Method for removing stem part of raw tea, method for manufacturing raw tea, and production line for raw tea

Abstract

To provide a method capable of efficiently removing a stalk part with regard to a raw material tea usable as a raw material for various tea products, suppressing a deterioration in a yield of the raw material tea.SOLUTION: A stalk part removal method of a raw material tea includes: cutting a plucked raw tea leaf to obtain a cut tea leaf; deactivating an oxidation enzyme in the cut tea leaf to obtain a deactivated tea leaf; cooling the deactivated tea leaf to obtain a cooled tea leaf; stamp-pressing the cooled tea leaf to obtain a stamp-pressed tea leaf; and removing a stalk part from the stamp-pressed tea leaf by a wind force screening.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for manufacturing raw tea that can be used as a raw material for various tea products such as tea beverages, tea extracts, and tea powders, as well as a production line, and more particularly, to a method for removing the stem portion from raw tea.

Background Art

[0002] Most of the green tea in Japan is produced through a series of processes including steaming the picked fresh leaves with steam to inactivate the oxidase contained in the fresh leaves (fixing), followed by rolling in each process such as rough rolling, rolling, intermediate rolling, and fine rolling, and further drying (Non-Patent Document 1).

[0003] When drinking green tea, it was typical to purchase commercially available dried green tea leaves, put the required amount into a teapot, and obtain an extract of the green tea leaves by extracting with hot water for a predetermined time, and then pour this into a cup or the like for drinking. However, with the changes of the times, consumer needs for green tea have become diverse in various ways. For example, as described above, the method of obtaining an extract of green tea leaves using a teapot and drinking it requires dealing with the extracted green tea leaves, that is, the tea leaves, but there is a need to avoid this trouble. To meet this need, there is a method of obtaining an extract of green tea leaves by immersing in hot water only in a teapot or hot water, etc., using a paper or nylon packaging material with a handle and enclosing dried green tea leaves (so-called tea bags), and this method has also spread widely.

[0004] Furthermore, in response to the need for greater simplicity, container-packed beverages (so-called RTD) in which the extract of green tea leaves (tea extract) is variously adjusted and packed in a container so that it can be drunk immediately after opening the cap, and products in which the extract of green tea leaves (tea extract) is dried in powder form (so-called instant tea) so that it can be drunk immediately by pouring hot water or water have also become popular.

[0005] Regarding a method for producing raw material tea for beverages or raw material extracts for beverages that can be suitably used as raw materials for these tea extracts, tea beverages, and instant tea, for example, in Patent Document 1, for the purpose of providing a method for producing raw material tea for beverages that can suppress the deterioration odor caused by long-term storage of tea beverages, it is characterized by including a step of reducing the kuchi-kura layer of tea leaves. The reduction treatment of the kuchi-kura layer is, for example, by pouring warm water at 60°C to 100°C flowing at a flow rate of 20 m / min to 120 m / min from a substantially horizontal direction onto one or both of the front and back surfaces of the tea leaves, and contacting the tea leaves with the warm water for 10 seconds to 120 seconds. A method for producing raw material tea for beverages is disclosed.

[0006] Further, Patent Document 2 discloses a method for efficiently producing tea extract, which is characterized by steaming fresh tea branches and leaves, cutting the steamed branches and leaves into small pieces, separating the cut branches and leaves into branches and leaves by wind power, and squeezing the separated leaves.

[0007] Patent Document 3 discloses a method for producing a processed tea product that can be drunk without separating the tea liquid and tea husks, which is to separate the green tea leaves into a tea leaf extract part and a non-tea leaf extract part, select the obtained non-tea leaf extract part into a tea leaf solid part and a non-tea leaf solid part, and mix the tea leaf extract part and the tea leaf solid part.

Prior Art Documents

Non-Patent Documents

[0008]

Non-Patent Document 1

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0010] As described above, tea products using green tea leaves have been developed and marketed in various forms according to different needs, such as canned tea beverages, tea extracts, and tea powders. For any tea product, if there are many branches and stems (collectively referred to as "stem parts" in the present invention) in the tea leaves used as raw materials, when kneaded, heated, dried, or stored for a long time, the components of the stem parts will migrate to the leaf parts, resulting in deterioration of the quality of the tea leaves or a so-called "autumn fall" state. In addition, since the stem parts are hard and difficult to dry, insufficient kneading may occur, and the energy and cost for drying the whole will increase. Therefore, for the raw material tea used as the raw material for various tea products, it is preferable that the stem parts are removed. However, even if the stem parts are removed, it is necessary to suppress the decrease in the yield of the raw material tea.

[0011] Therefore, an object of the present invention is to provide a method for removing stem parts of raw material tea, a method for manufacturing raw material tea, and a production line, which can efficiently remove stem parts and suppress the decrease in the yield of raw material tea for raw material tea that can be used as the raw material for various tea products.

Means for Solving the Problems

[0012] To solve such problems, the present invention proposes the following aspects.

