Bubble lactic acid bacteria product prepared by fermentation of heterolactic acid and method

Abstract

The invention discloses a sparkling lactic acid bacteria product prepared by heterolactic acid fermentation and a method, and the sparkling lactic acid bacteria product is prepared from the following raw materials in parts by weight on the basis of 1000 parts by weight of final products: 200-600 parts of raw milk, 1-8 parts of citrate, 1-90 parts of a sweetening agent, 1-10 parts of a stabilizer, 1-15 parts of an acidity regulator and 100-250 U / t zymophyte, and the balance of water. The zymophyte comprises aerogenic bacteria and acid-producing bacteria in a mass ratio of (1-10): 1; the stabilizer comprises a protein stabilizer and a gas stabilizer in a mass ratio of (1-3): 1; the content of protein in the lactic acid bacteria product is not more than 3 g / 100 g, and the viscosity is not more than 300 mPa.s. The viable bubble lactic acid bacteria are prepared by adopting a one-time fermentation and after-ripening process, a stabilizer and a fermentation strain are specifically selected, and large-scale popularization and production of viable bubble lactic acid bacteria products are creatively realized through acid regulation treatment before fermentation.

Description

Technical Field

[0001] This invention relates to the field of dairy product technology, specifically to the field of fermented dairy products, and particularly to a bubble-forming lactic acid bacteria product and method prepared by heterologous lactic acid fermentation. Background Technology

[0002] Lactic acid bacteria drinks and drinkable yogurts are popular with consumers due to their smooth and refreshing texture, balanced sweet and sour taste, and digestive benefits. However, limitations in formulas, processes, and equipment mean that traditional lactic acid bacteria drinks and drinkable yogurts undergo homolactic fermentation, meaning the bacteria produce lactic acid through metabolism. This limits product innovation. Sparkling beverages, with their refreshing texture and stimulating taste, have led a new consumer trend in recent years. Introducing the effervescence into traditional lactic acid bacteria drinks and yogurts allows for cross-category fusion, giving products the smooth texture of lactic acid bacteria drinks and drinkable yogurts while also providing the stimulating sensation of bubbles.

[0003] Most commercially available carbonated products are aerated, which can easily lead to microbial contamination in products with a certain protein content. Meanwhile, high-protein yogurts often suffer from excessive foaming. Research has found that some lactic acid bacteria, through heterolactic fermentation, not only produce lactic acid from sugars but also generate carbon dioxide through the metabolism of citric acid and citrate. By utilizing this characteristic in a well-designed formula, lactic acid bacteria can produce a large amount of carbon dioxide during fermentation, giving the product a stimulating bubbly texture. This makes it possible to produce aerated lactic acid bacteria products through direct fermentation rather than external aeration.

[0004] Patent CN114258951A discloses a multi-fermentation carbonated beverage and its preparation method. The beverage is obtained by using a three-stage fermentation technology and the principle of gas production through bacterial fermentation. Suitable bacterial strains are selected for fermentation. Although the product has the advantages of unique flavor, good stability, dense bubbles, and low production cost, the use of multiple fermentation methods has the disadvantages of long fermentation cycle, complex process, poor controllability, and low gas production due to the reduced concentration of fermentation substrate after multiple fermentations. These limitations restrict the large-scale promotion and production of the product.

[0005] To avoid the aforementioned problems, patent CN111011496A discloses a bubble yogurt and its preparation method. This bubble yogurt uses a combination of direct fermentation and post-ripening processes to create a "fluffy structure" in the yogurt, giving the final product a unique texture. Furthermore, it eliminates the need for external aeration, significantly reducing production costs while maintaining the yogurt's flavor, resulting in good economic benefits. However, while this bubble yogurt shortens the production cycle, simplifies the process, and reduces costs, this process is only suitable for producing set-type yogurt.

[0006] However, when producing drinking yogurt or lactic acid bacteria beverages with low viscosity or protein content, the fermentation environment gradually becomes acidic as the fermentation process progresses (due to the production of lactic acid and the formation of carbonic acid from dissolved carbon dioxide). This causes the proteins in the raw materials to denature as the acidity increases, leading to aggregation and stratification, and resulting in problems such as product instability.

[0007] Furthermore, the study found that a higher acidity environment not only inhibits the gas production of gas-producing fermenting bacteria but also affects the aroma and acid production of acid-producing fermenting bacteria, thus impacting the quality of carbonated lactic acid bacteria products. Therefore, while addressing the stability issues of carbonated stirred yogurt or lactic acid bacteria beverages caused by acidic environments, ensuring the quality of lactic acid bacteria products is also an urgent problem to be solved. Summary of the Invention

[0008] The purpose of this invention is to overcome the problems of poor stability and cumbersome fermentation processes in existing beverage-grade fermented effervescent products. It proposes a method and product for preparing effervescent lactic acid bacteria through heterologous lactic acid fermentation. This product is prepared using a single-stage fermentation and post-ripening process. Targeted stabilizers and fermentation bacteria species are selected, and the fermentation substrate is acidified before fermentation. This ensures that the product does not experience stability degradation due to an acidic environment during fermentation, while also guaranteeing normal fermentation by the fermenting bacteria. Consequently, the quality of the fermented product is significantly improved, which is beneficial for the large-scale promotion and production of effervescent lactic acid bacteria products.

