Invention related to jet mill for making powder of grain or the like and powder of grain produced by same

Abstract

According to the present invention, a jet mill for crushing grain or tea leaves into a powder by the impact of compressed air emitted from a pair of nozzles is configured such that the pair of nozzles are provided along the same axis within a casing that forms a crushing chamber, compressed air supplied by the pair of nozzles is compressed by a compressor and then cooled by a cooling device to at least room temperature, and the compressed air is used to make the grain or the tea leaves collide to become a powder.

Description

An invention relating to a jet mill that turns grains into powder and the powdered grain produced by the jet mill

[0001] One embodiment of the present invention relates to a jet mill for powdering grains or tea leaves, and the powder of grains or tea leaves produced thereby.

[0002] Conventionally, methods for producing powders of grains or tea leaves (see, for example, Patent Document 1 or Patent Document 2) have existed, producing barley leaf powder or germinated seed powder. For example, Patent Document 1 discloses that an impact plate jet mill is used to obtain barley leaf powder, which has rounded particle corners and a smoother, more rounded structure, thereby improving dispersibility in water and smoothness in the throat. However, when barley leaves are pulverized into powder using an impact plate jet mill, the barley leaves are exposed to high temperatures when they collide with the impact plate, making it difficult to maintain the nutrients inherent in the barley leaves even in the powdered state.

[0003] For example, Patent Document 2 describes a method of drying grains, beans, and the like by aeration and pulverizing them with a swirling air current pulverizer in order to prevent functional ingredients from denaturing or decomposing during drying. In the invention described in Patent Document 2, when the grains or beans to be pulverized are pulverized with a swirling air current pulverizer, which is a pulverizing device, the fluid is room temperature compressed air, thereby suppressing heat generation during pulverization. However, there is no description of the level of compressed air to be used, and it is unclear to what extent heat generation during pulverization is actually suppressed.

[0004] Furthermore, what is common to Patent Document 1 and Patent Document 2 is that both target the grinding of tea leaves and germinated seeds, which are relatively easy to grind, but do not target grains covered with hard shells, such as brown rice. Brown rice is highly nutritious and has a unique umami component, and in light of the recent trend toward health, there is a demand for using it in bread and noodles, but brown rice cannot be made into powder due to its hard shell.

[0005] Furthermore, while bread and noodles are basically made by kneading wheat and water, there has been an increasing demand in recent years for gluten-free bread and noodles that do not contain the gluten that is produced during the manufacturing process. Gluten is a sticky component necessary for the production of bread and noodles, but it is difficult to break down with digestive enzymes, and can cause allergic and inflammatory reactions, as well as destroy the intestinal barrier function and cause abdominal distension, abdominal pain, and diarrhea.

[0006] Bread and noodles made with rice flour have been increasing in recent years, but due to the need for sticky ingredients, bread and noodles made only from rice flour have not yet been realized.

[0007] JP 2021-136989 A JP 2003-334012 A

[0008] The present invention aims to provide a jet mill apparatus that can grind not only grains such as white rice, tea leaves, and dried foods that do not contain oil or sugar, but also brown rice, which has previously been difficult to grind, and further aims to provide a jet mill apparatus that can grind brown rice, which has previously been difficult to grind, into powder with a median diameter of, for example, 30 μm or less, or even 14 μm, without destroying or maintaining the nutrients before and after grinding.Furthermore, the present invention aims to provide a jet mill apparatus that can grind not only grains such as white rice and tea leaves, but also brown rice, which has previously been difficult to grind, into powder with a median diameter of less than 14 μm, for example, 3 to 14 μm, without destroying or maintaining the nutrients before and after grinding.

[0009] Another object of the present invention is to make it possible to produce bread using rice flour or brown rice flour, which has not previously been possible using rice flour alone, and to make it possible to produce gluten-free bread and gluten-free noodles that are chewy.

[0010] In order to solve the above problems, the jet mill device of the present invention has a raw material supply port that receives raw material from a pot containing raw material grains (including brown rice) to be milled or dried food that does not contain oil or sugar, and has a pair of nozzles arranged opposite each other within a casing, a compressor that generates compressed fluid to be supplied to the pair of nozzles, a cooling device that reduces the temperature of the fluid compressed by the compressor to room temperature, and piping that supplies the fluid compressed to room temperature output from the cooling device to each of the pair of nozzles.

