THE CREAMINCx ABILITY OF MARKET MILK 
19 
determine if possible the critical temperatures at which it is detri- 
mental to the cream volume to handle or agitate milk. 
Milk was heated in a can which was placed in hot water at a 
temperature of not over 155° F. Three samples were taken at 
various temperatures Avhile the milk was being pasteurized and 
while it was being subsequently cooled. The first sample in each 
group was cooled at once to 46°, the second was allowed to stand 
without agitation for 30 minutes and then cooled to 46°, and the 
third sample was agitated for 30 minutes and then cooled to 46°. 
The results of the first two tests are shown in Tables 19 and 20. 
The data in the tables seem to indicate that holding milk or agi- 
tating it for any length of time at temperatures between 60° and 
120° F. has generally a detrimental effect on the cream volume. 
The most marked effect at these temperatures occurred in the milk 
after pasteurization. Samples 5 and 6 in Table 20 were set at 130° 
and 120°, respectively, but before the expiration of the 30-minute 
holding period the temperature had dropped to 110° ; this may ac- 
count for the decrease in the cream volume in these samples. 
Table 19. — Effect of holding milk and of agitating it for 30 minutes at various 
temperatures before and after pasteurization — First experiment 
[All samples cooled to 46° F. before being placed in storage] 
Description 
Cream volume after 20 hours 
Sam- 
ple 
No. 
Temper- 
ature at 
which 
held and 
agitated 
Control 
(cooled 
at once) 
Allowed 
to stand 
one-half 
hour be- 
fore cool- 
ing 
Held and 
agitated 
for one- 
half hour 
before 
cooling 
1 
Fresh raw milk, butterfat 4.95 per cent . . 
o F 
60 
70 
80 
90 
145 
90 
80 
70 
60 
17.5 
17.0 
17.0 
16.5 
16.0 
16.0 
16.0 
15.0 
13.5 
10.0 
18.0 
17.5 
15.0 
16.0 
13.0 
13.5 
13.0 
14.0 
14.5 
2 
Heated to 70° 
16.0 
3 
Heated to80° 
16.0 
4 
Heated to 90° 
15.5 
5 
Heated and held 30 minutes - 
15.0 
6 
Pasteurized milk cooled in tank to 90° 
13.0 
Pasteurized milk cooled in tank to 80° . . ... _ 
13.0 
8 
Pasteurized milk cooled in tank to 70° - 
12.5 
9 
Pasteurized milk cooled in tank to 60°. _ _ 
12.5 
Table 20. — Effect of holding milk and of agitating it for 30 minutes' at various 
temperatures before and after pasteurization — Second experiment 
[All samples cooled to 46° F. before being placed in storage] 
Description 
/Temper- 
ature at 
which 
held and 
agitated 
Cream volume after 20 hours 
Sam- 
ple 
No. 
Control 
(cooled 
at once) 
Allowed 
to stand 
one-half 
hour be- 
fore cool- 
ing 
Held and 
agitated 
one- 
half hour 
before 
cooling 
1 
Raw milk, butterfat 3.60 ppr cent 
°F. 
45 
60 
70 
145 
130-110 
120-110 
110 
100 
90 
80 
70 
60 
14.0 
14.0 
13.5 
11.0 
11.0 
11.0 
11.0 
11.0 
11.0 
10.5 
9.0 
9.0 
2 
Heated to 60° .. 
12.5 
12.5 
13.0 
3 
Heated to 70°.. 
11.0 
4 
Heated to 145° for 30 minutes . - 
11.0 
5 
Cooled to 130° (110° at end of holding) 
10.0 
9.5 
9.0 
9.0 
8.5 
8.0 
8.5 
8.0 
9.0 
6 
Cooled in can to 120° (110° at end of holding) . . 
9.5 
7 
Cooled in can to 110° . 
8.5 
8 
Cooled in can to 100° .. - 
8.5 
9 
8.5 
10 
Cooled in can to 80° . - . . 
6.5 
11 
7.5 
12 
Cooled in can to 60° 
8.0 