[0009] To achieve the above-mentioned objectives, this invention provides a gas-producing lactic acid bacteria product prepared by heterologous lactic acid fermentation. Based on 1000 parts by weight of the final product, it comprises the following raw materials in parts by weight: 200-600 parts of raw milk, 1-8 parts of citrate, 1-90 parts of sweetener, 1-10 parts of stabilizer, 1-15 parts of acidity regulator, 100-250 U / ton of fermentation bacteria, and the balance being water. The fermentation bacteria include gas-producing bacteria and acid-producing bacteria in a mass ratio of 1-10:1. The stabilizer includes a protein stabilizer and a gas stabilizer in a mass ratio of 1-3:1. The protein content of the lactic acid bacteria product is not greater than 3 g / 100 g, and the viscosity is not greater than 300 mPa·s.

[0010] The preparation method of the bubble-filled lactic acid bacteria product includes the following steps:

[0011] S1: Dissolve the stabilizer and sweetener in water to obtain the first mixed solution;

[0012] S2: Mix the first mixed solution with the raw milk until homogeneous to obtain the second mixed solution;

[0013] S3: Add an acidity regulator and citrate to the second mixture, and adjust the pH to 4.3-5.2 at a temperature not exceeding 25℃ to obtain the third mixture;

[0014] S4: The third mixture is homogenized and sterilized sequentially to obtain the fermentation substrate;

[0015] S5: Inoculate the fermentation substrate with fermentation bacteria, then fill and ferment to obtain the fermentation product;

[0016] S6: After the fermentation product is refrigerated and matured, a bubble lactic acid bacteria product is obtained.

[0017] This invention discloses a bubble-forming lactic acid bacteria product prepared by heterologous lactic acid fermentation. It is prepared using a single-stage fermentation and post-ripening process, and specifically selects the type of stabilizer. Furthermore, the fermentation substrate is acidified before fermentation, placing the fermentation system in an acidic environment from the initial stage. This significantly improves the stabilizer's effect on protein denaturation under acidic conditions, thereby significantly enhancing the product's stability. Simultaneously, the type and ratio of fermentation bacteria are specifically selected, ensuring excellent fermentation performance even in an acidic environment, guaranteeing the quality of the bubble-forming lactic acid bacteria product. This bubble-forming lactic acid bacteria product not only has a strong aerobic sensation, good stability, and high quality, but also features a short production cycle, simple process, and good controllability, making it suitable for large-scale promotion and production.

[0018] Preferably, the sweetener includes at least one of white sugar, xylitol, erythritol, sucralose, acesulfame potassium, and steviol glycosides.

[0019] Preferably, the protein stabilizer is at least one of pectin and citrus fiber, and the gas stabilizer is at least one of cyclodextrin and xanthan gum. The gel formed by pectin or citrus fiber in the protein stabilizer can better coat the protein in the raw material under low-temperature acidic conditions, achieving protection and stabilization effects, thereby preventing the protein from agglomerating and precipitating due to high-temperature homogenization or sterilization treatment and increased acidity during fermentation, which would affect the fermentation effect and product quality. The gas stabilizer can stabilize bubbles in the liquid environment through its structure, thereby improving the stability of carbon dioxide in the product. The combination of multiple stabilizers has a better stabilizing effect and is conducive to improving the stability of the product. More preferably, the stabilizer is pectin, cyclodextrin and citrus fiber in a mass ratio of 2:3:3. Even more preferably, the stabilizer also includes at least one of sodium carboxymethyl cellulose, carrageenan, soybean polysaccharide and propylene glycol alginate.

[0020] Preferably, the acid regulator includes citric acid and lactic acid / malic acid in a mass ratio of 3-4:1; the preferred acid regulator can form a pH buffer system with citrate to keep the fermentation substrate in a high acidic environment in the early stage of fermentation, and can also cooperate with gas-producing bacteria to enable the gas-producing bacteria to ferment and produce gas rapidly under acidic conditions.

[0021] Preferably, the gas-producing bacteria are at least one of Lactobacillus fermentum DALI02 (culture preservation number CGMCC 16064) and Lactococcus lactis subsp. milk fat, Lactococcus lactis subsp. lactic acid, Lactococcus lactis subsp. diacetyl, Leuconostoc mesenteroides subsp. mesenteroides, and Lactobacillus reuteri. The preferred gas-producing bacteria have better fermentation effect and greater gas production under acidic conditions. Most preferably, the gas-producing bacteria are Lactobacillus fermentum DALI02, Lactococcus lactis subsp. milk fat, and Lactococcus lactis subsp. lactic acid in a mass ratio of 1-2:2-4:1.

[0022] Preferably, the acid-producing bacteria include *Streptococcus thermophilus* subsp. *salivarius* and *Lactobacillus delbrueckii* subsp. *bulgaricus* in a mass ratio of 1-100:1. The preferred acid-producing bacteria have high activity in acidic environments, thereby enabling rapid fermentation and acid production and the generation of characteristic flavor substances under acidic conditions, which can significantly improve the fermentation effect under acidic conditions.

[0023] Preferably, in step S3, the acidity regulator is diluted with water to a mass fraction of 5-20% before being added to the second mixture; this preferred method of adding the acidity regulator can prevent excessive acidity from causing protein denaturation during pH adjustment.

[0024] Preferably, the citrate is at least one of sodium citrate and potassium citrate.

