14 DEPARTMENT BULLETIN 319, U. S. DEPT. OF AGRICULTURE 
acidophilus bacteria. The product should be of a creamy consistency 
and have a mildly acid taste, absolutely free from off flavors or 
odors. Acidophilus milk has a characteristic flavor and aroma. 
From time to time the batch should be examined microscopically or 
culturally in order to be certain of the purity of the product as a 
culture of the acidophilus organism. This affords a means of check- 
ing the efficiency of the process. Acidophilus milk should always be 
distributed while fresh. 
For the production of acidophilus milk on a small scale, the method 
outlined for the preparation of the bulk starter may be followed. 
Thus any desired number of flasks of the milk may be prepared. 
Acidophilus milk is being produced in flasks in those localities where 
the population is small and the demand for the milk limited. 
THE PRODUCTION OF ACIDOPHILUS MILK EN THE HOME 
It is possible to prepare acidophilus milk in the home, but the 
procedure is so tedious and the possibilities of contamination are 
so great that few attempt it except when the commercial product is 
not available. As has been previously stated, the milk to be used in 
the preparation of acidophilus milk must be sterilized before the 
culture is added. Inasmuch as facilities in the home do not permit 
the sterilization of milk, canned evaporated milk, which is a sterile 
product, is used. The culture of Lactobacillus acidophilus to be used 
should be obtained from a reliable source. 
The following are the directions for preparing acidophilus milk 
in the home : 
After boiling water is poured over the top of a can of milk the 
can is cut about halfway around with an opener which has been 
previously boiled. Neither the can nor utensils to be used should be 
dried. The plug of the culture tube is removed carefully and the 
mouth of the tube passed through a flame. After the lid of the can 
is opened just sufficiently to permit the entrance of the mouth of 
the tube, the culture is poured into the can of milk. The contents 
of the can are stirred with a spoon which has been boiled in water. 
The top of the can is then pressed down and covered with a clean 
dish. The can is kept at a temperature as near 100° F. as possible 
for about 24 hours, or until the milk has curdled. The milk may be 
incubated in a tireless cooker. After the milk has curdled a spoonful 
of this milk is transferred to another can of milk, the same pre- 
cautions being observed as in the use of the culture. This process 
is repeated from day to day. 
With great care it is possible in this way to carry on the culture 
from day to day and to have a fresh supply of acidophilus milk every 
day that will contain a large number of viable acidophilus bacteria. 
The curdled milk may be diluted with fresh milk if the product is 
too concentrated to be palatable. If the product acquires an off 
flavor or odor, it is contaminated and should be discarded and a new 
culture obtained. Xo harm can result from allowing the milk to 
remain in the open can. 
Some information concerning the relative value of the commercial 
preparations of L. acidophilus now on the market may be found 
in a recent article by James (Jf6 a). 
