JPH0387157A - Production of natto (fermented soybean) - Google Patents

Abstract

PURPOSE:To obtain the title NATTO having improved qualities and flavor without fear of contamination with various germs by previously culturing Bacillus natto in a fermentation tank, subjecting to autodigestion to give an autodigestion solution of cell of Bacillus natto and sprinkling the solution upon boiled soybeans. CONSTITUTION:Bacillus natto is previously cultured in a fermentation tank separately, subjected to autodigestion to give an autodigestion solution of Bacillus natto, which is optionally concentrated, a crude enzyme solution of the Bacillus natto is sprinkled on boiled soybeans, then the soybeans are packed into a container. The container is stored in a fermentation chamber, enzyme of Bacillus natto is permeated into texture of the boiled soybeans and enzyme reaction is caused from the beginning of the fermentation process to give the objective NATTO. The boiled soybeans are preferably sprinkled with a complex enzyme solution prepared by blending the crude enzyme solution of the Bacillus natto with a crude enzyme solution derived from a microorganism except Bacillus natto or any of various kinds of enzyme agents.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for producing natto using a natto fermentation method.

(Prior Art) Natto is conventionally generally produced by a process as shown in FIG. That is, raw soybeans are carefully selected, washed, thoroughly soaked in water, drained, and steamed at a high pressure of 1.5 to 2.
The soybeans are steamed at 0 Kg/cm2 for 30 to 50 minutes, and then a bacterial solution prepared by diluting a spore suspension, usually called Bacillus natto, with sterilized water is spray inoculated onto the steamed soybeans. The amount of inoculation is usually 100 to 500 spores per gram of steamed soybeans.

Germination of the spores is promoted by heat shock, and the inoculated steamed soybeans are quickly filled into containers to prevent bacterial contamination.These containers are generally stored in plastic containers, and the containers are stacked and stored in a fermentation room. The fermentation chamber was set at a room temperature of around 40°C and a humidity of around 90%, and during fermentation, the fermentation was guided by a computer control panel that set the best fermentation conditions as shown in Figure 3, and the fermentation was completed in 16 to 18 hours.
After being forcedly cooled and packaged, it is cooled again and is ready for shipment.

The above is an overview of conventional natto manufacturing methods, and the details of the fermentation process, which is particularly involved in producing the flavor of natto, are as follows.

The inoculated natto that has been drawn into the fermentation chamber is cooled to around 40°C, which is the optimum temperature for the growth of natto bacteria, and then the product temperature is maintained at around 40°C.

The inoculated spores germinate within 2 hours after inoculation, producing vegetative cells, and thereafter cell division occurs about once every 30 minutes to proliferate. This period is called the lag period, but if division continues like this, it will enter the logarithmic phase from around the 8th hour, and the production of fermentation heat will gradually increase and the product temperature will rise and fall, exceeding 506C at around 12:00. Enters the stationary phase.

During this period, the fungal moss on the surface of soybeans becomes quite thick, and the production of mucilage peculiar to natto increases, but due to continued high temperatures, bacterial growth slows down, and natto bacterial cells begin to form spores and gradually self-digest. When the cell membrane is dissolved, the enzymes inside the bacteria are also dispersed on the surface of the soybean, and the soybean enters the death phase.

The metabolic heat of fermentation gradually decreases, and the remaining time until it is taken out of the room is cooled for after-ripening, and forced cooling is further performed to reduce enzyme activity.

Through this fermentation, more than 50% of the protein in natto becomes water-soluble nitrogen compounds in a short period of around 16 hours.
Approximately 50% of the fermented food is broken down to acnoic acids, and compared to other fermented foods, it becomes a product in an extremely short time.

However, if the fermentation is poorly controlled, the deacrification reaction in which the produced acetic acid is further decomposed progresses, and ammonia nitrogen is produced. becomes unfit for consumption.

(Problems to be Solved by the Invention) As mentioned above, natto production involves growing a bacterium called Bacillus natto, which has a short life cycle, on the surface of steamed soybeans, producing a large amount of acetic acid without producing ammonia, and ripening the soybean. There must be. It is generally accepted that it is a fermented food that matures for an extremely short period of time. However, if you want to produce natto with a richer taste, that is, natto with more advanced protein decomposition and a higher amount of free atomic acids, you can produce natto that has a higher level of protein decomposition and has a higher amount of free atomized acids. To this end, fermentation methods must be used to promote the decomposition of amino acids.

To achieve this, it is usually necessary to perform long-term fermentation at low temperatures to allow enzymes to penetrate slowly and to perform enzyme action.

When the inventor tasted the natto that he had left in the refrigerator and forgotten about after 45 days, he was surprised that there was no generation of ammonia or tyrosine crystals, and the rich taste, and he continued to eat it after that. The reproducibility was confirmed.

