PASTEURIZING MILK. 
21 
Table 6. — Number of bacteria per cubic centimeter in pasteurized milk bottled 
hot, cooled quickly and slowly, and subsequently held at room temperature. 
Method of cooling. 
Sample No. 
Aver- 
age of 
10 
1 
2 
3 
4 
5 
6 
7 
8 
9 
10 
sam- 
ples. 
Bacteria in the raw milk 
Bottle No. 1, cooled quickly: 
Directly after pasteur- 
95, 000 
600 
1,000 
176,000 
1,870 
i 2, 050 
5,750 
1,320 
1,180 
5,800 
176,000 
1,570 
i 2, 370 
8,400 
1,220 
5,520 
6,100 
97,500 
5,900 
97, 500 
5,900 
22, 900 
16,600 
450,000 
890 
1,700 
4,800 
2,500 
985,000 
8,300 
8,900 
2 9, 600 
7,500 
9,800 
2 8, 900 
38,000 
5,500 
5,200 
2 5, 200 
6,500 
5,200 
2 5, 300 
264,375 
5,823 
After one-half hour in 
ice water and 17J 
hours at 45° F 
5, 040 
After6hoursat86° F 
6,600 
5,900 
5,900 
5,900 
6,908 
Bottle No. 2, cooled slowly: 
Directly after pasteur- 
ization 
860 
500 
21,800 
12,300 
890 
2,200 
5,400 
715 
5,729- 
After 4 hours at room 
temperature and 14 
hours at 45° F 
4,678 
After6hoursat86°F 
3,700 
3,700 
5,583 
i Held at 45° F. for 21 hours in place, of 18 hours. 2 Held at 75° F. instead of 86° F. 
As may be seen from Table 6, bacterial counts were made of the 
raw milk on each bottle directly after pasteurization, at the end of 
the 18-hour cooling period, and again after the milk had been at 
room temperature for six hours. The bacterial results obtained 
showed that there was no more increase in the pasteurized milk cooled 
slowly than in similar milk cooled within half an hour and held at 
low temperatures for 18 hours. Neither was there any difference in 
the bacterial numbers even after milk cooled by both processes had 
been removed, after 18 hours' cooling, and allowed to stand for six 
hours. The various counts from 10 samples have been averaged and 
are given in the last column in order to show more plainly the effect 
of the two systems of cooling on the bacterial numbers in milk. It 
will be seen that the average bacterial counts of the milk cooled 
slowly are even lower than those of milk cooled quickly. While this 
difference is probably an experimental error, it is evident that bac- 
terial growth in the pasteurized milk was not increased by the slow- 
cooling process. 
The writers do not wish to convey the idea that pasteurized milk 
need not be cooled at all. The cooling of any milk is absolutely essen- 
tial in order to restrain bacterial growth, and the fact should be 
emphasized that the process of cooling pasteurized milk slowly does 
not dismiss the cooling process but simply makes use of a slower 
cooling process than is in use at present. 
In order to show, respectively, the effect on the bacterial content 
of cooling quickly, cooling slowly, and not cooling to low tempera- 
tures at all, three experiments were made. Milk was pasteurized in 
bulk and three steamed and hot quart bottles were filled with the Lot 
milk. One bottle was cooled in iced water in half an hour to 50° F. 
and refrigerated at 45° F. Another bottle was cooled in a blast of 
air at room temperature for half an hour during which time the 