[0013] [1] The first aspect of the present invention is a method for removing stem parts of raw material tea, which comprises cutting freshly picked tea leaves to obtain cut tea leaves, inactivating the oxidase of the cut tea leaves to obtain de-enzymed tea leaves, cooling the de-enzymed tea leaves to obtain cooled tea leaves, applying pressure to the cooled tea leaves to obtain pressurized tea leaves, and removing the stem parts from the pressurized tea leaves by air sorting. [2] The second aspect of the present invention is a method for removing the stem part of raw tea, which comprises cutting the picked fresh tea leaves to obtain cut tea leaves, inactivating the oxidase of the cut tea leaves to obtain de-enzymed tea leaves, applying pressure to the de-enzymed tea leaves to obtain pressed tea leaves, cooling the pressed tea leaves to obtain cooled tea leaves, and removing the stem part from the cooled tea leaves by air separation.

[0014] [3] The third aspect of the present invention is a method for manufacturing raw tea, which comprises cutting the picked fresh tea leaves to obtain cut tea leaves, inactivating the oxidase of the cut tea leaves to obtain de-enzymed tea leaves, cooling the de-enzymed tea leaves to obtain cooled tea leaves, applying pressure to the cooled tea leaves to obtain pressed tea leaves, and subjecting the pressed tea leaves to air separation to obtain a heavy part mainly composed of stem parts and a light part to be the raw tea. [4] The fourth aspect of the present invention is a method for manufacturing raw tea, which comprises cutting the picked fresh tea leaves to obtain cut tea leaves, inactivating the oxidase of the cut tea leaves to obtain de-enzymed tea leaves, applying pressure to the de-enzymed tea leaves to obtain pressed tea leaves, cooling the pressed tea leaves to obtain cooled tea leaves, and subjecting the cooled tea leaves to air separation to obtain a heavy part mainly composed of stem parts and a light part to be the raw tea.

[0015] [5] The fifth aspect of the present invention is a production line for raw tea, which is equipped with equipment for cutting the picked fresh tea leaves to obtain cut tea leaves, equipment for inactivating the oxidase of the cut tea leaves to obtain de-enzymed tea leaves, equipment for cooling the de-enzymed tea leaves to obtain cooled tea leaves, equipment for applying pressure to the cooled tea leaves to obtain pressed tea leaves, and equipment for subjecting the pressed tea leaves to air separation to obtain a heavy part mainly composed of stem parts and a light part to be the raw tea. [6] The sixth aspect of the present invention is a production line for raw tea, which is equipped with equipment for cutting the picked fresh tea leaves to obtain cut tea leaves, equipment for inactivating the oxidase of the cut tea leaves to obtain de-enzymed tea leaves, equipment for applying pressure to the de-enzymed tea leaves to obtain pressed tea leaves, equipment for cooling the pressed tea leaves to obtain cooled tea leaves, and equipment for subjecting the cooled tea leaves to air separation to obtain a heavy part mainly composed of stem parts and a light part to be the raw tea.

Advantages of the Invention

[0016] According to the present invention, it relates to a method for manufacturing raw tea that can be used as a raw material for various tea products (including green tea products and oolong tea products), and can efficiently remove the stems, and moreover, can suppress a decrease in the yield of the raw tea. Therefore, when using the raw tea obtained by the present invention, even when kneading, heating, drying, or storing for a long time, it can prevent the components of the stems from migrating to the leaf parts and deteriorating the quality of the tea leaves, or becoming in a so-called "autumn fall" state. In addition, it can eliminate insufficient kneading and also suppress the energy and cost for drying the whole.

Embodiments for Carrying Out the Invention

[0017] Hereinafter, an example of an embodiment of the present invention will be described. However, the present invention is not limited to the embodiments described below.

[0018] <Method for Manufacturing Raw Tea of the Present Invention> A method for manufacturing tea raw tea according to an example of an embodiment of the present invention (also referred to as "the method for manufacturing raw tea of the present invention") is to cut the freshly picked tea leaves to obtain cut tea leaves (cutting step), inactivate the oxidase of the cut tea leaves to obtain de-enzymed tea leaves (de-enzyming step), cool the de-enzymed tea leaves to obtain cooled tea leaves (cooling step), apply pressure to the cooled tea leaves to separate the stems and obtain pressed tea leaves (pressing step), and perform air classification on the pressed tea leaves to obtain a heavy part mainly composed of stems and a light part that becomes the raw tea (air classification step), which is characterized by the above.

[0019] Note that the above "steps" do not necessarily have to be carried out in a continuous production line, and may be intermittent. In that case, it may be carried out intermittently with a time interval, changing the equipment, or changing the location. In addition, the method for manufacturing raw tea of the present invention may be provided with other steps as long as the effects of the present invention are not hindered, and other treatments may be performed in each step. Further, the "mainly" in the "parts by weight mainly composed of the stem part" means that among those classified as parts by weight by wind power sorting, it occupies more than at least 50% by mass, 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more.

[0020] (Raw tea leaves) In the present invention, the "raw tea leaves" and the "raw leaves" refer to tea leaves that have not been subjected to enzyme inactivation treatment.

[0021] The tea to be harvested is not limited in terms of its variety, cultivation method, and harvesting time. For example, covered tea leaves harvested after being covered for a certain period before harvesting may be used, or tea leaves that are not covered may be used. Also, first flush tea, second flush tea, third flush tea, fourth flush tea, autumn and winter flush tea, etc. can be used. Moreover, it is also possible to use a combination of two or more types of tea leaves with different tea varieties, tea cultivation methods, harvesting times, etc.

[0022] The harvested tea leaves have a stem part and a leaf part. Usually, 2 to 8 tea leaves are attached to one stem part. In the present invention, among the harvested tea leaves, the part including branches and stems is referred to as the "stem part", and the other parts are referred to as the "leaf part".

