JP4773185B2 - Natto and its manufacturing method - Google Patents

Description

  The present invention relates to natto having a glutinous sensation and a method for producing the same, and in particular, in natto having a predetermined water-soluble pectin content and hardness, and in the steaming process of soybean, after increasing the pressure in the steamer, the steaming process The present invention relates to a method for producing natto, characterized in that steam input is limited to a certain amount until the end.

  Natto is a food that has been widely eaten in Japan since ancient times. In recent years, consumers' tastes have also been diversified, and in addition to the flavor of beans and the taste of sauce, the tastes of the food are also varied. There are many consumers who prefer a crisp texture as a texture, but natto that satisfies both a moderate hardness and a glutinous texture has not been provided to consumers yet.

In the production of natto, there is a process in which soybean is soaked in water and then steamed with hot water. This cooking process greatly affects the texture of natto, and also affects the fermentation efficiency of natto bacteria and the color of natto.
The soybean cooking process in the current natto production is generally performed by steaming with steam using a high-pressure kettle. Specifically, after the pressure in the kettle (gauge pressure) is increased to about 0.15 to 0.2 MPa, the pressure is maintained for about 20 to 30 minutes while supplying steam (see Non-Patent Document 1). . Thereafter, empirically, a process of quickly depressurizing to normal pressure over a period of about 5 to 20 minutes is performed.

As a steaming method for improving the quality of natto, (a) a method of improving quality maintenance by adding water to swollen soybeans and boiling under pressure (see Patent Document 1), (b) steaming A method for producing stable natto efficiently and stably by adsorbing steamed soup to steamed soybeans in the process (see Patent Document 2). (C) After depressurizing after pressure steaming and returning to normal pressure There has been proposed a method (see Patent Document 3) that has a moderate hardness by spraying hot water on steamed soybeans and finishes a plump texture.
However, none of the methods is intended to provide a glutinous texture, and has not yet produced a natto with a pleasing texture desired by consumers.

As described above, a method for improving the glutinous feeling of natto has not yet been reported, but it has been reported that water-soluble pectin is related to the stickiness of boiled beans. Specifically, soybeans contain pectin, which is decomposed by steaming at high temperatures, resulting in an increase in water-soluble pectin, but boiled beans rich in this water-soluble pectin are stronger than boiled beans with less water. (See Non-Patent Document 2).
From this report, it is inferred that using steamed beans with a high water-soluble pectin content makes it possible to produce natto with a longer texture than when using less steamed beans. In order for natto to have a mochi-motivated feeling, how much steamed beans containing water-soluble pectin should be used, and how much natto containing water-soluble pectin should be preferred by consumers Nothing has been reported.

  In addition, according to Non-Patent Document 2, the water-soluble pectin that dissolves in the broth is less when the soybeans are boiled in the pressure cooker than when the soybeans are cooked in a normal-pressure pan, and the water-soluble nature in the cooked beans It has been reported that pectin is increased. However, high-pressure kettles are already widely used in natto production, but the natto that has undergone the steaming process using this high-pressure kettle cannot be said to have a sufficient glutinous feeling. It is clear that natto with sufficient glutinous feeling cannot be produced by itself.

  On the other hand, as a technique for adding a large amount of nutrients (pectin or the like) to boiled beans, a technique for adding salt to water used for soybean soaking has been reported (see Non-Patent Document 3). However, when the immersing process with salt water is performed in natto production, not only is saltiness imparted to natto and the flavor is impaired, but also the growth of natto bacteria is inhibited, which is not suitable for natto production.

Further, as a means for containing a large amount of water-soluble pectin in soybean, it is conceivable to reduce the steamed soup itself. To that end, it is also proposed to reduce the amount of water and steam used for cooking, but in order to ensure adequate hardness as natto, sufficient steaming is necessary, and simply shortening the cooking time And just by reducing the steam pressure, it is impossible to produce steamed beans that can be used for natto production.
Thus, it has not yet been reported to produce natto with a texture that has a moist texture even if it contains a lot of water-soluble pectin in soybean while having a moderate hardness and a moderate flavor as natto, The development of such a method has been awaited.

