High-cream-fat milk skin yoghourt and preparation method thereof

Abstract

The invention discloses high-cream-fat milk skin yoghourt and a preparation method thereof, and belongs to the technical field of dairy product processing. The yoghourt is prepared from raw milk, unsalted butter, condensed milk, milk skin powder, white granulated sugar and fermentation strains, wherein the milk skin powder is prepared by performing enzymolysis treatment on traditional milk skin. The preparation method comprises the following steps: mixing part of the raw milk with the sugar and the condensed milk, and performing high-pressure homogenization to form basic whey; mixing the residual raw milk with milk skin powder, gellan gum and sodium caseinate, and performing low-pressure homogenization; and after sterilizing and cooling, adding a fermentation strain and unsalted butter, filling and fermenting, and naturally floating milk skin components to form a continuous milk skin layer during fermentation. Through enzymolysis treatment, a specific stabilizer and a two-step homogenizing process, the contradiction between shape maintenance and stability of the traditional milk skin in the yoghourt is solved, and the product has the flavor of the traditional milk skin, the skin-uncovering eating experience and the characteristics of uniformity, fineness and difficulty in bleeding of modern yoghourt, and is suitable for industrial production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of dairy processing, in particular to a high-lactose milk skin yogurt and a preparation method thereof. BACKGROUND

[0002] Yogurt, as a traditional dairy product, is very popular among consumers due to its high content of protein, calcium and active probiotics. In recent years, with the upgrading of consumption, the market has put forward higher requirements for the nutritional, functional and unique flavor of yogurt products. However, the current yogurt products on the market are highly homogeneous, and most of them lack breakthroughs in raw material combination, process design and flavor innovation, making it difficult to meet the needs of consumers for high-end dairy products with regional characteristics and modern technology.

[0003] Milk skin is a traditional dairy product in the Mongolian and Tibetan regions of China. It is made from raw cow milk through boiling, standing and peeling, and is rich in milk fat, protein and natural milk aroma, with high nutritional value and unique flavor. However, it has not been effectively developed and utilized in the modern dairy industry.

[0004] In the prior art, there have been some attempts to apply milk skin or its concept to modern dairy products, but these attempts have obvious limitations, which are as follows: First, the prior art mostly adds milk skin as a flavoring material after crushing it into the whole yogurt, or prepares it into a "jam" form with a bottom sediment. These methods completely destroy the core "complete milk skin layer" form of traditional milk skin, as well as the visual impact and ritual of peeling and eating, and cannot restore its essence, resulting in a lack of distinctive product characteristics and market appeal.

[0005] Second, the formation of traditional milk skin relies on the physical process of boiling and standing cooling, while modern yogurt production relies on homogenization, sterilization and constant temperature fermentation. If milk skin or roughly processed milk skin is added directly, the following problems may occur: (1) uneven texture: large particles of milk skin are difficult to blend with the smooth yogurt base, resulting in a rough mouthfeel; (2) poor stability: during fermentation and shelf life, due to the lack of effective homogenization and stabilization of fat globules, fat floating, whey separation (water separation) and layering may occur, resulting in deterioration of product appearance and texture; (3) flavor attenuation: during the long fermentation process, the unique flavor substances of milk skin may change or attenuate due to microbial metabolism.

[0006] Thirdly, simple homogenization and addition of conventional stabilizers cannot solve the above-mentioned stability problems. Excessive homogenization can destroy the ability of the milk skin to float to the surface; and non-homogenization or insufficient homogenization cannot guarantee the stability of the matrix. The prior art lacks a special raw material processing technology and a composite stabilizing system that can simultaneously meet the contradictory requirements of "natural skin formation on the upper layer" and "stability without water separation on the lower layer".

[0007] Therefore, there is an urgent need in the art for an innovative technical solution that can fundamentally solve the above-mentioned problems and develop a high-quality milk skin yogurt product that not only retains the traditional milk skin form and flavor but also has good stability and is suitable for industrial production. SUMMARY

[0008] In view of the above-mentioned defects in the prior art, the purpose of the present application is to provide a high-milk-fat milk skin yogurt and a preparation method thereof, so as to solve the technical bottleneck that traditional milk skin cannot adapt to modern yogurt industrial production. Through a brand-new technical solution, the traditional physical process of "natural skin formation on the upper layer" is simulated and stabilized in the modern yogurt system with forced homogenization, thereby developing a high-end dairy product that combines "traditional milk skin form" and "modern yogurt stability".

