Yeast protein fermented milk, preparation method, device and application

Abstract

The invention belongs to the technical field of dairy product processing, and discloses yeast protein fermented milk, a preparation method, a device and application, a raw material composition of the fermented milk comprises raw milk, a sweetening agent, yeast protein, a stabilizer and a leavening agent, the yeast protein is compound modified yeast protein, and a dispersion technology combining homogenization and ultrasonic-assisted dispersion is adopted in the preparation process. And a segmented gradient fermentation process and a segmented dynamic after-ripening process are matched. The invention solves the problems of high cost of protein supplement sources, easy generation of peculiar smell, serious whey separation of fermented milk, short shelf life and single nutrition in the prior art, and the obtained product is balanced in nutrition, fine and uniform in texture, pure and harmonious in flavor, obviously prolonged in shelf life, adaptive to industrial production requirements and suitable for industrial production. The method can be applied to production of flavored fermented milk and fermented milk-containing beverages, and has good application value.

Description

Technical Field

[0001] This invention belongs to the field of dairy processing technology, specifically relating to a yeast protein fermented milk, its preparation method, apparatus, and application. Background Technology

[0002] Fermented milk is a product with a lower pH value made from raw cow (sheep) milk or milk powder through sterilization and fermentation. After microbial fermentation, the minerals in raw milk are more easily absorbed, and it can also alleviate lactose intolerance and improve human immunity. National standards have certain requirements for the protein content of fermented milk, such as a minimum protein content of 2.9% for fermented milk and a minimum protein content of 2.3% for flavored fermented milk. In order to meet the minimum protein content requirements for yogurt, manufacturers usually need to add additional protein, mainly whey protein and soy protein. However, whey protein is expensive, and soy protein usually has a beany taste. Therefore, it is necessary to develop a fermented milk with a higher protein content.

[0003] CN101731337B provides a method for producing yogurt with added yeast peptides in fermentation raw materials. The steps include: adding 0.05wt% to 1wt% edible yeast peptides to raw milk, and adding one or more of the following: stabilizers, sugars, flavorings, and jams; mixing, homogenizing, sterilizing, inoculating, and fermenting. This yields a yogurt with high nutritional value containing edible yeast peptides, increasing the variety of yogurt products. This yogurt can be stirred or set. The yeast peptides used are small molecule products such as peptides and amino acids from the hydrolysis of yeast proteins. When used in yogurt, they must be processed separately, and the processing time and temperature have specific requirements; otherwise, it will have an adverse effect on the flavor and texture of the fermented product. Chinese patent CN102370001B discloses a rice protein yogurt and a method for preparing it. The method uses rice protein with a protein content of 60%–90% by weight as raw material. The rice protein is diluted with water, swelled at high temperature, and homogenized under high pressure to obtain a rice protein slurry. Then, agar, gelatin, sugar, fresh milk, or reconstituted milk are added. The mixture is then homogenized, sterilized, cooled, inoculated for fermentation, and refrigerated to obtain a rice protein yogurt. This rice protein yogurt has an acidity of 70–100°T, a yogurt solids content of 11.5%–12%, and a specific rice aroma. However, the rice protein used lacks lysine, resulting in a relatively simple nutritional profile. Chinese patent CN109566747A provides a pea protein vegan plant-based yogurt and its preparation method. The method includes crushing peas, adding water and enzymatically hydrolyzing, obtaining pea protein through alkaline extraction and acid precipitation, adding polysaccharides and adjusting the pH for incubation, then adding sugar, vegetable oil and flavor modifiers for homogenization, sterilization and fermentation with cold storage to obtain pea protein vegan plant-based yogurt. The process requires first extracting pea protein and then preparing pea protein yogurt, which is relatively complex. It is also a single plant protein yogurt with relatively simple nutrition.

[0004] The existing technologies described above use rice protein or pea protein to prepare fermented milk. Rice protein lacks lysine, resulting in a nutritionally unbalanced product. Pea protein requires extraction through crushing, enzymatic hydrolysis, alkaline extraction, and acid precipitation before being used in fermented milk preparation, making the process relatively complex. Furthermore, existing fermented milk still has room for quality improvement. Some products are prone to whey separation during storage, and their water-holding capacity needs improvement. Moreover, some fermented milks derived solely from plant proteins fail to meet consumers' demands for comprehensive nutrition. The starter culture is a key factor affecting the quality of fermented milk. Existing technologies include direct-inoculation yogurt starter cultures, some of which contain strains such as Streptococcus thermophilus and Lactobacillus bulgaricus, enabling coagulation and imparting certain probiotic functions. However, some fermented milks still require the addition of additives such as gelatin and pectin to ensure coagulation and firmness. Furthermore, existing technologies regarding the synergistic effect of protein supplements and starter cultures to improve fermentation efficiency and shelf-life stability still require further refinement. Summary of the Invention

[0005] In order to overcome the above-mentioned defects of the prior art, the present invention provides a yeast protein fermented milk, preparation method, apparatus and application, which solves the problem that it is difficult to balance the uniformity of glucan dispersion, the integrity of natural bioactive structure and industrial production adaptability in the prior art.

[0006] The first technical solution of the present invention is a yeast protein fermented milk, comprising, by weight, 890-940 parts of raw milk, 50-90 parts of sweetener, 1-20 parts of yeast protein, 4-8 parts of stabilizer, and 0.02-0.06 parts of starter culture. Preferably, by weight, it comprises 900-930 parts of raw milk, 60-80 parts of sweetener, 5-10 parts of yeast protein, 5-6 parts of stabilizer, and 0.03-0.05 parts of starter culture.

[0007] As a preferred formulation, by weight, it comprises 915 parts raw milk, 70 parts sweetener, 8 parts yeast protein, 5.5 parts stabilizer, and 0.04 parts starter culture. Raw milk is the main matrix of fermented milk, providing essential fermentation substances such as milk protein and lactose; sweetener adjusts the product flavor and balances the acidity produced during fermentation; yeast protein, as a key nutritional fortification component, replaces traditional high-priced whey protein or soy protein, which is prone to off-flavors, thus enhancing the product's nutritional value; stabilizer improves the texture of fermented milk and reduces whey separation; the starter culture is the core of achieving milk matrix fermentation, and its dosage range ensures stable fermentation. The weight range of each component has been optimized through experiments to achieve a synergistic balance between nutrition, flavor, and fermentation feasibility, avoiding fermentation failure or poor product quality due to component imbalance.

[0008] Preferably, the raw milk is selected from either fresh milk or reconstituted milk. The fresh milk is selected from either cow's milk or goat's milk. The reconstituted milk is prepared by mixing whole milk powder or skim milk powder with water, and the mass percentage of whole milk powder or skim milk powder in the reconstituted milk is 20wt% to 30wt%. The selection of either cow's milk or goat's milk from the fresh milk satisfies the different consumer demands for milk flavor while preserving its natural nutrients. The reconstituted milk, prepared by mixing whole milk powder or skim milk powder with water, solves the problem of inconvenient storage and transportation of fresh milk, and is suitable for different production scenarios. Limiting the mass percentage of whole milk powder or skim milk powder in the reconstituted milk ensures that the dry matter content of the reconstituted milk is close to that of the fresh milk, avoiding the impact of excessively high or low milk concentration on the fermentation process and product texture, and guaranteeing stable fermentation results regardless of whether fresh milk or reconstituted milk is used.

[0009] Preferably, the sweetener is selected from at least one of sucrose, lactose, fructose, and glucose. Sucrose, lactose, fructose, and glucose are all food-grade natural sweeteners with a pure taste, no off-flavor residue, and can form a harmonious flavor with the sourness of fermented milk. These sweeteners can be partially metabolized and utilized by the bacterial strains in the fermentation agent, providing energy for the fermentation process, promoting the growth and reproduction of the strains, and improving fermentation efficiency. At the same time, their chemical properties are stable, and no adverse reactions will occur during sterilization, fermentation, and other processes, ensuring the stability and safety of the product flavor and avoiding abnormal product flavor or fermentation obstruction due to the use of unsuitable sweeteners.

[0010] Preferably, the yeast protein contains ≥75wt% protein, and the total content of leucine, isoleucine, and valine in the yeast protein accounts for 18-25% of the total amino acids in the yeast protein. A protein content of ≥75wt% in the yeast protein meets the nutritional fortification requirements of fermented milk, effectively increases the protein content of the product, meets national standards, and replaces traditional high-cost protein sources. Leucine, isoleucine, and valine are essential branched-chain amino acids that play an important role in muscle synthesis and energy metabolism; limiting their total content to 18-25% ensures the high nutritional value of the yeast protein. Simultaneously, this proportion of branched-chain amino acids does not inhibit the activity of the starter culture; instead, it provides partial nutritional support for strain growth, balancing nutritional fortification and fermentation stability, and avoiding insufficient product nutrition or abnormal fermentation due to substandard yeast protein quality.

[0011] Preferably, the yeast protein is a composite modified yeast protein, and the preparation process of the composite modified yeast protein includes the following steps:

[0012] (A01) Take yeast protein, add 5 to 8 times its weight of deionized water, stir to disperse evenly, and adjust the pH of the system to obtain yeast protein dispersion.

[0013] (A02) Add neutral protease to the yeast protein dispersion in step (A01), perform enzymatic hydrolysis, and inactivate the protease by incubation after hydrolysis to obtain a partially hydrolyzed yeast protein solution; (A03) Add organic zinc to the partially hydrolyzed yeast protein solution in step (A02), adjust the pH of the system, and stir to obtain a zinc-complex yeast protein solution; (A04) Add fructooligosaccharides to the zinc-complex yeast protein solution in step (A03), stir and mix, and then spray dry to obtain the composite modified yeast protein. Unmodified yeast protein is prone to aggregation and has poor dispersibility in the milk matrix, which may affect the uniformity of fermentation and the texture of the product. Through stepwise modification by enzymatic hydrolysis, zinc complexation, and fructooligosaccharide formulation, the macromolecular structure of yeast protein can be broken to improve solubility, zinc and prebiotics can be introduced to enhance nutrition, and the compatibility of protein with the milk system can be enhanced, avoiding problems such as stratification and precipitation during fermentation.

[0014] Preferably, in step (A01), the pH of the system is adjusted to 6.0–7.5; more preferably, in step (A01), the pH of the system is adjusted to 6.5–7.0; even more preferably, in step (A01), the pH of the system is adjusted to 6.8. Yeast proteins have the worst solubility near their isoelectric point. Adjusting the pH to the 6.0–7.5 range moves away from their isoelectric point, allowing protein molecules to fully dissolve and disperse, preventing aggregation and precipitation. Further narrowing the range to 6.5–7.0 and defining the optimal value of 6.8 is based on optimizing the pH for the optimal action of neutral proteases, creating a stable environment for subsequent enzymatic hydrolysis, ensuring consistent hydrolysis efficiency and effect, and avoiding uneven dispersion or hydrolysis inhibition due to improper pH.

[0015] Preferably, in step (A02), the amount of neutral protease added is 0.05% to 0.35% of the yeast protein mass, and the enzyme is hydrolyzed at 40 to 55°C for 10 to 25 minutes, controlling the degree of hydrolysis to 3% to 12%. After hydrolysis, the enzyme is inactivated at 75 to 95°C for 8 to 12 minutes. Preferably, in step (A02), the amount of neutral protease added is 0.1% to 0.3% of the yeast protein mass, and the enzyme is hydrolyzed at 45 to 50°C for 15 to 20 minutes, controlling the degree of hydrolysis to 5% to 10%. After hydrolysis, the enzyme is inactivated at 80 to 90°C for 9 to 11 minutes. More preferably, in step (A02), the amount of neutral protease added is 0.2% of the yeast protein mass, and the enzyme is hydrolyzed at 48°C for 18 minutes, controlling the degree of hydrolysis to 7%. After hydrolysis, the enzyme is inactivated at 85°C for 10 minutes. The gradient of neutral protease addition, temperature, and time parameters is designed to adapt to the characteristics of different yeast protein raw materials. By controlling the degree of hydrolysis, it is possible to break down large protein molecules to improve solubility and digestibility without damaging their nutritional structure. The temperature and time parameters for the inactivation step are designed to completely terminate the enzymatic hydrolysis reaction, preventing excessive protein hydrolysis caused by the continued action of protease in subsequent processes, while ensuring the microbial safety of the product. The optimal combination of parameters achieves the best balance between enzymatic hydrolysis effect and product stability.

[0016] Preferably, in step (A03), the organic zinc is zinc gluconate or zinc lactate, added at 0.3%–1.4% of the yeast protein mass. After adjusting the pH of the system to 5.0–6.5, the reaction is stirred at 30–45°C for 20–40 min. More preferably, in step (A03), the organic zinc is zinc gluconate or zinc lactate, added at 0.5%–1.2% of the yeast protein mass. After adjusting the pH of the system to 5.5–6.0, the reaction is stirred at 35–40°C for 25–35 min. More preferably, in step (A03), the organic zinc is zinc gluconate or zinc lactate, added at 0.9% of the yeast protein mass. After adjusting the pH of the system to 5.7, the reaction is stirred at 38°C for 30 min. Zinc gluconate and zinc lactate are food-grade organic zincs with higher bioavailability than inorganic zinc. After binding with enzymatically hydrolyzed yeast protein, they can form a stable zinc-protein complex, preventing zinc precipitation during fermentation or storage. Adjusting the pH and controlling the reaction temperature and time are to promote the binding of zinc ions with amino and carboxyl groups in protein molecules, improve the binding rate and stability, ensure that the zinc content meets the standard, and not affect the flavor and texture of the product.

[0017] Preferably, in step (A04), after stirring and mixing for 25-35 minutes, spray drying is performed, with a mass ratio of fructooligosaccharides to yeast protein of 1:7 to 1:10, and the spray drying conditions are an inlet air temperature of 175-195°C and an outlet air temperature of 75-90°C. More preferably, in step (A04), after stirring and mixing for 20-30 minutes, spray drying is performed, with a mass ratio of fructooligosaccharides to yeast protein of 1:8 to 1:9, and the spray drying conditions are an inlet air temperature of 180-190°C and an outlet air temperature of 80-85°C. More preferably, in step (A04), after stirring and mixing for 25 minutes, spray drying is performed, with a mass ratio of fructooligosaccharides to yeast protein of 1:8.5, and the spray drying conditions are an inlet air temperature of 185°C and an outlet air temperature of 83°C. Fructooligosaccharides, as a prebiotic, can promote the growth of probiotics in fermented milk and synergistically enhance the intestinal health benefits of the product with yeast protein. The ratio range is optimized based on the probiotic proliferation effect and protein stability. The spray drying parameters are designed to quickly remove moisture to obtain powdered composite modified yeast protein, which is convenient for storage, transportation and production addition. The control of the inlet and outlet air temperatures can avoid high temperature damage to the nutritional activity of protein, zinc complex and oligofructose, ensuring that the product's nutritional components are fully preserved.

[0018] Preferably, the stabilizer is selected from at least one of hydroxypropyl distarch phosphate, agar, and pectin. Hydroxypropyl distarch phosphate, as a modified starch stabilizer, can improve the viscosity and water-holding capacity of the milk system and inhibit whey separation; agar, as a natural gelling agent, can form a dense gel network, enhancing the strength and elasticity of the curd structure; pectin can interact with milk protein molecules, improving protein aggregation and resulting in a uniform and delicate product texture. All three stabilizers are food-grade safe raw materials, have a neutral flavor, and are highly compatible with fermented milk systems, without interfering with the fermentation process or producing off-flavors. Limiting the selection to at least one stabilizer not only adapts to the needs of different production scenarios but also allows for precise control of the stabilization effect through single or combined use, avoiding problems such as loose product structure and severe whey separation caused by inappropriate stabilizer selection.

[0019] Preferably, the starter culture is a direct-inoculation yogurt starter culture; the yogurt starter culture is selected from at least one of YF-L811 starter culture, Yo-C975-F starter culture, Yo-cul973 starter culture, and a 12-strain starter culture; the YF-L811 yogurt starter culture contains *Streptococcus thermophilus* and *Lactobacillus bulgaricus*; the Yo-C975-F yogurt starter culture contains *Streptococcus thermophilus*, *Lactobacillus bulgaricus*, and *Lactobacillus plantarum*; the Yo-cul973 yogurt starter culture contains *Streptococcus thermophilus* and *Lactobacillus bulgaricus*; the 12-strain yogurt starter culture contains *Bifidobacterium adolescentis*, *Streptococcus thermophilus*, *Bifidobacterium breve*, *Bifidobacterium lactis*, *Bifidobacterium longum*, *Bifidobacterium infantis*, and *Lactobacillus bulgaricus*. Direct-inoculation yogurt starter cultures do not require prior activation and can be used directly after inoculation, simplifying the production process and reducing the risk of contamination, thus meeting the needs of continuous industrial production. The starter culture contains Streptococcus, Lactobacillus, and Bifidobacterium, all of which are probiotics specifically for fermented milk. Among them, Streptococcus thermophilus and Lactobacillus bulgaricus can efficiently metabolize lactose to produce acid and promote milk protein curdling; Lactobacillus plantarum and various Bifidobacteria can enhance the product's probiotic function, regulate the balance of intestinal flora, and help improve the flavor.

