COOLING HOT-BOTTLED PASTEURIZED MILK. 
31 
Table V. — Laboratory cream-line experiments showing comparison of raw milk and milk 
T at 145° F. for 30 minutes followed by various methods of cooling. 
Experi- 
ment No. 
Milk and process. 
Cream in 500 
c. c. cylinder 
after 24 hours' 
refrigeration 
at 45° F. 
C.c. 
64.5 
64.5 
65.0 
64 5 
1 
Pasteurized: 
Held above 105° F. for three hours and cooled in ice water 
65.0 
62.5 
52.5 
52.5 
2 
Pasteurized: 
Cooled in 15 seconds to 50° F 
Held above 100° F. for H hours 
Raw milk lost 
3 
Pasteurized: 
Cooled in 15 seconds to 50° F 
83 
Cooled slowly for 30 minutes in air blast, then cooled quickly in brine 
Held above 100° F. for 3 hours, then cooled quickly in brine 
85 
90 
(•Raw milk lost 
4 
Pasteurized: 
Cooled in 15 seconds to 50° F 
75 
Cooled slowly in air blast for 2^ hours, then cooled in ice water 
69 
Held above 100° F. for 2h hours and cooled in ice water 
75 
80 
Pasteurized: 
68 
55 
5 
After cooling in air blast for 2 hours the milk was cooled quickly in brine 
to50°F. 
Held above 100° F. for 5 hours 
62 
55 
After holding above 100° F. for 5 hours the milk was cooled quickly in 
brineto 50° F. 
62 
A study of the results shown in the table above indicates that 
cream-line formation is a variable factor. Sometimes it was reduced 
by pasteurization, even when the milk was cooled to low tempera- 
tures within 15 seconds, and at other times there was no difference. 
In some experiments the cream line was slightly less on milk cooled 
slowly. 
These laboratory experiments do not exactly duplicate conditions 
of air cooling on a commercial scale, for in no case was the hot 
pasteurized milk cooled to 50° F. (10° C.) within three hours, as it 
was in our later experiments. Throughout our experiments on a 
small commercial scale, when the milk was cooled to that tempera- 
ture within the time named no apparent reduction of the cream layer 
was observed, and the cream line was always distinct. When milk 
stood at temperatures above 80° F. (26.7° C.) for several hours 
without agitation, some of the melted butterfat rose to the top of 
the bottle and on cooling formed a small lump of butter. This was 
observed, however, when the cooling process was begun immediately 
after bottling, even though the cooling was gradual. 
As to the effect of the process on the flavor of the milk, it may be 
said that there was no more noticeable flavor than is the case with 
milk pasteurized and cooled rapidly, except when the milk was held 
above 100° F. (37.8° C.) for several hours. This was the case in 
