Method for producing fermented milk containing oligosaccharide

Abstract

The present invention provides a method for producing fermented milk and fermented milk produced by the production method. The above-mentioned method for producing fermented milk is characterized in that it is a method for producing fermented milk containing oligosaccharides and lactic acid bacteria as live bacteria, and the lactic acid bacteria are cultured using a culture medium containing oligosaccharides; in the fermented milk containing oligosaccharides and lactic acid bacteria as live bacteria, a high number of live bacteria can be maintained even during long-term storage.

Description

Technical Field

[0001] The present invention relates to a method for producing fermented milk containing oligosaccharides and lactic acid bacteria as live bacteria. Background Art

[0002] Fermented milk containing lactic acid bacteria has long been known, and it is also known that sugars are added in the form of syrup in order to impart various effects and sweetness.

[0003] For example, fermented milk containing live lactic acid bacteria and oligosaccharides as sugars is known, and is known to have excellent intestinal penetration (Patent Document 1).

[0004] However, it is known that fermented milk containing live lactic acid bacteria and oligosaccharides has excellent intestinal penetration, but when oligosaccharides are added as syrup, it is difficult to maintain a high number of live bacteria during long-term storage compared to when sugars other than oligosaccharides are added as syrup.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent No. 2571734 Summary of the invention

[0008] Therefore, an object of the present invention is to provide a technology for maintaining a high number of viable bacteria in fermented milk containing oligosaccharides and lactic acid bacteria as viable bacteria even during long-term storage.

[0009] The present inventors have conducted intensive studies to solve the above-mentioned problems and have found that, when producing fermented milk containing oligosaccharides and lactic acid bacteria as live bacteria, the above-mentioned problems can be solved by adding the oligosaccharides to the culture medium when culturing lactic acid bacteria instead of adding the oligosaccharides as syrup as in the conventional method, thereby completing the present invention.

[0010] That is, the present invention is a method for producing fermented milk, characterized in that the method contains oligosaccharides and lactic acid bacteria as live bacteria, and the lactic acid bacteria are cultured using a culture medium containing oligosaccharides.

[0011] Moreover, the present invention provides fermented milk produced by the above-mentioned method for producing fermented milk.

[0012] Furthermore, the present invention is a method for improving the survivability of lactic acid bacteria in fermented milk containing oligosaccharides and lactic acid bacteria as live bacteria, characterized in that the lactic acid bacteria are cultured in a culture medium containing oligosaccharides.

[0013] The method for producing fermented milk of the present invention is a simple method of adding oligosaccharides to a culture medium when culturing lactic acid bacteria. Therefore, there is no need to specially install new facilities, and existing facilities can be used as they are.

[0014] The fermented milk produced by the method for producing fermented milk of the present invention can not only maintain a high number of viable bacteria during long-term storage, but also has a good flavor and can enhance the sense of health.

[0015] In particular, the fermented milk obtained by the method for producing fermented milk of the present invention allows the ingestion of both probiotics produced by lactic acid bacteria and prebiotics produced by oligosaccharides (increasing lactic acid bacteria in the intestine), and is therefore a so-called synbiotic that further enhances the gastrointestinal health-protecting effect of probiotics. DETAILED DESCRIPTION

[0016] The method for producing fermented milk of the present invention (hereinafter referred to as "the production method of the present invention") is a method for producing fermented milk containing oligosaccharides and lactic acid bacteria as live bacteria, and is a method for producing lactic acid bacteria by culturing the lactic acid bacteria in a culture medium containing oligosaccharides.

[0017] The oligosaccharides used in the preparation method of the present invention are not particularly limited, and examples thereof include maltooligosaccharides, fructooligosaccharides, galacto-oligosaccharides, and the like. The oligosaccharides used in the present invention refer to transferred disaccharides or trisaccharides or more; among these oligosaccharides, oligosaccharides containing galactose in the sugar chain are preferred, galacto-oligosaccharides are more preferred, and galacto-oligosaccharides with 4'-GL as the main component are particularly preferred. Examples of such galacto-oligosaccharides include, for example, a mixture of 56.4% galacto-oligosaccharides with 4'-GL as the main component and 43% other sugars, i.e., OLIGOMATE 55N (manufactured by Yakult Pharmaceutical Industry Co., Ltd.: Brix sugar degree 75.0-76.0), and the like.

