Segmented variable pressure and temperature coordinated regulation and control steaming and stewing grain process for baijiu raw materials

Abstract

The application discloses a kind of for Baijiu raw material segmented variable pressure variable temperature coordinated regulation and control steaming and stewing grain process, belong to Baijiu brewing technical field.The process sequentially includes: S1 multistage variable pressure initial steaming, and grain is treated in 0.25-0.30 MPa high pressure, 0.15-0.20 MPa medium pressure, 0.05-0.10 MPa micro-pressure steam environment in turn;S2 multistage gradient stewing grain, 85-95 ℃ high temperature, 75-85 ℃ medium temperature, 65-75 ℃ low temperature water is sprayed to grain in turn, and each section spraying water amount respectively accounts for 20-30%, 50-60%, 15-25% of stewing grain total water addition amount, and stewing grain total water addition amount is 120-160% of raw material absolute dry weight;S3 constant pressure redistillation and open steaming, first redistillation under 0.01-0.05 MPa micro-positive pressure, and then atmospheric pressure open steaming.The application solves the problems of traditional process grain fragrance easy loss, uneven gelatinization, poor moisture distribution by the timing and parameter coordination of "variable pressure-temperature-variable", realizes grain fragrance high retention, uniform gelatinization, consistent moisture, and simultaneously has excellent raw material adaptability and batch stability, suitable for clear type Baijiu large-scale standardized production.

Description

Technical Field

[0001] This invention belongs to the field of baijiu brewing technology, specifically relating to a steaming and cooking process for baijiu brewing raw materials, which is particularly applicable to the steaming and cooking of raw materials such as glutinous sorghum, japonica sorghum, and wheat for light-aroma baijiu brewing. Background Technology

[0002] In the brewing process of light-aroma baijiu, the steaming and simmering of raw materials are the core processes that determine the flavor of the base liquor, the yield, and the batch stability. The core objective is to promote the full and uniform gelatinization of starch while retaining the flavor precursors of the grain to the maximum extent, thus laying an ideal substrate for subsequent saccharification and fermentation.

[0003] Currently, the baijiu brewing industry generally uses equipment such as stills and spherical pots for steaming and maturing grains. However, conventional processes still have many technical pain points that are difficult to balance: On the one hand, the initial steaming often uses constant pressure throughout the process. High-pressure steaming can easily result in grains that are "cooked on the outside but raw on the inside," with incomplete gelatinization in the center. Low-pressure steaming, on the other hand, results in slow surface gelatinization, which cannot quickly lock in the aroma of the grains, leading to a large loss of volatile flavor substances in subsequent processes. It is impossible to simultaneously meet the dual requirements of "aroma locking" and "uniform gelatinization." On the other hand, the maturing process often uses a one-time addition of constant-temperature hot water for soaking, which cannot match the phased pattern of grain water absorption: "rapid start-up - deep penetration - final equilibrium." This often results in the grains being overly soft and mushy on the surface and dry and hard in the center due to insufficient water absorption. The uneven distribution of moisture in the cooked grains directly affects the synchronicity of subsequent fermentation. In addition, the starch structure, amylose content and gelatinization temperature of different brewing raw materials vary significantly. Conventional processes often use a set of fixed parameters, which cannot be adapted to the characteristics of the raw materials, resulting in large batch-to-batch fluctuations in the quality of cooked grains and making it difficult to achieve large-scale standardized production.

[0004] To address the aforementioned issues, existing technologies have disclosed solutions such as pressurized steaming and segmented steaming processes. However, these solutions only optimize the initial steaming or steaming process individually and fail to achieve coordinated control of pressure changes during initial steaming and temperature changes during steaming. Consequently, they cannot simultaneously resolve the core contradictions of preserving grain aroma, achieving uniform gelatinization, and maintaining consistent moisture content, resulting in limited improvement in the quality of cooked grain. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention proposes a segmented pressure and temperature-controlled steaming and simmering process for baijiu raw materials. By coordinating the timing and parameters of "gradient pressure during initial steaming, gradient temperature during simmering, and constant pressure open steaming during re-steaming," the technical problems of easy loss of grain aroma, uneven gelatinization, poor moisture distribution, and weak raw material compatibility in traditional processes are solved simultaneously.

