3-hydroxybutyric acid ethyl ester fortified fermented yogurt and a method for preparing the same
Patent Information
- Application Number
- CN202611334760.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-08-31
- Publication Date
- 2026-10-20
AI Technical Summary
[0004]针对现有功能发酵酸奶现有外源添加物普遍存在干扰乳酸菌活性、改变酸奶原有风味及凝胶体系稳定性不足的技术问题，本发明提出了一种3-羟基丁酸乙酯强化发酵酸奶及其制备方法
[0017]（1）本发明能够改善酸奶的感官风味品质。添加3-羟基丁酸乙酯后，酸奶鲜味、丰富度及整体滋味协调性得到提升；挥发性风味物质组成得到优化，醇类、酯类及部分具有甜香特征的挥发性组分相对含量增加，使产品风味更加丰富、协调。
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of food biotechnology and functional fermented dairy products, and particularly relates to a method for preparing fermented yogurt. Background Technology
[0002] With the increasing emphasis on health-conscious consumption, fermented dairy products are gradually evolving from traditional nutritional foods towards functional and precision nutrition. Among them, fermented yogurt has garnered widespread attention due to its excellent digestibility, prominent prebiotic functions, and rich flavor. Currently, functional yogurts on the market primarily achieve quality improvement and nutritional fortification by adding plant-based active ingredients, polysaccharides, prebiotics, and functional lipids. However, existing functional fortification strategies still suffer from problems such as significant product homogenization, insufficient flavor harmony, poor structural stability, and low utilization rate of active ingredients.
[0003] The quality of fermented yogurt mainly depends on lactic acid bacteria metabolism, protein gel network formation, and changes in physicochemical properties during storage. Currently, yogurt quality is typically evaluated using a comprehensive approach, considering indicators such as pH, titratable acidity, water-holding capacity, viable cell count, sensory characteristics, volatile flavor, and rheological properties. However, in actual production and storage, issues such as gel shrinkage, whey separation, and flavor degradation are common. To address these shortcomings, the industry has attempted to introduce exogenous functional components such as plant polyphenols, polysaccharides, and enzymes into the fermentation system to enhance network structure, regulate flavor, and extend shelf life. However, these often suffer from limited compatibility with milk protein systems, potential impact on lactic acid bacteria activity, and fluctuations in gel network structure. Therefore, developing a novel functional enhancement system that can maintain normal lactic acid bacteria growth while simultaneously achieving flavor regulation, structural stability, and rheological performance optimization is of significant research value and application potential. Summary of the Invention
[0004] To address the common technical problems of existing exogenous additives in functional fermented yogurts, such as interference with lactic acid bacteria activity, alteration of the original flavor of the yogurt, and insufficient stability of the gel system, this invention proposes a 3-hydroxybutyrate-fortified fermented yogurt and its preparation method. By introducing an appropriate amount of 3-hydroxybutyrate into the yogurt fermentation system, the quality formation during the fermentation process and storage is regulated while ensuring normal fermentation and survival of lactic acid bacteria. This improves the volatile flavor composition of the product, maintains acidity stability and water-holding capacity, and optimizes the gel network structure and rheological properties, thereby obtaining a fermented yogurt product with good sensory quality, structural stability, and functional properties.
[0005] To achieve the above objectives, the technical solution of the present invention is implemented as follows:
[0006] A fermented yogurt fortified with ethyl 3-hydroxybutyrate, the raw materials of which include fresh milk, ethyl 3-hydroxybutyrate and a starter culture.
[0007] Furthermore, based on the weight of raw milk, the amount of ethyl 3-hydroxybutyrate added is 0.6-3 mg / kg, and the amount of starter culture added is 0.05-0.2 wt% of the weight of raw milk.
[0008] The aforementioned starter culture includes a combined starter culture of Lactobacillus bulgaricus and Streptococcus thermophilus. The viable count of the combined starter culture is 1 × 10⁻⁶. 6 CFU / g-1×10 7 CFU / g; the ratio of viable bacteria in Lactobacillus bulgaricus and Streptococcus thermophilus was 1:1.