[0020] The second technical solution of the present invention: a method for preparing yeast protein fermented milk, comprising the following steps: (S01) placing raw milk in a barrel installed between the base and the support shell, heating to a preset temperature, adding sweetener, stabilizer, and yeast protein, and stirring evenly to obtain a mixture;

[0021] (S02) Heat and keep the mixture in the tank in step (S01) warm; (S03) Homogenize the mixture in the tank after step (S02) using a homogenizer; (S04) Perform ultrasonic-assisted dispersion on the homogenized liquid in the tank after step (S03); (S05) Close the lid and seal it with locking piece A, and sterilize the liquid in the tank after step (S04); (S06) After the liquid in the tank after sterilization in step (S05) cools down, open locking piece A and lid, inoculate with fermentation agent, close the lid again and fix it with locking piece A, and carry out fermentation in the tank; (S07) Stir the fermented emulsion in the tank after step (S06) evenly, and keep the tank installed between the base and the support shell for cold storage and post-ripening treatment. First, heating and stirring promote the dissolution and dispersion of each component. Then, heat preservation, homogenization, and ultrasonic-assisted dispersion are carried out in a progressive process to solve the problem of yeast protein aggregation and enhance the system compatibility. The subsequent sterilization process takes into account both food safety and nutrient preservation. The segmented gradient fermentation is adapted to the growth and metabolic patterns of the strains to ensure sufficient fermentation. Finally, the cold-curing process refines the flavor and texture of the product. The overall design not only adapts to the characteristics of the raw material composition, but also ensures that the final product is nutritionally balanced, has a delicate texture, and has good stability through the complementary functions of each step.

[0022] Preferably, the preset temperature in step (S01) is 50–65°C, and the stirring time is 20–35 min; preferably, the preset temperature in step (S01) is 55–60°C, and the stirring time is 25–30 min; preferably, the preset temperature in step (S01) is 58°C, and the stirring time is 27 min. Heating the raw milk to the preset temperature reduces the viscosity of the system, increases the solubility of the sweetener and the hydration rate of the stabilizer, and promotes the initial integration of yeast protein and milk matrix. The stirring time is designed to adapt to the solubility characteristics of components at different temperatures, ensuring that the sweetener is completely dissolved without leaving crystals, the stabilizer is fully hydrated to form a stable network, and the yeast protein is evenly dispersed without agglomeration. Precise temperature and time matching can avoid particle formation, stratification, or uneven fermentation in subsequent processes due to insufficient dissolution.

[0023] Preferably, in step (S02), the mixture is heated to 85–98°C and held at this temperature for 8–12 minutes; more preferably, in step (S02), the mixture is heated to 90–96°C and held at this temperature for 9–11 minutes; more preferably, in step (S02), the mixture is heated to 93°C and held at this temperature for 10 minutes. Heating the mixture to 85–98°C and holding it at this temperature promotes the full hydration and cross-linking of stabilizers such as hydroxypropyl distarch phosphate and agar, enhancing their stabilizing effect on the milk system. Simultaneously, it can further activate the interactions between the components, such as promoting the binding of yeast protein and milk protein, thus improving the overall stability of the system. This avoids the stabilizer function being insufficient due to excessively low temperatures, or the natural structure of milk proteins being damaged by excessively high temperatures, ensuring a balance between stabilization effect and product flavor and nutrition.

[0024] Preferably, the homogenization conditions in step (S03) are: a processing temperature of 50–75°C, a homogenization pressure of 15–35 MPa, and a processing time of 5–25 min; more preferably, the homogenization conditions in step (S03) are: a processing temperature of 55–70°C, a homogenization pressure of 20–30 MPa, and a processing time of 10–20 min; even more preferably, the homogenization conditions in step (S03) are: a processing temperature of 62°C, a homogenization pressure of 25 MPa, and a processing time of 15 min. Homogenization breaks down fat globules in the raw milk under high pressure, dispersing them evenly in the system and preventing fat stratification in the finished product. It also refines the particle size of components such as yeast protein and stabilizers, improving their compatibility with the milk matrix. The design of the processing temperature, pressure, and time is to adapt to raw material systems with different milk fat contents and component ratios: excessively high temperatures may cause milk protein denaturation, insufficient pressure may not effectively break down fat globules, and excessively short times will result in uneven homogenization.

[0025] Preferably, the conditions for the ultrasonic-assisted dispersion treatment in step (S04) are: ultrasonic frequency 15–45 kHz, ultrasonic power 100–200 W, treatment temperature 50–65 °C, and treatment time 2–6 min; preferably, the conditions for the ultrasonic-assisted dispersion treatment in step (S04) are: ultrasonic frequency 20–40 kHz, ultrasonic power 130–170 W, treatment temperature 55–60 °C, and treatment time 3–5 min; more preferably, the conditions for the ultrasonic-assisted dispersion treatment in step (S04) are: ultrasonic frequency 30 kHz, ultrasonic power 150 W, treatment temperature 57 °C, and treatment time 4 min. Micro-agglomerates of yeast protein that may remain after homogenization can affect fermentation uniformity and product taste. The cavitation effect of ultrasound can effectively break down these agglomerates, refining the particle size to a more optimal range. The parameters of ultrasonic frequency, power, temperature, and time are limited based on a balance of multiple factors. Too low a frequency will not achieve the desired refinement effect, too high a power may damage the protein structure and nutrients, too high a temperature will affect the stability of the system, and too long a time may lead to excessive dispersion and component separation.

[0026] Preferably, the sterilization process in step (S05) is pasteurization or ultra-high temperature (UHT) sterilization. The pasteurization conditions are 60–90°C for 10–20 minutes, and the UHT sterilization conditions are 125–140°C for 2–9 seconds. More preferably, the pasteurization conditions in step (S05) are 65–85°C for 13–17 minutes, and the UHT sterilization conditions are 130–135°C for 3–8 seconds. More preferably, the pasteurization conditions in step (S05) are 70°C for 15 minutes, and the UHT sterilization conditions are 133°C for 5 seconds. Raw milk and added components may contain other microorganisms. If these are not completely eliminated, they will compete with the starter culture strains for nutrients, interfere with the fermentation process, and may even produce harmful substances. The design incorporates both pasteurization and ultra-high temperature (UHT) sterilization to meet diverse production needs. Pasteurization preserves more of the natural flavor and nutrients of milk, while UHT sterilization offers high efficiency and thorough sterilization, minimizing impact on milk protein function. The temperature and time parameters have been optimized for both microbial eradication and nutrient retention, ensuring thorough elimination of harmful bacteria while avoiding excessively harsh sterilization conditions that could lead to milk protein denaturation or lactose caramelization, thus balancing product safety, nutrition, and flavor.

[0027] Preferably, the fermentation process in step (S06) is a segmented gradient fermentation, comprising the following steps: (B01) a first stage, fermenting the inoculated liquid with the starter culture; (B02) a second stage, heating the liquid after the first stage of fermentation (B01) for further fermentation; and (B03) a third stage, cooling the liquid after the second stage of fermentation (B02) for further fermentation. Different strains in the starter culture have different optimal growth temperatures and metabolic stages. Fermentation at a single temperature makes it difficult to simultaneously achieve strain activation, efficient acid production, and flavor compound generation. Segmented gradient fermentation, through dynamic temperature adjustment, allows the strains to perform optimally at different stages, avoiding slow fermentation, uneven curdling, or a single flavor profile caused by constant temperature.

[0028] Preferably, the fermentation temperature in step (B01) is 36–42°C, and the fermentation time is 1–2.5 h; more preferably, the fermentation temperature in step (B01) is 38–40°C, and the fermentation time is 1.5–2 h; even more preferably, the fermentation temperature in step (B01) is 39°C, and the fermentation time is 1.8 h. The first stage serves as the strain adaptation period, and the temperature must match the initial growth requirements of the strain. This avoids both excessively low temperatures leading to insufficient strain activity and slow proliferation, and excessively high temperatures inhibiting strain growth. The timing is designed to adapt to the activation rates of different strain combinations, ensuring that the strains reach a sufficient quantity before entering the next stage, laying the foundation for efficient acid production and avoiding prolonged fermentation cycles or poor curdling effects due to insufficient strain proliferation.

[0029] Preferably, in step (BO2), the temperature is raised to 40–45°C and fermented for 1.5–3 hours until the acidity of the liquid reaches 55–70°T; more preferably, in step (BO2), the temperature is raised to 42–44°C and fermented for 2–2.5 hours until the acidity of the liquid reaches 60–65°T; even more preferably, in step (BO2), the temperature is raised to 43°C and fermented for 2.3 hours until the acidity of the liquid reaches 63°T. Raising the temperature significantly enhances the metabolic activity of the bacterial strain, accelerates lactose decomposition and acid production, and shortens the fermentation cycle. The defined time range is the optimal interval for acid production and curdling, ensuring that the milk protein fully coagulates to form a stable structure. Acidity, as a quantitative standard for the adequacy of fermentation, is directly related to the curd state and flavor balance of the product, avoiding loose curd due to insufficient fermentation or excessive fermentation resulting in high acidity and a sour taste.

[0030] Preferably, in step (B03), the temperature is lowered to 38–42°C and fermented for 0.3–1.2 hours; more preferably, the temperature is lowered to 39–41°C and fermented for 0.5–1 hour; even more preferably, the temperature is lowered to 40°C and fermented for 0.7 hours. After the second stage of efficient acid production, cooling slows down the acid production rate of the strain, preventing a continuous increase in acidity from disrupting the flavor balance. Simultaneously, it provides a suitable environment for the synthesis and transformation of flavor compounds, allowing the organic acids, alcohols, and other substances produced during fermentation to fully integrate, thus improving the harmony of the taste. The timing is designed to ensure stable flavor formation, avoiding insufficient flavor due to too short a fermentation time after cooling, or abnormal product texture due to too long a time, ultimately achieving a product with a rich flavor and smooth texture.

[0031] Preferably, the post-fermentation maturation process in step (S07) is a segmented dynamic maturation process, including the following steps: (C01) First stage: statically refrigerating the fermented emulsion; (C02) Second stage: intermittently stirring the emulsion while maintaining its temperature, continuously refrigerating; (C03) Third stage: cooling the emulsion after the second stage of refrigeration and statically refrigerating it at that temperature. The flavor compounds in the fermented emulsion are not yet fully balanced, and the curd structure needs further solidification. The segmented dynamic process, through a stepped design of static refrigeration, intermittent stirring, and static cooling, provides a time window for the transformation and fusion of flavor compounds, breaks up localized concentration imbalances through gentle stirring, and enhances structural stability through final cooling. This process framework balances flavor harmony and texture uniformity, avoiding flavor stratification, whey separation, or a rough texture caused by improper maturation methods.

[0032] Preferably, the static refrigeration temperature in step (C01) is 3–7°C, and the time is 7–11 hours; more preferably, the static refrigeration temperature in step (C01) is 4–6°C, and the time is 8–10 hours; even more preferably, the static refrigeration temperature in step (C01) is 5°C, and the time is 9 hours. The static refrigeration temperature slows down microbial metabolism, preventing excessive fermentation of the product, while providing a suitable environment for cross-linking between milk protein molecules, promoting the densification of the curd structure. The time range is determined based on the conversion rate of flavor substances, ensuring that the organic acids, esters, and other substances produced during fermentation are initially integrated, avoiding a bland flavor due to too short a time, or a stiff texture due to too long a time.

[0033] Preferably, in step (CO2), the emulsion temperature is 2–8°C, the stirring speed is 8–18 r / min, the intermittent stirring mode is 15 min followed by a 30 min pause, and the product is continuously refrigerated for 5.5–10 h; preferably, in step (CO2), the emulsion temperature is 4–6°C, the stirring speed is 10–15 r / min, and the product is continuously refrigerated for 6–9 h; more preferably, in step (CO2), the emulsion temperature is 5°C, the stirring speed is 13 r / min, and the product is continuously refrigerated for 7.5 h. Maintaining a stable emulsion temperature prevents temperature fluctuations from causing the curd to shrink and separate into whey; the low-speed intermittent stirring at 8–18 r / min allows incompletely blended flavor substances to diffuse evenly without damaging the initially solidified curd network, avoiding a loose product texture. The 15-minute stirring, 30-minute pause mode balances the mixing effect and the need for structural stability, promoting flavor fusion during stirring and allowing the curd structure to self-repair during pauses; the duration of 5.5–10 hours ensures sufficient flavor homogenization.

[0034] Preferably, the cooling temperature in step (CO3) is 1–5°C, and the product is statically refrigerated for 3–7 hours; more preferably, the cooling temperature in step (CO3) is 2–4°C, and the product is statically refrigerated for 4–6 hours; even more preferably, the cooling temperature in step (CO3) is 3°C, and the product is statically refrigerated for 5 hours. Lowering the temperature to 1–5°C can significantly inhibit microbial activity, slow down subsequent flavor deterioration and texture changes, and extend the product's shelf life. Simultaneously, the low-temperature environment allows the curd structure to fully stabilize, preventing deformation or whey separation during storage and transportation. The 3–7 hour static refrigeration time is to allow flavor substances to finally stabilize, ensuring that the product's flavor and texture are at their optimal state upon leaving the factory, avoiding incomplete flavor stabilization and taste fluctuations caused by direct shipment after cooling.

[0035] Preferably, the yeast protein fermented milk has an acidity of 70–90°T and a solids content of 8%–18%; more preferably, the yeast protein fermented milk has an acidity of 75–85°T and a solids content of 10%–15%; even more preferably, the yeast protein fermented milk has an acidity of 78°T and a solids content of 13%. Acidity is a core flavor indicator of fermented milk. The range of 70–90°T is suitable for consumers' acceptance of a balanced sweet and sour taste, avoiding both insufficient acidity leading to a bland flavor and poor antibacterial effect, and excessive acidity causing a sour and astringent taste. The solids content of 8%–18% is directly related to the rich taste and nutritional density of the product. Too low a content will result in a thin texture and insufficient nutrition, while too high a content may affect the swallowing experience.

[0036] The third technical solution of this invention is the application of yeast protein fermented milk, wherein the fermented dairy product is flavored fermented milk or fermented milk-containing beverage. This clarifies the applicable boundaries of the invention, provides manufacturing enterprises with a clear product development direction, adapts to the needs of different consumer groups, helps the technology move from the laboratory to large-scale production, and improves the efficiency of industrialization.

[0037] The fourth technical solution of the present invention: a preparation device for yeast protein fermented milk, comprising a base, a support shell, a barrel body, a barrel lid, and a homogenizer. Two support shells are symmetrically mounted on the surface of the base. The barrel body is rotatably mounted between the two support shells. The barrel lid is hinged to the top of the barrel body. The homogenizer is fixedly mounted on the top of the barrel lid. The barrel body and the barrel lid are detachably installed via a locking piece A. A tilting mechanism is provided inside the support shell, and a stirring mechanism is provided inside the barrel body.

[0038] Preferably, the tilting mechanism includes an electric push rod, the bottom output end of which is fixedly connected to one end of a crossbar, the other end of which is fixedly connected to the bottom end of a rack, an extension plate fixedly mounted on the top of the rack, a gear meshing on the side of the rack, the other end of the gear shaft being fixedly connected to a fixed plate, the bottom of the gear shaft being fixedly connected to the top of a swing arm, and the bottom of the swing arm being fixedly connected to a drag ring.

[0039] Preferably, the electric push rod is fixedly installed inside the bracket housing, the crossbar is located below the gear, the side of the rack is slidably mounted with a guide rail A, the two ends of the guide rail A are fixedly connected to the inner wall of the bracket housing, the gear is rotatably connected to the bracket housing through a shaft and bearings, the side of the fixing plate is fixedly connected to the outer surface of the barrel, the swing arm is located between the barrel and the bracket housing, and the drag ring is fixedly installed below the outer surface of the barrel.

[0040] Preferably, the barrel body has a cavity A and a cavity B. A vertical heating tube is fixedly installed inside the cavity A, and a horizontal heating tube is fixedly installed inside the cavity B. The vertical heating tube is arranged in a spiral upward shape, and the horizontal heating tube is arranged in a mosquito coil spiral shape.

