Am\uJg°u^'  iP884rm'}  Bitter  Substance  of  Hops.  427 
THE  BITTER  SUBSTANCE  OF  HOPS.1 
By  Dr.  H.  Bungener. 
Little  that  is  definite  is  known  of  the  substances  to  which  the  hop 
owes  its  bitterness.  Lermer  has  succeeded,  it  is  true,  in  separating 
from  hops  a  crystallized  odorless  substance,  insoluble  in  water,  an  alka- 
line solution  of  which  has  a  marked  bitter  flavor,  and  which  easily 
changes  on  exposure  to  the  air,  assuming  a  resinous  form.  According 
to  Lermer,  the  formula  of  this  substance  is  C32H50O7 ;  it  possesses  the 
properties  of  a  weak  acid  and  forms  a  characteristic  copper  salt,  which 
is  soluble  in  ether.  This  hop  bitter  is,  however,  produced  from  the 
hop  by  a  very  roundabout  process,  by  treatment  of  the  extract  with 
alkalies ;  it  is  not  therefore  regarded  by  many  as  present  in  this  form 
in  the  hop,  and  they  hold  that  it  is  only  produced  by  the  action  of  the 
alkalies.  On  the  other  hand,  however,  Etti,  by  a  complicated  extract- 
ing process,  but  without  using  an  alkali,  succeeded  in  producing  a  bitter 
substance  from  hops,  which  is,  however,  soluble  in  water. 
Several  experiments  convinced  me  that  there  really  existed  in  hops 
a  crystallizable  substance,  insoluble  in  water,  the  alcoholic  and  alkaline 
solution  of  which  had  a  bitter  flavor,  in  short,  which  possessed  all  the 
properties  of  Lermer's  hop-bitter  acid.  Petroleum  ether  is  the  best 
practical  solvent  in  use  for  its  isolation,  as  it  does  not  dissolve  the 
majority  of  the  remaining  constituents  of  the  hop,  especially  the  hop- 
resin,  which  they  contain  in  considerable  quantity.  Still,  the  extrac- 
tion of  hop-bitter  acid  from  hops  is  a  troublesome  and  thankless  job, 
the  petroleum  ether  taking  up  certain  substances  which  add  greatly  to 
the  difficulty  of  purifying  the  crystals.  On  the  other  hand,  we  can 
readily  and  quickly  attain  our  object,  if  we  employ  for  our  original 
material  fresh  lupulin  from  unsulphured  hops. 
The  following  process  has  furnished  me  the  best  results : 
The  lupulin  is  first  freed  from  gross  impurities  (hop  seed,  leaves, 
etc.),  and  then  covered  with  petroleum  ether  boiling  at  a  low  tempera- 
ture (40°  to  70°)  in  stoppered  flasks.  The  mixture  is  shaken  up  from 
time  to  time.  After  twenty-four  hours,  by  means  of  a  Zulkowsky 
filter  immersed  in  the  mass,  and  with  the  aid  of  a  suction  pump,  the 
dark  brown  solution  is  drawn  off ;  then  fresh  ether  is  poured  on  to 
the  lupulin  and  it  is  allowed  to  stand  for  another  twenty-four  hours. 
After  this  process  has  been  three  times  repeated,  nearly  everything  the 
l"The  Brewers'  Guardian,"  from  the  "  Zeit.  f.  d.  gesammte  Brauwesen." 
