Apparatus for increasing GABA content of tea leaves, method for increasing GABA content of tea leaves, and method for producing GABA tea

Abstract

Provided are an apparatus for increasing the GABA content of tea leaves, a method for increasing the GABA content of tea leaves, and a method for producing a GABA tea, by which it becomes possible to increase the GABA content in a short time and with a simple apparatus configuration.　The apparatus for increasing the GABA content of tea leaves is provided with: a low-temperature treatment means including a first low-temperature water vapor treatment means or a first low-temperature water immersion treatment means in which the temperature of the surface treatment of the tea leaves is maintained at a first temperature falling within the temperature range of 40-60°C for a predetermined set time; and a kill-green treatment means for deactivating an oxidation enzyme in the tea leaves that have been treated by the low-temperature treatment means.

Description

Apparatus for increasing GABA content in tea leaves, method for increasing GABA content in tea leaves, and method for producing GABA tea

[0001] The present invention relates to an apparatus for increasing the GABA (γ-aminobutyric acid) content of tea leaves, a method for increasing the GABA content of tea leaves, and a method for producing GABA tea.

[0002] GABA tea is a general term for teas with increased GABA (gamma-aminobutyric acid) content, which has a blood pressure lowering effect. A typical example is Gabaron tea, developed by the Ministry of Agriculture, Forestry and Fisheries' Vegetable and Tea Research Institute. Gabaron tea is said to contain more than 150 mg of GABA (gamma-aminobutyric acid) per 100 g of tea leaves.

[0003] According to a conventional method for producing green tea-type GABA tea, fresh tea leaves are placed in an airtight container such as a nitrogen-filled aluminum bag after harvest, and subjected to anaerobic treatment in which the air in the container is replaced with nitrogen gas. Enzymes are inactivated by steaming, and further treatment similar to that used in sencha production is carried out to produce GABA tea. Anaerobic treatment converts glutamic acid in the tea leaves to gamma-aminobutyric acid (GABA) through the action of glutamic acid decarboxylase (GAD), as shown in the chemical formula below. The duration of this anaerobic treatment varies depending on the temperature, with the optimum duration being 18 hours at 5°C and within 6 hours at 25°C.

[0004] Such anaerobic treatment of tea leaves requires replacing the air atmosphere around the tea leaves with nitrogen gas or carbon dioxide gas, which is not only time-consuming and laborious but also costly.

[0005] Patent Document 1 discloses a method for producing tea in which GABA production is increased by alternately repeating anaerobically and aerobic treatment of tea leaves, followed by anaerobic treatment.

[0006] Patent Document 2 discloses that the GABA content of tea leaves can be increased by irradiating the tea leaves with infrared rays, which have a heating effect, while stirring them under aerobic conditions rather than anaerobic conditions before steaming.

[0007] Patent No. 3038373 Patent No. 3089596

[0008] According to the technology disclosed in Patent Document 1, anaerobic treatment is performed, which takes a long time (6 to 18 hours), making it difficult to efficiently produce GABA tea, and there was room for improvement.

[0009] On the other hand, according to the technology disclosed in Patent Document 2, the treatment is carried out under aerobic conditions, which alleviates the above-mentioned problems caused by anaerobic treatment. However, since it is necessary to uniformly irradiate all tea leaves with infrared rays in a wavelength range that has a heating effect, the device configuration is complex when applied to actual tea leaf manufacturing equipment.

[0010] Therefore, an object of the present invention is to provide an apparatus for increasing the GABA content of tea leaves, a method for increasing the GABA content of tea leaves, and a method for producing GABA tea, which are capable of increasing the GABA content in a short amount of time with a simple device configuration.

[0011] The device for increasing the GABA content of tea leaves according to the present invention comprises a low-temperature treatment means having a first low-temperature steam treatment means or a first low-temperature water immersion treatment means for maintaining the treatment temperature of the surface of the tea leaves at a first temperature in the range of 40 to 60°C for a predetermined set time, and a blue killing treatment means for inactivating the oxidase enzymes in the tea leaves treated by the low-temperature treatment means.

[0012] This system is configured to subject freshly picked tea leaves or tea leaves that have been withered to a low-temperature treatment using low-temperature steam or low-temperature water immersion for a predetermined set time before undergoing a deactivation treatment such as steaming. This low-temperature treatment involves treatment with steam or immersion water, with the tea leaf surface maintained at a first temperature in the range of 40 to 60°C. Before deactivation treatment, tea leaves have closed stomata at normal room temperature to prevent water evaporation. However, when the temperature reaches 40°C or higher through anaerobic treatment or infrared irradiation in the above-mentioned conventional technology, the surface stomata open due to a defensive reaction, and the tea leaves are activated by releasing (transpiration) water from within the leaves and taking in oxygen from the outside through the stomata. It is presumed that activation rapidly promotes GABA production by GAD. It is believed that when the treatment temperature of the tea leaf surface exceeds 60°C, the enzyme (GAD) undergoes irreversible denaturation due to heat, resulting in a decrease in GABA content. In contrast, the present invention involves low-temperature steam treatment or low-temperature water soaking, which imposes water stress on the tea leaves and restricts the original function of the stomata at temperatures between 40 and 60°C. That is, the openings of the stomata and cuticles on the tea leaf surface are covered with steam or soaking water, making oxygen supply difficult and creating a pseudo-anaerobic stress. Furthermore, the stress is further increased when low-temperature steam treatment is performed in a sealed space, as well as in the case of low-temperature water soaking. This stress rapidly promotes GABA production by GAD, thereby increasing the GABA content of the tea leaves. Thus, according to the present invention, simply performing a low-temperature treatment in the range of 40 to 60°C before the blue-killing treatment can stress the tea leaves and significantly increase the GABA content in a short period of time.

[0013] The low-temperature treatment means preferably includes a first stationary treatment means for maintaining the treatment temperature of the tea leaves treated by the first low-temperature steam treatment means or the first low-temperature water immersion treatment means at a second temperature lower than the first temperature. The first low-temperature steam treatment means or the first low-temperature water immersion treatment means promotes the production of GABA by GAD, resulting in the consumption of glutamic acid, a precursor of GABA. However, by performing stationary treatment in which the treatment temperature of the tea leaves is maintained at a second temperature (for example, about 2 to 35°C) lower than the first temperature (40 to 60°C), glutamic acid can be replenished and produced from proteins contained in the tea leaves, thereby increasing the GABA content.

[0014] In this case, it is also preferable that the low-temperature treatment means further comprises a second low-temperature steam treatment means or a second low-temperature water immersion treatment means for maintaining the treatment temperature of the tea leaves treated by the first still treatment means at a third temperature equal to or higher than the first temperature. By maintaining the treatment temperature of the tea leaves at the third temperature equal to or higher than the first temperature after the initial still treatment, the GABA content is increased.

[0015] In this case, it is also preferable that the low-temperature treatment means is configured to perform the second low-temperature steam treatment or the second low-temperature water immersion treatment at a third temperature in the range of 47 to 58° C. By setting the third temperature, which is equal to or higher than the first temperature, in the range of 47 to 58° C., a sufficient increase in the GABA content can be ensured.

[0016] Furthermore, in this case, it is preferable to further include a second standing treatment means for maintaining the treatment temperature of the tea leaves treated by the second low-temperature steam treatment means or the second low-temperature water immersion treatment means at a fourth temperature equal to or higher than the second temperature. The second low-temperature steam treatment means or the second low-temperature water immersion treatment means promotes GABA production by GAD, resulting in further consumption of glutamic acid, a precursor of GABA. However, if, after the second low-temperature treatment, a second standing treatment is performed at a fourth temperature (e.g., about 2 to 35°C) equal to or higher than the second temperature (e.g., about 2 to 35°C) of the first standing treatment, glutamic acid can be replenished and produced from proteins contained in the tea leaves, thereby increasing the GABA content.

[0017] In this case, the low-temperature treatment means is preferably configured to repeat a low-temperature steam treatment or low-temperature water immersion treatment by the first low-temperature steam treatment means or the first low-temperature water immersion treatment means and a standing treatment by the first standing treatment means multiple times. By repeating the process multiple times, the GABA content increases in a shorter time.

[0018] It is also preferable that the low-temperature treatment means is configured to perform the first low-temperature steam treatment or the first low-temperature water soaking treatment at a first temperature in the range of 47 to 58° C. By setting the first temperature in the range of 47 to 58° C., more effective stress can be applied to the tea leaves, and the GABA content can be sufficiently increased.

[0019] It is also preferable that the low-temperature treatment means is configured to perform low-temperature treatment on tea leaves on a horizontal movement mechanism that transports the tea leaves horizontally. By using a horizontal movement mechanism that transports the tea leaves horizontally, damage to the tea leaves is minimized, making it less likely for the leaves to break and resulting in tea leaves with an excellent appearance.

[0020] Furthermore, according to the method for increasing the GABA content of the present invention, a first low-temperature steam treatment or a first low-temperature water immersion treatment is carried out in which the treatment temperature of the surface of the tea leaves is maintained at a first temperature in the range of 40 to 60°C for a predetermined set time, and then the oxidizing enzymes in the low-temperature treated tea leaves are inactivated to carry out a blue-killing treatment.

[0021] This system is configured to subject freshly picked tea leaves or tea leaves that have been withered to a low-temperature treatment using low-temperature steam or low-temperature water immersion for a predetermined set time before undergoing a deactivation treatment such as steaming. This low-temperature treatment involves treatment with steam or immersion water, with the tea leaf surface maintained at a first temperature between 40 and 60°C. At normal room temperature, tea leaves have closed stomata to prevent water evaporation. However, when exposed to temperatures above 40°C through anaerobic treatment or infrared irradiation using the above-mentioned conventional technology, the surface stomata open due to a defensive reaction, releasing (transpiration) water from within the tea leaves and respiration, which involves taking in oxygen from the outside. This activation rapidly accelerates the rate of GABA production by GAD. When the treatment temperature for the tea leaf surface exceeds 60°C, the effects of heat become too great, causing the cell walls of the tea leaves to dissolve and the GABA content to decrease. In contrast, in the present invention, low-temperature steam treatment or low-temperature water soaking treatment is performed, which presumably applies water stress to the tea leaves and limits the original function of the stomata in the temperature range of 40 to 60°C. In other words, the openings of the stomata and cuticles on the surface of the tea leaves are covered with steam or soaking water, making it difficult to supply oxygen and creating a pseudo-anaerobic stress. Furthermore, if low-temperature steam treatment is performed in a sealed space, as well as in the case of low-temperature water soaking, the stress is further increased, and the production of GABA by GAD is rapidly promoted, thereby increasing the GABA content of the tea leaves. Thus, according to the present invention, by simply performing a low-temperature treatment in the range of 40 to 60°C before the blue-killing treatment, it is possible to stress the tea leaves and significantly increase the GABA content in a short period of time.

[0022] The low-temperature treatment is preferably a first static treatment in which the treatment temperature of tea leaves that have been subjected to a first low-temperature steam treatment or a first low-temperature water soaking treatment is maintained at a second temperature lower than the first temperature. The first low-temperature steam treatment or the first low-temperature water soaking treatment described above promotes GABA production by GAD, resulting in the consumption of glutamic acid, a precursor of GABA. However, by performing a static treatment in which the treatment temperature of the tea leaves is maintained at a second temperature (for example, about 2 to 35°C) lower than the first temperature (40 to 60°C), glutamic acid can be replenished and produced from proteins contained in the tea leaves, thereby increasing the GABA content.

[0023] In this case, it is preferable to subject the tea leaves that have been subjected to the first standing treatment to a second low-temperature steam treatment or a second low-temperature water immersion treatment, in which the treatment temperature is maintained at a third temperature that is equal to or higher than the first temperature. By maintaining the treatment temperature of the tea leaves at the third temperature that is equal to or higher than the first temperature after the first standing treatment, the GABA content increases.

[0024] In this case, it is also preferable to perform the second low-temperature steam treatment or the second low-temperature water immersion treatment at a third temperature in the range of 47 to 58° C. By setting the third temperature, which is equal to or higher than the first temperature, in the range of 47 to 58° C., a sufficient increase in the GABA content can be ensured.

[0025] Furthermore, in this case, it is preferable to subject the tea leaves that have been subjected to the second low-temperature steam treatment or the second low-temperature water soaking treatment to a second standing treatment in which the treatment temperature is maintained at a fourth temperature that is equal to or higher than the second temperature. The second low-temperature steam treatment or the second low-temperature water soaking treatment described above promotes GABA production by GAD, which further consumes glutamic acid, a precursor of GABA. However, if the second standing treatment is followed by a second standing treatment at a fourth temperature (e.g., about 2 to 35°C) that is equal to or higher than the second temperature (e.g., about 2 to 35°C) of the first standing treatment, glutamic acid can be replenished and produced from proteins and the like contained in the tea leaves, thereby increasing the GABA content.

[0026] It is preferable to repeat the first low-temperature steam treatment or the first low-temperature water immersion treatment and the first standing treatment multiple times, which increases the GABA content in a shorter time.

[0027] It is also preferable to carry out the first low-temperature steam treatment or the first low-temperature water soaking treatment at a first temperature in the range of 47 to 58° C. By setting the first temperature in the range of 47 to 58° C., more effective stress can be applied to the tea leaves, and the GABA content can be sufficiently increased.

[0028] It is also preferable that the low-temperature treatment is carried out while the tea leaves are being transported horizontally. By using a horizontal transport mechanism that transports the tea leaves horizontally, damage to the tea leaves is minimized, resulting in tea leaves that are less likely to break and have an excellent appearance.

[0029] Furthermore, the method for producing GABA tea according to the present invention comprises a low-temperature treatment step which includes a first low-temperature steam treatment step or a first low-temperature water immersion treatment step in which the treatment temperature of the surface of the tea leaves is maintained at a first temperature in the range of 40 to 60°C for a predetermined set time, and a blue killing treatment step in which the oxidase enzymes in the tea leaves treated by this low-temperature treatment step are inactivated.

