JP2016182115A - Flavor improvement method of tea leaf with reduced caffeine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tea leaf high in palatability having tea original flavor while sufficiently reducing caffeine, and a manufacturing method of the same.SOLUTION: There is provided a manufacturing method of low caffeine tea leaf by conducting a firing treatment on a tea leaf extraction treated by supercritical carbon dioxide. There is provided a manufacturing method of low caffeine tea leaf with tea leaf temperature during the firing treatment of 130°C or more in the case of green tea leaf and 110°C to 130°C in the case of black tea leaf. There is provided a tea leaf having caffeine content of 0.5% or less and a ratio of peak area total when analyzed by a gas chromatograph mass spectrometry (GC/MS analysis method) for (A) a firing aroma component (2,5-dimethyl pyrazine or the like), (B) a green smell component (n-hexanal or the like) and (C) an oil smell component (1-pentene-3-ol or the like) of [(A)/(B)] of 3.0 or more and [(A)/(C)] of 1.5 or more.SELECTED DRAWING: None

Description

  The present invention relates to a method for improving the flavor of tea leaves treated with supercritical carbon dioxide, and more particularly to a method for removing the off-flavor that occurs when caffeine is reduced by supercritical carbon dioxide extraction and giving a good flavor. The present invention relates to a tea leaf having a good flavor while caffeine is sufficiently reduced, and a method for producing the tea leaf.

  Caffeine contained in teas such as green tea, black tea, oolong tea and the like has physiological effects such as arousal and diuretic effects, but excessive intake is thought to cause adverse effects such as nausea, insomnia, and increased heartbeat. . Therefore, methods for removing caffeine from tea leaves have been studied conventionally. Methods for removing caffeine include a method of immersing fresh leaves in hot water during the production of crude tea (Patent Document 1), a method of extracting and removing with supercritical carbon dioxide (Patent Document 2), and the like. Proposed.

JP 7-135902 A JP-A-1-289448

  Regarding the method of removing caffeine from tea, several methods as described above are disclosed. However, these methods have at least the following drawbacks. For example, in the method of immersing fresh leaves of Patent Document 1 in hot water and leaching caffeine, loss of useful components such as catechin, which is a component of astringency, and amino acid, a component of umami, occurs with caffeine. The caffeine removal efficiency was not sufficient. On the other hand, the method of extracting and removing caffeine with supercritical carbon dioxide has little loss of the useful components, and can be said to be a very excellent means in terms of selective caffeine removal. However, this method has a problem that a volatile aromatic component is lost together with caffeine.

  When drinking tea, a flavor that is formed by integrating the three elements of astringency, umami, and aroma inherent in tea leaves in a well-balanced manner is preferable. Therefore, the loss of the components related to the three elements described above causes a decrease in palatability even if caffeine is sufficiently reduced. For these reasons, there has been a strong demand for means for providing tea leaves that can enjoy the original flavor while caffeine is sufficiently reduced. Accordingly, an object of the present invention is to provide a highly-preferred tea leaf having a natural tea flavor and a method for producing the same while sufficiently reducing caffeine.

  The present inventors examined the cause of reducing the preference of tea leaves that have been reduced in caffeine by supercritical carbon dioxide extraction, which has an excellent caffeine removal effect, and have been reduced in caffeine by supercritical carbon dioxide extraction. The tea leaves not only have aroma components lost compared to the untreated tea leaves, but also have characteristic off-flavors such as raw smell, metal-like odor (golden odor) and unnatural acidity. It was recognized that these were the cause of the combined decrease in palatability. Then, the means for removing the off-flavor and odor present in the tea leaves treated with supercritical carbon dioxide was intensively studied. As a result, it was possible not only to remove the characteristic off-flavor by smelling the tea leaves above a certain condition, but also to restore the original aroma of tea to an acceptable level, thereby enhancing the palatability. As a result, the present invention was completed.

