JP4801948B2 - Method for changing the content ratio of catechins in tea leaves and tea extracts - Google Patents

Description

  The present invention relates to a method for changing the content ratio of catechins in tea leaves and tea extracts by the fungal fermentation.

  As an effect ingredient of green tea, the anti-obesity effect of catechins (green tea catechins) contained in green tea has attracted attention. The main “green tea catechins” include epigallocatechin gallate (EGCg), epigallocatechin (EGC), epicatechin gallate (ECg), epicatechin (EC), catechin gallate (Cg), catechin (C), gallocatechin There are gallate (GCg) and gallocatechin (GC), but each has different functionality and taste, particularly astringency (hereinafter, when each catechin is represented in this specification, an abbreviation in parentheses is also used).

  The following literature is shown as something that has recently become clear. Regarding blood cholesterol, Patent Document 1 discloses that (−) epicatechin (EC) has an effect of lowering blood cholesterol level, and Patent Document 2 particularly describes (−) epigallocatechin gallate among tea catechins. A cholesterol-lowering agent containing (EGCg) as an active ingredient is disclosed, and Patent Document 3 discloses a cholesterol excretion promoter containing epicatechin gallate (ECg) as an active ingredient.

  In addition, in the model in which the amount of insulin secretion after feeding is increased, catechin having a gallate ester (EGCg, ECg, Cg, GCg) suppresses glucose transport activity, and in the steady state model, gallate is present in the absence of insulin. It has been found that catechins without ester (EGC, EC, C, GC) increase glucose transport activity (Non-patent Document 1).

  In addition, compared to EGCg, EGC and Cg inhibit the accumulation of lipid droplets in mouse 3T3-L1-derived preadipocytes, and suppress the expression of PPARγ (peroxisome proliferator-activated receptor γ) and C / EBPα. Are known. PPARγ and C / EBPα are known to be deeply related to diabetes, and suppression of their expression is expected to be effective in suppressing induction of type II diabetes (Non-patent Documents 2 and 3). However, such an effect is not recognized in GC.

  On the other hand, the method of controlling the type of “green tea catechin” and increasing or decreasing the specific one of “green tea catechins” is only a laboratory-level method of fractionating specific catechin components by chromatography, This is unsuitable as a production method from the viewpoint of safety of tea to be produced and industrial production.

JP 52-116473 A JP-A-60-156614 JP-A-1-299224 Hitoshi Hirota presentation materials for the 5th Bioscience Research Meeting Furuyasiki T. et Biosci Biotechnol Biochem 68, (11), 2353-2359 (2004) 50 Fumiken Katsukawa et al., Bulletin of Sports Medicine Research Center, Keio University (1996)

  In view of the above circumstances, the present invention provides a method for increasing the content of a specific trace amount of catechin components expected to have a pharmacological effect in tea and changing the content ratio of catechins in tea leaves or tea extracts. With the goal. One of the objects of the present invention is to provide a method for increasing the content of EGC in tea and changing the content ratio of catechins in tea leaves or tea extracts. Under today's health boom, it is desirable to provide certain foods with high functionality by increasing the specific catechin ingredients that are notable for tea, but for which their efficacy has attracted attention, in tea leaves or tea extracts. It is.

  In order to solve the above problems, the present inventors have repeatedly studied. That is, as an industrial production method of a specific catechin component by hydrolysis of a catechin gallate group, thermal hydrolysis in an aqueous solution is conceivable. However, in this method by thermal hydrolysis, the gallate group of EGCg is hydrolyzed. At the same time, epimerization occurs as a side reaction, and the ratio of EGC to GC is about 1: 1, which is not suitable for specifically increasing a specific catechin component. In addition, if an enzyme is used as an industrial production method for a specific catechin component, hydrolysis can be performed while maintaining the three-dimensional structure, but the cost is high and the enzyme is inactivated by catechin. This method is not suitable for stably increasing a specific catechin component because it is easy.

As a result of the above studies, in order to solve the problems of the present invention, for example, in order to specifically hydrolyze EGCg and increase the content of EGC, specific and stable hydrolysis of EGCg is necessary. I came up with an idea.
As a result of repeated investigations for specific and stable hydrolysis of the gallate group of catechins, the present inventors have found the following.

