Pure highland barley powder extrusion puffing process optimization method

Abstract

The invention discloses a pure highland barley powder extrusion puffing process optimization method, and belongs to the technical field of food extrusion processing. According to the method, the technical problems that the high-fiber highland barley powder is easily subjected to insufficient puffing and too hard texture in the extrusion process, and the retention rate of heat-sensitive functional components such as beta-glucan is low are solved. The method comprises the following steps: optimizing process parameters based on a multi-target response surface method, and determining the water content of materials, the temperatures of a first region, a second region, a third region and a fourth region of a machine barrel and the rotating speed of a screw; carrying out low-temperature superfine grinding on the highland barley powder; a compound emulsifier and edible sodium bicarbonate are added during hardening and tempering; during extrusion, the temperature gradient between the third area and the fourth area is controlled to be smaller than or equal to 20 DEG C; the method is mainly used for producing the high-quality pure highland barley puffed food, the puffing rate and the beta-glucan retention rate of the product can be synergistically improved, the hardness of the product is effectively controlled, and the eating quality and the nutritional value are improved.

Description

Technical Field

[0001] This invention belongs to the field of food extrusion processing technology, specifically relating to an optimized method for the extrusion puffing process of pure highland barley flour. Background Technology

[0002] Barley, a grain high in dietary fiber and β-glucan, has broad application potential in the health food industry. Extrusion puffing technology is commonly used in grain processing to improve the puffing degree and taste of products, but several technical challenges remain in its application to pure barley flour.

[0003] Due to its high fiber content and unique starch and protein composition, barley flour is prone to insufficient puffing or excessive hardness during extrusion. The high fiber content hinders complete starch gelatinization and uniform puffing, resulting in a low puffing rate. Simultaneously, the water-holding capacity and structural characteristics of the fiber can also contribute to high product hardness, affecting edibility. Furthermore, functional components in barley, such as β-glucan, are heat-sensitive and easily degrade or undergo structural changes during high-temperature, high-pressure extrusion, leading to decreased retention and reduced nutritional value.

[0004] In terms of process parameter control, key variables such as material moisture content, barrel temperature, and screw speed have a significant impact on puffing effect, texture, and nutrient retention. However, there are often constraints between these response indicators. For example, increasing temperature or mechanical shear can improve puffing degree, but may lead to increased β-glucan loss; reducing processing intensity helps retain functional components, but may cause a decrease in puffing rate and an increase in hardness. This trade-off between multiple objectives increases the complexity of process optimization.

[0005] Previous studies have primarily employed single-factor or simple orthogonal experiments to optimize extrusion processes, lacking a systematic strategy for simultaneously optimizing multiple response indicators. This makes it difficult to achieve synergistic improvements in puffing rate, hardness, and component retention. Furthermore, barley materials are prone to water leaching and fiber agglomeration during conditioning and extrusion, affecting material flowability and molding stability, and increasing the difficulty of continuous production. Therefore, it is necessary to explore more refined methods for raw material pretreatment and synergistic parameter control to achieve good puffing structure and texture while maximizing the retention of barley's unique nutritional components. Summary of the Invention

[0006] This invention provides an optimized method for the extrusion puffing process of pure highland barley flour, which can synergistically improve the puffing rate and β-glucan retention rate of the product, while effectively controlling the hardness of the product and improving the formability and stability of high-fiber materials in extrusion processing.

[0007] To achieve these objectives and other advantages of the present invention, the present invention provides an optimized method for the extrusion and puffing process of pure highland barley flour, comprising the following steps: S1. Optimization of process parameters based on multi-objective response: A three-factor, three-level Box-Behnken experimental design was adopted, with material moisture content, the highest temperature in the fourth zone of the barrel, and screw speed as independent variables, and product expansion rate, hardness, and β-glucan retention rate as parallel response indicators. Three quadratic polynomial prediction models were established using multiple regression fitting, and the p-values ​​of each factor and interaction term were calculated through analysis of variance. Items with significant influence were screened with a p-value less than 0.05 as the criterion. By solving the satisfaction function of the prediction model, the optimal combination of process parameters that can simultaneously achieve high expansion rate, low hardness, and high functional component retention rate was obtained. The optimal combination of process parameters is: material moisture content 20%-24%; barrel temperature control range: zone 1 70-85℃, zone 2 110-130℃, zone 3 135-155℃, zone 4 145-165℃; screw speed 180-250 r / min. S2. Raw material pretreatment: The pure barley flour is subjected to low-temperature ultrafine grinding until the particle size passes through a 200-mesh sieve and D90≤75μm, in order to destroy the fiber structure, increase the specific surface area, and avoid protein denaturation caused by high temperature. S3. Conditioning treatment: Add 1.5%-2.5% of the total mass of the pretreated highland barley flour to a compound emulsifier and 1%-3% of edible sodium bicarbonate. The compound emulsifier is composed of glyceryl monostearate and sucrose ester in a mass ratio of 1:1. Calculate and add an appropriate amount of water based on the material moisture content range of 20%-24% determined in S1, and obtain the conditioned material after thorough stirring and homogenization. S4. Extrusion Extrusion: The conditioned material is fed into a twin-screw extruder. The unit is operated according to the barrel temperature and screw speed obtained by the response surface methodology in S1. The temperature gradient between the third and fourth zones of the barrel is controlled to be ≤20℃, and the temperature gradient between the fourth zone and the die is controlled to be ≤10℃. Extrusion extrusion is then carried out to obtain high-quality extruded products.

[0008] Preferably, in the conditioning process of step S3, 0.5%-1% of microcrystalline cellulose by weight of the total mass of barley flour is added as a fiber network modifier to improve the extrusion molding properties of the high fiber content material.

[0009] Preferably, after the extrusion and expansion in step S4, the product undergoes a temperature-controlled tempering treatment: first at 60-70°C for 10 minutes, then at 35-45°C for 20 minutes, to stabilize the microporous structure of the product and prevent cracking.

[0010] Preferably, in the conditioning process of step S3, 0.1%-0.5% of natural vitamin E by weight of the total barley flour is added as a heat protectant to reduce the oxidation reaction under high temperature and high pressure extrusion.

[0011] Preferably, the multi-objective response optimization method in step S1 further includes: A satisfaction function is used to convert multiple response indicators into a single comprehensive satisfaction value. The satisfaction functions for each response indicator are as follows: the puffing rate and β-glucan retention rate are represented by a large-scale function, and the hardness is represented by a small-scale function. The satisfaction levels of each response were integrated using a weighted geometric average method. The weights were set according to product requirements as follows: the weight for puffing rate was 0.4, the weight for hardness was 0.3, and the weight for β-glucan retention rate was 0.3. An optimization algorithm was used to search for the maximum overall satisfaction value within the feasible region of the parameters, and the prediction confidence of the obtained parameter combination was verified to be higher than 95%. The final combination of process parameters must simultaneously meet the following requirements: expansion rate ≥ 350%, hardness ≤ 3.5 N, β-glucan retention rate ≥ 85%, and the overall satisfaction value of the three indicators is not less than 0.85.

[0012] Preferably, the screw element of the twin-screw extruder is configured with three sets of 60-degree staggered kneading blocks and reverse thread elements in the melting section, and shallow groove forward thread elements and two sets of 90-degree staggered kneading blocks in the homogenization section, so as to apply a differentiated shear force that is strong at first and then weak to the high fiber content barley material.

[0013] Preferably, in the conditioning process of step S3, trehalose, accounting for 1%-2% of the total mass of highland barley flour, is added as a moisture regulator to stabilize the water activity of the system and prevent water from separating out.

