212 SWEETENED CONDENSED MILK 



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 package 

 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, Penicilium 

 Roqueforti, Cladosporium butyri, Oidium lactis, Actinomycoces 

 odorifora, yeast and various bacterial species, such as Bacterium 

 fluorescens, pjacterium prodigiosum, Bacillus mesentericus, etc., 

 and that these species are capable of making butter rancid, has 

 led to the conclusion that they may be the cause of rancidity, 

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

 zymes. It is, therefore, quite possible that some of these species, 

 or similar groups of species, may be instrumental in developing 

 rancidity in sweetened condensed milk. It has been further 

 found that the milk products from certain individual cows, or 

 cows under certain physiological conditions are more prone to 

 develop a rancid flavor, than milk products from other cows or 

 cows under other conditions. 



2 Hunziker, Results not published. 