(1) Tea leaves (Tea sinensis leaves) have antibacterial properties due to their catechins, and therefore appear frequently when other grains (soybeans and rice) are made and cause rot. It was found that contaminating fungi such as Bacillus natto and Micrococcus were inhibited by catechins when brewing tea leaves and did not propagate at all in tea leaves, whereas fungi could be propagated in tea leaves.
(2) The tea leaves used for fungal culture are tea sinensis leaves that have been adjusted to contain the prescribed moisture content. However, the present inventors have found that fungi can be favorably and preferentially propagated by using tea leaves adjusted to contain predetermined moisture. That is, since these tea leaves have a large volume ratio with respect to weight, the water content of the tea leaves is appropriately dispersed, and as a result, it has been found that fungi can be propagated well in crude tea. In addition, by limiting the amount of water, it has been found that only fungi that are relatively resistant to drying can preferentially reproduce.
(3) When fungi are propagated in tea leaves, fungi hydrolyze EGCg abundantly contained in tea leaves into EGC, but it is difficult to cause further degradation of EGC, so that only a small amount is inherently contained in tea leaves. It has been found that the content of EGC, which is not expected to have a pharmacological effect, can be specifically increased.

  Thus, the present invention has been completed by finding that fungi can grow in tea leaves under specific conditions, and that catechins in tea leaves change in components. That is, the present invention provides the following means.

[1] The content ratio of catechins in tea leaves is changed, including the steps of adjusting the raw tea leaves to contain water of 25 to 80% by weight, fermenting them by the action of fungi, and then heating and drying them Method.
[2] A method for changing the content ratio of catechins in a tea extract, comprising a step of fermenting a tea extract as a raw material by the action of fungi under a condition where water of 50% by weight or more exists.
[3] The method according to [1], wherein the raw tea leaves are fermented with fungi under conditions containing 20% by weight or less of sugar.
[4] The method according to [2], wherein the tea extract of the raw material is fermented with fungi under conditions containing 20% by weight or less of a saccharide.
[5] The method according to [1] or [3], wherein the fungus is Saccharomyces cerevisiae or Aspergillus oryzae.
[6] The method according to [2] or [4], wherein the fungus is Saccharomyces cerevisiae or Aspergillus oryzae.

  According to the method of the present invention, it is possible to increase the content of a specific trace amount of catechin components expected to have a pharmacological effect in tea, such as EGC, and to change the content ratio of catechins in tea leaves or tea extracts. .

  According to one embodiment of the method of the present invention, one of the fungi, baker's yeast (Saccharomyces cerevisiae) hydrolyzes the gallate group of EGCg and ECg in tea leaves to convert them to EGC and EC, respectively. Since further degradation of EC is not significant, the EGC and EC content in tea leaves can be increased. Thereby, the functions of EGC and EC in tea leaves (the action of suppressing the accumulation of lipid droplets in preadipocytes and the action of suppressing the expression of PPARγ and C / EBPα) can be enhanced.

  According to another aspect of the method of the present invention, Aspergillus oryzae, one of the fungi, hydrolyzes the gallate group portion of EGCg and ECg in tea leaves, and converts them into EGC and EC, respectively. Furthermore, since EC is selectively decomposed, the content of EGC in tea leaves can be increased. Compared with EC, EGC not only has an action of suppressing the accumulation of lipid droplets in preadipocytes and an action of suppressing the expression of PPARγ and C / EBPα, but also has an antioxidant capacity about 3 times higher. For this reason, when Neisseria gonorrhoeae is used, it may be accompanied by a decrease in EC content depending on fermentation time. Is suppressed, and the antioxidant effect is not significantly reduced. Furthermore, hydrolysates such as EGC and EC have less astringency than gallate bodies such as EGCg and ECg, and the astringency of EGC and EC is almost the same. Further, there is an advantage that astringency can be reduced without greatly reducing the antioxidant effect due to the decrease in EC.

  Similar effects can be obtained when the tea extract is fermented instead of tea leaves according to the method of the present invention.

