Technical Field

The present invention relates to a method for preparing green tea powder (powdered green tea) having good dispersibility and flowability through a granulation process, and more particularly to a method for preparing green tea powder having excellent liquid dispersibility, powder flowability and color stability, the method comprising grinding green tea leaves, fluidizing the green tea powder in a fluidized bed granulator while spraying a 0.01 fold to 1-fold weight of purified water, or a 0.01 -fold to 1-fold weight of purified water and a binder, into the green tea powder, and granulating and diying the resulting material so as to form granules 1 -fold to 10-fold larger than the original size of the green tea powder.

Background Art

Green tea is prepared by inactivating oxidase present in the sprout or leaf of Camellia sinensis, a member of the family Theaceae. Green tea has been used as a favorite beverage since at least 3000 years ago, and as the pharmacological mechanisms of various components contained in the green tea have recently been found, the value thereof has been seen in a new light. In addition, it is known that green tea contains large amounts of active ingredients, such as catechins, amino acids, vitamin C, beta-carotene, dietaiy fiber and the like, and has excellent effects on recovery from fatigue, skin beauty, the improvement of diabetes and constipation, and the detoxification of hangover and nicotine. Particularly, as catechins contained in the green tea in the largest amount have been proven to have various effects, such as antioxidant, antiaging, anticancer, blood cholesterol reduction, heavy metal

detoxification, tooth decay prevention and bad breath removal effects, green tea has been receiving great attention.

Particularly when the green tea is brewed with boiling water, water- soluble components contained in the green tea will be drank and the remainder will be discarded. In this case, powdered green tea has an advantage in that all the components of the green tea, for example, tocopherol, vitamin A, dietary fiber and the like, can be ingested. In addition to being used as a beverage, powdered green tea is increasingly used as a raw material of food, for example, and as an additive to milk, yogurt, ice cream and the like, and also as a material for the preparation of breads, noodles and confectionaries.

Powdered green tea is obtained by grinding green tea leaves with grinding machines. The grinding machines can be broadly divided into crushers and grinders. A crusher serves to crush a large solid mass to a size of 6-250 mm, and examples thereof include a jaw crusher and a gyratory crusher. A grinder serves to make a ground product having a size of about 1 - 500 μm from the powder primarily crashed in a crasher or to make fine powder without primary crashing, and examples thereof include a hammer mill, a roller mill, a ball mill, an attrition mill and an air-flow type mill. In the case of preparing powdered green tea by grinding green tea leaves, grinding machines, particularly electrical hand mills, ball mills and hammer mills, are used.

However, the powdered green tea prepared by means of the above- mentioned grinding machines shows reduced dispersibility and flowability upon addition to water due to the cohesive force between the fine particles, which reduces the tea's convenience of use in terms of processing, such as placing it in tea bags or packaging it in small amounts. Also, general green

tea placed in a tea bag is combined with cold water, the components of the green tea will not be easily dissolved out, indicating that it is unsuitable to use the green tea with cold water.

To enable drinking of the green tea in a simple and convenient manner, instant green tea is prepared by extracting green tea with purified water, filtering and concentrating the extract and powdering the concentrate by freeze drying or hot air drying. This instant green tea has a disadvantage in that it is made such that only the water-soluble components of the green tea are ingested, and the oil-soluble components of the green tea cannot be ingested. In the process of extracting the green tea, a 4-fold to 20-fold amount of purified water must be added to the green tea. After the concentration, extraction and additional granulation processes, the drying process is conducted for a long time of about 6-7 hours at a temperature of less than 40 ⁰ C, and thereby excessive energy consumption and costs occur. Further, in the case of improving the dispersibility of green tea through the freeze-diying method, there is a disadvantage in that, since the green tea is in contact with an excess of water, a change in the color of the powdered green tea and oxidation of polyphenols in the powder green tea occur, such that it is sensitive to changes with time and loses its flavor. A method of forming green tea granules generally comprises combining liquid sugar, tea extract, saccharides and dextrin in a mixer, forming the mixture into granules in a dryer-type manufacturing machine and drying the granules with hot air for 7-9 hours (Korean Patent Publication No. 10-2003- 0087105, entitled "A method for preparing granular tea using powdered green tea"). In this method, since the mixture has a high water content in the combining step, it must be dried for a long time so as to reach the desired water content. Accordingly, there are disadvantages in that the intrinsic

