Separation is the process of mechanically skimming the cream of the fat from the milk. This of course was done by hand by the consumer most of the times in Greenbelt during 1937-1945. The cream is either bottled or used to make butter and other products. This was also the case in Greenbelt but must have been done by hand though. The skim milk also was either bottled or used for other products such as cottage cheese. The remaining skim milk and cream is used to standardize the milk which has not been separated yet. This standardization produces different types of milk by adding either skim or cream into the milk which has either a lower or higher fat content than desired. (World Book Encyclopedia, 459-464)
This second step of the process involves heating the milk to high temperatures for a determined amount of time in order to kill the bacteria. Nearly all of the milk in the U.S. is now pasteurized due to health reasons. There are several methods to pasteurization including HTST method, the batch method, and ultrapasteurization method. HTST or High temperature short time requires heating the milk to 161 degrees farenheight for 15 seconds and then quickly cooling. The batch method involves heating the milk to 145 degrees farenheight for 30 minutes. Finally the ultrapasteurization method involves heating the milk to 280 degrees farenheight for two or more seconds and then cooling rapidly. The HTST method was most likely used in Greenbelt as it was the one of the first methods devised. (World Book Encyclopedia, 459-464)
Homogenization involves the breaking up of the fat globules in milk so that the fat does not rise to the top of the milk in the form of cream. This of course did not pertain to the early years in Greenbelt since homogenization was not used until later. Homogenization works by forcing the milk through small openings using great pressure with a machine called a homogenizer. (World Book Encylcopedia, 459-464)
This step in the process is done to improve the value of the milk by adding certain nutrients. vitamin D is usually added due to the low quantity of it in the milk. (World Book Encyclopedia, 459-464)
During the early years in Greenbelt, milk was packaged into glass bottles usually by hand. Today milk is packaged mechanically into either plastic or paper cartons by an automatic packaging machine. (World Bool Encyclopedia, 459-464)