JP7389438B2 - Natto, a method for producing natto, and a method for improving the aftertaste of natto - Google Patents

Description

The present disclosure discloses that by adding a specific aroma component to stringy natto (referring to all fermented soybeans produced by fermenting soybeans with Bacillus natto.Hereinafter, it may be simply referred to as "natto"). This paper relates to a technology that improves the aftertaste, which was an issue with stringy natto, especially when combined with foods other than natto, as well as improving the appearance and convenience.

Itobiki natto is an ancient Japanese fermented food that is rich in soy protein and has high nutritional value, making it one of the daily foods of the Japanese people.

On the other hand, when stringy natto fermented with natto bacteria is manufactured using the normal method, consumers' tastes differ due to its unique flavor, and it is particularly disliked by non-Japanese people who do not regularly eat stringy natto. There was a problem that there was a strong tendency to

Particularly in natto-containing foods in which natto is combined with food materials other than natto, the strong flavor unique to natto impairs the deliciousness of the natto-containing foods and reduces palatability.

In addition, the white film-like appearance caused by the metabolites of Bacillus natto and the stringiness mainly composed of γ-polyglutamic acid (hereinafter sometimes abbreviated as PGA) also reduce the palatability of the combined food ingredients. This was a contributing factor.

Therefore, there has been a need to establish a technology related to natto that allows natto to be freely combined with other food materials without reducing palatability even when combined with other food materials.

Examples of technologies that address these issues include technology related to natto produced using natto bacteria with less stringiness (see Patent Document 1) and technology related to natto that is desensitized to the stuffy odor (see Patent Document 2). .

However, these techniques are only involved in reducing the stringiness and unpleasant odor of natto, and do not contribute to improving the overall taste.

Japanese Patent Application Publication No. 2015-208319 Japanese Patent Application Publication No. 2000-354493

The present disclosure relates to a technique for solving the above-mentioned conventional problems and providing a novel natto with improved aftertaste, especially when natto is combined with other food materials.
The present disclosure also provides a technique for providing novel natto with a good appearance and a unique gloss on the natto surface.

The present discloser has made extensive studies to solve the above-mentioned conventional problems, and has found that 2,5-dimethylpyrazine and 2,3,5-trimethylpyrazine are contained at a predetermined concentration, and that isobutyric acid, isovaleric acid, The present disclosure has been completed based on the discovery that the above-mentioned conventional problems can be solved by a simple means of containing 4-vinyl-guaiacol at a predetermined concentration as needed.
It was also discovered that by adjusting the turbidity and color of the natto suspension within a predetermined range, it is possible to produce a new type of natto that has a highly palatable appearance with a glossy surface. Ta.

That is, the present disclosure relates to the following (1) to (13) (hereinafter, these will be referred to in order as "the first embodiment of the present disclosure" to "the thirteenth aspect of the present disclosure").
Note that the scope of the present disclosure is not interpreted to be limited by the existence of the following descriptions (1) to (13).
(1) Natto that meets the requirements (a) to (b) below.
(a) The content of 2,5-dimethylpyrazine (x) is 0.05 mg or more and 5 mg or less per 1 kg of natto wet weight,
(b) The content of 2,3,5-trimethylpyrazine (y) shall be 0.05 mg or more and 3 mg or less per 1 kg of natto wet weight.
(2) The natto described in (1) above, which further satisfies the following requirements (c) to (e).
(c) The content (α) of isovaleric acid is 1 mg or more and 15 mg or less per 100 g of natto wet weight,
(d) The content (β) of isobutyric acid is 5 mg or more and 40 mg or less per 100 g of wet natto weight,
(e) The above α and β satisfy the following relational expression 1.
2≧α/β≧0.025 (Formula 1)
(3) The natto described in (1) or (2) above, which further satisfies the following requirements (f) to (g).
(f) The content (z) of 4-vinylguaiacol is 0.1 mg or more and 5 mg or less per 1 kg of natto wet weight,
(g) The above x, y, and z satisfy the following relational expression 2.
50≧z /(x+y)≧0.02 (Formula 2)
(4) The natto according to any one of (1) to (3) above, which further satisfies the following requirement (h).
(h) The levan content (δ) shall be 1.5 mg or more and 20 mg or less per 1 g of wet natto weight.
(5) The natto described in (4) above, which further satisfies the following requirements (i) to (j).
(i) The content of PGA (ε) is 0.01 mg or more and 1.0 mg or less per 1 g of natto wet weight,
(j) δ and ε satisfy the following relational expression 3.
200≧δ/ε≧2 (Formula 3)
(6) The natto according to any one of (1) to (5) above, which further satisfies the following requirements (k) to (l).
(k) The turbidity of the extract obtained by stirring 40 g of natto in 80 mL of water and removing the bean part and measuring the extract at a wavelength of 660 nm with a spectrophotometer is 0.5 or more and 4.5 or less,
(l) After stirring 40 g of natto in 40 mL of water, the color of the extracted liquid obtained by removing the beans must be within the following range in the L ^* a ^* b ^* color space. .
80≧L ^* ≧40
5≧a ^* ≧-5
30≧b ^* ≧10
(7) The natto according to any one of (1) to (6) above, which further satisfies the following requirements (m).
(m) After stirring 40 g of natto in 40 mL of water, the viscosity of the extract obtained by removing the bean part is 5 mPa・s or more and 180 mPa・Must be less than or equal to s.
(8) A method for producing natto, which is characterized in that it is produced so that the following requirements (a) to (b) are satisfied upon completion of ripening.
(a) The content of 2,5-dimethylpyrazine (x) is 0.05 mg or more and 5 mg or less per 1 kg of natto wet weight,
(b) The content of 2,3,5-trimethylpyrazine (y) shall be 0.05 mg or more and 3 mg or less per 1 kg of natto wet weight.
(9) The method for producing natto according to (8) above, further comprising producing the natto so that it satisfies the following requirements (c) to (e) upon completion of ripening:
(c) The content (α) of isovaleric acid is 1 mg or more and 15 mg or less per 100 g of natto wet weight,
(d) The content (β) of isobutyric acid is 5 mg or more and 40 mg or less per 100 g of wet natto weight,
(e) The above α and β satisfy the following relational expression 1.
2≧α/β≧0.025 (Formula 1)
(10) Steamed soybeans or boiled soybeans are inoculated with Bacillus natto, and fermentation is carried out at a high temperature by maintaining the product temperature at 45°C or more and 54°C or less for 7 hours or more and 15 hours or less, or (8) or (2) above. 9) The method for producing natto as described in 9).
(11) The natto according to any one of (8) to (10) above, which uses natto bacteria with weak stringiness selected from natto strains that have been subplanted three or more times. Production method.
(12) A method for improving the aftertaste of natto, which comprises producing natto so that the natto satisfies the following requirements (a) to (b) upon completion of ripening.
(a) The content of 2,5-dimethylpyrazine (x) is 0.05 mg or more and 5 mg or less per 1 kg of natto wet weight,
(b) The content of 2,3,5-trimethylpyrazine (y) shall be 0.05 mg or more and 3 mg or less per 1 kg of natto wet weight.
(13) The method for improving the aftertaste of natto according to (12), further comprising producing the method to satisfy the following requirements (c) to (e) upon completion of ripening.
(c) The content (α) of isovaleric acid is 1 mg or more and 15 mg or less per 100 g of natto wet weight,
(d) The content (β) of isobutyric acid is 5 mg or more and 40 mg or less per 100 g of wet natto weight,
(e) The above α and β satisfy the following relational expression 1.
2≧α/β≧0.025 (Formula 1)

According to the present disclosure, it is possible to improve the aftertaste (hereinafter sometimes simply referred to as "aftertaste") when natto is combined with other food materials. Further, according to the present disclosure, it is possible to provide a novel natto with a good appearance and a unique gloss on the natto surface.
Therefore, the present disclosure makes it possible to improve the overall palatability of natto, expand the scope of utilization of natto-containing foods in combination with other food ingredients, and provide them in a highly convenient form, which improves the overall palatability of natto. It is possible to expand the contact between people and natto.
Therefore, the present disclosure can be effectively used as a technique for providing natto.

FIG. 1 is a graph showing representative examples of changes in fermented product temperature in each fermentation method and heating method in Examples.

The present disclosure will be described in detail below.
A first aspect of the present disclosure satisfies the following requirements (a) to (b) regarding natto.
(a) The content of 2,5-dimethylpyrazine (x) is 0.05 mg or more and 5 mg or less per 1 kg of natto wet weight,
(b) The content of 2,3,5-trimethylpyrazine (y) shall be 0.05 mg or more and 3 mg or less per 1 kg of natto wet weight.

In the first aspect of the present disclosure, it is necessary to satisfy both of the requirements (a) and (b) above, and even if only one of them is satisfied, the purpose of the first aspect of the present disclosure is not achieved. It is not possible to achieve this, and in particular it is not possible to achieve a better aftertaste improving effect.

In the first aspect of the present disclosure, the content of (a) 2,5-dimethylpyrazine (x) needs to be 0.05 mg or more and 5 mg or less per 1 kg of natto wet weight, preferably natto wet weight It is 0.1 mg or more and 4 mg or less per 1 kg, and more preferably 0.2 mg or more and 3 mg or less per 1 kg of natto wet weight.
If the content of 2,5-dimethylpyrazine (x) is below the lower limit, 2,5-dimethylpyrazine (x) will not exhibit sufficient effects, and the aftertaste improvement effect will not be obtained. On the other hand, if the content of 2,5-dimethylpyrazine (x) is outside the upper limit, a roasted aroma will be produced, which is undesirable.

Next, the content of (b) 2,3,5-trimethylpyrazine (y) needs to be 0.05 mg or more and 3 mg or less per 1 kg of natto wet weight, preferably 0.2 mg per 1 kg of natto wet weight. The amount is 2 mg or less, and more preferably 0.4 mg or more and 1.8 mg or less per 1 kg of natto wet weight.
Here, if the content of 2,3,5-trimethylpyrazine (y) falls below the lower limit (hereinafter simply referred to as "beyond the lower limit"), the aftertaste improving effect cannot be obtained. On the other hand, if the content of 2,3,5-trimethylpyrazine (y) exceeds the upper limit (hereinafter simply referred to as "beyond the upper limit"), a straw-like odor is produced, which is undesirable.