[0030] This system is configured to subject freshly picked tea leaves or tea leaves that have been withered to a low-temperature treatment using low-temperature steam or low-temperature water immersion for a predetermined set time before undergoing a deactivation treatment (deactivation) by steaming or the like. This low-temperature treatment involves treatment with steam or immersion water, with the tea leaf surface maintained at a first temperature between 40 and 60°C. At normal room temperature, tea leaves have closed stomata to prevent water evaporation. However, when exposed to temperatures above 40°C through anaerobic treatment or infrared irradiation using the above-mentioned conventional technology, the surface stomata open due to a defensive reaction, releasing (transpiration) water from within the tea leaves and respiration, which involves taking in oxygen from the outside, thereby activating the tea leaves. This activation rapidly promotes GABA production by GAD. When the treatment temperature for the tea leaf surface exceeds 60°C, the effects of heat become too great, causing the cell walls of the tea leaves to dissolve and the GABA content to decrease. In contrast, in the present invention, low-temperature steam treatment or low-temperature water soaking treatment is performed, which presumably applies water stress to the tea leaves and limits the original function of the stomata in this temperature range of 40 to 60°C. In other words, the openings of the stomata and cuticles on the surface of the tea leaves are covered with steam or soaking water, making it difficult to supply oxygen and creating a pseudo-anaerobic stress. Furthermore, if low-temperature steam treatment is performed in an enclosed space, as well as in the case of low-temperature water soaking treatment, the stress is further increased, and the GABA content of the tea leaves increases as a result. Thus, according to the present invention, by simply performing a low-temperature treatment in the range of 40 to 60°C before the blue-killing treatment, it is possible to stress the tea leaves and significantly increase the GABA content in a short period of time.

[0031] The low-temperature treatment step preferably includes a first standing treatment step in which the treatment temperature of the tea leaves treated in the first low-temperature steam treatment step or the first low-temperature water soaking treatment step is maintained at a second temperature lower than the first temperature. The first low-temperature steam treatment step or the first low-temperature water soaking treatment step promotes GABA production by GAD, resulting in the consumption of glutamic acid, a precursor of GABA. However, by performing a standing treatment in which the treatment temperature of the tea leaves is maintained at a second temperature (for example, about 2 to 35°C) lower than the first temperature (40 to 60°C), glutamic acid can be replenished and produced from proteins contained in the tea leaves, thereby increasing the GABA content.

[0032] In this case, it is preferable to further include a second low-temperature steam treatment step or a second low-temperature water soaking treatment step in which the treatment temperature of the tea leaves treated in the first standing treatment step is maintained at a third temperature equal to or higher than the first temperature. By maintaining the treatment temperature of the tea leaves at the third temperature equal to or higher than the first temperature after the first standing treatment, the GABA content is increased.

[0033] In this case, the low-temperature treatment step is preferably configured to perform the second low-temperature steam treatment step or the second low-temperature water immersion treatment step at a third temperature in the range of 47 to 58° C. By setting the third temperature, which is equal to or higher than the first temperature, in the range of 47 to 58° C., a sufficient increase in the GABA content can be ensured.

[0034] In this case, it is preferable to further include a second standing treatment step in which the treatment temperature of the tea leaves treated by the second low-temperature steam treatment step or the second low-temperature water soaking treatment step is maintained at a fourth temperature equal to or higher than the second temperature. The second low-temperature steam treatment step or the second low-temperature water soaking treatment step promotes GABA production by GAD, which further consumes glutamic acid, a precursor of GABA. However, if a second standing treatment is performed after the second low-temperature treatment at a fourth temperature (e.g., about 2 to 35°C) equal to or higher than the second temperature (e.g., about 2 to 35°C) of the first standing treatment, glutamic acid can be replenished and produced from proteins contained in the tea leaves, thereby increasing the GABA content.

[0035] Furthermore, in this case, the low-temperature treatment step is preferably configured to repeat the first low-temperature steam treatment step or the first low-temperature water immersion treatment step and the first standing treatment step multiple times, which increases the GABA content in a shorter time.

[0036] It is also preferable that the low-temperature treatment step is configured to perform the first low-temperature steam treatment step or the first low-temperature water soaking treatment step at a first temperature in the range of 47 to 58° C. By setting the first temperature in the range of 47 to 58° C., more effective stress can be applied to the tea leaves, and the GABA content can be sufficiently increased.

[0037] It is also preferable that the low-temperature treatment step is a step in which the low-temperature treatment is performed while the tea leaves are transported horizontally. By using a horizontal transport mechanism that transports the tea leaves horizontally, damage to the tea leaves is minimized, so that tea leaves with less breakage and excellent appearance can be obtained.

[0038] According to the present invention, GABA production by GAD is rapidly promoted by low-temperature steam treatment or low-temperature water immersion treatment at 40 to 60°C. That is, by simply performing a low-temperature treatment in the range of 40 to 60°C before the blue killing treatment, it is possible to stress the tea leaves and significantly increase the GABA content in a short period of time.

[0039] FIG. 1 is a block diagram showing a schematic configuration of a portion of a GABA content increasing device in a GABA tea manufacturing apparatus according to a first embodiment of the present invention. FIG. 2 is a block diagram showing a schematic configuration example of the hardware of low-temperature treatment means in the GABA content increasing device of FIG. 1. FIG. 3 is a diagram showing a schematic example of the mechanical configuration of the low-temperature treatment means in the GABA content increasing device of FIG. 1. FIG. 4 is a flowchart showing a schematic flow of low-temperature steam treatment in the GABA content increasing device of FIG. 1. FIG. 5 is a block diagram showing a schematic configuration example of the hardware of low-temperature treatment means in the GABA content increasing device of FIG. 5. FIG. 6 is a flowchart showing a schematic flow of low-temperature steam treatment in the GABA content increasing device of FIG. 5. FIG. 7 is a block diagram showing a schematic configuration of a portion of a GABA content increasing device in a GABA tea manufacturing apparatus according to a third embodiment of the present invention. FIG. 8 is a block diagram showing a schematic configuration example of the hardware of low-temperature treatment means in the GABA content increasing device of FIG. 10 is a flow chart showing the flow of low-temperature steam treatment in the GABA content increasing device of Figure 8. FIG. 11 is a block diagram showing the configuration of the GABA content increasing device portion of the GABA tea manufacturing apparatus as a fourth embodiment of the present invention. FIG. 12 is a block diagram showing the configuration of the hardware of the low-temperature treatment means in the GABA content increasing device of Figure 11. FIG. 13 is a flow chart showing the flow of low-temperature steam treatment in the GABA content increasing device of Figure 11. FIG. 14 is a graph showing the relationship between the GABA increase rate (%) of green tea samples h1 to h9 in the examples and the treatment temperature of the first low-temperature treatment.

[0040] FIG. 1 shows a schematic diagram of the configuration of a device for increasing the GABA content of tea leaves in a GABA tea manufacturing apparatus according to a first embodiment of the present invention.

[0041] In Figure 1, reference numeral 10 denotes a low-temperature treatment means for treating picked fresh tea leaves or tea leaves obtained by withering fresh tea leaves to produce black tea, with low-temperature steam, and reference numeral 11 denotes a green-killing treatment means, such as a steamer, for inactivating the oxidizing enzymes in the tea leaves sent from the low-temperature treatment means 10. Although not shown in Figure 1, when producing black tea, other means such as a rolling treatment means or a fermentation treatment means are naturally provided between the low-temperature treatment means 10 for treating withered tea leaves with low-temperature steam and the green-killing treatment means (fermentation-stopping means) 11. When producing black tea, a withering treatment means may be provided between the low-temperature treatment means 10 and the green-killing treatment means (fermentation-stopping means) 11. In this case, the green tea leaves are treated with low-temperature steam in the low-temperature treatment means 10, then withered in the withering treatment means, and then treated by other means such as the rolling treatment means or fermentation treatment means, before being subjected to the green-killing treatment in the green-killing treatment means (fermentation-stopping means) 11. Furthermore, when producing black tea, the low-temperature treatment means 10 can also be used as a means for performing both low-temperature steam treatment and withering treatment. In this case, the raw tea leaves are subjected to low-temperature steam treatment and withering treatment in the low-temperature treatment means 10, and then to other treatments such as rolling treatment and fermentation treatment, before being subjected to a blue-killing treatment in the blue-killing treatment means (fermentation-stopping means) 11. In this embodiment, since the temperature used to deactivate tea leaf oxidizing enzymes with steam is typically 80°C or higher, the treatment of applying steam below 80°C to the tea leaf surface is referred to as "low-temperature treatment" or "low-temperature steam treatment" to clearly distinguish it from the blue-killing treatment. The blue-killing treatment means 11 can be a rotary steam treatment device, and the function of the low-temperature treatment means 10 can be fulfilled by setting the treatment temperature below 80°C. In this case, the treatment means can be configured as a single device. Naturally, the low-temperature treatment means and the blue-killing treatment means can be provided separately, or multiple devices can be provided to form a production line.

[0042] In this embodiment, the low-temperature treatment means 10 includes a first low-temperature steam treatment means 10A. The first low-temperature steam treatment means 10A is configured to perform low-temperature steam treatment so that the treatment temperature of the tea leaf surface is maintained at a first temperature in the range of 40 to 60°C.

[0043] Although not shown, for example, a manufacturing apparatus for Sencha tea may include, following the blue killing treatment means 11, a cooling treatment means for quickly cooling the temperature of the steamed leaves to about room temperature in order to maintain the color of the steamed leaves, a leaf beating treatment means for shaking the leaves by blowing dry hot air into them to maintain the color of the cooled tea leaves and shorten the time for the next rough rolling treatment, a rough rolling treatment means for blowing dry hot air into the tea leaves and rolling them with moderate friction and pressure in order to soften the tea leaves and reduce the moisture inside, and a rolling means for making up for the lack of rolling in the rough rolling treatment. The system comprises a rolling and twisting processing means for massing and rolling the tea leaves under pressure in order to destroy the structure of the tea leaves and facilitate the infusion of the ingredients and to equalize the moisture content, a medium rolling processing means for rolling and rolling the tea leaves by blowing dry hot air into them to loosen them and give them a twisted shape so that they can be easily shaped in the subsequent fine rolling processing, a fine rolling processing means for rolling the tea leaves in only one direction while removing moisture from inside the tea leaves and drying them in order to shape them into a thin, elongated shape, and a drying processing means for drying the tea leaves to reduce the moisture content to about 5%, all of which are connected in sequence.The equipment for carrying out the greening treatment, cooling treatment, leaf beating treatment, rough rolling treatment, rolling and twisting treatment, medium rolling treatment, fine rolling treatment and drying treatment other than the low-temperature treatment are all commercially available and well-known in construction, so detailed explanations will be omitted. Furthermore, while the above description has been given of a sencha manufacturing apparatus, in the case of a tencha (matcha) manufacturing apparatus, the green tea killing means 11 is followed by a loose tea cooling means for quickly cooling the steamed leaves to about room temperature in order to maintain the color, etc. of the steamed leaves, and a drying means for drying the tea leaves to reduce the moisture content to about 5%, which are connected in sequence. Since the equipment for realizing the green tea killing, loose tea cooling, and drying processes other than the low-temperature treatment are all commercially available and well-known, detailed explanations will be omitted. This embodiment is applicable not only to green tea such as sencha and tencha, but also to fermented teas such as kamairicha, black tea, and oolong tea, as well as other teas. For example, in the case of a black tea manufacturing apparatus, a withering treatment means for withering raw tea leaves is provided before the low-temperature treatment means 10, and after the low-temperature treatment means 10, although not limited to, a rolling treatment means for destroying the tissue of the tea leaves and causing oxidative fermentation, a fermentation treatment means for promoting oxidative fermentation of the tea leaves, a greening treatment (fermentation stopping) means 11 for inactivating oxidizing enzymes, and a drying treatment means are connected in this order.Furthermore, in addition to the above-mentioned means, other means such as a disintegrating means or a sieving means may be added, and the anti-greening treatment (fermentation stopping) means 11 and the drying means may be configured as a single device or as separate devices. In another example of a black tea production apparatus, a withering means may be provided after the low-temperature treatment means 10, or the low-temperature treatment means 10, withering means, rolling means, fermentation means, anti-greening treatment (fermentation stopping) means 11, and drying means may be connected in sequence. In another example of a black tea production apparatus, the low-temperature treatment means 10 may be used as a means for performing both low-temperature treatment and withering, or the low-temperature treatment means 10 for low-temperature treatment and withering of raw tea leaves, rolling means, fermentation means, anti-greening treatment (fermentation stopping) means 11, and drying means may be connected in sequence. Note that the black tea production apparatus is not limited to the above-mentioned apparatus, and it is also possible to use an apparatus equipped with processing means used in a CTC production method using a CTC machine or a rotor van production method using a rotor van. Furthermore, in the case of an oolong tea manufacturing apparatus, a withering treatment means can be provided before the green killing treatment means 11, and for example, the withering treatment means, low temperature treatment means 10 and green killing treatment means 11 can be connected in sequence, or the low temperature treatment means 10, withering treatment means and green killing treatment means 11 can be connected in sequence, and then the rolling treatment means and drying treatment means can be connected in sequence.

[0044] 2 shows a schematic diagram of an example of the hardware configuration of the low-temperature treatment means 10. The low-temperature treatment means 10 in this embodiment comprises a low-temperature steam treatment chamber 10a for treating the transferred tea leaves with low-temperature steam, a temperature detection unit 10b for detecting a temperature corresponding to the treatment temperature of the surface of the tea leaves in this low-temperature steam treatment chamber 10a, a humidity detection unit 10c for detecting the internal humidity, a time detection unit 10d for detecting the treatment time, and a control unit 10e for inputting the temperature detected by the temperature detection unit 10b, the humidity detected by the humidity detection unit 10c, and the treatment time detected by the time detection unit 10d, and controlling the steam temperature and the end of the low-temperature steam treatment.

[0045] The control unit 10e uses a built-in computer to control the steam in the low-temperature steam treatment chamber 10a so as to maintain the treatment temperature of the tea leaf surface at a first temperature in the range of 40 to 60°C according to the detected treatment temperature, humidity, and treatment time. In this case, this first low-temperature steam treatment is performed until the steam treatment time reaches a predetermined set time, at which point the first low-temperature steam treatment is terminated. The predetermined set time is preferably 10 minutes or more, and more preferably 15 to 60 minutes, but may be around 1 to 15 minutes if the first temperature is high (near 60°C).

