SWEETENED CONDENSED MiLK DEFECTS 247 
such as Bacillus putrificus, Plectridium foetidum, Plectridium 
novum, etc., do not seem to thrive in sweetened condensed milk. 
The contamination may occur from dust of hay and other 
fodder, grain, bedding, or the unclean coat of the udder and sur- 
rounding portions of the animal, or from milking with wet and 
unclean hands, or from remnants of milk in unclean utensils. 
It is noticeable that the great majority of cases of blown 
milk appear during late summer and early fall, when the crops 
are harvested and the air in the barn is frequently loaded with 
dust from the incoming crops. Gelatin plates exposed in the 
stable before and during the filling of silos showed an enormous 
increase of colonies on the plates exposed during the filling of the 
silos. Milk drawn under such conditions is naturally subjected 
to excessive contamination, unless special precautions are ob- 
served. : 
A very common source of these butyric acid organisms also 
is remnants of milk in pails, strainers, coolers, cans and any 
other utensils with which the milk may come in contact, also 
polluted water used for rinsing the utensils. The cheese-cloth 
strainer, owing to the fact that it is difficult to thoroughly clean 
and that it is very seldom really clean, is a very serious menace in 
this respect. Under average farm conditions, unless a new cloth 
strainer is used at each milking, it 1s safe to condemn it entirely 
and to recommend the use of a fine wire mesh strainer containing 
about eighty meshes to the inch. On some farms the milk ts 
held in a set of old cans which are kept on the farm and which 
never reach the can washer at the factory. Just before hauling 
time these cans are emptied into the clean cans from the factory. 
These old cans are often not washed properly and sometimes not 
at all. The remnants of milk in these cans breed these undesir- 
able germs and contaminate the fresh milk. It is obvious that 
such a practice is bound to jeopardize the quality and life of the 
finished product and may constitute a continuous cause of blown 
milk. 
Effect of Amount of Sucrose.—Since the sucrose contained 
in sweetened condensed milk is the chief agent preserving it, 
it is obvious that enough of it must be added to insure adequate 
preservative action. Experience has shown that about 39 to 40 
per cent of sucrose is required to preserve the condensed milk 
