262 UNSWEETENED CoNbENSED Mirk Drrecrs 
the pressure and the intelligent use of the homogenizer, furnish 
a satisfactory and reliable means to prevent fat separation.’ 
Fermented Evaporated Milk. 
General Description. 
orated milk, which after sterilization, has undergone fermenta- 
Fermented evaporated milk is evap- 
tion. ‘The type of fermentations found in this product varies 
w'th locality, season of year and factory conditions. ‘The con- 
tents of the cans may have soured with curd formation, or a 
curd may have formed without acid development, or the fer- 
mentation may be gaseous, in which case the cans bulge, and 
these gaseous fermentations may be accompanied by acid forma- 
tion or by putrefactive products. In all cases of fermented milk 
the product is entirely worthless. These defects are usually, 
though not always, detected during the period of incubation. 
Fermented evaporated milk is the result, cither of incomplete 
sterilization, or of leaky cans. ‘The causes of fermented evap- 
orated milk differ with the specific type of fermentations pro- 
duced; they will be discussed separately and as relating to the 
respective types of fermentations. 
Acid Fermentation, Sour, Curdled, Evaporated Milk. 
General Description.—Upon opening the cans the contents 
are found to be sour and curdy. 
Causes and Prevention.—This condition is the result of the 
presence of acid-producing species of micro-organisms, usually 
of the lactic acid type, which sour the milk, and the acid produced 
curdles the casein. Since the majority of the lactic acid bacteria 
are not resistant to heat and are destroyed at relatively low heat, 
this defect is not usually caused by incomplete sterilization. ‘The 
temperature of sterilization, though it might be insufficient to 
kif] spore forms, 1s high enough to make it impossible for lactic 
acid bacteria to pass the process alive. 
The only way in which this defect can occur is through sub- 
sequent contamination of the contents of the cans with these 
germs, and the only possible channel, through which this sub- 
sequent contamination may occur, 1s leaky cans, or leaky seals. 
1¥Wor details on the use of homogenizer see Chapter IX on ‘“Homogeniz- 
ing.” 
