Raw material composition of normal-temperature high-protein yoghourt, normal-temperature high-protein yoghourt and preparation method of normal-temperature high-protein yoghourt

Abstract

The invention relates to the field of dairy product processing, in particular to a raw material composition of normal-temperature high-protein yoghourt, the normal-temperature high-protein yoghourt and a preparation method of the normal-temperature high-protein yoghourt. The raw material composition of the normal-temperature high-protein yoghourt comprises raw milk, white granulated sugar, micronized concentrated whey protein powder, a compound stable thickening agent containing tremella polysaccharide and apple fiber, and a leavening agent. The preparation method comprises the following steps: dry-mixing the protein powder and the white granulated sugar, adding the mixture into the raw milk, dispersing, and adding the compound stable thickener; preheating and homogenizing the feed liquid, sequentially carrying out two-stage sterilization treatment, cooling, inoculating a leavening agent, and carrying out variable-temperature fermentation until the pH value at the fermentation end point is 4.3-4.4; demulsifying after fermentation is finished, cooling to obtain a yoghourt base material, and filling after sterile homogenization and sterilization. The technical problem that the high-protein yoghurt is rough in taste and poor in stability when stored at normal temperature is systematically solved, the protein content of the obtained product reaches 6 wt% or above, the taste is smooth, and the product can be stably stored at normal temperature for a long time.

Description

Technical Field

[0001] This invention relates to the field of dairy processing, and in particular to a raw material composition for room-temperature high-protein yogurt, room-temperature high-protein yogurt, and a method for preparing the same. Background Technology

[0002] With increasing consumer health awareness and a faster pace of life, the dairy market is rapidly developing in two directions: nutritional fortification and convenient storage. On the one hand, high-protein yogurt, due to its clear nutritional benefits in promoting muscle synthesis, enhancing satiety, and supporting exercise recovery, is increasingly favored by fitness enthusiasts and health seekers, leading to continuous market demand growth. On the other hand, room-temperature yogurt (i.e., fermented dairy products that do not require cold chain storage and can remain stable at ambient temperature for extended periods) has become an important growth category in the dairy industry due to its significant cost and convenience advantages in logistics, warehousing, and retail sales.

[0003] However, combining the highly valued attributes of high protein content and room temperature to develop a truly market-approved room-temperature high-protein yogurt presents significant technical challenges and contradictions. Currently, the vast majority of high-protein yogurt products on the market fall into the category of refrigerated yogurt, requiring storage and sale under cold chain conditions of 2-6°C, resulting in a typically short shelf life. This is primarily because high-protein systems (usually referring to those with a protein content ≥6%) are more sensitive to heat treatment and long-term storage.

[0004] Specifically, the development of room-temperature high-protein yogurt faces two main technical challenges: First, the deterioration of texture and taste: A significant increase in protein content, especially the addition of exogenous protein powders (such as whey protein powder), easily introduces an unpleasant powdery and coarse texture into the product. This stems primarily from the decreased solubility of proteins in acidic, high-ionic-strength fermented milk systems, making them prone to aggregation and the formation of a rough texture. This problem is often exacerbated after room temperature and heat treatment. Second, storage stability: To achieve room-temperature storage, the product must undergo post-fermentation heat treatment (secondary sterilization) to inactivate microorganisms. This heat treatment process disrupts the gel network formed during yogurt fermentation and exacerbates protein denaturation and aggregation, leading to severe whey separation, protein precipitation, and stratification during the product's shelf life of several months, significantly impacting its appearance and consumer experience.

[0005] To address these challenges, some existing technologies attempt to use traditional stabilizers such as pectin, modified starch, and gelatin. While these can improve water retention to some extent, they often result in an overly thick and sticky texture, losing the natural smoothness of yogurt and clashing with current consumer trends emphasizing cleanliness. Other approaches adjust process parameters, such as increasing homogenization pressure or using enzymatic pretreatment of proteins, potentially improving protein dispersibility. However, these methods are complex, costly, and carry the risk of over-processing damaging protein function and producing undesirable flavors. Some technologies rely on specific protein ingredients; certain highly soluble and stable specialized protein ingredients are expensive, significantly increasing product costs.

[0006] Therefore, there is an urgent need in this field to develop a new product formula and preparation method that can achieve long-term stable storage of high-protein yogurt at room temperature without over-reliance on special raw materials or sacrificing taste. Summary of the Invention

[0007] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a room-temperature high-protein yogurt that can be stored and transported at room temperature, has a smooth taste, and good shelf-life stability, thereby systematically solving the core problems of poor taste and stability of room-temperature high-protein yogurt.

[0008] To achieve the above and other related objectives, a first aspect of the present invention provides a raw material composition for room-temperature high-protein yogurt, comprising, by weight percentage: 82.576%~89.34% raw milk, 4.5%~7% white sugar, 6%~10% protein powder, 0.15%~0.42% compound stabilizing thickener, and 0.004%~0.01% starter culture; wherein the protein powder is micronized concentrated whey protein powder; and the compound stabilizing thickener comprises tremella polysaccharide and apple fiber.

[0009] In some embodiments of the present invention, the particle size of the micronized concentrated whey protein powder is ≤420µm and the protein content is ≥50wt%.

[0010] In some embodiments of the present invention, the mass ratio of Tremella fuciformis polysaccharide to apple fiber in the compound stabilizing thickener is 1:3 to 1:2.

