High milk solid content dry choking yogurt and method for preparing the same

Abstract

This invention relates to the field of dry yogurt technology, and particularly to a dry yogurt with high milk solids content and its preparation method. The preparation method includes the following steps: preheating raw milk, adding concentrated milk protein powder and white sugar while stirring, mixing evenly to obtain mixture one; sterilizing mixture one, cooling to obtain mixture two; inoculating mixture two with fermentation starter, fermenting to obtain mixture three; sterilizing light cream to obtain sterilized light cream; adding sterilized light cream to mixture three, homogenizing twice, cooling to obtain mixture four; filling mixture four, fermenting, cooling, and ripening to obtain dry yogurt with high milk solids content. This application, through a method of fortifying protein and fat, can prepare high-protein yogurt with a protein content of 8.9-11.4% and a total solids content of 31.7-35.5% without membrane concentration or whey removal equipment.

Description

Technical Field

[0001] This invention relates to the field of dry yogurt technology, and in particular to a dry yogurt with high milk solids content and its preparation method. Background Technology

[0002] In recent years, with the popularization of health-conscious consumption concepts, modern consumers, especially young people and families, have shifted their demand for dairy products from the traditional "quenching thirst" or "pleasure of taste" to higher-level nutritional and functional needs. They pay more attention to the "nutrient density," "clean label," and specific health benefits, such as high protein, low sugar, and strong satiety. Under this trend, dry yogurt, with its extremely high protein content and thick, dense texture, has become an ideal choice for meal replacements or high-nutrition snacks, aligning with the consumption concept of "eating more nutritiously and meaningfully."

[0003] Traditional stirred yogurt typically has a total solids content of 12%–16%, with a protein content of about 3.0%–3.5%. Its texture is relatively thin, making it difficult to meet the needs of a high-protein diet. In contrast, dry yogurt usually has a total solids content as high as 28%–35%, with a protein content of over 10%. Its unique feature is that it significantly increases the solids concentration through physical or formula methods, thus forming a semi-solid texture between cheese and yogurt.

[0004] However, while high solids content brings nutritional advantages, it also poses a serious challenge to product texture control. Dry yogurt needs to achieve a delicate balance between "firmness" and "smoothness": if the texture is too dry and hard, it is easy to produce a "sticky" or "powdery" feeling or difficulty in swallowing; if it is too soft and mushy, it loses its characteristic shape and chewy satisfaction.

[0005] Currently, some dry yogurts on the market still rely on manual preparation, which involves first fermenting regular yogurt and then removing whey through gravity filtration using cheesecloth or other media. While this method is simple to operate, it is difficult to precisely control the degree of moisture removal, which can easily lead to an overly dry product with a rough texture or loss of flavor.

[0006] In industrial production, mainstream technologies include membrane concentration (such as ultrafiltration), centrifugal whey removal, or mechanical pressure filtration. While these physical concentration processes can effectively increase protein and total solids content, they inevitably lead to the loss of some water-soluble components (such as lactose, minerals, and flavor precursors), affecting the product's flavor richness and nutritional integrity. Furthermore, these equipment investments are high, energy consumption is high, and yields are relatively low.

[0007] To avoid high equipment investment, some manufacturers attempt to increase solids and fat content by directly adding protein concentrate or cream. However, if the formula design or process control is inadequate, such additions can easily lead to new technical problems: for example, excessive addition of protein powder may result in a powdery or gritty texture in the product; uneven fat distribution or a lack of natural milk fat structure makes it difficult to reproduce the rich, silky texture that high-quality yogurt should have; at the same time, decreased system stability may also cause whey separation or excessive coagulation, affecting shelf-life quality.

[0008] Therefore, there is an urgent need to produce a dry yogurt with excellent taste, flavor, and stability. (Invention Content)

[0009] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a dry yogurt with high milk solids content and its preparation method, so as to solve the problem that the dry yogurt prepared in the prior art is difficult to balance taste, flavor and stability.

[0010] To achieve the above and other related objectives, the present invention is obtained through the following technical solution.

