174 Dairy Bacteriology. 



not of the best quality, is certain to result in a much bet- 

 ter product than when higher temperatures are em- 

 ployed. 



Abnormal fermentations in cheese. As has been 

 previously shown, it is necessary to have an abundant 

 supply of acid-forming bacteria in the milk from which 

 cheese is to be made. If these bacteria are supplanted 

 by other kinds, the product will be more or less abnormal 

 either in texture or in flavor, or possibly in both. Many 

 of these abnormal fermentations have been studied and 

 the organisms concerned in the changes found. 



If the milk is handled carelessly, it will contain many 

 bacteria able to form acid and gas. As noted previously, 

 these organisms form products in milk that have an 

 offensive odor and a disagreeable taste. In cheese the 

 gases cause the formation of holes, more or less numer- 

 ous, depending on the number of the gas-forming bac- 

 teria in the milk. Where these bacteria are abundant, 

 gas may appear while the curd is in the vat, causing it 

 to float in the whey, when it is known as a "floater." 

 Again, the gas may not become evident until the cheese 

 is in the press or on the curing shelf, when it becomes 

 apparent by the swelling or bulging of the cheese. Such 

 cheese is termed "huffed" or "swelled." The internal 

 pressure may be so great as to cause the cheese to crack 

 and to force out some of the curd. The presence of gas 

 holes is indicative of a poor cheese, because the forma- 

 tion of gas is always accompanied by the presence of 

 other undesirable compounds. 



Pure culture starters are often used to overcome gassy 

 fermentations. In cheese a certain amount of acid can 

 be produced by the acid-forming bacteria. When the 

 pure lactic bacteria alone are present, the cheese is very 