[0009] The preparation method of the above-mentioned ethyl 3-hydroxybutyrate fortified fermented yogurt includes the following steps:
[0010] (1) Pasteurize the raw milk in a constant temperature water bath, and then quickly cool it to below 42°C to obtain pretreated raw milk. Use the pretreated raw milk as a fermentation base, add ethyl 3-hydroxybutyrate, mix well and pasteurize to obtain a mixture.
[0011] (2) After cooling the mixture obtained in step (1), inoculate it with the fermentation agent and seal it; then, place the sealed sample in a fermentation chamber for constant temperature fermentation.
[0012] (3) After fermentation, the mixture is transferred to a 4 ℃ temperature for post-ripening to obtain the ethyl 3-hydroxybutyrate fortified fermented yogurt.
[0013] In step (1) above, the pasteurization temperature is 75-90 ℃ and the time is 10-20 min.
[0014] In step (2) above, the temperature for constant temperature fermentation is 40-43 ℃ and the time is 6-12 h.
[0015] The ripening time in step (3) above is 12-24 hours.
[0016] The beneficial effects of this invention are:
[0017] (1) The present invention can improve the sensory flavor quality of yogurt. After adding ethyl 3-hydroxybutyrate, the umami, richness and overall flavor harmony of yogurt are improved; the composition of volatile flavor substances is optimized, and the relative contents of alcohols, esters and some volatile components with sweet aroma characteristics are increased, making the product flavor richer and more harmonious.
[0018] (2) By introducing ethyl 3-hydroxybutyrate as a functional enhancement factor, this invention does not affect the normal fermentation process of yogurt, can keep the final pH and titratable acidity of yogurt within a stable range, with small pH changes, can effectively alleviate the acidification phenomenon of yogurt and improve the shelf life stability of the product.
[0019] (3) The present invention can improve the survival stability of fermentation strains during cold storage. After 14 days of cold storage, the number of viable bacteria of Streptococcus thermophilus and Lactobacillus bulgaricus remained at a high level, and significantly exceeded the minimum viable bacteria count required by the national standard, effectively slowing down the decline of viable lactic acid bacteria count and improving the probiotic activity and storage quality of the product.
[0020] (4) This invention achieves synergistic optimization of yogurt flavor, storage stability and probiotic activity, so that the product maintains good overall quality throughout the shelf life and has good market application value.
[0021] (5) The preparation method of the present invention is simple, the processing conditions are mild and the repeatability is high, making it suitable for industrial production. Attached Figure Description
[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0023] Figure 1 This is a picture of the 3-hydroxybutyrate-fortified fermented yogurt prepared according to the present invention.
[0024] Figure 2 Electronic tongue images of different fermentation groups in the examples and comparative examples after the yogurt has matured.
[0025] Figure 3 The graph shows the relative content of different fermentation groups in the examples and comparative examples after yogurt ripening, as measured by GC-IMS.
[0026] Figure 4 The pH value changes of different fermentation groups in the examples and comparative examples over 1-14 days are shown in the graph.
[0027] Figure 5 The graph shows the changes in titratable acid value of different fermentation groups in the examples and comparative examples from 1 to 14 days.
[0028] Figure 6 The graph shows the water-holding capacity changes of different fermentation groups in the examples and comparative examples from 1 to 14 days.
[0029] Figure 7The graph shows the changes in L. bulgaricus colony size in different fermentation groups of the examples and comparative examples over 1-14 days.
[0030] Figure 8 The graph shows the changes in thermophilic streptococcal colonies in different fermentation groups of the examples and comparative examples from 1 to 14 days. Detailed Implementation
[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0032] The fermentation agent used in this invention is a compound solid-state fermentation agent of Lactobacillus bulgaricus and Streptococcus thermophilus, provided by Angel Yeast Co., Ltd.
[0033] Example 1
[0034] The preparation method of ethyl 3-hydroxybutyrate fortified fermented yogurt in this embodiment includes the following steps:
[0035] (1) Pasteurize the raw milk in a constant temperature water bath at 90℃ for 10 min, remove it and cool it rapidly to below 42℃ to obtain pretreated raw milk, which is then sealed for later use. Weigh 0.21 g of ethyl 3-hydroxybutyrate and add it to 69.79 g of pretreated raw milk, mix thoroughly to obtain mother liquor A.