[0006] This invention aims to overcome the shortcomings of existing technologies and provide a segmented variable pressure and temperature coordinated control process for steaming and simmering grains, which achieves high grain aroma retention, uniform gelatinization, and consistent moisture distribution, while also possessing excellent raw material compatibility and batch stability, providing reliable support for the standardized production of high-quality light-aroma baijiu.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows: A segmented variable pressure and temperature synergistic regulation process for steaming and cooking raw materials for baijiu (Chinese liquor) includes the following steps performed continuously: S1. Multi-stage variable pressure initial steaming: The soaked grain is sent to the initial steaming stage, where it is processed sequentially in a high-pressure steam environment, a medium-pressure steam environment, and a low-pressure steam environment; the gauge pressure of the high-pressure steam environment is 0.25-0.30 MPa, and the processing time is 5-10 min; the gauge pressure of the medium-pressure steam environment is 0.15-0.20 MPa, and the processing time is 10-20 min; the gauge pressure of the low-pressure steam environment is 0.05-0.10 MPa, and the processing time is 5-10 min.

[0008] This step employs a three-stage steaming process with gradient pressure reduction. First, high-pressure steam rapidly gelatinizes the surface of the grains, forming a dense starch protective layer that locks in flavor precursors within the grains, reducing aroma loss in subsequent processes. Next, medium-pressure steam provides continuous and stable heating, allowing heat and moisture to slowly penetrate the grains and ensure uniform starch gelatinization. Finally, low-pressure steam buffers the pressure, moderately evaporating excess moisture from the surface to prevent the grains from sticking together and creating favorable conditions for the subsequent steaming process.

[0009] S2, Multi-stage Grain Soaking: The grain treated in S1 is sent to the soaking stage, where it is sprayed sequentially with high-temperature hot water, medium-temperature warm water, and low-temperature warm water; the temperature of the high-temperature hot water is 85-95℃, and the spray volume accounts for 20%-30% of the total water added for soaking; the temperature of the medium-temperature warm water is 75-85℃, and the spray volume accounts for 50%-60% of the total water added for soaking; the temperature of the low-temperature warm water is 65-75℃, and the spray volume accounts for 15%-25% of the total water added for soaking; the total water added for soaking is 120%-160% of the oven-dry weight of the raw material before soaking.

[0010] In this step, the high-temperature section matches the gelatinization temperature of the grains, quickly starts the water absorption process, and solidifies the surface starch structure to prevent the surface from becoming too soft and mushy during subsequent spraying; the medium-temperature section is the core stage of water penetration, driving water to enter the center of the grains evenly and achieving internal and external moisture balance; the low-temperature section balances the internal and external temperatures of the grains, inhibits excessive starch gelatinization, and ensures that the cooked grains are of moderate softness and hardness.

[0011] S3. Constant pressure re-steaming and open steaming: The grain treated in S2 is first placed in a slightly positive pressure steam environment for re-steaming, and then transferred to an atmospheric pressure environment for open steaming; the gauge pressure of the slightly positive pressure steam environment is 0.01-0.05MPa, and the re-steaming time is 15-25min; the open steaming time at atmospheric pressure is 5-15min.

[0012] In this step, micro-positive pressure re-steaming achieves complete starch gelatinization, ensuring uniform cooking of the grains; atmospheric pressure open steaming volatilizes excess free water on the surface of the grains (collecting steam water), preventing cooked grains from sticking together and reducing the risk of contamination by miscellaneous bacteria. After discharge, the grains can be directly fed into the subsequent cooling and fermentation processes.