flavor of the green tea is substantially lost due to excessive hot air drying, and the shape and size of the previously formed granules is significantly lost, reducing its efficiency. A Japanese patent related to green tea powder granules, similar to this method, discloses a method comprising stirring green tea powder and liquid in a mixer and forming the mixture into granules (Japanese Patent Laid-Open Publication No. Hei 8-280328, entitled "Instant green tea"). Since this method is a method of forming the granules by fermentation, cooling and then crushing, the water content of the product is very high, significantly reducing quality stabilities, such as color and flavor. Also, a process of forming granules by mixing green tea powder and powder saccharides (Japanese Patent Publication No. 2002-177, entitled "A method for preparing powdered green tea granules") is a method comprising mixing raw materials and drying the mixture, similar to the above Korean patent. In this method, since the water of the mixture is transferred to the green tea, the mixture needs to be dried for a long time in order to maintain the color and flavor qualities of the green tea.

As spraying methods for forming granules, methods for powdering tea extract or tea extract liquid by a spray drying process were suggested long ago. Examples thereof include Japanese Patent Publication No. Hei 10-165095, entitled "A method for preparing instant tea", Japanese Patent Publication No. 2001-178368, entitled "A method for preparing high-quality instant tea, and Japanese Patent Publication No. 2001-108, entitled "Instant tea with improved flavor". In these methods, tea is extracted and the concentrate is powdered in an instant by a high-temperature spray drying process. In the powdering step, the content in the concentrate is exposed to high temperature so as to change its flavor, and thus it is difficult to expect the intrinsic green color of the green tea. Also, the spray drying process requires a large energy

consumption, since it is a process wherein the water of a green tea extract of

40-60 brix is dried in an instant.

Accordingly, the present inventors have conducted studies on a method which can eliminate a reduction in dispersibility caused by the fine particle size of the prior powdered green tea, a reduction in an ease-of-use property occurring in terms of processing due to low flowability, and a complex process for preparing granular green tea by a general extraction method, and allows the ingestion of all the components of green tea, and as a result, found that, when powdered green tea is fluidized in a special fluidized bed granulator and granulated while spraying purified water and a binder, green tea powder having uniform particle size distribution can be formed while being less influenced by water, and the dispersibility and flowability of the green tea powder can be improved so as to enable various packaging methods to be applied, thereby completing the present invention.

Disclosure of Invention

Accordingly, it is an object of the present invention to provide a method for preparing granular green tea powder, all the components of which can be ingested and which has excellent color, dispersibility and flowability. The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description.

The granular green tea powder provided according to the present invention is granulated while keeping all the components thereof, and has reduced powder agglomeration to show flowability suitable for various types of package specifications, thus being packable in small or large amounts.

Further, all the components of the green tea can be ingested, and the fluidized

bed granulator can perform uniform spraying and drying so as to uniformly distribute/spray a small amount of the desired raw materials, and is a process wherein spraying and drying are simultaneously conducted. Thus, the granular green tea powder is effectively formed and the color and dispersibility thereof are superior to other green tea products.

To achieve the above object, the present invention provides a method for preparing granular green tea powder, comprising the steps of: 1) placing and grinding a generally prepared green tea in a grinder and separating the powder of a size less than 100 μim, thus obtaining green tea powder; 2) adding and spraying purified water or a purified water/binder onto the green tea powder so as to obtain granular green tea powder; and 3) drying the granular green tea powder obtained in step 2) with drying air so as to obtain dried granular green tea powder.

In step 2) of the inventive method, the purified water is preferably used in an amount of 0.1 -fold to 1-fold relative to the total weight of the green tea powder, and the spraying is performed using a fluidized bed granulator.