  That is, the tea leaves of the present invention are obtained by a production method characterized in that after the caffeine is reduced by extracting the raw tea leaves by supercritical carbon dioxide extraction, a burning treatment is performed. In addition, the method of the present invention is characterized in that the off-flavor and odor peculiar to tea leaves in which caffeine is reduced using supercritical carbon dioxide is removed by a burning treatment. The method of the present invention differs in the order of the low caffeine treatment and the firing treatment as compared with the conventional method for producing low caffeine tea using supercritical carbon dioxide. Specifically, in the conventional low-caffeine tea manufacturing method, tea leaves that have been baked or tea leaves that have been baked to a dry degree were extracted and removed with supercritical carbon dioxide as the final product. On the other hand, in the production method of the present invention, after the extraction process with supercritical carbon dioxide, a flame treatment is performed. This order has an important meaning in the action of removing off-flavors and odors, which is an effect of the present invention. Moreover, it differs from a general tea leaf production method in the presence or absence of a low caffeine treatment.

  According to the production method of the present invention, it is possible to provide tea leaves having the original flavor of tea while sufficiently reducing caffeine.

Hereinafter, the present invention will be described in detail.
The tea leaf raw material in the production method of the present invention is a tea leaf manufactured from picked products such as leaves and stems of tea tree (scientific name: Camellia sinensis), and is not only a primary processed product called rough tea but also called finished tea Secondary processed products can also be used. Examples of tea leaves include non-fermented tea such as green tea and flower tea, semi-fermented tea such as oolong tea, fully fermented tea such as black tea, and rough and finished tea such as post-fermented tea such as puer tea. Any of the tea leaves that are generally available can be used in the production method of the present invention.

  In the production method of the present invention, the tea leaf material is extracted with supercritical carbon dioxide, and after caffeine is reduced, it is subjected to a burning treatment. The supercritical carbon dioxide treatment may be performed by a known method. For example, caffeine can be suitably reduced from tea leaves according to the conditions described in Patent Document 1 and the like. Such tea leaves can be obtained from the market by those skilled in the art, or can be obtained by consignment processing to a specialized manufacturer.

  A specific treatment method for reducing caffeine with supercritical carbon dioxide will be described. First, dry tea leaf raw material is charged into an extraction container, and carbon dioxide brought into a supercritical state by adjusting temperature and pressure is introduced therein. At this time, water and lower alcohol are added as extraction aids. The lower alcohol used is preferably ethanol from the viewpoint of safety. In addition to adding water to carbon dioxide, water may be added in advance to the extraction raw material so that the raw tea leaves are moistened. The supercritical carbon dioxide that has passed through the extraction vessel is temperature-adjusted and then sent to a separation device, where it is separated into an extract containing caffeine and carbon dioxide. The separated extract is discharged, and carbon dioxide is liquefied again by temperature control and circulated while being reused, and is continuously processed until the desired caffeine content is obtained. Finally, by collecting the extraction residue from the extraction container, tea leaves with reduced caffeine can be obtained. According to this method, caffeine contained in general tea leaves in an amount of about 2 to 3% on a dry weight basis can be reduced to about 0.001 to 0.5%. On the other hand, since the caffeine content of tea leaves treated by the method of leaching caffeine by immersing fresh tea leaves in hot water remains at about 0.5 to 0.7%, the supercritical carbon dioxide treatment method is effective against caffeine removal. It is a very effective means. In the present invention, tea leaves in which caffeine is reduced with liquid carbon dioxide at a supercritical temperature or lower are also treated synonymously in the present invention.

In the production method of the present invention, a low caffeine tea leaf obtained by the above operation is subjected to a burning treatment. In addition to hot air type and rotary drum type machines, microwave irradiation equipment and far-infrared radiation equipment can be used on the conveyor belt and in the hot air type and rotary drum type machines. There are those provided together, and any of these can be used in the production method of the present invention.
As the hot air type flame retardant, a dryer such as a batch type shelf type dryer or a continuous type automatic dryer can be used, and both of them can supply hot air into the drying chamber to heat the tea leaves. In an automatic dryer, a transfer zone carrying tea leaves is moved into a drying chamber to which hot air is sent and subjected to a burning treatment. In this apparatus, it can process continuously by setting the temperature and time according to the desired degree of burning.
The rotary drum firer puts tea leaves into a cylindrical drum, rotates the drum while heating from the outside of the lower part, and performs a burning process. There are two types of rotary drum-fired machines: a batch type and a continuous type. In the batch type, processing is performed for each unit of tea leaves. The continuous system has a spiral structure inside a long slanted drum. Tea leaves are introduced from one inlet, and when the drum is rotated, tea leaves gradually advance and tea leaves are discharged from the other outlet. Thus, by adjusting the amount of heat, the number of rotations of the drum, and the like, it is possible to obtain tea leaves having a desired degree of burning.

