has the characteristic of weak post-acidification ability.

[0064] Depend on Figure 3 It can be seen that the changes in microrheology-related parameters during the fermentation process show that Comparative Example 1 reaches the gel point first and the fermentation endpoint first, which is faster than Example 2.

[0065] EI reflects the degree of change in elasticity over time. It is calculated based on the inverse of the platform height in the MSD curve. It describes the elastic characteristics of the sample and can quickly and easily characterize the elastic modulus of a sample. The height of the MSD platform can reflect the elastic characteristics of the product. The larger the EI value, the stronger the elasticity of the gel. EI is related to the properties of the gel. Figure 3 The EI value of part (a) is greater than that of Example 1 and greater than that of Example 2, indicating that the gel elasticity of Example 2 is slightly lower than that of Example 1, but overall, it is very close to that of the commercial control group (Comparative Example 1).

[0066] MVI reflects the viscosity characteristics of the sample at the micrometer scale. It is calculated by the slope of the last part of MSD. MVI is proportional to the macroscopic viscosity of the sample and therefore directly reflects the change in the viscosity of fermented milk. Figure 3 It can be seen from part (d) that at the end of fermentation, the MVI value of Example 2 is close to that of the commercial control group (Comparative Example 1), indicating that the viscosity characteristics of the two groups are similar at this time, and the starter combination provided by the present invention exhibits better viscosity characteristics.

[0067] At the same time, it can be seen from Table 1 that the fermented milk prepared in Example 2 exhibits better texture characteristics.

[0068] In summary, the starter combination IMAU20229+IMAU20762 provided by the present invention shows good viscosity characteristics and weak post-acidification characteristics, which are very close to the commercial starter group and show good fermentation characteristics as a whole.

[0069] Therefore, a group of fermented milk starter combinations with good fermentation characteristics provided by the present invention comprises two new lactic acid bacteria strains, which can provide a new fermented milk flavor; it has the characteristics of fast fermentation speed and weak post-acidification ability, which can improve the production efficiency of fermented milk and is expected to extend the shelf life of fermented milk; it has a good viscoelastic change curve and good fermentation characteristics, which is expected to reduce the use of stabilizers and thickeners in fermented milk.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A fermented milk starter combination, characterized in that: The starter combination consists of thermophilic Streptococcus IMAU20229 and Lactobacillus delbrueckii subspecies bulgaricus IMAU20762. Both thermophilic Streptococcus IMAU20229 and Lactobacillus delbrueckii subspecies bulgaricus IMAU20762 were deposited in the China Center for Type Culture Collection (CCTCC) on July 12, 2023, with the deposit numbers being CCTCC M 20231266 and CCTCC M 20231267, respectively.

2. The fermented milk starter culture combination according to claim 1, characterized in that: The starter combination is also compounded with other conventional starters to prepare a composite starter for fermentation of dairy products. The dosage of each strain in the starter combination is adjusted under the premise of ensuring the smooth progress of the fermentation reaction.

3. The fermented milk starter culture combination according to claim 2, characterized in that: The conventional fermentation agent includes one or more of Lactobacillus delbrueckii subspecies bulgaricus, Streptococcus thermophilus, Lactobacillus acidophilus, Bifidobacterium, Lactobacillus casei and Lactobacillus mucosa rhamnosus.

4. Use of a fermented milk starter combination as claimed in any one of claims 1 to 3 in the preparation of fermented dairy products and dairy starter.

5. A fermented dairy product prepared by the starter combination according to any one of claims 1 to 3.

6. A method for preparing a fermented dairy product using the starter combination according to any one of claims 1 to 3, characterized in that: The method comprises the following steps: adding the starter combination to the sterilized dairy product, shaking and oscillating for 30 to 50 seconds, placing the dairy product-starter combination mixed system in a constant temperature incubator at 40 to 44° C. to insulate the mixture from oxygen for 6 to 9 hours, wherein the addition amounts of thermophilic Streptococcus IMAU20229 and Lactobacillus delbrueckii subspecies bulgaricus IMAU20762 in the starter combination are 1×10 6 CFU / mL and 1×10 3 CFU / mL.

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