JPWO2019058946A1 - Method for producing steamed soybeans for natto, method for producing natto using steamed soybeans for natto obtained by the method, and natto - Google Patents

Method for producing steamed soybeans for natto, method for producing natto using steamed soybeans for natto obtained by the method, and natto Download PDF

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JPWO2019058946A1
JPWO2019058946A1 JP2019543528A JP2019543528A JPWO2019058946A1 JP WO2019058946 A1 JPWO2019058946 A1 JP WO2019058946A1 JP 2019543528 A JP2019543528 A JP 2019543528A JP 2019543528 A JP2019543528 A JP 2019543528A JP WO2019058946 A1 JPWO2019058946 A1 JP WO2019058946A1
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natto
soybeans
steamed soybeans
steaming
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JP6911133B2 (en
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秀之 市瀬
秀之 市瀬
広倫 河
広倫 河
義高 森下
義高 森下
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Mizkan Holdings Co Ltd
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    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
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    • A23L11/00—Pulses, i.e. fruits of leguminous plants, for production of food; Products from legumes; Preparation or treatment thereof
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Abstract

納豆を製造した際に、色が明るく、適度な硬さを有するだけでなく、苦味とえぐ味が少なく、納豆の製造に適した納豆用蒸煮大豆を製造する方法と；当該方法により得られた納豆用蒸煮大豆を用いた納豆の製造方法と；これにより得られた納豆と；を提供することを目的とする。（Ａ）浸漬大豆を圧力0.02MPa以上0.18MPa以下で加圧蒸煮する第一蒸煮工程、（Ｂ）前記第一蒸煮工程後に加水する第一加水工程、（Ｃ）前記第一加水工程後に圧力0.06MPa以上0.30MPa以下で加圧蒸煮する第二蒸煮工程、を含み、前記第一蒸煮工程の圧力(P1)と前記第二蒸煮工程の圧力(P2)がP1<P2の関係式を満たすことを特徴とする、納豆用蒸煮大豆の製造方法を提供する。A method for producing steamed soybeans for natto suitable for producing natto, which is suitable for producing natto, as well as having a light color and moderate hardness when producing natto, and having little bitterness and astringent taste; An object of the present invention is to provide a method for producing natto using steamed soybeans for natto, and natto obtained thereby. (A) A first cooking step of steaming the soaked soybeans under a pressure of 0.02 MPa or more and 0.18 MPa or less, (B) a first water adding step of adding water after the first steaming step, and (C) a pressure of 0.06 after the first water adding step. Including a second steaming step of steaming under pressure from MPa to 0.30 MPa, the pressure of the first steaming step (P1) and the pressure of the second steaming step (P2) satisfy the relational expression of P1 <P2. A characteristic method for producing steamed soybeans for natto is provided.

Description

本開示は、納豆用蒸煮大豆（以下、”蒸煮大豆”と略すこともある）の製造方法、当該方法により得られた納豆用蒸煮大豆を用いた納豆の製造方法、並びにこれにより得られた納豆に関する。
The present disclosure relates to a method for producing steamed soybeans for natto (hereinafter, may be abbreviated as “steamed soybean”), a method for producing natto using steamed soybeans for natto obtained by the method, and natto obtained thereby. Regarding

大豆を納豆菌（枯草菌の一種）で発酵させた納豆は、日本古来の発酵食品であり、大豆タンパク質を豊富に含み栄養価が高い。また、栄養価に加えて、納豆はそれ自体の嗜好性が高いことから、日本人の日常食品の一つとなっている。
さらに、近年、納豆にはプロバイオティック作用、抗菌作用、機能性成分等による各種健康増進効果があることが報告されており、益々需要の増加が期待されている食品である。
Natto, which is fermented soybean with Bacillus subtilis (a type of Bacillus subtilis), is a fermented food from ancient Japan, and is rich in soy protein and high in nutritional value. Moreover, in addition to its nutritional value, natto has a high palatability by itself, and is therefore one of the daily foods of the Japanese.
Furthermore, in recent years, it has been reported that natto has various health-promoting effects due to its probiotic action, antibacterial action, functional ingredients, etc., and it is a food that is expected to increase in demand.

納豆は、納豆菌による発酵によって生じる多様な香気成分や旨味成分が複雑に含有して呈される独特な風味を有しているが、苦味、えぐ味が強すぎた場合納豆を食べ慣れないユーザーの嗜好性が低下する。また、納豆の外観は自然な明るい褐色を呈することが好まれており、製造中の加熱等により過度に着色している場合も、消費者の嗜好性が低下する。
Natto has a unique flavor with a complex mixture of various aroma components and umami components produced by fermentation by Bacillus natto, but users who are not accustomed to eating natto when the bitterness or astringency is too strong. Is less palatable. Further, it is preferable that the appearance of natto has a natural light brown color, and if it is excessively colored due to heating or the like during manufacturing, the taste of consumers is deteriorated.

納豆の製造においては、一般的に、納豆菌の植菌前に、水中に十分浸漬した大豆を蒸煮設備で加熱することで大豆を軟化させる蒸煮工程が用いられる。しかしながら、原料の大豆の品種や保管条件によっては、蒸煮により納豆の製造に適した硬度まで軟化させる過程で、しばしば、大豆が過度に着色するため、蒸煮途中や蒸煮後に加水を行うことで、蒸煮大豆の色調や硬度を調整する手法が知られている。
In the production of natto, a steaming step of softening soybeans by heating soybeans sufficiently immersed in water in a steaming facility is generally used before inoculation of natto bacteria. However, depending on the variety of soybeans used as a raw material and storage conditions, soybeans are often excessively colored in the process of softening to a hardness suitable for the production of natto by steaming. A method of adjusting the color tone and hardness of soybean is known.

例えば、特許文献１には、大豆の蒸煮後に熱水を所定量散布することで、大豆の皮剥けや潰れを引き起こすことなく、かつ蒸煮工程で付着した大豆表面の着色成分を除くと共に、適度な柔らかさを有する納豆用蒸煮大豆を製造する方法が開示されている。
また、特許文献２には、大豆の加熱後蒸煮工程の前に加水を行うことで、蒸煮大豆の硬度が高く、容器へ蒸煮大豆を充填する際の潰れや煮汁発生などを低減することができる納豆用蒸煮大豆の製造方法が開示されている。
For example, in Patent Document 1, by spraying a predetermined amount of hot water after steaming soybeans, a coloring component on the soybean surface adhered in the steaming step is removed without causing peeling or crushing of the soybeans, and appropriate amount. A method for producing steamed soybeans for natto having softness is disclosed.
Further, in Patent Document 2, by performing water addition after heating the soybean and before the steaming step, the hardness of the steamed soybean is high, and it is possible to reduce crushing and the generation of broth when the steamed soybean is filled in a container. A method for producing steamed soybeans for natto is disclosed.

しかしながら、特許文献１の製造方法は、特許文献２の公開公報において、加水前に浸漬大豆を長時間蒸煮するため、大豆の色が暗く黒くなり、加水による大豆の脱色が十分にできないといった問題点が指摘されている。
また、特許文献２の製法を用いても、大豆の着色の抑制は十分でなく、さらに、特許文献１〜２の製造方法はいずれも、蒸煮大豆を用いて製造した納豆の苦味、えぐ味の除去が十分ではなかった。
However, the manufacturing method of Patent Document 1 has a problem in that the soybeans are steamed for a long time before watering in the publication of Patent Document 2, so that the color of soybeans becomes dark and black, and decolorization of soybeans by watering cannot be sufficiently performed. Has been pointed out.
Moreover, even if the manufacturing method of patent document 2 is used, the suppression of the coloring of soybeans is not sufficient, and further, all the manufacturing methods of patent document 1 and 2 are the bitterness of natto manufactured using steamed soybeans, and an astringent taste. Removal was not sufficient.

なお、特許文献３には、蒸煮工程を第一蒸煮工程と第二蒸煮工程に分け、第二蒸煮工程と比較して第一蒸煮工程の蒸煮温度を高くし、加水工程を第一蒸煮工程の第二蒸煮工程の間で実施することで、蒸煮大豆中の水分量を確保しつつ、ふっくらとした食感の納豆が得られるという、納豆用蒸煮大豆の製造方法が開示されている。
In addition, in patent document 3, a steaming process is divided into a first steaming process and a second steaming process, the steaming temperature of the first steaming process is increased compared to the second steaming process, and the watering process of the first steaming process is performed. Disclosed is a method for producing steamed soybeans for natto, in which natto with a plump texture is obtained while ensuring the water content in the steamed soybeans by performing the process between the second steaming steps.

特許文献３の特許請求の範囲では、第一蒸煮工程の蒸煮温度Ｔ1を１２５℃〜１４０℃とし、第二蒸煮工程の蒸煮温度Ｔ2を１０５℃〜１２０℃と規定している。
そして、特許文献３の明細書の段落００１２には、第一および第二蒸煮工程は、夫々温度に応じた加圧条件下で行われると記載されており、第一蒸煮工程の圧力は２３０〜３７０Ｐａ、第二蒸煮工程の圧力は１２０〜２００Ｐａと記載されている。
ちなみに、実施例１では、「１３１．５℃（圧力２８５Ｐａ）、５分間の第一蒸煮工程」と、「１１５℃（圧力１７０Ｐａ）、４５分間の第二蒸煮工程」と記載されている。
しかしながら、このような温度、圧力条件は、実現（実施）不可能であった。
即ち、第一蒸煮工程を、圧力２８５Ｐａにて５分間蒸煮してみたが、温度が１３１．５℃になることはなかった。逆に、第一蒸煮工程を、温度１３１．５℃で５分間蒸煮してみたが、圧力が２８５Ｐａになることはなかった。第二蒸煮工程も同様であった。
従って、特許文献３の方法では、その課題を解決することが不可能であると考えられた（後述の比較例３を参照）。
In the claims of Patent Document 3, the cooking temperature T1 in the first cooking process is set to 125°C to 140°C, and the cooking temperature T2 in the second cooking process is defined to 105°C to 120°C.
Then, in paragraph 0012 of the specification of Patent Document 3, it is described that the first and second steaming steps are performed under pressure conditions corresponding to respective temperatures, and the pressure of the first steaming step is 230 to The pressure in the second cooking step is 370 Pa, and the pressure in the second cooking step is 120 to 200 Pa.
By the way, in Example 1, it is described as “131.5° C. (pressure 285 Pa), 5 minutes first cooking step” and “115° C. (pressure 170 Pa), 45 minutes second cooking step”.
However, such temperature and pressure conditions cannot be realized (implemented).
That is, the first steaming step was steamed for 5 minutes at a pressure of 285 Pa, but the temperature never reached 131.5°C. On the contrary, when the first steaming step was steamed for 5 minutes at a temperature of 131.5° C., the pressure never reached 285 Pa. The second cooking step was similar.
Therefore, it was considered that the method of Patent Document 3 could not solve the problem (see Comparative Example 3 described later).

特開２００４−２４１９７号公報JP 2004-24197 A 特開２０１０−０９９０３２号公報JP, 2010-099032, A 特開２００９−２３２７５３号公報JP, 2009-232753, A

本開示の目的は、納豆を製造した際に、色が明るく、しかも適度な硬さを有するだけでなく、納豆の苦味、えぐ味が少ない納豆用蒸煮大豆を製造する方法を提供することである。
また、本開示の目的は、色が明るく、しかも適度な硬さを有するだけでなく、納豆の苦味、えぐ味が少ない納豆を製造することのできる、納豆の製造方法を提供することである。
さらに、本開示の目的は、色が明るく、しかも適度な硬さを有するだけでなく、苦味、えぐ味が少ない納豆を提供することである。
An object of the present disclosure is to provide a method of producing steamed soybeans for natto, which has a bright color when producing natto, and has not only moderate hardness but also bitterness and a little bitter taste of natto. ..
Further, an object of the present disclosure is to provide a method for producing natto, which is capable of producing natto which is bright in color, has an appropriate hardness, and has little bitterness and astringent taste of natto.
Further, it is an object of the present disclosure to provide natto, which is light in color, has appropriate hardness, and has little bitterness and astringent taste.

本開示者は、上記従来の問題点を解消すべく鋭意検討を重ね、納豆の製造に供される大豆について、実現可能な蒸煮方法を検討した結果、驚くべきことに、加水工程を挟んで、その前後に蒸煮工程を行う場合において、加水後の蒸煮工程よりも、加水前の蒸煮工程を、より温和となるような（マイルドな）特定の条件で行うことにより、上記従来の問題点を解消し得ることを見出し、この知見に基づいて本開示を完成したものである。
The present disclosure has made extensive studies in order to solve the above conventional problems, soybeans to be used in the production of natto, as a result of studying a feasible steaming method, and, surprisingly, sandwiching the water addition step, When performing a steaming process before and after that, by performing the steaming process before watering under milder (mild) specific conditions than the steaming process after watering, the above conventional problems are solved. The present disclosure has been completed based on this finding.

