RESEARCHES ON THE MANUFACTURES, 
28 
all traces of reducing sugars, gelatinized and mixed with solu¬ 
tions of invertin that had been thrown down from yeast ex¬ 
tract by strong alcohol, washed, and redissolved in water 9 . 
Neither the gelatinized starch nor invertin reduced alkaline 
cupric solutions. The mixtures were kept for several hours 
at 45°C and then tested with Eehlinffs solution. Not a trace 
o 
of reducing sugar had been formed. A test with phenyl- 
hydrazin hydrochloride and sodium acetate also gave a ne¬ 
gative result. Hence we may safely conclude that starch is 
not acted on by the soluble ferment of yeast. 
Comparing now, by the light of the preceding researches, 
the effects of the two ferments,—yeast and koji—on the 
various carbohydrates, we find that neither of them acts on 
inulin or milk sugar, but that they strongly invert cane 
sugar, and also that the invertin of yeast does not affect 
gelatinized starch or maltose, while the ferment of koji 
hydrates both, converting starch into dextrins, maltose, and 
dextrose, and maltose into dextrose. There is accordingly 
an essential difference between the two ferments, that 
of koji having stronger hydrating properties than that of yeast. 
In order to discriminate between the two and at the same 
time give expression to their resemblance in respect to their 
identical action on cane sugar, we may be allowed to give to 
the soluble ferment of koji the name “ invertaae." 
When improp u-ly stored in a damp room without sufficient 
ventilation, koji is liable to turn sour, whereby the efficacy of 
the invertase is either diminished or entirely suspended. 
Some interest must accordingly be attached to a determination 
of the quantity of acid in the presence of which the ferment 
becomes ineffective. We investigated the subject, choosing 
that acid which is chiefly formed under natural conditions in 
moist starchy materials, viz. lactic acid. 
9 This solution of the ferment rapidly inverted cane sugar. 