[0011] In some embodiments of the present invention, the total polysaccharide content of the Tremella polysaccharide is ≥80wt%.

[0012] In some embodiments of the present invention, the total dietary fiber content of the apple fiber is ≥50wt%, and its particle size is ≤50 μm.

[0013] In some embodiments of the present invention, the fermenting agent comprises *Lactobacillus delbrueckii* subsp. *bulgaricus* and *Streptococcus salivarius* subsp. *thermophilus*.

[0014] A second aspect of the present invention provides a method for preparing the above-mentioned room-temperature high-protein yogurt, using the above-mentioned raw material composition of room-temperature high-protein yogurt as raw material, and proceeding according to the following steps: (1) After dry mixing the protein powder and white sugar, add it to raw milk at 40~50℃, stir and disperse to obtain liquid one; (2) Add the compound stabilizer and thickener to the liquid obtained in step (1), stir and disperse to obtain liquid two; (3) After preheating the liquid material, homogenize it, then sterilize it, cool it to the fermentation temperature, inoculate it with a starter culture and carry out temperature-switching fermentation. When the pH value drops to 4.3~4.4, stop the fermentation, break the emulsion, cool it, and obtain the yogurt base material. (4) The yogurt base is homogenized, sterilized and then packaged to obtain the room temperature high protein yogurt.

[0015] In some embodiments of the present invention, in step (1), the stirring rate is 600~800 rpm and the time is 15~30 min.

[0016] In some embodiments of the present invention, in step (1), after stirring and dispersing, the temperature is lowered to 15~20°C and left to stand for 15~30 minutes.

[0017] In some embodiments of the present invention, in step (2), the stirring rate is 1000~1600 rpm and the time is 15~20 min.

[0018] In some embodiments of the present invention, in step (3), the preheating temperature is 55~65°C.

[0019] In some embodiments of the present invention, in step (3), the homogenization is carried out in two stages, wherein the pressure of the first stage homogenization is 40~60 bar and the pressure of the second stage homogenization is 140~160 bar.

[0020] In some embodiments of the present invention, in step (3), the sterilization treatment adopts a two-stage sterilization process.

[0021] In some embodiments of the present invention, in step (3), cooling to the fermentation temperature is cooling to 42~44°C.

[0022] In some embodiments of the present invention, in step (3), the variable temperature fermentation specifically begins at 42~44°C, and when the pH drops to 5.2~5.3, the temperature is lowered to 35~37°C to continue fermentation until the pH drops to 4.3~4.4 and then terminates.

[0023] In some embodiments of the present invention, in step (4), the homogenization is performed using sterile homogenization, with a homogenization pressure of 50~80 bar and a homogenization temperature of 15~25°C.

[0024] In some embodiments of the present invention, in step (4), the sterilization conditions are maintained at 72~85°C for 15~30s.

[0025] A third aspect of the present invention provides a room-temperature high-protein yogurt, which is prepared by the above-described preparation method.

[0026] In some embodiments of the present invention, the room-temperature high-protein yogurt has a protein content of 6wt% to 8wt% and a fat content of 3.1wt% to 3.3wt%.

[0027] Compared with the prior art, the present invention has the following advantages: 1. This invention employs a micronized protein powder and a compound system of tremella polysaccharide / apple fiber, combined with key processes such as two-stage sterilization and variable-temperature fermentation, to synergistically work on a high-protein acidic system. This inhibits the coarse aggregation of proteins from the source and protects the gel structure during heat treatment. As a result, it systematically solves the long-standing technical contradiction between the coarse texture caused by high protein and the instability and water separation caused by room temperature storage, achieving a dual improvement in product texture and shelf-life stability.

[0028] 2. Due to the use of an optimized compound stabilizing thickener and a mild and efficient sterilization and homogenization process, the product exhibits excellent physical stability at room temperature. The products in Examples 1-3 of this invention show low instability indices (e.g., below 0.07) in accelerated stability tests, and minimal whey separation after 30 days of accelerated storage at 37°C (e.g., less than 0.75g), confirming that the product has the physical basis for stable storage at room temperature for more than 6 months, without stratification or sedimentation. Actual room temperature storage tests showed no significant stratification or quality deterioration within 6 months.

[0029] 3. This invention constructs an optimized protein gel network through fine dispersion of micronized concentrated whey protein powder and variable temperature fermentation process. The product exhibits ideal cohesion and smoothness. Sensory evaluation results show that the product has a smooth taste, is easy to swallow, and has low oral residue, basically eliminating the powdery and coarse texture common in traditional high-protein yogurt.

[0030] 4. This invention uses a combination of tremella polysaccharide and apple fiber as a stabilizing thickener, both of which are of natural origin and conform to the trend of clean labeling. At the same time, the preparation method does not rely on extreme or expensive special equipment. The core process steps (such as two-stage sterilization and variable temperature fermentation) can be precisely controlled and implemented on existing production lines. The process is stable and reliable, easy to scale up and promote, and has good economic benefits and market application potential. Detailed Implementation

[0031] This invention provides a raw material composition for room-temperature high-protein yogurt, the room-temperature high-protein yogurt, and a method for its preparation. By employing a specific compound system of micronized whey protein powder and tremella polysaccharide / apple fiber, combined with key processes of two-stage mild sterilization, variable-temperature fermentation, and precise homogenization, the core contradiction of rough texture and poor stability of high-protein systems at room temperature storage is successfully solved. This results in a product with uniform and stable texture, smooth and delicate taste, and a protein content of over 6 wt% within a 6-month shelf life, providing a reliable technical solution for the convenient consumption of high-nutrition dairy products.