[0011] The jet mill apparatus according to the present invention further includes a classifier, which repeatedly grinds the powder until the particle size falls within a predetermined size range, and which uses a classifying blade to eject coarse powder that is significantly affected by the centrifugal force caused by rotation, and returns it to the pot containing the raw grains.

[0012] The brown rice flour and rice flour produced according to the present invention are, for example, powders with a median diameter of 30 μm or less, or even about 14 μm, or even 14 μm to 3 μm, and are characterized in that the powder shape is not rounded but has corners and recesses, and has a large surface area.

[0013] Therefore, when the powder of the present invention is mixed with water, the powder of the present invention retains water in its recesses and in the gaps formed between the powder particles, allowing it to retain a significantly greater amount of water than rounded powder. Therefore, dough made by mixing the powder of the present invention with water is elastic, stretchy, and sticky. This characteristic makes it possible to produce bread and chewy noodles using only rice flour or brown rice flour, which previously could not be made using rice flour alone.

[0014] Schematic diagram of the jet mill device according to the present invention. Measurement results of the particle size of rice flour produced by the jet mill device according to the present invention using an Akita Komachi variety, measured with a scattering-type particle size distribution measuring device (Microtrac model MT3300EX). Nozzle equipped with a dish for the powder to collide. Measurement results of the particle size of rice flour produced by the jet mill device according to the present invention using Corona brown rice, measured with a scattering-type particle size distribution measuring device (Microtrac model MT3300EX). SEM photograph of brown rice flour pulverized by the jet mill device according to the present invention. SEM photograph of general rice flour. FE-SEM photograph of rice flour (average particle size 20 μm) pulverized by the jet mill device according to the present invention. Diagram showing the positions of partial enlarged views (FIGS. 7C) and (FIG. 7D) with squares. Image of a part of FIG. 7A magnified 2000 times. Image of a part of FIG. 7A magnified 10000 times. FE-SEM photograph of brown rice flour (average particle size 20 μm) pulverized by the jet mill device according to the present invention. Diagram showing the positions of partial enlarged views (FIGS. 8C) and (FIG. 8D) with squares. Image of a part of FIG. 8A magnified 2000 times. Image of a part of FIG. 8A magnified 10000 times. FE-SEM photograph of wet airflow-pulverized rice flour (manufactured by Tomizawa Shoten Co., Ltd., rice flour for bread made from Kyushu-produced rice (Mizuhotokara)). Diagram showing the positions of partial enlarged views (FIGS. 9C) and (FIG. 9D) with squares. Image of a part of FIG. 9A magnified 2000 times. Image of a part of FIG. 9A magnified 10000 times. Diagram showing the measurement area of ribs (lines that appear white like ridge lines) in rice flour (average particle size 20 μm) pulverized by the jet mill device according to the present invention. Diagram showing the measurement area of ribs (lines that appear white like ridge lines) in brown rice flour (average particle size 20 μm) pulverized by the jet mill device according to the present invention. Diagram showing the measurement area of ribs (lines that appear white like ridge lines) in wet airflow-pulverized rice flour (manufactured by Tomizawa Shoten Co., Ltd., rice flour for bread made from Kyushu-produced rice (Mizuhotokara)). Image tracing the observed ribs (lines that appear white like ridge lines) in the measurement area of rice flour (average particle size 20 μm) pulverized by the jet mill device according to the present invention. Image tracing the observed ribs (lines that appear white like ridge lines) in the measurement area of brown rice flour (average particle size 20 μm) pulverized by the jet mill device according to the present invention. Image tracing the observed ribs (lines that appear white like ridge lines) in the measurement area of wet airflow-pulverized rice flour (manufactured by Tomizawa Shoten Co., Ltd., rice flour for bread made from Kyushu-produced rice (Mizuhotokara)).The images show the change in the turbidity over time after each powdered tea was dissolved in water and made turbid. The figure shows the change in absorbance at a wavelength of 600 nm over time.

[0015] Hereinafter, various embodiments of the present invention will be described with reference to the drawings, etc. However, the present invention can be embodied in various forms without departing from the spirit of the present invention, and should not be construed as being limited to the description of the embodiments exemplified below.

[0016] In order to make the explanation clearer, the drawings may show the width, thickness, shape, etc. of each part schematically compared to the actual embodiment, but these are merely examples and do not limit the interpretation of the present invention.

