The manufacturing method of flavored tea

Abstract

To provide a production method capable of retaining a flavor intrinsic to a fresh plant such as a fruit and a flower in dry tea leaves.SOLUTION: When producing flavored tea leaves in which the flavor of the fresh plant is transferred to the tea leaves, an aroma intrinsic to the fresh plant can be retained in the dried tea leaves by drying the flavored tea leaves under reduced pressure. In addition, by isolating the tea leaves and fresh plants in the same space so that they do not come into contact with each other during aromatization, the influence on the taste is suppressed, and the efficiency of aromatization is also improved by slightly reducing the pressure in the space.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing flavored tea. [Background technology]

[0002] Black tea, green tea, and other tea leaves obtained by processing the leaves and stems of the tea plant (scientific name: Camellia sinensis) are scented with spices and essential oils, or mixed with dried fruit and flower petals. These are called flavored teas, and are popular for their enhanced flavor value, which utilizes the mellow aroma of flowers and fruits in addition to the natural flavor of the tea leaves. Typical flavored teas include Earl Grey, which is made by scenting black tea leaves with essential oils of the citrus fruit bergamot and spices, and jasmine tea, which is made by infusing the scent of fresh jasmine flowers into green tea leaves.

[0003] In recent years, due to the growing health consciousness, artificial aroma compounds are being avoided in favor of natural aroma compounds, and there is also interest in the relaxing effects of natural aroma compounds, so flavored teas, in which natural aroma compounds are added to tea leaves, are attracting attention.

[0004] For example, jasmine tea is produced through the following steps: picking jasmine flowers, leaving them to stand, sorting the flowers, piling them into green tea, leaving them to stand, mixing, leaving them to stand, removing the flowers, and drying (see, for example, Non-Patent Document 1). In addition, when flavoring tea, such as Earl Grey, is flavored using a flavoring component, it is produced by applying a liquid flavoring component such as essential oil to raw tea leaves, followed by drying as necessary (see, for example, Patent Document 1 and Non-Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 09-233998 [Non-patent literature]

[0006] [Non-Patent Document 1] Shizuoka Prefectural Tea Research Institute Research Report, 1985, No. 11, pp. 47-62 [Non-patent document 2] Kochi Prefectural Industrial Technology Center Research Report, 2014, No. 45, pp.10-12 Summary of the Invention [Problem to be solved by the invention]

[0007] When flavoring tea using fresh plants, such as jasmine tea, the moisture contained in the fresh plants is absorbed by the tea leaves as the aroma transfers. Therefore, to ensure the shelf life of the flavored tea leaves, the leaves must be dried after flavoring. Tea leaves are typically dried by exposing them to hot air, but this process results in the loss of aroma components in the tea leaves. Therefore, in the case of jasmine tea, for example, the aroma-infusing and hot air drying processes are repeated multiple times to compensate for the loss of aroma, which requires a large amount of fresh jasmine flowers. Furthermore, the heat load during this process can alter not only the flavored aroma but also the original aroma of the tea leaves. Therefore, a method is needed to preserve the natural aroma of the dried tea leaves.

[0008] On the other hand, there are many commercially available products that mix dried fruits and flowers with tea leaves, but these dried products are obtained by hot air drying, which causes the loss and deterioration of the fresh aroma. Therefore, it is difficult to maintain the fresh aroma using this method. Furthermore, even when adding essential oils extracted from fresh fruits to tea leaves, the essential oils are extracted using methods that involve heating, such as steam distillation, which makes it easy for the aroma to deteriorate and makes it difficult to maintain the fresh aroma. On the other hand, when chemically synthesized flavorings are added to tea leaves, the aroma composition becomes artificial and does not meet the need for a natural aroma.