[0025] In step S3, when adjusting the pH value, the temperature of the mixed solution should not exceed 25°C. If the temperature of the mixed solution is too high, the proteins in the solution will denature rapidly under acidic conditions, thereby reducing the quality of the product. Under low temperature and acidic conditions, the pectin or citrus fiber in the stabilizer can better encapsulate the protein molecules, achieving a protective effect and preventing the proteins from agglomerating and clumping due to high temperature or acidic conditions in subsequent processes. Preferably, the temperature of the mixed solution is 15-25°C.

[0026] Preferably, in step S4, the homogenization temperature is 50-60℃ and the pressure is 18-22MPa.

[0027] Preferably, in step S4, the sterilization temperature is 85-95℃ and the time is 5-30 minutes.

[0028] Preferably, in step S5, the fermentation temperature is 25-35℃ and the fermentation time is 12-24h; under the preferred fermentation conditions, the fermentation effect of the fermenting bacteria is the best and the product quality is the highest.

[0029] Preferably, in step S6, the temperature for post-cold ripening is 2-6℃, and the time is 8-20h.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] 1. Simple process and strong replicability and scalability: The bubble lactic acid bacteria product prepared by this invention includes a single fermentation process combined with low-temperature post-ripening. The process is simple, has good controllability, and low requirements for production equipment, which is conducive to the large-scale production and promotion of the product.

[0032] 2. Endogenous fermentation, rather than exogenous aeration: The aerated lactic acid bacteria product prepared by this invention induces the heterologous carbon source metabolic pathway of lactic acid bacteria through citrate, and generates sufficient CO2 through low-temperature slow fermentation, bringing a pleasant aerated taste to the product.

[0033] 3. CO2 Capture and Texture Stabilization Technology: The bubble-forming lactic acid bacteria product prepared by this invention has specifically screened stabilizers and their compounding ratios. The microporous structure and hydroxyl groups formed by the interaction of stabilizers capture and adsorb CO2, successfully achieving uniform dispersion and stable maintenance of CO2 gas in a low-protein, low-viscosity system. This invention creatively performs acidification treatment on the substrate before lactic acid bacteria inoculation. On the one hand, the slightly acidic environment initiates the rapid growth of gas-producing bacteria, and on the other hand, it significantly improves the effect of stabilizers on protein denaturation and flocculation under acidic conditions. In addition, the acidification process of this invention is carried out at a lower temperature. The low temperature slows down the thermal motion between protein molecules, ensuring that pectin can better exert its electrostatic stabilizing effect and improve product stability.

[0034] 4. Co-fermentation technology of microorganisms: The gas-producing lactic acid bacteria product prepared by this invention has specifically selected acid-producing bacteria, gas-producing bacteria and their ratio. In the co-fermentation process, on the one hand, the high activity of citrate transport enzyme of gas-producing bacteria is ensured to accumulate more CO2. On the other hand, the combination of multiple microorganisms enriches the beneficial metabolites and aroma components of the microorganisms, resulting in higher product quality and fuller flavor. Attached Figure Description

[0035] Figure 1 This is a graph showing the pH change of the substrate during fermentation in Experiment Example 3 of this invention. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to experimental examples and specific embodiments. However, this should not be construed as limiting the scope of the above-mentioned subject matter of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0037] Example 1:

[0038] A type of aerated lactic acid bacteria product prepared by heterologous lactic acid fermentation, based on 1000 parts by weight of the final product, is prepared from the following raw materials in parts by weight: 500 parts of fresh milk, 4 parts of sodium citrate, 45 parts of white sugar, 5 parts of stabilizer (pectin, cyclodextrin and citrus fiber in a mass ratio of 2:3:3), 6 parts of acid regulator (citric acid and malic acid in a mass ratio of 3:1), 150 U / ton of fermentation bacteria (5:1 gas-producing bacteria (Lactobacillus fermentum DALI02, Lactococcus lactis subsp. milk fat and Lactococcus lactis subsp. lactis in a mass ratio of 1:3:1) and acid-producing bacteria (Streptococcus salivarius subsp. thermophilus and Lactobacillus delbrueckii subsp. bulgaricus in a mass ratio of 3:1)), with the balance being water;

[0039] The preparation method of the bubble-filled lactic acid bacteria product includes the following steps:

[0040] S1: Dissolve the stabilizer and sweetener in water (70°C), then cool (20°C) to obtain the first mixed solution;

[0041] S2: Mix the first mixed solution with the raw milk until homogeneous to obtain the second mixed solution;

[0042] S3: Add an acidity regulator (dilute the acidity regulator with water to a 15% aqueous solution before adding) and sodium citrate to the second mixture, and adjust the pH to 4.8 at a temperature of 20°C to obtain the third mixture;

[0043] S4: The third mixture was subjected to homogenization (temperature 55℃, pressure 20MPa) and sterilization (temperature 90℃, time 10min) in sequence to obtain the fermentation substrate;

[0044] S5: Inoculate the fermentation substrate with fermentation bacteria, then fill and ferment (temperature 30℃, fermentation time 18h) to obtain fermented...

[0045] Fermentation products;

[0046] S6: After the fermentation product is refrigerated and matured (at a temperature of 4°C for 12 hours), the bubble lactic acid bacteria product is obtained.