(1) Method of changing content ratio of catechins in tea leaves Hereinafter, a method of changing the content ratio of catechins in tea leaves will be described in detail.
The raw tea leaves used in the method of the present invention can be any of non-fermented tea, fermented tea, and semi-fermented tea. Since unfermented tea is dried while it is teased after killing the tea leaves, the crude tea may be adjusted to contain 25 to 80% by weight of water, or the tea leaves ( That is, the tea leaves after blue killing, the tea leaves after coarse koji, the tea leaves after twisting, the tea leaves after churn, and the tea leaves after sperm may be adjusted to contain 25 to 80% by weight of water. Here, the raw tea leaves already contain 25 to 80% by weight of water, such as “tea leaves after killing, tea leaves after rough culm, tea leaves after twisting, and tea leaves after churn”. In this case, it may be used as it is without adjusting moisture. In addition, when the raw tea leaves are “tea leaves after rough brewing or rough tea”, in general, adjustment is made to include predetermined moisture by adding moisture. In the present invention, it is preferable to use crude tea as a raw material. In addition, fermented tea that does not have a blue-killing process and semi-fermented tea that has a slow blue-killing process can be used as a raw material by adjusting its water content.

  The adjustment of the moisture content of tea leaves will be described below using an example of “rough tea”. “Rough tea” already contains about 3 to 5% by weight of water. Therefore, the amount of water to be added needs to be adjusted in consideration of the water contained in the tea leaves. For example, by adding 357 mL of water to 1 kg of “raw raw tea” containing 5% by weight of water, “crude tea adjusted to contain about 30% by weight of water” can be obtained. Alternatively, “tea leaves adjusted to contain 25 to 80% by weight of water” can be prepared by shortening the drying time and drying to a desired water content.

  Here, the water content is the amount that the fungi used for fermentation can propagate and ferment, and can be in a wide range from low water content to high water content, but preferably low water content to simplify the subsequent drying process. Set to content. The low moisture content can simplify the subsequent drying process and can preferentially propagate fungi that are relatively resistant to drying, thereby preventing contamination with various bacteria. In the present invention, it has been found that fungi can propagate and ferment at a relatively low water content. Therefore, “tea leaves adjusted to contain 25 to 80% by weight of water” are used, preferably “25 to 25%. “Tea leaves adjusted to contain 50% by weight of water”, more preferably “tea leaves adjusted to contain 30 to 35% by weight of water” are used.

  In addition to the intermediate tea leaves after pruning in the present invention, the reason for using `` raw tea '' is (1) that it can be stored for a long time as a raw material, (2) it does not contain unnecessary enzymes such as browning enzymes, 3) Since the volume ratio with respect to the weight of tea leaves is large, the present inventors have found that water can be appropriately dispersed in tea leaves, which is suitable for fungal growth.

  The fungus usable in the present invention is not particularly limited as long as it is a strain that can change the content ratio of catechins contained in tea and specifically increase a desired catechin component. For example, EGCg As long as the strain can hydrolyze the gallate group of ECg and increase the EGC content, it is not particularly limited.

  Examples of fungi that can be used in the present invention include strains of the genus Saccharomyces and Aspergillus. Strains of the genus Mucor, Monascus, Pleurotus, Armillaria, Lentinus, Ganoderma, Pholiota, Flammulina, Agaricus, Grifola, and Schizophyllum can also be used. More specifically, Saccharomyces cerevisiae, S. carlsbergensis, S. rouxii, Baker ''s yeast, Wine yeast, Aspergillus oryzae, A. usamii, A. sirousamii, A. niger, A. kawachi, A. awamori, A sojae, Schizosaccharomyces pombe, Candida utilis, C. tropicalis, Torulopsis utilis, T. pulcherima, Mycotorula japonica, Oidium lactis, Debariomyces hansenii, Phaffia rhodozyma, Aureobasidium pullulans, Eurotium repens, Eurocium repens, Eurotium repens, , Armillaria mellea, Lentinus edodes, Ganoderma lucidum, Pholiota nameko, Flammulina velutipes, Agaricus blazei Murill, A. bisporus, Grifola frondosa, Schizophyllum commune. These strains include strain distribution agencies such as IFO, IAM, ATCC, NRRC, Japan Brewing Association (sake yeast, etc.) and commercial seed strain sales companies such as Rishoku Co., Ltd. It is available from mushroom inoculum sales).

  The fungi listed above have the property of degrading catechins of tea leaves in a stereospecific manner and the property of degrading speed depending on the type of catechins. Therefore, the content of specific catechin components in tea leaves can be increased by utilizing the difference in decomposition speed.