The inventive method for preparing granular green tea powder may further comprise the steps of: 4) preparing a granular green tea powder product in a unit of 0.1-10 g from said granular green tea powder in a tablet making machine or a capsule filling machine; and 5) packaging the granular green tea powder products in a unit of 0.1 - 100 g. See FIG. 2.

Hereinafter, the present invention will be described in further detail.

Preferred examples of the generally prepared green tea used in step 1) of the inventive method include steamed tea prepared by plucking, steaming, rolling, rubbing and drying the tea tree leaves, pan fired tea prepared by plucking, pan-firing, rubbing and drying the tea tree leaves, and Ten-cha prepared by steaming, cooling, drying, screening and diying tea leaves having

increased green chromaticity as a result of shielding the general tea tree leaves from light, but are not limited thereto.

The binder used in step 2) of the inventive method is preferably at least one compound selected from a thickener group consisting of guar gum, xantan gum, Arabic gum, agar, carrageenan, Konjac, tara gum, gellan gum and locust bean gum.

Also, as an additional or single binder in step 2), at least one compound selected from a tea extract group consisting of green tea extract powder, concentrated green tea extract, high-concentration catechin, low-concentration catechin and tea polyphenol compounds is preferably used.

In the case where a product requiring sweet taste need to be prepared, at least one compound selected from a sugar alcohol group (non-caries, sugarless) consisting of xylitol, isomalt, maltitol, sorbitol, erythritol, mannitol, lactitol and mannatol is preferably used as an additional or single binder in step 2).

Also, in the case where a product requiring sweet taste is to be prepared, at least one compound selected from a general saccharide group consisting of maltodextrin, cyclodextrin, sucrose, isomerized sugar, glucose, fructose, lactose, xylose, maltose, fructooligosaccharide, maltooligosaccharide, isomaltooligosaccharide, galactooligosaccharide, soybean-oligosaccharide, coupling sugar and palatinose is preferably used as an additional or single binder in step 2).

The binder in step 2) is used in an amount of 0.1-10 wt% based on the total weight of the purified water. If the content of the binder is less than 0.1 wt% relative to the total weight of the purified water, the binder will show insufficient binding force, and if it exceeds 10 wt%, the binder will be difficult to spray into the fluidized bed granulator due to the strong viscosity

of the binder solution.

Also, the binder in step 2) is preferably used in an amount of 1.0-10.0 wt% based on the total weight of the green tea powder. If the content of the binder is less than 1.0 wt% based on the total weight of the green tea powder, the binder will have insufficient binding force, and if it exceeds 10 wt%, the binder will have excessive binding force, making the powder particle too difficult to disperse in water and causing the powder particle to be easily precipitated.

In step 2) of the process, a solvent such as ethyl alcohol can be used in addition to the purified water. In this case, the ethyl alcohol is preferably used in an amount of 10-30 wt% based on the total weight of the purified water. If the amount of ethyl alcohol is less than 10 wt% based on the total weight of the purified water, the effect of use of ethyl will be insufficient, and if it exceeds 30 wt%, the ethyl alcohol will have strong volatility, making the mixed solvent difficult to uniformly spray onto the green tea powder.

In step 2), a sweetener may also be added in addition to adding the purified water or the mixture of purified water and a binder. As the sweetener, at least one compound selected from a synthetic sweetener group consisting of sucralose, acesulfam K, cyclamate, stevioside, aspartame, alitame, glycyrrhizine and thaumatin is preferably used.

The amount of the sweetener is preferably 0.001-1.0 wt% based on the weight of the purified water. If the content of the sweetener is less than 0.001 wt% based on the total weight of the purified water, the sweetener will have an insufficient sweetening effect, and if it exceeds 1.0 wt%, the sweetener will have excessive sweetening action, making the construction of products difficult. The sweetener is not mixed with the powder in trace amounts, but is sprayed after dissolution in the purified water or in the

mixture of purified water and a binder.