すなわち本開示は以下に関する。
納豆用蒸煮大豆の製造方法であって、
（Ａ）浸漬大豆を圧力0.02MPa以上0.18MPa以下で加圧蒸煮する第一蒸煮工程、
（Ｂ）前記第一蒸煮工程後に加水する第一加水工程、
（Ｃ）前記第一加水工程後に圧力0.06MPa以上0.30MPa以下で加圧蒸煮する第二蒸煮工程、を含み、かつ、前記第一蒸煮工程の圧力(P1)と前記第二蒸煮工程の圧力(P2)がP1<P2の関係式を満たすことを特徴とする、納豆用蒸煮大豆の製造方法に関する。

製造後の納豆用蒸煮大豆表面の表色が以下の関係式１を満たす納豆用蒸煮大豆を用いて製造した納豆に関する。

(関係式１)
37≦L*≦53
8.0≦a*≦12.0
3.9≦L*/a*≦6.7
L*：納豆用蒸煮大豆のL値(明度）
a*：納豆用蒸煮大豆のa値(赤色度)

製造後の納豆用蒸煮大豆表面の表色が以下の関係式１を満たす納豆用蒸煮大豆を用いることを特徴とする、納豆の苦味の抑制方法に関する。

(関係式１)
37≦L*≦53
8.0≦a*≦12.0
3.9≦L*/a*≦6.7
L*：納豆用蒸煮大豆のL値(明度）
a*：納豆用蒸煮大豆のa値(赤色度)
That is, the present disclosure relates to the following.
A method for producing steamed soybeans for natto, comprising:
(A) A first cooking step of steaming the soybeans under pressure at a pressure of 0.02 MPa or more and 0.18 MPa or less,
(B) a first watering step of adding water after the first cooking step,
(C) a second steaming step of pressure steaming at a pressure of 0.06 MPa or more and 0.30 MPa or less after the first water adding step, and the pressure of the first steaming step (P 1 ) and the pressure of the second steaming step. It relates to a method for producing steamed soybeans for natto, characterized in that (P 2 ) satisfies the relational expression P 1 <P 2 .

The present invention relates to natto produced by using steamed soybeans for natto, the surface color of the steamed soybeans for natto after production satisfies the following relational expression 1.

(Relational expression 1)
37 ≤ L * ≤ 53
8.0 ≤ a * ≤ 12.0
3.9 ≤ L * /a * ≤ 6.7
L * : L value (brightness) of steamed soybeans for natto
a * : a value (redness) of steamed soybeans for natto

The present invention relates to a method for suppressing bitterness of natto, which comprises using steamed soybeans for natto, the surface color of the steamed soybeans for natto after production satisfying the following relational expression 1.

(Relational expression 1)
37 ≤ L * ≤ 53
8.0 ≤ a * ≤ 12.0
3.9 ≤ L * /a * ≤ 6.7
L * : L value (brightness) of steamed soybeans for natto
a * : a value (redness) of steamed soybeans for natto

本開示によれば、第一加水工程前後の二回の蒸煮工程を特定の条件で実施することで、従来の加水を伴う蒸煮製法と同様に納豆にした際に色が明るく、しかも適度な硬さを有するだけでなく、納豆の苦味、えぐ味が少ない、納豆用蒸煮大豆の製造が可能となる。
また、本開示によれば、色が明るく、しかも適度な硬さを有するだけでなく、苦味、えぐ味が少ない納豆を製造することのできる、納豆の製造方法が提供される。
According to the present disclosure, by performing the two steaming steps before and after the first watering step under specific conditions, the color is bright when natto is made, as well as a conventional steaming method involving watering, and an appropriate hardness. It is possible to produce steamed soybeans for natto, which not only has a good taste but also has little bitterness and astringent taste of natto.
Further, according to the present disclosure, there is provided a method for producing natto, which is capable of producing natto having a bright color, an appropriate hardness, and a bitterness and an astringent taste.

したがって、本開示によれば、特別な製造設備の変更等を行うことなく、容易に苦味及びえぐ味の少ない納豆を製造できる。ここで「苦味」とは、舌を不快に感じさせる味であって、焦げ味を中心とする好まれない味を指し、納豆においては、大豆由来のポリフェノール、メラノイジン、大豆ペプチドなど複数の呈味物質によって「苦味」が生じると考えられる。
また「えぐ味」とは、舌の荒れを感じさせる味であって、収斂味を中心とする好まれない味を指し、納豆においては、メラノイジン、大豆由来のサポニンなどの複数の呈味物質によって「えぐ味」が生じると考えられる。
本開示によれば、このような「苦味」「えぐ味」が抑制された納豆が提供されることから、納豆を食することに抵抗のある消費者における納豆を食することへの抵抗感が低減される。
本開示の方法により製造された納豆用蒸煮大豆は、特別な設備を用いることなく「苦味」「えぐ味」の要因となる呈味物質が第一加水工程により効率的に除去されていると推測され、より高品質な納豆を製造する技術として、有効に用いることができる。
Therefore, according to the present disclosure, it is possible to easily manufacture natto with little bitterness and astringent taste without changing special manufacturing equipment. Here, "bitterness" is a taste that makes the tongue unpleasant, and refers to an unfavorable taste centered on charring taste, and in natto, soybean-derived polyphenols, melanoidins, soybean peptides, etc. It is thought that the substance causes "bitterness".
In addition, "egg taste" is a taste that makes the tongue feel rough and is an unfavorable taste centered on astringent taste. In natto, it is possible to use a plurality of taste substances such as melanoidin and soybean-derived saponin. It is thought that "astringent taste" will occur.
According to the present disclosure, since natto in which such "bitterness" and "astringency" are suppressed is provided, a consumer who is resistant to eating natto can feel resistance to eating natto. Will be reduced.
In the steamed soybeans for natto produced by the method of the present disclosure, it is assumed that the taste substances that cause the "bitterness" and "astringency" are efficiently removed by the first water addition step without using special equipment. And can be effectively used as a technique for producing higher quality natto.

本開示について、以下詳細に説明する。
本開示の第１〜第４の態様は、納豆用蒸煮大豆の製造方法に関する。
本開示の第１〜第４の態様において、納豆用蒸煮大豆の製造方法は基本的に共通している。従って、以下、共通の製法に関して、まとめて説明する。
The present disclosure will be described in detail below.
The 1st-4th aspect of this indication is related with the manufacturing method of the steamed soybeans for natto.
In the 1st-4th aspect of this indication, the manufacturing method of the steamed soybeans for natto is fundamentally common. Therefore, the common manufacturing methods will be collectively described below.

本開示の第１〜第４の態様において、納豆用蒸煮大豆の製造方法は、蒸煮工程を第一蒸煮工程と第二蒸煮工程の２回に分け、第一蒸煮工程、第二蒸煮工程の間に加水を実施することを特色とする。
以下に、納豆用蒸煮大豆の製造方法を例示するが、本開示の第１〜４の態様においては、納豆用蒸煮大豆の製造方法に用いられる方法に通常用いられる製法であれば、どのような方法でも用いることができる。
In the first to fourth aspects of the present disclosure, in the method for producing steamed soybeans for natto, the steaming step is divided into a first steaming step and a second steaming step, and the first steaming step and the second steaming step are performed. It is characterized by carrying out water addition.
Hereinafter, a method for producing steamed soybeans for natto will be exemplified, but in the first to fourth aspects of the present disclosure, any production method can be used as long as it is a method usually used for the method for producing steamed soybeans for natto. The method can also be used.

１．納豆用蒸煮大豆の製造方法
本開示の納豆用蒸煮大豆の製造方法では、通常の納豆用蒸煮大豆の製造に用いることができるものであれば、如何なる原料大豆をも用いることができる。
原料大豆としては、例えば、丸大豆、半割大豆、割砕大豆（挽き割り納豆の原料）、脱脂大豆などを使用できる。これら原料大豆の中でも、特に高品質の糸引き納豆製造時に使用される中粒や大粒のものが好適である。
これらの原料大豆は、生のまま用いることもできるが、乾燥処理を行ったもの（乾燥品）を用いることが一般的である。
1. Method for producing steamed soybeans for natto In the method for producing steamed soybeans for natto according to the present disclosure, any raw material soybean can be used as long as it can be used for ordinary production of steamed soybeans for natto.
As the raw material soybean, for example, whole soybean, half-divided soybean, cracked soybean (raw material for ground natto), defatted soybean, and the like can be used. Among these raw soybeans, medium-sized and large-sized soybeans that are used in the production of high-quality yarn-drawing natto are particularly preferable.
Although these raw material soybeans can be used as they are, it is common to use dried soybeans (dried products).

原料の乾燥丸大豆等は、水洗した後、常法にしたがって水に浸漬する。例えば、原料大豆を５℃〜２５℃程度の水に５〜２４時間程浸漬することができる。この浸漬工程によって得られた浸漬大豆は、続いて蒸煮工程に供する。
The dried whole soybeans as a raw material are washed with water and then immersed in water according to a conventional method. For example, the raw material soybean can be immersed in water at about 5°C to 25°C for about 5 to 24 hours. The soaked soybean obtained by this soaking step is subsequently subjected to a steaming step.

蒸煮工程においては、納豆用蒸煮大豆の製造に一般的に用いられている蒸煮設備を用いればよいが、上下方向に回転し得る型式の蒸煮釜が好適である。このような蒸煮釜としては、例えば、特開平１１−２２５７００号公報に開示されているものがある。
In the steaming process, steaming equipment generally used for producing steamed soybeans for natto may be used, but a steamer of a type that can be rotated in the vertical direction is preferable. An example of such a steam cooker is disclosed in JP-A-11-225700.

本開示の納豆用蒸煮大豆の製造においては、蒸煮工程を第一蒸煮工程と第二蒸煮工程の前後２回に分け、第一蒸煮工程と第二蒸煮工程との間に加水工程（第一加水工程）を実施する。
In the production of steamed soybeans for natto according to the present disclosure, the steaming step is divided into two steps before and after the first steaming step and the second steaming step, and the steaming step (the first steaming step) is performed between the first steaming step and the second steaming step. Process).

第一蒸煮工程、第二蒸煮工程はともに、一般的な蒸煮方法であれば、どのような方法でも採用可能であるが、典型的な蒸煮方法を以下に例示する。
まず、大豆を収容した蒸煮釜内に加圧蒸気を吹き込み、蒸煮釜内の温度が約100℃に達するまでは、蒸煮釜底部に設けた液排出管を開放しておき、大豆の蒸煮煮汁を排出させる。蒸煮釜内の温度が約100℃に達したならば、液排出管のバルブを閉じて釜内の所定の圧力（以下”目標圧力”ともいう）及び所定の温度（以下”目標温度”ともいう）に到達するまで加圧蒸気の吹き込みを続ける。
その後は、上記の所定の圧力と所定の温度が維持されるように調整しながら、蒸気の吹き込みを続け、一定時間この条件を保持する（以下、この保持時間を”蒸煮時間”ともいう）。
次いで、加圧蒸気の吹き込みを停止して、蒸煮釜内の圧力および温度を常圧、約100℃まで下降させ、液排出管を開放して蒸煮工程を終了させる。
Both the first cooking step and the second cooking step can be adopted by any method as long as it is a general cooking method, but a typical cooking method is exemplified below.
First, blow pressurized steam into the steaming pot containing soybeans, and open the liquid discharge pipe provided at the bottom of the steaming pot until the temperature inside the steaming pot reaches about 100°C, Let it drain. When the temperature inside the steamer reaches about 100°C, close the valve of the liquid discharge pipe to a predetermined pressure (hereinafter also referred to as "target pressure") and a predetermined temperature (hereinafter also referred to as "target temperature") inside the steamer. ) Continue to blow pressurized steam until it reaches.
After that, while adjusting so that the above-mentioned predetermined pressure and predetermined temperature are maintained, the blowing of steam is continued and this condition is maintained for a certain time (hereinafter, this holding time is also referred to as "steaming time").
Then, the blowing of the pressurized steam is stopped, the pressure and temperature in the steam cooker are lowered to atmospheric pressure at about 100° C., the liquid discharge pipe is opened, and the steaming process is terminated.

第一蒸煮工程の第一目標圧力(P1)と第二蒸煮工程の第二目標圧力(P2)は、P1＜P2の関係式を満たすことが必須であり、上記関係式を満たした上で、第一目標圧力P1は0.02MPa以上0.18MPa以下の範囲で、第二目標圧力P2は0.06MPa以上0.30MPa以下の範囲で、それぞれ所望の圧力とすることが可能である。
即ち、第一目標圧力P1より第二目標圧力P2をより高くすることが好ましい。
It is essential that the first target pressure (P 1 ) of the first cooking process and the second target pressure (P 2 ) of the second cooking process satisfy the relational expression P 1 <P 2 , and the above relational expression is satisfied. In addition, the first target pressure P 1 can be set to a desired pressure in the range of 0.02 MPa or more and 0.18 MPa or less, and the second target pressure P 2 can be set to a desired pressure in the range of 0.06 MPa or more and 0.30 MPa or less.
That is, it is preferable to make the second target pressure P 2 higher than the first target pressure P 1 .

ただし、蒸煮工程において圧力は、通常、蒸気の吹き込み量を調整することで制御を行うため、若干の圧力変動は避けられない。通常、特に蒸煮開始直後の数分間は、常圧状態から所定の圧力での加圧状態に速やかに移行させる目的で、蒸煮釜内にやや過剰な蒸気が吹き込まれることから、所定の圧力よりも高めの圧力となることが避けられない。
本開示においては、例えば、若干の圧力変動（±40%以内、好ましくは±20%以内）であり、かつ、圧力変動が若干の時間内（例えば2分以内、好ましくは1分以内）であれば、上記の圧力値に保持されたことを意味する。
However, in the steaming process, the pressure is usually controlled by adjusting the amount of steam blown in, so some pressure fluctuations cannot be avoided. Usually, especially for a few minutes immediately after the start of steaming, since a slight excess of steam is blown into the steaming pot for the purpose of rapidly shifting from a normal pressure state to a pressurized state at a predetermined pressure, the pressure is higher than the predetermined pressure. High pressure is inevitable.
In the present disclosure, for example, a slight pressure fluctuation (within ±40%, preferably ±20%) and a pressure fluctuation within a certain time (eg, within 2 minutes, preferably within 1 minute) For example, it means that the above pressure value is maintained.