As described above, the natto of the first aspect of the present disclosure contains 0.05 mg or more and 5 mg or less of 2,5-dimethylpyrazine (x) per 1 kg of natto wet weight, and 2,3,5-trimethyl It is sufficient to contain pyrazine (y) from 0.05 mg to 3 mg per 1 kg of natto wet weight, and the amount of 2,5-dimethylpyrazine (x) and 2,3,5-trimethylpyrazine (y), It may be contained by fermentation of natto (including secondary fermentation), it may be contained by addition, or it may be contained by both fermentation of natto and addition. You can. Since the good flavor of natto other than 2,5-dimethylpyrazine and 2,3,5-trimethylpyrazine can also be produced, it is most preferable to incorporate them by fermenting natto.

Note that in the following second to thirteenth aspects of the present disclosure, each component is either fermented with natto or added, or fermented with natto and added, as in the first aspect of the present disclosure. In addition, natto fermentation may include secondary fermentation, but secondary fermentation may contain ammonia and other unpleasant flavors of natto. It is not preferable to produce it during the next fermentation.

Next, a second aspect of the present disclosure, regarding natto, satisfies the following requirements (c) to (e) in addition to the requirements shown in the first aspect of the present disclosure.
(c) The content (α) of isovaleric acid is 1 mg or more and 15 mg or less per 100 g of natto wet weight,
(d) The content (β) of isobutyric acid is 5 mg or more and 40 mg or less per 100 g of wet natto weight,
(e) The above α and β satisfy the following relational expression 1.
2≧α/β≧0.025 (Formula 1)

In the second aspect of the present disclosure, in addition to the requirements (a) to (b) above shown in the first aspect of the present disclosure, all of the requirements (c) to (e) above are also satisfied. is necessary.

Here, the requirements (a) to (b) are as described in the first aspect of the present disclosure.
In the second aspect of the present disclosure, the content (α) of (c) isovaleric acid needs to be 1 mg or more and 15 mg or less per 100 g wet weight of natto, preferably 1.2 mg per 100 g wet weight of natto. The amount is 12.5 mg or less, and more preferably 1.5 mg or more and 10 mg or less per 100 g wet weight of natto.
Here, if the content (α) of (c) isovaleric acid is outside the lower limit, a good flavor of natto cannot be obtained. On the other hand, if the content (α) of (c) isovaleric acid is outside the upper limit, the unpleasant odor of natto hits the nose.

Next, in the second aspect of the present disclosure, the content (β) of (d) isobutyric acid needs to be 5 mg or more and 40 mg or less per 100 g of natto wet weight, preferably 5 mg or more and 40 mg or less per 100 g of natto wet weight. The amount is 5.1 mg or more and 40 mg or less, more preferably 5.2 mg or more and 20 mg or less per 100 g of wet natto weight.
Here, if the content (β) of (d) isobutyric acid is outside the lower limit value, a good flavor of natto cannot be obtained. On the other hand, if the content (β) of (d) isobutyric acid is outside the upper limit, an irritating taste will be felt.

In the second aspect of the present disclosure, it is further necessary that (e) α and β satisfy the following relational expression 1.
2≧α/β≧0.025 (Formula 1)

In particular, as the requirement (e), it is preferable that α and β satisfy the following relational expression 1A.
1.8≧α/β≧0.05 (Formula 1A)
Furthermore, as the requirement (e), it is more preferable that α and β satisfy the following relational expression 1B.
1.5≧α/β≧0.1 (Formula 1B)

Here, if the content ratio of α/β is out of the lower limit (that is, if the ratio of (d) isobutyric acid content (β) to isovaleric acid content (α) is too high), natto A good flavor cannot be obtained. On the other hand, if the content ratio of α/β is outside the upper limit (that is, if the ratio of (d) isobutyric acid content (β) to isovaleric acid content (α) is too small), natto The taste is unbalanced and undesirable.

Further, the third aspect of the present disclosure relates to natto, and in addition to the requirements shown in the first aspect of the present disclosure and/or the second aspect of the present disclosure, the following requirements (f) to (g) are further provided. It satisfies the following.
(f) The content (z) of 4-vinylguaiacol is 0.1 mg or more and 5 mg or less per 1 kg of natto wet weight, and (g) the above x, y, and z satisfy the following relational expression 2.
50≧z /(x+y)≧0.02 (Formula 2)

In the third aspect of the present disclosure, the above requirements (a) to (b) shown in the first aspect of the present disclosure and/or the above requirements (c) to (e) shown in the second aspect of the present disclosure are satisfied. In addition to the above requirements, it is also necessary to satisfy all of the requirements (f) to (g) above.
Here, "the requirements (a) to (b) above shown in the first aspect of the present disclosure and/or the requirements (c) to (e) above shown in the second aspect of the present disclosure" refer to "the requirements (a) to (b) above shown in the first aspect of the present disclosure" In addition to "both the requirements (a) to (b) above in the first aspect of the disclosure and the requirements (c) to (e) above in the second aspect of the disclosure," This is a concept that includes "only the requirements (a) to (b) above shown in the first aspect" or "only the requirements (c) to (e) above shown in the second aspect of the present disclosure."

In the third aspect of the present disclosure, the content (z) of (f) 4-vinylguaiacol needs to be 0.1 mg or more and 5 mg or less per 1 kg of natto wet weight, preferably 0.1 mg or more and 5 mg or less per 1 kg of natto wet weight. The amount is 0.2 mg or more and 3 mg or less, more preferably 0.3 mg or more and 2.5 mg or less per 1 kg of natto wet weight.
Here, if the content (z) of 4-vinylguaiacol is outside the lower limit, the aftertaste improving effect will not be enhanced. On the other hand, if the content (z) of 4-vinylguaiacol is outside the upper limit, an excessive fermentation odor (chemical odor) will be felt.

Next, in the third aspect of the present disclosure,
(g) It is necessary that x, y, and z satisfy the following relational expression 2.
50≧z /(x+y)≧0.02 (Formula 2)

In particular, in the third aspect of the present disclosure, as the requirement (g), it is preferable that x, y, and z satisfy the following relational expression 2A.
10≧z /(x+y)≧0.06 (Formula 2A)
Furthermore, as the requirement (g), it is more preferable that x, y, and z satisfy the following relational expression 2B.
8≧z /(x+y)≧0.08 (Formula 2B)

Here, as the requirement (g), even if the ratio of z to the total amount of x and y (z/(x+y)) is too small, or the ratio of z to the total amount of x and y ( If z/(x+y)) is too large, the balance of fermentation odor will be disrupted, which is not desirable.

Further, a fourth aspect of the present disclosure relates to natto and satisfies the requirements set forth in any one or more of the first aspect of the present disclosure, the second aspect of the present disclosure, and the third aspect of the present disclosure. In addition, the following requirements (h) must be met.
(h) The levan content (δ) shall be 1.5 mg or more and 20 mg or less per 1 g of wet natto weight.

In the fourth aspect of the present disclosure, the requirements (a) to (b) above shown in the first aspect of the present disclosure, the requirements (c) to (e) above shown in the second aspect of the present disclosure, In addition to any one or more of the requirements (f) to (g) shown in the third aspect of the present disclosure, it is necessary to satisfy the requirement (h) above.

In the fourth aspect of the present disclosure, the content (δ) of (h) levan needs to be 1.5 mg or more and 20 mg or less per 1 g of wet weight of natto, preferably 1.7 mg or more per 1 g of wet weight of natto. The amount is 9 mg or less, and more preferably 1.9 mg or more and 8 mg or less per 1 g of wet natto weight.
If the levan content (δ) is below the lower limit, the natto will be indistinguishable from mere steamed soybeans, and the appearance of the natto will be unfavorable. On the other hand, if the levan content (δ) is outside the upper limit, there will be too much thickening substance, which will affect the aftertaste.

Furthermore, a fifth aspect of the present disclosure relates to natto, and includes any one of the first aspect of the present disclosure, the second aspect of the present disclosure, the third aspect of the present disclosure, and the fourth aspect of the present disclosure. In addition to the requirements shown in item 1 or more, the following requirements (i) to (j) must be met.
(i) The content of PGA (ε) is 0.01 mg or more and 1.0 mg or less per 1 g of natto wet weight,
(j) δ and ε satisfy the following relational expression 3.
200≧δ/ε≧2 (Formula 3)

In the fifth aspect of the present disclosure, the requirements (a) to (b) above shown in the first aspect of the present disclosure, the requirements (c) to (e) above shown in the second aspect of the present disclosure, In addition to the requirements shown in any one or more of the requirements (f) to (g) above shown in the third aspect of the present disclosure and the requirement (h) above shown in the fourth aspect of the present disclosure, In addition, it is necessary to satisfy the requirements (i) to (j) above.

In the fifth aspect of the present disclosure, (i) the content (ε) of PGA needs to be 0.01 mg or more and 1.0 mg or less per 1 g wet weight of natto, preferably 0.05 mg per 1 g wet weight of natto. The amount is 0.9 mg or more, more preferably 0.1 mg or more and 0.7 mg or less per 1 g of wet natto weight.
In the fifth aspect of the present disclosure, if the PGA content (ε) is outside the lower limit, a natto-like texture cannot be obtained. On the other hand, if the PGA content (ε) is outside the upper limit, stringiness (hereinafter sometimes referred to as "stringiness") is too strong and affects the aftertaste.

Next, in the fifth aspect of the present disclosure,
(j) It is necessary that δ and ε satisfy the following relational expression 3.
200≧δ/ε≧2 (Formula 3)

In particular, in the fifth aspect of the present disclosure, it is preferable that the ratio (δ/ε) of the levan content (δ) to the PGA content (ε) satisfies the following relational expression 3A.
100≧δ/ε≧2.5 (Formula 3A)
Furthermore, in the fifth aspect of the present disclosure, it is more preferable that the ratio (δ/ε) of the levan content (δ) to the PGA content (ε) satisfies the following relational expression 3B.
50≧δ/ε≧3 (Formula 3B)

In the fifth aspect of the present disclosure, if the ratio of the levan content (δ) to the PGA content (ε) exceeds the lower limit, the texture will be unbalanced. On the other hand, even if the ratio of the levan content (δ) to the PGA content (ε) is outside the upper limit, the texture will be unbalanced.

