A hollow three-dimensional freeze-dried milk snack preparation device based on double nozzles and application thereof

Abstract

The present application relates to a kind of based on double nozzle's hollow three-dimensional freeze-dried milk snack preparation device and its application, belong to food processing and equipment manufacturing technical field.The device of the present application mainly includes food material printing system, structure support system, gas supply system, quick freezing system, microwave freeze-drying system, conveying system and control system.The present application is while using solid particle adjuvant to fill the gap inside and outside model, provides structural support for printing product, through quick freezing mode solidification printing product structure, through microwave freeze-drying quick dehydration method retains printing product structure and quality.The present application adopts double nozzle 3D printing and adjuvant filling support technology synergic quick freezing and microwave freeze-drying technology, solve the special modeling 3D printing food easy collapse, low efficiency and its dry product hardness, long rehydration time and other problems, widen 3D printing food application range, provide technical support for special modeling and easy swallow milk snack development.

Description

Technical Field

[0001] This invention belongs to the field of food processing and equipment manufacturing technology, specifically relating to a hollow three-dimensional freeze-dried milk snack preparation device based on dual nozzles and its application. Background Technology

[0002] Dairy snacks refer to snacks made primarily from cow's milk, goat's milk, soy milk, etc., through processing methods such as drying, baking, frying, and quick-freezing. With people's increasing pursuit of nutritious, healthy, leisurely, and novel-shaped delicacies, dairy snacks have gradually become popular products in the market. Currently, although there are many varieties of dairy snack products, they suffer from problems such as simple product structure, poor quality, poor taste, and short shelf life. 3D printing technology possesses powerful capabilities for personalized food manufacturing and strong support for design innovation, capable of meeting the needs of large-scale personalized food customization, revolutionizing traditional food processing methods, and has become a key research direction for high-quality development in the food industry. 3D printing technology has already seen practical applications in designing personalized foods. Countries such as China, the United States, Germany, and Spain have developed aesthetically pleasing foods based on shapes like pastries, biscuits, chocolates, candies, pizzas, and pasta, as well as healthy foods that meet the nutritional needs of special groups such as the elderly, children, athletes, and astronauts. However, due to the inherently weak structural support of the printed ingredients, the products are prone to collapse and the efficiency is low during the 3D printing process. Although improving the gel properties of the printed ingredients can improve the accuracy of the printed products, it still cannot achieve precise printing of specially shaped foods. Moreover, highly gelatinous printed foods have a poor taste after drying, failing to meet consumer demands for dairy snacks. Therefore, structural support has become a technical bottleneck in food 3D printing. Freeze-drying technology can maximize the preservation of food structure and nutritional quality, making it an important means of high-quality food processing. However, traditional freeze-drying technology suffers from long drying cycles and high costs. Microwave freeze-drying, which can significantly shorten drying time and reduce costs, has become a hot research topic in freeze-drying technology. Therefore, combining dual-nozzle filling auxiliary material structural support 3D printing technology with microwave freeze-drying technology can effectively solve the technical bottleneck in processing specially shaped dairy snacks.

[0003] Guo Danjun et al. (Application No.: CN202111101422.4) disclosed a 3D food printing method using coaxial nozzles to insert artificial muscle fibers. This patent can form a dense structure similar to muscle fibers, improving the taste and texture of 3D printed meat and facilitating the production of meat substitutes of various textures. The difference in this patent lies in the use of a dual-nozzle filling structure support technology, which improves the structural support of specially shaped 3D printed food and enables the development of specially shaped dairy snacks.

[0004] Su Xin et al. (Application No.: CN202320699533.8) disclosed a coaxial dual-nozzle 3D food printer. This patent can simultaneously print composite food structures containing two different materials, improving printing efficiency and accuracy. However, it lacks structural support and cannot print specially shaped foods. This patent differs in that it employs a dual-nozzle filling structural support technology, improving the structural support of specially shaped 3D printed foods.

[0005] Feng Guotong et al. (Application No.: CN202223189167.6) disclosed a microwave freeze-drying apparatus. This apparatus includes a vacuum chamber, a vacuum extraction device, a freezing device, a microwave heating device, a storage device, and a drive mechanism. During the material freezing process, the storage device is driven to rotate. The difference in this patent lies in the integrated design of the freezing chamber and freeze-drying chamber. The freezing / freeze-drying chamber door is located at the bottom, and a hoist is used for material entry and exit. Liquid nitrogen is used to freeze the material, resulting in high freezing efficiency. The freezing and microwave freeze-drying processes are conducted in a static state, maintaining the structural integrity of the material.

