I SWEETENED CONDENSED MILK DEFECTS 249 



rees F. If the filled and sealed cans are exposed to a very 

 low temperature, as may be the case in winter, in store houses or 

 in transit, the milk and the air in the cans contract. This con- 

 traction is intensified by the fact that the sweetened condensed 

 milk does not freeze. Its concentration is so great that its freez- 

 ing- point is usually below the most extreme cold storage tem- 

 perature. This contraction of milk and air in the cans produces 

 a partial vacuum, causing air to be drawn into the cans through 

 the microscopic openings of the seal. When the cans are sub- 

 sequently moved into places with a more moderate temperature, 

 the milk and the air in the cans expand, but the milk on the in- 

 side of the cans forms a seal preventing the escape of the sur- 

 plus air. The result is that the ends of the cans bulge. This, 

 phenomenon has been experimentally determined by the author. 1 

 While the contents of such cans are perfectly normal, the pack- 

 age suggests fermented milk and may be rejected on the market. 

 It is evident, from the above data, that the swelling of the 

 cans, as the result of exposure to excessively low temperatures, 

 can readily be avoided, either by protecting the cans against ex- 

 cessive cold, or by using cans that are sealed with solder. The 

 solder-seals are hermetical so that no air can be drawn into the 

 cans when a partial vacuum is formed in their interior as the 

 result of the contraction of air and milk. 



Rancid Sweetened Condensed Milk. 



General Description. Sweetened condensed milk may de- 

 velop a distinctly rancid flavor and odor, a defect which renders 

 it unmarketable. 



According to the best authority, there are many agents 

 which may be active in the production of rancidity. The fact that 

 in rancid butter are usually found to predominate certain species 

 of organisms, such as the fungi of Penicilium Glaucum, Penici- 

 lium Roqueforti, Cladosporium butyri, Oidiiim lactis, Actinomy- 

 coces odorifora, yeast and various bacterial species, such as Bac- 

 terium fluorescens, Bacterium prodigiosum, Bacillus mesenteri- 

 cus, etc., and that these species are capable of making butter ran- 

 cid, has led to the conclusion that they may be the cause of ran- 

 cidity, either by direct action, or by the secretion of fat-splitting 



1 Hunziker, Results not published. 



