A bubble-fermented milk having thixotropic properties and a method for preparing the same
By regulating carbon dioxide production during the fermentation process of kefir bacteria and constructing a bubble-protein network, the problem of the monotonous form of yogurt products was solved, and the form of fermented milk was transformed after standing and shaking, meeting the diverse needs of spoon-eating and drinking.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHONGQING TIANYOU DAIRY CO LTD
- Filing Date
- 2026-05-09
- Publication Date
- 2026-06-09
AI Technical Summary
Existing yogurt products cannot simultaneously satisfy the cohesive texture of spoon-eating and the smooth drinking experience in the same product, and traditional kefir products have a single form, with no kefir products exhibiting thixotropic properties.
By regulating the carbon dioxide production during the fermentation process of kefir bacteria, a bubble-protein network structure was constructed. Extracellular polysaccharides and microbubbles were used to form uniform gas chambers, enabling the fermented milk to transition from a solid state when standing to a liquid state after shaking. Appropriate amounts of protein, organic acids, and stabilizers were added to adjust thixotropy and effervescence.
It achieves a smooth texture in fermented milk that remains solid and edible when left to stand, and transforms into a liquid state after shaking, while also possessing a bubbly texture and excellent thixotropy, thus meeting diverse consumer needs.
Smart Images
Figure CN122162847A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of fermented products and their preparation technology, specifically relating to a bubble-fermented milk with thixotropic properties and its preparation method. Background Technology
[0002] Yogurt is beloved by consumers for its rich nutritional value and unique taste. Currently, commercially available yogurts are mainly divided into two categories: set yogurt and stirred yogurt. Set yogurt is typically eaten with a spoon and has a firm texture; stirred yogurt, on the other hand, is more fluid and suitable for drinking. However, existing products have a limited form and cannot simultaneously satisfy both the consumer demand for a "spoon-eating, set texture" and a "smooth drinking experience" within the same product. Consumers expect a fermented milk product whose physical form can change depending on the method of consumption—that is, remaining set when still for spoon-eating and transforming into a liquid state after shaking for easy drinking.
[0003] To achieve the aforementioned thixotropic fermented milk, existing technologies have been explored. For example, Chinese invention patent CN117397723A discloses a fermented milk with good thixotropic properties and its preparation method. This solution constructs a thixotropic structure by adding protein powder and egg-based substances (egg yolk liquid, egg yolk powder, etc.), allowing the product to be consumed directly after shaking. However, this solution requires the addition of egg-based ingredients, potentially limiting its application among vegetarians or those with egg allergies. Furthermore, this technology does not address imparting a fizzy texture through fermentation, nor does it achieve a synergistic effect between thixotropy and a microbubble texture.
[0004] Kefir, a traditional fermented dairy product, is made from kefir grains or a kefir culture. During fermentation, lactic acid bacteria produce lactic acid and carbon dioxide, creating a unique microbubble texture and refreshing flavor. However, most commercially available kefir products are currently liquid. While they possess a bubble-like texture, their product form is limited, and there are no reports of kefir products exhibiting thixotropic properties. Therefore, developing a fermented dairy product that can simultaneously achieve both thixotropy and a natural bubble-like texture is of great significance. Summary of the Invention
[0005] Based on this, the purpose of this invention is to provide a bubble-fermented milk with thixotropic properties and a method for preparing the same.
[0006] To achieve the above objectives, the present invention can adopt the following technical solutions: This invention provides a thixotropic bubble fermented milk, which is made from raw materials containing the following materials through fermentation with kefir bacteria: raw milk with a protein content of 2.3% to 3.8%; and a gas-producing regulator; wherein the gas-producing regulator is used to regulate the carbon dioxide production during the fermentation process of the kefir bacteria, so that the fermented milk contains microbubbles, and the amount of microbubbles is such that the pressure of the bubble fermented milk in a sealed container is ≥0.028 MPa; the bubble fermented milk changes from a solid state to a liquid state after shaking.
[0007] Preferably, in the above-mentioned bubble-fermented milk, the protein content of the raw milk is 2.6% to 3.0%; and / or the amount of microbubbles is such that the pressure of the bubble-fermented milk in the sealed container is 0.03 MPa to 0.05 MPa.
[0008] Preferably, in the above-mentioned bubble-fermented milk, the organic acid is selected from one or more combinations of concentrated lemon juice, citric acid, or malic acid; and / or the raw milk is selected from one or more combinations of raw milk, reconstituted milk, or skim milk.
[0009] Preferably, in the above-mentioned bubble-fermented milk, the organic acid is selected from concentrated lemon juice, and the amount of concentrated lemon juice added is 0.1‰ to 0.5‰ of the raw material mass.