[0011] The first aspect of this invention is to provide a method for preparing dry yogurt with high milk solids content, the method comprising the following steps:

[0012] (1) Preheat the raw milk, add concentrated milk protein powder and white sugar while stirring, mix well to obtain mixture one;

[0013] (2) Sterilize the mixture obtained in step (1) and cool it to obtain mixture two;

[0014] (3) Inoculate the mixture two obtained in step (2) with fermentation bacteria, ferment, and obtain mixture three;

[0015] (4) Sterilize the cream to obtain sterilized cream; add the sterilized cream to the mixture three obtained in step (3), and after secondary homogenization and cooling, obtain mixture four; the primary pressure of the homogenization is 3~4MPa; the secondary pressure is 0.5~1.5MPa;

[0016] (5) The mixture obtained in step (4) is packaged into four containers, fermented, cooled, and ripened to obtain dry yogurt with high milk solids content.

[0017] A second aspect of the present invention is to provide a dry yogurt with high milk solids content, which is prepared by the preparation method described above.

[0018] As described above, the dry yogurt with high milk solids content and its preparation method of the present invention have the following beneficial effects:

[0019] This application discloses a high-milk-solids dry yogurt. Through the combination of raw material selection and processing techniques, it successfully and stably produces high-protein, high-solids, and smooth-textured dry yogurt without any physical separation equipment or food additives. This method not only effectively overcomes the pumping and fermentation obstacles caused by high viscosity, enabling continuous production on general production lines, but also endows the product with excellent natural water-holding properties through the scientific ratio of raw materials and precise process control, ensuring stability throughout its shelf life. Detailed Implementation

[0020] To make the inventive objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to embodiments. Those skilled in the art can easily understand other advantages and effects of this invention from the content disclosed in this specification.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0022] When using “including,” “having,” and “contains” as described herein, the intention is to cover non-exclusive inclusion, unless an explicit qualifying term such as “only,” “consisting of,” etc., is used, in which case another component may be added.

[0023] In this invention, the terms "preferredly," "more preferably," "better," and "even better" refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of the invention. That is, in this invention, "preferredly," "more preferably," "better," and "even better" are merely descriptions of more effective implementations or examples, but do not constitute a limitation on the scope of protection of the invention.

[0024] In this invention, terms such as "further," "even more," and "particularly" are used for descriptive purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this invention.

[0025] In this invention, "at least one" means one or more, such as one, two, or more. "Multiple" or "several" means at least two, such as two, three, etc., and "multi-layered" means at least two layers, such as two layers, three layers, etc., unless otherwise explicitly specified. In the description of this invention, "several" means at least one, such as one, two, etc., unless otherwise explicitly specified.

[0026] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0027] Unless otherwise specified, all steps of this invention may be performed sequentially or randomly. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0028] Unless otherwise stated, a singular term may include a plural term and should not be understood as having a quantity of one.

[0029] In this invention, "above" or "below" both include the number itself. For example, "below 1" includes 1.

[0030] In this invention, room temperature refers to 0~40°C, including but not limited to 10~40°C, or further to 20~30°C.

[0031] This invention does not have any special limitations on the source of raw milk, concentrated milk protein powder, white sugar, light cream, and fermentation strains; commercially available products commonly used by those skilled in the art can be used.

[0032] The post-fermentation process refers to the process of cooling and storing yogurt for a period of time after fermentation to further improve its taste, flavor and stability.

[0033] To produce a dry yogurt with high milk solids content, high-protein ingredients are typically added directly to enhance its nutritional value. However, when using an equal amount of concentrated whey protein, the viscosity of the material increased dramatically after heat treatment, causing severe pumping difficulties and even interruptions in the production line. Simultaneously, the high viscosity and the resulting increase in osmotic pressure significantly inhibited the activity of fermentation bacteria, leading to abnormally prolonged fermentation times or even failure. This indicates that simple protein fortification directly disrupts the continuity of production and the reliability of fermentation. Subsequently, we turned to concentrated milk protein. Although its impact on initial viscosity was less than that of whey protein, increasing the amount added to achieve the target protein content still caused significant pumping resistance and fermentation stagnation. On the other hand, to improve the powdery texture and roughness that a high-protein system might result in, heavy cream must be added to provide a richer mouthfeel. However, there are also limitations to the addition of heavy cream: insufficient addition results in a dry mouthfeel; excessive addition, due to its high fat content, makes it difficult to effectively refine fat globules during homogenization, also affecting product quality. Furthermore, excessively high fat content can lead to excessively high viscosity due to homogenization, affecting continuous production. While using lower homogenization pressure can reduce viscosity, it may be difficult to effectively refine fat globules, thus affecting product quality.