[0009] As described above, conventional methods for producing flavored tea are not fully satisfactory in terms of preserving the aroma of fresh fruits and flowers in dried tea leaves, and further improvements are strongly desired. Therefore, an object of the present invention is to provide a method for producing flavored tea that can preserve the aroma inherent in fresh plants such as fruits and flowers in dried tea leaves. [Means for solving the problem]

[0010] The present inventors have noticed that when hot air drying is used for the final drying step in the production of flavored tea, the aroma immediately after flavoring is lost or altered, and have conducted extensive research with the aim of solving this problem. As a result, they have discovered that drying flavored tea leaves under reduced pressure can sufficiently reduce the moisture content while maintaining the fresh aroma at the time of flavoring, leading to the completion of the present invention. Furthermore, they have discovered that placing the tea leaves and fresh plants that are the source of the aroma in the same sealed space during the flavoring step and creating a slightly reduced pressure environment in the space can increase the efficiency of flavoring, and that by placing the fresh plants and tea leaves so that they do not come into contact with each other, only the natural aroma can be transferred to the tea leaves.

[0011] That is, the present invention is as follows. [1] A method for producing flavored tea in which the aroma of fresh plants is transferred to tea leaves, characterized in that the flavored tea leaves are dried under reduced pressure. [2] The method for producing flavored tea according to [1], characterized in that the tea leaves are dried under reduced pressure of 610 Pa or less. [3] The method for producing flavored tea according to either [1] or [2], wherein the fresh plant is at least one selected from the group consisting of fruits and flowers. [4] A method for producing flavored tea according to any one of [1] to [3], characterized in that the flavoring means comprises piling up fresh plants and tea leaves. [5] A method for producing flavored tea according to any one of [1] to [3], characterized in that the flavoring means places the fresh plants and tea leaves in the same sealed space, separating them so that they do not come into contact with each other. [6] The method for producing flavored tea according to [5], characterized in that the space is maintained in a slightly reduced pressure environment of 600 to 900 hPa. [Effects of the Invention]

[0012] According to the present invention, a production method can be provided that can retain the aroma inherent in fresh plants such as fruits and flowers in dried tea leaves. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be described in detail below. In this specification, unless otherwise specified, "%" indicates % by mass. Furthermore, a numerical range of "lower limit value to upper limit value" means a numerical range of "not less than the lower limit value and not more than the upper limit value," unless otherwise specified.

[0014] The present invention relates to a method for producing flavored tea. The flavored tea in this invention refers to raw tea leaves or stems obtained from the Chinese species (var. sinensis) or Assam species (var. assamica) of Camellia sinensis, an evergreen tree of the genus Camellia in the family Theaceae, or hybrids thereof, or dried tea leaves (such as crude tea or finished tea) produced from these as primary raw materials, with aromas volatilized from fresh plants such as fruits and flowers transferred to the dried tea leaves.

[0015] In the manufacturing method of the present invention, the dried tea leaves used as raw materials are not limited to the type of tea, such as green tea, oolong tea, or black tea, and can be appropriately selected depending on the desired aroma. The degree of dryness of the tea leaves affects the amount of aroma that can be adsorbed, with lower moisture content being preferable because it has a higher aroma adsorption capacity. From the perspective of aroma-imparting efficiency, tea leaves with a shape with many voids are desirable, allowing sufficient contact of aroma-containing gases with the tea leaves when placed in a container. For example, for green tea, pan-roasted green tea is preferable to steamed green tea, and for black tea, OP (Orange Pekoe) is preferable to BOPF (Broken Orange Pekoe Fannings).

