COOLING HOT-BOTTLED PASTEURIZED MILK. 
27 
Table I. — Bacterial growth in milk during a quick and slow cooling to 45° F., followed 
by holding for 6 hours at warm temperatures (bacteria in 1 c. c). 
Sample No. 
1 
2 
3 
4 
5 
6 
7 
8 
9 
10 
95, 0Q0 
176,000 
176,000 
97, 500 
97 500 
450, 000 
985,000 
38,000 
Milk cooled quickly: 
Directly after pasteuriza- 
600 
1,000 
1,870 
1 2, 050 
5, 750 
1,320 
1,180 
5,800 
1,570 
!2,370 
8,400 
1,220 
5,520 
6,100 
5,900 
5,900 
22, 900 
16, 600 
890 
1,700 
4,800 
2,500 
8,300 
8,900 
2 9, 600 
7,500 
9,800 
2 8,900 
5,500 
5,200 
2 5, 200 
After 18 hours held at 45° F. 
Sample then placed for 6 
hours at 86° F 
6,600 
5,900 
5,900 
5,900 
Milk cooled slowly: 
Directly after pasteuriza- 
. tion.". „ 
860 
500 
21, 800 
12,300 
890 
2,200 
5,400 
715 
6,500 
Cooled slowly at room 
temperature for 4 hours 
and placed for 14 hours 
in refrigerator at 45° F. . 
5,200 
Then placed for 6 hours at 
86° F 
3,700 
•3, 700 
2 5, 300 
Held at 45° F. for 21 hours, in place of 18 hours. 
2 Held at 75° F., instead of ! 
F. 
As may be seen in Table I, bacterial counts were made on each 
bottle of raw milk 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 results obtained showed that there 
was no mpre 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 num- 
bers, even after milk cooled by both processes had been removed, 
after 18 hours' cooling, and allowed to stand for 6 hours. 
The various counts from the 10 samples are averaged in Table II, 
in order to show more plainly the effect of the two systems of cooling 
on the bacterial numbers in milk. 
Table II. — Summary of results from Table I. 
Milk and stage of cooling process. 
Average 
bacteria 
per c.c. 
Cooled quickly: 
Directly after pasteurization ■. 
After 18 hours in refrigerator 
Taken from refrigerator and held 6 hours at temperatures from 75° to 86° F 
Cooled slowly: ' 
Directly after pasteurization 
Cooled "slowly at room temperature for 4 hours and held in refrigerator for 14 hours at 45° F 
Taken from refrigerator and held for 6 hours at temperatures from 75° to 86° F 
Raw milk 
5,823 
5,040 
5,729 
4,678 
5,583 
264, 375 
It will be seen in this table that the average bacterial counts of 
milk cooled slowly, made at different times, are even lower than those 
of milk cooled quickly. While this difference is possibly an experi- 
mental error, it is evident that bacterial growth in the pasteurized 
milk was not increased by the slow-cooling process. 