[0046] The low-temperature steam treatment chamber 10a may be a rotary steam treatment device, a low-temperature steamer, or a device with a net-structured transport belt installed inside the low-temperature steam treatment chamber 10a. In the case of low-temperature water immersion treatment, a device using a washer or a device using a horizontal movement mechanism (described later) in combination with a conveyor may also be used. The configuration of the device is not particularly limited as long as it can maintain the treatment temperature of the surface of the fresh tea leaves at a predetermined temperature for a set period of time.

[0047] In this embodiment, as an example of using a low-temperature steamer, a small two-chamber independent dough conditioner SS5022 manufactured by NIPPO Corporation, which has a chamber capable of controlling temperature and humidity, is used. Also, an example of using a low-temperature steam treatment chamber 10a equipped with a net-structured transport belt, will be described below.

[0048] FIG. 3 shows three examples of the low-temperature steam treatment chamber. FIG. 3(A) shows a single-stage net-type transport belt 10f. １ This low-temperature steam treatment chamber 10a is equipped with a single-stage net-structure transport belt 10f that moves horizontally inside. １ In the low-temperature steam treatment chamber 10a, a transport belt 10f １ The surface of the tea leaves placed on the net is treated with low-temperature steam at 40 to 60°C by passing through the net. １Since the steam treatment is performed while moving horizontally, damage to the tea leaves can be reduced and the occurrence of broken leaves can be suppressed. From the perspective of mass production of tea leaves, a rotary steam treatment device can be used, but considering the damage to the tea leaves, it is preferable to use a horizontally moving type using a net. Furthermore, "horizontal" does not only mean a completely horizontal movement, but also means a transfer at an angle.

[0049] As shown in FIG. 3(B), the low-temperature steam treatment chamber is a single-stage net-type transport belt 10f. １ ' and 10f ２ 3C, a low-temperature steam treatment chamber 10a' equipped with a multi-stage net-type transport belt 10f １ ", 10f ２ " and 10f ３ The low-temperature steam treatment chamber 10a may be provided with a low-temperature steam treatment chamber 10b.

[0050] FIG. 4 shows a schematic flow of control by the computer of the control unit 10e in the low-temperature treatment means 10.

[0051] First, the temperature detection unit 10b detects the processing temperature in the low-temperature steam processing chamber 10a (corresponding to the processing temperature on the surface of the tea leaves) (step S1), and determines whether the detected processing temperature is a first temperature in the range of 40 to 60°C (at or near the first temperature) (step S2).

[0052] If it is determined in step S2 that the processing temperature is not the first temperature (the first temperature or its vicinity) in the range of 40 to 60°C (NO), the control unit 10e adjusts the steam temperature in the low-temperature steam processing chamber 10a to this first temperature (the first temperature or its vicinity) (step S3), and then repeats the processing of steps S1 to S3.

[0053] If it is determined in step S2 that the treatment temperature is at a first temperature in the range of 40 to 60°C (at or near the first temperature) (YES), it is determined whether the treatment time is equal to or longer than a predetermined set time (e.g., 30 to 60 minutes) for the first low-temperature steam treatment (step S4).

[0054] If it is determined in step S4 that the treatment time is not equal to or longer than the predetermined installation time (NO), the process returns to step S1 and the above-described processes of steps S1 to S4 are repeated, thereby allowing the first low-temperature steam treatment by the low-temperature treatment means 10 to continue.

[0055] If it is determined in step S4 that the processing time is equal to or longer than the set time (YES), the first low-temperature steam processing by the low-temperature processing means 10 is terminated, and the low-temperature processing including the first low-temperature steam processing is terminated (step S5).

[0056] According to the control shown in Figure 4, a first low-temperature steam treatment is carried out for a predetermined time of 30 to 60 minutes, in which the treatment temperature of the tea leaf surface is maintained at a first temperature in the range of 40 to 60°C (at or near the first temperature). After this low-temperature treatment by low-temperature treatment means 10, a deactivation treatment by blue-killing treatment means 11 is carried out.

[0057] In this embodiment, the greening treatment means 11 is composed of a steamer that performs steaming treatment to inactivate oxidase in the tea leaves at a temperature of 80 to 100°C, but instead of steaming treatment, the oxidase may be inactivated by pan-frying treatment, hot air treatment, or microwave irradiation treatment.

[0058] In addition, in this embodiment, the tea leaves are subjected to low-temperature steam treatment in which they are steamed in low-temperature steam at a first temperature in the range of 40 to 60°C (at or near the first temperature). However, the same effect can be obtained by performing a low-temperature water immersion treatment in which the tea leaves are immersed in warm water at a first temperature in the range of 40 to 60°C (at or near the first temperature) instead of the low-temperature steam treatment.

[0059] As described above in detail, according to this embodiment, prior to a deactivation treatment (deactivation) by steaming or the like, freshly picked tea leaves or tea leaves obtained by withering the fresh tea leaves undergo a first low-temperature steam treatment in which the surface temperature of the tea leaves is set to a first temperature (at or near the first temperature) in the range of 40 to 60°C. Because the low-temperature steam treatment at 40 to 60°C is performed prior to the deactivation treatment, the tea leaves are subjected to a pseudo-anaerobic stress, thereby increasing the GABA content of the tea leaves. More specifically, at normal room temperature, tea leaves have closed stomata to prevent water evaporation. However, at temperatures above 40°C, the surface stomata open as a defensive reaction, allowing the tea leaves to release (transpire) moisture from within the leaves and take in oxygen from the outside through the stomata, thereby activating the tea leaves. It is presumed that this activation rapidly promotes GABA production by GAD. It is believed that when the treatment temperature of the tea leaf surface exceeds 60°C, the enzyme (GAD) undergoes irreversible denaturation due to heat, resulting in a decrease in GABA content. In contrast, in this embodiment, low-temperature steam treatment or low-temperature water soaking treatment is performed, which imposes water stress on the tea leaves and limits the original function of the stomata at temperatures between 40 and 60°C. That is, the openings of the stomata and cuticles on the tea leaf surface are covered with steam or soaking water, making it difficult to supply oxygen and creating a pseudo-anaerobic stress. Furthermore, in the case of low-temperature water soaking treatment, as well as in the case of low-temperature steam treatment, if performed in an enclosed space, the stress is further increased. This stress rapidly promotes GABA production by GAD, thereby increasing the GABA content of the tea leaves. Thus, simply performing a low-temperature treatment in the range of 40 to 60°C before the blue-killing treatment can stress the tea leaves and significantly increase the GABA content in a short period of time.

[0060] As a modification of this embodiment, low-temperature steam treatment may be performed so that the treatment temperature of the tea leaf surface reaches a first temperature (at or near the first temperature) in the range of 47 to 58°C. This process is carried out by determining whether the steam treatment temperature is at or near the first temperature in the range of 47 to 58°C in step S2 of the low-temperature steam treatment flow shown in Figure 4, and if it is not at or near the first temperature (the result is NO), performing the steam temperature adjustment process in step S3. According to this modification, GABA production by GAD is rapidly promoted, the glutamic acid content in the tea leaves is significantly reduced, and the GABA content in the tea leaves is further increased. Note that the other configurations and processes in this modification are the same as those in the first embodiment.

[0061] FIG. 5 shows a schematic diagram of the configuration of a device for increasing the GABA content of tea leaves in a GABA tea manufacturing apparatus according to a second embodiment of the present invention.

[0062] In Figure 5, reference numeral 110 denotes low-temperature treatment means for treating picked fresh tea leaves or tea leaves obtained by withering fresh tea leaves to produce black tea, and reference numeral 111 denotes green-killing treatment means, such as a steamer, for inactivating the oxidase in the tea leaves sent from the low-temperature treatment means 110. Although not shown in Figure 5, when producing black tea, other means such as rolling treatment means and fermentation treatment means are naturally provided between the low-temperature treatment means 110, which treats with low-temperature steam and leaves to stand, and the green-killing treatment means (fermentation stopping means) 111. Furthermore, when producing black tea, withering treatment means may be provided between the low-temperature treatment means 110 and the green-killing treatment means (fermentation-stopping means) 111, in which case the fresh tea leaves are subjected to low-temperature steam treatment and static treatment in the low-temperature treatment means 110, then withered in the withering treatment means, and then treated by other means such as rolling treatment means and fermentation treatment means, before being subjected to green-killing treatment in the green-killing treatment means (fermentation-stopping means) 111. Furthermore, when producing black tea, the low-temperature treatment means 110 can also be used as a means for performing low-temperature treatment (low-temperature steam treatment and static treatment) and withering treatment together, in which case the fresh tea leaves are subjected to low-temperature treatment and withering treatment in the low-temperature treatment means 110, then treated by other means such as rolling treatment means and fermentation treatment means, before being subjected to green-killing treatment in the green-killing treatment means (fermentation-stopping means) 111. In this embodiment, the low-temperature treatment means 110 comprises a first low-temperature steam treatment means 110A and a first stationary treatment means 110B. The first low-temperature steam treatment means 110A is configured to perform low-temperature steam treatment so that the treatment temperature of the tea leaf surface is maintained at a first temperature (at or near the first temperature) in the range of 40 to 60°C. The first stationary treatment means 110B is configured to perform stationary treatment so that the treatment temperature of the tea leaf surface treated by the first low-temperature steam treatment means 110A is maintained at a second temperature lower than the first temperature. This first stationary treatment means 110B is a treatment means that leaves the tea leaves stationary without performing low-temperature steam treatment and maintains them at the second temperature, but it may also be a treatment means that performs low-temperature steam treatment and maintains them at the second temperature.

[0063] Although not shown, for example, a manufacturing apparatus for Sencha tea may include, following the blue killing treatment means 111, a cooling treatment means for quickly cooling the temperature of the steamed leaves to about room temperature in order to maintain the color of the steamed leaves, a leaf beating treatment means for shaking the leaves by blowing dry hot air into them to maintain the color of the cooled tea leaves and shorten the time for the next rough rolling treatment, a rough rolling treatment means for blowing dry hot air into them to blow the tea leaves and apply moderate friction and pressure to the tea leaves in order to soften them and reduce their internal moisture, and a rolling treatment means for making up for insufficient rolling in the rough rolling treatment, The system comprises a rolling and twisting processing means for massing and rolling the tea leaves under pressure in order to destroy the structure of the tea leaves and facilitate the infusion of the ingredients and to equalize the moisture content, a medium rolling processing means for rolling and rolling the tea leaves by blowing dry hot air into them to loosen them and give them a twisted shape so that they can be easily shaped in the subsequent fine rolling processing, a fine rolling processing means for rolling the tea leaves in only one direction while removing moisture from inside the tea leaves and drying them in order to shape them into a thin, elongated shape, and a drying processing means for drying the tea leaves to reduce the moisture content to about 5%, all of which are connected in sequence.The equipment for carrying out the greening treatment, cooling treatment, leaf beating treatment, rough rolling treatment, rolling and twisting treatment, medium rolling treatment, fine rolling treatment and drying treatment other than the low-temperature treatment are all commercially available and well-known in construction, so detailed explanations will be omitted. Furthermore, while the above description has been given of a manufacturing apparatus for sencha, in the case of a manufacturing apparatus for tencha (matcha), the apparatus is equipped with a tea-scattering cooling means for rapidly cooling the steamed leaves to about room temperature in order to maintain the color, etc. of the steamed leaves, and a drying means for drying the tea leaves to reduce the moisture content to about 5%, which are connected in sequence following the green-killing treatment means 111. Since the equipment for realizing the green-killing treatment, the tea-scattering cooling treatment, and the drying treatment, other than the low-temperature treatment, are all commercially available and well-known, detailed explanations will be omitted. This embodiment is applicable not only to green tea such as sencha and tencha, but also to fermented teas such as kamairicha, black tea, and oolong tea, and other teas.For example, in the case of a black tea production apparatus, a withering treatment means for withering fresh tea leaves is provided before the low-temperature treatment means 110, and the low-temperature treatment means 110 is followed in sequence by, but is not limited to, a rolling treatment means for destroying the tea leaf tissue and causing oxidative fermentation, a fermentation treatment means for promoting oxidative fermentation of the tea leaves, a green-killing treatment (fermentation-stopping) means 111 for inactivating oxidizing enzymes, and a drying treatment means. Furthermore, in addition to the above-mentioned means, other means such as a ball-dissolving means or a sieving means may be added, and the green-killing treatment (fermentation-stopping) means 111 and the drying treatment means may be configured as a single device or as separate devices. In another example of a black tea production apparatus, a withering treatment means may be provided after the low-temperature treatment means 110, and the low-temperature treatment means 110, the withering treatment means, the rolling treatment means, the fermentation treatment means, the green-killing treatment (fermentation-stopping) means 111, and the drying treatment means may be connected in sequence. Furthermore, in another example of a black tea production apparatus, the low-temperature treatment means 110 can be used as a means for performing both low-temperature treatment and withering treatment, and the low-temperature treatment means 110 for low-temperature treatment and withering of raw tea leaves, rolling treatment means, fermentation treatment means, green-killing treatment (fermentation stop) means 111, and drying treatment means may be connected in sequence. Note that the black tea production apparatus is not limited to the above-mentioned apparatus, and it is also possible to use an apparatus equipped with treatment means used in a CTC production method using a CTC machine or a rotor van production method using a rotor van. Furthermore, in the case of an oolong tea production apparatus, a withering treatment means may be provided before the green-killing treatment means 111. For example, the withering treatment means, low-temperature treatment means 110, and green-killing treatment means 111 may be connected in sequence, or the low-temperature treatment means 110, withering treatment means, and green-killing treatment means 111 may be connected in sequence, followed by rolling treatment means and drying treatment means.