[0036] (2) Weigh 5.00 g of mother liquor A and add it to 495 g of pretreated raw milk. Mix thoroughly to obtain mother liquor B.
[0037] (3) Weigh 4 g of mother liquor B and add it to a sterilized yogurt bottle, then add 195.85 g of pretreated milk. Pasteurize at 75°C for 10 min, and allow to cool naturally to below 42°C. Then add 0.2 g of starter culture (the viable count of the compound starter culture is 1×10⁻⁶). 6 CFU / g; wherein the live count ratio of Lactobacillus bulgaricus and Streptococcus thermophilus was 1:1) was thoroughly mixed. The sample was fermented at a constant temperature of 42 ℃ for 6 h, and after fermentation, it was transferred to 4 ℃ for post-ripening for 24 h to finally obtain fermented yogurt with an added amount of ethyl 3-hydroxybutyrate of 0.6 mg / kg. The actual product image is shown below. Figure 1 As shown.
[0038] Example 2
[0039] The preparation method of ethyl 3-hydroxybutyrate fortified fermented yogurt in this embodiment includes the following steps:
[0040] (1) Pasteurize the raw milk in a constant temperature water bath at 90℃ for 10 min, remove it and cool it rapidly to below 42℃ to obtain pretreated raw milk, which is then sealed for later use. Weigh 0.21 g of ethyl 3-hydroxybutyrate and add it to 69.79 g of pretreated raw milk, mix thoroughly to obtain mother liquor A.
[0041] (2) Weigh 5.00 g of mother liquor A and add it to 495 g of pretreated raw milk. Mix thoroughly to obtain mother liquor B.
[0042] (3) Weigh 8 g of mother liquor B and add it to a sterilized yogurt bottle, then add 191.85 g of pretreated milk. Pasteurize at 75°C for 10 min, and allow to cool naturally to below 42°C. Then add 0.2 g of starter culture (the viable count of the compound starter culture is 1×10⁻⁶). 6 The sample was thoroughly mixed with CFU / g (where the ratio of viable Lactobacillus bulgaricus to Streptococcus thermophilus was 1:1). The sample was fermented at a constant temperature of 42 ℃ for 6 h, and then transferred to 4 ℃ for post-ripening for 24 h to finally obtain fermented yogurt with an added amount of ethyl 3-hydroxybutyrate of 1.2 mg / kg.
[0043] Example 3
[0044] The preparation method of ethyl 3-hydroxybutyrate fortified fermented yogurt in this embodiment includes the following steps:
[0045] (1) Pasteurize the raw milk in a constant temperature water bath at 90℃ for 10 min, remove it and cool it rapidly to below 42℃ to obtain pretreated raw milk, which is then sealed for later use. Weigh 0.21 g of ethyl 3-hydroxybutyrate and add it to 69.79 g of pretreated raw milk, mix thoroughly to obtain mother liquor A.
[0046] (2) Weigh 5.00 g of mother liquor A and add it to 495 g of pretreated raw milk. Mix thoroughly to obtain mother liquor B.
[0047] (3) Weigh 12 g of mother liquor B and add it to a sterilized yogurt bottle, then add 187.85 g of pretreated milk. Pasteurize at 75 ℃ for 10 min, and allow to cool naturally to below 42 ℃. Then add 0.2 g of starter culture (the viable count of the compound starter culture is 1×10⁻⁶). 6 The sample was thoroughly mixed with CFU / g (where the ratio of viable Lactobacillus bulgaricus to Streptococcus thermophilus was 1:1). The sample was fermented at a constant temperature of 42 ℃ for 6 h, and then transferred to 4 ℃ for post-ripening for 24 h to finally obtain fermented yogurt with an added amount of ethyl 3-hydroxybutyrate of 1.8 mg / kg.
