UNSWEETENED ConpbENSED MiiK DEFECTS 269 
temperature to which the cans are exposed at the high altitude 
is high, 
This type of swelled cans obviously has nothing to do with 
the quality of the contents, nor is it the result of fermentation or 
chemical changes. It is caused by the fact that the pressure in 
a can Sealed at the sea level is somewhat greater than the atmos- 
pheric pressure surrounding the can when transferred to a high 
altitude. If, at the same time, the milk packed at the sea level 
goes into the can at a low temperature and the atmospheric 
temperature at the high altitude, to which the sealed cans are 
shipped. happens to be high, the difference in pressure between 
the interior and exterior of the can is further increased, due to 
the expansion of the milk and of the air in the can. The com- 
bination of these factors is sufficient to cause the ends of the can 
to bulge, making it erroneously appear that the package contains 
fermented goods. 
This has actually happened in the case of one factory filling 
a Government war contract, the whole shipment of evaporated 
milk being rejected by the Government, because of the bulged 
cans. 
Occurrences of this type can be prevented by flling cans, 
intended for markets in high altitudes, with the evaporated milk 
while warm. 
Brown Evaporated Milk. 
General Description.—It is the aim of the processor to so 
govern the sterilizing process as to give the evaporated milk a 
rich, vellow. creamy color. Frequently, this color limit is over- 
stepped to the extent of imparting to the evaporated milk a brown 
color, suggesting coffee with milk in it. In this condition evap- 
orated milk fails to appeal to the consumer. 
Causes and Prevention.—The dark color in evaporated milk 
is due to the oxidizing action of excessive heat on the milk sugar, 
causing the milk sugar to caramelize. This can be avoided by 
reducing the sterilizing temperature, or shortening the sterilizing 
process, or both. The storing of evaporated milk at high temper- 
atures (summer heat) also tends to deepen its color with age. 