[0018] The oligosaccharide is preferably contained in the culture medium described later in an amount of 1.0 mass % (hereinafter referred to as "%") or more, preferably 5.0% or more, more preferably 5 to 20%, particularly preferably 5 to 15%.

[0019] The culture medium used in the production method of the present invention is not particularly limited as long as it is a culture medium that can cultivate lactic acid bacteria, and examples thereof include animal milk culture medium formed from raw milk such as cow's milk, goat's milk, horse's milk, and sheep's milk, skim milk powder, whole milk powder, fresh cream and other dairy products, and various synthetic culture media. Among these culture media, skim milk powder is preferred.

[0020] The above-mentioned culture medium may also contain carbohydrates that can be assimilated by lactic acid bacteria as needed. Examples of such carbohydrates include glucose, sucrose, fructose, etc. The content of carbohydrates that can be assimilated by lactic acid bacteria in the culture medium is not particularly limited, and can be appropriately set according to the lactic acid bacteria used for the culture, for example, 0.1 to 20%, preferably 1 to 10%.

[0021] The above-mentioned culture medium may further contain culture aids such as sweet tea extract, oolong tea extract, green tea extract, black tea extract, jasmine tea extract, oleic acid, etc. as needed. These culture aids may be used alone or in combination of two or more.

[0022] Among the culture aids, sweet tea extract, oolong tea extract, green tea extract, black tea extract, and jasmine tea extract may be commercially available or obtained by the methods described in Japanese Patent Application Laid-Open Nos. 2001-178413 and 2016-174589. The content of these extracts in the culture medium is not particularly limited, and for example, the content of sweet tea extract and oolong tea extract is 0.1 to 2%, preferably 0.22 to 0.33%.

[0023] In the culture aid, oleic acid is not particularly limited, and in addition to free oleic acid and inorganic salts of oleic acid, sugar esters, glycerides, sorbitan esters, propylene glycol esters, etc. generally used as emulsifiers, whose fatty acid moiety is oleic acid, can be cited. In addition, food materials containing a large amount of oleic acid can also be used.

[0024] Specific examples of oleic acids include oleic acid salts such as sodium oleate and potassium oleate, and oleic acid esters such as glycerol oleate, polyglycerol oleate, and sucrose oleate. At least one of these oleic acids may be used.

[0025] The content of oleic acid in the culture medium is not particularly limited, and is, for example, 5 to 200 ppm, preferably 10 to 100 ppm.

[0026] Furthermore, the above-mentioned culture medium may also contain components that can be added to the culture medium for culturing common lactic acid bacteria, such as vitamins such as vitamin A, vitamin B, vitamin C, and vitamin E, peptides such as milk peptides, amino acids, salts such as calcium and magnesium, sugars, etc.

[0027] The above-mentioned culture medium contains oligosaccharides, and there is no problem even if lactic acid bacteria are directly cultured. However, in order to improve the fermentability and increase both the bacterial count after culture and the bacterial count after storage, it is preferred to adjust the osmotic pressure. The osmotic pressure of the culture medium is set to 500-1400mOsm, preferably 800-1200mOsm. There is no particular limitation on the method for adjusting the osmotic pressure, and examples include methods for adjusting the amount of oligosaccharides and sugars contained in the culture medium. It should be noted that improving the fermentability means that the acidity after culture is 24 or more and the bacterial count is 5.0×10 9 cfu / ml and above.

[0028] As a preferred embodiment of the oligosaccharide-containing culture medium used in the production method of the present invention, the following embodiments are mentioned.

[0029]

[0030]

