A preparation method of low-calorie 3D printed coarse grain milk candy for children

Abstract

The present invention discloses a method for preparing low-calorie 3D printed coarse grain milk candy for children, which belongs to the field of food 3D printing and its processing technology. The present invention embeds milk candy gel through coaxial 3D printing technology, effectively reduces the viscosity of the milk candy gel and improves the phenomenon of discontinuous lines when the milk candy gel is directly extruded, and eliminates bubbles in the milk candy through ultrasonic technology to make its texture more uniform. In addition, the present invention replaces the gelatin required for traditional milk candy production with gellan gum to avoid the addition of animal protein, and uses starch-rich coarse grain powder as a texture modifier and flavor regulator. Erythritol (zero-calorie sugar), whole milk powder, and anhydrous butter are used as the main ingredients to prepare milk candy printing materials and produce low-calorie 3D three-dimensional milk candies with various appearances through food 3D printers.

Description

Technical Field

[0001] The present invention relates to the field of food 3D printing and processing technology, and in particular to a method for preparing low-calorie 3D printed coarse grain toffee for children. Background Art

[0002] Food 3D printing is a new food processing technology derived from 3D printing. It can provide personalized diets, tailored to consumers with diverse functional and nutritional needs. Furthermore, food 3D printing technology can utilize a variety of ingredients to rapidly produce diverse, richly textured 3D foods tailored to the needs and preferences of different groups of people, promoting the development of electronic cooking and increasing the enjoyment of eating. Therefore, food 3D printing is a new food processing and manufacturing technology that is transforming traditional food processing methods and subverting established dietary concepts.

[0003] Toffee is a traditional candy with a decades-long history in my country. Its sweet taste and rich nutritional value make it a popular treat. Many companies in China produce toffee, each with its own distinct production processes and equipment, and the expertise of its practitioners varies widely. Furthermore, few domestic researchers have reported on the topic. Gelatin is a key raw material in toffee production, primarily due to its excellent thermal stability. However, as an animal protein, gelatin is subject to significant ethical and religious influences. Studies have shown that finding a gelatin substitute in toffee would not only address the safety risks associated with gelatin use but also expand its consumer base. The research team behind the present invention has discovered that gellan gum, a hydrophilic colloid with similar properties, forms a flexible, soft gel upon heating, which then forms a hard, brittle gel upon cooling. This process is reversible. Therefore, gellan gum holds promise as a potential alternative to gelatin as a raw material for toffee production.

[0004] Children are the primary target audience for milk candy, so a unique appearance is essential. This is also one of the major challenges hindering the development of the milk candy industry. Integrating it with food 3D printing is an effective means of addressing this bottleneck. For food 3D printers to extrude ingredients that can be stacked and formed at room temperature, certain requirements must be met for the ingredients' viscosity, fluidity, and support properties. Therefore, developing 3D printing milk candy production processes as far as possible is essential.

[0005] Yang Ye et al. (2018) disclosed “A 3D toffee and its processing method” (Publication No.: CN 109090322A). This method involves adding egg whites that have been beaten to a dry foam to maltose syrup that has been boiled to 111-115°C, stirring to obtain a base material. Milk powder and anhydrous butter are then added to the base material, and stirring continues to obtain a toffee gel. The toffee gel is hot-filled using a 3D printing-specific material tube (cavity height 2 cm). Furthermore, the preheating temperature is 60°C and the preheating time is 10-15 minutes. A needle with an aperture of 0.4-1.55 mm is then used for 3D printing, and a variety of three-dimensional toffees are successfully produced. However, during the production process, some products are brittle and prone to breakage, and some products have a rough appearance.

[0006] Li Lin et al. (publication number: CN 113475612A) disclosed a low-calorie soft candy 3D printing material and soft candy 3D printing method with a sleep-aiding function in 2021, wherein the low-calorie soft candy 3D printing material with a sleep-aiding function includes a jujube seed saponin extract, a base material colloid, resistant starch, white sugar, and a sweetener. It overcomes the shortcomings of the existing technology and provides a low-calorie soft candy 3D printing material with simple components and reasonable proportions, which has the functions of relieving stress, resisting fatigue, calming the nerves, and helping sleep, and combines it with food 3D printing technology to manufacture soft candies. However, this method requires the printed product to be left to stand for demolding, and materials with higher viscosity are not suitable for this method.

[0007] In 2018, Wan Jiangling et al. (Publication No.: CN 108402264A) disclosed a 3D printing material for soft candies with an optional complex polysaccharide loading and its preparation method. This 3D printing material is obtained by boiling raw materials including gellan gum, agar, gelatin, starch, liquid maltitol, erythritol, polyglycerol ricinoleate, neotame, mint powder, and a complex polysaccharide. The solids content at the end of the boiling process is preferably 70% to 76%. This provides a low-calorie 3D printing material for soft candies with simple components and a reasonable proportion, which has the functions of relieving stress, resisting fatigue, calming the nerves, and promoting sleep. However, this method lacks flavor components, which may make it difficult to stimulate consumer interest in eating.

