JP2000116375A - Production of koji - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain koji (melt) for production of fermented food, fermented beverage or the like, hardly causing pollution due to microorganisms by using the cereals obtained by immersing cereals into water in the presence of lactobacillus having niacin-producing ability and denaturing the cereals according to an ordinary method and using the product as a koji substrate. SOLUTION: Cereals such as de-fatted soybeans are added to the water to which a lactobacillus suspension prepared by inoculating the lactobacillus having niacin-producing ability (e.g. Lactococcus lactis ATCC11454) into a medium and culturing the lactobacillus is added, and the cereals are immersed in the solution at 15-35 deg.C for 10-50 hr and excess water is filtered and the immersed cereals are boiled and cooled to <=40 deg.C and mixed with cereals such as wheat baked and crushed according to an ordinary method. The prepared denatured cereals are used as a koji substrate to readily provide the objective koji useful for production of high-quality fermented food, fermented beverage, or the like, not causing pollution due to microorganisms and excellent in quality.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing koji, and more particularly to a method for producing koji with less microbial contamination.

[0002]

2. Description of the Related Art The quality of fermented foods and beverages produced using koji greatly depends on the quality of koji used. In particular, in the brewing of miso, soy sauce and sake, etc., generally, cereals used as a raw material are immersed in water, swelled, heat-denatured, and then used as a substrate for koji.The heat-denatured cereals are suitable for microorganisms. Since it is a nutrient source, it is easily contaminated by contaminating microorganisms (hereinafter, also referred to as contaminating bacteria) such as bacteria of the genus Bacillus and genus Lactobacillus during the production of koji. Contamination by these microorganisms not only inhibits the growth of koji mold during koji making, but also causes contamination of contaminating microorganisms in the product and significantly reduces the taste and aroma of the product.

Recently, bacteriocin (such as nisin) produced by lactic acid bacteria attracts attention as an antibacterial substance having high antibacterial properties, being stable, safe for humans, and having excellent properties such as not affecting the quality of food. It has been. And
Food preservatives using bacteriocin produced by the lactic acid bacteria in combination with organic acids, amino acids, peptides or proteins, carbohydrates, alcohols and the like (see JP-A-7-39335) have been proposed.

In the production of koji, a koji substrate (eg, a filamentous fungus of the genus Aspergillus) and a lactic acid bacterium having a bacteriocin-producing ability are inoculated on a substrate of the koji, and the koji mold and the lactic acid bacterium are simultaneously grown to produce the bacteriocin produced by the lactic acid bacterium. Thus, a method for suppressing the growth of contaminating microorganisms has been studied. However, according to this method, the growth of lactic acid bacteria is greatly affected by the type of koji, the effect of the moisture of the koji substrate, and the like, and the growth inhibitory effect of the contaminated microorganisms cannot be obtained. There is a disadvantage that the growth is also inhibited and it is not possible to obtain an excellent quality koji.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for suppressing the growth of contaminating microorganisms in koji using bacteriocin produced by lactic acid bacteria, without the above-mentioned drawbacks, It is an object of the present invention to provide a method for producing koji having a small amount and good quality.

[0006]

Means for Solving the Problems The present inventors have conducted various studies to solve the above problems, and as a result, immersed cereals as a raw material for koji in the presence of lactic acid bacteria capable of producing nisin. It has been found that koji can be produced with less microbial contamination by performing koji production using a treated cereal obtained by heat denaturation of koji as a koji substrate by a conventional method, and completed the present invention. That is, the present invention is a method for producing koji, comprising immersing cereals in water in the presence of a lactic acid bacterium having a nisin-producing ability, and using, as a substrate, cereals obtained by heating and denaturing the cereals by a conventional method. .