[0009] To achieve the above-mentioned purposes, the present application adopts the following technical solutions: On the one hand, the present application provides a high-milk-fat milk skin yogurt, which comprises the following raw material components in mass percentage: raw cow milk 60% to 80%, light cream 10% to 18%, condensed milk 1% to 5%, milk skin powder 0.5% to 3%, white granulated sugar 2% to 6%, and fermentation bacteria 0.01% to 0.05%, and the sum of the mass percentages of the above-mentioned raw material components is 100%.

[0010] Preferably, the milk skin powder is a powdered product prepared by enzymolysis, low-temperature drying and crushing of traditional Inner Mongolian milk skin; and the enzymolysis is a treatment of the milk skin with neutral protease and lipase at 45 to 50℃ for 30 to 60 minutes. This pretreatment can generate small molecular peptides and free fatty acids, which significantly improve the hydration dispersibility, emulsification and flavor precursor content.

[0011] Preferably, the fermentation bacteria comprise one or more of Streptococcus thermophilus, Lactobacillus bulgaricus, Bifidobacterium lactis and Lactobacillus acidophilus.

[0012] Further, the high-milk-fat milk skin yogurt further comprises gellan gum and sodium caseinate; the addition amount of the gellan gum is 0.01% to 0.03% of the total mass of the yogurt; and the addition amount of the sodium caseinate is 0.05% to 0.15% of the total mass of the yogurt. The gellan gum and the sodium caseinate synergistically act as the core of forming a stable and peelable milk skin layer.

[0013] In another aspect, the present application provides a preparation method of the high-milk-fat milk skin yoghurt, comprising the following steps: Step one: preparation of base milk slurry The raw cow milk accounting for 70% to 90% of the total mass is heated to 60 to 65°C, white granulated sugar and condensed milk are added, and high-speed stirring is performed until complete dissolution to form a base milk slurry; the base milk slurry is subjected to first homogenization, the homogenization pressure is 18 to 25 MPa, and the temperature is 60 to 65°C. By homogenization under high pressure of 18 to 25 MPa, the purpose is to establish a fine and stable protein network structure of the lower yoghurt matrix.

[0014] Step two: addition of milk skin components and second homogenization The remaining raw cow milk is mixed with milk skin powder, gellan gum and sodium caseinate, and stirring is performed until complete dispersion to prepare a milk skin suspension; the milk skin suspension is mixed with the base milk slurry obtained in step one, uniform stirring is performed, and then second homogenization is performed to obtain a mixed emulsion, the homogenization pressure is 5 to 10 MPa, and the temperature is 60 to 65°C; the purpose of this step is to uniformly disperse the milk skin components in the system while intentionally retaining a part of larger fat globule aggregates to provide power for subsequent floating.

[0015] Step three: sterilization and cooling The mixed emulsion obtained in step two is subjected to sterilization treatment, the sterilization condition is 90 to 95°C for 5 to 10 minutes; and then cooled to 36 to 38°C.

[0016] Step four: inoculation and filling The fermentation bacteria and light cream are added to the cooled milk slurry, uniform stirring is performed, and then filling is performed, the light cream is added at this time and does not participate in the previous homogenization, which further guarantees the sufficient source of floating fat.

[0017] Step five: floating and fermentation The filled product is placed at 36 to 38°C for fermentation for 8 to 12 hours, in this process, the milk skin components naturally float and form a milk skin layer on the product surface (the milk skin components naturally float to the product surface and concentrate to form a continuous solid milk skin layer while the fermentation gel network is formed), and the terminal fermentation acidity is 70 to 80°T; Step six: cooling and ripening after fermentation After the fermentation is completed, the product is cooled to 2 to 6°C, and ripening after fermentation is performed at this temperature for at least 12 hours.

