238 SWEETENED CONDENSED MILK DEFECTS 



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 1 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 barrel, 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 



1 L. A. Rogers, A. O. Dahlberg and Alice C. Evans, The Cause and Control 

 of Buttons in Sweetened Condensed Milk, Jour. Dairy Science, Vol. Ill, No. 

 2, 1920. 



