A high-protein fermented milk and a method for preparing and using the same

Abstract

This invention provides a high-protein fermented milk, its preparation method, and its application, relating to the field of dairy product technology. The preparation method of the high-protein fermented milk of this invention includes the following steps: S1. Inoculating a fermentation substrate with a fermentation agent and applying ultrasonic treatment until the ultrasonic energy density of the fermentation system reaches 10-25 kJ / L, then ending the ultrasonic treatment. The ultrasonic treatment power is 100-200 W, and the frequency is 15-25 kHz; S2. Adding a neutral protease to the fermentation system for further fermentation treatment. The neutral protease activity is ≥5000 U, and the addition amount is 0.01 wt%-0.04 wt%. This invention, by combining ultrasonic treatment with protease treatment to ferment high-protein products, further accelerates the fermentation speed and effectively reduces the viscosity of the high-protein fermented milk system, improving the rough texture caused by high protein content. The fermented milk has a smaller particle size, which further helps to improve the product's fineness and stability.

Description

Technical Field

[0001] This invention relates to the field of dairy technology, and in particular to a high-protein fermented milk, its preparation method, and its application. Background Technology

[0002] High-protein yogurt (protein content ≥6g / 100g) has become a market hotspot due to its nutritional advantages, but its high-protein system also leads to drawbacks such as prolonged fermentation time (usually 5-6 hours), coarse texture, and high viscosity. Currently, the main technical methods to improve the shortcomings of high-protein fermented milk include: 1. Adding enzymatic hydrolysates to promote fermentation: Adding proteases can shorten fermentation time, but it cannot accelerate the lag phase of lactic acid bacteria, resulting in limited improvement in the final product's texture and viscosity. Furthermore, the introduction of hydrolysates may affect the functional properties of whey protein. 2. Physical modification techniques, such as ultrasonic treatment: Pre-treating lactic acid bacteria with ultrasound can improve their metabolic activity, but the effect is unstable, and the equipment cost is high. In addition, ultrasonic treatment parameters may cause excessive protein denaturation or emulsion stratification. Another example is high-pressure homogenization: Treating high-protein milk systems at 25MPa can significantly reduce casein micelle size to below 20μm, but it has high energy consumption and stringent equipment requirements. For example, microfluidic technology utilizes high-speed shear force to disperse casein aggregates, improving emulsion uniformity; however, it is complex to operate and difficult to scale up. 3. Other auxiliary methods, such as adding prebiotics like fructooligosaccharides and inulin, can partially promote lactic acid bacteria growth, but their overall effect on fermentation rate is limited, and they may alter the product's flavor characteristics, affecting consumer acceptance. Current technologies have alleviated some of the problems associated with high-protein fermented milk to a certain extent, but issues such as insufficient efficiency, incomplete texture improvement, and complex processes still exist.

[0003] The prior art CN112244089A discloses a high-protein yogurt and its preparation method, the steps of which are as follows: (1) Add skim milk powder, whey protein concentrate and sucrose to fresh milk, disperse, filter to remove residue, homogenize and prepare a high-protein milk base; the protein concentration of the fresh milk in step (1) is 3.0g / 100mL; the mass ratio of skim milk powder to whey protein concentrate is 1:1; the concentration of sucrose is 6.0g / 100mL; the protein concentration is 6.0g / 100mL~10.0g / 100mL; (2) Heat the high-protein milk base prepared in step (1) to 55℃ and perform high-pressure homogenization twice; (3) Heat the high-protein milk base treated in step (2) to 95℃, keep warm for 5min for sterilization, and then cool to 42℃ and inoculate with activated milk. The lactic acid bacteria starter is used for fermentation. When the pH of the high-protein milk-based fermentation broth drops to 6.0, high-intensity ultrasonic intermittent treatment is applied. When the pH of the high-protein milk-based fermentation broth drops to 5.0, the ultrasonic treatment is stopped, and fermentation continues for 0.5~1h. When the pH of the high-protein milk-based fermentation broth drops to 4.6, it is taken out and placed in a 4℃ refrigerator to cool. Fermentation is stopped, and high-protein yogurt is obtained. The conditions for the high-intensity ultrasonic intermittent treatment in step (3) are: the frequency of the ultrasonic device is 30KHz, the power is 200W, the ultrasonic probe is located 30mm below the surface of the high-protein milk-based liquid, the ultrasonic treatment is 0.3s, the interval is 1.7s, and every 2s is a cycle. The lactic acid bacteria starter in step (3) is Lactobacillus bulgaricus and Streptococcus thermophilus mixed at a mass ratio of 1:1. After inoculation with the activated lactic acid bacteria starter, fermentation is carried out for 5~7h. The existing technology uses ultrasonic waves to interfere with the formation of high-protein yogurt gel during the fermentation process, which can improve the water retention and gel hardness of high-protein yogurt to some extent. However, the overall improvement effect is limited, and multiple homogenization processes are required, and the fermentation time is also relatively long. Summary of the Invention

[0004] This invention addresses the shortcomings of current high-protein fermented milk preparation methods, such as insufficient efficiency, incomplete texture improvement, and complex processes. It provides a method for preparing high-protein fermented milk by using ultrasound to activate lactic acid bacteria and enhance their initial metabolic activity. Neutral protease targets and hydrolyzes κ-casein to generate peptides that promote lactic acid bacteria growth, thereby shortening fermentation time, reducing product viscosity, and improving smoothness. This simultaneously solves the fermentation rate and texture problems in the production of high-protein fermented milk.

