A snack food of extruded corn pellets coated with casein and a method of making the same

Abstract

The present application belongs to the technical field of leisure food processing, and particularly relates to a preparation method of a leisure food with a low-moisture puffed corn ball coated with casein, which comprises the following steps: preparing a low-moisture puffed corn ball core through double-screw extrusion puffing, using coconut oil and hydrogenated palm oil to prepare a compound functional oil with a melting point of 35-40 DEG C, adding lecithin to improve the interlayer adhesion, forming an oil layer through one-time coating by a polishing machine, and then performing gradient cooling and shaping, and finally performing dry coating of a casein barrier layer to obtain a three-layer structure leisure food. The present application is a non-frying process, and the parameters of each step are controllable. The outer layer of casein can isolate oxygen to prevent oil oxidation and deterioration, the compound oil melts immediately, the product has both the crisp and fragrant taste of grains and the rich and mellow milk flavor, the taste levels are distinct, the adhesion of casein is high, the product is stable at room temperature, the dry cheese flavor can be realized without high-cost original cheese, the raw material cost is low, the process is simple, and the present application is suitable for industrial large-scale production, and can effectively improve the product shelf life and eating experience.

Description

Technical Field

[0001] This invention belongs to the field of snack food processing technology, specifically relating to a snack food made by coating puffed corn balls with casein and its preparation method. Background Technology

[0002] Processed cheese is a homogenized product made from one or more natural cheeses as the main raw material through processes such as heating, melting, emulsification, and cooling. It features a mild flavor, long shelf life, stable texture, and excellent meltability and spreadability, and is widely used in the catering, baking, and snack food industries. Due to the high cost of natural cheese raw materials, processed cheese has become an important direction for the snackification of dairy products. However, existing processed cheese products still suffer from problems such as high raw material costs, limited flavor acceptance, and limited product variety.

[0003] Extruded corn products, with their crisp and porous structure, are a mainstream carrier for snack foods. Combining extruded grains with processed cheese can create a complex texture that combines crispness and a milky aroma. Existing technologies often inject cheese as a filling into extruded foods or simply mix it, making it difficult to create a stable three-layer structure with a crisp core, a smooth and stringy middle layer, and a flavorful powdery outer layer. Furthermore, these technologies generally suffer from drawbacks such as the outer cheese layer easily falling off, the internal fats easily oxidizing and becoming rancid, difficulty melting in the mouth, and poor stability during room temperature storage. Additionally, the resulting products have a limited range of flavor profiles and fail to achieve the complex taste experience of a flavorful outer layer, a smooth and stringy middle layer, and a crisp core.

[0004] Currently, most domestic and international technologies focus on processes such as emulsification, enzymatic hydrolysis, stringing, and flavor control of processed cheese, or on direct processing of natural cheese as raw material. These technologies have high raw material costs and limited target audiences. There are no known snack products or corresponding preparation processes that use puffed corn balls as the core, are completely coated with casein on the outside, and achieve stable anti-oxidation, storage and transportation resistance, and rich taste through a three-layer structure. Summary of the Invention

[0005] (a) Technical problems to be solved In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a snack food of puffed corn balls coated with casein and its preparation method, which is used to solve the following problems: First, the cost of raw materials for original cheese is high, and the production cost of processed cheese remains high, limiting its promotion; Second, it is rare to find a stable three-layer structure with a crispy core, a smooth and stringy middle layer, and a powdery outer layer with a distinct and rich flavor; Third, the oil contained in the product is prone to oxidation and rancidity, does not melt in the mouth, and has poor storage properties at room temperature; Fourth, existing processed cheeses mostly rely on imported original cheeses, and their flavors have limited acceptance among some groups, making it difficult to adapt to the domestic consumer market, etc.