JP-A-8-214821 JP 11-225700 A JP 2004-24197 A Teruo Ota "Basic Technology of Natto Production" Food and Science, 1987 Special Issue, 149-151) Shoko Shibukawa “About the characteristics of boiled beans by pressure cooker” Home Economics Journal, Vol.30, No.7, 1979, 591-595 Yoko Matsuoka et al. "Characteristics of Soaked and Heated Black Soybeans" Cooking Science, Vol. 23, No. 3, 1990, 311-314

As mentioned above, the conventional natto production method, soy cooking method, or only the device of the cooking process that can be easily thought of from such information, natto satisfying both a sufficient texture and moderate hardness at the same time. It could not be manufactured.
An object of the present invention is to provide a natto having a texture that has a hardness (softness) preferred by consumers while realizing an appropriate flavor and appearance as natto, and a method for producing the same. is there.

As a result of intensive studies to solve the above problems, the present inventors have found the following means.
That is, in order to make natto having a moist texture, it was found out how much water-soluble pectin is appropriate to be contained in steamed natto or natto, and at the same time, water-soluble pectin The present inventors have found a method for keeping the hardness, which has an influence when the content is controlled, in an appropriate range.
As a result, by setting both the water-soluble pectin content and the hardness within a certain range, a new natto having both moderate hardness and a feeling of stickiness, which was achieved for the first time, was completed. Furthermore, it discovered also about the method of manufacturing this novel natto.

In addition, the time required to depressurize the steaming pot (depressurization time), which is an important factor for keeping the water-soluble pectin content and hardness in an appropriate range, also affects the color that is the basic quality of natto. And an appropriate depressurization time was also found.
The present inventors have found from experience values that the hardness of natto is preferably 0.18 to 0.68 N, and the lightness (L value) is preferably 35.6 to 43.
Based on these findings, the present invention has been completed.

That is, the first invention in the present invention is a method for producing natto, wherein in the soybean cooking step, the pressure in the kettle (gauge pressure) is 0.12 to 0.22 MPa, preferably 0.16 to 0.22 MPa. The water-soluble pectin content per gram of natto is 3 mg or more, preferably 3.5 mg or more, characterized in that the amount of steam input from 0 to 1 kg / kg after the raising and until the end of the cooking process is The present invention relates to a method for producing natto having a hardness of 0.18 to 0.68 N, preferably 0.28 to 0.48 N.
2nd invention is a manufacturing method of natto, Comprising: In a soybean cooking process, after raising the pressure in a kettle (gauge pressure) to 0.12-0.22MPa, Preferably 0.16-0.22MPa, The water-soluble pectin content per gram of natto is 3 mg or more, preferably 3.5 mg or more, and the hardness of natto is 0, characterized in that the amount of steam input until the end of the cooking process is 0 to 1 kg / kg. .18 to 0.68N, preferably 0.28 to 0.48N, and a method for producing natto having a lightness (L value) of natto of 35.6 to 43, preferably 38.6 to 41.5. .
In the third aspect of the present invention , the pressure in the kettle (gauge pressure) is increased to 0.12 to 0.22 MPa, preferably 0.16 to 0.22 MPa, and then 30 minutes to 90 minutes, preferably 50 to 70 minutes. The present invention relates to the method according to the first or second invention , wherein the gauge pressure is reduced to 0.05 MPa within a time period.
4th invention is related with the natto manufactured by the method in any one of 1st-3rd invention .

  ADVANTAGE OF THE INVENTION According to this invention, the novel natto which was not able to be achieved conventionally can be provided. Specifically, it is possible to provide a natto that has a texture (softness) and a texture that is preferred by consumers, while realizing an appropriate flavor and appearance as natto.

