246 SWEETENED CONDENSED MILK DEFECTS 



though the factory observes the most rigid attention to scrupu- 

 lous 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 gase- 

 ous fermentation. The presence of invert sugar makes unneces- 

 sary the action of invertase in order to start fermentation ; thus, 

 microbes which do not secrete invertase and are otherwise harm- 

 less, may become detrimental in the presence of invert sugar, 

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

 In a similar wtay the use in condensed milk of commercial glu- 

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

 reduce the cost of manufacture, is bound to cause disastrous 

 results. 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 con- 

 densed, should be held down to the minimum in order to avoid 

 trouble from this source. 



Contamination with Butyric Acid Bacteria. Frequently the 

 troublesome microbe is not a yeast, but belongs to a species of 

 bacteria highly resistant to heat, and which fail to be destroyed 

 by heating the milk to the boiling point. In this case, the con- 

 tamination usually originates on the farm. Organisms of this 

 kind, which infest the milk on the farm in this connection, 

 largely belong to the butyric acid group. The most prominent 

 among them are Granulobacillus saccharo-butyricus mobilis or 

 Bacillus saccharobtttyricus, Bacillus esterificans, Bacillus dimor- 

 phobutyricus. The putrefactive forms of butyric acid organisms, 