[0018] Preferably, in step one, a composite stabilizer is further added to the base milk slurry, the composite stabilizer is composed of pectin and locust bean gum at a mass ratio of 1:1 to 2:1, and the addition amount is 0.1% to 0.5% of the total mass of the yoghurt. The composite stabilizer mainly acts on the lower yoghurt matrix to prevent whey separation, and complements the upper milk skin stable system.

[0019] Preferably, in step two, the second homogenization pressure is 7-9 MPa.

[0020] Preferably, in step five, the fermentation is divided into two stages: the first stage is carried out at 36-38℃ for 4-6 hours; when the acidity reaches 50-60°T, the second stage is carried out at 30-32℃ for 2-4 hours until the terminal acidity is reached. Two-stage fermentation is used to optimize the activity of the bacterial strain and the acidity.

[0021] Preferably, in step six, the cooling and ripening process is as follows: first, the product is cooled to 10-15℃ for 2-3 hours for flavor enhancement, and then rapidly cooled to 2-6℃ for storage.

[0022] In another aspect, the present application provides a high-milk-fat skin yogurt prepared by the above preparation method, and the final product of the high-milk-fat skin yogurt is characterized in that: a continuous solid skin layer with a thickness of 1.5-4.0 mm is formed on the top of the yogurt, and the dry matter content of the skin layer is ≥40%; the fat globule size D(4,3) of the lower layer of the yogurt is 0.5-2.0 μm, and the fat globule size D(4,3) of the skin layer is ≥5.0 μm, successfully realizing the directional aggregation and stratification of fat.

[0023] Compared with the prior art, the present application has the following advantages: (1) Successfully reproducing the traditional form and eating experience: through innovative formula design and two-step homogenization process, combined with specific fermentation conditions, the skin yogurt powder can naturally float up during fermentation, forming a continuous and dense solid skin layer on the top of the product, perfectly reproducing the core form of traditional skin yogurt and the unique ritual of "peeling and eating", with strong visual impact and high product recognition.

[0024] (2) Excellent product stability: by using a specific composite stabilizing system (gellan gum and sodium caseinate, and optionally pectin and locust bean gum), combined with step-by-step and step-pressure homogenization strategy, the contradiction between fat floating and whey separation is effectively solved. The first homogenization ensures the smoothness and stability of the base milk, and the second homogenization is carried out at a lower pressure, which ensures the moderate dispersion of the skin yogurt particles and their subsequent floating ability, and avoids excessive damage to the fat globule structure, finally realizing the stable formation of the upper skin layer and the uniformity and smoothness of the lower yogurt matrix without easy water separation.

[0025] (3) The flavor and nutritional value are improved: the use of enzyme-treated milk skin powder not only improves the solubility and dispersibility, but also pre-releases part of the flavor precursors and small molecule peptides and fatty acids that are easy to absorb during the enzyme treatment process, so that the final product has a stronger and more mellow milk skin flavor and is easier to be digested and absorbed by the human body. The process of phased fermentation and gradient cooling after-ripening helps to fully form and retain flavor substances, avoiding flavor attenuation.

[0026] (4) Suitable for industrial production: the preparation method provided by the present application has clear steps and clear parameters, and all processes can be realized on a conventional dairy production line, which has good operability and repeatability, and provides a reliable technical path for the modernization and large-scale production of traditional characteristic dairy products. DETAILED DESCRIPTION

[0027] The specific embodiments of the present application will be described below. Those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in the present specification. The described embodiments are only a part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application. Example 1: Basic formula and process

[0028] The present embodiment provides a high-fat milk skin yogurt, which comprises the following raw material components in mass percentage: 75% of raw cow milk, 12% of light cream, 3% of condensed milk, 1.5% of milk skin powder, 4% of white granulated sugar, 0.03% of fermentation bacteria (Streptococcus thermophilus: Lactobacillus bulgaricus = 1:1), 0.02% of gellan gum, and 0.1% of sodium caseinate The preparation steps of the high-fat milk skin yogurt in the present embodiment are as follows: Step one: 80% of raw cow milk is heated to 63℃, white granulated sugar and condensed milk are added, and high-speed stirring is performed to dissolve them, forming a basic milk slurry. The basic milk slurry is subjected to first homogenization at a pressure of 20 MPa and a temperature of 63℃.