[0031] The lactic acid bacteria used in the preparation method of the present invention is not particularly limited, and for example, it can be any of lactic acid bacteria found in nature, lactic acid bacteria preserved in a preservation unit, commercially available lactic acid bacteria, and lactic acid bacteria mutated therefrom. Specifically, lactobacillus casei, lactobacillus gasseri, lactobacillus acidophilus, lactobacillus cream, lactobacillus helveticus, lactobacillus salivarius, fermented lactobacillus, lactobacillus japonicus, lactobacillus delbrueckii subspecies bulgaricus, lactobacillus delbrueckii subspecies delbrueckii, lactobacillus johnsonii, lactobacillus genus such as Streptococcus thermophilus, lactococcus lactis subspecies lactic acid, lactococcus lactis subspecies creamy, lactococcus plantarum, lactococcus raffinose, lactococcus faecalis, lactococcus genus such as Enterococcus, etc. can be cited. Among these lactic acid bacteria, lactic acid bacteria that are substantially unable to assimilate oligosaccharides are preferred, and lactic acid bacteria such as Lactobacillus casei, Lactobacillus gasseri, Lactobacillus acidophilus, and Streptococcus thermophilus can be cited. The term "substantially unable to assimilate oligosaccharides" herein refers to the inability to assimilate oligosaccharides above trisaccharides. Assimilation ability can be confirmed by a known method, and for example, a method of confirming the presence or absence of colonies and the turbidity of the culture medium after culturing with a culture medium containing only oligosaccharides as a sugar source can be cited. Furthermore, among the lactic acid bacteria that are substantially unable to assimilate oligosaccharides, lactic acid bacteria of the genus Lactobacillus are preferred, and lactic acid bacteria such as Lactobacillus casei can be cited. In particular, among the lactic acid bacteria of the genus Lactobacillus, Lactobacillus casei YIT9029 (FERM BP-1366, deposit date: January 12, 1975) and the like are preferred. These lactic acid bacteria can be used in one kind or in combination of two or more kinds.

[0032] The lactic acid bacteria recorded in the above-mentioned deposit date are deposited in the National Institute of Advanced Industrial Science and Technology, International Patent Organism Depository Center (Room 120, 2-5-8, Kazusa Kamata, Kisarazu, Chiba Prefecture, Japan, 292-0818).

[0033] In the production method of the present invention, the conditions for culturing lactic acid bacteria using a culture medium containing oligosaccharides are not particularly limited and may be appropriately determined in accordance with the type of lactic acid bacteria etc. used.

[0034] Specifically, when lactic acid bacteria are cultured in a medium containing oligosaccharides, the number of lactic acid bacteria in the medium may be set to 0.5×10 6 The inoculation is carried out in a manner of about cfu / ml, and the lactic acid bacteria are cultured at the optimal culture temperature for the lactic acid bacteria, etc. until the pH reaches about 3.5 to 3.6 or the acidity reaches about 24.0. As the culture conditions at this time, a method suitable for the culture of the lactic acid bacteria used can be appropriately selected from standing, stirring, shaking, ventilation, etc.

[0035] The fermented milk containing oligosaccharides and live lactic acid bacteria obtained after the culture may be used as a final product as it is, or oligosaccharides may be further added. The amount of oligosaccharides added at this time is not particularly limited, but is 1 to 20%, preferably 3 to 10%, relative to the final product.

[0036] Furthermore, the fermented milk may further contain food materials such as carbohydrates, sugar alcohols, high-intensity sweeteners, thickeners, emulsifiers, vitamins, and flavors according to the need by conventionally known methods.

[0037] Examples of the food materials include carbohydrates such as sucrose, glucose, fructose, isomaltulose, trehalose, lactose, xylose, and maltose; sugar alcohols such as sorbitol, xylitol, erythritol, lactitol, isomalt, reduced starch syrup, and reduced maltose starch syrup; high-intensity sweeteners such as aspartame, thaumatin, sucralose, acesulfame potassium, and stevioside; agar, gelatin, carrageenan, guar gum, xanthan gum, pectin, locust bean gum, gellan gum, carboxymethyl cellulose, soybean polysaccharides, and various thickeners (stabilizers) such as propylene glycol alginate; sucrose fatty acids; Esters, glycerol fatty acid esters, polyglycerol fatty acid esters, sorbitan fatty acid esters, emulsifiers such as lecithin, milk fats such as cream, butter, sour cream, acidulants such as citric acid, lactic acid, acetic acid, malic acid, tartaric acid, gluconic acid, various vitamins such as vitamin A, vitamin B, vitamin C, vitamin E, minerals such as calcium, magnesium, zinc, iron, manganese, yogurt, berry, orange, papaya, shiso, citrus, apple, mint, grape, apricot, pear, custard, peach, melon, banana, tropical, herbal, black tea, coffee and other spices.