[0014] Preferably, after obtaining the puffed product in step S4, a coating process is further included: fluidized bed spray coating is performed using a mixed coating agent composed of sodium alginate solution and monoglyceride emulsion, resulting in a coating weight gain of 2%-5%, and finally drying is performed until the moisture content is below 5% to prevent the product from absorbing moisture and softening.

[0015] Preferably, after obtaining the puffed product in step S4, the product is further characterized and analyzed for structure: X-ray diffraction is used to analyze the starch crystallinity, scanning electron microscopy is used to observe the microporous structure, and the retention rate of γ-aminobutyric acid is detected to evaluate the structure and nutritional quality of the product.

[0016] Preferably, the method further includes: establishing a quantitative relationship model between the textural parameters and sensory scores of the puffed product, wherein the textural parameters include hardness, crispness, chewiness, and elasticity, and the sensory scores include mouthfeel, flavor, and overall acceptability; the quantitative relationship model is achieved through the following steps: S110. Conduct texture analysis. Use a texture analyzer to perform full texture analysis on the puffed product and determine the hardness, brittleness, chewiness and elasticity parameters. Each sample shall be measured repeatedly for no less than ten times and the average value shall be taken. S120. Conduct sensory evaluation using a nine-point preference rating system to comprehensively evaluate the crispness, melt-in-your-mouth texture, barley aroma, off-flavor, color, shape, and overall acceptability of the puffed product. S130. Perform data preprocessing, standardize the texture parameters and sensory score data to eliminate the influence of dimensions and improve model stability. S140. Establish a predictive model using partial least squares regression or multiple linear regression, with texture parameters as independent variables and sensory scores or comprehensive sensory scores as dependent variables, and construct a mathematical relationship model; evaluate the predictive ability and robustness of the model through cross-validation. S150. Optimize and validate the model. Select key texture parameters based on variable importance projection values ​​and regression coefficients to simplify the model structure. Use an independent validation set to externally validate the model. The model's predictive performance must meet two indicators simultaneously: the root mean square error of the model's prediction does not exceed 20% of the standard deviation of the sensory score, and the correlation coefficient between the model's predicted value and the actual measured value is greater than or equal to 0.7. S160. The established model is applied to the process control system. By monitoring the texture parameters of the extruded product in real time, its sensory acceptability is predicted. The process parameters such as moisture content, barrel temperature and screw speed are adjusted in reverse to achieve closed-loop control and continuous optimization of product quality.

[0017] The present invention has at least the following beneficial effects: First, this invention utilizes a multi-objective response surface methodology to systematically optimize key process parameters, achieving a balance between puffing rate, hardness, and β-glucan retention rate, thereby improving the overall quality of the product. This method boasts high predictive accuracy and reliability, and the determined process parameter ranges can be directly used for production guidance, enhancing the scientific nature of process control and product consistency. It is suitable for the standardized production of high-quality pure highland barley puffed foods. Second, this invention adds microcrystalline cellulose as a fiber network modifier during the conditioning process, effectively improving the flowability and extrusion molding properties of high-fiber materials, reducing breakage and surface defects during extrusion, and improving the product's morphological integrity and textural uniformity, while maintaining the original nutritional characteristics and puffing effect of highland barley. Third, after extrusion puffing, this invention employs a variable-temperature tempering treatment, allowing the internal structure of the product to fully relax and stabilize, effectively preventing the collapse and cracking of the microporous structure, improving the product's crispness and texture, extending its shelf life, and enhancing its market acceptance. This invention also incorporates natural vitamin E as a heat protectant during the conditioning process, reducing the oxidation and degradation of heat-sensitive functional components during high-temperature extrusion, improving the retention rate of nutrients such as β-glucan, and enhancing the product's oxidative stability while delaying undesirable flavors caused by lipid oxidation. Trehalose is also added during the conditioning process, effectively stabilizing the water activity of the conditioning system, preventing water migration and precipitation during extrusion, ensuring the uniformity of material consistency and extrusion stability, thereby improving the product's puffing uniformity and final texture.

[0018] Secondly, by establishing a multi-objective optimization algorithm based on a satisfaction function, this invention transforms conflicting response indicators into quantifiable comprehensive objectives, thereby achieving global optimization of process parameters, improving optimization efficiency and reliability, and ensuring that products simultaneously achieve high levels in multiple quality indicators.

[0019] Third, the present invention achieves precise control of the shear strength of materials through a specially configured screw element, avoiding the destruction of nutrients caused by excessive shearing or insufficient melting caused by insufficient shearing, thereby improving the texture uniformity and nutrient retention rate of the product and enhancing the adaptability and stability of the process.

[0020] Fourth, after obtaining the puffed product, the present invention also includes a coating process, which forms an effective moisture barrier on the product surface, reduces the product's hygroscopicity, maintains the crispness and crunchy texture of the puffed product, extends the product's shelf life, and improves the product's marketability and competitiveness.

[0021] Fifth, this invention uses a variety of modern analytical methods to comprehensively evaluate products, establishes the correlation between structure and composition, provides comprehensive data support for product quality control and new product development, and achieves objective and accurate evaluation of product quality.

[0022] Sixth, the quantitative relationship model established by this invention realizes an effective correlation between texture instrument data and human sensory evaluation, providing the possibility for online prediction and real-time control of product sensory quality, significantly improving the efficiency and accuracy of quality control, and laying the foundation for intelligent production.

[0023] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0024] Figure 1 This is a schematic flowchart of the optimized process for extrusion puffing of pure highland barley flour according to the present invention. Detailed Implementation

[0025] The present invention will now be described in further detail so that those skilled in the art can implement it based on the description.

[0026] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0027] like Figure 1 As shown, this embodiment of the invention provides an optimized method for the extrusion and puffing process of pure highland barley flour, comprising the following steps: S1. Optimization of process parameters based on multi-objective response: A three-factor, three-level Box-Behnken experimental design was adopted, with material moisture content, the highest temperature in the fourth zone of the barrel, and screw speed as independent variables, and product expansion rate, hardness, and β-glucan retention rate as parallel response indicators. Three quadratic polynomial prediction models were established using multiple regression fitting, and the p-values ​​of each factor and interaction term were calculated through analysis of variance. Items with significant influence were screened with a p-value less than 0.05 as the criterion. By solving the satisfaction function of the prediction model, the optimal combination of process parameters that can simultaneously achieve high expansion rate, low hardness, and high functional component retention rate was obtained. The optimal combination of process parameters is: material moisture content 20%-24%; barrel temperature control range: zone 1 70-85℃, zone 2 110-130℃, zone 3 135-155℃, zone 4 145-165℃; screw speed 180-250 r / min. S2. Raw material pretreatment: The pure barley flour is subjected to low-temperature ultrafine grinding until the particle size passes through a 200-mesh sieve and D90≤75μm, in order to destroy the fiber structure, increase the specific surface area, and avoid protein denaturation caused by high temperature. S3. Conditioning treatment: Add 1.5%-2.5% of the total mass of the pretreated highland barley flour to a compound emulsifier and 1%-3% of edible sodium bicarbonate. The compound emulsifier is composed of glyceryl monostearate and sucrose ester in a mass ratio of 1:1. Calculate and add an appropriate amount of water based on the material moisture content range of 20%-24% determined in S1, and obtain the conditioned material after thorough stirring and homogenization. S4. Extrusion Extrusion: The conditioned material is fed into a twin-screw extruder. The unit is operated according to the barrel temperature and screw speed obtained by the response surface methodology in S1. The temperature gradient between the third and fourth zones of the barrel is controlled to be ≤20℃, and the temperature gradient between the fourth zone and the die is controlled to be ≤10℃. Extrusion extrusion is then carried out to obtain high-quality extruded products.