Further, a sixth aspect of the present disclosure relates to natto, and includes the first aspect of the present disclosure, the second aspect of the present disclosure, the third aspect of the present disclosure, the fourth aspect of the present disclosure, and the third aspect of the present disclosure. In addition to the requirements shown in any one or more of the aspects 5, the following requirements (k) to (l) are further satisfied.
(k) The turbidity of the extract obtained by stirring 40 g of natto in 80 mL of water and removing the bean part and measuring the extract at a wavelength of 660 nm with a spectrophotometer is 0.5 or more and 4.5 or less,
(l) After stirring 40 g of natto in 40 mL of water, the color of the extracted liquid obtained by removing the beans must be within the following range in the L ^* a ^* b ^* color space. .
80≧L ^* ≧40
5≧a ^* ≧-5
30≧b ^* ≧10

That is, in the sixth aspect of the present disclosure, the requirements (a) to (b) above shown in the first aspect of the present disclosure and the requirements (c) to (e) above shown in the second aspect of the present disclosure are satisfied. requirements, the requirements (f) to (g) above shown in the third aspect of the present disclosure, the requirement (h) above shown in the fourth aspect of the present disclosure, and the above ((h) shown in the fifth aspect of the present disclosure). In addition to any one or more of the requirements i) to (j), it is necessary to satisfy the requirements (k) to (l) above.

In the sixth aspect of the present disclosure, by satisfying the requirements (k) to (l) above, it is possible to provide a novel natto with a good appearance and a unique gloss on the natto surface.

In other words, the requirement (k) is that the turbidity of the extract obtained by stirring 40 g of natto in 80 mL of water and then removing the bean portion using a spectrophotometer at a wavelength of 660 nm is 0.5 or more. 4.5 or less, preferably the turbidity is 1 or more and 4 or less, more preferably 1.5 or more and 3 or less.
In the sixth aspect of the present disclosure, if the turbidity of the extract falls below the lower limit, good gloss and luster cannot be obtained. On the other hand, if the turbidity of the extract exceeds the upper limit, cloudiness will adversely affect the palatability of the appearance.

In addition, the requirement (l) is that when the extract obtained by stirring 40 g of natto into 40 mL of water and then removing the bean part is measured using a transmission method, the color representation is in the L ^* a ^* b ^* color space. It must be within the following range.
80≧L ^* ≧40
5≧a ^* ≧-5
30≧b ^* ≧10

In the sixth aspect of the present disclosure, by satisfying the above requirement (l), it is possible to provide a novel natto with a good appearance and a unique gloss on the natto surface.
In the sixth aspect of the present disclosure, the value of L ^* is preferably in the range of 75≧L ^* ≧45, and particularly preferably in the range of 70≧L ^* ≧48.
Furthermore, in the sixth aspect of the present disclosure, the value of a ^* is preferably in the range of 4≧a ^* ≧-3, and particularly preferably in the range of 3≧a ^* ≧-2.5.
Furthermore, in the sixth aspect of the present disclosure, the value of b ^* is preferably in the range of 28≧b ^* ≧12, and particularly preferably in the range of 25≧b ^* ≧15.
In the sixth aspect of the present disclosure, when the value of L ^* is outside the lower limit value, the appearance gives a dark and old impression. On the other hand, if the value of L ^* is outside the upper limit, the appearance will be bright and give an artificial impression.
Next, when the value of a ^* is outside the lower limit, the bluishness is too strong, giving a dark impression. On the other hand, if the value of a ^* is outside the upper limit, the reddish tinge is too strong, giving an impression of browning.
Moreover, if the value of b ^* is outside the lower limit, the yellowish tinge will be insufficient, giving an aged impression. On the other hand, when the value of b ^* is outside the upper limit, the yellowish tinge is too strong, giving an impression of browning.

Here, "L ^* a ^* b ^* color space" is a color system most often used to express color differences, and is also expressed as "CIE1976L ^* a ^* b ^* color space."
As mentioned above, the color representation of natto extract in the L ^* a ^* b ^* color space is obtained by stirring a specific amount (40g) of natto into an equal amount (40mL) of water and then removing the bean part. It can be obtained by measuring the extracted liquid using a spectrophotometer using a transmission method.
The L ^* value represents lightness (brightness) and ranges from 0 to 100, with the higher the value, the brighter it is. Furthermore, both a ^* and b ^* represent color, and are numerical values up to ±60. This shows that the more a ^* goes in the positive direction, the stronger the redness becomes, and the more the b ^* goes in the positive direction, the more the greenness becomes stronger. It shows that you are getting stronger.
Therefore, "80≧L ^* ≧40" indicates that the lightness is relatively high.
Further, "5≧a ^* ≧-5" indicates that the color is an intermediate color that cannot be described as being either reddish or greenish.
Furthermore, "30≧b ^* ≧10" indicates that the color is slightly yellowish.
Therefore, when looking at this as a whole, it is understood that the natto of the sixth form of the present disclosure has a slightly yellowish color, is relatively bright, and has a good palatability for consumers.

Further, a seventh aspect of the present disclosure relates to natto, and relates to the first aspect of the present disclosure, the second aspect of the present disclosure, the third aspect of the present disclosure, the fourth aspect of the present disclosure, and the fifth aspect of the present disclosure. In addition to the requirements shown in any one or more of the aspects and the sixth aspect of the present disclosure, the following requirement (m) is further satisfied.
(m) After stirring 40 g of natto in 40 mL of water, the viscosity of the extract obtained by removing the bean part is 5 mPa・s or more and 180 mPa・Must be less than or equal to s.

In other words, the requirement for (m) is that the viscosity of the extract obtained by stirring 40 g of natto into 40 mL of water and removing the bean part under the conditions of a B-type viscometer (60 rpm, 25°C, rotor No. 2) It is 5 mPa·s or more and 180 mPa·s or less, preferably 7 mPa·s or more and 170 mPa·s or less, more preferably 8 mPa·s or more and 160 mPa·s or less under the above conditions.

If the above-mentioned viscosity is below the lower limit, the texture typical of natto cannot be obtained. On the other hand, if the viscosity is outside the upper limit, the viscosity will be too strong and the texture will be adversely affected.

The production of "natto according to the first to seventh aspects of the present disclosure" as described above does not require any special steps, and can be carried out according to conventional methods, except for invention-specific requirements.

That is, for example, the natto according to the first aspect of the present disclosure can be produced so as to satisfy the requirements (a) to (b) above upon completion of ripening.
The eighth aspect of the present disclosure provides the method for producing natto according to the first aspect of the present disclosure.

That is, the eighth aspect of the present disclosure relates to a method for producing natto, which is characterized in that the natto is produced so as to satisfy the following requirements (a) to (b) upon completion of ripening.
(a) The content of 2,5-dimethylpyrazine (x) is 0.05 mg or more and 5 mg or less per 1 kg of natto wet weight,
(b) The content of 2,3,5-trimethylpyrazine (y) shall be 0.05 mg or more and 3 mg or less per 1 kg of natto wet weight.

In the eighth aspect of the present disclosure, the requirements (a) to (b) are as described in the first aspect of the present disclosure.

Next, the natto according to the second aspect of the present disclosure can be produced so as to satisfy the requirements (c) to (e) above upon completion of ripening.
The ninth aspect of the present disclosure provides the method for producing natto according to the second aspect of the present disclosure.

That is, the ninth aspect of the present disclosure relates to a method for producing natto, which is characterized in that the natto is produced so as to satisfy the following requirements (c) to (e) upon completion of ripening.
(c) The content (α) of isovaleric acid is 1 mg or more and 15 mg or less per 100 g of natto wet weight,
(d) The content (β) of isobutyric acid is 5 mg or more and 40 mg or less per 100 g of wet natto weight,
(e) The above α and β satisfy the following relational expression 1.
2≧α/β≧0.025 (Formula 1)

In the ninth aspect of the present disclosure, the requirements (c) to (e) are as described in the second aspect of the present disclosure.

As described above, the production of "natto according to the first to seventh aspects of the present disclosure" does not require any special process, and the invention specification shown in the eighth aspect of the present disclosure or the ninth aspect of the present disclosure Although it can be carried out according to a conventional method except for certain requirements, it can be particularly easily produced by the production method of the tenth aspect of the present disclosure or the production method of the eleventh aspect of the present disclosure, which will be described later.
Therefore, the conventional method for making natto will be described below, and the manufacturing method according to the tenth aspect of the present disclosure and the manufacturing method according to the eleventh aspect of the present disclosure will also be described.

In addition, when producing natto, the aftertaste of natto can be improved by producing the natto so that it satisfies the requirements (a) to (b) above at the time of completion of ripening. This is the twelfth aspect of the present disclosure.
That is, the twelfth aspect of the present disclosure is to improve the aftertaste of natto, which is characterized in that when manufacturing natto, the natto is manufactured so that the natto satisfies the following requirements (a) to (b) at the time of completion of ripening. It's a method.
(a) The content of 2,5-dimethylpyrazine (x) is 0.05 mg or more and 5 mg or less per 1 kg of natto wet weight,
(b) The content of 2,3,5-trimethylpyrazine (y) shall be 0.05 mg or more and 3 mg or less per 1 kg of natto wet weight.

In the twelfth aspect of the present disclosure, the requirements (a) to (b) are as described in the first aspect of the present disclosure.

In addition, when manufacturing natto, the natto can be manufactured so that it satisfies the requirements (c) to (e) above in addition to the requirements (a) to (b) above, so that the natto at the time of completion of ripening is It is the thirteenth aspect of the present disclosure that provides this.
That is, a 13th aspect of the present disclosure provides the aftertaste of natto, which is further characterized in that it is produced to satisfy the following requirements (c) to (e) upon completion of ripening. This is an improvement method.
(c) The content (α) of isovaleric acid is 1 mg or more and 15 mg or less per 100 g of natto wet weight,
(d) The content (β) of isobutyric acid is 5 mg or more and 40 mg or less per 100 g of wet natto weight,
(e) The above α and β satisfy the following relational expression 1.
2≧α/β≧0.025 (Formula 1)

In the thirteenth aspect of the present disclosure, the requirements (c) to (e) are as described in the second aspect of the present disclosure.

As described above, the "natto according to the first to seventh aspects of the present disclosure" can be produced by any method that is normally used for producing natto.
Below, a typical method for producing stringy natto will be exemplified.

In the following description, 2,5-dimethylpyrazine, 2,3,5-trimethylpyrazine, isovaleric acid, isobutyric acid, and 4-vinylguaiacol, which are aroma components involved in the present disclosure, will be collectively referred to as specific components. It may also be written as

1. Method for producing stringy natto 1-1. Preparation of steamed soybeans or boiled soybeans by soaking raw soybeans and heating them in liquid First, in order to obtain steamed soybeans or boiled soybeans, raw soybeans are soaked and heated in liquid.
In the method for producing natto of the present disclosure, any raw soybean can be used as long as it can be used for producing ordinary stringy natto.
As raw soybeans, for example, whole soybeans, halved soybeans, crushed soybeans (raw material for ground and split natto), defatted soybeans, etc. can be used. Among these raw soybeans, medium-grained and large-grained soybeans used in producing high-quality stringy natto are particularly suitable.
Although these raw soybeans can be used raw, it is common to use dried soybeans (dried products).

