THE PREPARATION AND CHEMICAL COMPOSITION OP TOFU. 213 



pressed, and then cut into tabular shape. (I) I have tried to 

 arrive at a satisfactory explanation of the nature oitofu, and have 

 found that the salt-brine does not act by its chloride of 

 sodium, but by the calcium and magnesium salts which are 

 in it ; for we can at once obtain the precipitate from the 

 milky liquid if we add a little calcium nitrate or magnesium 

 sulphate, {Z) while we can not obtain any separation or precipita- 

 tion by adding even considerable quantities of sodium chloride 

 or sodium sulphate. (3) However, ammonium sulphate will, as 

 with cow's milk, bring on precipitation, if we add 60 % of it to 

 the milky liquid. This precipitate is so voluminous that the 

 liquid seems to solidify. The peculiar state of the solution of 

 soya bean casein resembles that of milk ; thus, if milk is 

 dropped upon porous clay, the liquid will be absorbed by the 

 clay, but the casein and fat will remain on the surface, and the 

 same is observed with the milk from soya beans. (4) 



I have analysed a sample of the salt brine used for tofu mak- 

 ing and found it to contain, besides chloride of sodium, 27.9 % of 

 chloride of magnesium and 7.0 % of chloride of calcium. As 

 casein has decidedly an acid character and is only very little 

 soluble in water in the free state, it seemed most probable that 

 the aqueous extract of soya beans contains a sodium or potas- 

 sium compound of casein' 51 yielding insoluble calcium and 

 magnesium compounds, which constitute tofu. 



(1) In this way about one fourth of the total amount of proteid in soya beans is 

 obtained in the tofu. 



(2) An excess of magnesium sulphate is to be avoided, as it would redissolve the 

 precipitate. 



(3) If the liquid is warm and saturated with sodium sulphate, a very slow and 

 imperfect separation may be noticed. 



(4) In order to see whether a product similar to Swiss cheese could be obtained 

 from the crude soya casein or tofu, I infected 50 grm. of fresh tofu with a small dose 

 of pulverised Swiss cheese, and added ten per cent of common salt to the mixture, 

 pressed it in cloth, and allowed it to stand in a moist beaker glass for several 

 months. The product resembled, only to a limited extent, the cheese from milk, but 

 further experiments with addition of small quantities of milk sugar are intended. 



(5) I observed that soya bean casein is easily digested by pepsin solution 

 acidulated with 0.2 o/ 0 hydrochloric acid, without leaving any insoluble residue ; 

 in this it resembles human casein, which, according to the valuable investigations 

 of Wroblewski (Berne, 1894) yields, unlike cow's-casein, no paranuclei. I found 

 also that peas and horse-beans yield aqueous extracts of similar behaviour to that 

 of soya beans. 