[0017] The following description focuses on the jet mill apparatus according to the present invention (hereinafter also referred to simply as the jet mill apparatus) and brown rice flour produced thereby, although the powder produced by the jet mill apparatus according to the present invention is not limited to brown rice flour.

[0018] 1 is a schematic diagram of a jet mill apparatus according to the present invention. A pair of nozzles 2 are arranged coaxially within a casing 3. Compressed fluid produced by a compressor 4 is supplied to each of the pair of nozzles 2. The compressed fluid is at a high temperature when produced by the compressor 4, but is cooled to room temperature by a cooling device 5 before being supplied to the pair of nozzles 2.

[0019] In the jet mill apparatus of the present invention, raw materials, including brown rice, grains, and tea leaves, are crushed by colliding them with the force of the fluid injected from a pair of coaxially arranged nozzles 2. Therefore, adjusting the flow rate and pressure of the fluid injected from the nozzle 2's outlet is an important parameter when producing powder. Theoretically, the greater the fluid flow rate and pressure, and the smaller the nozzle 2's diameter, the greater the air volume, air pressure, and wind speed, resulting in greater force when the raw materials collide with each other, allowing for the rapid production of smaller powder particles. However, increasing the fluid flow rate and pressure increases the power consumption of the compressor 4, which increases production costs. On the other hand, insufficient fluid flow rate and pressure can result in problems such as a long time required to produce powder of the desired size.

[0020] In the jet mill device according to the present invention, when raw materials such as tea leaves and white rice, which are relatively easy to grind compared to brown rice, are ground, for example, when the diameter of the nozzle is 30 mm, the flow rate of the fluid injected from the nozzle 2 is 20 m ３ / min, and it is advisable to adjust the compressed air generated by the compressor 4 so as to achieve an injection pressure of 6.2 kPa. While keeping costs relatively low, it is possible to obtain a powder having a median diameter of 30 μm or less when measured on a volume basis using, for example, a scattering-type particle size distribution measuring device (Microtrac Model MT3300EX).

[0021] Figure 2 shows the particle size of rice flour produced by grinding Akitakomachi rice using the jet mill device according to the present invention, measured using a scattering particle size distribution analyzer (Microtrac Model MT3300EX). The specific surface area was 2618 (cm ２ , cm ３ ), the median diameter was 32.818 μm, and the arithmetic mean diameter was 37.336098 μm. From the graph shown in FIG. 2, it can be seen that powder with extremely small deviation and uniform size was obtained.

[0022] When grinding raw materials that are surrounded by husks and are relatively difficult to grind, such as brown rice, for example, if the diameter of the nozzle 2 is 30 mm, the flow rate of the fluid discharged from the nozzle 2 is 20 m ３ / min, and it is advisable to adjust the compressed air generated by the compressor 4 so as to obtain an injection pressure of 7.3 kPa. While keeping costs relatively low, it is possible to obtain a powder having a median diameter of about 14 μm when measured on a volume basis using, for example, a scattering-type particle size distribution measuring device (Microtrac Model MT3300EX).

[0023] In the present invention, raw materials such as brown rice are crushed by colliding them with the force of the fluid sprayed from a pair of coaxially arranged nozzles 2. Therefore, the finer the powder, the lower the probability of collision between the raw materials. Therefore, the more finely the powder is crushed, the more difficult it becomes to crush it efficiently. Therefore, the nozzle 2 may be shaped to include a plate for the powder that does not collide with the raw materials, as shown in Figure 3.

[0024] The reason why brown rice is a relatively difficult ingredient to grind is as follows: Generally, when producing rice flour, rice is soaked in water and then ground. Rice absorbs water, making it easy to grind. On the other hand, brown rice is difficult to grind because its husk is hard and does not absorb water even when soaked in water. The jet mill device of the present invention makes it possible to grind even brown rice, which is difficult to grind, and therefore brown rice flour can be produced.

[0025] Figure 4 shows the particle size of rice flour produced by grinding Corona brown rice using the jet mill apparatus of the present invention, measured using a scattering-type particle size distribution analyzer (Microtrac Model MT3300EX). The median diameter was 13.6991 μm, the mode diameter was 14.2071 μm, the arithmetic mean diameter was 14.7578 μm, and the arithmetic standard deviation was 6.7707 μm. The arithmetic standard deviation and the shape of the graph shown in Figure 4 show that even with grains like brown rice, which have hard husks, powder of uniform size with very little deviation could be obtained.