[0010] Preferably, in the above-mentioned bubble-fermented milk, the kefir strain is one or more combinations of CHOOZIT@KefirMild_01, AiBiGolden Time DR 15.17, or DI-PROX K01.
[0011] Preferably, in the above-mentioned bubble-fermented milk, the raw materials also include sweeteners and / or stabilizers.
[0012] More preferably, in the above-mentioned bubble-fermented milk, the sweetener is selected from white sugar and / or sugar substitute; and / or the stabilizer is selected from one or more combinations of diacetyl tartaric acid mono- and diglycerides, gelatin or pectin.
[0013] More preferably, in the above-mentioned bubble-fermented milk, the sweetener is white sugar, and the amount of white sugar added is 0% to 10% of the raw material mass; and / or in the stabilizer, the amount of diacetyl tartaric acid mono- and diglycerides added is 0.08% to 0.12% of the raw material mass, the amount of gelatin added is 0.15% to 0.25% of the raw material mass, and the amount of pectin added is 0.1% to 0.2% of the raw material mass.
[0014] Another aspect of the present invention provides a method for preparing the above-mentioned bubble fermented milk, the method comprising: homogenizing the raw materials sequentially, sterilizing them, inoculating them with kefir bacteria for fermentation, and then ripening them to obtain bubble fermented milk; the fermentation endpoint is that the pressure of the product in a sealed container is ≥0.028 MPa.
[0015] Preferably, in the above preparation method, fermentation includes: static fermentation at 30℃±1℃ for 10 to 15 hours until the pH value drops to 4.2 to 4.6 and the acidity reaches 70°T to 90°T; and / or post-ripening includes: cooling the fermented product to 4℃ to 6℃ and statically ripening for 5 to 10 hours.
[0016] The beneficial effects of this invention include: (1) By constructing a “bubble-protein network composite structure”, the shear stress during shaking is preferentially concentrated at the interface between the bubble and the protein. The gel breaks down regularly along the bubble wall to form uniform and fine protein fragments. At the same time, the dissolved extracellular polysaccharides suspend the fragments uniformly through their pseudoplasticity and spatial stability. Experimental data show that the viscosity of the fermented milk (coagulation type) in this invention can be reduced to 3670 cp after shaking, and the particle size after shaking is “smooth and delicate with no visible particles”, thus achieving a smooth liquid texture without any particle feel.
[0017] (2) The present invention precisely regulates the metabolic activity of kefir bacteria by medium-temperature fermentation and the addition of a specific amount of gas-producing regulator. Experiments show that as the amount of concentrated lemon juice added increases from 0.1g to 0.5g, the pressure inside the bottle increases from 0.028MPa to 0.050MPa, the destruction rate increases from 79.29% to 90.21%, and the viscosity after shaking decreases from 5415cp to 2560cp. When the pressure is controlled at 0.03MPa to 0.05MPa, the product has a distinct astringent taste (bubblyness score ≥7.1) and will not cause gel structure destruction or whey separation due to excessive gas pressure, thus achieving an ideal balance between bubble sensation, thixotropy and flavor. Attached Figure Description
[0018] Figure 1 The fermented milk (coagulated type) obtained from schemes 1 to 4 is shaken to obtain fermented milk (liquid type); Figure 2 The bubble pattern of the fermented milk (coagulated type) obtained from schemes 5 to 9; Figure 3 The fermented milk (coagulated type) obtained from schemes 10 to 13 is shaken to obtain fermented milk (liquid type); Figure 4 The preferences for fermented milk obtained from Scheme 2 and Scheme 11; Figure 5 Radar charts showing the sensory characteristics of fermented milk obtained from schemes 2 and 11; Figure 6 The stability of fermented milk (coagulated type) obtained by Scheme 11 and Schemes 14 to 16 after shaking at different temperatures. Detailed Implementation
[0019] The embodiments described are provided to better illustrate the present invention, but are not intended to limit the scope of the invention to the embodiments described. Therefore, non-essential improvements and adjustments made to the embodiments by those skilled in the art based on the above description are still within the scope of protection of the present invention.
[0020] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. Singular expressions include plural expressions unless they have a distinct meaning in the context. As used herein, it should be understood that terms such as “comprising,” “having,” “including,” are intended to indicate the presence of features, numbers, operations, components, parts, elements, materials, or combinations thereof. The terminology of the invention is disclosed in the specification and is not intended to exclude the possibility that one or more other features, numbers, operations, components, parts, elements, materials, or combinations thereof may be present or added. As used herein, “ / ” may be interpreted as “and” or “or,” depending on the context.
