JP7519528B1 - Method for producing and processing tea leaf products for cold-brewed tea beverages - Google Patents

Abstract

[Problem] The object of the present invention is to provide a tea leaf product for cold brewing that uses unground tea leaves and has excellent ingredient extraction efficiency. [Solution] The present invention provides a method for producing a tea leaf product for cold brewing tea beverages, the method comprising a steeping step of steeping unground and unextracted dried tea leaves in water, and a freeze-drying step of freeze-drying the tea leaves after the steeping step. [Selected Figure] Figure 1

Description

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

A tea beverage is an extract obtained from tea leaves using water (H ₂ O) or the like.
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."

On the other hand, in the case of cold brewing, the efficiency of extracting ingredients from tea leaves is low, and extraction takes a long time (for example, several hours or more).
For this reason, various tea leaf products have been proposed that can be brewed in cold water in a short time, such as those made by shaping ground tea leaves and then simply pouring water into the shaped product to obtain a cold-brewed tea beverage (see, for example, Patent Documents 1 and 2).

Japanese Patent Application Publication No. 06-217695 Japanese Patent Application Publication No. 01-108939

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

Therefore, the inventors aimed to develop a tea leaf product for cold brewing that would have excellent efficiency in extracting ingredients from tea leaves without the need to crush the tea leaves.

The present invention was made in consideration of the above situation, and aims to provide a cold-brewed tea leaf product that uses unground tea leaves and has excellent ingredient extraction efficiency.

As a result of the inventors' investigations, they discovered that the above problems could 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 thus completed the present invention. More specifically, the present invention provides the following:

(1) A method for producing a tea leaf product for a cold-brewed tea beverage, comprising the steps of:
The manufacturing method comprises:
A steeping step of steeping unground and unextracted dried tea leaves in water;
A freeze-drying step of freeze-drying the tea leaves after the soaking step.
Production method.

(2) The method according to (1), wherein the soaking time of the dried tea leaves in the soaking step is 20 minutes or less.

(3) The manufacturing method described in (1), in which the temperature of the water in the soaking step is 20°C or less.

(4) A method for processing a tea leaf product for a cold-brewed tea beverage, comprising the steps of:
The processing method comprises:
A steeping step of steeping unground and unextracted dried tea leaves in water;
A freeze-drying step of freeze-drying the tea leaves after the soaking step.
Processing method.

The present invention provides a cold-brewed tea leaf product that uses unground tea leaves and has excellent ingredient extraction efficiency.

FIG. 2 shows the analysis results of the components dissolved from the tea leaf products of the examples. FIG. 2 shows the analysis results of the components dissolved from a tea leaf product of a comparative example.

The following describes an embodiment of the present invention, but the present invention is not limited to this.

<Method of manufacturing tea leaf products for cold-brewed tea beverages>
The method for producing a tea leaf product for a cold-brewed tea beverage according to the present invention (hereinafter also referred to as the "production method of the present invention") comprises, in one embodiment, all of the following steps.
- A steeping process in which unground, unextracted dried tea leaves are steeped in water.
- Freeze-drying process, in which the tea leaves after the soaking process are freeze-dried.

A tea beverage is a tea leaf extract obtained by extracting various components contained in tea leaves with water (H ₂ O) or the like.
Regarding the water used for extraction, it is known that the components extracted from tea leaves vary depending on the temperature of the water.
Generally, the higher the temperature of the water, the more efficiently the components contained in the tea leaves can be extracted in a short time. For example, when extraction is performed with hot water, caffeine and epigallocatechin gallate, an astringent component, are dissolved, resulting in a tea drink with a strong astringent taste.
On the other hand, when extraction (cold brewing) is performed using water at a lower temperature (for example, below 25°C), the elution of caffeine and epigallocatechin gallate is suppressed, while theanine and epigallocatechin are eluted, resulting in a tea beverage with a strong umami flavor.
However, to obtain a tea beverage using water at a low temperature, a long period of extraction (for example, several hours or more) is required, and the efficiency of component extraction is extremely low.

As a result of extensive research, the inventors have found that by processing tea leaves using the above steps, a tea leaf product can be obtained that has extremely good efficiency in extracting ingredients from the tea leaves, even when extraction is performed using water at a low temperature.