[0028] In the above implementation, step S1 focuses on determining the combination of process parameters that can simultaneously optimize multiple product indicators through system experiments and mathematical modeling. First, a three-factor, three-level Box-Behnken experimental design is employed, selecting material moisture content, the highest temperature in the four zones of the barrel, and screw speed as independent variables. These three factors have a decisive influence on the structure formation, textural properties, and nutrient retention of the extruded product. Box-Behnken design is a response surface methodology suitable for multi-factor, multi-level optimization problems, enabling the establishment of reliable predictive models with fewer experiments. Extrusion rate, hardness, and β-glucan retention rate are used as parallel response indicators, reflecting the comprehensive requirements of the product in terms of structure, edibility, and nutritional function.

[0029] Three quadratic polynomial prediction models were established using multiple regression analysis to describe the relationship between each response index and process parameters. Analysis of variance was used to identify the significance of each factor and its interactions, with a p-value less than 0.05 as the screening criterion to ensure the statistical significance of the established models. Based on this, a satisfaction function was introduced to transform the multiple response indices into a single comprehensive target value. The puffing rate and β-glucan retention rate used a large-scale function, while hardness used a small-scale function. The satisfaction levels of each response were integrated using a weighted geometric mean method, with weights set according to product requirements; for example, the weight for puffing rate was 0.4, hardness was 0.3, and β-glucan retention rate was 0.3. An optimization algorithm was used to search for the maximum overall satisfaction value within the feasible region of the parameters, and its prediction confidence was verified to be higher than 95%. The final optimal combination of process parameters was determined as follows: material moisture content 20%–24%; barrel temperature control range: zone 1 70–85℃, zone 2 110–130℃, zone 3 135–155℃, zone 4 145–165℃; screw speed 180–250 r / min. This combination can simultaneously achieve high expansion rate, low hardness, and high functional component retention rate, and has strong practicality and operability.

[0030] In step S2, raw material pretreatment is fundamental to achieving good puffing results and preserving nutrients. This step requires low-temperature ultrafine grinding of pure barley flour to ensure its particle size passes through a 200-mesh sieve, with a D90 ≤ 75μm. Low-temperature ultrafine grinding refers to fine grinding of materials under low-temperature conditions, which effectively breaks down the fiber structure in barley, increases the specific surface area of ​​the material, and facilitates uniform moisture absorption and efficient heat transfer, while avoiding protein denaturation or loss of functional components caused by high temperatures. This treatment not only improves the material's flowability and extrusion performance but also helps to enhance the puffing uniformity and texture of the final product.

[0031] In step S3, conditioning is performed to further optimize the physicochemical properties of the material, making it more suitable for extrusion puffing. 1.5%–2.5% by weight of a compound emulsifier and 1%–3% by weight of edible sodium bicarbonate are added to the pretreated barley flour. The compound emulsifier is a 1:1 mass ratio of glyceryl monostearate and sucrose ester, which enhances the emulsification and stability of the material, improves the interaction between starch and fiber, and promotes the uniform formation and stability of bubbles during puffing. Edible sodium bicarbonate acts as a leavening agent, releasing carbon dioxide during heating, which helps improve the degree of puffing. Furthermore, based on the material moisture content range (20%–24%) determined in step one, an appropriate amount of water is calculated and added, and the mixture is thoroughly stirred and homogenized to obtain the conditioned material. This step ensures that the material has suitable rheological properties and moisture distribution before extrusion, providing a good material foundation for subsequent extrusion puffing.

[0032] In step S4, extrusion puffing is a crucial step in achieving the final product structure and quality. The conditioned material is fed into a twin-screw extruder, and the unit is operated according to the barrel temperature and screw speed optimized in step one. Specifically, the temperature gradient between zones three and four of the barrel is controlled to not exceed 20°C, and the temperature gradient between zone four and the die is controlled to not exceed 10°C. This temperature control strategy helps the material to gradually melt, homogenize, and puff within the barrel, avoiding product structural defects or component degradation caused by sudden temperature changes. By precisely controlling the temperature gradient and mechanical shear conditions, high puffing rates can be maintained while maximizing the retention of heat-sensitive components such as β-glucan, thereby obtaining high-quality puffed products.

[0033] This invention, through the systematic coordination of the above four steps, achieves multi-objective optimization of the pure highland barley flour extrusion puffing process, thereby improving the overall quality of the product. Compared with existing technologies, this method not only achieves a good balance between puffing rate and hardness but also effectively preserves the functional components of highland barley, overcoming the molding difficulties of high-fiber materials in extrusion processing. The synergistic effect of raw material pretreatment and conditioning improves the processing performance of the material and product consistency; and the multi-objective optimization algorithm and temperature control strategy enhance the controllability of the process and the nutritional value of the product.

[0034] In one specific embodiment, in the conditioning process of step S3, 0.5%-1% of microcrystalline cellulose by weight of the total mass of barley flour is added as a fiber network modifier to improve the extrusion molding properties of the high fiber content material.

[0035] In the above embodiments, microcrystalline cellulose is a partially purified dehydrated glucose polymer obtained from natural cellulose through acid hydrolysis. Its microstructure consists of porous microparticles with extremely high specific surface area and water-holding capacity. The working principle is that the large amount of dietary fiber in barley flour easily aggregates during conditioning and extrusion, forming an overly dense network structure. This hinders the continuity of the starch matrix, leading to poor material transport in the screw extruder, fluctuations in extrusion pressure, and ultimately defects such as broken strips, rough surfaces, or uneven expansion in the product. The addition of microcrystalline cellulose allows its microparticles to penetrate and partially interrupt the aggregation of barley fibers, effectively "diluting" and "modifying" the original fiber network, thereby improving the rheological properties of the material.

[0036] The specific addition ratio of microcrystalline cellulose is limited to 0.5% to 1% of the total mass of barley flour. This range is based on an equilibrium point derived from extensive process experiments. When the addition is below 0.5%, its effect on modifying the fiber network is not significant, and it cannot effectively improve the material's formability. However, if the addition exceeds 1%, the strong water absorption of microcrystalline cellulose and its excessive structuring effect on the material system may lead to an overly thick or hard texture, affecting the uniform distribution of moisture and potentially causing new problems such as increased extrusion energy consumption and an overly dense product. In practical applications, operators can fine-tune this range based on the fiber content of specific batches of barley flour and actual extrusion observations, for example, choosing specific values ​​such as 0.6%, 0.8%, or 1.0% to find the optimal addition amount for the current material state.

[0037] Finally, during implementation, the operator adds a suitable proportion of microcrystalline cellulose to the barley flour, which has already contained a compound emulsifier, edible sodium bicarbonate, and the calculated amount of water. Then, through thorough stirring and homogenization, the microcrystalline cellulose, emulsifier, and other additives are uniformly mixed with the barley flour matrix. After absorbing an appropriate amount of water, the microcrystalline cellulose swells, fully realizing its role in modifying the fiber network. Combined with the lubricating effect of the emulsifier and the gas-generating effect of sodium bicarbonate, this creates a conditioned material with suitable viscoelasticity, cohesion, and flowability. This comprehensively optimized material, when fed into the extruder, results in a more stable and smooth extrusion process, significantly improving the product's molding integrity and textural uniformity.

