Method for producing blueberry tea leaves and its uses

Abstract

This invention provides a method for producing blueberry tea leaves with a high total polyphenol content. [Solution] A method for producing blueberry tea leaves comprising the following steps: (1) A process of preparing frozen blueberry leaves by freezing fresh blueberry leaves, (2) A step of storing the frozen leaves under low temperature conditions of 5°C to 15°C, (3) A step of drying the leaves obtained in the above step.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing blueberry tea leaves. The present invention also relates to the use of blueberry tea leaves obtained by the manufacturing method of the present invention or processed products thereof.

Background Art

[0002] Tea leaves are generally classified into fermented tea leaves and unfermented tea leaves. Generally, fermented tea leaves represented by black tea (tea leaves) are obtained by withering (drying) the picked tea leaves and buds, squeezing them (rolling), and destroying the cells, so that the oxidase in the cells contacts the components contained in the leaves and oxidizes and ferments these components. On the other hand, unfermented tea leaves represented by green tea (tea leaves) are tea leaves produced by suppressing oxidative fermentation by inactivating oxidase by steaming or frying the picked tea leaves. In addition, there are also tea leaves (semi-fermented tea leaves, partially fermented tea leaves) that are fermented only by oxidase, represented by oolong tea and Baozhong tea.

[0003] As the leaves of plants used as raw materials for tea leaves, in addition to the leaves of Camellia sinensis of the genus Camellia in the family Theaceae, the leaves of many plants such as loquat leaves, rose leaves, and blueberry leaves have been used for a long time. For example, Patent Document 1 describes a method for manufacturing fermented tea leaves using loquat leaves as a raw material. Patent Document 2 also describes a method for manufacturing fermented tea leaves (black tea leaves) using rose leaves as a raw material. Furthermore, Patent Documents 3 and 4 describe methods for manufacturing tea leaves using blueberry leaves as a raw material.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

[0005] The object of this invention is to provide a method for producing blueberry tea leaves. Preferably, the object of this invention is to provide a method for producing fermented blueberry tea leaves with a high total polyphenol content. More preferably, the object of this invention is to provide a method for producing fermented blueberry tea leaves that can be used to prepare tea products (including tea beverages) that have a high total polyphenol content and good flavor.

[0006] Furthermore, the present invention aims to provide uses for blueberry tea leaves or processed products thereof obtained by the manufacturing method of the present invention as food and beverages. More preferably, it aims to provide uses as health food and beverages, in particular as food and beverages for improving sleep. [Means for solving the problem]

[0007] The inventors of this invention produced fermented tea leaves using blueberry leaves as raw material by wilting (drying) leaves picked from blueberry bushes, rolling them, and then fermenting them at room temperature (hereinafter also referred to as the "conventional method"). They found that this method had the following problems: (1) uneven fermentation occurred, (2) the total amount of polyphenols in the obtained tea leaves decreased, and (3) the extract obtained from the obtained tea leaves had a distinctive grassy odor. The problem in (1) is due to the fact that blueberry leaves are hard and difficult to roll uniformly.

[0008] In order to solve these problems, we conducted thorough research and discovered that by adopting the freeze-low temperature fermentation method described later, instead of the conventional manufacturing method, the problems in (1) and (2) above can be resolved, and more preferably, the problem in (3) can also be resolved in addition to (1) and (2), and tea leaves can be prepared that yield an extract with good flavor. This invention was completed through further research based on the aforementioned findings, and has the following embodiments.

[0009] (I) Method of producing blueberry tea leaves (I-1) A method for producing blueberry tea leaves comprising the following steps: (1) A process of preparing frozen blueberry leaves by freezing fresh blueberry leaves (freezing process), (2) A step of storing the frozen leaves under low temperature conditions of 5°C to 15°C (low temperature storage step), (3) A step of drying the leaves obtained in the above step (drying step). (I-2) The manufacturing method according to (I-1), further comprising the following steps between step (2) and step (3): (2-2) A step of storing the low-temperature preserved leaves at a temperature greater than 15°C and 40°C or less. (I-3) A method of manufacturing according to (I-1) or (I-2), which does not include a kneading step.

[0010] (II) Blueberry tea leaves and their uses Blueberry tea leaves or processed products thereof manufactured by any of the methods described in (II-1), (I-1), to (I-3). A food and beverage composition containing blueberry tea leaves or processed products thereof as described in (II-2)(II-1). (II-3) A food or beverage composition described in (II-2) that is a composition for improving sleep. [Effects of the Invention]

[0011] The manufacturing method of the present invention makes it possible to produce blueberry fermented tea leaves with a higher total polyphenol content compared to fermented tea leaves produced by conventional methods. Furthermore, the manufacturing method of the present invention makes it possible to produce fermented tea leaves with a reduced grassy odor and better flavor compared to fermented tea leaves produced by conventional methods.

