142 EVAPORATED M11,K—STERILIZING 
understand that the size of the cans may influence the sterilizing 
efficiency. It takes more time and agitation to sterilize gallon 
cans than small cans. At a time of the year when the milk con- 
tains micro-organisms of relatively high resistance to heat, as 
is often the case especially in fall and winter, the per cent loss 
of gallon cans due to “swell heads’”’ may become disastrously 
large, unless the manufacturer makes a special effort to adjust 
his process for gallon cans. Gallon size cans require about one 
degree F. more heat on a 15 minute run of holding than tall-size 
cans, and tall-size cans require about one degree F. more than 
family- and baby-size cans. 
The installation and efficient use of automatic temperature 
controllers and recorders is of material assistance for securing 
uniform results of sterilization. These accessories are made use 
of in numerous factories, and have proven to be of valuable 
help to the manufacturer. Aside from the fact that they actu- 
ally do facilitate the temperature control, they automatically 
Fig. 63. Bulb for automatic temperature control 
Courtesy of Taylor Instrument Co. 
make for increased efficiency of the operator. The knowledge 
of the operator that his work is permanently recorded and 
checked up exerts a beneficial effect on his performance. 
The operation of an experimental or pilot sterilizer also has 
proven a great help in the accurate determination of the amount 
of heat which the evaporated milk of anv batch requires, to 
produce the desired viscosity, body and color and that it will 
stand without becoming hopelessly curdy. ‘hese machines are 
of small size, accommodating only a few cans. 
A few sample cans of each batch are placed in the pilot 
sterilizer and run through the process. Thus the proper process 
to be used for the entire batch in the large sterilizer may he 
adjusted according to the behavior of the contents of the sample 
cans in the pilot sterilizer. 
Qualifications of the Processer.—The operator, or the person 