[0048] Example 4
[0049] The preparation method of ethyl 3-hydroxybutyrate fortified fermented yogurt in this embodiment includes the following steps:
[0050] (1) Pasteurize the raw milk in a constant temperature water bath at 90℃ for 10 min, remove it and cool it rapidly to below 42℃ to obtain pretreated raw milk, which is then sealed for later use. Weigh 0.21 g of ethyl 3-hydroxybutyrate and add it to 69.79 g of pretreated raw milk, mix thoroughly to obtain mother liquor A.
[0051] (2) Weigh 5.00 g of mother liquor A and add it to 495 g of pretreated raw milk. Mix thoroughly to obtain mother liquor B.
[0052] (3) Weigh 16 g of mother liquor B and add it to a sterilized yogurt bottle, then add 183.85 g of pretreated milk. Then pasteurize at 75 ℃ for 10 min, and allow to cool naturally to below 42 ℃ before adding 0.2 g of starter culture (the viable count of the compound starter culture is 1×10⁻⁶). 6 The sample was thoroughly mixed with CFU / g (where the ratio of viable Lactobacillus bulgaricus to Streptococcus thermophilus was 1:1). The sample was fermented at a constant temperature of 42 ℃ for 6 h, and after fermentation, it was transferred to 4 ℃ for post-ripening for 24 h to finally obtain fermented yogurt with an added amount of ethyl 3-hydroxybutyrate of 2.4 mg / kg.
[0053] Example 5
[0054] The preparation method of ethyl 3-hydroxybutyrate fortified fermented yogurt in this embodiment includes the following steps:
[0055] (1) Pasteurize the raw milk in a constant temperature water bath at 90℃ for 10 min, remove it and cool it rapidly to below 42℃ to obtain pretreated raw milk, which is then sealed for later use. Weigh 0.21 g of ethyl 3-hydroxybutyrate and add it to 69.79 g of pretreated raw milk, mix thoroughly to obtain mother liquor A.
[0056] (2) Weigh 5.00 g of mother liquor A and add it to 495 g of pretreated raw milk. Mix thoroughly to obtain mother liquor B.
[0057] (3) Weigh 20 g of mother liquor B and add it to a sterilized yogurt bottle, then add 179.85 g of pretreated milk. Pasteurize at 75 ℃ for 10 min, and allow to cool naturally to below 42 ℃. Then add 0.2 g of starter culture (the viable count of the compound starter culture is 1×10⁻⁶). 6The sample was thoroughly mixed with CFU / g (where the ratio of viable Lactobacillus bulgaricus to Streptococcus thermophilus was 1:1). The sample was fermented at a constant temperature of 42 ℃ for 6 h, and after fermentation, it was transferred to 4 ℃ for post-ripening for 24 h to finally obtain fermented yogurt with an added amount of 3.0 mg / kg of ethyl 3-hydroxybutyrate.
[0058] Example 6
[0059] The preparation method of ethyl 3-hydroxybutyrate fortified fermented yogurt in this embodiment includes the following steps:
[0060] (1) Pasteurize the raw milk in a constant temperature water bath at 90℃ for 10 min, remove it and cool it rapidly to below 42℃ to obtain pretreated raw milk, which is then sealed for later use. Weigh 0.21 g of ethyl 3-hydroxybutyrate and add it to 69.79 g of pretreated raw milk, mix thoroughly to obtain mother liquor A.
[0061] (2) Weigh 5.00 g of mother liquor A and add it to 495 g of pretreated raw milk. Mix thoroughly to obtain mother liquor B.
[0062] (3) Weigh 12 g of mother liquor B and add it to a sterilized yogurt bottle, then add 187.85 g of pretreated milk. Then pasteurize at 90 ℃ for 10 min, and allow to cool naturally to below 42 ℃ before adding 0.4 g of starter culture (the viable count of the compound starter culture is 1×10⁻⁶). 7 The sample was thoroughly mixed with CFU / g (where the ratio of viable Lactobacillus bulgaricus to Streptococcus thermophilus was 1:1). The sample was fermented at a constant temperature of 43 ℃ for 8 h, and then transferred to 4 ℃ for post-ripening for 20 h to finally obtain fermented yogurt with an added amount of ethyl 3-hydroxybutyrate of 1.8 mg / kg.