[0034] To address the aforementioned issues, at the raw material level, the inventors, through systematic screening and verification, determined that concentrated milk protein and light cream in a specific ratio were the core ingredients. The amount of concentrated milk protein added was precisely limited to a range that achieved the target protein content without reaching an unacceptable viscosity threshold during production. The amount of light cream added was set within a narrow window: its lower limit had to be sufficient to provide the necessary lubrication and full-bodied texture, while its upper limit ensured the smooth operation of the homogenization process. At the process level, to adapt to the characteristics of the high-solids, high-viscosity raw material system, a "fill-first, ferment-later" process was adopted. This involves aseptic filling directly after ingredient preparation, homogenization, and sterilization, followed by fermentation in an insulated storage facility. This improved the difficulty of transporting and filling high-viscosity materials after fermentation and ensured the aseptic nature of the production process. Secondly, addressing the issue of excessive pressure or clogging in homogenizing high-viscosity materials, we optimized the homogenization parameters, employing specific pressure conditions significantly lower than those in conventional yogurt production. This pressure is sufficient to effectively refine fat globules and uniformly disperse the material, while ensuring continuous and stable operation of the production line. Finally, to overcome the initial inhibition of fermentation by the high-solids environment, we developed a segmented fermentation program. By controlling the temperature and time during the initial fermentation stage, we create suitable start-up conditions for the bacteria, thereby ensuring a thorough and uniform fermentation process.

[0035] The first aspect of this invention is to provide a method for preparing dry yogurt with high milk solids content, the method comprising the following steps:

[0036] (1) Preheat the raw milk, add concentrated milk protein powder and white sugar while stirring, mix well to obtain mixture one;

[0037] (2) Sterilize the mixture obtained in step (1) and cool it to obtain mixture two;

[0038] (3) Inoculate the mixture two obtained in step (2) with fermentation bacteria, ferment, and obtain mixture three;

[0039] (4) Sterilize the cream to obtain sterilized cream; add the sterilized cream to the mixture three obtained in step (3), and after secondary homogenization and cooling, obtain mixture four; the primary pressure of the homogenization is 3~4MPa; the secondary pressure is 0.5~1.5MPa;

[0040] (5) The mixture obtained in step (4) is packaged into four containers, fermented, cooled, and ripened to obtain dry yogurt with high milk solids content.

[0041] This invention effectively reduces product viscosity by adjusting homogenization pressure, replacing whey protein powder with milk protein powder, and changing the order of adding cream, thereby achieving smooth filling and significantly shortening fermentation time. Specifically, by appropriately reducing homogenization pressure, excessive homogenization is avoided, which leads to excessive protein exposure and premature viscosity increase. Replacing whey protein powder with milk protein powder utilizes its natural casein-to-whey protein ratio to reduce heat-induced aggregation and viscosity spikes during fermentation. Simultaneously, the order of cream addition is changed, employing a two-step fermentation method—first, pre-fermentation is carried out to approximately pH 6.0 to fully activate lactic acid bacteria and enhance their activity; then, cream is added. This avoids early interference from fat in the cream with bacterial activation, and because the bacteria are already in the logarithmic growth phase, even if the system viscosity increases due to the later addition of cream, the overall fermentation time will not be significantly prolonged. Through the synergistic adjustment of homogenization pressure, protein raw material replacement, and cream addition order (in conjunction with two-step fermentation), the fermentation viscosity of the product is effectively reduced, achieving smooth filling and significantly shortening fermentation time, thus producing a fermented dairy product with the required protein or solids content.

[0042] In some embodiments of the present invention, in step (1), based on the mass of raw milk, the protein content of the raw milk is 3.2-3.4 wt%; for example, 3.2-3.3 wt% or 3.3-3.4 wt%; and the fat content is 3.4-3.8 wt%; for example, 3.4-3.5 wt% or 3.5-3.6 wt% or 3.6-3.7 wt% or 3.7-3.8 wt%.

[0043] In some embodiments of the present invention, in step (1), the protein content of the concentrated milk protein powder is 70-80 wt%, based on the mass of the concentrated milk protein powder; for example, 70-71 wt%, 71-72 wt%, 72-73 wt%, 73-74 wt%, 74-80 wt%.

[0044] In some embodiments of the present invention, the preheating temperature in step (1) is 45~55℃; for example, 45~47℃, 47~49℃, 49~51℃, 51~53℃, 53~55℃.

[0045] In some embodiments of the present invention, the sterilization temperature in step (2) is 90~95℃, for example 90~91℃, 91~92℃, 92~93℃, 93~94℃, 94~95℃. The sterilization time is 5~7min; for example 5~5.5min, 5.5~6min, 6~6.5min, 6.5~7min.