[0021] In a first aspect, embodiments of the present invention provide a bubble-fermented milk with thixotropic properties. The bubble-fermented milk is made from raw materials containing the following materials through fermentation with kefir bacteria: raw milk with a protein content of 2.3% to 3.8%; and a gas-producing regulator. The gas-producing regulator is used to regulate the carbon dioxide production during the fermentation process of the kefir bacteria, so that the fermented milk contains microbubbles, and the amount of microbubbles is such that the pressure of the bubble-fermented milk in a sealed container is ≥0.028 MPa. The bubble-fermented milk changes from a solid state to a liquid state after shaking.
[0022] It should be noted that this invention aims to overcome the shortcomings of existing technologies and solve three major technical problems: ① to achieve excellent thixotropy in set-type yogurt without adding exogenous thickeners, stabilizers, or egg-based substances; ② to combine kefir fermentation CO2 bubbles with a thixotropic structure to achieve a smooth, particle-free liquid state after shaking; ③ to balance the effervescence, thixotropy, and flavor through the fermentation process. Based on bubble theory, this invention achieves a smooth texture and fineness by controlling gas production and matching appropriate protein dry matter indicators to ensure easy shaking, ultimately achieving the ideal effect of "smooth, easy to shake, and delicious." The fermented milk of this invention uses kefir bacteria to construct a reversible protein gel network using metabolized extracellular polysaccharides (EPS), while CO2 microbubbles form uniform gas cells within the network. These two elements synergistically impart thixotropy. In its static state, it is a set-type yogurt with a firm texture that can be scooped with a spoon. After gentle shaking, it transforms into a drinkable yogurt with a significantly reduced viscosity, a smooth texture, no particles or lumps, and contains CO2 microbubbles, providing a smooth, carbonated beverage-like taste upon tasting. The raw milk protein content is controlled between 2.3% and 3.8%, such as 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.5%, or 3.7%. The pressure of the fermented milk in the sealed container is controlled at ≥0.028MPa, such as 0.03MPa, 0.04MPa, or 0.05MPa. A quantifiable thixotropic index system is constructed: the puncture force of the static texture analyzer meets the standard, the viscosity after shaking is ≤4000cp, the thixotropic recovery rate is 30% to 40%, and the thixotropic ring area is quantifiable. The product achieves two forms: static coagulation and ready to drink after shaking, expanding consumption scenarios with one product for two uses.
[0023] In some specific examples, in the above-mentioned bubble-fermented milk, the protein content of the raw milk is 2.6% to 3.0%; and / or the amount of microbubbles makes the pressure of the bubble-fermented milk in the sealed container 0.03 MPa to 0.05 MPa.
[0024] It should be noted that the protein content of the raw milk in this invention is preferably 2.6% to 3.0%, such as 2.6%, 2.7%, 2.8%, 2.9%, or 3.0%. The amount of microbubbles allows the pressure of the fermented milk in the sealed container to preferably be 0.03 MPa to 0.05 MPa, such as 0.03 MPa, 0.04 MPa, or 0.05 MPa. The fermented milk prepared under the above conditions exhibits excellent stability in both its coagulated and liquid forms, and also shows better thixotropy.
[0025] In some specific examples, in the above-mentioned bubble-fermented milk, the organic acid is selected from one or more combinations of concentrated lemon juice, citric acid, or malic acid; and / or the raw milk is selected from one or more combinations of raw milk, reconstituted milk, or skim milk.
[0026] It should be noted that organic acids, as the core gas-producing regulators, can be used alone or in combination to precisely control the metabolic rate and CO2 production of Kefir bacteria. Combined with the raw milk system, they maintain the stability of the bubble-protein network. The raw milk can be raw milk, reconstituted milk, or skim milk, all of which can achieve protein standardization, adapt to the needs of full-fat / low-fat products, and do not affect thixotropy and microbubble formation.
[0027] In some specific examples, in the above-mentioned bubble-fermented milk, the organic acid is selected from concentrated lemon juice, and the amount of concentrated lemon juice added is 0.1‰ to 0.5‰ of the raw material mass.
[0028] It should be noted that concentrated lemon juice is the preferred gas-producing regulator, and the specific amount added can be 0.1‰ to 0.5‰, which can be further preferred to be 0.2‰ to 0.5‰, such as 0.2‰, 0.3‰, 0.4‰ or 0.5‰, etc., and more preferably 0.3‰. Through medium-temperature fermentation (30℃±1℃) and this amount of addition, the metabolism of the strain is synergistically regulated, which ensures high production of EPS to form a stable gel, while avoiding excessive gas production that damages the structure. Under these conditions, the bubble fermented milk has a bubble sensation score of ≥7.1, and the viscosity after shaking is reduced to 2560cp~3760cp, achieving the optimal balance between bubble sensation, gel stability and flavor.