[0006] Haskell Noah (application number: CN202180082387.8) discloses a method for preparing freeze-dried yogurt block snack products. This patent includes steps such as forming a mixed frozen yogurt mixture, filling molds with a filling machine, demolding with a demolding machine, freeze-drying, and bagging. The difference in this patent lies in the synergy between a dual-nozzle filling structure support technology and microwave freeze-drying technology to develop specially shaped, casual freeze-dried yogurt block products, with a short freeze-drying time and low cost.

[0007] Zhang Min et al. (Application No.: CN201911002892.8) disclosed a highly efficient and high-quality method for preparing kale-flavored vegetable melt-in-your-mouth snacks. This patent uses kale and yogurt as the main raw materials, and cassava pregelatinized starch slurry, whey protein powder, skim milk powder, xylitol, and citric acid as auxiliary materials, to prepare melt-in-your-mouth snacks through a combination of infrared freeze-drying and microwave vacuum drying. The difference in this patent lies in the synergy between a dual-nozzle filling structure support technology and microwave freeze-drying technology to develop specially shaped freeze-dried snack products, with a short freeze-drying time and low cost.

[0008] Wang Shaoyun et al. (Application No.: 202310374141.9) disclosed a method for preparing composite fish paste 3D printing ink and its application. The composite fish paste described in that patent, after 3D printing and repeated freeze-thaw cycles, is not prone to collapse and exhibits good stability; however, this patent is applicable to the preparation of frozen 3D printed products. The difference in this patent lies in the use of a dual-nozzle filling structure support technology to improve the structural support of specially shaped 3D printed food products, enabling the development of specially shaped dairy snacks.

[0009] Lü Fei et al. (application number: 202211067553.X) disclosed a method for preparing a 3D food printing material of potato puree as a protein-polysaccharide mixed gel. This patent uses fresh potato puree as raw material and improves the mechanical strength after 3D printing by adding hydrocolloids (carrageenan, gelatin), enabling the printing of complex shapes. However, the printed products have a short shelf life and are only suitable for fresh consumption. This patent differs in that it uses a dual-nozzle filling structure support technology combined with microwave freeze-drying technology to develop specially shaped dairy snacks, extending the shelf life of printed food.

[0010] Li Guojie et al. (application number: 202210612189.4) disclosed a multi-nutritional black rice and goat milk puzzle biscuit made using 3D printing technology and its preparation method. This patent uses rice flour and black rice flour as the main raw materials, and goat milk, walnuts, honey, etc. as auxiliary raw materials, to produce puzzle biscuits using 3D food printing. However, this patent cannot develop specially shaped food products. The difference with this patent lies in the synergy between a dual-nozzle filling structure support technology and microwave freeze-drying technology, enabling the development of specially shaped dairy snacks.

[0011] In summary, existing 3D printing technology is suitable for printing solid models, but the printed products have a short shelf life and are mainly suitable for fresh consumption. For special-shaped models with few support points (hollowed-out, suspended, extended, twisted, or tilted models), the printing process is prone to collapse, a problem that has not yet been solved, thus limiting the application of 3D printed food. The dual-nozzle 3D printing and microwave freeze-drying synergistic technology provided by this invention overcomes this technical deficiency. Currently, there are no reports on dual-nozzle 3D printing and microwave freeze-drying synergistic technology and equipment both domestically and internationally. Summary of the Invention

[0012] The purpose of this invention is to overcome the shortcomings of the prior art by providing a hollow three-dimensional freeze-dried milk snack preparation device based on dual nozzles and its application. The dual nozzles fill the gaps inside and outside the model with auxiliary materials while printing the model, thereby improving the support of the product in the 3D printing process. The printed food shape is further solidified by rapid freezing in the later stage, and the filling auxiliary materials are removed by microwave freeze drying.

