Industrialized double-skin milk pre-skinning stage-by-stage and finished product preparation method and system

Abstract

The application discloses an industrial double-skin milk pre-skin stage temperature control and finished product preparation method and system, which can form double-skin milk skin with uniform thickness and excellent texture by accurately controlling heating temperature and time in stages, improve the consistency of product quality, meet the requirements of consumers on the taste and flavor of traditional double-skin milk, make the complete rate of milk skin after reheating greater than or equal to 97%, the difference between the taste and traditional fresh milk less than or equal to 10%, and the storage time long. The whole preparation process realizes automatic continuous production, reduces manual intervention, improves production efficiency, and can meet the needs of industrial large-scale production. The heating and cooling processes are reasonably designed, and suitable heating and cooling modes are adopted, so that the energy consumption is effectively reduced, and the production cost is reduced.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology, and in particular relates to a pre-skinning stage, finished product preparation method and system for industrial double-skin milk. Background Technology

[0002] Double-skin milk pudding, a popular traditional dessert, is beloved by consumers for its delicate texture and unique flavor. Traditionally, its production relies heavily on manual experience, ensuring high quality in small-batch handmade production. However, with increasing market demand, industrial production of double-skin milk pudding has become an inevitable trend.

[0003] Traditional double-skin milk pudding production relies on manual experience and has the following drawbacks: difficulty in standardizing the process: the milk boiling temperature and skin formation time depend on manual judgment, resulting in large quality fluctuations (the standard deviation of milk skin thickness reaches ±0.2mm); low production efficiency: a single production takes more than 40 minutes, which cannot meet the needs of industrialization; short shelf life: freshly made products need to be consumed immediately, and the refrigerated shelf life is less than 48 hours; poor end-user experience: after reheating, the milk skin is easily damaged and separated, losing the traditional characteristics of "sweet and fragrant on top and tender and smooth on the bottom".

[0004] While existing industrial technologies simplify the process through additives or high-temperature sterilization, they compromise the core texture and structure of double-skin milk pudding. The formation of the pre-skin is a crucial step in the industrial production of double-skin milk pudding. Traditional industrial methods struggle to precisely control the skin-forming process, resulting in uneven skin thickness and inconsistent quality. Common problems include excessively thick skin affecting the texture, or excessively thin skin that is easily damaged during subsequent processing, failing to meet the quality standards of traditional double-skin milk pudding. Furthermore, existing preparation methods are energy-intensive and inefficient, making them unsuitable for large-scale industrial production. Summary of the Invention

[0005] The purpose of this invention is to provide a pre-skin formation stage, finished product preparation method and system for industrial double-skin milk, which can precisely control the pre-skin formation process, making the double-skin milk skin uniform in thickness and stable in quality, while improving production efficiency, reducing energy consumption, and meeting the needs of large-scale industrial production.

[0006] To solve the above-mentioned technical problems, the specific technical solution of the present invention is as follows:

[0007] In some embodiments of this application, a pre-skinning stage, finished product preparation method and system for industrial double-skin milk is provided, including the following steps: 1) Raw material preparation: Fresh milk is filtered and homogenized to remove impurities and disperse fat globules evenly. Appropriate amounts of white sugar and egg white liquid are added and stirred until completely dissolved. The mixture is then passed through an 80-mesh sieve to remove the egg white fascia and degassed under vacuum (-0.08 MPa, 10 minutes) to obtain mixture A.

[0008] 2) Temperature control for pre-formed milk skin can be achieved in two ways: a stepped intelligent temperature control line or a segmented hot air circulation tunnel.

[0009] a. Pass the mixture A through the heat exchange zone of the pasteurizer, raising it from 4°C to 75°C within 25 seconds and holding it at that temperature for 15 seconds;

[0010] b. Pour mixture A into a food-grade PP bowl (or other food container), and circulate hot air at 85-90℃ for 5-8 minutes (simulating the traditional milk boiling process).