[0029] In some specific examples, the kefir strains in the above-mentioned bubble-fermented milk are one or more combinations of CHOOZIT@KefirMild_01, AiBi Golden Time DR 15.17, or DI-PROX K01.
[0030] It should be noted that the above-mentioned strains all possess the dual characteristics of high extracellular polysaccharide production and moderate gas production. AiBiGolden Time DR 15.17 is the preferred strain, which can autonomously construct a reversible protein gel network and generate uniform CO2 microbubbles. It can achieve thixotropic properties of static solidification and liquefaction after shaking without the need for exogenous additives, while giving the product the unique refreshing fermented flavor of kefir, meeting the needs of clean label and dual-form consumption.
[0031] In some specific examples, the ingredients in the above-mentioned bubble-fermented milk also include sweeteners and / or stabilizers.
[0032] It should be noted that the sweetener is used to neutralize the fermented sourness and improve palatability. It does not interfere with kefir fermentation, microbubble generation, or the bubble-protein complex network structure, nor does it compromise the product's thixotropic properties or clean label attributes, thus catering to diverse consumer taste preferences. Furthermore, stabilizers are added to enhance long-term storage stability after shaking. These compound stabilizers improve the product's water-holding capacity, resolving the issue of easy stratification after prolonged cooling following shaking, without damaging the bubble-protein network or affecting the thixotropic properties of static solidification / re-liquidation after shaking.
[0033] In some specific examples, in the above-mentioned bubble-fermented milk, the sweetener is selected from white sugar and / or sugar substitutes.
[0034] It should be noted that granulated sugar can enhance the richness of the flavor, while sugar substitutes meet the demand for low-sugar / sugar-free products. The two can be used alone or in combination without affecting the fermentation process, pressure control, thixotropic properties, or microbubble distribution, thus balancing flavor and health benefits.
[0035] In some specific examples, in the above-mentioned bubble-fermented milk, the sweetener is white sugar, and the amount of white sugar added is 0% to 10% of the raw material mass.
[0036] In some specific examples, in the above-mentioned bubbly fermented milk, the stabilizer is selected from one or more combinations of diacetyl tartrate mono- and diglycerides, gelatin, or pectin.
[0037] It should be noted that the stabilizer in this invention can be a stabilizer known in the art, such as one or more combinations of diacetyl tartrate mono- and diglycerides, gelatin, or pectin listed above.
[0038] In some specific examples, in the above-mentioned bubble-fermented milk, the amount of diacetyl tartaric acid mono- and diglycerides added to the stabilizer is 0.08% to 0.12% of the raw material mass, the amount of gelatin added is 0.15% to 0.25% of the raw material mass, and the amount of pectin added is 0.1% to 0.2% of the raw material mass.
[0039] It should be noted that the specific proportions of stabilizer additions are as follows: the proportion of diacetyl tartaric acid mono- and diglycerides can be 0.08%, 0.09%, 0.10%, 0.11%, or 0.12%, etc.; the proportion of gelatin can be 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.20%, 0.21%, 0.22%, 0.23%, 0.24%, or 0.25%, etc.; and the proportion of pectin can be 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%, etc. This formulation allows the product to be stored at 4℃, 10℃, and 15℃ for 7 days without significant whey separation, significantly improving water retention capacity, while maintaining the core performance of thixotropic degradation rate ≥80% and recovery rate 30%-40%, preserving the dual-form consumer experience.
[0040] Secondly, embodiments of the present invention provide a method for preparing the above-mentioned bubble fermented milk. The preparation method includes: homogenizing the raw materials sequentially, sterilizing them, inoculating them with Kefir bacteria for fermentation, and then ripening them to obtain bubble fermented milk; the fermentation endpoint is that the pressure of the product in a sealed container is ≥0.028 MPa.
[0041] It should be noted that the preferred preparation method of this invention is as follows: ① Raw material pretreatment: Standardize the raw milk to a protein content of 2.6%–3.0%, add other raw materials, dissolve, homogenize, and sterilize; ② Inoculation: Inoculate with kefir bacteria after cooling to 28℃–32℃; ③ Mesophilic fermentation: Ferment at 30℃±1℃ for 10–15 hours until pH 4.2–4.6 and acidity 70°T–90°T; ④ Post-ripening: Cool to 4℃–6℃ and let stand for 5–10 hours; ⑤ Finished product. By quantitatively controlling the amount of bubbles using the pressure of a sealed container, the prepared fermented milk achieves a spoon-eating palatability score of 9.3, a drinking palatability score of 9.3, a total sensory score of 45.1, and a consumer preference score of 8.1, realizing both spoon-eating (like cola pudding) and drinking (like carbonated yogurt) scenarios.