また、第一目標圧力P1と第二目標圧力P2は、加水前に適当な熱負荷を与えることで加水により不要な大豆由来の成分の除去を促進できるように、本開示の第２に示す如く、1.1 × P1≦P2を満たすように設定することが好ましい。加水前の熱負荷を最適化する観点で、さらに好ましくは1.7 × P1≦P2の関係式を満たすように、つまり第二目標圧力P2が、第一目標圧力P1の1.7倍以上となるように、調整した方がより好ましい。
In addition, the first target pressure P 1 and the second target pressure P 2 are set in the second embodiment of the present disclosure so that removal of unnecessary soybean-derived components can be promoted by adding water by applying an appropriate heat load before adding water. As shown, it is preferable to set so as to satisfy 1.1×P 1 ≦P 2 . From the viewpoint of optimizing the heat load before water addition, more preferably so that the relational expression of 1.7 × P 1 ≤ P 2 is satisfied, that is, the second target pressure P 2 is 1.7 times or more of the first target pressure P 1. It is more preferable to adjust so that

さらに、第一目標圧力P1は、加水前に適度な熱負荷をかけて浸漬大豆を軟化させるため、下限値を0.02MPa以上とすることが好ましい。また、加水前の浸漬大豆の過度の加温を避けるため、上限値を0.18MPa以下、好ましくは0.14MPa以下、より好ましくは0.12MPa以下で調整することが好ましい。
一方、第二目標圧力P2は十分に大豆を軟化させるため、下限値を0.06MPa以上、好ましくは0.09MPa以上、さらに好ましくは0.12MPa以上とすることが好ましい。また、第二目標圧力P2は納豆用蒸煮大豆を用いて製造した納豆の食感を維持するため、上限値を0.30MPa以下、好ましくは0.28MPa以下、さらに好ましくは0.27Mpa以下とすることが好ましい。
Further, the first target pressure P 1 is preferably a lower limit value of 0.02 MPa or more in order to soften the dipped soybean by applying an appropriate heat load before adding water. In addition, in order to avoid excessive heating of the soaked soybeans before water addition, it is preferable to adjust the upper limit value to 0.18 MPa or less, preferably 0.14 MPa or less, more preferably 0.12 MPa or less.
On the other hand, the second target pressure P 2 is sufficient to soften soybeans, so that the lower limit value is preferably 0.06 MPa or more, preferably 0.09 MPa or more, and more preferably 0.12 MPa or more. Further, the second target pressure P 2 is to maintain the texture of natto produced using steamed soybeans for natto, the upper limit is 0.30MPa or less, preferably 0.28MPa or less, more preferably 0.27Mpa or less. preferable.

本開示において、加水前の浸漬大豆の過度の加温を避けるため、第一蒸煮工程の第一目標温度(T1)と第二蒸煮工程の第二目標温度 (T2)は、本開示の第３に示す如く、T1＜T2とするのが好ましい。つまり、第一目標温度T1よりも第二目標温度T2をより高くすることが好ましい。
In the present disclosure, in order to avoid excessive heating of soaked soybeans before water addition, the first target temperature (T 1 ) of the first cooking step and the second target temperature (T 2 ) of the second cooking step are the same as those of the present disclosure. As shown in the third, it is preferable that T 1 <T 2 . That is, it is preferable to make the second target temperature T 2 higher than the first target temperature T 1 .

本開示において、加水前の過剰な熱負荷により浸漬大豆の表面が過剰に着色しないようにするため、第一蒸煮工程の第一蒸煮時間(M1)と第二蒸煮工程の第二蒸煮時間(M2)は、M1＜M2とするのが好ましく、さらに好ましくは1.8 x M1 ≦ M2とするのが好ましい。
つまり、本開示の第４の態様に示す如く、第一蒸煮時間M1より第二蒸煮時間M2をより長くすることが好ましく、特にM2が、M1の1.8倍以上となるようにすることがより好ましい。
第一蒸煮時間M1及び 第二蒸煮時間M2は上記関係式を持たす範囲であれば、どのような蒸煮時間とすることもできる。ただ、加水前の過剰な熱負荷を避けるため、好ましくは、第一蒸煮時間M1は5分以上15分以下、より好ましくは5分以上10分以下とすることができる。第二蒸煮時間M2は浸漬大豆の表面の着色を抑えつつ十分に豆を軟化させるため、好ましくは10分以上90分以下、より好ましくは12分以上40分以下、さらに好ましくは12分以上30分以下とすることができる。
In the present disclosure, in order to prevent the surface of the soybeans from being excessively colored due to an excessive heat load before watering, the first cooking time (M 1 ) in the first cooking step and the second cooking time in the second cooking step ( M 2 ) is preferably M 1 <M 2, and more preferably 1.8 x M 1 ≦M 2 .
That is, as shown in the fourth aspect of the present disclosure, it is preferable to make the second cooking time M 2 longer than the first cooking time M 1 , and especially M 2 should be 1.8 times or more of M 1. Is more preferable.
The first cooking time M 1 and the second cooking time M 2 can be any cooking time as long as they have the above relational expressions. However, in order to avoid an excessive heat load before water addition, the first cooking time M 1 can be preferably 5 minutes or more and 15 minutes or less, more preferably 5 minutes or more and 10 minutes or less. Since the second cooking time M 2 is to soften sufficiently beans while suppressing the coloration of the surface of the soaked soybean, preferably 90 minutes or less than 10 minutes, more preferably 12 minutes or more 40 minutes or less, still more preferably at least 12 minutes 30 It can be less than a minute.

従って、全体的に、加水後に行う第二蒸煮工程よりも、加水前に行う第一蒸煮工程の方が、より温和（マイルド）な条件であるということができる。
Therefore, it can be said that, as a whole, the first cooking step performed before the water addition is milder than the second cooking step performed after the water addition.

次に、第一蒸煮工程と第二蒸煮工程との間に行う第一加水工程について説明する。
第一加水工程において加える水の温度は、例えば、10℃以上100℃以下とすることができる。不要な大豆由来の成分の除去を促進する観点で、好ましくは25℃以上95℃以下、さらに好ましく50℃以上90℃以下とすることができる。
Next, the first water addition step performed between the first steaming step and the second steaming step will be described.
The temperature of the water added in the first water addition step can be, for example, 10°C or higher and 100°C or lower. From the viewpoint of accelerating the removal of unnecessary soybean-derived components, the temperature can be preferably 25°C or higher and 95°C or lower, and more preferably 50°C or higher and 90°C or lower.

また、加水時に加える水の量は、例えば浸漬大豆の重量に対して5%以上80%以下とすることができるが、加水により不要な大豆由来の成分の除去を促進する観点で、好ましくは15%以上70%以下、さらに好ましくは30%以上60%以下とすることができる。
The amount of water added at the time of water addition can be, for example, 5% or more and 80% or less with respect to the weight of the soaked soybean, but from the viewpoint of promoting removal of unnecessary soybean-derived components by water addition, preferably 15 It can be set to not less than 70% and not more than 70%, more preferably not less than 30% and not more than 60%.

加水の方法は一般的な方法であればいずれの方法も採用でき、蒸煮釜内に直接加水する方法でも、別の設備に移送してから加水する方法のいずれで実施してもよい。なお、均一に蒸煮大豆に加水した水を効率よく浸透させるために、脱圧した蒸煮釜内に配管等を通じて所定量の加水を行った後、蒸煮釜を上下方向に回転させることで加水した水を釜内の蒸煮大豆に均一に接触させることが好ましい。
加水した水は、加水後、第二蒸煮工程の前に排水する。排水の方法としては、例えば、蒸煮釜下部の配管等を通じて排水する方法が例示できる。
As the method of water addition, any method can be adopted as long as it is a general method, and either a method of directly adding water into the steamer or a method of transferring to another facility and then adding water may be used. In order to efficiently permeate the water soaked in the steamed soybeans, a predetermined amount of water is added to the depressurized steamer through piping etc., and then the water is added by rotating the steamer vertically. It is preferable to bring the soybeans into uniform contact with the steamed soybeans in the kettle.
The hydrated water is drained after hydration and before the second cooking step. As a method of draining, for example, a method of draining through a pipe or the like at the bottom of the steam cooker can be exemplified.

上記のようにして第一加水工程を行った後に、前記したようにして第二蒸煮工程を行う。
即ち、蒸煮釜下部の配管等を通じて排水した後、再度、蒸煮釜内に加圧蒸気を吹き込み、蒸煮釜内の温度が約100℃に達するまでは、蒸煮釜底部に設けた液排出管を開放しておき、大豆の蒸煮煮汁を排出させる。蒸煮釜内の温度が約100℃に達したならば、液排出管のバルブを閉じて釜内が目標圧力及び目標温度に到達するまで加圧蒸気の吹き込みを続ける。
その後は、上記の目標圧力と目標温度が維持されるように調整しながら、蒸気の吹き込みを続け、所定時間蒸煮を行う。
次いで、加圧蒸気の吹き込みを停止して、蒸煮釜内の圧力および温度を常圧、約100℃まで下降させ、液排出管を開放して、第二蒸煮工程を終了させる。
After performing the first water addition step as described above, the second steaming step is performed as described above.
That is, after draining water through the piping at the bottom of the steam cooker, blow steam again into the steam cooker, and open the liquid discharge pipe provided at the bottom of the steam cooker until the temperature in the steam cooker reaches about 100°C. Then, let the soybean soup boil out. When the temperature in the boiling pot reaches about 100°C, the valve of the liquid discharge pipe is closed and the pressurized steam is continuously blown in until the inside pressure of the pot reaches the target pressure and the target temperature.
After that, the steam is continuously blown in while adjusting the target pressure and the target temperature so that the steam is cooked for a predetermined time.
Then, the blowing of the pressurized steam is stopped, the pressure and temperature in the steam cooker are lowered to normal pressure and about 100° C., the liquid discharge pipe is opened, and the second steaming step is completed.

次に、本開示の第５の態様について説明する。本開示の第５の態様は、納豆用蒸煮大豆を製造するにあたり、第二蒸煮工程の後に加水（第二加水工程）を行うことを特徴とするものである。
Next, the fifth aspect of the present disclosure will be described. A fifth aspect of the present disclosure is characterized in that, when producing steamed soybeans for natto, water is added (second watering step) after the second steaming step.

第二加水工程において加える水の温度は、例えば、10℃以上100℃以下とすることができる。不要な大豆由来の成分の除去を促進する観点で、好ましくは25℃以上95℃以下、さらに好ましく50℃以上90℃以下とすることができる。
The temperature of the water added in the second water addition step can be, for example, 10°C or higher and 100°C or lower. From the viewpoint of accelerating the removal of unnecessary soybean-derived components, the temperature can be preferably 25°C or higher and 95°C or lower, and more preferably 50°C or higher and 90°C or lower.

また、第二加水工程において、加水時に加える水の量は、例えば浸漬大豆の重量に対して5%以上80%以下、好ましくは5%以上50%以下、さらに好ましくは5%以上30%以下とすることができる。
しかしながら、一般的に、同程度の温度の温水を用いて加水を行う場合、第一加水工程と第二加水工程に分けて二度の加水を行うことで、第一加水工程のみで加水を行った場合と比較して、加える水の量の積算値を減らしても納豆用蒸煮大豆の品質向上に十分な効果を得ることができる。
それゆえ、加水により不要な大豆由来の成分の除去を効率よく実施する観点から、第一加水工程と第二加水工程で加える水の量の積算値を10%以上65%以下とするのがより好ましく、さらに好ましくは15%以上60%以下、特に好ましくは15%以上50%以下とすることができる。
In the second watering step, the amount of water added during watering is, for example, 5% or more and 80% or less, preferably 5% or more and 50% or less, more preferably 5% or more and 30% or less, with respect to the weight of the soaked soybeans. can do.
However, in general, when performing the water addition using warm water of the same temperature, the water addition is performed only in the first water addition step by performing the water addition twice in the first water addition step and the second water addition step. Even if the integrated value of the amount of water to be added is reduced, compared to the case described above, a sufficient effect can be obtained for improving the quality of steamed soybeans for natto.
Therefore, from the viewpoint of efficiently removing unnecessary soybean-derived components by water addition, it is more preferable to set the integrated value of the amount of water added in the first water addition step and the second water addition step to 10% or more and 65% or less. It is more preferably 15% or more and 60% or less, and particularly preferably 15% or more and 50% or less.

産業的規模で納豆用蒸煮大豆の製造を行う際に、加水する水の加熱にはボイラー等の大規模な設備が必要となる。このような設備の導入コストや稼動時のエネルギーコストが製造原価に占める割合は大きく、加水工程を二度に分ける本開示は、産業上有用である。
When producing steamed soybeans for natto on an industrial scale, heating the water for hydration requires large-scale equipment such as a boiler. The introduction cost of such equipment and the energy cost during operation account for a large proportion of the manufacturing cost, and the present disclosure in which the water addition step is divided into two is industrially useful.