[0008] In 2021, Yang Qingyu et al. (Publication No.: CN 112314767A) disclosed a sugar gel 3D printing soft material and its preparation method. Sugar and protein are grafted together to form a glycoprotein complex. This complex is then mixed with an emulsifier, a curing agent, and a coagulant in appropriate proportions. The complex is then printed using a 3D printer, resulting in a printed product with uniform lines and high precision. However, the production process is prone to problems such as bubbles and rough lines, resulting in low product precision.

[0009] Shen Binbin et al. (publication number: CN 114946986A) disclosed a kind of sour jujube kernel soft candy and its preparation method in 2022. The raw materials for the preparation of sour jujube kernel soft candy include: Hericium erinaceus, yam, lily, agar-agar, tremella, red date, poria, sour jujube kernel, γ-aminobutyric acid, sweetener and acidity regulator. It does not contain traditional coagulants. The resulting product has a chewy texture and has the effects of replenishing qi and blood, promoting qi and relieving depression, and calming the mind. It has no odor and tastes good. However, this method belongs to mold casting, the obtained product needs to be demolded, and the appearance of the product is subject to certain restrictions. Summary of the Invention

[0010] The purpose of the present invention is to provide a method for preparing low-calorie 3D printed coarse grain milk candy for children. The present invention embeds milk candy gel through coaxial 3D printing technology, effectively reduces the viscosity of milk candy gel and improves the phenomenon of discontinuous lines when the milk candy gel is directly extruded, and eliminates bubbles in the milk candy through ultrasonic technology to make its texture more uniform. In addition, the present invention replaces the gelatin required for traditional milk candy production with gellan gum to avoid the addition of animal protein, and uses starch-rich coarse grain powder as a texture modifier and flavor regulator, and uses erythritol (zero calorie sugar), whole milk powder, and anhydrous butter as the main ingredients to prepare milk candy printing materials and produce low-calorie 3D three-dimensional milk candies with various appearances through food 3D printers.

[0011] The technical solution of the present invention:

[0012] A method for preparing low-calorie 3D printed coarse grain toffee for children comprises the following steps:

[0013] (1) Preparation of sol solution: Add low acyl gellan gum to water and stir until the low acyl gellan gum is completely dissolved in the water.

[0014] Furthermore, in the step (1), the low acyl gellan gum is gellan gum from which the acyl groups are completely removed.

[0015] Furthermore, in the step (1), the addition ratio of low acyl gellan gum to water is 0.9%-1% (w / v), and the unit is g / mL or kg / L.

[0016] Furthermore, in the step (1), the ambient temperature for dissolving low acyl gellan gum in water is 90-95°C.

[0017] (2) Boiling sugar: Add erythritol to the sol solution of step (1) and stir until a fine and viscous sugar solution is formed.

[0018] Furthermore, in the step (2), the addition ratio of erythritol is 47%-50% (w / v) of the solution in step (1), and the unit is g / mL or kg / L.

[0019] Furthermore, in the step (2), the stirring condition is: stirring in an oil bath at 105-110°C.

[0020] (3) Starch gelatinization: Add the coarse grain powder to the sugar solution in step (2), heat and stir until the starch is completely gelatinized, and use it as the printing base material.

[0021] Furthermore, in step (3), the amount of coarse grain powder added is 10%-12% of the mass of the sugar solution in step (2). The coarse grain powder is freeze-dried coarse grain powder that can pass through a 200-mesh sieve, and the coarse grain powder is selected from one or a mixture of two or more of freeze-dried corn flour, freeze-dried purple sweet potato flour, or freeze-dried coix seed flour.

[0022] Furthermore, in step (3), the gelatinization temperature condition is: in a water bath at 85-90° C. The center temperature of the printed substrate after gelatinization must exceed 100° C. to ensure complete gelatinization.

[0023] (4) Preparation of toffee gel: Add whole milk powder and anhydrous butter to the printing substrate obtained in step (3) and continue stirring until a fine and uniform toffee gel is obtained.

[0024] Furthermore, in the step (4), the added amounts of whole milk powder and anhydrous butter account for 35%-40% and 8%-10% of the mass of the printing substrate in step (3), respectively.

[0025] Furthermore, in step (4), the stirring environment conditions are: stirring in a water bath at 90-95° C., with a stirring speed of 30-50 r / min and a stirring time of 20-30 min.

[0026] (5) Ultrasonic treatment: The prepared toffee gel is placed in an ultrasonic device to eliminate bubbles and uniform the texture, enhance the pseudoplastic fluid behavior of the toffee gel, and obtain the inner layer printing material for 3D printing.

[0027] Furthermore, in the step (5), the storage modulus of the inner layer printing material is 1500-6000 Pa, the loss modulus is 500-2000 Pa, and the viscosity is 2500-6000 Pa·s.

[0028] (6) Preparation of outer layer wrapping material: Prepare a starch suspension, and heat and stir until the starch is completely gelatinized to obtain the outer layer wrapping material.