  The conditions at the time of firing depend on the moisture content of the raw tea leaves and the desired roasting degree, so it cannot be said unconditionally, but in the production method of the present invention, in order to remove off-flavors, in the case of green tea leaves At least the condition where the product temperature, that is, the tea leaf temperature reaches 130 ° C. is necessary. Below 130 ° C., the effect of removing the distinctive odors of raw odor and odor, and offensive sourness becomes insufficient. In addition, tea leaves tend to carbonize at temperatures above 200 ° C. For this reason, it is preferable that the firing process is terminated when the tea leaf temperature reaches 130 ° C. to 190 ° C. as the firing condition in the present invention. The end temperature of the firing may be adjusted so that a desired flavor is obtained within this range, but from the viewpoint of removing off-flavors and flavor balance, 140 ° C to 180 ° C is preferable, and 150 ° C to 170 ° C is further preferable. For example, in the case of a rotary drum type quencher, the heating power is set to a constant condition, and the treatment is performed for about 1 to 30 minutes until the temperature of the tea leaves reaches about 130 ° C to 190 ° C. Furthermore, in consideration of production efficiency and heating effect, the treatment time is preferably 2 minutes to 20 minutes, and preferably 5 minutes to 15 minutes. As a means for adjusting the degree of burning, the processing time and the reaching temperature can be set by adjusting the drum rotation speed, heating temperature, tea leaf supply speed, and the like.

  Even in the case of fermented tea leaves such as black tea and oolong tea, a nasty and unpleasant odor is produced when treated with supercritical carbon dioxide, as in the case of green tea leaves. These off-flavors and odors can be removed by burning as with green tea. The heating temperature may be terminated when the tea leaf temperature reaches at least 100 ° C, preferably 110 ° C to 130 ° C, more preferably 115 ° C to 120 ° C. The treatment time is preferably 2 to 20 minutes, and preferably 5 to 15 minutes, as with green tea leaves.

  In the method for producing tea leaves of the present invention, tea leaves may be selected as necessary. The selection of tea leaves is one of the purposes of adjusting the shape (size), and the quality is improved by separating coarse tea leaves, stems and powders. For the selection, a known means using a sieve, a wind power sorter, a color sorter, an electrostatic sorter or the like may be used. Examples of the sieve machine include a reciprocating-type parallel sieve machine, a rotary-motion type rotary sieve machine, and a vibrating sieve machine that vibrates perpendicularly to the mesh surface, which are selected or combined according to the purpose. In the production method of the present invention, when the shape is adjusted before the burning operation, the strength of the burning can be made constant, so that it becomes more effective for removing off-flavors. Moreover, you may control the shape of a tea leaf combining a cutting machine as needed.

  The caffeine content of the tea leaves obtained by the production method of the present invention is 0.001 to 0.5% on a dry weight basis. Processing conditions that reduce caffeine to 0.001% or less are not preferable because they cause loss of other flavor components. Moreover, if it exceeds 0.5%, the original purpose of reducing caffeine cannot be achieved. The caffeine content is preferably 0.001 to 0.2, and more preferably 0.005 to 0.1%. The caffeine content in tea leaves can be adjusted by appropriately adjusting the treatment conditions in the supercritical carbon dioxide treatment step. The value determined by the HPLC method is adopted as the caffeine content in tea leaves in the present invention. Detailed conditions are described in the Examples section herein. The tea polyphenol content of the tea leaves obtained by the production method of the present invention is preferably 10 to 25000 times, more preferably 25 to 4000 times, and further preferably 50 to 1000 times the caffeine content on a dry weight basis. is there. The analysis conditions for tea polyphenols are the iron tartrate absorptiometry described in the “5th edition: Japanese Food Standards Component Analysis Manual” (edited by the Japan Food Analysis Center, Central Regulations, July 2001). Detailed conditions are described in the Examples section herein.