Hereinafter, the present invention will be described in detail.
In the present invention according to claim 1, the water-soluble pectin content per gram of natto is 3 mg or more, preferably 3.5 mg or more, and the hardness of natto is 0.18 to 0.68 N, preferably 0.28 to 0. It provides natto that is 48N. The natto of the present invention having such properties has a texture that is preferred by consumers, and at the same time has a softness suitable as natto.
In addition, the natto of the present invention has a lightness (L value) of 35.6 to 43, preferably 38.6 to 41.5, as described in claim 2. It is preferable because it is a preferred color.

The manufacturing method of the natto of this invention provided with this feature is demonstrated below.
There are no particular restrictions on the soybean as a natto raw material used in the present invention, and round soybeans, fine soybeans, half soybeans, defatted soybeans, etc. can be used, but the difference in hardness (softness) and glutinous feeling is easy to understand. Whole soybeans are preferable, and medium and large soybeans used for producing high-quality natto are particularly preferable. Moreover, even if these soybeans have been subjected to a drying treatment, they can be used as they are without being subjected to a drying treatment.
The raw material soybean is washed with water and then immersed in cold water according to a conventional method. For example, it is immersed in 5-20 degreeC cold water for 5 to 24 hours. The obtained soaked soybeans are transferred to a steaming pot and subjected to a steaming process.

As a process for producing natto of the present invention, there is a feature in the soybean cooking process, and for the other processes, basically a conventional natto production method may be adopted. An example of a conventional natto production method is: a soaking process in which raw soybeans absorb water, a soybean steaming process in which soybeans are steamed under pressure and then depressurized to normal pressure, a process in which soybeans are inoculated with natto, and a container is filled with soybeans. Product natto is obtained through the process and the fermentation process.
Therefore, after completion of the steaming step in the present invention, the desired natto can be obtained by inoculating and fermenting natto bacteria by a conventional method. In addition, Bacillus subtilis is not particularly limited as long as it is a bacterium that can be used for the production of natto. In addition to the common commercially available bacteria, Miyagino, Takahashi, and Naruse, their mutations In-house developed bacteria such as strains and genetically modified strains can also be used.

In the soybean steaming step in the method of the present invention, the steam input amount between the pressurization of the soaked soybean to a certain pressure (gauge pressure) and the end of the cooking step (that is, until the pressure is released to normal pressure) is a certain amount or less. As other conditions, the conditions of the steaming step in normal natto production can be adopted.
As the steaming pot used for soybean cooking, a high-pressure pot having a structure generally used for producing natto may be used.
Pressurized steaming is carried out by a conventional method in which pressurized steam is blown into a steamer containing soybeans. As the pressurized steam, a pressure used in a steaming process in a normal natto manufacturing method, for example, steam of about 0.4 to 0.6 MPa can be used. Note that the amount of pressurized steam blown at this time is not particularly limited, and an amount necessary for obtaining desired steaming conditions may be used.
Until the temperature in the steaming pot reaches about 100 ° C, in order to make the steam flow in the steaming pot uniform, the liquid discharge pipe usually provided at the bottom of the steaming pot is opened and the steamed soybean soup is used. Let it drain. Thus, until the temperature in the steaming pot reaches about 100 ° C., the steam flow in the steaming pot is usually made uniform over a period of about 10 to 20 minutes, preferably 15 to 20 minutes, Variation in the quality of steamed beans can be eliminated. When the temperature in the steaming pot reaches about 100 ° C., the valve of the liquid discharge pipe is closed and the blowing of pressurized steam is continued until the pressure (gauge pressure) and temperature in the pot reach a predetermined value.

In the present invention, as described in claim 3, the pressurized steam is continuously blown until the pressure in the hook (gauge pressure) reaches 0.12 MPa to 0.22 MPa, preferably 0.16 MPa to 0.22 MPa. . In the present invention, the maximum gauge pressure at this time is called steaming pressure. When the cooking pressure is lower than the lower limit, the softness is not sufficiently soft, that is, the hardness is 0.18 to 0.68 N, and the texture is not good. On the other hand, when the steaming pressure is higher than the upper limit value, it is not preferable because the steamed beans are peeled or crushed during the steaming process. In addition, a normal high-pressure kettle is equipped with a steam safety valve, and pressurization exceeding 0.22 MPa cannot be performed.
In addition, it is appropriate to blow in pressurized steam so that it may become 123 degreeC-135 degreeC as the temperature in a pot in this case, Preferably it is 128 degreeC-133 degreeC.