[0013] The technical solution of the present invention: A hollow, three-dimensional freeze-dried milk snack preparation device based on dual nozzles mainly includes: a food ingredient printing system, a structural support system, a gas supply system, a rapid freezing system, a microwave freeze-drying system, a conveying system, and a control system. The food ingredient printing system mainly includes a printing platform 2, a material tray 3, and a food ingredient extruder 5. The structural support system mainly includes an auxiliary material extruder 6 for loading structural support auxiliary materials. The gas supply system mainly includes: a two-position three-way valve 9, a solenoid valve 10, a throttle valve 11, a pressure regulating valve 12, and a nitrogen storage tank 13. The rapid freezing system mainly includes an atomizing nozzle 17 and a throttle valve 11. Liquid nitrogen storage tank 18; the microwave freeze-drying system mainly includes a freeze-drying chamber 14, a water trap 19, a vacuum pump 20, a refrigerator 21, and a microwave source 22; the conveying system mainly includes a conveying cylinder 1; the control system mainly includes a control cabinet 23; the food printing system and the structural support system are connected through a food extruder 5 and an auxiliary material extruder 6; the gas supply system is connected to the structural support system through the auxiliary material extruder 6; the rapid freezing system is connected to the microwave freeze-drying system through the freeze-drying chamber 14; the food printing system and the structural support system are connected to the rapid freezing system and the microwave freeze-drying system through the conveying system.

[0014] The printing platform 2 is installed in the Z-axis direction, and the Z-axis drive device 8 controls the vertical movement of the printing platform 2. The printing platform 2 is designed with guide rails. The material tray 3 is placed on the guide rails of the printing platform 2. The material tray 3 is made of microwave-resistant material and is designed with positioning function. A conveying cylinder 1 is designed below the printing platform 2. The conveying cylinder 1 is parallel to the lowest position of the material tray 3.

[0015] The food extruder 5 and the auxiliary material extruder 6 are integrated and positioned on the guide rail of the Y-axis drive device 7. The food extruder 5 and the auxiliary material extruder 6 are controlled to move in the X-axis and Y-axis planes by the X-axis drive device 4 and the Y-axis drive device 7. The food extruder 5 adopts a screw extrusion method, and the screw is driven by a continuously variable speed motor.

[0016] The auxiliary material extruder 6 includes a cylinder 24, a filling container 28, and a nozzle 30. The cylinder 24 is connected to a needle 27, and a sealing element 29 is designed at the lower part of the needle 27. The filling container 28 is designed with a feed port 25 and an air inlet 26 at the upper part. The air inlet 26 is connected to a nitrogen storage tank 13 through a solenoid valve 10, a throttle valve 11, and a pressure regulating valve 12. The cylinder 24 is connected to the nitrogen storage tank 13 through a two-position three-way valve 9 and a pressure regulating valve 12.

[0017] The freeze-drying chamber 14 is equipped with guide rails, and the freeze-drying chamber 14 moves up and down by the elevator 16 to control the entry and exit of the material tray 3. The material inlet and outlet door of the freeze-drying chamber 14 is designed at the bottom, and the freeze-drying chamber 14 is vacuum sealed by the sealing cover 15. The sealing cover 15 is equipped with guide rails. The liquid nitrogen storage tank 18 is connected to the freeze-drying chamber 14 through the throttle valve 11 and the atomizing nozzle 17 to quickly freeze the printed products in the material tray 3.

[0018] The water trap 19 is connected to the freeze-drying chamber 14 via a vacuum hose, which facilitates the vertical movement of the freeze-drying chamber 14. The refrigerator 21 and the vacuum pump 20 are respectively connected to the water trap 19. The microwave source 22 is a solid-state microwave generator and is installed on the microwave feed port of the freeze-drying chamber 14 via a waveguide.

[0019] The conveying cylinder 1 conveys the material tray 3 into the freeze-drying chamber 14 via the guide rails of the printing platform 2 and the inner guide rails of the freeze-drying chamber 14 for rapid freezing and microwave freeze-drying; the control cabinet 23 is equipped with an industrial computer; the industrial computer is equipped with 3D printing operation software and is connected to the food printing system, structural support system, air supply system, rapid freezing system, microwave freeze-drying system and conveying system.