[0038] This implementation improves the applicability of high-fiber pure barley materials in extrusion processing. By adding a specific proportion of microcrystalline cellulose, the processing difficulties caused by fiber agglomeration are effectively overcome, making the extrusion process more stable and reliable, reducing production interruptions and defect rates, and resulting in puffed products with more complete shapes, smoother surfaces, and more uniform internal structures. This not only improves the product's appearance and taste but also provides a practical process solution for the industrial continuous production of high-fiber healthy grain foods.

[0039] In one specific embodiment, after the extrusion and expansion in step S4, the product is subjected to a temperature-controlled tempering treatment: first, it is treated at 60-70°C for 10 minutes, and then at 35-45°C for 20 minutes, in order to stabilize the microporous structure of the product and prevent cracking.

[0040] In the above embodiment, after extrusion puffing, the product is immediately transferred to a precisely temperature-controlled processing environment and maintained at 60-70°C for 10 minutes. The purpose of this stage is to utilize the higher ambient temperature to gently evaporate any remaining moisture inside the product, while simultaneously promoting the initial relaxation and rearrangement of starch molecular chains and protein networks under conditions where there is still high thermal energy. The selection of this temperature range is crucial. If the temperature is below 60°C, the provided heat energy is insufficient to effectively drive the movement of molecular chains and moisture migration; if it is above 70°C, there is a risk of excessive heat causing excessive water loss, hardening, or even charring of the product surface. In actual operation, operators can select specific settings such as 62°C, 65°C, or 68°C within this range based on the actual humidity and shape of the product upon demolding.

[0041] After the initial high-temperature treatment, the ambient temperature of the product is lowered to the lower range of 35-45°C and maintained at this temperature for 20 minutes. The principle behind this stage is that after the initial relaxation, the internal temperature of the product is still relatively high, and molecular motion remains active. Providing a gentle cooling environment significantly lower than the previous stage but higher than room temperature allows the product to cool at a controlled, slow rate. This slow cooling process allows starch molecules and the protein network sufficient time to stabilize at their new equilibrium positions, effectively "freezing" the formed microporous structure and releasing the internal stress accumulated from rapid expansion and sudden cooling. The lower limit of this temperature range ensures cooling efficiency, while the upper limit prevents uneven structural shrinkage due to excessively rapid cooling. Specific temperature settings, such as 38°C, 40°C, or 43°C, can be adjusted in actual production.

[0042] These two temperature stages, combined with specific time parameters, constitute a complete "variable-temperature tempering" treatment cycle. The entire process is typically carried out in a temperature-controlled oven or a specialized tempering bed. During operation, the freshly extruded and cut puffed product is evenly spread on a conveyor belt and passed through the two pre-set temperature zones sequentially, with the entire process lasting approximately 30 minutes. This synergistic method of first using a higher temperature to promote structural and moisture adjustment, and then using a lower temperature to achieve a smooth transition and stress release, effectively avoids common problems caused by uneven internal stress release during subsequent storage, such as the propagation of microcracks, cracking of the overall structure, or abnormal brittleness.

[0043] In one specific embodiment, during the conditioning process in step S3, 0.1%-0.5% of natural vitamin E by weight of the total barley flour is added as a heat protectant to reduce oxidation under high temperature and high pressure extrusion conditions.

[0044] In the above embodiments, the selected additive is natural vitamin E, a collective term for a series of fat-soluble compounds (including tocopherols and tocotrienols), known for their powerful antioxidant properties. The principle behind adding natural vitamin E is that the extrusion puffing process is a harsh environment involving high temperature, high pressure, and high shear. Under these conditions, lipids, β-glucan, and other easily oxidized components in the material are highly susceptible to oxidative degradation, leading not only to a decrease in nutritional value but also potentially the formation of undesirable flavor compounds. The phenolic hydroxyl groups in the natural vitamin E molecule can provide hydrogen atoms, effectively capturing and neutralizing free radicals generated under thermal and mechanical stress, thereby blocking the chain reaction of lipid oxidation and acting as a "sacrificial agent" to protect other oxidation-sensitive functional components.

[0045] The specific addition ratio of natural vitamin E is limited to 0.1% to 0.5% of the total mass of barley flour. This relatively narrow range is a result of balancing its effectiveness and cost-effectiveness. At levels below 0.1%, its concentration in the complex material system is insufficient to effectively capture all free radicals, providing negligible protection. Conversely, if the addition exceeds 0.5%, due to its fat-soluble nature, excessive vitamin E may be difficult to disperse evenly in barley flour, which is primarily composed of carbohydrates and fiber, potentially affecting the overall uniformity of the material and reducing cost-effectiveness. In practical production applications, operators can choose specific addition amounts within this range, such as 0.2%, 0.3%, or 0.4%, based on the oxidative sensitivity of the barley raw material, the expected product shelf life, and cost considerations.

[0046] During the process, operators add precisely weighed natural vitamin E to the prepared highland barley flour base material, along with ingredients such as compound emulsifiers and edible sodium bicarbonate. Since vitamin E is oily, to ensure uniform dispersion in the powdered material, it is generally recommended to premix it with a small amount of powdered material to form a masterbatch, or to prepare it into a powdered formulation using a suitable food-grade carrier before adding it. Subsequently, all components, along with the calculated amount of water, are added to a mixing device for thorough homogenization. This allows trace amounts of vitamin E to be evenly distributed throughout the material system, effectively exerting its antioxidant protective effect at every localized point during the subsequent extrusion and puffing process.

[0047] This implementation method improves the oxidative stability of puffed products during processing and subsequent storage. By introducing natural vitamin E as a heat protectant, the oxidation reaction caused by high-temperature and high-pressure extrusion is effectively reduced, thereby better preserving the nutritional activity of valuable heat-sensitive functional components such as β-glucan in highland barley.

[0048] In one specific embodiment, the multi-objective response optimization method in step S1 further includes: A satisfaction function is used to convert multiple response indicators into a single comprehensive satisfaction value. The satisfaction functions for each response indicator are as follows: the puffing rate and β-glucan retention rate are represented by a large-scale function, and the hardness is represented by a small-scale function. The satisfaction levels of each response were integrated using a weighted geometric average method. The weights were set according to product requirements as follows: the weight for puffing rate was 0.4, the weight for hardness was 0.3, and the weight for β-glucan retention rate was 0.3. An optimization algorithm was used to search for the maximum overall satisfaction value within the feasible region of the parameters, and the prediction confidence of the obtained parameter combination was verified to be higher than 95%. The final combination of process parameters must simultaneously meet the following requirements: expansion rate ≥ 350%, hardness ≤ 3.5 N, β-glucan retention rate ≥ 85%, and the overall satisfaction value of the three indicators is not less than 0.85.

[0049] In the above implementation, the method first uses a satisfaction function to uniformly convert multiple response indicators—namely, expansion rate, hardness, and β-glucan retention rate—into dimensionless satisfaction values, thereby achieving standardized processing of indicators with different properties and dimensions. Expansion rate and β-glucan retention rate are large-scale function indicators, calculated using the formula: Satisfaction = (Actual measured value - Lower limit) / (Upper limit - Lower limit). That is, the larger the value, the higher the satisfaction. Hardness, on the other hand, is a small-scale function indicator, calculated using the formula: Satisfaction = (Upper limit - Actual measured value) / (Upper limit - Lower limit). The smaller the value, the higher the satisfaction. By setting upper and lower thresholds for each indicator—for example, expansion rate could have a lower limit of 250% and an upper limit of 450%, β-glucan retention rate a lower limit of 70% and an upper limit of 95%, and hardness a lower limit of 2N and an upper limit of 5N—the actual measured values ​​are mapped to a satisfaction range of 0-1, thus achieving consistent measurement of the performance of different indicators.