[0063] Example 7
[0064] The preparation method of ethyl 3-hydroxybutyrate fortified fermented yogurt in this embodiment includes the following steps:
[0065] (1) Pasteurize the raw milk in a constant temperature water bath at 90℃ for 10 min, remove it and cool it rapidly to below 42℃ to obtain pretreated raw milk, which is then sealed for later use. Weigh 0.21 g of ethyl 3-hydroxybutyrate and add it to 69.79 g of pretreated raw milk, mix thoroughly to obtain mother liquor A.
[0066] (2) Weigh 5.00 g of mother liquor A and add it to 495 g of pretreated raw milk. Mix thoroughly to obtain mother liquor B.
[0067] (3) Weigh 12 g of mother liquor B and add it to a sterilized yogurt bottle, then add 187.85 g of pretreated milk. Pasteurize at 80 ℃ for 20 min, and allow to cool naturally to below 42 ℃. Then add 0.1 g of starter culture (the viable count of the compound starter culture is 1×10⁻⁶). 7 The sample was thoroughly mixed with CFU / g (where the ratio of viable Lactobacillus bulgaricus to Streptococcus thermophilus was 1:1). The sample was fermented at a constant temperature of 40 °C for 12 h, and then transferred to 4 °C for further ripening for 12 h to obtain fermented yogurt with an added amount of ethyl 3-hydroxybutyrate of 1.8 mg / kg.
[0068] Comparative Example 1
[0069] The preparation method of the fermented yogurt in this comparative example is as follows:
[0070] Fresh milk was pasteurized in a 90℃ constant temperature water bath for 10 minutes, then rapidly cooled to below 42℃ to obtain pretreated fresh milk, which was then sealed for later use. 200 g of the pretreated fresh milk was weighed and added to a sterilized yogurt bottle, along with 0.2 g of starter culture (the compound starter culture had a viable count of 1×10⁻⁶). 6 The sample was thoroughly mixed (CFU / g, with a live bacteria ratio of 1:1 for Lactobacillus bulgaricus and Streptococcus thermophilus). The sample was fermented at a constant temperature of 42 °C for 6 h, and then transferred to 4 °C for further ripening for 24 h to obtain fermented yogurt.
[0071] Implementation Results Example
[0072] Yogurt samples prepared according to Examples 1-5 and Comparative Example 1 were used to determine their flavor characteristics, physicochemical properties, microbiological characteristics and rheological behavior.
[0073] (1) Electronic tongue analysis: Yogurt samples were diluted with distilled water at a volume ratio of 1:1 and mixed thoroughly. After filtering through double-layer gauze to remove suspended matter, the filtrate was diluted again at a volume ratio of 1:10 for later use and evaluated using the Japanese Insent taste analyzer (electronic tongue).
[0074] like Figure 2 As shown, the electronic tongue radar image compares the taste characteristics of the control group and each embodiment. The overall taste profiles of each embodiment are similar, with bitterness, bitter aftertaste, astringent aftertaste, umami, richness, and saltiness all significantly higher than the control group, while sourness shows little difference. This indicates that the treatment of this invention can enhance the positive tastes such as umami and richness of the samples, while also strengthening bitter-related flavors, thus improving the taste characteristics of the product.
[0075] (2) Determination of relative flavor content: Volatile signals were collected by GC-IMS, retention index (RI) was calculated by C4-C9 n-ketones, qualitative analysis was performed by combining NIST and IMS databases, and the relative content of each flavor substance was calculated by peak volume normalization method.
[0076] like Figure 3 As shown, the stacked bar chart compares the relative contents of volatile components in the comparative example and each embodiment. The results indicate that ketones are the dominant volatile components in the system. After treatment with this invention, the proportion of alcohols increases, the content of esters increases significantly in Examples 4 and 5, the proportion of ketones decreases slightly, and the aldehyde component remains basically stable. Simultaneously, the relative contents of organic acids and ketones with sweet aroma characteristics increase. These changes demonstrate that the method of this invention can effectively control the composition ratio of volatile components in yogurt, optimizing flavor harmony and fullness.
