238 SWEETENED CONDENSED Mik Derrects 
densed milk. ‘They themselves have, and they give the con- 
densed milk, a cheesy, stale flavor and lend the entire product 
an unsightly appearance. They depreciate the market value of 
sweetened condensed milk. 
Causes of Buttons.—Experience has demonstrated that but- 
tons are most prone to appear in stored condensed milk, in the 
packing of which no attention was given to sanitary conditions 
in the factory and of the cans or barrels, and that the use of 
clean sterile cans and barrels and a high standard of sanitation 
in the handling of the product before packing greatly minimizes 
this defect. ‘That they are the result of biological action, direct 
or indirect, is fairly obvious, and the fact that the milk during the 
process of manufacture is heated to temperatures destructive to 
most vegetative types of germlife, strongly suggests, that they 
are the product of recontamination of the finished product. 
Rogers, Dahlberg and Evans! of the United States Dairy 
Division investigated the causes and control of buttons experi- 
mentally. They found that the buttons are caused by the growth 
of the mold Aspergillus repens, and possibly by other molds; 
that the development of the mold colony is restricted by the 
exhaustion of the oxygen in the can or barre!, and that the button 
itself is probably due to enzyme action, continued after the 
death of the mold. 
These findings corroborate earlier experimental results by 
the author, who was unable to develop growing mold colonies 
in normal sweetened condensed milk from inoculations with full- 
grown buttons. 
Rogers and his co-workers demonstrated that the time re- 
quired for the development of the various stages resulting in 
button formation varies with temperature, amount of air avail- 
able and possibly other factors. The mold colony usually ap- 
peared in 5 to 10 days. Mold growth is supposed to cease in 
two to three weeks on account of the exhaustion of the air. In 
one month a reddish-brown discoloration became quite evident 
and at the end of two months the button had usually assumed 
1L. A. Rogers, A. O. Dahlberg and Alice C. Evans, The Cause and Control 
of Buttons in Sweetened Condensed Milk, Jour. Dairy Science, Vol. III, No. 
2, 1920. 