[0012] In addition, the fermented tea leaves obtained by the production method of the present invention and processed products thereof contain a large amount of polyphenols, and thus can be suitably used as food and drink, particularly healthy food and drink. Further, food and drink using the fermented tea leaves obtained by the production method of the present invention as a raw material have a good sleep improvement effect, and thus can be suitably used as a functional food with a functional indication or a food for specified health use as a composition for improving sleep.

Brief Description of the Drawings

[0013] [Figure 1] Left figure: An image showing the state of tea leaves after each step ((1) withering, (2) rolling, (3)) fermentation, (4) drying) by the conventional production method (Comparative Example 1). Right figure: An image showing the state of tea leaves after each step ((1) freezing, (2) thawing / fermentation, (3) drying) by the production method of the present invention (Example 2). [Figure 2] The results of Experimental Example 1 are shown. The total polyphenol content (mg_GAE. / 100 ml) analyzed for the hot water extracts of the tea leaves of Comparative Examples 1 to 4 and Examples 1 to are shown. Here, "GAE" means "gallic acid equivalent". The same applies to Figure 3. [Figure 3] The results of Experimental Example 1 are shown. The total polyphenol content (mg_GAE. / 100 ml) analyzed for the hot water extracts of the tea leaves of Examples 6 to 11 are shown. [Figure 4] The results of Experimental Example 2 are shown. The amount of cis-3-hexen-1-ol analyzed for the water extracts of the tea leaves of Comparative Example 1 and Examples 1 to 5 are shown. [Figure 5] In Experimental Example 4, the results (mid-awakening time) of a sleep improvement test using the hot water extract (active food) of Example 5 and a placebo food are shown. [Figure 6] In Experimental Example 4, the results (sleep efficiency) of a sleep improvement test using the hot water extract (active food) of Example 5 and a placebo food are shown.

Modes for Carrying Out the Invention

[0014] (I) Method of producing blueberry tea leaves The method for manufacturing blueberry tea leaves of the present invention is characterized by having the following steps (1) to (3). (1) A step of freezing fresh blueberry leaves to prepare frozen leaves (freezing step), (2) A step of storing the frozen leaves under low temperature conditions of 5°C or higher and 15°C or lower (low temperature storage step), and (3) A step of drying the leaves obtained in the above steps (drying step).

[0015] Also, the low temperature stored leaves obtained in the low temperature storage step of (2) can be further subjected to the following step (2-2) before being subjected to the drying step of (3): (2-2) A step of storing the low temperature stored leaves at a temperature exceeding 15°C and 40°C or lower. <......><......>The original plant of the blueberry tea leaves is a small fruit tree of the genus Rhododendron in the Ericaceae family, and can be roughly classified into three varieties: the Northern highbush blueberry, the Southern highbush blueberry, and the Rabbiteye blueberry. The original plant used in the present invention is not particularly limited to these classifications, and any blueberry species can be used, or a hybrid species obtained by cross-breeding these species may also be used. Although not limited, among the above, from the point of view of having a large total polyphenol content, it is preferably a Rabbiteye blueberry.

[0017] The part of the original plant used is preferably the leaves. However, in addition to the leaves, the use of other parts is not particularly restricted. Examples of parts other than the leaves include branches and leaves, branches, flowers, flower spikes, flower petals, fruits, or seeds. These parts of the source plant are preferably subjected to the freezing process in (1) in their raw state after being picked from the source plant and, if necessary, washed to remove surface dirt. In other words, it is preferable that they be subjected to the freezing process directly in their raw state after being picked from the source plant, without being subjected to shredding (including crushing and grinding), drying, wilting, heating, steaming, or kneading. More preferably, they are subjected to the freezing process on the same day they are picked from the source plant, or at the latest the following day. While there are no restrictions, it is preferable to harvest blueberry leaves while they are still green, from spring to autumn. More preferably, it is done from summer to autumn (July to October).

[0018] (1) Freezing process The freezing process involves freezing the freshly picked blueberry leaves. Generally, there are two types of freezing processes: rapid freezing and slow freezing. Rapid freezing is a method of freezing an object so that its core temperature passes through the maximum ice crystal formation temperature range (-1°C to -5°C) within 30 minutes. On the other hand, slow freezing is a method of freezing an object over a period of 30 minutes or more, passing through the aforementioned maximum ice crystal formation temperature range. When fresh leaves are frozen during the freezing process, the water inside the leaf cells freezes, resulting in the destruction of cellular organelles such as vacuoles and cellular tissues such as cell walls. This destruction of cellular tissue is thought to cause enzymes inside the cells to leach out of the cells, effectively promoting subsequent fermentation. The freezing process employed in this invention is not limited to rapid freezing or slow freezing; any freezing process that more effectively achieves this effect is acceptable, but slow freezing is preferred.