[0011] 3) Transfer to a constant temperature resting area of ​​40-45℃ to enter the constant temperature resting stage (40-45℃ closed environment, 70% humidity) to promote the uniform coagulation of milk skin (20-30 minutes) and form the first layer of milk skin;

[0012] 4) Transfer the product to the rapid cooling zone, where it is quickly cooled by 2-4℃ cold air to lock in the milk skin structure (10 minutes). This allows for the cold chain storage and transportation of semi-finished products with pre-formed milk skin.

[0013] 5) During the final stage of reheating, the egg and milk liquid in the container is directly heated. The heat convection penetrates the pre-formed milk skin to form a secondary skin and solidifies the mixture A to form the final product.

[0014] In some embodiments of this application, a method for preparing a direct finished product of industrial double-skin milk is characterized by comprising the following steps:

[0015] 1) Raw material preparation: Filter and homogenize fresh milk to remove impurities and disperse fat globules evenly. Add appropriate amount of white sugar and egg white liquid, stir until completely dissolved, pass through an 80-mesh sieve to remove egg white fascia, and degas under vacuum (-0.08MPa, 10 minutes) to obtain mixture A;

[0016] 2) Temperature control for pre-formed milk skin can be achieved in two ways: a stepped intelligent temperature control line or a segmented hot air circulation tunnel.

[0017] a. Pass the mixture A through the heat exchange zone of the pasteurizer, raising it from 4°C to 75°C within 25 seconds and holding it at that temperature for 15 seconds;

[0018] b. Pour mixture A into a food-grade PP bowl (or other food container), and circulate hot air at 85-90℃ for 5-8 minutes (simulating the traditional milk boiling process).

[0019] 3) Transfer to a constant temperature resting area of ​​40-45℃ to enter the constant temperature resting stage (40-45℃ closed environment, 70% humidity) to promote the uniform coagulation of milk skin (20-30 minutes) and form the first layer of milk skin;

[0020] 4) Transfer the product to the rapid cooling zone, where it is quickly cooled by 2-4℃ cold air to lock in the milk skin structure (10 minutes). This allows for the cold chain storage and transportation of semi-finished products with pre-formed milk skin.

[0021] 5) During the “terminal reheating” or “consumer reheating” stage, the egg and milk liquid in the container is directly heated. The heat convection penetrates the pre-formed milk skin to form a secondary skin and solidifies the mixture A to form the final product.

[0022] 6) Factory-side secondary coagulation of finished products: The semi-finished products are heated by steam at 85-90℃ or by water bath for 10-35 minutes. The bottom layer of milk coagulates to form a second layer structure. After final sterilization (UHT / HPP / pasteurization), the finished products can be stored at 0-8℃ for 21 days or at room temperature for 30 days.

[0023] In some embodiments of this application, the milk content is 75-85%, the egg white content is 10-20%, and the white sugar content is 5-15%.

[0024] In some embodiments of this application, terminal sterilization is performed using HPP treatment at a pressure of 500-600 MPa for 2-4 minutes.

[0025] In some embodiments of this application, the residual oxygen content in the packaging is ≤0.5%, and 0.1-0.3 g / kg of ε-polylysine is added.

[0026] In some embodiments of this application, a dual-mode production system employs the above-described preparation method, comprising:

[0027] Pre-skinning module: high-speed mixer, vacuum degassing tank, 80-mesh vibrating screen, hot air tunnel, constant temperature settling cabinet;

[0028] Semi-finished modules: quick-freezing machine, cold chain storage and transportation unit

[0029] Filling module: Adapted to aseptic filling lines for semi-finished and finished products.

[0030] Finished product sterilization module: compatible with HPP / UHT / pasteurization sterilization equipment

[0031] Compared with existing technologies, the advantages of this invention lie in its ability to precisely control the heating temperature and time in stages, thereby forming a uniformly thick and high-quality double-skin milk pudding skin. This improves product quality consistency, meets consumer demands for the traditional taste and flavor of double-skin milk pudding, ensures a milk skin integrity rate of ≥97% after reheating, a taste difference of ≤10% compared to traditional freshly made milk pudding, and a longer shelf life. The entire preparation process is automated and continuous, reducing manual intervention and improving production efficiency, meeting the needs of large-scale industrial production. The rational design of the heating and cooling processes, employing appropriate heating and cooling methods, effectively reduces energy consumption and production costs. Detailed Implementation

[0032] The specific embodiments of the present invention will be described in further detail below with reference to the examples. These examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0033] To better understand the purpose, structure, and function of this invention, the invention will be further described in detail below with reference to embodiments.