第二加水工程において、加水の方法は一般的な方法であればいずれの方法も採用でき、蒸煮釜内に直接加水する方法でも、別の設備に移送してから加水する方法のいずれで実施してもよい。なお、均一に蒸煮大豆に加水した水を効率よく浸透させるために、脱圧した蒸煮釜内に配管等を通じて所定量の加水を行った後、蒸煮釜を上下方向に回転させることで加水した水を釜内の蒸煮大豆に均一に接触させることが好ましい。
加水した水は、加水後、後述する植菌工程の前に排水する。排水の方法としては、例えば、蒸煮釜下部の配管等を通じて排水する方法が例示できる。
In the second watering step, any watering method can be adopted as long as it is a general method, and either the method of directly watering in the steamer or the method of watering after being transferred to another facility can be used. May be. In order to efficiently permeate the water soaked in the steamed soybeans, a predetermined amount of water is added to the depressurized steamer through piping etc., and then the water is added by rotating the steamer vertically. It is preferable to bring the soybeans into uniform contact with the steamed soybeans in the kettle.
After hydration, the hydrated water is drained before the inoculation step described later. As a method of draining, for example, a method of draining through a pipe or the like at the bottom of the steam cooker can be exemplified.

第二加水工程は、第二蒸煮工程終了後、後述する植菌工程の前であれば、いつでも実施できるが、加熱によって大豆の着色が進行する前に加水を行うことが好ましいため、第二蒸煮工程終了後1時間以内に加水を行うのが好ましく、さらに30分以内に加水を行うのが好ましく、特に10分以内に加水を行うのが好ましい。
The second watering step can be carried out at any time after the completion of the second steaming step and before the inoculation step described below, but it is preferable to carry out watering before the coloring of soybeans progresses by heating, so the second steaming is performed. It is preferable to add water within 1 hour after completion of the step, more preferably within 30 minutes, and particularly preferably within 10 minutes.

次に、本開示の第６の態様について説明する。
本開示の第６の態様は、納豆の製造方法に関し、納豆を製造するにあたり、上記した本開示の第１〜第５の態様のいずれかに記載の製造方法で製造された納豆用蒸煮大豆を用い、納豆発酵工程において大豆の品温を37℃以上53℃以下の範囲で10時間以上24時間以内維持することを特徴とするものである。
Next, the sixth aspect of the present disclosure will be described.
A sixth aspect of the present disclosure relates to a method for producing natto, in which, when producing natto, the steamed soybean for natto produced by the method according to any one of the first to fifth aspects of the present disclosure described above is used. It is characterized by maintaining the temperature of soybeans in the range of 37°C to 53°C for 10 hours to 24 hours in the natto fermentation process.

２．納豆の製造方法
本開示の第６の態様における納豆の製造方法においては、本開示の第１〜第５の態様のいずれかの方法により製造した納豆用蒸煮大豆に対して、納豆菌を植菌し、発酵、熟成させて納豆を製造する。
2. Method for producing natto In the method for producing natto according to the sixth aspect of the present disclosure, inoculated with natto bacteria on the steamed soybean for natto produced by the method according to any one of the first to fifth aspects of the present disclosure. Then fermented and aged to produce natto.

２−１．納豆菌の植菌工程
まず、本開示の第１〜第５の態様のいずれかの方法により製造した納豆用蒸煮大豆に対して、納豆菌を植菌する「植菌工程」を行う。
添加する納豆菌の状態としては特に制限はないが、雑菌汚染を防ぐため、蒸煮直後の高温の大豆に直接植菌可能な、胞子状態のものを用いることが好適である。
2-1. First, the "inoculation step" of inoculating natto bacteria on the steamed soybeans for natto produced by the method according to any one of the first to fifth aspects of the present disclosure is performed.
The state of the natto bacteria to be added is not particularly limited, but in order to prevent contamination of various bacteria, it is preferable to use a spore state that can directly inoculate high temperature soybeans immediately after cooking.

納豆菌は、如何なる納豆菌も採用することができる。例えば、一般的な市販菌である宮城野菌（商品名：宮城野納豆菌）（有限会社宮城野製造所製）、高橋菌（商品名：納豆素）（有限会社高橋祐三研究所製）、成瀬菌（商品名：粉末納豆菌）（成瀬発酵化学研究所製）やその変異株を用いることができる。
As the natto bacterium, any natto bacterium can be adopted. For example, Miyagino fungus (product name: Miyagino Natto bacteria) (manufactured by Miyagino Manufacturing Co., Ltd.), Takahashi fungus (product name: Nattomoto) (manufactured by Yuzo Takahashi Research Co., Ltd.), and Naruse bacteria ( Trade name: powdered natto bacterium) (manufactured by Naruse Fermentation Institute) and its mutants can be used.

蒸煮大豆への上記納豆菌の植菌は、発酵を均一に行うため、大豆等と納豆菌が均一になるように、接種又は散布などにより添加した後、混合等を行うことが望ましい。好ましくは、上記納豆菌の胞子懸濁液を調製し、液体状態にて添加して用いることが好適である。
In order to inoculate the steamed soybeans with the above-mentioned Bacillus natto, the fermentation is carried out uniformly. Therefore, it is desirable that the soybeans and the Bacillus natto are added by inoculation or sprinkling and then mixed so that the soybeans and the Bacillus natto are uniformly mixed. Preferably, a spore suspension of Bacillus natto is prepared and added in a liquid state for use.

ここで胞子懸濁液としては、胞子形成に適当な成分を有する液体培地にて上記納豆菌を培養した培養液を用いることができる。
上記液体培地の成分としては、納豆菌の胞子形成と成育を可能にし、納豆菌の培養に通常使用される、炭素源、窒素源、無機塩類等の培地成分を含む液体培地であれば、特に限定はされず、合成培地であっても天然培地であってもよい。
Here, as the spore suspension, a culture solution obtained by culturing the above-mentioned Bacillus natto in a liquid medium containing components suitable for sporulation can be used.
As a component of the liquid medium, which enables spore formation and growth of Bacillus natto, is usually used for culturing Bacillus natto, a liquid medium containing medium components such as carbon source, nitrogen source, inorganic salts, The medium is not limited and may be a synthetic medium or a natural medium.

植菌する納豆菌の数は、常法に準じた菌濃度で特に限定はないが、通常、蒸煮大豆1gあたり103〜106個である。植菌する際の大豆の品温は、特に限定はないが、植菌時の雑菌汚染を防ぐため、55〜95℃程度の高温状態で植菌することが好ましい。
The number of Bacillus natto to be inoculated is not particularly limited as long as it is a bacterial concentration according to a conventional method, but it is usually 10 3 to 10 6 per 1 g of steamed soybean. The soybean product temperature at the time of inoculation is not particularly limited, but it is preferable to inoculate at a high temperature of about 55 to 95°C to prevent contamination of various bacteria at the time of inoculation.

上記納豆菌を植菌した大豆は、1食分〜数食分用の個別容器（通常20g〜100g程度の蒸煮大豆を充填可能な容器）に充填した後、個別容器内にて後述する発酵を行うことが好適である。また、伝統的な方法として、煮沸した藁苞に充填して行うことも可能である。
また、数リットルの容積の容器等にて発酵を行うことも可能であるが、表面積に対する体積の値が大きくなると、中央部の豆に温度変化が伝わりにくくなることを考慮すると、大きめの容器を用いることは好ましくない。
Soybeans inoculated with the above-mentioned Bacillus natto should be filled in individual containers for one to several servings (containers that can be filled with steamed soybeans of about 20 g to 100 g) and then fermented as described below in the individual containers. Is preferred. It is also possible to fill the boiled straw bracts as a traditional method.
It is also possible to perform fermentation in a container with a volume of several liters, but considering that the temperature change is less likely to be transmitted to the beans in the central part when the value of the volume relative to the surface area increases, a larger container should be used. It is not preferable to use it.

ここで個別容器としては、大豆の充填が可能であれば、いかなる容器を用いることもできる。具体的には、納豆で一般に用いられるようなスチレン改質ポリオレフィン系樹脂、ポリスチレン、ハイインパクトポリスチレン、スチレン−エチレン共重合体等のポリスチレン系樹脂、ポリエチレン、ポリプロピレン、エチレン−酢酸ビニル共重合体等のポリオレフィン系樹脂、ポリエチレンテレフタレート等のポリエステル系樹脂等の各種の合成樹脂製の発泡シートで成形した容器や、カップ状の紙製の容器を用いることができる。
また、容器の形状として、当該容器を用いて直接、喫食のための掻き混ぜ（攪拌）ができるような形状のものが好適である。
また、発酵後は、蓋やシーリングによる封を行うことができる態様のものが好適である。
Here, as the individual container, any container can be used as long as it can be filled with soybeans. Specifically, styrene-modified polyolefin resins such as those commonly used in natto, polystyrene, high-impact polystyrene, polystyrene resins such as styrene-ethylene copolymer, polyethylene, polypropylene, ethylene-vinyl acetate copolymer, etc. A container formed of a foamed sheet made of various synthetic resins such as a polyolefin resin and a polyester resin such as polyethylene terephthalate, or a cup-shaped paper container can be used.
Further, as the shape of the container, it is preferable to use a shape that allows stirring (stirring) for eating directly using the container.
Moreover, after fermentation, the thing of the aspect which can be sealed by a lid or sealing is suitable.

２−２．納豆発酵工程
本開示の第６の態様においては、このようにして蒸煮大豆に納豆菌を植菌する植菌工程を行った後に、納豆発酵工程を行い、納豆を発酵させる。
この納豆発酵工程は、通常、蒸煮後の大豆を、発酵室等（発酵室、恒温室、恒温器、インキュベーター等を指す。）に入れて行われる。
2-2. Natto Fermentation Step In the sixth aspect of the present disclosure, after performing the inoculation step of inoculating the steamed soybean with the natto bacterium in this manner, the natto fermentation step is performed to ferment the natto.
This natto fermentation step is usually carried out by putting the soybeans after steaming into a fermentation chamber or the like (which indicates a fermentation chamber, a temperature-controlled room, an incubator, an incubator, etc.).

本開示の第６の態様においては、発酵開始から、所定時間の間、大豆の品温を特定の温度帯に維持して、発酵を行う。
具体的には、納豆の発酵は、大豆の品温を実質的に37℃以上53℃以下の温度帯に、好ましくは40℃以上50℃以下の温度帯に、10時間以上24時間以内、好ましくは14時間以上20時間以内、維持することで行う。
大豆の品温を上記特定の温度帯に維持して、上記した所定時間の間、発酵を行うと、植菌した納豆菌は、発酵作用が全般的に活発となる発酵特性を示す。一般的には、納豆らしい風味の付与、糸引きの付与、菌膜の形成などが促進される。
In the sixth aspect of the present disclosure, fermentation is performed by maintaining the product temperature of soybeans in a specific temperature zone for a predetermined time from the start of fermentation.
Specifically, fermentation of natto is soybean product temperature substantially in the temperature range of 37 ℃ or more 53 ℃ or less, preferably in the temperature range of 40 ℃ or more 50 ℃ or less, 10 hours or more within 24 hours, preferably Is maintained for 14 to 20 hours.
When the product temperature of soybean is maintained in the above-mentioned specific temperature zone and fermentation is carried out for the above-mentioned predetermined time, the inoculated Bacillus natto exhibits fermentative properties such that the fermentation action is generally active. In general, the addition of a natto-like flavor, the addition of string, and the formation of a pellicle are promoted.

本開示の第６の態様に示される納豆の製法においては、発酵室等の室温を30℃以上50℃以下の温度帯に、好ましくは35℃以上50℃以下の温度帯に、維持することによって、発酵中の大豆の品温を上記温度帯に維持することが可能となる。発酵熱によって豆の品温が上昇し、上記納豆発酵温度帯に維持されるためである。
In the method for producing natto according to the sixth aspect of the present disclosure, by maintaining the room temperature of the fermentation chamber or the like in a temperature range of 30°C or higher and 50°C or lower, preferably in a temperature range of 35°C or higher and 50°C or lower, It is possible to maintain the product temperature of soybeans during fermentation in the above temperature range. This is because the fermentation heat raises the product temperature of the beans and keeps them in the natto fermentation temperature range.

なお、「大豆の品温を実質的に37℃以上53℃以下の温度帯に維持する」とは、完全に当該温度帯を外れないことを意味するものではなく、例えば、若干の温度範囲（例えば、2℃以内、好ましくは1℃以内）であって、かつ、短時間（例えば、10分以内、好ましくは5分以内）であれば、当該温度帯を外れた品温となった場合も、当該発酵条件を満たすことを意味する。
本開示における発酵では、上記温度帯に含まれる温度であれば、途中で温度を上昇及び／又は低下させる条件で発酵を行うことも可能である。
It should be noted that “maintaining the product temperature of soybeans in a temperature range of 37° C. or higher and 53° C. or lower” does not mean that the temperature range is not completely deviated, and for example, a slight temperature range ( For example, if the temperature is within 2°C, preferably within 1°C) and for a short time (for example, within 10 minutes, preferably within 5 minutes), the product temperature may be outside the temperature range. , Means that the fermentation conditions are satisfied.
In the fermentation according to the present disclosure, it is possible to perform the fermentation under the conditions of increasing and/or decreasing the temperature on the way as long as the temperature is within the above temperature range.