In the method for producing natto of the present disclosure, these raw soybeans are soaked and heated in a liquid using a conventional method, and used as steamed soybeans or boiled soybeans.
That is, in the present disclosure, in order to convert raw soybeans into steamed soybeans or boiled soybeans by a conventional method, submerged heating is performed. Steamed soybeans are preferable in terms of preventing components from flowing away.
Note that before steaming or boiling, it is desirable to soak the raw soybeans in water and swell them before use.

Here, the specific preparation procedure for steamed soybeans includes, for example, soaking the raw soybeans in water at room temperature for about 6 to 24 hours, then draining them, and steaming them with steam at 100 to 135°C for 5 to 30 minutes. A method can be adopted. At this time, for example, a method of steaming under pressure under high pressure conditions of 0.10 to 0.22 MPa can also be adopted. The steaming step may not be carried out all at once, but may be divided into multiple steps by once depressurizing and then pressurizing again. Moreover, water can also be added after each steaming step.
In addition, as a specific procedure for preparing boiled soybeans, for example, raw soybeans may be soaked in water at room temperature for about 6 to 24 hours, and then boiled in hot water at 90 to 100 degrees Celsius for 20 to 50 minutes. can.

1-2. Inoculation The steamed soybeans or boiled soybeans thus obtained are inoculated with Bacillus natto.
That is, in the present disclosure, in producing natto, an inoculation step is performed in which the steamed soybeans or boiled soybeans obtained as described above are inoculated with Bacillus natto.

In the natto production method of the present disclosure, there are no particular restrictions on the state of Bacillus natto added as a Bacillus natto starter, but it is in a spore state that can be directly inoculated into high-temperature soybeans immediately after steaming to prevent bacterial contamination. It is preferable to use

Any Bacillus natto can be used as the Bacillus natto starter. For example, common commercially available bacteria Miyagino Bacterium (product name: Pure Cultured Natto Bacterium (Miyagino Natto Bacterium)) (manufactured by Miyagino Seisakusho Co., Ltd.), Takahashi Bacterium (product name: Natto Soup) (product name: Yuzo Takahashi Research Co., Ltd.) (manufactured by Naruse Hakko Kagaku Kenkyusho), Naruse Bacterium (trade name: powdered natto bacteria) (manufactured by Naruse Hakko Kagaku Kenkyusho), etc.; however, various strains such as mutant strains with specific properties, genetically modified strains, etc. can be used. You can also do it.
In addition, when producing the natto described in the eleventh aspect of the present disclosure, Bacillus subtilis (Bacillus subtilis) MIZ-21800 strain, Bacillus subtilis (Bacillus subtilis) MIZ-21801 strain, etc., which are exemplified in the examples described later. In addition, a strain that can be easily prepared so that the amounts of PGA and levan fall within a predetermined range during fermentation is preferred.

The above-mentioned bacterial strain was obtained from a group of natto strains that had undergone natural mutation by subplanting three or more times in a row, as described in the Examples below, and the viscosity of the colony on a glutamic acid-rich medium and the time when natto was produced. It is possible to obtain this by selecting natto strains that produce stringy natto. In order to efficiently obtain the desired natto strain, the number of subcultures is preferably four or more times. The sub-planting operation can be carried out by repeatedly producing natto using the natto strain remaining in the natto produced using the parent natto strain in accordance with a conventional method, or by growing natto on a solid medium containing powdered soybeans. Although the culturing operation may be repeated, it is preferable to repeat the process of producing natto, which is closer to the actual product.

Bacillus subtilis (Bacillus subtilis) MIZ-21800 strain and MIZ-21801 strain are both natto bacterial strains obtained through in-house breeding and selection from natto bacterial strains that the company owns. Both strains were entrusted to the National Institute of Technology and Evaluation (NPMD) (2-5-8 Kazusa Kamatari, Kisarazu City, Chiba Prefecture, Japan 292-0818) on November 27, 2019. Internationally deposited as numbers NITE BP-03082 (Identification indication: MIZ-21800) and NITE BP-03083 (Identification indication: MIZ-21801).
Here, Bacillus subtilis MIZ-21800 strain uses Bacillus subtilis No. 7 strain (NITE BP-01805) as a parent strain, and Bacillus subtilis MIZ-21801 strain uses Bacillus subtilis K-2 strain (NITE BP-1577) as a parent strain. A strain of natto with particularly weak stringiness of natto produced using the strain obtained by successively subplanting the parent strain four or five times (hereinafter referred to as " This is a stringing-deficient strain obtained by selecting Bacillus natto, which has weak stringing.

Regarding the mycological properties of Bacillus subtilis MIZ-21800 and MIZ-21801, as mentioned above, they are mutant strains obtained by breeding and selecting the natto bacteria strain owned by the company. The cell morphology is rod-shaped, and the colonies are white, round, flat, with complete edges, smooth, opaque, and viscous.

As described above, in the inoculation step of the natto production method of the present disclosure, there are no particular limitations on the natto bacteria used as a starter.
It is also possible to use Bacillus natto that has been bred and improved, and there are no particular restrictions on the original Bacillus natto (parent strain) that is the target of breeding, but the Bacillus natto that is usually used in the natto industry, It is desirable to use Bacillus natto isolated and obtained from nature, as well as Bacillus natto obtained through further improvement.
As described above, Bacillus natto with weak stringiness can be obtained by performing the subplanting operation three or more times in succession, preferably four to five times or more. In this way, by repeating the selection of natural mutant strains produced by subculture of Bacillus natto three or more times, preferably four to five times or more, it is possible to obtain Bacillus natto with improved breeding and weak stringiness. can.
An eleventh aspect of the present disclosure is one of the eighth to tenth aspects, characterized in that natto bacteria with weak stringiness is selected from natto strains that have been subplanted three or more times. The method for producing natto according to any one of the above.
Specific examples of natto bacteria with weak stringiness include Bacillus subtilis MIZ-21800 strain and MIZ-21801 strain as described above.

Bacillus natto is classified as Bacillus subtilis, but it is generally called Bacillus subtilis var. natto or Bacillus subtilis (natto) as a variant of Bacillus subtilis. ) is classified as distinct from Bacillus subtilis, or as Bacillus natto, a closely related species of Bacillus subtilis.

When inoculating steamed soybeans or boiled soybeans with the Bacillus natto starter, in order to ensure uniform fermentation, it is recommended to add the soybeans, etc. and Bacillus natto evenly by inoculation or spraying, and then mix. desirable. Preferably, a spore suspension of Bacillus natto is prepared and added in a liquid state for use.

Here, as the spore suspension, a culture solution obtained by culturing the above-mentioned Bacillus natto in a liquid medium containing components suitable for spore formation can be used.
As for the components of the above-mentioned liquid medium, if it is a liquid medium that enables spore formation and growth of Bacillus natto and contains medium components such as a carbon source, a nitrogen source, and inorganic salts, which are usually used for culturing Bacillus natto, There is no limitation, and it may be a synthetic medium or a natural medium.
Among the medium components, carbon sources include sugars such as glucose, sucrose, galactose, mannose, starch, and starch decomposition products, organic acids such as citric acid, and nitrogen sources include peptone, meat extract, casein hydrolyzate, Examples include ammonia, ammonium sulfate, ammonium chloride, etc. Inorganic salts include sodium chloride, potassium chloride, calcium chloride, sodium sulfate, sodium hydrogen sulfate, sodium nitrate, potassium phosphate, ferric chloride hexahydrate, and sulfuric acid. Examples include magnesium heptahydrate, manganese chloride tetrahydrate, and ferrous sulfate.
Further, the medium may contain yeast extract, malt extract, soybean flour, vitamins (biotin, etc.), and the like. When using a Bacillus natto mutant strain that requires specific nutritional components due to gene defects, etc., the culture medium composition may be changed as appropriate.

The number of Bacillus natto to be inoculated is not particularly limited as long as the concentration is determined according to a conventional method, but it is usually 10 ³ to 10 ⁶ per gram of steamed soybeans or boiled soybeans. The temperature of soybeans during inoculation is not particularly limited, but it is preferable to inoculate at a high temperature of about 55 to 95°C to prevent bacterial contamination during inoculation.

It is preferable to fill the soybeans inoculated with Bacillus natto into individual containers for one to several servings, and then perform the fermentation described below in the individual containers. It is also possible to fill boiled straw bracts as a traditional method.
It is also possible to carry out fermentation in a container with a volume of several liters, but if the value of the volume relative to the surface area becomes large, it will be difficult for temperature changes to be transmitted to the beans in the center, so a larger container is recommended. It is not recommended to use it.

Any container can be used as the individual container as long as it can be filled with soybeans. Specifically, styrene-modified polyolefin resins such as those commonly used in natto, polystyrene resins such as polystyrene, high impact polystyrene, styrene-ethylene copolymers, polyethylene, polypropylene, ethylene-vinyl acetate copolymers, etc. Containers made of foamed sheets made of various synthetic resins such as polyolefin resins and polyester resins such as polyethylene terephthalate, and cup-shaped paper containers can be used.
Further, it is preferable that the shape of the container is such that the food can be stirred (stirred) directly for consumption using the container.
Further, after fermentation, it is preferable to use a container that can be sealed with a lid or a seal.

1-3. Natto Fermentation In the present disclosure, fermentation is performed after performing the inoculation step of inoculating the steamed soybeans or boiled soybeans with Bacillus natto.
- Fermentation conditions In the fermentation of the present disclosure, the temperature of the beans is maintained substantially within the normal fermentation temperature range for a predetermined period of time from the start of fermentation.
Here, the normal fermentation temperature range refers to a temperature range of 37 to 54°C. If the fermentation temperature is lower than a predetermined value, the natto will not have a good flavor, and it will be difficult to keep the specific components within a predetermined range. If the fermentation temperature is higher than a predetermined value, ammonia, lower fatty acids, etc. will be generated in excess, which is not preferable.

Note that "maintaining the temperature of the beans substantially within the normal fermentation temperature range for a predetermined period of time from the start of fermentation" does not mean that the temperature does not completely deviate from the temperature range; (for example, within 3℃, preferably within 2℃), and for a short period of time (for example, within 20 minutes, preferably within 10 minutes), the temperature of the product outside the temperature range This also means that the fermentation conditions are satisfied.

