JP3972132B2

JP3972132B2 - Natto manufacturing method

Info

Publication number: JP3972132B2
Application number: JP2003028139A
Authority: JP
Inventors: 健川島; 雄二郎青木; 謙一川島
Original assignee: タカノフーズ株式会社
Priority date: 2003-02-05
Filing date: 2003-02-05
Publication date: 2007-09-05
Anticipated expiration: 2023-02-05
Also published as: JP2004236557A

Description

【０００１】
【発明の属する技術分野】
本発明は納豆の製造方法に関し、特に品質が良好であって冷蔵保存性の改良された納豆を安定して製造することができる、改良された納豆の製造方法に関するものである。
【０００２】
【従来の技術】
納豆は、原料大豆の選別、洗浄、蒸煮、納豆菌の接種、容器への充填、発酵、熟成の後、外包装の工程を経て製造され、出荷されているのが一般的である。このような従来の納豆の製造方法において、大豆を蒸煮して軟化させるには、従来から加圧蒸煮、或いは水煮という手段のみが実施されており、最適な軟らかさを持つ納豆を得るために、使用する原料大豆の品種、品質や粒径に応じて、蒸煮温度を高めたり、或いは蒸煮時間を延長するなどの蒸煮条件の調整を行うことが必要であった。
【０００３】
しかし、蒸煮条件を変化させると、製品の納豆の色などの外観、硬さ、発酵状態、味、日持ちなどの納豆の品質に対して大きな影響があり、前記のように、大豆を充分に軟化させるために蒸煮条件を強めると、豆の色が暗褐色化しやすくなるうえ、発酵終了後の冷蔵保存中にシャリつきが発生しやすく、更に豆のしぼみや乾燥が進み、日持ちがしなくなるという問題があった。
【０００４】
その一方で、納豆の品質や風味などを改善するための種々の手段が提案されており、大豆に対して、例えば米、麦、はと麦、そば、雑穀などをそれぞれ併用した納豆製品が知られている。そして、これらの従来技術の中で、特開平２−１１９７５９号には、蒸煮大豆に穀物粉末を混合して納豆菌により発酵させた納豆が、色や軟らかさと共に日持ちも改善されることが開示されている。
【０００５】
【発明が解決しようとする課題】
しかしながらかかる従来技術においても、納豆の品質を高めようとすると、原料大豆の品種、品質、粒径等に対する蒸煮条件の調整は必要であり、それに併せて一層の日持ちの改善も望まれている。
そこで本発明は、豆の色が明るく且つ鮮やかであって品質がよく、発酵終了後の冷蔵保存においても、日数経過によるシャリつきの発生、豆のしぼみ、乾燥などの進行が遅い、改良された納豆の製造方法を提供することを目的としたものである。
【０００６】
【課題を解決するための手段】
上記の目的を達成するために、本発明の納豆の製造方法は、浸漬大豆を１２６℃又はこれより１℃〜２℃低い蒸煮温度で１４分〜１８分間蒸煮して低軟化度の蒸煮大豆を製造し、この蒸煮大豆１００重量部に、濃度２〜７重量％の糊化米粉水溶液２〜２０重量部を添加した後、納豆菌を接種して発酵させるようにしたもので、豆の色が黄褐色ないし明茶褐色であり、日数経過による豆のしぼみや乾燥が進まず、アンモニアの発生やシャリつきの発生が遅く、日持ち日数も格段に長いなど、品質が大幅に改良された納豆を安定して製造できる。
【０００７】
そして特に、浸漬大豆を１２６℃又はこれより１℃〜２℃低い蒸煮温度で１４分〜１８分間蒸煮した低軟化度の蒸煮大豆によって製造でき、低い蒸煮温度と短い蒸煮時間とによって製造できる低軟化度の蒸煮大豆を用いることができる。
【０００８】
【発明の実施の形態】
前述のように、納豆の製造工程の中で、大豆の蒸煮条件を強化すると蒸煮大豆の組織破壊が進み、製品納豆の暗褐色化と、冷蔵保存中のシャリつきの発生、豆のしぼみ、乾燥等の品質の劣化がすすみ易くなることは知られている。そして、これに対して、蒸煮条件を緩和すると、このような品質の劣化は抑制されるものの、得られた納豆は硬くて、品質がよいとは言えないものであった。
【０００９】