[0038] The fermented milk containing oligosaccharides and lactic acid bacteria as live bacteria described above is not only fermented milk such as dairy products formulated according to provincial and ministerial regulations, but also includes dairy lactic acid bacteria beverages, lactic acid bacteria beverages and other beverages, kefir, yogurt and other types containing live bacteria. In addition, as its form, for example, hard type, soft type, original flavor type, sweet type, fruit type, beverage type, frozen type, etc. can be cited.

[0039] The fermented milk can improve the survival of lactic acid bacteria and maintain a high number of viable bacteria during long-term storage. Specifically, the fermented milk has a survival rate of 95% or more when stored at 10°C or less for 25 days. It should be noted that the survival rate is a value measured by the method described in the Examples.

[0040] In addition, the fermented milk has an enhanced sense of health. Here, the healthy fermented milk flavor refers to a flavor that is not too sweet and has a moderate sour taste due to the fermentation of lactic acid bacteria, thereby giving an impression of low calories, low carbohydrates, and fermented milk style.

[0041] Example

[0042] Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to these Examples.

[0043] Reference Example 1

[0044] Existing production of fermented milk:

[0045] A culture medium containing 14.7% skim milk powder, 9.2% glucose-fructose liquid sugar, and 0.14% oolong tea extract (YOE-N: manufactured by Yakult Material Co., Ltd.) dissolved in water was sterilized at 100°C for 60 minutes. A starter culture of Lactobacillus casei YIT9029 (FERM BP-1366) was inoculated at 0.5% (initial bacterial count: 5.0×10 6 cfu / ml) was added to the culture medium, and the culture was carried out while adjusting the temperature until the acidity reached 24.3. The obtained fermented milk was mixed with a stabilizer solution containing 2.9% skim milk powder and 2.7% soybean polysaccharide (SM-YT manufactured by Saneigen FFI Co., Ltd.) as a stabilizer, and then homogenized. Then, it was mixed with sucrose syrup or galacto-oligosaccharide liquid sugar (a mixture of 56.4% galacto-oligosaccharide and 43% other sugars relative to the solid content: OLIGOMATE 55N: manufactured by Yakult Pharmaceutical Industry Co., Ltd.) as shown in Table 1 to obtain a viable bacterial count of 1.4×10 9 cfu / ml, acidity of 5.8, and pH of 3.7 (Products 1 and 2). The lactic acid bacteria beverages were placed in containers and stored at 10°C, and then the survival rate was measured by the following method. The results are shown in Table 1.

[0046] <Acidity measurement method>

[0047] 40 g of ion-exchanged water was added to 9 g of the culture, and neutralization titration was performed with 0.1 N sodium hydroxide so that the pH became 8.5. The titration value (unit: ml / 9 g) at this time was defined as the acidity.

[0048] <Osmotic pressure measurement method>

[0049] The osmotic pressure was measured using an osmotic pressure analyzer "OSMOSTATION OM-6060" manufactured by ARKRAY Inc.

[0050] <Method for determination of viable bacterial count>

[0051] The assay was performed using BCP medium (Eiken Chemical Co., Ltd.).

[0052] <Survival rate calculation method>

[0053] Survival rate on the Xth day of storage (%) = (number of viable bacteria on the Xth day of storage / number of viable bacteria on the 0th day of storage) × 100

[0054] [Table 1]

[0055]

[0056] When galacto-oligosaccharide was added as syrup to fermented milk after fermentation, the survival rate decreased compared with the case where sucrose was added as syrup to fermented milk after fermentation.

[0057] Example 1

[0058] Production of fermented milk:

[0059] A culture medium containing 14.6% skim milk powder, 0.14% oolong tea extract (YOE-N: manufactured by Yakult Material Co., Ltd.), and 19.5% galacto-oligosaccharide liquid sugar (a mixture of 56.4% galacto-oligosaccharide and 43% other sugars relative to the solid content: OLIGOMATE 55N: manufactured by Yakult Pharmaceutical Industry Co., Ltd.) dissolved in water was sterilized at 100°C for 60 minutes. A starter culture of Lactobacillus casei YIT9029 (FERM BP-1366) was inoculated at 0.5% (initial bacterial count: 5.0×10 6 cfu / ml) was added to the culture medium and cultured while adjusting the temperature until the acidity reached 24.3. The fermented milk obtained was mixed with a stabilizer solution containing 2.9% skim milk powder and 2.7% soybean polysaccharide (SM-YT manufactured by Saneigen FFI Co., Ltd.) as a stabilizer and homogenized, and then mixed with a syrup containing 16.1% of galacto-oligosaccharide liquid sugar as shown in Table 2 to obtain a culture medium with a viable bacterial count of 6.3×10 8 cfu / ml, titrated acidity of 4.9ml / 9g, and pH of 3.8 (implementation product 1). This lactic acid bacteria beverage was placed in a container and stored at 10°C, and the survival rate was measured according to the above method. These results are recorded in Table 2. It should be noted that the comparison object is product 2 manufactured in Reference Example 1.

