166 Milk and Its Products. 
Aération.—Passing the milk through an elevated 
strainer in such a manner that it may fall in 
finely divided drops or streams through the air be- 
fore it reaches the can, is one of the best means 
of bringing about this end. This is known as 
aération. It cannot be depended 
upon to destroy or even check the 
germs of fermentations which may be 
present in the milk, beyond that 
due to the reduction of temperature. 
It is not desirable that milk in- 
tended for cheese making should 
be cooled much helow the tempera- 
ture of the air, and one of the best 
preparations of milk intended for 
“cheese making is to allow it to 
remain where it will be freely ex- 
posed to a pure and moderately cool 
Fig. 3 errr atmosphere. Under ordinary condi- 
elevated strainer. tions, the milk of the evening and 
the succeeding morning are manufactured together, 
and the treatment indicated is naturally that of the 
night’s milk. It is highly desirable, however, that 
the milk of the morning should be cooled to the 
temperature of the atmosphere before it is taken to 
the factory, and under ordinary conditions the milk 
of the night and morning should be taken to the 
factory in separate cans. 
Ripening.—The lactic acid fermentation is prob- 
ably one of the most important factors in all the 
steps of cheese making, and to know to what ex- 
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