[0005] Another object of the present invention is to provide a high-protein fermented milk.

[0006] Another object of the present invention is to provide an application of high-protein fermented milk in food preparation.

[0007] In a first aspect, the present invention provides a method for preparing high-protein fermented milk, comprising the following steps:

[0008] S1. Inoculate the fermentation substrate with fermentation agent and apply ultrasonic treatment. The ultrasonic treatment is stopped when the ultrasonic energy density of the fermentation system is 10~25kJ / L. The ultrasonic treatment power is 100~200W and the frequency is 15~25kHz.

[0009] S2. Add neutral protease to the fermentation system and continue fermentation. The neutral protease activity should be ≥5000U, and the addition amount should be 0.01wt%~0.04wt%.

[0010] After ultrasonic treatment in S1, the viscosity of the fermentation substrate system was 40-55 mPa·s, and the viable cell count in the fermentation system was greater than or equal to 6 × 10⁻⁶ after 1 hour. 6 .

[0011] According to the method for preparing high-protein fermented milk provided by the present invention, preferably, the ultrasonic energy density of the fermentation base system in S1 is 15~20kJ / L.

[0012] According to the method for preparing high-protein fermented milk provided by the present invention, preferably, the neutral protease in S2 is a microbial neutral protease.

[0013] According to the method for preparing high-protein fermented milk provided by the present invention, preferably, the fermentation agent in S1 is selected from one or more of Streptococcus thermophilus, Lactobacillus bulgaricus, Lactobacillus acidophilus, Bifidobacterium and Lactobacillus casei.

[0014] According to the method for preparing high-protein fermented milk provided by the present invention, preferably, the fermentation start temperature in S1 is 40~45℃.

[0015] According to the method for preparing high-protein fermented milk provided by the present invention, preferably, fermentation is continued in S2 until the pH ≤ 4.6 or the acidity ≥ 60, then fermentation is stopped, and the milk is broken down and cooled to obtain high-protein fermented milk.

[0016] According to the method for preparing high-protein fermented milk provided by the present invention, preferably, the fermentation base material in S1 is subjected to homogenization and sterilization treatment, the homogenization temperature is 60~70℃, and the homogenization pressure is 150~200 bar.

[0017] Secondly, the present invention also provides a method for preparing high-protein fermented milk to obtain high-protein fermented milk.

[0018] The high-protein fermented milk provided by the present invention has a viscosity of 1000~1600 mPa·s and a particle size D50 of 27~29 μm.

[0019] Thirdly, the present invention also provides an application of high-protein fermented milk in food preparation.

[0020] Beneficial effects:

[0021] This invention provides a method for preparing high-protein fermented milk. By combining ultrasonic treatment with protease treatment, the high-protein product is fermented. Low-intensity ultrasound promotes the growth of lactic acid bacteria in the lag phase, while the protease enzymatically hydrolyzes the protein into peptides, providing nutrients for the growth of lactic acid bacteria in the middle stage of fermentation, further accelerating fermentation. This method saves production time and reduces energy costs for the industrial production of high-protein fermented milk.

[0022] Furthermore, the preparation method of the high-protein fermented milk of this invention effectively reduces the viscosity of the high-protein fermented milk system through the synergistic effect of ultrasonic treatment and enzymatic hydrolysis, improving the rough texture caused by high protein content. This not only enhances the product's eating experience but also solves the process difficulties such as filling difficulties that may arise due to texture issues during the processing of high-protein fermented milk. Moreover, the smaller particle size of the fermented milk further contributes to improving the product's smoothness and stability. Detailed Implementation

[0023] The following examples are for illustrative purposes only and are not intended to limit the scope of the invention. Where specific techniques or conditions are not specified in the examples, they should be performed according to the techniques or conditions described in the literature in this field, or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased from legitimate channels.

[0024] The relevant raw material information mentioned in the embodiments and comparative examples of this invention is explained as follows:

[0025] Neutral protease ADMIL (oenon, Japan), enzyme activity >5000U;

[0026] Neutral protease Galaya smooth (Novogene, Denmark), enzyme activity >5000U;

[0027] Streptococcus thermophilus and Lactobacillus bulgaricus (Novo Nordisk, Denmark).