[0006] (II) Technical Solution The technical solution adopted in this invention is as follows: In a first aspect, the present invention provides a method for preparing a snack food consisting of puffed corn balls coated with casein, comprising the following steps: S1. Preparation of puffed corn kernels: Corn flour is mixed with water to obtain wet material, which is then fed into a twin-screw extruder. After mixing, cooking, and high-temperature puffing, the material is extruded and cut through a spherical mold to obtain porous puffed corn kernels, which are then dried. S2. Preparation of composite functional oils: Coconut oil and hydrogenated palm oil are compounded until the melting point of the mixed oils reaches 35-40℃. Then, 0.3-0.5wt% lecithin is added to obtain composite functional oils. The mixture is heated to 45-55℃ and melted into a liquid state for later use. S3. One-time coating and molding: The dried puffed corn cobs are fed into a polishing and coating machine, and molten composite functional grease is sprayed on them to form a grease adhesion layer with a thickness of 0.1-0.3mm on the surface of the corn cobs, thus obtaining the intermediate. S4. Cooling and setting: Cooling the intermediate to allow the grease layer to solidify completely and set the shape. S5. Secondary dry coating barrier layer: The intermediate after cooling and shaping is coated with casein by rolling or spraying for 15-25 seconds to form an outer protective film that isolates oxygen, resulting in a three-layer structure product with core, oil flavor layer and casein barrier layer. S6. Pre-packaged in fixed quantities, store at room temperature or refrigerated.

[0007] According to a preferred embodiment of the present invention, in S1, the moisture content of the wet material is controlled at 15-18%, the feeding frequency of the wet material is 12-12.5Hz, and the porous puffed corn cob is dried to a moisture content of 3%-8%.

[0008] According to a preferred embodiment of the present invention, in S2, the mass ratio of coconut oil to hydrogenated palm oil is 1:1-4.

[0009] According to a preferred embodiment of the present invention, in step S3, the polishing coating machine rotates at a speed of 20-40 r / min and the polishing time is 3-5 min, so that a grease adhesion layer with a thickness of 0.1-0.3 mm is formed on the surface of the ball core; preferably, the polishing coating machine is an octagonal elliptical polishing machine. Under the aforementioned conditions, the obtained intermediate has no missed coating and a smooth surface.

[0010] According to a preferred embodiment of the present invention, in S4, the surface hardness of the solidified intermediate reaches 10~15HA, with no cracking and no stickiness.

[0011] According to a preferred embodiment of the present invention, in S4, the cooling and shaping adopts a gradient cooling mechanism, that is: first cooling at 25-30℃ for 5-10 minutes, and then cooling at 18-22℃ for 10-15 minutes.

[0012] According to a preferred embodiment of the present invention, in step S5, before rolling or spraying the intermediate, the casein is first adjusted to a moisture content of 3-6%. Random sampling inspection shows that the adhesion strength of the casein to the product surface is ≥95%.

[0013] Secondly, the present invention provides a snack food in which puffed corn balls are coated with casein, which is prepared by any of the above-described embodiments.

[0014] (III) Beneficial Effects This invention overcomes the technical limitations of existing puffed cereal and cheese snack foods through unique processes such as step-by-step coating, gradient cooling and shaping, and precise control of compound oils. It abandons high-cost raw cheese ingredients and relies on a low-cost vegetable oil and casein compound system to achieve comprehensive optimization of structure, taste, processing, and shelf life. Compared with existing technologies, it has the following outstanding and beneficial technical effects: 1. This invention successfully constructs a stable three-layer composite structure consisting of a crispy puffed corn kernel, a smooth and molten oil middle layer, and a dense casein outer layer, completely solving the problems of weak interlayer bonding and easy detachment of the outer powder layer in existing similar products. By adding 0.3-0.5wt% lecithin to the composite functional oil, the emulsifying and adhesion-enhancing effects of lecithin are utilized to simultaneously strengthen the bonding strength between the molten oil layer and the puffed corn kernel and the outer casein barrier layer. Combined with a secondary dry coating process, the casein adhesion strength on the product surface is ≥95%, eliminating problems such as powder shedding, missed coating, and delamination cracking, and significantly improving structural integrity.

[0015] 2. This invention precisely controls the melting point of the composite functional oil within the range of 35-40℃ through the targeted blending of coconut oil and hydrogenated palm oil, which is close to the temperature of the human mouth and achieves a smooth texture that melts in the mouth without the defects of hard lumps or failure to melt in the mouth. Among them, coconut oil can naturally enhance the milky flavor of the product, and the blended hydrogenated palm oil can synergistically regulate the oil's shape retention and consistency, ensuring that the oil layer is not sticky, does not seep oil, and does not soften or deform at room temperature, thus taking into account both room temperature shape retention and in-mouth melting.

[0016] 3. In a preferred embodiment of the present invention, a gradient cooling and setting process is adopted, which first cools at 25-30°C and then solidifies at 18-22°C, so that the oil layer can be quickly solidified and set. After setting, the surface hardness of the intermediate is stable at 10-15HA, without cracking or sticking, further ensuring the stability of the taste.

