Bacteria in the Cheese Industry. 151 



forms to such an extent that the necessary acid is not 

 produced. 



If bacteria are present in the milk that are able to 

 peptonize or digest the same, a not inconsiderable amount 

 of the cheese-producing solids may be dissolved and be 

 lost in the whey. Organisms of this class are usually 

 derived from dust and animal filth. By the use of the fer- 

 mentation or curd test (182), it is possible to detect a 

 condition of this sort in the milk. 



158. Starters in cheese-making 1 . Where the milk 

 reaches the factorv in an extra sweet condition, it is 

 sometimes advisable to add a starter to hasten the ripen- 

 ing of the milk. Usually sour milk is employed, but 

 with any starter, great care should be taken to add noth- 

 ing that will introduce into the milk any undesirable taint. 



Where "gassy " milks prevail, the proper development 

 of the acid is also interfered with, and in such cases, the 

 addition of a lactic ferment is of great aid in repressing 

 these abnormal fermentations. 



While the ordinary starter used is one of domestic 

 origin, as skim or sour milk, within recent years the 

 attempt has been made to introduce pure cultures 1 of va- 

 rious lactic acid-producing forms. These cannot be used 

 in pasteurized milk as is the case in butter-making, but 

 even where added to the raw milk, they exert a material 

 effect. By their use the necessary impetus is given to 

 the formation of acid, and the development of this re- 

 tards the growth of the gas-forming organisms. The 

 period of manufacture is also materially shortened. Their 

 use should, however, be carefully governed, as sour cheese 

 is apt to develop if employed too freely. 



Campbell 2 has also used the lactic starter to overcome 



1 Russell, 13th Kept. Wis. Expt. Stat., p. 108, 1896. 



2 Campbell, North Brit. Agric., May 12, 1897. 