本発明者等は、このような納豆の品質に対する製造条件の関係について鋭意研究を進めた結果、蒸煮大豆に糊化米粉水溶液を添加した後に、納豆菌を接種して発酵させるという手段を採用すると、蒸煮条件を緩和して得た硬めの蒸煮大豆を用いても、軟らかく且つ旨みの豊かな納豆が得られることを始めて見出し、かかる新しい知見に基づいて本発明に到達したものである。
【００１０】
本発明の納豆の製造方法は、蒸煮大豆１００重量部に、濃度１〜１０重量％の糊化米粉水溶液１〜２５重量部を添加した後、納豆菌を接種して発酵させるものであるが、糊化米粉水溶液の代わりに、水のみ、米粉のみ、或いは米粉を懸濁した水を用いた場合には、本発明の効果は達成されない。また、大豆の蒸煮に際して米粉を共存させるときは、蒸煮操作が不安定となって蒸煮ムラが生じたり、米粉の添加効果がばらついたりして、高品質の納豆を安定して製造することができない。すなわち本発明においては、大豆を蒸煮した後に、予め調製した糊化米粉水溶液を添加することが必要なのである。
【００１１】
また、本発明において用いられる糊化米粉水溶液中の米粉の濃度は、１〜１０重量％であることが必要であり、特に５〜７重量％であることが好ましい。濃度が下限値を下回るときは、蒸煮大豆と分離し易くて均一な混合状態が得られず、冷蔵保存中のしぼみや乾燥を抑制する効果が不十分となり、また上限値を越えても均一な混合状態が得られず、安定した効果が得られない。
【００１２】
更に、糊化米粉水溶液の添加量は、蒸煮大豆１００重量部に対して１〜２５重量部、望ましくは４〜１０重量部であり、この範囲内の添加量であれば大豆に対する軟化効果があるが、下限値を下回るときは、充分な軟化効果を期待することはできない。逆に添加量が上限値より多すぎるときは、納豆菌の生育が妨げられて発酵不良を起こしやすく、好ましくない。
【００１３】
【実施例】
（第１比較例）
原料の極小粒大豆を篩にかけて異物を除去したのち、水で洗浄し、常温の水に１８時間浸漬して充分に膨潤させた。そして、従来品の標準蒸煮条件である１２６℃で２２分に合わせた蒸煮条件で、強く蒸煮した大豆を得、この蒸煮大豆１kgに対して宮城野納豆製造所製の納豆菌液０．０１mLを接種して、発泡ポリスチレン製の納豆容器（５０ｇ容）に５０ｇずつ充填した。そして、これを３７〜４２℃で１８時間発酵させ、更に３〜７℃で２４時間熟成して、従来技術における標準条件を適用した、比較例の納豆Ａを得た。
【００１４】
（第１実施例）
水９３０mLに米粉７０ｇを混合し、攪拌しながら加熱して、液温が９０℃に達してから更に２時間、９０℃に保持して、７重量％糊化米粉水溶液を得た。
次に、第１比較例で用いたのと同じ膨潤大豆を用い、蒸煮条件を上記の従来品の標準条件から弱めた１２４℃で１８分の条件で蒸煮大豆を得、この蒸煮大豆１kgに対して上記の７重量％糊化米粉水溶液５０ｇを添加して均一に混合した。そして、以後は第１比較例と同様にして、納豆菌液を接種し、発酵し、熟成して、本発明による納豆Ｂを得た。
【００１５】
（第２比較例）
この納豆Ｂと比較するために、第１実施例で用いた蒸煮大豆に対し、糊化米粉水溶液を添加することなく納豆菌液を接種したほかは、第１実施例と全く同様にして発酵し、熟成して比較例の納豆Ｃを得た。
【００１６】
（第３比較例）
更に、第１実施例で用いた蒸煮大豆１kgに対して、糊化米粉水溶液を添加する代わりに水１２０mLを添加して、納豆菌液を接種したほかは、第１実施例と全く同様にして発酵し、熟成して比較例の納豆Ｄを得た。
【００１７】
（第２実施例）
水９８０mLに米粉２０ｇを混合し、攪拌しながら加熱して、液温が９０℃に達してから更に２時間、９０℃に保持して得た、２重量％糊化米粉水溶液を用いた他は、第１実施例と全く同様にして発酵し、熟成して本発明の納豆Ｅを得た。
【００１８】
（第４比較例）
水８８０mLに米粉１２０ｇを混合し、攪拌しながら加熱して、液温が９０℃に達してから更に２時間、９０℃に保持して得た、１２重量％糊化米粉水溶液を用いた他は、第１実施例と全く同様にして発酵し、熟成して比較例の納豆Ｆを得た。
【００１９】
（第１試験例）
このようにして製造した納豆Ａ〜Ｆについて、製造直後の性状を検査した後、冷蔵庫に入れて１５日間保存して、豆の色、味及び香り、糸引き、硬さ、シャリの発生、豆の乾燥及びしぼみ、の各項目について評価したところ、以下の表１の通りであった。
【００２０】
【表１】