[0019] In this invention, specifically, although not limited, fresh leaves can be frozen by placing them in a freezer maintained at approximately -20°C to -80°C and holding them for approximately 30 minutes to 24 hours. Although not limited, it is preferable to hold them at a temperature of -20°C for 2 hours or more. The freezing temperature can be within the above temperature range, but preferably, a temperature range of -20°C to -60°C can be exemplified. In addition to 2 hours or more, the freezing period can be, for example, 24 hours or more, or in the range of 24 to 168 hours. However, this does not limit the storage of the frozen state for a long period of time (for example, 1 month to several months) for purposes such as production adjustment or storage.

[0020] (2) Low temperature storage process The low-temperature storage process can be carried out by storing the frozen leaves obtained in step (1) under low-temperature conditions. The low-temperature conditions used here include temperatures between 5°C and 15°C. While not limited, temperatures between 5°C and 10°C are preferred. The storage time is not limited, but can usually be selected from a range of 6 hours to 120 hours. Preferably, it is between 6 hours and 72 hours, more preferably between 12 hours and 36 hours, and particularly preferably between 24 hours and 36 hours. The low-temperature storage process can be carried out using a temperature-controlled device, such as a warming cabinet. While not limited, it is preferable that the low-temperature storage process be carried out under controlled humidity conditions. In this case, it can be carried out using a warming cabinet set and adjusted so that the relative humidity is in the range of 60-100%, more preferably 70-100%.

[0021] It is believed that by storing frozen leaves under the aforementioned low-temperature conditions for a certain period, the water in the frozen cells slowly thaws, causing the cells to break down. Furthermore, as the cells thaw, enzymes contained within them come into contact with components in the leaves, and an enzymatic reaction (fermentation) proceeds. Therefore, by storing the frozen leaves under the aforementioned low-temperature conditions for a certain period of time, the leaves undergo a fermentation process. In other words, this low-temperature storage process is both a thawing process and a low-temperature fermentation process (thawing and fermentation process).

[0022] The leaves stored at low temperature may be stored at room temperature after the low-temperature storage process and before being subjected to the drying process described later in (3). Here, room temperature can be exemplified as a temperature greater than 15°C and 40°C or less. Preferably, it is greater than 15°C and 35°C or less, and more preferably 20°C or more and 30°C or less. As shown in the experimental examples described later, even if the leaves that have been fermented at low temperature by the low-temperature storage process described above are subsequently stored at room temperature, the total amount of polyphenols they contain does not decrease, and they can have a good flavor (initial taste [no grassy smell, moderate bitterness, moderate herbaceous flavor], aftertaste [refreshing]).

[0023] (3) Drying process The low-temperature preserved leaves obtained in the above step (or the leaves subsequently preserved at room temperature) can then be subjected to a drying step. The drying process can be any method commonly used for drying tea leaves in general processing methods, and is not particularly limited. For example, hot air drying can be used. Hot air drying can be carried out by setting the air temperature to 50°C or higher, preferably 60°C or higher, and more preferably around 70°C. Although not limited, it is preferable to dry the leaves so that their moisture content is about 5%.

[0024] The blueberry leaves prepared by steps (1) to (3) above can be suitably used as tea leaves. As shown in the experimental examples described later, the extract prepared from the blueberry leaves prepared by steps (1) to (3) above is characterized by a high total polyphenol content and good flavor (initial taste and aftertaste). If necessary, finishing processing may be performed after steps (1) to (3).

[0025] (4) Finishing process Finishing processes include sorting, sieving, cutting, shredding (including crushing and grinding; the same applies hereinafter), sieving of shredded tea leaves, classification, sterilization, and individual packaging (tea bag packaging). These processes can be selected and combined as appropriate.

[0026] (II) Blueberry tea leaves and processed products thereof The blueberry tea leaves covered by this invention are blueberry leaves produced by the method described above. While the term "tea leaves" generally refers to leaves used in the preparation of tea or tea beverages, the blueberry tea leaves targeted by this invention can be used in a wide range of food and beverage preparations, not just tea or tea beverages. Tea-based beverages and processed tea foods and beverages will be discussed later. As shown in the experimental examples described later, the blueberry tea leaves produced by the method of the present invention differ from tea leaves produced by conventional methods (rolling followed by room temperature fermentation) and tea leaves produced by freezing followed by room temperature fermentation in that they have a high total polyphenol content. Furthermore, as shown in Experimental Example 3 described later, the blueberry tea leaves produced by the method of the present invention differ from tea leaves produced by conventional methods (rolling followed by room temperature fermentation) and tea leaves produced by freezing followed by room temperature fermentation in that they have a good flavor without the grassy odor caused by cis-3-hexen-1-ol.