[0046] In some embodiments of the present invention, the cooling temperature in step (2) is 40~44°C. For example, it is 40~41°C, 41~42°C, 42~43°C, or 43~44°C.

[0047] In some embodiments of the present invention, the fermentation temperature in step (3) is 40~44℃; for example, 40~41℃, 41~42℃, 42~43℃, 43~44℃. The pH at the end of fermentation is 5.5~6.5; for example, 5.5~6, 6~6.5.

[0048] In some embodiments of the present invention, the fermentation strain in step (3) is selected from one or more of Streptococcus thermophilus, Lactobacillus bulgaricus, Bifidobacterium, Lactobacillus plantarum, Lactobacillus paracasei, or Lactobacillus acidophilus.

[0049] In some embodiments of the present invention, the sterilization temperature in step (4) is 90~95℃, for example 90~91℃, 91~92℃, 92~93℃, 93~94℃, 94~95℃. The sterilization time is 5~7min; for example 5~5.5min, 5.5~6min, 6~6.5min, 6.5~7min.

[0050] In some embodiments of the present invention, the temperature of the secondary homogenization in step (4) is 50~54℃; for example, 50~51℃, 51~52℃, 52~53℃, 53~54℃. The primary pressure of the secondary homogenization is 3~4MPa, for example, 3~3.2MPa, 3.2~3.4MPa, 3.4~3.6MPa, 3.6~3.8MPa, 3.8~4.0MPa; the secondary pressure is 0.5~1.5MPa, for example, 0.5~0.7MPa, 0.7~0.9MPa, 0.9~1.1MPa, 1.1~1.3MPa, 1.3~1.5MPa.

[0051] In some embodiments of the present invention, the cooling temperature in step (4) is 40~44℃; for example, 40~41℃, 41~42℃, 42~43℃, 43~44℃.

[0052] In some embodiments of the present invention, in step (4), the fat content of the cream is 35-40 wt%, based on the mass of the cream. For example, it is 35-36 wt%, 36-37 wt%, 37-38 wt%, 38-39 wt%, or 39-40 wt%.

[0053] In some embodiments of the present invention, the fermentation temperature in step (5) is 40~44℃; the pH at the end of fermentation is 4.68~4.78; this means that the pH of the fermentation system is measured after fermentation, and the fermentation product is harvested when the pH reaches 4.68~4.78, for example, 4.68~4.70, 4.70~4.72, 4.72~4.74, 4.74~4.76, 4.76~4.78.

[0054] In some embodiments of the present invention, the cooling temperature in step (5) is 2~8°C; for example, 2~3°C, 3~4°C, 4~5°C, 5~6°C, 6~7°C, 7~8°C.

[0055] In some embodiments of the present invention, the temperature of the post-ripening treatment in step (5) is 2~8℃; for example, 2~3℃, 3~4℃, 4~5℃, 5~6℃, 6~7℃, 7~8℃; and the time of the post-ripening treatment is 10~24h; for example, 10~12h, 12~14h, 14~16h, 16~18h, 18~20h, 20~22h, 22~24h.

[0056] A second aspect of the present invention is to provide a dry yogurt with high milk solids content, which is prepared by the preparation method described above.

[0057] In some embodiments of the present invention, the fermentation base of the dry yogurt comprises the following components by weight percentage: 55.2–59.5 wt% raw milk, 10–12 wt% concentrated milk protein powder, 3.5–4.8 wt% white sugar, and 27–28 wt% light cream; the dry yogurt also contains a starter culture, and the inoculation amount of the starter culture is 1 × 10⁻⁶ based on the total mass of the fermentation base. 6 ~8×10 6 CFU / g.

[0058] In some embodiments of the present invention, the amount of raw milk added is 55.2–56.2 wt%, 56.2–57.2 wt%, 57.2–58.2 wt%, 58.2–59.2 wt%, or 59.2–59.5 wt%.

[0059] In some embodiments of the present invention, the amount of concentrated milk protein powder added is 10-10.5 wt%, 10.5-11 wt%, 11.0-11.5 wt%, or 11.5-12.0 wt%.

[0060] In some embodiments of the present invention, the amount of cream added is 27.0-27.2 wt%, 27.2-27.4 wt%, 27.4-27.6 wt%, 27.6-27.8 wt%, or 27.8-28.0 wt%.

