JPH04620B2 - - Google Patents

Description

[Detailed description of the invention]

[Object of the Invention] (Industrial Application Field) The present invention relates to a method for producing natto. (Prior art) In order to promote the smooth growth of natto bacteria in the currently commonly used warm air circulation type natto fermentation chamber, it is necessary to have high humidity conditions effectively and to It has been confirmed that evaporation of soybean moisture by increasing heat is necessary. The production of natto using wet straw can be said to be a method that fulfills this principle. Currently, PSP (Poly-styrene Paper) containers are most commonly used as natto fermentation containers placed in fermentation chambers. This PSP container is convenient for natto production, as well as being convenient for natto production, as it is lightweight, easy to process, has excellent heat retention in both hot and cold environments, is hygienic, and is relatively sturdy. It is very convenient to transport and handle at the stage, and it also has excellent preservability after purchase by consumers and can be used as a tableware substitute, making it a major contribution to expanding natto consumption. However, on the other hand, this PSP container has good ventilation and
Because it has poor moisture permeability, it is difficult for enzymes and moisture required in the natto manufacturing process to pass through, and it contains factors that inhibit the normal growth of natto bacteria. In other words, although it has excellent heat retention, it cannot control the increase in the fermentation heat of natto bacteria, which prevents water evaporation (dehumidification in the latter half of fermentation) as the product temperature rises, and condensation due to water condensation causes natto products to become watery. This can lead to stickiness due to bacteriolysis, which impairs shelf life. This is the reason why consumers are dissatisfied with the fact that they cannot obtain the same quality and flavor as Waratsuto natto. Some conventional PSP containers have thin needle holes in their lids, etc., but not only do they not provide sufficient air permeability and moisture permeability, but the surface of the natto inside is covered with a polyethylene film. In the end, there is no way to solve the above problems. (Problems to be Solved by the Invention) The present invention was made in light of the above-mentioned conventional circumstances in natto production.・Using a bag made of a highly moisture-permeable and water-resistant sheet, sufficient humidity is supplied from the outside of the container during the growth period of the natto bacteria, and the fermentation of the natto bacteria becomes active. We control the resulting rise in product temperature, and effectively dehumidify during the period when the water from the soybeans evaporates (in the second half of fermentation).
A production method has been established for producing natto that has a low moisture content, has a long shelf life, and has an excellent flavor. [Structure of the Invention] That is, the method for producing natto according to the present invention involves sealing steamed soybeans inoculated with natto bacteria in a bag 1 made of a waterproof sheet with high air permeability and moisture permeability, and fermenting the soybeans under high humidity. This method is characterized in that natto 2 is obtained using the method. (Example) An example will be explained below in order of process: (a) Raw soybeans: Pesticide-free soybeans from China (b) Raw material processing: After washing the soybeans with water, soak them in tap water overnight and drain them in a stainless steel wire mesh colander. I moved it and drained it for an hour. After that, leave it in a colander and steam it in a pressure cooker (steam pressure 1.3Kg/cm2 ⁾ for 8 minutes after reaching the pressure.
Simmer for 15 minutes over low heat. The target hardness of steamed soybeans was set to 120g or less. (c) Inoculation of natto bacteria: commercially available natto starter solution (3.9×10 ⁸
The diluted bacterial solution was adjusted to the order of 3.9×10 ³ cells/ml with sterilized water, and the diluted bacterial solution was injected into steamed soybeans to inoculate them with Bacillus natto. (d) Natto fermentation container: A roll of rayon paper was selected as a water-resistant sheet with high air permeability and moisture permeability, and this was cut and heat-sealed into a size of 10 x 15 cm to make bag body 1 (hereinafter referred to as " (Fig. 1). (e) Loading soybeans: 80g of soybeans inoculated with Bacillus natto were filled through the opening of a rayon paper bag and sealed with a heat seal (Figure 2). (f) Fermentation conditions: The filled rayon paper bags were placed in a stainless steel colander and placed on a shelf inside the natto fermenter. The temperature inside the tank was consistently set at 40°C, and fermentation was continued for 18 hours with continuous humidification. (G) Commercialization: After fermentation is complete, wrap the rayon paper bags in appropriate packaging materials, store them in a cool storage room to prevent the intrusion of germs, and then ship them sequentially with label tags, etc. (Analysis and investigation) Regarding the above manufacturing process, we conducted a comparison experiment with the case using a conventional PSP container (hereinafter referred to as the "control group"), analyzed and investigated, and found the following Table 1 (moisture, hardness) and Table 1. The results shown in Figure 2 (sensory examination), Figure 4 (temperature inside the fermenter and progress of product temperature), and Figure 5 (change of humidity inside the fermenter) were obtained.