[0016] In the production method of the present invention, the fresh plant used as the second raw material specifically refers to fresh fruits, flowers, and other plants, and a wide variety of fresh plants can be used depending on the desired aroma. Examples of fruits that can be used include citrus fruits such as bergamot and lemon, stone fruits such as plums and peaches, pome fruits such as pears and apples, and various other fruits such as berries and grapes. Citrus fruits, which have particularly strong aromas, are particularly preferred. Examples of flowers suitable for use in the present invention include Daphne, Gardenia, Osmanthus, Wintersweet, Jasmine, Lily of the Valley, Rose, Plum, and Orchid. Other suitable plants include leaves such as mint, basil, lemongrass, chamomile, and tea, as well as bark such as cinnamon and Japanese spicebush. In the aroma-imparting step, one or more fresh plants selected from the group consisting of these fresh plants can be used. When using these fresh plants for flavoring, it is preferable to cut them into small pieces using a cutting machine such as a cutter mill, which will allow the fragrance to be released more easily, and it is also preferable to select and use the parts with the strongest fragrance. For example, when using citrus fruits, it is recommended to extract only the peel with the strongest fragrance and finely chop it.

[0017] The process for producing flavored tea consists of an aroma-infusing step in which dried tea leaves are brought into contact with the aroma emitted from fragrant fresh plants to adsorb the aroma onto the tea leaves, and a drying step in which the flavored tea leaves are dried. This invention is characterized by the use of fresh plants as the fragrant raw material in the aroma-infusing step and the use of a reduced-pressure drying method in the drying step.

[0018] In the aromatization step of the present invention's flavored tea production method, dried tea leaves are exposed to the aroma of fresh plants. The aromatization method can be either stacking or placing both materials in an enclosed space. The ratio of dried tea leaves to fresh plants during the aromatization step can be adjusted appropriately depending on the type and part of the fresh plants used and the desired aroma potency of the flavored tea. For example, when using citrus fruit peels such as bergamot, a suggested ratio is 30 parts by weight of peels per 100 parts by weight of dried tea leaves. The duration of the aromatization step, depending on the nature of the raw materials, can be adjusted to a range of approximately 30 minutes to 3 days. If the aromatization time is too short, the aroma transfer will be insufficient, while if it is too long, the freshness of the fresh plants will decrease and, in some cases, they may spoil, resulting in an undesirable aroma.

[0019] If it is acceptable for fresh plants to remain in the final flavored tea, piling is a good method for flavoring. Piling involves stacking alternating layers of tea leaves and fresh plants to bring the two ingredients into contact. Periodic mixing during flavoring is preferable for more efficient aroma transfer. Areas with a small contact area between the tea leaves and fresh plants result in a smaller transfer of volatile components, leading to uneven distribution. Therefore, periodic mixing is necessary. While there are no limitations on the mixing method, a V-type mixer or drum-type mixer may be used. Mixing conditions can be appropriately determined based on the target flavor and physical properties of the tea leaves and the characteristics of the equipment used.

[0020] Furthermore, if it is desirable to avoid the transfer of components other than aroma components to the final flavored tea, for example, if direct contact would transfer unnecessary flavor components such as bitterness, astringency, or sourness, which would undesirably affect the flavor of the flavored tea, or if fresh plants remain after drying and are difficult to separate, it is advisable to use a means of separating the two raw materials so that they do not come into contact with each other in the same sealed space where tea leaves can be taken in and out. In this case, it is preferable to prevent direct contact between the dried tea leaves and the fresh raw materials in the sealable container, and the two can be separated by, for example, a shelf, a partition, a mesh, etc.

[0021] While the aforementioned method of isolating the materials in a sealed container can prevent the transfer of unnecessary flavor components, it can sometimes result in a decrease in the efficiency of aroma component transfer. In such cases, creating a slightly reduced pressure inside the sealed container can improve aroma transfer efficiency and increase the final aroma potency. Specifically, the two raw materials are isolated and placed in a container that can withstand reduced pressure, and the pressure inside the container is reduced using a vacuum pump and pressure regulator, and maintained for a predetermined period of time. A slightly reduced pressure of 600 to 900 hPa is preferred, with 700 to 800 hPa being even more preferred. A pressure within this range promotes the release of aroma components from fresh plants and allows the tea leaves to absorb the released aroma components. Pressures below 600 hPa are undesirable because the tea leaves' ability to absorb the released aroma weakens, causing the aroma to escape from the system. On the other hand, pressures above 900 hPa result in a saturated interior, reducing the efficiency of aroma absorption.