The reason for the production of this deep flavor is that sufficient numbers of Bacillus natto are grown on the surface of soybeans until the stationary period, and the extracellular enzymes produced so far and the autolysis of Bacillus natto that occurs from this stage are used to spread the soybean surface. Dispersed internal enzyme molecules slowly penetrate into the tissue of the steamed soybean, and the enzymatic reaction gradually progresses in the low-temperature environment provided after the death stage, increasing the release rate of acenoic acid. We obtained the knowledge that

In this case, since the temperature is kept low, the de-atomization reaction does not proceed, resulting in the production of natto with a deep flavor without the generation of ammonia.

Looking back, as mentioned above, natto production involves one day of fermentation, followed by about one day of ripening and refrigeration before shipping, and the factory equipment is commensurate with this scale, so it takes such a long time. It is difficult to ferment and improve.

The present invention was made in view of the above circumstances, and aims to improve the conventional natto manufacturing method.

(Means for Solving the Problems) The present invention is directed to the natto fermentation method during the natto production process, in which natto bacteria is cultured in a separate culture tank in advance, and the natto bacteria autolyzed solution is produced by an autolysis method. and a crude enzyme solution produced by concentrating this as necessary, or a crude enzyme solution produced from microorganisms other than Bacillus natto, or a composite crude enzyme mixed with various enzyme agents such as protease, acrylase, and cellulase. A sufficient amount of the solution is sprayed on the surface of the steamed soybeans, and from the start of fermentation, the enzyme molecules immediately permeate from the surface of the soybeans, penetrating the center of the soybeans and promoting fermentation. To produce natto with excellent quality and rich flavor within a time.

(Effects) In the conventional fermentation method for producing natto, after inoculating the fermented soybeans with Bacillus natto, the stationary phase is reached after about 12 hours have elapsed due to the above-mentioned lag phase and logarithmic phase. On the other hand, according to the present invention, the cultivation, proliferation, and enzyme production steps of Bacillus natto or other bacteria are performed in advance in a culture tank, so the conventional steps corresponding to the lag phase and logarithmic phase are omitted.
Fermentation begins when the crude enzyme solution or composite crude enzyme solution is sprayed onto the steamed soybeans and the enzyme directly diffuses and permeates into the steamed soybeans, so sufficient fermentation and ripening can be achieved within the conventional manufacturing process time.

In addition, in the conventional method, Bacillus natto is directly inoculated into steamed soybeans, and the steamed soybeans serve as a direct medium. In contrast, according to the present invention, the culture of Bacillus natto is carried out in a separate fermenter, and there is no need to worry about deficiencies. Incidentally, components such as carbohydrates can be supplemented at the stage of preparing the culture medium raw materials, so it is possible to improve the overall quality and taste. In addition, various enzymes with different characteristics can be used to reinforce the Bacillus natto enzyme and also to replace the Bacillus natto enzyme, so overall quality can be improved and natto with different taste characteristics can be produced. It becomes possible.

Furthermore, conventionally, after inoculating Bacillus natto, it was cultured in an open container and there was a risk of contamination with bacteria, but Bacillus natto can be separately cultured in a pure manner, thereby avoiding contamination with bacteria. I can do it.

(Example) FIG. 1 is a flowchart showing the natto manufacturing method according to the present invention.

In the example shown here, Bacillus natto that has been purified and isolated on an agar medium in a veterinary dish 1 is cultured and stored in a test tube 2, and during production, cultured with shaking in a flask 3 to measure the growth.

The grown Bacillus natto is transplanted to the culture tank 4 and continues to be cultured.

In this culture tank 4, a sterile liquid medium is prepared.

The medium raw materials used are soybean powder, protein, anoic acids, sugars, organic bases, inorganic salts, Vitakun, etc. that are suitable for breeding natto bacteria and enzyme production, and these are placed in medium raw material tanks 5 and 5, respectively.
The medium is then transferred to the culture medium adjustment tank 6 where it is mixed and sterilized, and then supplied to the culture tank 4 which has been sterilized in advance.

Since Bacillus natto is an aerobic bacterium, stirring culture is usually performed, and the culture medium in the fermenter 4 is stirred by a motor 7, and sterile air is supplied into the tank 4 by a compressor 8 via a sterilizing filter 9. The above-mentioned Bacillus natto culture and the culture medium in the fermentation tank 4 are maintained at an appropriate temperature for culturing Bacillus natto by a heating coil using steam from the boiler 10 and a cooling coil using a refrigerator. The temperature conditions of the culture medium in the culture tank 4 are made variable, and gas is supplied and exhausted to make the culture conditions variable, and if necessary, fermentation metabolic gases in the culture tank are measured using a mass spectrometer. Concentrated culture may be performed by measuring and adding a medium.

In this manner, Bacillus natto is cultured in the culture tank 4, and the culture time is 20 to 30 hours in the example, but can be varied.