[0026] The cooling device 5 reduces the temperature of the fluid compressed by the compressor 4 to room temperature. As described above, the flow rate of the fluid discharged from the nozzle 2 is set to 20 m ３ / min and the injection pressure is adjusted to 6.2 kPa or 7.3 kPa, when the temperature of the compressed fluid is lowered to room temperature, the temperature of the fluid injected from the nozzle 2 can be made at least 0°C or less by adiabatic expansion. Therefore, it is possible to powder the raw material buckwheat, rice, or brown rice while maintaining the nutrients.

[0027] The classification method is not particularly limited. Therefore, any classifier commonly used in the flour milling industry may be used, such as an air classification method using centrifugal force due to rotation. By classification, powder exceeding a predetermined size is returned to the pot 10 to which the raw grain is supplied so as to be crushed again, and powder within the predetermined size range is collected in the powder pot 7 as crushed powder.

[0028] Table 1 below compares the nutritional content of brown rice and brown rice flour produced using the jet mill apparatus of the present invention. The analysis results for the nutrients in brown rice are the values ​​for the nutrients in brown rice shown in the 2020 edition (8th revision) of the Standard Tables of Food Composition in Japan compiled by the Ministry of Education, Culture, Sports, Science and Technology. The nutritional content of brown rice flour is the result of analysis by the Japan Food Research Laboratories.

[0029]

[0030] The nutritional values ​​for brown rice listed in the Ministry of Education, Culture, Sports, Science and Technology's 2020 Edition (8th Edition) of the Standard Tables of Food Composition in Japan are merely standard values ​​and represent the results of analysis of brown rice different from the brown rice used to produce the brown rice flour milled using the jet mill device of the present invention. Therefore, due to differences in the raw brown rice itself, Table 1 shows that, although some nutrients are found to be higher in the brown rice flour of the present invention than in brown rice, there is almost no significant difference in nutritional value between brown rice and the brown rice flour of the present invention. This indicates that the brown rice flour milled using the jet mill device of the present invention is powdered while maintaining most of the nutrients contained in the brown rice. Therefore, the brown rice flour of the present invention can be said to have almost the same nutritional value as brown rice, containing at least 0.8 mg of pantothenic acid and at least 25 μg of folic acid.

[0031] The reason why brown rice flour milled by the jet mill device of the present invention retains most of the nutrients it had when it was brown rice is because, as mentioned above, the temperature during milling is kept at at least 0°C or below. By keeping the temperature during milling at at least 0°C or below, the problem of the object to be milled being exposed to high temperatures during milling, which causes thermal friction and thermal denaturation and results in the loss of nutrients, is avoided. Furthermore, milling by the jet mill device of the present invention is carried out by using a jet of air, for example, 20m from the pair of nozzles 2. ３ The particles are crushed by colliding with each other on the fluid jetted at a flow rate of 6.2 kPa or 7.3 kPa at a flow rate of 1 / min, so the crushing is instantaneous. This instantaneous crushing is also the reason why the nutrients in the powder according to the present invention are not lost.

[0032] Regarding the shape of the brown rice flour milled by the jet mill device of the present invention, the shape has sharp points or recesses, which give it a large surface area, and it does not have a smooth surface, because the milling process is carried out by the raw brown rice particles riding on the fluid and colliding with each other.

[0033] Figure 5 is an SEM photograph of brown rice flour milled by the jet mill device of the present invention. The image on the left side of Figure 5 shows the powder clumping together (finer powders tend to clump more easily), making it appear as relatively large lumps. However, the image on the right side of Figure 5 shows that the brown rice flour has been finely ground into various shapes, such as elongated shapes with pointed ends or triangles. Figure 6 is an SEM photograph of ordinary rice flour. Compared to Figure 6, it is clear that the brown rice flour milled by the jet mill device of the present invention has a pointed shape.

[0034] Therefore, brown rice flour pulverized using the jet mill apparatus of the present invention easily retains water on its own, and when it aggregates into powder, gaps form between the grains, allowing water to be retained in those gaps. When water is added until it achieves a predetermined stretchability and elasticity, the water retention capacity of conventional rice flour is 30% or less compared to rice flour, while rice flour pulverized using the jet mill apparatus of the present invention can retain more than 55% and up to 60% of the water compared to rice flour. The reason for comparing rice flour rather than brown rice flour here is that brown rice flour pulverized to a level suitable for use in bread dough, etc., can only be achieved using the jet mill apparatus according to the embodiment of the invention, and there is no comparable brown rice flour available. However, brown rice flour pulverized using the jet mill apparatus of the present invention can also retain more than 55% and up to 60% of the water compared to brown rice flour.