[0027] The subject of the present invention may be the blueberry tea leaves themselves produced by the method described above, or it may be a processed tea leaf product prepared by further processing using the blueberry tea leaves as a raw material. Tea leaf products include blueberry tea leaves produced by the method described above that have been shredded (including crushing and pulverizing) (shredded material, crushed material, pulverized material), solidified versions of these, shredded material that has been classified as needed and individually packaged (tea bag packaging), a liquid obtained by extracting blueberry tea leaves with water or aqueous ethanol, etc. (extract), a concentrated extract (concentrate, extract), and a product formed into a solid after drying the extract (powder, granules, tablets, pills, etc.). Preferred tea leaf products include blueberry tea leaf powder or solidified blueberry tea leaf powder, tea bag packaging, blueberry tea leaf extract or concentrated blueberry tea leaf extract, and a product formed after drying the extract.

[0028] (III) Uses of blueberry tea leaves and processed products thereof The blueberry tea leaves of the present invention described above can be suitably used as a raw material for food and beverages. Furthermore, the processed products of the blueberry tea leaves described above (processed tea leaves) can be suitably used as food and beverages or as raw materials for food and beverages. For this reason, the present invention provides the use of the blueberry tea leaves and processed products described above as food and beverages or as raw materials for food and beverages.

[0029] Food and beverages are not restricted, but examples include: beverages such as tea, bottled tea drinks, soft drinks, carbonated drinks, lactic acid drinks, lactic acid bacteria drinks, milk drinks, and alcoholic beverages; rice crackers, senbei crackers, manju and various other Japanese sweets; cookies, biscuits, crackers, pies, sponge cakes, chiffon cakes, castella, donuts, waffles, custard cream, cream puffs, chocolate confectionery, jelly, pancakes, bread and various other Western sweets; dairy products such as yogurt, pudding, bavarian cream, and mousse; candies such as caramel, soft candy, hard candy, gummy candy, and tablets (including ramune candy, tablet-shaped confectionery, and refreshing candy); chewing gum and bubble gum; potato chips and various other snack foods; ice cream, ice milk, lacto ice, soft serve ice cream and other ice cream products; ice pops, sherbet, gelato and various other frozen desserts; sauces, bouillon cubes, stew mixes, soup mixes and various other seasonings. These various food and beverage products can be manufactured by any method known to those skilled in the art.

[0030] Furthermore, the food and beverage may also be a supplement in the form of a formulation such as lozenges, drinks, granules, powders, tablets, and capsules. Such a supplement may contain any other ingredients in addition to the blueberry tea leaf product. Other ingredients include various additives necessary for preparing the formulation, such as excipients, binders, disintegrants, lubricants, wetting agents, fluidizing agents, preservatives, surfactants, stabilizers, diluents, solvents, isotonic agents, antiseptics, and colorants.

[0031] These foods and beverages include foods for special dietary uses (including foods for the sick and foods for the elderly), and foods with health claims (foods for specified health uses, foods with nutritional function claims, and foods with functional claims), which are commonly referred to as health foods. In this case, the amount of blueberry tea leaf processed product to be incorporated into the food or beverage can be appropriately determined by a person skilled in the art, depending on the expected function, use, purpose, and / or palatability.

[0032] The food and beverages of the present invention can preferably be used for sleep improvement purposes. As shown in Experimental Example 4 described later, taking the blueberry tea leaf processed product (extract) of the present invention can shorten the time spent awake during sleep and improve sleep efficiency (sleep quality). Therefore, the sleep improvement applications targeted by the present invention preferably include improving sleep efficiency (sleep quality) by suppressing or shortening the time spent awake during sleep. Furthermore, the sleep improvement applications targeted by the present invention also include obtaining (improving) a feeling of deep sleep by improving sleep quality by suppressing or shortening the time spent awake during sleep.

[0033] The amount of the blueberry tea leaf processed product of the present invention to be ingested in order to suitably obtain the above effect is not limited to the amount that the above effect is obtained, but can be appropriately selected from the range of 1 to 10 g, preferably 2 to 8 g, and more preferably 4 to 8 g per day, when converted to the amount of dried tea leaves. Although not limited, one of the functional components of the blueberry tea leaf processed product is the flavonoid glycoside (hyperoside) contained in the blueberry tea leaf processed product. Although not limited, the amount of the blueberry tea leaf processed product of the present invention can also be appropriately selected from the range of 1 to 10 mg, preferably 2 to 8 mg, and more preferably 4 to 8 mg per day, when converted to the amount of hyperoside. The number of times the blueberry tea leaf processed product is ingested (administered) is arbitrary; for example, it may be ingested (administered) once a day or multiple times a day, but it is preferable to ingest (administer) it continuously.