【００２１】
なお、上記の試験結果について、評価の基準を、◎：非常に良好、○：僅かに劣化が認められるが合格、×：不合格、のように３段階として整理した結果を、以下の表２にまとめて示した。
この結果から、糊化米粉水溶液を用いないと、品質と日持ちを同時に改善することはできず、また糊化米粉水溶液の添加量が多すぎても品質の低下が起こることが分かる。
【００２２】
【表２】

【００２３】
（第２試験例）
また、納豆Ａと納豆Ｂについて、冷蔵保存中のアンモニア態窒素含有量、水分含有量、及び色度の経日変化をそれぞれ調べて、それらの結果を表３、表４及び表５にそれぞれ示した。
なお、アンモニア態窒素含有量は蒸留法により測定し、水分含有量は乾燥法により測定した。そして色度は、分光式色差計を用いて明度と彩度を測定して表示した。
これらの結果から、納豆Ｂ（本発明品）は、納豆Ａ（従来同等品）に比べて劣化が少ないことが分かる。
【００２４】
【表３】

【００２５】
【表４】

【００２６】
【表５】

【００２７】
（第３実施例）
大豆の蒸煮条件を１２３℃で２２分とした他は、第１実施例と全く同様にして発酵し、熟成して本発明の納豆Ｇを得た。
【００２８】
（第４実施例）
大豆の蒸煮条件を１２６℃で１４分とした他は、第１実施例と全く同様にして発酵し、熟成して本発明の納豆Ｈを得た。
【００２９】
（第５実施例）
大豆の蒸煮条件を１２６℃で２２分とした他は、第１実施例と全く同様にして発酵し、熟成して本発明の納豆Ｉを得た。
【００３０】
（第６実施例）
７重量％糊化米粉水溶液の添加量を、蒸煮大豆１kgに対して２０ｇとした他は、第１実施例と全く同様にして発酵し、熟成して本発明の納豆Ｊを得た。
【００３１】
（第７実施例）
７重量％糊化米粉水溶液の添加量を、蒸煮大豆１kgに対して２００ｇとした他は、第１実施例と全く同様にして発酵し、熟成して本発明の納豆Ｋを得た。
【００３２】
（第５比較例）
７重量％糊化米粉水溶液の添加量を、蒸煮大豆１kgに対して２８０ｇとした他は、第１実施例と全く同様にして発酵し、熟成して比較例の納豆Ｌを得た。
【００３３】
（第３試験例）
このようにして製造した納豆Ｇ〜Ｌについて、製造直後の性状を検査した後、冷蔵庫に入れて１５日間保存し、豆の色、味及び香り、糸引き、硬さ、シャリの発生、豆の乾燥及びしぼみ、の各項目について、第１試験例と同様にして評価した結果を、第１試験例の評価結果と併せて表６に示した。
この結果を見ると、大豆の蒸煮条件の如何にかかわらず、納豆の劣化は糊化米粉水溶液の添加により改善されるが、糊化米粉水溶液の添加量は多すぎても、また少なすぎても好ましくないことが分かる。
【００３４】
【表６】

