JP2024015857A - Production method of after-fermented tea - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an after-fermented tea which contains much gallic acid.

SOLUTION: A production method of an after-fermented tea leaf includes the steps of: giving water to a tea leaf, with enzymes contained in the tea leaf being inactivated, to adjust its water content to 25 w/w% or more and 45 w/w% or less; and fermenting the tea leaf having the adjusted water content with a microorganism such as a bacterium classified into, preferably, the genus Aspergillus. After an acidity of the tea leaf falls below a local minimum point after a start of the fermentation, the fermentation is terminated within a range of a pH of 5.0±0.2. The obtained tea leaf contains gallic acid of 3.0 w/w% or more, preferably 4.0 w/w% or more.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a method for producing post-fermented tea.

Tea (tea leaves), which is mainly used for drinking, is roughly divided into unfermented tea called green tea, semi-fermented tea called oolong tea, fully fermented tea called black tea, and post-fermented tea called black tea, depending on the manufacturing method. Ru. Among these, post-fermented tea is produced by steaming or roasting raw tea leaves to perform a blue killing treatment, and then inoculating them with microorganisms such as Aspergillus oryzae to allow sedimentation fermentation. Post-fermented tea is not fermented by enzymes derived from raw tea leaves, but is produced by the decomposition of catechins with gallate groups in tea leaves by the action of enzymes derived from planted microorganisms, especially tannase. It contains gallic acid and the components derived from tea leaves are broken down by various enzymes derived from microorganisms, resulting in the umami and richness unique to black tea. Therefore, products that have been fermented for a long period of time are considered to be of good quality and are preferred.

Gallic acid produced in this manufacturing process is also called 3,4,5-trihydroxybenzoic acid, and is said to not only have an antioxidant effect but also be effective in treating and preventing obesity. For example, Non-Patent Document 1 discloses that oolong tea, which is a fermented tea after being fermented for several months, showed a decrease in BMI and weight loss. It is said that about 27 mg is contained in 1 g of tea leaves of the oolong tea used here (Non-Patent Document 2).

In addition, Patent Document 1 (Japanese Patent Application Laid-open No. 2005-278519) discloses that although it contains a large amount of gallic acid and a large amount of catechins, it has little bitterness and astringency, and has a strong umami and richness. In order to provide tea, a method has been proposed in which fermentation using Aspergillus oryzae is carried out in the form of a slurry in which ground tea leaves, which have been subjected to blue killing treatment, are suspended in water.

However, in this method, it is necessary to crush the blue-killing raw material tea leaves into a slurry state, and the number of steps is increased compared to the conventional post-fermented tea manufacturing process. Furthermore, according to Non-Patent Document 1, it was considered that a fermentation period of several months is required to provide post-fermented tea containing gallic acid in amounts exhibiting various physiological activities.

Japanese Patent Application Publication No. 2005-278519

K. Kubota et al. Nutrition Research 31, 2011, 421-428 H. Fujita et al. Phytother Res. 22, 2008, 1275-81

The present invention provides a method for producing post-fermented tea with a high content of gallic acid capable of sufficiently expressing physiological activity in a shorter period of time than before, using a method substantially similar to the production process of conventional post-fermented tea. The task is to

The present invention is a method for producing post-fermented tea leaves, which includes a step of fermenting so-called blue-killed tea leaves with Aspergillus oryzae. It is characterized by stopping fermentation.

According to the production method of the present invention, tea leaves with a high content of gallic acid capable of sufficiently expressing physiological activity can be produced through substantially the same steps as the previous steps.

FIG. 1 is a diagram showing changes over time in gallic acid content in the manufacturing process of post-fermented tea, which is one embodiment of the present invention. FIG. 2 is a diagram showing changes over time in the gallic acid content in the post-fermented tea manufacturing process, which is another embodiment. FIG. 3 is a diagram showing changes over time in the pH of tea leaves in the manufacturing process of post-fermented tea, which is one embodiment of the present invention. FIG. 4 is a diagram showing the change in pH of tea leaves over time in another embodiment of the post-fermented tea manufacturing process. FIG. 5 is a diagram showing changes over time in the pH of tea leaves in the manufacturing process of post-fermented tea, which is one embodiment of the present invention. FIG. 6 is a diagram showing the change in pH of tea leaves over time in another embodiment of the post-fermented tea manufacturing process.

The method for producing post-fermented tea of the present invention is a method for producing post-fermented tea leaves that includes a step of fermenting green-killed tea leaves with microorganisms. It is characterized by stopping the fermentation of tea leaves within the range of 0±0.2.

The present invention was conducted during the conventional post-fermented tea production process, and as a result of investigating changes over time in the gallic acid content of tea leaves, it was found that as the fermentation period became longer, the gallic acid content decreased and This was based on the finding that the pH value of 100% also started to rise after falling once. That is, the present invention provides post-fermented tea with a high content of gallic acid by stopping fermentation in a relatively short period of time.

