240 SWEETENED CONDENSED MII.K DEFECTS 



The empty tin cans in many of the plants are kept under 

 undesirable conditions. They are exposed to diverse channels 

 of contamination during transportation to the factory and dur- 

 ing storage in the factory. If these contaminated cans are sub- 

 sequently filled with the condensed milk, contamination is un- 

 avoidable and buttons are likely to follow. 



The tin cans should therefore be protected against avoidable 

 contamination, or better yet, they sHould be sterilized before 

 filling. 



A practical sterilizer of empty cans may be readily devised 

 by permitting the cans to pass bottom-side-up over a series of 

 gas flames, under a hood. This method is used successfully 

 in some of the European condenseries and has for them solved, 

 in a large measure, the prevention of buttons. The caps and 

 filling machines obviously should receive such treatment as to 

 prevent them, from becoming sources of contamination. Barrels 

 should be steamed till piping hot and then paraffined, before 

 filling. 



In factories with wooden floors where the filling and sealing 

 is done, the danger of mold contamination is much greater than 

 in the case of concrete floors. 



According to Thorn and Ayres 1 the spores of the mold Asper- 

 gillus repens, as well as of most other common molds, are killed 

 in 30 minutes at 140 degrees P. The preheating of the milk in 

 the hot wells, which is done at 180 degrees to 200 degrees F., 

 and again evaporation in the vacuum pan at 135 to 150 degrees 

 F. are, therefore, sufficient to destroy any mold present in the 

 original milk, so that the cause must be confined very largely 

 to contamination after the finished product leaves the vac- 

 uum pan. 



Low Temperature. The growth of most molds is retarded, 

 if not entirely inhibited at low temperatures. This also is the 

 case with the button-forming mold Aspergillus repens. Rogers 

 et al., state that this mold grows very poorly at temperatures 

 of 68 degrees F. or below. They report that they have never 



1 Thorn and Ayres, Effect of Pasteurization on Mold Spores, Jour. Agr. 

 Res., Vol. VI, 153-166, 1916. 