【００３５】
【発明の効果】
本発明は、蒸煮大豆に糊化米粉水溶液を添加して発酵させることにより、豆を軟化させるので、従来方法における大豆の蒸煮条件より温和な条件で蒸煮でき、従来方法による納豆製品に比較して、風味や糸引き性が優れ、色が明るくて食欲をそそり、また保存による色の茶褐色化、豆のしぼみや乾燥などの劣化が抑制され、更にシャリつきがなく、納豆製品の風味を長く保持できる効果がある。そのうえ、原料大豆の品種や品質に合わせて米粉を糊化した水溶液の添加量を調整することで、良質の納豆を大量に安定して提供できる利点があり、産業上極めて有益である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing natto, and more particularly, to an improved method for producing natto, which can stably produce natto with good quality and improved refrigerated storage stability.
[0002]
[Prior art]
Natto is generally manufactured and shipped through an outer packaging process after selection of raw soybeans, washing, steaming, inoculation with natto bacteria, filling into containers, fermentation, and aging. In such a conventional natto manufacturing method, in order to steam and soften soybean, conventionally, only the means of pressure steaming or water boiling has been carried out, and in order to obtain natto having the optimum softness It was necessary to adjust the cooking conditions such as increasing the cooking temperature or extending the cooking time according to the variety, quality and particle size of the raw soybean used.
[0003]
However, changing the cooking conditions has a significant impact on the appearance of natto, such as the color of natto, the hardness, the fermented state, the taste, and the shelf life, and as described above, the soybeans are sufficiently softened. If the steaming conditions are strengthened to make it easier to darken the color of the bean, it will be prone to stickiness during refrigerated storage after fermentation, and the beans will continue to squeeze and dry, making it difficult to keep was there.
[0004]
On the other hand, various means for improving the quality and flavor of natto have been proposed, and natto products that use rice, wheat, wheat, buckwheat, millet, etc. in combination with soybeans are known. It has been. Of these conventional techniques, Japanese Patent Application Laid-Open No. 2-119759 discloses that natto fermented with natto bacteria by mixing cereal powder with steamed soybeans improves the shelf life as well as color and softness. Has been.
[0005]
[Problems to be solved by the invention]
However, even in such prior art, in order to improve the quality of natto, it is necessary to adjust the cooking conditions for the variety, quality, particle size, etc. of the raw soybean, and further improvement of the shelf life is also desired.
Therefore, the present invention is an improved natto in which the color of the beans is bright and vivid, and the quality is good, and even in refrigerated storage after the end of fermentation, the occurrence of crispness due to the passage of days, the squeezing of the beans, the progress of drying etc. is slow. It aims at providing the manufacturing method of this.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the method for producing natto according to the present invention is a method of cooking soy beans with low softening degree by steaming soaked soybeans at a cooking temperature of 126 ° C. or 1 ° C. to 2 ° C. lower than that for 14 to 18 minutes. After adding 2 to 20 parts by weight of gelatinized rice flour solution having a concentration of 2 to 7% by weight to 100 parts by weight of this cooked soybean, it is inoculated with natto bacteria and fermented. It is yellow-brown or light brown, and the natto with improved quality is stable, such as the aging of the beans does not progress and the drying of the beans does not progress, the generation of ammonia and the crushing is slow, and the shelf life is much longer. Can be manufactured.
[0007]
And in particular, low softening that can be produced by low-softening steamed soybeans that have been soaked at 126 ° C or a steaming temperature that is 1 ° C to 2 ° C lower than this for 14 to 18 minutes. Degree of steamed soybeans can be used.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
As mentioned above, strengthening the steaming conditions of soybeans during the natto manufacturing process will lead to tissue destruction of the steamed soybeans, darkening of the product natto, occurrence of crispness during refrigerated storage, bean squeezing, drying, etc. It is known that the deterioration of the quality of the product becomes easier. On the other hand, when the cooking conditions are relaxed, such deterioration in quality is suppressed, but the obtained natto is hard and cannot be said to have good quality.
[0009]
As a result of diligent research on the relationship between the production conditions for the quality of natto, the present inventors have adopted a means of inoculating and fermenting natto bacteria after adding gelatinized rice flour aqueous solution to steamed soybeans. It has been found for the first time that natto that is soft and rich in flavor can be obtained even by using hard steamed soybeans obtained by relaxing steaming conditions, and has reached the present invention based on such new knowledge.
[0010]