[0029] Step two: the remaining 20% of raw cow milk is mixed with milk skin powder, gellan gum, and sodium caseinate, and stirred to disperse uniformly to prepare a milk skin suspension. The suspension is mixed with the basic milk slurry after first homogenization in step one, and then stirred uniformly to perform second homogenization to obtain a mixed emulsion, at a pressure of 8 MPa and a temperature of 63℃.

[0030] Step three: the mixed emulsion after second homogenization is sterilized at 93℃ for 8 minutes, and then cooled to 37℃.

[0031] Step four: add the fermentation bacteria and light cream, and stir uniformly before filling.

[0032] Step five: Incubate at 37℃ for 10 hours, and the final acidity is 75°T.

[0033] Step six: After fermentation, quickly cool to 4℃, and then post-ripen at 4℃ for 24 hours.

[0034] Example 2: High milk fat Pizi yogurt with composite stabilizer and two-stage fermentation This example provides a high milk fat Pizi yogurt, which is based on the raw material formula of Example 1, and additionally adds a composite stabilizer composed of pectin and locust bean gum (mass ratio 1.5:1), with an addition amount of 0.3%.

[0035] In the preparation steps of the high milk fat Pizi yogurt described in this example, steps one, two, three, four, and six are consistent with the preparation steps of Example 1, with the difference being in step five. The specific step five of this example is: the fermentation is divided into two stages. The first stage is incubated at 37℃ for 5 hours, and when the acidity reaches 55°T, the second stage is continued at 31℃ for 3 hours until the final acidity is 75°T.

[0036] Example 3: Optimization of cooling and post-ripening process This example provides a high milk fat Pizi yogurt, which has the same raw material formula as Example 2.

[0037] In the preparation steps of the high milk fat Pizi yogurt described in this example, steps one, two, three, four, and five are consistent with the preparation steps of Example 2. The difference is in step six. The specific step six of this example is: after fermentation, the product is first cooled to 12℃ and maintained for 2.5 hours for flavor enhancement, and then quickly cooled to 4℃ for storage. Key indicator measurement and comparative analysis:

[0038] 1. Key indicator measurement: The products prepared in Examples 1-3 were measured for key indicators, including milk skin layer thickness, milk skin layer continuity, lower layer yogurt fat globule D(4,3), milk skin layer fat globule D(4,3), whey separation rate, mouthfeel evaluation, and flavor intensity. The measurement results are shown in Table 1: Table 1 Comparison of key indicator data of products prepared in Examples 1-3

[0039] 2. Comparative analysis of key indicator data of products prepared in Examples 1-3 Table 1 compares the product performance of Example 1 (basic formula), Example 2 (addition of composite stabilizer and two-stage fermentation), and Example 3 (optimization of cooling and post-ripening process) in the following aspects: (1) Cream layer thickness and continuity: the cream layer thickness of Example 1 is 2.5 mm, and that of Examples 2 and 3 is increased to 3.0 mm and 3.2 mm, respectively, and the continuity is improved from "continuous" to "continuous and dense". This indicates that the addition of composite stabilizers (pectin and locust bean gum) and the two-stage fermentation process promote the floating and aggregation of cream, forming a thicker and denser cream layer. Optimizing the cooling maturation (Example 3) further strengthens the structure of the cream layer.

[0040] (2) Fat globule size: In the products of Examples 1-3, the fat globule size D(4,3) of the lower layer yogurt is in the range of 1.0-1.2 μm, indicating that the first homogenization (high pressure) ensures the fineness and stability of the matrix; the fat globule size D(4,3) of the cream layer is increased from 6.8 μm in Example 1 to ≥8.0 μm in Examples 2 and 3, demonstrating that the second homogenization (low pressure) retains larger fat globules, facilitating the formation of a cream layer by floating. The composite stabilizers and two-stage fermentation contribute to the directional aggregation of fat globules.

[0041] (3) Whey separation rate: the whey separation rate of Example 1 is 1.5%, which is reduced to 0.8% in Example 2 and further to 0.5% in Example 3. This indicates that the composite stabilizers enhance the water-holding capacity of the yogurt matrix, and the gradient cooling maturation reduces phase separation, significantly improving the stability of the product.