[0042] To better understand the present invention, specific examples are provided below to further illustrate the content of the present invention, but the content of the present invention is not limited to the examples below.
[0043] The testing methods for different performance characteristics of the fermented milk are as follows: Viscosity test: The viscosity was measured using a BROOKFIELDDV2T viscometer with a No. 64 rotor. The measurement parameters were 10 rpm and 30 s. Texture testing: The texture was measured using a TA.XT ExpressC texture analyzer with an A / BE probe. The measurement parameters were: test speed 1 mm / s, forward distance 10 mm, and sensing force 0.5 g.
[0044] Thixotropy test: A Brookfield (DV2T) rotational viscometer with an LV-4 rotor was used. The first stage involved measuring the initial apparent viscosity (η0) at 10 rpm. The second stage involved high-shear destruction of the structure at 100 rpm, with the viscosity measured at η1. The third stage involved recovery (recovery time 3 min) to 10 rpm, with the recovered viscosity measured at η2. The thixotropic destruction rate and recovery rate were then calculated. Thixotropic degradation rate (%) = (η0-η1) / η0×100% Thixotropic recovery rate (%) = (η2-η1) / (η0-η1)×100% Water-holding capacity test: Accurately weigh the fermented milk sample mo, centrifuge at 4000 r / min for 15 minutes, let stand for 10 minutes and discard the supernatant, weigh the precipitate mass m; water-holding capacity (%) = m / mo × 100%.
[0045] The particle size of the fermented milk (liquid type) obtained after shaking the fermented milk (coagulated type) was tested according to the test method described in the published patent CN116298145A.
[0046] I. Strain Screening
[0047] (a) Preparation of fermented milk
[0048] (1) Standardize 919.4g of raw milk to a protein content of 3.0%, add 80g of white sugar and 0.1g of concentrated lemon juice (Gree Food Technology (Tianjin) Co., Ltd.; GZ201 concentrated lemon juice), and stir until dissolved. (2) After homogenization and sterilization, cool to 30°C; (3) Inoculate with 0.5g of bacterial agent and stir well; (4) Let it ferment at 30℃±1℃ until the pH is 4.5 and the acidity is about 80°T; (5) Cool to 4℃~10℃, let stand for 8 hours to ripen, and obtain fermented milk (coagulated type). (6) Fill the fermented milk (coagulated type) into a sealed container.
[0049] Schemes 1 to 4 use different microbial agents and are prepared according to the above preparation methods to obtain fermented milk (coagulated type). The names of the microbial agents and the microbial strains in Schemes 1 to 4 are shown in Table 1 below.
[0050] Table 1. Information on microbial agents for schemes 1 to 4
[0051] (ii) Fermented milk test
[0052] The texture and viscosity of the fermented milk (coagulated type) obtained by schemes 1 to 4 were tested respectively, and the results are shown in Table 2 below.
[0053] Table 2. Texture and viscosity of fermented milk (coagulated type) obtained from schemes 1 to 4
[0054] In addition, the thixotropy of the fermented milk (coagulated type) obtained by schemes 1 to 4 was tested respectively, and the results are shown in Table 3 below.
[0055] Table 3. Thixotropic properties of fermented milk (set-type) obtained from schemes 1 to 4
[0056] In addition, the fermented milk (coagulated type) obtained from schemes 1 to 4 was shaken (shaking incubator WY-250C (Tianjin Tester Instrument Co., Ltd.) 400rpm, 5min, the same below), and the texture and viscosity of the shaken fermented milk (liquid type) were tested. The results are shown in Table 4 below.
[0057] Table 4. Texture and viscosity of fermented milk (coagulated type) obtained from schemes 1 to 4 after shaking.
[0058] In addition, the fermented milk (set type) obtained from schemes 1 to 4, after being shaken, becomes fermented milk (liquid type) as follows: Figure 1 As shown in Table 5, the particle size after shaking is as follows.
[0059] Table 5. Particle size of fermented milk (coagulated type) obtained from schemes 1 to 4 after shaking.
[0060] In addition, sensory evaluations were conducted on the fermented milk (coagulated type) obtained from schemes 1 to 4 and the fermented milk (liquid type) after shaking. The evaluation criteria are shown in Table 6 below, and the evaluation results are shown in Table 7 below.