The manufacturing method of the present invention is described in detail below.

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

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

In the present invention, the term "tea leaf product for cold-brewed 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.

In the present invention, the "cold-brewed tea beverage" refers to a tea leaf extract obtained by pouring water for cold-brewing into a tea leaf product for cold-brewing.
However, the present invention does not exclude the use of the tea leaf product obtained by the manufacturing method of the present invention in an embodiment in which the tea leaf product is extracted using hot water or warm water instead of cold brewing water.

In the present invention, "component extraction efficiency" can be expressed in terms of the amount of a specific component (e.g., theanine or epigallocatechin) dissolved from tea leaves when the extraction conditions are the same when tea leaves are extracted with water or the like.
When different tea leaf products are extracted under the same extraction conditions, the greater the amount of a particular component that dissolves from the tea leaves, the higher the component extraction efficiency for that component.

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

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

(2-1) Unground, unextracted dried tea leaves In the production method of the present invention, unground, unextracted dried tea leaves are the raw material for the tea leaf product from which a cold-brewed tea beverage is obtained.
The dried tea leaves may be used alone or in combination of two or more kinds.

(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.

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

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

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. Examples include any drying method used in the manufacturing method of sencha (including coarse rolling, rolling, medium rolling, fine rolling, etc.), the manufacturing method of pan-fried tea (including rolling, water drying, tight roasting, etc.), and the manufacturing methods of white tea, green tea (oolong tea, baozhong tea, etc.), and black tea (including withering, etc.).

The type of dried tea leaves is not particularly limited, and may be, for example, any of unfermented tea, slightly fermented tea, semi-fermented tea, fermented tea, post-fermented tea, etc.
Examples of non-fermented tea include green tea (sencha, gyokuro, kabusecha, bancha, tamaryokucha, tencha, matcha, roasted green tea, etc.).
Examples of slightly fermented teas include Baihao Yinzhen and Bai Mutan.
Examples of semi-fermented tea include oolong tea and baguette tea.
Fermented teas include black teas.
An example of post-fermented tea is Pu-erh tea.

Dried tea leaves can be not only tea leaves dried by the tea product manufacturer itself, but also commercially available dried tea leaves.

In one aspect of the present invention, the dried tea leaves are preferably unfermented tea, more preferably green tea.

(2-1-2) Unground Dried Tea Leaves In the present invention, the term "unground dried tea leaves" includes dried tea leaves that have not been subjected to a powdering process, a grinding process or the like.
Therefore, unground dried tea leaves do not include powdered tea (dried tea leaves ground into powder). However, in the present invention, the dried tea leaves may be mixed with powdered tea leaves (such as powdered tea (powder produced during the manufacturing process of green tea)) to the extent that the effects of the present invention are not impaired.

The term "uncrushed dried tea leaves" includes not only leaves that have retained their shape, but also cut leaves and leaves obtained by the CTC method. The CTC method includes a method in which dried tea leaves are subjected to the processes of "crushing,""tearing," and "curling."
These dried tea leaves are preferred from the viewpoint of efficiently carrying out the steeping step described below.

There are no particular limitations on the length of cut dried tea leaves or dried tea leaves obtained by the CTC method, but they are usually 0.5 mm or longer.

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

(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 or the like.
Therefore, unextracted dried tea leaves exclude tea leaves (the residue remaining after extraction from the tea leaves).

(2-2) Soaking in Water In the soaking step, unground and unextracted dried tea leaves are soaked in water.
The inventors have made the unexpected discovery that by freeze-drying the tea leaves (described below) after this soaking process, a tea leaf product can be obtained from which the components contained in the tea leaves can be easily extracted, even in water at a low temperature.

There are no particular limitations on the conditions for soaking dried tea leaves in water, so long as the entire dried tea leaves can be fully soaked in water. However, it is preferable to avoid soaking for long periods of time, as this will cause excessive leaching of the components in the dried tea leaves.

The immersion process may be continuous or intermittent throughout. The immersion conditions (temperature, etc.) during the immersion process may be constant or may change during the process.