[0028] In a specific embodiment, the present invention provides a method for preparing high-protein fermented milk, comprising the following steps:

[0029] S1. Inoculate the fermentation substrate with fermentation agent, start fermentation and simultaneously apply ultrasonic treatment until the ultrasonic energy density of the fermentation substrate system is 10~25kJ / L, the ultrasonic treatment power is 100~200W, and the frequency is 15~25kHz.

[0030] S2. After ultrasonic treatment in S1, add neutral protease for further fermentation. The enzyme activity should be ≥5000U, and the addition amount should be 0.01wt%~0.04wt%.

[0031] After ultrasonic treatment in S1, the viscosity of the fermentation substrate system was 40-55 mPa·s, and the viable cell count in the fermentation system was greater than or equal to 6 × 10⁻⁶ after 1 hour. 6 .

[0032] It should be noted that:

[0033] The high-protein fermented milk of the present invention is a high-protein yogurt with a protein content ≥6g / 100g.

[0034] The high-protein fermented milk preparation method provided by this invention utilizes specific ultrasonic treatment conditions to ultrasonically treat the inoculated fermentation substrate to a specific ultrasonic energy density of 10-25 kJ / L. Low-intensity ultrasound promotes the growth of lag phase lactic acid bacteria, resulting in a rapid increase in the number of viable bacteria in the inoculated fermentation substrate, thus improving fermentation efficiency. The resulting system viscosity is 40-55 mPa·s. After ultrasonic treatment, the increased viable bacteria in the fermentation substrate system makes it more suitable for subsequent neutral protease action. Furthermore, this invention introduces neutral protease after ultrasonic treatment to a specific degree for continued fermentation. Neutral protease hydrolysis not only specifically cleaves proteins to produce specific cleavage products that promote the formation of specific fermentation product texture and flavor, but also enzymatically hydrolyzes proteins into peptides, providing nutrients for lactic acid bacteria growth during the mid-fermentation stage, further accelerating fermentation. This shortens the mid-stage growth time of lactic acid bacteria, improving overall fermentation efficiency and saving production time and reducing energy costs for the industrial production of high-protein fermented milk.

[0035] The amount of neutral protease added not only affects fermentation efficiency but also the quality of fermented products. In the preparation method of high-protein fermented milk mentioned in this invention, the amount of neutral protease added can be, for example, 0.01wt%, 0.02wt%, 0.03wt%, 0.04wt%, or any range of values.

[0036] The preparation method of high-protein fermented milk of the present invention also effectively reduces the viscosity of the high-protein fermented milk system through the synergistic effect of ultrasonic treatment and enzymatic hydrolysis, and improves the problem of rough texture caused by high protein content. This not only improves the eating experience of the product, but also solves the process difficulties such as filling difficulties that may be caused by texture problems in the processing of high-protein fermented milk.

[0037] In some specific embodiments, the viscosity of the fermentation substrate after ultrasonic treatment in S1 is 40~55 mPa·s, for example, it can be a point value such as 40 mPa·s, 44 mPa·s, 46 mPa·s, 52 mPa·s, 54 mPa·s, or any range of values.

[0038] In some specific embodiments, in order to further improve the mouthfeel and viscosity of high-protein fermented milk products, obtain high-protein fermented milk products with smaller particle sizes, and improve the fineness and stability of the products, the ultrasonic energy density of the ultrasonic treatment applied to the fermentation base system in S1 mentioned in this invention is 15~20kJ / L, for example, it can be a point value of 15kJ / L, 16kJ / L, 17kJ / L, 18kJ / L, 19kJ / L, 20kJ / L, or any range of values.

[0039] In some specific embodiments, the neutral protease mentioned in S2 of the present invention is a microbial neutral protease, such as neutral protease ADMIL, neutral protease Galaya smooth, etc., and more preferably neutral protease ADMIL.

[0040] This invention does not specifically limit the fermentation agent mentioned in S1. It can be any fermentation agent conventionally used in the preparation of fermented milk in the art. In some specific embodiments, the fermentation agent mentioned in S1 of this invention is selected from one or more of Streptococcus thermophilus, Lactobacillus bulgaricus, Lactobacillus acidophilus, Bifidobacterium, and Lactobacillus casei. For example, it can be a compound agent of Streptococcus thermophilus and Lactobacillus bulgaricus, wherein the ratio of Streptococcus thermophilus to Lactobacillus bulgaricus is 1:1.

[0041] In some specific embodiments, the fermentation start temperature mentioned in S1 of the present invention is 40~45℃. For example, it can be a point value such as 40℃, 41℃, 42℃, 43℃, 44℃, 45℃, or any range of values.

[0042] In some specific embodiments, the method for preparing high-protein fermented milk mentioned in this invention may further include the following steps:

[0043] Fermentation continues in S2 until pH ≤ 4.6 or acidity ≥ 60, then fermentation is stopped, and the milk is broken down and cooled to obtain high-protein fermented milk.