[0013] Furthermore, the gauge pressure of the high-pressure steam environment described in S1 is set according to the amylose content of the grain being processed; the higher the amylose content, the higher the set gauge pressure. Amylose molecules have a dense molecular structure, and gelatinization requires higher energy to break down their crystal structure. Through this correlation adjustment, the process can be precisely adapted to different raw materials. Specifically: when the amylose content of the grain is ≥25%, the gauge pressure of the high-pressure steam environment is set to 0.28-0.30 MPa; when the amylose content of the grain is 20% ≤ < 25%, the gauge pressure is set to 0.26-0.28 MPa; when the amylose content of the grain is <20%, the gauge pressure is set to 0.25-0.27 MPa.

[0014] Furthermore, the absolute value of the difference between the temperature of the high-temperature hot water mentioned in S2 and the gelatinization temperature of the grain being treated is ≤2℃. This temperature range can maximize the driving force for starch water absorption and gelatinization reaction, providing the strongest driving force for water migration, while avoiding excessive melting and cracking of the surface starch due to excessive temperature difference, which is the key to achieving deep and uniform water penetration.

[0015] Furthermore, the processing time ratios of each stage in S1 and the spraying time ratios of each stage in S2 are adjusted according to the raw material variety, and the duration of each stage falls within the corresponding duration range defined in claim 1. Specifically, when the raw material is glutinous sorghum, the duration ratio of each stage in S1 is 1:2:1, and the duration ratio of each stage in S2 is 1:2:1; when the raw material is japonica sorghum, the duration ratio of each stage in S1 is 1.2:2.7:1, and the duration ratio of each stage in S2 is 0.5:2.5:1.5; when the raw material is wheat, the duration ratio of each stage in S1 is 1:2.3:1.3, and the duration ratio of each stage in S2 is 1:1.5:1.5.

[0016] Compared with existing conventional processes, the present invention achieves the following unexpected technical effects: First, by simultaneously coordinating the timing of pressure regulation during initial steaming and temperature regulation during grain steaming, the long-standing technical contradictions of traditional processes have been overcome. Through rapid gelatinization and aroma locking in the outer layer in the high-pressure section, ensuring uniform gelatinization of the internal starch in the medium-pressure section, and buffering the transition in the low-pressure section, coupled with gradient water temperature spraying to match the grain's water absorption patterns, this approach not only solves the problem of "inability to simultaneously lock in aroma and gelatinize" in single-pressure steaming, but also avoids the defects of "uneven water absorption, resulting in a mushy exterior and a hard interior" in constant-temperature steaming. This achieves multiple goals: high retention of grain aroma, thorough starch gelatinization, and uniform moisture distribution.

[0017] Secondly, the quality and batch production stability of cooked grains are significantly improved. Cooked grains processed using this technology have a moisture standard deviation that can be stably controlled below 0.45%, a gelatinization degree of over 97.8%, and a relative retention rate of grain aroma substances that is more than 16% higher than that of traditional processes, resulting in a 1-2 percentage point increase in alcohol yield. Between continuous production batches, the moisture content fluctuation of cooked grains can be controlled within 1.6%, far lower than the fluctuation level of traditional processes, fully meeting the needs of large-scale standardized production.

