Intelligent production process of ultramicro dietary nutrition flour rich in active organic selenium

Abstract

The invention relates to the technical field of food processing, and discloses an intelligent production process of active organic selenium-rich ultramicro dietary nutrition flour, which comprises the following steps: (1) preparing raw materials; (2) pretreatment; (3) performing mixed fermentation; (4) carrying out ultra-micro machining; (5) post-treatment and stability improvement; and (6) obtaining a finished product. By adopting the process disclosed by the invention, inorganic selenium can be converted into organic selenium through a specific microbial fermentation process, so that the bioavailability of selenium is improved, and the flour is more easily absorbed and utilized by a human body; the low-temperature drying and ultra-micro processing technology is adopted, so that the damage to nutritional ingredients in the high-temperature processing process is effectively prevented; the ultrafine processing technology enables the particle size of the flour to be obviously reduced, the taste is improved, and the solubility is improved; and by adding auxiliary components such as the antioxidant, the stability and shelf life of the flour are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of food processing, and specifically to an intelligent production process for ultrafine dietary nutrient flour rich in active organic selenium. Background Art

[0002] With the improvement of global health awareness, people's attention to the nutritional value of food has been increasing. Especially in the supplementation of trace elements, consumers not only pursue sufficient intake but also pay more attention to the absorption efficiency and bioavailability of nutritional components. As an important trace element, active organic selenium has become the focus of attention due to its significant health benefits in aspects such as antioxidant, immune enhancement, and prevention of cardiovascular diseases. However, due to the large differences in the selenium content in the soil affected by geographical location, the selenium content in the food of many regions is insufficient, making it difficult to meet the human body's needs.

[0003] In addition, traditional food processing methods often damage the nutritional components in food during the processing process, especially the retention of trace elements such as selenium. Even in the production of selenium-rich foods, most of the selenium forms are inorganic selenium rather than organic selenium that is more easily absorbed by the human body. This not only reduces the nutritional value of food but also decreases the bioavailability of selenium. Summary of the Invention

[0004] The present invention mainly provides an intelligent production process for ultrafine dietary nutrient flour rich in active organic selenium, aiming to solve the problems that traditional processing methods often damage the nutritional components in food during the processing process, especially the retention of trace elements such as selenium, and that in the production of selenium-rich foods, most of the selenium forms are inorganic selenium rather than organic selenium that is more easily absorbed by the human body.

[0005] To solve the above technical problems, the present invention adopts the following technical solutions:

[0006] An intelligent production process for ultrafine dietary nutrient flour rich in active organic selenium, and the specific steps of this processing technology are as follows:

[0007] (1) Raw material preparation: Select wheat or corn grown in high-selenium areas as the raw material base, clean and remove impurities from the selected raw material base, and dry the raw material base by means of low-temperature drying; after washing the raw materials, it can avoid the influence of impurities on subsequent processing;

[0008] (2) Pretreatment: Coarsely grind the dried raw material base to obtain coarse powder with a particle size of 500 - 700 μm; it can reduce the moisture in the raw materials, prevent microbial contamination, and at the same time maximize the retention of the nutritional components of the raw materials; and the form of coarse powder can improve the fermentation efficiency and the effect of subsequent ultrafine processing;

[0009] (3) Mixing fermentation: Mix the obtained coarse powder with the fermentation medium and inorganic selenium source, and carry out fermentation; it can effectively convert inorganic selenium into an organic selenium form that is more easily absorbed and utilized by the human body.

[0010] (4) Ultra-fine processing: Carry out ultra-fine processing on the product obtained after fermentation to obtain a fine powder with a particle size less than 10 μm; it can improve the solubility and absorption rate of the flour, and retain the biological activity and uniform distribution of selenium.

[0011] (5) Post-treatment and stability improvement: Carry out secondary drying treatment on the obtained fine powder and add antioxidants; it can ensure the stability and safe storage of the flour.

[0012] (6) Obtain the finished product.

[0013] Among them, the raw materials mainly use wheat or corn base: accounting for 80% - 90% of the total weight. The ratio can be adjusted according to specific product requirements. For example, after adding the fermentation medium and active organic selenium according to a certain proportion of the total weight, quinoa or soybeans can be added to increase the protein content, or specific vitamins can be added to supplement the remaining proportion of the total weight.