[0035] The water-retaining properties of buckwheat flour, rice flour, and brown rice flour milled by the jet mill device of the present invention make them useful for producing foods that require gluten-like stickiness, such as bread and noodles. Buckwheat flour according to the present invention can easily produce 100% buckwheat noodles without the need for wheat flour as a binder. Buckwheat flour, rice flour, and brown rice flour that contain sufficient water have elasticity, stretchiness, and stickiness similar to gluten-containing dough, even without gluten.

[0036] Dried noodles made from rice flour with added modified starch have existed for some time. However, it has traditionally been nearly impossible to produce dried noodles using brown rice flour. As mentioned above, brown rice flour is more difficult to grind than rice flour, and the only size that can be produced is an average particle size of approximately 100 μm. Brown rice flour with an average particle size of approximately 100 μm absorbs less water than rice flour, so the powder particles do not stick together, making it extremely difficult to use in processed foods such as dried noodles. However, the applicant was able to produce dried noodles using brown rice flour ground using the jet mill device of the present patent invention.

[0037] Dried noodles made with brown rice flour pulverized using the jet mill device of the present patent invention are 80% brown rice flour and 20% rice flour, and no modified starch is added. These dried noodles can be produced with a thickness (cross-sectional diameter) of 1 mm. Therefore, when producing dried ramen noodles using brown rice flour pulverized using the jet mill device of the present patent invention, the thickness (cross-sectional diameter) of the dried noodles should be 1 mm or more and 2 mm or less, preferably 1.6 mm. When producing dried udon noodles, the thickness (cross-sectional diameter) of the dried noodles should be 2 mm or more and 3 mm or less, preferably 2.5 mm. Regardless of the thickness, the dried noodles have a chewy texture and can be used as dried noodles for ramen, somen, and other dishes that require a chewy texture.

[0038] FIG. 7A is an FE-SEM photograph of rice flour (average particle size 20 μm) ground using the jet mill apparatus according to the present invention. FIGS. 7C and 7D are partial enlarged views of FIG. 7A at 2000x and 10,000x magnifications, respectively. FIG. 7B is a diagram showing the positions of the partial enlargements (FIG. 7C) and (FIG. 7D) with squares. The relatively large squares indicate the areas in FIG. 7C, and the relatively small squares indicate the areas in FIG. 7D. Note that the particle sizes in this experiment are median sizes obtained by measurement using a HORIBA LA-300 scattering particle size distribution analyzer. FIG. 8A is an FE-SEM photograph of brown rice flour (average particle size 20 μm) ground using the jet mill apparatus according to the present invention. FIGS. 8C and 8D are partial enlarged views of FIG. 8A at 2000x and 10,000x magnifications, respectively. 0x magnification. Enlarged views. Figure 8B is a diagram showing the locations of the partial enlargements (Figure 8C) and (Figure 8D) with squares. The larger squares indicate the area in Figure 8C, and the smaller squares indicate the area in Figure 8D. Figure 9A is an FE-SEM photograph of wet-air-milled rice flour (bread flour made by Tomizawa Shoten Co., Ltd. using Kyushu-grown rice (Mizuho Chikara)). Figures 9C and 9D are 2000x and 10,000x magnifications of a portion of Figure 9A, respectively. Figure 9B is a diagram showing the locations of the partial enlargements (Figure 9C) and (Figure 9D) with squares. The larger squares indicate the area in Figure 9C, and the smaller squares indicate the area in Figure 9D. Note that wet-air-milling is a milling method conventionally used to produce rice flour.

[0039] In both rice flour and brown rice flour milled using the jet mill apparatus according to the present invention, no starch cells were visible and the surfaces were more irregular than rice flour milled using wet air milling. As is clear from comparing Figures 7D and 8D with Figure 9D, the surfaces of rice flour and brown rice flour milled using the jet mill apparatus according to the present invention are characterized by fine irregularities and visible corners compared to rice flour milled using wet air milling.