本開示では、上述の通り、納豆菌を植菌した大豆の品温を37〜53℃の範囲に所定の時間維持することが必須である。通常、納豆菌の植菌は55〜95℃程度の高温の大豆に対して実施するため、植菌直後に発酵室等に移動した場合は大豆の品温が53℃を超えており、長時間室温で放置した後に発酵室等に移動した場合は大豆の品温が37℃未満となっていることが想定される。ただし、通常、個別容器に充填した植菌大豆に対する発酵室の温度制御能力は十分大きく、発酵室に移動後30分〜2時間程度で大豆の品温を37〜53℃の範囲に調整することが可能である。
したがって、本開示において納豆菌を植菌した大豆を品温が37〜53℃の範囲に維持する時間は、発酵室内で大豆の品温が37〜53℃の範囲に到達するのに要する時間を考慮の上、適宜設定することができる。
In the present disclosure, as described above, it is essential to maintain the product temperature of soybeans inoculated with Bacillus natto within the range of 37 to 53°C for a predetermined time. Usually, inoculation of Bacillus natto is performed on soybeans at a high temperature of about 55 to 95°C, so if you move to a fermentation room immediately after inoculation, the product temperature of soybeans exceeds 53°C and If the soybeans are left at room temperature and then moved to a fermentation room, etc., the product temperature of soybeans is assumed to be below 37°C. However, the temperature control ability of the fermenting chamber for the inoculated soybeans filled in individual containers is usually sufficiently large, and the soybean product temperature should be adjusted within the range of 37 to 53°C within 30 minutes to 2 hours after moving to the fermentation chamber. Is possible.
Therefore, the time for maintaining the soybeans inoculated with Bacillus natto in the present disclosure in the temperature range of 37 to 53°C is the time required for the product temperature of soybeans to reach the range of 37 to 53°C in the fermentation chamber. It can be set as appropriate in consideration.

ここで、発酵を行うための部屋や装置としては、前記したように、「発酵室等」と称した発酵室、恒温室、恒温器、インキュベーター等を挙げることができる。
このような発酵を行うための部屋や装置としては、後述の熟成工程も同じ装置で実施する場合には、0℃〜55℃程度の温度範囲で調節可能なものが用いられる。
Here, as the room and apparatus for performing fermentation, as described above, there may be mentioned a fermentation chamber called "fermentation chamber, etc.", a temperature-controlled room, a thermostat, an incubator and the like.
As a room or apparatus for carrying out such fermentation, a room or apparatus that can be adjusted in a temperature range of about 0°C to 55°C is used when the aging step described later is also performed by the same device.

具体的には例えば、(i) 昇温及び冷却機能を有する発酵室等を用いて温度調節する手段を採用することができる。当該手段を採用した場合、温度条件を正確に調節することが可能となる。また、発酵中に大きく発酵温度を変更する場合には、(ii) 最初に発酵温度帯に温度設定された恒温室等で発酵を行い、所定時間経過後に異なる温度帯に設定された恒温室等に豆を容器ごと移動することによって、豆の品温を調節することもできる。当該温度調節手段を採用した場合、容器の移動を自動化することにより、温度調節の無駄を省き、納豆の大量生産を効率良く行うことが可能となる。
Specifically, for example, (i) a means for adjusting the temperature by using a fermentation chamber or the like having a temperature raising and cooling function can be adopted. When this means is adopted, the temperature condition can be adjusted accurately. Further, when the fermentation temperature is largely changed during fermentation, (ii) the fermentation is first performed in a temperature-controlled room or the like whose temperature is set to the fermentation temperature zone, and after a predetermined period of time, the temperature-controlled room or the like is set to a different temperature zone. It is also possible to control the temperature of the beans by moving the beans together with the container. When the temperature adjusting means is adopted, the movement of the container is automated, so that the waste of temperature adjustment can be eliminated and the mass production of natto can be efficiently performed.

２−３．熟成工程
発酵工程終了後、二次発酵による糸引き劣化、アンモニアの産生等の品質劣化を抑制するために、通常、3℃以上10℃未満、好ましくは3℃以上8℃未満、より好ましくは3℃以上6℃未満の低温になるようにして6時間〜3日間、好ましくは8時間〜2日間、より好ましくは24時間程度、熟成を行い納豆の製造が完了する。
2-3. Aging step After the completion of the fermentation step, in order to suppress threading deterioration due to secondary fermentation, quality deterioration such as production of ammonia, usually 3 ℃ or more and less than 10 ℃, preferably 3 ℃ or more and less than 8 ℃, more preferably 3 The natto production is completed by aging the mixture for 6 hours to 3 days, preferably 8 hours to 2 days, and more preferably about 24 hours so that the temperature is from ℃ to less than 6 ℃.

２−４．保管
なお、製造後の納豆を保管する際には、二次発酵による納豆の糸引き性の低下やチロシンの析出等の品質劣化を抑えるために、好ましくは3℃以上10℃未満、より好ましくは3〜6℃の品温になるように冷蔵状態にて保管することが好適である。
以上のようにして、本開示の第６の態様により、納豆を製造することができる。
上記工程を経て製造された納豆は、以下に述べる本開示の第７の態様において示す性質を有する納豆となる。
2-4. Storage When storing the natto after production, in order to suppress quality deterioration such as decrease in stringiness of natto due to secondary fermentation and precipitation of tyrosine, preferably 3°C or more and less than 10°C, more preferably It is preferable to store in a refrigerated state so that the product temperature is 3 to 6°C.
As described above, according to the sixth aspect of the present disclosure, natto can be manufactured.
The natto produced through the above steps becomes natto having the properties shown in the seventh aspect of the present disclosure described below.

本開示の第７の態様は、本開示の第１〜第５の態様に記載の納豆用蒸煮大豆の製造方法であって、製造後の納豆用蒸煮大豆表面の表色が以下の関係式１を満たすことを特徴とした、納豆用蒸煮大豆の製造方法に関する。
A seventh aspect of the present disclosure is the method for producing steamed soybeans for natto according to the first to fifth aspects of the present disclosure, wherein the surface color of the steamed soybeans for natto after production has the following relational expression 1 The present invention relates to a method for producing steamed soybeans for natto characterized by satisfying the following conditions.

関係式１
37≦L*≦53
8.0≦a*≦12.0
3.9≦L*/a*≦6.7
L*：納豆用蒸煮大豆のL値(明度）
a*：納豆用蒸煮大豆のa値(赤色度)
Relational expression 1
37 ≤ L * ≤ 53
8.0 ≤ a * ≤ 12.0
3.9 ≤ L * /a * ≤ 6.7
L * : L value (brightness) of steamed soybeans for natto
a * : a value (redness) of steamed soybeans for natto

本開示の第７の態様、納豆用蒸煮大豆を製造するにあたり、上述の関係式１の範囲となるように、製造後の納豆用蒸煮大豆表面の表色を調整する。この結果、特別な設備を用いることなく、納豆を製造した際に色が明るく、苦味とえぐ味も抑制された嗜好性の高い納豆を製造することが可能となる。
In producing the steamed soybeans for natto according to the seventh aspect of the present disclosure, the surface color of the steamed soybeans for natto after production is adjusted so as to fall within the range of the relational expression 1 described above. As a result, it becomes possible to manufacture natto having a high taste, which has a bright color when the natto is manufactured and which suppresses the bitterness and the astringent taste without using special equipment.

本開示の第７の態様に示される納豆用蒸煮大豆の製造方法においては、製造後の納豆用蒸煮大豆表面の表色が、適度な明るさを有しつつ、苦味とえぐ味を抑制するという観点で上述の関係式１を満たすのが好ましい。
In the method for producing steamed soybeans for natto according to the seventh aspect of the present disclosure, the color of the surface of the steamed soybeans for natto after production has moderate brightness and suppresses bitterness and acridness. From the viewpoint, it is preferable to satisfy the above relational expression 1.

さらに、本開示の第７の態様に示される納豆用蒸煮大豆の製造方法においては、製造後の納豆用蒸煮大豆表面の表色は、生産効率を向上させるために、以下の関係式２を満たすことが好ましく、さらに関係式３を満たすことがより好ましい。
Furthermore, in the method for producing steamed soybeans for natto according to the seventh aspect of the present disclosure, the surface color of the steamed soybeans for natto after production satisfies the following relational expression 2 in order to improve production efficiency. It is preferable that the relational expression 3 is further satisfied.

関係式２
37≦L*≦53
8.0≦a*≦12.0
4.3≦L*/a*≦6.0
L*：納豆用蒸煮大豆のL値(明度）
a*：納豆用蒸煮大豆のa値(赤色度)
Relational expression 2
37 ≤ L * ≤ 53
8.0 ≤ a * ≤ 12.0
4.3 ≤ L * /a * ≤ 6.0
L * : L value (brightness) of steamed soybeans for natto
a * : a value (redness) of steamed soybeans for natto

関係式３
37≦L*≦53
8.0≦a*≦12.0
4.6≦L*/a*≦5.5
L*：納豆用蒸煮大豆のL値(明度）
a*：納豆用蒸煮大豆のa値(赤色度)
Relational expression 3
37 ≤ L * ≤ 53
8.0 ≤ a * ≤ 12.0
4.6≦L * /a * ≦5.5
L * : L value (brightness) of steamed soybeans for natto
a * : a value (redness) of steamed soybeans for natto

なお、納豆用蒸煮大豆表面の表色を調整する際は、一般的な色彩計（例えば、日本電色工業社製 SD-3000）を用いて、L*a*b*表色計測定モードで測定を行い、得られたL* (L値）と、a* (a値)を指標として調整することができる。表色の測定は、蒸煮工程の途中の納豆でも蒸煮終了後に冷却した納豆用蒸煮大豆のいずれでも可能であるが、納豆製造時の納豆用蒸煮大豆の品質を反映している蒸煮工程終了後の納豆用蒸煮大豆で評価するのが好適である。
なお、工業的な納豆用蒸煮大豆の製造を行う場合、小規模なスケールでプレテストを行って蒸煮工程後の納豆用蒸煮大豆が確実に上記関係式に含まれる条件を検討してから、実生産を行う方が効率的である。
When adjusting the surface color of steamed soybeans for natto, use a general colorimeter (for example, SD-3000 manufactured by Nippon Denshoku Industries Co., Ltd.) in L * a * b * colorimeter measurement mode. The measurement can be performed and the obtained L * (L value) and a * (a value) can be used as an index for adjustment. The color measurement can be either natto in the middle of the steaming process or steamed soybeans for natto cooled after the steaming is finished, but after the completion of the steaming process that reflects the quality of the steamed soybeans for natto at the time of natto production. It is preferable to evaluate with steamed soybeans for natto.
In addition, when industrially producing steamed soybeans for natto, a pre-test is performed on a small scale to ensure that the steamed soybeans for natto after the steaming step are thoroughly examined for the conditions included in the above relational expression. It is more efficient to carry out production.

次に、本開示の第８の態様は、製造後の納豆用蒸煮大豆表面の表色が、上記関係式１を満たす納豆用蒸煮大豆を用いて製造した納豆に関する。
即ち、本開示の第８の態様に係る納豆は、製造後の納豆用蒸煮大豆表面の表色が、上記関係式１を満たす納豆用蒸煮大豆を用いて製造した納豆であって、特定の特性を有する納豆用蒸煮大豆を用いた点に特色を有する納豆である。
なお、生産効率を考慮すると、製造後の納豆用蒸煮大豆表面の表色が、上記関係式２を満たす納豆用蒸煮大豆を用いて製造した納豆であることが、より好ましく、さらに関係式３を満たすことがより好ましい。
本開示の第８の態様によれば、製造後の納豆用蒸煮大豆表面の表色が、上記関係式１を満たす納豆用蒸煮大豆を用いて製造することで、特別な設備を用いることなく、納豆を製造した際に色が明るく、苦味とえぐ味も抑制された嗜好性の高い納豆が提供される。
Next, an eighth aspect of the present disclosure relates to natto produced using steamed soybeans for natto whose surface color after production of steamed soybeans for natto satisfies the above relational expression 1.
That is, the natto according to the eighth aspect of the present disclosure is natto produced by using the steamed soybeans for natto whose color of the surface of the steamed soybean for natto after production satisfies the above relational expression 1, and has specific characteristics. It is a natto having a feature in using steamed soybeans for natto.
Considering the production efficiency, it is more preferable that the color of the surface of the steamed soybeans for natto after production is natto produced using steamed soybeans for natto satisfying the above relational expression 2, and further the relational expression 3 It is more preferable to satisfy.
According to the eighth aspect of the present disclosure, the color of the surface of the steamed soybeans for natto after manufacturing is manufactured using steamed soybeans for natto satisfying the above relational expression 1, without using special equipment, When natto is manufactured, it is bright in color, and bitterness and astringent taste are suppressed.

さらに、本開示の第９の態様は、製造後の納豆用蒸煮大豆表面の表色が、上記関係式１を満たす納豆用蒸煮大豆を用いることを特徴とする、納豆の苦味の抑制方法に関する。
なお、生産効率を考慮すると、製造後の納豆用蒸煮大豆表面の表色が、上記関係式２を満たす納豆用蒸煮大豆を用いることが、より好ましく、さらに関係式３を満たすことがより好ましい。
本開示の第９の態様によれば、製造後の納豆用蒸煮大豆表面の表色が、上記関係式１を満たす納豆用蒸煮大豆を用いることで、特別な設備を用いることなく、製造された納豆について、色が明るく、苦味とえぐ味も抑制することができる。
Further, a ninth aspect of the present disclosure relates to a method for suppressing bitterness of natto, characterized by using steamed soybeans for natto satisfying the above relational expression 1 on the surface of steamed soybeans for natto after production.
Considering the production efficiency, it is more preferable to use steamed soybeans for natto whose color of the surface of the steamed soybeans for natto that satisfies the above relational expression 2 is more preferable, and it is more preferable to satisfy the relational expression 3 further.
According to the ninth aspect of the present disclosure, the steamed soybean soybean for natto after the production is manufactured by using steamed soybean for natto satisfying the above relational expression 1 without using special equipment. As for natto, the color is bright and the bitterness and astringent taste can be suppressed.