[0050] Furthermore, a weighted geometric average method is used to aggregate the above multiple satisfaction values ​​into a comprehensive satisfaction value, which represents the overall quality of the process. The weighting is determined based on product positioning and market demand. For example, the weight of puffing rate could be 0.4, hardness 0.3, and β-glucan retention rate 0.3. Therefore, the comprehensive satisfaction score = (puffing rate satisfaction score + hardness retention rate + β-glucan retention rate + β-glucan retention rate). 0.4 ) × (Retention rate and satisfaction) 0.3 ) × (Hardness satisfaction) 0.3 In actual production, adjustments can be made according to the specific product type; for example, the weight of β-glucan can be appropriately increased when nutritional retention is emphasized. This polymerization method emphasizes the coordination between various indicators; if any indicator performs too poorly, it will significantly lower the overall value, thereby guiding the optimization process to take into account the performance of all parties and avoid over-optimization of a single indicator.

[0051] After determining the overall satisfaction function, numerical optimization algorithms such as genetic algorithms or response surface methodology are used to search within the pre-defined feasible region of process parameters to find the parameter combination that maximizes the overall satisfaction. During the search, parameter constraints and actual equipment limitations must be considered to ensure the feasibility of the results. The final parameter combination must also undergo statistical validation, requiring a prediction confidence level higher than 95%, meaning that the parameter set exhibits high stability in repeated experiments. Furthermore, the combination must simultaneously meet three quality baselines: an expansion rate of no less than 350%, a hardness of no more than 3.5 N, and a β-glucan retention rate of no less than 85%, and an overall satisfaction value of 0.85 or higher, to be considered the optimal process setting.

[0052] This implementation method improves the efficiency and reliability of parameter optimization by transforming a multi-objective optimization problem into a solution of a single comprehensive objective, achieving a good balance between different indicators. The final determined combination of process parameters has high prediction accuracy and stability, and can be directly used to guide actual production, improving the overall quality and consistency of products. This method has strong adaptability and scalability, and the weights and thresholds can be adjusted according to different product requirements, making it suitable for the process development and quality control of various grain puffed foods.

[0053] In one specific embodiment, the screw element of the twin-screw extruder is configured with three sets of 60-degree staggered kneading blocks and reverse thread elements in the melting section, and shallow groove forward thread elements and two sets of 90-degree staggered kneading blocks in the homogenization section, so as to apply a differentiated shear force that is strong at first and then weak to the high fiber content barley material.

[0054] In the above embodiment, the melting section is equipped with three sets of kneading block elements with a 60-degree staggered angle, combined with a reverse threaded element. The main function of the kneading blocks is to apply strong shearing force and disperse and mix the material through their staggered structure. This is particularly crucial for high-fiber barley materials, helping to break fiber agglomeration, promote starch gelatinization, and make the moisture distribution more uniform. The 60-degree staggered angle provides a relatively intense shear environment, which is conducive to energy input and initial plasticization of the material. At the same time, the intervention of the reverse threaded element generates a certain back pressure, preventing the material from passing through the area too quickly, thereby prolonging the time that the material is subjected to thermomechanical treatment in the melting section, ensuring that the starch can be fully melted, laying the foundation for subsequent puffing. In actual assembly, the operator can adjust the specific number of kneading blocks or the staggered angle within a certain range according to the actual moisture content and fiber content of the material. For example, two or four sets of kneading blocks can be used, or a staggered angle of 45 degrees or 75 degrees can be tried to fine-tune the shear intensity.

[0055] The homogenization section utilizes shallow-groove forward-threaded elements and two sets of 90-degree staggered kneading blocks. Upon entering the homogenization section, the material is essentially melted and homogenized, at which point the process objective shifts from strong mechanical shearing to gentle conveying, homogenization, and pressurization. The shallow-groove forward-threaded elements provide stable and gentle conveying, and their pressurization capability is more gradual compared to deep-groove elements, helping to maintain the stability of the material state. The accompanying 90-degree staggered kneading blocks provide a gentler shearing effect, with their mixing action primarily focused on dispersive mixing rather than vigorous dispersive mixing. This facilitates further homogenization of the final material system while avoiding excessive mechanical degradation of the already formed starch gel structure and heat-sensitive functional components (such as β-glucan).

[0056] This differentiated design, with strong shear in the melting section and weak shear in the homogenization section, creates a shear force field that is strong initially and then weakens. The material first undergoes a relatively high-intensity thermomechanical treatment in the melting section to ensure thorough gelatinization and fiber dispersion. Subsequently, it transitions to a gentler treatment phase in the homogenization section, stabilizing the material and building pressure for die extrusion while minimizing unnecessary mechanical energy input. This staged shearing strategy ensures that high-fiber barley is adequately processed to achieve good puffing characteristics while avoiding nutrient degradation or product texture deterioration caused by continuous excessive shearing. In actual operation, operators need to adjust the screw speed and temperature of each zone in conjunction with the extrudate's appearance and puffing effect to adapt to the screw configuration.

[0057] It should be noted that the 60-degree and 90-degree staggered angle kneading blocks, reverse thread elements, and shallow groove forward thread elements mentioned above are all standard screw elements that can be purchased in the field of twin-screw extruders.

[0058] This embodiment achieves precise control over the material shearing process through the specific combination and segmented setting of screw elements, thereby significantly improving the processing adaptability and product quality of high-fiber materials. This configuration effectively coordinates the contradiction between full starch gelatinization and nutrient retention, and can better maintain the activity of functional components while promoting puffing. The provided flexible design allows for a certain range of adjustments according to raw material batches and product requirements, enhancing the robustness and applicability of the process.

[0059] In one specific embodiment, during the conditioning process in step S3, trehalose, accounting for 1%-2% of the total mass of highland barley flour, is added as a moisture regulator to stabilize the water activity of the system and prevent water from separating out.

[0060] In the above embodiments, trehalose is a naturally occurring non-reducing disaccharide with an extremely stable molecular structure that remains intact under harsh processing conditions such as high temperature and high shear. Its function lies in its unique water-retention capacity and ability to form hydrogen bonds with water molecules, effectively reducing the water activity (Aw value) of the entire material system. In this way, trehalose can partially convert free water into bound water, thereby stabilizing the moisture state of the entire conditioning material and preventing water migration or precipitation from the material due to heat and mechanical shear during subsequent extrusion and puffing. This is crucial for maintaining the uniformity of material consistency and extrusion stability.

[0061] The recommended addition amount is 1% to 2% of the total mass of highland barley flour, a range determined by extensive process trials. In actual production, operators first add a compound emulsifier, edible sodium bicarbonate, and other additives to the ultrafinely pulverized pure highland barley flour, and then add trehalose according to a calculated ratio. For example, specific addition amounts such as 1.2%, 1.5%, or 1.8% can be selected within this range based on different preferences for the final product texture. The addition process requires thorough dry mixing of the trehalose powder with other dry material components to ensure uniform distribution. Then, a measured amount of water is added according to the target total moisture content, and the mixture is stirred and homogenized. This allows the trehalose to fully dissolve and function during the conditioning process, integrating seamlessly with the entire material system.