[0041] Preferably, the stirring mechanism includes a stirring motor, which is fixedly installed in the interlayer of the barrel. A sealing seat is fitted on the outer side of the output end of the stirring motor, and the sealing seat is embedded in the inner wall of the barrel. A rod is fixedly installed on the top of the output end of the stirring motor. The cross-section of the rod is square. A stirring shaft is inserted through the top of the rod. Four equally spaced fixing rings are fixedly installed on the outer side of the stirring shaft. Four circumferentially arranged stirring rods are fixedly installed on the outer side of the fixing rings. The stirring rods in the upper and lower layers are arranged at a 30-degree angle. Magnetic strips are fixedly installed on the tail ends of the two staggered stirring rods. The magnetic strips are arranged at an angle.

[0042] Preferably, the bottom of the stirring shaft has a slot corresponding to the insert rod. Ribs are fixedly installed on two sides of the insert rod, and mounting grooves are opened on the other two sides of the insert rod. There are three mounting grooves on one side, which are equally spaced, and two mounting grooves on the other side, which are staggered. A spring A is fixedly installed inside the mounting groove, and a locking head is fixedly installed on the other end of the spring A. Rib grooves corresponding to the ribs are opened on two inner walls of the slot, and locking grooves corresponding to the locking heads are opened on the other two inner walls of the slot.

[0043] Preferably, the inner wall of the barrel is fixedly installed with guide rails B, and there are eight guide rails B arranged in a ring array. A sliding plate is slidably installed inside the guide rails B. A sealing seat is inserted through the top of the guide rails B. A spring B is fixedly installed on the surface of the sliding plate. There are several springs B arranged at equal intervals. The springs B are magnetic and correspond to the magnetic strip.

[0044] Preferably, a temperature sensor and a pressure sensor are fixedly installed on the inner top wall of the bucket lid, a control panel is fixedly installed on the surface of the bucket lid, and a locking piece B corresponding to locking piece A is fixedly installed on the outer periphery of the bucket lid. The control panel is electrically connected to the electric push rod, the vertical heating tube, the horizontal heating tube, and the stirring motor, respectively. The output terminals of the temperature sensor and the pressure sensor are connected to the input terminal of the control panel.

[0045] Preferably, the homogenizer includes a housing, which is fitted onto the top of a bucket lid. A cap is threaded to the top of the housing, and a threaded ring is embedded in the top of the cap. A threaded rod is threaded to the inner wall of the threaded ring, and a plug is rotatably connected to the bottom of the threaded rod. A corresponding plug seat is fixedly installed inside the housing. A mesh plate is threaded to the bottom of the housing, and a filter screen is provided between the mesh plate and the plug seat. A limiting ring is fixedly installed on the right side of the inside of the housing, and a spring C is provided on the right side of the limiting ring. A ball is fixedly installed on the right side of the spring C, and a ball ring is provided on the right side of the ball. A connecting nozzle is fixedly installed on the right side of the ball ring.

[0046] Preferably, the bottom of the plug body is provided with a frustum, the top of the plug seat is provided with a conical surface corresponding to the frustum, the side of the ball near the spring C is a plane, the side of the ball away from the spring C is a spherical surface, the side of the ball ring is provided with an inclined surface tangent to the ball, the diameter of the ball is smaller than the diameter of the inclined surface of the ball ring, and the ball ring is fixedly installed on the inner wall of the outer shell.

[0047] This device is a dedicated equipment for the preparation method of the second technical solution. The functions of each component are as follows: the vertical heating tube and the horizontal heating tube are used to achieve the heating in step (S01) and the heat preservation treatment in step (S02); the stirring mechanism is used for the stirring operation in steps (S01) and (S07), and the cooperation between the magnetic strip and spring B can help achieve fine homogenization; the homogenizer is used for the homogenization treatment in step (S03), and the gap between the plug and the plug seat is controlled by adjusting the threaded rod to achieve homogenization under different pressures; the temperature sensor and the pressure sensor are used to monitor the temperature and pressure in the fermentation, sterilization and other processes; the pouring mechanism is used to pour out the product after fermentation; this device can be programmed and controlled through the control panel to realize automated processes such as segmented gradient fermentation and segmented dynamic after-ripening.

[0048] The present invention has the following beneficial effects: (1) The present invention uses compound modified yeast protein as the core nutritional supplement source, taking into account the essential branched-chain amino acids, organic zinc elements and prebiotics, forming a multi-nutrient system, while replacing traditional high-priced whey protein or soybean protein that is prone to producing off-flavors, thereby improving the nutritional value of the product while reducing production costs; (2) The segmented gradient fermentation process of the present invention is adapted to the growth and metabolism of the fermentation agent strain, combined with the nutritional support provided by yeast protein, so that the strain can exert optimal activity at different stages, which shortens the fermentation cycle and avoids the problems of insufficient or excessive fermentation, ensuring that each batch The product fermentation effect is consistent; (3) This invention solves the problem of yeast protein aggregation by homogenization and ultrasonic-assisted dispersion process, and is matched with a suitable stabilizer system. Then, the curd structure is solidified by the segmented dynamic post-ripening process, so that the product has a uniform and delicate texture, effectively reduces whey separation during storage and transportation, and improves the sensory quality and shelf-life stability of the product; (4) The yeast protein of this invention has no bad odor and forms a good flavor balance with sweeteners and organic acids produced by fermentation. The intermittent stirring in the segmented dynamic post-ripening process promotes the full integration of flavor substances, avoids flavor layering or blandness, and ensures that the product is sweet and sour and has a pure flavor; (5) The shelf life of this invention is significantly extended. The low-temperature segmented ripening process can inhibit microbial activity. Combined with the active polysaccharides contained in yeast protein, it synergistically slows down the deterioration of product flavor and changes in texture, thus extending the product's shelf life and meeting the needs of industrial production, long-distance transportation, and market circulation. (6) This invention has diverse and adaptable application scenarios. The formula and process design are compatible with the production needs of flavored fermented milk and fermented dairy beverages. The yeast protein has a neutral flavor and will not interfere with the flavor expression of additional ingredients such as fruits, vegetables, and grains. The stabilizer and ripening process ensure that the product can maintain a stable texture under different processing scenarios, thus broadening its industrial application. Space; (7) The extension of the electric push rod can drive the crossbar to move down, and the rack will also move down. The rack will drive the gear to rotate. While the gear is rotating, it will also drive the barrel to tilt. At the same time, the rotating gear shaft will also drive the swing arm and drag ring to rotate. The drag ring will lift the bottom of the barrel, reducing the rotation resistance of the barrel. After tilting, the fermented milk inside the barrel can be poured out, which improves the efficiency of pouring out the fermented milk; (8) The stirring motor drives the stirring shaft to rotate. The stirring shaft drives the stirring rod and the magnetic strip to rotate, which can stir and mix the liquid inside the barrel. At the same time, the rotating magnetic strip will drive the spring B The suction force is generated, causing the spring B to swing back and forth, which homogenizes and disperses the liquid into finer particles, thus improving the homogenization effect; (9) Liquid is added into the barrel through the connecting nozzle. The pressurized liquid pushes the ball backward and then the plug is moved upward through the threaded rod. The bottom cone of the plug and the plug seat form a gap. Once the liquid passes through this point, it can be pressure homogenized and broken, increasing the small particle size of the liquid. At the same time, pressure can be injected into the barrel using the homogenizer to increase the pressure value of the barrel and give the liquid in the barrel pressure to break. Attached Figure Description

[0049] Figure 1 These are sensory rating comparison charts of embodiments 1-8 of the present invention; Figure 2 This is a comparison chart of sensory ratings for Comparative Examples 1-9 of this invention; Figure 3 These are comparison charts of the shelf life of Embodiments 1-8 and Comparative Examples 1-9 of the present invention; Figure 4 This is a three-dimensional structural diagram of the present invention; Figure 5 This is a schematic diagram of the bucket lid structure of the present invention;

[0050] Figure 6 This is a top view of the structure of the present invention; Figure 7 This is a schematic diagram of the cross-sectional structure of the present invention; Figure 8 This is a schematic diagram of the three-dimensional structure of the present invention after the barrel body is removed;

[0051] Figure 9 This is a schematic diagram of the three-dimensional structure of the gear and rack of the present invention; Figure 10 This is a schematic diagram of the connection structure between the stirring shaft and spring B of the present invention; Figure 11 This is a schematic diagram of the guide rail B and spring B structure of the present invention; Figure 12 This is a schematic diagram of the stirring rod and magnetic strip structure of the present invention; Figure 13 This is a schematic diagram of the insertion rod and stirring shaft structure of the present invention; Figure 14 This is a schematic diagram of the insertion rod and stirring shaft structure of the present invention; Figure 15 This is a schematic diagram of the cross-sectional structure of the homogenizer of the present invention; Figure 16 This is a schematic diagram of the exploded structure of the homogenizer of the present invention.

[0052] The markings in the attached diagram are as follows: 100, base; 200, support shell; 300, barrel body; 400, barrel lid; 500, lock A; 600, homogenizer; 201, electric push rod; 202, crossbar; 203, rack; 204, gear; 205, guide rail A; 206, fixing plate; 207, swing arm; 208, drag ring; 209, extension plate; 301, cavity A; 302, cavity B; 303, vertical heating tube; 304, horizontal heating tube; 305, stirring motor; 306, sealing seat; 307, insertion rod; 308, stirring shaft; 309, slot. 310. Rib; 311. Mounting groove; 312. Spring A; 313. Clip; 314. Rib groove; 315. Slot; 316. Fixing ring; 317. Stirring rod; 318. Magnetic strip; 319. Guide rail B; 320. Slide plate; 321. Sealing seat; 322. Spring B; 601. Outer shell; 602. Sealing cap; 603. Threaded ring; 604. Threaded rod; 605. Plug; 606. Plug seat; 607. Mesh plate; 608. Filter screen; 609. Limiting ring; 610. Spring C; 611. Ball; 612. Ball ring; 613. Connecting nozzle. Detailed Implementation

[0053] To facilitate understanding of the present invention, the invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0054] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0055] Unless otherwise specified, all raw materials, reagents, instruments, and equipment used in this invention are commercially available or can be prepared using existing methods. Unless otherwise specified, all parts mentioned in the embodiments herein refer to parts by weight; the proportions of each component may be scaled up or down proportionally and do not represent absolute mass. The content of each component in the embodiments is illustrative and can be adjusted without departing from the scope of this invention.

[0056] Yeast protein fermented milk, by weight, contains 890-940 parts raw milk, 50-90 parts sweetener, 1-20 parts yeast protein, 4-8 parts stabilizer and 0.02-0.06 parts starter.

[0057] Fermented milk with yeast protein, by weight, contains 900-930 parts raw milk, 60-80 parts sweetener, 5-10 parts yeast protein, 5-6 parts stabilizer and 0.03-0.05 parts starter.

[0058] Yeast protein fermented milk, by weight, contains 915 parts raw milk, 70 parts sweetener, 8 parts yeast protein, 5.5 parts stabilizer and 0.04 parts starter.

[0059] The raw milk is selected from either fresh milk or reconstituted milk. Fresh milk is selected from either cow's milk or goat's milk. Reconstituted milk is prepared by mixing whole milk powder or skim milk powder with water, and the mass percentage of whole milk powder or skim milk powder in the reconstituted milk is 20wt% to 30wt%. The sweetener is selected from at least one of sucrose, lactose, fructose, and glucose. The yeast protein contains ≥75wt% protein, and the total content of leucine, isoleucine, and valine in the yeast protein accounts for 18% to 25% of the total amino acids in the yeast protein. The stabilizer is selected from at least one of hydroxypropyl distarch phosphate, agar, and pectin. The starter culture is a direct-inoculation yogurt starter culture; the yogurt starter culture is selected from at least one of YF-L811 starter culture, Yo-C975-F starter culture, Yo-cul973 starter culture, and 12-strain starter culture; YF-L811 yogurt starter culture contains Streptococcus thermophilus and Lactobacillus bulgaricus; Yo-C975-F yogurt starter culture contains Streptococcus thermophilus, Lactobacillus bulgaricus, and Lactobacillus plantarum; Yo-cul973 yogurt starter culture contains Streptococcus thermophilus and Lactobacillus bulgaricus; the 12-strain yogurt starter culture contains Bifidobacterium adolescentis, Streptococcus thermophilus, Bifidobacterium breve, Bifidobacterium lactis, Bifidobacterium longum, Bifidobacterium infantis, and Lactobacillus bulgaricus.

[0060] The yeast protein is a composite modified yeast protein. The preparation process of the composite modified yeast protein includes the following steps:

[0061] (A01) Take yeast protein, add 5 to 8 times its weight of deionized water, stir and disperse evenly, and adjust the pH of the system to obtain yeast protein dispersion; in step (A01), adjust the pH of the system to 6.0 to 7.5; in step (A01), adjust the pH of the system to 6.5 to 7.0; in step (A01), adjust the pH of the system to 6.8;

[0062] (A02) Add neutral protease to the yeast protein dispersion from step (A01), perform enzymatic hydrolysis, and incubate at a suitable temperature to inactivate the protease, obtaining a partially hydrolyzed yeast protein solution; the amount of neutral protease added in step (A02) is 0.05%–0.35% of the yeast protein mass, and the hydrolysis is carried out at 40–55℃ for 10–25 min, controlling the degree of hydrolysis to 3%–12%. After the hydrolysis is completed, incubate at 75–95℃ for 8–12 min to inactivate the protease; step (A02) The amount of neutral protease added in step (A02) is 0.1%–0.3% of the yeast protein mass. Enzymatic hydrolysis is carried out at 45–50℃ for 15–20 min, with the degree of hydrolysis controlled at 5%–10%. After hydrolysis, the protease is inactivated by incubation at 80–90℃ for 9–11 min. The amount of neutral protease added in step (A02) is 0.2% of the yeast protein mass. Enzymatic hydrolysis is carried out at 48℃ for 18 min, with the degree of hydrolysis controlled at 7%. After hydrolysis, the protease is inactivated by incubation at 85℃ for 10 min.

[0063] (A03) Add organic zinc to the partially enzymatically hydrolyzed yeast protein solution in step (A02), adjust the pH of the system, and stir to react to obtain a zinc-complex yeast protein solution; in step (A03), the organic zinc is zinc gluconate or zinc lactate, and the amount added is 0.3% to 1.4% of the yeast protein mass. After adjusting the pH of the system to 5.0 to 6.5, stir to react at 30 to 45°C for 20 to 40 minutes; in step (A03), the organic zinc is zinc gluconate or zinc lactate, and the amount added is 0.5% to 1.2% of the yeast protein mass. After adjusting the pH of the system to 5.5 to 6.0, stir to react at 35 to 40°C for 25 to 35 minutes; in step (A03), the organic zinc is zinc gluconate or zinc lactate, and the amount added is 0.9% of the yeast protein mass. After adjusting the pH of the system to 5.7, stir to react at 38°C for 30 minutes.

[0064] (A04) Add fructooligosaccharides to the zinc-composite yeast protein solution in step (A03), stir and mix, and then spray dry to obtain composite modified yeast protein; in step (A04), after stirring and mixing for 25-35 minutes, spray dry, the mass ratio of fructooligosaccharides to yeast protein is 1:7-1:10, and the spray drying conditions are inlet air temperature 175-195℃ and outlet air temperature 75-90℃; in step (A04), after stirring and mixing for 20-30 minutes, spray dry, the mass ratio of fructooligosaccharides to yeast protein is 1:8-1:9, and the spray drying conditions are inlet air temperature 180-190℃ and outlet air temperature 80-85℃; in step (A04), after stirring and mixing for 25 minutes, spray dry, the mass ratio of fructooligosaccharides to yeast protein is 1:8.5, and the spray drying conditions are inlet air temperature 185℃ and outlet air temperature 83℃.

[0065] The method for preparing yeast protein fermented milk includes the following steps:

[0066] (S01) Place the raw milk in a container installed between the base and the support shell, heat it to the preset temperature, add sweetener, stabilizer, and yeast protein, and stir evenly to obtain a mixture; the preset temperature in step (S01) is 50-65℃, and stirring is performed for 20-35 minutes; the preset temperature in step (S01) is 55-60℃, and stirring is performed for 25-30 minutes; the preset temperature in step (S01) is 58℃, and stirring is performed for 27 minutes;

[0067] (S02) The mixture in the tank in step (S01) is heated and kept at that temperature; in step (S02), the mixture is heated to 85-98°C and kept at that temperature for 8-12 minutes; in step (S02), the mixture is heated to 90-96°C and kept at that temperature for 9-11 minutes; in step (S02), the mixture is heated to 93°C and kept at that temperature for 10 minutes.

