Alcohol-free kefir fermented milk and preparation method thereof

Abstract

The invention relates to the technical field of food, in particular to alcohol-free kefir fermented milk and a preparation method thereof.Based on the total weight of the kefir fermented milk, the kefir fermented milk is prepared from, by mass, 7%-15% of sweetening agents, 0%-5% of concentrated lemon juice, 0.01%-0.015% of compound lactic acid bacteria and the balance raw milk, the compound lactic acid bacteria contain leuconostoc mesenteroides subsp. Mesenteroides, the mass percentage of protein in the prepared fermented milk is 2.6-3.0%, the mass percentage of fat is 2.8-3.2%, the pH value is 4.2-4.5, and the acidity is 80-110 degree T.

Description

Technical Field

[0001] This invention relates to the field of food technology, and in particular to an alcohol-free kefir fermented milk and its preparation method. Background Technology

[0002] Kefir is a traditional fermented milk beverage made from milk fermented with kefir grains (a complex colony of lactic acid bacteria and yeast). It is known for its rich microbial diversity, unique flavor, and potential health benefits. Typically, kefir grains contain mesophilic fermenting lactic acid bacteria and yeast, which work synergistically. The yeasts are often Kluyveromyces or Candida, and their fermentation produces lactic acid and ethanol, giving the product an alcoholic flavor. Therefore, traditional kefir often contains trace amounts of alcohol.

[0003] While traditional kefir has a unique flavor and health benefits, its inherent alcohol content limits its widespread appeal to certain consumer groups. For example, even trace amounts of alcohol can be a barrier for children, pregnant women, drivers, and consumers who are sensitive to alcohol or require strict abstinence. Furthermore, food labeling regulations in many countries and regions require alcoholic beverages to be labeled, putting it at a disadvantage in the modern health food market that prioritizes "clean labels" and "alcohol-free" concepts.

[0004] Currently, in order to reduce the alcohol content in kefir, existing technologies typically employ the following approaches: screening or domesticating yeast strains that produce low alcohol, optimizing fermentation processes (such as controlling temperature and time), and physical dealcoholization treatment. However, these approaches are time-consuming and may come at the cost of sacrificing the unique yeast flavor of kefir (such as ester aroma and microbubble texture).

[0005] Therefore, there is an urgent need to develop a kefir fermented milk that is alcohol-free, has a rich milky flavor, strong effervescence, and no added stabilizers. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide an alcohol-free kefir fermented milk and its preparation method, so as to solve the problems in the prior art.

[0007] To achieve the above and other related objectives, the present invention first provides an alcohol-free kefir fermented milk, which, based on the total weight of the kefir fermented milk, comprises the following raw material components in the following mass percentages: sweetener 7%–15%, concentrated lemon juice 0%–5%, compound lactic acid bacteria 0.01%–0.015%, and the balance being raw milk, wherein the compound lactic acid bacteria includes *Enteromorpha moniliformis* subsp. *moniliformis*.

[0008] This invention also provides a method for preparing alcohol-free kefir fermented milk, the method comprising the following steps:

[0009] 1) Mix the sweetener with raw milk to obtain the base material;

[0010] 2) Homogenize the substrate obtained in step 1), sterilize and cool it, and then inoculate it with compound lactic acid bacteria for fermentation;

[0011] 3) After fermentation, the milk is broken and aseptically filled to obtain the kefir fermented milk.

[0012] As described above, the alcohol-free kefir fermented milk and its preparation method of the present invention have the following beneficial effects:

[0013] The fermented milk prepared by this invention meets the requirements of the national food safety standards for flavored fermented milk. It is fermented with a special compound fermenting agent (compound lactic acid bacteria), has a strong kefir characteristic flavor, a rich milky aroma and a refreshing taste. Without the addition of external stabilizers, the system is stable, with no obvious stratification during the shelf life. The preparation process is similar to the traditional fermentation process for fermented milk, making it suitable for large-scale production in dairy factories.