In step 3), the drying air preferably has a temperature not higher than 40 ⁰ C, and the drying time is preferably 30 minutes to 1 hour.

Further, in step 3) of the inventive method, the granular green tea powder preferably has a water content of 3-10 wt%. If the water content is less than 3 wt%, most of the granular particles will be lost or the flavor thereof will be lost, and if it exceeds 10 wt%, the oxidation of catechins in the green tea will accelerate, so that the color of the green color will disappear within a short time. At the final time point of drying in step 3) of the inventive method, green tea flavor or other flavor can be sprayed in a liquid or powder phase. In this case, the flavor is preferably added in an amount of 0.1-5.0 wt% based on the total weight of the green tea powder. If the content of the flavor is less than 0.1 wt% based on the total weight of the green tea powder, the addition of flavor will be insufficient, and if it exceeds 5 wt%, the added flavor will have excessive intensity, causing the intrinsic flavor of the green tea to be lost.

In step 4) of the inventive method, the granular green tea powder is preferably pressed and molded into a tablet or capsule form having a weight of 0.1-1Og. If the weight of the granular green tea powder is less than 0.1 g, it will be insufficient for the green tea to be pressed and molded as a unit dosage form, and if it exceeds 1O g, the amount of a unit dosage form will increase, reducing the preference of the resulting product.

In addition, when the green tea powder is molded, processed and packaged in tablet and capsule forms, products can be constructed with a small-sized package container so as to be easy to carry, and the active ingredient content of the green tea can be ensured and the variability thereof in a distribution process can be reduced.

In step 5) of the inventive method, the granular green tea powder is preferably packaged in the form of a stick having a weight of 0.1-2 g for drinking, and is preferably packaged in the form of a square bulk having a weight of 2-100 g for drinking. In the inventive method for preparing granular green tea, the size of the granules is preferably 1-fold to 10-fold larger in size than the original green tea powder. If the size of the granules is less than 1 -fold, the green tea will be in a state where the granules have not been formed, and have poor flowability, making it unsuitable to package in small amounts, and if it exceeds 10-fold, the green tea will require a long hydration time, lowering the taste thereof. Preferably, the size of the granules is in a range of 100-400 μm.

Brief Description of Drawings

FIG. 1 schematically shows improvements in the hydration and dispersion of granular green tea powder.

FIG. 2 shows each step of the inventive method for preparing granular green tea powder of the present invention.

FIg. 3 is a photograph showing the comparison of dispersibility between granular green tea powders prepared in Examples 1 and 2 and granular green tea powders prepared in Comparative Examples 1 and 2 (after 1 second;

Example 1, Example 2, Comparative Example 1 and Comparative 2, starting from the left side).

FIG. 4 is a photograph showing the comparison of dispersibility between granular green tea powders prepared in Examples 1 and 2 and granular green tea powders prepared in Comparative Examples 1 and 2 (after 5 seconds;

Example I ₅ Example 2, Comparative Example 1 and Comparative 2, starting from the left side).

FIG. 5 is a photograph showing the comparison of dispersibility between granular green tea powders prepared in Examples 1 and 2 and granular green tea powders prepared in Comparative Examples 1 and 2 (after 10 seconds;

Example 1, Example 2, Comparative Example 1 and Comparative 2, starting from the left side).

FIG. 6 is a photograph showing the comparison of dispersibility between granular green tea powders prepared in Examples 1 and 2 and granular green tea powders prepared in Comparative Examples 1 and 2 (after 15 seconds; upper left: Comparative Example 1, upper right: Comparative Example 2, lower left: Example 1, and lower right: Example 2).

FIG. 7 is a curve showing the dry particle size distribution of each of granular green tea powders in Examples 1 and 2 and Comparative Examples 1 and 2 (ex 1 : Example 1 , ex 2 : Example 2, cf 1 : Comparative Example 1 , and cf 2 : Comparative Example 2).