本開示は、上記したとおりのものである。
なお、後述する本開示の実施例において、アミノ酸類とその測定法及び各種糖類とその測定法は、それぞれ以下のとおりである。
The present disclosure is as described above.
In the examples of the present disclosure described below, amino acids and their measuring methods and various sugars and their measuring methods are as follows, respectively.

２−５．アミノ酸類の測定法
本開示において、「アミノ酸総量」は、試料に含まれる右記（括弧内）のアミノ酸の合算値を意味する（アスパラギン酸 、スレオニン、セリン、グルタミン酸、プロリン、グリシン、アラニン、バリン、シスチン、メチオニン、イソロイシン、ロイシン、チロシン、フェニルアラニン、ヒスチジン、リジン、トリプトファン、アルギニン）。
また、本開示において、「塩基性アミノ酸量」は、上記アミノ酸のうち、リジン、ヒスチジン、アルギニンの合算値を意味する。
2-5. In the present disclosure, the “total amount of amino acids” means the total value of amino acids in the sample (in parentheses) contained in the sample (aspartic acid, threonine, serine, glutamic acid, proline, glycine, alanine, valine, Cystine, methionine, isoleucine, leucine, tyrosine, phenylalanine, histidine, lysine, tryptophan, arginine).
Further, in the present disclosure, the “basic amino acid amount” means the total value of lysine, histidine, and arginine among the above amino acids.

アミノ酸類の測定方法には特に制限はないが、ニンヒドリンを用いたポストカラム誘導体法によるHPLC分析が採用できる。測定機器としては、高速アミノ酸分析計 L-8900（株式会社日立ハイテクサイエンス）が例示できる。試料の前処理の方法には特に制限はないが、蒸煮大豆や納豆を試料として用いる場合、乳鉢やホモジナイザーなどで粉砕した粉砕物に50%エタノールを添加し、超音波処理を実施し、液相に水溶性成分を抽出した抽出液をろ過し、さらにクエン酸リチウム緩衝液で希釈して測定に用いる方法が例示できる。
The method of measuring amino acids is not particularly limited, but HPLC analysis by the post column derivative method using ninhydrin can be adopted. A high-speed amino acid analyzer L-8900 (Hitachi High-Tech Science Co., Ltd.) can be exemplified as a measuring instrument. The method of pretreatment of the sample is not particularly limited, but when using steamed soybeans or natto as the sample, 50% ethanol is added to the pulverized product pulverized with a mortar or homogenizer, ultrasonic treatment is performed, and the liquid phase is applied. An example is a method in which the extract obtained by extracting the water-soluble component is filtered, diluted with a lithium citrate buffer and used for the measurement.

２−６．各種糖類の測定法
本開示において、「糖総量」は、試料に含まれる右記（括弧内）の糖類の合算値を意味する（グリセリン、フラクトース、グルコース、シュクロース、マルトース、ラフィノース、スタキオース）。
2-6. Method for Measuring Various Sugars In the present disclosure, “total sugar amount” means a total value of sugars shown in the right (in parentheses) contained in a sample (glycerin, fructose, glucose, sucrose, maltose, raffinose, stachyose).

糖類の測定方法には特に制限はないが、例えば、ポリマー系親水性相互作用クロマトグラフィ用のカラムと示差屈折計を用いたHPLC分析が採用できる。使用できるカラムとしては、HILICpak VG-50 4E（昭和電工株式会社）が例示できる。試料の前処理の方法には特に制限はないが、蒸煮大豆や納豆を試料として用いる場合、乳鉢やホモジナイザーなどで粉砕した粉砕物に50%エタノールを添加し、超音波処理を実施し、液相に水溶性成分を抽出した抽出液をろ過し、さらに水で希釈して測定に用いる方法が例示できる。
The method for measuring saccharides is not particularly limited, and for example, HPLC analysis using a column for polymer-based hydrophilic interaction chromatography and a differential refractometer can be adopted. Examples of columns that can be used include HILICpak VG-50 4E (Showa Denko KK). The method of pretreatment of the sample is not particularly limited, but when using steamed soybeans or natto as the sample, 50% ethanol is added to the pulverized product pulverized with a mortar or homogenizer, ultrasonic treatment is performed, and the liquid phase is applied. An example is a method in which the extract obtained by extracting the water-soluble component is filtered, diluted with water and used for the measurement.

以下、実施例を挙げて本開示を説明するが、本開示の範囲はこれらにより限定されるものではない。
Hereinafter, the present disclosure will be described with reference to examples, but the scope of the present disclosure is not limited thereto.

Ｉ．実施例１〜実施例３、並びに、比較例１〜比較例４
表１に示す各種製造条件にて蒸煮大豆並びに納豆を製造し、得られた蒸煮大豆と納豆について、アミノ酸類の測定と各種糖類の測定を行うと共に、表面の表色、硬度、品質等の評価を行った（実施例１〜実施例３、並びに、比較例１〜比較例４）。これらの条件及び結果を表１、表２、表３に示す。
なお、蒸煮大豆の調製、納豆の調製、アミノ酸類の分析、各種糖類の分析、硬度の測定、表面の表色の測定、品質評価は、下記のとおりにして行った。
I. Examples 1 to 3 and Comparative Examples 1 to 4
Steamed soybeans and natto were produced under the various production conditions shown in Table 1, and the obtained steamed soybeans and natto were measured for amino acids and various sugars and evaluated for surface color, hardness, quality, etc. Was performed (Examples 1 to 3 and Comparative Examples 1 to 4). These conditions and results are shown in Table 1, Table 2 and Table 3.
The preparation of steamed soybeans, the preparation of natto, the analysis of amino acids, the analysis of various sugars, the measurement of hardness, the measurement of surface color and the quality evaluation were carried out as follows.

Ｉ−１．蒸煮大豆の調製
実施例１〜実施例３、並びに、比較例１〜比較例４の蒸煮大豆は、以下の方法で調製した。
まず、原料の乾燥丸大豆を、軽く水洗し、常温(約25℃）の水に一昼夜浸漬を行うことで大豆に水を十分に吸水させた後、金ざるで水を切った。
続いて、実施例１〜実施例３、並びに、比較例１、３、４については、浸漬大豆を第一蒸煮工程に供した。具体的には、浸漬大豆を金属製容器に入れ、蒸煮釜（原田産業製テスト用蒸煮釜）に入れ、表１記載の圧力(P1)、蒸煮時間(M1)となるように設定して蒸煮に供した。
一方、比較例２については、第一蒸煮工程は実施せずに釜内温度が９０℃になるまで加熱のみを行った。
なお、上記条件において、実施例１〜実施例３、並びに、比較例１、３、４の第一蒸煮工程における蒸煮温度（T1)は表１記載の通りであった。
なお、特許文献３を想定して実施した比較例３に関しては、上述のとおり、蒸煮温度と蒸煮圧力を所定の範囲に調整することができず、実施が不可能であったため、以降の工程は実施しなかった。
I-1. Preparation of Steamed Soybeans Steamed soybeans of Examples 1 to 3 and Comparative Examples 1 to 4 were prepared by the following method.
First, the dried whole soybean as a raw material was lightly washed with water, and immersed in water at room temperature (about 25° C.) for one day to allow the soybean to absorb water sufficiently, and then drained with a gold sieve.
Subsequently, in Examples 1 to 3 and Comparative Examples 1, 3 and 4, the soaked soybeans were subjected to the first cooking step. Specifically, put the soaked soybeans in a metal container, put them in a steamer (Harada Sangyo test steamer), and set the pressure (P 1 ) and steaming time (M 1 ) as shown in Table 1. And steamed it.
On the other hand, in Comparative Example 2, the first cooking step was not performed, and only the heating was performed until the temperature inside the pot reached 90°C.
Under the above conditions, the cooking temperature (T 1 ) in Examples 1 to 3 and Comparative Examples 1, 3, and 4 in the first cooking step was as shown in Table 1.
Regarding Comparative Example 3 performed assuming Patent Document 3, as described above, the cooking temperature and the cooking pressure could not be adjusted within a predetermined range, and the implementation was impossible. Didn't do it.

続いて、第一蒸煮工程完了後の大豆について、比較例３を除き第一加水工程に供した。具体的には、第一蒸煮完了後、脱圧を行い、蒸煮釜の蓋を空け、約75℃の温水を表１の“加水量”(％;蒸煮大豆質量比)に記載した割合となるように浸漬大豆を入れた容器に注水した。注水後約1分経過後、金属製のザルで加水した温水を水切りして第一加水工程を完了させた。
Then, the soybeans after the completion of the first steaming step were subjected to the first watering step except for Comparative Example 3. Specifically, after the completion of the first steaming, depressurization is performed, the lid of the steaming pot is opened, and the warm water at about 75°C becomes the ratio described in "Water content"(%; steamed soybean mass ratio) of Table 1. Water was poured into the container containing the soybeans. Approximately 1 minute after pouring water, the warm water hydrated in a metal colander was drained to complete the first hydration step.

第一加水工程完了後の大豆について、さらに第二蒸煮工程に供した。具体的には、釜のフタをしっかりと閉めてから、表１記載の圧力(P2)、蒸煮時間(M2)、蒸煮温度（T2)となるように設定して第二蒸煮に供することで蒸煮工程を完了させた。
なお、上記条件において、実施例１〜実施例３、並びに、比較例１、比較例２及び比較例４の（T2)は表１記載の通りであった。
なお、蒸煮大豆の品質評価は、上記方法で製造直後に4℃で3日間、冷蔵保管した検体を用いて実施した。
The soybeans after the completion of the first water addition step were further subjected to the second cooking step. Specifically, after closing the lid of the kettle firmly, the pressure (P 2 ), the cooking time (M 2 ) and the cooking temperature (T 2 ) shown in Table 1 are set so that they are subjected to the second cooking. This completed the steaming process.
In addition, under the above conditions, (T 2 ) in Examples 1 to 3 and Comparative Examples 1, 2, and 4 was as shown in Table 1.
The quality of steamed soybeans was evaluated by the above method using samples that had been refrigerated and stored at 4° C. for 3 days immediately after production.

II．実施例４
実施例４の蒸煮大豆は、以下の方法で調製した。
まず、原料の乾燥丸大豆を、軽く水洗し、常温(約25℃）の水に一昼夜浸漬を行うことで大豆に水を十分に吸水させた後、金ざるで水を切った。
続いて、表４記載の条件で、第一蒸煮工程、第一加水工程、第二蒸煮工程に供した後、さらに第二蒸煮工程終了直後に加水（第二加水工程）を行った。
加水や蒸煮方法、及び蒸煮大豆の品質評価は実施例１〜３、並びに比較例１、比較例２及び比較例４と同様の方法で実施した。
II. Example 4
The steamed soybean of Example 4 was prepared by the following method.
First, the dried whole soybean as a raw material was lightly washed with water, and immersed in water at room temperature (about 25° C.) for one day to allow the soybean to absorb water sufficiently, and then drained with a gold sieve.
Subsequently, under the conditions shown in Table 4, after being subjected to the first cooking step, the first watering step, and the second steaming step, water was further added (second watering step) immediately after the completion of the second cooking step.
The water addition and steaming methods, and the quality evaluation of steamed soybeans were carried out in the same manner as in Examples 1 to 3 and Comparative Examples 1, 2 and 4.

II−１．納豆発酵
上記の手順で蒸煮直後の高温状態の蒸煮大豆、実施例４については第二加水工程直後に水切りした蒸煮大豆、それぞれについて、以下の手順で納豆発酵を行った。
まず、蒸煮大豆1gあたり約5000個の納豆菌を含むように水で希釈した納豆菌スターターを添加し、軽く均一化した。納豆菌としては、Bacillus subtilis No.7株（NITE BP-01805)を用い、Bacillus subtilis No.7株を液体培地で培養した胞子懸濁液そのものを納豆菌スターターとして用いた。
その後、大豆45gずつをポリスチレン製納豆容器に入れて蓋をして納豆発酵室（原田産業社製テスト用発酵室）内で発酵を行った。各実施例、比較例の発酵は、表１又は表４の“室温”、“発酵時間”欄に記載の条件で実施した。
発酵工程終了後の納豆は、4℃もしくは10℃の冷蔵庫で冷却することで熟成を行った。
なお、納豆の品質評価は、通常の出荷時点における熟成を想定した4℃で3日間保存した検体と、賞味期限相当の保存を想定して4℃で7日間保存した後に、さらに10℃で13日間保存した検体とについて、それぞれ評価を行った。
II-1. Natto Fermentation The fermented soybeans were fermented according to the following procedure for the steamed soybeans in the high temperature state immediately after steaming according to the above procedure and the steamed soybeans drained immediately after the second water adding step in Example 4.
First, a natto starter diluted with water so as to contain about 5000 natto bacteria per 1 g of steamed soybean was added and lightly homogenized. As the Bacillus natto, Bacillus subtilis No. 7 strain (NITE BP-01805) was used, and the spore suspension itself obtained by culturing the Bacillus subtilis No. 7 strain in a liquid medium was used as a Bacillus natto starter.
Then, 45 g of each soybean was placed in a natto container made of polystyrene, covered with a lid, and fermented in a natto fermentation room (a test fermentation room made by Harada Sangyo Co., Ltd.). The fermentation of each Example and Comparative Example was carried out under the conditions described in the "room temperature" and "fermentation time" columns of Table 1 or Table 4.
After the fermentation process, the natto was aged by cooling in a refrigerator at 4°C or 10°C.
In addition, the quality evaluation of natto was performed by storing samples for 3 days at 4°C, which is assumed to be matured at the time of normal shipment, and 7 days at 4°C, assuming that they would be stored until the expiration date. Each of the samples stored for a day was evaluated.