[0020] An application of a hollowed-out three-dimensional freeze-dried milk snack preparation device based on dual nozzles mainly includes the following steps: (1) Preliminary preparation: Prepare the ingredients for printing milk snacks and load them into the ingredient extruder 5; select structural support materials and load them into the auxiliary material extruder 6; (2) 3D printing: Import the model from the control cabinet 23, slice it, set the printing parameters, print and shape it to obtain a 3D printed milk snack placed on the material tray 3; the printing parameters during the 3D printing process are set as follows: the temperature of the food extruder 5 is 50-60℃, the printing speed is 10-15 mm / s; the air pressure of the auxiliary material extruder 6 is 0.1-0.15 MPa, the cylinder running frequency is 1 time / 10s, and the outflow is 0.3-0.5 mL / s; (3) Rapid freezing and microwave freeze-drying: The material tray 3 containing the 3D printed milk snacks is moved into the freeze-drying chamber 14, sealed, and the throttle valve 11 is opened. After 30 seconds, the throttle valve 11 is closed. After 2 minutes, the throttle valve 11 is opened again and closed after 30 seconds. The freezing time is maintained for 10 to 15 minutes. After rapid freezing, microwave freeze-drying with 6-stage temperature control is performed. During the 6-stage temperature control microwave freeze-drying process, the vacuum degree is set to 60 Pa, and the temperatures are -30℃, -20℃, -10℃, 0℃, 30℃, and 50℃, respectively. The total running time is 6 to 6.5 hours. (4) Remove structural support materials: After microwave freeze drying is completed, start the elevator 16, take out the hollow three-dimensional freeze-dried milk snack product from the material tray 3, place it in the auxiliary equipment vibrating bed to remove the structural support materials, and then package it in aluminum foil bags.

[0021] Furthermore, the method for preparing the printed ingredients for the milk snack is as follows: according to the formula, the modified starch, maltodextrin, β-cyclodextrin and lactose are mixed, cold water is added and stirred, the mixture is rapidly heated to 75-100°C, the heating is stopped, freeze-dried milk powder or fresh milk is added, the mixture is stirred and cooled to room temperature, and then filtered through a 1.0 mm mesh for later use. Furthermore, the modified starch in the printed ingredients of the milk snack is 5-12 parts, maltodextrin 8-11 parts, β-cyclodextrin 6-9 parts, lactose 12-16 parts, cold water 40-113 parts, freeze-dried milk powder 1-57 parts, or fresh milk 1-113 parts.

[0022] The beneficial effects of this invention compared to the prior art are as follows: (1) Compared with existing 3D printing methods, this invention uses dual nozzles to fill the gaps inside and outside the food model while printing the food model, thereby improving the structural support of the printed food. Using the same printing material to print a ring, existing 3D printing methods will result in collapse after 15 layers, while this method can print a complete ring with 33 layers. This invention solves the problem of easy collapse during the printing of specially shaped foods, improves printing efficiency, and expands the application scope of food 3D printing technology.

[0023] (2) Compared with existing 3D printed food, the present invention combines 3D printing with liquid nitrogen freezing, which enables the special structure of printed food to be quickly solidified and shaped; and combines it with microwave freeze drying, which enables the 3D printed food to be quickly dehydrated, maintain the special structure of the 3D printed food, improve the precision of the printed product, retain the nutritional quality of the 3D printed food, and extend the storage period.

[0024] (3) This invention promotes the development of dried special-shaped leisure snacks: By using a dual-nozzle 3D printing structure support, the amount of colloid added in the printed ingredients is reduced, making the special-shaped 3D printed microwave freeze-dried food quick-dissolving and crispy, meeting the requirements of milk snacks. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the system structure of the present invention; Figure 2 This is a schematic diagram of the control principle of the present invention; Figure 3 Specially designed children's milk snack models; Figure 4 Model of milk snacks that are easy for the elderly to swallow ( Figure 4 The small spheres inside the model are pores, and these pores protrude from the surface. Reference numerals: 1. Conveying cylinder; 2. Printing platform; 3. Material tray; 4. X-axis drive device; 5. Food extruder; 6. Auxiliary material extruder; 7. Y-axis drive device; 8. Z-axis drive device; 9. Two-position three-way valve; 10. Solenoid valve; 11. Throttle valve; 12. Pressure regulating valve; 13. Nitrogen storage tank; 14. Freeze-drying chamber; 15. Sealing cover; 16. Elevator; 17. Atomizing nozzle; 18. Liquid nitrogen storage tank; 19. Water trap; 20. Vacuum pump; 21. Refrigeration unit; 22. Microwave source; 23. Control cabinet; 24. Cylinder; 25. Feed inlet; 26. Air inlet; 27. Needle; 28. Filling container; 29. ​​Seal. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0027] Example 1