[0068] (S03) The mixture in the tank after step (S02) is homogenized using a homogenizer; the homogenization conditions in step (S03) are: treatment temperature 50-75℃, homogenization pressure 15-35MPa, and treatment time 5-25min; the homogenization conditions in step (S03) are: treatment temperature 55-70℃, homogenization pressure 20-30MPa, and treatment time 10-20min; the homogenization conditions in step (S03) are: treatment temperature 62℃, homogenization pressure 25MPa, and treatment time 15min.

[0069] (S04) The homogenized liquid in the tank after step (S03) is subjected to ultrasonic-assisted dispersion treatment; the conditions for ultrasonic-assisted dispersion treatment in step (S04) are: ultrasonic frequency 15-45kHz, ultrasonic power 100-200W, treatment temperature 50-65℃, and treatment time 2-6min; the conditions for ultrasonic-assisted dispersion treatment in step (S04) are: ultrasonic frequency 20-40kHz, ultrasonic power 130-170W, treatment temperature 55-60℃, and treatment time 3-5min; the conditions for ultrasonic-assisted dispersion treatment in step (S04) are: ultrasonic frequency 30kHz, ultrasonic power 150W, treatment temperature 57℃, and treatment time 4min.

[0070] (S05) Close the barrel lid and secure it with locking piece A to sterilize the liquid in the barrel after the treatment in step (S04); the sterilization treatment in step (S05) is pasteurization or ultra-high temperature instantaneous sterilization. The pasteurization conditions are 60-90℃ for 10-20 min, and the ultra-high temperature instantaneous sterilization conditions are 125-140℃ for 2-9 s; the pasteurization conditions in step (S05) are 65-85℃ for 13-17 min, and the ultra-high temperature instantaneous sterilization conditions are 130-135℃ for 3-8 s; the pasteurization conditions in step (S05) are 70℃ for 15 min, and the ultra-high temperature instantaneous sterilization conditions are 133℃ for 5 s;

[0071] (S06) After the liquid in the barrel has cooled down after sterilization in step (S05), open the lock A and the barrel lid, inoculate the fermentation agent, and close the barrel lid again and fix it with the lock A to carry out fermentation in the barrel.

[0072] The fermentation process in step (S06) is a staged gradient fermentation, which includes the following steps:

[0073] (B01) In the first stage, the inoculated liquid is fermented; the fermentation temperature in step (B01) is 36-42℃ and the fermentation time is 1-2.5h; the fermentation temperature in step (B01) is 38-40℃ and the fermentation time is 1.5-2h; the fermentation temperature in step (B01) is 39℃ and the fermentation time is 1.8h.

[0074] (B02) In the second stage, the fermented liquid after the first stage of fermentation in step (B01) is heated and fermented. In step (B02), the temperature is raised to 40-45°C and fermented for 1.5-3 hours until the acidity of the liquid reaches 55-70°T. In step (B02), the temperature is raised to 42-44°C and fermented for 2-2.5 hours until the acidity of the liquid reaches 60-65°T. In step (B02), the temperature is raised to 43°C and fermented for 2.3 hours until the acidity of the liquid reaches 63°T.

[0075] (B03) In the third stage, the fermented liquid after the second stage of fermentation in step (B02) is cooled down for further fermentation; in step (B03), the temperature is lowered to 38-42℃ and fermented for 0.3-1.2h; in step (B03), the temperature is lowered to 39-41℃ and fermented for 0.5-1h; in step (B03), the temperature is lowered to 40℃ and fermented for 0.7h.

[0076] (S07) Stir the fermented emulsion in the tank from step (S06) until it is homogeneous, and keep the tank installed between the base and the support shell for refrigerated ripening; the acidity of the yeast protein fermented milk is 70-90°T, and the solid content is 8%-18%; the acidity of the yeast protein fermented milk is 75-85°T, and the solid content is 10%-15%; the acidity of the yeast protein fermented milk is 78°T, and the solid content is 13%;

[0077] Step (S07) involves a segmented dynamic ripening process using cold storage, which includes the following steps:

[0078] (C01) First stage: Static refrigeration of the fermented emulsion; the static refrigeration temperature in step (C01) is 3-7℃ and the time is 7-11h; the static refrigeration temperature in step (C01) is 4-6℃ and the time is 8-10h; the static refrigeration temperature in step (C01) is 5℃ and the time is 9h.

[0079] (C02) Second stage: Maintain emulsion temperature and intermittently stir the emulsion while continuously refrigerating; In step (C02), the emulsion temperature is 2-8℃, the stirring speed is 8-18 r / min, the intermittent stirring mode is 15 min followed by a 30 min pause, and continuous refrigeration is 5.5-10 h; In step (C02), the emulsion temperature is 4-6℃, the stirring speed is 10-15 r / min, and continuous refrigeration is 6-9 h; In step (C02), the emulsion temperature is 5℃, the stirring speed is 13 r / min, and continuous refrigeration is 7.5 h;

[0080] (C03) In the third stage, the emulsion after the second stage of refrigeration is cooled down and statically refrigerated at this temperature; in step (C03), the cooling temperature is 1-5℃ and static refrigeration is performed for 3-7 hours; in step (C03), the cooling temperature is 2-4℃ and static refrigeration is performed for 4-6 hours; in step (C03), the cooling temperature is 3℃ and static refrigeration is performed for 5 hours.

[0081] The application of yeast protein fermented milk is that fermented dairy products are flavored fermented milk or fermented milk-containing beverages.

[0082] A yeast protein fermented milk preparation apparatus includes a base 100, a support shell 200, a barrel 300, a barrel lid 400, and a homogenizer 600. The apparatus is characterized in that: two support shells 200 are symmetrically mounted on the surface of the base 100; the barrel 300 is rotatably mounted between the two support shells 200; the barrel lid 400 is hinged to the top of the barrel 300; the homogenizer 600 is fixedly mounted on the top of the barrel lid 400; the barrel 300 and the barrel lid 400 are detachably installed via a locking piece A500; a tilting mechanism is provided inside the support shell 200; and a stirring mechanism is provided inside the barrel 300.

[0083] The tilting mechanism includes an electric push rod 201. The bottom output end of the electric push rod 201 is fixedly connected to one end of a crossbar 202. The other end of the crossbar 202 is fixedly connected to the bottom end of a rack 203. An extension plate 209 is fixedly installed on the top of the rack 203. A gear 204 meshes with the side of the rack 203. The other end of the shaft of the gear 204 is fixedly connected to a fixed plate 206. The bottom of the shaft of the gear 204 is fixedly connected to the top of a swing arm 207. The bottom of the swing arm 207 is fixedly connected to a drag ring 208. The electric push rod 201 is fixedly installed inside the bracket housing 200. The crossbar 202 is located below the gear 204. The side of the rack 203 is slidably mounted with the guide rail A205. The two ends of the guide rail A205 are fixedly connected to the inner wall of the bracket housing 200. The gear 204 is rotatably connected to the bracket housing 200 through the shaft and bearing. The side of the fixing plate 206 is fixedly connected to the outer surface of the barrel 300. The swing arm 207 is located between the barrel 300 and the bracket housing 200. The drag ring 208 is fixedly installed below the outer surface of the barrel 300.

[0084] The barrel 300 has two cavities, A301 and B302, respectively. A vertical heating tube 303 is fixedly installed inside the cavity A301, and a horizontal heating tube 304 is fixedly installed inside the cavity B302. The vertical heating tube 303 is arranged in a spiral upward shape, and the horizontal heating tube 304 is arranged in a mosquito coil spiral shape. The stirring mechanism includes a stirring motor 305, which is fixedly installed in the interlayer of the tank body 300. A sealing seat 306 is fitted on the outer side of the output end of the stirring motor 305, and the sealing seat 306 is embedded in the inner wall of the tank body 300. A plug rod 307 is fixedly installed on the top of the output end of the stirring motor 305. The plug rod 307 has a square cross-section. A stirring shaft 308 is inserted through the top of the plug rod 307. Four equally spaced fixing rings 316 are fixedly installed on the outer side of the stirring shaft 308. Four circumferentially arranged stirring rods 317 are fixedly installed on the outer side of the fixing rings 316. The stirring rods 317 in the upper and lower layers are set at a 30-degree angle. Magnetic strips 318 are fixedly installed at the tail ends of the two staggered stirring rods 317. The magnetic strips 318 are set at an angle. The bottom of the stirring shaft 308 is provided with a slot 309 corresponding to the insert rod 307. Ribs 310 are fixedly installed on two sides of the insert rod 307, and mounting grooves 311 are provided on the other two sides of the insert rod 307. There are three mounting grooves 311 on one side, which are equally spaced, and two mounting grooves 311 on the other side, which are staggered. A spring A312 is fixedly installed inside the mounting groove 311, and a clip 313 is fixedly installed on the other end of the spring A312. Rib grooves 314 corresponding to the ribs 310 are provided on two inner walls of the slot 39, and clip grooves 315 corresponding to the clips 313 are provided on the other two inner walls of the slot 39. The inner wall of the barrel 300 is fixedly equipped with guide rails B319, eight of which are arranged in a ring array. A sliding plate 320 is slidably installed inside the guide rails B319. A sealing seat 321 is inserted through the top of the guide rails B319. A spring B322 is fixedly installed on the surface of the sliding plate 320, several of which are arranged at equal intervals. The springs B322 are magnetic and correspond to a magnetic strip 318. A temperature sensor 401 and a pressure sensor 402 are fixedly installed on the inner top wall of the barrel lid 400. A control panel 403 is fixedly installed on the surface of the barrel lid 400. A locking piece B404, corresponding to the locking piece A500, is fixedly installed on the outer periphery of the barrel lid 400. The control panel 403 is electrically connected to the electric push rod 201, the vertical heating tube 303, the horizontal heating tube 304, and the stirring motor 305. The output terminals of the temperature sensor 401 and the pressure sensor 402 are connected to the input terminal of the control panel 403.

[0085] The homogenizer 600 includes a housing 601, which is embedded in the top of the lid 400. A cap 602 is threadedly connected to the top of the housing 601. A threaded ring 603 is embedded in the top of the cap 602. A threaded rod 604 is threadedly connected to the inner wall of the threaded ring 603. A plug 605 is rotatably connected to the bottom of the threaded rod 604. A corresponding plug seat 606 is fixedly installed inside the housing 601. A mesh plate 607 is threadedly connected to the bottom of the housing 601. A filter screen 608 is provided between the mesh plate 607 and the plug seat 606. A limiting ring 609 is fixedly installed on the right side of the inside of the housing 601. A spring C610 is provided on the right side of the limiting ring 609. A ball 611 is fixedly installed on the right side of the spring C610. A ball ring 612 is provided on the right side of the ball 611. A connecting nozzle 613 is fixedly installed on the right side of the ball ring 612. The bottom of the plug body 605 is provided with a frustum, and the top of the plug seat 606 is provided with a conical surface corresponding to the frustum. The side of the ball 611 close to the spring C610 is a flat surface, and the side of the ball 611 away from the spring C610 is a spherical surface. The side of the ball ring 612 is provided with an inclined surface tangent to the ball 611. The diameter of the ball 611 is smaller than the diameter of the inclined surface of the ball ring 612. The ball ring 612 is fixedly installed on the inner wall of the outer shell 601.

[0086] Example 1: The raw material composition of the yeast protein fermented milk in this example, by weight, comprises 924 parts raw milk, 70 parts sweetener, 1 part yeast protein, 5 parts stabilizer, and 0.05 parts starter culture. The sweetener is sucrose; the yeast protein contains ≥75wt% protein, and the total content of leucine, isoleucine, and valine in the yeast protein accounts for 25% of the total amino acids in the yeast protein; the stabilizer is hydroxypropyl distarch phosphate; the starter culture is a direct-inoculation yogurt starter culture; the yogurt starter culture is YF-L811 starter culture; YF-L811 yogurt starter culture contains Streptococcus thermophilus and Lactobacillus bulgaricus.

[0087] The yeast protein is a composite modified yeast protein. The preparation process of the composite modified yeast protein includes the following steps: (A01) Take yeast protein, add 8 times its weight of deionized water, stir and disperse evenly, and adjust the pH of the system to 7.5 to obtain a yeast protein dispersion; (A02) Add neutral protease to the yeast protein dispersion in step (A01), the amount of neutral protease added is 0.35% of the yeast protein mass, enzymatically hydrolyze at 55℃ for 25 min, control the degree of hydrolysis to 12%, after the enzymatic hydrolysis is completed, incubate at 95℃ for 12 min to inactivate the protease, and obtain a partially hydrolyzed yeast protein solution. (A03) Add organic zinc, specifically zinc gluconate, to the partially enzymatically hydrolyzed yeast protein solution in step (A02). The amount of organic zinc added is 1.4% of the yeast protein mass. After adjusting the pH of the system to 6.5, stir and react at 45°C for 40 min to obtain a zinc-complex yeast protein solution. (A04) Add fructooligosaccharides to the zinc-complex yeast protein solution in step (A03). After stirring and mixing for 35 min, spray dry to obtain a composite modified yeast protein. The mass ratio of fructooligosaccharides to yeast protein is 1:7. The spray drying conditions are an inlet air temperature of 195°C and an outlet air temperature of 90°C.

[0088] The method for preparing yeast protein fermented milk in this embodiment includes the following steps: (S01) placing raw milk in a tank installed between the base and the support shell, heating to 55°C, adding sweetener, stabilizer, and yeast protein, and stirring for 20 minutes to obtain a mixture; (S02) heating the mixture in the tank from step (S01) to 95°C and keeping it at that temperature for 10 minutes; (S03) homogenizing the mixture in the tank after step (S02) using a homogenizer at a temperature of 75°C, a homogenization pressure of 35 MPa, and a processing time of 25 minutes; (S04) subjecting the homogenized liquid in the tank from step (S03) to ultrasonic-assisted dispersion treatment. Frequency 45kHz, ultrasonic power 200W, processing temperature 65℃, processing time 6min; (S05) Close the barrel lid and fix it with lock A to seal it. Pasteurize the liquid in the barrel after the treatment in step (S04). The sterilization conditions are 65℃ for 20min; (S06) After the liquid in the barrel after sterilization in step (S05) has cooled down, open lock A and barrel lid, inoculate the fermentation agent and close the barrel lid again and fix it with lock A. Perform segmented gradient fermentation in the barrel; (S07) Stir the fermented emulsion in the barrel in step (S06) evenly and keep the barrel installed between the base and the support shell for cold storage and ripening treatment.

[0089] The fermentation process in step (S06) is a segmented gradient fermentation, which includes the following steps: (B01) First stage: ferment the liquid after inoculation with the starter culture; the fermentation temperature is 42℃ and the fermentation time is 2.5h; (B02) Second stage: raise the temperature of the liquid after fermentation in step (B01) to 45℃ and ferment for 3h until the acidity of the liquid reaches 70°T; (B03) Third stage: lower the temperature of the liquid after fermentation in step (B02) to 42℃ and ferment for 1.2h.

[0090] The post-fermentation treatment in step (S07) is a segmented dynamic post-fermentation process, which includes the following steps: (C01) First stage: statically refrigerate the fermented emulsion at 7°C for 11 hours; (C02) Second stage: maintain the emulsion temperature at 8°C and intermittently stir the emulsion. The intermittent stirring mode is 15 minutes followed by a 30-minute pause, with a speed of 18 r / min, and continue refrigeration for 10 hours; (C03) Third stage: cool the emulsion after the second stage of refrigeration to 5°C and statically refrigerate it at this temperature for 7 hours.

[0091] Example 2: This example is basically the same as Example 1, except that the raw material composition of the yeast protein fermented milk in this example, by weight, contains 913 parts raw sheep milk, 60 parts sweetener, 20 parts yeast protein, 7 parts stabilizer, and 0.04 parts starter culture; the sweetener is sucrose; the yeast protein contains ≥75wt% protein, and the total content of leucine, isoleucine, and valine in the yeast protein accounts for 18% of the total amino acids in the yeast protein; the stabilizer is hydroxypropyl distarch phosphate; the starter culture is a direct-inoculation yogurt starter culture; the yogurt starter culture is Yo-C975-F starter culture; the Yo-C975-F yogurt starter culture contains Streptococcus thermophilus, Lactobacillus bulgaricus, and Lactobacillus plantarum.

[0092] The yeast protein is a composite modified yeast protein. The preparation process of the composite modified yeast protein includes the following steps: (A01) Take yeast protein, add 5 times its mass of deionized water, stir and disperse evenly, and adjust the pH of the system to 6.0 to obtain a yeast protein dispersion; (A02) Add neutral protease to the yeast protein dispersion in step (A01), the amount of neutral protease added is 0.05% of the yeast protein mass, enzymatically hydrolyze at 40℃ for 10 min, control the degree of hydrolysis to 3%, and after the enzymatic hydrolysis is completed, keep warm at 75℃ for 8 min to inactivate the protease and obtain a partially hydrolyzed yeast protein solution;

[0093] (A03) Add organic zinc, specifically zinc gluconate, to the partially enzymatically hydrolyzed yeast protein solution in step (A02). The amount of organic zinc added is 0.3% of the yeast protein mass. After adjusting the pH of the system to 5.0, stir and react at 30°C for 20 min to obtain a zinc-complex yeast protein solution. (A04) Add fructooligosaccharides to the zinc-complex yeast protein solution in step (A03). After stirring and mixing for 25 min, spray dry to obtain a composite modified yeast protein. The mass ratio of fructooligosaccharides to yeast protein is 1:10. The spray drying conditions are an inlet air temperature of 175°C and an outlet air temperature of 75°C.