[0077] (3) Store the finished product prepared above at 4°C for 1-14 days, and periodically take samples to test key indicators such as pH, titratable acidity and viable count.
[0078] a) Determination of pH value and titratable acidity: pH values were measured for each group of yogurt samples using a pH meter. Titratable acidity: 5 g of yogurt sample was placed in a 50 mL Erlenmeyer flask, 10 mL of ultrapure water was added, and after stirring well, 2-3 drops of phenolphthalein indicator were added. Then, 0.1 mol / L NaOH standard solution was slowly added dropwise using an alkaline burette until the solution in the Erlenmeyer flask turned pink and remained pink for 30 seconds. After titration, the burette reading was taken at eye level, and the volume of NaOH solution consumed was recorded. The titratable acidity value of the yogurt sample was calculated using the formula:
[0079]
[0080] In the formula: c is the molar concentration of NaOH solution, in mol / L; V is the volume of 0.1 mol / L NaOH standard solution consumed, in mL; m is the mass of yogurt sample, in g.
[0081] like Figure 4 As shown, during the storage period of 1-14 days, the pH of each group decreased slightly overall, indicating that the treatment of the present invention does not interfere with the initial acidification process of yogurt. After refrigeration at 4°C to day 14, the pH of each group showed a slow downward trend overall. This phenomenon is due to post-acidification caused by the residual metabolic activity of lactic acid bacteria. Among them, the pH of Comparative Example 1 decreased significantly (except for Example 7), indicating post-acidification; the pH of each example group remained basically stable, with no significant difference compared with the group on day 1 of storage.
[0082] like Figure 5As shown, during the storage period of 1-14 days, the initial TA of both Comparative Example 1 and the Example Group was higher than 80 °T, which meets the requirements for titratable acidity of yogurt in GB 19302-2010. During refrigeration at 4 °C, the post-acidification phenomenon of increased TA was observed, with the TA values of both Comparative Example 1 and the Example Group showing a significant stepwise increase during the 1-14 day period. Combined with the pH results, it can be seen that although the TA of all groups increased with prolonged storage time, the pH of the Example Group remained relatively stable, indicating that the treatment of the present invention can, to a certain extent, regulate the acidity changes of the system and improve the storage stability of the product.
[0083] b) Water-holding capacity test: First, weigh a 50 mL empty centrifuge tube. Then, weigh 10 g of yogurt sample into the same centrifuge tube and centrifuge at low temperature using a refrigerated centrifuge. The specific conditions are: centrifuge at 4 ℃ and 5000 r / min for 15 min. Let it stand for 10 min and discard the supernatant. Finally, weigh the remaining precipitate and the total mass of the centrifuge tube. The formula for calculating the water-holding capacity of the yogurt sample is as follows:
[0084]
[0085] In the formula: m is the mass of the empty centrifuge tube, in g; m1 is the mass of the centrifuge tube containing the yogurt sample, in g; m2 is the total mass of the remaining precipitate and the centrifuge tube after the supernatant is removed, in g.
[0086] like Figure 6 As shown, during refrigerated storage at 4℃, the water-holding capacity of all yogurt groups gradually decreased with prolonged storage time. On day 1 of storage, the water-holding capacity of each group was in the range of 78%-80%, with no significant difference between groups (P>0.05), indicating that the treatment of this invention does not affect the initial water-holding capacity of the yogurt. Throughout the 14-day refrigerated period, the water-holding capacity of each sample showed a significant stepwise decrease with prolonged storage time (P<0.05), dropping to 74.18%~76.70% by day 14. This continuous weakening of water retention is due to the typical dehydration and shrinkage of the fermented milk gel system, which is a normal physical change. The above results demonstrate that the treatment of this invention does not accelerate the aging and deterioration of the gel network, and the product can maintain the same excellent physical structural stability as pure fermented yogurt during its shelf life.
[0087] c) Microbial Counting: Weigh 1 g of yogurt sample and perform 10-fold serial dilutions with sterile physiological saline to obtain 10... -6 and 10 -7Diluent. Take 100 μL of the above diluent and spread it evenly on MRS agar (for counting Lactobacillus bulgaricus) and M17 agar (for counting Streptococcus thermophilus). Incubate anaerobically at 37 °C for 48 h ± 2 h. Select plates with colony counts between 30 and 300 for counting, and calculate the corresponding colony forming units (CFU / g) per gram of sample. The results are expressed as CFU / g.