[0042] (4) Taste and flavor: the taste of Example 1 is "upper layer fragrant and mellow, lower layer fine", which is improved to "upper layer mellow, lower layer smooth" in Example 2 and "best flavor, balanced texture" in Example 3. The flavor intensity is increased from 8 points to 9 points, indicating that the two-stage fermentation and gradient cooling promote the generation and retention of flavor substances, avoiding flavor decay.

[0043] In summary, as shown in Table 1, Examples 2 and 3, by adding composite stabilizers, two-stage fermentation and optimizing cooling maturation, are superior to Example 1 in terms of cream layer thickness, continuity, stability and flavor, reflecting the enhancing effect of process optimization on product quality. Comparative Experiment 1: Comparison of key processes and formulations

[0044] To verify the key role of enzymatic cream powder, specific stabilizer system and two-step homogenization strategy on product quality.

[0045] Comparative Example 1: No enzymatic cream powder and conventional homogenization This comparative example provides a high-lactose cream yogurt, which has the same raw material formula as Example 1, but the cream powder is not enzymatically treated, but only simply pulverized traditional cream granules.

[0046] The preparation steps of the high-lactose cream yogurt in this comparative example are as follows: Preparation method: Step 1 : Heat all raw milk (75%) to 63°C, add white sugar, condensed milk, traditional milk skin crumb, gellan gum and sodium caseinate.

[0047] Step 2: Mix the materials at high speed to ensure that the milk skin crumb is as dispersed as possible. Then homogenize the mixed emulsion once, with a pressure of 20 MPa and a temperature of 63°C.

[0048] Step 3: Sterilize the mixed emulsion at 93°C for 8 minutes, then cool it to 37°C.

[0049] Step 4: Add the fermentation strain and whipping cream, mix well and then fill.

[0050] Step 5: Ferment at 37°C for 10 hours, with a final acidity of 75°T.

[0051] Step 6: After fermentation is complete, quickly cool to 4°C and post-ferment at 4°C for 24 hours.

[0052] Comparative Example 2: No specific stabilizer This comparative example provides a high-milk-fat milk skin yogurt, with the same raw material formula as Example 1, but without the addition of gellan gum and sodium caseinate.

[0053] The preparation steps of the high-milk-fat milk skin yogurt described in this comparative example differ from Example 1 in that, in Step 2, gellan gum and sodium caseinate are not added, and the remaining preparation steps are consistent with Example 1.

[0054] Comparative Example 3: Milk skin powder uniformly dispersed in the matrix (no floating skin) This comparative example provides a high-milk-fat milk skin yogurt, with the same raw material formula as Example 1.

[0055] The preparation steps of the high-milk-fat milk skin yogurt described in this comparative example differ from Example 1 in that Steps 1 and 2 are different. Specifically, in this comparative example, Step 1 and Step 2 are as follows: Step 1 : Take 80% of the raw milk and heat it to 63°C, then add white sugar and condensed milk and stir at high speed to dissolve, forming a basic milk slurry.

[0056] Step 2: Mix the remaining 20% of the raw milk with milk skin powder, gellan gum and sodium caseinate, and stir until evenly dispersed to obtain a milk skin suspension. Mix it with the basic milk slurry from Step 1, stir until uniform, and then homogenize to obtain a mixed emulsion, with a pressure of 25 MPa and a temperature of 63°C. The remaining steps are the same as in Example 1.

[0057] Key indicator measurement and comparative analysis: 1. Key indicators determination: The key indicators of the products prepared in Comparative Examples 1-3 were determined and compared with the corresponding key indicators of Example 1, including the thickness of the cream layer, the cream layer continuity, the fat globule size D(4,3) of the lower layer yogurt, the fat globule size D(4,3) of the cream layer, the whey separation rate, the mouthfeel evaluation, and the flavor intensity, and the results are shown in Table 2: Table 2: Key indicators of the products prepared in Example 1 and Comparative Examples 1-3