[0034] In this specification, the terms “contains” and “includes” include the meanings of “consisting of” and “substantially consisting of.” [Examples]

[0035] The present invention will be described below using experimental examples to aid in understanding its structure and effects. However, the present invention is not limited in any way by these experimental examples. Unless otherwise specified, the following experiments were conducted at room temperature (25±5℃) and under atmospheric pressure conditions. Unless otherwise specified, "%" below means "mass percent" and "parts" means "parts by mass".

[0036] 1. Production of blueberry tea leaves Rabbit-eye blueberries were used as the blueberry variety, and fermented tea leaves were produced using the following method. Fresh leaves harvested in August and September were also used.

[0037] Examples 1-5 Freshly picked blueberry leaves were placed in a freezer (VT-208, Nippon Freezer Co., Ltd.) on the same day they were picked and frozen at -20°C or below for at least 2 hours (slow freezing). Next, the frozen leaves were placed in a warming cabinet (prefabricated refrigerator, outdoor unit: ACT-035VR3, unit cooler: PEP-55RH4, Fukushima Galilei Co., Ltd.) set to 5°C and kept there for a certain period of time to thaw and ferment the leaves. The holding time in the warming cabinet was varied to 12 hours, 24 hours, 36 hours, and 48 hours (Examples 1-4). After this thawing and fermentation process, the fermented tea leaves were removed from the warming cabinet and placed in a hot air dryer (ND4-60, Terada Seisakusho Co., Ltd.) set to 70°C and dried at the same temperature for 3 hours until the moisture content was about 5% to produce fermented tea leaves (Examples 1-4). Furthermore, fermented tea leaves (Example 5) were produced by carrying out the same process as described above, except that after the thawing and fermentation process was performed at 5°C for 24 hours, an additional step was added to hold the tea leaves at room temperature (25°C) for 1 hour before the drying process.

[0038] For reference, Figure 1 (right side) shows images of the state of the tea leaves after each manufacturing step ((1) freezing, (2) thawing and fermentation, (3) drying) using Example 2 as an example. The changes in leaf color are as follows. Green when harvested, green after freezing, brown after thawing and fermentation, and brown after drying.

[0039] Comparative Example 1 Using blueberry leaves harvested on the same day as in Examples 1-5 described above, fermented tea leaves were produced using a conventional method. Specifically, the harvested blueberry leaves were left overnight in a well-ventilated place at room temperature (25°C) to wither, and then rolled for 15 minutes at 25°C using a rolling machine (2K type, Kawasaki Kiko Co., Ltd.). Next, the resulting rolled leaves were fermented at 25°C for 1 hour, and then placed in a hot air dryer set to 70°C and dried at the same temperature for 3 hours to produce fermented tea leaves (Comparative Example 1). For reference, Figure 1 (left) shows images illustrating the state of the tea leaves after each step of this conventional manufacturing method ((1) wilting, (2) rolling, (3) fermentation, (4) drying). The changes in leaf color are as follows. At harvest: green; after wilting: green and partially reddish-brown; after rolling: green and partially reddish-brown; after fermentation: brown and partially green; after drying: brown.

[0040] Comparative Examples 2-4 Using blueberry leaves harvested on the same day as in Examples 1-4, fermented tea leaves were produced using the same process as in Examples 1-4, except that the thawing and fermentation process was carried out at room temperature (25°C) for 3 hours, 6 hours, and 12 hours (Comparative Examples 2-4).

[0041] Comparative Example 5 Unfermented tea leaves were produced using a pan-frying method with blueberry leaves harvested on the same day as in Examples 1-5 described above. Specifically, first, in order to deactivate the oxidizing enzymes contained in the leaves (de-greening), the harvested blueberry leaves were placed in a leaf-frying machine (Custom Japan Co., Ltd.) with the pan bottom temperature set to 220°C on the day of harvesting and heated at the same temperature for 3 minutes and 30 seconds. Then, they were placed in a fixed pan (Custom Japan Co., Ltd.) with the pan bottom temperature set to 110°C and heated at the same temperature for 5 minutes (leaf-frying process). Next, the de-greened leaves were placed in a rolling machine (same as above) and rolled for 15 minutes, and then placed in a water-drying machine (Custom Japan Co., Ltd.) with the pan bottom temperature set to 160°C and dried at the same temperature for 30 minutes (water-drying process). Finally, they were placed in a hot-air dryer (same as above) set to 70°C and dried at the same temperature for 1 hour to produce tea leaves (unfermented tea leaves) (Comparative Example 5).

[0042] Examples 6-11 Tea leaves were produced using blueberry leaves picked on a different day than those used in Examples 1-5 described above. Specifically, the freezing and drying processes were carried out under the same conditions as in Examples 1-5, and the thawing and fermentation process was carried out by either maintaining the temperature of the incubator at 5°C, 10°C, or 15°C for 36 hours (Examples 6-8), or maintaining the temperature of the storage chamber at 5°C for 24 hours, 72 hours, or 120 hours (Examples 9-11) to produce various types of fermented tea leaves. Similar to Examples 1-5, the color of the tea leaves after the thawing and fermentation process was reddish-brown.

