CoNbDENSED ButTTERMILK 179 
of curd. The residue, consisting largely of casein, water and 
some lactic acid and milk sugar, represents the condensed butter- 
milk. The concentration, or more correctly speaking, the reduc- 
tion in volume thus offered, is at the ratio of about 4 to 5 parts 
of fluid buttermilk to one part of condensed buttermilk. It 1s 
obvious that in this form of concentration all of the valuable food 
elements of the buttermilk are not reclaimed. Most of the milk 
sugar and much of the lactic acid escape with the whey and,are 
lost. However, the equipment required for this process is very 
simple and inexpensive and the process requires no_ special 
knowledge on the part of the creamery personnel. 
Concentration by Centrifugal Separation.—For many vears. 
efforts have been made to remove the water from the buttermilk 
by centrifugal separation. Machines are now on the market and 
in use, in which the curd of-the buttermilk collects on the walls 
of a revolving basket while the whey is centrifuged out. These 
machines are similar in principle to the well-known laundry 
centrifuge. Thev have been successfully used by creameries 
that are engaged in the manufacture of buttermilk cheese. “Their 
operation, however, is intermittent only. \When the basket fills 
up with the curd, the machine must be stopped and the curd 
removed. 
For the purpose of handling large volumes of buttermilk 
daily, these centrifuges are obviously not well adapted. They 
are too limited in capacity, in speed and in volume of per- 
formance. Efforts to devise a centrifuge for continuous opera- 
tion. similar to the cream separator, have so far failed. The spe- 
cific gravity of the curd in the buttermilk is so nearly like that 
of the whey, that the centrifugal separator refuses to discharge 
a liquid rich in curd and one of practically clear whey. Exper- 
iments by the author have demonstrated that, no matter how 
the outlets of the discharges are adjusted, both liquids have prac- 
tically the same compcsition, 
Evaporation in Vacuo.—This method for condensing butter- 
milk is rapidly gaining in favor and today vast volumes of but- 
termilk are concentrated in this manner. The equipment used 
and the method of operation are principally the same as those 
used in the manufacture of condensed milk and evaporated 
milk, The buttermilk is condensed in the vacuum pan, 