[0032] To achieve the above and other related objectives, a first aspect of the present invention provides a raw material composition for room-temperature high-protein yogurt, comprising, by weight percentage: 82.576%~89.34% raw milk, 4.5%~7% white sugar, 6%~10% protein powder, 0.15%~0.42% compound stabilizing thickener, and 0.004%~0.01% starter culture; wherein the protein powder is micronized concentrated whey protein powder; and the compound stabilizing thickener comprises tremella polysaccharide and apple fiber.

[0033] The raw milk mentioned in this invention refers to fresh milk that has undergone pre-pasteurization and should meet the relevant requirements of GB 19301-2010 "National Food Safety Standard for Raw Milk", with a protein content of 3.2%~3.4%, a fat content of 3.5%~3.7%, a lactose content of 4.8%~5.0%, and a titratable acidity ≤18°T.

[0034] In some embodiments of the present invention, the particle size of the micronized concentrated whey protein powder is ≤420µm (passing through a 40-mesh sieve), for example, it can be 250~300µm, 300~350µm, 350~400µm, or 400~420µm, and the protein content is ≥50wt%, which can be 50wt%~55wt%, 55wt%~60wt%, or 60wt%~65wt%, preferably 51.5wt%~55.5wt%.

[0035] In the room-temperature high-protein yogurt of the present invention, the mass percentage of the compounded stabilizing thickener, based on the total mass of raw materials, is 0.15%~0.42%, which can be 0.15%~0.2%, 0.2%~0.25%, 0.25%~0.3%, 0.3%~0.35%, 0.35%~0.4%, or 0.4%~0.42%, preferably 0.3%~0.42%.

[0036] In some embodiments of the present invention, the mass ratio of Tremella fuciformis polysaccharide to apple fiber in the compound stabilizing thickener is 1:3 to 1:2, for example, 1:3, 1:2.5, or 1:2, preferably 1:2.5 to 1:2. Tremella fuciformis polysaccharide is an anionic polysaccharide with excellent hydrophilic colloidal properties. Its molecular chains form a highly hydrated three-dimensional network structure in the aqueous phase through hydrogen bonds and van der Waals forces. Under acidic conditions, positively charged casein and negatively charged Tremella fuciformis polysaccharide form a casein-Tremella fuciformis polysaccharide complex through electrostatic adsorption. Simultaneously, due to electrostatic repulsion and steric hindrance, the proteins in the yogurt remain stable and do not separate, significantly improving the smooth texture and initial uniformity of the product. Apple fiber contains soluble and insoluble dietary fiber. The insoluble dietary fiber can form a physical support network in the system, anchoring water and protein gels, effectively resisting whey precipitation and sedimentation caused by gravity and phase separation during long-term storage and heat treatment, providing long-term structural stability. Soluble dietary fiber can lock in moisture through cross-linking, providing a smooth texture to yogurt. At an optimal ratio of 1:3 to 1:2, the lubricating and encapsulating effect of tremella polysaccharides and the network support of apple fiber achieve the best balance and synergy. The apple fiber network provides the framework for the system, while the tremella polysaccharides fill and lubricate the gaps in the network, together constructing a strong yet smooth and stable composite system. This simultaneously overcomes the two major challenges of high-protein room-temperature yogurt being unstable and lacking smoothness.

[0037] In some embodiments of the present invention, the total polysaccharide content of the Tremella polysaccharide is ≥80wt%, preferably 80wt%~95wt%.

[0038] In some embodiments of the present invention, the total dietary fiber content of the apple fiber is ≥50wt%, preferably 60wt%~80wt%, and its particle size is ≤50 μm, preferably ≤48 μm.

[0039] In some embodiments of the present invention, the starter culture comprises *Lactobacillus delbrueckii* subsp. bulgaricus and *Streptococcus salivarius* subsp. thermophilus, with a viable count of not less than 1 × 10¹¹ CFU / g. These two bacteria are classic symbiotic strains for yogurt preparation. Their combination is not only safe and reliable, but also, through their synergistic metabolic effects, efficiently produces acid and forms a typical fermented milk flavor, which is a prerequisite for constructing the basic flavor framework of the product. To achieve efficiency in industrial production and control the consistency of acidity at the fermentation endpoint, the present invention preferably uses a rapid-fermentation starter culture, which has stronger acid-producing activity and a shorter fermentation time. In the high-protein system of the present invention, rapid passage through the fermentation stage helps reduce the risk of adverse protein aggregation due to prolonged exposure to changing environments in the fermenter, and is beneficial for obtaining a more uniform and finer curd structure. In specific implementations, commercially available compound starter cultures that meet the above requirements can be used. For example, Danisco's YO-MIX Fast1.0 starter culture is a rapid fermentation starter culture containing the aforementioned strain.