  The tea leaves obtained by the production method of the present invention have a conventional low-caffeine tea leaf (supercritical carbon dioxide treated), in addition to the reduction of the golden odor that is the subject of the present invention. On the other hand, in the evaluation of green tea, there is a characteristic that “blue odor” and “oil odor”, which are subject to negative evaluation, are reduced. In the present invention, (A) incense incense component is 2,5-dimethylpyrazine, 2,6-dimethylpyrazine, ethylpyrazine, 2 2,3-dimethylpyrazine, trimethylpyrazine, 2-ethyl-3,5-dimethylpyrazine, furfral and 3 -Ethyl-3,6-dimethylpyrazine, (B) blue odor component is n-hexanal, (z) -4-heptenal ((z) -4-heptenal), green leaf alcohol ((Z) -3-hexen-1-ol), (EZ) -3,5-octadien-2-one ((EZ) -3,5-octadien-2-one) And (E, E) -3,5-octadien-2-one ((E, E) -3,5-octadien-2-one), (C) the oily odor component is 1-penten-3-ol (1-penten-3-ol), (E) -2-octenal ((E) -2-octenal), (E, Z) -2,4-heptadienal ((E, Z)- 2,4-heptadienal) and (E, E) -2,4-heptadienal ((E, E) -2,4-heptadienal), and tea leaves were analyzed by gas chromatography mass spectrometry (GC / MS analysis) The peak area of each fragrance component is analyzed and evaluated as a result of totalization for each group (A) to (C). In the tea leaves obtained by the production method of the present invention, (B) the ratio of (A) burning incense component to (B) blue odor component is [3.0 (A) / (B)] of 3.0 or more, and (C) to the oil odor component ( A) [(A) / (C)], which is the ratio of the incense components, is 1.5 or more. These ratios are preferably as large as possible in terms of flavor, preferably [(A) / (B)] is 5.0 or more, [(A) / (C)] is 2 or more, more preferably [(A) / (B )] Is 7.0 or more, and [(A) / (C)] is preferably 3.0 or more. The peak area of the aroma component in the tea leaves in the present invention employs a value obtained by gas chromatograph mass spectrometry (GC / MS analysis) using solid phase micro extraction (SPME). . Detailed conditions are described in the Examples section herein.

The tea leaves obtained by the production method of the present invention can be used for various purposes. For example, tea leaves can be packaged into various containers to make a product, and can also be used in the form of tea bags. Moreover, it can also be used as a raw material for instant tea and packaged tea beverages. Further, the powder may be pulverized to form a fine powder. Furthermore, plant raw materials other than tea, such as fruit skin and herbs, may be blended, or a fragrance may be imparted using a fragrance. However, the usage of the tea leaves obtained by the production method of the present invention is not limited to these.

  Examples The present invention will be described more specifically with reference to examples. However, the present invention is not limited to the examples.

<Test Example 1>
Implementation evaluation of the present invention was performed using green tea leaves (from Shizuoka Prefecture autumn / winter number, crude tea) as raw materials.
The tea leaves of Comparative Example 1 were not subjected to any treatment on the raw material. The tea leaves of Comparative Examples 2 and 3 were subjected to a quenching process using a small drum-type quencher. After the drum surface temperature was set to 230 ° C and heating started, 600g of tea leaves were added when the drum temperature reached 100 ° C, and the product temperature (tea leaf temperature) was removed when the temperature reached 160 ° C ( The treatment time was 7 minutes 43 seconds). The sample was taken out when the drum temperature reached 180 ° C. under the same conditions (treatment time 11 minutes 00 seconds) as Comparative Example 3. The tea leaves of Comparative Examples 4 to 6 were subjected to caffeine reduction treatment by supercritical carbon dioxide extraction of the tea leaves of Comparative Examples 1 to 3, respectively. The tea leaves of Examples 1 and 2 were obtained by subjecting the tea leaves of Comparative Example 4 subjected to low caffeine treatment with supercritical carbon dioxide to a fire treatment using a small drum-type quencher, under the same conditions as in Comparative Example 2. A sample that was subjected to a quenching treatment under the same conditions as in Example 1 and Comparative Example 3 was designated as Example 2.