II−２．アミノ酸類の分析用、各種糖類の分析用の試料の前処理
蒸煮大豆についてのアミノ酸類、各種糖類の分析検体は、それぞれ以下の方法で前処理を行った後、アミノ酸類の分析、各種糖類の分析に供した。
まず、試料として、蒸煮大豆をホモジナイザーで粉砕し、十分に均質化した後、粉砕した試料10ｇを精密ばかりで計量し、100mlメスフラスコに移した。なお、採取量を精密ばかりで計量するのは、試料の希釈率を正確に算出するためである。試料を入れた後、メスフラスコに50%エタノールを添加して100mlまで充填した。試料と50%エタノールを入れたメスフラスコはそのままソニケーターで30分間超音波処理し、液相に試料中の水溶性成分を抽出した。超音波処理後の試料は、ろ紙（No.2)でろ過することで固形分を除去した後、それぞれアミノ酸分析、各種糖組成分析に供した。
II-2. Pretreatment of samples for analysis of amino acids and various sugars Analysis samples of amino acids and various sugars for steamed soybeans are pretreated by the following methods, respectively, and then analyzed for amino acids and various sugars. It was submitted for analysis.
First, as a sample, steamed soybeans were crushed with a homogenizer and sufficiently homogenized, and then 10 g of the crushed sample was weighed with a precision balance and transferred to a 100 ml volumetric flask. The reason why the sampled amount is precisely measured is to accurately calculate the dilution rate of the sample. After placing the sample, 50% ethanol was added to the volumetric flask to fill up to 100 ml. The volumetric flask containing the sample and 50% ethanol was sonicated as it was for 30 minutes with a sonicator to extract the water-soluble components in the sample into the liquid phase. The sample after ultrasonic treatment was subjected to amino acid analysis and various sugar composition analysis after removing solid content by filtering with filter paper (No. 2).

II−３．アミノ酸類の分析
アミノ酸類の分析は上記の前処理を行った試料について、クエン酸リチウム緩衝液で希釈し（蒸煮大豆は2培希釈）した後、0.45μmフィルターでろ過した希釈液を測定に供した。測定は、ニンヒドリンを用いたポストカラム誘導体法によるHPLC分析で実施し、測定機器としては、高速アミノ酸分析計 JLC-500/V（日本電子）を用いた。
測定用のアミノ酸の標準品は、アミノ酸自動分析用 アミノ酸混合標準液ＡＮ−II
型（和光純薬）、アミノ酸自動分析用 アミノ酸混合標準液Ｂ型（和光純薬）、アミノ酸自動分析用 L-アスパラギン酸標準液（和光純薬）、L-グルタミン（和光純薬）、L-トリプトファン（和光純薬）をクエン酸リチウム溶液(pH2.2)で希釈して混合標準液調製することで作成した。
得られた実測値については、試料の希釈率に応じて換算して測定値を算出した。総アミノ酸に関しては、右記（括弧内）のアミノ酸の測定値の合算値で算出した（アスパラギン酸 、スレオニン、セリン、グルタミン酸、プロリン、グリシン、アラニン、バリン、シスチン、メチオニン、イソロイシン、ロイシン、チロシン、フェニルアラニン、ヒスチジン、リジン、トリプトファン、アルギニン）。塩基性アミノ酸に関しては、右記（括弧内）のアミノ酸の合算値で算出した（リジン、ヒスチジン、アルギニン）。
II-3. Amino acid analysisAmino acid analysis was performed by diluting the above pretreated sample with lithium citrate buffer (diluted steamed soybeans by 2 cultures) and then filtering with a 0.45 μm filter. did. The measurement was performed by HPLC analysis by the post-column derivative method using ninhydrin, and a high-speed amino acid analyzer JLC-500/V (JEOL) was used as the measuring instrument.
The standard amino acid for measurement is the amino acid mixed standard solution AN-II for automatic amino acid analysis.
Type (Wako Pure Chemical), amino acid automatic analysis amino acid mixed standard solution type B (Wako Pure Chemical), amino acid automatic analysis L-aspartic acid standard solution (Wako Pure Chemical), L-glutamine (Wako Pure Chemical), L- It was prepared by diluting tryptophan (Wako Pure Chemical Industries, Ltd.) with a lithium citrate solution (pH 2.2) to prepare a mixed standard solution.
The measured value obtained was converted according to the dilution rate of the sample to calculate the measured value. Total amino acids were calculated as the sum of the measured values of the amino acids shown in the right column (in parentheses) (aspartic acid, threonine, serine, glutamic acid, proline, glycine, alanine, valine, cystine, methionine, isoleucine, leucine, tyrosine, phenylalanine). , Histidine, lysine, tryptophan, arginine). The basic amino acid was calculated as the sum of the amino acids shown in the right column (in parentheses) (lysine, histidine, arginine).

II−４．各種糖類の分析
各種糖類の分析は上記の前処理を行った試料について、0.45μmフィルターでろ過したろ液をHPLCでの測定に供した。HPLCシステムはProminence（島津製作所）を用いた。
測定カラムは、HILICpak VG-50 4E HPLCを用い、移動相として80%アセトニトリルを用い、示唆屈折計（Shodex RI-201H)で検出を行った。
標準品としては、グリセリン(関東化学）、フラクトース（シグマアルドリッチ）、グルコース（シグマアルドリッチ）、シュクロース（シグマアルドリッチ）、マルトース（和光純薬工業）、ラフィノース（和光純薬工業）、スタキオース（MA Biomedicals)の各標準品を混合した混合標準液を用いた。
得られた実測値については、試料の希釈率に応じて換算して測定値を算出した。糖総量に関しては、右記（括弧内）の糖類の測定値の合算値で算出した（グリセリン、フラクトース、グルコース、シュクロース、マルトース、ラフィノース、スタキオース）。
II-4. Analysis of various saccharides For the analysis of various saccharides, a filtrate obtained by filtering a 0.45 μm filter of the sample subjected to the above pretreatment was subjected to HPLC measurement. The HPLC system used was Prominence (Shimadzu Corporation).
HILICpak VG-50 4E HPLC was used as the measurement column, 80% acetonitrile was used as the mobile phase, and detection was performed with a suggestive refractometer (Shodex RI-201H).
Standard products include glycerin (Kanto Chemical), fructose (Sigma-Aldrich), glucose (Sigma-Aldrich), sucrose (Sigma-Aldrich), maltose (Wako Pure Chemical Industries), raffinose (Wako Pure Chemical Industries), stachyose (MA Biomedicals) The mixed standard solution prepared by mixing the respective standard products of 1) was used.
The measured value obtained was converted according to the dilution rate of the sample to calculate the measured value. The total amount of sugar was calculated as the sum of the measured values of sugars (in parentheses) (glycerin, fructose, glucose, sucrose, maltose, raffinose, stachyose).

II−５．硬度の測定
蒸煮大豆と納豆についての硬度の測定は、デジタルフォースゲージ（日本電産シンポ社 FGP-5）を用いて以下の方法で実施した。
まずは、デジタルフォースゲージを測定台の上部に設置し、検体となる蒸煮大豆または納豆1粒を測定台の測定部分のクボミに設置した状態で、検体のほぼ中心をフォースゲージのプランジャーが突き刺すように位置調整を行った。その上で、1検体あたり14粒の蒸煮大豆または納豆について測定を行い、最大値の2点、最小値の2点を除いた10点の平均値を測定値とした。
II-5. Measurement of hardness The hardness of steamed soybeans and natto was measured by the following method using a digital force gauge (FGP-5, Nidec Shinpo Co., Ltd.).
First, place the digital force gauge on the upper part of the measuring table, and place one sample of steamed soybeans or natto as the sample in Kubomi of the measuring part of the measuring table so that the plunger of the force gauge pierces the center of the sample. I adjusted the position. Then, 14 samples of steamed soybean or natto per sample were measured, and the average value of 10 points excluding the maximum value of 2 points and the minimum value of 2 points was taken as the measured value.

II−６．蒸煮大豆表面および納豆表面の表色の測定
蒸煮大豆表面または納豆表面の表色は色彩計（日本電色工業社製 SD-3000）を用いて測定を行った。具体的には、色彩計の測定部に蒸煮大豆または納豆を設置した後、L*a*b*表色計測定モードで測定を行う。得られたL*(L値）を明度の指標、a*(a値)を赤色度（赤−緑方向）の指標、b*(b値)を黄色度（黄−青方向）の指標、計算式[C*=((a*)2+(b*)2)1/2]で算出されるC*(C値)を彩度の指標として用いた。
II-6. Measurement of color of steamed soybean surface and natto surface The color of steamed soybean surface or natto surface was measured using a colorimeter (SD-3000 manufactured by Nippon Denshoku Industries Co., Ltd.). Specifically, after setting steamed soybeans or natto in the measurement part of the colorimeter, measurement is performed in the L * a * b * colorimeter measurement mode. The obtained L * (L value) is an index of lightness, a * (a value) is an index of redness (red-green direction), b * (b value) is an index of yellowness (yellow-blue direction), equation [C * = ((a * ) 2 + (b *) 2) 1/2] of C * (C value) calculated by using as an index of saturation.

II−７．品質評価
実施例、比較例で取得した納豆の品質評価は、納豆関連業務に従事した経験があり、蒸煮大豆、納豆の品質を十分に熟知した者、延べ８名で以下の尺度を基準に実施し、評価結果の算術平均値を評点とした。
II-7. Quality evaluation The quality evaluation of natto obtained in the examples and comparative examples is based on the following scale with a total of 8 people who have experience in natto-related work and who are fully familiar with the quality of steamed soybeans and natto. Then, the arithmetic average value of the evaluation results was used as the score.

納豆の糸引きは、納豆を箸で30回／10秒撹拌を行った後、納豆粒の塊を持ち上げた時の箸からの納豆粒の落ちにくさの程度により、次の５段階で評価した。

５：非常に強い（混ぜた納豆粒の塊を箸で持ち上げた際に、空中で保持され５秒以上落下しない）
４：強い（混ぜた納豆粒の塊を箸で持ち上げた際に、空中で保持され落下するまで３秒かかる）
３：普通（混ぜた納豆粒の塊を箸で持ち上げた際に空中で保持できずに納豆粒が落ちる）
２：弱い（糸は引くが納豆粒の塊が形成されない）
１：非常に弱い（糸をひかない）
The natto stringing was evaluated in the following 5 grades according to the degree of difficulty of falling natto grains from the chopsticks when the natto grains were lifted after the natto was stirred 30 times/10 seconds with the chopsticks. ..

5: Very strong (when a lump of mixed natto grains is lifted with chopsticks, it is held in the air and does not fall for more than 5 seconds)
4: Strong (it takes 3 seconds for the mixed natto grains to be held in the air and fall when picked up with chopsticks)
3: Normal (when the lump of mixed natto grains cannot be held in the air when picked up with chopsticks, the natto grains fall)
2: Weak (pull thread, but lumps of natto grains are not formed)
1: Very weak (does not pull thread)

納豆の苦味は、次の５段階で評価した。

５：苦味が感じられず良好、４：苦味があまり感じられず良好、３：普通２：苦味
がやや感じられ不快、１：苦味が強く感じられ不快
The bitterness of natto was evaluated according to the following 5 grades.

5: Good bitterness is not felt, 4: Good bitterness is not felt, 3: Normal 2: Slight bitterness and discomfort, 1: Strong bitterness and discomfort

納豆のえぐ味は、次の５段階で評価した。

５：えぐ味が感じられず良好、４：えぐ味があまり感じられず良好、３：普通２：えぐ味がやや感じられ不快、１：えぐ味が強く感じられ不快
The astringency of natto was evaluated according to the following 5 grades.

5: Good taste without feeling astringent, 4: Good feeling without feeling astringent, 3: Normal 2: Slight feeling of astringent taste, discomfort, 1: Strong feeling of astringent taste, discomfort

納豆の硬さ（食感）は、次の５段階で評価した。

５：柔らかく歯ごたえが感じられない（舌と口腔内部で豆を1粒ずつ潰したときに10粒中6粒以上つぶれる）、４：歯ごたえを感じない（ただし、簡単に舌と口腔内部でつぶれない）、３：やや歯ごたえが感じられる、２：歯ごたえを感じる、１：強く歯ごたえを感じる
The hardness (texture) of natto was evaluated according to the following 5 grades.

5: Soft and crunchy (6 or more out of 10 grains crushed when crushing 1 bean on the tongue and inside the mouth) 4: No chewyness (however, not easily crushed on the tongue and inside the mouth) ) 3: Slightly chewy, 2: Chewy, 1: Strong chewy

納豆の色は、次の５段階で評価した。

５：非常に明るく適度な赤みを有している、４：やや明るく適度な赤みを有している、３：普通、２：やや暗く赤みもやや過剰、１：暗く赤みも過剰
The color of natto was evaluated according to the following 5 grades.

5: very bright and moderately reddish 4: slightly bright and moderately reddish 3: normal 2: slightly dark and slightly reddish, 1: dark and excessively reddish

納豆の香りは、次の３段階で評価した。

３：アンモニア等の異臭がない、２：アンモニア等の異臭が僅かに感じられる、１：アンモニア等の異臭が感じられる
The scent of natto was evaluated according to the following three grades.

3: No offensive odor of ammonia etc. 2: Slight offensive odor of ammonia etc. 1: Offensive odor of ammonia etc.