[0061] In some embodiments of the present invention, the amount of white sugar added is 3.5-3.8 wt%, 3.8-4.1 wt%, 4.1-4.4 wt%, 4.4-4.8 wt%, or 27.8-28.0 wt%.

[0062] In some embodiments of the present invention, the inoculum amount of the fermenting agent is 1×10⁻⁶. 6 ~2×10 6 CFU / g, 2×10 6 ~4×10 6 CFU / g, 4×10 6 ~6×10 6 CFU / g, 6×10 6 ~8×10 6 CFU / g.

[0063] In some embodiments of the present invention, the total solids content of the dry yogurt is 31.7–35.5 g / 100g, based on the mass of the dry yogurt. For example, it is 31.7–32.5 g / 100g, 32.5–34 g / 100g, or 34–35.5 g / 100g. The solids mentioned in this invention mainly refer to the sum of protein, fat, and lactose.

[0064] In some embodiments of the present invention, based on the mass of the dry yogurt, the protein content in the dry yogurt is 8.9–11.4 wt%, for example, 8.9–10 wt% or 10–11.4 wt%; the fat content is 11.4–13.2 wt%, for example, 11.4–12 wt% or 12–13.2 wt%; and the carbohydrate content is 10.8–11.4%, for example, 10.8–11.1% or 11.1–11.4%.

[0065] The present invention will be further illustrated by the following examples, but these examples do not limit the scope of the invention.

[0066] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. All reagents or instruments whose manufacturers are not specified are conventional products that can be purchased commercially. In addition to the specific methods, equipment, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description of this invention, any prior art methods, equipment, and materials similar to or equivalent to those described, used, and materials in the embodiments of this invention may be used to implement this invention.

[0067] The raw milk and light cream of this invention are from Bright Dairy Co., Ltd.

[0068] The manufacturer of the concentrated milk protein of this invention is GRASSLAND DAIRY PRODUCTS, INC.

[0069] The thermophilic streptococcus and Lactobacillus bulgaricus of this invention are manufactured by Danisco Inc.

[0070] The Bifidobacterium of this invention is Bifidobacterium longum BD3150, and the Lactobacillus plantarum is Lactobacillus plantarum ST-III, produced by Bright Dairy & Food Co., Ltd.

[0071] The Lactobacillus acidophilus strain of this invention is Howaru Dophilus, manufactured by Danisco Inc.

[0072] Example

[0073] Example 1

[0074] This embodiment provides a method for preparing dry yogurt with high milk solids content, including the following steps:

[0075] (1) Weigh out 55.2 wt% raw milk, 12 wt% concentrated milk protein (MPC), 28 wt% light cream and 4.8 wt% white sugar according to the formula. Preheat the raw milk, and under high-speed shearing conditions, slowly add concentrated milk protein powder and white sugar to mix, ensuring that it is completely dispersed and free of lumps, to obtain mixture one; wherein, the protein content of the raw milk is 3.4 wt% and the fat content is 3.8 wt%, the protein content of the concentrated milk protein is 80 wt%, and the fat content of the light cream is 40 wt%; the preheating temperature is 45℃;

[0076] (2) Sterilize mixture one, and then quickly cool it to the fermentation temperature to obtain mixture two; the sterilization temperature is 90℃, the sterilization time is 7min, and the cooling temperature is 40℃.

[0077] (3) Inoculate the cooled mixture II with fermentation bacteria and ferment until the pH value reaches 6.0 to obtain mixture III; wherein: the fermentation agent is Streptococcus thermophilus 3×10 5 CFU / g, Lactobacillus bulgaricus 4×10 5 CFU / g, Bifidobacterium inoculation amount was 3×10 5 CFU / g, total inoculation amount 1×10 6 CFU / g; fermentation temperature: 40℃;

[0078] (4) Sterilize the light cream to obtain sterilized light cream. Add the sterilized light cream to the mixture three obtained in step (3), homogenize it in two stages, and cool it to obtain mixture four. The temperature of the second homogenization is 50°C, the first stage pressure of the homogenization is 3MPa, the second stage pressure is 1.5MPa, the cooling temperature is 40°C, the sterilization temperature is 90°C, and the sterilization time is 7min.

[0079] (5) The mixture obtained in step (4) is packaged into four containers and placed in a heat-insulated warehouse for continued fermentation until the end point. The temperature of the heat-insulated warehouse is 40℃, and the end point of fermentation is a pH value of 4.78.