[0040] Using the partially enlarged views (Figs. 7C, 8C, and 9C), the image analysis software ImageJ was used to analyze the surface structures of rice flour particles milled using the jet mill apparatus according to the present invention, brown rice flour particles milled using the jet mill apparatus according to the present invention, and rice flour particles milled using a wet airflow mill. For the analysis, eight 6 μm × 6 μm measurement areas were randomly selected within the partially enlarged views (Figs. 7C, 8C, and 9C). Within these measurement areas, the lines visible as ribs in the images (white lines resembling ridges) were assumed to represent the irregularities in the surface structure of each powder, and the total lengths of the ribs (white lines resembling ridges) were measured.

[0041] FIG. 10 shows the measurement area of ​​ribs (white lines that look like ridgelines) in rice flour (average particle size 20 μm) ground using a jet mill device according to the present invention. FIG. 11 shows the measurement area of ​​ribs (white lines that look like ridgelines) in brown rice flour (average particle size 20 μm) ground using a jet mill device according to the present invention. FIG. 12 shows the measurement area of ​​ribs (white lines that look like ridgelines) in rice flour (bread flour made by Tomizawa Shoten Co., Ltd., using Kyushu-grown rice (Mizuho Chikara)) that has been wet-air-milled.

[0042] Figure 13 is an image of a trace of ribs (white lines that look like ridgelines) observed in the measurement area of ​​rice flour (average particle size 20 μm) ground using a jet mill device according to the present invention. Figure 14 is an image of a trace of ribs (white lines that look like ridgelines) observed in the measurement area of ​​brown rice flour (average particle size 20 μm) ground using a jet mill device according to the present invention. Figure 15 is an image of a trace of ribs (white lines that look like ridgelines) observed in the measurement area of ​​wet-air-milled rice flour (Kyushu-grown rice (Mizuho Chikara) rice flour for bread, manufactured by Tomizawa Shoten Co., Ltd.).

[0043] Table 2 below shows the results of tracing and measuring ribs (white lines that look like ridgelines and edges of cracks) in the observation areas of rice flour (average particle size 20 μm) milled using the jet mill device of the present invention, brown rice flour (average particle size 20 μm) milled using the jet mill device of the present invention, and rice flour (bread flour made by Tomizawa Shoten Co., Ltd. using Kyushu-grown rice (Mizuho Chikara)) that was wet-air milled. The ribs were traced and measured using "Analyze" - "Measure."

[0044]

[0045] According to Table 2, the average length of the ribs (white lines that look like ridges) of rice flour (average particle size 20 μm) pulverized using the jet mill apparatus of the present invention was 61.0 μm, while the average length of the ribs (white lines that look like ridges) of brown rice flour (average particle size 20 μm) pulverized using the jet mill apparatus of the present invention was 77.8 μm. On the other hand, the average length of the ribs (white lines that look like ridges) of rice flour (bread flour made by Tomizawa Shoten Co., Ltd., Kyushu-grown rice (Mizuho Chikara)) pulverized using the wet air milling method was 50.5 μm. This experiment revealed that the rice flour and brown rice flour pulverized using the jet mill apparatus of the present invention had more irregularities (ribs) formed on the flour surface than the rice flour pulverized using the wet air milling method.

[0046] The irregularities (ribs) formed on the surface of the flour are thought to make it easier for the powder to retain moisture, and are thought to have a significant effect on the water retention capacity of the flour. The irregularities (ribs) formed on the surface of rice flour, brown rice flour, or buckwheat flour milled using the jet mill device of the present invention increase the water retention capacity of the flour, which is thought to make it possible to produce foods that require gluten-like stickiness, such as bread and noodles. Therefore, although analysis based on FE-SEM photographs has not been performed on the buckwheat flour milled using the jet mill device of the present invention, it is thought that, like rice flour and brown rice flour, a large number of irregularities (ribs) are formed on the surface compared to general buckwheat flour.

[0047] Figure 16 shows images showing the change in the cloudiness over time after preparing 0.25 g of each of the following powdered teas: tea leaves pulverized using the jet mill device of the present invention (reference number (1) in Figure 16 ), "Oi Ocha" (registered trademark) manufactured by Ito En Co., Ltd. (reference number (2) in Figure 16 ), "Asahi Tea Industry" (powdered Uji tea) manufactured by MC Foods Co., Ltd. (reference number (3) in Figure 16 ), and "Asahi Tea Industry" powdered Chiran tea manufactured by MC Foods Co., Ltd. (reference number (4) in Figure 16 ), and adding each of these to a beaker containing 100 ml of water. Each beaker was shaken well to make the tea cloudy, and then the images show the change in the cloudiness over time.