[0014] The fermentation medium includes microbial strains and nutritional supplements. The microbial strains are usually added in the form of a culture medium, accounting for 1% - 5% of the total amount of the fermentation medium, and the specific ratio depends on the fermentation activity of the strain and the required selenium conversion rate. Nutritional supplements are added with necessary nutritional supplements such as sugars and amino acids to ensure the efficiency of the fermentation process and serve as a nutrient source for microbial growth. The microbial strains can use any existing strain that can convert inorganic selenium into organic selenium, such as the single-spore Saccharomyces kazakhstanensis KU2 strain, specific Saccharomyces cerevisiae, Candida yeast, etc.

[0015] Active organic selenium, that is, an organic selenium supplement, is an inorganic selenium source added to the medium during the fermentation process. For example, selenium yeast is fermented into a more easily absorbed organic selenium form. Among them, the addition amount of the inorganic selenium source (such as selenium yeast): about 0.1% - 0.5% of the total weight, which is adjusted according to the target selenium content and the selenium background value of the raw materials, that is, the inorganic selenium source is added according to the selenium content in the final target product in combination with the selenium content in the raw materials. Active organic selenium, as an important active ingredient of nutritional flour, provides significant health benefits such as antioxidant and immune enhancement.

[0016] Auxiliary components are added after ultrafine processing. For example, enzyme preparations account for about 0.01% - 0.1% of the weight of the fine powder, which helps break cell walls to release nutrients, improve the biological utilization rate and digestibility of flour, and antioxidant vitamin E, which accounts for about 0.01% - 0.05% of the weight of the fine powder; it is used to improve the stability of flour and extend the shelf life, and at the same time as an additional nutritional supplement. As long as ultrafine processing can be carried out, it is not limited to jet mills and ultrasonic crushing technologies, and nanotechnology or high-pressure homogenization technologies can also be considered. These technologies can further reduce the powder particle size and improve the bioavailability of nutrients. When using a jet mill, the operating pressure is 2 - 6 bar, and when using ultrasonic crushing, the power is 100 - 500W.

[0017] Among them, stabilizers and emulsifiers can be selectively added: used in specific products, such as when flour is used for liquid food or specific functional food processing, to increase the stability and uniformity of the product. Added according to the product application and processing technology requirements, usually not exceeding 0.5% of the total weight of the ingredients.

[0018] Among them, coarse grinding treatment yields coarse powder with a particle size of 500 - 700μm, which improves the fermentation efficiency and the effect of subsequent ultrafine processing.

[0019] Among them, after obtaining the final product, quality inspection is carried out: the flour sample is analyzed for nutrient components, with a focus on detecting selenium content and indicators such as protein and fat, and microbial detection as well as detection of heavy metals and other potential harmful substances are carried out to ensure product safety. Packaging and storage are carried out: the flour is hermetically packaged under sterile conditions, using food-grade packaging materials to protect the product from contamination. The packaged product is stored in a dry and cool environment, avoiding direct sunlight and high temperatures, to ensure the stability of product quality.

[0020] Among them, the pretreatment equipment includes: a low-temperature dryer, which is used to dry the raw materials at a controlled temperature to ensure that the moisture content is controlled at an appropriate level while avoiding the destruction of nutrients. A coarse grinder, which is used to grind the raw materials into coarse grains to facilitate subsequent fermentation and ultrafine processing. The fermentation equipment includes: a fermentation tank, a fermentation tank with temperature, pH value, and oxygen concentration control functions, which is used to carry out the microbial fermentation process to convert inorganic selenium into organic selenium. A stirrer, which is arranged in the fermentation tank to ensure uniform mixing of the raw materials and microbial strains during the fermentation process and promote effective selenium conversion. The ultrafine processing equipment includes: a jet mill or an ultrasonic crusher, which is used to process the fermented product into ultrafine powder. This step is crucial for improving the nutritional absorption rate of the flour and improving the taste. A screening equipment, which is used to screen and classify the ultrafine powder to ensure the particle size consistency of the product. The post-treatment and stability improvement equipment includes: a secondary dryer, which is used to further reduce the moisture content in the ultrafine powder to ensure the stability of the product and extend the shelf life. A mixer, which is used to uniformly mix the flour and auxiliary ingredients (such as enzyme preparations and antioxidants) to ensure the balanced and consistent nutritional components of each product.