[0028] like Figure 1 The aforementioned hollow three-dimensional freeze-dried milk snack preparation device based on dual nozzles includes an ingredient printing system, a structural support system, an air supply system, a rapid freezing system, a microwave freeze-drying system, a conveying system, and a control system. The food printing system mainly includes a printing platform 2, a material tray 3, and a food extruder 5; the structural support system mainly includes an auxiliary material extruder 6 for loading structural support auxiliary materials; the gas supply system mainly includes a two-position three-way valve 9, a solenoid valve 10, a throttle valve 11, a pressure regulating valve 12, and a nitrogen storage tank 13; the rapid freezing system mainly includes an atomizing nozzle 17, a throttle valve 11, and a liquid nitrogen storage tank 18; the microwave freeze-drying system mainly includes a freeze-drying chamber 14, a water trap 19, a vacuum pump 20, a refrigerator 21, and a microwave source 22; the conveying system mainly includes a conveying cylinder 1; the control system mainly includes a control cabinet 23; the food printing system and the structural support system are connected through the food extruder 5 and the auxiliary material extruder 6; the gas supply system is connected to the structural support system through the auxiliary material extruder 6; the rapid freezing system is connected to the microwave freeze-drying system through the freeze-drying chamber 14; the food printing system and the structural support system are connected to the rapid freezing system and the microwave freeze-drying system through the conveying system; The printing platform 2 is installed in the Z-axis direction, and the Z-axis drive device 8 controls the vertical movement of the printing platform 2. The printing platform 2 is designed with guide rails. The material tray 3 is placed on the guide rails of the printing platform 2 and is designed with a positioning function. A conveying cylinder 1 is designed below the printing platform 2. The conveying cylinder 1 is parallel to the material tray 3. The conveying cylinder 1 pushes the material tray 3 into the freeze-drying chamber 14 for rapid freezing and microwave freeze-drying. The food extruder 5 and the auxiliary material extruder 6 are integrated and positioned on the guide rail of the Y-axis drive device 7. The food extruder 5 and the auxiliary material extruder 6 are controlled to move in the X-axis and Y-axis planes by the X-axis drive device 4 and the Y-axis drive device 7. The food extruder 5 adopts a single-screw extrusion method, with the screw driven by a continuously variable speed motor to extrude printed food ingredients; The auxiliary material extruder 6 includes a filling container 28, a cylinder 24, and a nozzle 30; the upper part of the filling container 28 is designed with a feed inlet 25 and an air inlet 26; the lower part of the cylinder 24 is connected to a needle 27, and the lower part of the needle 27 is designed with a sealing element 29 to control the auxiliary material to flow out of the nozzle 30. The air inlet 26 is connected to the nitrogen storage tank 13 through the solenoid valve 10, the throttle valve 11, and the pressure regulating valve 12 to control the auxiliary material to flow out from the nozzle 30; The cylinder 24 is connected to the nitrogen storage tank 13 via a two-position three-way valve 9 and a pressure regulating valve 12, which controls the outflow of auxiliary material in the nozzle 30 and prevents the auxiliary material in the nozzle 30 from becoming blocked. The feed inlet of the freeze-drying chamber 14 is designed at the bottom, and the sealing cover 15 is located below the freeze-drying chamber 14; the elevator 16 controls the up and down movement of the freeze-drying chamber 14, and vacuum seals it with the sealing cover 15; the liquid nitrogen storage tank 18 is connected to the freeze-drying chamber 14 through the throttle valve 11 and the atomizing nozzle 17 to quickly freeze the printed products in the material tray 3; the water trap 19 is connected to the freeze-drying chamber 14 through the vacuum hose to facilitate the up and down movement of the freeze-drying chamber 14; the refrigerator 21 and the vacuum pump 20 are respectively connected to the water trap 19; the microwave source 22 is installed on the microwave feed port of the freeze-drying chamber 14 through the waveguide, and the microwave feed port is vacuum sealed with glass or PTFE plate.

[0029] The conveying cylinder 1 conveys the material tray 3 into the freeze-drying chamber 14 for rapid freezing and microwave freeze-drying via the guide rail of the printing platform 2 and the guide rail inside the freeze-drying chamber 14. The control cabinet 23 is equipped with an industrial computer; the industrial computer is equipped with 3D printing software and is connected to the food printing system, structural support system, air supply system, rapid freezing system, microwave freeze-drying system and conveying system.