[0043] Comparative Example 6 Comparative Example 6 involved using blueberry leaves harvested on the same day as in Examples 6-11 to produce tea leaves (unfermented tea leaves) by immediately drying them after the freezing process, without going through the thawing and fermentation process. In this case, the freezing and drying processes were carried out under the same conditions as in Examples 6-11.

[0044] 2. Manufacturing of blueberry tea leaf processed product (test sample) The various tea leaves prepared in the above examples and comparative examples were crushed using a food cutter (MK-K48P, Panasonic), then passed through 12-mesh and 30-mesh sieves. The tea leaves that passed through the 12-mesh sieve and remained on the 30-mesh sieve were collected and used in the experiments described below.

[0045] 3. Experimental Examples Experimental Example 1. Determination of Total Polyphenol Content Using a glass teapot (HARIO Corporation), 200 ml of hot water was poured over 2 g of tea leaves, and the mixture was allowed to stand for 3 minutes to perform hot water extraction. The extract was filtered through filter paper (No. 5A, ADVANTEC) to collect the hot water extract. The total amount of polyphenols in the hot water extract was quantitatively analyzed using a modified version of the Folin-Ciocalteu method (Kenichiro Kanaya, "Total Amount of Polyphenols," New Food Analysis Methods (II), Japan Society for Food Science and Technology, Food Analysis Research Group, Korin, 2006, pp. 68-73). Specifically, 15 μl of the test solution (hot water extract) was sequentially mixed with 120 μl of distilled water, 15 μl of phenol reagent (Folin-Ciocalteu reagent diluted twice with distilled water), and 30 μl of saturated sodium carbonate aqueous solution. Finally, 120 μl of distilled water was added and thoroughly mixed. After standing at room temperature (25°C) for 30 minutes, the absorbance at 760 nm was measured using a microplate reader (SynergyMX, BioTek). The total polyphenol content was expressed as the gallic acid equivalent in mg per 100 ml of hot water extract.

[0046] Figure 2 shows the results of the analysis of tea leaves from Examples 1-5 and Comparative Examples 1-4, and Figure 3 shows the results of the analysis of tea leaves from Examples 6-11. As shown in Figure 2, fermented tea leaves produced by the conventional method (rolling followed by room temperature fermentation) (Comparative Example 1), and fermented tea leaves produced by freezing followed by room temperature fermentation (Comparative Examples 2-4), all had low total polyphenol content. In contrast, fermented tea leaves produced by freezing followed by low-temperature fermentation (5°C) (Examples 1-4) were found to have generally high total polyphenol content. Furthermore, it was confirmed that once fermented at low temperature after freezing, the total polyphenol content did not decrease even when left at room temperature afterward (Example 5).

[0047] Furthermore, as shown in Figure 3, it was confirmed that fermented tea leaves with a high total polyphenol content can be prepared by using a temperature of at least 5°C to 15°C, preferably less than 5°C to 15°C, as the low-temperature fermentation temperature after freezing (Examples 6-8).

[0048] Experimental Example 2. Quantitative determination of the grassy odor component (cis-3-hexen-1-ol) cis-3-hexen-1-ol is known as the main component responsible for the grassy smell of green tea leaves and other teas. Therefore, aroma component analysis was performed on the nine types of fermented tea leaves prepared in Examples 1-5 and Comparative Examples 1-4 using a headspace solid-layer microextraction / gas chromatography-mass spectrometry, and cis-3-hexen-1-ol was quantified.

[0049] Specifically, 0.2 g of tea leaves was weighed into a glass vial (15 mL, SUPELCO), 20 μl of 0.01 wt% cyclohexanol aqueous solution and 5 ml of drinking water maintained at 98°C were added as internal standards, the cap was closed, and the vial was left to stand at room temperature (25°C) for 3 minutes to perform hot water extraction. After extraction, the vial containing the extract was equilibrated at 55°C for 10 minutes. Then, a solid-layer microextraction (SPME) fiber with Divinylbenzene / Carboxen / Polydimethylsiloxane (film thickness: 50 / 30 μm, SUPELCO) as an adsorbent was inserted into the vial, and volatile components in the vial's headspace were collected at 55°C for 40 minutes. The collected volatile components were measured using a gas chromatograph-mass spectrometer (GC: 7890B, MS: 5977A, Agilent Technologies, Inc.). The SPME fiber was inserted into the vaporization chamber of the analyzer to release the collected components (250°C, 3 minutes), and measurements were taken under the conditions shown in Table 1. The volatile component (cis-3-hexen-1-ol) was identified using the NIST Mass Spectrometry Database. The relative peak area ratio to the internal standard (cyclohexanol) was determined, and the average value was calculated from three repeated measurements.