[0018] Third, it has a wide range of raw material compatibility and is easy to implement industrially. The core parameters of this process can be flexibly adjusted according to the amylose content and gelatinization temperature of the raw materials, making it suitable for a variety of mainstream baijiu brewing raw materials such as glutinous sorghum, japonica sorghum, and wheat. At the same time, it does not require large-scale modification of existing production lines and can be directly connected to continuous grain steaming equipment, making it easy to promote and apply in baijiu brewing enterprises. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] The detection methods for relevant parameters in this invention are uniformly described as follows: 1. Amylose content: Tested according to GB 5009.9-2016 "National Food Safety Standard - Determination of Starch in Food"; 2. Gelatinization temperature: Differential scanning calorimetry (DSC) was used to detect the gelatinization temperature, and the starting temperature of the starch gelatinization endothermic peak was taken as the gelatinization temperature; 3. Standard deviation of moisture content in cooked grains: 100 grains were randomly and evenly sampled from the same batch of cooked grains, and the absolute moisture content of each grain was measured using a rapid moisture analyzer. The standard deviation of the 100 sets of data was calculated. 4. Degree of gelatinization: determined using the AACC 76-13 standard iodine blue colorimetric method; 5. Relative retention rate of grain aroma substances: The total ion current chromatographic peak area of ​​key volatile flavor substances such as ethyl hexanoate, ethyl valerate, ethyl nonanoate, and ethyl palmitate in cooked grain was detected by headspace solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). The relative percentage was calculated based on the detection value of cooked grain of the same raw material processed by traditional process (defined as 100%). 6. Yield: Each group of cooked grains is processed according to the same saccharification, fermentation and distillation process for light-aroma baijiu. The raw liquor with an alcohol content of 65% vol is collected and its mass percentage relative to the dry weight of the raw materials is calculated.

[0021] The standard process for soaking grains in this invention is uniformly described as follows: After removing impurities, the raw materials are soaked in hot water at 80-85℃ for 12-16 hours. After soaking, the water is drained until there is no free water on the surface of the raw materials, which is the soaked grain.

[0022] Example 1: Steaming and stewing process of glutinous sorghum raw material The raw material in this embodiment is high-quality glutinous sorghum with an amylose content of 10% and a gelatinization temperature of 87°C.

[0023] The process steps are as follows: S1. Multi-stage variable pressure pre-evaporation: High pressure section gauge pressure 0.25MPa, processing time 8min; Medium pressure section gauge pressure 0.18MPa, processing time 15min; Low pressure section gauge pressure 0.08MPa, processing time 7min; The time ratio of each section is 1:2:1. S2, Multi-stage Gradient Stewing: The total water added to the stewed grain is 140% of the dry weight of the raw materials; the high-temperature stage sprays 88℃ hot water (difference from the gelatinization temperature +1℃) for 5 minutes, accounting for 25% of the total water added; the medium-temperature stage sprays 78℃ warm water for 9 minutes, accounting for 55% of the total water added; the low-temperature stage sprays 68℃ warm water for 5 minutes, accounting for 20% of the total water added; the time ratio of each stage is 1:2:1. S3. Constant pressure re-evaporation and open evaporation: micro-positive pressure re-evaporation gauge pressure 0.03MPa, duration 20min; atmospheric pressure open evaporation duration 10min.

[0024] Example 2: Steaming and steaming process of japonica sorghum raw material The raw material in this embodiment is japonica sorghum with an amylose content of 26% and a gelatinization temperature of 89°C.

[0025] The process steps are as follows: S1, Multi-stage variable pressure pre-evaporation: High pressure section gauge pressure 0.29MPa, processing time 7min; Medium pressure section gauge pressure 0.19MPa, processing time 16min; Low pressure section gauge pressure 0.06MPa, processing time 6min; The ratio of processing time for each section is 1.2:2.7:1. S2, Multi-stage Gradient Stewing: The total water added for stewing the grain is 130% of the dry weight of the raw materials; the high-temperature stage sprays 90℃ hot water (difference from the gelatinization temperature +1℃) for 4 minutes, accounting for 22% of the total water added; the medium-temperature stage sprays 79℃ warm water for 10 minutes, accounting for 58% of the total water added; the low-temperature stage sprays 69℃ warm water for 7 minutes, accounting for 20% of the total water added; the duration ratio of each stage is 0.5:2.5:1.5. S3. Constant pressure re-evaporation and open evaporation: micro-positive pressure re-evaporation gauge pressure 0.04MPa, duration 22min; atmospheric pressure open evaporation duration 12min.

[0026] Example 3: Steaming and steaming process for wheat raw materials The raw material in this embodiment is brewing wheat with a straight-chain starch content of 22% and a gelatinization temperature of 86°C.

