Production method and processing method of tea leaf product for cold-brewed tea beverage

Abstract

The problem of the present invention is to provide a tea leaf product for cold-brewing that uses unground tea leaves and exhibits excellent component extraction efficiency.　The present invention provides a method for producing a tea leaf product for a cold-brewed tea beverage, the method including an immersion step for immersing unground and unextracted dried tea leaves in water, and a freeze-drying step of freeze-drying the tea leaves after the immersion step.

Description

Method for producing and processing tea leaf products for cold-brewed tea drinks

[0001] The present invention relates to a method for producing and processing tea leaf products for cold-brewed tea beverages.

[0002] Tea drinks are made by extracting tea leaves from water (H ２ The water used for extraction is usually hot water (e.g., water at 80°C or higher) or warm water (e.g., water at 50 to 70°C), but in recent years, extraction using water at lower temperatures has also become popular. Extraction using such low-temperature water is known as "cold brewing."

[0003] On the other hand, cold brewing has a low efficiency of extracting components from tea leaves, and requires a long time for extraction (e.g., several hours or more). Therefore, various tea leaf products have been proposed to achieve cold brewing in a short time. Examples of such tea leaf products include those in which ground tea leaves are molded and a cold brew tea beverage is obtained by simply pouring water over the molded product (e.g., Patent Documents 1 and 2).

[0004] JP-A No. 06-217695 JP-A No. 01-108939

[0005] Here, the conventional cold-brewed tea leaf products described above are produced by pouring water over a molded product made from ground tea leaves, which is then consumed as a tea beverage. In other words, conventional cold-brewed tea leaf products aim to allow the ingestion of all components contained in the tea leaves. However, the present inventors have found that tea beverages obtained from conventional cold-brewed tea leaf products may be less palatable because tea leaves also contain components that impart unpleasant flavors and astringency.

[0006] Therefore, the present inventors aimed to develop a tea leaf product for cold brewing that is highly efficient in extracting ingredients from tea leaves without the need to crush the tea leaves.

[0007] The present invention has been made in view of the above circumstances, and aims to provide a tea leaf product for cold brewing that uses unground tea leaves and has excellent ingredient extraction efficiency.

[0008] As a result of investigations, the inventors have discovered that the above-mentioned problems can be solved by soaking specific dried tea leaves in water and then freeze-drying them in a method for producing tea leaf products for cold brewing, and have thus completed the present invention. More specifically, the present invention provides the following.

[0009] (1) A method for producing a tea leaf product for cold-brewed tea beverages, the method comprising: a steeping step of steeping unground, unextracted dried tea leaves in water; and a freeze-drying step of freeze-drying the tea leaves after the steeping step.

[0010] (2) The method according to (1), wherein the soaking time of the dried tea leaves in the soaking step is 24 hours or less.

[0011] (3) The method according to (1), wherein the temperature of the water in the soaking step is 20° C. or less.

[0012] (4) A method for processing tea leaf products for cold-brewed tea beverages, the method comprising: a soaking step of soaking unground, unextracted dried tea leaves in water; and a freeze-drying step of freeze-drying the tea leaves after the soaking step.

[0013] According to the present invention, a tea leaf product for cold brewing is provided which uses unground tea leaves and has excellent ingredient extraction efficiency.

[0014] 1 shows the results of analysis of components eluted from a tea leaf product of an example, and FIG. 2 shows the results of analysis of components eluted from a tea leaf product of a comparative example.

[0015] Hereinafter, an embodiment of the present invention will be described, but the present invention is not limited to this.

[0016] <Method for manufacturing a tea leaf product for a cold-brewed tea beverage> In one aspect, the method for manufacturing a tea leaf product for a cold-brewed tea beverage according to the present invention (hereinafter also referred to as the "manufacturing method of the present invention") comprises all of the following steps: a steeping step in which unground, unextracted dried tea leaves are steeped in water; and a freeze-drying step in which the tea leaves after the steeping step are freeze-dried.

