CONDENSED BUTTERMILK 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 is 

 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 years, 

 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. They have been successfully used by creameries 

 that are engaged in the manufacture of buttermilk cheese. Their 

 operation, however, is intermittent only. AYhen 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 composition. 



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 nan. 



