JPWO2011049131A1 - Tea flavor improvement method - Google Patents

Abstract

The present invention is a method capable of reducing the astringency and bitterness of tea leaves and enhancing the taste and sweetness by a simple technique, and irradiates fresh tea leaves with visible light having a peak wavelength at 380 to 560 nm. I did it.

Description

  The present invention relates to a method capable of reducing the astringency and bitterness of tea leaves and enhancing the taste and sweetness by a simple method.

  Conventionally, it is known that the state of irradiation of sunlight on tea leaves affects the flavor of tea. This is because theanine, which is a component related to tea taste and sweetness, is changed to catechin, a component related to astringency and bitterness, by irradiation with sunlight. That is, theanine, the central component of amino acids involved in umami and sweetness, is synthesized at the root of tea tree and transferred to the leaves, but when theanine is exposed to light, it decomposes to produce ethylamine, and catechin is synthesized from the ethylamine. The

  For this reason, in gyokuro, known as high-quality sencha, the tea leaves used as a raw material are covered with sunlight for a minimum of about two weeks before harvesting. Thus, tea leaves grown by blocking sunlight are rich in umami and sweetness, and less astringent and bitter. In addition, it is known that Ichibancha has a lower catechin content and a higher theanine content than Nibancha.

  Even after tea leaves have been picked, the catechin content increases when exposed to sunlight, so in order not to increase astringency and bitterness (to reduce umami and sweetness), tea leaves after picking are also included. It is necessary to shield the light.

  By the way, various attempts have recently been made to improve the flavor of tea using light. For example, in Patent Document 1, ultraviolet rays are irradiated before tea leaves are steamed to wilt fresh tea leaves. A technique for improving the scent is disclosed.

Japanese Patent Laid-Open No. 11-106

  Therefore, the present invention is intended to provide a method capable of reducing the astringency and bitterness of tea leaves and enhancing the taste and sweetness by a simple method.

  As a result of diligent study, the present inventor found that the astringency of tea leaves by irradiating light of a specific wavelength, contrary to the conventional knowledge that astringency / bitterness increases and umami / sweetness decreases when light is applied to tea leaves. -While reducing bitterness, it succeeded in increasing umami and sweetness, and came to complete this invention based on this knowledge.

  That is, the tea flavor improving method according to the present invention includes a step of irradiating fresh tea leaves with visible light having a peak wavelength of 380 to 560 nm. This light irradiation step can reduce the astringency and bitterness of tea leaves and / or increase the taste and sweetness. The tea flavor improving method according to the present invention may be used to reduce the astringency and bitterness of tea leaves, may be used to increase the umami and sweetness of tea leaves, It may be used to reduce bitterness and at the same time increase umami and sweetness.

  The fresh tea leaves are preferably just after picking.

  Examples of visible light having a peak wavelength at 380 to 560 nm include blue light and green light.

  The irradiation time of visible light having a peak wavelength at 380 to 560 nm is preferably 6 hours or less.

  A method for producing tea, which comprises a step of irradiating fresh tea leaves with visible light having a peak wavelength of 380 to 560 nm, is also one aspect of the present invention.

  A light irradiation apparatus that is used in these tea flavor improving methods and tea manufacturing methods and includes a light source capable of irradiating visible light having a peak wavelength of 380 to 560 nm is also included in the present invention. One.

  According to the present invention having such a configuration, tea leaves after picking can be easily subjected to light irradiation treatment for a short period of time without being subjected to light-shielding treatment for a long period of time. Can reduce astringency and bitterness, and increase taste and sweetness.

The typical block diagram which shows the light irradiation apparatus which concerns on one Embodiment of this invention. The top view which shows the light irradiation part in the embodiment. The equipment block diagram of the information processing apparatus in the embodiment. The chart which shows the spectrum of each irradiation light in the conditions 2 and 3 of Experiment 1 (LED light irradiation experiment). The graph which shows the result of the taste test of Experiment 1 (LED light irradiation experiment). The chart which shows the spectrum of each irradiation light in Experiment 2 (sunlight irradiation experiment). The graph which shows the analysis result about EGCG (a) and ECG (b) in Experiment 3 (Astringency / bitter component analysis). The graph which shows the analysis result about EGC (a) and EC (b) in Experiment 3 (Astringency / bitter component analysis). The graph which shows the analysis result about caffeine (a) and total catechin (b) in Experiment 3 (Astringency / bitter component analysis). The graph which shows the analysis result of various free amino acids in Experiment 4 (umami / sweetness component analysis).