[0022] When aromatization is performed using fresh plants, moisture is transferred to the tea leaves along with the aroma of the fresh plants, and therefore drying is necessary to ensure the shelf life of the tea leaves. The method for producing flavored tea of ​​the present invention is characterized by carrying out drying under reduced pressure. By adopting these conditions, loss or deterioration of the aroma transferred to the tea leaves during the aromatization process can be suppressed, and dried tea leaves can be obtained while maintaining the state of aroma components immediately before drying. When hot air drying is performed in a wet state, aroma components inevitably volatilize along with moisture. However, the method of the present invention allows moisture to evaporate preferentially, thereby retaining more aroma components, which is clearly superior to conventional hot air drying methods.

[0023] The apparatus used for vacuum drying can be any apparatus capable of reducing the internal pressure of a sealed container that can accommodate tea leaves and capturing or releasing the moisture volatilized from the tea leaves. The pressure during vacuum drying is preferably 610 Pa or less, more preferably 110 Pa or less, and even more preferably 10 Pa or less. By maintaining a pressure of 610 Pa or less, the tea leaves are cooled by the heat of vaporization, and the moisture sublimes in a frozen state. In other words, freeze-drying can be performed. If the pressure can be lowered, external heating can be used to promote sublimation. In this case, the conditions can be set to maintain the frozen state, preferably 60°C or less, more preferably 40°C or less. While tea leaves can be frozen by the heat of vaporization at room temperature during vacuum drying, pre-freezing is preferable in terms of preserving aroma components. Drying is continued until the moisture content of the tea leaves is 10% or less, but it is not necessary to remove the bound water from the tea leaves. Therefore, the moisture content of the tea leaves after drying is 2 to 10%, preferably 3 to 8%.

[0024] The flavored tea obtained by the production method of the present invention contains highly volatile, light aroma components that are lost when conventional tea leaves are dried, and is therefore suitable for use in forms such as leaf tea or tea bags for drinking in a teapot or teapot. [Example]

[0025] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0026] [Test Example 1] A flavored tea was produced using black tea leaves (origin: Shizuoka Prefecture, variety: Benifuki, tea season: second tea season) as dried tea leaves and fresh bergamot (origin: Kagawa Prefecture) as fresh plants. Harvested bergamots were washed with tap water, and the moisture adhering to the peel was wiped off with a paper towel. The peel was then peeled off from the fruit. The peel was cut into strips with a knife and processed in a food processor (Cuisinart, DLC-1JBS) for 30 seconds to coarsely pulverize to approximately 0.5 to 3 mm. For the flavoring process, 50 parts by weight of the pulverized peel and 100 parts by weight of black tea leaves were thoroughly mixed and stored in a refrigerator at 4°C for 48 hours, stirring for 1 minute every 6 hours. This mixture was then divided into two, and one half was dried at 40°C for approximately 36 hours using a thermal dryer (Yamato Scientific, DV400), to obtain the flavored tea of ​​Comparative Example 1. The other tea was dried under reduced pressure for approximately 36 hours at a vacuum of 4.0 Pa using a vacuum freeze dryer (freeze dryer FDU-2110, manufactured by Tokyo Rikakikai) to obtain the flavored tea of ​​Example 1. These were then subjected to instrumental analysis using the SPME-GC / MS method described below to determine the content of linalool and linalyl acetate, which are characteristic aroma components of bergamot. The flavor was also evaluated according to the sensory evaluation criteria described below. The analytical values ​​of the aroma components are shown in Table 1, and the results of the sensory evaluation are shown in Table 2.