[0029] Furthermore, in the step (6), the gelatinization temperature condition is: gelatinization under the conditions of magnetic stirring and 85-90°C water bath.

[0030] Furthermore, in the step (6), the mass concentration of the starch suspension is 18%-20%.

[0031] (7) Loading: Cool the inner layer printing material and the outer layer wrapping material to 60-65°C, then move them to the printing barrel and preheat them respectively; the printing nozzle adopts a coaxial nozzle, in which the inner layer nozzle is filled with the inner layer printing material and the outer layer nozzle is filled with the outer layer wrapping material.

[0032] Furthermore, in the step (7), the preheating temperature is set as the target printing temperature at 60-65° C.; and the preheating time is 10 to 15 minutes.

[0033] Furthermore, in the step (7), the diameter of the coaxial nozzle varies according to the type of coarse grain and the printing model, and the size of the coaxial nozzle is set as follows: the nozzle diameter of the inner layer material is 0.8-1.2 mm, and the thickness of the outer layer material is 0.08-0.1 mm.

[0034] (8) 3D printing: Import the target model into the printing software, start the preheating process of the printing barrel, set the printing program parameters and print.

[0035] Furthermore, in step (8), the filling rate of the printed model is 80%-85%, the size of the printed model is within 35mm×30mm×25mm, and the internal filling routing method during printing is honeycomb 80-90° filling or triangle 55-60° filling.

[0036] Furthermore, in step (8), the barrel temperature must be preset to the target printing temperature before printing. Before the printing process begins, the temperature of the printing material in the barrel must be stabilized to the target printing temperature. Before starting printing, the printing program parameters are set: the default printing speed is 28-30 mm / s, the material fill rate is 80%-85%, the printing filament diameter is 18-20 mm, and the z-axis offset is 1.4-1.6 mm.

[0037] Furthermore, the low-calorie 3D printed children's coarse grain toffee has a hardness of 200-220g, an adhesiveness of -50-40g*s, an adhesiveness of 140-170g, a cohesion of 0.9 or more, and a calorie content (per 100g) of less than 1300 kilojoules.

[0038] Furthermore, when the inner layer printing material and the outer layer wrapping material are extruded at the same time, they must be continuous and unbroken, and the outer layer wrapping material must wrap the inner layer printing material. The outer layer wrapping material avoids the line adhesion phenomenon caused by direct contact with the inner layer printing material during the printing process, so that the printing material can be continuously stacked to complete the printing progress.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] (1) The present invention provides a milk candy material that does not require gelatin, reduces the use of animal protein, and can form a milk candy gel system with uniform texture under the action of gellan gum. Compared with the materials for preparing milk candy in other inventions, it effectively solves the safety hazards of gelatin in traditional milk candy. The use of gellan gum replaces traditional gelatin and reduces the use of animal protein. Unlike other inventions involving multiple gelling agents, the milk candy gel in the present invention does not require the additional use of other polysaccharide or protein gelling agents, effectively reducing production costs and the problem of uneven texture of some products caused by the presence of multiple gelling agents during storage.

[0041] (2) The toffee gel involved in the present invention contains coarse grain powder, which is rich in starch and dietary fiber. The starch is gelatinized under high temperature treatment so that the base material obtains a dense gel network structure. Under this condition, the inner layer of toffee gel has better extrusion performance, so that the product has high-quality shape retention ability and pseudoplastic fluid behavior. Dietary fiber has significant advantages in regulating blood sugar, controlling weight, maintaining cardiovascular and cerebrovascular health, and promoting intestinal absorption. Unlike other inventions that add flavors and curing agents in the preparation of toffee gel, the present invention uses coarse grain powder as a flavor regulator and texture improver, which effectively reduces production costs and reduces the use of chemical food additives.

[0042] (3) The present invention uses erythritol to replace the fructose-glucose syrup used in traditional milk candy production, which reduces the operating temperature and the total calorie content of the milk candy. The lower viscosity of erythritol makes the prepared milk candy gel more suitable for shaping through food 3D printing, making the product appearance more refined.

[0043] (4) The present invention uses coaxial 3D printing technology, using corn starch gel as the outer fluid to embed the inner layer of toffee gel, thereby avoiding direct contact between the lines of toffee gel during extrusion and stacking. The toffee gel used in the present invention is ultrasonically treated to eliminate bubbles, resulting in a uniform and fine texture, which is more conducive to the extrusion and stacking process. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a comparison diagram of the product displays in Examples 1, 2, and 3 of the present invention;

[0045] FIG2( a ) is a comparison diagram of hardness indexes of a comparative example and an embodiment of the present invention;

[0046] FIG2( b ) is a comparison chart of adhesion indexes of the comparative example and the embodiment of the present invention;

[0047] FIG2( c ) is a comparison chart of the adhesion indexes of the comparative example and the embodiment of the present invention;

[0048] FIG2( d ) is a comparison diagram of the cohesion index of the comparative example and the embodiment of the present invention. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0050] In all examples, low acyl gellan gum was purchased from Opel Biotechnology Co., Ltd., and the gellan gum used was LAJ type low acyl gellan gum.