[0040] A second aspect of the present invention provides a method for preparing the above-mentioned room-temperature high-protein yogurt, using the above-mentioned raw material composition of room-temperature high-protein yogurt as raw material, and proceeding according to the following steps: (1) After dry mixing the protein powder and white sugar, add it to raw milk at 40~50℃, stir and disperse to obtain liquid one; (2) Add the compound stabilizer and thickener to the liquid obtained in step (1), stir and disperse to obtain liquid two; (3) After preheating the liquid material, homogenize it, then sterilize it, cool it to the fermentation temperature, inoculate it with a starter culture and carry out temperature-switching fermentation. When the pH value drops to 4.3~4.4, stop the fermentation, break the emulsion, cool it, and obtain the yogurt base material. (4) The yogurt base is homogenized, sterilized and then packaged to obtain the room temperature high protein yogurt.

[0041] In some embodiments of the present invention, in step (1), the stirring rate is 600-800 rpm, which can be 600-650 rpm, 650-700 rpm, 700-750 rpm, or 750-800 rpm, preferably 650-750 rpm; the time is 15-30 min, which can be 15-20 min, 20-25 min, or 25-30 min, preferably 20-25 min. Generally, a shear force of 600 rpm or higher is required to effectively break up protein powder clumps and promote the swelling of colloids such as Tremella polysaccharide. Excessively high rotation speeds (e.g., >900 rpm) will violently entrain air and generate a large amount of foam, affecting subsequent processes and the texture of the final product; at the same time, it may cause unnecessary excessive shearing of the protein. A rotation speed in the range of 600-800 rpm provides sufficient shear force for good dispersion, while being relatively gentle, making it suitable for dairy product liquids with high solids content and medium viscosity. Preferably, the stirring rate is 700 rpm and the stirring time is 20 min.

[0042] In some embodiments of the present invention, in step (1), after stirring and dispersing, the temperature is lowered to 15-20°C and allowed to stand for 15-30 minutes. The cooling refers to reducing the dispersion temperature of the liquid from 40-50°C to 15-20°C. Immediately cooling after dispersion can moderately increase the viscosity of the system, which helps to suspend the dispersed particles, preventing them from rapidly settling or re-aggregating, and providing a stable environment for hydration. This avoids prolonged exposure of the material to high temperatures, reducing the early occurrence of the Maillard reaction (between sugar and protein) and potential thermal denaturation, thus protecting the functional properties of the protein. The standing period refers to maintaining the material at a low temperature after cooling for 15-30 minutes to allow for sufficient hydration.

[0043] In some embodiments of the present invention, in step (2), the stirring rate is 1000~1600 rpm, which can be 1000~1100 rpm, 1100~1200 rpm, 1200~1300 rpm, 1300~1400 rpm, or 1400~1500 rpm. It can also be 1500~1600 rpm, and the time is 15~20 min, which can be 15~16 min, 16~17 min, 17~18 min, 18~19 min, or 19~20 min. Preferably, the stirring rate is 1200 rpm, and the time is 18 min.

[0044] In some embodiments of the present invention, in step (3), the preheating temperature is 55~65℃, which can be 55~56℃, 56~57℃, 57~58℃, 58~59℃, 59~60℃, 60~61℃, 61~62℃, 62~63℃, 63~64℃, or 64~65℃.

[0045] In some embodiments of the present invention, in step (3), the homogenization is a two-stage homogenization, wherein the first-stage homogenization pressure is 40~60 bar, which can be 40~45 bar, 45~50 bar, 50~55 bar, or 55~60 bar, preferably 45~55 bar, and the second-stage homogenization pressure is 140~160 bar, which can be 140~145 bar, 145~150 bar, 150~155 bar, or 155~160 bar, preferably 145~155 bar.

[0046] In some embodiments of the present invention, in step (3), the sterilization process employs a two-stage sterilization process, which is a refined heat treatment scheme designed for high-protein yogurt systems containing stabilizers. Its purpose is not simply to kill microorganisms, but rather to treat different components in the system in stages and in a differentiated manner, so as to maximize the protection of protein structure and stabilizer function while achieving commercial sterility. The first stage of sterilization in the two-stage sterilization process is held at 67~70℃ for 180~300s, for example, at 67℃ for 300s, or at 68℃ for 240s, or at 70℃ for 180s, preferably at 68~70℃ for 180~240s; the second stage of sterilization is held at 95~137℃ for 4~300s, for example, at 137℃ for 4s, or at 121℃ for 15s, or at 95℃ for 300s, preferably at 95~121℃ for 15~300s. The first stage of sterilization focuses on inactivating heat-resistant enzymes in the raw materials and gently and controllably denaturing milk proteins, providing a heat adaptation process for high-protein systems. The second stage of sterilization aims to achieve commercial sterility requirements and complete further cross-linking of protein molecules, forming a stable gel network to ensure the product can be stored at room temperature. The two processes work together to achieve sterilization goals while maximizing the protection of the product's texture and taste.

[0047] In some embodiments of the present invention, in step (3), the cooling to the fermentation temperature is cooling to 42~44℃, which can be 42~43℃ or 43~44℃.