  Specifically, hydrolysis of the gallate group of catechins is performed while maintaining the three-dimensional structure of catechins in all fungi. That is, EGCg contained in tea is hydrolyzed to EGC, and ECg is hydrolyzed to EC. However, EGC, which has higher antioxidant activity than EC, is less susceptible to subsequent degradation by fungi. Therefore, content of EGC with high antioxidant activity can be specifically increased by performing fermentation of tea leaves using the above fungi.

  As described above, EGC has been reported to have an action of suppressing the accumulation of lipid droplets of preadipocytes and an action of suppressing the expression of PPARγ and C / EBPα, unlike EGCg. Therefore, by specifically increasing the EGC content, it is possible to specifically enhance the function of EGC, which is originally contained in a small amount in tea leaves.

  However, depending on the type of fungus, the ability to hydrolyze the EGCg gallate group into EGC and further decompose EGC is different. Therefore, when increasing the content of EGC using a specific fungus, select “a fungus that hydrolyzes EGCg to EGC but does not further degrade EGC, or has a low ability to degrade EGC” or “EGCg It is desirable to set in advance a “fermentation period in which is converted to EGC but has not yet been further decomposed by EGC”. Examples of the fungus that hydrolyzes EGCg to EGC but does not further degrade EGC or has a low ability to degrade EGC include Saccharomyces cerevisiae. In addition, when Aspergillus oryzae is used as a fungus, the fermentation period of 1 to 14 days depends on the fermentation conditions as “fermentation period in which EGCg is converted to EGC but has not led to further degradation of EGC”. Can be set. As described above, in the present invention, it is possible to increase the content of EGC using a specific fungus that has the ability to convert EGCg to EGC but does not have the ability to degrade EGC, or is low. Can be used as preferred in the present invention.

  In the present invention, fermentation is performed by inoculating the above-mentioned fungi on the tea leaves whose water content has been adjusted as described above, and generally allowing the fungi to propagate at 20-50 ° C, preferably 20-40 ° C for 1-10 days. Can do.

  In a preferred embodiment of the present invention, when fermenting tea leaves, any sugars, preferably monosaccharides or disaccharides such as sugar, fructose, glucose, maltose or honey can be added under the conditions of fermentation. That is, some fungi may need sugar for growth, and some do not need it, so depending on the fungus, add sugar in the range of 0 to 20% by weight (final concentration). Some are desirable. For example, when Saccharomyces cerevisiae is used as a fungus, it is desirable to add a carbohydrate during fermentation. In addition, it is not preferable that the saccharide content is 50% by weight or more with respect to the total weight because growth of any microbial species is suppressed.

  Fermentation of tea leaves with fungi by adding saccharides promotes fungal growth and at the same time promotes fermentation, and ethanol production is often prominent. It is done. This is probably due to the formation of ethanol esters.

  Tea leaves that have undergone the fermentation process with fungi are heat-dried at 80 to 120 ° C. to sterilize the fungi and reduce the water content to 5 wt% or less (generally 3 to 5 wt%). As a result, a highly functional fermented tea that can be stored at room temperature and has increased specific catechins is produced. As described above, the fermented tea obtained according to the present invention not only excels in specific catechins and is excellent in functionality, but also shows good results in sensory evaluation as shown in Examples described later. .

(2) Method of changing the content ratio of catechins in the tea extract The method of changing the content ratio of catechins in the tea extract can be performed in the same manner as in the above-described method of tea leaves. Therefore, only the differences from the method for tea leaves described above will be described below.

  As a tea extract as a raw material, a tea extract obtained by extracting tea leaves with a solvent such as warm water, or a tea leaf is extracted with a solvent such as warm water, and the extract is spray-dried together with excipients and the like. Any tea extract such as dried tea extract can be used. For example, a commercially available instant tea extract, a commercially available dried tea extract, or Sanphenon (manufactured by Taiyo Kagaku) can be used.

  In this method, the tea extract as a raw material is fermented by the action of fungi in the presence of moisture that allows fungi to grow. This condition is used when a tea extract is used as the tea extract. Water may not be added, but water may be added so as to contain 50% by weight or more, preferably 50 to 95% by weight, more preferably 70 to 95% by weight of water at a final concentration. Alternatively, when a tea extract dried product is used as the tea extract, water is added so as to contain 50% by weight or more, preferably 50 to 95% by weight, more preferably 70 to 95% by weight of water at the final concentration. To do.