[0051] Comparative Example 1

[0052] Compared with Example 1, the low acyl gellan gum in step (1) is replaced by gelatin of the same mass ratio in this comparative example.

[0053] Comparative Example 2

[0054] Compared with Example 2, this comparative example replaces the erythritol in step (2) with white sugar of the same mass ratio.

[0055] Comparative Example 3

[0056] Compared with Example 3, this comparative example eliminated the preparation of the outer wrapping material in step (6), and replaced the coaxial nozzle in step (7) with a common extrusion nozzle having an aperture of 0.8 mm.

[0057] Example 1

[0058] A method for preparing low-calorie 3D printed children's corn candy based on gellan gum, comprising the following steps:

[0059] (1) Preparation of sol solution: Weigh 1% (w / v) low acyl gellan gum according to the specific gravity of water and add it to 90°C water. Stir in a constant temperature water bath at 90°C for 20 min until the sol is completely free of particles.

[0060] (2) Boiling sugar: Weigh 50% (w / v) erythritol and add it to the sol solution of step (1), and stir it thoroughly in an oil bath at 105°C until a fine and viscous sugar solution is formed.

[0061] (3) Starch gelatinization: Weigh 10% corn flour and add it to the sugar solution in step (2). Heat and stir in a 90°C water bath to ensure that the starch is completely gelatinized. This material will be used as a precursor material for the subsequent toffee gel.

[0062] (4) Preparation of toffee gel: Weigh 40% and 10% (w / w) whole milk powder and anhydrous butter respectively and add them to the printing substrate obtained in step (3) and continue stirring. The water bath temperature is 90°C, the stirring speed is 30 r / min, and the stirring time is 30 min. Stir until a fine and uniform toffee gel is obtained.

[0063] (5) Ultrasonic treatment: The prepared milk candy gel was placed in an ultrasonic water bath for 20 minutes to eliminate bubbles and achieve uniform texture, thereby enhancing the pseudoplastic fluid behavior of the milk candy gel. The material prepared by steps (3), (4), and (5) is the inner layer printing material. The storage modulus of the inner layer printing material is 5985 Pa, the loss modulus is 1988 Pa, and the viscosity is 5674 Pa·s.

[0064] (6) Preparation of outer coating material: A corn starch suspension with a concentration of 20% was prepared and gelatinized for 30 min under magnetic stirring and a 90°C water bath to ensure that the starch was fully gelatinized.

[0065] (7) Loading: The printing nozzle is a coaxial nozzle, wherein the inner layer printing material is the toffee gel prepared in steps (3), (4), and (5), and the outer layer wrapping material is the starch gel prepared in step (6). The inner layer printing material and the outer layer wrapping material are cooled to about 60°C, and then respectively transferred to the printing barrel and transferred to the 3D printer dedicated preheating device for preheating; further, the preheating temperature is 60°C and the preheating time is 12 minutes. The coaxial nozzle size setting: the inner layer material aperture is 0.8mm and the outer layer material thickness is 0.1mm.

[0066] (8) 3D printing: The target model was imported into the printing software and the preheating program of the printing barrel was started, and the preheating temperature was set to 60°C. Then, the printing speed was set to 30 mm / s and the printing was performed. The infill rate of the printed model was 80%, the printed model size was within 35 mm × 30 mm × 25 mm, the internal infill routing method during printing was honeycomb 80°, the printing filament diameter was 20 mm, and the z-axis offset was 1.4 mm.

[0067] The test results show that, in comparison, the extrusion stress of the toffee gel using freeze-dried corn flour and gellan gum is significantly reduced (976.34Pa), and the water distribution is mainly semi-bound water (87.88%), with bound water (10.12%) and free water (2.02%) accounting for a small part of the gel system. The gel's ability to bind water has been significantly improved, and the sample wetted area in the synergistic experiment has reached 502.77mm 2The total colony count of the printed 3D toffee was 6.75 log CFU / g, the quality deviation rate of the product was 1.09%, the sensory evaluation score was 9.27, the hardness of the printed product was 212.35g, the adhesion was -45.32g*s, the jellyability was 168.43g, the cohesion was 0.91, and the energy per 100g was 1211.8 kilojoules. After being embedded in the corn starch gel as the outer layer fluid, the lines were extruded very smoothly without breakage or adhesion. The surface of the corn toffee product is smooth and stable when pressed without collapse. Its lower viscosity and extrusion stress are more suitable for shaping by food 3D printers. The comparison of relevant test indicators of toffee gels with different components is shown in Table 1.

[0068] Example 2

[0069] A method for preparing low-calorie 3D-printed purple sweet potato candy for children based on gellan gum, comprising the following steps:

[0070] (1) Preparation of sol solution: Weigh 1% (w / v) low acyl gellan gum according to the specific gravity of water and add it to 90°C water. Stir in a constant temperature water bath at 90°C for 20 min until the sol is completely free of particles.