  After the gauge pressure reaches the predetermined value, in a general natto manufacturing process, a method is generally adopted in which the reached high pressure state is maintained for about 20 to 30 minutes in order to make the soybean hardness appropriate. ing. In order to maintain this high pressure state, it is necessary to put steam of 1.5 kg / kg or more into the steamer. Next, after maintaining the high pressure state for the above time, the valve of the above-mentioned liquid discharge pipe is opened and the pressure is released. In general, the depressurization is rapidly returned to normal pressure in about 5 to 20 minutes.

  On the other hand, the soybean cooking process of the present invention is characterized in that after increasing the gauge pressure to 0.12 to 0.22 MPa, depressurization is started immediately without holding the pressure. For this purpose, as described in claim 3, after the gauge pressure reaches a predetermined value, the amount of steam input between the start of depressurization and the return to normal pressure (that is, until the end of the cooking step) is reduced to 0. It is necessary to set it to ˜1 kg / 俵, preferably 0 to 0.5 kg / 俵. As described above, in order to maintain a high pressure state, a large amount of steam must be input. In the present invention, depressurization is performed by limiting the amount of steam input to a certain amount or less. .

In the present invention, as described in claim 4, after the pressure in the kettle (gauge pressure) is increased from 0.12 to 0.22 MPa, the gauge is increased to 0.05 MPa within 30 minutes to 90 minutes. It is preferable to reduce the pressure. Such control of the depressurization time (time required for depressurization) can be performed by adjusting the amount of steam input, the opening of the valve of the liquid discharge pipe, and the like.
When the pressure is rapidly released in a shorter time than 30 minutes, the soybean does not have a sufficient softness, that is, a hardness of 0.18 to 0.68 N, which is not preferable as natto. In addition, when the pressure is gradually reduced over 90 minutes, the steamed beans turn brown due to the chemical reaction between the protein and sugar, resulting in steamed beans that are unfavorable for natto.
In addition, after depressurizing to 0.05 MPa, until it returns to normal pressure, it hardly affects the hardness and hue of steamed beans.

The steamed beans obtained by the soybean steaming step contain 4 mg or more, preferably 4.5 mg or more of water-soluble pectin per gram.
The present invention according to claim 5 is a natto produced by a conventional method using the production method according to claim 3 or 4, that is, the steamed beans obtained through the soybean steaming step. As described in claims 1 and 2, the natto contains 3 mg or more, preferably 3.5 mg or more of water-soluble pectin per gram, and has a lightness (L value) of 35.6 to 43, preferably It is 38.6 to 41.5 and the hardness is 0.18 to 0.68N, preferably 0.28 to 0.48N. Such natto has a sticky texture, moderate softness, and has a favorable appearance and flavor as natto.

  Hereinafter, the present invention will be described with reference to examples and the like, but the present invention is not limited thereto.

Example 1
Here, the following test was carried out in order to determine the amount of steam to be introduced after the steaming pot internal pressure (gauge pressure) was raised and until the steaming process was completed until the pressure was released to normal pressure.
1000 kg of soaked soybeans prepared by immersing 450 kg (7.5 kg) of dried soybeans (very small soybeans) in cold water at 4 ° C. for 16 hours is placed in a steaming pot (Harada Sangyo Co., Ltd., Natto Automatic Small Steaming Pot). Steaming was performed while blowing 4 MPa pressurized steam. Until the temperature in the steaming pot reached about 100 ° C., the liquid discharge pipe provided at the bottom of the steaming pot was opened to discharge the steamed soybean soup. When the temperature in the kettle reached about 100 ° C., the valve of the liquid discharge pipe was closed, and the blowing of pressurized steam was continued, and the gauge pressure was adjusted to 0.18 MPa (about 131 ° C.) in about 5 minutes.
After the gauge pressure reached 0.18 MPa, the gauge pressure was depressurized to normal pressure while supplying a predetermined amount (0 to 2 kg / kg) of steam with respect to the weight of the steamed beans. At this time, while the pressure was released from 0.18 MPa to 0.05 MPa, the pressure was linearly released in 50 minutes by automatic control (PID control).
Further, the amount of steam input was calculated by forcibly opening the valve of the liquid discharge pipe and the steam pressure, flow rate, and valve opening.
About the obtained steamed beans, the water-soluble pectin content was analyzed.