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Koji is a so-called koji mold, for example, a yellow koji mold used for the production of soy sauce, miso, soy sauce, etc. [Aspergillus oryzae] )], Black koji mold used in the production of shochu [Aspergillus awamori (Asp.
ergillus awamori), white koji mold (Aspergillus kawachii), and koji mold (Aspergillus sja) used in the production of soy sauce.
e)) This is a culture obtained by adding microorganisms such as seed koji and culturing them. Koji is produced by the action of enzymes produced in koji.
The raw material is decomposed and used for the production of various fermented beverages and fermented foods.

[0008] Grains used in the present invention include rice, wheat,
Examples include millet, potato, soybean, red bean, corn, peas, and the like. These may be used as they are, but refined ones can also be used.

In order to carry out the present invention, first, grains used for the production of koji are immersed in water in the presence of lactic acid bacteria capable of producing nisin. The lactic acid bacterium having nisin-producing ability used here may be any lactic acid bacterium as long as it has nisin-producing ability.
Lactococcus lactis ATCC11454
And so on. The amount of lactic acid bacteria added to the immersion water varies depending on the type of cereal used, but generally the number of bacteria in the immersion water is 10 ² / ml or more, preferably 10 ² / ml.
^It is preferable that the concentration be ³ to 10 ⁷ / ml. When the number of the added lactic acid bacteria is smaller than the above number, the growth of the lactic acid bacteria during immersion in water becomes insufficient, and as a result, sufficient nisin is not generated to suppress the growth of the contaminating bacteria. No effect can be obtained. In order to obtain the desired effect, the water immersion time must be further extended.

The water immersion is performed at a temperature of 15 to 35 ° C. and the number of lactic acid bacteria capable of producing nisin in the immersion water is 10 ⁸ / ml.
It is preferable to carry out the reaction for a time sufficient for the above, for example, 10 to 50 hours. When the water immersion temperature is 15 ° C. or lower, the growth of lactic acid bacteria becomes slow, and it becomes difficult to obtain the effect of suppressing the growth of the obtained cereal contaminating bacteria.
When the temperature is higher than or equal to ° C., the components of the cereal are eluted in the immersion water, so that the raw material utilization rate is reduced and the growth of lactic acid bacteria is also suppressed.

Next, the grains soaked in water are denatured by heating by a conventional method such as steaming. The conditions such as pressure and temperature in the steaming treatment at the time of heat denaturation vary depending on the type of immersed cereals and koji used, but are arbitrary conditions, for example, 0.5 to 3 hours under no pressure, and a shorter time under pressure. Can be processed. If necessary, the raw cereals can be heat-denatured, and then the denatured cereals can be immersed in water in the presence of the lactic acid bacteria.

The added lactic acid bacteria are killed by the heat treatment, but the nisin produced during the water immersion is not destroyed by the heat treatment and remains stably in the cereals after the heat treatment. .

The heat-modified cereals (hereinafter referred to as treated cereals) are cooled to 20 to 40 ° C. To this koji substrate, a seed koji suitable for the purpose of the fermented product is added, and the koji mold is grown by a conventional method, for example, at a temperature of 20 to 40 ° C. At the same time, the moisture and temperature of the koji can be controlled, and the desired koji can be obtained. The method of the present invention can be effectively used in the production of liquid koji as well as the production of solid koji.

As a specific example of koji making, in the case of koji making of sake brewing using, for example, Aspergillus oryzae, lactic acid bacteria having nisin-producing ability are added to immersion water when polished rice is immersed in water. Then, after immersion for a certain time, heat denaturation treatment is performed to obtain steamed rice. The obtained steamed rice contains nisin generated by lactic acid bacteria added during immersion in water, and has the ability to strongly inhibit the growth of contaminating microorganisms by nisin. After cooling this steamed rice to around 35 ° C,
About 100 g of sake koji is added per 100 kg of white rice, mixed well, and usually left at 31 to 35 ° C. for about 10 hours. Next, rub this (return), and then
After elapse of 20 to 25 hours, the koji lid is divided (heavy), and then, after 6 to 8 hours, stirring (intermediate work) is performed.
Eight hours later, after stirring (finish work) again, 6-8
Over time, it is possible to produce a desired koji, which is made into koji and has less contaminating microorganisms.