[0017] Tea drinks are made by mixing various components contained in tea leaves with water (H ２0) or the like. It is known that the components extracted from tea leaves vary depending on the temperature of the water used for extraction. Generally, the higher the water temperature, the more efficiently the components contained in the tea leaves can be extracted in a short time. For example, extraction using high-temperature water dissolves caffeine and epigallocatechin gallate, an astringent component, resulting in a tea beverage with a strong astringent taste. On the other hand, extraction (cold brewing) using water at a lower temperature (e.g., 25°C or lower) suppresses the dissolution of caffeine and epigallocatechin gallate, resulting in a tea beverage with a strong umami flavor, in which theanine and epigallocatechin are dissolved. However, obtaining a tea beverage using low-temperature water requires a long extraction time (e.g., several hours or more), resulting in significantly low component extraction efficiency.

[0018] Therefore, the inventors conducted extensive research and found that by processing tea leaves using the above steps, a tea leaf product can be obtained that has extremely good efficiency in extracting components from the tea leaves, even when extraction is performed using water at a low temperature.

[0019] The production method of the present invention will be described in detail below.

[0020] (1) Definitions The terms used in the present invention include the following meanings.

[0021] In the present invention, "cold brewing (of tea leaves)" includes extraction with water at a temperature lower than hot water (e.g., water at 80°C or higher) or warm water (e.g., water at 50 to 70°C). For example, the temperature of water used for cold brewing is preferably 25°C or lower, more preferably between 0°C and 20°C, and even more preferably between 4°C and 10°C. Hereinafter, water within this temperature range may be referred to as "water for cold brewing" to distinguish it from hot water or warm water.

[0022] In the present invention, the term "tea leaf product for cold-brewing tea beverages" or "tea leaf product for cold-brewing" includes any form of tea leaf product that can be used for cold-brewing. In one embodiment of the present invention, the tea leaf product is in the form of a freeze-dried product.

[0023] In the present invention, the term "cold-brewed tea beverage" refers to a tea leaf extract obtained by pouring cold-brew water into a tea leaf product for cold brewing. However, the present invention does not exclude the use of tea leaf products obtained by the manufacturing method of the present invention extracted with hot water or warm water instead of cold-brew water.

[0024] In the present invention, "component extraction efficiency" can be expressed by the amount of a specific component (e.g., theanine or epigallocatechin) eluted from tea leaves when the extraction conditions are the same in extraction from tea leaves using water, etc. When different tea leaf products are extracted under the same extraction conditions, the greater the amount of a specific component eluted from the tea leaves, the higher the component extraction efficiency for that component.

[0025] In the present invention, "excellent efficiency in extracting components (from tea leaves)" includes, for example, when the extraction conditions are the same, eluting a larger amount of a specific component from tea leaves in a shorter time.

[0026] (2) Steeping Step In the steeping step, water is allowed to permeate unground and unextracted dried tea leaves.

[0027] (2-1) Unground and unextracted dried tea leaves In the production method of the present invention, unground and unextracted dried tea leaves are the raw material for the tea leaf product used to obtain a cold-brewed tea beverage. The dried tea leaves may be used alone or in combination of two or more types.

[0028] (2-1-1) Dried Tea Leaves In the present invention, the term "dried tea leaves" includes dried parts (leaves and stems) of any plant that is used as a raw material for tea beverages.

[0029] The moisture content of the dried tea leaves is not particularly limited, but is preferably 12% by mass or less, more preferably 5% by mass or less, based on the mass of the dried tea leaves.

[0030] The type of plant from which the dried tea leaves are derived is not particularly limited, and examples thereof include Camellia sinensis, Camellia taliensis, and Camellia irrawadiensis.

[0031] The method for drying tea leaves is not particularly limited and may be appropriately selected depending on the type of tea beverage to be obtained, etc. Examples include any drying method employed in the production of sencha (including coarse rolling, rolling, medium rolling, fine rolling, etc.), the production of kamairicha (including rolling, water drying, and steeping), and the production of white tea, green tea (oolong tea, baozhong tea, etc.), and black tea (including withering, etc.).