[0014] The fermented milk obtained has a protein content of 2.6-3.0%, a fat content of 2.8-3.2%, a pH of 4.2-4.5, and an acidity of 80-110°T. Detailed Implementation

[0015] This invention uses Leuconostoc mesenteroides subsp. mesenteroides to replace traditional yeast fermentation, and the resulting kefir fermented milk has a strong characteristic flavor and a stable system without the addition of flavorings or external stabilizers.

[0016] The present invention first provides an alcohol-free kefir fermented milk, which, based on the total weight of the kefir fermented milk, comprises the following raw material components by mass percentage: sweetener 7% to 15%, concentrated lemon juice 0% to 5%, compound lactic acid bacteria 0.01% to 0.015%, and the balance being raw milk, wherein the compound lactic acid bacteria includes Enteromorpha subsp. melioides.

[0017] In some embodiments of the present invention, the sweetener is white sugar.

[0018] In some embodiments of the present invention, the mass percentage of the sweetener is selected from any of the following ranges: 7%–8%, 8%–9%, ​​9%–10%, 10%–11%, 11%–12%, 12%–13%, 13%–14%, and 14%–15%.

[0019] In some embodiments of the present invention, the concentration ratio of the concentrated lemon juice is 5 to 10 times. The concentration ratio of the concentrated lemon juice is selected from any of the following ranges: 5 to 6 times, 6 to 7 times, 7 to 8 times, 8 to 9 times, and 9 to 10 times.

[0020] In a preferred embodiment of the present invention, the concentrated lemon juice is concentrated 8 times.

[0021] In some embodiments of the present invention, the mass percentage of the concentrated lemon juice is selected from any of the following ranges: 0% to 0.5%, 0.5% to 1%, 1% to 1.5%, 1.5% to 2%, 2% to 2.5%, 2.5% to 3%, 3% to 3.5%, 3.5% to 4%, 4% to 4.5%, and 4.5% to 5%.

[0022] In one specific embodiment of the present invention, the concentrated lemon juice has a mass percentage of 0%, meaning that the kefir fermented milk does not contain concentrated lemon juice. In another specific embodiment of the present invention, the concentrated lemon juice has a mass percentage of 5%.

[0023] In some embodiments of the present invention, the proportion of *Enterobacterium moniliforme* subsp. *moniliforme* is 15% to 25% based on the total number of *Lactobacillus* in the complex. The proportion of *Enterobacterium moniliforme* subsp. *moniliforme* based on the total number of *Lactobacillus* in the complex is selected from any of the following ranges: 15%–16%, 16%–17%, 17%–18%, 18%–19%, 19%–20%, 20%–21%, 21%–22%, 22%–23%, 23%–24%, and 24%–25%.

[0024] In one specific embodiment of the present invention, based on the total number of compound lactic acid bacteria, the proportion of *Enteromorpha stenosalis* subsp. *enterosalis* is 16.7%, that is, the ratio of *Enteromorpha stenosalis* subsp. *enterosalis* to the other lactic acid bacteria is 1:5. In another specific embodiment of the present invention, based on the total number of compound lactic acid bacteria, the proportion of *Enteromorpha stenosalis* subsp. *enterosalis* is 25%, that is, the ratio of *Enteromorpha stenosalis* subsp. *enterosalis* to the other lactic acid bacteria is 1:3.

[0025] In some embodiments of the present invention, the compound lactic acid bacteria further includes one or more of the following: Streptococcus thermophilus, Lactobacillus acidophilus, Lactobacillus paracasei, Lactobacillus bulgaricus, Lactobacillus delbrueckii subsp. bulgaricus, Lactococcus lactis subsp. lactis, Lactococcus lactis subsp. lactis, Lactococcus lactis diacetyl subspecies, and Leuconostocpseudomesenteroides.

