CHAPTER IV. 
COOLING AND AERATION OF MILK AND CREAM, 
Importance of Low Temperature. Milk always con- 
tains bacteria no matter how cleanly the conditions under 
which it is drawn. At ordinary temperatures these bac- 
teria increase with marvelous rapidity; at low. tempera- 
tures their growth practically ceases. The effect of tem- 
perature on bacterial development is graphically shown 
in Fig. 57. my 
\l «V4 
AN WHIN 
dy YIN 
WUIN\\\\\N 
Fig. 4.—Relation of temperature to bacterial growth. 
@ represents a single bacterium; 4, its progeny in twenty-four hours in 
milk kept at 50° F.;c, its progeny in twenty-four hours in milk kept at 70° F. 
(Bul. 26, Storrs, Conn.) 
At a temperature of 50° F. the bacteria multiplied: five 
times; at 70° F. they multiplied seven hundred and fifty 
times. 
Roughly speaking, at 98° F. bacteria multiply one hun- 
39 