[0023] (Cutting step) In the method for manufacturing the raw material tea of the present invention, the raw leaves of the harvested tea are cut to obtain cut tea leaves. That is, cutting the tea leaves before blanching is one of the features of the method for manufacturing the raw material tea of the present invention. Conventionally, when cutting the raw leaves of the harvested tea, fermentation and withering are likely to progress, so cutting the tea leaves before blanching has not been technically common sense. However, the present inventor has found that it is preferable to cut the tea leaves before blanching from the viewpoint of efficiently removing the stem part.

[0024] As a method for cutting fresh leaves, conventionally known equipment and techniques may be employed. For example, cutting processes using a fresh leaf cutter, a cross cutter, a hood processor, etc. can be mentioned.

[0025] As the size for cutting, it is preferable to cut into a size that does not clog the inside of each device or the conveyance path between devices and is easy to separate leaves and stems by air classification. Since tea leaves are irregular in shape, it is difficult to define the size, but as a guideline, from the above viewpoints, it is preferably a size equivalent to 20 mm × 20 mm to 70 mm × 70 mm, and more preferably a size equivalent to 30 mm × 30 mm or more or 60 mm × 60 mm or less.

[0026] (Enzyme inactivation step) In the enzyme inactivation step, the cut tea leaves may be heated to inactivate the enzyme to obtain de-enzymed tea leaves, and the method and equipment thereof may adopt currently known methods and equipment, or methods and equipment to be developed in the future. For example, in addition to steam heat treatment and stir-fry steaming using a steam machine, inactivation methods such as hot air drying that generates steam, direct fire heating such as pan-frying, hot air inactivation by applying hot air, hot water inactivation by hot water, and electromagnetic wave heating inactivation using microwaves can be adopted. Also, these can be combined. For example, after performing steam heat treatment using a steam machine, hot air inactivation by applying hot air may be performed. As a specific example of the inactivation method, methods such as "steam heat" by steaming with heating steam for about several tens of seconds or "pan-frying" by direct heating can be mentioned. These inactivation treatments are preferably performed at 80 to 400°C for 10 to 180 seconds, and more preferably at 90 to 350°C for 20 to 120 seconds.

[0027] Among the above inactivation treatments, treatments by direct fire heating such as pan-frying treatment are preferable in that the moisture content difference, in other words, the specific gravity difference between the stem part and the leaf part can be made larger, so that the stem part and the leaf part can be separated more accurately by air classification.

[0028] (Cooling step) Next, it is preferable to cool the fixed-form tea leaves to obtain cooled tea leaves. Since the quality of the tea leaves is likely to deteriorate if they remain hot after fixation, it is preferable to cool them.

[0029] As the cooling method, various methods and equipment can be adopted. For example, a cooling method using a loose tea machine, a wind-powered (blowing, hot air, suction) steamed leaf processing machine, etc. can be mentioned.

[0030] As a preferable example, a method can be mentioned in which a loose tea machine or the like is used to stir the tea leaves to cool the tea leaves and disperse the tea leaves. In this way, by cooling the tea leaves and suppressing the tea leaves from overlapping and adhering to each other, the effect of the treatment in the next process can be enhanced and the treatment can be performed uniformly. Stirring in loose tea processing can be performed using a known loose tea machine. However, as long as it is a device that can cool the tea leaves and at the same time eliminate the state where the tea leaves overlap and adhere to each other, an effect comparable to that of a loose tea machine can be obtained.

[0031] (Pressing process) Next, it is preferable to continuously apply pressure to the cooled tea leaves to separate the stem part from the tea leaves and obtain pressed tea leaves containing both.

[0032] As an example of a method of applying pressure to the leaves, a method can be mentioned in which a shaft provided with a pressing part standing on the shaft is rotated in the cylinder and the tea leaves are struck with the pressing part. At this time, it is preferable to set the rotation speed of the shaft to 150 rpm or more and 1200 rpm or less to strike the tea leaves. By applying a rotation of 150 rpm or more to the tea leaves, the tissue fluid (internal components) inside the tea leaves can be brought to the surface. On the other hand, by applying pressure with the rotation speed of 1200 rpm or less, leaf spillage and leaf fragmentation can be suppressed. From this perspective, regarding the method of the above-mentioned pressing process, it is preferable to apply pressure to the tea leaves by adjusting the rotational speed of the shaft to be 150 rpm or more and 1200 rpm or less. Among them, it is more preferable to set it to 180 rpm or more or 1000 rpm or less, and among them, it is even more preferable to set it to 200 rpm or more or 800 rpm or less to apply pressure to the tea leaves.

[0033] As an example of the device for applying pressure, a device provided with a rotating shaft and a number of stirring blades as a pressing part in a rotating cylinder capable of moving the tea leaves in a certain direction can be cited. At this time, it is preferable that convex strip portions extending in the length direction of the rotating cylinder are provided at appropriate intervals in the circumferential direction on the inner peripheral surface of the rotating cylinder. According to such a device, instead of simply applying pressure to the tea leaves by a number of stirring blades, frictional pressure can be applied to the tea leaves at the tip of the rotating blade and the convex strip portion on the inner periphery of the rotating cylinder, and the stem portion can be peeled off from the leaf portion and the stem portion can be separated from the leaf portion.