[0044] The overall fermentation time required for the preparation method of the high-protein fermented milk of the present invention can be shortened to less than 6 hours, compared with the conventional fermentation process which requires at least 6.6 hours or more of processing time. This greatly shortens the fermentation time, and the resulting high-protein fermented milk product has a lower viscosity range, which improves the texture of the product and avoids the rough taste problem caused by the high viscosity of traditional high-protein fermented milk. The reduction in particle size also helps to improve the fineness and stability of the product.

[0045] In some specific embodiments, the fermentation cessation mentioned in this invention refers to stopping fermentation when the pH drops to 4.6, stirring to break the emulsion, cooling to 8~15℃, and then refrigerating at 2~10℃ after bottling.

[0046] In some specific embodiments, the method for preparing high-protein fermented milk mentioned in this invention may also include conventionally required processing steps, such as a process for preparing a fermentation base. The fermentation base in S1 mentioned in this invention can be prepared by the following method:

[0047] The fermentation base (including high-protein concentrated milk) is homogenized and sterilized at a temperature of 60-70°C and a pressure of 150-200 bar.

[0048] In some specific embodiments, the homogeneous pressure mentioned in this invention can be a point value such as 150 bar, 160 bar, 170 bar, 180 bar, 190 bar, 200 bar, or any range of values.

[0049] The raw material mixture containing high-protein concentrated milk mentioned in this invention can use high-protein concentrated milk with a protein content >6g / 100mL as the main raw material, and other ingredients such as white sugar or natural sweeteners can be added as auxiliary ingredients (the amount of white sugar added is 2~8%, and the amount of sweetener added does not exceed the amount specified in the national standard GB2760 food additives).

[0050] In some specific embodiments, the high-protein concentrated milk mentioned in this invention can be prepared using fresh raw milk, and the specific method is as follows:

[0051] Fresh raw milk is purified using a sterile centrifuge to separate the milk fat and obtain preliminarily sterilized milk.

[0052] The milk that has been preliminarily sterilized is concentrated twice using an ultrafiltration membrane filtration device to obtain high-protein concentrated milk with a protein content of >6g / 100mL.

[0053] In a specific embodiment, the present invention also specifically protects a method for preparing high-protein fermented milk to obtain high-protein fermented milk.

[0054] In some specific embodiments, the high-protein fermented milk mentioned in this invention has a viscosity of 1000~1600 mPa·s and a particle size D50 of 27~29 μm.

[0055] In some specific high-protein fermented milk products, the viscosity can be a point value or any range of values ​​such as 1000 Pa·s, 1100 Pa·s, 1200 Pa·s, 1298 Pa·s, 1300 Pa·s, 1394 Pa·s, 1400 Pa·s, 1438 Pa·s, 1500 Pa·s, 1517 Pa·s, and 1600 Pa·s, and the particle size D50 can be, for example, 27 μm, 28 μm, or 29 μm.

[0056] The high-protein fermented milk provided by this invention has a lower viscosity range, significantly improving the texture of high-protein fermented milk products and avoiding the rough texture problem caused by the high viscosity of traditional high-protein fermented milk. At the same time, the high-protein fermented milk provided by this invention also has a smaller particle size (D50 value), which further contributes to improving the product's smoothness and stability.

[0057] In a specific embodiment, the present invention also specifically protects the application of a high-protein fermented milk in food preparation.

[0058] The high-protein fermented milk product provided by this invention has a more delicate taste, pure flavor, and rich milk aroma. It can be widely used in the food preparation field. For example, it can be combined with fruit pieces (strawberry, blueberry), cereal crisps, nut crumbs, etc. to prepare ready-to-eat high-protein dairy products. It can also be fortified with vitamins and other nutrients to prepare high-protein fermented milk drinks. It can also be used in the preparation of sports nutrition foods or special dietary foods.

[0059] Example 1

[0060] A method for preparing high-protein fermented milk includes the following steps:

[0061] S1. Fresh raw milk is purified and separated from milk fat using a sterile centrifuge to obtain pre-sterilized milk. The pre-sterilized milk is then concentrated twice using an ultrafiltration membrane filtration device to obtain high-protein concentrated milk with a protein content of 6g / 100mL.

[0062] Add 5% white sugar by weight of concentrated milk to concentrated milk, mix well, homogenize and sterilize, maintain homogenization temperature at 60℃, pressure at 180 bar, sterilize at 95℃ for 300 seconds, and then cool to 42℃.

[0063] Inoculate with 80U of starter culture (Streptococcus thermophilus + Lactobacillus bulgaricus = 1:1), stir well, start fermentation at 42℃, and simultaneously apply ultrasonic treatment until the ultrasonic energy density is 10kJ / L, the ultrasonic treatment power is 150W, and the frequency is 20kHz.