[0017] 4. The snack food of this invention forms a distinct and contrasting triple texture and flavor layer, breaking through the limitation of the single texture of existing puffed foods: upon entering the mouth, the outer casein film dissolves instantly, releasing a rich cheese flavor first; during chewing, the middle layer of composite fats with a melting point of 35-40℃ melts rapidly, presenting a smooth and dense milky texture, restoring the unique smooth texture of cheese; finally, the loose and crispy texture of the puffed corn ball in the core and the caramelized aroma of grains are highlighted, with a natural flavor transition, the milky aroma and grain aroma complementing each other, possessing both a rich cheese flavor and a refreshing grain aroma, making it far more fun and enjoyable than existing similar products. More importantly, this invention takes a unique approach with ingenious design, achieving a flavor and nutrition comparable to cheese without using high-cost original cheese, with casein accounting for more than 15% of the dry basis content, resulting in stronger nutritional adaptability and a wider audience coverage.

[0018] 5. Utilizing the outer layer of casein to form a complete and dense oxygen barrier membrane, combined with a dry coating process using casein with a suitable moisture content of 3-6%, it achieves comprehensive sealing and isolation of the middle layer of complex oils. This completely prevents external air from contacting the internal oils, fundamentally preventing oil oxidation and rancidity (commonly known as rancidity, referring to the phenomenon where oils oxidize and deteriorate due to prolonged contact with air, producing a pungent sour and rancid odor and a poor taste), effectively extending the product's shelf life. The product can be stored at room temperature or refrigerated, adapting to diverse storage and transportation scenarios, and solving the industry pain points of existing oil-based puffed snacks, such as easy oxidation, short shelf life, and poor stability at room temperature.

[0019] 6. In a preferred embodiment of the present invention, the corn flour core is processed using a non-fried method, which is safe and healthy and meets the consumption needs of modern snack foods. A step-by-step coating mode is adopted, first preparing low-moisture puffed corn flour cores (moisture content 3%-8%), then performing oil spray coating, gradient cooling, and dry casein coating. The parameters of each process are precisely controllable, including wet material moisture content of 15-18%, feeding frequency of 12-12.5Hz, polishing and coating speed of 20-40r / min, coating time of 3-5min, and casein coating time of 15-25s. This allows for precise control of the thickness and uniformity of each layer, resulting in stable product quality, small batch differences, and suitability for continuous industrial production, significantly improving production efficiency and product qualification rate.

[0020] 7. This invention does not rely on expensive imported original cheese as a core ingredient, thus avoiding the problems of high cost and limited flavor acceptance of original cheese. It uses conventional and readily available raw materials such as corn flour, vegetable oil, and casein, and achieves cheese flavor and nutrition through process innovation, which greatly reduces raw material costs and production thresholds, making it suitable for large-scale promotion and application. Detailed Implementation

[0021] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to specific embodiments.

[0022] This invention provides a method for preparing a snack food made of puffed corn balls coated with casein, comprising the following steps: S1. Preparation of puffed corn cobs: Corn flour is mixed with water to obtain a wet material with a moisture content of 15-18%. The wet material is fed into a twin-screw extruder at a feeding frequency of 12-12.5Hz. After mixing, maturing, and high-temperature puffing, the material is extruded and cut through a spherical die to obtain porous puffed corn cobs. The cobs are then dried to a moisture content of 3%-8%.

[0023] S2. Preparation of compound functional oils: Coconut oil and hydrogenated palm oil are compounded until the melting point of the mixed oils reaches 35-40℃. Then, 0.3-0.5wt% lecithin is added to obtain compound functional oils. The mixture is heated to 45-55℃ and melted into a liquid state for later use.

[0024] When formulating multifunctional oils, the ratio of coconut oil to hydrogenated palm oil does not need to be strictly limited, but coconut oil is an essential ingredient, with a content of 20% or higher, adjusted according to the desired flavor intensity. The optimal ratio of coconut oil to hydrogenated palm oil is sufficient to adjust the oil mixture to a melting point of 35-40℃, achieving a smooth, melt-in-your-mouth texture. Coconut oil itself has a natural, mild milky aroma, which can simulate the creamy flavor of cheese; combined with hydrogenated palm oil, it helps to control the melting point of the multifunctional oil to 35-40℃, ensuring room temperature setting and a melt-in-your-mouth texture. Preferably, the mass ratio of coconut oil to hydrogenated palm oil is 1:1-4.

