Sweetened Condensed Milk Defects 199 



development of acid. In this condition it usually has a peculiar 

 stale and cheesy flavor, disagreeable to the palate. Such milk is in- 

 variably rejected on the market. 



Causes and Prevention : Effect of Colostrum on Thickening. 

 — It has been suggested that this spontaneous thickening is due 

 to the presence in the fresh milk of colostrum milk, because this 

 defect appears at a time when the majority of the cows supply- 

 ing the condensery freshen. This explanation can hardly be 

 considered correct and there is no experimental evidence avail- 

 able substantiating it. H the presence of colostrum milk were 

 the cause of it, the thickening would take place during the 

 process, as the result of the action of heat on the albuminoids. 

 This is not the case. This thickening begins some days and 

 often some weeks after manufacture and increases as the milk 

 grows older. 



Effect of Cow's Feed on Thickening. — Again, the cause of 

 this defect has been attributed to the change in feed, the cows 

 being turned from dry to succulent feed at the time when this 

 tendency of the condensed milk to thicken occurs. There is 

 no reliable evidence, however, of how the succulent pasture 

 grasses on which the cows feed can bring about this thickening 

 action in the condensed milk. 



Effect of Bacteria on Thickening. — A third and far more rea- 

 sonable explanation is that this thickening is the result of a 

 fermentation process. It is quite probable that the thickening 

 of sweetened condensed milk is closely related to the sweet- 

 curdling fermentation in fresh milk. The sweet-curdling of 

 fresh milk is a fermentation characteristic of, and frequent dur- 

 ing late spring and summer. It is caused by certain species of 

 bacteria which are capable of producing a rennet-like enzyme, 

 which has the power to curdle milk in the sweet state. These 

 bacteria are known to be closely associated with dirt and filth, 

 especially from the feces, and gain access to the milk usually 

 on the farms where the production and handling of milk is not 

 accomplished under most sanitary conditions. 



It is further known, as the result of analyses that, in spite 

 of the large per cent, of cane sugar which sweetened condensed 

 milk contains, the bacteria in it increase with the age of the 