[0048] In some embodiments of the present invention, in step (3), the variable temperature fermentation specifically begins at 42~44°C, and when the pH drops to 5.2~5.3, the temperature is lowered to 35~37°C to continue fermentation until the pH drops to 4.3~4.4 and then terminates. The fermentation process is divided into three stages: (1) High temperature start-up period: Fermentation begins at 42~44℃. This temperature is the optimal growth temperature of Streptococcus salivarius subsp. thermophilus in the starter culture, which enables it to start up quickly and produce acid efficiently, pushing the pH value of the system down rapidly from about 6.5. Rapid acid production makes the pH value approach the isoelectric point of proteins (especially casein) (about pH 4.6), and a gel network begins to form, providing a solid texture foundation for the product; (2) Key turning point: When the pH drops to 5.2~5.3, the fermentation temperature is adjusted to 35~37℃. At this time, the protein begins to gel. After cooling, the activity of Streptococcus salivarius subsp. thermophilus is relatively weakened, while Lactobacillus delbrueckii subsp. bulgaricus (whose optimal growth temperature is slightly lower) plays a prominent role in the subsequent fermentation. The fermentation shifts from being mainly focused on rapid acid production to a stage where acid production and the synthesis of flavor substances (such as acetaldehyde, dimethylglyoxal, etc.) are equally important, bringing a harmonious and full fermentation flavor to the product. (3) Low temperature completion period: Fermentation is completed at 35~37℃, which not only helps to enrich flavor substances, but also slows down the formation of protein gel network, allowing protein molecules and water molecules to have more time to arrange and combine in an orderly manner, which helps to form a more delicate, compact and water-holding gel microstructure, directly improving the smooth taste and stability of the final product.

[0049] Demulsification refers to the physical shearing and breaking down of the curd (protein gel network structure) formed after milk fermentation by lactic acid bacteria, thereby creating a uniform, smooth, and fluid yogurt to obtain the target yogurt (stirred yogurt, drinking yogurt) or to facilitate subsequent processing. This invention does not limit the demulsification method; for example, it can be stirring demulsification, homogenization demulsification, etc. In some specific embodiments of this invention, in step (3), after fermentation, demulsification is performed by stirring to break down the curd structure and obtain a uniform and fine base material, which is then cooled to 6-15°C for later use, for example, to 8°C, 10°C, or 12°C.

[0050] In some embodiments of the present invention, in step (4), the homogenization is performed using sterile homogenization, the homogenization pressure is 50~80 bar, which can be 50~60 bar, 60~70 bar, or 70~80 bar, preferably 60~70 bar, and the homogenization temperature is 15~25℃, which can be 15~20℃, or 20~25℃, preferably 18~22℃, more preferably 20℃.

[0051] In some embodiments of the present invention, in step (4), the sterilization conditions are maintained at 72-85°C for 15-30 seconds, preferably at 75-80°C for 20-25 seconds, and more preferably at 75°C for 25 seconds. Since the material is acidic at this time (pH approximately 4.3-4.4), the heat resistance of microorganisms is significantly reduced, thus relatively mild conditions can be used. The purpose of sterilization is to kill any small amount of environmental microorganisms that may be introduced before filling, ensuring the commercial sterility of the final product.

[0052] A third aspect of the present invention provides a room-temperature high-protein yogurt, which is prepared by the above-described preparation method.

[0053] In some embodiments of the present invention, the protein content of the room-temperature high-protein yogurt is 6wt%~8wt%, which can be 6wt%~6.5wt%, 6.5wt%~7wt%, 7wt%~7.5wt%, or 7.5wt%~8wt%, preferably 6.5wt%~7.5wt%; the fat content is 3.1wt%~3.3wt%, which can be 3.1wt%~3.2wt%, or 3.2wt%~3.3wt%.

[0054] In some specific embodiments of the present invention, the room-temperature high-protein yogurt not only has a high protein content (over 6 wt%) and a smooth texture, but also achieves excellent room-temperature storage stability. For example, in accelerated stability testing, the product's instability index can be below 0.07; after accelerated storage at 37°C for 30 days, its whey precipitation can be less than 0.75g, proving that the product can maintain long-term stability at room temperature without significant quality deterioration.

[0055] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0056] Before further describing specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terminology used in the embodiments of the present invention is for describing specific embodiments and not for limiting the scope of protection of the present invention. Test methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the respective manufacturers.

[0057] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. In addition to the specific methods, apparatus, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description of this invention, any prior art methods, apparatus, and materials similar to or equivalent to those described, apparatus, and materials in the embodiments of this invention may be used to implement the present invention.

[0058] The present invention will be further illustrated by the following examples, but these examples do not limit the scope of the invention.

[0059] Unless otherwise specified, all raw materials used in the following examples were purchased commercially.

[0060] Raw milk, with a protein content of 3.2%, a fat content of 3.5%, a lactose content of 4.8%, and a titratable acidity of 18°T, is sourced from Bright Dairy & Food Co., Ltd.

[0061] Micronized concentrated whey protein powder, with a particle size of 420µm and a protein content of 51.5wt%~55.5wt%, was purchased from Spico (Shandong) Biological Products Co., Ltd.

[0062] Tremella polysaccharide, with a total polysaccharide content ≥80wt%, was purchased from Mingfu (Shanghai) Health Technology Co., Ltd.

[0063] Apple fiber, with a total dietary fiber content of ≥50wt% and a particle size of ≤50 μm, was purchased from Pingdingshan Jinjing Biotechnology Co., Ltd.

[0064] Fermentation agent, YO-MIX Fast 1.0, Danisco.

[0065] Example 1 This embodiment provides a raw material composition for room temperature high-protein yogurt. Based on the total mass of the raw material composition, the mass percentage of each raw material is as follows: raw milk 89.34%, white sugar 4.5%, micronized concentrated whey protein powder (particle size 420µm, protein content 51.5-55.5%) 6%, tremella polysaccharide 0.05%, apple fiber 0.1%, and starter culture (YO-MIX Fast 1.0) 0.01%.