[0032] The type of dried tea leaves is not particularly limited, and may be any of non-fermented tea, slightly fermented tea, semi-fermented tea, fermented tea, post-fermented tea, etc. Non-fermented teas include green teas (sencha, gyokuro, kabusecha, bancha, tamaryokucha, tencha, matcha, roasted green tea, etc.). Lightly fermented teas include Baihao Yinzhen and Bai Mutan. Semi-fermented teas include Baozhong tea and oolong tea. Fermented teas include black tea, etc. Post-fermented teas include Pu-erh tea, etc.

[0033] The dried tea leaves may be not only tea leaves dried by the tea leaf product manufacturer itself, but also commercially available dried tea leaves.

[0034] In one embodiment of the present invention, the dried tea leaves are preferably unfermented tea, more preferably green tea.

[0035] (2-1-2) Unground dried tea leaves In the present invention, "unground dried tea leaves" includes dried tea leaves that have not been subjected to a powdering process, a grinding process, or the like. Therefore, powdered tea (dried tea leaves ground into powder) is excluded from unground dried tea leaves. However, the present invention does not exclude embodiments in which powdered tea leaves (such as powdered tea (powder produced during the production of green tea)) are mixed into the dried tea leaves to the extent that the effects of the present invention are not impaired.

[0036] Uncrushed dried tea leaves include not only those that maintain their leaf shape, but also those that have been cut, those that have been rolled into granules by wrapping or the like, and those obtained by the CTC manufacturing method. The "CTC manufacturing method" includes manufacturing methods in which dried tea leaves are subjected to the processes of "Crush," "Tear," and "Curl." These dried tea leaves are preferred from the viewpoint of efficiently performing the soaking process described below.

[0037] The length of the cut dried tea leaves or dried tea leaves obtained by the CTC method is not particularly limited, but is usually 0.5 mm or longer.

[0038] Whether or not dried tea leaves are unground can be determined, for example, by using a sieve. For example, dried tea leaves with a mesh size specified in ASTM E11 of preferably 35 or more (openings of 500 μm or less), more preferably 40 or more (openings of 425 μm or less) can be preferably used as unground dried tea leaves.

[0039] (2-1-3) Unextracted Dried Tea Leaves In the present invention, the term "unextracted dried tea leaves" includes dried tea leaves that have not been subjected to an extraction process with water, etc. Therefore, unextracted dried tea leaves do not include tea leaves (residue remaining after extraction from tea leaves).

[0040] (2-2) Soaking in Water In the soaking step, unground and unextracted dried tea leaves are soaked in water. The present inventors have unexpectedly discovered that by soaking the tea leaves and then freeze-drying them (described below), a tea leaf product can be obtained from which components contained in the tea leaves can be easily extracted, even in water at a low temperature.

[0041] The conditions for soaking the dried tea leaves in water are not particularly limited as long as the dried tea leaves can be fully soaked in water. However, soaking for a long period of time is preferably avoided because it will cause excessive leaching of the components in the dried tea leaves.

[0042] The immersion step may be continuous or intermittent throughout, and the immersion conditions (temperature, etc.) in the immersion step may be constant or may be changed during the immersion step.

[0043] The water to be soaked in the dried tea leaves is not particularly limited as long as it is a liquid containing water, and water (H ２ It may be a liquid consisting of only water (H ２ The liquid may contain components other than water together with the tea beverage containing the active ingredient O. In the latter case, the components other than water may be appropriately selected from components that can be blended into the tea beverage and in amounts that do not impair the effects of the present invention. Examples of such components include antioxidants (such as ascorbic acid).

[0044] In a preferred embodiment of the present invention, the water used in the steeping step does not contain any substances that decompose or alter the components contained in the dried tea leaves. For example, it is preferable that the water used in the steeping step does not contain any enzymes.

[0045] The amount of water in which the dried tea leaves are soaked is not particularly limited as long as the entire dried tea leaves are soaked. The upper limit of the amount of water in which the dried tea leaves are soaked is preferably 8 times or less, more preferably 6 times or less, and even more preferably 5 times or less, the dry mass of the dried tea leaves, from the viewpoint of easily preventing excessive outflow of components. The lower limit of the amount of water in which the dried tea leaves are soaked is preferably 1 time or more, more preferably 2 times or more, the dry mass of the dried tea leaves, from the viewpoint of easily achieving sufficient soaking.