[0026] In a preferred embodiment of the present invention, the compound lactic acid bacteria further includes *Streptococcus thermophilus*, *Lactobacillus acidophilus*, *Lactobacillus paracasei*, *Lactobacillus delbrueckii* subsp. bulgaricus, *Lactobacillus delbrueckii* subsp. lactic acid, and *Lactococcus lactis* subsp. milk fat, with a bacterial count ratio of 50:(1-2):(1-2):(1-2):(1-2):(1-2):(1-2). Based on the total bacterial count of the compound lactic acid bacteria, the proportion of the total bacterial count of *Streptococcus thermophilus*, *Lactobacillus acidophilus*, *Lactobacillus paracasei*, *Lactobacillus delbrueckii* subsp. bulgaricus, *Lactobacillus delbrueckii* subsp. lactic acid, and *Lactococcus lactis* subsp. milk fat is 75% to 85%.

[0027] In a preferred embodiment of the present invention, the compound lactic acid bacteria further includes Streptococcus thermophilus, Lactobacillus acidophilus, Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus delbrueckii subsp. lactic acid, and Lactococcus lactis subsp. milk fat, with a bacterial count ratio of 50:(1-2):(1-2):(1-2):(1-2). Based on the total bacterial count of the compound lactic acid bacteria, the total bacterial count of Streptococcus thermophilus, Lactobacillus acidophilus, Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus delbrueckii subsp. lactic acid, and Lactococcus lactis subsp. milk fat accounts for 75% to 85%.

[0028] This invention also provides a method for preparing alcohol-free kefir fermented milk, the method comprising the following steps:

[0029] 1) Mix the sweetener with raw milk to obtain the base material;

[0030] 2) Homogenize the substrate obtained in step 1), sterilize and cool it, and then inoculate it with compound lactic acid bacteria for fermentation;

[0031] 3) After fermentation, the milk is broken and aseptically filled to obtain the kefir fermented milk.

[0032] In some embodiments of the present invention, in step 1), the mixing temperature is 10–20°C. In a specific embodiment of the present invention, the mixing temperature is 15°C.

[0033] In some embodiments of the present invention, in step 2), the pressure of homogenization is 160 bar to 200 bar.

[0034] In some embodiments of the present invention, in step 2), the homogenization temperature is 50°C to 70°C.

[0035] In some embodiments of the present invention, in step 2), the sterilization temperature is 90°C to 95°C.

[0036] In some embodiments of the present invention, in step 2), the sterilization time is 5 min to 10 min.

[0037] In some embodiments of the present invention, in step 2), the temperature is cooled to 25–35°C.

[0038] In some embodiments of the present invention, in step 2), the fermentation temperature is 28°C to 32°C.

[0039] In some embodiments of the present invention, in step 2), the fermentation time is 15h to 21h.

[0040] In some embodiments of the present invention, step 3) further includes adding concentrated lemon juice after demulsification and mixing it evenly.

[0041] In some embodiments of the present invention, in step 3), it is recommended to use 200mL rigid plastic cups for filling. Because fermentation produces gas, rigid plastic bottles can effectively prevent damage to the bottle body caused by changes in internal and external gas pressure.

[0042] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0043] Before further describing specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terminology used in the embodiments of the present invention is for describing specific embodiments and not for limiting the scope of protection of the present invention; in the specification and claims of the present invention, unless otherwise expressly stated in the text, the singular forms "a", "an" and "this" include the plural forms.

[0044] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. In addition to the specific methods, apparatus, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description of this invention, any prior art methods, apparatus, and materials similar to or equivalent to those described, apparatus, and materials in the embodiments of this invention may be used to implement the present invention.