Next, the temperature of the medium in culture tank 4 is increased from about 40°C to about 55°C.
The temperature is raised to °C to promote autolysis of Bacillus natto. This will be completed in about 3 hours.

As described above, Bacillus natto is cultured in the culture tank 4 and allowed to self-digest. A natto bacteria autolysed solution is obtained by culturing and autolyzing only Bacillus natto, and if necessary, it is concentrated by filtration 14 and vacuum drying 15 to obtain a Bacillus natto crude enzyme solution having the required titer.

On the other hand, as shown in FIG. 2, a culture tank 4 may be provided separately to culture microorganisms other than Bacillus natto, and this may be used in place of Bacillus natto. As microorganisms other than Bacillus natto, Bacillus subtilis (B, 5ubl 1l
is), Aspergillus aspergillus (Asp, 01yze), black koji (Asp)
, n-iger), (Rhizopu
s), etc., but each crude enzyme solution can be obtained by culturing according to the characteristics of each. Although Bacillus natto crude enzyme solution is used in this example, it may also be a crude enzyme solution of other microorganisms or a composite crude enzyme solution obtained by adding an enzyme preparation to this.
By appropriately selecting these, it becomes possible to produce natto that satisfies the desired quality and taste.

On the other hand, soybeans undergo the conventional process to obtain steamed soybeans.

That is, raw soybeans are carefully selected and washed, immersed in water in a dipping tank 11, drained, and steamed in a high-pressure steamer 12 to obtain steamed soybeans.

The steamed soybeans are then quickly cooled down to a temperature of about 60'C, and the Bacillus natto crude enzyme solution is sprayed to avoid deactivation of the enzyme, which is then filled into a container and drawn into a fermentation chamber, where the fermentation process begins. to do. For spraying the solution onto the steamed soybeans, the conventional natto bacteria spraying device 13 can be used. Furthermore, the fermentation itself in the fermentation chamber may also be carried out using conventional patterns. However, in the case of the present invention, the lag phase and logarithmic phase, which were performed in the conventional method, are unnecessary, so fermentation starts from the stationary phase of the conventional method.

In Figure 3, a indicates the temperature of the fermented soybean at 50% by heating and cooling control device in the fermentation room after spraying the Bacillus natto crude enzyme solution onto the steamed soybeans.
The temperature was maintained at °C for 4 to 5 hours to ensure sufficient penetration of the enzyme into the soybean fibers, enzyme action, and production of mucilage.After that, maintain the optimal temperature required depending on the product and continue cooling for 18 hours.
Let the temperature drop to around 5°C to mature. b is 500C
After maintaining the temperature for 4 to 5 hours, the temperature is brought to about 15°C for 3 hours, maintained at this temperature for 24 hours, and then lowered to around 5°C over 3 hours for ripening. As a result of producing in this way, we have seen the emergence of natto with more flavor than conventional products in a conventional time.

[Brief explanation of drawings]

1 and 2 are flowcharts showing the natto manufacturing method according to the present invention, and FIG. 3 is a diagram of fermentation temperature control according to the method,
FIG. 4 is a process diagram showing a conventional natto manufacturing method, and FIG. 5 is a fermentation temperature control diagram according to the conventional method.

Claims (3)

[Claims] (1) In the natto fermentation method during the natto production process, natto bacteria is cultured in advance in a separate fermenter and self-digested to obtain a natto bacteria autolysed liquid, which is concentrated as necessary and the natto bacteria crude The method is characterized in that an enzyme solution is sprayed on the steamed soybeans, and then the soybeans are filled into a container and drawn into a fermentation chamber, allowing the Bacillus natto enzyme to penetrate into the steamed soybean tissue and cause an enzyme reaction from the start of the fermentation process. Natto manufacturing method. (2) In the natto fermentation method during the natto production process, Bacillus natto is cultured in a separate fermenter in advance and self-digested to obtain a natto cell autolysed liquid, which is concentrated as necessary to obtain the crude Bacillus natto. A composite enzyme solution obtained by adding a crude enzyme solution originating from microorganisms other than Bacillus natto or various enzyme agents to the enzyme solution is sprayed on the steamed soybeans, and then the soybeans are filled into a container and placed in a fermentation chamber. A method for producing natto, which comprises infiltrating the steamed soybean tissue with Bacillus natto enzymes and enzymes produced by microorganisms other than Bacillus natto from the start of the fermentation process and causing an enzymatic reaction. (3) In the natto fermentation method during the natto production process, a crude enzyme solution originating from microorganisms other than Bacillus natto is obtained in advance in a separate fermenter, and various enzyme agents are added to this as necessary to obtain a complex enzyme. Spraying the liquid on the steamed soybeans, then filling the soybeans into a container and drawing them into a fermentation chamber, allowing enzymes produced by microorganisms other than Bacillus natto to penetrate into the tissue of the steamed soybeans and cause an enzyme reaction from the start of the fermentation process. A natto manufacturing method characterized by