[0066] Using the above-mentioned raw material composition as raw material, the preparation method is as follows: (1) Mix micronized concentrated whey protein powder and white sugar evenly in advance, slowly add to raw milk at 40°C, stir at 800 rpm for 15 minutes, disperse until there are no obvious lumps, then cool the liquid to 15°C, let it stand and hydrate for 30 minutes to obtain liquid one.

[0067] (2) After mixing the tremella polysaccharide and apple fiber in proportion, slowly add them to the liquid obtained in step (1) and stir and disperse for 15 minutes to obtain liquid two.

[0068] (3) Preheat the liquid to 65°C and perform two-stage homogenization, with the first-stage homogenization pressure being 50 bar and the second-stage homogenization pressure being 200 bar. The homogenized liquid is immediately sterilized: the first-stage sterilization condition is 67°C for 300 seconds, and the second-stage sterilization condition is 137°C for 4 seconds. After sterilization, it is quickly cooled to 42°C and inoculated with starter culture (YO-MIX Fast 1.0) for fermentation. The fermentation process is controlled by temperature variation: fermentation is first carried out at 42°C. When the pH value of the system drops to 5.2, the fermentation temperature is lowered to 35°C to continue fermentation. When the pH value of the system reaches 4.3, the fermentation is terminated. After fermentation, the mixture is stirred to break the emulsion until the curd structure is smooth and there are no visible particles. The mixture is then cooled to 20°C to obtain the yogurt base.

[0069] (4) The above yogurt base material is aseptically homogenized at a pressure of 50 bar and a temperature of 20°C. The homogenized material is then sterilized by a sterilizer at 75°C for 25 seconds. After sterilization, it is immediately hot-filled to obtain the room temperature high-protein yogurt.

[0070] Example 2 This embodiment provides a raw material composition for room temperature high-protein yogurt. Based on the total mass of the raw material composition, the mass percentage of each raw material is as follows: raw milk 85.672%, white sugar 6%, micronized concentrated whey protein powder (particle size 420µm, protein content 51.5-55.5%) 8%, tremella polysaccharide 0.08%, apple fiber 0.24%, and starter culture (YO-MIX Fast 1.0) 0.008%.

[0071] Using the above-mentioned raw material composition as raw material, the preparation method is as follows: (1) Mix micronized concentrated whey protein powder and white sugar evenly in advance, slowly add to raw milk at 45°C, stir at 800 rpm for 20 minutes, disperse until there are no obvious lumps, then cool the liquid to 17°C, let it stand and hydrate for 30 minutes to obtain liquid one.

[0072] (2) After mixing the tremella polysaccharide and apple fiber in a ratio of 1:3, slowly add it to the liquid obtained in step (1) and stir and disperse for 17 minutes to obtain liquid two.

[0073] (3) Preheat the liquid to 60°C and perform two-stage homogenization, with the first-stage homogenization pressure being 50 bar and the second-stage homogenization pressure being 200 bar. The homogenized liquid is immediately sterilized: the first-stage sterilization condition is 68°C for 240 seconds, and the second-stage sterilization condition is 121°C for 15 seconds. After sterilization, it is quickly cooled to 43°C and inoculated with starter culture (YO-MIX Fast 1.0) for fermentation. The fermentation process is controlled by temperature variation: fermentation is first carried out at 43°C. When the pH value of the system drops to 5.3, the fermentation temperature is lowered to 37°C to continue fermentation. When the pH value of the system reaches 4.3, the fermentation is terminated. After fermentation, the mixture is stirred to break the emulsion until the curd structure is smooth and there are no visible particles. The mixture is then cooled to 20°C to obtain the yogurt base.

[0074] (4) The above yogurt base material is aseptically homogenized at a pressure of 65 bar and a temperature of 20°C. The homogenized material is then sterilized by a sterilizer at 75°C for 25 seconds. After sterilization, it is immediately hot-filled to obtain the room temperature high-protein yogurt.

[0075] Example 3 This embodiment provides a raw material composition for room temperature high-protein yogurt. Based on the total mass of the raw material composition, the mass percentage of each raw material is as follows: raw milk 82.576%, white sugar 7%, micronized concentrated whey protein powder (particle size 420µm, protein content 51.5-55.5%) 10%, tremella polysaccharide 0.12%, apple fiber 0.3%, and starter culture (YO-MIX Fast 1.0) 0.004%.

[0076] Using the above-mentioned raw material composition as raw material, the preparation method is as follows: (1) Mix micronized concentrated whey protein powder and white sugar evenly in advance, slowly add to raw milk at 50°C, stir at 800 rpm for 30 minutes, disperse until there are no obvious lumps, then cool the liquid to 20°C, let it stand and hydrate for 30 minutes to obtain liquid one.

[0077] (2) After mixing the tremella polysaccharide and apple fiber in a ratio of 2:5, slowly add it to the liquid obtained in step (1) and stir and disperse for 20 minutes to obtain liquid two.