[0021] Furthermore, the raw material base for production accounts for 80%-90% of the total weight, the fermentation medium accounts for 0.5%-2% of the total weight, the inorganic selenium source accounts for 0.1%-0.5% of the total weight, and the balance is supplemented with optional materials.

[0022] Among them, the optional materials are such as soybeans, quinoa, etc., which are selected according to specific nutritional goals to enrich the protein content and amino acid types of the product, as well as trace elements beneficial to the human body.

[0023] Furthermore, in the step (3): during the mixed fermentation, the temperature in the fermentation tank is 28-32°C, the pH value is 5.5-7.0, and the fermentation time is 24-48 hours.

[0024] Furthermore, in the step (1): the temperature of the low-temperature drying is 35-45°C, and the time is 8-12 hours. Adopting this step can reduce the moisture in the raw materials, prevent microbial contamination, and retain the nutrients in the raw materials to the greatest extent.

[0025] Furthermore, in the step (5): the temperature of the secondary drying is 45-55°C, and it stops until the fine powder is dried to a moisture content lower than 5%.

[0026] Furthermore, in the step (5): the addition amount of the antioxidant is less than 0.1% of the weight of the fine powder.

[0027] Furthermore, in the step (4): the specific particle size obtained is between 5-10 μm.

[0028] Furthermore, in the step (4): the temperature during the ultrafine processing is less than 50°C.

[0029] Among them, during the whole production process, especially in the fermentation and drying steps, precise temperature control effectively prevents the destruction of nutrients and ensures the activity of microorganisms.

[0030] Among them, in the step of mixed fermentation, this application adopts a fermentation tank with a multi-layer stirring structure, and a temperature sensor and temperature control equipment for heating and cooling are arranged on each layer of the stirring structure. The temperature sensor is used to detect the temperature of the material at this level, and the temperature control equipment is used for heating or cooling work; thus, it can more evenly control the layered temperature of the coarse powder, fermentation medium, and inorganic selenium source accumulated in the fermentation tank through each layer of the stirring structure, making the temperature of each part more stable during the fermentation process, thereby effectively preventing the destruction of nutrients and ensuring the activity of microorganisms. The specific calculation formula is as follows:

[0031] 1. Calculation of single-layer temperature deviation:

[0032] Let the target temperature of the i-th layer be The real-time detected temperature is Then the temperature deviation is:

[0033]

[0034] 2. Stratified temperature control formula

[0035] (1) Dynamic allocation of heating / cooling power

[0036] According to the deviation direction and amplitude, allocate the weight of the control quantity:

[0037]

[0038] Among them, K p is the proportionality coefficient (determining the response speed, recommended 0.5 - 1.2), K d is the differential coefficient (suppressing overshoot, recommended 0.1 - 0.3), P i (t) is the heating (positive value) or cooling (negative value) power of the ij-th layer.

[0039] 3. Multi-layer collaborative optimization control

[0040] (1) Inter-layer temperature equilibrium coefficient

[0041] Define the inter-layer temperature difference influence factor to avoid local overheating / overcooling:

[0042]

[0043] (2) Global correction term

[0044] Adjust the control quantity of this layer according to the temperature difference between adjacent layers:

[0045]

[0046] Among them, β3 is the collaborative correction coefficient (recommended value: 0.05 - 0.15), and n is the number of adjacent layers (usually taking 1 layer each for the upper and lower layers, a total of 2 layers).

[0047] 4. Equipment Execution Rules

[0048] (1) Heating / Cooling Threshold Limit

[0049] To prevent the equipment from starting and stopping frequently, a dead zone range is set:

[0050] For example, when the temperature deviation is within ±0.5°C, the system does not perform heating or cooling operations to avoid unnecessary adjustments. That is: -0.5°C < ΔT i (t) < 0.5°C, and the equipment heating / cooling is not started.