The koji according to the present invention thus obtained is immersed in water without adding the above-mentioned lactic acid bacteria, and compared with the koji obtained using heat-denatured cereals, Bacillus (Bacillus).
There are few contaminating microorganisms such as bacteria belonging to the genus illus, bacteria belonging to the genus Lactobacillus and bacteria belonging to the genus Micrococcus, and the quality is good. By using the koji obtained according to the present invention, a fermented product of excellent quality can be obtained.

[0016]

EXAMPLES The present invention will be described more specifically with reference to the following examples. However, the technical scope of the present invention is not limited by these examples. [Example 1] (Production of soy sauce koji) Lactic acid bacteria [Lactococcus lactis ATCC11 having nisin-producing ability in advance]
454] was inoculated into 200 ml of MRS medium (manufactured by Difco), cultured at 30 ° C. for 22 hours, and suspended in a lactic acid bacterium (3 cells).
× 10 ⁸ / ml). Raw material defatted soybeans 1 in 300g
800 ml of water was added, and left at 30 ° C. for 16 hours to perform a dipping treatment. In the immersion treatment, in the present invention section A, the lactic acid bacteria suspension was added to the immersion water at 1%, and in the present invention section B, the lactic acid bacteria suspension was added at 3%. The section subjected to the immersion treatment without adding the lactic acid bacteria suspension was used as a control. For each section, after immersion in water, excess water was removed by filtration, and the immersed soybeans were steamed at 100 ° C. for 60 minutes and cooled to 40 ° C. or lower. Next, a commercially available soy sauce seed koji was added to a koji substrate obtained by mixing the obtained steamed beans and roasted and cracked wheat at a ratio of 55:45 by a conventional method, to obtain a koji substrate of 0.1 to 0%. 0.3% (% by weight) was added, mixed well, incorporated into a koji lid, and cultured. Simultaneously with the addition of the seed koji, Bacillus subtilis NISL4025 was added as a contaminating microorganism to the substrate of each experimental plot.
It was added so that the bacterial amount was 9 × 10 ⁵ / g. afterwards,
The temperature of the koji substrate is kept at 25 to 30 ° C. to grow the koji mold.
After 42 hours, the koji making was completed, and the koji was made.

For each of the experimental plots, the koji at the time of first trimming, the second trimming, and the start of koji were sampled, and the number of contaminating microorganisms in the koji was measured. Table 1 shows an example of the measurement results of the number of contaminating bacteria per gram of koji.

[0018]

Table 1 Koji-making time Control section Invention section A Invention section B Inclusion (0 hour) 4.9 × 10 ⁵ 4.9 × 10 ⁵ 4.9 × 10 ⁵ First care (17 hours) 4.5 × 10 ⁹ 4.4 × 10 ⁵ 3.7 × 10 ⁴ 2nd maintenance (23 hours) 9.3 × 10 ⁹ 1.6 × 10 ⁷ 4.3 × 10 ⁵ Outer koji (42 hours) 2.9 × 10 ⁸ 5.3 × 10 ⁵ 1.3 × 10 ^{5 From} Table 1, it can be seen that the number of contaminated microorganisms increased about 10 ² to 10 ³ times in the control plot when the koji was made. On the other hand, in the present invention section A (1% lactic acid bacteria suspension added) and the present invention section B (3% lactic acid bacteria suspension added), the number of the contaminated microorganisms hardly increased or decreased. Thus, according to the method of the present invention, it was found that the growth of contaminating microorganisms was significantly suppressed. Further, the koji in the control plot showed a strong contaminated odor (natto odor) due to the contaminating microorganisms, whereas the koji in the plot of the present invention A or the plot of the present invention B showed no organoleptic odor and was also organoleptically excellent. It was koji. That is, by using the method of the present invention in soy sauce brewing, it was possible to produce high-quality koji with less microbial contamination. [Example 2] (Production of sake koji) Here, evaluation was performed by a laboratory-level koji production experiment in which actual production of koji was simplified. A lactic acid bacterium [Lactococcus lactis (L
actococcus lactis) ATCC11454] was inoculated into 20 ml of MRS medium (manufactured by Difco) and cultured at 30 ° C. for 24 hours to obtain a lactic acid bacteria suspension (5 × 10 ⁸ / ml). For each experimental plot shown below,
g was washed with water, water was added to the washed rice so that the final volume became 400 ml, and the rice was left at 30 ° C. for 18 hours to perform a water immersion treatment. In this water immersion treatment, in the present invention section, 0.25 ml of the lactic acid bacteria suspension was added. A section subjected to the same water immersion treatment without adding the lactic acid bacteria suspension was used as a control section. Each section was drained, and after 1 hour, steamed at 100 ° C. for 40 minutes and allowed to cool to 40 ° C. or lower to obtain steamed rice.