[0078] (3) Preheat the liquid to 55°C and perform two-stage homogenization, with the first-stage homogenization pressure being 50 bar and the second-stage homogenization pressure being 200 bar. The homogenized liquid is immediately sterilized: the first-stage sterilization condition is 70°C for 180s, and the second-stage sterilization condition is 95°C for 300s. After sterilization, it is quickly cooled to 44°C and inoculated with starter culture (YO-MIX Fast 1.0) for fermentation. The fermentation process is temperature-controlled: fermentation is first carried out at 44°C. When the pH of the system drops to 5.2, the fermentation temperature is lowered to 35°C to continue fermentation. When the pH of the system reaches 4.4, the fermentation is terminated. After fermentation, the mixture is stirred to break the emulsion until the curd structure is smooth and there are no visible particles. The mixture is then cooled to 20°C to obtain the yogurt base.

[0079] (4) The above-mentioned yogurt base material is aseptically homogenized at a pressure of 80 bar and a temperature of 20°C. The homogenized material is then sterilized by a sterilizer at 75°C for 25 seconds. After sterilization, it is immediately hot-filled to obtain the room temperature high-protein yogurt.

[0080] Comparative Example 1 The only difference between this comparative example and Example 1 is that the micronized whey protein concentrate in the raw material composition is ordinary whey protein concentrate (Textrion PROGEL800, protein ≥80%), and its addition amount is adjusted to 3.8% (to ensure that the total protein content it provides is equivalent to the total protein content provided by the 6% micronized whey protein concentrate in Example 1). The other raw material types, ratios and preparation steps are exactly the same as in Example 1.

[0081] Comparative Example 2 The only difference between this comparative example and Example 1 is that the compound stabilizing thickener in the raw material composition is a conventional combination (1.5% modified starch and 0.3% low-ester pectin), while the other raw material types, ratios and preparation steps are exactly the same as in Example 1.

[0082] Comparative Example 3 The only difference between this comparative example and Example 1 is the ratio and amount of the compound stabilizing thickener in the raw material composition, specifically 0.05% Tremella polysaccharide and 0.05% apple fiber (ratio 1:1). The other raw material types, ratios, and preparation steps are exactly the same as in Example 1.

[0083] Comparative Example 4 The only difference between this comparative example and Example 2 is that constant temperature fermentation is used in the fermentation process, that is, the cooling step at pH 5.3 is eliminated, and fermentation is carried out at 43°C until pH 4.3. The other raw material types, ratios and preparation steps are exactly the same as in Example 2.

[0084] Comparative Example 5 The only difference between this comparative example and Example 2 is that the sterilization process in step (3) adopts a single-stage sterilization process, which is maintained at 121°C for 15 seconds. The two-stage sterilization steps in Example 2 are cancelled. The other raw material types, proportions and preparation steps are exactly the same as in Example 2.

[0085] Comparative Example 6 The only difference between this comparative example and Example 3 is that the aseptic homogenization pressure in step (4) is adjusted to 120 bar, while the other raw material types, ratios and preparation steps are exactly the same as in Example 3.

[0086] The room-temperature high-protein yogurts obtained by the preparation methods of the above embodiments and comparative examples were tested for the following indicators.

[0087] Texture properties (viscosity, cohesion, and adhesion) were measured using a TA-XT Plus texture analyzer. The test conditions were: P4.0 disc probe, pressure mode, pre-test speed 5 mm / s, test speed 3 mm / s, post-test speed 10 mm / s, test depth 50%, and trigger force 0.5 g.

[0088] The instability index was determined using a Lumisizer stability analyzer with the following parameters: temperature 25°C, centrifugation speed 300 rpm, scan interval 10 s, number of scans 100, and light factor 1.0.

[0089] The amount of whey separated was determined by an enhanced experiment, under the condition of being placed at 37°C for 30 days and then weighing the separated whey.

[0090] Protein and fat content were determined using the Kjeldahl method and Soxhlet extraction method, respectively.

[0091] All data are averages from multiple tests.

[0092] The key performance indicators of the products in each embodiment and comparative example are compared in Table 1 below.

[0093] Table 1 Comparison of key product indicators for each embodiment and comparative example

[0094] Sensory tests were conducted on the room-temperature high-protein yogurts prepared by the methods described in the above embodiments and comparative examples, with the main focus on evaluating the taste of the yogurts.

[0095] Ten dairy product R&D personnel were selected for taste evaluation training, and five were randomly chosen as taste evaluators for this test. Detailed scoring criteria are shown in Table 2 below: Table 2 Scoring Criteria

[0096] The total score is 100 points. After the evaluation, the scores from the five evaluators were tallied, and the average scores for each item were summed to obtain the total score. The higher the score, the better the taste of the yogurt. The evaluation results are shown in Table 3 below: Table 3 Scoring Results

[0097] The room-temperature high-protein yogurts prepared in Examples 1-3 of this invention exhibited excellent performance in terms of texture, storage stability, and sensory taste. Among them, Example 2, with a protein content of 7 wt%, showed the best overall performance: it had moderate viscosity, low cohesion, resulting in a smooth texture; reasonable adhesion; the lowest instability index (0.036); the least whey separation; and the highest total sensory evaluation score of 93 points. This indicates that the product maintains a suitable texture while possessing excellent shelf-life stability and sensory acceptability.

[0098] In contrast, Comparative Example 1, which used non-micronized whey protein concentrate, showed a significant increase in cohesiveness to 211.5g and a decrease in roughness and smoothness scores, indicating that the use of micronized whey protein plays a key role in improving the smoothness of the product.

[0099] Comparative Example 2 used conventional modified starch and pectin as stabilizers. Its viscosity, cohesiveness and adhesion were significantly higher. At the same time, the instability index and whey separation amount were also significantly increased. The total sensory score was the lowest, only 36 points. This indicates that conventional stabilizer combinations are prone to causing sticky texture, strong swallowing residue, and are not conducive to product stability.