[0027] <<Aroma component analysis and quantification method using SPME-GC / MS>> 500 mg of tea leaves were mixed with 50 ml of 80% methanol and extracted in an ultrasonic bath for 30 minutes, then diluted to 100 ml with ultrapure water. This extract was diluted 200-fold, and 10 ml of this solution was placed in a 20 ml SPME vial along with 3.0 g of sodium chloride. Cycloheptanol (Tokyo Chemical Industry Co., Ltd.) was added as an internal standard to a final concentration of 50 ppb to prepare the analytical sample. Aroma components were collected using solid phase microextraction (SPME) and subjected to gas chromatography / mass spectrometry (GC / MS). The SPME-GC / MS analytical conditions were as follows: The peak area ratio of each aroma component to the internal standard (IS ratio) was used as the peak area value.

[0028] <SPME-GC / MS Conditions> ·GC:TRACE GC ULTRA (Thermo Fisher Scientific) ·MS:TSQ QUANTUM XLS (Thermo Fisher Scientific) ·SPME Fiber: 50 / 30μm Divinylbenzene / Carboxen / Polydimethylsiloxane Stableflex (Sigma-Aldrich) ·Extraction: 60°C, 30 minutes ·Column: SUPELCO WAX10 0.25mm I.D.×60m×0.25μm (Sigma-Aldrich) ·Oven Program: Hold at 40°C for 2 minutes, then heat to 160°C at 3°C / min, and then heat to 280°C at 10°C / min ·Carrier Gas: Helium (100 kPa, constant pressure) ·Injector Temperature: Splitless, 240°C ·Ion Source Temperature: 200°C ·Ionization: Electron Ionization ·Ionization Voltage: 70 eV ·Measurement Mode: Scan ·Evaluated Components and Their Monitoring Ions: Linalool: m / z = 71, Linalyl acetate: m / z = 93

[0029] <Sensory Evaluation> The evaluators were four expert panelists who were trained in identifying aromas and off-flavors and their concentrations, and who routinely appraise tea leaves. For the evaluation, 3.0 g of each tea leaf was extracted with 180 g of hot water at 95°C for 3 minutes to obtain an extract. The evaluation criteria were defined as the aroma perceived by the evaluators as a fresh bergamot aroma. The fresh bergamot aroma was evaluated on a scale of 1 (weak, low rating) to 20 (strong, high rating), with the tea leaves of Comparative Example 1 being the standard (10 points). The intensity of bitterness, astringency, and harshness was also evaluated on a scale of 1 (weak, high rating) to 20 (strong, low rating), with the tea leaves of Comparative Example 1 being the standard (10 points).

[0030] [Table 1]

[0031] [Table 2]

[0032] The results of the instrumental analysis shown in Table 1 confirmed that Example 1 of the present invention contained approximately twice as much linalool and linalyl acetate, which are typical aroma components of bergamot, as compared to Comparative Example 1. The results of the sensory evaluation shown in Table 2 support the advantages of these component contents, confirming that the characteristic bergamot aroma is maintained in the final flavored tea. These results demonstrate that the production method of the present invention can transfer the fresh aroma of fresh plants to tea leaves and suppress the loss or deterioration of these aroma components during the production process.

[0033] [Test Example 2] Test Example 1 demonstrated that the manufacturing method of the present invention can impart the fresh aroma of fresh plants to tea leaves. However, there were comments that the bitterness derived from the bergamot peel used was noticeable, and countermeasures were investigated. Specifically, the aroma imparting effect was confirmed using a method that did not allow direct contact between the tea leaves and the aroma source during the aroma imparting process. As in Test Example 1, black tea leaves (origin: Shizuoka Prefecture, variety: Benifuki, tea season: second tea season) were prepared as dried tea leaves, and fresh bergamot (origin: Kagawa Prefecture) was prepared as fresh plants. A coarsely crushed peel product was prepared from the fresh bergamot. Two test sieves (diameter: 75 mm, mesh size: 250 μm, manufactured by Tokyo Screen) were stacked, and 10 g of crushed bergamot peel was placed on the bottom sieve, and 20 g of black tea leaves were placed on the top sieve. In other words, the tea leaves and the bergamot, the source of the aroma, were prevented from coming into contact with each other. These were placed in a freeze-drying bottle (volume: 900 ml, diameter: 102 mm, manufactured by Tokyo Rikakikai Co., Ltd.), and the container was left to stand for 24 hours while maintaining a reduced pressure using a vacuum pump (model number: V-600 / I-300, manufactured by Buchi Co., Ltd.) to aromatize the tea leaves. The reduced pressure was atmospheric pressure (Example 2), 900 hPa (Example 3), 750 hPa (Example 4), 600 hPa (Example 5), and 500 hPa (Example 6). After the aromatization process, only the tea leaves were removed and dried under reduced pressure for approximately 36 hours using a vacuum freeze dryer (freeze dryer model FDU-2110, manufactured by Tokyo Rikakikai Co., Ltd.) at a reduced pressure of 4.0 Pa, to obtain the flavored teas of Examples 2 to 6. Similar to Test Example 1, these flavored teas were subjected to sensory evaluation of their flavors using Comparative Example 1 as the standard. The results are shown in Table 3.