In the fermentation of the present disclosure, the predetermined time (fermentation time) for maintaining the fermentation temperature range can be 8 to 16 hours. The lower limit of the fermentation time is 8 hours or more, preferably 9 hours or more, and more preferably 9.5 hours or more. In the fermentation, if the fermentation time is shorter than a predetermined value, the fermentation will not proceed sufficiently and the specific component will likely fall outside the predetermined range.
The upper limit of the fermentation time is 16 hours or less, preferably 15 hours or less, and more preferably 14 hours or less. If the fermentation time is longer than a predetermined value, the fermentation will proceed too much and the content of lower fatty acids in particular will increase, which is not preferable.

In order to adjust the specific components within a predetermined range, the natto of the present disclosure has a temperature range higher than the normal fermentation temperature range (product temperature is 45°C or higher and 54°C or lower) as shown in the tenth embodiment of the present disclosure. It is preferable to ferment at a high temperature by maintaining the temperature for 7 to 15 hours because it makes it easier to keep the specific components within the specified range.
A tenth embodiment of the present disclosure is characterized in that steamed soybeans or boiled soybeans are inoculated with Bacillus natto, and the product temperature is maintained at 45°C or more and 54°C or less for 7 hours or more and 15 hours or less for high-temperature fermentation. It is.
Here, the lower limit of the fermentation temperature in the case of high temperature fermentation can be 37°C or higher, preferably 43°C or higher, more preferably 45°C or higher, preferably 46°C or higher, and more preferably 47°C or higher. The upper limit of the fermentation temperature in the case of high temperature fermentation can be 54°C or lower, preferably 53.75°C or lower, more preferably 53.5°C or lower. Therefore, the fermentation temperature in high-temperature fermentation is 45°C or higher and 54°C or lower, preferably 46°C or higher and 53.75°C or lower, and more preferably 47°C or higher and 53.5°C or lower.
The lower limit of the high temperature fermentation time is preferably 7 hours or more, preferably 8 hours or more, more preferably 8.5 hours or more. The upper limit of the high temperature fermentation time is preferably maintained at 15 hours or less, preferably 14 hours or less, more preferably 13 hours or less. Therefore, the fermentation time in high temperature fermentation is 7 hours or more and 15 hours or less, preferably 8 hours or more and 14 hours or less, more preferably 8.5 hours or more and 13 hours or less.

In the present disclosure, a heating step may be performed after fermentation if necessary. What is the heating process? After the fermentation process and before the ripening process, for a predetermined period of time (more than 0 hours and less than 3 hours), the temperature of the beans is raised to a heating temperature range (55℃) that is substantially higher than the normal fermentation temperature range. -80℃).
The lower limit of the heating temperature in the heating step is 55°C or higher, preferably 56°C or higher, more preferably 56.5°C or higher, even more preferably 57°C or higher. On the other hand, the upper limit of the heating temperature can be 80°C or lower, preferably 72°C or lower, more preferably 65°C or lower, even more preferably 62°C or lower. Therefore, the heating temperature in the heating step is 55°C or more and 80°C or less, preferably 56°C or more and 72°C or less, more preferably 56.5°C or more and 65°C or less, and still more preferably 57°C or more and 62°C or less.
Further, the lower limit of the heating time in the heating step is more than 0 hours, preferably 0.25 hours or more, more preferably 0.5 hours or more, and still more preferably 0.75 hours or more. On the other hand, the upper limit of the heating time can be 3 hours or less, preferably 2.5 hours or less, more preferably 2 hours or less, and even more preferably 1.5 hours or less.
Therefore, the heating time in the heating step is more than 0 hours and less than 3 hours, preferably more than 0.25 hours and less than 2.5 hours, more preferably more than 0.5 hours and less than 2 hours, even more preferably more than 0.75 hours and less than 1.5 hours.
The heating time refers to the period during which the fermented natto is heated, from when the temperature of the beans reaches a predetermined temperature range to when it falls outside the predetermined temperature range.

In the method for producing natto according to the present disclosure, characteristic specific components are produced in the fermentation step under conditions where secondary fermentation is sufficiently suppressed during the aging step described below or during the storage and distribution of natto products. Therefore, the content of a specific component contained in natto can be monitored as appropriate during the fermentation process using the measuring method described below, and the fermentation process can be stopped when a predetermined content is reached. In addition, if the amount of the specific component is insufficient until the end of fermentation, the specific component that is insufficient may be added to the amount within a predetermined range.

In order to accurately adjust the temperature conditions in this fermentation process, it is preferable to use a fermentation chamber or the like having temperature raising and cooling functions.

1-4. Aging After the fermentation process is completed, in order to suppress quality deterioration such as stringy deterioration and ammonia production due to secondary fermentation, the temperature is usually 3°C or higher and lower than 10°C, preferably 3°C or higher and lower than 8°C, more preferably 3°C. The fermentation is carried out at a low temperature below 6°C for 6 hours to 3 days, preferably 8 hours to 2 days, more preferably about 24 hours, and the production of natto is completed.

2. Measurement 2-1. Measurement of 2,5-dimethylpyrazine, 2,3,5-trimethylpyrazine, and 4-vinylguaiacol
2,5-dimethylpyrazine, 2,3,5-trimethylpyrazine, and 4-vinylguaiacol are measured by direct headspace injection into GC-MS. Examples of equipment used include Gestel's one-dimensional and two-dimensional switching GC-MS (GC section: HP7890 Series GC System connected to LTM series II (both manufactured by Agilent), injection port: TDU2/CIS4 (Gestel), Auto sampler: MPS (Gestel).

2-2. Measurement of isovaleric acid and isobutyric acid There are no particular limitations on the measurement of isovaleric acid and isobutyric acid, but for example, high performance liquid chromatography (separation is performed with a cation exchange resin column and detection is performed with an electrical conductivity detector) can be used. Can be used. An example of the device used is LC-10ADVP (manufactured by Shimadzu Corporation).

2-3. Pretreatment for PGA analysis and levan analysis in natto For samples to be subjected to PGA analysis and levan analysis in natto, natto obtained by performing protein removal treatment as described below and purification treatment using ethanol. An extract of the thickening substance is used as the sample.

1. 50 mL of 2.5% trichloroacetic acid (hereinafter also referred to as TCA) is added to 10 g of natto, and the mixture is heated to 50° C. for 10 minutes and stirred.
2. After removing the beans from the above mixture, perform centrifugation (12000 rpm, 10 min) to obtain a supernatant.
3. The obtained supernatant was adjusted to pH 7.0 with sodium hydroxide, diluted twice with ion-exchanged water, and then an equal amount of ethanol pre-cooled to -30°C as the neutralized liquid was added and stirred.
4. After standing on ice for 10 minutes, centrifugation (12000 rpm, 10 min) is performed, and the supernatant is discarded and dried.
5. The precipitate obtained by drying is used as a thickening substance, and the one dissolved in 20mM phosphate buffer (pH 7.0) is used as a mucilage extract.

2-4. Measurement of PGA To measure PGA in natto, perform quantitative analysis by measuring the absorbance of the solution treated with the following method for the mucilage extract that has been pretreated as described above, and comparing the absorbance with that of a standard substance. For example, an ultraviolet-visible spectrophotometer UV-1800 (manufactured by Shimadzu Corporation) can be used to measure the absorbance.

1. To create a standard calibration curve, a diluted solution of "poly-γ-glutamic acid" (average molecular weight 1,500,000 to 2,500,000) (Fujifilm Wako Pure Chemical Industries, Ltd.) in 20mM phosphate buffer (pH 7.0) 0, 25 as a PGA standard solution. , 50, 100 μg/mL standard solutions are prepared.
2. The mucilage extract obtained by the above method is diluted with 20 mM phosphate buffer (pH 7.0) so that the concentration falls within the concentration range of the calibration curve.
3. Add 2.0 mL of 20 mM phosphate buffer (pH 7.0) to 0.5 mL of the PGA standard solution and analysis sample, add 0.5 mL of 0.1 M cetylmethyltrimethylammonium bromide (cetabron)/1 M NaCl solution, and stir.
4. After standing for 20 minutes at room temperature, Abs (absorbance) at a wavelength of 400 nm is measured, and the PGA concentration of the sample is calculated using a calibration curve prepared from the standard solution.

2-5. Measurement of levan Levan in natto is measured by measuring the absorbance of the pretreated mucilage extract as described above, using the method below, and comparing the absorbance with a standard substance using fructose as an indicator. Perform quantitative analysis. For example, an ultraviolet-visible spectrophotometer UV-1800 (manufactured by Shimadzu Corporation) can be used to measure the absorbance.

1. To create a standard calibration curve, prepare fructose standard solutions of 0, 10, 25, 50, and 100 μg/mL diluted in 20 mM phosphate buffer (pH 7.0).
2. The thickening substance extract obtained above is diluted with 20 mM phosphate buffer (pH 7.0) according to the concentration so that it falls within the range of the above calibration curve.
3. Gently mix 0.6 mL of fructose standard solution and analytical sample with 0.3 mL of resorcinol-thiourea reagent in a test tube and 2.1 mL of 30% HCl.
Cover the mixed solution with a marble or the like to prevent bumping, and incubate at 80°C for 10 minutes.
4. Abs (absorbance) at a wavelength of 500 nm was measured, and the concentration of levan was calculated using a calibration curve prepared from standard solutions. Note that the levan concentration is calculated by subtracting the water in the binding part and multiplying the fructose calibration curve by 0.9.

2-6. Measurement of turbidity of natto extract The turbidity of natto extract is determined by stirring 40 g of natto in 80 mL of water, then removing the bean part, and measuring the absorbance at a wavelength of 660 nm using a spectrophotometer. It can be calculated by There are no particular restrictions on the method of separating the liquid part and the bean part, as long as the bean part is not crushed by pressure during separation or otherwise affects the measurement, but for example, separation with a metal colander or separation with a coarse synthetic resin filter is possible. For example, Although there is no restriction on the measuring device, for example, UV-1800 (manufactured by Shimadzu Corporation) can be mentioned.

2-7. Measurement of the color of natto extract The color of natto extract in the L ^* a ^* b ^* color space is determined by stirring 40 g of natto in 40 mL of water, then removing the bean part. It can be calculated by measuring the L ^* a ^* b ^* value of There are no particular restrictions on the method of separating the liquid part and the bean part, as long as the bean part is not crushed by pressure during separation or otherwise affects the measurement, but for example, separation with a metal colander or separation with a coarse synthetic resin filter is possible. For example, There are no restrictions on the measuring device, but an example is SD-3000 (Nippon Denshoku Industries Co., Ltd.).

