214 
M. INOUYE ; 
I found that, after extracting ioo grms. of fresh tofu with 
i % acetic acid, the filtrate contained lime 1.91 % and magnesia 
3.82 % of the dry matter of tofu. A part of this lime and mag¬ 
nesia may have been present as phosphate in the tofu , but another 
part must have been in it in combination with the casein, as 
also becomes evident from the different behaviour of tofu towards 
a diluted solution of disodium phosphate. If tofu is boiled with a 
i % solution of this salt, the casein goes into solution and soon 
forms an opalescent liquid, while the calcium of the tofu yields 
calcium phosphate ; if we, however, prepare at first the free casein 
from tofu by treatment with very dilute acetic acid and thorough 
washing, we find that it will be soluble only in traces in disodium 
phosphate even after prolonged boiling, (I) while it is easily soluble 
in the carbonate. The free soya bean casein thus obtained will, 
after complete removal of the fatty matters by alcohol and ether, 
still give an opalescent solution when treated with dilute potash, 
showing that the opalescence is due not only to suspended fatty 
matters, but also in part to the casein itself. Such a pure 
solution of the potassium compound of the casein behaves to¬ 
wards calcium and magnesium salts exactly like the original 
liquid from which tofu is made. 
The results which we arrive at in regard to the prépara- 
lion of tofu is as follows : In the soya beans there are contained 
compounds of casein with potassium or sodium which are not 
t 
coagulated by boiling, but which yield with the calcium and 
magnesium salts of the brine that precipitate of insoluble 
calcium and magnesium compounds of the casein, which con¬ 
stitutes tofu. The separation of tofu is therefore not due to 
coagulation but simply to precipitation. 
The great similarity between concentrated extract of soya 
beans and animal milk is also exhibited by the formation of thin 
surface films on evaporating it at high temperatures. These 
films contain not only the proteids of the liquid but also include 
suspended fatty particles and other impurities which are present 
in the solution. Such films are prepared in this country by 
evaporating the extract of soya bean, and when dried form 
(i) Therefore we can safely infer that the solubility of the crude soya bean 
casein in hot water is not due to the presence of alkaline phosphates. 