[0064] 6 shows a schematic diagram of an example of the hardware configuration of the low-temperature treatment means 110. The low-temperature treatment means 110 in this embodiment comprises a low-temperature steam treatment chamber 110a for treating the transferred tea leaves with low-temperature steam, a temperature detection unit 110b for detecting a temperature corresponding to the treatment temperature of the surface of the tea leaves in this low-temperature steam treatment chamber 110a, a humidity detection unit 110c for detecting the internal humidity, a time detection unit 110d for detecting the treatment time, and a control unit 110e for inputting the temperature detected by the temperature detection unit 110b, the humidity detected by the humidity detection unit 110c, and the treatment time detected by the time detection unit 110d, and controlling the steam temperature and the end of the low-temperature steam treatment.

[0065] The control unit 110e controls the steam in the low-temperature steam treatment chamber 110a using a built-in computer to maintain the treatment temperature of the tea leaf surface at a first temperature (at or near the first temperature) in the range of 40 to 60°C, depending on the detected treatment temperature, humidity, and treatment time. In this case, this first low-temperature steam treatment is performed until the steam treatment time reaches a predetermined set time, at which point the first low-temperature steam treatment is terminated. The predetermined set time is preferably 10 minutes or more, more preferably 15 to 60 minutes, but may be approximately 1 to 15 minutes if the first temperature is high (near 60°C). Following this first low-temperature steam treatment, the control unit 110e performs a first standing treatment. This first standing treatment is a standing treatment performed for 10 to 30 minutes, maintaining the tea leaf at a second temperature (e.g., approximately 2 to 35°C) lower than the first temperature (40 to 60°C).

[0066] The mechanical configuration of the low-temperature steam processing chamber in this embodiment is the same as that described in the first embodiment with reference to FIG. 3, and therefore a description thereof will be omitted.

[0067] FIG. 7 shows a schematic flow of control by the computer of the control unit 110e in the low-temperature treatment means 110.

[0068] First, the temperature detection unit 110b detects the processing temperature in the low-temperature steam processing chamber 110a (corresponding to the processing temperature on the surface of the tea leaves) (step S11), and determines whether the detected processing temperature is a first temperature in the range of 40 to 60°C (the first temperature or nearby) (step S12).

[0069] If it is determined in step S12 that the processing temperature is not the first temperature (the first temperature or its vicinity) in the range of 40 to 60°C (NO), the control unit 110e adjusts the steam temperature in the low-temperature steam processing chamber 110a to this first temperature (the first temperature or its vicinity) (step S13), and then repeats the processing of steps S11 to S13.

[0070] If it is determined in step S12 that the treatment temperature is at a first temperature in the range of 40 to 60°C (at or near the first temperature) (YES), it is determined whether the treatment time is equal to or longer than a predetermined set time (e.g., 30 to 60 minutes) for the first low-temperature steam treatment (step S14).

[0071] If it is determined in step S14 that the treatment time is not equal to or longer than the predetermined installation time (NO), the process returns to step S11, and the above-described processes of steps S11 to S14 are repeated, thereby allowing the first low-temperature steam treatment by the low-temperature treatment means 110 to continue.

[0072] If it is determined in step S14 that the processing time is equal to or longer than the set time (YES), the first low-temperature steam processing by the low-temperature processing means 110 is terminated (step S15).

[0073] Next, a first standing treatment is carried out (step S16). The first standing treatment is a treatment in which the treatment temperature of the tea leaf surface is maintained at a second temperature lower than the first temperature. Here, the second temperature is, for example, 2 to 35°C.

[0074] Next, it is determined whether the processing time is equal to or longer than a preset time (for example, 10 to 30 minutes) for the first standing process (step S17).

[0075] If it is determined in step S17 that the treatment time is not equal to or longer than the predetermined setting time (NO), the process returns to step S16 and the first standing treatment is repeated, whereby the first standing treatment by the low-temperature treatment means 110 is continuously performed.

[0076] If it is determined in step S17 that the processing time is equal to or longer than the set time (YES), the first static processing by the low-temperature processing means 110 is terminated (step S18), and the low-temperature processing including the first low-temperature steam processing and the first static processing by the low-temperature processing means 110 is terminated.

[0077] According to the control shown in Figure 7, a first low-temperature steam treatment is carried out for a predetermined time of 30 to 60 minutes, in which the treatment temperature of the tea leaf surface is maintained at a first temperature in the range of 40 to 60°C (at or near the first temperature), and then a first standing treatment is carried out for a predetermined time of 30 minutes, in which the treatment temperature of the tea leaf surface is maintained at a second temperature lower than the first temperature, for example, 2 to 35°C. After the above low-temperature treatment by low-temperature treatment means 110, a deactivation treatment by blue-killing treatment means 111 is carried out.

[0078] In this embodiment, the greening treatment means 111 is composed of a steamer that performs steaming treatment to inactivate the oxidase in the tea leaves at a temperature of 80 to 100°C, but instead of steaming treatment, the oxidase may be inactivated by pan-frying treatment, hot air treatment, or microwave irradiation treatment.

[0079] In addition, in this embodiment, the tea leaves are subjected to low-temperature steam treatment in which they are steamed in low-temperature steam at a first temperature in the range of 40 to 60°C (at or near the first temperature). However, the same effect can be obtained by performing a low-temperature water immersion treatment in which the tea leaves are immersed in warm water at a first temperature in the range of 40 to 60°C (at or near the first temperature) instead of the low-temperature steam treatment.

[0080] As described above in detail, according to this embodiment, prior to a deactivation treatment (deactivation) by steaming or the like, freshly picked tea leaves or tea leaves that have been withered from such fresh tea leaves are subjected to a first low-temperature steam treatment in which the treatment temperature of the tea leaf surface is set to a first temperature (at or near the first temperature) in the range of 40 to 60°C, followed by a first standing treatment in which the tea leaves are maintained at a second temperature (at or near the second temperature) lower than the first temperature. Because the low-temperature steam treatment at 40 to 60°C is performed prior to the deactivation treatment, the tea leaves are subjected to a pseudo-anaerobic stress, thereby increasing the GABA content of the tea leaves. More specifically, at normal room temperature, tea leaves have closed stomata to prevent water evaporation. However, at temperatures above 40°C, the surface stomata open as a defensive reaction, allowing the tea leaves to release (transpire) moisture from within the leaves and take in oxygen from the outside through the stomata, thereby activating the leaves. It is presumed that activation of the enzyme rapidly promotes GABA production by GAD. It is presumed that when the treatment temperature of the tea leaf surface exceeds 60°C, the enzyme (GAD) undergoes irreversible denaturation due to heat, resulting in a decrease in GABA content. In contrast, in this embodiment, low-temperature steam treatment or low-temperature water soaking treatment is performed, which imposes water stress on the tea leaves, limiting the original function of the stomata in the temperature range of 40 to 60°C. That is, the openings of the stomata and cuticles on the tea leaf surface are covered with steam or soaking water, making it difficult to supply oxygen and creating a pseudo-anaerobic stress. Furthermore, if low-temperature steam treatment is performed in a sealed space, as well as in the case of low-temperature water soaking treatment, the stress is further increased. This stress rapidly promotes GABA production by GAD, thereby increasing the GABA content of the tea leaves. In this way, by simply performing a low-temperature treatment in the range of 40 to 60°C before the blue-killing treatment, it is possible to stress the tea leaves and significantly increase the GABA content in a short period of time.When GABA production is promoted by this low-temperature steam treatment or low-temperature water immersion treatment, glutamic acid, a precursor of GABA, is consumed. However, by further performing a first standing treatment in which the treatment temperature of the tea leaves is maintained at a second temperature (for example, about 2 to 35°C) lower than the first temperature (40 to 60°C), glutamic acid can be replenished and produced from proteins and the like contained in the tea leaves, thereby increasing the GABA content.

[0081] As a modification of this embodiment, low-temperature steam treatment may be performed so that the treatment temperature of the tea leaf surface reaches a first temperature (at or near the first temperature) in the range of 47 to 58°C. This process is carried out by determining in step S12 of the low-temperature steam treatment flow shown in Figure 7 whether the steam treatment temperature is at or near the first temperature in the range of 47 to 58°C, and if it is not at or near the first temperature (NO), performing the steam temperature adjustment process in step S13. According to this modification, GABA production by GAD is rapidly promoted, the glutamic acid content in the tea leaves is significantly reduced, and the GABA content in the tea leaves is further increased. Note that the other configurations and processes in this modification are the same as those in the second embodiment.

[0082] As another modification of this embodiment, the first low-temperature steam treatment (or low-temperature water immersion treatment) by the first low-temperature steam treatment means 110A (or first low-temperature water immersion treatment means) and the stationary treatment by the first stationary treatment means 110B may be repeated multiple times. By repeating this process multiple times, the GABA content can be further increased in a shorter time. Note that the other configurations and processes in this modification are the same as those in the second embodiment.

[0083] FIG. 8 shows a schematic diagram of the configuration of a device for increasing the GABA content in tea leaves in a GABA tea manufacturing apparatus according to a third embodiment of the present invention.

[0084] In Figure 8, reference numeral 210 denotes low-temperature treatment means for treating picked fresh tea leaves or tea leaves obtained by withering fresh tea leaves to produce black tea, and reference numeral 211 denotes green-killing treatment means, such as a steamer, for inactivating the oxidase in the tea leaves sent from the low-temperature treatment means 210. Although not shown in Figure 8, when producing black tea, other means such as rolling treatment means and fermentation treatment means are naturally provided between the low-temperature treatment means 210 for treating withered tea leaves with low-temperature steam and leaving them to stand and the green-killing treatment means (fermentation stopping means) 211. Furthermore, when producing black tea, withering treatment means may be provided between the low-temperature treatment means 210 and the green-killing treatment means (fermentation-stopping means) 211, in which case the fresh tea leaves are subjected to low-temperature steam treatment and static treatment in the low-temperature treatment means 210, then withered in the withering treatment means, and then treated by other means such as rolling treatment means and fermentation treatment means, before being subjected to green-killing treatment in the green-killing treatment means (fermentation-stopping means) 211. Furthermore, when producing black tea, the low-temperature treatment means 210 can also be used as a means for performing low-temperature treatment (low-temperature steam treatment and static treatment) and withering treatment together, in which case the fresh tea leaves are subjected to low-temperature treatment and withering treatment in the low-temperature treatment means 210, then treated by other means such as rolling treatment means and fermentation treatment means, before being subjected to green-killing treatment in the green-killing treatment means (fermentation-stopping means) 211. In this embodiment, the low-temperature treatment means 210 comprises a first low-temperature steam treatment means 210A, a first still-standing treatment means 210B, and a second low-temperature steam treatment means 210C. The first low-temperature steam treatment means 210A is configured to perform low-temperature steam treatment so that the treatment temperature of the tea leaf surface is maintained at a first temperature (at or near the first temperature) in the range of 40 to 60°C. The first still-standing treatment means 210B is configured to perform still-standing treatment so that the treatment temperature of the tea leaf surface treated by the first low-temperature steam treatment means 210A is maintained at a second temperature lower than the first temperature. This first still-standing treatment means 210B is a treatment means that leaves the tea leaves still without performing low-temperature steam treatment and maintains them at the second temperature, but it may also be a treatment means that performs low-temperature steam treatment and maintains them at the second temperature.The second low-temperature steam treatment means 210C is configured to perform low-temperature steam treatment so that the treatment temperature of the tea leaves treated by the first static treatment means 210B is maintained at a third temperature (at or near the third temperature) in the range of 47 to 58°C, which is higher than the first temperature.

[0085] Although not shown, for example, a manufacturing apparatus for Sencha tea may include, following the blue killing treatment means 211, a cooling treatment means for quickly cooling the temperature of the steamed leaves to about room temperature in order to maintain the color of the steamed leaves, a leaf beating treatment means for shaking the leaves by blowing dry hot air while pressing them down in order to maintain the color of the cooled tea leaves and shorten the time for the next rough rolling treatment, a rough rolling treatment means for rolling the tea leaves while blowing dry hot air and pressing them down with moderate friction and pressure in order to soften the tea leaves and reduce the moisture inside, and a rolling means for making up for the lack of rolling in the rough rolling treatment. The system comprises a rolling and twisting processing means for massing and rolling the tea leaves under pressure in order to destroy the structure of the tea leaves and facilitate the infusion of the ingredients and to equalize the moisture content, a medium rolling processing means for rolling and rolling the tea leaves by blowing dry hot air into them to loosen them and give them a twisted shape so that they can be easily shaped in the subsequent fine rolling processing, a fine rolling processing means for rolling the tea leaves in only one direction while removing moisture from inside the tea leaves and drying them in order to shape them into a thin, elongated shape, and a drying processing means for drying the tea leaves to reduce the moisture content to about 5%, all of which are connected in sequence.The equipment for carrying out the greening treatment, cooling treatment, leaf beating treatment, rough rolling treatment, rolling and twisting treatment, medium rolling treatment, fine rolling treatment and drying treatment other than the low-temperature treatment are all commercially available and well-known in construction, so detailed explanations will be omitted. Furthermore, while the above description has been given of a sencha manufacturing apparatus, in the case of a tencha (matcha) manufacturing apparatus, the green tea killing means 211 is followed by a loose tea cooling means for quickly cooling the steamed leaves to about room temperature in order to maintain the color, etc. of the steamed leaves, and a drying means for drying the tea leaves to reduce the moisture content to about 5%, which are connected in sequence. Since the equipment for realizing the green tea killing, loose tea cooling, and drying processes other than the low-temperature treatment are all commercially available and well-known, detailed explanations will be omitted. This embodiment is applicable not only to green tea such as sencha and tencha, but also to fermented teas such as kamairicha, black tea, and oolong tea, and other teas.For example, in the case of a black tea production apparatus, a withering treatment means for withering fresh tea leaves is provided before the low-temperature treatment means 210, and the low-temperature treatment means 210 is followed in sequence by, but is not limited to, a rolling treatment means for destroying the tea leaf tissue and causing oxidative fermentation, a fermentation treatment means for promoting oxidative fermentation of the tea leaves, a green-killing treatment (fermentation-stopping) means 211 for inactivating oxidizing enzymes, and a drying treatment means. Furthermore, in addition to the above-mentioned means, other means such as a ball-dissolving means or a sieving means may be added, and the green-killing treatment (fermentation-stopping) means 211 and the drying treatment means may be configured as a single device or as separate devices. In another example of a black tea production apparatus, a withering treatment means may be provided after the low-temperature treatment means 210, and the low-temperature treatment means 210, the withering treatment means, the rolling treatment means, the fermentation treatment means, the green-killing treatment (fermentation-stopping) means 211, and the drying treatment means may be connected in sequence. Furthermore, in another example of a black tea production apparatus, the low-temperature treatment means 210 can be used as a means for performing both low-temperature treatment and withering treatment, and the low-temperature treatment means 210 for performing low-temperature treatment and withering treatment on raw tea leaves, the rolling treatment means, the fermentation treatment means, the green-killing treatment (fermentation stop) means 211, and the drying treatment means may be connected in sequence. Note that the black tea production apparatus is not limited to the above-mentioned apparatus, and it is also possible to use an apparatus equipped with treatment means used in the CTC production method using a CTC machine or the rotor van production method using a rotor van. Furthermore, in the case of an oolong tea production apparatus, a withering treatment means may be provided before the green-killing treatment means 211. For example, the withering treatment means, low-temperature treatment means 210, and green-killing treatment means 211 may be connected in sequence, or the low-temperature treatment means 210, withering treatment means, and green-killing treatment means 211 may be connected in sequence, and then the rolling treatment means and drying treatment means may be connected in sequence.