[0071] (2) Boiling sugar: Weigh 50% (w / v) erythritol and add it to the sol solution of step (1), and stir it thoroughly in an oil bath at 105°C until a fine and viscous sugar solution is formed.

[0072] (3) Starch gelatinization: Weigh 10% of purple sweet potato powder and add it to the sugar solution in step (2). Heat and stir in a 90°C water bath to ensure that the starch is completely gelatinized. This material is used as a precursor material for the subsequent toffee gel.

[0073] (4) Preparation of toffee gel: Weigh 40% and 10% (w / w) whole milk powder and anhydrous butter respectively and add them to the printing substrate obtained in step (3) and continue stirring at a water bath temperature of 90°C, a stirring speed of 40 r / min, and a stirring time of 25 min until a fine and uniform toffee gel is obtained.

[0074] (5) Ultrasonic treatment: The prepared milk candy gel was placed in an ultrasonic water bath for 20 minutes to eliminate bubbles and achieve uniform texture, thereby enhancing the pseudoplastic fluid behavior of the milk candy gel. The material prepared by steps (3), (4), and (5) is the inner layer printing material. The storage modulus of the inner layer printing material is 4235 Pa, the loss modulus is 1503 Pa, and the viscosity is 4783 Pa·s.

[0075] (6) Preparation of outer coating material: A corn starch suspension with a concentration of 20% was prepared and gelatinized for 30 min under magnetic stirring and a 90°C water bath to ensure that the starch was fully gelatinized.

[0076] (7) Loading: The printing nozzle is a coaxial nozzle, wherein the inner layer printing material is the toffee gel prepared in steps (3), (4), and (5), and the outer layer wrapping material is the starch gel prepared in step (6). The inner layer printing material and the outer layer wrapping material are cooled to about 60°C, and then respectively transferred to the printing barrel and transferred to the 3D printer dedicated preheating device for preheating; furthermore, the preheating temperature is 60°C and the preheating time is 14 minutes. The coaxial nozzle size setting: the inner layer material aperture is 1mm, and the outer layer material thickness is 0.1mm.

[0077] (8) 3D printing: The target model was imported into the printing software and the preheating program of the printing barrel was started, and the preheating temperature was set to 60°C. Then, the printing speed was set to 30 mm / s and the printing was performed. The infill rate of the printed model was 82%, the printed model size was within 35 mm × 30 mm × 25 mm, the internal infill routing method during printing was a honeycomb 90°, the printing filament diameter was 19 mm, and the z-axis offset was 1.5 mm.

[0078] The test results show that, in comparison, the extrusion stress of the toffee gel using freeze-dried purple sweet potato powder and gellan gum is significantly reduced (698.27Pa), and the water distribution is mainly semi-bound water (91.23%), with bound water (4.76%) and free water (4.01%) accounting for a small part of the gel system. The gel's ability to bind water has been significantly improved, and the sample wetted area under the synergistic experiment has reached 531.76mm 2 . After being embedded with corn starch gel as the outer layer fluid, the lines are extruded very smoothly without breakage or adhesion. The ultrasonic treatment significantly enhances the uniformity of the toffee gel, making it delicate and free of bubbles. The total colony count of the printed 3D toffee is 7.12log CFU / g, the quality deviation rate of the product is 2.01%, the sensory evaluation score is 9.16, the hardness of the printed product is 205.33g, the adhesion is -42.36g*s, the gelling property is 157.87g, the cohesion is 0.92, and the energy per 100g is 1237.2 kilojoules. The surface of the purple sweet potato toffee product is smooth and stable when pressed without collapse. Its lower viscosity and extrusion stress are more suitable for shaping by food 3D printers. The comparison of relevant test indicators of toffee gels with different components is shown in Table 1.

[0079] Example 3

[0080] A method for preparing low-calorie 3D-printed children's coix seed milk candy based on gellan gum, comprising the following steps:

[0081] (1) Preparation of sol solution: Weigh 1% (w / v) low acyl gellan gum according to the specific gravity of water and add it to 90°C water. Stir in a constant temperature water bath at 90°C for 20 min until the sol is completely free of particles.

[0082] (2) Boiling sugar: Weigh 50% (w / v) erythritol and add it to the sol solution of step (1), and stir it thoroughly in an oil bath at 105°C until a fine and viscous sugar solution is formed.

[0083] (3) Starch gelatinization: Weigh 10% coix seed powder and add it to the sugar solution in step (2). Heat and stir in a 90°C water bath to ensure that the starch is completely gelatinized. This material is used as a precursor material for the subsequent toffee gel.

[0084] (4) Preparation of toffee gel: Weigh 40% and 10% (w / w) whole milk powder and anhydrous butter respectively and add them to the printing substrate obtained in step (3) and continue stirring. The water bath temperature is 90°C, the stirring speed is 50 r / min, and the stirring time is 20 min. Stir until a fine and uniform toffee gel is obtained.

