688 EXPERIMENT STATION RECORD. 



used alone or combined with other forms, and the cheese did not ripen 

 with the liquefying bacilli alone. 



As the pasteurized milk was not eutiiely free from micro-organisms, 

 experiments were undertaken with milk which was obtained under tlie 

 greatest precautions in the hope of securing aseptic milk. This milk 

 was found, however, to contain from 92 to 500 bacteria per cubic centi- 

 meter. The cheese molded, although it was kept under a sterilized bell 

 glass, and was then scraped and dipped in a solution of paraffin, which, 

 in some cases, promoted the growth of an amerobic bacillus. This, 

 however, is not believed to have interfered with the experiment. " These 

 experiments indicate anew that the ripening of cheese is invariably 

 associated with the presence of lactic-acid organisms and under the 

 exclusion of so-called tyrothrix bacilli; the latter were not to be found 

 in the ripened portion of the cheese or on the surface." 



Studies were then made on the effect of lactic acid in changing the 

 casein, to determine definitely whether the change in the casein was 

 due to the action of the lactic organisms or to the acid produced. The 

 lactic acid produced in the milk cultures was neutralized by calcium 

 carbonate, the bottles being frequently shaken for this purpose. The 

 results showed that the change in the casein could not be attributed to 

 the action of lactic acid. 



Finally the results are recorded of 12 experiments in inoculating into 

 milk various pure cultures of micro-organisms isolated from cheese. 



The author's final conclusion is that the lactic acid organisms, espe- 

 cially those isolated from cheese, are able to dissolve and decompose 

 casein, and that there is no further ground for doubt that the cause of 

 the ripening of hard cheese is to be found in the lactic organisms. He 

 suggests that, knowing the cause of the ripening, a practical applica- 

 tion may be made as has been done in butter making in using pure 

 cultures for ripening cream. 



The fungi taking part in cheese ripening, O. Johan-Olsen (Gentbl. 

 Bald, u. Par., 2. AM., 4 (1898), No. J, pp. lt;i-l<;9, pis. 6).— The author 

 gives a condensed account of his studies on the cause of the ripening 

 of Gammelost, a Norwegian cheese made from pasteurized skim milk, 

 and the use of a mixture of pure cultures in the manufacture of this 

 cheese. From the various forms of micro-organisms found in different 

 samples of the cheese, it was found by practical experiments extending 

 over quite a period that the best results were obtained by the use of 

 pure cultures of lactic-acid organisms from Gammelost cheese, Chlamy- 

 domucor casei, Mucor casei I, and Penicillum aromaticum casei. The 

 character of the cheese could be changed at will by partial changes in 

 the organisms used. The method of making the cheese by the old and 

 the new ways is described. The cheese made with the pure cultures was 

 much more uniform in quality, kept better, had a liner flavor, and a less 

 objectionable odor. The ripening can be so well regulated that less 

 than 10 per cent of the cheeses are inferior. These pure cultures are 