  The present invention is described in detail below.

  The present invention is a method for improving the flavor of tea. The tea leaf used in the present invention is not particularly limited as long as it is a leaf collected from chanoki, which is an evergreen tree of the camellia camellia family, and various varieties can be used.

  The method for improving the flavor of tea according to the present invention comprises a light irradiation step of irradiating fresh tea leaves with visible light having a peak wavelength of 380 to 560 nm. Examples of visible light having a peak wavelength at 380 to 560 nm include violet light, blue light, and green light. Among them, blue light having a peak wavelength in a wavelength region of about 430 to 490 nm, and 490 When green light having a peak wavelength in a wavelength region of about 550 nm is irradiated, the effect of reducing the astringency / bitterness of tea leaves and increasing the taste / sweetness is remarkably observed. Catechin (especially astringency) and caffeine (especially bitterness) are mentioned as such components involved in astringency / bitterness, and amino acids such as theanine are exemplified as components involved in umami / sweetness.

  In the tea flavor improving method according to the present invention, it is preferable that the fresh tea leaves to be irradiated with light are those immediately after picking. The term “immediately after picking” refers to within about 12 hours after the fresh tea leaves are picked from the tea tree. This is because fresh tea leaves tend to increase astringency and bitterness as time elapses (paste and sweetness tend to decrease).

The light intensity of visible light having a peak wavelength at 380 to 560 nm is not particularly limited, and can be appropriately selected within the range of 0.5 to 800 μmol ⁻² s ⁻¹ , but an LED is used as a light source. When doing, it is preferable that it is 0.5-2micromol ^- 2s ^{- 1} , for example, More preferably, it is 1-1.5micromol ^- 2s ^{- 1} . If it is less than 0.5μmolm ^-2 s ^-1, the light intensity is insufficient, but may not be seen sufficient flavor-improving effect, even beyond 2μmolm ^-2 s ^-1, the further effect There is no improvement.

  Moreover, although it does not specifically limit as a light source of the visible light which has a peak wavelength in said 380-560 nm, LED is used suitably. Since the wavelength of the light emitted from the LED is determined by the band gap of the semiconductor, a desired single color can be obtained. However, the light source used in the present invention is not limited to an LED as long as it can irradiate visible light having a peak wavelength at 380 to 560 nm. For example, it selectively transmits visible light at 380 to 560 nm. You may comprise so that sunlight may be irradiated to a fresh tea leaf via a cut sheet. In the present invention, visible light having a peak wavelength of 380 to 560 nm may be irradiated alone, but other light is used in combination or other as long as the effect of reducing astringency and bitterness is not hindered. Light may be mixed.

  The irradiation time of visible light having a peak wavelength at 380 to 560 nm is preferably 6 hours or less, more preferably 2 to 4 hours. Exceeding 6 hours may increase astringency and bitterness and decrease umami and sweetness.

  In such a light irradiation process, for example, a light irradiation apparatus including a blue LED and / or a green LED as a light source and means for adjusting the light intensity is used. Thus, such a light irradiation apparatus used in the light irradiation step is also one aspect of the present invention.

  One embodiment of a light irradiation apparatus according to the present invention is illustrated in FIG.

  The light irradiation apparatus 1 illustrated in FIG. 1 includes a light emitting unit 2 that emits light, and a power supply unit 3 that supplies power so that the intensity of the light emitted to the light emitting unit 2 can be changed. Furthermore, in order to perform finer control, a determination unit 4 and a light irradiation condition setting unit 5 are provided.

  Each part will be described in detail. As shown in FIG. 2, the light emitting unit 2 is configured by laying a large number of blue LEDs and / or green LEDs 21 on one surface of a flat substrate 22, and the LED 21 is, for example, a bullet type.