[0030] Application Example 1: Preparation of specially shaped children's milk snacks using a dual-nozzle, hollowed-out, three-dimensional freeze-drying process. ① Preparation of printing ingredients: According to the formula, weigh 5 parts of modified starch, 8 parts of maltodextrin, 6 parts of β-cyclodextrin and 12 parts of lactose, add 113 parts of cold water and stir, heat quickly to boiling, stop heating, add 57 parts of freeze-dried milk powder, stir and cool to room temperature, filter through a 1.0 mm mesh and set aside for use. ②Preparation of structural support materials: Weigh the spray-dried whole milk powder, filter it through a 1.0 mm mesh sieve, and vacuum dry it until the moisture content is <2%, then set aside for use; ③ Model import and slicing: Select a special model from the industrial computer model library of the control cabinet, import it into the printing software, select the slicing software, and perform slicing processing; ④ Insertion of printed ingredients and structural support materials: Place the prepared printed ingredients into the ingredient extruder 5, with a nozzle inner diameter of 1 mm; place the structural support materials into the auxiliary material extruder 6, with a nozzle inner diameter of 1.5 mm. ⑤ Printer parameter settings and operation: Set the printer operating parameters: food extruder 5 temperature is 60℃, printing speed is 15 mm / s; auxiliary material extruder 6 air inlet pressure is 0.15 MPa, cylinder operation frequency is 1 time / 10 s, and outflow is 0.5 mL / s; turn on the 3D printer and the printer will start running. ⑥ Rapid freezing: After printing, turn on the elevator 16 to move the freeze-drying chamber 14 upward, start the conveying cylinder 1 to push the material tray 3 into the freeze-drying chamber 14, move the elevator 16 down to the sealing cover 15, open the throttle valve 11, close the throttle valve 11 after 30 seconds, open the throttle valve 11 again after 2 minutes, close the throttle valve 11 after 30 seconds, and maintain the freezing time for 10 minutes; ⑦ Microwave freeze drying: Set the vacuum level to 60 Pa, and set 6 product control temperatures: -30℃, -20℃, -10℃, 0℃, 30℃, and 50℃. Start the refrigeration unit 21. When the water trap temperature reaches -35℃, start the vacuum pump. When the vacuum reaches 60 Pa, maintain it for 10 minutes and then start the microwave source. The microwave freeze drying will run according to the set program for 6.5 hours.

[0031] ⑧ Remove structural support materials: After microwave freeze drying is completed, start the elevator 16 to take out the product from the material tray 3, place it in the vibrating bed of the auxiliary equipment to remove the auxiliary materials, and then package it in aluminum foil bags.

[0032] ⑨ Results: The precision of the specially shaped children's milk snack products reached 92%, and the hardness, crispness, adhesiveness and rehydration time were 860.20±280.92 gf, 373.49±231.91 gf, -4.95±7.62 gf*sec and 18.13±5.21 s, respectively.

[0033] Application Example 2: Preparation of Hollowed-out Three-dimensional Freeze-dried Milk Snacks for the Elderly Based on Dual Sprayers ① Preparation of printing ingredients: According to the formula, weigh 12 parts of modified starch, 11 parts of maltodextrin, 9 parts of β-cyclodextrin and 16 parts of lactose, add 40 parts of cold water and stir, heat quickly to 75℃, stop heating, add 113 parts of fresh milk, stir and cool to room temperature, filter through a 1.0mm mesh and set aside for use. ②Preparation of structural support materials: Weigh vacuum-dried skim milk powder, filter it through a 1.0 mm mesh sieve, control the moisture content to <2%, and set aside for later use; ③ Model import and slicing: Select the model of food that is easy for the elderly to swallow from the model library of the industrial control computer in the control cabinet, import it into the printing software, select the slicing software, and perform slicing processing; ④ Inserting printed ingredients and structural support materials: Place the prepared printed ingredients into the ingredient extruder 5, with a nozzle inner diameter of 1 mm; place the structural support materials into the auxiliary material extruder 6, with a nozzle inner diameter of 1.5 mm.

