SOY AXD RELATED FERMENTATIONS. 11 
the surface to mature speculation throughout the interstices of the 
mass of beans and wheat. Mature koji has a clear yellow to yellow- 
green color on the surface and throughout the whole mass. If 
well ripened it may be lifted from the tray as one entire block. 
The koji may become infected with Rhizopus nigricans if the at- 
mosphere of the koji chamber is moist to the point of condensation 
as drops. A little Mucor or Rhizopus is disregarded in the material, 
unless a bad flavor or odor is also present. It is poor practice, how- 
ever, to allow the Rhizopus to enter. If allowed to gain a foot- 
hold, its fruiting to any extent may be prevented by breaking up 
the koji into chunks and turning these chunks bottomside up. In- 
stead of exposing a large surface, as in the case of bacterial infection, 
care should be taken to have only surfaces where Rhizopus has se- 
cured no firm footing exposed to the air. Trays of koji infected 
with Rhizopus should be stacked in a cool, dry place until the 
material is mature or needed for the shoyu-moromi. 
Proportion of Wheat. 
Experiments were conducted to determine the proportions by 
weight of prepared beans and wheat necessary for shoyu-koji. The 
quantity of wheat by weight to be used was made the varying factor. 
Soy beans were put to soak in running water. The water was 
always very cold and no warmth resulted among the beans, even at 
the bottom of the container. Initial bacterial contamination was 
thus made negligible. After being cooked for 50 minutes, at 15 
pounds pressure, the beans were divided into four lots of 600 grams 
each. Roasted and crushed wheat was added to the beans in the 
proportions of 3 to 6, 2 to 6, and 1 to 6, there being one lot to which 
no wheat was added. 
Where wheat was used with the beans in the proportion of 3 to 6, 
the resulting shoyu-koji was satisfactory and had a clean, sweet odor. 
Similarly, where wheat was used in the proportion of 2 to 6, the koji 
was excellent, with a sweet odor and fine fruiting of the mold below 
the surface of the mixture. The proportion of 1 part of wheat to 
6 parts of beans did not afford conditions for satisfactory maturing 
of the koji. An odor of ammonia was present under these circum- 
stances, as well as a slightly putrid condition. The mold, however, 
fruited in large quantities. This shoyu-koji was discarded as unfit 
for use in shoyu, for the ammoniacal odor and slightly putrid condi- 
tion indicated that bacteria capable of rapidly breaking down protein 
were present to a large extent. Where no wheat was added to the 
beans the koji resulting under the method of fermentation followed 
was rotten and had a strong odor of ammonia. The mold was fruit- 
ing in a restricted fashion even in this instance. This shoyu-koji 
also was discarded as unfit for use. 
These results indicate that koji for shoyu prepared after the 
Japanese fashion requires for a satisfactory development and ripen- 
ing at least one part of prepared wheat to three parts of prepared 
beans by weight. This proportion of wheat is somewhat less than 
equal parts of the unprepared ingredients by volume. Successful 
shoyu-koji having been made day after day for many weeks in the 
Microbiological Laboratory, sufficient previous experience had un- 
doubtedly been acquired to judge fairly these four experimental 
lots of koji. 