[0047] Example 2:

[0048] A type of aerated lactic acid bacteria product prepared by heterologous lactic acid fermentation, based on 1000 parts by weight of the final product, is prepared from the following raw materials in parts by weight: 600 parts of fresh milk, 7 parts of sodium citrate, 60 parts of white sugar, 10 parts of stabilizer (pectin, cyclodextrin and citrus fiber in a mass ratio of 2:3:3), 14 parts of acid regulator (citric acid and malic acid in a mass ratio of 4:1), 200 U / ton of fermentation bacteria (10:1 of gas-producing bacteria (Lactobacillus fermentum DALI02, Lactococcus lactis subsp. milk fat and Lactococcus lactis subsp. lactis in a mass ratio of 2:2:1) and acid-producing bacteria (Streptococcus salivarius subsp. thermophilus and Lactobacillus delbrueckii subsp. bulgaricus in a mass ratio of 5:1)), with the balance being water;

[0049] The preparation method of the bubble-filled lactic acid bacteria product includes the following steps:

[0050] S1: Dissolve the stabilizer and sweetener in water (70°C), then cool (25°C) to obtain the first mixed solution;

[0051] S2: Mix the first mixed solution with the raw milk until homogeneous to obtain the second mixed solution;

[0052] S3: Add an acidity regulator (dilute the acidity regulator with water to a 10% aqueous solution before adding) and sodium citrate to the second mixture, and adjust the pH to 4.3 at a temperature of 25°C to obtain the third mixture;

[0053] S4: The third mixture was subjected to homogenization (temperature 50℃, pressure 22MPa) and sterilization (temperature 85℃, time 30min) in sequence to obtain the fermentation substrate;

[0054] S5: Inoculate the fermentation substrate with fermentation bacteria, then fill and ferment (temperature 25℃, fermentation time 24h) to obtain fermented...

[0055] Fermentation products;

[0056] S6: After the fermentation product is refrigerated and matured (at a temperature of 2°C for 20 hours), the bubble-forming lactic acid bacteria product is obtained.

[0057] Example 3:

[0058] A type of aerated lactic acid bacteria product prepared by heterologous lactic acid fermentation, based on 1000 parts by weight of the final product, is prepared from the following raw materials in parts by weight: 250 parts of fresh milk, 2 parts of sodium citrate, 10 parts of erythritol, 0.3 parts of sucralose, 0.3 parts of steviol glycosides, 3 parts of stabilizer (pectin, cyclodextrin and citrus fiber in a mass ratio of 2:3:3), 2 parts of acid regulator (citric acid and lactic acid in a mass ratio of 4:1), 100 U / ton of fermentation bacteria (1:1 gas-producing bacteria (Lactobacillus fermentum DALI02, Lactococcus lactis subsp. milk fat and Lactococcus lactis subsp. lactis in a mass ratio of 1:4:1) and acid-producing bacteria (Streptococcus salivarius subsp. thermophilus and Lactobacillus delbrueckii subsp. bulgaricus in a mass ratio of 2:1)), with the balance being water;

[0059] The preparation method of the bubble-filled lactic acid bacteria product includes the following steps:

[0060] S1: Dissolve the stabilizer and sweetener in water (70°C), then cool (15°C) to obtain the first mixed solution;

[0061] S2: Mix the first mixed solution with the raw milk until homogeneous to obtain the second mixed solution;

[0062] S3: Add an acidity regulator (dilute the acidity regulator with water to a 5% (w / w) aqueous solution before adding) and sodium citrate to the second mixture, and adjust the pH to 5.0 at a temperature of 15°C to obtain the third mixture;

[0063] S4: The third mixture was subjected to homogenization (temperature 60℃, pressure 18MPa) and sterilization (temperature 95℃, time 5min) in sequence to obtain the fermentation substrate;

[0064] S5: Inoculate the fermentation substrate with fermentation bacteria, then fill and ferment (temperature 35℃, fermentation time 12h) to obtain fermented...

[0065] Fermentation products;

[0066] S6: After the fermentation product is refrigerated and matured (at a temperature of 6°C for 8 hours), the bubble lactic acid bacteria product is obtained.

[0067] Example 4:

[0068] A type of aerated lactic acid bacteria product prepared by heterologous lactic acid fermentation, based on 1000 parts by weight of the final product, is prepared from the following raw materials in parts by weight: 300 parts of browned reconstituted milk (12% by weight of skim milk powder, 4% by weight of glucose, with water as the remainder; the water is heated to 55°C, skim milk powder and glucose are added, stirred for 10 min, homogenized at 55°C and 20 MPa, sterilized at 95°C for 5 min, browned at 95°C for 2 h, and cooled to 25°C), and 3 parts of potassium citrate. 70 parts white sugar, 5 parts stabilizer (pectin, cyclodextrin and citrus fiber in a 2:3:3 mass ratio), 3 parts acid regulator (citric acid and malic acid in a 4:1 mass ratio), 250 U / ton of fermentation bacteria (2:1 gas-producing bacteria (Lactobacillus fermentum DALI02, Lactococcus lactis subsp. lactis and Lactococcus lactis subsp. lactis in a 1:2:1 mass ratio) and acid-producing bacteria (Streptococcus salivarius subsp. thermophilus and Lactobacillus delbrueckii subsp. bulgaricus in a 2:1 mass ratio) and the remainder is water;

[0069] The preparation method of the bubble-filled lactic acid bacteria product includes the following steps:

[0070] S1: Dissolve the stabilizer and sweetener in water (70°C), then cool (20°C) to obtain the first mixed solution;

[0071] S2: Mix the first mixed solution with the raw milk until homogeneous to obtain the second mixed solution;

[0072] S3: Add an acidity regulator (dilute the acidity regulator with water to a 10% aqueous solution before adding) and potassium citrate to the second mixture, and adjust the pH to 4.5 at 20°C to obtain the third mixture;

[0073] S4: The third mixture was subjected to homogenization (temperature 55℃, pressure 20MPa) and sterilization (temperature 90℃, time 15min) in sequence to obtain the fermentation substrate;

[0074] S5: Inoculate the fermentation substrate with fermentation bacteria, then fill and ferment (temperature 25℃, fermentation time 20h) to obtain fermented...