[0062] The addition of trehalose is not an isolated operation, but rather works synergistically with the established optimal moisture content range of 20%-24% and other components such as compound emulsifiers. The compound emulsifiers primarily act at the oil-water interface, improving the emulsion stability of the material; while trehalose focuses on regulating the state of the aqueous phase. Together, they optimize the rheological properties of the conditioned material from different dimensions. A conditioned material with stable water activity and uniform consistency experiences a smoother and more predictable conveying, melting, and expansion process after entering the extruder. This directly results in a final product with higher expansion uniformity and more consistent texture, avoiding product defects caused by uneven moisture distribution or precipitation.

[0063] This embodiment improves the moisture stability of high-fiber highland barley materials during conditioning and extrusion by adding a specific proportion of trehalose, effectively preventing moisture migration and precipitation during processing. It exhibits good synergy with existing processes and formulation components, jointly contributing to the optimization of material rheological properties, thereby enhancing the stability of the extrusion process and the consistency of product quality. This additive is a natural ingredient with high safety, conforms to the clean label trend, and provides an effective process aid for the production of high-quality pure highland barley puffed foods.

[0064] In one specific embodiment, after obtaining the puffed product in step S4, a coating process is further included: fluidized bed spray coating is performed using a mixed coating agent composed of sodium alginate solution and monoglyceride emulsion, resulting in a coating weight gain of 2%-5%, and finally drying until the moisture content is below 5% to prevent the product from absorbing moisture and softening.

[0065] In the above embodiment, the coating treatment uses a mixed coating agent composed of sodium alginate solution and monoglyceride emulsion, which complement each other functionally. Sodium alginate is a natural polysaccharide, and its aqueous solution has good film-forming and barrier properties, forming a continuous and dense protective film on the product surface. This film effectively prevents moisture from the environment from penetrating into the product, thereby slowing down the product's moisture absorption rate. Monoglyceride, as an emulsifier and lubricant, improves the spray characteristics of the coating solution, enhances the adhesion between the coating film and the product substrate, and may improve the film's flexibility and moisture-proof effect to some extent. The combined use of sodium alginate to construct the main barrier framework and monoglyceride to fill and optimize the film structure together forms an effective moisture barrier.

[0066] The coating process is carried out in a fluidized bed apparatus, a highly efficient coating method that utilizes airflow to suspend the expanded product, ensuring uniform contact of all its surfaces with the sprayed coating liquid. During operation, a pre-prepared sodium alginate solution and monoglyceride emulsion are mixed and stirred thoroughly, then atomized and sprayed onto the fluidized surface of the expanded product using the fluidized bed spray system. A key control indicator is the coating weight gain, which is controlled between 2% and 5% of the product weight. In practical applications, operators can select specific target values ​​within this range, such as 3% or 4%, depending on environmental humidity conditions and the product's requirements for maintaining brittleness. Too low a coating weight gain may prevent the formation of a complete and effective protective film, while too high a weight gain may result in an overly sticky product surface or unnecessary cost increases.

[0067] After spray coating, the product surface is wet and must be dried and cured immediately to allow the coating film to take shape and function. The drying process is typically carried out in a fluidized bed, using controlled hot air to remove moisture from the coating layer. The drying endpoint is set at an overall product moisture content of less than 5%. Maintaining this low moisture level is crucial; it not only ensures the coating film itself cures quickly and forms a stable structure but also completely eliminates the core problem of softening due to moisture absorption, thus preserving the characteristic crisp texture of puffed products for a long time. The specific drying temperature and time need to be adjusted flexibly based on the coating amount and the initial moisture content of the product; for example, using an inlet air temperature of 50°C to 65°C for 10 to 20 minutes.

[0068] This embodiment applies a special composite coating film to the surface of the puffed product, which slows down the rate at which the product absorbs moisture from the environment during storage, thereby effectively maintaining its ideal crisp texture and lightweight puffed structure. This coating process is seamlessly integrated with existing production processes, has highly controllable parameters, and is easy to standardize, providing a reliable and efficient solution for improving the shelf stability and commercial value of highly hygroscopic puffed grain products.

[0069] In one specific embodiment, after obtaining the puffed product in step S4, the product is further characterized and analyzed for structure: X-ray diffraction is used to analyze the crystallinity of starch, scanning electron microscopy is used to observe the microporous structure, and the retention rate of γ-aminobutyric acid is detected to evaluate the structure and nutritional quality of the product.

[0070] In the above embodiments, the principle of X-ray diffraction analysis is based on the diffraction effect of X-rays on the starch molecule lattice to analyze its crystalline state. The extrusion puffing process is a high-temperature, high-pressure, and high-shear process that severely damages the original crystalline structure of starch granules, causing them to gelatinize, melt, and then reform into new arrangements. X-ray diffraction analysis can obtain the diffraction pattern of the product. By analyzing the position, intensity, and broadening of characteristic diffraction peaks in the pattern, the crystallinity, crystal type (such as type A, type B, or type V complex), and degree of amorphization of the starch in the product can be qualitatively and semi-quantitatively determined. This structural information is key to understanding the puffed texture, hydration characteristics, and digestibility of the product. In practice, the puffed product needs to be ground into a uniform fine powder and compressed into tablets to prepare test samples. Then, diffraction patterns are acquired within a specific scanning speed and angle range. Finally, parameters such as relative crystallinity are calculated using specialized software to objectively assess the degree of influence of the process on the starch structure.

[0071] Scanning electron microscopy (SEM) provides high-resolution three-dimensional microscopic images, directly revealing the true morphology of the internal pore structure of a product—a capability difficult to replicate with other detection methods. During sample preparation, the expanded product is brittle-fractured with liquid nitrogen to obtain a clear cross-section. This cross-section is then sputter-coated with gold to enhance conductivity and obtain a clear secondary electron image. Observing the SEM images clearly reveals the thickness of the pore walls, the size distribution of the pores, their shape (whether uniformly circular or flat and irregular), and the connectivity between pores. An ideal expanded product should possess relatively uniform pore size, thin and intact pore walls, and a continuous structure. These microstructural characteristics directly determine the product's brittleness, density, and water absorption capacity. Analyzing images from multiple fields of view allows for a reliable assessment of the product's textural uniformity.

[0072] Gamma-aminobutyric acid (GABA) is a natural amino acid derivative found in highland barley and has important physiological functions, but it is sensitive to heat and shear stress. The high temperature and pressure environment during extrusion puffing may cause partial degradation. Therefore, detecting its retention rate is an important part of evaluating the mildness of the process and the nutritional value of the product. High-performance liquid chromatography (HPLC) is typically used for detection. The procedure involves: accurately extracting GABA from the puffed product, then separating it using an HPLC instrument through a specific chromatographic column and mobile phase, and performing qualitative and quantitative analysis by comparing the retention time with that of a standard and the UV absorption intensity. By comparing the content in the final product with the initial content in the raw materials, the retention rate during processing can be calculated, thus directly reflecting the protective effect of the process conditions on the heat-sensitive functional component.

[0073] This implementation method integrates multiple modern analytical techniques to conduct a comprehensive and objective quality analysis of puffed products from multiple dimensions, including microstructure and molecular composition. This breaks through the limitations of traditional evaluation methods that rely solely on sensory or simple physical indicators. The obtained data can establish the intrinsic relationship between process, structure, and nutrition, providing a highly reliable scientific basis and data support for a deeper understanding of processing mechanisms, precise optimization of process parameters, and targeted development of new products. Ultimately, it constructs a comprehensive and efficient product quality evaluation system, improving the accuracy and foresight of product quality control.

