326 THE FERMENTATION OF CHEESE. 



certain constant temperature, the degree and duration of exposure 

 varying in different kinds of cheese. In the case of Emmenthal 

 cheese, Schaffer showed that a merely gentle after-warming of the 

 curd results in a quicker and more perfect ripening, so that the 

 finished cheese contains a large proportion of products formed by 

 the decomposition of albumin. Freudenreich investigated this 

 condition from a bacteriological point of view, and explained the 

 fact already recorded in 177 viz., that the ripening of hard cheese 

 is almost exclusively brought about by bacteria, whilst that of soft 

 cheese is chiefly occasioned by higher fungi (budding fungi, oidium) 

 as due to the inferior powers of resistance to high tempera- 

 tures exhibited by the latter organisms. Thus the cheese-maker's 

 old rule that " curd for soft cheese should be only gently warmed " 

 is shown to be well founded. 



Certain prescriptive methods of preparation for a large num- 

 ber of different kinds of cheese have been gradually built up 

 as the outcome of practical experience. The possibility of such 

 a result is a proof that the bacterial species necessary in the 

 ripening of cheese are present everywhere and at all times. The 

 exact observance of these recipes can, however, only continue to 

 indefinitely yield uniform results where the composition of the 

 bacterial flora of the milk set for cheese undergoes merely un- 

 important fluctuations. This is the case in the Alpine dairies, 

 where the grazing grounds seldom, if ever, receive any application 

 of manure from external sources, and consequently the same 

 species of bacteria are continually returned to the ground anew 

 in the dung of the grazing cattle. For this reason the cheese- 

 dairying industry necessarily developed first in the High Alps, 

 since there the business is, in a bacteriological sense, exposed to 

 the minimum of danger. The case is different in the lowlands, 

 where the cows are fed with fodder of highly diversified origin, 

 frequently consisting of the residues of agricultural industries 

 (grains, distillery residue, grape skins, &c.). The bacterial flora 

 of the dung of such animals will be liable to frequent changes ; 

 and since the bacterial content in the milk is for the most part 

 derived from the dung, it will be evident that the cheese-making 

 process will be affected by this change. Greater difficulties conse- 

 quently attend the pursuit of the industry in lowland districts, 

 and much less reliance can be placed on recipes. To explain this 

 more clearly by an example, reference may bo made to an observa- 

 tion which chemists have been unable to explain, but which 

 regarded from a bacteriological standpoint seems almost self- 

 evident, viz., the difficulty experienced in the working up of milk 

 at such times of the year as a change is made from dry to green 

 fodder, and vice versa. The bacterial flora of fresh grass is of a 

 much more diversified character than that on dry hay ; only a 

 few species remaining alive and capable of development in the 

 latter. 



