74 BULLETIN 98, U. S. DEPARTMENT OF AGRICULTURE. 
as soon as the milk is received it is weighed and dumped into a vat 
from which it runs over the cooler to the bottling machine or into 
cans. Ice water or brine, or often a combination of the two, is cir- 
culated through the pipes of the cooler; ice water being run through 
the upper tubes and brine through the lower. The principal work, 
therefore, of the receiving station is that of cooling and preparing 
the milk for shipment. The lower the temperature of the milk, so 
long as it is kept above the freezing point, the better. With the 
present state of development of refrigerator cars used in the trans- 
portation of milk, they can not be depended upon for lowering the 
temperature to any great extent during transit; consequently the milk 
should be thoroughly cooled before loading on the cars. Usually 
several hours elapse between the time the milk is drawn from the 
cow until it is loaded on board the cars, which makes it imperative 
that it be precooled. 
The cooling takes placed early in the morning and late in the 
afternoon, as the milk is received. The time required for cooling 
seldom exceeds two hours for each period, making the total time 
employed in cooling about four hours daily. Owing to the short 
time in which the cooling is done the capacity of the refrigerating 
apparatus is necessarily large for the amount of work required. It is 
possible, however, to decrease the capacity of the plant by running 
the machine a longer time and storing refrigeration in brine, which 
can be held for quick action when needed. 
COOLING MILK IN BOTTLING PLANTS. 
Milk-bottling plants are usually located in cities or towns. The 
milk is generally shipped in cans direct from the farms or receiving 
stations, arriving at the bottling plants at a temperature of approxi- 
mately 60° F. As soon as the milk is received at the city plant it is 
cooled to a temperature of 45° or 50° F., bottled, and placed in a 
refrigerated room, and held until the following morning, when it is 
delivered to the consumer. As the temperature of the room is around 
32° F., the milk will come out in the morning at 35° or 40° F. 
PASTEURIZING PLANTS. 
In those plants where the milk is pasteurized previous to cooling 
the refrigeration required is, of course, considerably greater than in 
raw-milk plants, where the temperature of the incoming milk is 
simply reduced to 35° or 40° F. The amount of refrigeration required, 
however, depends upon the pasteurizing equipment employed. 
There are in use at the present time two systems of pasteurization, 
known as the "holder" and " flash" processes. 
The holder process consists in holding the milk or cream for about 
30 minutes after it has been heated to the pasteurizing temperature 
of 140° to 150° F., either in the same apparatus in which the pasteur- 