[0034] In the above-mentioned device, from the above perspective, the distance when the tip of the rotating blade and the convex strip portion on the inner periphery of the rotating cylinder are closest is preferably 2 mm or more and 20 mm or less, more preferably 3 mm or more or 15 mm or less, and even more preferably 4 mm or more or 12 mm or less.

[0035] Also, in the above-mentioned device, it is also preferable to provide a difference between the rotational speed of the rotating cylinder and the rotational speed of the rotating shaft. At this time, it is preferable to make the rotational speed of the rotating shaft faster than the rotational speed of the rotating cylinder. The rotations of the rotating cylinder and the rotating shaft may be in the same direction or in the opposite direction.

[0036] (Air separation process) The pressed tea leaves can be separated by air separation, that is, by a method and equipment that utilize air to scatter and separate or select according to the specific gravity difference, into a lightweight part that is blown far away and used as raw material tea (mainly leaf part) and a removed part that falls in the near field (mainly stem part). According to the wind power sorting in the present invention, as shown in the examples, it has been confirmed that the stem and leaf parts of tea can be sorted with higher accuracy compared to other sorting methods, such as sieving and color sorting. Note that the "mainly" in the "non-removal part (mainly leaf part)" and "removal part (mainly stem part)" means that the leaf part in the non-removal part or the stem part in the removal part occupies more than at least 50% by mass, 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more.

[0037] Wind power sorting can be carried out by a wind power sorter. The types of wind power sorters are not particularly limited. For example, a blowing type wind power sorter, a suction type wind power sorter, a closed type wind power sorter, etc. can be mentioned.

[0038] When performing wind power sorting, the temperature of the wind is preferably normal temperature (the temperature without heating or cooling) or a heated temperature. If it is cooled in the process of separating the leaf part and the stem part, the leaf part and the stem part are likely to adhere, and the separation accuracy will decrease. On the other hand, wind power sorting can be carried out with normal temperature or heated wind while drying the surface of the tea leaves, and the separation accuracy can be improved. From this perspective, the temperature of the wind applied to the tea leaves is preferably 25 to 130 °C, and more preferably 30 °C or more or 120 °C or less.

[0039] (Order of processes) It has been confirmed that even if the order of the cooling process and the pressing process is reversed, the reduction in the stem removal effect and the yield similar to that of the method for producing raw material tea of the present invention can be suppressed. Therefore, after applying pressure to the de-enzymed tea leaves to obtain pressed tea leaves, the pressed tea leaves may be cooled to obtain cooled tea leaves. That is, a method for manufacturing raw material tea for tea according to another example of an embodiment of the present invention (also referred to as "the method for manufacturing raw material tea of the present invention") includes cutting the picked fresh tea leaves to obtain cut tea leaves (cutting step), inactivating the oxidase of the cut tea leaves to obtain de-enzymed tea leaves (de-enzyming step), applying pressure to the de-enzymed tea leaves to separate the stem parts to obtain pressed tea leaves (pressing step), cooling the pressed tea leaves to obtain cooled tea leaves (cooling step), and subjecting the cooled tea leaves to air classification to obtain a heavy part mainly composed of stem parts and a light part to be the raw material tea (air classification step). This manufacturing method may be characterized by these steps.

[0040] <Manufacturing line of the present invention> The method for manufacturing raw material tea of the present invention can be implemented by a manufacturing line for raw material tea for tea according to an example of an embodiment of the present invention (also referred to as "the manufacturing line of raw material tea of the present invention"), that is, equipment for cutting the picked fresh tea leaves to obtain cut tea leaves, equipment for inactivating the oxidase of the cut tea leaves to obtain de-enzymed tea leaves, equipment for applying pressure to the de-enzymed tea leaves to obtain pressed tea leaves, equipment for cooling the pressed tea leaves to obtain cooled tea leaves, and equipment for subjecting the cooled tea leaves to air classification to obtain a heavy part mainly composed of stem parts and a light part to be the raw material tea. Also, it can be implemented by a manufacturing line for raw material tea that includes equipment for cutting the picked fresh tea leaves to obtain cut tea leaves, equipment for inactivating the oxidase of the cut tea leaves to obtain de-enzymed tea leaves, equipment for applying pressure to the de-enzymed tea leaves to obtain pressed tea leaves, equipment for cooling the pressed tea leaves to obtain cooled tea leaves, and equipment for subjecting the cooled tea leaves to air classification to obtain a heavy part mainly composed of stem parts and a light part to be the raw material tea.

[0041] <Effect of the method for manufacturing raw material tea of the present invention> According to the method for manufacturing raw material tea of the present invention, the mass ratio of the stem parts in the removed part classified into the heavy part by the air classifier can be set to 50 - 90%, preferably 55% or more, and more preferably 65% or more. At the same time, the yield of the raw material tea, that is, the mass ratio of the non-removed part (mainly leaf parts) classified into the light part to the mass of the tea leaves input into the air classifier can be set to 80 - 98%, preferably 83% or more, and more preferably 85% or more, and the decrease in the yield of the raw material tea can be suppressed and maintained relatively high.