[0058] 2. Comparative analysis of the key indicators of the products prepared in Example 1 and Comparative Examples 1-3: Table 2 mainly compares the product performance of Example 1 with Comparative Example 1 (without enzyme-treated cream layer powder and conventional homogenization), Comparative Example 2 (without specific stabilizers), and Comparative Example 3 (cream layer powder uniformly dispersed in the base) from the following aspects: (1) Cream layer formation: Example 1 successfully formed a continuous cream layer (thickness 2.5 mm), while Comparative Example 1 only had an irregular flocculent layer (<0.5 mm), Comparative Example 2 had no cream layer, and Comparative Example 3 also had no cream layer. This indicates that enzyme treatment, specific stabilizers (gellan gum and sodium caseinate), and two-step homogenization are key to the formation of the cream layer. The high homogenization pressure (25 MPa) used in Comparative Example 3 destroyed the fat globule aggregation, resulting in the inability of the cream layer to float.

[0059] (2) Fat globule size: The fat globule size of the lower layer in Example 1 was 1.2 μm, and the cream layer was 6.8 μm; the fat globule size of the lower layer in Comparative Example 1 reached 3.5 μm, and the cream layer could not be measured, indicating that the enzyme-treated cream layer powder had poor dispersibility, resulting in a grainy sensation; the fat globule size of the lower layer in Comparative Example 2 was 2.8 μm, but there was no cream layer, indicating that the lack of stabilizers caused the fat to be unstable; the fat globule size of the lower layer in Comparative Example 3 was 0.8 μm, but there was no cream layer, proving that excessive homogenization inhibited the floating.

[0060] (3) Whey separation rate: Example 1 had a whey separation rate of only 1.5%, while Comparative Examples 1 and 2 had whey separation rates of 8.5% and 12.0%, respectively, indicating that products lacking enzyme treatment or stabilizers were prone to water separation. The whey separation rate of Comparative Example 3 was low (1.0%), but the cream layer characteristics were sacrificed, losing the core value of the product.

[0061] (4) Mouthfeel and flavor: Example 1 had a delicate mouthfeel and rich flavor (8 points), while Comparative Example 1 had a "strong grainy sensation and residue" and poor flavor (6 points), Comparative Example 2 had a "thin texture and easy to separate layers" and an average flavor (7 points), and Comparative Example 3 had "no cream layer sensation and a bland flavor" (5 points). Enzyme treatment improved the emulsification and flavor precursors of the cream layer powder, while stabilizers and homogenization strategies ensured a balanced texture.

[0062] In summary, it can be seen from Table 1 that enzymatic milk skin powder, a specific stabilizer system and a two-step homogenization process are indispensable, otherwise it will lead to the absence of milk skin layer, poor stability or deteriorated taste, which verifies the necessity of the present application. Comparative Experiment Two: Influence of Secondary Homogenization Pressure

[0063] The present comparative experiment is used to explore the key influence of the second homogenization pressure on the formation of the milk skin layer and the texture of the product. All the comparative examples are based on Example 1, only the second homogenization pressure is changed, and the rest of the raw material formula and process steps are consistent with Example 1.

[0064] Comparative Example 4a: Second Homogenization Pressure 3 MPa The present comparative example only adjusts the second homogenization pressure in step two of the preparation step to 3 MPa, and the rest of the raw material formula and preparation steps are the same as Example 1.

[0065] Comparative Example 4b: Second Homogenization Pressure 5 MPa The present comparative example only adjusts the second homogenization pressure in step two of the preparation step to 5 MPa, and the rest of the raw material formula and preparation steps are the same as Example 1.

[0066] Comparative Example 4c: Second Homogenization Pressure 12 MPa The present comparative example only adjusts the second homogenization pressure in step two of the preparation step to 12 MPa, and the rest of the raw material formula and preparation steps are the same as Example 1.

[0067] Comparative Example 4d: Second Homogenization Pressure 15 MPa The present comparative example only adjusts the second homogenization pressure in step two of the preparation step to 15 MPa, and the rest of the raw material formula and preparation steps are the same as Example 1.