Thereafter, natto was produced according to a conventional method. That is, after the steamed beans taken out from the steamer were transferred to a container, natto bacteria (Bacillus subtilis) were inoculated so that about 10 ⁴ natto bacteria per 1 g of steamed beans were obtained. Specifically, a Bacillus natto spore suspension of 10 ⁹ cells / ml concentration diluted to 10 ⁶ / ml in hot water (90 ° C.), was sprayed into the cooking beans so that the cell concentration of the , Stirred.
Next, about 50 g of steamed soybeans inoculated with natto bacteria were filled in styrene natto containers (tray) made of foamed polystyrene, and the upper surface of the tray was covered with a film, followed by fermentation at 40 ° C. for 18 hours. After completion of the fermentation, the tray was transferred to a refrigerated room, refrigerated and stored at 5 ° C. for 24 hours to produce natto.

The natto thus obtained was analyzed for water-soluble pectin content, hardness, and brightness, and sensory evaluation was conducted by 20 experienced panelists. In sensory evaluation, the texture (mochi-mochi) was evaluated in the following four stages, the hardness, color, and the state of the fungus film were evaluated in the following five stages, and the crushing state was evaluated in the following three stages.
In addition, the weight (g) and Brix (%) of the broth produced after the end of cooking were measured, and the weight of the eluted component (g) was calculated from Weight × Brix.

Texture (feeling of stickiness)
1: A texture that is crunchy and cracks when chewed
2: Soft, but watery, less textured
3: The skin and contents are uniformly soft and sticky (moist texture)
3+: Mochi-mochi texture is remarkable

Hardness
1: Remarkably hard and unsuitable as natto
2: Hard and unsuitable as natto
3: There is softness that feels crunchy
4: Soft and almost non-crisp
5: Too soft and unsuitable as natto

color
1: Remarkably dark and unsuitable as natto
2: Dark and unsuitable as natto
3: Appropriate brown color
4: Brown is light
5: Too bright and unsuitable as natto

Fungal membrane
1: There is very little
2: Partially recognized, but insufficient
3: Recognized over the entire surface, but slightly uneven
4: Spreads evenly across the entire surface
5: Thick and uniformly spread over the entire surface

Crush
1: Level that can be confirmed at first glance
2: Crushing is not recognized at first glance, but is a level that exists when you look closely.
3: No crushing is observed.

  The result of sensory evaluation is displayed as an average value of the panel, but 3 or 3+ is desirable for the texture (mochi-mochi feeling) that is determined to be preferable as a natto product by sensory evaluation. Also, the hardness is 3.0 to 4.0, preferably 3.5, the color is 3.0 to 4.0, preferably 3.5, the fungus membrane is 2.5 to 3.5, preferably Is 3.0. As for crushing, 2 or 3 is desirable.

  As for the hardness, 20 grains of natto were sampled and used for a hardness meter (made by Nidec Shinpo Co., Ltd.), and the force (Newton (N)) required for crushing natto was measured to obtain an average value. It shows that it is so hard that N value is large. The N value of commercially available natto is about 0.50 to 0.60.

  As for the brightness, 20 natto grains were collected, filled in a measurement cell, and subjected to a color difference meter (ColorReader CR-13, manufactured by Minolta) to measure the L value indicating the degree of brightness, and the average value was obtained. The larger the L value, the brighter it is. In addition, L value of commercial natto is about 35.0 to 38.0.