The tea leaves used in the present invention may be of any variety as long as they are tea leaves that can be used for drinking, and are preferably tea leaves that have been used as a raw material for post-fermented tea. The tea leaves used for fermentation are blue-killed tea leaves. Blue-killing treatment is a process that deactivates various enzyme activities in raw tea leaves, such as steaming (applying heat by steaming) and roasting (roasting), which have been used in the production of conventional post-fermented tea. This is done by applying heat (by applying heat). The tea leaves used in the production method of the present invention may contain tea stems.

Water is added to the tea leaves after the green killing treatment to adjust the moisture content of the tea leaves to 25 w/w% or more and 45 w/w% or less, preferably 30 w/w% or more and 40 w/w% or less. Moisture content means the amount of water in tea leaves containing water, and is determined from the mass of tea leaves before and after drying, with the mass when dried at 105° C. until the mass becomes constant as the mass after drying. If the moisture content exceeds 45w/w%, bacteria will increase at the start of fermentation and the tea will rot, the moisture content in the tea leaves will not decrease sufficiently, and the acidity of the tea leaves will increase as the fermentation period progresses. As a result, the content of gallic acid decreases rapidly. Furthermore, if the water content is less than 25 w/w%, the fermentation itself will not proceed, and not only will the amount of gallic acid produced not increase, but it will also become impossible to produce post-fermented tea.

The tea leaves, whose moisture content has been adjusted, are mixed with microorganisms and fermented to produce post-fermented tea. The microorganisms may also be the same type of microorganisms that have been used in the production of post-fermented tea. The microorganisms used are typically bacteria classified into the genus Aspergillus, such as Aspergillus luchuensis, Aspergillus nigar, Aspergillus oryzae, and Aspergillus awamori. (Aspergillus awamori), Aspergillus saitoi (Aspergillus saitoi), bacteria belonging to the genus Rhizopus, such as Rhizopus delemar, bacteria belonging to the genus Penicillin, such as Penicillium camemberti, other genus Tempeh, etc. microorganisms that can be used in food processing.

The amount of microorganisms to be mixed can also be determined as appropriate. The mixing amount may be the same as in the conventional method, and may be 0.001 to 1% by mass, preferably 0.01 to 0.5% by mass, based on the tea leaves whose water content has been adjusted. The method of mixing with tea leaves is similar, for example, a method of directly mixing microorganism cells or spores with tea leaves as a powder, or a method of mixing microorganism cells or spores with a food excipient such as wheat flour, rice flour, barley flour, etc. Examples include a method in which powder is mixed and then mixed with tea leaves, and a method in which microbial cells or spores are suspended in physiological saline or the like and sprayed onto tea leaves.

The tea leaves mixed with microorganisms are stirred well and left to ferment. The fermentation method may be the same as the conventional method for producing post-fermented tea, and the tea is spread out to a certain thickness and left at a room temperature of 1 to 35°C, preferably 10 to 30°C. As the fermentation progresses, the temperature of the tea leaves rises, so to prevent excessive temperature rise and ensure as uniform fermentation as possible, the tea leaves are thoroughly stirred every two to three days. At this time, the standard is to ensure that the temperature during fermentation does not exceed 65°C, and it is preferable to cover the container with straw to prevent the temperature during fermentation from dropping excessively. Further, rolling may be performed before or immediately after mixing the microorganisms.

During the fermentation period, the acidity of the fermenting tea leaves is measured every few days, preferably every other day, preferably every day. Acidity is expressed by pH measured by the method described in Examples. Acidity decreases as fermentation progresses, reaches a minimum value several days after the start of fermentation, approximately 5 to 10 days, and then begins to rise. After this, it gradually increases, but the upward trend becomes more gradual as the days pass (see Figure 2). On the other hand, the gallic acid content in tea leaves gradually increases after the start of fermentation, reaches a maximum value approximately 10 days after the start of fermentation, and then begins to decline. Post-fermented tea is often considered to be of good quality if it has a long fermentation period, but as the fermentation period increases, the content of gallic acid decreases, so after the acidity of the tea leaves reaches a minimum value, the value rises slowly. The fermentation of tea leaves is stopped when the pH reaches a plateau of 5.0±0.2.

Additionally, the acidity of the tea leaves must once reach its minimum point. This requires microbial fermentation to decompose tea catechins (gallic acid esters) in tea leaves to produce gallic acid, and further fermentation to produce polyphenols derived from tea catechins and other substances. This is because it is necessary to polymerize and decompose the polyphenols in the tea leaves to produce the aroma and taste unique to post-fermented tea, or to bring the aroma and taste closer to those of good quality post-fermented tea. The pH at the minimum point should be less than 4.8, which is the fermentation end point, but considering the decrease in gallic acid content after the minimum point, the minimum point is preferably 4.7, more preferably 4. It is preferable that it be about 5.

Fermentation can be stopped by drying the tea leaves. Drying may be performed in the same manner as conventional methods, and may be mechanically dried at 90 to 105°C, preferably about 95°C, or may be dried in the sun. At this time, the tea leaves are dried so that the water content becomes 15 w/w%, preferably 12 w/w% or less, and fermentation is stopped to obtain fermented tea.