[0086] 9 shows a schematic diagram of an example of the hardware configuration of the low-temperature treatment means 210. The low-temperature treatment means 210 in this embodiment comprises a low-temperature steam treatment chamber 210a for treating the transferred tea leaves with low-temperature steam, a temperature detection unit 210b for detecting a temperature corresponding to the treatment temperature of the surface of the tea leaves in this low-temperature steam treatment chamber 210a, a humidity detection unit 210c for detecting the internal humidity, a time detection unit 210d for detecting the treatment time, and a control unit 210e for inputting the temperature detected by the temperature detection unit 210b, the humidity detected by the humidity detection unit 210c, and the treatment time detected by the time detection unit 210d, and controlling the steam temperature and the end of the low-temperature steam treatment.

[0087] The control unit 210e controls the steam in the low-temperature steam treatment chamber 210a using a built-in computer to maintain the treatment temperature of the tea leaf surface at a first temperature (at or near the first temperature) in the range of 40 to 60°C according to the detected treatment temperature, humidity, and treatment time. In this case, the first low-temperature steam treatment is performed until the steam treatment time reaches a predetermined set time, at which point the first low-temperature steam treatment is terminated. The predetermined set time is preferably 15 to 60 minutes, but may be 1 minute if the first temperature is high (near 60°C). Following the first low-temperature steam treatment, the control unit 210e performs a first standing treatment. This first standing treatment is a standing treatment for 10 to 30 minutes, maintaining the tea leaf at a second temperature (e.g., approximately 2 to 35°C) lower than the first temperature (40 to 60°C). The control unit 210e then performs a second low-temperature steam treatment following the first standing treatment. This second low-temperature steam treatment is a low-temperature steam treatment that is maintained at a third temperature (47 to 58° C.) that is higher than the first temperature and is carried out for 1 to 60 minutes.

[0088] The mechanical configuration of the low-temperature steam processing chamber in this embodiment is the same as that described in the first embodiment with reference to FIG. 3, and therefore a description thereof will be omitted.

[0089] FIG. 10 shows a schematic flow of control by the computer of the control unit 210e in the low-temperature treatment means 210.

[0090] First, the temperature detection unit 210b detects the processing temperature in the low-temperature steam processing chamber 210a (corresponding to the processing temperature on the surface of the tea leaves) (step S21), and determines whether the detected processing temperature is a first temperature in the range of 40 to 60°C (at or near the first temperature) (step S22).

[0091] If it is determined in step S22 that the processing temperature is not the first temperature (the first temperature or its vicinity) in the range of 40 to 60°C (NO), the control unit 210e adjusts the steam temperature in the low-temperature steam processing chamber 210a to this first temperature (the first temperature or its vicinity) (step S23), and then repeats the processing of steps S21 to S23.

[0092] If it is determined in step S22 that the treatment temperature is at a first temperature in the range of 40 to 60°C (at or near the first temperature) (YES), it is determined whether the treatment time is equal to or longer than a predetermined set time (e.g., 30 to 60 minutes) for the first low-temperature steam treatment (step S24).

[0093] If it is determined in step S24 that the treatment time is not equal to or longer than the predetermined installation time (NO), the process returns to step S21 and the above-described processes of steps S21 to S24 are repeated, thereby allowing the first low-temperature steam treatment by the low-temperature treatment means 210 to continue.

[0094] If it is determined in step S24 that the processing time is equal to or longer than the set time (YES), the first low-temperature steam processing by the low-temperature processing means 210 is terminated (step S25).

[0095] Next, a first standing treatment is carried out (step S26). The first standing treatment is a treatment in which the treatment temperature of the tea leaf surface is maintained at a second temperature lower than the first temperature. Here, the second temperature is, for example, 2 to 35°C.

[0096] Next, it is determined whether the processing time is equal to or longer than a preset time (for example, 30 minutes) for the first standing process (step S27).

[0097] If it is determined in step S27 that the treatment time is not equal to or longer than the predetermined setting time (NO), the process returns to step S26 and the first standing treatment is repeated, whereby the first standing treatment by the low-temperature treatment means 210 is continuously performed.

[0098] If it is determined in step S27 that the processing time is equal to or longer than the set time (YES), the second low-temperature steam processing is performed. First, the processing temperature in the low-temperature steam processing chamber 210a (corresponding to the processing temperature on the surface of the tea leaves) is detected by the temperature detection unit 210b (step S28), and it is determined whether the detected processing temperature is a third temperature in the range of 47 to 58°C (at or near the third temperature) (step S29).

[0099] If it is determined in step S29 that the processing temperature is not the third temperature (the third temperature or its vicinity) in the range of 47 to 58°C (NO), the control unit 210e adjusts the steam temperature in the low-temperature steam processing chamber 210a to the third temperature (the third temperature or its vicinity) (step S30), and then repeats the processing of steps S28 to S30.

[0100] If it is determined in step S29 that the treatment temperature is a third temperature in the range of 47 to 58°C (the third temperature or its vicinity) (YES), it is determined whether the treatment time is equal to or longer than a predetermined set time (e.g., 1 to 60 minutes) for the second low-temperature steam treatment (step S31).

[0101] If it is determined in step S31 that the treatment time is not equal to or longer than the predetermined installation time (NO), the process returns to step S28, and the above-described processes of steps S28 to S31 are repeated, thereby allowing the low-temperature treatment means 210 to continue the second low-temperature steam treatment.

[0102] If it is determined in step S31 that the processing time is equal to or longer than the set time (YES), the second low-temperature steam processing by the low-temperature processing means 210 is terminated (step S32), and the low-temperature processing including the first low-temperature steam processing, the first static processing, and the second low-temperature steam processing by the low-temperature processing means 210 is terminated.

[0103] According to the control shown in Figure 10, a first low-temperature steam treatment is carried out for a predetermined time of 30 to 60 minutes, maintaining the treatment temperature of the tea leaf surface at a first temperature in the range of 40 to 60°C (at or near the first temperature), followed by a first standing treatment for a predetermined time of 30 minutes, maintaining the treatment temperature of the tea leaf surface at a second temperature lower than the first temperature, for example 2 to 35°C, and then a second low-temperature steam treatment is carried out for 1 to 60 minutes, maintaining the temperature at a third temperature higher than the first temperature, for example 47 to 58°C. After the above low-temperature treatments by low-temperature treatment means 210, a deactivation treatment is carried out by blue-killing treatment means 211.

[0104] In this embodiment, the greening treatment means 211 is composed of a steamer that performs steaming treatment to inactivate the oxidase in the tea leaves at a temperature of 80 to 100°C, but instead of steaming treatment, the oxidase may be inactivated by pan-frying treatment, hot air treatment, or microwave irradiation treatment.

[0105] In addition, in this embodiment, the tea leaves are subjected to low-temperature steam treatment in which they are steamed in low-temperature steam at a first temperature in the range of 40 to 60°C (at or near the first temperature). However, the same effect can be obtained by performing a low-temperature water immersion treatment in which the tea leaves are immersed in warm water at a first temperature in the range of 40 to 60°C (at or near the first temperature) instead of the low-temperature steam treatment.

[0106] As explained in detail above, according to this embodiment, before being subjected to a deactivation treatment by steaming or the like, freshly picked tea leaves or tea leaves that have been withered from such fresh tea leaves are subjected to a first low-temperature steam treatment in which the treatment temperature on the tea leaf surface is set to a first temperature in the range of 40 to 60°C (the first temperature or nearby), followed by a first standing treatment in which the tea leaves are maintained at a second temperature lower than the first temperature (the second temperature or nearby), and then a second low-temperature steam treatment in which the tea leaves are maintained at a third temperature in the range of 47 to 58°C (the third temperature or nearby), which is higher than the first temperature. Because the low-temperature steam treatment at 40 to 60°C is performed before the deactivation treatment, the tea leaves are subjected to a pseudo-anaerobic stress, which increases the GABA content of the tea leaves. To explain in more detail, at normal room temperature, tea leaves have closed stomata to prevent water evaporation. However, at temperatures above 40°C, the surface stomata open due to a defensive reaction, and the tea leaves are activated through respiration, releasing (transpiration) water from within the leaves and taking in oxygen from the outside. It is presumed that activation rapidly promotes GABA production by GAD. It is presumed that when the treatment temperature of the tea leaf surface exceeds 60°C, the enzyme (GAD) undergoes irreversible denaturation due to heat, resulting in a decrease in GABA content. In contrast, in this embodiment, low-temperature steam treatment or low-temperature water immersion treatment is performed, which applies water stress to the tea leaves, limiting the original function of the stomata at temperatures between 40 and 60°C. In other words, the openings of the stomata and cuticles on the surface of the tea leaves are covered with steam or steeping water, making it difficult to supply oxygen, and imposing a pseudo-anaerobic stress on the leaves. Furthermore, not only in the case of low-temperature water steeping treatment, but also when low-temperature steam treatment is carried out in an enclosed space, the stress is further increased, and the production of GABA by GAD is rapidly promoted by the stress, and the GABA content of the tea leaves increases. Thus, by simply carrying out a low-temperature treatment in the range of 40 to 60°C before the blue-killing treatment, it is possible to stress the tea leaves and significantly increase the GABA content in a short period of time.When GABA production is promoted by this low-temperature steam treatment or low-temperature water soaking treatment, glutamic acid, a precursor of GABA, is consumed, but by further carrying out a first standing treatment in which the treatment temperature of the tea leaves is maintained at a second temperature (e.g., 2 to 35°C) lower than the first temperature (40 to 60°C), glutamic acid can be replenished and produced from proteins contained in the tea leaves. Subsequently, by carrying out a second low-temperature steam treatment in which the temperature is maintained at a third temperature (e.g., 47 to 58°C) higher than the first temperature, the stress applied to the tea leaves is further increased, and the GABA content can be greatly increased.

[0107] As a modification of this embodiment, low-temperature steam treatment may be performed so that the treatment temperature of the tea leaf surface reaches a first temperature (at or near the first temperature) in the range of 47 to 58°C. This process is carried out by determining in step S22 of the low-temperature steam treatment flow shown in Figure 10 whether the steam treatment temperature is at or near the first temperature in the range of 47 to 58°C, and if it is not at or near the first temperature (NO), performing the steam temperature adjustment process in step S23. According to this modification, GABA production by GAD is rapidly promoted, the glutamic acid content in the tea leaves is significantly reduced, and the GABA content in the tea leaves is further increased. Note that the other configurations and processes in this modification are the same as those in the second embodiment.

[0108] As another modification of this embodiment, the first low-temperature steam treatment (or low-temperature water immersion treatment) by the first low-temperature steam treatment means 210A (or first low-temperature water immersion treatment means) and the stationary treatment by the first stationary treatment means 210B may be repeated multiple times. By repeating this process multiple times, the GABA content can be further increased in a shorter time. Note that the other configurations and processes in this modification are the same as those in the third embodiment.

[0109] FIG. 11 shows a schematic diagram of the configuration of a device for increasing the GABA content in tea leaves in a GABA tea manufacturing apparatus according to a fourth embodiment of the present invention.

[0110] In Figure 11, reference numeral 310 denotes low-temperature treatment means for treating picked fresh tea leaves or tea leaves that have been withered from those fresh tea leaves with low-temperature steam, and 311 denotes green-killing treatment means, such as a steamer, for inactivating the oxidase enzymes in the tea leaves sent from low-temperature treatment means 310. Although not shown in Figure 11, when producing black tea, other means such as rolling treatment means and fermentation treatment means are naturally provided between low-temperature treatment means 310, which treats withered tea leaves with low-temperature steam and leaves to stand, and green-killing treatment means (fermentation stopping means) 311. Furthermore, when producing black tea, withering treatment means may be provided between the low-temperature treatment means 310 and the green-killing treatment means (fermentation-stopping means) 311, in which case the fresh tea leaves are subjected to low-temperature steam treatment and static treatment in the low-temperature treatment means 310, then withered in the withering treatment means, and then treated by other means such as rolling treatment means and fermentation treatment means, before being subjected to green-killing treatment in the green-killing treatment means (fermentation-stopping means) 311. Furthermore, when producing black tea, the low-temperature treatment means 310 can also be used as a means for performing low-temperature treatment (low-temperature steam treatment and static treatment) and withering treatment together, in which case the fresh tea leaves are subjected to low-temperature treatment and withering treatment in the low-temperature treatment means 310, then treated by other means such as rolling treatment means and fermentation treatment means, before being subjected to green-killing treatment in the green-killing treatment means (fermentation-stopping means) 311. In this embodiment, the low-temperature treatment means 310 comprises a first low-temperature steam treatment means 310A, a first still-standing treatment means 310B, a second low-temperature steam treatment means 310C, and a second still-standing treatment means 310D. The first low-temperature steam treatment means 310A is configured to perform low-temperature steam treatment so that the treatment temperature of the tea leaf surface is maintained at a first temperature (at or near the first temperature) in the range of 40 to 60°C. The first still-standing treatment means 310B is configured to maintain the treatment temperature of the tea leaf surface treated by the first low-temperature steam treatment means 310A at a second temperature lower than the first temperature. This first still-standing treatment means 310B is a treatment means that leaves the tea leaves to stand still and maintains them at the second temperature without performing low-temperature steam treatment, but it may also be a treatment means that performs low-temperature steam treatment and maintains them at the second temperature.The second low-temperature steam treatment means 310C is configured to perform low-temperature steam treatment so that the treatment temperature of the tea leaves treated by the first still-standing treatment means 310B is maintained at a third temperature (at or near the third temperature) in the range of 47 to 58°C, which is higher than the first temperature. The second still-standing treatment means 310D is configured to perform low-temperature steam treatment so that the treatment temperature of the tea leaves treated by the second low-temperature steam treatment means 310C is maintained at a fourth temperature (at or near the fourth temperature), for example, 2 to 35°C, which is higher than the second temperature. This second still-standing treatment means 310D is a treatment means that leaves the tea leaves to stand still and maintains them at the fourth temperature without performing low-temperature steam treatment, but it may also be a treatment means that performs low-temperature steam treatment and maintains them at the fourth temperature.