[0061] Table 6 Sensory Rating Criteria
[0062] Table 7 Sensory scores of fermented milk (before and after shaking) obtained from schemes 1 to 4
[0063] In summary, strains with stronger gas-producing capabilities produce more bubbles, but have lower texture and viscosity. The fermented milk (coagulated type) prepared by Scheme 4 has the highest texture and viscosity. Due to its compact texture, it has the worst thixotropy, is the most difficult to shake, has the highest viscosity after shaking, and the worst fluidity in the mouth; after shaking, it resembles tofu curds, is full of particles, has the worst taste, and lacks any unpleasant aftertaste. The fermented milk (coagulated type) prepared by Scheme 1 has the next best texture and viscosity, with the highest rate of thixotropy disruption among the four schemes, and the lowest viscosity after shaking; however, its recovery rate is also high, which will affect the taste of the product during actual consumption, and after shaking, it contains 1.12mm–8.94mm yogurt curd particles, with only average effervescence. The fermented milk (set-type) prepared by Scheme 3 had the second-best texture and viscosity, and the lowest recovery rate in thixotropy. However, its own destruction rate was also low, making it difficult to shake. After shaking, it contained yogurt curd particles of 4.56mm to 12.55mm, with poor effervescence and a very weak astringent taste. The fermented milk (set-type) prepared by Scheme 2 had the lowest texture and viscosity, a higher destruction rate in thixotropy, and a lower recovery rate. After shaking, it was smooth and delicate, with no visible particles. Its effervescence and astringent taste were the strongest among all strains, but still insufficient. In addition, considering the comprehensive sensory evaluation results (Scheme 2 scored the highest), Scheme 2 was preferentially selected for subsequent screening experiments in this invention.
[0064] II. Gas Production Capacity Screening
[0065] (a) Preparation of fermented milk
[0066] Scheme 5 is the same as Scheme 2, and Schemes 6 to 9 are largely the same as Scheme 5, except that the amount of each raw material is different. The amount of raw materials used in Schemes 5 to 9 is shown in Table 8 below.
[0067] Table 8 Raw material consumption of Schemes 5 to 9
[0068] (ii) Fermented milk test
[0069] The texture and viscosity of the fermented milk (coagulated type) obtained by schemes 5 to 9 were tested respectively, and the results are shown in Table 9 below.
[0070] Table 9. Texture and viscosity of fermented milk (coagulated type) obtained from schemes 5 to 9
[0071] In addition, the thixotropy of the fermented milk (coagulated type) obtained by schemes 5 to 9 was tested respectively, and the results are shown in Table 3 below.
[0072] Table 10 Thixotropic properties of fermented milk (set-type) obtained from schemes 5 to 9
[0073] In addition, the bubble formation of the fermented milk (coagulated type) obtained from schemes 5 to 9 was observed, and the results are as follows: Figure 2 As shown.
[0074] In addition, the pressure of the fermented milk (coagulated type) obtained by schemes 5 to 9 in a closed container was tested respectively, and the results are shown in Table 11 below.
[0075] Table 11 Pressure of fermented milk (coagulated type) obtained from schemes 5 to 9 in a closed container
[0076] In addition, the fermented milk (coagulated type) obtained from schemes 5 to 9 was shaken (shaking for 20 seconds), and the texture and viscosity of the shaken fermented milk (liquid type) were tested. The results are shown in Table 12 below.
[0077] Table 12 Texture and viscosity of fermented milk (coagulated type) obtained from schemes 5 to 9 after shaking.
[0078] In addition, sensory evaluations were conducted on the fermented milk (coagulated type) obtained from schemes 5 to 9 and the fermented milk (liquid type) after shaking. The evaluation criteria are shown in Table 6 above, and the evaluation results are shown in Table 13 below.
[0079] Table 13 Sensory scores of fermented milk (before and after shaking) obtained from schemes 5 to 9
[0080] In summary, the more concentrated lemon juice added, the more bubbles the bacteria produce. These bubbles fill the gaps in the yogurt sample; the more bubbles there are, the worse the texture and the lower the viscosity. The thixotropic degradation rate is stronger, and the recovery rate is weaker; the texture and viscosity after shaking are also weaker. However, excessive bubbles can cause whey separation, resulting in whey water precipitation after fermentation, as seen in schemes 8 and 9. Excessive bubbles also negatively impact texture and viscosity, directly affecting sensory evaluation scores, as shown in Table 13, with scheme 7 achieving the highest sensory score. Therefore, this invention can optimize the amount of concentrated lemon juice added in scheme 7 for subsequent experiments.
[0081] III. Protein Content Screening
[0082] (a) Preparation of fermented milk
[0083] Option 10 to Option 13
[0084] Schemes 10 to 13 are largely the same as Scheme 7, except that the protein content of the raw milk is different (the protein index of the raw milk is adjusted by membrane filtration). Otherwise, they are the same as Scheme 7. The protein content of the raw milk in Schemes 10 to 13 is shown in Table 14 below.