[0042] Meanwhile, at the same time, the removal rate of the leaf part as a mass ratio correlated with the yield of the raw material tea can be set to 10% or less, more preferably 8% or less, and most preferably 6% or less. Note that for teas picked later such as third flush tea, fourth flush tea, and autumn and winter flush tea, the stem part tends to lead to a decrease in quality. Therefore, the later the tea is picked, the more the effects of the method for producing the raw material tea of the present invention can be enjoyed.

[0043] <Utilization of the lightweight part and the heavyweight part> The lightweight part (mainly the leaf part, also referred to as "the raw material tea of the present invention") obtained by the method for producing the raw material tea of the present invention can be used as the raw material tea leaves for various products. For example, the raw material tea of the present invention can be juiced to obtain tea extract, which can be used as a raw material for various beverages such as green tea beverages and oolong tea beverages. In addition, the raw material tea of the present invention can be kneaded in each process such as rough rolling, rolling, medium rolling, and fine rolling in the same manner as conventional rough tea, and further dried to produce rough green tea. Moreover, through rough rolling, rolling, mincing, loosening, and drying, it can also be made into rough green tea. Furthermore, oolong tea can be produced by known processes.

[0044] On the other hand, the heavyweight part (mainly the stem part) obtained by the method for producing the raw material tea of the present invention can, for example, be juiced to obtain tea extract, which can be used as a raw material for various beverages. It can also be dried to make stem tea, or after drying, it can be roasted to make roasted tea.

[0045] <Explanation of terms, etc.> In the present invention, when described as "α to β" (α and β are arbitrary numbers), unless otherwise specified, it includes the meaning of "α or more and β or less", as well as the meaning of "preferably greater than α" or "preferably less than β". Also, when described as "α or more" or "α ≦" (α is an arbitrary number), unless otherwise specified, it includes the meaning of "preferably greater than α", and when described as "β or less" or "≦ β" (β is an arbitrary number), unless otherwise specified, it also includes the meaning of "preferably less than β". In the present invention, "equipment" is a general term encompassing tools, instruments, machines, and devices.

Example

[0046] Hereinafter, an example of an embodiment of the present invention will be described. However, the present invention is not limited to the embodiments described below.

[0047] (Example 1) Fresh tea leaves (produced in Shizuoka Prefecture, Yabukita variety, second flush tea, tea temperature 27.6°C) within 24 hours after picking were cut with a cross cutter to obtain cut tea leaves with an average size of 40 mm × 40 mm. The cut tea leaves were heat-treated with non-pressure steam for 40 seconds using a continuous rotary drum steamer (steam setting: 300 kg / h, steam volume 50 kg / h) to inactivate the oxidase and obtain de-enzymed tea leaves (tea temperature 58.3°C), which were then cooled with a pneumatic cooler to obtain cooled tea leaves (tea temperature 34.5°C). Next, the cooled tea leaves were passed through a rotary drum with rotary stirring blades (when the tip of the rotary blade and the rib portion on the inner circumference of the rotary drum are closest, the distance is 4 mm, the rotational speed of the shaft is 450 rpm) provided with a rotary shaft and a number of rotary blades inside the rotary drum, and a pressing process was continuously performed on the tea leaves in the rotary drum to separate the stem portion from the tea leaves (tea temperature 29.1°C). Then, pneumatic sorting was performed using a pneumatic sorter with hot air at 120°C to obtain a removed portion that is the weighted portion (mainly the stem portion) that fell on the near side and a non-removed portion that is the lightweight portion (mainly the leaf portion) that was blown to the far side (tea temperature 32.6°C). The tea temperature was measured by contacting the sensor of a digital thermometer with the tea leaves, and the average value of three measurements was adopted.

[0048] (Example 2) In Example 1, instead of the enzyme inactivation treatment by heat treatment with steam, stir-frying in a kettle where the tea leaves were directly contacted with the inner wall of the rotary drum at 270°C (kettle setting 450 kg / h, input 265°C, output 270°C, exhaust 9 m 3Except for inactivating the oxidase enzyme by heating at 120°C for 180 seconds (rotation speed of the cylinder: 26 rpm) to obtain the de-enzymed tea leaves (tea temperature: 61.8°C), the removal part and the non-removal part (tea temperature: 37.0°C) were obtained in the same manner as in Example 1.

[0049] (Example 3) In Example 1, except that instead of the air separation by warm air at 120°C, air separation was carried out with air at normal temperature (without heating or cooling), the removal part and the non-removal part (tea temperature: 26.2°C) were obtained in the same manner as in Example 1.

[0050] (Example 4) In Example 2, except that instead of the air separation by warm air at 120°C, air separation was carried out with air at normal temperature (without heating or cooling), the removal part and the non-removal part (tea temperature: 29.7°C) were obtained in the same manner as in Example 2.

[0051] (Example 5) In Example 3, as the raw tea leaves, instead of the tea leaves of Yabukita variety, second flush, produced in Shizuoka Prefecture with a tea temperature of 27.6°C, the autumn and winter flush tea leaves of Yabukita variety, produced in Shizuoka Prefecture with a tea temperature of 22.6°C were used. Otherwise, the removal part and the non-removal part (tea temperature: 21.8°C) were obtained in the same manner as in Example 3.

[0052] (Comparative Example 1) In Example 1, except that air separation was not carried out after the pressure treatment, the raw tea leaves were obtained in the same manner as in Example 1.

[0053] (Comparative Example 2) In Example 2, except that air separation was not carried out after the pressure treatment, the raw tea leaves were obtained in the same manner as in Example 2.