Best Mode for Carrying Out the Invention

Hereinafter, the present invention will be described in detail with reference to examples and test examples, however the scope of the present invention is not limited only to these examples and test examples. It will be obvious to those skilled in the art that these examples and test examples are presented to explain the present invention and are not construed to limit the scope of the present invention.

[Example 1] Preparation 1 of granular green tea powder 20 kg of green tea leaves, including stems, were ground with an air-flow type mill and passed through a classifier so as to prepare green tea powder having a size of less than 100 μm. 800 g of the prepared green tea powder

was placed and fluidized in a Glatt fluidized bed granulator and then sprayed with a 0.3 -fold weight of purified water. Drying air supplied in this fluidizing and spraying step had a relative humidity of 30% and a temperature of 7O ⁰ C, and the green tea powder had a temperature of 35 ⁰ C. After completion of the spraying, the same drying air was supplied at 4O ⁰ C to dry the granules to a water content of less than 5%, and the granules were sieved through a 600-mesh sieve, thus preparing granular green tea powder.

[Example 2] Preparation 2 of granular green tea powder 20 kg of green tea leaves, including stems, were ground with an air-flow type mill and passed through a classifier so as to prepare green tea powder having a size of less than 100 μm. 800 g of the prepared green tea powder was placed and fluidized in a Glatt fluidized bed granulator and then sprayed with a 0.5-fold weight of purified water. As a binder, guar gum was added in an amount of 0.3wt% based on the weight of the purified water. Drying air supplied in this fluidizing and spraying step had a relative humidity of 30% and a temperature of 70 ⁰ C, and the green tea powder had a temperature of 35°C. After completion of the spraying, the same drying air was supplied at 40 ⁰ C to dry the granules to a water content of less than 5%, and the granules were sieved through a 600-mesh sieve, thus preparing granular green tea powder.

[Example 3] Preparation 3 of granular green tea powder

20 kg of green tea leaves, including stems, were ground with an air-flow type mill and passed through a classifier so as to prepare green tea powder having a size of less than 100 μm. 800 g of the prepared green tea powder was placed and fluidized in a Glatt fluidized bed granulator and then sprayed

with a 0.5-fold weight of purified water. As a binder, green tea extract powder was added in an amount of 10wt% based on the weight of the purified water. Drying air supplied in this fluidizing and spraying step had a relative humidity of 30% and a temperature of 7O ⁰ C, and the green tea powder had a temperature of 35 ⁰ C. After completion of the spraying, the same drying air was supplied at 4O ⁰ C to dry the granules to a water content of less than 5%, and the granules were sieved through a 600-mesh sieve, thus preparing granular green tea powder.

[Example 4] Preparation 4 of granular green tea powder

20 kg of green tea leaves, including stems, were ground with an air- flow type mill and passed through a classifier so as to prepare green tea powder having a size of less than 100 μm. 800 g of the prepared green tea powder was placed and fluidized in a fluidized bed granulator and then sprayed with a 0.5-fold weight of purified water. As a binder, dextrin was added in an amount of 5 wt% based on the weight of the purified water. Drying air supplied in this fluidizing and spraying step had a relative humidity of 30% and a temperature of 7O ⁰ C, and the green tea powder had a temperature of 35°C. After completion of the spraying, the same drying air was supplied at 40 ⁰ C to dry the granules to a water content of less than 5%, and the granules were sieved through a 600-mesh sieve, thus preparing granular green tea powder.

[Comparative Example 1] Preparation of green tea powder using ball mill 250 ceramic balls (ø25 mm) were placed into a rotating drum having a rotation speed of 60 rpm, and 20 kg of green tea leaves, including stems, were ground with the ball mill for 1 hour. The powder was passed through a 100-

mesh sieve, thus preparing green tea powder having a size of less than 1 mesh.

[Comparative Example 2] Preparation 2 of green tea powder using airflow type mill 20 kg of green tea leaves, including stems, were ground with an air-flow type mill and then passed through a classifier, thus preparing green tea powder having a size of less than 1 mesh.