[0074] In one specific embodiment, the method further includes: establishing a quantitative relationship model between the textural parameters and sensory scores of the puffed product, wherein the textural parameters include hardness, brittleness, chewiness, and elasticity, and the sensory scores include mouthfeel, flavor, and overall acceptability; the quantitative relationship model is implemented through the following steps: S110. Conduct texture analysis. Use a texture analyzer to perform full texture analysis on the puffed product and determine the hardness, brittleness, chewiness and elasticity parameters. Each sample shall be measured repeatedly for no less than ten times and the average value shall be taken. S120. Conduct sensory evaluation using a nine-point preference rating system to comprehensively evaluate the crispness, melt-in-your-mouth texture, barley aroma, off-flavor, color, shape, and overall acceptability of the puffed product. S130. Perform data preprocessing, standardize the texture parameters and sensory score data to eliminate the influence of dimensions and improve model stability. S140. Establish a predictive model using partial least squares regression or multiple linear regression, with texture parameters as independent variables and sensory scores or comprehensive sensory scores as dependent variables, and construct a mathematical relationship model; evaluate the predictive ability and robustness of the model through cross-validation. S150. Optimize and validate the model. Select key texture parameters based on variable importance projection values ​​and regression coefficients to simplify the model structure. Use an independent validation set to externally validate the model. The model's predictive performance must meet two indicators simultaneously: the root mean square error of the model's prediction does not exceed 20% of the standard deviation of the sensory score, and the correlation coefficient between the model's predicted value and the actual measured value is greater than or equal to 0.7. S160. The established model is applied to the process control system. By monitoring the texture parameters of the extruded product in real time, its sensory acceptability is predicted. The process parameters such as moisture content, barrel temperature and screw speed are adjusted in reverse to achieve closed-loop control and continuous optimization of product quality.

[0075] In the above implementation, the necessary data collection and preprocessing work was established. This process begins with the precise measurement of the objective physical properties of the puffed products, namely, using a texture analyzer to conduct full texture analysis tests, quantifying key parameters such as hardness, brittleness, chewiness, and elasticity. To ensure the reliability and representativeness of the data, each sample needs to be measured repeatedly, for example, more than ten times, and the final average value is taken as the texture characteristic value of the sample. At the same time, a trained sensory evaluation team is organized to conduct subjective preference evaluations of the same batch of products, using a nine-point scoring method to comprehensively evaluate the crispness, melt-in-your-mouth texture, barley aroma, off-flavor, color, shape, and overall acceptability of the products. After obtaining these two sets of data, data preprocessing is required, usually using standardization methods (such as Z-score standardization) to eliminate the influence of different dimensions such as hardness and sensory scores, and to improve the stability and convergence of subsequent mathematical models.

[0076] A predictive model between the sensory rating and the sensory rating is constructed and validated using mathematical tools. The processed texture parameters are used as independent variables, and the sensory rating (either a single indicator or a weighted composite score) is used as the dependent variable. Algorithms such as partial least squares regression or multiple linear regression are employed to establish the mapping relationship model. Partial least squares regression is particularly suitable for cases where multicollinearity exists among the independent variables, as it effectively extracts the latent factors that have the strongest explanatory power for the dependent variable. After the model is established, its predictive power and robustness are evaluated through cross-validation, such as using leave-one-out cross-validation or K-fold cross-validation. Furthermore, based on the magnitude of the variable importance projection values ​​or regression coefficients, the key texture parameters that have the greatest impact on the sensory rating are selected to simplify the model structure. Finally, the model must be tested on an independent validation set. Its prediction error should not exceed a certain percentage of the standard deviation of the sensory rating, for example, within 20%, and the correlation coefficient R between the predicted and actual values ​​should reach a high level, such as 0.7 or above, to demonstrate its good external predictive effectiveness.

[0077] This involves putting validated mathematical models into practice to realize intelligent production control scenarios. The finalized model is integrated into the existing process control system. Its core function is to use real-time, rapidly measured texture parameters as input to the model, predicting the sensory acceptability of the current product in real time. Once the predicted value deviates from the set optimal range, the system can automatically, or issue instructions to the operator, adjust key process parameters in reverse, such as the moisture content of the material, the temperature settings of each zone of the extruder barrel, and the screw speed, thereby intervening in and optimizing the production process. This forms a closed-loop control system from detection to prediction to regulation, ensuring that product quality remains stable at a high level of sensory acceptability and achieving continuous self-optimization of the production process.

[0078] This implementation successfully links objective instrument measurements with subjective human sensory evaluation, constructing a mathematical model that can scientifically predict the sensory quality of products, reducing the absolute dependence on time-consuming and labor-intensive sensory evaluation; it provides a core technological foundation for realizing online monitoring and real-time control of product sensory quality, greatly improving the accuracy, foresight, and intelligence of production process control; through closed-loop feedback control, it can proactively stabilize product quality fluctuations at a high level, thereby significantly improving production efficiency and product quality consistency. Specific implementation examples: First, raw materials and equipment Raw material: Pure highland barley flour (β-glucan content ≥8%) Additives: compound emulsifier (glyceryl monostearate: sucrose ester = 1:1); edible sodium bicarbonate; microcrystalline cellulose (fiber network modifier); natural vitamin E (heat protectant); trehalose (moisture regulator).

[0080] Equipment: Twin-screw extruder; ultrafine pulverizer (low temperature); fluidized bed coating machine; texture analyzer, HPLC, XRD, SEM and other analytical equipment.

[0081] Second, process steps and parameters.

[0082] S1. Optimization of process parameters.

[0083] Independent variable range: Material moisture content: 20%–24%; Barrel zone four temperature: 145–165℃; Screw speed: 180–250r / min.

[0084] Target performance indicators: Expansion rate ≥ 350%; Hardness ≤ 3.5 N; β-glucan retention rate ≥ 85%.

[0085] Optimization results, simulation data: material moisture content: 22%; barrel temperature: zone 1 80℃, zone 2 120℃, zone 3 145℃, zone 4 155℃; screw speed: 200 r / min; prediction satisfaction: 0.89.

[0086] S2. Raw material pretreatment. The barley flour is pulverized at low temperature and passed through a 200-mesh sieve, with D90 = 70 μm.

[0087] S3. Conditioning. Add the following additives (as a percentage of the barley flour mass): compound emulsifier: 2.0%; edible sodium bicarbonate: 2.0%; microcrystalline cellulose: 0.8%; natural vitamin E: 0.3%; trehalose: 1.5%. Add water to a total moisture content of 22% and stir to homogenize for 20 minutes.

[0088] S4, Extrusion puffing.

[0089] Use a twin-screw extruder and run it according to the S1 optimized parameters; Temperature gradient control: gradient from zone 3 to zone 4: 15℃, gradient from zone 4 to the die head: 8℃; After extrusion, the product undergoes a temperature-controlled tempering process: 65℃ for 10 minutes and 40℃ for 20 minutes.

[0090] S5. Coating treatment. Use a coating agent made of sodium alginate solution (2%) and monoglyceride emulsion (1%); fluidized bed spray coating, weight gain 3%; dry to moisture content ≤ 5%.

[0091] Third, the product performance test results (simulation results) are shown in Table 1.

[0092] Table 1 index Test Results Target value puffing rate 368% ≥350% Hardness (N) 3.2 ≤3.5 β-glucan retention rate 88% ≥85% γ-aminobutyric acid retention rate 82% - Moisture content 4.8% ≤5% Sensory rating (out of 9) 7.5 ≥6.5 Fourth, structural characterization and composition analysis.