[0075] Fermentation products;

[0076] S6: After the fermentation product is refrigerated and matured (at a temperature of 4°C for 16 hours), the bubble lactic acid bacteria product is obtained.

[0077] Example 5:

[0078] A type of aerated lactic acid bacteria product prepared by heterologous lactic acid fermentation, based on 1000 parts by weight of the final product, is prepared from the following raw materials in parts by weight: 500 parts of fresh milk, 4 parts of potassium citrate, 1.1 parts of steviol glycosides, 5 parts of stabilizer (pectin, sodium carboxymethyl cellulose and xanthan gum in a mass ratio of 2:3:3), 7 parts of acid regulator (citric acid and malic acid in a mass ratio of 3:1), 150 U / ton of fermentation bacteria (5:1 of gas-producing bacteria (Lactobacillus fermentum DALI02, Lactococcus lactis subsp. lactis and Leuconostoc mesenteroides subsp. mesenteroides in a mass ratio of 1:3:1) and acid-producing bacteria (Streptococcus salivarius subsp. thermophilus and Lactobacillus delbrueckii subsp. bulgaricus in a mass ratio of 3:1)), with the balance being water;

[0079] The preparation method of the bubble-filled lactic acid bacteria product includes the following steps:

[0080] S1: Dissolve the stabilizer and sweetener in water (70°C), then cool (20°C) to obtain the first mixed solution;

[0081] S2: Mix the first mixed solution with the raw milk until homogeneous to obtain the second mixed solution;

[0082] S3: Add an acidity regulator (dilute the acidity regulator with water to a 20% aqueous solution before adding) and potassium citrate to the second mixture, and adjust the pH to 4.8 at 20°C to obtain the third mixture;

[0083] S4: The third mixture was subjected to homogenization (temperature 55℃, pressure 20MPa) and sterilization (temperature 90℃, time 10min) in sequence to obtain the fermentation substrate;

[0084] S5: Inoculate the fermentation substrate with fermentation bacteria, then fill and ferment (temperature 30℃, fermentation time 18h) to obtain fermented...

[0085] Fermentation products;

[0086] S6: After the fermentation product is refrigerated and matured (at a temperature of 4°C for 12 hours), the bubble lactic acid bacteria product is obtained.

[0087] Comparative Example 1:

[0088] A type of aerated lactic acid bacteria product prepared by heterologous lactic acid fermentation, based on 1000 parts by weight of the final product, is prepared from the following raw materials in parts by weight: 500 parts of fresh milk, 4 parts of sodium citrate, 45 parts of white sugar, 5 parts of stabilizer (pectin, cyclodextrin and citrus fiber in a mass ratio of 2:3:3), 6 parts of acid regulator (citric acid and malic acid in a mass ratio of 3:1), 150 U / ton of fermentation bacteria (5:1 gas-producing bacteria (Lactobacillus fermentum DALI02, Lactococcus lactis subsp. milk fat and Lactococcus lactis subsp. lactis in a mass ratio of 1:3:1) and acid-producing bacteria (Streptococcus salivarius subsp. thermophilus in a mass ratio of 3:1)), with the balance being water;

[0089] The preparation method of the bubble-filled lactic acid bacteria product includes the following steps:

[0090] S1: Heat the raw milk to 55°C, add sweetener to dissolve, and obtain the first mixed solution;

[0091] S2: The second mixture is homogenized (temperature 55℃, pressure 20MPa) and sterilized (temperature 90℃).

[0092] The fermentation time was 10 minutes, and the first fermentation substrate was obtained.

[0093] S3: Inoculate acid-producing bacteria into the first fermentation substrate, then fill and ferment (temperature 42℃, fermentation time 6h) to obtain...

[0094] To the fermentation broth;

[0095] S4: Dissolve the stabilizer in water (70°C) and then cool (20°C) to obtain the first mixed solution;

[0096] S5: Mix the fermentation broth with the first mixed solution until homogeneous to obtain the second mixed solution;

[0097] S6: Add an acidity regulator (dilute the acidity regulator with water to a 15% (w / w) aqueous solution before adding) and sodium citrate to the second mixture, and adjust the pH to 4.8 at a temperature of 20°C to obtain the third mixture;

[0098] S7: The third mixture was subjected to homogenization (temperature 55℃, pressure 20MPa) and sterilization (temperature 90℃, time 10min) in sequence to obtain the second fermentation substrate;

[0099] S8: Inoculate gas-producing bacteria into the fermentation substrate, then fill and ferment (temperature 30℃, fermentation time 18h) to obtain fermented...

[0100] Fermentation products;

[0101] S9: After the fermentation product is refrigerated and matured (at a temperature of 4°C for 12 hours), the bubble lactic acid bacteria product is obtained.