[0034] [Table 3]

[0035] As shown in the results in Table 3, compared to Comparative Example 1, in which tea leaves and crushed peel were mixed and aromatized, the aroma of bergamot was reliably imparted, while the bitterness was significantly reduced. These results confirmed that the aroma alone can be transferred to the tea leaves even when the tea leaves and the peel, which are the source of the aroma, are not in contact with each other. Furthermore, it was shown that by maintaining a slightly reduced pressure (slightly lower than atmospheric pressure) during the aromatization operation, the bitterness can be reduced while maintaining the aroma intensity. It was confirmed that a pressure range of 600 to 900 hPa was particularly effective in terms of maintaining aroma intensity.

[0036] [Manufacturing Example 1] A flavored tea was produced using bananas as the fresh produce. One imported banana, including the peel, was sliced ​​into approximately 2 cm slices with a knife and processed for 1 minute in a food processor (Cuisinart, DLC-1JBS) to form a paste. Two test sieves (75 mm diameter, 100 μm mesh, Tokyo Screen) were stacked, with 10 g of banana paste placed on the bottom sieve and 10 g of black tea leaves placed on the top sieve. The contents were placed in a freeze-drying bottle (900 ml capacity, 102 mm diameter, Tokyo Rika Kikai) and the container was kept at a reduced pressure of 750 hPa using a vacuum pump (V-600 / I-300, Buchi) while the bottle was left at room temperature for 24 hours to flavor the tea leaves. After aromatization, the tea leaves were removed and dried under reduced pressure at a final vacuum of 4.0 Pa for approximately 24 hours using a vacuum freeze dryer (freeze dryer FDU-2110, manufactured by Tokyo Rikaki Co., Ltd.), to obtain the aromatized tea of ​​Production Example 1. The obtained tea leaves were extracted with hot water and subjected to a sensory evaluation, which confirmed that they had a strong sweet and fruity aroma characteristic of ripe bananas.

Claims

1. This is a method for producing aroma-added tea in which the aroma of fresh plants is transferred to tea leaves, and is characterized by drying the aroma-added tea leaves under reduced pressure under the following conditions (1) and (2): (1) Under reduced pressure of 610 Pa or less (2) Temperatures below 60°C

2. 2. The method for producing flavored tea according to claim 1, wherein the drying of the tea leaves is continued until the moisture content of the tea leaves is reduced to 10% or less.

3. 3. The method for producing flavored tea according to claim 1, wherein the fresh plant is at least one selected from the group consisting of fruits and flowers.

4. 4. The method for producing flavored tea according to claim 1, wherein the flavoring means comprises piling up fresh plants and tea leaves.

5. 4. The method for producing flavored tea according to claim 1, wherein the flavoring means is arranged to separate the fresh plants and the tea leaves in the same sealed space so that they do not come into contact with each other.

6. The method for producing flavored tea according to claim 5, characterized in that the space is maintained in a slightly reduced pressure environment of 600 to 900 hPa.

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