[0046] The temperature of the water used to soak the dried tea leaves is preferably not too high, from the viewpoint of preventing the outflow of components from the dried tea leaves. The upper limit of the temperature of the water used to soak the dried tea leaves is preferably 20°C or lower, more preferably 15°C or lower, even more preferably 10°C or lower, and even more preferably 5°C or lower, from the viewpoint of easily preventing excessive outflow of components. The lower limit of the temperature of the water used to soak the dried tea leaves is preferably -4°C or higher, more preferably 1°C or higher, and even more preferably 4°C or higher, from the viewpoint of easily achieving sufficient water absorption.

[0047] The upper limit of the soaking time for the dried tea leaves in water is not particularly limited, but from the viewpoint of easily preventing excessive outflow of components, it is preferably 24 hours or less, preferably 12 hours or less, preferably 5 hours or less, more preferably 1 hour or less, more preferably 40 minutes or less, more preferably 30 minutes or less, even more preferably 20 minutes or less, and still more preferably 15 minutes or less. The lower limit of the soaking time for the dried tea leaves in water is not particularly limited, but from the viewpoint of easily achieving sufficient soaking, it is preferably 1 minute or more, more preferably 10 minutes or more.

[0048] The means for soaking dried tea leaves in water is not particularly limited as long as it allows contact between the dried tea leaves and water, but examples include the following methods. All methods are preferably carried out in a low-temperature environment (for example, in an environment of 4°C or below, such as inside a refrigerator). - Dried tea leaves are placed in any container (such as a resin container) together with water, and absorption is carried out by standing or shaking (vibration). - Dried tea leaves are soaked in water using a vacuum or pressurizer. - Water is sprayed onto the dried tea leaves using a coating machine or the like.

[0049] (3) Freeze-drying Step In the freeze-drying step, the tea leaves after soaking are freeze-dried.

[0050] The freeze-drying process can employ any conditions that can be employed in freeze-drying food and beverage products, and typically includes the following steps: - Freezing the tea leaves after soaking is complete; - Drying the frozen tea leaves while maintaining their frozen state. In the above steps, it is preferable that the soaking process and the freezing of the tea leaves are continuous (without any other process between the two). Furthermore, from the viewpoint of easily suppressing deterioration in the quality of the resulting tea leaf product, it is preferable to carry out freezing promptly (for example, within one hour) after completing the soaking process. However, once frozen, the tea leaves may be dried as is after freezing, or may be stored in a freezer or the like until they are dried.

[0051] The conditions for freezing the tea leaves after steeping are not particularly limited. The freezing temperature is usually −30° C. or higher and −1° C. or lower.

[0052] The drying conditions for the frozen tea leaves are not particularly limited and can be set appropriately depending on the mass of the tea leaves and the degree of vacuum. The trap cooling temperature is usually −45° C. or lower. The ultimate vacuum is usually 10 Pa or lower.

[0053] In the freeze-drying step, any device known as a freeze-dryer (such as a flask type or dry chamber type) can be used.

[0054] (4) Tea Leaf Product The freeze-dried tea leaves obtained after the freeze-drying step correspond to the tea leaf product for the cold-brewed tea beverage of the present invention.

[0055] The obtained tea leaf product may be directly subjected to extraction or the like to prepare a tea beverage, or may be appropriately packaged and stored.

[0056] The obtained tea leaf product may be processed as appropriate and prepared, for example, into the following forms: - Leaf tea product placed in a container - Tea bag product - Cup product in which the tea leaf product is fixed together with a filter, etc. - Tea leaf product for use in a tea dispenser

[0057] (5) Preparation example of tea beverage The tea leaf product obtained by the production method of the present invention can be used to prepare a tea beverage by any extraction method known as a method for producing tea beverages. However, since the tea leaf product obtained by the production method of the present invention is particularly suitable for preparing a cold-brewed tea beverage, a preferred preparation example will be described below.