[0054] (Comparative Example 3) In Example 3, the order of cutting and de-enzyming was reversed. That is, in Example 3, fresh tea leaves (produced in Shizuoka Prefecture, Yabukita variety, second flush tea, tea temperature 27.6°C) within 24 hours after picking were heat-treated with non-pressurized steam for 40 seconds using a continuously rotating drum steaming machine (steam setting: 300 kg / h, steam volume 50 kg / h) to inactivate the oxidase and obtain green tea leaves (tea temperature 58.3°C). These green tea leaves were cut with a cross cutter, but they could not be cut neatly. As a result, cut tea leaves and uncut tea leaves of uneven sizes of about 20 to 80 mm were obtained. Except for subjecting these tea leaves to a pressing process, a removed portion and a non-removed portion (tea temperature 25.7°C) were obtained in the same manner as in Example 3.

[0055] (Comparative Example 4) In Example 4, the order of cutting and green tea making was reversed. That is, in Example 4, fresh tea leaves (produced in Shizuoka Prefecture, Yabukita variety, second flush tea, tea temperature 27.6°C) within 24 hours after picking were directly brought into contact with the inner wall of a 270°C rotating drum for pan-firing (pan setting 450 kg / h, input 265°C, output 270°C, exhaust 9 m 3 / min, drum rotation 26 rpm) to inactivate the oxidase and obtain green tea leaves (tea temperature 61.8°C). These green tea leaves were cut with a cross cutter, but they could not be cut neatly. As a result, cut tea leaves and uncut tea leaves of uneven sizes of about 20 to 80 mm were obtained. Except for subjecting these tea leaves to a pressing process, a removed portion and a non-removed portion (tea temperature 28.1°C) were obtained in the same manner as in Example 4.

[0056] (Comparative Example 5) In Example 3, a removed portion and a non-removed portion (tea temperature 25.9°C) were obtained in the same manner as in Example 3, except that the pressing process was not performed after green tea making.

[0057] (Comparative Example 6) In Example 3, instead of wind sorting, raw tea leaves were obtained in the same manner as in Example 3, except that a sieve with a mesh size of 6.58 mm was used to separate a removed portion (mainly stems) below the sieve and a non-removed portion (mainly leaves) above the sieve.

[0058] (Comparative Example 7) In Example 3, except that instead of wind sorting, bright-colored and brown-colored removal parts (mainly the stem parts) and green non-removal parts (mainly the leaf parts) were separated by CCD color sorting using a color sorter, raw tea leaves were obtained in the same manner as in Example 3.

[0059] (Comparative Example 8) Fresh tea leaves (produced in Shizuoka Prefecture, Yabukita variety, second flush tea, tea temperature 27.6 °C) within 24 hours after picking were heat-treated with non-pressurized steam for 40 seconds using a continuous rotating drum steamer to inactivate the oxidase and obtain green tea leaves (tea temperature 58.3 °C). These green tea leaves were cut with a cross cutter but could not be cut neatly. As a result, cut tea leaves and uncut tea leaves of uneven sizes of about 20 to 80 mm were obtained. Next, the cut tea leaves (tea temperature 28.5 °C) were sorted by wind using a cold air of 18 °C using a wind sorting wind type sorter to obtain a removal part and a non-removal part (tea temperature 25.8 °C).

[0060] <Measurement of moisture content> The removal parts and non-removal parts after wind sorting obtained in the examples and comparative examples were used as samples respectively. When dried at 105 °C for 6 hours using a forced circulation ventilation dryer by the normal pressure heating drying method, the mass loss of the samples was taken as moisture, and the moisture content (mass%, moisture content) was measured. The average value of three times was adopted and shown in the table as the "moisture content at separation".

[0061] <Measurement of stem and leaf separation accuracy> The mass of the tea leaves put into the wind sorter and the mass of the non-removal part (also referred to as the "non-removal part mass") separated into the lightweight part blown far away by wind sorting (mainly the leaf part) were measured respectively. The percentage of the non-removal part mass to the mass of the input tea leaves was calculated and shown in Table 1 as the "non-removal part". The value obtained by subtracting the non-removal part mass from the mass of the tea leaves put into the wind sorter was shown in Table 1 as the "removal part". From among the group separated into the removal part that fell to the near side by the air classifier, visually remove the leaf part to select only the stem part, measure the mass of this "only stem part" (also referred to as "removal part stem mass"), calculate the percentage of the removal part stem mass with respect to the removal part mass, and show it in Table 1 as the "proportion of stems in the removal part". Also, multiply the proportion of the removal part by the proportion of stems in the removal part to calculate the mass proportion of stems in the removal part (the "stem removal rate") with respect to the mass of tea leaves input into the air classifier and show it in Table 1. Furthermore, subtract the "stem removal rate" from the "removal part" to calculate the "leaf removal rate" and show it in Table 1.

[0062] <Evaluation> If the mass proportion of stems in the removal part classified into the weight part by the air classifier, that is, the "proportion of stems in the removal part", is 50% or more, it can be evaluated that the stems have been removed efficiently. Also, if the mass proportion of the non-removal part classified into the light part with respect to the mass of tea leaves input into the air classifier, that is, the "non-removal part", is 80% or more, it can be evaluated that the yield of the raw tea is relatively high. Therefore, those with a "proportion of stems in the removal part" of 50% or more and a "non-removal part" of 80% or more were evaluated as "〇 (qualified)", and those where either one or both did not meet the criteria were evaluated as "× (unqualified)".