II−８．納豆用蒸煮大豆の評価結果
実施例１〜実施例３、並びに、比較例１、２、４で製造した納豆用蒸煮大豆についての評価結果は表１記載の通りである。評価は、製造後4℃で3日保存した蒸煮大豆について実施した。
実施例１〜３として製造した納豆用蒸煮大豆は、比較例１、２、４として製造した納豆用蒸煮大豆と比較して、L値が大きく、a値が小さいことからL*/a*の値が大きかった。この原因は不明であるが、実施例の方が総アミノ酸および、糖総量が少なく、特にシュクロースが少ないことから加熱により生じるメイラード反応の進行が遅いことが推測される。
蒸煮大豆のC値は測定した検体すべてでほぼ同等、硬度に関しては、加水工程を実施していない比較例４を除きほぼ同等であった。
II-8. Evaluation Results of Steamed Soybeans for Natto The evaluation results of the steamed soybeans for natto produced in Examples 1 to 3 and Comparative Examples 1, 2 and 4 are as shown in Table 1. The evaluation was carried out on steamed soybeans stored at 4° C. for 3 days after production.
Natto for steamed soybeans produced as Examples 1-3, as compared with natto for steamed soybeans produced as a comparative example l, 2,4, L value is large, since a value smaller L * / a * of The value was large. The cause of this is unknown, but it is presumed that the Maillard reaction caused by heating progresses slower in the Examples since the total amount of amino acids and the total amount of sugars are smaller and sucrose is particularly small.
The C values of the steamed soybeans were almost the same for all the measured samples, and the hardness was almost the same except for Comparative Example 4 in which the water addition step was not performed.

II−９．納豆の評価結果
実施例１〜実施例３、並びに、比較例１、２、４で製造した納豆についての評価結果は、表２、表３記載の通りである。
なお、納豆の品質評価は、通常の出荷時点における熟成を想定した4℃で3日間保存した検体（表２に記載）と、賞味期限相当の保存を想定した4℃で7日間保存後にさらに10℃で13日間保存した検体（表３に記載）の二点で評価を行った。
その結果、4℃で3日間保存した検体では、実施例１〜３として製造した納豆は、比較例１、２、４として製造した納豆と比較して、L値が大きく、a値が小さいことからL*/a*の値が大きかった。
さらに、納豆の品質評価においては、実施例１〜３として製造した納豆は苦味、えぐ味、色の評価が比較例１、２ 、４と比較して明らかに優れていた。
一方、糸引き、香りの品質評価は実施例１〜３と比較例１、２、４はほぼ同等であった。硬さの品質評価は、加水工程を行っていない比較例４を除きほぼ同等であった。
次に、4℃で7日間保存後にさらに10℃で13日間保存した検体は、4℃で3日間保存した検体と比較して全体的にL値が小さく、a値が大きくなったため、L*/a*の値が小さくなっており、品質評価において苦味、えぐ味、色の評価が下がっていた。
ただし、実施例１〜３については、いずれの評点も3点以上であり、賞味期限相当まで保存した場合でも、十分な嗜好性を有していることが確認できた。
なお、前記したように、特許文献３を想定して実施した比較例３に関しては、上述のとおり、蒸煮温度と蒸煮圧力を所定の範囲に調整することができず、実施が不可能であったため、表２と表３において、「実施不能の為測定未実施」と表記した。
II-9. Evaluation results of natto The evaluation results of natto produced in Examples 1 to 3 and Comparative Examples 1, 2 and 4 are as shown in Tables 2 and 3.
In addition, the quality evaluation of natto was carried out for 10 days after storing samples (stored in Table 2) that were stored at 4°C for 3 days assuming aging at the time of normal shipping, and 7 days at 4°C for storage equivalent to the expiration date. Evaluation was carried out on two points of the samples (listed in Table 3) stored at 13°C for 13 days.
As a result, in the sample stored at 4° C. for 3 days, the natto produced in Examples 1 to 3 had a large L value and a small a value as compared with the natto produced in Comparative Examples 1, 2, and 4. Therefore , the value of L * /a * was large.
Further, in the quality evaluation of natto, the natto produced in Examples 1 to 3 were obviously excellent in bitterness, astringent taste, and color evaluation as compared with Comparative Examples 1, 2, and 4.
On the other hand, the stringiness and scent quality evaluations of Examples 1 to 3 and Comparative Examples 1, 2, and 4 were almost the same. The quality evaluation of hardness was almost the same except for Comparative Example 4 in which the water addition step was not performed.
Next, the L value of the sample stored at 4°C for 7 days and further stored at 10°C for 13 days was smaller than that of the sample stored at 4°C for 3 days . The value of /a * was small, and the bitterness, astringent taste, and color were poor in the quality evaluation.
However, with respect to Examples 1 to 3, all the scores were 3 points or more, and it was confirmed that the samples had sufficient palatability even when they were stored until the expiration date.
In addition, as described above, in Comparative Example 3 performed on the assumption of Patent Document 3, as described above, the cooking temperature and the cooking pressure could not be adjusted within a predetermined range, and thus the implementation was impossible. In Tables 2 and 3, it was described as "Not measured because it was impossible to carry out".

実施例４の評価結果は表４〜表６に記載の通りである。納豆用蒸煮大豆については、実施例１〜３と比較してアミノ酸が多いように思われたが、L値、a値、L*/a*の値は同等であり、色の明るい良好な納豆用蒸煮大豆が得られた。
納豆の品質評価においても、実施例１〜３同様に官能評価の値は、比較例１、２、４と比較して明らかに優れており、賞味期限相当の保存を想定して4℃で7日間保存した後に、さらに10℃で13日間保存してもいずれの評点も3点以上であった。
The evaluation results of Example 4 are as shown in Tables 4 to 6. The steamed soybeans for natto seemed to have more amino acids as compared with Examples 1 to 3, but the L value, a value, and L * /a * values were the same, and good natto with a bright color. Steamed soybeans were obtained.
Also in the quality evaluation of natto, similarly to Examples 1 to 3, the value of the sensory evaluation is obviously superior to Comparative Examples 1, 2 and 4, and it is 7 at 4° C. assuming storage corresponding to the expiration date. After being stored for 10 days, even after being stored at 10°C for 13 days, all scores were 3 or higher.

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 関連出願の相互参照Cross-reference of related applications

本出願は、２０１７年９月２０日に日本国特許庁に出願された特願２０１７−１７９７２６に基づいて優先権を主張し、その全ての開示は完全に本明細書で参照により組み込まれる。
This application claims priority based on Japanese Patent Application No. 2017-179726 filed with the Japan Patent Office on September 20, 2017, the entire disclosure of which is incorporated by reference herein in its entirety.

Claims (9)

納豆用蒸煮大豆の製造方法であって、
（Ａ）浸漬大豆を圧力0.02MPa以上0.18MPa以下で加圧蒸煮する第一蒸煮工程、
（Ｂ）前記第一蒸煮工程後に加水する第一加水工程、
（Ｃ）前記第一加水工程後に圧力0.06MPa以上0.30MPa以下で加圧蒸煮する第二蒸煮工程、を含み、かつ、前記第一蒸煮工程の第一目標圧力(P1)と前記第二蒸煮工程の第二目標圧力(P2)がP1<P2の関係式を満たす、納豆用蒸煮大豆の製造方法。
A method for producing steamed soybeans for natto, comprising:
(A) A first cooking step of steaming the soybeans under pressure at a pressure of 0.02 MPa or more and 0.18 MPa or less,
(B) a first watering step of adding water after the first cooking step,
(C) a second steaming step of pressure steaming at a pressure of 0.06 MPa or more and 0.30 MPa or less after the first watering step, and the first target pressure (P 1 ) of the first steaming step and the second steaming A method for producing steamed soybeans for natto, wherein the second target pressure (P 2 ) of the process satisfies the relational expression of P 1 <P 2 .
前記第一目標圧力(P1)と前記第二目標圧力(P2)が1.1 × P1≦ P2の関係式を満たす、請求項１に記載の納豆用蒸煮大豆の製造方法。
The method for producing steamed soybeans for natto according to claim 1, wherein the first target pressure (P 1 ) and the second target pressure (P 2 ) satisfy the relational expression of 1.1×P 1 ≦P 2 .
前記第一蒸煮工程の第一目標温度(T1)と前記第二蒸煮工程の第二目標温度(T2)が T1＜T2の関係式を満たす、請求項１または２に記載の納豆用蒸煮大豆の製造方法。
Natto according to claim 1 or 2, wherein the first target temperature (T 1 ) of the first cooking step and the second target temperature (T 2 ) of the second cooking step satisfy the relational expression of T 1 <T 2. Of steamed soybeans for cooking.
前記第一蒸煮工程の第一蒸煮時間(M1)と前記第二蒸煮工程の第二蒸煮時間(M2)がM1＜ M2の関係式を満たす、請求項１〜３のいずれかに記載の納豆用蒸煮大豆の製造方法。
The first cooking time (M 1 ) of the first cooking step and the second cooking time (M 2 ) of the second cooking step satisfy the relational expression of M 1 <M 2. A method for producing steamed soybeans for natto as described.
前記第二蒸煮工程後にさらに加水する第二加水工程を含む、請求項１〜４のいずれかに記載の納豆用蒸煮大豆の製造方法。
The method for producing steamed soybeans for natto according to claim 1, further comprising a second watering step of further adding water after the second steaming step.
請求項１〜５のいずれかに記載の製造方法で製造された納豆用蒸煮大豆を用い、納豆発酵工程において、大豆の品温を実質的に37℃以上53℃以下の温度帯に、10時間以上24時間以内維持する、納豆の製造方法。
Using steamed soybeans for natto produced by the production method according to any one of claims 1 to 5, in the natto fermentation step, the temperature of soybeans is substantially in the temperature range of 37°C to 53°C for 10 hours. The method of manufacturing natto is maintained within the above 24 hours.
請求項１〜５のいずれか記載の納豆用蒸煮大豆の製造方法であって、製造後の納豆用蒸煮大豆表面の表色が以下の関係式１を満たす、納豆用蒸煮大豆の製造方法。

(関係式１)
37≦L*≦53
8.0≦a*≦12.0
3.9≦L*/a*≦6.7
L*：納豆用蒸煮大豆のL値(明度)
a*：納豆用蒸煮大豆のa値(赤色度)
The method for producing steamed soybeans for natto according to any one of claims 1 to 5, wherein the color of the surface of the steamed soybeans for natto after production satisfies the following relational expression 1:

(Relational expression 1)
37 ≤ L * ≤ 53
8.0 ≤ a * ≤ 12.0
3.9 ≤ L * /a * ≤ 6.7
L * : L value (brightness) of steamed soybeans for natto
a * : a value (redness) of steamed soybeans for natto
製造後の納豆用蒸煮大豆表面の表色が以下の関係式１を満たす納豆用蒸煮大豆を用いて製造した納豆。

(関係式１)
37≦L*≦53
8.0≦a*≦12.0
3.9≦L*/a*≦6.7
L*：納豆用蒸煮大豆のL値(明度)
a*：納豆用蒸煮大豆のa値(赤色度)
Natto produced using steamed soybeans for natto whose surface color after the production satisfies the following relational expression 1 on the surface of steamed soybeans for natto.

(Relational expression 1)
37 ≤ L * ≤ 53
8.0 ≤ a * ≤ 12.0
3.9 ≤ L * /a * ≤ 6.7
L * : L value (brightness) of steamed soybeans for natto
a * : a value (redness) of steamed soybeans for natto
製造後の納豆用蒸煮大豆表面の表色が以下の関係式１を満たす納豆用蒸煮大豆を用いる、納豆の苦味の抑制方法。

(関係式１)
37≦L*≦53
8.0≦a*≦12.0
3.9≦L*/a*≦6.7
L*：納豆用蒸煮大豆のL値(明度)
a*：納豆用蒸煮大豆のa値(赤色度)
A method for suppressing bitterness of natto using steamed soybeans for natto, the surface color of the steamed soybeans for natto after production satisfying the following relational expression 1.

(Relational expression 1)
37 ≤ L * ≤ 53
8.0 ≤ a * ≤ 12.0
3.9 ≤ L * /a * ≤ 6.7
L * : L value (brightness) of steamed soybeans for natto
a * : a value (redness) of steamed soybeans for natto
JP2019543528A 2017-09-20 2018-09-03 A method for producing steamed soybeans for natto, a method for producing natto using steamed soybeans for natto obtained by the method, and natto. Active JP6911133B2 (en)

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JPS519750A (en) * 1974-07-10 1976-01-26 Ryoji Sekiguchi Tanshokunatsutono seizohoho
JP2521610B2 (en) * 1992-02-17 1996-08-07 東洋エンジニアリング株式会社 Continuous steaming method for manufacturing whole soybean natto and continuous steaming apparatus thereof
JPH05308915A (en) * 1992-05-13 1993-11-22 Iseki Eng Kk Continuous grain treating equipment
JP4009149B2 (en) * 2002-06-28 2007-11-14 株式会社ミツカングループ本社 Method for producing steamed soybeans for natto
JP2004337007A (en) * 2003-05-13 2004-12-02 Mitsukan Group Honsha:Kk Fermented soybean with bacillus natto and method for producing the same
JP4773185B2 (en) * 2005-11-15 2011-09-14 株式会社ミツカングループ本社 Natto and its manufacturing method
JP2009232753A (en) * 2008-03-27 2009-10-15 Takano Foods Kk Method for producing steamed soybean by two-step steaming, and fermented soybean using the steamed soybean
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