  The power supply unit 3 supplies power so that the emission intensity can be changed independently for each LED 21.

  The discriminating unit 4 discriminates, for example, the type and state of the tea leaf 6 that is the light irradiation target, based on an input by an operator.

  The light irradiation condition setting unit 5 generates an external control signal for setting the light emission intensity and the irradiation time according to the type and state of the tea leaf 6 and transmits the external control signal to the power supply unit 3. is there. Specifically, for example, the control signal specifying data storage unit D1 storing a pair of an identifier indicating the type / status of the tea leaf 6 and the identifier of the external control signal is accessed, and the type / status, etc. of the tea leaf 6 is accessed. A corresponding external control signal is specified, and the external control signal is transmitted to the power supply unit 3.

  In addition, the determination unit 4, the light irradiation condition setting unit 5, and the control signal specifying data storage unit D1 are configured using the information processing apparatus 7 in the present embodiment. As shown in FIG. 3, for example, the information processing apparatus 7 includes a CPU 101, an internal memory 102, an external storage device 103 such as an HDD, a communication interface 104 such as a modem, a display 105, an input means 106 such as a mouse and a keyboard, and the like. . Then, the CPU 101 and its peripheral devices are operated according to a program set in a predetermined area such as the internal memory 102 or the external storage device 103, whereby the determination unit 4, the light irradiation condition setting unit 5, and the control signal specifying data storage unit D1. Is configured to function as The information processing apparatus 7 may be a general-purpose computer or a dedicated computer.

  Thus, by irradiating the raw tea leaves with visible light having a specific wavelength, the astringency and bitterness of the tea leaves can be reduced, and the umami and sweetness can be enhanced. Further, by freezing and storing fresh tea leaves subjected to the light irradiation treatment, it is possible to maintain a state in which astringency and bitterness are reduced and umami and sweetness are increased.

  The method for producing tea provided with the light irradiation step described above is also one aspect of the present invention. When tea is produced using the light irradiation step, a tea with less astringency and bitterness and strong umami and sweetness can be obtained. The kind of tea manufactured using the manufacturing method of the tea which concerns on this invention is not specifically limited, For example, green tea, black tea, oolong tea, etc. are mentioned.

  For example, when the manufacturing method according to the present invention is a method for manufacturing sencha, which is a general green tea, each of the general sencha manufacturing processes can be used as a process other than the light irradiation process. For example, (1) steamed and heated (steamed heat), (2) stirred and pressed tea leaves in hot air, dried uniformly (coarse), and (3) wilted. It moves circularly while applying weight to the softened tea leaves and breaks them evenly, destroying the tea leaf tissue to make the fermentation uniform (twisting), and (4) proceeding with drying while gently rubbing the tea leaves, making the tea leaves thinner and thinner ( The middle step), (5) The tea leaves are gradually dried on a heated platen, shaped into a unique shape of Sencha (spinning), and (6) dried. Even in the case where the production method according to the present invention produces other types of tea, as the steps other than the light irradiation step, each production step common to that type of tea can be used.

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples.

<Experiment 1> LED Light Irradiation Experiment With the introduction of Shizuoka Prefectural Chuto Agricultural and Forestry Office, Yabuki was cultivated by the Hakuba Tea Farming Cooperative, Shuchi-gun, Shizuoka Prefecture, and grew as it was without harvesting the most tea. Was harvested in the morning (around 9-11am) with 1 core and 2 leaves. The leaves were packed in a plastic bag, transferred at room temperature, stored in a refrigerator (dark place) for several hours, and then used for this experiment. In addition, since this experiment started from 16:00, about 5 to 7 hours passed from harvesting to the start of the experiment.

  The contents of this experiment are as follows. About 10 tea leaves were placed on a 545 mL transparent plastic cup, the cup was sealed with polyethylene wrap, and stored in a simple integrating sphere-like box with a white inner surface under each light irradiation condition.

The light irradiation conditions in this experiment are as follows.
Condition 1: Dark condition 2: Green light (peak wavelength 522 nm) irradiation condition 3: Blue light (peak wavelength 470 nm) LED is used as the light source in irradiation conditions 2 and 3, and the intensity of each irradiation light is about 1 μmol ⁻² It was set as s- ¹ . In addition, the spectrum (vertical axis is light intensity) of each irradiation light in conditions 2 and 3 was shown to Fig.4 (a) and (b).