[0094] The method for preparing yeast protein fermented milk in this embodiment includes the following steps: (S01) placing raw goat milk in a barrel installed between the base and the support shell, heating it to 60°C, adding sweetener, stabilizer, and yeast protein, and stirring for 20 minutes to obtain a mixture; (S02) heating the mixture in the barrel from step (S01) to 95°C and keeping it at that temperature for 10 minutes; (S03) homogenizing the mixture in the barrel after step (S02) using a homogenizer at a temperature of 70°C, a homogenization pressure of 30 MPa, and a processing time of 20 minutes; (S04) subjecting the homogenized liquid in the barrel from step (S03) to ultrasonic-assisted dispersion treatment. Frequency 15kHz, ultrasonic power 100W, processing temperature 50℃, processing time 2min; (S05) Close the barrel lid and fix it with lock A to seal it. Pasteurize the liquid in the barrel after the treatment in step (S04). The sterilization conditions are 85℃ for 10min; (S06) After the liquid in the barrel after sterilization in step (S05) has cooled down, open lock A and barrel lid, inoculate the fermentation agent and close the barrel lid again and fix it with lock A. Perform segmented gradient fermentation in the barrel; (S07) Stir the fermented emulsion in the barrel in step (S06) evenly and keep the barrel installed between the base and the support shell for cold storage and ripening treatment.

[0095] The fermentation process in step (S06) is a segmented gradient fermentation, which includes the following steps: (B01) First stage: ferment the liquid after inoculation with the starter culture; the fermentation temperature is 36℃ and the fermentation time is 1h; (B02) Second stage: raise the temperature of the liquid after fermentation in step (B01) to 40℃ and ferment for 1.5h until the acidity of the liquid reaches 55°T; (B03) Third stage: lower the temperature of the liquid after fermentation in step (B02) to 38℃ and ferment for 0.3h.

[0096] The post-fermentation cooling process in step (S07) is a segmented dynamic post-fermentation process, which includes the following steps: (C01) First stage: statically refrigerate the fermented emulsion at 3°C ​​for 7 hours; (C02) Second stage: maintain the emulsion temperature at 2°C and intermittently stir the emulsion. The intermittent stirring mode is 15 minutes followed by a 30-minute pause, with a speed of 8 r / min, and continue refrigeration for 5.5 hours; (C03) Third stage: cool the emulsion after the second stage of refrigeration to 1°C and statically refrigerate it at this temperature for 3 hours.

[0097] Example 3: This example is basically the same as Example 1, except that the raw material composition of the yeast protein fermented milk in this example, by weight, contains 903 parts raw milk, 80 parts sweetener, 5 parts yeast protein, 6 parts stabilizer, and 0.03 parts starter culture; the sweetener is sucrose; the yeast protein contains ≥75wt% protein, and the total content of leucine, isoleucine, and valine in the yeast protein accounts for 25% of the total amino acids in the yeast protein; the stabilizer is hydroxypropyl distarch phosphate; the starter culture is a direct-inoculation yogurt starter culture; the yogurt starter culture is Yo-cul973 starter culture; the Yo-cul973 yogurt starter culture contains Streptococcus thermophilus and Lactobacillus bulgaricus.

[0098] The yeast protein is a composite modified yeast protein. The preparation process of the composite modified yeast protein includes the following steps: (A01) Take yeast protein, add 8 times its weight of deionized water, stir and disperse evenly, and adjust the pH of the system to 7.0 to obtain a yeast protein dispersion; (A02) Add neutral protease to the yeast protein dispersion in step (A01), the amount of neutral protease added is 0.3% of the yeast protein mass, enzymatically hydrolyze at 50℃ for 20 min, control the degree of hydrolysis to 10%, and after the enzymatic hydrolysis is completed, keep warm at 90℃ for 11 min to inactivate the protease and obtain a partially hydrolyzed yeast protein solution;

[0099] (A03) Add organic zinc, specifically zinc gluconate, to the partially enzymatically hydrolyzed yeast protein solution in step (A02). The amount of organic zinc added is 1.2% of the yeast protein mass. After adjusting the pH of the system to 6.0, stir and react at 40°C for 35 min to obtain a zinc-complex yeast protein solution. (A04) Add fructooligosaccharides to the zinc-complex yeast protein solution in step (A03), stir and mix for 30 min, and then spray dry to obtain a composite modified yeast protein. The mass ratio of fructooligosaccharides to yeast protein is 1:8. The spray drying conditions are an inlet air temperature of 190°C and an outlet air temperature of 85°C.

[0100] The method for preparing yeast protein fermented milk in this embodiment includes the following steps: (S01) placing raw milk in a tank installed between the base and the support shell, heating to 60°C, adding sweetener, stabilizer, and yeast protein, and stirring for 15 minutes to obtain a mixture; (S02) heating the mixture in the tank from step (S01) to 96°C and holding it at that temperature for 11 minutes; (S03) homogenizing the mixture in the tank after step (S02) using a homogenizer at a temperature of 60°C, a homogenization pressure of 20 MPa, and a processing time of 15 minutes; (S04) subjecting the homogenized liquid in the tank from step (S03) to ultrasonic-assisted dispersion treatment. Frequency 40kHz, ultrasonic power 170W, processing temperature 60℃, processing time 5min; (S05) Close the barrel lid and fix it with lock A to seal it. Perform ultra-high temperature instantaneous sterilization on the liquid in the barrel after the treatment in step (S04). The sterilization conditions are 130℃ for 3s; (S06) After the liquid in the barrel after sterilization in step (S05) cools down, open lock A and barrel lid, inoculate the fermentation agent and close the barrel lid again and fix it with lock A. Perform segmented gradient fermentation in the barrel; (S07) Stir the fermented emulsion in the barrel in step (S06) evenly and keep the barrel installed between the base and the support shell for cold storage and ripening treatment.

[0101] The fermentation process in step (S06) is a segmented gradient fermentation, which includes the following steps: (B01) First stage: ferment the liquid after inoculation with the starter culture; the fermentation temperature is 40℃ and the fermentation time is 2h; (B02) Second stage: raise the temperature of the liquid after fermentation in step (B01) to 44℃ and ferment for 2.5h until the acidity of the liquid reaches 65°T; (B03) Third stage: lower the temperature of the liquid after fermentation in step (B02) to 41℃ and ferment for 1h.

[0102] Step (S07) involves a segmented dynamic post-ripening process, which includes the following steps: (C01) First stage: statically refrigerate the fermented emulsion at 6°C for 10 hours; (C02) Second stage: maintain the emulsion temperature at 6°C and intermittently stir the emulsion. The intermittent stirring mode is 15 minutes followed by a 30-minute pause, with a rotation speed of 15 r / min, and continue refrigeration for 9 hours; (C03) Third stage: cool the emulsion after the second stage of refrigeration to 4°C and statically refrigerate it at this temperature for 6 hours.

[0103] Example 4: This example is basically the same as Example 1, except that the raw material composition of the yeast protein fermented milk in this example, by weight, contains 914 parts of raw milk, 70 parts of sweetener, 10 parts of yeast protein, 6 parts of stabilizer, and 0.03 parts of starter culture; the sweetener is glucose; the yeast protein contains ≥75wt% protein, and the total content of leucine, isoleucine, and valine in the yeast protein accounts for 18% of the total amino acids in the yeast protein; the stabilizer is hydroxypropyl distarch phosphate; the starter culture is a direct-inoculation yogurt starter culture; the yogurt starter culture is a 12-strain starter culture; the 12-strain yogurt starter culture contains Bifidobacterium adolescentis, Streptococcus thermophilus, Bifidobacterium breve, Bifidobacterium lactis, Bifidobacterium longum, Bifidobacterium infantis, and Lactobacillus bulgaricus.

[0104] The yeast protein is a composite modified yeast protein. The preparation process of the composite modified yeast protein includes the following steps: (A01) Take yeast protein, add 5 times its mass of deionized water, stir and disperse evenly, and adjust the pH of the system to 6.5 to obtain a yeast protein dispersion; (A02) Add neutral protease to the yeast protein dispersion in step (A01), the amount of neutral protease added is 0.1% of the yeast protein mass, enzymatically hydrolyze at 45℃ for 15 min, control the degree of enzymatic hydrolysis to 5%, and after the enzymatic hydrolysis is completed, keep warm at 80℃ for 9 min to inactivate the protease and obtain a partially hydrolyzed yeast protein solution;

[0105] (A03) Add organic zinc, specifically zinc gluconate, to the partially enzymatically hydrolyzed yeast protein solution in step (A02). The amount of organic zinc added is 0.5% of the yeast protein mass. After adjusting the pH of the system to 5.5, stir and react at 35°C for 25 min to obtain a zinc-complex yeast protein solution. (A04) Add fructooligosaccharides to the zinc-complex yeast protein solution in step (A03). After stirring and mixing for 20 min, spray dry to obtain a composite modified yeast protein. The mass ratio of fructooligosaccharides to yeast protein is 1:9. The spray drying conditions are an inlet air temperature of 180°C and an outlet air temperature of 80°C.

[0106] The method for preparing yeast protein fermented milk in this embodiment includes the following steps: (S01) placing raw milk in a barrel installed between the base and the support shell, heating to 55°C, adding sweetener, stabilizer, and yeast protein, and stirring for 15 minutes to obtain a mixture; (S02) heating the mixture in the barrel from step (S01) to 95°C and keeping it at that temperature for 10 minutes; (S03) homogenizing the mixture in the barrel after step (S02) using a homogenizer at a temperature of 70°C, a homogenization pressure of 30 MPa, and a processing time of 20 minutes; (S04) subjecting the homogenized liquid in the barrel from step (S03) to ultrasonic-assisted dispersion treatment. Frequency 20kHz, ultrasonic power 130W, processing temperature 55℃, processing time 3min; (S05) Close the barrel lid and fix it with lock A to seal it. Pasteurize the liquid in the barrel after the treatment in step (S04). The sterilization conditions are 70℃ for 15min; (S06) After the liquid in the barrel after sterilization in step (S05) has cooled down, open lock A and barrel lid, inoculate the fermentation agent and close the barrel lid again and fix it with lock A. Perform segmented gradient fermentation in the barrel; (S07) Stir the fermented emulsion in the barrel in step (S06) evenly and keep the barrel installed between the base and the support shell for cold storage and ripening treatment.

[0107] The fermentation process in step (S06) is a segmented gradient fermentation, which includes the following steps: (B01) First stage: ferment the liquid after inoculation with the starter culture; the fermentation temperature is 38℃ and the fermentation time is 1.5h; (B02) Second stage: raise the temperature of the liquid after fermentation in step (B01) to 42℃ and ferment for 2h until the acidity of the liquid reaches 60°T; (B03) Third stage: lower the temperature of the liquid after fermentation in step (B02) to 39℃ and ferment for 0.5h.

[0108] The post-fermentation cooling process in step (S07) is a segmented dynamic cooling process, which includes the following steps: (C01) First stage: statically refrigerate the fermented emulsion at 4°C for 8 hours; (C02) Second stage: maintain the emulsion temperature at 4°C and intermittently stir the emulsion. The intermittent stirring mode is 15 min, paused for 30 min, with a speed of 10 r / min, and continuously refrigerate for 6 hours; (C03) Third stage: cool the emulsion after the second stage of refrigeration to 2°C and statically refrigerate it at this temperature for 4 hours.

[0109] Example 5: This example is basically the same as Example 1, except that the raw material composition of the yeast protein fermented milk in this example, by weight, contains 898.5 parts of raw milk, 80 parts of sweetener, 15 parts of yeast protein, 6.5 parts of stabilizer, and 0.05 parts of starter culture; the sweetener is lactose; the yeast protein has a protein content ≥75wt%, and the total content of leucine, isoleucine, and valine in the yeast protein accounts for 21.5% of the total amino acids in the yeast protein; the stabilizer is hydroxypropyl distarch phosphate; the starter culture is a direct-inoculation yogurt starter culture; the yogurt starter culture is YF-L811 starter culture; the YF-L811 yogurt starter culture contains Streptococcus thermophilus and Lactobacillus bulgaricus.

[0110] The yeast protein is a composite modified yeast protein. The preparation process of the composite modified yeast protein includes the following steps: (A01) Take yeast protein, add 6.5 times its mass of deionized water, stir and disperse evenly, and adjust the pH of the system to 6.8 to obtain a yeast protein dispersion; (A02) Add neutral protease to the yeast protein dispersion in step (A01), the amount of neutral protease added is 0.2% of the yeast protein mass, enzymatically hydrolyze at 48℃ for 18 min, control the degree of hydrolysis to 7%, and after the enzymatic hydrolysis is completed, keep warm at 85℃ for 10 min to inactivate the protease and obtain a partially hydrolyzed yeast protein solution;

[0111] (A03) Add organic zinc, specifically zinc gluconate, to the partially enzymatically hydrolyzed yeast protein solution in step (A02). The amount of organic zinc added is 0.9% of the yeast protein mass. After adjusting the pH of the system to 5.7, stir and react at 38°C for 30 min to obtain a zinc-complex yeast protein solution. (A04) Add fructooligosaccharides to the zinc-complex yeast protein solution in step (A03), stir and mix for 25 min, and then spray dry to obtain a composite modified yeast protein. The mass ratio of fructooligosaccharides to yeast protein is 1:8.5, and the spray drying conditions are an inlet air temperature of 185°C and an outlet air temperature of 83°C.

[0112] The method for preparing yeast protein fermented milk in this embodiment includes the following steps: (S01) placing raw milk in a barrel installed between the base and the support shell, heating to 55°C, adding sweetener, stabilizer, and yeast protein, and stirring for 15 minutes to obtain a mixture; (S02) heating the mixture in the barrel from step (S01) to 95°C and keeping it at that temperature for 10 minutes; (S03) homogenizing the mixture in the barrel after step (S02) using a homogenizer at a temperature of 70°C, a homogenization pressure of 25 MPa, and a processing time of 20 minutes; (S04) subjecting the homogenized liquid in the barrel from step (S03) to ultrasonic-assisted dispersion treatment. Frequency 30kHz, ultrasonic power 150W, processing temperature 57℃, processing time 4min; (S05) Close the barrel lid and fix it with lock A to seal it. Pasteurize the liquid in the barrel after the treatment in step (S04). The sterilization conditions are 70℃ for 15min; (S06) After the liquid in the barrel after sterilization in step (S05) has cooled down, open lock A and barrel lid, inoculate the fermentation agent and close the barrel lid again and fix it with lock A. Perform segmented gradient fermentation in the barrel; (S07) Stir the fermented emulsion in the barrel after step (S06) evenly and keep the barrel installed between the base and the support shell for cold storage and ripening treatment.

[0113] The fermentation process in step (S06) is a segmented gradient fermentation, which includes the following steps: (B01) First stage: ferment the liquid after inoculation with the starter culture; the fermentation temperature is 39℃ and the fermentation time is 1.8h; (B02) Second stage: raise the temperature of the liquid after fermentation in step (B01) to 43℃ and ferment for 2.3h until the acidity of the liquid reaches 63°T; (B03) Third stage: lower the temperature of the liquid after fermentation in step (B02) to 40℃ and ferment for 0.7h.

[0114] The post-fermentation cooling process in step (S07) is a segmented dynamic post-fermentation process, which includes the following steps: (C01) First stage: statically refrigerate the fermented emulsion at 5°C for 9 hours; (C02) Second stage: maintain the emulsion temperature at 5°C and intermittently stir the emulsion. The intermittent stirring mode is 15 minutes followed by a 30-minute pause, with a speed of 13 r / min, and continue refrigeration for 7.5 hours; (C03) Third stage: cool the emulsion after the second stage of refrigeration to 3°C and statically refrigerate it at this temperature for 5 hours.

[0115] Example 6: This example is basically the same as Example 1, except that the raw material composition of the yeast protein fermented milk in this example, by weight, contains 926.5 parts of raw milk, 60 parts of sweetener, 8 parts of yeast protein, 5.5 parts of stabilizer, and 0.045 parts of starter culture; the sweetener is lactose; the yeast protein has a protein content ≥75wt%, and the total content of leucine, isoleucine, and valine in the yeast protein accounts for 25% of the total amino acids in the yeast protein; the stabilizer is hydroxypropyl distarch phosphate; the starter culture is a direct-inoculation yogurt starter culture; the yogurt starter culture is Yo-C975-F starter culture; the Yo-C975-F yogurt starter culture contains Streptococcus thermophilus, Lactobacillus bulgaricus, and Lactobacillus plantarum.