The tea polyphenol content and caffeine content of the tea leaves of Comparative Examples 1 to 6 and Examples 1 and 2 obtained by the above operation were measured under the following conditions, and the results are shown in Table 1.
<Method for preparing tea polyphenol and caffeine measurement sample solution>
About 150 mg of tea leaves crushed by a food processor were weighed and transferred to a 100 mL volumetric flask, 40 mL of 80% methanol (v / v) was added, and ultrasonic extraction was performed for 30 minutes. Next, 0.4 mL of 1M hydrochloric acid was added and the volume was assumed to be ultra pure water. After leaving to return to room temperature, the volume was adjusted to 100 mL with ultra pure water. The extract was filtered with a hydrophilic PTFE filter (manufactured by Advantech Co., Ltd., DISMIC-13HP; 0.45 μm), and 2 mL or more of the filtrate was used as a measurement sample solution.
<Method for measuring tea polyphenol>
Tea polyphenols were quantified according to the iron tartrate absorptiometric method described on pages 252 to 254 of the “Explanation of the 5th edition, Japan Food Standards Component Analysis Manual” (edited by the Japan Food Analysis Center, Central Regulations, July 2001). In addition, ethyl gallate (manufactured by Tokyo Chemical Industry Co., Ltd.) was used as the standard substance for determination, and 32% methanol (v / v) added with 0.4% of 1M hydrochloric acid was used as the preparation solution. In the present invention, tea polyphenol is a polyphenol contained in tea, and is treated synonymously with terms such as tannin and tea tannin.
<Caffeine analysis conditions>
Caffeine was quantified by HPLC analysis under the following conditions.
Reference material: Caffeine (manufactured by Kanto Chemical Co., Inc.)
・ Device: Alliance HPLC system (manufactured by Waters)
・ Column: Poroshell 120 EC-C18 (4.6 × 100mm, particle size 2.7μm, manufactured by Agilent)
・ Column temperature: 40 ℃
-Mobile phase: A solution 0.05% phosphoric acid water / acetonitrile = 1000/25 (volume ratio), B solution methanol-Gradient program: 0 to 1 minute (B solution 0%), 1 to 11 minutes (B solution 0 to 33 %), 11-11.25 minutes (B solution 33-95%), 11.25-13.25 minutes (B95%), 13.25-13.5 minutes (B solution 95-0%), 13.5-15.5 minutes (B solution 0%)
・ Flow rate: 1.5mL / min
・ Detection: UV275nm

  Moreover, flavor evaluation was performed by four specialized panelists about the tea leaf leaching solutions of Comparative Examples 1 to 6 and Examples 1 and 2 obtained by the above operation. The leachate was prepared by pouring 150 ml of hot water into 3 grams of tea leaves, extracting for 3 minutes, and removing the tea leaves. Evaluation items include the presence and strength of raw odor and gold odor as off-flavour, the presence and strength of acidity as off-flavor, roasted incense obtained by incineration, overall flavor evaluation, and comprehensive evaluation including caffeine content Went. The results are shown in Table 1. The decaffeination in the table is a low caffeine treatment by supercritical carbon dioxide extraction.

Furthermore, the aromatic component was evaluated on the conditions shown below about the tea leaves of Comparative Examples 1-6 and Examples 1-2 obtained by the said operation. The results are shown in Table 2.
《Aroma component analysis method》
200 mg tea leaves and 3 g sodium chloride crushed with a food processor were placed in a 20 mL vial, and 10 mL water (cycloheptanol (manufactured by Tokyo Chemical Industry Co., Ltd.) as an internal standard substance was added to a final concentration of 500 ppb) was added. . This sample solution was subjected to GC / MS analysis using a solid phase micro extraction (SPME). Evaluation was determined by the ratio of the peak area of each aromatic component to the peak area of the internal standard substance.
<SPME-GC / MS conditions>
GC: TRACE GC ULTRA (manufactured by Thermo Fisher Scientific)
MS: TSQ QUANTUM XLS (manufactured by Thermo Fisher Scientific)
SPME fiber: 50 / 30μm Divinylbenzene / Carboxen / Polydimethylsiloxane Stableflex
Extraction: 60 ° C., 30 minutes Column: SUPELCO WAX10 (0.25 mm ID x 60 m x 0.25 μm, manufactured by Sigma-Aldrich)
Oven program: Hold at 40 ° C for 2 minutes, then heat up to 160 ° C at 3 ° C / minute, then heat up to 280 ° C at 10 ° C / minute Carrier gas: Helium (100 kPa, constant pressure)
Injector: Splitless, 240 ° C
Ionization: Electron ionization Ionization voltage: 70eV