[0025] S3. One-time coating and molding: The dried puffed corn cobs are fed into an octagonal oval polishing machine, and molten composite functional grease is sprayed on them. Under the conditions of a rotation speed of 20-40 r / min and polishing for 3-5 minutes, a grease adhesion layer with a thickness of 0.1-0.3 mm is formed on the surface of the corn cobs, thus obtaining the intermediate. Polishing under the aforementioned conditions can ensure that the intermediate has no missed coating and a smooth surface, resulting in a higher product qualification rate. However, excessive rotation speed leads to severe centrifugal collision, while excessively low rotation speed can easily cause adhesion, making it difficult to obtain an intermediate with a smooth surface and no missed coating.

[0026] S4. Cooling and Setting: The intermediate is cooled to allow the oil layer to completely solidify and set, achieving a surface hardness of 10-15 HA, with no cracking or stickiness. Preferably, a gradient cooling mechanism is used, i.e., first cooling at 25-30℃ for 5-10 minutes, then cooling at 18-22℃ for 10-15 minutes for deep solidification, ensuring sufficient and stable surface hardness of the set intermediate, without cracking or sticking, further guaranteeing the stability of the taste.

[0027] S5. Secondary dry coating barrier layer: The cooled and set intermediate is coated with casein (3-6% moisture content) by rolling or spraying for 15-25 seconds to form an oxygen-isolated outer protective film, resulting in a three-layer structure: core, oil flavor layer, and casein barrier layer. Random sampling inspection shows that the adhesion strength of casein on the product surface is ≥95%.

[0028] S6. Quantitative packaging, ready for storage at room temperature or refrigeration.

[0029] The raw materials used in this invention are readily available. The core ingredients—corn flour, coconut oil, hydrogenated palm oil, and casein—are all common bulk raw materials in the food industry, with wide procurement channels and ample supply. This eliminates the need to rely on imported original cheese or special functional additives, which are scarce and expensive. This significantly reduces raw material procurement costs from the source, overcoming the industry bottleneck of traditional processed cheese snacks being constrained by the high price and limited production capacity of original cheese. Simultaneously, it avoids the problems of strong flavor and low acceptance among some groups associated with original cheese, adapting to the tastes of the general domestic consumer and broadening the product's appeal. The entire production process requires no particularly stringent equipment requirements; large-scale production can be achieved using conventional extrusion puffing, polishing, coating, and cooling equipment without the need for additional specialized production lines. This low-barrier-to-entry approach, moderate energy consumption, and balance of economic benefits and market promotion value make it highly potential for industrialization.

[0030] The following description is based on preferred embodiments of the present invention.

[0031] Example 1 This embodiment provides a snack food made by coating puffed corn balls with casein, the preparation of which includes: (1) Preparation of puffed corn kernels: 100 mesh corn flour is mixed with water and adjusted to a moisture content of 14%. The feeding frequency is 12Hz. The feed is sent to a twin-screw extruder. After mixing, cooking and high-temperature puffing, the powder is extruded and cut into spheres with a diameter of about 8mm by a spherical die head. The powder is then dried to a moisture content of 3% to obtain puffed corn kernels.

[0032] (2) Preparation of compound functional oils: Coconut oil: hydrogenated palm oil = 1:1 compound, with a specific mass ratio of 500g coconut oil and 500g hydrogenated palm oil. The melting point of the mixed oils is controlled within the range of 35-40℃. 0.3wt% lecithin is added, and after mixing, the temperature is raised to 45℃ to liquid state for later use.

[0033] (3) First coating: The puffed corn kernels are fed into an octagonal elliptical polishing machine, the rotation speed is controlled at 30 r / min, the coating time is 3 min, and the composite grease is sprayed to form an grease adhesion layer with an average thickness of 0.17 mm, thus obtaining the intermediate.

[0034] (4) Gradient cooling and shaping: first cool at 25℃ for 5 minutes, then cool at 18℃ for 10 minutes. After shaping, the surface hardness of the intermediate is 10HA, with no cracks and no stickiness.

[0035] (5) Secondary coating: The casein is adjusted to 3% moisture (the lower limit of casein moisture in claim 7), and the intermediate is rolled for 15 seconds (the lower limit of coating time in claim 5) to obtain a three-layer structure product, which is quantitatively packaged and stored at room temperature.