[0085] Table 14 Raw milk protein content of schemes 10 to 13
[0086] (ii) Fermented milk test
[0087] The texture and viscosity of the fermented milk (coagulated type) obtained by schemes 10 to 13 were tested respectively, and the results are shown in Table 15 below.
[0088] Table 15 Texture and viscosity of fermented milk (coagulated type) obtained from schemes 10 to 13
[0089] In addition, the thixotropy of the fermented milk (coagulated type) obtained by schemes 10 to 13 was tested respectively, and the results are shown in Table 16 below.
[0090] Table 16 Thixotropic properties of fermented milk (set-type) obtained from schemes 10 to 13
[0091] In addition, the fermented milk (coagulated type) obtained from schemes 10 to 13 was shaken (shaking for 20 seconds), and the texture and viscosity of the shaken fermented milk (liquid type) were tested. The results are shown in Table 17 below.
[0092] Table 17 Texture and viscosity of fermented milk (coagulated type) obtained from schemes 10 to 13 after shaking.
[0093] In addition, the fermented milk (set type) obtained from schemes 10 to 13, after being shaken, becomes fermented milk (liquid type) as follows: Figure 3 As shown in Table 18, the particle size after shaking is as follows.
[0094] Table 18. Particle size of fermented milk (coagulated type) obtained from schemes 10 to 13 after shaking.
[0095] In addition, sensory evaluations were conducted on the fermented milk (coagulated type) obtained from schemes 10 to 13 and the fermented milk (liquid type) after shaking. The evaluation criteria are shown in Table 6 above, and the evaluation results are shown in Table 19 below.
[0096] Table 19 Sensory scores of fermented milk (before and after shaking) obtained from schemes 10 to 13
[0097] In summary, higher protein content results in stronger texture, higher viscosity, and a thicker, more compact overall sample. Lower thixotropic degradation and higher recovery rates lead to higher texture and viscosity after shaking, larger particle size, and a less smooth mouthfeel. The results show that Scheme 11 is optimal, exhibiting lower viscosity and texture, stronger degradation and recovery rates, a smooth and delicate texture without visible particles, and the highest mouthfeel score.
[0098] IV. Comparison between Scheme 11 and Scheme 2
[0099] The fermented milk (set type) and fermented milk (liquid type) prepared by Scheme 11 and Scheme 2 were subjected to a comprehensive sensory evaluation. Specifically, the differences and sensory attributes of the samples before and after formula optimization were analyzed using the three-point test, consumer preference test, pairwise preference test, and quantitative descriptive analysis.
[0100] The results of the three-point test are shown in Table 20. A total of 32 sensory evaluators participated. According to GB / T 12311-2012 Sensory Analysis Three-Point Test, at the α=0.05 level, the critical number of correctly selected individuals is 15. In this test, 30 individuals correctly selected individuals, indicating a significant difference between the two samples. P≤ (0.05), therefore, subsequent consumer preference testing can be conducted.
[0101] Table 20. Three-point test results of fermented milk prepared by schemes 11 and 2.
[0102] In addition, 92 consumers participated in the evaluation of consumer preference and paired preference tests. The average preference scores for Scheme 2 and Scheme 11 were 6.3 and 8.1 respectively (on a 1–9 scale, where 5 indicates "neither like nor dislike"), both above the neutral threshold, indicating that consumers accepted both samples, thus meeting the prerequisite for conducting a preference test. Further analysis showed that the preference score of the control sample was 2.1 points higher than that of the control sample, an increase of 28.57%. The results of the paired preference test showed that the number of consumers choosing Scheme 2 and Scheme 11 were 11 and 81 respectively, with the number of consumers choosing the control sample exceeding the critical value of α=0.05 (55 people) specified in GB / T 12310-2012. Therefore, there was a significant difference in the degree of consumer preference between the two samples. P≤ 0.05), and prefers option 11 (see Figure 4 ).
[0103] In addition, in the quantitative descriptive evaluation, 10 top-tier evaluators participated, using a 15-point intensity scale (0 indicating no sensation, 15 indicating extremely strong) to score 12 sensory attributes of the samples, including astringency, fermentation flavor, smoothness, viscosity, milkiness, sourness, sweetness, cheese flavor, astringency, powderiness, sweetener taste, and off-flavor. The analysis results are as follows: Figure 5 As shown, the main differences between the two samples lie in their mouthfeel, fermented flavor, smoothness, and viscosity; the remaining differences are minor. It is noteworthy that the adjusted scheme 11 exhibits significant differences in both flavor and mouthfeel.