[0045] Example 1

[0046] This example provides a non-alcoholic kefir fermented milk, the ingredients of which are shown in Table 1:

[0047] Table 1

[0048] Ingredients Mass percentage Fresh cow milk 100% White granulated sugar 5% Compound lactic acid bacteria 0.015% (inoculation amount of 1 x 10^8 CFU / mL) Ingredients Mass percentage Fresh cow milk 100% White granulated sugar 5% Compound lactic acid bacteria 0.015% (inoculation amount of 1 x 10^8 CFU / mL) Ingredients Mass percentage Fresh cow milk 100% White granulated sugar 5% Compound lactic acid bacteria 0.015% (inoculation amount of 1 x 10^8 CFU / mL) 85％ Ingredients Mass percentage Fresh cow milk 100% White granulated sugar 5% Compound lactic acid bacteria 0.015% (inoculation amount of 1 x 10^8 CFU / mL) 14.985％ Ingredients Mass percentage Fresh cow milk 100% White granulated sugar 5% Compound lactic acid bacteria 0.015% (inoculation amount of 1 x 10^8 CFU / mL) Ingredients Mass percentage Fresh cow milk 100% White granulated sugar 5% Compound lactic acid bacteria 0.015% (inoculation amount of 1 x 10^8 CFU / mL)

[0049] In the compound lactic acid bacteria, the ratio of viable Leuconostoc mesenteroides subsp. mesenteroides to the remaining lactic acid bacteria is 1:5, that is, the viable number of Leuconostoc mesenteroides subsp. mesenteroides accounts for 16.7% of the total viable number of the compound lactic acid bacteria.

[0050] The remaining lactic acid bacteria include *Streptococcus thermophilus*, *Lactobacillus acidophilus*, *Lactobacillus paracasei*, *Lactobacillus delbrueckii* subsp. bulgaricus, *Lactobacillus delbrueckii* subsp. lactis, and *Lactococcus lactis* subsp. milk fat, with a bacterial count ratio of 50:1.5:1:1:1.05:1. The production process is carried out according to the following steps:

[0051] (1) Dissolve the white sugar evenly in the raw milk at a temperature of 15°C and stir for 10 minutes to obtain the base material;

[0052] (2) Heat the base material obtained in step (1) to 62°C, and then homogenize it under a homogenization pressure of 200 bar;

[0053] (3) The product obtained in step (2) is sterilized under the following conditions: 95°C for 5 min, cooled to 28°C, inoculated with compound lactic acid bacteria and fermented at 30°C for 17 h.

[0054] (4) After fermentation, the emulsion is broken directly and aseptically filled into 200mL plastic cups to obtain the final product.

[0055] The final product, kefir fermented milk, has a protein content of 2.9%, a fat content of 3.1%, a pH of 4.4, and an acidity of 87°T. After being stored at 6°C for 20 days, it showed no significant water separation and exhibited a rich, characteristic flavor.

[0056] Example 2

[0057] This example provides a non-alcoholic kefir fermented milk, the ingredients of which are shown in Table 2:

[0058] Table 2

[0059] 8-fold concentrated lemon juice Ingredients Mass percentage Fresh cow milk 100% White granulated sugar 5% Compound lactic acid bacteria 0.015% (inoculation amount of 1 x 10^8 CFU / mL) Ingredients Mass percentage Fresh cow milk 100% White granulated sugar 5% Compound lactic acid bacteria 0.015% (inoculation amount of 1 x 10^8 CFU / mL) 85％ 8-fold concentrated lemon juice 9.985％ Ingredients Mass percentage Fresh cow milk 100% White granulated sugar 5% Compound lactic acid bacteria 0.015% (inoculation amount of 1 x 10^8 CFU / mL) Ingredients Mass percentage Fresh cow milk 100% White granulated sugar 5% Compound lactic acid bacteria 0.015% (inoculation amount of 1 x 10^8 CFU / mL) 8-fold concentrated lemon juice 5％

[0060] In the compound lactic acid bacteria, the ratio of viable Leuconostoc mesenteroides subsp. mesenteroides to the remaining lactic acid bacteria is 1:5, that is, the viable number of Leuconostoc mesenteroides subsp. mesenteroides accounts for 16.7% of the total viable number of the compound lactic acid bacteria.