  As the storage time (light irradiation time) in the simple integrating sphere-like box, seven times of 0, 2, 4, 8, 17, 26, and 48 hours are set, and each time the set time elapses. Three tea leaves were taken out, taste-tested (sensory test), and then stored frozen. In the taste test, the astringency / bitterness was evaluated by a numerical value of 0 to 5, and the higher the astringency / bitterness, the higher the evaluation.

  This experiment was performed at room temperature (RT: 21 ° C.) and 4 ° C. In addition, about 30 minutes before the start of the experiment, a sample with a light irradiation time of 0 hour for use as a control was stored frozen at about -25 ° C. The experimental results are shown in Table 1 and FIGS. 5 (a) and 5 (b). In addition, the vertical axis | shaft of FIG. 5 shows astringency and bitterness.

  As a result of this experiment, when the experiment was carried out at room temperature, a phenomenon in which the astringency and bitterness of tea leaves decreased was observed when irradiated with blue light or green light for 2 to 4 hours. However, it was confirmed that, even when blue light or green light was irradiated, if the light irradiation time was 8 hours or more, astringency and bitterness increased. Moreover, it was confirmed that the flavor improving effect of tea leaves by light irradiation for a short time of 2 to 4 hours is more markedly expressed at room temperature than at 4 ° C.

<Experiment 2> Sunlight irradiation experiment Tea leaves (Yabukita) from Kurematsu-cho, Nishi-ku, Hamamatsu City were collected at around 10:30 on the day of the experiment, and then exposed to sunlight under various conditions from 11:30 to 14:00. Left alone. In addition, the temperature at the time of tea leaf collection was 30 degreeC.

  As the sample 1, a tea leaf left as it was under sunlight was used.

  Sample 2 was a tea leaf wrapped in a blue filter and left under sunlight. The spectrum of the irradiation light to each sample (the vertical axis indicates the light intensity) is shown in FIGS. In addition, from these spectrum charts, it can be seen that the sunlight by the blue filter dimming is a mixed color light of blue, green, and long wavelength red with 560 to 690 nm cut.

  After leaving it under sunlight, a taste test (sensory test) was performed. In the taste test, the astringency / bitterness was evaluated by a numerical value of 0 to 5, and the higher the astringency / bitterness, the higher the evaluation. The experimental results are shown in Table 2.

本実験の結果、太陽光由来の青色光及び緑色光にも渋み・苦みの低減効果があることがわかった。なお、旨み・甘みの増強効果は確認されなかった。また、本実験より、長波長側の赤色光の混入によっては、渋み・苦みの低減効果が阻害されないことが分かった。

As a result of this experiment, it was found that blue light and green light derived from sunlight also have an effect of reducing astringency and bitterness. In addition, the enhancement effect of umami and sweetness was not confirmed. In addition, from this experiment, it was found that mixing of red light on the long wavelength side does not inhibit the astringency / bitterness reduction effect.

<Experiment 3> Analysis of bitterness and bitterness components "Yabukita" second tea was plucked in a thin field in Morimachi, Shuchi-gun, Shizuoka Prefecture, and 250 g of fresh tea leaves one hour after plucking were stored in a light irradiation apparatus as samples. As the light irradiation device, an LED mounted on the ceiling surface of a box of about 40 cm cubic was used, and the storage (light irradiation) conditions were as follows.

[Storage (light irradiation) conditions]
Dark: Storage in dark place Blue: Storage under blue light irradiation (peak wavelength: 470 nm, light irradiation intensity: about ¹ μmolm ⁻² s ⁻¹ )
Storage temperature: Room temperature (about 26.5 ° C)
Storage (light irradiation) time: 0, 2, 4, 24 hours

  The sample was stored in the light irradiation device for a predetermined time while stirring every 30 minutes so that light was evenly irradiated to the whole tea leaf, and then the sample was taken out 50 g at a time, and a sensory test was performed on each sample. . In the sensory test, as in Experiment 1, a result that astringency and bitterness decreased in the sample irradiated with blue light for 2 to 4 hours was obtained (data not shown). Next, the sample was blanched in a microwave oven and then dried with hot air for about 2 hours. The sample was deaerated and stored frozen at about -21 ° C.

