COMPOSITION, AND PROPERTIES OF KOJI. 
29 
Suintions of cane sugar, which, as we have seen, are so 
speedily affected by in vertase, w r ere mixed with gradually increa¬ 
sing quantities of lactic acid, filled up in each trial to a uniform 
volume, mixed with the same quantity of koji extract and 
kept in warm water at 40-45°C for 2 hours. For each trial 
] 00 c c. of a solution containing 10 grms. of cane sugar, 50 c.c. 
of a standardized solution of lactic acid and 50 c.c. of freshly 
prepared koji extract were used. In one trial the solution of 
lactic acid was replaced by an equal volume of water. After 
heating, all the mixtures were cooled to the same temperature 
and then examined in the polaristrobometcr. The rotations 
observed, were, as follows : 
Lactic acid, 
% of the mixtures. 0 0.25 0.50 0.75 1.0 
Optical rotation. 0.(5° 8.2° 8.5° 8.7° 8.7° 
Four other mixtures of the same solutions, containing 1.25, 
1.5, 2.0 resp. 2.5% of lactic acid also showed, after heating, 
8.7°. Here we see that the smallest quantity of acid applied 
(0.25%) already interfered with the action of the in vertase 
and that 0.75% probably entirely suspended the inversion. 
As in this experiment the solution of the ferment applied 
was not very effective owing to the too short digestion of the 
koji with water, we made a second series of trials heating the 
mixtures to 40-45° for 2| hours and using the same proportions 
of koji extract and solutions of cane sugar and lactic acid as 
before, viz. 100 c.c. of a solution of cane sugar, 50 c c. of 
lactic acid, and 50 c.c. of koji extract. Along with these 
mixtures we heated also 1) 50 c.c. of koji extract diluted with 
150 c.c. of water, 2) 100 c c. of cane sugar + 50 c.c. of koji 
extract+ 50 c.c. of water, 3) 100 c.c. of cane sugar+100 c c. of 
a solution containing 4 grms. of lactic acid, and4) 50 c.c. of 
koji extract+150 c.c. of a solution containing 2 grms. of 
lactic acid. After heating, the optical rotations were found 
to be, as follows : 