[0061] The remaining lactic acid bacteria include Streptococcus thermophilus, Lactobacillus acidophilus, Lactobacillus paracasei, Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus delbrueckii subsp. lactic acid, and Lactococcus lactis subsp. milk fat, with a bacterial count ratio of 50:1.2:1.05:1.05:1.05:1.05:1.

[0062] Its production process is carried out according to the following steps:

[0063] (1) Dissolve the white sugar evenly in the raw milk at a temperature of 15°C and stir for 10 minutes to obtain the base material;

[0064] (2) Heat the base material obtained in step (1) to 62°C, and then homogenize it under a pressure of 200 bar.

[0065] (3) The product obtained in step (2) is sterilized under the following conditions: 95°C for 5 min, cooled to 28°C, inoculated with compound lactic acid bacteria and fermented at 30°C for 15 h.

[0066] (4) After fermentation, break the emulsion, add concentrated lemon juice, mix well and fill into 200mL plastic cups to obtain the final product.

[0067] The final product, kefir fermented milk, has a protein content of 2.8%, a fat content of 3.0%, a pH of 4.2, and an acidity of 87°T. After being stored at 6°C for 20 days, it showed no significant water separation and exhibited a rich, characteristic flavor.

[0068] Example 3

[0069] This example provides a non-alcoholic kefir fermented milk, the ingredients of which are shown in Table 3:

[0070] Table 3

[0071] Item Ethanol content (mg / kg) ​ ​ 85％ ​ 9.9％ ​ 0.01％ ​ 5％

[0072] In the compound lactic acid bacteria, the ratio of the number of viable Leuconostoc mesenteroides subsp. mesenteroides to the number of viable bacteria of the other lactic acid bacteria is 1:3, that is, the number of viable Leuconostoc mesenteroides subsp. mesenteroides accounts for 25% of the total number of viable bacteria in the compound lactic acid bacteria.

[0073] The remaining lactic acid bacteria include Streptococcus thermophilus, Lactobacillus acidophilus, Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus delbrueckii subsp. lactic acid, and Lactococcus lactis subsp. milk fat, with a bacterial count ratio of 50:1.8:2:1.95:1.

[0074] Its production process is carried out according to the following steps:

[0075] (1) Dissolve the white sugar evenly in the raw milk at a temperature of 15°C and stir for 10 minutes to obtain the base material;

[0076] (2) Heat the base material obtained in step (1) to 62°C, and then homogenize it under a pressure of 200 bar.

[0077] (3) The product obtained in step (2) is sterilized under the following conditions: 95°C for 5 min, cooled to 28°C, inoculated with compound lactic acid bacteria and fermented at 30°C for 15 h.

[0078] (4) After fermentation, break the emulsion, add concentrated lemon juice, mix well and fill into 200mL plastic cups to obtain the final product.

[0079] The final product, kefir fermented milk, has a protein content of 2.9%, a fat content of 3.1%, a pH of 4.3, and an acidity of 82°T. After being stored at 6°C for 20 days, it shows no significant water separation and exhibits a rich, characteristic flavor.

[0080] Comparative Example 1

[0081] The ingredients for this comparative example are shown in Table 4:

[0082] Table 4

[0083]

[0084]

[0085] In the compound lactic acid bacteria, the ratio of the number of viable Leuconostoc mesenteroides subsp. mesenteroides to the number of viable bacteria of the other lactic acid bacteria is 1:3, that is, the number of viable Leuconostoc mesenteroides subsp. mesenteroides accounts for 16.7% of the total number of viable bacteria in the compound lactic acid bacteria.

[0086] The remaining lactic acid bacteria include Streptococcus thermophilus, Lactobacillus acidophilus, Lactobacillus paracasei, Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus delbrueckii subsp. lactic acid, and Lactococcus lactis subsp. milk fat, with a bacterial count ratio of 50:1.8:2:1.8:1.95:1.