[0034] Example 1

[0035] Semi-finished product business (central kitchen collaborative model)

[0036] Pre-skinning stage: Egg and milk mixture ratio: milk (preferably buffalo milk with high fat content) 75-85%, egg white liquid (10-20%), white sugar (5-10%);

[0037] Pre-skinning initial heating process: Inject the mixture into a high-temperature resistant PP container and heat with hot air circulation at 85±2℃ for 5-8 minutes;

[0038] Constant temperature skin formation: Transfer to a constant temperature and static area of ​​40±3℃ (humidity 70-80%) to form the first layer of milk skin (thickness 0.3-0.5mm);

[0039] Cooling and shaping: Rapid cooling zone, 2-4℃ cold air for rapid cooling, to lock in the milk skin structure (10 minutes);

[0040] Quick-freezing storage and transportation: After the container is sealed, it is stored and transported at a low temperature of 2-4℃ or quick-frozen in liquid nitrogen (-35℃) for shaping, and then stored and transported at -18℃.

[0041] Store reheating: Remove the sealing film, heat with steam at 90±5℃ for 8-15 minutes, the bottom milk liquid will boil slightly and penetrate the milk skin to form a secondary skin, and the bottom egg and milk liquid will solidify.

[0042] Example 2

[0043] Finished product business (full-process factory production model)

[0044] Egg and milk liquid ratio: same as semi-finished product business format;

[0045] Pre-skin formation stage heating process and constant temperature setting: The egg and milk liquid is passed through the heat exchange zone of the pasteurizer, heated from 4℃ to 75℃ within 25 seconds and held at that temperature for 15 seconds. The egg and milk liquid is then poured into a food-grade PP bowl (or other food container) and transferred to a constant temperature standing zone of 40±3℃ (humidity 70-80%) to form the first layer of milk skin (thickness 0.3-0.5mm).

[0046] Secondary coagulation: Heating with steam at 90±5℃ for 15-25 minutes, the bottom layer of milk coagulates to form a second layer structure.

[0047] Sterilization process:

[0048] Refrigerated version: After pasteurization (85℃ / 15 seconds), immediately cool to 4℃;

[0049] Room temperature version: Ultra-high temperature sterilization (UHT, 138℃ / 2 seconds) or ultra-high pressure sterilization (HPP, 600MPa / 3 minutes).

[0050] Aseptic filling: nitrogen-filled sealing.

[0051] Example 3 (Semi-finished product business)

[0052] Ingredient ratio: 800g buffalo milk, 150g egg white liquid (18.75%), 80g white sugar;

[0053] Pre-skinning parameters: 85℃ hot air for 6 minutes → 40℃ standing for 25 minutes → liquid nitrogen quick-freezing for 10 minutes;

[0054] Store reheating: 90℃ steam for 10 minutes, milk skin thickness 0.42mm (CV=3.8%), integrity rate 97.2%.

[0055] Example 4 (Finished Product Format - Refrigerated Version):

[0056] Ingredient ratio: 820g buffalo milk, 160g egg white liquid (19.5%), 85g white sugar;

[0057] Sterilization process: pasteurization (85℃ / 15 seconds) + modified atmosphere packaging (CO2 30%);

[0058] Shelf life: 21 days when stored at 0-8℃, total bacterial count ≤500 CFU / g;

[0059] Taste evaluation: 95% satisfaction rate in blind tests, milk fat oxidation value (AV) ≤ 0.3 mg / g.

[0060] Example 5 (Finished Product Format - Room Temperature Version):

[0061] Egg liquid ratio: 830g milk, 130g egg white liquid (accounting for 12.4%), 90g white sugar;

[0062] Pre-skinning parameters: 85℃ hot air for 6 minutes → 40℃ standing for 25 minutes

[0063] Secondary coagulation: The bottom layer of egg and milk mixture is steamed at 90±5℃ for 20 minutes to coagulate.