[0034] ⑤ Printer parameter settings and operation: Set the printer operating parameters: food extruder 5 temperature is 50℃, printing speed is 10 mm / s; auxiliary material extruder 6 air inlet pressure is 0.1 MPa, cylinder operation frequency is 1 time / 10 s, and outflow is 0.3 mL / s; turn on the 3D printer and the printer will start operating. ⑥ Rapid freezing: After printing, turn on the elevator 16 to move the freeze-drying chamber 14 upward, start the conveying cylinder 1 to push the material tray 3 into the freeze-drying chamber 14, move the elevator 16 down to the sealing cover 15, open the throttle valve 11, close the throttle valve 11 after 30 seconds, open the throttle valve 11 again after 2 minutes, close the throttle valve 11 after 30 seconds, and maintain the freezing time for 15 minutes; ⑦ Microwave freeze drying: The vacuum degree is set to 40 Pa, and the product control temperature is set to 6 segments: -30℃, -20℃, -10℃, 0℃, 30℃, and 50℃. Start the refrigeration unit 21. When the water trap temperature reaches -35℃, start the vacuum pump. When the vacuum reaches 40 Pa, maintain it for 15 minutes and then start the microwave source. The microwave freeze drying will run according to the set program for 6 hours.

[0035] ⑧ Remove structural support materials: After microwave freeze drying is completed, start the elevator 16 to take out the product from the material tray 3, place it in the vibrating bed of the auxiliary equipment to remove the auxiliary materials, and then package it in aluminum foil bags.

[0036] ⑨ Results: The accuracy of the milk snack product that is easy for the elderly to swallow reached 93%. The hardness, brittleness, adhesiveness and rehydration time were 579.83±158.28 gf, 264.16±122.89 gf, -1.01±0.47 gf*sec and 3.72±0.18 s, respectively.

Claims

1. A hollow three-dimensional freeze-dried milk snack preparation device based on dual nozzles, characterized in that, The system mainly includes: a food printing system, a structural support system, a gas supply system, a rapid freezing system, a microwave freeze-drying system, a conveying system, and a control system; the food printing system mainly includes a printing platform (2), a material tray (3), and a food extruder (5); the structural support system mainly includes an auxiliary material extruder (6) for loading structural support auxiliary materials; the gas supply system mainly includes: a two-position three-way valve (9), a solenoid valve (10), a throttle valve (11), a pressure regulating valve (12), and a nitrogen storage tank (13); the rapid freezing system mainly includes an atomizing nozzle (17), a throttle valve (11), and a liquid nitrogen storage tank (18); the microwave freeze-drying system mainly includes: a food printing system, a structural support system, a gas supply system, a rapid freezing system, a microwave freeze-drying system, a conveying system, and a control system; the food printing system mainly includes a printing platform (2), a material tray (3), and a food extruder (5); the structural support system mainly includes an auxiliary material extruder (6) for loading structural support auxiliary materials; the gas supply system mainly includes: a two-position three-way valve (9), a solenoid valve (10), a throttle valve (11), a pressure regulating valve (12), and a nitrogen storage tank (13); the rapid freezing system mainly includes an atomizing nozzle (17), a throttle valve (11), and a liquid nitrogen storage tank (18); the micro The microwave freeze-drying system mainly includes a freeze-drying chamber (14), a water trap (19), a vacuum pump (20), a refrigerator (21), and a microwave source (22); the conveying system mainly includes a conveying cylinder (1); the control system mainly includes a control cabinet (23); the food printing system and the structural support system are connected through a food extruder (5) and an auxiliary material extruder (6); the gas supply system is connected to the structural support system through the auxiliary material extruder (6); the rapid freezing system is connected to the microwave freeze-drying system through the freeze-drying chamber (14); the food printing system and the structural support system are connected to the rapid freezing system and the microwave freeze-drying system through the conveying system. The printing platform (2) is installed in the Z-axis direction. The Z-axis drive device (8) controls the vertical movement of the printing platform (2). The printing platform (2) is designed with guide rails. The material tray (3) is placed on the guide rail of the printing platform (2). The material tray (3) is made of microwave-resistant material and is designed with positioning function. A conveying cylinder (1) is designed below the printing platform (2). The conveying cylinder (1) is parallel to the lowest position of the material tray (3). The food extruder (5) and the auxiliary material extruder (6) are designed as an integrated unit and positioned on the guide rail of the Y-axis drive device (7); the food extruder (5) and the auxiliary material extruder (6) are controlled by the X-axis drive device (4) and the Y-axis drive device (7) to move in the X-axis and Y-axis planes; the food extruder (5) adopts the screw extrusion method and is driven by a continuously variable speed motor. The auxiliary material extruder (6) includes a cylinder (24), a filling container (28), and a nozzle (30); the cylinder (24) is connected to a needle (27), and a sealing element (29) is designed at the lower part of the needle (27); the filling container (28) is designed with a feed inlet (25) and an air inlet (26) at the upper part; the air inlet (26) is connected to a nitrogen storage tank (13) through a solenoid valve (10), a throttle valve (11), and a pressure regulating valve (12); the cylinder (24) is connected to the nitrogen storage tank (13) through a two-position three-way valve (9) and a pressure regulating valve (12); The freeze-drying chamber (14) is equipped with guide rails. The freeze-drying chamber (14) moves up and down by the elevator (16) to control the material tray (3) to enter and exit. The material inlet and outlet gate of the freeze-drying chamber (14) is designed at the bottom and the freeze-drying chamber (14) is vacuum sealed by the sealing cover (15). The sealing cover (15) is equipped with guide rails. The liquid nitrogen storage tank (18) is connected to the freeze-drying chamber (14) through the throttle valve (11) and the atomizing nozzle (17) to quickly freeze the printed products in the material tray (3). The water trap (19) is connected to the freeze-drying chamber (14) via a vacuum hose, which facilitates the up-and-down movement of the freeze-drying chamber (14); the refrigerator (21) and the vacuum pump (20) are respectively connected to the water trap (19); the microwave source (22) is a solid-state microwave generator and is installed on the microwave feed port of the freeze-drying chamber (14) via a waveguide; The conveying cylinder (1) conveys the material tray (3) into the freeze-drying chamber (14) for rapid freezing and microwave freeze-drying via the guide rail of the printing platform (2) and the guide rail inside the freeze-drying chamber (14); the control cabinet (23) is equipped with an industrial computer; the industrial computer is equipped with 3D printing operation software and is connected to the food printing system, structural support system, air supply system, rapid freezing system, microwave freeze-drying system and conveying system.