[0068] Key Index Determination and Comparative Analysis: 1. Key Index Determination: Determine the key indexes of the products prepared in Comparative Examples 4a-4d and compare them with the corresponding key indexes of Example 1, including milk skin layer thickness, milk skin layer continuity, lower layer yogurt fat globule D(4,3), milk skin layer fat globule D(4,3), whey separation rate, taste evaluation, flavor intensity, and the results are shown in Table 3: Table 3: Key indexes of products prepared in Example 1 and Comparative Examples 4a-4d

[0069] 2. Comparative Analysis of Key Indexes of Products Prepared in Example 1 and Comparative Examples 4a-4d: Table 3 mainly compares the influence of different second homogenization pressures (3-15 MPa) on the product from the following aspects: (1) Cream layer thickness and continuity: Example 1 formed a continuous cream layer (2.5 mm) at 8 MPa. Comparative Examples 4a (3 MPa) and 4b (5 MPa) had thicker cream layers (5.2 mm and 4.0 mm), but were "severely layered" or "loose", indicating that too low pressure resulted in too large fat globules, excessive floating, and unstable structure; Comparative Examples 4c (12 MPa) and 4d (15 MPa) had thinner or discontinuous cream layers, or even no cream layer, indicating that too high pressure destroyed fat globule aggregation and inhibited floating.

[0070] (2) Fat globule size: Example 1 had 1.2 pm lower layer fat globules and 6.8 pm cream layer fat globules; Comparative Examples 4a and 4b had larger lower layer fat globules (2.5 pm and 1.8 pm) and cream layer fat globules > 10.0 pm and 9.5 pm, confirming that low pressure retained large fat globules but resulted in a coarse base; Comparative Examples 4c and 4d had smaller lower layer fat globules (0.9 pm and 0.8 pm), but no cream layer could be formed, indicating that high pressure over-homogenized.

[0071] (3) Whey separation rate: Example 1 was 1.5%, Comparative Examples 4a and 4b were higher (6.0% and 3.2%), as large fat globules easily separated water; Comparative Examples 4c and 4d were lower (1.8% and 1.5%), but had no cream layer, losing the product characteristics.

[0072] (4) Mouthfeel and flavor: Example 1 had a "upper layer fragrant and lower layer delicate" mouthfeel and an 8-point flavor; Comparative Examples 4a and 4b had a "greasy" or "coarse" mouthfeel and a poor flavor; Comparative Examples 4c and 4d had a "weak cream layer" or "no cream layer" and a flat flavor.

[0073] In summary, from Table 3, the second homogenization pressure significantly affected cream layer formation and product stability. Too low pressure (3-5 MPa) resulted in excessive floating and unstable texture; too high pressure (12-15 MPa) inhibited floating and lacked a cream layer. Example 1's 8 MPa was the optimal pressure, balancing floating and stability, and ensuring an ideal product structure.

[0074] In summary, through comparative analysis, the high-milk-fat cream layer yogurt and its preparation method of the present application solve the technical bottleneck through the following technical points: 1. Enzymolyzed cream layer powder: improves dispersibility and flavor, providing a basis for cream layer formation.

[0075] 2. Specific stabilizer system (gellan gum, sodium caseinate, and composite stabilizer): synergistic effect, stabilizing the cream layer and preventing whey separation.

[0076] 3. Two-step homogenization process: the first homogenization (high pressure) ensures a delicate base, and the second homogenization (low pressure, preferably 7-9 MPa) retains fat globule aggregation and promotes natural floating.

[0077] 4. Optimized fermentation and cooling: Two-stage fermentation and gradient cooling enhance flavor and texture.

[0078] Comparative experiments show that the absence of any one of the above steps will result in a failed product, while the optimized parameters (as in Examples 1-3) enable the unique structure of "upper layer of milk skin, lower layer of stability", combining traditional flavor and modern industrial stability.

[0079] Other details of the present application are well known to those skilled in the art.

[0080] It should be noted that the terms "comprising", "including", or any other variant thereof, are intended to cover non-exclusive inclusions, such that processes, methods, articles, or devices that comprise a list of elements not only include those elements, but also include other elements not expressly listed, or inherent to such processes, methods, articles, or devices.

[0081] The scope of protection of the present application is not limited to the technical solutions disclosed in the specific embodiments, and any modifications, equivalent replacements, improvements, etc. made according to the technical essence of the present application to the above embodiments all fall within the scope of protection of the present application.

