158 Condensed Milk and Milk Powder 



back into the condensed milk of succeeding batches. If these sam- 

 ples happen to be contaminated with the fermenting germs, the 

 defect is naturally propagated from batch to batch and it is exceed- 

 ingly difficult to locate the source of the trouble. It is obvious that 

 all suspicious "cut-opens" should be rejected and that all "cut-opens" 

 that are utilized should be emptied into the hot well where their 

 contents are boiled up again. 



Dangerous Effect of Poor Quality of Sugar. — 'Sweetened con- 

 densed milk is not sterile. There is no part of the process that 

 would render it sterile and, from the time it leaves the vacuum pan 

 to the time when the tin cans are hermetically sealed, it is exposed 

 to contamination with microbes, even though the factory observes 

 the most rigid attention to scrupulous sanitation and cleanliness. 

 Most of these microbes are harmless and their growth is inhibited 

 by the preservative action of the cane sugar. If, however, a poor 

 quality of sucrose is used, which may contain traces of invert sugar, 

 or acid, etc., many of these common species of micro-organisms, 

 harmless in normal condensed milk, find an opportunity tO' develop 

 and cause gaseous fermentation. The presence of invert sugar 

 makes unnecessary the action of invertase in order to start fer- 

 mentation; thus, microbes which do not secrete invertase and are 

 otherwise harmless, may become detrimental in the presence of in- 

 vert sugar, added to the milk in the form of a poor quality of cane 

 sugar. In a similar way the use in condensed milk of commercial 

 glucose, as a substitute of a part of the cane sugar, and in order to 

 reduce the cost of manufacture, is bound to cause disastrous re- 

 sults. Nothing but the best refined, granulated sucrose should be 

 used, the best is the cheapest. 



Dangerous Effect of High Acid in Milk. — Acids have the power 

 of inverting sucrose. The inversion by acid is especially active in 

 the presence of heat. The milk in the vacuum pan is condensing at 

 130 to 150 degrees F. These temperatures are most favorable to 

 inversion of a portion of the sucrose in the presence of acid. The 

 higher the acid content of the milk, the more active is the inversion. 

 Since invert sugar is the very ingredient necessary to cause bacterial 

 action in the finished product, it is essential that the acidity of the 

 milk to be condensed, should be held down to the minimum in order 

 to avoid trouble from this source. 



