BACTERIOLOGY IN PRACTICAL CHEESE MAKING. 247 



knowledge of the bacteria concerned was obtained long after 

 the material was in common use. This whey is cultivated 

 something as yeast was in earlier years, and is carried from 

 farm to farm. A quantity added to the milk before it is made 

 into cheese is found to have a noticeable effect upon the 

 ripening. The ripening is hastened, the inoculated cheeses 

 being ready for market in about a third less time than other 

 cheeses not thus inoculated. The ripening is also more uni- 

 form. There are smaller numbers of abnormal ripened 

 cheeses than if the cheese is allowed to ripen without such 

 inoculation. The character of the cheese is slightly inferior 

 to the best type of cheese ripened without such inoculation, 

 and the cheeses do not keep quite so well and are less favor- 

 able for export. In spite of these disadvantages, the unifor- 

 mity of the product has made the use of slimy whey very 

 popular in Holland, and its use has extended until quite a 

 large proportion of the cheeses of that country (at least one 

 third) are now manufactured by this method of artificial 

 ripening. 



In the manufacture of other types of cheese also the use of 

 pure cultures of microorganisms is being adopted and is 

 slowly extending. The immense financial interests in the 

 cheese industry hold out great promises to any one who can 

 successfully discover a means of preventing the irregularities 

 of the cheese ripening and bring the process under strict con- 

 trol. But great obstacles have appeared in the way of prac- 

 tical results. In the first place, even after the proper micro- 

 organisms have been discovered, in order to insure their 

 proper action upon milk, it would seem that there must be 

 some means of depriving the milk of the bacteria already 

 present. This has been accomplished in the ripening of 

 cream by the simple process of pasteurization. In the manu- 

 facture of cheeses, however, pasteurization presents a serious 

 difficulty. Milk which has been pasteurized and subse- 

 quently made into cheese does not ripen normally, pasteuriza- 



