2I 4 



M. INOUYli ; 



I found that, after extracting 100 grms. of fresh tofu with 

 I % acetic acid, the filtrate contained lime i.gi % 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 

 1 % 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 prepara- 

 tion of tofu is as follows : In the soya beans there are contained 

 compounds of casein with potassium or sodium which are not 

 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 



(1) 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. 