Next, for each section, the steamed rice obtained was spread on a dish, and 85 mg of a commercially available sake seed koji was inoculated per dish to start koji making. As contaminating microorganism, Bacillus (B
acillus) bacteria in a nutrient broth medium
Extract 0.3%, Polypeptone 0.5%, Salt 0.8
%, PH 7.3) A culture solution cultured in 10 ml for 16 hours was used. At the same time as the above seed koji addition,
0.5 ml of the culture was inoculated so that the number of bacteria per 1 g of koji was 2.5 × 10 ⁵ . A constant temperature and humidity chamber (made by Futaba Kagaku Co., Ltd.) to perform koji making under certain conditions (temperature and humidity)
The following experiment was performed using. On the first day, the temperature is 35
The cells were cultured at a temperature of 95 ° C. and a humidity of 95%, and were cared for 24 hours later. Furthermore, the temperature was kept at 35 ° C., the humidity was reduced to 90%, the culture was continued for 18 hours, and the resulting koji was made (42 hours from the start of koji making).

In each of the experimental plots, sampling was performed at the time of care and dekoji, and the number of Bacillus bacteria contained in the koji was measured by a dilution plate method. Play
A nutrient agar medium (manufactured by Difco) was used as the culture medium. Table 2 shows an example of the measurement results of the number of contaminating bacteria per gram of koji.

[0021]

[Table 2] Koji making time Control section The present invention section At the start of koji making (0 hour) 2.5 × 10 ⁵ 2.5 × 10 ^{5 At} care (24 hours) 1.3 × 10 ⁷ 2.8 × 10 ⁵ At the time of koji start (42 hours) 5.6 × 10 ⁵ 8.5 × 10 ⁴ As can be seen from Table 2, the number of contaminated microorganisms increased about 100 times in the control group at the time of care, compared to the start of koji production. On the other hand, in the koji of the present invention group, the number of the added contaminating microorganisms hardly increased. Also, at the time of dekoji,
In any of the experimental plots, the number of added contaminating microorganisms was reduced as compared to the time of care, but the koji of the present invention group had a smaller number of added contaminated microorganisms than the control plot, and even in sake brewing, According to the method of the present invention, koji with less microbial contamination could be produced.

[0022]

According to the present invention, microbial contamination is reduced.
It is possible to easily obtain a koji excellent in quality, and by using the koji, it is possible to expect production of high-quality fermented foods and beverages.

Claims (2)

[Claims] 1. A method for producing koji, comprising immersing cereals in water in the presence of a lactic acid bacterium capable of producing nisin and subjecting the cereals to heat denaturation by a conventional method to use the cereals as a koji substrate. 2. The condition of immersion of cereals in water at 15 to 35 ° C.
The method for producing koji according to claim 1, which is performed for 0 to 10 hours.