[0080] (6) After cooling and post-ripening, dry yogurt with high milk solids content is obtained. The cooling temperature is 8℃, and the post-ripening refrigeration conditions are 8℃ for 24 hours.

[0081] The prepared fermented milk had a protein content of 11.4 wt%, a fat content of 13.2 wt%, a carbohydrate content of 10.8%, and a total solids content of 35.4 wt%.

[0082] Example 2

[0083] This embodiment provides a method for preparing dry yogurt with high milk solids content, including the following steps:

[0084] (1) Weigh out 59.5 wt% raw milk, 10 wt% concentrated milk protein (MPC), 27 wt% light cream, and 3.5 wt% white sugar according to the formula. Preheat the raw milk, and under high-speed shearing conditions, slowly add the concentrated milk protein powder and white sugar to mix, ensuring complete dispersion and no lumps, to obtain mixture one. Among them, the protein content of the raw milk is 3.2 wt%, the fat content is 3.4 wt%, the protein content of the concentrated milk protein is 70 wt%, and the fat content of the light cream is 35 wt%; the preheating temperature is 55℃;

[0085] (2) Sterilize mixture one, and then quickly cool it to the fermentation temperature to obtain mixture two; the sterilization temperature is 95℃, the sterilization time is 5min; the cooling temperature is 42℃;

[0086] (3) Inoculate the cooled mixture II with fermentation bacteria and ferment until the pH value reaches 6.2 to obtain mixture III; wherein: thermophilic streptococci 2×10 6 CFU / g, Lactobacillus bulgaricus 1×10 6 CFU / g, Lactobacillus acidophilus 5×10 5 CFU / g, Lactobacillus plantarum 5×10 5 CFU / g, total inoculation amount 4×10 6 CFU / g; fermentation temperature: 42℃;

[0087] (4) Sterilize the light cream to obtain sterilized light cream. Add the sterilized light cream to the mixture three obtained in step (3), homogenize it in two stages, and cool it to obtain mixture four. The temperature of the second homogenization is 50°C, the first stage pressure of the homogenization is 4MPa, and the second stage pressure is 0.5MPa. The cooling temperature is 42°C. The sterilization temperature is 95°C and the sterilization time is 5min.

[0088] (5) The homogenized mixture is bottled and placed in a heat-insulated warehouse for continued fermentation until the end point. The temperature of the heat-insulated warehouse is 44℃, and the end point of fermentation is a pH value of 4.68.

[0089] (6) After cooling and post-ripening, dry yogurt with high milk solids content is obtained. The cooling temperature is 2℃, and the post-ripening refrigeration conditions are 2℃ for 12h.

[0090] The prepared fermented milk had a protein content of 8.9 wt%, a fat content of 11.4 wt%, a carbohydrate content of 11.4%, and a total solids content of 31.7 wt%.

[0091] Example 3

[0092] This embodiment provides a method for preparing dry yogurt with high milk solids content, including the following steps:

[0093] (1) Weigh out 57.5 wt% raw milk, 11 wt% concentrated milk protein (MPC), 27.5 wt% light cream and 4.00 wt% white sugar according to the formula. Preheat the raw milk, and under high-speed shearing conditions, slowly add concentrated milk protein powder and white sugar to mix, ensuring that it is completely dispersed and free of lumps, to obtain mixture one; wherein the protein content of the raw milk is 3.3 wt% and the fat content is 3.6 wt%, the protein content of the concentrated milk protein is 75 wt%, and the fat content of the light cream is 38 wt%; the preheating temperature is 55℃;

[0094] (2) Sterilize mixture one, and then quickly cool it to the fermentation temperature to obtain mixture two; the sterilization temperature is 92℃, the sterilization time is 6min; the cooling temperature is 44℃.

[0095] (3) Inoculate the cooled mixture II with fermentation bacteria and ferment until the pH value reaches 6.0 to obtain mixture III; wherein the mixture contains 1×10⁻⁶ thermophilic streptococci. 6 CFU / g, Lactobacillus bulgaricus 4×10 6 CFU / g, Lactobacillus acidophilus 8×10 5 CFU / g, Lactobacillus plantarum 4×10 5 CFU / g, total inoculation amount 6.2×10 6 CFU / g; fermentation temperature: 44℃;

[0096] (4) Sterilize the light cream to obtain sterilized light cream. Add the sterilized light cream to mixture three obtained in step (3), homogenize it in two stages, and cool it to obtain mixture four. The temperature of the second-stage homogenization is 52℃, the first-stage pressure of the homogenization is 3.5MPa, and the second-stage pressure is 1MPa. The cooling temperature is 42℃; the sterilization temperature is 92℃, and the sterilization time is 6min.

