312  Recent  Liierature  on  the  Soja  Bean.  {Xm'i^;\m™' 
for  twenty-four  hours,  after  which  the  product  is  ready  for  consump- 
tion. Although  the  moderate  heat  of  the  cellar  acts  for  only 
twenty-four  hours,  still  there  is  considerable  bacterial  growth  going 
on.  The  product  has  a  peculiar,  but  not  putrid  odor.  K.  Yabe 
{Bulletin  of  Imp.  College  of  Agriculture,  Vol.  2,  No.  2)  found  in 
this  substance  four  kinds  of  microbes  present,  and  he  believes  the 
chemical  decomposition  of  the  proteids  to  be  due  to  one  or  more  of 
these  microbes.  In  Japan  this  natto  is  regarded  as  a  vegetable 
cheese.  A  chemical  investigation  by  the  author  just  mentioned 
revealed  tyrosin,  peptone,  guanine,  leucin  and  xanthine.  The  total 
proteids  amounted  to  considerably  more  in  the  natto,  when  allow- 
ance was  made  for  increase  of  moisture,  than  existed  in  the  original 
bean,  and  the  artificial  product  is  also  considered  to  be  much  more 
digestible. 
A  still  more  interesting  preparation  of  the  soja  bean  than  either 
of  the  preceding  is  tofu.  This  has  been  described  and  investigated 
by  M.  Inouye  (Bulletin  Imp.  College  of  Agriculture,  Vol.  2,  No.  4). 
The  beans  are  first  soaked  for  about  twelve  hours  in  water,  and 
then  crushed  between  two  millstones  until  a  uniform  pulpy  mass  is 
obtained.  This  is  then  boiled  with  about  three  times  its  weight  of 
water,  and  filtered  through  cloth.  The  liquid  filtrate  is  white  and 
opaque,  very  closely  resembling  cow's  milk,  while  the  odor  and 
taste  remind  one  of  fresh  malt.  On  standing,  the  liquid  becomes 
sour  from  the  formation  of  lactic  acid,  and  a  coagulation  of  the  casein 
takes  place.  The  freshly  boiled  and  filtered  liquid  is  coagulated 
either  by  the  addition  of  a  portion  of  the  sour  liquid  which  has  been 
set  aside  from  a  previous  lot,  or  it  is  treated  with  about  2  per  cent, 
of  a  concentrated  brine,  such  as  is  obtained  as  mother  liquor  from 
the  preparation  of  sea  salt.  In  either  case,  the  addition  of  the  pre- 
cipitant causes  the  separation  of  a  flocculent  substance,  which  soon 
coagulates,  and  is  collected  on  a  cloth  filter,  slowly  pressed,  and 
then  cut  into  tabular  pieces  of  about  150  grammes  each.  These, 
when  dipped  in  a  mixture  of  turmeric  and  brine,  are  ready  for  con- 
sumption. Only  about  one-fourth  of  the  total  amount  of  the  pro- 
teids in  the  original  beans  is  recovered  in  the  tofu.  This  vegetable 
casein  is  not  precipitated  from  the  milky  liquid  by  the  sodium  chlo- 
ride of  the  brine,  but  by  the  magnesium  and  calcium  chlorides. 
Calcium  nitrate  or  magnesium  sulphate  will  produce  the  same 
result,  although  an  excess  of  the  latter  must  be  avoided  or  the  pre- 
