SOY AND RELATED FERMENTATIONS. V 
SHOYU-KOJI. 
Ripening. 
After the beans and wheat are thoroughly mixed, a very small 
quantity of previously molded material, such as mature rice koji 
(tane-koji), some shoyu-koji, or a pure mold culture, is thoroughly 
mixed into the ingredients. The whole mass is then distributed in the 
small flat koji trays (PL II) which are immediately placed in the 
koji fermentation room before they cool further. Each tray holds 
about 1.8 liters, or about 2 quarts, of raw material. The koji 
trays are placed in tiers along the wall of the room. (Fig. 3.) 
Unless provided with little legs, they are not placed closely over 
one another but in a zigzag fashion, so that there is free space 
between each tray and the next. The favorable aeration thus se- 
cured is extremely important in shoyu-koji fermentation because 
moisture and the lack of oxygen induce the development of mucors 
and bacteria, and are said to cause the diastatic enzyme to develop 
at the expense of the proteolytic enzyme. 
In some localities in Japan no such trays are used, but a broad 
straw mat with which very good koji can be secured. The mat may 
be as large as or larger in area than the tray and the immature koji 
is spread on it to the same depth as on the tray. 
If the trays have been previously used to produce clean molded 
material for shoyu, no further inoculation than that to be obtained 
from the spores already on the trays is necessary. When koji trays 
are used over again without being washed or disinfected, they should 
be carefully wiped with dry cotton or clean waste of some kind in 
order to remove small masses of koji or heavy spore inoculation. 
Otherwise, the fresh koji will be too heavily inoculated with spore 
material. 
After the ingredients of the koji have been distributed in the 
koji trays, they are leveled to the depth of 3 \ centimeters, or \\ 
inches, or they may be heaped in one pile in such a manner that 
they do not touch the sides of the tray. Piling the beans is a good 
method when the temperature is slightly low, but care should be 
taken not to pile them to a depth of over 4 centimeters. A deeper 
pile heats excessively. Overheating is usually brought about by the 
development of undesirable bacteria, which by their rapid growth 
increase the condensation of moisture. Further bacterial activity 
is fostered by this condition. 
The koji room or compartment is kept at a temperature of 24° to 
25° C, with a definite humidity. The temperature of the koji is at 
the start between 24° and 28° C, if the mixing has not been too 
greatly delayed, or it may be as low as that of the mixing room. 
Eighteen hours after the trays have been stacked in the koji room 
they need to be examined. (PL II, A.) The koji should have at 
this time a temperature of from 27° to 29° C. Any higher tempera- 
ture is due to serious bacterial contamination, or to unsatisfactory 
conditions of temperature and humidity in the koji room. 
At the end of 18 hours the koji is stirred, the bottom being brought 
to the top, and the beans are broken apart. Thorough stirring is 
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