[0063]

Table 1

[0064] (Discussion) In Examples 1 to 5, since the proportion of the "non-removal part" after air classification was 80% or more and the proportion of "stems in the removal part" was 50% or more, while maintaining a high proportion of the non-removal part, that is, suppressing the decrease in yield, the stems could be removed efficiently. Regarding Examples 1 to 4 using second flush tea, by setting the air classification at normal temperature or hot air, the ratio of the non-removed part and the ratio of the stem part in the removed part increased, and the tendency was that the hot air showed a more improved tendency, and the stem part could be removed more efficiently. Furthermore, the greater the moisture difference at the time of separation, the more the removal rate of the stem part tended to increase. On the other hand, regarding Example 5 using autumn and winter flush tea, even when the moisture difference at the time of separation was low, the removal rate of the stem part tended to be high. Also, even with normal temperature air classification, the ratio of the non-removed part and the ratio of the stem part in the removed part were high, suggesting that the ratio of the non-removed part and the removal efficiency of the stem part vary depending on the tea season.

[0065] In Comparative Examples 3 and 4 where the tea leaves were cut after fixation, the ratio of the non-removed part was less than 80%, and the ratio of the stem part in the removed part was also less than 50%. This is presumably because the size of the cut became uneven by cutting the tea leaves after they became soft by fixation, resulting in a decrease in the separation accuracy in air classification. In Comparative Example 5 where the pressing process was not carried out, the ratio of the non-removed part was 80% or more, but the ratio of the stem part in the removed part was low. When actually visually checking the non-removed part, many stem parts were confirmed in the non-removed part, and it was confirmed that the separation accuracy was poor. This is presumably because the separation of the stem part from the tea leaves was insufficient due to the absence of the pressing process.

[0066] In Comparative Example 6, the separation of the stem part from the tea leaves was carried out by sieving instead of air classification, and in Comparative Example 7, the separation of the stem part from the tea leaves was carried out by color sorting instead of air classification. Compared with Example 3, in Comparative Examples 6 and 7, the ratio of the non-removed part was low, and the ratio of the stem part in the removed part was also low. It became clear that air classification is suitable for the separation of the stem part and the leaf part in the present invention.

[0067] In Comparative Example 8, the tea leaves were cut after fixation, and further air classification was carried out with cold air. Although the ratio of the non-removed part was good, the ratio of the stem part in the removed part was low, and the stem part could not be removed efficiently. This is presumably because the size of the cut became uneven due to cutting after fixation, and furthermore, since air classification was carried out with cold air, the leaf part and the stem part were likely to adhere.

[0068] From the test results and the like that the inventors have conducted so far, if the freshly picked tea leaves are cut before the deactivation step of the oxidase, compared with the case where the tea leaves are cut after the deactivation step, the ratio of the non-removal part as the raw material tea is high, and the ratio of the stem part in the removal part can be increased. That is, it has been found that the stem part can be efficiently removed while suppressing the decrease in the yield of the raw material tea.

[0069] Also, before the deactivation step of the oxidase, the freshly picked tea leaves are cut, and further, after applying pressure to the tea leaves to separate the stem part from the tea leaves, if they are separated into a heavy part (mainly the stem part) and a light part (mainly the leaf part) by air classification, it has been found that the stem part can be efficiently removed compared with the prior art. Furthermore, when performing air classification, by setting the temperature of the wind that becomes the wind pressure to normal temperature or even the temperature of heated warm air, compared with cold air, the removal rate of the leaf part can be kept low, and it has been found that the ratio of the stem part in the removal part is high and the classification accuracy can be further improved.

Claims

1. The freshly picked tea leaves are cut to obtain cut tea leaves, the oxidase of the cut tea leaves is inactivated to obtain de-enzymed tea leaves, the de-enzymed tea leaves are cooled to obtain cooled tea leaves, A device provided with a rotating shaft and a plurality of stirring blades as a pressing part in a rotating cylinder capable of moving the tea leaves in a certain direction, and on the inner peripheral surface of the rotating cylinder, convex strip parts extending in the length direction of the rotating cylinder are provided at intervals in the circumferential direction. In the rotating cylinder of the device where the distance when the tip of the rotating blade and the convex strip part on the inner circumference of the rotating cylinder are closest is 2 mm or more and 20 mm or less, the cooled tea leaves are supplied, and the cooled tea leaves are pressed by a large number of stirring blades, and at the tip of the rotating blade and the convex strip part on the inner circumference of the rotating cylinder, a frictional pressure is applied to the cooled tea leaves to strip the leaf part from the stem part to separate the stem part from the tea leaves to obtain pressed tea leaves containing the stem part, A method for removing the stem part of raw tea by wind force sorting to remove the stem part from the pressed tea leaves.