2-8. Measurement of viscosity of natto extract The viscosity of natto extract was determined by stirring 40 g of natto in 40 mL of water and then removing the bean portion using a B-type viscometer (60 rpm, 25°C, rotor No. 2) Measure. There are no particular restrictions on the method of separating the liquid part and the bean part, as long as the bean part is not crushed by pressure during separation or otherwise affects the measurement, but for example, separation with a metal colander or separation with a coarse synthetic resin filter is possible. For example, Although there is no restriction on the measuring device, for example, a BII type viscometer (manufactured by Toki Sangyo Co., Ltd.) can be mentioned.

2-9. Measuring the stringiness of natto The stringiness of natto is measured by pressing two natto beans closely together and then lifting only one bean upward at a speed of 100 mm/min. It is measured by measuring the distance until the threads, mainly made of polyglutamic acid, formed between the grains of beans break. For measurements, devices that can pull up the specimen at a constant speed can be used; examples include a digital force gauge (model number FGP-0.5 (manufactured by Nidec-Shimpo Corporation)) and a force gauge stand (model number FGS-50E). (manufactured by Nidec-Shimpo Corporation)) can be used.

The present disclosure will be described below with reference to Examples, but the scope of the present disclosure is not limited thereto.

Examples a1 to a12, aa1 to aa4, and comparative examples b1 to b5 were prepared by the following method.

I. Preparation of steamed soybeans Except for comparative example b4 (commercially available natto 1: Mamenoka (manufactured by Kanasago Foods)) and comparative example b5 (commercially available natto 2: extra small grain mini 3 (manufactured by Takano Foods)), commercially available products were used as they were. Steamed soybeans used in Examples and Comparative Examples were prepared in the following manner. However, in Comparative Example b1, steamed soybeans that were stored in a refrigerator after steaming were used as they were. In other Examples and Comparative Examples, natto was produced by inoculating natto bacteria into steamed soybeans immediately after steaming using the method described below.

First, the raw material, dried whole soybeans, was lightly washed with water and soaked in water at room temperature (approximately 25°C) overnight to allow the soybeans to fully absorb water, and then drained using a metal colander.
Subsequently, the soaked soybeans were subjected to a steaming process. Specifically, soaked soybeans were placed in a metal container, placed in a steamer (test steamer made by Harada Sangyo), heated to 98℃, maintained at 0.08MPa for 10 minutes, and then increased to 0.20MPa for 6 minutes. The pressure was increased to reach 0.20 MPa, maintained at 0.20 MPa for 30 seconds, and then depressurized to 0.14 MPa over 14 minutes, followed by steaming under the conditions of depressurizing to atmospheric pressure.

The quality evaluation of Comparative Example b1 (steamed soybeans) was conducted using a sample that was refrigerated at 4° C. for 3 days immediately after production using the above method.

II. Fermentation of Natto After completing the steaming process as described above, each steamed soybean was fermented using the following procedure. Examples of Bacillus natto include Bacillus subtilis No. 7 strain (NITE BP-01805), Bacillus subtilis K-2 strain (NITE BP-1577), pure culture Bacillus natto (Miyagino Bacillus) (manufactured by Miyagino Natto Manufacturing Co., Ltd.), and the above-mentioned No. Bacillus subtilis MIZ-21800 strain (NITE BP-03082), a stringing defective strain whose parent strain is the .7 strain, Bacillus subtilis MIZ-21801 strain, a stringing defective strain whose parent strain is the K-2 strain (NITE BP -03083) was used.
These Bacillus natto strains were inoculated into 10 ml/test tube of the spore-forming medium (YE) shown in Table 1 below, and cultured with shaking at 37° C. and 150 rpm for 24 hours to prepare a spore suspension.

III. Breeding and selection of MIZ-21800 strain and MIZ-21801 strain Breeding and selection of MIZ-21800 strain and MIZ-21801 strain used for this natto production was carried out in the following manner.

Bacillus subtilis MIZ-21800 strain was obtained from Bacillus subtilis No. 7 strain as a parent strain, and Bacillus subtilis MIZ-21801 strain was obtained from Bacillus subtilis K-2 strain as a parent strain through breeding and selection using the method described below.
In addition, in Table 4 below (referring to Tables 4-1 and 4-2; the same applies hereinafter), Bacillus subtilis MIZ-21800 strain is referred to as "String-defective strain (MIZ-21800 strain)" and Bacillus subtilis MIZ-21800 strain. subtilis MIZ-21801 strain is referred to as "thread-pulling defective strain (MIZ-21801 strain)".

1. Put 40 g of steamed soybeans that were steamed according to the above method into a conical flask, cover with Silicocene (manufactured by Shin-Etsu Polymer) to ensure air permeability, and then autoclave (121°C, 20 min) to sterilize the flask. Ta. Thereafter, the spore suspensions of Bacillus subtilis strain No. 7 (NITE BP-01805) and Bacillus subtilis strain K-2 (NITE BP-1577) prepared by the method described above were added to approximately 5,000 natto particles per 1 g of steamed soybeans. After diluting it with water to make it a fungus, it was inoculated into steamed soybeans.
2. Each inoculated specimen was kept at 40°C in an incubator for 20 hours to ferment natto, and then cooled to 4°C.
3. Add 40 ml of sterilized water to the cooled natto, use the well-mixed Bacillus natto suspension as a starter, dilute it with water so that there are approximately 5000 Bacillus natto per 1 g of steamed soybeans, and then add 40 ml of sterilized water to the natto. was inoculated, and natto was produced using the same method as described above.
4. For Bacillus subtilis No. 7 strain, operations 1 to 3 were performed 4 times in a row, and for Bacillus subtilis K-2, an equal amount of 30% glycerol was added to the Bacillus natto suspension obtained by performing 5 times in a row. The mixture was dispensed into 1 ml portions to make a glycerol stock and stored frozen at -80°C.
5. One bottle of frozen stored glycerol stock was thawed at room temperature and diluted 10,000 times and 100,000 times with 0.01M phosphate buffered saline (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.). It was spread on a cold + bcfa agar medium plate and cultured at 37°C overnight.
6. In order to estimate the glutamic acid production ability of Bacillus natto picked from a colony on a standard cold + bcfa agar medium plate, a GSP agar medium plate prepared with the composition shown in Table 3 was replica inoculated and cultured overnight at 37°C.
7. On the GSP agar plate, 40 strains derived from Bacillus subtilis No. 7 strain and 18 strains derived from Bacillus subtilis K-2 strain were observed, mainly colonies that were flat due to weak polyglutamic acid production and low viscosity. Regarding the strain, a Bacillus natto starter was created using the method described above.
8. Steamed soybeans that have been steamed according to the above method are inoculated with the natto bacteria starter of the above-mentioned breeding strain at a rate of about 5,000 natto bacteria per 1g of steamed soybeans, placed in a polystyrene natto container, covered with a lid, and placed in a natto container. Fermentation was performed in a fermentation chamber (test fermentation chamber manufactured by Harada Sangyo). The temperature of the chamber during fermentation was 39°C, and after 18 hours it was cooled to 4°C.
9. Regarding the prototype natto, one strain of each strain had particularly weak stringiness, no off-odor, and weak natto bitterness, and the parent strain Bacillus subtilis strain No. 7 (NITE BP-01805) was Bacillus subtilis MIZ-21800. The strain using Bacillus subtilis K-2 strain (NITE BP-1577) as the parent strain was selected as Bacillus subtilis MIZ-21801 strain. For the selected bacterial strains, an equal amount of 30% glycerol was added to the prepared starter and mixed, and the mixture was stored at -80°C as a glycerol stock.
In addition, two strains that met the above conditions were created using the prototype Bacillus subtilis No. 7 strain (NITE BP-01805) as the parent strain, and two strains were created using the Bacillus subtilis K-2 strain (NITE BP-1577) as the parent strain. There were 7 stocks.

The natto bacteria strain used in the Examples and Comparative Examples was prepared by using the above natto bacteria strain, culturing the spore suspension in a liquid medium, diluting it with water to give about 5,000 natto bacteria per 1 g of steamed soybeans, and then steaming it. Inoculated soybeans.
Thereafter, 45 g of each was placed in a polystyrene natto container, covered with a lid, and fermented in a natto fermentation chamber (test fermentation chamber manufactured by Harada Sangyo).
Among the Examples and Comparative Examples, for the samples described as "high temperature fermentation" in the fermentation method column of Table 4, the room temperature was changed to the right for 11 hours from the start of fermentation (51℃ for 7 hours, followed by 50℃ for 4 hours). ) was controlled. As a result, the temperature of natto was maintained within the normal fermentation temperature range of 37°C to 54°C for 11 hours, during which time it was maintained at 45°C to 54°C, which is on the higher end of the normal fermentation temperature range. The time taken was 10.9 hours.
Among the Examples and Comparative Examples, for the samples described as "normal fermentation" in the fermentation method column of Table 4, the room temperature was controlled as shown on the right (39° C. for 18 hours) for 18 hours from the start of fermentation. As a result, the temperature of natto was maintained within the normal fermentation temperature range of 37°C to 54°C for 17.5 hours, during which time it was maintained at 45°C to 54°C, which is on the higher end of the normal fermentation temperature range. The time taken was 0 hours.
Among the samples, for the samples that underwent the heating process, the temperature of the room was controlled at the temperature shown on the right (60°C for 1.5 hours) immediately after the completion of fermentation. As a result, the time that the temperature of natto was maintained within the heating temperature range of 55°C to 80°C was 1.2 hours. Specimens that were subjected to the heating process were indicated as "Yes" in the heating column of Table 4.
FIG. 1 shows representative examples of changes in fermented product temperature for each fermentation method and heating method.

After the fermentation process, the natto was aged by cooling it in a refrigerator at 4°C. Quality evaluation was performed on each sample after ripening.

IV. Preparation after producing natto For Examples a7 to a12 and aa1 to aa4, the specific ingredients 2,5-dimethylpyrazine, 2,3,5-trimethylpyrazine, Isovaleric acid, isobutyric acid, and 4-vinylguaiacol were added to the concentrations listed in the amounts of reagents added in Table 4 (more precisely, Table 4-1). In Table 4 (more precisely, Table 4-1), products to which reagents with specific components have been added are indicated along with the example number of Bacillus natto used (for example, Table 4 -1, it was written as "Example a1 + reagent additive product", etc.). Each specific component was diluted to a high concentration with ultrapure water and then added. The following standard substances were used for specific components.

