MILK-PLANT EQUIPMENT. 23 
Table 5. — Types of pasteurizers used at 237 plants of various sizes. 
Milk handled 
daily. 
Vat. 
Tubular. 
Film or 
drum. 
Kettle. 
In the 
bottle. 
In the 
can. 4 
' Total 
all types. 
Number 
of these 
plants 
using the 
flash 
system. 
Gallons. 
Up to 100 
14 
27 
26 
3 24 
14 
8 
2 
- \ 
1 
2 
6 
10 
7 
10 
4 
5 
2 
1 
3 
1 
3 
12 
15 
38 
52 
48 
40 
18 
5 
101 to 250 
1 
2 
8 
12 
9 
12 
1 
251 to 500... 
1 
9 
12 
12 
4 
3 
3 
1 
4 
501 to 1,000 . 
4 
1,001 to 2,000 
3 
2,001 to 4,000 
2 
4,001 to 6,000 
1 
6,001 to 10,000 
Over 10,000 
4 
1 
Total 
88 
44 
48 
37 
10 
4 
237 
1 Two of these were starter cans. 
2 One was the " spray " vat system. 
3 Two were the "spray" vat system. 
4 Cans set in vat of water which is heated with live steam. 
TEMPERATURE REGULATOR. 
Automatic temperature control is essential to the pasteurizing 
plant. It is very difficult and often impossible to control the tem- 
perature by means of hand valves, but there are many automatic 
devices on the market which control the temperature with great 
accuracy. In a plant without an automatic control a large propor- 
tion of a man's time must be spent at the steam valve if the tem- 
perature is to be kept within proper limits. During the process of 
pasteurization one man has to spend the greater part of his time 
there, and even then it is very difficult to prevent frequent varia- 
tions in temperature, Not only may the cream line be injured by 
such irregular temperatures, but the results, both from bacteriologi- 
cal and chemical points of view, are unsatisfactory. 
RECORDING THERMOMETER. 
The recording thermometer is another appliance that should be 
used in all plants where milk is pasteurized. By means of this de- 
vice a record of the temperatures of the milk during the whole 
day's run is made. Each day the superintendent has a report which 
shows the temperature to which the milk is heated at any period 
of the process and also, within certain limits, how long it was held 
at the pasteurizing temperature. Thus, although not necessarily 
present himself, he can keep a reliable check on the operator. These 
records can also be shown to complaining customers or to health 
officials as evidence as to how the milk was pasteurized. 
Recording thermometers must be tested after being set up and 
checked with an accurate hand thermometer. They may get out 
of adjustment and should be checked up frequently. 