[0097] (5) The mixture obtained in step (4) is packaged into four containers and placed in a heat-insulated warehouse for continued fermentation until the end point. The temperature of the heat-insulated warehouse is 44℃, and the end point of fermentation is a pH value of 4.72.

[0098] (6) After cooling and post-ripening, dry yogurt with high milk solids content is obtained. The cooling temperature is 5℃, and the post-ripening refrigeration conditions are 5℃ for 18h.

[0099] The prepared fermented milk has the following contents: protein content 10.1 wt%, fat content 12.5 wt%, carbohydrate content 11.4%, and total solids content 34.0 wt%.

[0100] Comparative Example

[0101] Comparative Example 1

[0102] This comparative example provides a method for preparing dry yogurt with high milk solids content. The difference from Example 3 is that concentrated whey protein powder is used to replace concentrated milk protein powder in an equal amount.

[0103] The viscosity of the material obtained in step (2) was too high, and the pH value dropped to the target pH value of 6.1 after adding the inoculum, which took about 2 hours longer than in Example 3 (2 hours). Moreover, the viscosity increased further after homogenization, which seriously affected the filling process.

[0104] Comparative Example 2

[0105] This comparative example provides a method for preparing dry yogurt with high milk solids content. The difference from Example 3 is that the first-stage pressure of the secondary homogenization in step (4) is 17 MPa and the second-stage pressure is 2 MPa.

[0106] After homogenization, the viscosity of the material was too high, almost losing its fluidity, making it impossible to conduct further experiments.

[0107] Comparative Example 3

[0108] This comparative example provides a method for preparing dry yogurt with high milk solids content. The difference from Example 3 is that the mixture obtained in step 1 is first mixed evenly with light cream, then homogenized, sterilized, cooled, and an equal amount of starter culture is added before direct bottling and incubation for fermentation. Specifically:

[0109] (1) Weigh out 57.5 wt% raw milk, 11 wt% concentrated milk protein (MPC), 27.5 wt% light cream and 4.00 wt% white sugar according to the formula. Preheat the raw milk, and under high-speed shearing conditions, slowly add concentrated milk protein powder, white sugar and light cream to mix, ensuring that it is completely dispersed and free of lumps, to obtain mixture one; wherein the protein content of the raw milk is 3.3 wt% and the fat content is 3.6 wt%, the protein content of the concentrated milk protein is 75 wt%, and the fat content of the light cream is 38 wt%; the preheating temperature is 55℃;

[0110] (2) Mixture 1 is sterilized, homogenized in two stages, and cooled to obtain mixture 2; wherein, the temperature of the second stage homogenization is 52℃, the first stage pressure of homogenization is 3.5MPa, and the second stage pressure is 1MPa; the cooling temperature is 42℃; the sterilization temperature is 92℃, and the sterilization time is 6min;

[0111] (3) Inoculate the cooled mixture 2 with fermentation starter culture, fill the container, and place it in a heat-insulated warehouse to continue fermentation until the end point. The starter culture contains 1×10⁻⁶ thermophilic streptococci. 6 CFU / g, Lactobacillus bulgaricus 4×10 6 CFU / g, Lactobacillus acidophilus 8×10 5 CFU / g, Lactobacillus plantarum 4×10 5CFU / g, total inoculation amount 6.2×10 6 CFU / g; the temperature in the incubator was 44℃, and the fermentation endpoint was a pH of 4.72; the fermentation temperature was 44℃.

[0112] (4) After cooling and post-ripening, dry yogurt with high milk solids content is obtained. The cooling temperature is 5℃, and the post-ripening refrigeration conditions are 5℃ for 18h.

[0113] The viscosity of the material after homogenization was too high, making it easy for milk to drip during filling. After adding the inoculum, the pH value dropped to the target pH value of 4.72, which was about 4 hours longer than in Example 3 (7 hours).

[0114] Performance testing

[0115] Taste evaluation test:

[0116] Taste tests were conducted on the dry yogurts prepared in Examples 1-3 and Comparative Example 3. A total of 38 people participated in the tests, all of whom were valid participants. The tasting method involved anonymous scoring. The smoothness, powdery texture, milky aroma, sourness, and sweetness of the samples from each example were scored individually, with a maximum score of 20 points for each item. The total score was calculated, and the average score was determined. A higher average score indicates a better result. The scoring criteria are shown in Table 1, and the statistical results are recorded in Table 2.