[0064] S2. After ultrasonic treatment in S1, add neutral protease ADMIL for continued fermentation at a rate of 0.03%. When the pH drops to 4.6, stir to break the emulsion.

[0065] Cool the liquid to 10°C, fill it, and then store it at 6°C.

[0066] Example 2

[0067] A method for preparing high-protein fermented milk includes the following steps:

[0068] S1. Fresh raw milk is purified and separated from milk fat using a sterile centrifuge to obtain pre-sterilized milk. The pre-sterilized milk is then concentrated twice using an ultrafiltration membrane filtration device to obtain high-protein concentrated milk with a protein content of 6g / 100mL.

[0069] Add 5% white sugar by weight of concentrated milk to concentrated milk, mix well, homogenize and sterilize, maintain homogenization temperature at 60℃, pressure at 180 bar, sterilize at 95℃ for 300 seconds, and then cool to 42℃.

[0070] Inoculate with 80U of starter culture (Streptococcus thermophilus + Lactobacillus bulgaricus = 1:1), stir well, start fermentation at 42℃, and simultaneously apply ultrasonic treatment until the ultrasonic energy density is 25kJ / L, the ultrasonic treatment power is 150W, and the frequency is 20kHz.

[0071] S2. After ultrasonic treatment in S1, add neutral protease ADMIL for continued fermentation at a rate of 0.04%. When the pH drops to 4.6, stir to break the emulsion.

[0072] Cool the liquid to 10°C, fill it, and then store it at 6°C.

[0073] Example 3

[0074] A method for preparing high-protein fermented milk includes the following steps:

[0075] S1. Fresh raw milk is purified and separated from milk fat using a sterile centrifuge to obtain pre-sterilized milk. The pre-sterilized milk is then concentrated twice using an ultrafiltration membrane filtration device to obtain high-protein concentrated milk with a protein content of 6g / 100mL.

[0076] Add 5% white sugar by weight of concentrated milk to concentrated milk, mix well, homogenize and sterilize, maintain homogenization temperature at 60℃, pressure at 180 bar, sterilize at 95℃ for 300 seconds, and then cool to 42℃.

[0077] Inoculate with 80U of starter culture (Streptococcus thermophilus + Lactobacillus bulgaricus = 1:1), stir well, start fermentation at 42℃, and simultaneously apply ultrasonic treatment until the ultrasonic energy density is 18kJ / L, the ultrasonic treatment power is 150W, and the frequency is 20kHz.

[0078] S2. After ultrasonic treatment in S1, add neutral protease ADMIL for continued fermentation at a rate of 0.03%. When the pH drops to 4.6, stir to break the emulsion.

[0079] Cool the liquid to 10°C, fill it, and then store it at 6°C.

[0080] Example 4

[0081] A method for preparing high-protein fermented milk includes the following steps:

[0082] S1. Fresh raw milk is purified and separated from milk fat using a sterile centrifuge to obtain pre-sterilized milk. The pre-sterilized milk is then concentrated twice using an ultrafiltration membrane filtration device to obtain high-protein concentrated milk with a protein content of 6g / 100mL.

[0083] Add 5% white sugar by weight of concentrated milk to concentrated milk, mix well, homogenize and sterilize, maintain homogenization temperature at 60℃, pressure at 180 bar, sterilize at 95℃ for 300 seconds, and then cool to 42℃.

[0084] Inoculate with 80U of starter culture (Streptococcus thermophilus + Lactobacillus bulgaricus = 1:1), stir well, start fermentation at 42℃, and simultaneously apply ultrasonic treatment until the ultrasonic energy density is 18kJ / L, the ultrasonic treatment power is 150W, and the frequency is 20kHz.

[0085] S2. After ultrasonic treatment in S1, add neutral protease Galayasmooth and continue fermentation treatment at a rate of 0.01%. When the pH drops to 4.6, stir to break the emulsion.

[0086] Cool the liquid to 10°C, fill it, and then store it at 6°C.

[0087] Example 5

[0088] A method for preparing high-protein fermented milk includes the following steps:

[0089] S1. Fresh raw milk is purified and separated from milk fat using a sterile centrifuge to obtain pre-sterilized milk. The pre-sterilized milk is then concentrated twice using an ultrafiltration membrane filtration device to obtain high-protein concentrated milk with a protein content of 6g / 100mL.

[0090] Add 5% white sugar by weight of concentrated milk to concentrated milk, mix well, homogenize and sterilize, maintain homogenization temperature at 60℃, pressure at 180 bar, sterilize at 95℃ for 300 seconds, and then cool to 42℃.

[0091] Inoculate with 80U of starter culture (Streptococcus thermophilus + Lactobacillus bulgaricus = 1:1), stir well, start fermentation at 42℃, and simultaneously apply ultrasonic treatment until the ultrasonic energy density is 18kJ / L, the ultrasonic treatment power is 150W, and the frequency is 20kHz.