[0102] Comparative Example 2:

[0103] A type of aerated lactic acid bacteria product prepared by heterologous lactic acid fermentation, based on 1000 parts by weight of the final product, is prepared from the following raw materials in parts by weight: 500 parts of fresh milk, 4 parts of sodium citrate, 45 parts of white sugar, 5 parts of stabilizer (pectin, cyclodextrin and citrus fiber in a mass ratio of 2:3:3), 150 U / ton of fermentation bacteria (5:1 gas-producing bacteria (Lactobacillus fermentum DALI02, Lactococcus lactis subsp. milk fat and Lactococcus lactis subsp. lactis in a mass ratio of 1:3:1) and acid-producing bacteria (Streptococcus salivarius subsp. thermophilus and Lactobacillus delbrueckii subsp. bulgaricus in a mass ratio of 3:1)), with the balance being water;

[0104] The preparation method of the bubble-filled lactic acid bacteria product includes the following steps:

[0105] S1: Dissolve the stabilizer and sweetener in water (70°C), then cool (20°C) to obtain the first mixed solution;

[0106] S2: Mix the first mixed solution with the raw milk until homogeneous to obtain the second mixed solution;

[0107] S3: Add sodium citrate to the second mixture to obtain the third mixture;

[0108] S4: The third mixture was subjected to homogenization (temperature 55℃, pressure 20MPa) and sterilization (temperature 90℃, time 10min) in sequence to obtain the fermentation substrate;

[0109] S5: Inoculate the fermentation substrate with fermentation bacteria, then fill and ferment (temperature 30℃, fermentation time 18h) to obtain fermented...

[0110] Fermentation products;

[0111] S6: After the fermentation product is refrigerated and matured (at a temperature of 4°C for 12 hours), the bubble lactic acid bacteria product is obtained.

[0112] Comparative Example 3:

[0113] A type of aerated lactic acid bacteria product prepared by heterologous lactic acid fermentation, based on 1000 parts by weight of the final product, is prepared from the following raw materials in parts by weight: 500 parts of fresh milk, 85 parts of protein powder, 4 parts of sodium citrate, 45 parts of white sugar, 5 parts of stabilizer (pectin, cyclodextrin and citrus fiber in a mass ratio of 2:3:3), 150 U / ton of fermentation bacteria (5:1 gas-producing bacteria (Lactobacillus fermentum DALI02, Lactococcus lactis subsp. milk fat and Lactococcus lactis subsp. lactis in a mass ratio of 1:3:1) and acid-producing bacteria (Streptococcus salivarius subsp. thermophilus and Lactobacillus delbrueckii subsp. bulgaricus in a mass ratio of 3:1)), with the balance being water;

[0114] The preparation method of the bubble-filled lactic acid bacteria product includes the following steps:

[0115] S1: Dissolve the stabilizer and sweetener in water (70°C), then cool (20°C) to obtain the first mixed solution;

[0116] S2: Mix the first mixed solution with the raw milk until homogeneous to obtain the second mixed solution;

[0117] S3: Add sodium citrate to the second mixture to obtain the third mixture;

[0118] S4: The third mixture was subjected to homogenization (temperature 55℃, pressure 20MPa) and sterilization (temperature 90℃, time 10min) in sequence to obtain the fermentation substrate;

[0119] S5: Inoculate the fermentation substrate with fermentation bacteria, then fill and ferment (temperature 30℃, fermentation time 18h) to obtain fermented...

[0120] Fermentation products;

[0121] S6: After the fermentation product is refrigerated and matured (at a temperature of 4°C for 12 hours), the bubble lactic acid bacteria product is obtained.

[0122] Comparative Example 4:

[0123] A gas-generating lactic acid bacteria product prepared by heterologous lactic acid fermentation is prepared using the same process as in Example 1, except that the stabilizer does not contain a gas stabilizer. The stabilizer is pectin and citrus fiber in a mass ratio of 2:3.

[0124] Comparative Example 5:

[0125] A bubble-forming lactic acid bacteria product prepared by heterologous lactic acid fermentation is prepared using the same process as in Example 5, except that the stabilizer does not contain a protein stabilizer. The stabilizer is sodium carboxymethyl cellulose, cyclodextrin, and carrageenan in a mass ratio of 2:3:3.

[0126] Comparative Example 6:

[0127] A type of aerated lactic acid bacteria product prepared by heterologous lactic acid fermentation has the same preparation process as in Example 1, except that the composition ratio of the fermentation bacteria is different. The fermentation bacteria are composed of gas-producing bacteria (Lactobacillus fermentum DALI02, Lactococcus lactis subsp. milk fat and Lactococcus lactis subsp. lactis in a mass ratio of 1:3:1) and acid-producing bacteria (Streptococcus salivarius subsp. thermophilus and Lactobacillus delbrueckii subsp. bulgaricus in a mass ratio of 3:1)).

[0128] Comparative Example 7:

[0129] A type of aerated lactic acid bacteria product prepared by heterologous lactic acid fermentation is prepared using the same process as in Example 1, except that the composition of the fermentation bacteria strains is different. The fermentation bacteria consist of gas-producing bacteria (Lactobacillus fermentum DALI02, Lactococcus lactis subsp. milk fat and Lactococcus lactis subsp. lactis in a mass ratio of 1:3:1) and acid-producing bacteria (Streptococcus salivarius subsp. thermophilus and Lactobacillus rhamnosus HF01 in a mass ratio of 3:1 (accession number: CCTCCNO.M20211319)).