[0111] Although not shown, for example, a Sencha manufacturing device may include, following the blue killing treatment means 311, a cooling treatment means for quickly cooling the temperature of the steamed leaves to about room temperature in order to maintain the color of the steamed leaves, a leaf beating treatment means for shaking the leaves by blowing dry hot air into them to maintain the color of the cooled tea leaves and shorten the time for the next rough rolling treatment, a rough rolling treatment means for blowing dry hot air into the tea leaves and rolling them with moderate friction and pressure in order to soften the tea leaves and reduce their internal moisture, and a rolling means for making up for insufficient rolling in the rough rolling treatment to roll the tea leaves. The system comprises a rolling and twisting processing means for massing and rolling the tea leaves under pressure in order to destroy the structure of the tea leaves and facilitate the infusion of the ingredients and to equalize the moisture content, a medium rolling processing means for rolling and rolling the tea leaves by blowing dry hot air into them to loosen them and give them a twisted shape so that they can be easily shaped in the subsequent fine rolling processing, a fine rolling processing means for rolling the tea leaves in only one direction while removing moisture from inside the tea leaves and drying them in order to shape them into a thin, elongated shape, and a drying processing means for drying the tea leaves to reduce the moisture content to about 5%, all of which are connected in sequence.The equipment for carrying out the greening treatment, cooling treatment, leaf beating treatment, rough rolling treatment, rolling and twisting treatment, medium rolling treatment, fine rolling treatment and drying treatment other than the low-temperature treatment are all commercially available and well-known in construction, so detailed explanations will be omitted. Furthermore, while the above description has been given of a manufacturing apparatus for sencha, in the case of a manufacturing apparatus for tencha (matcha), the apparatus is equipped with a loose tea cooling means for rapidly cooling the steamed leaves to about room temperature in order to maintain the color, etc. of the steamed leaves, following the green-killing treatment means 311, and a drying means for drying the tea leaves to reduce the moisture content to about 5%, which are connected in sequence. Since the equipment for realizing the green-killing treatment, loose tea cooling treatment, and drying treatment other than the low-temperature treatment are all commercially available and well-known, detailed explanations will be omitted. This embodiment is applicable not only to green tea such as sencha and tencha, but also to fermented teas such as kamairicha, black tea, and oolong tea, and other teas.For example, in the case of a black tea production apparatus, a withering treatment means for withering fresh tea leaves is provided before the low-temperature treatment means 310, and the low-temperature treatment means 310 is followed in sequence by, but not limited to, a rolling treatment means for destroying the tea leaf tissue and causing oxidative fermentation, a fermentation treatment means for promoting oxidative fermentation of the tea leaves, a green-killing treatment (fermentation-stopping) means 311 for inactivating oxidizing enzymes, and a drying treatment means. Furthermore, in addition to the above-mentioned means, other means such as a ball-dissolving means or a sieving means may be added, and the green-killing treatment (fermentation-stopping) means 311 and the drying treatment means may be configured as a single device or as separate devices. In another example of a black tea production apparatus, a withering treatment means may be provided after the low-temperature treatment means 310, and the low-temperature treatment means 310, the withering treatment means, the rolling treatment means, the fermentation treatment means, the green-killing treatment (fermentation-stopping) means 311, and the drying treatment means may be connected in sequence. In another example of a black tea production apparatus, the low-temperature treatment means 310 can be used as a means for performing both low-temperature treatment and withering treatment, and the low-temperature treatment means 310, which performs low-temperature treatment and withering of raw tea leaves, the rolling treatment means, the fermentation treatment means, the green-killing treatment (fermentation stop) means 311, and the drying treatment means can be connected in sequence. The black tea production apparatus is not limited to the above-mentioned apparatus, and can also be an apparatus equipped with treatment means used in the CTC production method using a CTC machine or the rotor van production method using a rotor van. Furthermore, in the case of an oolong tea production apparatus, a withering treatment means can be provided before the green-killing treatment means 311. For example, the withering treatment means, low-temperature treatment means 310, and green-killing treatment means 311 can be connected in sequence, or the low-temperature treatment means 310, withering treatment means, and green-killing treatment means 311 can be connected in sequence, followed by the rolling treatment means and drying treatment means.

[0112] 12 shows a schematic diagram of an example of the hardware configuration of the low-temperature treatment means 310. The low-temperature treatment means 310 in this embodiment comprises a low-temperature steam treatment chamber 310a for treating the transferred tea leaves with low-temperature steam, a temperature detection unit 310b for detecting a temperature corresponding to the treatment temperature of the surface of the tea leaves in this low-temperature steam treatment chamber 310a, a humidity detection unit 310c for detecting the internal humidity, a time detection unit 310d for detecting the treatment time, and a control unit 310e for inputting the temperature detected by the temperature detection unit 310b, the humidity detected by the humidity detection unit 310c, and the treatment time detected by the time detection unit 310d, and controlling the steam temperature and the end of the low-temperature steam treatment.

[0113] The control unit 310e controls the steam in the low-temperature steam treatment chamber 310a using an internal computer to maintain the treatment temperature of the tea leaf surface at a first temperature (at or near the first temperature) in the range of 40 to 60°C according to the detected treatment temperature, humidity, and treatment time. In this case, the first low-temperature steam treatment is performed until the steam treatment time reaches a predetermined set time, at which point the first low-temperature steam treatment is terminated. The predetermined set time is preferably 15 to 60 minutes, but may be 1 minute if the first temperature is high (near 60°C). Following the first low-temperature steam treatment, the control unit 310e performs a first standing treatment. This first standing treatment is a standing treatment for 10 to 30 minutes, maintaining the tea leaf at a second temperature (e.g., 2 to 35°C) lower than the first temperature (40 to 60°C). The control unit 310e then performs a second low-temperature steam treatment following the first standing treatment. This second low-temperature steam treatment is a low-temperature steam treatment that is performed for 1 to 60 minutes while maintaining a third temperature (47 to 58°C) that is equal to or higher than the first temperature. Following this second low-temperature steam treatment, the control unit 310e performs a second standing treatment. This second standing treatment is a standing treatment that is performed for 15 minutes while maintaining a fourth temperature (e.g., 2 to 35°C) that is equal to or higher than the second temperature (approximately 2 to 35°C).

[0114] The mechanical configuration of the low-temperature steam processing chamber in this embodiment is the same as that described in the first embodiment with reference to FIG. 3, and therefore a description thereof will be omitted.

[0115] FIG. 13 shows a schematic flow of control by the computer of the control unit 310e in the low-temperature treatment means 310.

[0116] First, the temperature detection unit 310b detects the processing temperature in the low-temperature steam processing chamber 310a (corresponding to the processing temperature on the surface of the tea leaves) (step S41), and determines whether the detected processing temperature is a first temperature in the range of 40 to 60°C (the first temperature or nearby) (step S42).

[0117] If it is determined in step S42 that the processing temperature is not the first temperature (the first temperature or its vicinity) in the range of 40 to 60°C (NO), the control unit 310e adjusts the steam temperature in the low-temperature steam processing chamber 310a to the first temperature (the first temperature or its vicinity) (step S43), and then repeats the processing of steps S41 to S43.

[0118] If it is determined in step S42 that the treatment temperature is a first temperature in the range of 40 to 60°C (the first temperature or its vicinity) (YES), it is determined whether the treatment time is equal to or longer than a predetermined set time (e.g., 30 to 60 minutes) for the first low-temperature steam treatment (step S44).

[0119] If it is determined in step S44 that the treatment time is not equal to or longer than the predetermined installation time (NO), the process returns to step S41, and the above-described processes of steps S41 to S44 are repeated, thereby allowing the first low-temperature steam treatment by the low-temperature treatment means 310 to continue.

[0120] If it is determined in step S44 that the processing time is equal to or longer than the set time (YES), the first low-temperature steam processing by the low-temperature processing means 310 is terminated (step S45).

[0121] Next, a first standing treatment is carried out (step S46). The first standing treatment is a treatment in which the treatment temperature of the tea leaf surface is maintained at a second temperature that is lower than the first temperature. Here, the second temperature is, for example, 2 to 35°C.

[0122] Next, it is determined whether the processing time is equal to or longer than a preset time (for example, 30 minutes) for the first standing process (step S47).

[0123] If it is determined in step S47 that the treatment time is not equal to or longer than the predetermined setting time (NO), the process returns to step S46 and the first standing treatment is repeated, whereby the first standing treatment by the low-temperature treatment means 310 is continuously performed.

[0124] If it is determined in step S47 that the treatment time is equal to or longer than the set time (YES), the first low-temperature steam treatment and the first standing treatment by the low-temperature treatment means 310 are terminated.

[0125] In this second low-temperature steam treatment, the temperature detection unit 310b first detects the treatment temperature in the low-temperature steam treatment chamber 310a (corresponding to the treatment temperature on the tea leaf surface) (step S48), and determines whether the detected treatment temperature is a third temperature in the range of 47 to 58°C (at or near the third temperature) (step S49).

[0126] If it is determined in step S19 that the processing temperature is not the third temperature (the third temperature or its vicinity) in the range of 47 to 58°C (NO), the control unit 310e adjusts the steam temperature in the low-temperature steam processing chamber 310a to the third temperature (the third temperature or its vicinity) (step S50), and then repeats the processing of steps S48 to S50.

[0127] If it is determined in step S49 that the treatment temperature is a third temperature in the range of 47 to 58°C (the third temperature or its vicinity) (YES), it is determined whether the treatment time is equal to or longer than a predetermined set time (e.g., 1 to 60 minutes) for the second low-temperature steam treatment (step S51).

[0128] If it is determined in step S51 that the treatment time is not equal to or longer than the predetermined installation time (NO), the process returns to step S48, and the above-described processes of steps S48 to S51 are repeated, thereby allowing the second low-temperature steam treatment by the low-temperature treatment means 310 to continue.

[0129] If it is determined in step S51 that the processing time is equal to or longer than the set time (YES), the second low-temperature steam processing by the low-temperature processing means 310 is terminated (step S52).

[0130] Next, a second standing treatment is carried out (step S53). The second standing treatment is a treatment in which the treatment temperature of the tea leaf surface is maintained at a fourth temperature that is equal to or higher than the second temperature. Here, the fourth temperature is, for example, 2 to 35°C.

[0131] Next, it is determined whether the processing time is equal to or longer than a preset time (for example, 15 minutes) for the second standing process (step S54).

[0132] If it is determined in step S54 that the treatment time is not equal to or longer than the predetermined setting time (NO), the process returns to step S53 and the second standing treatment is repeated, whereby the second standing treatment by the low-temperature treatment means 310 is continuously performed.

[0133] If it is determined in step S54 that the processing time is equal to or longer than the set time (YES), the low-temperature processing including the first low-temperature steam processing, the first still processing, the second low-temperature steam processing, and the second still processing by the low-temperature processing means 310 is terminated.

[0134] 13, a first low-temperature steam treatment is carried out for a predetermined time of 30 to 60 minutes, maintaining the treatment temperature of the tea leaf surface at a first temperature in the range of 40 to 60°C (at or near the first temperature), followed by a first standing treatment for a predetermined time of 30 minutes, maintaining the treatment temperature of the tea leaf surface at a second temperature lower than the first temperature, for example, 2 to 35°C, followed by a second low-temperature steam treatment for a predetermined time of 1 to 60 minutes, maintaining the treatment temperature of the tea leaf at a third temperature higher than the first temperature, for example, 47 to 58°C, followed by a second standing treatment for a predetermined time of 15 minutes, maintaining the treatment temperature of the tea leaf surface at a fourth temperature higher than the second temperature, for example, 2 to 35°C. After the above low-temperature treatments by low-temperature treatment means 310, a deactivation treatment is carried out by blue-killing treatment means 311.

[0135] In this embodiment, the greening treatment means 311 is composed of a steamer that performs steaming treatment to inactivate the oxidase in the tea leaves at a temperature of 80 to 100°C, but instead of steaming treatment, the oxidase may be inactivated by pan-frying treatment, hot air treatment, or microwave irradiation treatment.

[0136] In addition, in this embodiment, a low-temperature steam treatment is performed in which the tea leaves are exposed to low-temperature steam at 40 to 60°C, but the same effect can be obtained by performing a low-temperature water soaking treatment in which the tea leaves are soaked in low-temperature water at 40 to 60°C instead of the low-temperature steam treatment.

