JP7807771B2 - An invention relating to a jet mill that turns grains into powder and the powdered grain produced by the jet mill - Google Patents

Description

One embodiment of the present invention relates to a jet mill for grinding grains or tea leaves into powder and the grain or tea leaf powder produced thereby.

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 and germinated seed powder. For example, Patent Document 1 discloses the use of an impact plate jet mill, which removes the corners of the particles, giving the resulting barley leaf powder a smoother, more rounded structure, improving dispersibility in water and improving the smoothness of the powder. However, when barley leaves are ground 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 powder form.

For example, Patent Document 2 describes a method of drying grains, beans, and other functional ingredients by aeration and then grinding them in a swirling air mill to prevent them from denaturing or decomposing during drying. In the invention described in Patent Document 2, when grinding the grains or beans to be ground in a swirling air mill, which is a grinding device, the fluid is room-temperature compressed air, thereby suppressing heat generation during grinding. However, there is no description of how much compressed air should be used, and it is unclear to what extent heat generation during grinding is actually suppressed.

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 with hard shells, such as brown rice. Brown rice is highly nutritious and has a unique umami flavor, and given the recent trend toward health, there is demand for it to be used in bread and noodles. However, due to the hard shell of brown rice, it has not been possible to grind it into powder.

Furthermore, while bread and noodles are basically made by kneading wheat and water, there has been an increasing demand in recent years for so-called 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.

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 solely from rice flour have yet to be realized.

Japanese Patent Application Laid-Open No. 2021-136989 Japanese Patent Application Laid-Open No. 2003-334012

The objective of the present invention is to provide a jet mill device 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 to provide a jet mill device that can produce 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. The objective of the present invention is to provide a jet mill device that can produce not only grains such as white rice and tea leaves, but also brown rice, which has previously been difficult to grind, 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.

Another goal is to make it possible to produce bread using rice flour or brown rice flour, which previously could not be made using rice flour alone, and to make it possible to produce gluten-free bread and chewy noodles despite being gluten-free.

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 ground 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.

The jet mill device of the present invention further includes a classifier. The classifier repeatedly grinds the powder until the particle size falls within a specified size range. For example, coarse powder that is significantly affected by the centrifugal force caused by rotation is ejected by the classifying blades and returned to the pot containing the raw grain.

The brown rice flour and rice flour produced by the present invention are, for example, powders with a diameter of 30 μm or less, or even a median diameter of approximately 14 μm, or even a median diameter of 14 μm to 3 μm. Furthermore, the powder is not rounded, but has corners and recesses, giving it a large surface area.

As a result, 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. As a result, 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.

1 is a schematic diagram of a jet mill device according to the present invention. The particle size of rice flour produced from Akitakomachi rice using the jet mill device of the present invention was measured using a scattering particle size distribution measuring device (Microtrac model MT3300EX). A nozzle with a dish for the powder to impact. The particle size of rice flour produced from Corona brown rice using the jet mill device of the present invention was measured using a scattering type particle size distribution measuring device (Microtrac model MT3300EX). 1 is an SEM photograph of brown rice flour milled by the jet mill device according to the present invention. SEM photo of ordinary rice flour. FE-SEM photograph of rice flour (average particle size 20 μm) milled using the jet mill device according to the present invention. The positions of the partially enlarged views (FIG. 7C) and (FIG. 7D) are indicated by squares. A portion of Figure 7A magnified 2000 times. A portion of Figure 7A magnified 10,000 times. FE-SEM photograph of brown rice flour (average particle size 20 μm) milled using the jet mill device according to the present invention. The positions of the partially enlarged views (FIG. 8C) and (FIG. 8D) are indicated by squares. A portion of Figure 8A magnified 2000 times. A portion of Figure 8A magnified 10,000 times. FE-SEM photograph of wet air-milled rice flour (Kyushu-grown rice (Mizuho Chikara), bread flour, manufactured by Tomizawa Shoten Co., Ltd.). The positions of the partially enlarged views (FIG. 9C) and (FIG. 9D) are indicated by squares. A portion of Figure 9A magnified 2000 times. A portion of Figure 9A magnified 10,000 times. FIG. 1 shows the measurement area of ribs (white lines that look like ridges) in rice flour (average particle size 20 μm) ground using a jet mill device according to the present invention. FIG. 1 shows the measurement area of ribs (white lines that look like ridges) in brown rice flour (average particle size 20 μm) ground using a jet mill device according to the present invention. This figure shows the measurement area of ribs (white lines that look like ridges) in wet-air-milled rice flour (bread flour made by Tomizawa Shoten Co., Ltd., using Kyushu-grown rice (Mizuho Chikara)). This is an image in which ribs (white lines that look like ridges) observed in the measurement area of rice flour (average particle size 20 μm) milled using the jet mill device according to the present invention are traced. This is an image in which ribs (white lines that look like ridges) observed in the measurement area of brown rice flour (average particle size 20 μm) milled using the jet mill device according to the present invention are traced. This is an image of the ribs (white lines that look like ridges) observed in the measurement area of wet-air-milled rice flour (bread flour made by Tomizawa Shoten Co., Ltd., using Kyushu-grown rice (Mizuho Chikara)). Images showing the change in cloudiness over time after each powdered tea was dissolved in water and made cloudy. FIG. 10 is a graph showing the change in absorbance at a wavelength of 600 nm over time.