[0051] (2) Power Limitation

[0052] Output is limited according to the maximum capacity of the equipment:

[0053] For example, if the maximum heating power of the equipment is 5 kW and the cooling power is -3 kW, then:

[0054] P max = 5, P min = -3

[0055] Beneficial effects: By adopting the process of the present invention, inorganic selenium can be converted into organic selenium through a specific microbial fermentation process, greatly improving the biological availability of selenium. Compared with traditional chemical methods or the method of directly adding inorganic selenium, the selenium in the flour produced by this method is more easily absorbed and utilized by the human body; by adopting low-temperature drying and ultra-fine processing technology, the destruction of nutrients during the high-temperature processing process is effectively prevented, especially sensitive components such as vitamins and proteins. This ensures that other nutrients in the flour except selenium are also retained to the greatest extent; the ultra-fine processing technology significantly reduces the particle size of the flour, not only improving the taste of the product and making it more delicate, but also improving its solubility in water, providing possibilities for diversified applications of the product; at the same time, by adding auxiliary components such as antioxidants, the stability and shelf life of the flour are improved. Description of the Drawings

[0056] Figure 1 It is a schematic diagram of the intelligent production process flow of a kind of ultra-fine dietary nutrition flour rich in active organic selenium of the present invention;

[0057] Figure 2 It is a schematic diagram of the multi-layer stirring structure of the fermentation tank of the present invention;

[0058] Reference numerals: fermentation tank 1, stirring structure 2. Detailed implementation manners

[0059] The following will further elaborate in detail on the technical solution of the intelligent production process of a kind of ultrafine dietary nutrient flour rich in active organic selenium in combination with embodiments.

[0060] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installation", "connection", and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0061] Embodiment 1: As Figure 1 shown, an intelligent production process of a kind of ultrafine dietary nutrient flour rich in active organic selenium, and the specific steps of this processing technology are as follows:

[0062] (1), Raw material preparation: Select wheat or corn grown in high selenium areas to make the raw material base, and clean and remove impurities from the selected raw material base, and dry the raw material base by means of low-temperature drying;

[0063] (2), Pretreatment: Coarsely grind the dried raw material base to obtain coarse powder with a particle size of 500 μm;

[0064] (3), Mixed fermentation: Mix the obtained coarse powder with a fermentation medium and an inorganic selenium source, and carry out fermentation;

[0065] (4), Ultrafine processing: Carry out ultrafine processing on the product obtained after fermentation to obtain fine powder with a particle size less than 10 μm;

[0066] (5), Post-treatment and stability improvement: Carry out secondary drying treatment on the obtained fine powder, and add antioxidants;

[0067] (6), Obtain the finished product.

[0068] The raw material base made accounts for 90% of the total weight, the fermentation medium accounts for 2% of the total weight, the inorganic selenium source accounts for 0.1% of the total weight, and the balance is supplemented with optional materials.

[0069] When carrying out mixed fermentation, the temperature in the fermentation tank is 28 °C, the pH value is 5.5, and the fermentation time is 24 hours.

[0070] The temperature of low-temperature drying is 45 °C and the time is 8 hours.

[0071] The temperature of the secondary drying is 45 °C and it stops until the fine powder is dried to a moisture content of less than 5%.

[0072] The addition amount of the antioxidant is less than 0.1% of the weight of the fine powder.

[0073] Fine powder with a specific particle size of 6 μm is obtained.

[0074] The temperature during the ultra-fine processing is less than 50 °C.

[0075] Example 2: As Figure 1 shown, an intelligent production process of ultra-fine dietary nutrition flour rich in active organic selenium, the specific steps of this processing technology are as follows:

[0076] (1) Raw material preparation: Select wheat or corn grown in high-selenium areas to make the raw material base, clean and remove impurities from the selected raw material base, and dry the raw material base by low-temperature drying;

[0077] (2) Pretreatment: Coarsely grind the dried raw material base to obtain coarse powder with a particle size of 700 μm;

[0078] (3) Mixed fermentation: Mix the obtained coarse powder with the fermentation medium and inorganic selenium source and carry out fermentation;

[0079] (4) Ultra-fine processing: Carry out ultra-fine processing on the product obtained after fermentation to obtain fine powder with a particle size of less than 10 μm;

[0080] (5) Post-treatment and stability improvement: Carry out secondary drying treatment on the obtained fine powder and add an antioxidant;

[0081] (6) Obtain the finished product.