[0036] Example 2 This embodiment provides a snack food made by coating puffed corn balls with casein, the preparation of which includes: (1) Preparation of puffed corn kernels: 100-mesh corn flour is mixed with water and adjusted to a moisture content of 16%. The feeding frequency is 12Hz. The mixture is fed into a twin-screw extruder. After mixing, cooking and high-temperature puffing, the mixture is extruded and cut into spheres with a diameter of about 8mm by a spherical die head. The mixture is then dried to a moisture content of 5.5% to obtain puffed corn kernels.

[0037] (2) Preparation of compound functional oils: Coconut oil: hydrogenated palm oil = 1:2, with a specific mass ratio of 350g coconut oil and 700g hydrogenated palm oil. The melting point of the mixed oils is controlled within the range of 35-40℃. 0.4wt% lecithin is added, and after mixing, the temperature is raised to 50℃ to liquid state for later use.

[0038] (3) First coating: The puffed corn kernels are fed into an octagonal oval polishing machine, the rotation speed is controlled at 30 r / min, the coating time is 4 min, and the composite grease is sprayed to form a grease adhesion layer with a thickness of 0.2 mm, thus obtaining the intermediate.

[0039] (4) Gradient cooling and shaping: First, cool at 27.5℃ for 7.5 min, then cool at 20℃ for 12.5 min. After shaping, the surface hardness of the intermediate is 12.5HA, with no cracks and no stickiness.

[0040] (5) Secondary coating: Adjust the casein to 4.5% moisture content, roll the intermediate for 20 seconds to obtain a three-layer structure product, package it quantitatively and store it at room temperature.

[0041] Example 3 This embodiment provides a snack food made by coating puffed corn balls with casein, the preparation of which includes: (1) Preparation of puffed corn kernels: 100 mesh corn flour is mixed with water and adjusted to a moisture content of 18%. The feeding frequency is 12.5 Hz. The mixture is fed into a twin-screw extruder. After mixing, cooking and high-temperature puffing, the mixture is extruded and cut into spheres with a diameter of about 8 mm by a spherical die head. The mixture is then dried to a moisture content of 8% to obtain puffed corn kernels.

[0042] (2) Preparation of compound functional oils: Coconut oil: hydrogenated palm oil = 1:3, with a specific mass ratio of 250g coconut oil and 750g hydrogenated palm oil. The melting point of the mixed oils is controlled within the range of 35-40℃. 0.5wt% lecithin is added, and after mixing, the temperature is raised to 50℃ to liquid state for later use.

[0043] (3) First coating: The puffed corn kernels are fed into an octagonal elliptical polishing machine, the rotation speed is controlled at 35 r / min, the coating time is 5 min, and the composite grease is sprayed to form a grease adhesion layer with a thickness of 0.3 mm, thus obtaining the intermediate.

[0044] (4) Gradient cooling and shaping: First, cool at 30℃ for 10 minutes, then cool at 18℃ for 15 minutes. After shaping, the surface hardness of the intermediate is 15HA, with no cracks and no stickiness.

[0045] (5) Secondary coating: Adjust the casein to 6% moisture content, roll the intermediate for 25 seconds to obtain a three-layer structure product, package it quantitatively and store it in the refrigerator.

[0046] Example 4 This embodiment provides a snack food made by coating puffed corn balls with casein, the preparation of which includes: (1) Preparation of puffed corn kernels: 100-mesh corn flour is mixed with water to adjust the moisture content to 16%, the feeding frequency is 12Hz, and after twin-screw extrusion puffing, it is cut into shape by a spherical die head and dried to a moisture content of 5% to obtain puffed corn kernels.

[0047] (2) Preparation of compound functional oils: Coconut oil: hydrogenated palm oil = 1:4, with a specific mass ratio of 200g coconut oil and 800g hydrogenated palm oil. The melting point of the mixed oils is controlled within the range of 35-40℃. 0.4wt% lecithin is added, and after mixing, the temperature is raised to 50℃ to liquid state for later use.

[0048] (3) First coating: The puffed corn core is fed into an octagonal oval polishing machine, the rotation speed is controlled at 30 r / min, the coating time is 4 min, the grease layer thickness is 0.2 mm, and the intermediate is obtained.

[0049] (4) Gradient cooling and shaping: first cool at 28℃ for 8 minutes, then cool at 20℃ for 13 minutes. The surface hardness of the intermediate is 13HA, with no cracks and no stickiness.

[0050] (5) Secondary coating: Casein with 4% moisture content is rolled for 20 seconds to obtain the finished product, which is then packaged in a quantitative manner and stored at room temperature.