  As shown in the results of Table 1, Comparative Examples 4 to 6 and Examples 1 and 2 that were subjected to caffeine reduction treatment were compared with Comparative Examples 1 to 3 that were not subjected to caffeine reduction treatment. It was confirmed that approximately 98% of caffeine was removed while maintaining the polyphenol content. Of these, for Comparative Examples 4 to 6, a strong smell and sour taste such as a fresh smell and a golden odor peculiar to the tea leaves subjected to supercritical carbon dioxide extraction were strongly felt, and a green tea-like scent and pre-burning treatment were performed. The roasting incense due to was extremely reduced, and the taste was low. On the other hand, for Examples 1 and 2 that were subjected to the quenching treatment after the caffeine reduction treatment, no off-flavor was felt as in Comparative Examples 4 to 6, and the roast imparted by the firing treatment was not observed. Senka also felt comfortable. Furthermore, in Examples 1 and 2, the blue odor peculiar to the autumn / winter bancha used as a raw material was also removed, and it was confirmed that the tea leaves had excellent palatability and very high palatability.

  As shown in the fragrance component analysis results in Table 2, in the tea leaves of Comparative Examples 5 and 6 where caffeine reduction treatment was performed after the firing treatment, (A) almost no inflamed components were detected, whereas the present invention In the tea leaves of Examples 1 and 2, the presence of the (A) incense incense component was observed at the same level as the tea leaves of Comparative Examples 2 and 3 that had been subjected to the quenching treatment without performing the low caffeine treatment. In addition, regarding (B) blue odor component and (C) oil odor component, which are negative factors in the evaluation of the flavor of green tea, the tea leaves of Examples 1 and 2 of the present invention are significantly reduced compared to the tea leaves of Comparative Examples 1 to 6. It has been confirmed. In addition, (B) blue odor component or (C) ratio of (A) flame scented component to oily odor, [(A) / (B)] and [(A) / (C)] have an effect of improving flavor. The tea leaves of Examples 1 and 2 were confirmed to have an excellent flavor balance even when compared with the tea leaves of Comparative Examples 2 and 3. The analytical values of these aroma components support the sensory evaluation results of the tea leaves of the present invention, and it was confirmed that the tea leaves of the present invention have an excellent flavor balance and high palatability.

<Test Example 2>
Next, a study was conducted on the firing temperature for the tea leaves subjected to the caffeine reduction treatment. The tea leaves of Comparative Example 4 prepared in Test Example 1 as raw materials, that is, tea leaves that have been caffeinated with supercritical carbon dioxide, are subjected to a flame treatment at various temperatures using a small drum-type flame retardant, and the effects are evaluated. did. In the firing process, the surface temperature of the drum was set to 230 ° C., and the tea leaves at each firing temperature (Comparative Example 7) were taken out when the product temperature (tea leaf temperature) reached the temperature shown in “Heating Temperature” in Table 3. ~ 8, Examples 4-8) were prepared. Caffeine quantification, flavor evaluation and comprehensive evaluation were carried out in the same manner as in Test Example 1, and the results are shown in Table 3.

  As shown in the results of Table 3, it was confirmed that the effect of removing the off-flavor peculiar to the tea leaves treated with caffeine reduction with supercritical carbon dioxide (tea leaves of Comparative Example 4) depends on the temperature of the firing. It was. Although a slight off-flavor odor reduction effect is observed at a firing temperature of less than 130 ° C, it is not acceptable as a flavor, and a treatment of 130 ° C or higher has effectively reduced or removed off-flavor odor. The firing temperature in the present invention was considered to be preferably 130 ° C. or higher.