The water in which the dried tea leaves are soaked is not particularly limited as long as it is a liquid containing water, and it may be a liquid consisting of only water (H ₂ O) or a liquid containing water (H ₂ O) and components other than water.
In the latter case, the components other than water may be appropriately selected from the components and amounts that can be blended into the tea beverage within a range that does not impair the effects of the present invention. Examples of such components include antioxidants (such as ascorbic acid).

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 loss of components.
The lower limit of the amount of water with which the dried tea leaves are soaked is preferably at least 1 time, and more preferably at least 2 times, the dry mass of the dried tea leaves, from the viewpoint of facilitating sufficient soaking.

It is preferable that the temperature of the water in which the dried tea leaves are soaked is 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 in which the dried tea leaves are soaked is preferably 20°C or less, more preferably 15°C or less, even more preferably 10°C or less, and even more preferably 5°C or less, from the viewpoint of easily preventing excessive loss of components.
The lower limit of the temperature of the water for soaking 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 facilitating sufficient water absorption.

There is no particular upper limit to the time for soaking the dried tea leaves in water, but from the viewpoint of preventing excessive loss of components, it is preferably 24 hours or less, more preferably 1 hour or less, even more preferably 20 minutes or less, and even more preferably 15 minutes or less.
There is no particular lower limit to the time for soaking the dried tea leaves in water, but from the standpoint of facilitating sufficient soaking, it is preferably 1 minute or more, more preferably 10 minutes or more.

The means for soaking the 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 of the methods are preferably carried out in a low-temperature environment (for example, in an environment of 4° C. or less, such as in a refrigerator).
・Put the dried tea leaves together with water into a container (such as a plastic container) and allow to absorb or shake (vibrate) to absorb.
- Immerse the dried tea leaves in water using a vacuum or pressure machine.
- Water is sprayed onto the dried tea leaves using a coating machine etc.

(3) Freeze-drying Step In the freeze-drying step, the tea leaves after the steeping are freeze-dried.

In the freeze-drying process, any conditions that can be used in the freeze-drying of foods and beverages can be used, and the process usually includes the following steps.
- Freeze the tea leaves once steeping is complete.
The frozen tea leaves are dried while still remaining frozen.
In the above steps, it is preferable that the soaking step and the freezing of the tea leaves are continuous (without any other steps between the two steps). Also, from the viewpoint of easily suppressing deterioration in the quality of the obtained tea leaf product, it is preferable to carry out the freezing promptly (for example, within one hour) after the completion of the soaking step.
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.

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.

The drying conditions for the frozen tea leaves are not particularly limited and can be appropriately set 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 less.

In the freeze-drying process, any device known as a freeze-dryer (flask type, dry chamber type, etc.) can be used.

(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.

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.

The resulting tea leaf product may be appropriately processed and prepared, for example, into the following forms:
・Tea leaf products in containers ・Tea bag products ・Cup products with tea leaf products fixed inside together with filters, etc. ・Tea leaf products for tea dispensers

(5) Examples of Tea Beverage Preparation From the tea leaf product obtained by the production method of the present invention, a tea beverage can be prepared by any extraction method known as a method for producing tea beverages.
However, since the tea leaf product obtained by the manufacturing method of the present invention is particularly suitable for preparing a cold-brewed tea beverage, a preferred preparation example will be described below.

There are no particular limitations on the method for preparing a tea beverage from a tea leaf product, and any method that brings a tea leaf product into contact with water can be used.
However, in order 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.

According to the present invention, since the component extraction efficiency is excellent as described above, 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 takes many hours of extraction time to obtain a cold-brewed tea beverage (see, for example, the Comparative Example 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 efficiency of component extraction.

As described above, by using low-temperature water and extracting 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 dissolved while suppressing the dissolution of caffeine and epigallocatechin gallate.

<Method of processing tea leaf products for cold-brewed tea beverages>
As described above, according to the present invention, a tea leaf product for cold brewing can be obtained that has excellent ingredient extraction efficiency.
Thus, in one aspect, the present invention also includes a method for processing a tea leaf product for a cold-brewed tea beverage, comprising the steps of:
- A steeping process in which unground, unextracted dried tea leaves are steeped in water.
- Freeze-drying process, in which the tea leaves after the soaking process are freeze-dried.