  Also in this method, if a saccharide is added and fermentation is performed with fungi, the growth of the fungus is improved and at the same time the fermentation is promoted. Therefore, it is preferable to add the saccharide under the above conditions. The concentration of the saccharide added can be 0 to 20% by weight in the final concentration. As in Example 3 described later, a malt extract containing sugar as a main component may be added as a saccharide.

  The tea extract that has been subjected to the fermentation process can be dried after sterilization and can be stored at room temperature. At this time, a drying aid such as cyclodextrin may be added.

According to another aspect of the present invention,
(1) A tea leaf with a changed content ratio of catechins, comprising a step of adjusting the raw tea leaves to contain water of 25 to 80% by weight, fermenting them by the action of fungi, and then heating and drying them Production method, and (2) Tea extract in which the content ratio of catechins is changed, comprising the step of fermenting the tea extract as a raw material by the action of fungi under conditions where water of 50% by weight or more is present It relates to the manufacturing method.
According to the methods (1) and (2) above, fermented tea and fermented tea extract in which the content ratio of catechins is changed are provided.

In addition, according to the method of the present invention, by controlling the content ratio of catechins contained in tea and increasing a specific catechin component, for example, EGC, the functions of EGC (that is, suppression of diabetes induction and preadipocytes) It is possible to enhance the lipid droplet accumulation suppressing action and the PPARγ and C / EBPα expression suppressing action. Therefore, according to the present invention,
A blood sugar elevation inhibitor containing as an active ingredient a fermented tea produced by the method (1) or a fermented tea extract produced by the method (2), and a fermentation produced by the method (1) There is provided a body fat accumulation inhibitor containing tea or a fermented tea extract produced by the method of (2) as an active ingredient.

[Example 1]
Mix 3 kg of green tea (Tea sinensis leaves that have been killed and dried) and 1 liter of water with 150 g of sugar (Dai Nippon sugar) dissolved in 1.15 kg. A “fermented tea raw material” containing 3.6% by weight of sugar was prepared. This was inoculated with 1 g of dry yeast (Nisshin Flour Milling, trade name Camellia), placed in a 10 L stainless steel container, and fermented at 30 ° C. for 6 days in static culture. Then, after the dryer temperature was 120 ° C. and the tea temperature reached 90 ° C., it was dried by heating for 10 minutes to prepare “fermented tea”. The catechins were analyzed by liquid chromatography (Shinichi Hirose et al. Tea Industry Research Report 50 51 (1979)), and the flavor was evaluated by sensory examination of 100 mL hot water extract of 2 g tea leaves by 5 panelists. did.

The change in the content of catechins is shown in Table 1, and the sensory test results are shown in Table 2.

  In tea leaves fermented with yeast, EGCg decreases and EGC increases even though the sum of EGCg and EGC (EGCg + EGC) hardly changes. In addition, although the sum of ECg and EC (ECg + EC) has hardly changed, ECg has decreased and EC has increased. From the above, it can be seen that EGCg and ECg were quantitatively converted to EGC and EC, respectively, by hydrolysis of these gallate groups. Moreover, it turns out that the flavor of "fermented tea" is mellow compared with the extract of the tea leaf which is not fermented from the result of Table 2.

[Example 2]
Mix 3 kg of green tea (Tea sinensis leaves, dried with mastication) and 1 L of water, and in the same way as in Example 1, "Fermented tea ingredients containing 28% water and 3.6% sugar" Was prepared. This includes A.kawachi HS-185 for shochu, A.oryzae HW-08 for white miso, A.oryzea HF-101 for red miso (all from Hiroku Corporation) Was inoculated, placed in a 10 L stainless steel container, and fermented at 30 to 40 ° C. for 6 days in a stationary culture. Then, after the dryer temperature was 120 ° C. and the tea temperature reached 90 ° C., it was dried by heating for 10 minutes to prepare “fermented tea”. In addition, the A. oryzea HF101 for red miso was fermented quickly, so that it was also fermented for 2 days and then dried by heating. The catechins were analyzed by liquid chromatography, and the flavor was evaluated by a sensory examination of 5 panelists of 2 g tea leaf hot water extract by 5 panelists.

Changes in the content of catechins are shown in Table 3, and sensory test results are shown in Table 4.