[0027] The process steps are as follows: S1, Multi-stage variable pressure pre-evaporation: High pressure section gauge pressure 0.27MPa, processing time 6min; Medium pressure section gauge pressure 0.17MPa, processing time 14min; Low pressure section gauge pressure 0.09MPa, processing time 8min; The ratio of processing time for each section is 1:2.3:1.3. S2, Multi-stage Gradient Stewing: The total water added for stewing the grain is 150% of the dry weight of the raw materials; the high-temperature stage sprays 87℃ hot water (difference from the gelatinization temperature +1℃) for 6 minutes, accounting for 28% of the total water added; the medium-temperature stage sprays 77℃ warm water for 8 minutes, accounting for 52% of the total water added; the low-temperature stage sprays 67℃ warm water for 6 minutes, accounting for 20% of the total water added; the time ratio of each stage is 1:1.5:1.5; S3. Constant pressure re-evaporation and open evaporation: micro-positive pressure re-evaporation gauge pressure 0.02MPa, duration 18min; atmospheric pressure open evaporation duration 8min.

[0028] Comparative Example To verify the technical effects, synergy, and parameter criticality of the present invention, the following comparative examples are set up: 1. Comparative Example 1 (Traditional Process): Glutinous sorghum (using the same raw materials as in Example 1) was processed using the industry-standard ball pot steaming and stewing process. The initial steaming stage used only atmospheric pressure steam (approximately 100°C) for 40 minutes; the stewing stage involved adding approximately 75°C hot water (the same amount as in Example 1) at once and soaking for 30 minutes; the re-steaming was done at atmospheric pressure for 20 minutes, without a dedicated open steaming step.

[0029] 2. Comparative Example 2: Glutinous sorghum was processed using a pressurized steaming process. The initial steaming was performed at a single pressure of 0.18 MPa for 30 minutes; the grain was then sprayed with 80°C warm water (total water volume same as in Example 1); the second steaming was performed in the same manner as in Comparative Example 1.

[0030] 3. Comparative Example 3 (Some features of this invention are missing: only the initial steaming is performed under varying pressure): Glutinous sorghum was used as the raw material, and the initial steaming steps were the same as in Example 1. However, the steaming step was changed to: spraying 80°C warm water once, with the total water volume and total time being the same as the steaming step in Example 1. The re-steaming and open steaming were the same as in Example 1.

[0031] 4. Comparative Example 4 (Some features of this invention are missing: only the gradient temperature change during grain steaming): Using glutinous sorghum as raw material, the initial steaming step was changed to: steaming at a single pressure of 0.18 MPa throughout the entire process, with the total time the same as the initial steaming step in Example 1. The grain steaming step was the same as in Example 1. The re-steaming and open steaming were the same as in Example 1.

[0032] 5. Comparative Example 5 (parameters deviate from the scope of this invention): Using glutinous sorghum as raw material, the process steps were exactly the same as in Example 1, but the pressure of the initial steaming high-pressure section was adjusted to 0.22 MPa (lower than the 0.25 MPa of this invention). (Range of 0.30MPa).

[0033] 6. Comparative Example 6 (Traditional Process Comparison of Raw Materials - Japonica Sorghum): The same batch of Japonica sorghum as in Example 2 was used as raw material and processed using the traditional process described in Comparative Example 1.

[0034] 7. Comparative Example 7 (Traditional Process Control of Raw Materials - Wheat): The same batch of wheat as in Example 3 was used as raw material and processed using the traditional process described in Comparative Example 1.

[0035] Performance testing and effect verification All cooked grains and subsequent brewing products obtained from the above-described embodiments and comparative treatments were subjected to standardized and uniform testing. 1. Relative Retention Rate of Grain Aroma Compounds: The total ion current chromatographic peak area of ​​key volatile flavor compounds such as ethyl hexanoate and ethyl valerate in cooked grains was determined using headspace solid-phase microextraction-gas chromatography-mass spectrometry. The detection value of the same raw material cooked grains treated with Comparative Example 1 (traditional process) was defined as 100% as the baseline, and the relative percentages of other groups were calculated. This indicator is used to evaluate the process's ability to retain the intrinsic aroma of the raw materials.