The method for producing natto of the present invention is to inoculate and ferment natto bacteria after adding 1 to 25 parts by weight of a gelatinized rice flour aqueous solution having a concentration of 1 to 10% by weight to 100 parts by weight of steamed soybeans. When only water, only rice flour, or water in which rice flour is suspended is used instead of the gelatinized rice flour aqueous solution, the effect of the present invention is not achieved. In addition, when rice flour coexists during steaming of soybean, the cooking operation becomes unstable, resulting in uneven cooking, and the effect of adding rice flour varies, making it impossible to stably produce high quality natto. . That is, in the present invention, it is necessary to add a gelatinized rice flour aqueous solution prepared in advance after steaming soybeans.
[0011]
The concentration of the rice flour in the gelatinized rice flour aqueous solution used in the present invention needs to be 1 to 10% by weight, and particularly preferably 5 to 7% by weight. When the concentration is lower than the lower limit, it is easy to separate from steamed soybeans and a uniform mixed state is not obtained, and the effect of suppressing deflation and drying during refrigerated storage is insufficient, and even if the upper limit is exceeded, it is uniform. A mixed state cannot be obtained, and a stable effect cannot be obtained.
[0012]
Furthermore, the addition amount of the gelatinized rice flour aqueous solution is 1 to 25 parts by weight, preferably 4 to 10 parts by weight with respect to 100 parts by weight of the steamed soybean. If the addition amount is within this range, there is a softening effect on soybeans. However, when it is below the lower limit, a sufficient softening effect cannot be expected. On the other hand, when the amount added is too much higher than the upper limit, the growth of natto bacteria is hindered and fermentation is liable to occur, which is not preferable.
[0013]
【Example】
(First comparative example)
Foreign materials were removed by sieving the raw material, very small soybeans, washed with water, and immersed in normal temperature water for 18 hours to swell sufficiently. And the soybeans which were steamed strongly were obtained under the steaming conditions which were 22 minutes at 126 ° C which is the standard steaming conditions of the conventional product. Then, 50 g each was filled into a natto container (50 g capacity) made of expanded polystyrene. And this was fermented at 37-42 degreeC for 18 hours, and also it matured at 3-7 degreeC for 24 hours, and the natto A of the comparative example which applied the standard conditions in a prior art was obtained.
[0014]
(First embodiment)
70 g of rice flour was mixed with 930 mL of water, heated with stirring, and kept at 90 ° C. for 2 hours after the liquid temperature reached 90 ° C. to obtain a 7 wt% gelatinized rice flour aqueous solution.
Next, using the same swollen soybean as used in the first comparative example, the steaming conditions were weakened from the standard conditions of the above-mentioned conventional product, and the steamed soybeans were obtained at 124 ° C. for 18 minutes. Then, 50 g of the above 7% by weight gelatinized rice flour aqueous solution was added and mixed uniformly. Thereafter, in the same manner as in the first comparative example, the natto fungus solution was inoculated, fermented, and aged to obtain natto B according to the present invention.
[0015]
(Second comparative example)
For comparison with this natto B, fermented in the same way as in the first example, except that the steamed soybean used in the first example was inoculated with the natto fungus solution without adding the gelatinized rice flour aqueous solution. A comparative example of natto C was obtained.
[0016]
(Third comparative example)
In addition, 1 kg of steamed soybean used in the first example was added in the same manner as in the first example except that 120 mL of water was added instead of adding the gelatinized rice flour aqueous solution and inoculated with the natto fungus solution. Fermented and matured to obtain comparative natto D.
[0017]
(Second embodiment)
20 g of rice flour was mixed with 980 mL of water, heated with stirring, and the solution was kept at 90 ° C. for 2 hours after the liquid temperature reached 90 ° C. Fermentation and aging were carried out in exactly the same manner as in the first example to obtain natto E of the present invention.
[0018]
(Fourth comparative example)
120 g of rice flour was mixed with 880 mL of water and heated with stirring. After the liquid temperature reached 90 ° C., the mixture was further maintained for 2 hours at 90 ° C. Fermentation and aging were carried out in exactly the same manner as in the first example, and comparative natto F was obtained.
[0019]
(First test example)
About natto AF manufactured in this way, after examining the properties immediately after production, put in a refrigerator and store for 15 days, bean color, taste and fragrance, stringing, hardness, occurrence of shari, beans Evaluation of each item of drying and squeezing was as shown in Table 1 below.
[0020]
[Table 1]