[0093] XRD: The relative crystallinity of starch is 12%, indicating that it has been fully gelatinized; Scanning electron microscopy reveals a uniform porous structure with a concentrated pore size distribution and intact pore walls. Texture-sensory model: The model is built using partial least squares regression, R 2 = 0.82; Key texture parameters: hardness, brittleness; Prediction error <15%, meeting control requirements.

[0094] The number of devices and processing scale described herein are for the purpose of simplifying the description of the invention. Applications, modifications, and variations of the invention will be readily apparent to those skilled in the art.

[0095] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details.

Claims

1. An optimized method for the extrusion and puffing process of pure highland barley flour, characterized in that, Includes the following steps: S1. Optimization of process parameters based on multi-objective response: A three-factor, three-level Box-Behnken experimental design was adopted, with material moisture content, the highest temperature in the fourth zone of the barrel, and screw speed as independent variables, and product expansion rate, hardness, and β-glucan retention rate as parallel response indicators. Three quadratic polynomial prediction models were established using multiple regression fitting, and the p-values ​​of each factor and interaction term were calculated through analysis of variance. Items with significant influence were screened with a p-value less than 0.05 as the criterion. By solving the satisfaction function of the prediction model, the optimal combination of process parameters that can simultaneously achieve high expansion rate, low hardness, and high functional component retention rate was obtained. The optimal combination of process parameters is: material moisture content 20%-24%; barrel temperature control range: zone 1 70-85℃, zone 2 110-130℃, zone 3 135-155℃, zone 4 145-165℃; screw speed 180-250 r / min. S2. Raw material pretreatment: Pure highland barley flour is subjected to low-temperature ultrafine grinding until the particle size passes through a 200-mesh sieve, with D90≤75μm; S3. Conditioning treatment: Add 1.5%-2.5% of the total mass of the pretreated highland barley flour to a compound emulsifier and 1%-3% of edible sodium bicarbonate. The compound emulsifier is composed of glyceryl monostearate and sucrose ester in a mass ratio of 1:

1. Calculate and add an appropriate amount of water based on the material moisture content range of 20%-24% determined in S1, and obtain the conditioned material after thorough stirring and homogenization. S4. Extrusion Extrusion: The conditioned material is fed into a twin-screw extruder. The unit is operated according to the barrel temperature and screw speed obtained by the response surface methodology in S1. The temperature gradient between the third and fourth zones of the barrel is controlled to be ≤20℃, and the temperature gradient between the fourth zone and the die is controlled to be ≤10℃. Extrusion extrusion is then carried out to obtain high-quality extruded products.

2. The optimized method for the extrusion and puffing process of pure highland barley flour according to claim 1, characterized in that, In the conditioning process of step S3, 0.5%-1% of microcrystalline cellulose, accounting for the total mass of highland barley flour, is added as a fiber network modifier.

3. The optimized method for the extrusion and puffing process of pure highland barley flour according to claim 1, characterized in that, After the extrusion and puffing in step S4, the product is subjected to a temperature-controlled tempering treatment: first at 60-70℃ for 10 minutes, and then at 35-45℃ for 20 minutes.

4. The optimized method for the extrusion and puffing process of pure highland barley flour according to claim 1, characterized in that, In the conditioning process of step S3, 0.1%-0.5% of natural vitamin E, accounting for the total mass of barley flour, is added as a heat protectant.

5. The optimized method for the extrusion and puffing process of pure highland barley flour according to claim 1, characterized in that, The multi-objective response optimization method in step S1 also includes: A satisfaction function is used to convert multiple response indicators into a single comprehensive satisfaction value. The satisfaction functions for each response indicator are as follows: the puffing rate and β-glucan retention rate are represented by a large-scale function, and the hardness is represented by a small-scale function. The satisfaction levels of each response were integrated using a weighted geometric average method. The weights were set according to product requirements as follows: the weight for puffing rate was 0.4, the weight for hardness was 0.3, and the weight for β-glucan retention rate was 0.

3. An optimization algorithm was used to search for the maximum overall satisfaction value within the feasible region of the parameters, and the prediction confidence of the obtained parameter combination was verified to be higher than 95%. The final combination of process parameters must simultaneously meet the following requirements: expansion rate ≥ 350%, hardness ≤ 3.5 N, β-glucan retention rate ≥ 85%, and the overall satisfaction value of the three indicators is not less than 0.

85.

6. The optimized method for the extrusion and puffing process of pure highland barley flour according to claim 1, characterized in that, The twin-screw extruder has three sets of 60-degree staggered kneading blocks and reverse threaded elements in the melting section, and shallow groove forward threaded elements and two sets of 90-degree staggered kneading blocks in the homogenization section.

7. The optimized method for the extrusion and puffing process of pure highland barley flour according to claim 1, characterized in that, In the conditioning process of step S3, trehalose, accounting for 1%-2% of the total mass of highland barley flour, is added as a moisture regulator.

8. The optimized method for the extrusion and puffing process of pure highland barley flour according to claim 1, characterized in that, After obtaining the puffed product in step S4, a coating process is also included: fluidized bed spray coating is performed using a mixed coating agent composed of sodium alginate solution and monoglyceride emulsion, resulting in a weight gain of 2%-5%, and finally drying until the moisture content is less than 5%.

9. The optimized method for the extrusion puffing process of pure highland barley flour according to claim 1, characterized in that, After obtaining the puffed product in step S4, the product is further characterized and analyzed for structure and composition: X-ray diffraction is used to analyze the starch crystallinity, scanning electron microscopy is used to observe the microporous structure, and the retention rate of γ-aminobutyric acid is detected to evaluate the product’s structure and nutritional quality.

10. The optimized method for the extrusion puffing process of pure highland barley flour according to claim 1, characterized in that, It also includes: establishing a quantitative relationship model between the textural parameters and sensory scores of puffed products, wherein the textural parameters include hardness, crispness, chewiness, and elasticity, and the sensory scores include mouthfeel, flavor, and overall acceptability; the quantitative relationship model is achieved through the following steps: S110. Conduct texture analysis. Use a texture analyzer to perform full texture analysis on the puffed product and determine the hardness, brittleness, chewiness and elasticity parameters. Each sample shall be measured repeatedly for no less than ten times and the average value shall be taken. S120. Conduct sensory evaluation using a nine-point preference rating system to comprehensively evaluate the crispness, melt-in-your-mouth texture, barley aroma, off-flavor, color, shape, and overall acceptability of the puffed product. S130. Perform data preprocessing, standardize the texture parameters and sensory score data to eliminate the influence of dimensions and improve model stability. S140. Establish a predictive model using partial least squares regression or multiple linear regression, with texture parameters as independent variables and sensory scores or comprehensive sensory scores as dependent variables, and construct a mathematical relationship model; evaluate the predictive ability and robustness of the model through cross-validation. S150. Optimize and validate the model. Select key texture parameters based on variable importance projection values ​​and regression coefficients to simplify the model structure. Use an independent validation set to externally validate the model. The model's predictive performance must meet two indicators simultaneously: the root mean square error of the model's prediction does not exceed 20% of the standard deviation of the sensory score, and the correlation coefficient between the model's predicted value and the actual measured value is greater than or equal to 0.

7. S160. The established model is applied to the process control system. By monitoring the texture parameters of the extruded product in real time, its sensory acceptability is predicted. The process parameters such as moisture content, barrel temperature and screw speed are adjusted in reverse to achieve closed-loop control and continuous optimization of product quality.

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