[Experimental Example 1] Comparison of dispersibility 0.8 g of each of the granular green tea powders of Examples 1 and 2 and the green tea powders of Comparative Examples 1 and 2 was placed in 250 ml of purified water at 10 ⁰ C and photographed for dispersion in a conical beaker (see FIGS. 3, 4, 5 and 6). FIg. 3 was photographed at 1 second after placing the green tea powder in purified water, FIG. 4 was photographed at 5 seconds after placing the green tea powder in purified water, and FIG. 5 was photographed at 10 seconds after placing the green tea powder in purified water. FIG. 6 shows the liquid surface photographed at 15 seconds after placing the green tea powder in purified water.

As shown in FIGS. 3, 4, 5 and 6, the granular green tea powder prepared in Example 1 had excellent dispersibility compared to the green tea powder prepared in Comparative Example 1 , indicating that the green tea powder of Example 1 was dispersed quickly in purified water.

[Experimental Example 2] Comparison of dispersibility 0.5 g of each of the granular green tea powders of Examples 1 and 2 and the green tea powders of Comparative Examples 1 and 2 was placed in 50 ml of purified water and dispersed in a conical tube for 2 minutes, then measured

for particle size using a particle size analyzer.

[Table 1]

As described above, the granular green tea powders prepared in Examples 1, 2, 3 and 4 had excellent dispersibility. Thus, in the case of the green tea powders of Examples 1-4, the powder sizes of D50 and D90, which indicate particle size distribution, were small and the particle size distribution was uniform. Also, before hydration, the particle size of the granular green tea powders of Examples 1-4 was larger than that of the Comparative Examples due to the formation of granules, but after hydration, the particle size was restored to the particle size of the original green tea powder. FIG. 7 is a curve showing the particle size distribution after hydration.

[Experimental Examples 3] Comparison of flowability (package suitability)

1 ,000 g of the granular green tea powder of Example 1 and of the green tea powder of Comparative Example 1 were tested for package suitability in a content weight of 0.8 g per package using a stick-type automatic packaging machine (n=100).

[Table 2]

As can be seen from the results in Table 2, the granular green tea powder of Example 1 has excellent flowability and thus is suitable to be packaged in small amounts, whereas general green tea powder, such as that of Comparative Example 1, has strong cohesive force and thus is difficult to package in a metered amount and also is very difficult to package in a constant amount.

[Experimental Example 4] Measurement of powder color

11 g of each of the granular green tea powders of Examples 1 to 4 and the green tea powders of Comparative Examples 1 and 2 were measured for chromaticity using a Minolta color meter.

[Table 3]

As shown in Table 3, in the case of the granular green tea powders of Examples 1 to 4, the L value (center) was placed at about 50 (not become

dark), the absolute value of a was decreased by about 2 (the higher the absolute a value, the closer to the green color), and the b value was decreased by about 3, compared to the green tea powder of Comparative Example 2. This suggests that, although the granular green tea powders of Examples 1 to 4 contained water and were granulated, they were maintained with respect to color quality without a great change, compared to the green tea powder of Comparative Example 2 not containing water.

Comparative Example 1, a method for preparing green tea commercially available, has a high L value, indicating that it is very light and has low green chromaticity. This is because if green tea powder is prepared using a ball mill, the color quality of the green tea deteriorates due to a long processing time.

[Experimental Example 5] Sensory Test 0.8 g of each of the granular green tea powders prepared in Example 1 and the green tea powder prepared in Comparative Example 2 were dispersed in 100 ml of water at 1O ⁰ C and then evaluated by a panel of 10 trained experts in a ranking method. The results are shown in Table 4 below.

[Table 4]

As can be seen in Table 4, the green tea prepared in Example 1 using granulation technology had color, taste and flavor similar to those of the general green tea powder of Comparative Example 2.

Industrial Applicability

As described above, by granulating ground green tea powder with purified water or a purified water/binder mixture in the fluidized bed granulator, a granular green tea powder having excellent powder flowability, liquid dispersibility and color stability compared to general green tea powder can be prepared.

Although a preferred embodiment of the present invention has been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.