[0050] [Table 1]

[0051] The results are shown in Figure 4. As shown in Figure 4, tea leaves produced by the conventional method (rolling followed by room temperature fermentation) (Comparative Example 1) contained a large amount of cis-3-hexen-1-ol, while tea leaves produced by freezing followed by low-temperature fermentation (Examples 1-4, Comparative Examples 2-4) contained extremely low amounts of this component. Furthermore, the same result was observed even when the tea leaves were left at room temperature after being frozen and then fermented at low temperature (Example 5).

[0052] Experimental Example 3. Sensory Evaluation The flavors (initial taste and aftertaste) of various tea leaves prepared by the above method (Examples 1-11, Comparative Examples 1-5) were evaluated using a sensory evaluation panel. Note that the tea leaves of Comparative Example 6 (unfermented tea leaves) were excluded from the panel's sensory evaluation because a prior sensory evaluation test showed a taste similar to that of fresh tea leaves.

[0053] (1) Evaluation method The sensory evaluation test was conducted using a sensory evaluation panel of four individuals who had been trained in and passed in-house tests for the sensory evaluation of tea's taste and aroma. 3g of tea leaves (ground and sieved) were placed in a teapot (Koransha Co., Ltd., porcelain tea testing equipment), 140ml of 95°C hot water was poured in, the lid was closed, and it was allowed to steep for 3 minutes. After steeping, the tea leaves were filtered off, and the collected extract was adjusted to 50°C to be used as the test sample.

[0054] The panel was asked to comprehensively evaluate the initial taste (the sensations in the mouth (taste and aroma) and the sensations that escape from the mouth to the nasal cavity (aroma) when each test beverage was taken into the mouth and swallowed) and the aftertaste (the sensations in the mouth after drinking). Specifically, each participant first evaluated the flavor (initial and aftertaste) according to the evaluation criteria below, and then discussed their results with the other panel members to arrive at the final result. They were also asked to fill out an evaluation sheet with their impressions of drinking each test beverage.

[0055] [First impression] (grassy smell) A grassy smell +: Feel -: I don't feel it. (Astringency) The astringency you feel when drinking black tea, the tingling sensation on your tongue. +: Feeling → Assign a score from 1, 2, 3, 4, 5 in order of strongest feeling. If the strength is the same, it receives the same score. -: I don't feel it. (Herbal) A scent like herbs (lemongrass, chamomile). +: Feeling → Assign scores from 1, 2, 3, 4, 5 in order of weakest to strongest. If the strength is the same, they receive the same score. -: I don't feel it.

[0056] [aftertaste] (Clean feeling) A clean aftertaste, free of any unpleasant flavors. +: Feeling → Assign scores from 1, 2, 3, 4, 5 in order of weakest to strongest. If the strength is the same, they receive the same score. -: I don't feel it.

[0057] [comprehensive evaluation] ◎: Grassy taste rating (-) & Astringency rating of 2 or higher & Herbaceous taste rating of 4 or higher & Aftertaste rating of 4 or higher ○: Grassy taste rating (-) & Astringency rating of 2 or higher & Herbaceous taste rating of 3 or higher & Aftertaste rating of 3 or higher △: Grassy taste rating (-) & Astringency rating of 1 or less OR Herbaceous taste rating of 2 or less OR Aftertaste rating of 2 or less ×: Rating for grassy taste (+)

[0058] (2) Evaluation results The results are shown in Table 2.

[0059] [Table 2]

[0060] As shown in Table 2, the test beverage prepared from fermented tea leaves produced through the rolling process (Comparative Example 1) exhibited a grassy odor, but none of the fermented tea leaves produced without the rolling process (Comparative Examples 2-4, Examples 1-11) or unfermented tea leaves (Comparative Example 5) exhibited a grassy odor. This result was consistent with the result of Experimental Example 2. Therefore, it is possible to suppress the generation of a grassy odor, mainly caused by cis-3-hexen-1-ol, by producing fermented tea leaves without the rolling process.

[0061] As shown in Table 2, it was confirmed that tea leaves exhibiting good flavor (initial taste [no grassy smell, moderate astringency, moderate herbal flavor], aftertaste [refreshing]) can be obtained by freezing the tea leaves and then keeping them under low-temperature conditions of 5°C to 15°C, preferably 5°C to 10°C, for a certain period of time. In particular, it was confirmed that tea leaves with very good flavor can be obtained by freezing the tea leaves and then keeping them under low-temperature conditions of 5°C to 15°C, preferably 5°C to 10°C, for 12 to 36 hours.