[0137] As explained in detail above, according to this embodiment, before being subjected to a deactivation treatment by steaming or the like, freshly picked tea leaves or tea leaves that have been withered from such fresh tea leaves are subjected to a first low-temperature steam treatment in which the treatment temperature on the tea leaf surface is set to a first temperature (at or near the first temperature) in the range of 40 to 60°C, followed by a first standing treatment in which the tea leaves are maintained at a second temperature (at or near the second temperature) lower than the first temperature, a second low-temperature steam treatment in which the tea leaves are maintained at a third temperature equal to or higher than the first temperature, and a second standing treatment in which the tea leaves are maintained at a fourth temperature equal to or higher than the second temperature. Because the low-temperature steam treatment at 40 to 60°C is performed before the deactivation treatment, the tea leaves are subjected to a pseudo-anaerobic stress, which increases the GABA content of the tea leaves. To explain in more detail, at normal room temperature, tea leaves have closed stomata to prevent water evaporation. However, at temperatures above 40°C, the surface stomata open due to a defensive reaction, and the tea leaves are activated through respiration, releasing (transpiration) water from within the leaves and taking in oxygen from the outside. It is presumed that activation rapidly promotes GABA production by GAD. It is presumed that when the treatment temperature of the tea leaf surface exceeds 60°C, the enzyme (GAD) undergoes irreversible denaturation due to heat, resulting in a decrease in GABA content. In contrast, in this embodiment, low-temperature steam treatment or low-temperature water immersion treatment is performed, which applies water stress to the tea leaves, limiting the original function of the stomata at temperatures between 40 and 60°C. In other words, the openings of the stomata and cuticles on the surface of the tea leaves are covered with steam or steeping water, making it difficult to supply oxygen, and imposing a pseudo-anaerobic stress on the leaves. Furthermore, not only in the case of low-temperature water steeping treatment, but also when low-temperature steam treatment is carried out in an enclosed space, the stress is further increased, and the GABA content of the tea leaves increases as a result. Thus, by simply carrying out a low-temperature treatment in the range of 40 to 60°C before the blue-killing treatment, it is possible to stress the tea leaves, rapidly promote the production of GABA by GAD, and greatly increase the GABA content in a short period of time.When GABA production is promoted by this low-temperature steam treatment or low-temperature water soaking treatment, glutamic acid, a precursor of GABA, is consumed. Furthermore, by performing a first standing treatment in which the treatment temperature of the tea leaves is maintained at a second temperature (e.g., about 2 to 35°C) lower than the first temperature (40 to 60°C), glutamic acid can be replenished and produced from proteins contained in the tea leaves. Subsequently, by performing a second low-temperature steam treatment in which the treatment temperature is maintained at a third temperature (e.g., about 47 to 58°C) equal to or higher than the first temperature, the stress applied to the tea leaves is further increased, resulting in a significant increase in the GABA content. Furthermore, by performing a second standing treatment in which the treatment temperature is maintained at a fourth temperature (e.g., about 2 to 35°C) equal to or higher than the second temperature (2 to 35°C), glutamic acid can be replenished and produced from proteins contained in the tea leaves, resulting in a further increase in the GABA content.

[0138] As a modification of this embodiment, low-temperature steam treatment may be performed so that the treatment temperature of the tea leaf surface reaches a first temperature (at or near the first temperature) in the range of 47 to 58°C. This process is carried out by determining in step S42 of the low-temperature steam treatment flow shown in Figure 13 whether the steam treatment temperature is at or near the first temperature in the range of 47 to 58°C, and if it is not at or near the first temperature (NO), performing the steam temperature adjustment process in step S43. According to this modification, GABA production by GAD is rapidly promoted, the glutamic acid content in the tea leaves is significantly reduced, and the GABA content in the tea leaves is further increased. Note that the other configurations and processes in this modification are the same as those in the first embodiment.

[0139] As another modification of this embodiment, the low-temperature steam treatment (or low-temperature water immersion treatment) by the first low-temperature steam treatment means 310A (or first low-temperature water immersion treatment means) and the static treatment by the first static treatment means 310B may be repeated multiple times. By repeating this process multiple times, the GABA content can be further increased in a shorter time. Note that the other configurations and processes in this modification are the same as those in the fourth embodiment.

[0140] 1. Among the "Yabukita" variety fresh tea leaves, "Yutakamidori" variety fresh tea leaves, and "Saemidori" variety fresh tea leaves, picked the day before or the day of the GABA green tea production test, samples a1-a8, c1-c3, d1-d3, e1, f1, g1, and h1-h9 were subjected to the first low-temperature treatment (low-temperature steam treatment or low-temperature water immersion treatment) and then subjected to a steaming treatment to kill the blue color, as in the first embodiment. The steaming treatment was performed by placing 200 g of tea leaves per sample in a laundry bag and steaming them for 180 seconds using a household steamer. After the steaming treatment, the steamed tea leaves were placed in a constant-temperature drying chamber and dried at 105°C for 60 minutes and then at 85°C for 90 minutes until the moisture content of the tea leaves was 5% or less, producing tencha-type green tea. The low-temperature steam treatment was carried out by blowing steam at a predetermined temperature into a net-type drying apparatus (ND3-800) manufactured by Kawasaki Kiko Co., Ltd., and the low-temperature water immersion treatment carried out on samples c3 and d3 was carried out using a cylindrical pot filled with warm water at a predetermined temperature. The treatment temperature and treatment time for the first low-temperature treatment are as shown in Tables 1 and 3 to 6 below. Fresh tea leaves from the same lot as the fresh tea leaves used in each sample (fresh tea leaves picked on the same day from the same tea plant) were not subjected to the first low-temperature treatment, but were instead subjected to the degreening treatment and drying treatment to produce a control green tea sample.

[0141] For samples g2 and g5 of fresh tea leaves of the "Yabukita" variety, picked the day before or the day of the test, the first low-temperature treatment (low-temperature steam treatment) was performed, followed by the first static treatment, followed by a steaming treatment to remove blue color, as in the second embodiment. The steaming treatment was performed by steaming the leaves for 180 seconds using a household steamer, as described above. After the steaming treatment, the steamed tea leaves were placed in a constant-temperature drying chamber and dried at 105°C for 60 minutes and then at 85°C for 90 minutes until the moisture content of the tea leaves was 5% or less, producing tencha-type green tea. The low-temperature steam treatment was performed by blowing steam at a predetermined temperature into a net-type drying device (ND3-800) manufactured by Kawasaki Kiko Co., Ltd. The static treatment was performed by leaving the tea leaves statically in a constant-temperature chamber set at a predetermined temperature. The treatment temperatures and treatment times for the first low-temperature treatment and the first static treatment are shown in Table 5 below. A control sample of green tea was produced by subjecting fresh tea leaves from the same lot (fresh tea leaves picked on the same day from the same tea plant) used in each sample to the blue killing treatment and drying treatment without carrying out the first low-temperature treatment and the first standing treatment.

[0142] Samples b1, b2, d4, d5, and g3, g6 of "Yabukita" and "Saemidori" fresh tea leaves, picked the day before or the day of the test, were subjected to the first low-temperature treatment (low-temperature steam treatment), followed by the first standing treatment, followed by the second low-temperature treatment (low-temperature steam treatment), and then subjected to a steaming treatment to kill the blue color, as in the third embodiment. The steaming treatment was carried out by steaming the leaves for 180 seconds using a household steamer, as described above. After the steaming treatment, the steamed tea leaves were placed in a constant-temperature drying chamber and dried at 105°C for 60 minutes and then at 85°C for 90 minutes until the moisture content of the tea leaves was 5% or less, producing tencha-type green tea. The low-temperature steam treatment was carried out by blowing steam at a predetermined temperature into a net-type dryer (ND3-800) manufactured by Kawasaki Kiko Co., Ltd. The standing treatment was carried out by leaving the tea leaves standing in a thermostatic chamber set at a predetermined temperature. The treatment temperatures and treatment times for the first and second low-temperature treatments and the first standing treatment are as shown in Tables 2, 3 and 5. A control sample of green tea was produced by subjecting fresh tea leaves from the same lot (fresh tea leaves picked on the same day from the same tea plant) as those used in each sample to the green killing treatment and drying treatment without carrying out the first and second low-temperature treatments and the first standing treatment.

[0143] For samples e2, e3, f2, f3, and g4, g7 of the "Yabukita" variety of fresh tea leaves, harvested the day before or the day of the test, the first low-temperature treatment (low-temperature steam treatment), the first standing treatment, the second low-temperature treatment (low-temperature steam treatment), the second standing treatment, and then the degreening treatment by steaming were performed in the same manner as in the fourth embodiment. The steaming treatment was performed by steaming the tea leaves for 180 seconds using a household steamer, as described above. After the steaming treatment, the steamed tea leaves were placed in a constant-temperature drying chamber and dried at 105°C for 60 minutes and then at 85°C for 90 minutes until the moisture content of the tea leaves was 5% or less, producing tencha-type green tea. The low-temperature steam treatment was performed by blowing steam at a predetermined temperature into a net-type dryer (ND3-800) manufactured by Kawasaki Kiko Co., Ltd. The standing treatment was carried out by leaving the tea leaves standing in a thermostatic chamber set at a predetermined temperature. The treatment temperatures and treatment times for the first and second low-temperature treatments and the first and second standing treatments are as shown in Tables 4 and 5. A control sample of green tea was produced by subjecting fresh tea leaves from the same lot (fresh tea leaves picked on the same day from the same tea plant) as those used in each sample to the green killing treatment and drying treatment without carrying out the first and second low-temperature treatments or the first and second standing treatments.

[0144] Furthermore, as a comparative sample, fresh tea leaves from the same lot as the fresh tea leaves used in samples h1 to h9 were placed in an airtight nitrogen gas-filled aluminum bag and subjected to anaerobic treatment for 3 hours, followed by a steaming treatment to kill the blue color. The steaming treatment was carried out in the same manner as above, using a household steamer for 180 seconds. After the steaming treatment, the steamed tea leaves were placed in a constant-temperature drying chamber and dried at 105°C for 60 minutes and then at 85°C for 90 minutes until the moisture content of the tea leaves was 5% or less, producing tencha-type green tea.

[0145] For samples i1 and j1 of fresh tea leaves of the "Yabukita" variety picked on the day of the test, the first low-temperature treatment (low-temperature steam treatment) was performed, as in the first embodiment, followed by a steaming treatment to remove blue color. The steaming treatment was performed using a household steamer, as described above, by steaming for 300 seconds while turning the leaves over every 60 seconds. After the steaming treatment, the steamed tea leaves were placed in a constant-temperature drying chamber and dried at 85°C for 120 minutes until the moisture content of the tea leaves was 5% or less, producing tencha-type green tea. The low-temperature steam treatment was performed by blowing steam at a predetermined temperature into a net-type dryer (ND3-800) manufactured by Kawasaki Kiko Co., Ltd. The treatment temperature and treatment time for the first low-temperature treatment are shown in Table 7 below. The control sample of green tea was produced by subjecting fresh tea leaves from the same lot (fresh tea leaves picked on the same day from the same tea plant) used in each sample to the degreening treatment and drying treatment without the first low-temperature treatment.

[0146] For samples i2-i4 (same lot as sample i1 described above) and j2-j4 (same lot as sample j1 described above) of fresh tea leaves of the "Yabukita" variety, picked on the day of the test, the following treatments were performed: the first low-temperature treatment (low-temperature steam treatment), the first standing treatment, the second low-temperature treatment (low-temperature steam treatment), and then the degreening treatment by steaming, as in the third embodiment. The steaming treatment was performed using a household steamer, similar to the above, by steaming for 300 seconds while turning the leaves over every 60 seconds. After the steaming treatment, the steamed tea leaves were placed in a constant-temperature drying chamber and dried at 85°C for 120 minutes until the moisture content of the tea leaves was reduced to 5% or less, producing tencha-type green tea. The low-temperature steam treatment was performed by blowing steam at a predetermined temperature into a net-type dryer (ND3-800) manufactured by Kawasaki Kiko Co., Ltd. The still-standing treatment was carried out by leaving the tea leaves in a thermostatic chamber set at a predetermined temperature. The treatment temperatures and treatment times for the first and second low-temperature treatments and the first still-standing treatment are as shown in Table 7 below.

[0147] The glutamic acid and GABA contents of the green tea samples a1-a8, b1-b2, c1-c3, d1-d5, e1-e3, f1-f3, g1-g7, h1-h9, i1-i4, and j1-j4 obtained by the above-described tea processing, as well as the 10 control and comparative (anaerobic) green tea samples, were measured by high-performance liquid chromatography. The increase in glutamic acid (mg / 100 g) was calculated by subtracting the measured glutamic acid content of the corresponding control sample from the measured glutamic acid content of each sample. The increase in GABA (mg / 100 g) was calculated by subtracting the measured GABA content of the corresponding control sample from the measured GABA content of each sample. The GABA increase rate (%) was calculated by dividing the measured GABA content of each sample by the measured GABA content of the control sample. Samples with a GABA content of 150 mg / 100 g or more were evaluated as excellent (◎), those with a GABA increase rate (%) of over 150% were evaluated as good (○), those with a GABA increase rate (%) of over 100% but not more than 150% were evaluated as fair (△), and those with a GABA increase rate (%) of 100% or less were evaluated as unacceptable (×).

[0148] The treatment conditions for each sample, the amount of glutamic acid contained in the green tea of ​​each sample, the control sample, and the comparative sample, the amount of increased glutamic acid, the GABA content, the amount of increased GABA, the rate of increase in GABA, and the evaluation are shown in Tables 1 to 7 below.

[0149]

[0150]

[0151]

[0152]

[0153]

[0154]

[0155]

[0156] When only the first low-temperature treatment was performed as in the first embodiment, looking at the results for samples a1 to a8 in Table 1, samples c1 to c3 and d1 to d3 in Table 3, sample e1 and sample f1 in Table 4, sample g1 in Table 5, samples h1 to h9 in Table 6, and samples i1 and j1 in Table 7, it was found that tea with an increased GABA content can be obtained by setting the treatment temperature in the range of 40 to 60°C and the treatment time in the range of 10 to 60 minutes as the treatment conditions for the low-temperature treatment.

[0157] Furthermore, looking at the results for samples h1 to h9 in Table 6, the GABA increase rate exceeded 600% when the treatment temperature for the first low-temperature treatment was set to 47°C to 57°C, and the GABA increase rate exceeded 1100% and the GABA content was 150 mg / 100 g or more when the treatment temperature was set to 50°C to 55°C. This relationship is shown in the graph in Figure 14. From these data, it was found that the treatment temperature for the first low-temperature treatment is preferably 40 to 60°C, more preferably 47°C to 58°C, and even more preferably 49°C to 55°C.