[0060] [Table 2]

[0061]

[0062] Compared with the case where galacto-oligosaccharide was added as a syrup to the fermented milk after fermentation, the survival rate was significantly improved when galacto-oligosaccharide was added to the medium.

[0063] Example 2

[0064] Production of fermented milk:

[0065] A culture medium containing 14.6% skim milk powder, 0.14% oolong tea extract (YOE-N: manufactured by Yakult Material Co., Ltd.), and 12.8% galacto-oligosaccharide liquid sugar (a mixture of 56.4% galacto-oligosaccharide and 43% other sugars relative to the solid content: OLIGOMATE 55N: manufactured by Yakult Pharmaceutical Industry Co., Ltd.) dissolved in water was sterilized at 100°C for 60 minutes. A starter culture of Lactobacillus casei YIT9029 (FERM BP-1366) was inoculated at 0.5% (initial bacterial count: 5.0×10 6 cfu / ml) was added to the culture medium and cultured while adjusting the temperature until the acidity reached 24.3. The fermented milk obtained was mixed with a stabilizer solution containing 2.9% skim milk powder and 2.7% soybean polysaccharide (SM-YT manufactured by Saneigen FFI Co., Ltd.) as a stabilizer and homogenized, and then mixed with a syrup containing 18.3% of galacto-oligosaccharide liquid sugar as shown in Table 3 to obtain a culture medium with a viable bacterial count of 1.2×10 9 cfu / ml, a titrated acidity of 5.6, and a pH of 3.7 (implementation product 2). After the lactic acid bacteria beverage is placed in a container and stored at 10°C, the number of viable bacteria (and survival rate) is determined according to the above method. The results are recorded in Table 3. It should be noted that the comparison objects are product 3 in which the galacto-oligosaccharide added to the culture medium is replaced with 2.3% glucose and 0.014% sucralose, and product 4 in which the galacto-oligosaccharide added to the culture medium is replaced with 2.3% glucose and 10.8% maltitol. In addition, for these products, the fermentability is evaluated according to the following evaluation criteria. The results are also recorded in Table 3.

[0066] <Fermentability Evaluation Criteria>

[0067] (evaluation)(content)

[0068] ○: The acidity after culture is 24 or more and the number of viable bacteria is 5.0×10 9 cfu / ml or more

[0069] △: The acidity after culture is 24 or higher and the number of viable bacteria is less than 5.0×10 9 cfu / ml

[0070] ×: The acidity after culture is less than 24

[0071] [Table 3]

[0072]

[0073] *The unit of bacterial count is cfu / ml

[0074] ※The target acidity was not reached

[0075] It is known that by adjusting the osmotic pressure of the culture medium to between 800 and 1200 mOsm, the fermentability is good, and both the bacterial count after culture and the bacterial count after storage can be increased (implementation product 2). In addition, when sucralose or maltitol other than galacto-oligosaccharide is added to the culture medium, it is believed that the acidity after culture does not reach the target, which has an adverse effect on the fermentability, and the acidity of the product also does not reach the target. (Products 3 and 4).