[0088] like Figure 7 As shown in Figure 8, at the end of 14 days of refrigerated storage at 4 ℃, the viable counts of *Streptococcus thermophilus* in Comparative Example 1 and each of the example groups remained between 8.08–8.52 lg (CFU / g), and the viable counts of *Lactobacillus bulgaricus* remained between 7.72–8.10 lg (CFU / g). Compared with Comparative Example 1, each example group significantly slowed down the decline in viable counts of the two fermentation strains during storage, maintaining a high viable count level even in the later stages of storage. This indicates that the present invention not only does not disrupt the symbiotic fermentation balance between *Streptococcus thermophilus* and *Lactobacillus bulgaricus*, but also effectively improves the survival stability of the two fermentation strains under refrigerated conditions. The viable counts of each example group at the end of storage were all higher than the minimum viable count standard (≥6.0 lg (CFU / g)) currently specified for commercially available yogurt, meeting the relevant product quality requirements. As storage time increases, the number of viable bacteria in both fermentation bacteria gradually decreases. However, this invention can significantly slow down the rate of decline, thereby improving the survival rate of probiotics and the stability of product quality in yogurt during cold storage.
[0089] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A fermented yogurt fortified with ethyl 3-hydroxybutyrate, characterized in that, Its raw materials include raw milk, ethyl 3-hydroxybutyrate, and starter culture.
2. The ethyl 3-hydroxybutyrate-fortified fermented yogurt according to claim 1, characterized in that, Based on the weight of raw milk, the amount of ethyl 3-hydroxybutyrate added is 0.6-3 mg / kg; the amount of starter culture added is 0.05-0.2 wt% of the weight of raw milk.
3. The ethyl 3-hydroxybutyrate-fortified fermented yogurt according to claim 2, characterized in that, The fermentation agent includes a compound fermentation agent of Lactobacillus bulgaricus and Streptococcus thermophilus.
4. The ethyl 3-hydroxybutyrate-fortified fermented yogurt according to claim 3, characterized in that, The viable count of the compound fermentation agent is 1×10⁻⁶. 6 CFU / g-1×10 7 CFU / g; the ratio of live bacteria in Lactobacillus bulgaricus and Streptococcus thermophilus was 1:
1.
5. The method for preparing ethyl 3-hydroxybutyrate-fortified fermented yogurt according to any one of claims 1-4, characterized in that, The steps are as follows: (1) Pasteurize the raw milk in a constant temperature water bath, remove it and cool it quickly to obtain pretreated raw milk; add ethyl 3-hydroxybutyrate to the pretreated raw milk, mix well and pasteurize to obtain a mixture. (2) After cooling the mixture obtained in step (1), inoculate it with the fermentation agent and seal it; then, place the sealed sample in a fermentation chamber for constant temperature fermentation. (3) After fermentation, the mixture is transferred to a 4 ℃ temperature for post-ripening to obtain the ethyl 3-hydroxybutyrate fortified fermented yogurt.
6. The method for preparing ethyl 3-hydroxybutyrate-fortified fermented yogurt according to claim 5, characterized in that, The pasteurization temperature in step (1) is 75-90 ℃.
7. The method for preparing ethyl 3-hydroxybutyrate-fortified fermented yogurt according to claim 6, characterized in that, The pasteurization time in step (1) is 10-20 min.
8. The method for preparing ethyl 3-hydroxybutyrate-fortified fermented yogurt according to claim 5, characterized in that, The temperature for constant temperature fermentation in step (2) is 40-43 ℃.
9. The method for preparing ethyl 3-hydroxybutyrate-fortified fermented yogurt according to claim 8, characterized in that, The constant temperature fermentation time in step (2) is 6-12 h.
10. The method for preparing ethyl 3-hydroxybutyrate-fortified fermented yogurt according to claim 9, characterized in that, The post-ripening time in step (3) is 12-24 hours.