2,5-dimethylpyrazine (CAS No.123-32-0) (manufactured by Tokyo Chemical Industry Co., Ltd.)
2,3,5-trimethylpyrazine (CAS No. 14667-55-1) (manufactured by Tokyo Chemical Industry Co., Ltd.)
Isovaleric acid (CAS No.503-74-2) (manufactured by Fujifilm Wako Pure Chemical Industries)
Isobutyric acid (CAS NO.79-31-2) (manufactured by Fujifilm Wako Pure Chemical Industries)
4-Vinylguaiacol (CAS No. 7786-61-0) (manufactured by Takasago International Corporation)

V. Measurement/Evaluation V-1. Measurement of 2,5-dimethylpyrazine, 2,3,5-trimethylpyrazine, 4-vinylguaiacol
2,5-dimethylpyrazine, 2,3,5-trimethylpyrazine, and 4-vinylguaiacol were measured by direct headspace injection into GC-MS. The measurement equipment is Gestel's 1-dimensional 2-dimensional switching GC-MS (GC section: HP7890 Series GC System connected to LTM series II (both made by Agilent), inlet: TDU2/CIS4 (Gestel), autosampler: MPS (Gestel)) was used.

Injection of the sample into the instrument was performed using the direct headspace method.
Specifically, 0.5 g of the natto sample was weighed into a 10 mL flat-bottom vial, the vial was sealed, and the sample was volatilized with a 60 mL nitrogen gas purge. The sample was adsorbed with an adsorption resin (Tenax column) according to the nature of the analyzed component. The injection process was performed using a thermal desorption system.

V-2. GC-MS conditions (dynamic headspace (DHS) injection method)
・Equipment: Agilent 7890B (GC), 5977B (MS), Gester MultiPurpose Sampler (auto-sampler)
・Adsorption resin: TENAX
・Incubation temperature: 80℃
・Nitrogen gas purge amount: 60ml
・Nitrogen gas purge flow rate: 10mL/min

As a capillary column, DB-WAX (length 30 m, inner diameter 250 μm, film thickness 0.25 μm, for LTM) (Agilent) was used as a one-dimensional column. Helium was used as a carrier gas.

Measurement of 2,5-dimethylpyrazine, 2,3,5-trimethylpyrazine, and 4-vinylguaiacol was performed by the following method.
The sample injection conditions were as follows.
・CIS4:
Hold at 10°C for 0.5 min, then increase the temperature to 240°C at 720°C/min.
・TDU2:
Hold at 30°C for 0.2 minutes, then increase the temperature to 240°C at 240°C/min.

To measure 2,5-dimethylpyrazine, 2,3,5-trimethylpyrazine, and 4-vinylguaiacol, perform injection under the above injection conditions, perform separation using a one-dimensional column, and switch to selected ion detection (SIM) mode. provided. Note that the column oven conditions for DB-WAX (one-dimensional column) were as follows.
・DB-WAX (one-dimensional column):
Hold at 40°C for 3 minutes, then increase temperature to 240°C at 5°C/min and hold for 7 minutes.

For each measurement sample, select ion detection (SIM) mode is used to determine the absolute concentration of the measurement sample from the area of the quantification ion when 2 ml of a solution prepared by diluting standard substances with the components listed in Table 5 below with water is measured in the same manner as the sample. Calculated using the calibration curve method.

V-3. Measurement of isovaleric acid and isobutyric acid V-3-1. Isovaleric acid and isobutyric acid were measured using the following method.
Pretreatment of the specimen was performed using the following method.
50% ethanol was added little by little to 10 g of the natto sample and mixed with a glass rod to dilute the natto paste. When the liquid became thick, it was transferred to a 100 ml volumetric flask. This process was repeated until no sample remained on the tray or glass rod.
Once all the samples were in a volumetric flask, the volume was filled up to 100 ml with 50% ethanol. Furthermore, after performing filter paper filtration, the sample was filtered through a 0.45 μm filter and used as a measurement sample.

The measurement sample was injected into high performance liquid chromatography (HPLC) for measurement.
The HPLC measurement conditions were as follows. A measuring device (manufactured by Shimadzu Corporation, model LC-10ADVP) was used. The measurement time was 50 minutes, and the concentrations of isovaleric acid and isobutyric acid were calculated by comparing the peak areas with standard solutions of isovaleric acid and isobutyric acid (both manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (approximately 10 mg/100 ml). did.

V-3-2. Measurement conditions/Measurement method Ion exclusion mode/Detection method Electric conductivity detection method/Mobile phase p-Toluenesulfonic acid monohydrate 0.761g
Fill up to 1L with ultrapure water.

・Reaction phase p-toluenesulfonic acid monohydrate 0.761g
EDTA 0.029g
Bis-Tris 3.348g
Fill up to 1L with ultrapure water

・Pump flow rate Mobile phase: 0.9ml/min, reaction phase: 0.9ml/min
・Oven temperature 52℃
・Detector cell temperature 55℃
・Injection volume 50μL
・Column Shodex RS pak KC-811 x 2 (manufactured by Showa Denko)
・Guard column Shodex RS pak KC-G (manufactured by Showa Denko)
・Guard filter SUMIPAX Filter (manufactured by Sumika Analysis Center)

V-4. Pretreatment for PGA analysis and levan analysis in natto For samples to be subjected to PGA analysis and levan analysis in natto, natto obtained by performing the protein removal treatment described below and then purification treatment using ethanol. An extract of a thickening substance was used.

1. 50 mL of 2.5% trichloroacetic acid was added to 10 g of natto, and the mixture was heated to 50° C. for 10 minutes and stirred.
2. After removing the bean portion from the above mixture, centrifugation (12000 rpm, 10 min) was performed to obtain a supernatant.
3. The obtained supernatant was adjusted to pH 7.0 with sodium hydroxide, diluted twice with ion-exchanged water, and then an equal amount of ethanol pre-cooled to -30°C as the neutralized liquid was added and stirred.
4. After standing on ice for 10 minutes, centrifugation (12000 rpm, 10 min) was performed, and the supernatant was discarded and dried.
5. The precipitate obtained by drying was used as a thickening substance, which was dissolved in 20mM phosphate buffer (pH 7.0) and used as a mucilage extract.

V-5. Measurement of PGA The PGA in natto was measured by measuring the absorbance of the pretreated mucilage extract as described above, using the method below, and comparing the absorbance with a standard substance for quantitative analysis. . A UV-visible spectrophotometer UV-1800 (manufactured by Shimadzu Corporation) was used to measure the absorbance.

1. To create a standard calibration curve, a 20mM water diluted solution of "poly-γ-glutamic acid" (average molecular weight 1,500,000 to 2,500,000) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) at 0, 25, 50, and 100 μg/mL was used as a PGA standard solution. A diluted standard solution of phosphate buffer (pH 7.0) was prepared.
2. The mucilage extract obtained by the above method was diluted with 20 mM phosphate buffer (pH 7.0) so as to fall within the concentration range of the calibration curve.
3. 2.0 mL of 20 mM phosphate buffer (pH 7.0) was added to 0.5 mL of the PGA standard solution and the analysis sample, and 0.5 mL of 0.1 M cetylmethyltrimethylammonium bromide (cetabron)/1 M NaCl solution was added and stirred.
4. After standing for 20 minutes at room temperature, Abs (absorbance) at a wavelength of 400 nm was measured, and the PGA concentration of the sample was calculated using a calibration curve prepared from the standard solution.

V-6. Measurement of levan Levan in natto is measured by measuring the absorbance of the pretreated mucilage extract as described above, using the method below, and comparing the absorbance with a standard substance using fructose as an indicator. Quantitative analysis was performed. A UV-visible spectrophotometer UV-1800 (manufactured by Shimadzu Corporation) was used to measure the absorbance.

1. To create a standard calibration curve, diluted standard solutions of 0, 10, 25, 50, and 100 μg/mL in 20 mM phosphate buffer (pH 7.0) were prepared as fructose standard solutions.
2. The thickening substance extract obtained above was diluted with 20 mM phosphate buffer (pH 7.0) according to the concentration so as to fall within the range of the above calibration curve.
3. Gently mix 0.6 mL of fructose standard solution and analytical sample with 0.3 mL of resorcinol-thiourea reagent in a test tube and 2.1 mL of 30% HCl.
The mixed solution was covered with a marble to prevent bumping, and incubated at 80° C. for 10 minutes.
4. Abs (absorbance) at a wavelength of 500 nm was measured, and the concentration of levan was calculated using a calibration curve prepared from standard solutions. The levan concentration was calculated by subtracting the water in the binding part and multiplying the fructose calibration curve by 0.9.

V-7. Measurement of turbidity of natto extract The turbidity of natto extract is determined by stirring 40 g of natto as a sample in 80 mL of water, then removing the bean portion, and measuring the absorbance at a wavelength of 660 nm using a spectrophotometer. It was calculated by measuring. A polyester filter (Kitchen Drainer Stocking C WF-1740 (Cecile)) was used to separate the beans and liquid part. The measurement was carried out using a UV-1800 (manufactured by Shimadzu Corporation) as a spectrophotometer, and was carried out in a 10 mm square plastic cell.

V-8. Measurement of color of natto extract The color of natto extract in L ^* a ^* b ^* color space is SD- 3000 (Nippon Denshoku Kogyo Co., Ltd.) was used for measurement. A polyester filter (Kitchen Drainer Stocking C WF-1740 (Cecile)) was used to separate the beans and liquid part. The colorimetry was calculated by measuring the L ^* value, a ^* value, and b ^* value using a transmission method.

V-9. Measuring the viscosity of natto extract The viscosity of natto extract is determined by stirring 40 g of natto in 40 mL of water, then removing the bean portion and measuring the extract using a B-type viscometer, more specifically, BII-type viscosity. It was measured using a meter (manufactured by Toki Sangyo Co., Ltd.).
A polyester filter (Kitchen Drainer Stocking C WF-1740 (Cecile)) was used to separate the beans and liquid part. The liquid portion after separation was transferred to a 50 ml plastic container (φ30 x 115 mm) (HARMONY centrifuge tube CFT5000 (LMS)) and the viscosity was measured. The conditions for viscosity measurement were 60 rpm and 25°C, and the measurement was performed using rotor No. 2.