[0104] V. Water-holding capacity test of fermented milk
[0105] (a) Preparation of fermented milk
[0106] Option 14 to Option 16
[0107] (1) Standardize the raw milk to a protein content of 2.8%, add 80g of white sugar, 0.3g of concentrated lemon juice (Gree Food Technology (Tianjin) Co., Ltd.; GZ201 concentrated lemon juice) and stabilizer, and stir until dissolved. (2) to (6) are the same as in method 11 (0.5g of starter).
[0108] Schemes 14 and 16 are prepared according to the stabilizer and raw milk amount set in Table 21 below, and fermented milk (coagulated type) is obtained by following the above preparation method.
[0109] Table 21 Stabilizers and Raw Milk Information for Schemes 14 to 16
[0110] (ii) Fermented milk test
[0111] Fermented milk (coagulated type) obtained from schemes 11 and 14 to 16 was shaken (shaking for 20 seconds) to obtain fermented milk (liquid type). The water-holding capacity of the fermented milk (liquid type) was tested respectively, and the results are shown in Table 22 below.
[0112] Table 22 Water-holding capacity of fermented milk (liquid type) obtained from schemes 11 and 14 to 16
[0113] In addition, the stability of the fermented milk (set type) obtained from schemes 11 and 14 to 16 after shaking was tested. Specifically, the different fermented milks (liquid type) were stored at 4°C, 10°C, and 15°C for 7 days, and the water separation was observed. The results are as follows. Figure 6 As shown, the results indicate that, at different storage temperatures, schemes 14 to 16, which added stabilizers, all exhibited significantly better water retention compared to scheme 11 (i.e., the control sample).
[0114] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.
Claims
1. A bubble-fermented milk with thixotropic properties, characterized in that, Bubble fermented milk is made from raw materials containing the following ingredients through fermentation with kefir bacteria: Raw milk, with a protein content of 2.3% to 3.8%; And gas production regulators; Among them, the gas-producing regulator is used to regulate the carbon dioxide production during the fermentation process of the Kefir strain, so that the fermented milk contains microbubbles, and the amount of microbubbles makes the pressure of the bubbly fermented milk in the sealed container ≥0.028MPa. After being shaken, the bubble-fermented milk changes from a coagulated state to a liquid state.
2. The bubble-fed fermented milk according to claim 1, characterized in that, The protein content of the raw milk is 2.6%–3.0%; and / or The amount of microbubbles results in a pressure of 0.03 MPa to 0.05 MPa in the fermented milk within a sealed container.
3. The bubble-fermented milk according to claim 1 or 2, characterized in that, The organic acid is selected from one or more combinations of concentrated lemon juice, citric acid, or malic acid; and / or The raw milk is selected from one or more combinations of raw milk, reconstituted milk, or skim milk.
4. The bubble-fermented milk according to claim 3, characterized in that, The organic acid is selected from concentrated lemon juice, and the amount of concentrated lemon juice added is 0.1‰ to 0.5‰ of the raw material mass.
5. The bubble-fermented milk according to claim 1, 2, or 4, characterized in that, The kefir strain is one or a combination of CHOOZIT@KefirMild_01, AiBi Golden Time DR 15.17, or DI-PROX K01.
6. The bubble-fermented milk according to claim 1, 2, or 4, characterized in that, The ingredients also include sweeteners and / or stabilizers.
7. The bubble-fermented milk according to claim 6, characterized in that, Sweeteners are selected from white sugar and / or sugar substitutes; and / or The stabilizer is selected from one or more combinations of diacetyl tartrate mono- and diglycerides, gelatin, or pectin.
8. The bubble-fermented milk according to claim 7, characterized in that, The sweetener is white granulated sugar, and the amount of white granulated sugar added is 0% to 10% of the raw material mass; and / or In the stabilizer, the amount of diacetyl tartaric acid mono- and diglycerides added is 0.08% to 0.12% of the raw material mass, the amount of gelatin added is 0.15% to 0.25% of the raw material mass, and the amount of pectin added is 0.1% to 0.2% of the raw material mass.
9. The method for preparing bubble-fermented milk according to any one of claims 1 to 8, characterized in that, The preparation method includes: homogenizing the raw materials sequentially, sterilizing them, inoculating them with Kefir bacteria for fermentation, and then ripening them to obtain bubble-fermented milk; the fermentation endpoint is when the pressure of the product in a sealed container is ≥0.028MPa.
10. The preparation method according to claim 9, characterized in that, Fermentation includes: static fermentation at 30℃±1℃ for 10 to 15 hours, until the pH value drops to 4.2 to 4.6 and the acidity reaches 70°T to 90°T; and / or Post-fermentation includes cooling the fermented product to 4℃~6℃ and allowing it to stand for 5 to 10 hours to mature.