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

In order to clarify the explanation, 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.

The following description focuses on the jet mill device of the present invention (hereinafter simply referred to as the jet mill device) and the brown rice flour produced thereby. However, the powder produced by the jet mill device of the present invention is not limited to brown rice flour.

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

The jet mill device of the present invention uses the force of the fluid sprayed from a pair of coaxially arranged nozzles 2 to crush raw materials, including brown rice, other grains, and tea leaves, by colliding them together. Therefore, adjusting the flow rate and pressure of the fluid sprayed from the nozzle 2 outlet is an important parameter when producing powder. Theoretically, the greater the fluid flow rate and pressure, and the smaller the nozzle 2 diameter, the greater the air volume, pressure, and wind speed. This causes the raw materials to collide with greater force, resulting in the more rapidly smaller powder particles can be produced. 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 specified size.

In the jet mill apparatus according to the present invention, when grinding raw materials that are relatively easier to grind than brown rice, such as tea leaves or polished rice, for example, if the nozzle diameter is 30 mm, the flow rate of the fluid injected from the nozzle 2 is 20 m ³ /min, and the compressed air generated by the compressor 4 can be adjusted to an injection pressure of 6.2 kPa. While keeping costs relatively low, it is possible to obtain a powder with a median diameter of 30 μm or less when measured on a volume basis using, for example, a scattering-type particle size distribution analyzer (Microtrac Model MT3300EX).

Figure 2 shows the particle size of rice flour produced by grinding Akitakomachi rice using the jet mill device of the present invention, measured using a scattering particle size distribution analyzer (Microtrac Model MT3300EX). The specific surface area was 2618 ( ^cm2 , ^cm3 ), the median diameter was 32.818 μm, and the arithmetic mean diameter was 37.336098 μm. The graph in Figure 2 shows that powder of uniform size with very little deviation was obtained.

When grinding raw materials that are surrounded by husks and are relatively difficult to grind, such as brown rice, 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 the compressed air generated by the compressor 4 can be adjusted to an injection pressure of 7.3 kPa. While keeping costs relatively low, it is possible to produce powder with a median diameter of approximately 14 μm when measured on a volume basis using, for example, a scattering-type particle size distribution measuring device (Microtrac Model MT3300EX).

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 nozzles 2 arranged on the same axis. Therefore, the finer the powder, the lower the probability of collisions between the raw materials. Therefore, the more finely one tries to crush the powder, the more difficult it becomes to crush it efficiently. Therefore, the nozzle 2 may be shaped to include a tray for the powder that is not able to collide with the raw materials to collide with each other, as shown in Figure 3, for example.

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.

Figure 4 shows the particle size of rice flour produced by grinding Corona brown rice with the jet mill device 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, it was possible to obtain powder of uniform size with very little deviation.

The cooling device 5 lowers the temperature of the fluid compressed by the compressor 4 to room temperature. As described above, if 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 below by adiabatic expansion. This makes it possible to powder the raw buckwheat, rice, or brown rice while maintaining the nutrients of the raw material.

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

Table 1 below compares the nutritional content of brown rice and brown rice flour produced using the jet mill device 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 nutrients in brown rice flour are the results of analysis by the Japan Food Research Laboratories.