[0158] Furthermore, data has been obtained showing that the GABA content increases when the treatment time for the first low-temperature treatment is 10 to 60 minutes, so it was found that a treatment time of 10 minutes or more is preferable, and 15 to 60 minutes is more preferable. The comparative green tea samples treated with anaerobic treatment shown in Table 6 were treated for a long period of 180 minutes, while the green tea samples h5 to h7 were treated with low-temperature steam for only 30 minutes, and showed a higher GABA content than the anaerobically treated samples. This demonstrates that the present invention can produce tea with a significantly increased GABA content in a short period of time.

[0159] Furthermore, it was found that not only low-temperature steam treatment (samples a1 to a8, samples c1 to c2, samples d1 to d2, sample e1, sample f1, sample g1, and samples h1 to h9) but also low-temperature water immersion treatment (sample c3 and sample d3) were effective as low-temperature treatment methods.

[0160] From these findings, it was found that the GABA content in tea leaves can be significantly increased by performing low-temperature steam treatment or low-temperature water immersion treatment so that the treatment temperature of the tea leaf surface reaches the first temperature in the range of 40 to 60°C.

[0161] When the first standing treatment was performed following the first low-temperature treatment, as in the second embodiment, the results for samples g2 and g5 in Table 5 show that the GABA increase rate of the green tea in sample g5, which underwent the first standing treatment but at a lower temperature (5°C), was greater. Based on these findings, it is preferable to use the same treatment conditions (treatment temperature and treatment time) for the first low-temperature treatment as in the first embodiment described above. The treatment temperature for the first standing treatment is preferably approximately 2 to 35°C, more preferably approximately 3 to 20°C, and even more preferably approximately 4 to 15°C. Furthermore, the treatment time for the first standing treatment is preferably 5 to 60 minutes, more preferably approximately 10 to 30 minutes, and even more preferably approximately 10 to 20 minutes. Therefore, it was found that the GABA content of the resulting tea increases when the first standing treatment is performed at a lower temperature following the first low-temperature treatment.

[0162] When the first low-temperature treatment is followed by the first standing treatment and the second low-temperature treatment as in the third embodiment, the results for samples b1 and b2 in Table 2, samples d4 and d5 in Table 3, samples g3 and g6 in Table 5, and samples i2 to i4 and j2 to j4 in Table 7 show that the rate of increase in GABA is greater when the first low-temperature treatment is followed by the first standing treatment and the second low-temperature treatment. Based on these results, it is preferable to use the same treatment conditions (treatment temperature and treatment time) for the first and second low-temperature treatments as in the first embodiment described above, or to use a higher treatment temperature for the second low-temperature treatment than for the first low-temperature treatment, and it is preferable to use the same treatment conditions (treatment temperature and treatment time) for the first standing treatment as in the second embodiment described above. Therefore, it was found that the GABA content of the resulting tea is increased by performing the first low-temperature treatment followed by the first standing treatment and the second low-temperature treatment.

[0163] When the first low-temperature treatment is followed by the first standing treatment and the second low-temperature treatment, and then the second standing treatment is performed as in the fourth embodiment, the results for samples e2, e3 and f2, f3 in Table 4 and samples g4, g7 in Table 5 show that the rate of increase in GABA is increased by performing the first low-temperature treatment followed by the first standing treatment and the second low-temperature treatment, and then the second standing treatment. For these reasons, it is preferable that the treatment conditions (treatment temperature and treatment time) for the first and second low-temperature treatments be the same as those in the first embodiment described above, and it is preferable that the treatment conditions (treatment temperature and treatment time) for the first and second standing treatments be the same as those in the second embodiment described above.

[0164] 2. For samples k1-k3 and l1-l2 of fresh tea leaves of the "Yabukita" variety, picked on the day of the GABA black tea production test, the fresh tea leaves were placed in a withering machine (a drum-type withering machine manufactured by Kawasaki Kiko Co., Ltd.), and withered for approximately 16 hours by blowing cold air and automatically stirring the leaves. These withered tea leaves were subjected to the first low-temperature treatment (low-temperature steam treatment) as in the first embodiment. The treatment temperature and treatment time for the first low-temperature treatment are shown in Table 8 below. The tea leaves that had undergone the first low-temperature treatment were then placed in a rolling machine specifically for black tea, and rolled for 60 minutes, after which they were left to stand for approximately 60 minutes in an environment of approximately 25°C and 90% humidity for fermentation. Subsequently, the fermented tea leaves were placed in a water dryer (combined water dryer, manufactured by Kawasaki Kiko Co., Ltd.) and heated for approximately 12 minutes at an exhaust heat temperature setting of approximately 180°C to carry out a green sterilization treatment (stop fermentation). After the green sterilization treatment, the tea leaves were placed in a shelf-type dryer, and hot air at 60°C was supplied into the drying chamber to dry the tea leaves until their moisture content was 5% or less, thereby obtaining black tea. For the raw tea leaves from the same lot (raw tea leaves picked on the same day from the same tea plant) as those used in each sample, the same withering, rolling, fermentation, green sterilization (stop fermentation), and drying treatments were carried out, except that the first low-temperature treatment was not carried out, to produce black tea as a control sample.

[0165] The glutamic acid and GABA contents of the black tea samples k1-k3 and l1 and l2 obtained by the above-described tea processing, as well as the two control samples, were measured by high-performance liquid chromatography. The increase in glutamic acid (mg / 100 g) was calculated by subtracting the measured glutamic acid content of the corresponding control sample from the measured glutamic acid content of each sample. The increase in GABA (mg / 100 g) was calculated by subtracting the measured GABA content of the corresponding control sample from the measured GABA content of each sample. The percentage increase in GABA (%) was calculated by dividing the measured GABA content of each sample by the measured GABA content of the control sample. Those with a GABA content of 150 mg / 100 g or more were rated as excellent (◎), those with a GABA increase rate (%) of over 150% were rated as good (○), those with a GABA increase rate (%) of over 100% but not more than 150% were rated as fair (△), and those with a GABA increase rate (%) of 100% or less were rated as unacceptable (×).

[0166] The treatment conditions for each sample, the amount of glutamic acid contained in the black tea, the increased amount of glutamic acid, the GABA content, the increased amount of GABA, the rate of increase in GABA, and the evaluation of each sample and the control sample are shown in Table 8 below.

[0167]

[0168] These results demonstrate that, similar to green tea, black tea with increased GABA content can be obtained by subjecting withered tea leaves to the first low-temperature treatment. Looking at the results for samples k1-k3 and samples l1 and l2 in Table 8, black tea with increased GABA content was obtained when the first low-temperature treatment temperature was in the range of 40-60°C, but sample k3 (first low-temperature treatment temperature: 50°C) and sample l1 (first low-temperature treatment temperature: 55°C) had particularly excellent GABA content and GABA increase rates. This demonstrates that, similar to the green tea described above, the first low-temperature treatment temperature for black tea is preferably 40-60°C, more preferably 47-58°C, and even more preferably 49-55°C.

[0169] The above-described embodiments and examples are merely illustrative of the present invention and are not limiting, and the present invention can be embodied in various other modified and altered forms. Therefore, the scope of the present invention is defined only by the claims and their equivalents.

[0170] 10, 110, 210, 310 Low-temperature treatment means 10A, 110A, 210A, 310A First low-temperature steam treatment means 10a, 10a', 10a'', 110a, 210a, 310a Low-temperature steam treatment chamber 10b, 110b, 210b, 310b Temperature detection unit 10c, 110c, 210c, 310c Humidity detection unit 10d, 110d, 210d, 310d Time detection unit 10e, 110e, 210e, 310e Control unit 10f １ , 10f １ ', 10f １ ", 10f ２ ', 10f ２ ", 10f ３ " Transport belt 11, 111, 211, 311 Anti-blue treatment means 110B, 210B, 310B First still treatment means 210C, 310C Second low-temperature steam treatment means 310D Second still treatment means

Claims

1. An apparatus for increasing the GABA content of tea leaves, comprising a low-temperature treatment means having a first low-temperature steam treatment means or a first low-temperature water immersion treatment means for maintaining the treatment temperature of the surface of the tea leaves at a first temperature in the range of 40 to 60°C for a predetermined set time, and a blue killing treatment means for inactivating the oxidizing enzymes in the tea leaves treated by the low-temperature treatment means.

2. The device for increasing the GABA content of tea leaves as described in claim 1, characterized in that the low-temperature treatment means is provided with a first static treatment means for maintaining the treatment temperature of tea leaves treated by the first low-temperature steam treatment means or the first low-temperature water soaking treatment means at a second temperature lower than the first temperature.

3. The device for increasing the GABA content of tea leaves as described in claim 2, characterized in that the low-temperature treatment means further comprises a second low-temperature steam treatment means or a second low-temperature water immersion treatment means for maintaining the treatment temperature of the tea leaves treated by the first static treatment means at a third temperature higher than the first temperature.

4. The device for increasing the GABA content of tea leaves as described in claim 3, characterized in that the low-temperature treatment means is configured to perform the second low-temperature steam treatment or the second low-temperature water soaking treatment at the third temperature in the range of 47 to 58°C.

5. An apparatus for increasing the GABA content of tea leaves as described in claim 3, further comprising a second static treatment means for maintaining the treatment temperature of tea leaves treated by the second low-temperature steam treatment means or the second low-temperature water soaking treatment means at a fourth temperature higher than the second temperature.

6. The device for increasing the GABA content of tea leaves as described in claim 2, characterized in that the low-temperature treatment means is configured to repeat the low-temperature steam treatment or the low-temperature water immersion treatment by the first low-temperature steam treatment means or the first low-temperature water immersion treatment means and the static treatment by the first static treatment means multiple times.

7. The device for increasing the GABA content of tea leaves as described in claim 1, characterized in that the low-temperature treatment means is configured to perform the first low-temperature steam treatment or the first low-temperature water soaking treatment at the first temperature in the range of 47 to 58°C.

8. An apparatus for increasing the GABA content of tea leaves as described in claim 1, characterized in that the low-temperature treatment means is configured to perform low-temperature treatment on tea leaves on a horizontal moving mechanism that transports tea leaves horizontally.

9. A method for increasing the GABA content of tea leaves, comprising carrying out a first low-temperature steam treatment or a first low-temperature water immersion treatment in which the treatment temperature of the surface of the tea leaves is maintained at a first temperature in the range of 40 to 60°C for a predetermined set time, and then carrying out a blue killing treatment by inactivating the oxidizing enzymes in the low-temperature treated tea leaves.

10. A method for increasing the GABA content of tea leaves as described in claim 9, characterized in that the low-temperature treatment comprises a first static treatment in which the treatment temperature of tea leaves that have undergone the first low-temperature steam treatment or the first low-temperature water soaking treatment is maintained at a second temperature lower than the first temperature.

11. A method for increasing the GABA content of tea leaves as described in claim 10, characterized in that the low-temperature treatment comprises a second low-temperature steam treatment or a second low-temperature water immersion treatment, which maintains the treatment temperature of the tea leaves that have undergone the first static treatment at a third temperature higher than the first temperature.

12. A method for increasing the GABA content of tea leaves as described in claim 11, characterized in that the second low-temperature steam treatment or the second low-temperature water soaking treatment is carried out at the third temperature in the range of 47 to 58°C.

13. A method for increasing the GABA content of tea leaves as described in claim 11, characterized in that a second static treatment is performed on the tea leaves that have undergone the second low-temperature steam treatment or the second low-temperature water soaking treatment, maintaining the treatment temperature at a fourth temperature that is higher than the second temperature.

14. A method for increasing the GABA content of tea leaves as described in claim 10, characterized in that the first low-temperature steam treatment or the first low-temperature water soaking treatment and the first standing treatment are repeated multiple times.

15. A method for increasing the GABA content of tea leaves as described in claim 9, characterized in that the first low-temperature steam treatment or the first low-temperature water soaking treatment is carried out at the first temperature in the range of 47 to 58°C.

16. The method for increasing the GABA content of tea leaves according to claim 9, wherein the low-temperature treatment is performed while the tea leaves are transported horizontally.

17. A method for producing GABA tea, comprising a low-temperature treatment step including a first low-temperature steam treatment step or a first low-temperature water immersion treatment step in which the treatment temperature of the surface of the tea leaves is maintained at a first temperature in the range of 40 to 60°C for a predetermined set time, and a blue killing treatment step in which the oxidizing enzymes in the tea leaves treated by the low-temperature treatment step are inactivated.

18. A method for producing GABA tea as described in claim 17, characterized in that the low-temperature treatment process includes a first static treatment process in which the treatment temperature for tea leaves treated by the first low-temperature steam treatment process or the first low-temperature water soaking treatment process is maintained at a second temperature lower than the first temperature.

19. A method for producing GABA tea as described in claim 18, characterized in that the low-temperature treatment process further includes a second low-temperature steam treatment process or a second low-temperature water soaking treatment process, which maintains the treatment temperature of the tea leaves treated by the first still-standing treatment process at a third temperature higher than the first temperature.

20. A method for producing GABA tea as described in claim 19, characterized in that the low-temperature treatment process is configured to perform the second low-temperature steam treatment process or the second low-temperature water soaking treatment process at the third temperature in the range of 47 to 58°C.

21. A method for producing GABA tea as described in claim 19, further comprising a second static treatment step of maintaining the treatment temperature of the tea leaves treated by the second low-temperature steam treatment step or the second low-temperature water soaking treatment step at a fourth temperature higher than the second temperature.

22. A method for producing GABA tea as described in claim 18, characterized in that the low-temperature treatment process is configured to repeat the first low-temperature steam treatment process or the first low-temperature water soaking treatment process and the first stationary treatment process multiple times.

23. A method for producing GABA tea as described in claim 17, characterized in that the low-temperature treatment process is configured to perform the first low-temperature steam treatment process or the first low-temperature water soaking treatment process at the first temperature in the range of 47 to 58°C.

24. A method for producing GABA tea as described in claim 17, characterized in that the low-temperature treatment step is a step in which the low-temperature treatment is performed while the tea leaves are transported horizontally.

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