PRODUCTION. OF MILK OF LOW BACTERIAL CONTENT. orlen 
e 
As a matter of additional interest, some experiments were con- 
ducted which show that bacteria grow in washed cans which are 
closed before they are thoroughly dried. To illustrate the point, two 
5-gallon cans were sterilized, then one was filled with milk, which 
was immediately poured into the other, and that in turn immediately 
emptied. The operation was performed in order to introduce into 
each can approximately the same number of bacteria. Each can 
was then washed in exactly the same manner, the excess of water 
being shaken out and the cover replaced. A determination of the 
number of bacteria in one of the freshly washed cans was then made. 
The other can, which it may be assumed contained approximately the 
same number of bacteria at that time, was allowed to stand at a 
warm temperature for 24 hours, when the number of bacteria was 
determined. An examination of the results in Table 13 shows that 
in each of the seven tests there was a great increase in the number 
of bacteria in the cans during the holding period of 24 hours. The 
importance of drying cans thoroughly after washing, particularly 
when they are immediately covered, is therefore evident. 
TaBLE 13.—Bacterial growth in cans covered before being dried. 
Bacteria per can. Bacteria per can 
Series No. Series No. . 
Freshly 24 hours after Freshly 24 hours after 
washed. washing. washed. washing. 
1 Dict aen ne ees tasaned sec aEe Sie | 960, 000 S47 MOCO OOO a mere satus cet aes | 99, €06 320, 000, 000 
YA a Bhs ORR a al ats 618, 000 201-2 10008 OOOH AG Sess cok Wa | 5, 570, 000 748, 000, 000 
CBs nas ine BT ae 137, 000 SSOMOOOROOO | eee se ee 305, 000 138, 000, 000 
G5 eo Ee eee Ae eae 91, 000 428, 000, 000 
_ Utensils that have not been sterilized, besides adding large num- 
bers of bacteria to milk, introduce types which greatly affect the re- 
lation of the various bacterial groups in it. This matter also was in- 
vestigated, determinations having been made of the bacterial groups 
in milk drawn directly from the udder, from sterilized utensils, from 
unsterilized utensils, and from washings of unsterilized cans. Table 
14 summarizes the results of this work. Numerous samples from 
different sources have been averaged in the table. The bacterial 
groups were determined by the milk-tube method, which has been 
described. 
The bacterial groups in the samples of milk drawn directly from 
the udder compare very closely with those in the milk from sterilized 
utensils. It will be noted that in the milk from unsterilized utensils 
there was a great increase in the percentage of the alkali-forming 
and peptonizing groups. While the acid-coagulating peptonizing 
group was not found in milk from utensils not sterilized, it was pres- 