[0082] The raw material base produced accounts for 80% of the total weight, the fermentation medium accounts for 0.5% of the total weight, the inorganic selenium source accounts for 0.5% of the total weight, and the balance is supplemented with optional materials.

[0083] When carrying out mixed fermentation, the temperature in the fermentation tank is 32 °C, the pH value is 7.0, and the fermentation time is 48 hours.

[0084] The temperature of the low-temperature drying is 35 °C and the time is 12 hours.

[0085] The temperature of the secondary drying is 55 °C and it stops until the fine powder is dried to a moisture content of less than 5%.

[0086] The addition amount of the antioxidant is less than 0.1% of the weight of the fine powder.

[0087] Fine powder with a specific particle size of 9 μm is obtained.

[0088] The temperature during the ultra-fine processing is less than 50°C.

[0089] Example 3: As Figure 1 shown, an intelligent production process for ultra-fine dietary nutrition flour rich in active organic selenium, characterized in that the specific steps of the processing technology are as follows:

[0090] (1) Raw material preparation: Select wheat or corn grown in high-selenium areas to make the raw material base, and clean and remove impurities from the selected raw material base, and dry the raw material base by means of low-temperature drying;

[0091] (2) Pretreatment: Coarsely grind the dried raw material base to obtain coarse powder with a particle size of 500 μm;

[0092] (3) Mixed fermentation: Mix the obtained coarse powder with a fermentation medium and an inorganic selenium source, and carry out fermentation;

[0093] (4) Ultra-fine processing: Carry out ultra-fine processing on the product obtained after fermentation to obtain fine powder with a particle size less than 10 μm;

[0094] (5) Post-treatment and stability improvement: Carry out secondary drying treatment on the obtained fine powder, and add an antioxidant;

[0095] (6) Obtain the finished product.

[0096] The raw material base used accounts for 80% of the total weight, the fermentation medium accounts for 1.5% of the total weight, the inorganic selenium source accounts for 0.5% of the total weight, and the balance is supplemented with optional materials.

[0097] During the mixed fermentation, the temperature in the fermentation tank is 30°C, the pH value is 6, and the fermentation time is 36 hours.

[0098] The temperature of the low-temperature drying is 40°C and the time is 10 hours.

[0099] The temperature of the secondary drying is 50°C and it stops until the moisture content of the fine powder is dried to less than 5%.

[0100] The addition amount of the antioxidant is less than 0.1% of the weight of the fine powder.

[0101] Fine powder with a specific particle size between 5.5 μm is obtained.

[0102] The temperature during the ultra-fine processing is less than 50°C.

[0103] As Figure 2 shown, the fermentation tank in this example has a three-layer stirring structure, and the control of each layer of the stirring structure at a certain instantaneous detection during fermentation is as follows:

[0104] Specifically: the target temperature is 30°C for all, and the currently detected temperature is:

[0105] Upper layer (i = 1): 28.5°C (heating required)

[0106] Middle layer (i = 2): 30.2°C (cooling required)

[0107] Lower layer (i = 3): 29.8°C (fine adjustment required)

[0108] Calculation steps:

[0109] Calculate ΔT for each layer i (t), e.g.:

[0110] ΔT for the upper layer 1 (t) = 30 - 28.5 = 1.5°C, ΔT for the middle layer 2 (t) = 30 - 30.2 = -0.2°C, ΔT for the lower layer 3 (t) = 30 - 29.8 = 0.2°C.

