152 POPULAR SCIENCE MONTHLY. 



sheep's milk, goat's milk, etc., differences in the handling of the soft 

 curd, differences in the amount of salting and drying, differences in the 

 temperature and moisture of the 'cheese cellar/ all result in the growth 

 of different kinds of molds and bacteria, producing variously flavored 

 products. It is evident, too, that the character of the product will de- 

 pend upon the abundance and varieties of the plants which furnish the 

 flavor. Unless a dairy is supplied with the proper species of molds and 

 bacteria, it is hopeless to expect the desired results. Here lies the work 

 which the scientist must perform for the further development of the 

 cheese industry. 



The second type of cheeses, with which we are more familiar in 

 this country, is the type of hard cheeses. These are not only of denser 

 consistency, but they have commonly a less pronounced taste and odor 

 and are not so suggestive of decomposition. They are, also, commonly 

 made in much larger form, their denser nature making it possible for 

 them to be made in very large sizes. They keep longer and are, there- 

 fore, much more generally exported into different countries. 



The difference between the hard and soft cheeses, great as it is in the 

 perfected article, is due to quite slight variations in the method of manu- 

 facture. The hard cheeses are made from curdled milk, curdled in just 

 the same way as in the making of soft cheeses. But, after the curdling 

 and the cutting up the curd to allow the whey to separate, the curd is 

 broken up into small bits and placed in forms, where it is subjected to 

 heavy pressure. Sometimes, immediately after the cutting of the curd, 

 it is subjected to a moderate heat. For example, the Swiss cheeses are 

 heated to about 110° Fahr. for a short time after cutting up the curd. 

 This heating changes the nature of the curd somewhat and gives it 

 a tougher and more elastic texture. In all the hard cheeses the curd is 

 finally placed in wooden forms and then subjected to pressure, moderate 

 at first, but soon increased until the pressure is quite high. This pres- 

 sure converts the curd into a very dense, compact mass, and one in which 

 microscopic plants cannot so readily grow. 



But the hard cheeses require a ripening to develop the flavor as well 

 as the soft cheeses, and the ripening is a longer and slower process. The 

 pressed cheese is placed in rooms, or caves, or other locality where the 

 temperature is not very variable or where it can, perhaps, be artificially 

 controlled. Here it remains for weeks and frequently for months, dur- 

 ing which time it slowly changes its chemical nature as a result of the 

 action of the chemical or organic ferments, and simultaneously acquires 

 the flavors which characterize the perfected product. 



It is generally believed that the flavors here, as well as in the soft 

 cheeses, are due to the growth of microscopic plants; but the subject 

 has proved a very difficult one to investigate. Molds play little or no 

 part in ripening the hard cheeses. Indeed, their growth is prevented by 