[0064] Sterilization process: HPP sterilization (600MPa / 3 minutes) + nitrogen packaging;

[0065] Shelf life: 30 days at room temperature, commercially sterile (pathogenic bacteria not detected).

[0066] Example 6

[0067] Preparation method

[0068] Raw material pretreatment: Fresh milk is filtered and homogenized to remove impurities and evenly disperse fat globules, ensuring product quality stability. Then, according to the formula ratio, an appropriate amount of egg white liquid and granulated sugar are added and stirred until completely dissolved. The mixture is then sieved through an 80-mesh sieve to remove the gluten.

[0069] Pre-skinning stage: The pretreated egg and milk mixture is pumped into the pre-skinning reactor. The jacketed circulating heating system is turned on, and the milk temperature is raised to 75°C at a heating rate of 10°C / min. This temperature is maintained for 2 minutes, and then the mixture is poured into food-grade heat-resistant PP bowls or other food-grade heat-resistant containers while still hot. The containers containing the egg and milk mixture are then transferred to a constant temperature and humidity settling zone at 40-45°C and 70% humidity. During this settling process, milk fat globules rise and coagulate, beginning to form a preliminary milk skin. The formation of the milk skin can be monitored in real time by a high-definition camera, and the image data is transmitted to the control system.

[0070] Milk skin cooling and setting stage: Transfer the product to the rapid cooling zone, where it is quickly cooled by 2-4℃ cold air to lock in the milk skin structure (10 minutes).

[0071] Secondary heating stage: After the milk skin has initially formed, the secondary temperature-controlled heating stage begins. Using steam or a water bath, the temperature of the egg and milk mixture is raised to 90℃ at a rate of 10-15℃ / min and maintained for 8-10 minutes, further solidifying the milk skin and initially cooking the milk inside. In the second stage, the temperature is lowered to 80±3℃ at a rate of 10-15℃ / min and maintained for 5-10 minutes to completely cook the milk, while ensuring the milk skin remains intact and has a delicate texture. The temperature, heating / cooling rates, and time parameters for each stage are precisely controlled by the control system according to a preset program.

[0072] Packaging and Cooling: After maturation, the double-skin milk is transported through pipelines to an aseptic packaging machine for nitrogen-filled packaging. After final sterilization (UHT / HPP / pasteurization), the finished product can be refrigerated at 0-8℃ for 21 days or stored at room temperature for 30 days.

[0073] Example 7

[0074] Hot Air Tunnel: The pre-treated egg and milk liquid is filled into food-grade heat-resistant PP bowls or other food-grade heat-resistant containers, and then conveyed into an 85-90℃ circulating hot air tunnel. Infrared thermometers monitor the temperature of the egg and milk liquid in real time, maintaining it at 75±1℃ for 20-30 seconds. The circulating hot air tunnel is made of stainless steel, offering excellent thermal conductivity and corrosion resistance. A jacketed circulating heating system allows for precise control of the heating temperature; a high-definition camera is installed at the top to monitor the formation of the milk skin.

[0075] The constant temperature settling cabinet cools the heated egg and milk mixture, thus keeping the milk in a constant temperature and humidity environment to allow the milk skin to form initially.

[0076] Temperature control system: Composed of temperature sensors, controller, and actuators. The temperature sensors collect milk temperature data in real time and transmit it to the controller; the controller controls the opening and closing of actuators (such as heating valves and cooling valves) according to the preset temperature curve and process parameters, thereby achieving precise control of the heating and cooling process.

[0077] Packaging and cooling equipment: Aseptic nitrogen-filled packaging machine ensures that double-skin milk is packaged under aseptic conditions; liquid nitrogen quick-freezing machine quickly freezes finished and semi-finished products through rapid cooling.

[0078] Central control system: Integrates monitoring data, temperature control data, and operating data from filling and cooling equipment. Operators can monitor the production process in real time through a human-machine interface and adjust various parameters. Simultaneously, the system has data storage capabilities, recording production data for each batch of double-skin milk pudding, facilitating quality traceability and process optimization.