[0116] The yeast protein is a composite modified yeast protein. The preparation process of the composite modified yeast protein includes the following steps: (A01) Take yeast protein, add 8 times its weight of deionized water, stir and disperse evenly, and adjust the pH of the system to 7.0 to obtain a yeast protein dispersion; (A02) Add neutral protease to the yeast protein dispersion in step (A01), the amount of neutral protease added is 0.3% of the yeast protein mass, enzymatically hydrolyze at 50℃ for 20 min, control the degree of hydrolysis to 10%, and after the enzymatic hydrolysis is completed, keep warm at 90℃ for 11 min to inactivate the protease and obtain a partially hydrolyzed yeast protein solution;

[0117] (A03) Add organic zinc, specifically zinc gluconate, to the partially enzymatically hydrolyzed yeast protein solution in step (A02). The amount of organic zinc added is 1.2% of the yeast protein mass. After adjusting the pH of the system to 6.0, stir and react at 40°C for 35 min to obtain a zinc-complex yeast protein solution. (A04) Add fructooligosaccharides to the zinc-complex yeast protein solution in step (A03), stir and mix for 30 min, and then spray dry to obtain a composite modified yeast protein. The mass ratio of fructooligosaccharides to yeast protein is 1:8. The spray drying conditions are an inlet air temperature of 190°C and an outlet air temperature of 85°C.

[0118] The method for preparing yeast protein fermented milk in this embodiment includes the following steps: (S01) placing raw milk in a barrel installed between the base and the support shell, heating to 60°C, adding sweetener, stabilizer, and yeast protein, and stirring for 20 minutes to obtain a mixture; (S02) heating the mixture in the barrel from step (S01) to 95°C and keeping it at that temperature for 10 minutes; (S03) homogenizing the mixture in the barrel after step (S02) using a homogenizer at a temperature of 65°C, a homogenization pressure of 30 MPa, and a processing time of 10 minutes; (S04) subjecting the homogenized liquid in the barrel from step (S03) to ultrasonic-assisted dispersion treatment. Frequency 40kHz, ultrasonic power 170W, processing temperature 60℃, processing time 5min; (S05) Close the barrel lid and fix it with lock A to seal it. Perform ultra-high temperature instantaneous sterilization on the liquid in the barrel after the treatment in step (S04). The sterilization conditions are 135℃ for 5s; (S06) After the liquid in the barrel after sterilization in step (S05) cools down, open lock A and barrel lid, inoculate the fermentation agent and close the barrel lid again and fix it with lock A. Perform segmented gradient fermentation in the barrel; (S07) Stir the fermented emulsion in the barrel in step (S06) evenly and keep the barrel installed between the base and the support shell for cold storage and ripening treatment.

[0119] The fermentation process in step (S06) is a segmented gradient fermentation, which includes the following steps: (B01) First stage: ferment the liquid after inoculation with the starter culture; the fermentation temperature is 40℃ and the fermentation time is 2h; (B02) Second stage: raise the temperature of the liquid after fermentation in step (B01) to 44℃ and ferment for 2.5h until the acidity of the liquid reaches 65°T; (B03) Third stage: lower the temperature of the liquid after fermentation in step (B02) to 41℃ and ferment for 1h.

[0120] Step (S07) involves a segmented dynamic post-ripening process, which includes the following steps: (C01) First stage: statically refrigerate the fermented emulsion at 6°C for 10 hours; (C02) Second stage: maintain the emulsion temperature at 6°C and intermittently stir the emulsion. The intermittent stirring mode is 15 minutes followed by a 30-minute pause, with a rotation speed of 15 r / min, and continue refrigeration for 9 hours; (C03) Third stage: cool the emulsion after the second stage of refrigeration to 4°C and statically refrigerate it at this temperature for 6 hours.

[0121] Example 7: This example is basically the same as Example 1, except that the raw material composition of the yeast protein fermented milk in this example, by weight, contains 909 parts reconstituted milk, 70 parts sweetener, 10 parts yeast protein, 6 parts stabilizer, and 0.03 parts starter culture; the reconstituted milk is prepared by mixing whole milk powder and water, and the mass percentage of whole milk powder in the reconstituted milk is 25%; the sweetener is sucrose; the yeast protein contains ≥75wt% protein, and the total content of leucine, isoleucine, and valine in the yeast protein accounts for 18% of the total amino acids in the yeast protein; the stabilizer is hydroxypropyl distarch phosphate; the starter culture is a direct-inoculation yogurt starter culture; the yogurt starter culture is Yo-cul973 starter culture; the Yo-cul973 yogurt starter culture contains Streptococcus thermophilus and Lactobacillus bulgaricus.

[0122] The yeast protein is a composite modified yeast protein. The preparation process of the composite modified yeast protein includes the following steps: (A01) Take yeast protein, add 5 times its mass of deionized water, stir and disperse evenly, and adjust the pH of the system to 6.5 to obtain a yeast protein dispersion; (A02) Add neutral protease to the yeast protein dispersion in step (A01), the amount of neutral protease added is 0.1% of the yeast protein mass, enzymatically hydrolyze at 45℃ for 15 min, control the degree of enzymatic hydrolysis to 5%, and after the enzymatic hydrolysis is completed, keep warm at 80℃ for 9 min to inactivate the protease and obtain a partially hydrolyzed yeast protein solution;

[0123] (A03) Add organic zinc, specifically zinc gluconate, to the partially enzymatically hydrolyzed yeast protein solution in step (A02). The amount of organic zinc added is 0.5% of the yeast protein mass. After adjusting the pH of the system to 5.5, stir and react at 35°C for 25 min to obtain a zinc-complex yeast protein solution. (A04) Add fructooligosaccharides to the zinc-complex yeast protein solution in step (A03). After stirring and mixing for 20 min, spray dry to obtain a composite modified yeast protein. The mass ratio of fructooligosaccharides to yeast protein is 1:9. The spray drying conditions are an inlet air temperature of 180°C and an outlet air temperature of 80°C.

[0124] The method for preparing yeast protein fermented milk in this embodiment includes the following steps: (S01) placing raw milk in a barrel installed between the base and the support shell, heating to 80°C, adding sweetener, stabilizer, and yeast protein, and stirring for 20 minutes to obtain a mixture; (S02) heating the mixture in the barrel from step (S01) to 90°C and keeping it at that temperature for 10 minutes; (S03) homogenizing the mixture in the barrel after step (S02) using a homogenizer at a temperature of 60°C, a homogenization pressure of 20 MPa, and a processing time of 15 minutes; (S04) subjecting the homogenized liquid in the barrel from step (S03) to ultrasonic-assisted dispersion treatment. Frequency 20kHz, ultrasonic power 130W, processing temperature 55℃, processing time 3min; (S05) Close the barrel lid and fix it with lock A to seal it. Perform ultra-high temperature instantaneous sterilization on the liquid in the barrel after the treatment in step (S04). The sterilization conditions are 135℃ for 3s; (S06) After the liquid in the barrel after sterilization in step (S05) cools down, open lock A and barrel lid, inoculate the fermentation agent and close the barrel lid again and fix it with lock A. Perform segmented gradient fermentation in the barrel; (S07) Stir the fermented emulsion in the barrel in step (S06) evenly and keep the barrel installed between the base and the support shell for cold storage and ripening treatment.

[0125] The fermentation process in step (S06) is a segmented gradient fermentation, which includes the following steps: (B01) First stage: ferment the liquid after inoculation with the starter culture; the fermentation temperature is 38℃ and the fermentation time is 1.5h; (B02) Second stage: raise the temperature of the liquid after fermentation in step (B01) to 42℃ and ferment for 2h until the acidity of the liquid reaches 60°T; (B03) Third stage: lower the temperature of the liquid after fermentation in step (B02) to 39℃ and ferment for 0.5h.

[0126] The post-fermentation cooling process in step (S07) is a segmented dynamic cooling process, which includes the following steps: (C01) First stage: statically refrigerate the fermented emulsion at 4°C for 8 hours; (C02) Second stage: maintain the emulsion temperature at 4°C and intermittently stir the emulsion. The intermittent stirring mode is 15 min, paused for 30 min, with a speed of 10 r / min, and continuously refrigerate for 6 hours; (C03) Third stage: cool the emulsion after the second stage of refrigeration to 2°C and statically refrigerate it at this temperature for 4 hours.

[0127] Example 8: This example is basically the same as Example 1, except that the raw material composition of the yeast protein fermented milk in this example, by weight, contains 909 parts reconstituted milk, 80 parts sweetener, 5 parts yeast protein, 6 parts stabilizer, and 0.03 parts starter culture; the sweetener is sucrose; the yeast protein contains ≥75wt% protein, and the total content of leucine, isoleucine, and valine in the yeast protein accounts for 21.5% of the total amino acids in the yeast protein; the stabilizer is hydroxypropyl distarch phosphate; the starter culture is a direct-inoculation yogurt starter culture; the yogurt starter culture is Yo-cul973 starter culture; the Yo-cul973 yogurt starter culture contains Streptococcus thermophilus and Lactobacillus bulgaricus.

[0128] The yeast protein is a composite modified yeast protein. The preparation process of the composite modified yeast protein includes the following steps: (A01) Take yeast protein, add 6.5 times its mass of deionized water, stir and disperse evenly, and adjust the pH of the system to 6.8 to obtain a yeast protein dispersion; (A02) Add neutral protease to the yeast protein dispersion in step (A01), the amount of neutral protease added is 0.2% of the yeast protein mass, enzymatically hydrolyze at 48℃ for 18 min, control the degree of hydrolysis to 7%, and after the enzymatic hydrolysis is completed, keep warm at 85℃ for 10 min to inactivate the protease and obtain a partially hydrolyzed yeast protein solution;

[0129] (A03) Add organic zinc, specifically zinc gluconate, to the partially enzymatically hydrolyzed yeast protein solution in step (A02). The amount of organic zinc added is 0.9% of the yeast protein mass. After adjusting the pH of the system to 5.7, stir and react at 38°C for 30 min to obtain a zinc-complex yeast protein solution. (A04) Add fructooligosaccharides to the zinc-complex yeast protein solution in step (A03), stir and mix for 25 min, and then spray dry to obtain a composite modified yeast protein. The mass ratio of fructooligosaccharides to yeast protein is 1:8.5, and the spray drying conditions are an inlet air temperature of 185°C and an outlet air temperature of 83°C.

[0130] The method for preparing yeast protein fermented milk in this embodiment includes the following steps: (S01) placing raw milk in a barrel installed between the base and the support shell, heating to 80°C, adding sweetener, stabilizer, and yeast protein, and stirring for 20 minutes to obtain a mixture; (S02) heating the mixture in the barrel from step (S01) to 90°C and keeping it at that temperature for 10 minutes; (S03) homogenizing the mixture in the barrel after step (S02) using a homogenizer at a temperature of 60°C, a homogenization pressure of 20 MPa, and a processing time of 15 minutes; (S04) subjecting the homogenized liquid in the barrel from step (S03) to ultrasonic-assisted dispersion treatment. Frequency 30kHz, ultrasonic power 150W, processing temperature 57℃, processing time 4min; (S05) Close the barrel lid and fix it with lock A to seal it. Perform ultra-high temperature instantaneous sterilization on the liquid in the barrel after the treatment in step (S04). The sterilization conditions are 135℃ for 3s; (S06) After the liquid in the barrel after sterilization in step (S05) has cooled down, open lock A and barrel lid, inoculate the fermentation agent and close the barrel lid again and fix it with lock A. Perform segmented gradient fermentation in the barrel; (S07) Stir the fermented emulsion in the barrel in step (S06) evenly and keep the barrel installed between the base and the support shell for cold storage and ripening treatment.

[0131] The fermentation process in step (S06) is a segmented gradient fermentation, which includes the following steps: (B01) First stage: ferment the liquid after inoculation with the starter culture; the fermentation temperature is 39℃ and the fermentation time is 1.8h; (B02) Second stage: raise the temperature of the liquid after fermentation in step (B01) to 43℃ and ferment for 2.3h until the acidity of the liquid reaches 63°T; (B03) Third stage: lower the temperature of the liquid after fermentation in step (B02) to 40℃ and ferment for 0.7h.

[0132] The post-fermentation cooling process in step (S07) is a segmented dynamic post-fermentation process, which includes the following steps: (C01) First stage: statically refrigerate the fermented emulsion at 5°C for 9 hours; (C02) Second stage: maintain the emulsion temperature at 5°C and intermittently stir the emulsion. The intermittent stirring mode is 15 minutes followed by a 30-minute pause, with a speed of 13 r / min, and continue refrigeration for 7.5 hours; (C03) Third stage: cool the emulsion after the second stage of refrigeration to 3°C and statically refrigerate it at this temperature for 5 hours.

[0133] Example 9: This example is basically the same as Example 1, except that the raw material composition of the yeast protein fermented milk in this example, by weight, contains 940 parts of raw milk, 90 parts of sweetener, 20 parts of yeast protein, 8 parts of stabilizer, and 0.06 parts of starter culture; the sweetener is sucrose; the yeast protein contains ≥75wt% protein, and the total content of leucine, isoleucine, and valine in the yeast protein accounts for 25% of the total amino acids in the yeast protein; the stabilizer is hydroxypropyl distarch phosphate; the starter culture is a direct-inoculation yogurt starter culture; the yogurt starter culture is YF-L811 starter culture; the YF-L811 yogurt starter culture contains Streptococcus thermophilus and Lactobacillus bulgaricus.

[0134] The yeast protein is a composite modified yeast protein. The preparation process of the composite modified yeast protein includes the following steps: (A01) Take yeast protein, add 8 times its weight of deionized water, stir and disperse evenly, and adjust the pH of the system to 7.5 to obtain a yeast protein dispersion; (A02) Add neutral protease to the yeast protein dispersion in step (A01), the amount of neutral protease added is 0.35% of the yeast protein mass, enzymatically hydrolyze at 55℃ for 25 min, control the degree of hydrolysis to 12%, after the enzymatic hydrolysis is completed, incubate at 95℃ for 12 min to inactivate the protease, and obtain a partially hydrolyzed yeast protein solution. (A03) Add organic zinc, specifically zinc gluconate, to the partially enzymatically hydrolyzed yeast protein solution in step (A02). The amount of organic zinc added is 1.4% of the yeast protein mass. After adjusting the pH of the system to 6.5, stir and react at 45°C for 40 min to obtain a zinc-complex yeast protein solution. (A04) Add fructooligosaccharides to the zinc-complex yeast protein solution in step (A03). After stirring and mixing for 35 min, spray dry to obtain a composite modified yeast protein. The mass ratio of fructooligosaccharides to yeast protein is 1:7. The spray drying conditions are an inlet air temperature of 195°C and an outlet air temperature of 90°C.

[0135] The method for preparing yeast protein fermented milk in this embodiment includes the following steps: (S01) placing raw milk in a barrel installed between the base and the support shell, heating to 65°C, adding sweetener, stabilizer, and yeast protein, and stirring for 35 minutes to obtain a mixture; (S02) heating the mixture in the barrel from step (S01) to 98°C and keeping it at that temperature for 12 minutes; (S03) homogenizing the mixture in the barrel after step (S02) using a homogenizer at a temperature of 75°C, a homogenization pressure of 35 MPa, and a processing time of 25 minutes; (S04) subjecting the homogenized liquid in the barrel from step (S03) to ultrasonic-assisted dispersion treatment. Frequency 45kHz, ultrasonic power 200W, processing temperature 65℃, processing time 6min; (S05) Close the barrel lid and fix it with lock A to seal it. Pasteurize the liquid in the barrel after the treatment in step (S04). The sterilization conditions are 90℃ for 20min; (S06) After the liquid in the barrel after sterilization in step (S05) has cooled down, open lock A and barrel lid, inoculate the fermentation agent and close the barrel lid again and fix it with lock A. Perform segmented gradient fermentation in the barrel; (S07) Stir the fermented emulsion in the barrel in step (S06) evenly and keep the barrel installed between the base and the support shell for cold storage and ripening treatment.

[0136] The fermentation process in step (S06) is a segmented gradient fermentation, which includes the following steps: (B01) First stage: ferment the liquid after inoculation with the starter culture; the fermentation temperature is 42℃ and the fermentation time is 2.5h; (B02) Second stage: raise the temperature of the liquid after fermentation in step (B01) to 45℃ and ferment for 3h until the acidity of the liquid reaches 70°T; (B03) Third stage: lower the temperature of the liquid after fermentation in step (B02) to 42℃ and ferment for 1.2h.