In addition, for determination of water-soluble pectin, ethyl alcohol was added to steamed natto or natto to a concentration of 70% or more, ground and filtered with a homogenizer, and dehydrated and dried with anhydrous alcohol by a conventional method to prepare a sample. . For the obtained dried samples, water-soluble pectin is extracted according to a conventional method (see Home Economics Journal, 26, 173, 1975, etc.), and uronic acid is analyzed by a carbazole correction method (see Anal. Biochem., 4, 330, 1962). By quantifying the amount, the water-soluble pectin was quantified. In order to obtain a chewy texture, the water-soluble pectin content is desirably 4 mg or more per 1 g of steamed beans and 3 mg or more per 1 g of natto.
The results are shown in Table 1.

As is clear from Table 1, the water-soluble pectin content decreased with increasing steam input, and the texture of natto was reduced. In particular, when it exceeds 1.5 kg / kg, the sticky feeling is reduced, and it tends to be soft, watery and less chewy.
In addition, steamed beans go through a fermentation process with natto bacteria, so that the water-soluble pectin content is reduced by about 1 mg / g, the steamed beans with a water-soluble pectin content of 4 mg / g or more, and 3 mg / g or more natto, It can be seen that it has a sticky texture.
In the conventional natto manufacturing technology, a steaming method is generally used in which the pressure is maintained while adding steam after raising the gauge pressure to about 0.15 to 0.2 MPa. In order to maintain this high-pressure state, it is necessary to throw in steam of 1.5 kg / kg or more, and for this reason, although it has an appropriate hardness, it is thought that the texture that it has is reduced.

  In addition, the sensory evaluation results of hardness and color did not change much like the analysis values of hardness and brightness, but the fungus membrane tends to become thicker when the steam input is 1.0 kg / 俵 or less. It was in. This means that if the amount of steam input in the steaming process is small, the elution of the nutrients into the broth (the weight of the elution components) is small, that is, the nutrients remain in the steamed beans and the growth of Bacillus natto is promoted. Is done. Therefore, it seems that the fungus film becomes thick and affects the texture of natto.

From the above, after increasing the gauge pressure to 0.18 MPa and then releasing the pressure to 0.05 MPa, the amount of water-soluble pectin per 1 g of steamed beans is 4 mg or more if the amount of steam input is 1 kg / kg or less. The water-soluble pectin content per gram of the finished natto was 3 mg or more, and it was found that the natto had a sticky feeling.
In addition, in the natto of all the steam input amounts in this example, hardness and lightness are appropriate values as natto, that is, hardness 0.18 to 0.68 (N), lightness (L value) 35.6 to 43 I found out that

(Example 2)
Here, the effects of steaming pressure and depressurization time (depressurization time) were examined.
In the steaming process using the soaked soybeans prepared in the same manner as in Example 1, blowing of pressurized steam was continued in the same manner as in Example 1, and the gauge pressure was increased to 0.1 to 0.22 MPa in about 5 minutes. . Further, after raising the gauge pressure to a predetermined value, control was performed to linearly depressurize to 0.05 MPa over 15 to 120 minutes without introducing steam. The depressurization time was controlled by adjusting the opening degree of the valve of the liquid discharge pipe at the bottom of the cooking pot. About the obtained steamed beans, natto was manufactured by the same method as Example 1 in any case.
The steamed beans and natto obtained by the above method were analyzed and sensory evaluated in the same manner as in Example 1. The results are shown in Table 2-1 and Table 2-2.

As is clear from the table, when the cooking pressure is 0.10 MPa, the soybeans are not sufficiently cooked in the cooking time of 30 to 90 minutes, the hardness exceeds 0.68 N, and the softness (hard Was not obtained. Further, since pectin was not water-solubilized due to insufficient steaming, the water-soluble pectin content of natto was less than 3 mg / g, and a satisfactory food texture (mochi-mochi) was not obtained.
In addition, when the cooking pressure is 0.10 MPa and 0.12 MPa, if the time for depressurization to 0.05 MPa is prolonged after reaching the final pressure, the cooking kettle will cool down. It was not approved.