[0036] 2. Standard deviation of moisture content in cooked grain: Randomly and uniformly sample 100 grains from the same batch of cooked grain, and use a rapid moisture analyzer to measure the moisture content (absolute moisture content) of each grain. Calculate the standard deviation of these 100 data points. The smaller the value, the more uniform the moisture distribution of the cooked grain.

[0037] 3. Degree of gelatinization: The iodine blue colorimetric method (AACC 76) was used. The degree of starch gelatinization is determined by measuring the starch gelatinization process according to the 13 standard.

[0038] 4. Alcohol yield: Each group of cooked grains is processed according to a uniform saccharification, fermentation and distillation process. The distilled raw alcohol is collected, and its mass at an alcohol content of 65% vol is measured. The percentage of its mass relative to the dry weight of the raw materials consumed is calculated.

[0039] Table 1 Comparison of Process Effects between Examples and Comparative Examples

[0040] Note: The retention rate of grain aroma substances is calculated based on Comparative Example 1 as a baseline of 100%.

[0041] Based on a comprehensive comparison of the embodiments and comparative examples, the technical solution of the present invention has achieved unexpected and significant technical effects, and its inventiveness and progressiveness have been fully verified. Specifically: First, the complete process of this invention (Examples 1-3) is comprehensively and significantly superior to traditional processes (Comparative Examples 1, 6, and 7) and existing technologies that describe pressurized cooking (Comparative Example 2) in all core evaluation indicators. Compared to traditional processes, this invention reduces the standard deviation of cooked grain moisture from over 1.65% to below 0.45%, increases the degree of gelatinization from less than 92.3% to over 97.8%, and increases the alcohol yield by 1-3 percentage points, which demonstrates the overall technological advancement of this solution.

[0042] More importantly, the experimental data strongly demonstrates a strong, non-obvious synergistic effect between "segmented pressure variation during initial steaming" and "gradient temperature variation during grain steaming." The results of Comparative Example 3 (segmented pressure variation only) and Comparative Example 4 (segmented temperature variation only) show that while using only some features of this invention improves the technical effect compared to Comparative Example 2, there is a significant gap compared to the complete scheme (Example 1) in terms of the key indicators determining the homogeneity of cooked grain: "moisture standard deviation" and "degree of gelatinization." This confirms that the two must work synergistically according to the specific timing and parameter relationships described in this invention to achieve the optimal match between starch gelatinization and moisture migration processes, thereby resolving multiple contradictions such as "fragrance retention" and "uniform gelatinization," and "rapid water absorption" and "prevention of soggy texture," producing an unexpected technical effect of "1+1>>2."

[0043] Furthermore, the core parameter range defined in the claims of this invention is an optimized critical window. The decreased effect of Comparative Example 5 (insufficient initial steaming pressure) demonstrates that the lower limit of the pressure range (0.25 MPa) is a key threshold to ensure effective aroma retention and gelatinization, and is not a broad selection that can be easily obtained by those skilled in the art through conventional experiments.

[0044] Finally, the successful implementation of Example 2 (japonica sorghum) and Example 3 (wheat), combined with their respective significant advantages over traditional processes (Comparative Examples 6 and 7), not only verified the universality and excellent adaptability of the process of the present invention to different raw materials, but also demonstrated the effectiveness and necessity of the intelligent design concept of "adjusting parameters according to the characteristics of raw materials" in the present invention by overcoming the high amylose gelatinization resistance of japonica sorghum with higher pressure and achieving a higher degree of gelatinization in Example 2.