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 analysis results 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 little 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 nearly the same nutritional value as brown rice, containing at least 0.8 mg of pantothenic acid and at least 25 μg of folic acid.

As described above, the reason why brown rice flour milled using the jet mill apparatus of the present invention retains most of the nutrients it had when it was brown rice is because 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 thermal friction and thermal denaturation occurring when the object to be milled is exposed to high temperatures during milling, which could result in the loss of nutrients, is avoided. Furthermore, milling using the jet mill apparatus of the present invention is performed instantaneously because the particles are crushed by riding on fluid sprayed from a pair of nozzles 2 at a flow rate of, for example, 20 ^m3 /min with a pressure of 6.2 kPa or 7.3 kPa and colliding with each other. This instantaneous milling is also the reason why the nutrients in the powder of the present invention are not lost.

Regarding the shape of the brown rice flour milled by the jet mill device of the present invention, its shape has sharp points or recesses, giving it a large surface area, and it does not have a smooth surface. This is because the milling process occurs when the raw brown rice particles are carried by a fluid and collide with each other.

Figure 5 is an SEM photograph of brown rice flour milled using the jet mill device of the present invention. The image on the left side of Figure 5 shows that the powder has agglomerated (finer powders tend to agglomerate 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 and triangles. Figure 6 is an SEM photograph of ordinary rice flour. Compared to Figure 6, it is clear that the brown rice flour milled using the jet mill device of the present invention has a pointed shape.

As a result, brown rice flour milled using the jet mill apparatus of the present invention easily retains water on its own. Furthermore, when the flour aggregates into powder, gaps form between the individual particles, allowing water to be retained in those gaps. When water is added until the desired elongation and elasticity are achieved, conventional rice flour has a water retention capacity of 30% or less compared to rice flour, whereas rice flour milled 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 of the present invention, and no comparable brown rice flour exists. However, brown rice flour milled 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.

The water-retaining properties of buckwheat flour, rice flour, and brown rice flour milled using 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 be used to produce 100% buckwheat noodles without the need for wheat flour as a binder, even if the flour is 100% buckwheat. Buckwheat flour, rice flour, and brown rice flour that contains sufficient water have the same elasticity, stretchiness, and stickiness as gluten-containing dough, even without gluten.

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 moisture 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.

Dried noodles made from brown rice flour pulverized using the jet mill device of the patented 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 patented 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. Dried noodles of any thickness have a chewy texture and can be used as dried noodles for dishes that require a chewy texture, such as ramen and somen noodles.

Figure 7A is an FE-SEM photograph of rice flour (average particle size 20 μm) ground using the jet mill device of the present invention. Figures 7C and 7D are magnifications of a portion of Figure 7A at 2000x and 10,000x magnifications, respectively. Figure 7B is a diagram showing the locations of the partial enlargements (Figure 7C) and (Figure 7D) with squares. The relatively larger squares indicate the area of Figure 7C, and the relatively smaller squares indicate the area of Figure 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. Figure 8A is an FE-SEM photograph of brown rice flour (average particle size 20 μm) ground using the jet mill device of the present invention. Figures 8C and 8D are magnifications of a portion of Figure 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.

In both rice flour and brown rice flour milled using the jet mill device of the present invention, no starch cells were visible and there was more unevenness compared to 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 device of the present invention have finer unevenness and visible corners compared to rice flour milled using wet air milling.

Based on the partially enlarged images (Figures 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 device of the present invention, brown rice flour particles milled using the jet mill device of the present invention, and rice flour particles milled using a wet airflow mill. For the analysis, eight 6 μm x 6 μm measurement areas were randomly selected within the partially enlarged images (Figures 7C, 8C, and 9C). Within these measurement areas, the lines visible as ribs in the images (white lines that resemble ridges) were considered to represent the irregularities in the surface structure of each powder, and the total length of the ribs (white lines that resemble ridges) was measured.

Figure 10 shows the measurement area of ribs (white lines that look like ridgelines) in rice flour (average particle size 20 μm) ground using the jet mill device of the present invention, Figure 11 shows the measurement area of ribs (white lines that look like ridgelines) in brown rice flour (average particle size 20 μm) ground using the jet mill device of the present invention, and Figure 12 shows the measurement area of ribs (white lines that look like ridgelines) in wet air-milled rice flour (bread flour made from Kyushu rice (Mizuho Chikara), manufactured by Tomizawa Shoten Co., Ltd.).