[0085] (5) Ultrasonic treatment: The prepared milk candy gel was placed in an ultrasonic water bath for 20 minutes to eliminate bubbles and achieve uniform texture, thereby enhancing the pseudoplastic fluid behavior of the milk candy gel. The material prepared by steps (3), (4), and (5) is the inner layer printing material. The storage modulus of the inner layer printing material is 2344 Pa, the loss modulus is 829 Pa, and the viscosity is 2378 Pa·s.

[0086] (6) Preparation of outer coating material: A corn starch suspension with a concentration of 20% was prepared and gelatinized for 30 min under magnetic stirring and a 90°C water bath to ensure that the starch was fully gelatinized.

[0087] (7) Loading: The printing nozzle is a coaxial nozzle, wherein the inner layer printing material is the toffee gel prepared in steps (3), (4), and (5), and the outer layer wrapping material is the starch gel prepared in step (6). The inner layer printing material and the outer layer wrapping material are cooled to about 60°C, and then respectively transferred to the printing barrel and transferred to the 3D printer dedicated preheating device for preheating; further, the preheating temperature is 60°C and the preheating time is 15 minutes. The coaxial nozzle size setting: the inner layer material aperture is 1.2mm, and the outer layer material thickness is 0.1mm.

[0088] (8) 3D printing: The target model was imported into the printing software and the preheating program of the printing barrel was started, and the preheating temperature was set to 60°C. Then, the printing speed was set to 30 mm / s and printing was performed. The infill rate of the printed model was 85%, the printed model size was within 35 mm × 30 mm × 25 mm, the internal infill routing method during printing was triangular 60°, the printing filament diameter was 20 mm, and the z-axis offset was 1.6 mm.

[0089] The test results show that, in comparison, the extrusion stress of the toffee gel using freeze-dried coix seed powder and gellan gum is significantly reduced (576.39Pa), in which the water distribution is mainly semi-bound water (87.92%), and bound water (7.24%) and free water (4.84%) account for a small part of the gel system. The gel's ability to bind water has been significantly improved, and the sample wetted area under the synergistic experiment has reached 577.83mm 2 . After being embedded with corn starch gel as the outer layer fluid, the lines are extruded very smoothly without breakage or adhesion. The ultrasonic treatment significantly enhances the uniformity of the toffee gel, making it delicate and free of bubbles. The total colony count of the printed 3D toffee is 7.66log CFU / g, the quality deviation rate of the product is 1.72%, the sensory evaluation score is 8.77, the hardness of the printed product is 206.35g, the adhesion is -49.79g*s, the gelling property is 143.29g, the cohesion is 0.91, and the energy per 100g is 1255.3 kilojoules. The surface of the Job's tears toffee product is smooth and stable when pressed without collapse. Its lower viscosity and extrusion stress are more suitable for shaping by food 3D printers. The comparison of relevant test indicators of toffee gels with different components is shown in Table 1.

[0090] Experimental methods:

[0091] 1. Toffee gel extrusion stress test

[0092] The rheological properties of different whole grain toffee gels were tested using a DHR-3 rheometer. The plywood parameters used in the rheological tests were: 40 mm diameter and 1000 μm gap. All tests were performed with a 2-minute equilibration time. Yield stress was measured at 1 Hz in the range of 1–2000 Pa. Each toffee gel was tested three times, and the average of the three measurements was used.

[0093] 2. Moisture distribution test of toffee gel

[0094] Low-field nuclear magnetic resonance (LF-NMR) spectrometer (MicroMR20-030V–I) was used to perform LF-NMR experiments on toffee gels. Prior to testing, the instrument was calibrated using a calibration sample (oil sample) according to the calibration procedure (Q-FID, Quence Free Induction Decay). Approximately 3.5 g of toffee gel was weighed and individually wrapped in plastic wrap. Each sample was tested in a test container (30 mm × 200 mm). The instrument parameters were adjusted as follows: time echo (TE) = 0.6 ms, wait time (TW) = 8000 ms, number of scans (NS) = 6, preamplifier gain (PRG) = 3, and number of echoes (NECH) = 10000. Each toffee gel was tested three times, and the average of the three measurements was calculated.

[0095] 3. Total colony count

[0096] The total colony count (CFU) was calculated using the CFU method. A 5.0g toffee sample was placed in a 70% sodium chloride solution and homogenized for 90 seconds using a slapping homogenizer. 100μL of the resulting solution was diluted into three dilutions. 100μL of each dilution was evenly spread onto sterile culture medium and incubated in a 28°C incubator for 48 hours before colony count on the plate.

[0097] 4. Quality deviation rate

[0098] The measurement is carried out by weighing method. Deviation rate (%) = | Print product quality - Software slice sample quality | / Software slice sample quality.

[0099] 5. Sensory evaluation

[0100] A nine-point sensory evaluation scale was used. A panel of 10 professionals aged between 20 and 30 years old evaluated the sensory attributes of 3D-printed whole grain milk candy for consumer acceptance. The nine-point scale evaluated the product's color, flavor, mouthfeel, texture, and overall acceptability, with 1 indicating extremely dislike, 5 indicating neutral, and 9 indicating extremely like.