[0117] Table 1 Scoring Criteria

[0118]

[0119] Table 2 Sensory Tasting Results of Dry Yogurt from Examples 1-3 and Comparative Example 3

[0120]

[0121] Combining Examples 1-3 and Comparative Example 3, and referring to the data in Table 2, it can be seen that the taste evaluation of Examples 1-3 is better than that of Comparative Example 3. This is mainly because the process and long fermentation time of Comparative Example 3 result in a higher viscosity of the product system, which affects the flavor release and mouthfeel of the product, thereby affecting the evaluation scores of milky aroma, sweetness, sourness, smoothness and powdery texture.

[0122] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing dry yogurt with high milk solids content, characterized in that, The preparation method includes the following steps: (1) Preheat the raw milk, add concentrated milk protein powder and white sugar while stirring, mix well to obtain mixture one; (2) Sterilize the mixture obtained in step (1) and cool it to obtain mixture two; (3) Inoculate the mixture two obtained in step (2) with fermentation bacteria, ferment, and obtain mixture three; (4) Sterilize the cream to obtain sterilized cream; add the sterilized cream to the mixture three obtained in step (3), and after secondary homogenization and cooling, obtain mixture four; the primary pressure of the homogenization is 3~4MPa; the secondary pressure is 0.5~1.5MPa; (5) The mixture obtained in step (4) is packaged into four containers, fermented, cooled, and ripened to obtain dry yogurt with high milk solids content.

2. The preparation method according to claim 1, characterized in that: It also includes one or more of the following features: 11) In step (1), based on the mass of the raw milk, the protein content of the raw milk is 3.2–3.4 wt%; the fat content is 3.4–3.8 wt%. 12) In step (1), based on the mass of the concentrated milk protein powder, the protein content of the concentrated milk protein powder is 70-80 wt%; 13) The preheating temperature in step (1) is 45~55℃.

3. The preparation method according to claim 1, characterized in that: It also includes one or more of the following features: 21) The sterilization temperature in step (2) is 90~95℃ and the sterilization time is 5~7min; 22) The cooling temperature in step (2) is 40~44℃.

4. The preparation method according to claim 1, characterized in that: It also includes one or more of the following features: 31) The fermentation temperature in step (3) is 40~44℃; the pH at the end of fermentation is 5.5~6.5; 32) The fermentation strains in step (3) are selected from one or more of Streptococcus thermophilus, Lactobacillus bulgaricus, Bifidobacterium, Lactobacillus plantarum, Lactobacillus paracasei, or Lactobacillus acidophilus.

5. The preparation method according to claim 1, characterized in that: It also includes one or more of the following features: 41) The sterilization temperature in step (4) is 90~95℃ and the sterilization time is 5~7min; 42) The temperature of the secondary homogenization in step (4) is 50~54℃; 43) The cooling temperature in step (4) is 40~44℃; 44) In step (4), the fat content of the cream is 35-40 wt%, based on the mass of the cream.

6. The preparation method according to claim 1, characterized in that: It also includes one or more of the following features: 51) The fermentation temperature in step (5) is 40~44℃; the pH at the end of fermentation is 4.68~4.78; 52) The cooling temperature in step (5) is 2~8℃; 53) The temperature of the post-ripening treatment in step (5) is 2~8℃; the time of the post-ripening treatment is 10~24h.

7. A dry yogurt with high milk solids content, characterized in that: It is prepared by the preparation method described in any one of claims 1-6.

8. The dry yogurt with high milk solids content according to claim 7, characterized in that: The fermentation base of the dry yogurt comprises the following components by weight percentage: 55.2–59.5 wt% raw milk, 10–12 wt% concentrated milk protein powder, 3.5–4.8 wt% white sugar, and 27–28 wt% light cream; the dry yogurt also contains a starter culture, and the inoculation amount of the starter culture is 1 × 10⁻⁶ based on the total mass of the fermentation base. 6 ~8×10 6 CFU / g.

9. The dry yogurt with high milk solids content according to claim 7, characterized in that: Based on the quality of the dry yogurt, the total solids content of the dry yogurt is 31.7–35.5 g / 100g.

10. The dry yogurt with high milk solids content according to claim 7, characterized in that: Based on the quality of the dry yogurt, the protein content in the dry yogurt is 8.9-11.4 wt%, and the fat content is 11.4-13.2 wt%.

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