July 15, 1914 
Pasteurization of Streptococci 
3 2 3 
dally, 89, or 64.03 per cent, withstood the heating. When a tempera¬ 
ture of 62.8° C. (145 0 F.) was used 46, or 33.07 per cent, of the strep- 
tococd survived. This temperature of 62.8° C. (145 0 F.) maintained 
for 30 minutes is the temperature generally used in the process of Pas¬ 
teurization. At the higher temperatures the number of cultures which 
survived grew less as the temperature was increased. At 71.1 0 C. 
(160 0 F.) 3, or 2.58 per cent, of the streptococci survived, while at 73.9 0 C. 
(165° F.) all were destroyed. 
These results are seen more clearly in figure 1, where they have been 
plotted. Some of the streptococci were destroyed at 54.5 0 C. (130° F.) 
and more at 57.2 0 C. (135 0 F.). It is particularly interesting to note 
that at 6o° C. (140° F.) 89 of the cultures survived, while at 62.8° C. 
(145 0 F.), a difference of only 2.8° C., or 5 0 F., only 46 survived; there¬ 
fore, 51.6 per cent of the streptococci which withstood 6o° C. (140° F.) 
were destroyed at 62.8° C. (145 0 F.). 
It is evident in the consideration of streptococci as a whole that a 
large percentage are able to survive Pasteurization. 
Table) I. — Effect of heat on streptococci—all cultures 
Cultures surviving after 30 minutes heating at— 
Item. 
48.9° c. 
5 t. 7 °C. 
54 - 5 ° C. 
57 . 2 °C. 
6 o°C. 
62.8° C. 
65.6° C. 
68.3 °c. 
7i.r°C. 
73 - 9 ° C. 
(l20°F.), 
(l2 5 °F.). 
(i 3 o°F.). 
(i 35 °F.). 
(i 4 o°F.). 
(i 4 S°F.). 
(150* F.). 
(iS 5 °F.). 
(i6o°F.). 
(165 F.). 
Number.. 
139 
*39 
138 
118 
89 
46 
26 
13 
3 
0 
Per cent.. 
100-00 
100. 00 
99. 28 
84.89 
64*03 
33-07 
18. 71 
9 * 35 
2.58 
0 