It is necessary that the gallic acid in the tea leaves whose fermentation has been stopped contains enough gallic acid to exhibit physiological activity. The gallic acid content that can sufficiently exhibit physiological activity here means that the content of gallic acid in the dried tea leaves is at least 3.0 w/w% or more, preferably 4.0 w/w, as can be said from Non-Patent Document 1. % or more is desirable. If the water content at the start of fermentation is high, for example at around 40 w/w%, if the pH exceeds 5.2 and fermentation continues, the gallic acid content will rapidly increase from around 3 w/w%. There is a risk that it will decrease. In addition, even if fermentation is started at a water content of 30 to 35 w/w%, which is considered preferable in the conventional production method, if fermentation is continued when the pH exceeds 5.2, the gallic acid content will drop to about 4 w/w. /w% or less, and in some cases, about 3w/w% or less, the gallic acid content decreases and the meaning of stopping fermentation in the pH range of 5.0±0.2 is lost.

The obtained tea leaves are used as a raw material for so-called tea drinks. The tea beverage may be made by mixing not only the obtained tea leaves but also unfermented green tea or semi-fermented tea oolong tea and then extracting with water, or using only the obtained tea leaves. The tea beverage of the present invention can also be prepared by appropriately mixing the resulting extract (tea beverage) with a green tea or oolong tea extract (tea beverage). However, tea leaves with a pH of 5.0±0.2 may be used as a raw material for the extract without stopping the fermentation.

Furthermore, the tea extract in the present invention is not limited to an extract extracted with water, but may also be an extract obtained using various solvents such as ethanol or a mixture of water and ethanol, and furthermore, these extracts may be concentrated or extracted. There may also be viscous extracts or solid extracts obtained by drying. In addition to tea beverages, these extracts can also be used as raw materials for food production, so-called health foods, and the like.

As described above, in the production method of the present invention, by measuring the pH during fermentation, it is possible to provide post-fermented tea with a high gallic acid content in substantially the same process as the previous process.

The present invention will be described below based on Examples, but it goes without saying that the present invention is not limited to the following Examples.

Water was added to 1200 kg of Chinese tea leaves to adjust the initial moisture content to 33 w/w%. After adjusting the water content, 0.01 w/w% (120 g) of koji mold (Aspergillus luthiensis) was added to the tea leaves, and the mixture was sufficiently stirred and mixed. The tea leaves mixed with koji mold were piled up to a height of about 1 m and leveled (ground leveling), and to prevent excessive drying, the tea leaves were covered with jute bags and fermentation was started at room temperature below 35 degrees Celsius. The temperature of the tea leaves at this time (temperature measured by inserting a thermometer into the ground tea leaves) was 20°C. Thereafter, on the second day after the start of fermentation and every three days after that, stirring was performed as appropriate so that the temperature of the tea leaves did not exceed 65° C., and fermentation was continued.

During fermentation, the amount of gallic acid, acidity (pH value), and water content in the tea leaves were measured during stirring. After sampling tea leaves in the middle of fermentation from several locations and mixing them, 1 g of tea leaves was weighed out and water was added to make 50 g. This was boiled in hot water and extracted at 80°C or higher for 10 minutes. Thereafter, the tea leaves were removed with a tea strainer, cooled to room temperature, and used as a sample. The amount of gallic acid in the sample was measured using high-performance liquid chromatography, and the content (w/w%) per gram of tea leaves during fermentation was determined. Acidity was determined by measuring the pH of the sample with a pH meter. To determine the water content, an appropriate amount of the sampled tea leaves was dried in a constant temperature bath at 105° C. for about 1 hour, and the mass after drying was determined when there was almost no change in mass. The moisture content was determined from the mass before and after drying. The results are shown in FIGS. 1, 3, and 5, respectively. In another embodiment, the initial moisture content was adjusted to 43 w/w% and fermentation was carried out in the same manner as above. The results in this case are shown in FIGS. 2, 4, and 6, respectively.

According to the present invention, post-fermented tea containing a relatively large amount of gallic acid can be produced using substantially the same process as the conventional production process.

Claims (6)

A method for producing post-fermented tea leaves comprising a step of fermenting blue-killed tea leaves with microorganisms,
A method for producing post-fermented tea leaves, which comprises stopping the fermentation of tea leaves in a pH range of 5.0±0.2 after the acidity of the tea leaves falls below the minimum point after the start of fermentation. 2. The method for producing post-fermented tea leaves according to claim 1, wherein fermentation is started after adding water to the green-killed tea leaves and adjusting the water content to 25 w/w% or more and 45 w/w% or less. The manufacturing method according to claim 1 or 2, wherein the minimum point is less than pH 4.8. The manufacturing method according to claim 1 or 2, wherein the gallic acid content in the tea leaves after the fermentation is stopped is 3.0 w/w% or more. 5. The manufacturing method according to claim 4, wherein the minimum point is less than pH 4.8. It is obtained from post-fermented tea leaves obtained by starting fermentation of blue-killed tea leaves with microorganisms, and then stopping the fermentation of tea leaves in the pH range of 5.0 ± 0.2 after the acidity of the tea leaves falls below the minimum point. extract.