[0021]
For the above test results, the evaluation criteria are arranged in three stages, such as ◎: very good, ◯: slight deterioration is accepted but x: rejected, and the results are shown in Table 2 below. Are summarized in
From this result, it can be seen that the quality and the shelf life cannot be improved at the same time without using the gelatinized rice flour aqueous solution, and the quality deteriorates even if the amount of the gelatinized rice flour aqueous solution added is too large.
[0022]
[Table 2]

[0023]
(Second test example)
In addition, for natto A and natto B, the daily changes in ammonia nitrogen content, water content, and chromaticity during refrigerated storage were examined, and the results are shown in Table 3, Table 4, and Table 5, respectively. It was.
The ammonia nitrogen content was measured by a distillation method, and the water content was measured by a drying method. The chromaticity was displayed by measuring brightness and saturation using a spectroscopic color difference meter.
From these results, it can be seen that Natto B (the product of the present invention) is less deteriorated than Natto A (the conventional equivalent).
[0024]
[Table 3]

[0025]
[Table 4]

[0026]
[Table 5]

[0027]
(Third embodiment)
Fermentation and aging were carried out in exactly the same manner as in Example 1 except that soybean cooking conditions were set at 123 ° C. for 22 minutes to obtain Natto G of the present invention.
[0028]
(Fourth embodiment)
Fermentation and aging were performed in exactly the same manner as in Example 1 except that the soybean cooking conditions were set at 126 ° C. for 14 minutes to obtain Natto H of the present invention.
[0029]
(5th Example)
Fermentation and aging were carried out in exactly the same manner as in Example 1 except that the soybean cooking conditions were 126 ° C. for 22 minutes to obtain Natto I of the present invention.
[0030]
(Sixth embodiment)
Fermentation and aging were carried out in the same manner as in Example 1 except that the amount of 7 wt% gelatinized rice flour aqueous solution was 20 g per 1 kg of steamed soybeans, and natto J of the present invention was obtained.
[0031]
(Seventh embodiment)
Fermentation and aging were carried out in exactly the same manner as in Example 1 except that the amount of 7% by weight gelatinized rice flour aqueous solution added was 200 g per 1 kg of steamed soybeans to obtain natto K of the present invention.
[0032]
(Fifth comparative example)
Fermentation and aging were performed in exactly the same manner as in Example 1 except that the amount of 7 wt% gelatinized rice flour aqueous solution added was 280 g per 1 kg of steamed soybeans to obtain Natto L as a comparative example.
[0033]
(Third test example)
About natto GL manufactured in this way, after examining the properties immediately after production, put in a refrigerator and store for 15 days, the color of the beans, taste and fragrance, stringing, hardness, occurrence of shari, Table 6 shows the results of evaluation in the same manner as in the first test example for each item of drying and squeezing, together with the evaluation results in the first test example.
This result shows that, regardless of the steaming conditions of soybean, the deterioration of natto is improved by the addition of the gelatinized rice flour aqueous solution, but the addition amount of the gelatinized rice flour aqueous solution is too large or too small. It turns out that it is not preferable.
[0034]
[Table 6]

[0035]
【The invention's effect】
Since the present invention softens beans by adding gelatinized rice flour aqueous solution to fermented steamed soybeans, it can be steamed under milder conditions than the conventional soybean steaming conditions, compared to natto products by conventional methods Excellent flavor and stringiness, light color and appetizing, browning of the color due to storage, deterioration of bean squeezing and drying, etc. are suppressed, and there is no crispness and the flavor of natto products is kept longer There is an effect. In addition, by adjusting the amount of the aqueous solution obtained by gelatinizing rice flour in accordance with the variety and quality of the raw soybeans, there is an advantage that a large amount of high quality natto can be stably provided, which is extremely useful industrially.

Claims

The soaked soybean is cooked at 126 ° C. or at a cooking temperature lower by 1 ° C. to 2 ° C. for 14 to 18 minutes to produce a low-softening steamed soybean,
A method for producing natto, comprising adding 2 to 20 parts by weight of a gelatinized rice flour aqueous solution having a concentration of 2 to 7% by weight to 100 parts by weight of this steamed soybean, then inoculating and fermenting natto bacteria.