[0087] Its production process is carried out according to the following steps:

[0088] (1) Dissolve the white sugar evenly in the raw milk at a temperature of 15°C and stir for 10 minutes to obtain the base material;

[0089] (2) Heat the base material obtained in step (1) to 62°C, and then homogenize it under a pressure of 200 bar.

[0090] (3) The product obtained in step (2) is sterilized under the following conditions: 95°C for 5 min, cooled to 28°C, inoculated with compound lactic acid bacteria and fermented at 30°C for 15 h.

[0091] (4) After fermentation, break the emulsion, add concentrated lemon juice, mix well and fill into 200mL plastic cups to obtain the final product.

[0092] The final product, kefir fermented milk, has a protein content of 2.7%, a fat content of 3.9%, a pH of 3.9, and an acidity of 88°T.

[0093] Comparative Example 2

[0094] Kefir fermented milk was prepared using the existing yeast + lactic acid bacteria method. The ingredients for this comparative example are shown in Table 5.

[0095] Table 5

[0096] ​ ​ ​ 85％ ​ 14.985％ ​ 0.015％

[0097] The compound fermentation agent includes multiple lactic acid bacteria and Kluyveromyces marxoiris, with a live count ratio of 5:1 for the multiple lactic acid bacteria and Kluyveromyces marxoiris. The multiple lactic acid bacteria include Streptococcus thermophilus, Lactobacillus acidophilus, Lactobacillus paracasei, Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus delbrueckii subsp. lactic acid, and Lactococcus lactis subsp. milk fat, with a count ratio of 50:1.8:2:1.8:1.95:1.

[0098] Its production process is carried out according to the following steps:

[0099] (1) Dissolve the white sugar evenly in the raw milk at a temperature of 15°C and stir for 10 minutes to obtain the base material;

[0100] (2) Heat the base material obtained in step (1) to 62°C, and then homogenize it under a pressure of 200 bar.

[0101] (3) The product obtained in step (2) is sterilized under the following conditions: 95°C for 5 min, cooled to 28°C, inoculated with compound fermentation agent and fermented at 30°C for 15 h.

[0102] (4) After fermentation, break the emulsion, mix evenly, and fill into 200mL plastic cups to obtain the final product.

[0103] The final product, kefir fermented milk, has a protein content of 2.9%, a fat content of 3.1%, a pH of 4.3, and an acidity of 82°T.

[0104] Comparative Example 3

[0105] Kefir fermented milk was prepared using the existing yeast + lactic acid bacteria method. The ingredients for this comparative example are shown in Table 6.

[0106] Table 6

[0107] ​ ​ ​ 80％ ​ 14.985％ ​ 0.01％ ​ 5％

[0108] The compound fermentation agent includes multiple lactic acid bacteria and Kluyveromyces marxoiris, with a live count ratio of 3:1 for the multiple lactic acid bacteria and Kluyveromyces marxoiris. The multiple lactic acid bacteria include Streptococcus thermophilus, Lactobacillus acidophilus, Lactobacillus paracasei, Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus delbrueckii subsp. lactic acid, and Lactococcus lactis subsp. milk fat, with a count ratio of 50:1.8:2:1.8:1.95:1.

[0109] Its production process is carried out according to the following steps:

[0110] (1) Dissolve the white sugar evenly in the raw milk at a temperature of 15°C and stir for 10 minutes to obtain the base material;

[0111] (2) Heat the base material obtained in step (1) to 62°C, and then homogenize it under a pressure of 200 bar.

[0112] (3) The product obtained in step (2) is sterilized under the following conditions: 95°C for 5 min, cooled to 28°C, inoculated with compound fermentation agent and fermented at 30°C for 15 h.

[0113] (4) After fermentation, break the emulsion, add concentrated lemon juice, mix well and fill into 200mL plastic cups to obtain the final product.