[0101] 6. Toffee texture test

[0102] The texture of the toffee was tested using a TA-XT-plus texture analyzer. Prior to testing, the instrument was calibrated based on the sample's weight and height. During the experiment, a printed test sample with a side length of 15 mm was placed in the center of the instrument's test platform. The cylindrical probe used in the test was a 35 mm diameter probe. The measurement parameters were: pre-test speed = 2 mm / s, test speed = 2 mm / s, post-test speed = 2 mm / s, and compressive strain = 45%. Hardness, adhesion, gluing, and cohesion were measured.

[0103] 7. Toffee texture enhancement test

[0104] Synergistic effect is an indicator of the degree of liquid exudation in a food system. Foods experiencing synergistic effect are often accompanied by poor visual appearance. A 20 mm diameter circle was drawn in the center of the filter paper, and each set of toffee printed material (2 grams) was pressed within the circle. The filter paper containing the printed material was then allowed to rest for 30 minutes. The wetted area of ​​the filter paper was calculated to reflect the water stability of different toffee gels.

[0105] 8. Calorie measurement of milk candy

[0106] The calories in milk candy are calculated based on the standard values ​​and conversion factors of protein, fat, carbohydrates, etc. provided in the Chinese Food Nutrition Composition Table and the nutrient reference values ​​combined with the milk candy component analysis.

[0107] (1) Performance test of different toffee printing materials, see Table 1 for details:

[0108] Table 1 Comparison of test indicators of different embodiments (one starch toffee and three coarse grain toffees)

[0109]

[0110]

[0111] The toffees improved by the conditions of the present invention in Examples 1-3 and the toffees in Comparative Examples 1-3 were tested for rheological properties, moisture distribution, total bacterial count, mass deviation, sensory evaluation, texture, water holding capacity, and energy. The results showed that, at the same addition amount, the extrusion stress of the toffee gel containing low-acyl gellan gum (Example 1) was significantly lower than that of the toffee gel containing gelatin (Comparative Example 1). This demonstrates that the strategy of replacing gelatin with low-acyl gellan gum not only reduces the use of animal protein but also improves the rheological properties of the toffee gel, enhancing its printability and sensory acceptance. The moisture distribution results show that low-acyl gellan gum can better limit the water flow of the gel. The water loss of gellan gum corn toffee (Example 1) is significantly lower than that of gelatin corn toffee (Comparative Example 1). In addition, there is no significant difference in colony count, hardness, and adhesiveness between gellan gum corn toffee (Example 1) and gelatin corn toffee (Comparative Example 1). At the same addition amount, the calories of the toffee gel containing erythritol (Example 2) are significantly lower than those of the toffee gel containing white sugar (Comparative Example 2). This shows that erythritol significantly reduces the calories of the toffee, achieving the purpose of low calorie. The mass deviation of the purple sweet potato toffee in Comparative Example 2 is 7.48%, which indicates that the toffee gel has broken lines and faults during printing. In contrast, the mass deviation of the purple sweet potato toffee in Example 2 is 2.01. This is because the addition of erythritol reduces the flow stress, hardness, adhesion, and water dissipation of the toffee gel, enhancing the printability of the toffee gel. In addition, there were no significant differences in moisture distribution, total bacterial count, and adhesiveness between the milk candies of Comparative Example 2 and Example 2. However, there were significant differences in quality deviation, sensory evaluation, and cohesion between the coix seed milk candies produced using a conventional nozzle (Comparative Example 3) and a coaxial nozzle (Example 3). This suggests that the use of a coaxial nozzle improves printing suitability and print completion rate, and reduces line breakage and faulting during printing. The use of a coaxial nozzle significantly improves the printing performance of high-viscosity milk candy gels.

[0112] It can be seen that the low-calorie 3D printed children's coarse grain candy prepared by the present invention has significant improvements in reducing the use of animal protein, reducing calories and improving printing suitability, and can effectively ensure the quality of all aspects of 3D printed candy.

[0113] (2) Product display of different toffee printing materials, see Figure 1:

[0114] Figure 1 Product display of different embodiments (three kinds of coarse grain toffee).

[0115] (3) Texture indicators of different toffee printing products, see Figure 2(a) to Figure 2(d) :

[0116] Figure 2(a) to Figure 2(d) It is the texture index of different embodiments (three kinds of coarse grain toffee).