  Moreover, in the case where the cooking pressure is 0.12 MPa and 0.22 MPa, when the depressurization time up to 0.05 MPa is 15 minutes, the soybean is not sufficiently cooked and the hardness exceeds 0.68 N, Satisfactory softness (hardness) was not obtained as natto. Furthermore, due to insufficient steaming, the water-soluble pectin content was also less than 3 mg / g, and a satisfactory texture was not obtained. From this result, it was found that the steaming pressure needs to be 0.12 MPa or more, and further, the time for depressurization to 0.05 MPa after reaching the pressure is required to be 30 minutes or more.

  In addition, when the steaming pressure is 0.18 MPa and 0.22 MPa, when the depressurization time up to 0.05 MPa is 120 minutes, the softness (hardness) and texture (mochi-mochi feeling) are satisfactory. However, the browning of natto progressed and the color became dark, which was not very preferable as the basic quality of natto. From this result, it was found that the time for depressurizing to 0.05 MPa is preferably within 90 minutes.

(Comparative example)
For comparison, tests were also conducted on steamed beans and natto obtained by a conventional steaming process in which the pressure was maintained after increasing the gauge pressure.
In other words, 1000 kg of soaked soybeans prepared by immersing 450 kg (7.5 kg) of dried soybeans (very small soybeans) in cold water at 4 ° C. for 16 hours is placed in a steamer (Harada Sangyo Co., Ltd., Natto Automatic Small Steamer). Then, steaming was performed while blowing pressurized steam of 0.4 MPa. Until the temperature in the steaming pot reached about 100 ° C., the liquid discharge pipe provided at the bottom of the steaming pot was opened to discharge the steamed soybean soup. When the temperature in the kettle reached about 100 ° C., the valve of the liquid discharge pipe was closed, and the blowing of pressurized steam was continued, and the gauge pressure was adjusted to 0.18 MPa (about 131 ° C.) in about 5 minutes. Then, after maintaining the pressure for about 20 minutes by introducing pressurized steam, the pressure was released to normal pressure in 10 minutes. About the obtained steamed beans, natto was manufactured by the same method as Example 1.

The steamed beans and natto obtained by the above method were analyzed and sensory evaluated in the same manner as in Example 1. The results are shown in Table 3.
From the table, the steamed beans and natto obtained by the conventional steaming process have the softness and appearance that are preferable as natto, but the water-soluble pectin content is as low as 2.68 mg / g, and a satisfactory texture ) Was not obtained.

  ADVANTAGE OF THE INVENTION According to this invention, the new natto which has both the feeling of being liked by consumers and moderate softness, and has a preferable external appearance and flavor as natto, and a method for producing the same can be provided. Therefore, the present invention can contribute to the food industry.

Claims (4)

This is a method for producing natto, and in the soybean steaming process, the steam input from 0 to 1 kg / kg after the steam pressure (gauge pressure) is increased to 0.12 to 0.22 MPa and the steaming process is completed. A method for producing natto, wherein the water-soluble pectin content per gram of natto is 3 mg or more and the hardness of natto is 0.18 to 0.68 N. This is a method for producing natto, and in the soybean steaming process, the steam input from 0 to 1 kg / kg after the steam pressure (gauge pressure) is increased to 0.12 to 0.22 MPa and the steaming process is completed. The water-soluble pectin content per gram of natto is 3 mg or more, the natto hardness is 0.18 to 0.68 N, and the lightness (L value) of natto is 35.6 to 43 A method of manufacturing a natto. After raising the kettle inside pressure (gauge pressure) until 0.12～0.22MPa, characterized in that lowering the gauge pressure to 0.05MPa at 30 minutes to 90 minutes of time, to claim 1 or 2 The method described. Natto manufactured by the method according to any one of claims 1 to 3 .