V-10. Measuring the stringiness of natto The stringiness of natto is measured by pressing two natto beans closely together and then lifting only one bean upward at a speed of 100 mm/min. It was measured by measuring the distance until the threads mainly composed of polyglutamic acid formed between the beans break. For measurement, a digital force gauge (model number FGP-0.5 (manufactured by Nidec-Shimpo Corporation)) and force gauge stand (model number FGS-
50E (manufactured by Nidec-Shimpo Corporation) was used.
Note that the stringability of natto was measured only for Examples a1 to a3 and Comparative Examples b2 and b5. The results were recorded in 0.5 mm increments and expressed as the average value of the results measured and recorded a total of 5 times.
The above results are shown in Table 4 (Table 4-1 and Table 4-2).
As is clear from the results in Table 4 (particularly Table 4-2), the stringability measurement results for natto were 200 mm or more in Comparative Examples b2 and b5, while in Examples a1 to a3. , 2.4 mm, 1.3 mm, and 1.7 mm, respectively, indicating extremely low stringability.

V-11. Sensory evaluation Sensory evaluation was performed using the following method.
Evaluation of each sample was performed under the following conditions. Each evaluation was conducted by four sensory testers who had undergone the following training, and the average score was rounded off to the first decimal place and is listed in Table 4 (particularly Table 4-2).

The sensory inspector conducted the following discrimination tests A) and B) and selected those with particularly excellent results.
A) For the five tastes (sweet taste: sugar taste, sour taste: tartaric acid taste, umami taste: monosodium glutamate taste, salty taste: taste of sodium chloride, bitter taste: taste of caffeine), each aqueous solution with a concentration close to the threshold value of each component was prepared. A taste discrimination test that accurately identifies each flavor sample from a total of 7 samples prepared one by one and two samples of distilled water added.
B) Concentration difference discrimination test that accurately identifies the concentration differences between five types of saline solutions and acetic acid aqueous solutions with slightly different concentrations.

The sensory test item was the following "aftertaste of natto" and was evaluated on the following five scales.
The evaluation was conducted on natto alone, assuming the aftertaste that natto would have when combined with other foods. In particular, the evaluation focused on the balance between the persistence of good flavor and the persistence of unpleasant flavor in the aftertaste of natto.

・Natto aftertaste:
5 The flavor with a good aftertaste is very strong and very desirable.
4 The aftertaste has a strong good flavor, which is preferable.
3 There is some unpleasant flavor in the aftertaste, but the good flavor is superior.
2 The unpleasant aftertaste outweighs the good flavor, making it undesirable.
1 The unpleasant aftertaste is felt very strongly and is very undesirable.

The results of the sensory test are shown in Table 4 below (particularly Tables 4-5).
As is clear from the results in Table 4 (particularly Tables 4-5), the Examples generally achieved 3 points or more, meeting the standard value, but the Comparative Examples generally achieved 2 points or less, meeting the standard value. I didn't meet it.
Although not listed in Table 4-5, the samples of Examples had improved aftertaste when combined with other food materials such as liquid seasonings, cereals, and noodles.

Cross-reference of related applications

This application claims priority based on Japanese Patent Application No. 2020-14279 filed with the Japan Patent Office on January 31, 2020, the entire disclosure of which is fully incorporated herein by reference.

Claims (15)

Natto that meets the requirements (a) to (e) below.
(a) The content of 2,5-dimethylpyrazine (x) is 0.05 mg or more and 5 mg or less per 1 kg of natto wet weight,
(b) The content of 2,3,5-trimethylpyrazine (y) shall be 0.05 mg or more and 3 mg or less per 1 kg of natto wet weight.
(c) The content (α) of isovaleric acid is 1 mg or more and 15 mg or less per 100 g of natto wet weight,
(d) The content (β) of isobutyric acid is 5 mg or more and 40 mg or less per 100 g of wet natto weight,
(e) The above α and β satisfy the following relational expression 1.
2≧α/β≧0.025 (Formula 1) Natto that meets the requirements of (a) to (b) and (f) to (g) below.
(a) The content of 2,5-dimethylpyrazine (x) is 0.05 mg or more and 5 mg or less per 1 kg of natto wet weight,
(b) The content of 2,3,5-trimethylpyrazine (y) shall be 0.05 mg or more and 3 mg or less per 1 kg of natto wet weight.
(f) The content (z) of 4-vinylguaiacol is 0.1 mg or more and 5 mg or less per 1 kg of natto wet weight,
(g) The above x, y, and z satisfy the following relational expression 2.
50≧ z /(x+y)≧0.02 (Formula 2) Natto that meets the requirements of (a) to (b) and (h) below.
(a) The content of 2,5-dimethylpyrazine (x) is 0.05 mg or more and 5 mg or less per 1 kg of natto wet weight,
(b) The content of 2,3,5-trimethylpyrazine (y) shall be 0.05 mg or more and 3 mg or less per 1 kg of natto wet weight.
(h) The levan content (δ) shall be 1.5 mg or more and 20 mg or less per 1 g of wet natto weight. The natto according to claim 3 , which further satisfies the following requirements (i) to (j).
(i) The content (ε) of the PGA is 0.01 mg or more and 1.0 mg or less per 1 g of natto wet weight,
(j) δ and ε satisfy the following relational expression 3.
200≧δ/ε≧2 (Formula 3) Natto that meets the requirements of (a) to (b) and (k) to (l) below.
(a) The content of 2,5-dimethylpyrazine (x) is 0.05 mg or more and 5 mg or less per 1 kg of natto wet weight,
(b) The content of 2,3,5-trimethylpyrazine (y) shall be 0.05 mg or more and 3 mg or less per 1 kg of natto wet weight.
(k) The turbidity of the extract obtained by stirring 40 g of natto in 80 mL of water and removing the bean part and measuring the extract at a wavelength of 660 nm with a spectrophotometer is 0.5 or more and 4.5 or less,
(l) After stirring 40g of natto in 40mL of water, the color of the extract obtained by removing the beans is measured using the transmission method. ^* a ^* b ^* Must be within the following range in color space.
80≧L ^* ≧40
5≧a ^* ≧-5
30≧b ^* ≧10 Natto that meets the requirements of (a) to (b) and (m) below.
(a) The content of 2,5-dimethylpyrazine (x) is 0.05 mg or more and 5 mg or less per 1 kg of natto wet weight,
(b) The content of 2,3,5-trimethylpyrazine (y) shall be 0.05 mg or more and 3 mg or less per 1 kg of natto wet weight.
(m) After stirring 40 g of natto in 40 mL of water, the viscosity of the extract obtained by removing the bean part is 5 mPa・s or more and 180 mPa・Must be less than or equal to s. The natto according to any one of claims 2 to 6, which further satisfies the following requirements (c) to (e).
(c) The content (α) of isovaleric acid is 1 mg or more and 15 mg or less per 100 g of natto wet weight,
(d) The content (β) of isobutyric acid is 5 mg or more and 40 mg or less per 100 g of wet natto weight,
(e) The above α and β satisfy the following relational expression 1.
2≧α/β≧0.025 (Formula 1) The natto according to any one of claims 1 and 3 to 6, which further satisfies the following requirements (f) to (g).
(f) The content (z) of 4-vinylguaiacol is 0.1 mg or more and 5 mg or less per 1 kg of natto wet weight,
(g) The above x, y, and z satisfy the following relational expression 2.
50≧ z /(x+y)≧0.02 (Formula 2) The natto according to any one of claims 1 to 2 and 4 to 6, which further satisfies the following requirement (h).
(h) The levan content (δ) shall be 1.5 mg or more and 20 mg or less per 1 g of wet natto weight. The natto according to claim 9 , which further satisfies the following requirements (i) to (j).
(i) The content (ε) of the PGA is 0.01 mg or more and 1.0 mg or less per 1 g of natto wet weight,
(j) δ and ε satisfy the following relational expression 3.
200≧δ/ε≧2 (Formula 3) The natto according to any one of claims 1 to 4 and 6, which further satisfies the following requirements (k) to (l).
(k) The turbidity of the extract obtained by stirring 40 g of natto in 80 mL of water and removing the bean part and measuring the extract at a wavelength of 660 nm with a spectrophotometer is 0.5 or more and 4.5 or less,
(l) After stirring 40 g of natto in 40 mL of water, the color of the extracted liquid obtained by removing the beans must be within the following range in the L ^* a ^* b ^* color space. .
80≧L ^* ≧40
5≧a ^* ≧-5
30≧b ^* ≧10 The natto according to any one of claims 1 to 5, which further satisfies the following requirement (m).
(m) After stirring 40 g of natto in 40 mL of water, the viscosity of the extract obtained by removing the bean part is 5 mPa・s or more and 180 mPa・Must be less than or equal to s. A method for producing natto, which involves inoculating steamed soybeans or boiled soybeans with natto bacteria and fermenting at a high temperature by maintaining the product temperature at 45°C or higher and 54°C or lower for 7 hours or more and 15 hours or less, and upon completion of ripening. A method for producing natto, which is characterized in that the production satisfies the following requirements (a) to (b).
(a) The content of 2,5-dimethylpyrazine (x) is 0.05 mg or more and 5 mg or less per 1 kg of natto wet weight,
(b) The content of 2,3,5-trimethylpyrazine (y) shall be 0.05 mg or more and 3 mg or less per 1 kg of natto wet weight. A method for producing natto, which uses natto bacteria with weak stringiness selected from natto strains that have been subcultured three times or more, and satisfies the following requirements (a) to (b) upon completion of ripening: A method for producing natto, which is characterized in that it is produced as follows.
(a) The content of 2,5-dimethylpyrazine (x) is 0.05 mg or more and 5 mg or less per 1 kg of natto wet weight,
(b) The content of 2,3,5-trimethylpyrazine (y) shall be 0.05 mg or more and 3 mg or less per 1 kg of natto wet weight. A method for improving the aftertaste of natto, which comprises producing natto so that the natto satisfies the following requirements (a) to (e) upon completion of ripening.
(a) The content of 2,5-dimethylpyrazine (x) is 0.05 mg or more and 5 mg or less per 1 kg of natto wet weight,
(b) The content of 2,3,5-trimethylpyrazine (y) shall be 0.05 mg or more and 3 mg or less per 1 kg of natto wet weight.
(c) The content of isovaleric acid (α) is 1 mg or more and 15 mg or less per 100 g of wet natto weight.
(d) The content of isobutyric acid (β) is 5 mg or more and 40 mg or less per 100 g of wet natto weight.
(e) The above α and β satisfy the following relational expression 1.
2≧α/β≧0.025 (Formula 1)

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