[Table] In the table, when comparing the changes in moisture content, the natto in the control group has the same or higher moisture content than the steamed soybeans. On the other hand, the amount of natto produced by the method of the present invention is about 2% less than this. This difference becomes even larger because the inoculation of Bacillus natto liquid increases the moisture content of the steamed soybeans by about 3%. From this analysis result, the following was derived. In other words, the moisture content of natto in the control group using a PSP container and polyethylene film was 63.1% under continuous humidification conditions of 40℃, but the moisture content of natto according to the present invention using a rayon paper bag was 63.1% under continuous humidification conditions of 40℃ continuously. Under humidified conditions, natto 2 was obtained with a moisture content of 59.6%, which was considerably lower than the former. Due to the air permeability and moisture permeability properties of rayon paper, during the breeding period of Bacillus natto, sufficient oxygen and moisture close to the saturated state are effective in promoting the growth of Bacillus natto, and the activity of Bacillus natto becomes active. This is thought to be due to the effect of preventing the accumulation of heat by evaporating the moisture in the soybeans when the fermentation heat is generated. Next, Table 2 shows a comparison of the sensory characteristics of the control natto and the natto produced by the method of the present invention under the fermentation conditions of 18 hours at a constant temperature of 40° C. and continuous humidification in the above example.

[Table] Next, we used a self-recorder to compare and measure the room temperature in the fermenter, the temperature of the fermented soybeans, and the humidity in the tank during the fermentation period, and the results shown in Figures 4 and 5 were obtained. It was done. In other words, Figure 4 shows the room temperature inside the fermenter and the progress of product temperature in the case of 18-hour fermentation at a constant temperature of 40°C and continuous humidification.The room temperature was set at 40°C, but when humidified with a heating steam generator, it rose to about 42°C. rise to In the case of the control plot, as shown by the progress of E, the product temperature begins to rise around 7 hours after the start of fermentation, peaks at 52°C around 15 hours, and then decreases. On the other hand, in the method of the present invention, the temperature is shown by the curve A, which follows almost the same curve as at room temperature W. Furthermore, Fig. 5 shows the evolution of humidity in the fermenter during fermentation at a constant temperature of 40°C and continuous humidification for 18 hours. In other words, it turns on and off about 3 times an hour, 95
High humidity is maintained in the range of ~100% RH. In order to obtain the optimum fermentation conditions in the method of the present invention, the present inventor also conducted experiments using condition settings other than those in the above-mentioned examples. In other words, the temperature inside the fermenter was set at a constant temperature of 30°C, 40°C, 50°C, and a mountain-shaped temperature progression that reached a maximum temperature of 50°C. , fermentation of Bacillus natto does not occur normally,
There was a tendency for natto to settle poorly or to become unripe, resulting in natto that did not have a natto odor, had a green taste, and had an unpleasant flavor that was not refreshing. In the end, it was confirmed that the temperature setting of 40° C. to 45° C. in this example was the most desirable condition in terms of the tendency for room temperature and product temperature to be synchronized and the ease of product temperature control. In this example, a heating type steam generator is used to replenish moisture, so the room temperature is kept at 40°C.
If set to , the above optimal conditions will be obtained. Regarding humidity conditions, high humidity conditions close to 100% RH are effective in order to promote the smooth growth of natto bacteria; humidity below 80% will result in unfavorable results such as drying of natto. Regarding the relationship with temperature, a humidity close to 100% RH was obtained at a room temperature of around 40°C, but when the room temperature was raised to 50°C,
It turned out that it only reached about 70%RH. [Effects of the Invention] As described above, the method of the present invention uses an air-permeable and moisture-permeable water-resistant sheet as a packaging material, fills it with steamed soybeans and seals it, and then puts it on the fermentation process.
By consistently setting the minimum temperature condition and then continuously filling the fermentation with warm humidity throughout the entire fermentation period, and achieving a dehumidifying effect in the latter half of the fermentation, the moisture content of natto can be kept to a minimum, thereby making it possible for soybeans to grow. Shirako bites firmly into the natto, making it possible to produce flavorful natto with less stickiness. By suppressing the moisture content, natto can be provided with excellent shelf life.

[Brief explanation of drawings]

Figure 1 is a perspective view of a bag made of rayon paper used in the method of the present invention, Figure 2 is a perspective view of the same bag filled with steamed natto and sealed, and Figure 3 is a bag opened after fermentation. FIG. 4 is a graph showing the progress of the room temperature in the fermenter and the temperature of the fermented natto product during the fermentation process; FIG. 5 is a graph showing the progress of the humidity in the fermenter. 1...Bag body made of water-resistant sheet with high breathability and moisture permeability, 2...Natto.

Claims (1)

[Scope of Claims] 1. A method for producing natto, which is characterized in that steamed soybeans inoculated with Bacillus natto are sealed in a bag made of a water-resistant sheet with high air permeability and moisture permeability, and fermented under high humidity. . 2. The method for producing natto according to claim 1, wherein the material of the bag body made of a waterproof sheet is rayon paper.