[0092] S2. After ultrasonic treatment in S1, add neutral protease Galayasmooth for continued fermentation treatment at a dosage of 0.02%. When the pH drops to 4.6, stir to break the emulsion.

[0093] Cool the liquid to 10°C, fill it, and then store it at 6°C.

[0094] Comparative Example 1

[0095] A method for preparing high-protein fermented milk, differing from Example 1 in that it does not involve the synergistic treatment of ultrasound and neutral protease, and includes the following steps:

[0096] S1. Fresh raw milk is purified and separated from milk fat using a sterile centrifuge to obtain preliminarily sterilized milk;

[0097] The milk that has been preliminarily sterilized is concentrated twice using an ultrafiltration membrane filtration device to obtain high-protein concentrated milk with a protein content of 6g / 100mL.

[0098] Add 5% white sugar by weight of concentrated milk to concentrated milk, mix well, homogenize and sterilize, maintain homogenization temperature at 65℃, pressure at 180 bar, sterilize at 95℃ for 300 seconds, and then cool to 42℃.

[0099] Inoculate with 80U of starter culture (Streptococcus thermophilus + Lactobacillus bulgaricus = 1:1), stir well, and start fermentation at 42℃;

[0100] S2. When the pH drops to 4.6, stir to break the emulsion, cool the liquid to 10°C, and store it at 2~10°C after filling.

[0101] Comparative Example 2

[0102] A method for preparing high-protein fermented milk, differing from Example 1 in that it does not involve treatment with neutral protease, includes the following steps:

[0103] S1. Fresh raw milk is purified and separated from milk fat using a sterile centrifuge to obtain pre-sterilized milk. The pre-sterilized milk is then concentrated twice using an ultrafiltration membrane filtration device to obtain high-protein concentrated milk with a protein content of 6g / 100mL.

[0104] Add 5% white sugar by weight of concentrated milk to concentrated milk, mix well, homogenize and sterilize, maintain homogenization temperature at 60℃, pressure at 180 bar, sterilize at 95℃ for 300 seconds, and then cool to 42℃.

[0105] Inoculate with 80U of starter culture (Streptococcus thermophilus + Lactobacillus bulgaricus = 1:1), stir well, start fermentation at 42℃, and simultaneously apply ultrasonic treatment until the ultrasonic energy density is 10kJ / L, the ultrasonic treatment power is 150W, and the frequency is 20kHz.

[0106] S2. When fermentation reaches a pH of 4.6, stir to break the emulsion;

[0107] Cool the liquid to 10°C, fill it, and then store it at 6°C.

[0108] Comparative Example 3

[0109] A method for preparing high-protein fermented milk, differing from Example 5 in that it does not involve ultrasonic treatment, and includes the following steps:

[0110] S1. Fresh raw milk is purified and separated from milk fat using a sterile centrifuge to obtain pre-sterilized milk. The pre-sterilized milk is then concentrated twice using an ultrafiltration membrane filtration device to obtain high-protein concentrated milk with a protein content of 6g / 100mL.

[0111] Add 5% white sugar by weight of concentrated milk to concentrated milk, mix well, homogenize and sterilize, maintain homogenization temperature at 60℃, pressure at 180 bar, sterilize at 95℃ for 300 seconds, and then cool to 42℃.

[0112] Inoculate with 80U of starter culture (Streptococcus thermophilus + Lactobacillus bulgaricus = 1:1), stir well, and start fermentation at 42℃;

[0113] S2. Add neutral protease ADMIL at a rate of 0.02%, and ferment until the pH drops to 4.6, then stir to break the emulsion.

[0114] Cool the liquid to 10°C, fill it, and then store it at 6°C.

[0115] Comparative Example 4

[0116] A method for preparing high-protein fermented milk includes the following steps:

[0117] S1. Fresh raw milk is purified and separated from milk fat using a sterile centrifuge to obtain pre-sterilized milk. The pre-sterilized milk is then concentrated twice using an ultrafiltration membrane filtration device to obtain high-protein concentrated milk with a protein content of 6g / 100mL.

[0118] Add 5% white sugar by weight of concentrated milk to concentrated milk, mix well, homogenize and sterilize, maintain homogenization temperature at 60℃, pressure at 180 bar, sterilize at 95℃ for 300 seconds, and then cool to 42℃.

[0119] Inoculate with 80U of starter culture (Streptococcus thermophilus + Lactobacillus bulgaricus = 1:1), stir well, start fermentation at 42℃, and simultaneously apply ultrasonic treatment until the ultrasonic energy density is 30kJ / L, the ultrasonic treatment power is 150W, and the frequency is 20kHz.

[0120] S2. After ultrasonic treatment in S1, add neutral protease ADMIL for continued fermentation at a rate of 0.03%. When the pH drops to 4.6, stir to break the emulsion.

[0121] Cool the liquid to 10°C, fill it, and then store it at 6°C.

