148 DAIRY BACTERIOLOGY 



an undesirable taste. The moulds should not completely over- 

 grow the surface, neither should they form too many conidia. 

 The drying is regulated by providing for a suitable draught and 

 by laying the cheeses on straw mats ; after three weeks, when 

 the cheeses have softened at the corners, they are transferred to 

 another room and placed direct on the shelves, or sometimes on 

 mats infected with bacteria. The moulds are now displaced by 

 rod bacteria resembling Bacterium casei limburgensis, which 

 appear as red and brown spots between the mouldy ridges, and 

 the ammoniacal fermentation which starts under these spots 

 gradually penetrates to the centre, resulting in the production 

 of ammonium caseinate and other soluble proteins. The quicker 

 the cheese ripens, the quicker will it become perfectly liquid and 

 putrefying. A good saleable cheese should, therefore, be made 

 firm and ripened at a low temperature ; during the first few days, 

 when the cheeses are salted and develop acid fermentation, they 

 should be kept at 18 to 20 C. ; the drying room should be kept 

 at 13 to 15C., and the ripening room, to which the cheeses are 

 finally transferred for the chief fermentation to take place, at 

 10 to 12 C., or even lower. Frequently the process is completed 

 in the boxes in which the cheeses are packed for transport. 

 Cheeses never get the proper taste if they are put in the boxes 

 too early. As soon as the interior of the cheese has become 

 neutral in reaction the lactic acid bacteria will be able to act as 

 in hard cheeses, but they act slowly and have no time to produce 

 any noteworthy change before consumption. While Oidium 

 lactis and the necessary bacteria will establish themselves of their 

 own accord, there is some difficulty in establishing the desired 

 species of Penicillium in places where the manufacture of Camem- 

 bert is to be started. Thorn recommends their cultivation on 

 dry, sterilised rusks, wetted with a suspension of the conidia in 

 water. After keeping for ten days at 20 C., the rusks will be 

 overgrown by the mould ; these mouldy rusks are then shaken 

 vigorously with water, in which the cheeses are dipped immediately 

 before salting. The French mode of procedure is more scientific ; 

 the Institut Pasteur (Service des vaccins. 35, Rue Dutot, Paris) 

 supplies three different cultures for the purpose, consisting of 

 an ordinary lactic acid starter, a culture of moulds, and a culture 

 of the ammonia-producing bacteria. The two first-mentioned of 

 these, or sometimes all three, are added to the milk before the 

 rennet. The mould culture need only be used for the first ten 

 days, after which it will have established itself in the mats used 

 in the drying room, from which subsequent batches of cheese 

 will become inoculated. The third culture is applied directly to 

 the mats on which the cheeses rest during the last stage of 