[0045] In summary, the above comparative experiments systematically and comprehensively demonstrate the synergistic advantages and outstanding effects of the process of the present invention in enhancing the preservation of grain aroma, achieving uniform gelatinization and water absorption, increasing alcohol yield, and enhancing raw material compatibility, which fully meets the requirements of invention patent for inventiveness and practicality.

[0046] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A segmented variable pressure and temperature synergistic control process for steaming and simmering grains for baijiu raw materials, comprising sequentially performed initial steaming, simmering, and re-steaming steps, characterized in that, The process includes the following steps performed continuously: S1. Multi-stage variable pressure initial steaming: The soaked grain is sent to the initial steaming stage, where it is processed sequentially in a high-pressure steam environment, a medium-pressure steam environment, and a low-pressure steam environment; the gauge pressure of the high-pressure steam environment is 0.25-0.30 MPa, and the processing time is 5-10 min; the gauge pressure of the medium-pressure steam environment is 0.15-0.20 MPa, and the processing time is 10-20 min; the gauge pressure of the low-pressure steam environment is 0.05-0.10 MPa, and the processing time is 5-10 min. S2, Multi-stage Grain Soaking: The grain treated in S1 is sent to the soaking stage, where it is sequentially sprayed with high-temperature hot water, medium-temperature warm water, and low-temperature warm water. The high-temperature hot water has a temperature of 85-95℃ and accounts for 20%-30% of the total water added for soaking. The medium-temperature warm water has a temperature of 75-85℃ and accounts for 50%-60% of the total water added for soaking. The low-temperature warm water has a temperature of 65-75℃ and accounts for 15%-25% of the total water added for soaking. The total water added for soaking is 120%-160% of the oven-dry weight of the raw material before soaking. S3. Constant pressure re-steaming and open steaming: The grain treated in S2 is first placed in a slightly positive pressure steam environment for re-steaming, and then transferred to an atmospheric pressure environment for open steaming; the gauge pressure of the slightly positive pressure steam environment is 0.01-0.05MPa, and the re-steaming time is 15-25min; the open steaming time at atmospheric pressure is 5-15min.

2. The process according to claim 1, characterized in that, The gauge pressure value of the high-pressure steam environment described in S1 is set according to the amylose content of the grain being processed. The higher the amylose content, the higher the set gauge pressure value.

3. The process according to claim 2, characterized in that: When the amylose content of the grain is ≥25%, the gauge pressure of the high-pressure steam environment is set to 0.28-0.30 MPa; When the amylose content of the grain is 20% ≤ content < 25%, the gauge pressure of the high-pressure steam environment is set to 0.26-0.28 MPa; When the amylose content of the grain is <20%, the gauge pressure of the high-pressure steam environment is set to 0.25-0.27 MPa.

4. The process according to claim 1, characterized in that, The absolute value of the difference between the temperature of the high-temperature hot water mentioned in S2 and the gelatinization temperature of the grain being processed is ≤2℃.

5. The process according to claim 1, characterized in that, The processing time ratios for each stage of S1 and the spraying time ratios for each stage of S2 are adjusted according to the raw material type, and the duration of each stage falls within the corresponding duration range defined in claim 1, specifically as follows: When the raw material is glutinous sorghum, the ratio of treatment time for the S1 high-pressure section, medium-pressure section, and low-pressure section is 1:2:1, and the ratio of spraying time for the S2 high-temperature section, medium-temperature section, and low-temperature section is 1:2:

1. When the raw material is japonica sorghum, the processing time ratio of the S1 high-pressure section, medium-pressure section, and low-pressure section is 1.2:2.7:1, and the spraying time ratio of the S2 high-temperature section, medium-temperature section, and low-temperature section is 0.5:2.5:1.

5. When the raw material is wheat, the treatment time ratio of the S1 high-pressure section, medium-pressure section, and low-pressure section is 1:2.3:1.3, and the spraying time ratio of the S2 high-temperature section, medium-temperature section, and low-temperature section is 1:1.5:1.5.

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