[0137] The post-fermentation treatment in step (S07) is a segmented dynamic post-fermentation process, which includes the following steps: (C01) First stage: statically refrigerate the fermented emulsion at 7°C for 11 hours; (C02) Second stage: maintain the emulsion temperature at 8°C and intermittently stir the emulsion. The intermittent stirring mode is 15 minutes followed by a 30-minute pause, with a speed of 18 r / min, and continue refrigeration for 10 hours; (C03) Third stage: cool the emulsion after the second stage of refrigeration to 5°C and statically refrigerate it at this temperature for 7 hours.

[0138] Example 10: This example is basically the same as Example 1, except that the raw material composition of the yeast protein fermented milk in this example, by weight, contains 890 parts of raw milk, 50 parts of sweetener, 1 part of yeast protein, 4 parts of stabilizer, and 0.02 parts of starter culture; the sweetener is sucrose; the yeast protein contains ≥75wt% protein, and the total content of leucine, isoleucine, and valine in the yeast protein accounts for 18% of the total amino acids in the yeast protein; the stabilizer is hydroxypropyl distarch phosphate; the starter culture is a direct-inoculation yogurt starter culture; the yogurt starter culture is YF-L811 starter culture; the YF-L811 yogurt starter culture contains Streptococcus thermophilus and Lactobacillus bulgaricus.

[0139] The yeast protein is a composite modified yeast protein. The preparation process of the composite modified yeast protein includes the following steps: (A01) Take yeast protein, add 5 times its mass of deionized water, stir and disperse evenly, and adjust the pH of the system to 6.0 to obtain a yeast protein dispersion; (A02) Add neutral protease to the yeast protein dispersion in step (A01), the amount of neutral protease added is 0.05% of the yeast protein mass, enzymatically hydrolyze at 40℃ for 10 min, control the degree of hydrolysis to 3%, and after the enzymatic hydrolysis is completed, keep warm at 75℃ for 8 min to inactivate the protease and obtain a partially hydrolyzed yeast protein solution;

[0140] (A03) Add organic zinc, specifically zinc gluconate, to the partially enzymatically hydrolyzed yeast protein solution in step (A02). The amount of organic zinc added is 0.3% of the yeast protein mass. After adjusting the pH of the system to 5.0, stir and react at 30°C for 20 min to obtain a zinc-complex yeast protein solution. (A04) Add fructooligosaccharides to the zinc-complex yeast protein solution in step (A03). After stirring and mixing for 25 min, spray dry to obtain a composite modified yeast protein. The mass ratio of fructooligosaccharides to yeast protein is 1:10. The spray drying conditions are an inlet air temperature of 175°C and an outlet air temperature of 75°C.

[0141] The method for preparing yeast protein fermented milk in this embodiment includes the following steps: (S01) placing raw milk in a barrel installed between the base and the support shell, heating it to 50°C, adding sweetener, stabilizer, and yeast protein, and stirring for 20 minutes to obtain a mixture; (S02) heating the mixture in the barrel from step (S01) to 85°C and keeping it at that temperature for 8 minutes; (S03) homogenizing the mixture in the barrel after step (S02) using a homogenizer at a temperature of 50°C, a homogenization pressure of 15 MPa, and a processing time of 5 minutes; (S04) subjecting the homogenized liquid in the barrel from step (S03) to ultrasonic-assisted dispersion at an ultrasonic frequency of 15 kHz, an ultrasonic power of 100 W, a processing temperature of 50°C, and a processing time of 2 minutes.

[0142] (S05) Close the barrel lid and secure it with locking piece A. Pasteurize the liquid in the barrel after the treatment in step (S04) at 60°C for 10 minutes. (S06) After the liquid in the barrel has cooled down after sterilization in step (S05), open locking piece A and the barrel lid, inoculate the fermentation agent, close the barrel lid again and secure it with locking piece A. Perform segmented gradient fermentation in the barrel. (S07) Stir the fermented emulsion in the barrel after step (S06) evenly and keep the barrel installed between the base and the support shell for cold storage and post-ripening treatment.

[0143] The fermentation process in step (S06) is a segmented gradient fermentation, which includes the following steps: (B01) First stage: ferment the liquid after inoculation with the starter culture; the fermentation temperature is 36℃ and the fermentation time is 1h; (B02) Second stage: raise the temperature of the liquid after fermentation in step (B01) to 40℃ and ferment for 1.5h until the acidity of the liquid reaches 55°T; (B03) Third stage: lower the temperature of the liquid after fermentation in step (B02) to 38℃ and ferment for 0.3h.

[0144] The post-fermentation cooling process in step (S07) is a segmented dynamic post-fermentation process, which includes the following steps: (C01) First stage: statically refrigerate the fermented emulsion at 3°C ​​for 7 hours; (C02) Second stage: maintain the emulsion temperature at 2°C and intermittently stir the emulsion. The intermittent stirring mode is 15 minutes followed by a 30-minute pause, with a speed of 8 r / min, and continue refrigeration for 5.5 hours; (C03) Third stage: cool the emulsion after the second stage of refrigeration to 1°C and statically refrigerate it at this temperature for 3 hours.

[0145] Example 11: This example is basically the same as Example 1, except that the raw material composition of the yeast protein fermented milk in this example, by weight, contains 915 parts of raw milk, 70 parts of sweetener, 8 parts of yeast protein, 5.5 parts of stabilizer, and 0.04 parts of starter culture; the sweetener is sucrose; the yeast protein has a protein content ≥75wt%, and the total content of leucine, isoleucine, and valine in the yeast protein accounts for 21.5% of the total amino acids in the yeast protein; the stabilizer is hydroxypropyl distarch phosphate; the starter culture is a direct-inoculation yogurt starter culture; the yogurt starter culture is YF-L811 starter culture; the YF-L811 yogurt starter culture contains Streptococcus thermophilus and Lactobacillus bulgaricus.

[0146] The yeast protein is a composite modified yeast protein. The preparation process of the composite modified yeast protein includes the following steps: (A01) Take yeast protein, add 6.5 times its mass of deionized water, stir and disperse evenly, and adjust the pH of the system to 6.8 to obtain a yeast protein dispersion; (A02) Add neutral protease to the yeast protein dispersion in step (A01), the amount of neutral protease added is 0.2% of the yeast protein mass, enzymatically hydrolyze at 48℃ for 18 min, control the degree of hydrolysis to 7%, and after the enzymatic hydrolysis is completed, keep warm at 85℃ for 10 min to inactivate the protease and obtain a partially hydrolyzed yeast protein solution;

[0147] (A03) Add organic zinc, specifically zinc gluconate, to the partially enzymatically hydrolyzed yeast protein solution in step (A02). The amount of organic zinc added is 0.9% of the yeast protein mass. After adjusting the pH of the system to 5.7, stir and react at 38°C for 30 min to obtain a zinc-complex yeast protein solution. (A04) Add fructooligosaccharides to the zinc-complex yeast protein solution in step (A03), stir and mix for 25 min, and then spray dry to obtain a composite modified yeast protein. The mass ratio of fructooligosaccharides to yeast protein is 1:8.5, and the spray drying conditions are an inlet air temperature of 185°C and an outlet air temperature of 83°C.

[0148] The method for preparing yeast protein fermented milk in this embodiment includes the following steps: (S01) placing raw milk in a tank installed between the base and the support shell, heating to 58°C, adding sweetener, stabilizer, and yeast protein, and stirring for 27 minutes to obtain a mixture; (S02) heating the mixture in the tank from step (S01) to 93°C and keeping it at that temperature for 10 minutes; (S03) homogenizing the mixture in the tank after step (S02) using a homogenizer at a temperature of 62°C, a homogenization pressure of 25 MPa, and a processing time of 15 minutes; (S04) subjecting the homogenized liquid in the tank from step (S03) to ultrasonic-assisted dispersion treatment. Frequency 30kHz, ultrasonic power 150W, processing temperature 57℃, processing time 4min; (S05) Close the barrel lid and fix it with lock A to seal it. Pasteurize the liquid in the barrel after the treatment in step (S04). The sterilization conditions are 70℃ for 15min; (S06) After the liquid in the barrel after sterilization in step (S05) has cooled down, open lock A and barrel lid, inoculate the fermentation agent and close the barrel lid again and fix it with lock A. Perform segmented gradient fermentation in the barrel; (S07) Stir the fermented emulsion in the barrel after step (S06) evenly and keep the barrel installed between the base and the support shell for cold storage and ripening treatment.

[0149] The fermentation process in step (S06) is a segmented gradient fermentation, which includes the following steps: (B01) First stage: ferment the liquid after inoculation with the starter culture; the fermentation temperature is 39℃ and the fermentation time is 1.8h; (B02) Second stage: raise the temperature of the liquid after fermentation in step (B01) to 43℃ and ferment for 2.3h until the acidity of the liquid reaches 63°T; (B03) Third stage: lower the temperature of the liquid after fermentation in step (B02) to 40℃ and ferment for 0.7h.

[0150] The post-fermentation cooling process in step (S07) is a segmented dynamic post-fermentation process, which includes the following steps: (C01) First stage: statically refrigerate the fermented emulsion at 5°C for 9 hours; (C02) Second stage: maintain the emulsion temperature at 5°C and intermittently stir the emulsion. The intermittent stirring mode is 15 minutes followed by a 30-minute pause, with a speed of 13 r / min, and continue refrigeration for 7.5 hours; (C03) Third stage: cool the emulsion after the second stage of refrigeration to 3°C and statically refrigerate it at this temperature for 5 hours.

[0151] Comparative Example 1: The preparation method of the yeast protein fermented milk in this comparative example includes the following steps: (S01) 914 parts by weight of fresh milk are placed in a mixing tank. Under normal temperature (25℃) and normal pressure, 80 parts by weight of white sugar and 6 parts by weight of hydroxypropyl distarch phosphate are added. The mixture is stirred at 100 r / min for 10 min to fully dissolve and disperse the white sugar and hydroxypropyl distarch phosphate to obtain a mixture; (S02) The mixture obtained in step (S01) is transferred to a preheating tank, heated to 85℃ and kept at that temperature for 5 min to complete the preheating treatment of the raw materials; (S03) The mixture after preheating in step (S02) is cooled to 60℃ and homogenized in a homogenizer at a homogenizing pressure of 15 MPa for 5 min to obtain a homogenized liquid. (S04) Place the homogenized liquid from step (S03) into a sterilization device and sterilize it at 63℃ for 30 minutes to complete the sterilization process; (S05) Allow the sterilized liquid from step (S04) to cool naturally to 40℃, inoculate it with 0.03 parts of Yo-cul973 direct-inoculation yogurt starter, and stir to obtain the fermentation base material; (S06) Place the fermentation base material from step (S05) in a 42℃ constant temperature incubator for fermentation, and stop fermentation when the acidity of the liquid reaches 70°T; (S07) Stir the emulsion after fermentation in step (S06) at a low speed of 80r / min for 5 minutes to make the emulsion structure uniform, and then place it in a 5℃ cold storage environment for static refrigeration for 24 hours to obtain the finished product.

[0152] Comparative Example 2: This comparative example is basically the same as Comparative Example 1, except that in step (S01), the amount of fresh milk used is 893 parts by weight, and 21 parts by weight of yeast protein are added at the same time. The amount of hydroxypropyl distarch phosphate used is still 6 parts by weight.

[0153] Comparative Example 3: This comparative example is basically the same as Comparative Example 1, except that in step (S01), the amount of fresh milk used is 913.2 parts by weight, and 0.8 parts by weight of yeast protein is added at the same time. The amount of hydroxypropyl distarch phosphate used is still 6 parts by weight.

[0154] Comparative Example 4: This comparative example is basically the same as Comparative Example 1, except that in step (S01), the amount of fresh milk used is 912 parts by weight, and 5 parts by weight of yeast protein are added at the same time, and the amount of hydroxypropyl distarch phosphate is adjusted to 3 parts by weight.

[0155] Comparative Example 5: This comparative example is basically the same as Comparative Example 1, except that in step (S01), the amount of fresh milk used is 909 parts by weight, and 5 parts by weight of yeast protein are added at the same time, and the amount of hydroxypropyl distarch phosphate is adjusted to 9 parts by weight.

[0156] Comparative Example 6: This comparative example is basically the same as Comparative Example 1, except that in step (S01), the amount of fresh milk used is 909 parts by weight, and 5 parts by weight of yeast protein is added at the same time. The amount of hydroxypropyl distarch phosphate is still 6 parts by weight. In step (S06), the fermentation temperature is adjusted to 37°C, and fermentation is terminated when the acidity of the liquid reaches 70°T.

[0157] Comparative Example 7: This comparative example is basically the same as Comparative Example 1, except that in step (S01), the amount of fresh milk used is 909 parts by weight, and 5 parts by weight of yeast protein are added at the same time. The amount of hydroxypropyl distarch phosphate used is still 6 parts by weight. In step (S06), the fermentation temperature is adjusted to 46°C, and fermentation is terminated when the acidity of the liquid reaches 72°T.

[0158] Comparative Example 8: This comparative example is basically the same as Comparative Example 1, except that in step (S01), the amount of fresh milk used is 909 parts by weight, and 5 parts by weight of yeast protein is added at the same time. The amount of hydroxypropyl distarch phosphate used is still 6 parts by weight. The homogenization step in step (S03) is omitted in the process. The preheated liquid in step (S02) is directly subjected to the sterilization treatment in step (S04). In step (S06), fermentation is terminated when the acidity of the liquid reaches 70°T.

[0159] Comparative Example 9: This comparative example is basically the same as Comparative Example 1, except that in step (S01), the amount of fresh milk used is 909 parts by weight, and 5 parts by weight of yeast protein are added at the same time, and the amount of hydroxypropyl distarch phosphate is adjusted to 9 parts by weight; in step (S07), the operation of stirring at low speed of 80 r / min for 5 min after fermentation is omitted, and the emulsion after fermentation in step (S06) is directly placed in a 5℃ refrigerated environment for static refrigeration for 24 h.

[0160] To enable those skilled in the art to accurately implement this invention, the following parameter measurement methods are described herein:

[0161] Degree of enzymatic hydrolysis: The protein content in the samples before and after enzymatic hydrolysis was determined using the Kjeldahl method and calculated according to the following formula:

[0162] Degree of hydrolysis (%) = (Protein mass before hydrolysis - Protein mass after hydrolysis) / Protein mass before hydrolysis × 100%

[0163] Acidity (°T): Determined by acid-base titration method according to the method for determining acidity of fermented milk in national standard GB 5009.239 "Determination of Acidity of Food".

[0164] Soluble solids content: determined using a refractometer at 25°C, in °Brix.

[0165] Water-holding capacity and whey separation rate: As described in the test methods section of this article, the centrifugation method was used for determination.

[0166] Intermittent stirring mode: refers to a cycle in which stirring is repeated continuously for 15 minutes during the aforementioned phase, followed by a 30-minute pause.

[0167] The testing method is as follows:

[0168] 1. Whey separation rate: Take 5.0 mL of homogenized fermented milk sample at 25℃ into a 10 mL stoppered graduated centrifuge tube, pre-cool at 4℃ for 10 min, and centrifuge at 3000 r / min for 15 min. Calculate the whey separation rate (%) by the ratio of the volume of separated whey to the initial volume of the sample. Perform 3 parallel experiments on the same sample and take the average value.

[0169] 2. Water-holding capacity: Dry a 10 mL stoppered graduated centrifuge tube to constant weight at 105℃, add 5.0 mL of homogenized fermented milk sample at 25℃ and weigh it, pre-cool at 4℃ for 10 min, centrifuge at 3000 r / min for 15 min, pour out the free whey, and calculate the water-holding capacity (%) by the ratio of the mass of the curd precipitate to the initial mass of the sample. Perform 3 parallel experiments on the same sample and take the average value.

[0170] 3. Soluble solids content: After homogenizing the fermented milk sample at 25℃, it was lightly filtered through medium-speed qualitative filter paper. A 0-20°Brix handheld refractometer was used. After calibrating the instrument with distilled water at 25℃, 1-2 drops of sample filtrate were taken to measure the refractive index and the soluble solids content (°Brix) was directly read. Three parallel experiments were performed on the same sample and the average value was taken.

[0171] 4. Sensory evaluation: The results were analyzed and compared by 20 trained sensory evaluation specialists. The sensory evaluation criteria are shown in Table 1.

[0172] Table 1: Sensory Evaluation Criteria

[0173]

[0174] Experimental data for the examples and comparative examples are shown in Tables 2-4 and 4-4. Figure 1-2 As shown.