[0076] Example 3

[0077] Production of fermented milk:

[0078] A culture medium containing 14.6% skim milk powder, 0.14% oolong tea extract (YOE-N: manufactured by Yakult Material Co., Ltd.), and 12.8% galacto-oligosaccharide liquid sugar (a mixture of 56.4% galacto-oligosaccharide and 43% other sugars relative to the solid content: OLIGOMATE 55N: manufactured by Yakult Pharmaceutical Industry Co., Ltd.) dissolved in water was sterilized at 100°C for 60 minutes. A starter culture of Lactobacillus casei YIT9029 (FERM BP-1366) was inoculated at 0.5% (initial bacterial count: 5.0×10 6 cfu / ml) was added to the culture medium, and the culture was continued while adjusting the temperature until the acidity reached 24.3. The fermented milk obtained was mixed with a stabilizer solution containing 2.9% skim milk powder and 2.7% soybean polysaccharide (SM-YT manufactured by Saneigen FFI Co., Ltd.) as a stabilizer, and then homogenized. It was then mixed with a syrup containing 0.02% stevioside and 18.3% galacto-oligosaccharide liquid sugar as shown in Table 4 to obtain a culture medium with a viable bacterial count of 1.2×10 9 cfu / ml, a titrated acidity of 5.2, and a lactic acid bacteria beverage of pH 3.8 (implementation product 3). After the lactic acid bacteria beverage was placed in a container and stored at 10°C, the number of viable bacteria (and survival rate) was determined according to the above method. The results are recorded in Table 4. It should be noted that the comparison object is product 5 in which the galacto-oligosaccharide added to the culture medium was replaced with 9.2% glucose-fructose liquid sugar. In addition, implementation products 3 and 5 were unified in that the product acidity was 5.2 and the relative sweetness was 110. The relative sweetness mentioned here refers to the relative value when the sweetness of a 10w / v% aqueous solution of sucrose is set to 100. Furthermore, for these products, the sweetness, sourness, and healthiness were evaluated according to the following evaluation criteria, and the flavor was evaluated in the free description. The results are also recorded in Table 4.

[0079] <Evaluation Criteria for Sweetness and Sourness>

[0080] (Rating)(Content)

[0081] 1: weak

[0082] 2: Slightly weak

[0083] 3: Just

[0084] 4: Slightly stronger

[0085] 5: Strong

[0086] <Evaluation criteria for healthiness>

[0087] (Rating)(Content)

[0088] 1: No

[0089] 2: Almost none

[0090] 3: None of the cases

[0091] 4: Slightly

[0092] 5: Yes

[0093] [Table 4]

[0094]

[0095] Generally, in fermented milk, if the sour taste is relatively stronger than the sweet taste, it will lead to a decrease in the palatability, but if the sweet taste is too strong, it will damage the refreshing drinking taste and healthy flavor impression required for fermented milk and lactic acid bacteria beverages. In the case of product 5, the rich sweetness of glucose-fructose liquid sugar instead gives an impression of high calories and damages the sense of health, and in the case of implementation product 3, only galacto-oligosaccharide liquid sugar is used as the sugar raw material, so it is not too sweet, and it is a refreshing drinking taste that is balanced with sourness, and a sense of health is achieved.

[0096] Industrial Applicability

[0097] The present invention can be utilized in the production of fermented milk containing oligosaccharides and lactic acid bacteria as live bacteria, in which a high number of live bacteria is maintained even during long-term storage.

Claims

1. A method for producing fermented milk, characterized in that: The invention relates to a method for producing fermented milk containing oligosaccharides and lactic acid bacteria as live bacteria, wherein the lactic acid bacteria are cultured in a culture medium containing oligosaccharides, and the oligosaccharides in the culture medium are 5.0% by mass or more.

2. The method for producing fermented milk according to claim 1, wherein The osmotic pressure of the culture medium during culture was 800 to 1200 mOsm.

3. The method for producing fermented milk according to claim 1 or 2, wherein The oligosaccharide is galacto-oligosaccharide.

4. The method for producing fermented milk according to claim 1 or 2, wherein The lactic acid bacteria are lactic acid bacteria that are substantially unable to assimilate oligosaccharides.

5. The method for producing fermented milk according to claim 1 or 2, wherein The lactic acid bacteria are lactic acid bacteria of the genus Lactobacillus.

6. The manufacturing method according to claim 1 or 2, wherein: After the lactic acid bacteria are cultured in a medium containing oligosaccharides, oligosaccharides are further added.

7. Fermented milk produced by the method for producing fermented milk according to any one of claims 1 to 6.

8. A method for improving the viability of lactic acid bacteria in fermented milk, the fermented milk containing oligosaccharides and lactic acid bacteria as live bacteria, characterized in that: The lactic acid bacteria are cultured in a culture medium containing oligosaccharides, wherein the oligosaccharides in the culture medium are 5.0% by mass or more.

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