[0122] Comparative Example 5

[0123] A method for preparing high-protein fermented milk includes the following steps:

[0124] Fresh raw milk is purified and separated from milk fat using a sterile centrifuge to obtain pre-sterilized milk. The pre-sterilized milk is then concentrated twice using an ultrafiltration membrane filtration device to obtain high-protein concentrated milk with a protein content of 6g / 100mL.

[0125] Add 5% white sugar by weight of concentrated milk to concentrated milk, mix well, homogenize and sterilize, maintain homogenization temperature at 60℃, pressure at 180 bar, sterilize at 95℃ for 300 seconds, and then cool to 42℃.

[0126] Inoculate with 80U of starter culture (Streptococcus thermophilus + Lactobacillus bulgaricus = 1:1) and add 0.03% of neutral protease ADMIL. Stir well and start fermentation at 42℃. At the same time, apply ultrasonic treatment until the ultrasonic energy density reaches 10kJ / L, the ultrasonic treatment power is 150W, and the frequency is 20kHz. When the fermentation pH drops to 4.6, stir to break the emulsion.

[0127] Cool the liquid to 10°C, fill it, and then store it at 6°C.

[0128] Result detection

[0129] The viable cell count and viscosity of the intermediate reaction system and demulsification system of the above embodiments and comparative examples were tested. The specific testing methods are as follows:

[0130] Method for detecting viable bacteria count: The viable bacteria count of lactic acid bacteria in the sample shall be detected according to the method in GB4789.35-2023.

[0131] Viscosity testing method: The viscosity of the sample was measured using an Anton Paar MCR302e rheometer, with a shear rate γ set to 64 s. -1 The temperature is set to 10℃.

[0132] The particle size (D50) and water-holding capacity of the final high-protein fermented milk were tested using the following methods:

[0133] Particle size determination method: wet injection, with deionized water (refractive index 1.33) as the dispersed phase; particle refractive index 1.46, absorption coefficient 0.1; pump speed 2000 rpm; light blocking 10–20%; measurement time 10 s; both background and sample were cycled 3 times. The result was the average of the volume distribution (Dx50) measured independently in 3 separate measurements.

[0134] Water-holding capacity test method: The water-holding capacity of the sample was determined by centrifugation. Take 20g of fermented milk sample into a 50mL centrifuge tube (the weight of the empty centrifuge tube is recorded as W0, and the total weight is recorded as W1), centrifuge at 4000r / min for 10min, discard the supernatant, weigh the remaining mass W2, and calculate the water-holding capacity: Water-holding capacity (%) = (W2-W0) / (W1-W0)×100%.

[0135] The specific test results are shown in Tables 1 and 2 below:

[0136] Table 1

[0137]

[0138] Table 2

[0139]

[0140] In Tables 1 and 2 above, the viscosity after 1 hour of inoculation is the viscosity of the material after ultrasonic treatment. It can be seen that within the ultrasonic treatment range protected by this invention, the viscosity of the fermentation substrate can be significantly reduced.

[0141] As can be seen from the data in Tables 1 and 2 above, this invention significantly improves the fermentation efficiency and product quality of high-protein fermented milk by utilizing the synergistic effect of ultrasonic treatment and enzymatic hydrolysis. Regarding fermentation efficiency, compared to the traditional process (Comparative Example 1), the fermentation time in Examples 1-5 of this invention was shortened by 1.1-1.2 hours, with an efficiency increase of approximately 16.7%-18.2%. Compared to ultrasonic treatment alone (Comparative Example 2) and enzymatic hydrolysis alone (Comparative Example 3), the fermentation time was also shortened by 0.7-1 hour, indicating that the synergistic effect is more significant in accelerating the fermentation process. Comparative Example 4, due to the use of ultrasonic treatment exceeding energy density limits, had a fermentation time comparable to Comparative Example 1. Comparative Example 5, which added protease before ultrasonic treatment, showed that the final fermentation time and viscosity at demulsification were inferior to the examples, failing to achieve the desired technical effect.

[0142] Regarding viable cell count, one hour after inoculation, the viable cell count in the examples was higher than that in Comparative Examples 1 and 3, indicating that the combination of ultrasound and enzymatic hydrolysis can effectively promote the proliferation of lactic acid bacteria in the initial stage. At demulsification, the viable cell count in the examples increased by 18.7% to 23.2% compared to Comparative Example 1, and also showed varying degrees of improvement compared to Comparative Examples 2 and 3. Comparative Example 4, however, had the lowest viable cell count in both stages due to the higher intensity of ultrasound treatment. This indicates that the intensity range of ultrasound treatment in the examples is the suitable range for promoting the growth and reproduction of lactic acid bacteria; excessively high ultrasound energy density will inhibit bacterial activity and instead prolong fermentation time.