[0130] Comparative Example 8:

[0131] A bubble-forming lactic acid bacteria product prepared by heterologous lactic acid fermentation uses the same raw materials and preparation process as in Example 1, except that in step S3, the temperature of the second mixed solution is 30°C during acid adjustment.

[0132] Comparative Example 9:

[0133] A bubble-forming lactic acid bacteria product prepared by heterologous lactic acid fermentation uses the same raw materials and preparation process as in Example 1, except that in step S3, the pH value after acidification is 4.0.

[0134] Comparative Example 10:

[0135] A bubble-forming lactic acid bacteria product prepared by heterologous lactic acid fermentation uses the same raw materials and preparation process as in Example 1, except that in step S3, the pH value after acidification is 5.5.

[0136] Experiment Example 1: Determination of Carbon Dioxide Content, Viscosity, Protein Content, and Centrifugal Sedimentation Rate of the Product

[0137] Carbon dioxide content detection method: Refer to GB / T10792-2008 Carbonated Beverages (Soft Drinks) 6.2.1.1 Carbon dioxide volumetric pressure reducer method (routine test method)

[0138] Viscosity testing method: The apparent viscosity of the sample is measured using a viscometer. The sample is added to the measuring cup and the measurement is performed at a temperature of 25℃. The viscosity value corresponding to the 30th second is taken.

[0139] Protein content detection method: Refer to Method I, Kjeldahl method, of the National Food Safety Standard GB5009.5-2016, "Determination of Protein in Food".

[0140] Centrifugal sedimentation rate detection method: Experimental method:

[0141] Weigh a certain mass (m1) of sample and place it in a centrifuge tube (m0). Centrifuge at 4000 r / min for 20 min at 4℃. Discard the supernatant, invert and let stand for 5 min. Then weigh the total mass (m2) of the precipitate and the centrifuge tube and calculate the centrifugation precipitation rate.

[0142] Centrifugal sedimentation rate = (m2 - m0) / m1 × 100%

[0143] m1 — Mass of the sample, in grams;

[0144] m2 — the mass of the precipitate, in grams;

[0145] m0 — mass of centrifuge tube, g.

[0146] The test results are shown in Table 1.

[0147] Table 1. Detection results of Experiment Example 1

[0148]

[0149]

[0150] Results Analysis: "-" indicates that the product was not further tested due to protein aggregation and settling at the bottom. Comparative Example 1 used a multiple fermentation process, fermenting gas-producing and acid-producing bacteria at different stages. The metabolic products of the acid-producing bacteria affected the gas production effect of the gas-producing bacteria, resulting in a significant decrease in carbon dioxide capacity and an overall poor performance. Comparative Example 2 had a higher centrifugal sedimentation rate than Examples 1-4, and showed obvious protein clumping and aggregation, indicating that direct fermentation without acid adjustment cannot guarantee product stability, thus verifying that the acid adjustment process ensured product stability. Comparative Example 3 had a high protein content and was not acid-adjusted, resulting in a viscous texture that could not achieve the texture of drinkable yogurt. Comparative Example 4 reduced the amount of stabilizer needed to maintain gas stability, therefore, after being left open for a period of time, the effervescence was weak, and it could not maintain good effervescence stability. Comparative Example 5 exhibited the same phenomenon as Comparative Example 3 without the addition of a protein stabilizer, demonstrating the importance of selecting the right protein stabilizer. Comparative Example 6 showed high product viscosity and severely impacted gas production when the proportion of acid-producing bacteria was too high. Comparative Example 7 showed that changing the type and proportion of acid-producing bacteria affected gas production. Comparative Example 8 showed that when the mixing temperature was too high, the protein could not be protected by the colloid during denaturation, resulting in aggregation and precipitation. Comparative Example 9 showed that the pH was too low during acidification, severely affecting the fermentation effect of both gas-producing and acid-producing bacteria. Comparative Example 10 showed that the pH was too high during acidification, and the protein stabilizer failed to provide adequate protection, resulting in protein precipitation and aggregation.

[0151] Experiment Example 2: Sensory Evaluation Experiment of Products

[0152] Sensory evaluation experiments were conducted on the products obtained in Examples 1-5 and Comparative Examples 1-10 that did not exhibit protein precipitation or aggregation. The evaluation team consisted of 20 sensory experts specializing in food science. These 20 evaluators received two sensory evaluation training sessions before the evaluation and scored the samples according to the evaluation criteria. The specific sensory evaluation reference standards are shown in Table 2 below:

[0153] Table 2 Sensory Evaluation Scoring Criteria

[0154]

[0155] The sensory evaluation results are shown in Table 3:

[0156] Table 3 Sensory Evaluation Score Table

[0157] Serial Number astringent taste Organizational status smell and taste Example 1 8.7 8.8 8.7 Example 2 9.0 8.2 8.2 Example 3 7.0 9.3 7.0 Example 4 7.2 9.2 7.7 Example 5 8.7 7.8 8.7 Comparative Example 1 3.6 8.0 6.7 Comparative Example 3 5.8 2.3 8.4 Comparative Example 4 6.0 7.9 7.5 Comparative Example 6 4.5 5.1 4.8 Comparative Example 7 3.1 4.4 4.3 Comparative Example 9 1.5 6.9 2.1