<Test Example 3>
Using black tea leaves (Kenya black tea leaves) as raw materials, an implementation evaluation was performed on the firing temperature of the tea leaves subjected to the caffeine reduction treatment.
The tea leaves of Comparative Examples 9-12 and Examples 9-11 were each subjected to caffeine reduction treatment by supercritical carbon dioxide extraction. Next, a fire treatment was performed at each temperature with a small drum-type fire-fired machine, and the influence was evaluated. In the firing process, the surface temperature of the drum was set to 230 ° C., and the tea leaves at each firing temperature (Comparative Example 9) were taken out when the product temperature (tea leaf temperature) reached the temperature shown in “Heating Temperature” in Table 4. -12, Examples 9-11) were prepared. Caffeine quantification, flavor evaluation and comprehensive evaluation were carried out in the same manner as in Test Example 1, and the results are shown in Table 4.

  As shown in the results of Table 4, it is confirmed that the effect of removing the off-flavor peculiar to tea leaves treated with caffeine reduction with supercritical carbon dioxide is also dependent on the temperature of the firing, as is the case with green tea. It was. That is, it was evaluated that the burning odor of 110 ° C. to 130 ° C. effectively reduced the medicinal odor and taste, and at 120 ° C., it was evaluated as a good flavor with a slight roasted aroma.

  The tea leaves produced by the method of the present invention have a good flavor and are reduced in caffeine, while having a good flavor and a unique odor that is characteristic of tea leaves treated with supercritical carbon dioxide. Can be used widely.

Claims (7)

A method for producing low-caffeine tea leaves, which comprises subjecting tea leaves extracted with supercritical carbon dioxide to a firing process. The method for producing low caffeine tea leaves according to claim 1, wherein the tea leaf temperature is set to 130 ° C or higher in the case of green tea leaves and 110 ° C to 130 ° C in the case of black tea leaves. A method for removing off-flavors and odors, which comprises subjecting tea leaves extracted with supercritical carbon dioxide to a firing process. Tea leaves that have been cleaved with supercritical carbon dioxide and then fired. 5. The tea leaves according to claim 4, wherein the temperature of the tea leaves is set to 130 ° C. or higher for green tea leaves and 110 ° C. to 130 ° C. for black tea leaves. The caffeine content is 0.5% or less, and each of the following fragrance ingredient groups (A), (B) and (C):
(A) Incense incense component (2,5-dimethylpyrazine, 2,6-dimethylpyrazine, ethylpyrazine, 2,3-dimethylpyrazine, trimethylpyrazine, 2-ethyl-3,5-dimethylpyrazine, furfural and 3-ethyl -3,6-dimethylpyrazine),
(B) Blue odor component (n-hexanal, (z) -4-heptenal, green leaf alcohol, (EZ) -3,5-octadien-2-one and (E, E) -3,5-octadien-2-one ),
(C) About oily odor components (1-penten-3-ol, (E) -2-octenal, (E, Z) -2,4-heptadienal and (E, E) -2,4-heptadienal),
The ratio of the total peak area in each group when analyzed by gas chromatograph mass spectrometry (GC / MS analysis) is [(A) / (B)] of 3.0 or more and [(A) / (C)] Tea leaves that are over 1.5. The caffeine content is 0.5% or less, and each of the following fragrance ingredient groups (A), (B) and (C):
(A) Incense incense component (2,5-dimethylpyrazine, 2,6-dimethylpyrazine, ethylpyrazine, 2,3-dimethylpyrazine, trimethylpyrazine, 2-ethyl-3,5-dimethylpyrazine, furfural and 3-ethyl -3,6-dimethylpyrazine),
(B) Blue odor component (n-hexanal, (z) -4-heptenal, green leaf alcohol, (EZ) -3,5-octadien-2-one and (E, E) -3,5-octadien-2-one ),
(C) About oily odor components (1-penten-3-ol, (E) -2-octenal, (E, Z) -2,4-heptadienal and (E, E) -2,4-heptadienal),
The ratio of the total peak area in each group when analyzed by gas chromatograph mass spectrometry (GC / MS analysis) is [(A) / (B)] of 3.0 or more and [(A) / (C)] The tea leaves according to claim 4 or 5, wherein is at least 1.5.