[0114] The final product, kefir fermented milk, has a protein content of 2.7%, a fat content of 2.9%, a pH of 4.1, and an acidity of 87°T.

[0115] Example 1: Sensory Evaluation

[0116] Sensory evaluations were conducted on the kefir fermented milk products prepared in each embodiment and comparative example, including aspects such as taste, flavor, and appearance. The sensory scoring criteria are shown in Table 7.

[0117] In the sensory evaluation of the kefiric acid prepared in each embodiment or comparative example, 30 people participated in the experiment, and the average score of the 30 people was taken as the final score result. The experimental record results are shown in Table 8.

[0118] Table 7

[0119]

[0120] Table 8

[0121]

[0122]

[0123] As shown in Table 8, Examples 2 and 3 exhibited the best overall sensory qualities, possessing a distinct burnt taste while also having a more palatable and acceptable flavor. Example 1's overall sensory qualities were very similar to Examples 2 and 3, and its acceptance was also relatively high. Comparative Example 1 had a weaker burnt taste, resulting in lower relative acceptance compared to the Examples. Comparative Example 2 had an uneven burnt taste and even lower acceptance of its characteristic flavor, thus its overall acceptance was lower than the Examples. Comparative Example 3 had an excessively strong burnt taste and was too acidic, therefore its acceptance was significantly lower than the others.

[0124] Example 2: Stability Test

[0125] Stability analysis of the samples was performed using a LUMiSizer stability analyzer. 1.8 mL of the final product was slowly injected into the bottom of the sample tube (no residue or air bubbles were allowed on the tube wall). The temperature was set at 25°C, and the centrifugation speed was 4000 rpm. –1 The transmittance characteristic line of the sample was recorded every 10 seconds, and a total of 300 scans were performed. The middle section of the transmittance curve was taken and the instability index was calculated (Table 9).

[0126] Table 9

[0127]

[0128]

[0129] As shown in Table 9, Example 1 exhibits the lowest instability index and the best stability. Examples 2, 3, and Comparative Example 1 show slightly lower stability than Example 1, but relatively good stability. Comparative Examples 2 and 3 show poor stability and may exhibit significant water separation during their shelf life. In summary, Example 1 demonstrates the best relative stability and overall water retention capacity. In the other examples, stability slightly decreases as the blanching effect becomes more pronounced.

[0130] Example 3: Alcohol content test

[0131] Alcohol content was determined by gas chromatography. Chromatographic conditions: PEG-20M column (30m × 0.32mm × 0.5um); temperature program: initial temperature 70℃, held for 1 min, then increased to 220℃ at 20℃ / min, held for 12 min; injector temperature: 250℃; flame ionization detector temperature: 220℃; carrier gas flow rate: N2: 6mL / min; split ratio: 5:1; injection volume: 1uL.

[0132] Sample preparation: Accurately transfer 2 mL of the final product into a 10 mL volumetric flask, dilute with ultrapure water, adjust the pH to 2.0 with H3PO4, bring the volume to 10 mL, mix thoroughly, and centrifuge at 12000 r / min for 10 min. Filter the supernatant through a 0.45 μm filter membrane (Table 10).

[0133] Table 10

[0134] ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 1.76×10^3 ​ 2.78×10^3

[0135] As shown in Table 10, ethanol was detected in Comparative Examples 2 and 3, indicating that *Kluyveromyces marquezii* produces ethanol. However, no ethanol was detected in the other cases where *Enteromorpha melioides* was used as a substitute, verifying that this invention is an alcohol-free product.

[0136] The above embodiments are for illustrating the implementation schemes disclosed in this invention and should not be construed as limiting the invention. Furthermore, various modifications and variations of the methods listed herein will be apparent to those skilled in the art without departing from the scope and spirit of the invention. Although the invention has been specifically described in conjunction with various specific preferred embodiments, it should be understood that the invention should not be limited to these specific embodiments. In fact, various modifications as described above that are obvious to those skilled in the art to obtain the invention should be included within the scope of this invention.