[0143] Regarding viscosity, the viscosity of the embodiment was generally lower than that of the comparative example 1 hour after inoculation; the viscosity at demulsification was significantly lower than that of the comparative example 1, which improved the texture of the product and avoided the rough taste problem caused by the high viscosity of traditional high-protein fermented milk.

[0144] The particle size (Dx50) index shows that the casein micelles in the examples are significantly smaller than those in Comparative Examples 1 and 2, and are close to but more stable than those in Comparative Example 3. The smaller particle size helps to improve the fineness and stability of the product.

[0145] In terms of water retention, although the water retention of the example is slightly lower than that of the comparative example 1, it still remains above 85%, which meets the product quality requirements. Moreover, considering other indicators, the overall quality has been optimized.

[0146] In addition, sensory evaluation was conducted on the high-protein fermented milk samples prepared in the examples and comparative examples: 28 personnel with professional sensory training were selected to score the samples' texture, mouthfeel, and flavor and aroma, with each item scored out of 10 points. The average scores of each item were then summed. The evaluation criteria are shown in Table 3, and the evaluation results are shown in Table 4.

[0147] Table 3

[0148]

[0149] Table 4

[0150]

[0151] In the evaluation criteria and scores in Tables 3 and 4, it can be seen that the total sensory scores of Examples 1-5 are all higher than those of the comparative examples. Among them, Examples 2 and 3 have the highest total scores, reaching 22.9 points, which is 2.1 points, 2.2 points, 1.4 points and 2 points higher than those of Comparative Example 1 (20.8 points), Comparative Example 2 (20.7 points), Comparative Example 3 (21.5 points) and Comparative Example 4 (20.9 points), respectively.

[0152] In terms of organizational state, the examples generally scored higher than the comparative examples, with better surface smoothness and gloss, which is consistent with the results of the particle size reduction index test.

[0153] In terms of texture, the smoothness of the embodiments was significantly better than that of the comparative examples, indicating that the synergistic effect of ultrasound and enzymatic hydrolysis was effective in improving the rough texture. In terms of flavor and aroma, the milk aroma of each embodiment was similar to that of comparative examples 1 and 3, indicating that the technical solution did not have a negative impact on the inherent flavor of the product while improving fermentation efficiency and texture.

[0154] Based on comprehensive testing results and sensory evaluation, this invention achieves comprehensive optimization of high-protein fermented milk in terms of fermentation efficiency, viable cell count, textural properties, and sensory quality through a synergistic technical solution of ultrasonic treatment and neutral protease hydrolysis, providing a feasible path for the industrial production of high-protein fermented milk.

[0155] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing high-protein fermented milk, characterized in that, Includes the following steps: S1. Inoculate the fermentation substrate with fermentation agent, start fermentation and simultaneously apply ultrasonic treatment until the ultrasonic energy density of the fermentation substrate system is 10~25kJ / L, the ultrasonic treatment power is 100~200W, and the frequency is 15~25kHz. S2. After ultrasonic treatment in S1, add neutral protease for further fermentation. The neutral protease activity should be ≥5000U, and the addition amount should be 0.01wt%~0.04wt%. After ultrasonic treatment in S1, the viscosity of the fermentation substrate system is 40~55 mPa·s, and the viable cell count is greater than or equal to 6.0×10⁻⁶. 6 ; The high-protein fermented milk has a particle size D50 of 27~29μm and a protein content ≥6g / 100g.

2. The method for preparing high-protein fermented milk according to claim 1, characterized in that, The ultrasonic energy density of the fermentation substrate system described in S1 is 15~20kJ / L.

3. The method for preparing high-protein fermented milk according to claim 1 or 2, characterized in that, The neutral protease mentioned in S2 is a neutral protease of microbial origin.

4. The method for preparing high-protein fermented milk according to claim 1 or 2, characterized in that, The fermentation agent described in S1 is selected from one or more of Streptococcus thermophilus, Lactobacillus bulgaricus, Lactobacillus acidophilus, Bifidobacterium and Lactobacillus casei.

5. The method for preparing high-protein fermented milk according to claim 4, characterized in that, The fermentation start temperature described in S1 is 40~45℃.

6. The method for preparing high-protein fermented milk according to claim 1 or 2, characterized in that, Fermentation continues in S2 until pH ≤ 4.6 or acidity ≥ 60, then fermentation is stopped, and the milk is broken down and cooled to obtain high-protein fermented milk.

7. The method for preparing high-protein fermented milk according to claim 1 or 2, characterized in that, The fermentation substrate described in S1 undergoes homogenization and sterilization treatment. The homogenization temperature is 60~70℃ and the homogenization pressure is 150~200 bar.

8. A high-protein fermented milk prepared by the method of any one of claims 1 to 7.

9. The high-protein fermented milk according to claim 8, characterized in that, The viscosity of the high-protein fermented milk is 1000~1600 mPa·s, and the particle size D50 is 27~29 μm.

10. The use of the high-protein fermented milk as described in claim 8 or 9 in food preparation.

Images