[0058] The method for preparing a tea beverage from a tea leaf product is not particularly limited, and any method for bringing a tea leaf product into contact with water can be used. However, to obtain a cold-brewed tea beverage, it is preferable to use water for cold brewing (described above) as the water to be brought into contact with the tea leaf product.

[0059] According to the present invention, as described above, the component extraction efficiency is excellent, and therefore a cold-brewed tea beverage can be obtained in a short time. For example, according to the present invention, a cold-brewed tea beverage can be obtained in an extraction time of preferably 20 minutes or less, more preferably 15 minutes or less, even more preferably 10 minutes or less, and even more preferably 5 minutes or less. When using conventional tea leaf products, it took many hours of extraction time to obtain a cold-brewed tea beverage (see, for example, the comparative examples described below). Therefore, the present invention has an important technical significance in that it significantly shortens the extraction time for cold brewing and improves the component extraction efficiency.

[0060] As described above, by using low-temperature water and performing extraction for a short time, it is possible to obtain a cold-brewed tea beverage with a strong umami flavor, in which theanine and epigallocatechin are eluted while suppressing the elution of caffeine and epigallocatechin gallate.

[0061] <Method for processing a tea leaf product for a cold-brewed tea beverage> As described above, according to the present invention, a tea leaf product for cold-brewing that has excellent component extraction efficiency can be obtained. Therefore, in one aspect, the present invention also encompasses a method for processing a tea leaf product for a cold-brewed tea beverage, which includes the following steps: a steeping step in which unground, unextracted dried tea leaves are steeped in water; and a freeze-drying step in which the tea leaves after the steeping step are freeze-dried.

[0062] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0063] <Production of Tea Leaf Products> Tea leaves were processed to produce tea leaf products by the following method.

[0064] (1) Preparation of Dried Tea Leaves Commercially available sencha tea made from the leaves (scientific name: Camellia sinensis) was used as the dried tea leaves. This tea leaf is a so-called green tea (unfermented tea) and corresponds to "unground and unextracted dried tea leaves."

[0065] (2) Soaking process: The dried tea leaves were soaked in water placed in a rectangular container so that the entire tea leaves were immersed. The amount of water used was five times the amount of the dried tea leaves (approximately 4°C). The container and the dried tea leaves were then placed in a refrigerator (approximately 4°C) and left to stand for about 15 minutes to allow the tea leaves to fully absorb water.

[0066] (3) Freeze-drying step After the immersion step was completed, the container was promptly removed from the refrigerator and frozen in a freezer (approximately −20° C.), then placed in a freeze-dryer (flask type) and dried under vacuum conditions. The freeze-drying conditions were a trap cooling temperature of −50° C. or less, a vacuum of 30 Pa or less, and a time of 24 hours.

[0067] (4) Obtaining the Tea Leaf Product After the freeze-drying process was completed, the tea leaf product (freeze-dried product) was obtained, which was subjected to the following extraction test.

[0068] <Extraction Test> The obtained tea leaf products were subjected to the following tests to evaluate the efficiency of component extraction.

[0069] (1) Preparation of samples Example: Tea leaf product (freeze-dried product) obtained in the above "Production of tea leaf products" Comparative example: Dried tea leaves (corresponding to normal green tea) obtained in "(1) Preparation of dried tea leaves" in the above "Production of tea leaf products"

[0070] (2) Extraction Treatment Each sample was placed in a container of water (approximately 10°C) so that the entire sample was immersed. The container was then placed in a refrigerator (approximately 4°C), and the solution samples (cold-brewed tea beverages) were collected, avoiding the tea leaves, at various time points from 3 minutes after the sample was placed in the refrigerator to 24 hours later.

[0071] (3) Component Analysis The contents (component elution rates) of epigallocatechin (EGC), epigallocatechin gallate (EGCG), caffeine, and theanine contained in each solution sample were analyzed using high performance liquid chromatography. Detailed analysis conditions are as follows.