Claims

1. A high-fat milk skin yogurt, characterized in that, The raw material components include the following percentages by weight: 60%–80% raw milk, 10%–18% light cream, 1%–5% condensed milk, 0.5%–3% milk skin powder, 2%–6% white sugar, and 0.01%–0.05% fermentation starter. The sum of the percentages of the above raw material components is 100%.

2. The high-fat milk skin yogurt according to claim 1, characterized in that: The milk skin powder is a powdered product obtained by enzymatic hydrolysis, low-temperature drying, and pulverization of traditional Inner Mongolian milk skin; the enzymatic hydrolysis is performed by treating the milk skin with neutral protease and lipase at 45-50℃ for 30-60 minutes.

3. The high-fat milk skin yogurt according to claim 1, characterized in that: The fermentation strains include one or more of Streptococcus thermophilus, Lactobacillus bulgaricus, Bifidobacterium lactis, and Lactobacillus acidophilus.

4. The high-fat milk skin yogurt according to any one of claims 1-3, characterized in that: include: Gellan gum and sodium caseinate; the amount of gellan gum added is 0.01% to 0.03% of the total mass of yogurt; the amount of sodium caseinate added is 0.05% to 0.15% of the total mass of yogurt.

5. A method for preparing high-fat milk skin yogurt as described in claim 4, characterized in that, Includes the following steps: Step 1: Preparation of the basic emulsion 70%–90% of the total mass of raw milk is heated to 60–65°C, and white sugar and condensed milk are added. The mixture is stirred at high speed until completely dissolved to form a basic milk paste. The basic milk paste is then subjected to a first homogenization at a pressure of 18–25 MPa and a temperature of 60–65°C. Step 2: Add milk skin components and homogenize twice. The remaining raw milk is mixed with milk skin powder, gellan gum and sodium caseinate, and stirred until completely dispersed to obtain a milk skin suspension; the milk skin suspension is mixed with the basic emulsion obtained in step one, stirred evenly, and then subjected to a second homogenization to obtain a mixed emulsion. The homogenization pressure is 5-10 MPa and the temperature is 60-65℃. Step 3: Sterilization and Cooling The mixed emulsion obtained in step two is sterilized at 90–95°C for 5–10 minutes, and then cooled to 36–38°C. Step 4: Inoculation and Filling Add the starter culture and heavy cream to the cooled milk mixture, stir well, and then divide into portions; Step 5: Floating and Fermentation After being packaged, the product is left to ferment at 36-38°C for 8-12 hours. During this process, the milk skin component naturally floats to the surface and forms a milk skin layer on the product. The fermentation is terminated at an acidity of 70-80°T. Step Six: Cool and Cook After fermentation, cool the product to 2-6°C and refrigerate it at this temperature for at least 12 hours for post-fermentation.

6. The preparation method according to claim 5, characterized in that: In step one, the base emulsion contains A compound stabilizer was also added, which consisted of pectin and locust bean gum in a mass ratio of 1:1 to 2:1, and its addition amount was 0.1% to 0.5% of the total mass of the yogurt.

7. The preparation method according to claim 5, characterized in that: In step two, the pressure of the second homogenizer is 7-9 MPa.

8. The preparation method according to claim 5, characterized in that: In step five, the fermentation is divided into two stages: the first stage is fermentation at 36-38°C for 4-6 hours; when the acidity reaches 50-60°T, the second stage is started at 30-32°C for 2-4 hours until the acidity is terminated.

9. The preparation method according to claim 5, characterized in that: In step six, the cooling and ripening process specifically involves: first cooling the product to 10-15°C, maintaining it for 2-3 hours to enhance the flavor, and then rapidly cooling it to 2-6°C for storage.

10. A high-fat milk skin yogurt prepared by the method of claim 5, characterized in that: The yogurt has a continuous solid milk skin layer with a thickness of 1.5 to 4.0 mm on top, and the dry matter content of the milk skin layer is ≥40%; the fat globule particle size D(4,3) of the lower layer of the yogurt is 0.5 to 2.0 μm, and the fat globule particle size D(4,3) of the milk skin layer is ≥5.0 μm.

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