Figure 13 is an image of the ribs (white lines that look like ridgelines) observed in the measurement area of rice flour (average particle size 20 μm) ground using the jet mill device of the present invention. Figure 14 is an image of the ribs (white lines that look like ridgelines) observed in the measurement area of brown rice flour (average particle size 20 μm) ground using the jet mill device of the present invention. Figure 15 is an image of the 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.).

Table 2 below summarizes the results of tracing and measuring the ribs (white lines that look like ridges and the edges of cracks) in each observation area using "Analyze" - "Measure" for rice flour (average particle size 20 μm) ground using the jet mill device of the present invention, brown rice flour (average particle size 20 μm) ground using the jet mill device of the present invention, and wet air-milled rice flour (bread flour made by Tomizawa Shoten Co., Ltd., using Kyushu-grown rice (Mizuho Chikara)).

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

The unevenness (ribs) formed on the surface of flour is thought to make it easier for the powder to retain moisture, and is thought to have a significant impact on the flour's water retention capacity. The unevenness (ribs) formed on the surface of rice flour, brown rice flour, or buckwheat flour milled using the jet mill device of the present invention increases the flour's water retention capacity, 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 unevenness (ribs) is formed on the surface compared to regular buckwheat flour.

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 ground using the jet mill device of the present invention (symbol (1) in Figure 16), "Oi Ocha" (registered trademark) manufactured by Ito En Co., Ltd. (symbol (2) in Figure 16), "Asahi Tea Industry" (powdered Uji tea) manufactured by MC Foods Co., Ltd. (symbol (3) in Figure 16), and "Asahi Tea Industry" powdered Chiran tea manufactured by MC Foods Co., Ltd. (symbol (4) in Figure 16). Each of these was added to a beaker containing 100 ml of water, and each beaker was shaken well to create a cloudy mixture.

The first row is an image taken immediately after turbidity, the second row is an image taken 10 minutes after turbidity, the third row is an image taken 20 minutes after turbidity, and the fourth row is an image taken 55 minutes after turbidity. 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 sedimentation than powdered Uji tea and powdered Chiran tea. Furthermore, Oi Ocha (registered trademark) contains dextrin as a dispersant, resulting in less color change and less sedimentation. In the case of tea leaves ground using the jet mill device of the present invention, even without dextrin as a dispersant, there is similarly little change in the amount of sedimentation of the tea powder over time, and it can be said that the dispersed state can be maintained.

Changes in turbidity were confirmed not only by visual inspection, but also by measuring absorbance, which indicates how much light of a specific wavelength is absorbed when it passes 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."

In Table 3, the tea leaves ground using the jet mill device of the present invention are also identified by "UMF." As is clear from the absorbance measurements, it has been proven that tea leaves ground using the jet mill device of the present invention can maintain a dispersed state with similarly little change in the amount of tea powder settling over time, even without the use of dextrin as a dispersant.

The above describes an embodiment of the present invention, but any product in which the operator appropriately adds or removes components or modifies the design of the jet mill device according to the present invention, or in which processes are added, omitted, or conditions are changed, is also included within the scope of the present invention as long as it contains the essence of the present invention.

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 the person skilled in the art, they will naturally be understood to be brought about by the present invention.

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

Claims (3)

A jet mill that pulverizes grains, tea leaves, or dried foods that do not contain oil or sugar into powder by the collision of compressed air jetted from a pair of nozzles,
The pair of nozzles are arranged coaxially within a casing that 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;
a pot into which the grain, tea leaves, or dried food that does not contain oil or sugar is supplied;
The pair of nozzles are each provided with a supply port for supplying the grain, tea leaves, or dried food that does not contain oil or sugar from the pot,
This jet mill is characterized in that the grains, tea leaves, or dried foods that do not contain oil or sugar are sprayed from the pair of nozzles together with the compressed air that has been cooled to at least room temperature, causing them to collide with each other and turn into powder. The jet mill described in claim 1 is characterized in that it grinds ground grains, tea leaves, or dried foods that do not contain oil or sugar until they become powder with a median diameter of 10 μm or less. The jet mill described in claim 1 or 2, characterized in that the injection pressure of the compressed air injected from the pair of nozzles is 6.2 kPa to 7.3 kPa.