2. The application of the hollow three-dimensional freeze-dried milk snack preparation device based on dual nozzles according to claim 1, characterized in that, The main steps include: (1) Preliminary preparation: Prepare the ingredients for printing milk snacks and load them into the ingredient extruder (5); select structural support materials and load them into the auxiliary material extruder (6). (2) 3D printing: Import the model from the control cabinet (23), slice it, set the printing parameters, print and shape it to obtain a 3D printed milk snack placed on the material tray (3); The printing parameters during the 3D printing process are set as follows: the temperature of the food extruder (5) is 50-60℃, the printing speed is 10-15 mm / s; the air pressure of the auxiliary material extruder (6) is 0.1-0.15 MPa, the cylinder running frequency is 1 time / 10 s, and the outflow is 0.3-0.5 mL / s; (3) Rapid freezing and microwave freeze drying: The material tray (3) containing the 3D printed milk snacks is moved into the freeze drying chamber (14), sealed and the throttle valve (11) is opened. After 30 seconds, the throttle valve (11) is closed. After 2 minutes, the throttle valve (11) is opened again. After 30 seconds, the throttle valve (11) is closed. The freezing time is maintained for 10 to 15 minutes. After rapid freezing, microwave freeze drying with 6 temperature control is carried out. During the 6 temperature control microwave freeze drying process, the vacuum degree is set to 60 Pa, and the temperatures are -30℃, -20℃, -10℃, 0℃, 30℃ and 50℃ respectively. The total running time is 6 to 6.5 hours. (4) Remove structural support materials: After microwave freeze drying is completed, start the elevator (16) to take out the hollow three-dimensional freeze-dried milk snack product from the material tray (3), place it in the vibration bed of the auxiliary equipment to remove the structural support materials, and then package it with aluminum foil bags.

3. The application of the hollow three-dimensional freeze-dried milk snack preparation device based on dual nozzles according to claim 2, characterized in that, The method for preparing the milk snack printing ingredients in step (1) is as follows: Mix modified starch, maltodextrin, β-cyclodextrin and lactose according to the formula, add cold water and stir, heat quickly to 75-100℃, stop heating, add freeze-dried milk powder or fresh milk, stir and cool to room temperature, filter through a 1.0 mm mesh and set aside for use.

4. The application of the hollow three-dimensional freeze-dried milk snack preparation device based on dual nozzles according to claim 3, characterized in that, The modified starch in the printed ingredients of the milk snack is 5-12 parts, maltodextrin is 8-11 parts, β-cyclodextrin is 6-9 parts, lactose is 12-16 parts, cold water is 40-113 parts, freeze-dried milk powder is 1-57 parts or fresh milk is 1-113 parts.

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