66o 
Concentrated  Milk  Products. 
{Am.  Jour.  Pharm. 
September,  1920. 
fluffy  powder  that  is  readily  miscible  with  water,  forming  a  milk- 
hke  Hquid  having  a  cooked  milk  taste.  Dried  half -cream  milk 
is  similar  but  is  made  of  milk  from  which  one-half  the  cream  has  been 
removed,  and  is  a  light  yellow,  fluffy  powder.  Dried  skim  milk 
is  made  from  skim  milk  and  is  a  yellowish  white,  granular  powder. 
Commercially,  according  to  "Milk"  (191 8,  21),  milk  powder  is 
made  by  one  of  the  following  processes:  (i)  By  feeding  the  milk 
in  a  thin  stream  over  two  steam  heated  cylinders  or  drums,  about 
one-eighth  inch  apart,  revolving  in  opposite  directions.  The  milk 
exposed  to  the  heat  of  the  cylinders  dries  as  a  thin  film  and  comes 
off  the  revolving  cylinder  as  a  sheet,  which  is  easily  crushed  into  a 
fine  powder.  The  cylinders  which  are  some  60  inches  long  and  24 
inches  in  diameter  are  charged  with  steam  under  two  or  three 
atmospheres  of  pressure,  causing  the  heating  surfaces  to  have  a 
temperature  of  about  250°  to  280°  F.  This  process,  known  as  the 
Just  patent  in  the  United  States  and  as  the  Just-Hatmaker  patent 
in  England,  is  said  to  have  been  the  invention  of  J.  R.  Hatmaker 
of  London;  (2)  by  pasteurizing  milk  and  then  condensing  in  the 
vacuum  pan,  at  a  low  temperature  (130°  F.)»  to  about  one-fourth 
its  bulk,  after  which  the  condensed  product  is  forced  under  high 
pressure  through  minute  openings  in  a  metal  disk  into  a  hot  air 
chamber.  The  atomized  liquid  surrounded  by  a  current  of  hot  air 
instantly  dries  and  falls  to  the  bottom  of  the  chamber  as  a  snowy 
powder,  the  moisture  rising  as  a  cloud  of  steam.  The  mixture  of 
the  liquid  and  air  in  the  evaporating  chamber  is  stated  to  be  about 
180°  F.  The  method  was  developed  in  France  and  is  called  there 
and  in  England  the  Bevenot  de  Neveu  process.  In  this  country 
it  is  known  as  the  Merrell-Gere  process;  (3)  by  condensing  milk  to 
approximate  dryness  in  a  vacuum  pan  equipped  with  a  mechanical 
stirrer. 
The  Federal  regulations  (Food  Inspection  Decision  No.  170), 
U.  S.  Department  of  Agriculture,  March  31,  191 7),  require  that 
dried  milk  must  contain  "not  less  than  26  per  cent,  milk  fat  and  not 
more  than  5  per  cent,  of  moisture."  There  are  no  Federal  standards, 
apparently,  for  dried  half-cream  milk  and  dried  skim  milk,  except 
that  the  latter  "shall  not  contain  more  than  5  per  cent,  of  moisture." 
Dried  milk  and  dried  half  cream  milk  are  sterile  and  in  sealed 
cans  keep  almost  indefinitely.  Exposed  to  air,  warmth  and  mois- 
ture, however,  they  slowly  become  rancid;  dried  skim  milk,  however, 
