390 BACTERIA IN OTHER FOODS 



boy returned from the "Twin Cities" after an attack of diphtheria. 

 The milk from the farm where he lived was sent to a creamery and 

 every family in the place, in which there was diphtheria, was found 

 to have used butter from this creamery. Experiments have shown 

 that the diphtheria bacilli can live in butter for a month. 



Bacteria in Cheese. If undesirable species of microorganisms are 

 present in the milk they will pass into the cheese and there produce 

 their harmful effect. This is more important in cheese-making 

 than in butter-making since it has not been found possible to 

 make many of the important varieties of cheese from pasteurized 

 milk. The bacteria most dreaded by the cheese manufacturer are 

 those of the B. coli aerogens group. These give rise to the formation 

 of large holes which can be often taken to indicate bad flavor as the 

 organisms produce in addition to hydrogen and carbon dioxid 

 offensive smelling and tasting compounds. 



The bacteria of cheese increase during the first few weeks (Fig. 

 45), after which there is a decrease, but even in ripened cheese there 

 are millions of bacteria. 



Pathogenic bacteria which are in the milk will find their way into 

 the cheese, as Schroeder and Brett purchased 256 sample s of cheese 

 on the Washington market and examined them for tubercle bacilli 

 by means of guinea-pig inoculation; 7.42 per cent, contained tubercle 

 bacilli. Probably many of the tubercle bacilli die during the ripening 

 process, but this cannot be entirely depended upon, as Washburn 

 and Done prepared a cheese from infected milk and after 220 days 

 produced generalized tuberculosis by injection into guinea-pigs, 

 and even after 260 days injection of emulsions caused slight lesions. 

 According to the findings of Rowland, B. typhosus and M. choleroe 

 soon perish in cheese. 



Bacteria in Ice Cream. The number of bacteria in ice cream may 

 at times be enormous. There is only a slight decrease on storage, 

 as is seen from the following results of Hammer and Goss: 



SHOWING THE EFFECT OF STORAGE ON THE NUMBER OF BACTERIA IN 



ICE CREAM. 



Mixed . 236,000 32,800,000 120,000 172,500,000 110,000,000 120,000,000 



Frozen . 735,000 30,850,000 146,000 271,000,000 170,000,000 140,000,000 

 Days old: 



1 . . 360,000 7,750,000 137,000 157,000,000 194,000,000 70,000,000 



2 . . 310,000 4,450,000 216,000* 128,000,000 216,000,000 71,000,000 



3 . . 260,000 2,435,000 52,000,000 102,000,000 



4 . . 1,150,000 152,000 



5 . . 310,000 . . 300,000 34,000,000 39,000,000 41,000,000 



6 . 139,000 



7 156,000 31,000,000 54,000,000 



8 . .. .. .. 61,000,000 



9 . . . . 36,000,000 



10 



11 .. .. .. 15,000,000 



12 