[0158] Results Analysis: Comparative Example 1 had a lower kick due to reduced gas production caused by multiple fermentations. Comparative Example 3's high protein content resulted in a relatively coarse product texture. Comparative Example 4, lacking a gas stabilizer, had its kick somewhat affected by the absence of bubbles. Comparative Examples 6 and 7, due to changes in the proportion and type of acid-producing bacteria, had a weaker kick, affected fermentation aroma, and were more acidic. Comparative Example 9, with a lower pH, saw almost no metabolism from acid-producing and gas-producing bacteria, resulting in minimal fermentation aroma and bubbles. Experiment 3: Method for detecting pH changes in the substrate during fermentation in Example 1 and Comparative Examples 1, 3, 4, 6, 7, and 9: The pH value of the product was measured using a pH meter at 20℃. The pH value was measured three times and the average value was taken.

[0159] Test results: The detected pH values ​​are plotted on the graph and connected by lines to obtain a pH value curve, as shown below. Figure 1 As shown. Results Analysis: Comparative Example 1 had a higher pH due to the impact of acidification on the further metabolism of gas-producing bacteria. Comparative Example 3, with its high protein content, provided more nutrients to both gas-producing and acid-producing bacteria, causing its pH to drop rapidly to a lower level, resulting in a more acidic product. Changes in the ratio of gas-producing and acid-producing bacteria in Comparative Example 6, and changes in the composition of acid-producing bacteria in Comparative Example 7, both led to faster acid production during fermentation, resulting in an overall acidic product that affected its effervescence, aroma, and taste. Comparative Example 9, due to prolonged exposure to a low-acid environment, was unable to further grow and metabolize its gas-producing and acid-producing bacteria.

Claims

1. A bubble-forming lactic acid bacteria product prepared by heterologous lactic acid fermentation, characterized in that, Based on 1000 parts by weight of the final product, it is prepared from the following raw materials in parts by weight: 200-600 parts of raw milk, 1-8 parts of citrate, 1-90 parts of sweetener, 1-10 parts of stabilizer, 1-15 parts of acidity regulator, 100-250 U / ton of fermentation bacteria, and the balance being RO water; the fermentation bacteria include gas-producing bacteria and acid-producing bacteria in a mass ratio of 1-10:1; the stabilizer includes protein stabilizer and gas stabilizer in a mass ratio of 1-3:1; the protein stabilizer is at least one of pectin and citrus fiber, and the gas stabilizer is at least one of cyclodextrin and xanthan gum; the protein content of the lactic acid bacteria product is not greater than 3 g / 100g, and the viscosity is not greater than 300 mPa·s; The preparation method of the bubble-filled lactic acid bacteria product includes the following steps: S1: Dissolve the stabilizer and sweetener in water to obtain the first mixed solution; S2: Mix the first mixed solution with the raw milk until homogeneous to obtain the second mixed solution; S3: Add acidity regulator and citrate to the second mixture and adjust the pH to 4.3-5.2 to obtain the third mixture; S4: The third mixture is homogenized and sterilized sequentially to obtain the fermentation substrate; S5: Inoculate the fermentation substrate with fermentation bacteria, then fill and ferment to obtain the fermentation product; S6: After the fermentation product is refrigerated and matured, a bubble lactic acid bacteria product is obtained.

2. The bubble-filled lactic acid bacteria product according to claim 1, characterized in that, The stabilizer is pectin, cyclodextrin and citrus fiber in a mass ratio of 2:3:

3.

3. The bubble-filled lactic acid bacteria product according to claim 2, characterized in that, The stabilizer also includes at least one of sodium carboxymethyl cellulose, carrageenan, soybean polysaccharide, and propylene glycol alginate.

4. The bubble-filled lactic acid bacteria product according to claim 1, characterized in that, The acid regulator comprises citric acid and lactic acid / malic acid in a mass ratio of 3-4:

1.

5. The bubble-filled lactic acid bacteria product according to claim 1, characterized in that, The gas-producing bacteria are at least one of Lactobacillus fermentum, Lactococcus lactis subsp. milk fat, Lactococcus lactis subsp. lactic acid, Lactococcus lactis subsp. diacetyl, Leuconostoc mesenteroides subsp. mesenteroides, and Lactobacillus reuteri.

6. The bubble-filled lactic acid bacteria product according to claim 5, characterized in that, The gas-producing bacteria are Lactobacillus fermentum DALI02, Lactococcus lactis subsp. milk fat, and Lactococcus lactis subsp. lactic acid, with a mass ratio of 1-2:2-4:

1.

7. The bubble-filled lactic acid bacteria product according to claim 1, characterized in that, The acid-producing bacteria include *Streptococcus salivarius* subsp. *thermophilus* and *Lactobacillus delbrueckii* subsp. *bulgaricus* in a mass ratio of 1-100:

1.

8. The bubble-filled lactic acid bacteria product according to any one of claims 1-7, characterized in that, In step S4, the homogenization temperature is 50-60℃ and the pressure is 18-22 MPa.

9. The bubble-filled lactic acid bacteria product according to any one of claims 1-7, characterized in that, In step S5, the fermentation temperature is 25-35℃ and the fermentation time is 12-24 h.

10. The bubble-filled lactic acid bacteria product according to any one of claims 1-7, characterized in that, In step S6, the temperature for post-cold ripening is 2-6℃, and the time is 8-20 h.

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