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

<Production of tea leaf products>
The tea leaves were processed to produce tea leaf products as follows:

(1) Preparation of Dried Tea Leaves As dried tea leaves, commercially available sencha tea produced from leaves (new shoots) of the tea plant (scientific name: Camellia sinensis) was used.
The tea leaves are so-called green tea (unfermented tea) and correspond to "unground and unextracted dried tea leaves."

(2) Soaking Step The dried tea leaves were soaked in water contained in a rectangular container so that the entire leaves were immersed. The amount of water used was five times the amount of the dried tea leaves (about 4°C).
Next, the container containing the dried tea leaves was placed in a refrigerator (about 4° C.) and left to stand for about 15 minutes to allow the tea leaves to fully absorb water.

(3) Freeze-drying step After the immersion step was completed, the container was promptly taken out of the refrigerator and frozen in a freezer (at about -20°C), and then placed in a freeze-dryer (flask type) and dried under vacuum conditions.
The freeze-drying conditions were set as follows: trap cooling temperature -50° C. or less, vacuum degree 30 Pa or less, and freeze-drying time 24 hours.

(4) Obtaining the tea leaf product After the freeze-drying process was completed, a tea leaf product (freeze-dried product) was obtained, which was subjected to the following extraction test.

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

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

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

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

(3-1) Analytical conditions and apparatus for EGC, EGCG, and caffeine: Shimadzu LC-20AD system, Shimadzu Corporation; Guard column: Security Guard Cartridge C18 (id 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.

(3-2) Analytical conditions for theanine: Equipment: Automatic precolumn derivatization with o-phthalaldehyde using the Shimadzu LC-20AD, SIL-40C system (Shimadzu Corporation); Guard column: Security Guard Cartridge C18 (id 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.

(3-3) Results The analysis results are shown in FIG.
Fig. 1 shows the results of analysis of components eluted from the tea leaf product of the Example, and Fig. 2 shows the results of analysis of components eluted from the dried tea leaves of the Comparative Example.

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

As shown in FIG. 1, the tea leaf product obtained by the manufacturing method of the present invention produced an extract (tea beverage) in which epigallocatechin and theanine were sufficiently dissolved in a short period of time of less than 5 minutes, even when extracted in a refrigerator.
This result indicates that the tea leaf product obtained by the production method of the present invention has extremely excellent efficiency in extracting ingredients from tea leaves.

In contrast, as shown in FIG. 2(A), in the case of the dried tea leaves of the comparative example (normal green tea), it took a very long time for the components to dissolve during extraction in a refrigerator, and it took nearly half a day for the dissolution rate to reach the same level as the tea leaf product obtained by the manufacturing method of the present invention.
For the dried tea leaves of the comparative example, extraction was also performed at room temperature (about 26°C) instead of in a refrigerator (Figure 2(B)), but it still took a long time for the ingredients to dissolve, and it took nearly an hour for the dissolution rate to reach the same level as that of the tea leaf product obtained by the manufacturing method of the present invention.

From the above, it has been 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 achieve efficient ingredient extraction.

Claims (4)

A method for producing a tea leaf product for cold brew tea beverage comprising the steps of:
The manufacturing method comprises:
A soaking step of soaking unground and unextracted dried tea leaves in water (excluding the aqueous solution containing the enzyme produced by Hiirotake mushroom) ;
A freeze-drying step of freeze-drying the tea leaves after the soaking step.
Production method. The manufacturing method according to claim 1, wherein the soaking time of the dried tea leaves in the soaking step is 20 minutes or less. The manufacturing method according to claim 1, wherein the temperature of the water in the soaking step is 20°C or less. 1. A method for processing a tea leaf product for a cold-brewed tea beverage, comprising the steps of:
The processing method comprises:
A soaking step of soaking unground and unextracted dried tea leaves in water (excluding the aqueous solution containing the enzyme produced by Hiirotake mushroom) ;
A freeze-drying step of freeze-drying the tea leaves after the soaking step.
Processing method.

Images