160 Condensed Milk and Milk Powder 



fresh milk. It is obvious that such a practice is bound to jeopardize 

 the quality and life of the finished product and may constitute a 

 continuous cause of blown milk. 



Effect of Amount of Sucrose. — Since the sucrose contained in 

 sweetened condensed milk is the chief agent preserving it, it is ob- 

 vious that enough of it must be added to insure adequate preserva- 

 tive action. Experience has shown that about 39 to 40 per cent, of 

 sucrose is required to preserve the condensed milk under average 

 conditions. A higher per cent, of sucrose would naturally intensify 

 the preservative action and inhibit the growth of the bacteria 

 normally present more completely; but if enough sugar were added 

 to also inhibit the growth of and make harmless those violent gas 

 producing butyric acid bacteria and yeast cells, which thrive in 

 sweetened condensed milk containing 40 per cent, sucrose, the 

 product would be objectionable from the consumer's point of view. 

 The logical avoidance of "swell heads" as the result of these un- 

 desirable germs, therefore, must ever lie in prevention, rather than 

 cure. The sanitary standard of production on the farm and O'f the 

 process in the factory must be raised to and maintained oh a level 

 where the milk is protected from contamination with these micro- 

 organisms. 



The writer 1 has isolated yeast from fermented sweetened con- 

 densed milk that produced vigorous gas formation in media contain- 

 ing as high as 85 per cent, sucrose (600 grams sucrose in 100 c.c. 

 whey bouillon). 



Effect of Too Thin Condensed Milk. — Condensed milk that is 

 too thin is, also, prone to start fermenting, since it is deficient in 

 the chief preserving agents, i. e.,' density and per cent, of sucrose. . 

 It is not safe to put goods on the market, with a ratio of concen- 

 tration much less than 2.5:1. 



Effect of Excessively Low Temperatures. — The cans of sweet- 

 ened condensed milk may also bulge in the case of cans with non- 

 hermetical seals, exposed successively to excessive cold and to room 

 temperature. In this case, the condensed milk is entirely normal 

 and unaffected, and the bulging is the result of mechanical con- 

 traction and expansion by cold and heat. This is possible only 

 where the seal of the cans is not entirely hermetical. In the case of 



2 Hunziker, Results not published 



