SWEETENED CONDENSED MILK DEFECTS 205 



milk, the contents of which have undergone gaseous fermenta- 

 tion, the resulting pressure causing the ends of the cans to bulge 

 or swell, and frequently to burst open the seams. In the case 

 of barrel goods, the pressure may cause the barrel head to blow 

 out. This gaseous fermentation is usually, though not always, 

 accompanied by the development of acid and the formation of 

 lumps. 



This fermented milk is worthless for any purpose and means 

 a total loss to the manufacturer. The loss is generally aug- 

 mented by the fact that this trouble does not become noticeable 

 at once; its development requires several weeks, so that large 

 quantities of condensed milk may have been manufactured before 

 it is apparent that the milk is defective. Some of the goods may 

 have reached the market before the cans begin to swell, in which 

 case the reputation of the respective brand is jeopardized. In 

 some instances entire batches show this defect, while in others 

 only a few cans or cases of each batch are blown. 



Causes and Prevention. This defect may be brought about 

 through various channels. In most cases it is due to contamina- 

 tion of the milk, on the farm or in the factory, with specific 

 micro-organisms which are capable of fermenting one or more 

 of its ingredients, in spite of the preservative action of the 

 sucrose; or the condensed milk may contain highly fermentable 

 substances such as glucose or invert sugar, so that the germs 

 normally present in the condensed milk become active and pro- 

 duce gas ; or the milk may not be condensed to a sufficient degree 

 of concentration, or may not contain adequate quantities of 

 sucrose, to render it immune to the bacteria normally present. 

 The cans may also bulge without bacterial action, as the result 

 of exposure to a w r ide range of temperatures, causing mechanical 

 contraction and expansion of the contents. 



Contamination With Specific, Gas-Producing Bacteria and 

 Yeast. This is by far the most common cause of blown milk. 

 While the. micro-organisms which, under normally sanitary pro- 

 duction of milk and factory conditions, gain access to the con- 

 densed mik, are largely inhibited and do not ferment the sweet- 

 ened condensed milk, there are certain specific forms of bacteria 

 and yeast whose growth is not retarded by the concentrated 