Claims

1. A method for preparing low-calorie 3D printed coarse grain candy for children, characterized in that: The following steps are involved: (1) Preparation of sol solution: low acyl gellan gum is added to water and stirred until the low acyl gellan gum is completely dissolved in the water; (2) Boiling sugar: adding erythritol to the sol solution of step (1) and stirring until a fine and viscous sugar solution is formed; (3) Starch gelatinization: add the coarse grain powder to the sugar solution in step (2), heat and stir until the starch is completely gelatinized, and use it as the printing substrate; (4) Preparation of toffee gel: Add whole milk powder and anhydrous butter to the printing substrate obtained in step (3) and continue stirring until a fine and uniform toffee gel is obtained; (5) Ultrasonic treatment: placing the prepared milk candy gel in an ultrasonic device to eliminate bubbles and homogenize the texture, enhance the pseudoplastic fluid behavior of the milk candy gel, and obtain the inner layer printing material for 3D printing; (6) Preparation of outer layer wrapping material: preparing a starch suspension, and heating and stirring until the starch is completely gelatinized to obtain an outer layer wrapping material; (7) Loading: Cool the inner printing material and the outer wrapping material to 60-65°C, then move them to the printing barrel and preheat them respectively; the printing nozzle uses a coaxial nozzle, where the inner nozzle is filled with the inner printing material and the outer nozzle is filled with the outer wrapping material; (8) 3D printing: import the target model into the printing software, start the preheating process of the printing barrel, set the printing program parameters and print; In the step (1), the low acyl gellan gum is gellan gum from which the acyl groups have been completely removed; the addition ratio of the low acyl gellan gum to water is 0.9%-1% w / v; and the ambient temperature at which the low acyl gellan gum dissolves in water is 90-95° C.; In the step (2), the addition ratio of erythritol is such that, based on the volume ratio of the solution in step (1), the proportion of erythritol in the solution is 47%-50% w / v; In the step (3), the amount of coarse grain powder added is: the coarse grain powder accounts for 10%-12% of the mass of the sugar solution in step (2); the coarse grain powder is freeze-dried coarse grain powder that can pass through a 200-mesh sieve, and the type of coarse grain powder is: one of freeze-dried corn flour, freeze-dried purple sweet potato flour or freeze-dried coix seed flour; the gelatinization temperature condition is: in a water bath at 85-90°C; the center temperature of the printing substrate after gelatinization is completed needs to exceed 100°C to ensure complete gelatinization.

2. The method for preparing a low-calorie 3D printed coarse grain toffee for children according to claim 1, characterized in that: In the step (2), the stirring condition is: stirring in an oil bath at 105-110°C.

3. The method for preparing a low-calorie 3D printed coarse grain toffee for children according to claim 1, characterized in that: In the step (4), the added amounts of whole milk powder and anhydrous butter account for 35%-40% and 8%-10% of the mass of the printing substrate in step (3), respectively; the stirring environmental conditions are: stirring in a 90-95°C water bath; the stirring speed is 30-50r / min, and the stirring time is 20-30min.

4. The method for preparing a low-calorie 3D printed coarse grain toffee for children according to claim 1, characterized in that: In the step (5), the storage modulus of the inner layer printing material is 1500-6000 Pa, the loss modulus is 500-2000 Pa, and the viscosity is 2500-6000 Pa·s.

5. The method for preparing a low-calorie 3D printed coarse grain toffee for children according to claim 1, characterized in that: In the step (6), the mass concentration of the starch suspension is 18%-20%; the gelatinization temperature conditions are: gelatinization under the conditions of magnetic stirring and 85-90°C water bath.

6. The method for preparing a low-calorie 3D printed coarse grain toffee for children according to claim 1, characterized in that: In the step (7), the preheating temperature is set as the target printing temperature at 60-65°C; the preheating time is 10-15 minutes; the diameter of the coaxial nozzle varies according to the type of coarse grain and the printing model, and the coaxial nozzle size is set as follows: the nozzle diameter of the inner layer material is 0.8-1.2 mm, and the thickness of the outer layer material is 0.08-0.1 mm.

7. The method for preparing a low-calorie 3D printed coarse grain toffee for children according to claim 6, characterized in that: In the step (8), the filling rate of the printing model is 80%-85%, the size of the printing model is within 35mm×30mm×25mm, and the internal filling routing method during printing is honeycomb 80-90° filling or triangle 55-60° filling; before printing, the barrel temperature needs to be preset to the target printing temperature, and before the printing process starts, it is necessary to wait for the temperature of the printing material in the printing barrel to stabilize to the target printing temperature; before starting printing, the printing program parameters are set: the default printing speed is 28-30mm / s, the material filling rate is 80%-85%, the printing wire diameter is 18-20mm, and the z-axis offset is 1.4-1.6mm.

8. The method for preparing a low-calorie 3D printed coarse grain toffee for children according to claim 1, characterized in that: The low-calorie 3D printed children's coarse grain toffee has a hardness of 200-220g, an adhesion of -50-40g.s, a glutinousness of 140-170g, a cohesion of 0.9 or more, and a calorie content of less than 1300 kilojoules per 100 grams. When the inner layer printing material and the outer layer wrapping material are extruded at the same time, they must be continuous and unbroken, and the outer layer wrapping material must wrap the inner layer printing material. The outer layer wrapping material avoids the line adhesion phenomenon caused by direct contact of the inner layer printing material during the printing process, so that the printing material can be continuously stacked to complete the printing progress.

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