[0079] In the description of this application, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the embodiments. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0080] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0081] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0082] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0083] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method and system for staged temperature-controlled preparation of pre-formed milk skin for industrial double-skin milk, characterized in that, To meet different needs and environments: a. Semi-finished products: Reheated in 5 minutes for end users or consumers, with a milk skin integrity rate of ≥95%; b. Finished products: Full-process production at the factory level, supporting refrigeration at 0-8℃ for 21 days (total bacterial count ≤10). 4 (CFU / g) or store at room temperature for 30 days (commercially sterile); Includes the following steps: 1) Raw material preparation: Filter and homogenize fresh milk to remove impurities and disperse fat globules evenly. Add appropriate amount of white sugar and egg white liquid, stir until completely dissolved, pass through an 80-mesh sieve to remove egg white fascia, and vacuum degas at -0.08MPa for 10 minutes to obtain mixture A. 2) Temperature control for pre-formed milk skin can be achieved in two ways: a stepped intelligent temperature control line or a segmented hot air circulation tunnel. a. Pass the mixture A through the heat exchange zone of the pasteurizer, raising it from 4°C to 75°C within 25 seconds and holding it at that temperature for 15 seconds; b. Pour mixture A into a food-grade PP bowl and circulate hot air at 85-90℃ for 5-8 minutes to simulate the traditional milk boiling process. 3) Transfer to a constant temperature resting area of ​​40-45℃, and enter the constant temperature resting stage. The environment is closed at 40-45℃ with 70% humidity to promote the uniform coagulation of the milk skin for 20-30 minutes to form the first layer of milk skin. 4) Transfer the product to the rapid cooling zone, where it is quickly cooled by 2-4℃ cold air to lock in the milk skin structure for 10 minutes. This allows for the cold chain storage and transportation of semi-finished products with pre-formed milk skin. 5) During the "terminal reheating" or "consumer reheating" stage, the egg and milk liquid in the container is directly heated. The heat convection penetrates the pre-formed milk skin to form a secondary skin and causes the bottom mixture A to solidify, forming the final product. 6) "Factory-side" secondary coagulation finished product: The semi-finished product is heated by steam at 85-90℃ or by water bath for 10-35 minutes. The bottom layer of milk coagulates to form a second layer structure. After final sterilization, the finished product can be refrigerated at 0-8℃ for 21 days or stored at room temperature for 30 days. Sterilization process: Refrigerated version: Pasteurize at 85°C for 15 seconds, then immediately cool to 4°C; Room temperature version: Ultra-high temperature sterilization (UHT), 138℃ / 2 seconds or ultra-high pressure sterilization (HPP), 600MPa / 3 minutes.

2. The pre-skin formation stage, finished product preparation method and system for industrialized double-skin milk according to claim 1, characterized in that, Milk 75-85%, egg white liquid 10-20%, white sugar 5-15%.

3. The method for preparing industrial-grade double-skin milk pudding directly according to claim 1, characterized in that, Milk 75-85%, egg white liquid 10-20%, white sugar 5-15%.

4. The method for preparing industrial-grade double-skin milk pudding directly according to claim 1, characterized in that, Final sterilization is performed using HPP treatment at a pressure of 500-600 MPa for 2-4 minutes.

5. The method for preparing industrial-grade double-skin milk pudding directly according to claim 1, characterized in that, The residual oxygen content in the packaging is ≤0.5%, and 0.1-0.3g / kg of ε-polylysine is added.

6. A dual-mode production system, using any of the preparation methods described in claims 1-6, characterized in that, include: Pre-skinning module: high-speed mixer, vacuum degassing tank, 80-mesh vibrating screen, hot air tunnel, constant temperature settling cabinet; Semi-finished modules: quick-freezing machine, cold chain storage and transportation unit Filling module: Adapted to aseptic filling lines for semi-finished and finished products. Finished product sterilization module: compatible with HPP / UHT / pasteurization sterilization equipment.