[0175] Table 2: Sensory evaluation scores of samples obtained from the examples and comparative examples

[0176]

[0177] Table 3: Sensory evaluation scores of samples obtained from the examples and comparative examples after 21 days of storage.

[0178]

[0179] Table 4: Whey separation rate and water-holding capacity test data of the examples and comparative examples

[0180]

[0181] Please see Figure 4-7 The apparatus for preparing yeast protein fermented milk includes a base 100, a support shell 200, a barrel 300, a barrel lid 400, and a homogenizer 600. Two support shells 200 are symmetrically mounted on the surface of the base 100. The barrel 300 is rotatably mounted between the two support shells 200. The barrel lid 400 is hinged to the top of the barrel 300. The homogenizer 600 is fixedly mounted on the top of the barrel lid 400. The barrel 300 and the barrel lid 400 are detachably installed via a locking piece A500. The support shell 200 is equipped with a tilting mechanism to tilt the barrel 300 for easy pouring of the liquid medium. The barrel 300 is equipped with a stirring mechanism to stir and mix the liquid medium inside.

[0182] Please see Figure 8-9The tilting mechanism includes an electric push rod 201, which is fixedly installed inside the support housing 200. The bottom output end of the electric push rod 201 is fixedly connected to one end of the crossbar 202, and the other end of the crossbar 202 is fixedly connected to the bottom end of the rack 203. A guide rail A205 is slidably installed on the side of the rack 203, and both ends of the guide rail A205 are fixedly connected to the inner wall of the support housing 200. An extension plate 209 is fixedly installed on the top of the rack 203 to prevent excessive sliding of the rack 203.

[0183] Please see Figure 8-9 The rack 203 has a gear 204 meshing on its side. The crossbar 202 is located below the gear 204. The gear 204 is rotatably connected to the support shell 200 through a shaft and bearing. The other end of the shaft of the gear 204 is fixedly connected to the fixing plate 206. The side of the fixing plate 206 is fixedly connected to the outer surface of the barrel 300. The bottom of the shaft of the gear 204 is fixedly connected to the top of the swing arm 207. The swing arm 207 is located between the barrel 300 and the support shell 200. The bottom of the swing arm 207 is fixedly connected to the drag ring 208. The drag ring 208 is fixedly installed below the outer surface of the barrel 3.

[0184] Please see Figure 7-10 The barrel 300 has two cavities, A301 and B302, respectively. A vertical heating tube 303 is fixedly installed inside the cavity A301, and a horizontal heating tube 304 is fixedly installed inside the cavity B302. The vertical heating tube 303 is arranged in a spiral upward shape and is used to heat the outer periphery of the barrel 300. The horizontal heating tube 304 is arranged in a mosquito coil spiral shape and is used to heat the bottom of the barrel 300.

[0185] Please see Figure 10-13 The stirring mechanism includes a stirring motor 305, which is fixedly installed in the interlayer of the tank body 300. A sealing seat 306 is fitted on the outer side of the output end of the stirring motor 305, and the sealing seat 306 is embedded in the inner wall of the tank body 300. A plug rod 307 is fixedly installed on the top of the output end of the stirring motor 305. The cross-section of the plug rod 307 is square to prevent slippage during rotation. A stirring shaft 308 is inserted through the top of the plug rod 307. Four equally spaced fixing rings 316 are fixedly installed on the outer side of the stirring shaft 308. Four circumferentially arranged stirring rods 317 are fixedly installed on the outer side of the fixing rings 316. The upper and lower stirring rods 317 are set at a 30-degree angle. Magnetic strips 318 are fixedly installed at the tail ends of the two staggered stirring rods 317. The magnetic strips 318 are set at an incline. Rotating the stirring rods 317 and magnetic strips 318 can mix the liquid medium inside the tank body 3.

[0186] Please see Figure 10-11The inner wall of the barrel 300 is fixedly installed with guide rails B319. There are eight guide rails B319 arranged in a ring array. A slide plate 320 is slidably installed inside the guide rails B319. A sealing seat 321 is inserted through the top of the guide rails B319. A spring B322 is fixedly installed on the surface of the slide plate 320. There are several springs B322, which are arranged at equal intervals. The springs B322 are magnetic and correspond to the magnetic strip 318. When the magnetic strip 318 rotates, it attracts the springs B322, which can make the springs B322 swing back and forth. This can capture lint and impurities in the liquid and also pulverize the liquid medium.

[0187] Please see Figure 13-14 The bottom of the stirring shaft 308 has a slot 309 corresponding to the insertion rod 307. Ribs 310 are fixedly installed on two sides of the insertion rod 307, and mounting grooves 311 are opened on the other two sides of the insertion rod 307. There are three mounting grooves 311 on one side, which are equally spaced, and two mounting grooves 311 on the other side, which are staggered. A spring A312 is fixedly installed inside the mounting groove 311, and a locking head 313 is fixedly installed on the other end of the spring A312. Rib grooves 314 corresponding to the ribs 310 are opened on two inner walls of the slot 309, and locking grooves 315 corresponding to the locking head 313 are opened on the other two inner walls of the slot 309. The stirring shaft 308 is installed on the outside of the insertion rod 307 through the slot 309. The locking head 313 is inserted into the locking groove 315 by the push of the spring A312, which can lock the stirring shaft 308 and prevent it from falling off when rotating.

[0188] Please see Figure 4-7 Temperature sensor 401 and pressure sensor 402 are fixedly installed on the inner top wall of the lid 400. Control panel 403 is fixedly installed on the surface of lid 400. Locking piece B404 corresponding to locking piece A500 is fixedly installed on the outer periphery of lid 400. Control panel 403 is electrically connected to electric push rod 201, vertical heating tube 303, horizontal heating tube 304 and stirring motor 305 respectively. The output terminals of temperature sensor 401 and pressure sensor 402 are connected to the input terminal of control panel 403.

[0189] Please see Figure 15-16The homogenizer 600 includes a housing 601, which is embedded in the top of the lid 400. A cap 602 is threadedly connected to the top of the housing 601, and a threaded ring 603 is embedded in the top of the cap 602. A threaded rod 604 is threadedly connected to the inner wall of the threaded ring 603, and a plug 605 is rotatably connected to the bottom of the threaded rod 604. A truncated cone is provided at the bottom of the plug 605. A corresponding plug seat 606 is fixedly installed inside the housing 601. The top of the plug seat 606 has a conical surface corresponding to the truncated cone. By moving the plug 605 up and down to match the plug seat 606, it can be used as a valve to control the entry of liquid. A mesh plate 607 is threadedly connected to the bottom of the housing 601, and a filter screen 608 is provided between the mesh plate 607 and the plug seat 606 to perform simple filtration of the entering liquid.

[0190] Please see Figure 15-16 A limiting ring 609 is fixedly installed on the right side of the inner shell 601. A spring C610 is provided on the right side of the limiting ring 609. A ball 611 is fixedly installed on the right side of the spring C610. The side of the ball 611 close to the spring C610 is flat, and the side of the ball 611 away from the spring C610 is spherical. A ball ring 612 is provided on the right side of the ball ring 612. A bevel tangent to the ball 611 is opened on the side of the ball ring 612. The diameter of the ball 611 is smaller than the diameter of the bevel of the ball ring 612. The ball ring 612 is fixedly installed on the inner wall of the outer shell 61. A connecting nozzle 613 is fixedly installed on the right side of the ball ring 612. The connecting nozzle 613 is connected to an external pipe, and external liquid can be injected into the interior of the barrel 3.

[0191] Working principle: When in use, open the lid 400 and add the liquid into the container 300. The liquid inside the container 300 is heated by the vertical heating tube 303 and the horizontal heating tube 304. The stirring motor 305 drives the stirring shaft 308 to rotate. The stirring shaft 308 stirs and mixes the liquid in the container 300 through the stirring rod 317 and the magnetic strip 318. At the same time, the rotating magnetic strip 318 forms a magnetic force on the spring B322, causing the spring B322 to swing back and forth. This serves two purposes: first, it captures fibrous impurities in the liquid; second, the elasticity of the spring B322 can shear the liquid, making the suspended particles in the liquid smaller.

[0192] After the lid 400 and the body 300 are closed and locked, they can be connected to an external pipe through the connector 613. The external liquid pushes the ball 611 to contract, and the liquid enters the gap between the plug 605 and the plug seat 606 through the gap between the ball 611 and the outer shell 61, and finally enters the interior of the body 300. The liquid entering the gap between the plug 605 and the plug seat 606 will form high pressure, which can homogenize and break the liquid, making it easier to mix more perfectly with the liquid in the body 300.

[0193] In summary, the yeast protein fermented milk preparation device can drive the crossbar 202 to move downward by extending the electric push rod 201. The rack 203 will also move downward, and the rack 203 will drive the gear 204 to rotate. While the gear 204 is rotating, it will also drive the barrel 300 to tilt. At the same time, the rotating shaft of the gear 204 will also drive the swing arm 207 and the drag ring 208 to rotate. The drag ring 208 supports the bottom of the barrel 300, reducing the rotational resistance of the barrel 300. After tilting, the fermented milk inside the barrel 300 can be poured out, which improves the efficiency of pouring out the fermented milk.

[0194] The yeast protein fermented milk preparation device uses a stirring motor 305 to drive the stirring shaft 308 to rotate. The stirring shaft 308 drives the stirring rod 317 and the magnetic strip 318 to rotate, which can stir and mix the liquid inside the tank 300. At the same time, the rotating magnetic strip 318 generates a suction force on the spring B 322, causing the spring B 322 to swing back and forth, homogenizing and dispersing the liquid, and improving the homogenization effect.

[0195] The apparatus for preparing yeast protein fermented milk adds liquid to the tank 300 through the connecting nozzle 613. The pressurized liquid pushes the ball 611 backward, and then the threaded rod 604 moves the plug 605 upward. The bottom cone of the plug 605 forms a gap with the plug seat 606. Once the liquid passes through this gap, it can be pressure homogenized and broken up to increase the particle size of the liquid. At the same time, the homogenizer 600 can be used to inject pressure into the tank 300 to increase the pressure value of the tank 300 and to break up the liquid in the tank 300 under pressure.

[0196] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A yeast protein fermented milk, characterized in that: The raw milk comprises 890-940 parts by weight of raw milk, 50-90 parts by weight of sweetener, 1-20 parts by weight of yeast protein, 4-8 parts by weight of stabilizer and 0.02-0.06 parts by weight of leavening agent.

2. The yeast protein fermented milk according to claim 1, characterized in that: The raw milk is selected from one of fresh milk and reconstituted milk, the fresh milk is selected from one of cow milk and goat milk, and the reconstituted milk is prepared from whole milk powder or skim milk powder and water, and the mass percentage of the whole milk powder or skim milk powder in the reconstituted milk is 20wt%-30wt%.

3. The yeast protein fermented milk according to claim 1, characterized in that: The content of protein in the yeast protein is greater than or equal to 75wt%, and the total content of leucine, isoleucine and valine in the yeast protein accounts for 18-25% of the total amino acids in the yeast protein.

4. The yeast protein fermented milk according to claim 1, characterized in that: The yeast protein is a complex modified yeast protein, and the preparation process of the complex modified yeast protein comprises the following steps, including the following steps, (A01) taking yeast protein, adding 5-8 times the mass of deionized water, stirring and dispersing uniformly, and adjusting the pH of the system to obtain a yeast protein dispersion; (A02) adding neutral protease to the yeast protein dispersion in step (A01), and performing enzymolysis, and after the enzymolysis is completed, the protease is inactivated by heat preservation to obtain a partially enzymolyzed yeast protein solution; (A03) adding organic zinc to the partially enzymolyzed yeast protein solution in step (A02), adjusting the pH of the system, and then stirring and reacting to obtain a zinc complex yeast protein solution; (A04) adding fructooligosaccharide to the zinc complex yeast protein solution in step (A03), stirring and mixing, and then performing spray drying to obtain the complex modified yeast protein.

5. The yeast protein fermented milk according to claim 4, characterized in that: In step (A01), the pH of the system is adjusted to 6.0-7.5; in step (A01), the pH of the system is adjusted to 6.5-7.0; in step (A02), the addition amount of neutral protease is 0.05%-0.35% of the mass of yeast protein, the enzymolysis is carried out at 40-55°C for 10-25min, the degree of enzymolysis is controlled to be 3%-12%, and after the enzymolysis is completed, the protease is inactivated by heat preservation at 75-95°C for 8-12min; In step (A03), the organic zinc is zinc gluconate or zinc lactate, and the addition amount is 0.3%-1.4% of the mass of yeast protein, and after the pH of the system is adjusted to 5.0-6.5, the stirring and reaction are carried out at 30-45°C for 20-40min; in step (A04), after stirring and mixing for 25-35min, spray drying is performed, the mass ratio of fructooligosaccharide to yeast protein is 1:7-1:10, and the spray drying conditions are an inlet air temperature of 175-195°C and an outlet air temperature of 75-90°C.

6. A process for the preparation of a yeast protein fermented milk, characterized in that: including the following steps, (S01) placing raw milk in a barrel body installed between a base and a support shell, heating to a preset temperature, adding sweetener, stabilizer and yeast protein, and stirring uniformly to obtain a mixed solution; (S02) heating and heat preserving the mixed solution in the barrel body in step (S01); (S03) homogenizing the mixed solution in the barrel body treated in step (S02) by a homogenizer; (S04) performing ultrasonic-assisted dispersion treatment on the material liquid in the barrel body after homogenization in step (S03); ​ (S05) Cover the barrel cover and fix it by locking piece A to seal, and sterilize the material liquid in the barrel after step (S04); (S06) After the material liquid in the barrel after step (S05) is cooled, open the locking piece A and the barrel cover, inoculate the fermenting agent, and cover the barrel cover again by locking piece A to carry out fermentation treatment in the barrel; (S07) Stir the emulsion after fermentation in the barrel in step (S06) uniformly, and keep the barrel installed between the base and the support shell to carry out cold ripening treatment.

7. The method for preparing yeast protein fermented milk according to claim 6, characterized in that: The preset temperature in step (S01) is 50-65 DEG C, and the stirring time is 20-35 min; the mixed liquid is heated to 85-98 DEG C in step (S02), and the temperature is kept for 8-12 min; the homogenization treatment temperature is 50-75 DEG C, the homogenization pressure is 15-35 MPa, and the treatment time is 5-25 min in step (S03); the ultrasonic auxiliary dispersion treatment conditions are ultrasonic frequency 15-45 kHz, ultrasonic power 100-200 W, treatment temperature 50-65 DEG C, and treatment time 2-6 min; the sterilization treatment in step (S05) is pasteurization or ultra-high temperature instantaneous sterilization, the pasteurization conditions are 60-90 DEG C for 10-20 min, and the ultra-high temperature instantaneous sterilization conditions are 125-140 DEG C for 2-9 s.

8. The method for preparing yeast protein fermented milk according to claim 6, characterized in that: The fermentation treatment in step (S06) is staged gradient fermentation, Comprising the following steps, (B01) The first stage, the material liquid after inoculating the fermenting agent is fermented; (B02) The second stage, the material liquid after the first stage fermentation in step (B01) is heated and fermented; (B03) The third stage, the material liquid after the second stage fermentation in step (B02) is cooled and fermented.

9. The method for preparing yeast protein fermented milk according to claim 6, characterized in that: The cold ripening treatment in step (S07) is a staged dynamic ripening process, comprising the following steps, (C01) The first stage, the fermented emulsion is statically cooled; (C02) The second stage, the emulsion is intermittently stirred by keeping the temperature, and the cooling is continued; (C03) The third stage, the emulsion after the second stage cooling is cooled statically at the temperature.

10. An apparatus for the preparation of a yeast protein fermented milk, characterised in that: Comprise base (100), support shell (200), barrel (300), barrel cover (400) and homogenizer (600), the surface of the base (100) is symmetrically installed with two support shells (200), the barrel (300) is rotatably installed between the two support shells (200), the barrel cover (400) is hingedly connected to the top of the barrel (300), the homogenizer (600) is fixedly installed on the top of the barrel cover (400), the barrel (300) and the barrel cover (400) are detachably installed through the locking piece A (500), the inside of the support shell (200) is provided with a pouring mechanism, and the inside of the barrel (300) is provided with a stirring mechanism; The pouring mechanism comprises an electric push rod (201), the bottom output end of the electric push rod (201) is fixedly connected with one end of a crossbar (202), the other end of the crossbar (202) is fixedly connected with the bottom end of a rack (203), the top of the rack (203) is fixedly installed with an extension plate (209), the side surface of the rack (203) is engaged with a gear (204), the other end of the shaft rod of the gear (204) is fixedly connected with a fixed plate (206), the bottom of the shaft rod of the gear (204) is fixedly connected with the top of a swing arm (207), and the bottom of the swing arm (207) is fixedly connected with a pull ring (208).

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