PASTEURIZATION 215 
stroy pathogenic organisms by the “flash” method than 
by the “holder” method. Pasteurization in the final con- 
tainer is the best method, because it does not afford any 
opportunity for the milk to be reinfected. But most 
of the apparatus constructed to pasteurize milk in bot- 
tles is rather costly and it is also more expensive to oper- 
ate than that of the “ flash” or “ holder ” variety. Fur- 
thermore, the bottles must be tightly sealed, and this 
requires the use of a cap which is more expensive than 
the ordinary kind. Space must be allowed for the ex- 
pansion of the milk when it is heated, consequently the 
bottles cannot be entirely filled. Larger bottles must 
therefore be provided or the consumer will receive short 
measure. The vacant space permits the milk to be 
shaken about, which may disturb the cream. The cream 
may also “butter” if the milk is subjected to sufficient 
agitation while warm. 
The milk should be cooled immediately after pasteur- 
ization. Sudden cooling following exposure to heat 
has no effect in destroying bacteria, as was formerly sup- 
posed, but prompt cooling will retard the development 
of the bacteria or spores which survive pasteurization. 
The regulations of the Philadelphia Board of Health 
require that the milk shall be cooled to 50° F. (10° C.) 
or below immediately after pasteurization, held at that 
temperature or below while at the pasteurizing plant, 
and delivered to the consumer within 24 hours. The 
requirements of the New York Commission on Milk 
Standards specify that the milk must be cooled imme- 
diately to a temperature not exceeding 50° F. (10° C.) 
and held at that temperature until delivered to the con- 
sumer. 
Types of Pasteurizers.—Various types of pasteuriz- 