The sample stored frozen was crushed immediately before analysis and extracted with 50% acetonitrile. And using the obtained extract, quantification was performed about catechins and caffeine by HPLC. The experimental results are shown in Tables 3 and 4 and FIGS. In addition, the abbreviation in each table | surface and figure shows the following compounds, respectively.
EGCG: epigallocatechin gallate ECG: epicatechin gallate EGC: epigallocatechin EC: epicatechin

  From the analysis results obtained, it was confirmed that ester-type catechins (EGCG, ECG) involved in astringency in green tea tend to decrease by blue light irradiation for several hours. On the other hand, it was confirmed that free catechin (EGC, EC) changes with time regardless of the presence or absence of blue light irradiation. In addition, it was confirmed that the total catechin amount also decreased in a few hours after the start of blue light irradiation, like the ester-type catechin having a high content. On the other hand, it was confirmed that the content of caffeine, which is a bitter component of green tea, also tends to decrease due to the blue light irradiation for several hours, like the ester type catechin. From these results, it was found that the trend of decreasing the astringency and bitterness of fresh tea leaves over time due to the blue light irradiation observed in the sensory test was due to the reduction of the astringency and bitterness components in the fresh tea leaves.

<Experiment 4> Umami / Sweet Component Analysis “Yabukita” second tea was plucked in a thin field in Mori Town, Shuchi-gun, Shizuoka Prefecture, and about 60 kg of fresh tea leaves were stored in a light irradiation apparatus as a sample. As the light irradiation device, the same one as in Experiment 3 was used, and the storage (light irradiation) conditions were the same as those in Experiment 3 except that the storage (light irradiation) time was set at 0 and 2.5 hours. It was.

  The sample was stored in the light irradiation device for a predetermined time while stirring every 30 minutes so that the entire tea leaf was evenly irradiated with light, and then the sample was processed with a tea machine. The resulting crude tea was dried with hot air for about 1 hour, then degassed and stored frozen at about -21 ° C. Samples stored frozen were crushed immediately before analysis and extracted, and 6 kinds of free amino acids were quantified by HPLC using the resulting extract. The experimental results are shown in Table 5 and FIG.

  From the analysis results obtained, it was confirmed that theanine, which is considered to be involved in the taste and sweetness of green tea, was significantly increased by blue light irradiation. In addition, aspartic acid and glutamine tended to increase slightly. On the other hand, it was confirmed that serine decreases by 30% or more by blue light irradiation. From these results, it was confirmed that the umami and sweetness components increased in tea leaves after tea making by irradiating fresh tea leaves with blue light.

  According to the present invention, tea leaf astringency and bitterness can be reduced and umami and sweetness can be increased by a simple method, so that tea with higher commercial value can be easily produced.

DESCRIPTION OF SYMBOLS 1 ... Light irradiation apparatus 2 ... Light emission part 21 ... LED
DESCRIPTION OF SYMBOLS 3 ... Electric power supply part 4 ... Discrimination part 5 ... Light irradiation condition setting part 6 ... Tea leaf

Claims (6)

  A method for improving the flavor of tea by irradiating fresh tea leaves with visible light having a peak wavelength of 380 to 560 nm to reduce the astringency and bitterness of tea leaves and / or increase the taste and sweetness.   The method for improving the flavor of tea according to claim 1, wherein the fresh tea leaves are just after picking.   The method for improving the flavor of tea according to claim 1, wherein the visible light having a peak wavelength at 380 to 560 nm is blue light or green light.   The method for improving the flavor of tea according to claim 1, wherein the irradiation time of visible light having a peak wavelength at 380 to 560 nm is 6 hours or less.   A method for producing tea, comprising a step of irradiating a raw tea leaf with visible light having a peak wavelength of 380 to 560 nm. It is used for the method according to claim 1,
A light irradiation apparatus comprising a light source capable of irradiating visible light having a peak wavelength of 380 to 560 nm.

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