[0072] (3-1) Analytical conditions for EGC, EGCG, and caffeine Apparatus: "Shimadzu LC-20AD system", Shimadzu Corporation Guard column: "Security Guard Cartridge C18" (i.d. 4*3 mm), Phenomenex Column: "Wakopak Navi C18-5" (5 μm, i.d. 4.6*150 mm), Fujifilm Wako Pure Chemical Corporation Eluent: (Mobile phase A) DW: acetonitrile: phosphoric acid in a volume ratio of 400:10:1 (Mobile phase B) methanol: mobile phase A in a volume ratio of 1:2 Detector: "SPD-40V" (242 nm, EGC; 272 nm, EGCG, caffeine), Shimadzu Corporation Flow rate: 1 mL / min Column temperature: 40°C Injection volume: 20 μL Gradient: See the table below.

[0073]

[0074] (3-2) Analytical conditions for theanine: Apparatus: o-phthalaldehyde automatic pre-column derivatization method using "Shimadzu LC-20AD, SIL-40C system" (Shimadzu Corporation); Guard column: "Security Guard Cartridge C18" (i.d. 4*3 mm), Phenomenex; Column: "Inertsil ODS-4 C18" (3 μm, i.d. 4.6*150 mm), GL Sciences Inc.; Eluent: (Mobile phase A) 20 mM potassium phosphate buffer (pH 6.4); (Mobile phase B) DW: acetonitrile: methanol in a volume ratio of 15:45:40; Detector: "RF-20Axs" (excitation wavelength 350 nm, fluorescence wavelength 450 nm), Shimadzu Corporation; Flow rate: 0.8 mL / min Column temperature: 40°C Injection volume: 1 μL Internal standard: glycylglycine Gradient: See the table below.

[0075]

[0076] (3-3) Results The analysis results are shown in Figure 1. Figure 1 shows the analysis results of the components eluted from the tea leaf product of the Example. Figure 2 shows the analysis results of the components eluted from the dried tea leaves of the Comparative Example.

[0077] The results were expressed as the relationship between the dissolution time (the time elapsed from the time the sample was added) and the dissolution rate of each component. The dissolution rate of each component was shown as a relative value, with the amount of component when the tea leaves of the "Comparative Example" were extracted with hot water at 80°C for 2 minutes being taken as "100%."

[0078] As shown in Figure 1, the tea leaf product obtained by the manufacturing method of the present invention was able to produce an extract (tea beverage) in which epigallocatechin and theanine were sufficiently eluted in a short time of less than 5 minutes, even when extracted in a refrigerator. This result demonstrates that the tea leaf product obtained by the manufacturing method of the present invention has extremely excellent component extraction efficiency from tea leaves.

[0079] In contrast, as shown in Figure 2(A), the comparative dried tea leaves (ordinary green tea) took a very long time to dissolve the components when extracted in a refrigerator, and it took nearly half a day to reach a dissolution rate equivalent to that of the tea leaf product obtained by the manufacturing method of the present invention. Extraction was also performed on the comparative dried tea leaves at room temperature (about 26°C) instead of in a refrigerator (Figure 2(B)), but it still took a long time for the components to dissolve, and it took nearly an hour to reach a dissolution rate equivalent to that of the tea leaf product obtained by the manufacturing method of the present invention.

[0080] From the above, it was found that the tea leaf product obtained by the manufacturing method of the present invention can significantly shorten the extraction time even when extracted with water (about 4°C), and can achieve efficient component extraction.

Claims

1. A method for manufacturing a tea leaf product for a cold-brewed tea beverage, the manufacturing method including: a soaking step of soaking water into unground and unextracted dried tea leaves; and a freeze-drying step of freeze-drying the tea leaves after the soaking step.

2. The manufacturing method according to claim 1, wherein the soaking time of the dried tea leaves in the soaking step is 24 hours or less.

3. The manufacturing method according to claim 1, wherein the temperature of the water in the soaking step is 20°C or less.

4. A processing method for a tea leaf product for a cold-brewed tea beverage, the processing method including: a soaking step of soaking water into unground and unextracted dried tea leaves; and a freeze-drying step of freeze-drying the tea leaves after the soaking step.

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