[0100] In Comparative Example 3, the ratio of Tremella polysaccharide to apple fiber was not within the preferred range of this invention. Its viscosity was too low, the instability index was as high as 0.194, and the whey precipitation was the largest, reaching 4.68g. This indicates that maintaining the addition ratio of Tremella polysaccharide to apple fiber between 1:3 and 1:2 is crucial for maintaining the stability of the system.

[0101] Comparative Example 4 used a constant temperature fermentation process, and Comparative Example 5 used a single 121°C, 15-second sterilization process. The stability data and sensory scores of both were lower than those of the corresponding Example 2, which used variable temperature fermentation and two-stage sterilization. This indicates that the variable temperature fermentation and two-stage sterilization process used in this invention helps to coordinate the texture and flavor of the product.

[0102] Comparative Example 6 increased the post-homogenization pressure to 120 bar. Although its sensory score was acceptable at 88 points, the instability index increased to 0.110, and the whey separation amount also increased to 2.65g. This indicates that excessively high aseptic homogenization pressure can damage the protein network structure and thus affect the storage stability of the product.

[0103] In summary, this invention, by employing a stable system of micronized whey protein, tremella polysaccharide, and apple fiber, combined with variable-temperature fermentation, two-stage sterilization, and appropriate homogenization processes, successfully prepares room-temperature high-protein yogurt with a smooth texture, stable consistency, and minimal whey separation within a protein content range of 6wt% to 8wt%. Among these, Example 2, with a protein content of 7wt%, exhibits the best overall performance.

[0104] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A raw material composition of a normal temperature high-protein yogurt, characterized by comprising, Comprise by mass percentage: raw milk 82.576%~89.34%, white granulated sugar 4.5%~7%, protein powder 6%~10%, compound stable thickening agent 0.15%~0.42%, fermenting agent 0.004%~0.01%; wherein, the protein powder is microparticulated concentrated whey protein powder; the compound stable thickening agent comprises tremella polysaccharide and apple fiber.

2. The raw material composition of normal temperature high-protein yogurt according to claim 1, characterized by, Comprise one or more of the following technical features: a) the particle size of the microparticulated concentrated whey protein powder is ≤420µm, and the protein content is ≥50wt%; b) in the compound stable thickening agent, the mass ratio of tremella polysaccharide to apple fiber is 1:3~1:2; c) the total polysaccharide content of the tremella polysaccharide is ≥80wt%; d) the total dietary fiber content of the apple fiber is ≥50wt%, and the particle size is ≤50µm; e) the fermenting agent comprises lactobacillus delbrueckii bulgarian subspecies and streptococcus salivarius thermophilic subspecies.

3. A method for preparing a room temperature high protein yogurt, characterized by, Take the raw material composition of the normal-temperature high-protein yogurt of claim 1 or 2 as raw materials, and perform the following steps: (1) dry mix the protein powder and white granulated sugar, then add raw milk at 40~50℃, stir and disperse to obtain a liquid one; (2) add the compound stable thickening agent to the liquid one obtained in step (1), stir and disperse to obtain a liquid two; (3) preheat the liquid two, then homogenize, then perform sterilization treatment, cool to fermentation temperature, inoculate the fermenting agent to perform temperature-variable fermentation, terminate the fermentation when the pH value drops to 4.3~4.4, break the emulsion, cool, and obtain a yogurt base; (4) homogenize and sterilize the yogurt base, then fill it, and the normal-temperature high-protein yogurt is obtained.

4. The production method according to claim 3, wherein In step (1), one or more of the following technical features are included: (a) the stirring rate is 600~800rpm, and the time is 15~30min; (b) after stirring and dispersing, cool to 15~20℃, and stand for 15~30min.

5. The production method according to claim 3, wherein In step (2), the stirring rate is 1000~1600rpm, and the time is 15~20min.

6. The production method according to claim 3, wherein In step (3), one or more of the following technical features are included: a) the preheating temperature is 55~65℃; b) the homogenization adopts two-stage homogenization, wherein the first-stage homogenization pressure is 40~60bar, and the second-stage homogenization pressure is 140~160bar; c) the sterilization treatment adopts two-stage sterilization process; d) the cooling to fermentation temperature is cooling to 42~44℃; e) the temperature-variable fermentation specifically is starting fermentation at 42~44℃, when the pH drops to 5.2~5.3, the temperature is lowered to 35~37℃ to continue fermentation, and the fermentation is terminated when the pH value drops to 4.3~4.

4.

7. The production method according to claim 6, wherein In the two-stage sterilization process, the first-stage sterilization conditions are 67~70℃ for 180~300s, and the second-stage sterilization conditions are 95~137℃ for 4~300s.

8. The production method according to claim 3, wherein In step (4), one or more of the following technical features are included: a) the homogenization adopts sterile homogenization, the homogenization pressure is 50~80bar, and the homogenization temperature is 15~25℃; b) the sterilization condition is 72~85℃ for 15~30s.

9. A normal temperature high protein yogurt prepared by the method of any one of claims 3~8.

10. The normal temperature high protein yogurt according to claim 9, characterized in that, The normal temperature high protein yogurt has a protein content of 6wt%~8wt% and a fat content of 3.1wt%~3.3wt%.

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