[0111] Distribute the basic power according to the single-layer formula: Assume K p = 1, K d = 0.2, assume e.g.:

[0112] Upper layer (i = 1): P i (t) = 1×1.5 + 0.2×0 = 1.5 kW (positive value indicates heating power);

[0113] Middle layer (i = 2): P 2 (t) = 1×(-0.2) + 0.2×0 = -0.2 kW (negative value indicates cooling power);

[0114] Lower layer (i = 3): P 3 (t) = 1×0.2 + 0.2×0 = 0.2 kW;

[0115] Add collaborative correction: Assume β3 = 0.1, n = 2 (one layer above and one layer below);

[0116] The upper layer is affected by the middle layer:

[0117] Let P′ 1 (t) be the power of the upper layer after correction. The adjacent layer of the upper layer is the middle layer, and the temperature deviation of the middle layer ΔT 2 (t) = -0.2°C, then P′ 1 (t) = P 1 (t) + β × n × ΔT 2 (t) = 1.5 + 0.1×2×(-0.2) = 1.46 kW;

[0118] The middle layer is affected by the upper and lower layers:

[0119] Let P′ 2 (t) be the corrected middle - layer power, the upper - layer temperature deviation T 1 (t) = 1.5 °C, and the lower - layer temperature deviation ΔT 3 (t) = 0.2 °C. Then P′ 2 (t) = P 2 (t)+β×n×(ΔT 1 (t)+ΔT 3 (t))=-0.2 + 0.1×2×(1.5 + 0.2)=0.14 kW (here the calculated result of the middle - layer is positive, but the middle - layer actually needs to be cooled, and the actual execution power is finally determined by combining the power limit).

[0120] The lower - layer is affected by the middle - layer:

[0121] Let P′ 3 (t) be the corrected upper - layer power, and the middle - layer temperature deviation ΔT 2 (t)= - 0.2 °C. Then P′ 3 (t)=P 3 (t)+β×n×ΔT 2 (t)=0.2 + 0.1×2×(-0.2)=0.16 kW.

[0122] Considering the power limit (the maximum heating power is 5 kW and the cooling power is - 3 kW), the final execution power:

[0123] For the upper - layer: P″ 1 (t)=1.46 kW, 1.46 kW < 5 kW, so the final execution power of the upper - layer is 1.46 kW (heating);

[0124] For the middle - layer: P″ 2 (t)=0.14 kW, but the middle - layer needs to be cooled, and 0.14 kW > - 3 kW (comparing with the absolute value of the cooling power), so the final execution power of the middle - layer is - 0.14 kW (cooling);

[0125] For the lower - layer: P″ 3 (t)=0.16 kW, 0.16 kW < 5 kW, so the final execution power of the lower - layer is 0.16 kW (heating).

[0126] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An intelligent production process for ultrafine dietary nutrition flour rich in active organic selenium, characterized in that: The specific steps of this processing technology are as follows: (1) Raw material preparation: wheat or corn grown in high-selenium areas is selected to make a raw material base, and the selected raw material base is cleaned and impurities are removed, and the raw material base is dried by low-temperature drying; (2) Pretreatment: The dried raw material substrate is coarsely ground to obtain a coarse powder with a particle size of 500-700 μm; (3) Mixed fermentation: mixing the obtained coarse powder with a fermentation medium and an inorganic selenium source, and fermenting; (4) Ultrafine processing: The product obtained after fermentation is ultrafine processed to obtain fine powder with a particle size of less than 10 μm; (5) Post-treatment and stability improvement: the obtained fine powder is subjected to secondary drying treatment and antioxidants are added; (6) Obtain the finished product.

2. The process according to claim 1, characterized in that: The raw material base accounts for 80%-90% of the total weight, the fermentation medium accounts for 0.5%-2% of the total weight, the inorganic selenium source accounts for 0.1%-0.5% of the total weight, and the balance is supplemented by optional materials.

3. The process according to claim 2, characterized in that In the step (3): during mixed fermentation, the temperature in the fermentation tank is 28-32° C., the pH value is 5.5-7.0, and the fermentation time is 24-48 hours.

4. The process according to claim 1, characterized in that In the step (1), the low-temperature drying is carried out at a temperature of 35-45° C. and a drying time of 8-12 hours.

5. The process according to claim 1, characterized in that In the step (5), the secondary drying temperature is 45-55° C., and the drying is stopped until the fine powder has a moisture content of less than 5%.

6. The process according to claim 1, characterized in that In the step (5), the amount of antioxidant added is less than 0.1% of the weight of the fine powder.

7. The process according to claim 1, characterized in that In the step (4), a fine powder with a specific particle size between 5 and 10 μm is obtained.

8. The process according to claim 1, characterized in that In the step (4), the temperature during the ultra-fine processing is less than 50°C.

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