[0048] The first row is an image taken immediately after turbidation, the second row is an image taken 10 minutes after turbidation, the third row is an image taken 20 minutes after turbidation, and the fourth row is an image taken 55 minutes after turbidation. As can be seen from these images, tea leaves ground using the jet mill device of the present invention show less color change and less precipitation than powdered Uji tea and powdered Chiran tea. Note that Oi Ocha (registered trademark) contains dextrin as a dispersant, resulting in less color change and less precipitation. In the case of tea leaves ground using the jet mill device of the present invention, even without dextrin as a dispersant, the amount of precipitation of the tea powder changes little over time, and it can be said that the dispersed state can be maintained.

[0049] The change in turbidity was confirmed not only by visual inspection but also by measuring the absorbance, which indicates how much light of a specific wavelength is absorbed when passing through a substance, at 0, 5, 10, 20, and 30 minutes immediately after turbidity. Figure 17 (Graph 1) shows the change in absorbance at a wavelength of 600 nm over time. Table 2 summarizes the measurement results. In Figure 17, the tea leaves ground using the jet mill device of the present invention are identified by "UMF."

[0050]

[0051] In Table 3, the tea leaves pulverized using the jet mill apparatus according to the present invention are also identified by "UMF." As is clear from the absorbance measurements, it has been proven that the tea leaves pulverized using the jet mill apparatus according to the present invention can maintain a dispersed state with similarly little change over time in the amount of precipitation of the tea powder, even without the inclusion of dextrin as a dispersion medium.

[0052] Although the embodiments of the present invention have been described above, any jet mill device according to the present invention to which the operator has appropriately added or deleted components or modified the design, or to which a process has been added or omitted or conditions have been modified, is also included within the scope of the present invention as long as it contains the gist of the present invention.

[0053] Even if there are other effects and advantages different from those brought about by the aspects of each of the above-mentioned embodiments, if they are clear from the description in this specification or can be easily predicted by a person skilled in the art, they will naturally be understood to be brought about by the present invention.

[0054] 2: Nozzle, 3: Casing, 4: Compressor, 5: Cooling device, 6: Classifier, 7: Powder pot, 9: Raw material supply port

Claims

1. A jet mill which pulverizes grains, tea leaves or dried foods which do not contain oil or sugar into powder by the collision of compressed air sprayed from a pair of nozzles, wherein the pair of nozzles are arranged on the same axis within a casing which forms a grinding chamber, the compressed air supplied to the pair of nozzles is compressed by a compressor and then cooled to at least room temperature by a cooling device, the pair of nozzles are provided with supply ports for supplying the grains or tea leaves, and the grains, tea leaves or dried foods which do not contain oil or sugar supplied from the supply ports are pulverized into powder by colliding with each other together with a fluid formed by the compressed air which has been cooled to at least room temperature sprayed from the nozzles.

2. A jet mill as claimed in claim 1, characterized in that it pulverizes pulverized grains, tea leaves or dried foods that do not contain oil or sugar until they become a powder with a median diameter of 10 μm or less.

3. A jet mill which pulverizes grains, tea leaves or dried foods which do not contain oil or sugar into powder by the collision of compressed air sprayed from a pair of nozzles, said pair of nozzles being arranged on the same axis within a casing which forms a grinding chamber, said compressed air supplied to said pair of nozzles being compressed by a compressor and then cooled to at least room temperature by a cooling device, said pair of nozzles being provided with a supply port for supplying said grains, tea leaves or dried foods which do not contain oil or sugar, said grains, tea leaves or dried foods which do not contain oil or sugar supplied from said supply port being pulverized by causing the grains, tea leaves or dried foods which do not contain oil or sugar supplied from said supply port to collide with a fluid formed by the compressed air which has been cooled to at least room temperature sprayed from the nozzles, said powder of said grains, tea leaves or dried foods which do not contain oil or sugar produced by the jet mill.

4. Rice flour or brown rice flour, characterized in that eight measurement areas of 6 μm x 6 μm are selected in a single image taken at 2000x magnification using an EF-SEM, the total length of the ribs observed at each of the measurement areas is calculated, and the average total length of each rib at each of the measurement areas is 61.0 or more and 77.8 or less.

5. Bread or noodles comprising the grain powder according to claim 3 or the rice flour or brown rice flour according to claim 4.

Images