MILK AND CREAM AT FARM 231 



The ceiling should he about 10 feet high and made of well 

 matched ceiling lumber. A ventilating shaft should ex- 

 tend from the middle of the ceiling to the top of the roof 

 to carry off vapors and impure air. 



Essentially .the same plan of construction may be fol- 

 lowed as that outlined for the construction of the cream- 

 ery. 



Equipment. For those furnishing milk, the equipment 

 should consist of a cooler, cooling tank, water heater, and 

 wash sinks. When cream is sold, a cream separator, some 

 form of power, and preferably an ice box, are added to 

 the equipment needed for milk. 



COOUNG 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. 54. At a temperature of 50 F. the bacteria mul- 

 tiplied five times ; at 70 F. they multiplied seven hundred 

 and fifty times. 



Roughly speaking, at 98 F. bacteria multiply one hun- 

 dred times faster than 70 F. At 32 F. bacterial devel- 

 opment practically ceases. 



Milk or cream may be kept sweet a long time at 40 

 to 45 F. because the lactic acid bacteria practically stop 

 growing at these temperatures. But there are other 

 classes of bacteria that can grow at these temperatures, 

 as evidenced by the production of urrdesirable flavors. 