[0051] The products of Examples 1 to 4 of the present invention are compared with two commercially available traditional processed cheese blocks of well-known brands A and B, including quality comparison, weighing, taste, quantitative analysis, etc. In addition, the casein shedding rate of the products of Examples 1 to 4 is tested. The test method is: after centrifugation at 200 r / min for 5 min, a casein shedding amount of ≤5% is qualified, and a casein shedding amount of more than 5% is unqualified, and the broken ball rate is calculated. The above comparison results are summarized in Table 1.

[0052] Table 1: Further, after the product prepared by the present invention is stored at indoor natural temperature (35°C) through the summer and then the package is opened for observation, the product still has uniform color, no shedding of the outer casein, no adhesion. After tasting, it has good melt-in-mouth property, crispness, rich flavor layers, the taste is still as fresh and fragrant as the beginning, no rancid off-flavor (no rancid taste), and has grain roasted aroma and compound milk flavor.

[0053] In summary, the preparation method of the puffed corn ball snack coated with casein of the present invention does not need to rely on expensive imported natural cheese as the core raw material, avoids the problems of high cost and limited flavor acceptance of natural cheese, adopts conventional and easily available raw materials such as corn flour, vegetable oil and casein, realizes cheese-like flavor and nutrition through process innovation, greatly reduces raw material cost and production threshold, and is suitable for large-scale popularization and application.

[0054] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present invention, not to limit them; although the present invention has been described in detail with reference to the foregoing examples, those of ordinary skill in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacements for some or all of the technical features therein; and these modifications or replacements, or in the case that the technical features in the above examples do not conflict with each other, can be combined in the manner recorded in the examples, and these modifications, replacements or combinations do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the examples of the present invention.

Claims

1. A method for preparing a snack food made of puffed corn balls coated with casein, characterized in that, It includes the following steps: S1. Preparation of puffed corn kernels: Corn flour is mixed with water to obtain wet material, which is then fed into a twin-screw extruder. After mixing, cooking, and high-temperature puffing, the material is extruded and cut through a spherical mold to obtain porous puffed corn kernels, which are then dried. S2. Preparation of composite functional oils: Coconut oil and hydrogenated palm oil are compounded until the melting point of the mixed oils reaches 35-40℃. Then, 0.3-0.5wt% lecithin is added to obtain composite functional oils. The mixture is heated to 45-55℃ and melted into a liquid state for later use. S3. One-time coating and molding: The dried puffed corn cobs are fed into a polishing and coating machine, and molten composite functional grease is sprayed on them to form a grease adhesion layer with a thickness of 0.1-0.3mm on the surface of the corn cobs, thus obtaining the intermediate. S4. Cooling and setting: Cool the intermediate to allow the grease layer to solidify completely and set the shape. S5. Secondary dry coating barrier layer: The intermediate after cooling and shaping is coated with casein by rolling or spraying for 15-25 seconds to form an outer protective film that isolates oxygen, resulting in a three-layer structure product with core, oil flavor layer and casein barrier layer. S6. Pre-packaged in fixed quantities, store at room temperature or refrigerated.

2. The preparation method according to claim 1, characterized in that, In S1, the moisture content of the wet material is controlled at 15-18%, the feeding frequency of the wet material is 12-12.5Hz, and the porous puffed corn cobs are dried to a moisture content of 3%-8%.

3. The preparation method according to claim 1, characterized in that, In S2, the mass ratio of coconut oil to hydrogenated palm oil is 1:1-4.

4. The preparation method according to claim 1, characterized in that, In S3, the polishing and coating machine rotates at 20-40 r / min and polishes for 3-5 min, forming a grease adhesion layer with a thickness of 0.1-0.3 mm on the surface of the ball core; the polishing and coating machine is an octagonal elliptical polishing machine.

5. The preparation method according to claim 1, characterized in that, In S4, the surface hardness of the solidified intermediate reaches 10~15HA, with no cracking and no stickiness.

6. The preparation method according to claim 5, characterized in that, In S4, the cooling and shaping process adopts a gradient cooling mechanism, namely: first cooling at 25-30℃ for 5-10 minutes, and then cooling at 18-22℃ for 10-15 minutes.

7. The preparation method according to claim 1, characterized in that, In S5, before rolling or spraying the intermediate, the casein is first adjusted to a moisture content of 3-6%.

8. A snack food made by coating puffed corn balls with casein, characterized in that, It is prepared by the preparation method according to any one of claims 1-7.

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