[0062] Experiment Example 4. Sleep Improvement Test This study investigated the effects of consuming tea leaves prepared from blueberry leaves on improving sleep in humans. This study was reviewed and approved by the Life Science Research Ethics Committee of Otsuma Women's University. The study was conducted as a randomized, double-blind, placebo-controlled, parallel-group trial.

[0063] (1) Test method As test foods and beverages, the tea leaves from Example 5 above (hereinafter referred to as "active food") and a placebo food were used. The placebo food was made by adding flavorings and acidulants to commercially available barley tea leaves that contained almost no polyphenols and no hyperosides, so that subjects could not distinguish it as barley tea by flavor. The test foods and beverages (active food and placebo food) were processed into identical tea bag form (contents: 2g / packet) to have the same appearance so that subjects could not distinguish them by appearance.

[0064] The study included 50 healthy adult men and women aged 20 to 69 who regularly experienced dissatisfaction with their sleep. These participants received a thorough explanation of the study's content and voluntarily submitted informed consent. Prior to the start of the study, the Pittsburgh Sleep Quality Index (PSQI-J) (Doi, Yuriko et al.: Psychiatric Therapeutics 13, 755-769 (1998), Seiwa Shoten) was administered to obtain the participants' PSQI-J scores. Participants were divided into groups with approximately equal age, gender ratio, and mean PSQI-J scores, and assigned to either an active food intake group or a placebo food intake group.

[0065] The study period was four weeks. For the first week, subjects did not consume the test food or beverage (one week without consumption), and for the next three weeks, from the second to the fourth week, they consumed the test food or beverage (three weeks of consumption). When consuming the test food or beverage, subjects were instructed to perform a hot water extraction using the specified method (pour 200 ml of hot water over one sachet of the test food or beverage, let it stand for 3 minutes, then remove the tea bag), and then consume the resulting extract. The test food or beverage was consumed at breakfast, lunch, and dinner, for a total of three sachets per day for three weeks. No special dietary restrictions were imposed during the four-week study period, and subjects were instructed to maintain their normal daily routine.

[0066] (2) Test results Excluding two participants who withdrew from the study for personal reasons, 48 ​​participants completed the study. Of these, 42 participants (20 in the active food intake group and 22 in the placebo food intake group) were included in the analysis, after excluding one participant with missing data and five participants who were taking antihistamines, hormones, or antidepressants.

[0067] Figures 5 and 6 show the results of measuring the duration of wakefulness during the night (minutes) and sleep efficiency (%) using an actigraph (an activity tracker worn on the arm) three weeks after ingestion. Here, "mid-sleep awakening time" refers to the amount of time spent awake (in minutes) during the total sleep time as measured by an actigraph. "Sleep efficiency" refers to the percentage of total sleep time (excluding mid-sleep awakening time) measured by an actigraph during the total time spent in bed. As shown in Figures 4 and 5, the group consuming the active food showed a reduction in the duration of awakenings during the night and a significant improvement in sleep efficiency (sleep quality) compared to the group consuming the placebo food. In all evaluation items, statistically significant differences were observed in the analysis of covariance using the initial values ​​before the start of the study as covariates. Thus, it was demonstrated that consuming three packets of tea leaves (6g of tea leaves, with a hyperoside content of 5.4mg in the hot water extract of the tea leaves) produced using the method of the present invention, using blueberry leaves as the raw material, for three weeks improved sleep quality.

[0068] Based on the above results, tea leaves produced using the method of the present invention (freeze-freeze low-temperature fermentation method) with blueberry leaves as the raw material have a high sleep-improving effect. As shown in Experimental Example 1, the tea leaves produced by the method of the present invention contain many polyphenols. These polyphenols are thought to contain many hyperosides (flavonoid compounds) which have been reported to have a sleep-improving effect. Therefore, the manufacturing method of the present invention makes it possible to obtain tea leaves containing many polyphenols, including hyperosides, and to provide food and beverages that have beneficial effects on mind and body, such as improving sleep.

Claims

1. A method for producing blueberry tea leaves, comprising the following steps: (1) A process of preparing frozen blueberry leaves by freezing fresh blueberry leaves, (2) A step of storing the frozen leaves under low temperature conditions of 5°C to 15°C, (3) A step of drying the leaves obtained in the above step.

2. The manufacturing method according to claim 1, further comprising the following steps between steps (2) and (3): (2-2) A step of storing the low-temperature preserved leaves at a temperature greater than 15°C and 40°C or less.

3. The manufacturing method according to claim 1 or 2, which does not involve a kneading step.

4. Blueberry tea leaves or processed products thereof produced by the method described in claim 1 or 2.

5. A food and beverage composition containing blueberry tea leaves or a processed product thereof as described in claim 4.

6. A food and beverage composition according to claim 5, which is a composition for improving sleep.

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