  In tea leaves fermented with shochu lees and white miso lees, EGCg decreased and EGC increased even though the sum of EGCg and EGC (EGCg + EGC) hardly changed. On the other hand, the ECg and EC total (ECg + EC) of these “fermented teas” are reduced. From the above, in tea leaves fermented with shochu lees and white miso lees, EGCg is quantitatively converted to EGC by hydrolysis of its gallate group, but ECg is further converted after hydrolysis of its gallate group. It was suggested that EC itself was decomposed. As a result, it is also shown from the results in Table 4 that the flavor of these “fermented teas” is mellow (astringency is reduced). In other words, when tea leaves are fermented with shochu lees and white miso lees, EC is selectively decomposed, leaving only EGC with high antioxidant activity, thereby reducing astringency and having high antioxidant activity. It is thought that you can. In addition, EGC has been reported to have a stronger effect of inhibiting the induction of diabetes, an accumulation of lipid droplets of preadipocytes, and an effect of suppressing the expression of PPARγ and C / EBPα than other catechins. "Is expected to be effective for obesity, diabetes and the like.

  On the other hand, in tea leaves fermented with red miso koji, a decrease was observed in both the sum of EGCg and EGC (EGCg + EGC) and the sum of ECg and EC (ECg + EC). That is, it was suggested that the gallate group of EGCg and ECg was decomposed and that both EGC and EC were decomposed. However, paying attention to the result that the sum of ECg and EC is as low as 0.1, it can be seen that red miso koji also has a higher priority for EC decomposition than EGC decomposition. Therefore, the EGC content is increased (in this example, from 1.1% to 2.0% by weight) by shortening the fermentation time with the red miso koji (in this example, shortening from 6 days to 2 days). Can). Thus, it is considered that tea can be reduced in astringency and high in antioxidant activity by selecting a fermentation time that reduces EC and increases EGC even in fermentation with red miso koji. In addition, since EGC has been reported to have a stronger effect of inhibiting adipocyte differentiation and PPARγ expression than other catechins, the obtained “fermented tea” is expected to be effective for obesity, diabetes and the like. Is done.

  When preparing catechins having a high ability to decompose catechins such as red miso koji, fermentation time can be set short when preparing fermented tea having a high EGC content. Thus, it is possible to control the content of catechins by changing the type of koji mold used or the fermentation time.

[Example 3]
A solution (1.02 kg) of malt extract (BACT) 20 g dissolved in 1 L of water was mixed and pasteurized, then 300 g of green tea extract (Taiyo Kagaku) was added, and 76 wt% water and 2 A “fermented tea extract raw material” containing wt% malt extract was prepared. This was inoculated with 1 g of dry yeast (Nisshin Flour Milling, trade name Camellia), placed in a 2 L stainless steel container, and fermented at 30 ° C. for 6 days in static culture. Then, after the dryer temperature was 120 ° C. and the tea temperature reached 90 ° C., it was dried by heating for 10 minutes to prepare “fermented tea extract”. Catechins were analyzed by liquid chromatography.

Table 5 shows changes in the content of catechins.

  In the tea extract fermented with yeast, the total of EGCg and EGC (EGCg + EGC) hardly changed compared to the tea extract not fermented, EGCg decreased, and EGC increased. Yes. Further, ECg and EC total (ECg + EC) hardly change, ECg decreases, and EC increases. From the above, it can be seen that EGCg and ECg were quantitatively converted to EGC and EC, respectively, by hydrolysis of these gallate groups. Unlike EGCg, EGC has been reported to have a strong effect of suppressing differentiation of adipocytes and suppression of PPARγ expression, and therefore, the fermented green tea extract is expected to be effective for obesity, diabetes and the like.

Claims (5)

  A method of changing the content ratio of catechins in tea leaves, comprising adjusting the raw tea leaves to contain 25 to 50% by weight of water, fermenting them by the action of Saccharomyces cerevisiae, and then heating and drying them.   The method according to claim 1, wherein the 25 to 50 wt% water is 30 to 35 wt% water. The method according to claim 1 or 2, wherein the raw tea leaves are fermented with Saccharomyces cerevisiae under conditions containing 20% by weight or less of sugar.   The method according to any one of claims 1 to 3, wherein the fermentation is performed for 1 to 14 days.   The method according to any one of claims 1 to 3, wherein the fermentation is performed for 1 to 10 days.