Claims

1. A non-alcoholic kefir fermented milk, characterized in that, Based on the total weight of the kefir fermented milk, the kefir fermented milk comprises the following raw material components by mass percentage: sweetener 7% to 15%, concentrated lemon juice 0% to 5%, compound lactic acid bacteria 0.01% to 0.015%, and the balance being raw milk, wherein the compound lactic acid bacteria include Enteromorpha moniliformis subsp.

2. The kefir fermented milk according to claim 1, characterized in that, The sweetener is white granulated sugar; And / or, the concentration ratio of the concentrated lemon juice is 5 to 10 times; And / or, based on the total number of compound lactic acid bacteria, the proportion of *Enteromorpha beadica* subsp. *mongolica* is 15%–25%.

3. The kefir fermented milk according to claim 1, characterized in that, The compound lactic acid bacteria also include one or more of the following: Streptococcus thermophilus, Lactobacillus acidophilus, Lactobacillus paracasei, Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus delbrueckii subsp. lactic acid, Lactococcus lactis subsp. milk fat, Lactococcus lactis subsp. lactic acid, Lactococcus lactis subsp. diacetyl, and Leuconostoc pseudoenteroides.

4. The kefir fermented milk according to claim 3, characterized in that, The compound lactic acid bacteria also includes *Streptococcus thermophilus*, *Lactobacillus acidophilus*, *Lactobacillus paracasei*, *Lactobacillus delbrueckii* subsp. bulgaricus, *Lactobacillus delbrueckii* subsp. lactic acid, and *Lactococcus lactis* subsp. milk fat, with a bacterial count ratio of 50:(1-2):(1-2):(1-2):(1-2):(1-2). Based on the total bacterial count of the compound lactic acid bacteria, the proportion of the total bacterial count of *Streptococcus thermophilus*, *Lactobacillus acidophilus*, *Lactobacillus paracasei*, *Lactobacillus delbrueckii* subsp. bulgaricus, *Lactobacillus delbrueckii* subsp. lactic acid, and *Lactococcus lactis* subsp. milk fat is 75%-85%.

5. The kefir fermented milk according to claim 3, characterized in that, The compound lactic acid bacteria also includes Streptococcus thermophilus, Lactobacillus acidophilus, Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus delbrueckii subsp. lactic acid, and Lactococcus lactis subsp. milk fat, with a bacterial count ratio of 50:(1-2):(1-2):(1-2):(1-2). Based on the total bacterial count of the compound lactic acid bacteria, the total bacterial count of Streptococcus thermophilus, Lactobacillus acidophilus, Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus delbrueckii subsp. lactic acid, and Lactococcus lactis subsp. milk fat accounts for 75% to 85%.

6. The method for preparing kefir fermented milk according to any one of claims 1 to 5, characterized in that, The preparation method includes the following steps: 1) Mix the sweetener with raw milk to obtain the base material; 2) Homogenize the substrate obtained in step 1), sterilize and cool it, and then inoculate it with compound lactic acid bacteria for fermentation; 3) After fermentation, the milk is broken and aseptically filled to obtain the kefir fermented milk.

7. The method according to claim 6, characterized in that, In step 1), the mixing temperature is 10–20°C.

8. The method according to claim 6, characterized in that, Step 2) includes one or more of the following features: a) The homogenization temperature is 50℃~70℃; b) The pressure of the homogeneous material is 160 bar to 200 bar; c) The sterilization temperature is 90℃~95℃; d) The sterilization time is 5 min to 10 min.

9. The method according to claim 6, characterized in that, Step 2) includes one or more of the following features: e) Cool to 25–35°C; f) The fermentation temperature is 28℃~32℃; g) The fermentation time is 15h to 21h.

10. The method according to claim 6, characterized in that, Step 3) also includes adding concentrated lemon juice after demulsification and mixing well.

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