2. The freshly picked tea leaves are cut to obtain cut tea leaves, and the oxidase of the cut tea leaves is inactivated to obtain de-enzymed tea leaves, A device provided with a rotating shaft and a plurality of stirring blades as a pressing part in a rotating cylinder capable of moving the tea leaves in a certain direction, and on the inner peripheral surface of the rotating cylinder, convex strip parts extending in the length direction of the rotating cylinder are provided at intervals in the circumferential direction. In the rotating cylinder of the device where the distance when the tip of the rotating blade and the convex strip part on the inner circumference of the rotating cylinder are closest is 2 mm or more and 20 mm or less, the de-enzymed tea leaves are supplied, and the de-enzymed tea leaves are pressed by a large number of stirring blades, and at the tip of the rotating blade and the convex strip part on the inner circumference of the rotating cylinder, a frictional pressure is applied to the de-enzymed tea leaves to strip the leaf part from the stem part to separate the stem part from the tea leaves to obtain pressed tea leaves containing the stem part, The pressed tea leaves are cooled to obtain cooled tea leaves, A method for removing the stem part of raw tea by wind force sorting to remove the stem part from the cooled tea leaves.

3. The freshly picked tea leaves are cut to obtain cut tea leaves, the oxidase of the cut tea leaves is inactivated to obtain de-enzymed tea leaves, and the de-enzymed tea leaves are cooled to obtain cooled tea leaves, A device comprising a rotating shaft and a plurality of stirring blades as a pressing part in a rotating cylinder capable of moving tea leaves in a certain direction, and provided with ridge parts extending in the length direction of the rotating cylinder at intervals in the circumferential direction on the inner peripheral surface of the rotating cylinder, wherein the distance when the tip of the rotating blade and the ridge part on the inner circumference of the rotating cylinder are closest is 2 mm or more and 20 mm or less. The cooled tea leaves are supplied into the rotating cylinder of the device, and the cooled tea leaves are pressed by a number of stirring blades, and at the tip of the rotating blade and the ridge part on the inner circumference of the rotating cylinder, a frictional pressure is applied to the cooled tea leaves to strip the stem part from the leaf part, separate the stem part from the tea leaves, and obtain pressed tea leaves containing the stem part. A method for manufacturing raw tea, which comprises wind-separating the pressed tea leaves to obtain a heavy part mainly composed of stem parts and a light part to be the raw tea.

4. The fresh leaves of the picked tea are cut to obtain cut tea leaves, and the oxidase of the cut tea leaves is inactivated to obtain de-enzymed tea leaves. A device comprising a rotating shaft and a plurality of stirring blades as a pressing part in a rotating cylinder capable of moving tea leaves in a certain direction, and provided with ridge parts extending in the length direction of the rotating cylinder at intervals in the circumferential direction on the inner peripheral surface of the rotating cylinder, wherein the distance when the tip of the rotating blade and the ridge part on the inner circumference of the rotating cylinder are closest is 2 mm or more and 20 mm or less. The de-enzymed tea leaves are supplied into the rotating cylinder of the device, and the de-enzymed tea leaves are pressed by a number of stirring blades, and at the tip of the rotating blade and the ridge part on the inner circumference of the rotating cylinder, a frictional pressure is applied to the de-enzymed tea leaves to strip the stem part from the leaf part, separate the stem part from the tea leaves, and obtain pressed tea leaves containing the stem part. The pressed tea leaves are cooled to obtain cooled tea leaves. A method for manufacturing raw tea, which comprises wind-separating the cooled tea leaves to obtain a heavy part mainly composed of stem parts and a light part to be the raw tea.

5. A production line for raw tea, comprising equipment for cutting the fresh leaves of the picked tea to obtain cut tea leaves, equipment for inactivating the oxidase of the cut tea leaves to obtain de-enzymed tea leaves, equipment for cooling the de-enzymed tea leaves to obtain cooled tea leaves, equipment for applying pressure to the cooled tea leaves to separate the stem part from the tea leaves to obtain pressed tea leaves containing the stem part, and equipment for wind-separating the pressed tea leaves to obtain a heavy part mainly composed of stem parts and a light part to be the raw tea. The equipment for applying pressure to tea leaves to obtain pressed tea leaves is provided with a rotating shaft and a plurality of stirring blades as a pressing part in a rotating cylinder capable of moving tea leaves in a certain direction. On the inner peripheral surface of the rotating cylinder, ridge parts extending in the length direction of the rotating cylinder are provided at intervals in the circumferential direction. The distance when the tip of the rotating blade and the ridge part on the inner circumference of the rotating cylinder are closest is 2 mm or more and 20 mm or less. It is a production line for raw tea.

6. A production line for raw tea, comprising equipment for cutting freshly picked tea leaves to obtain cut tea leaves, equipment for inactivating the oxidase of the cut tea leaves to obtain de-enzymed tea leaves, equipment for applying pressure to the de-enzymed tea leaves to separate the stem part from the tea leaves to obtain pressed tea leaves containing the stem part, equipment for cooling the pressed tea leaves to obtain cooled tea leaves, and equipment for wind sorting the cooled tea leaves to obtain a heavy part mainly composed of the stem part and a light part to be the raw tea. The equipment for applying pressure to tea leaves to obtain pressed tea leaves is provided with a rotating shaft and a plurality of stirring blades as a pressing part in a rotating cylinder capable of moving tea leaves in a certain direction. On the inner peripheral surface of the rotating cylinder, ridge parts extending in the length direction of the rotating cylinder are provided at intervals in the circumferential direction. The distance when the tip of the rotating blade and the ridge part on the inner circumference of the rotating cylinder are closest is 2 mm or more and 20 mm or less. It is a production line for raw tea.

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