162 PLAIN CONDENSED BuLK MILK 
slight and soft curd in his produet, that can be shaken out in 
the shaker in one-fourth to one-half minute. When the curd 
produced is firm, even prolonged shaking will not prevent the 
appearance in the finished product of specks and small lumps 
of curd. Such milk is rejected on the market. 
The formation of curd during the sterilizing process is not 
desirable and 1s not necessary as far as the marketable properties 
of the evaporated milk is concerned. It is unavoidable, however, 
under many conditions and as long as it can be confined to a soft 
curd that readily shakes out, no harm is done. 
INCUBATING. 
From the shaker, the cans are transferred to the incubating 
room. This is a room with a temperature of 70 degrees to 90 
degrees F. The evaporated milk remains there ten to thirty days. 
The purpose of incubation is to detect defective milk and de- 
fective cans before they leave the factory. If the contents of 
any of the cans have not been completely sterilized, or if any 
cans have the minutest leak, the evaporated milk therein will 
spoil within the time of incubation. Such milk either sours, 
curdles or becomes solid, or it undergoes gaseous fermentation, 
causing the appearance of “swell heads.’ The more nearly per- 
fect the process of sterilization and the better the construction 
and seal of the cans, the fewer are the spoiled cans. This incu- 
bation process is strictly a preventative measure. It is omitted 
in many factories where the cans are labeled, packed and ship- 
ped to their destination at once, or put in ordinary storage in 
the factory. 
CuHaprer XII. 
PLAIN CONDENSED BULK MILK. 
Definition.— This is an unsweetened condensed milk made 
from whole milk, or partly, or wholly skimmed milk, condensed 
in vacuo at the ratio of about three or four parts of fluid milk to 
one part of condensed milk. It is usually superheated to swell 
