530 ^A Study of Ropy Bread [June 



constant appearance of infection in the bread of the immediate 

 vicinity. In one family attempts had been made to discover the 

 cause of the trouble, but without success. The yeast had been 

 varied, the bread had been most thoroughly baked, and the flour 

 had been changed, but the odor and flavor peculiar to ropy bread 

 continued to develop within a few days after baking. However, 

 the same flour bin and Utensils had been used persistently, and the 

 bread had been kept in a tight bread-box. 



Investigations were begun in order ( i ) to discover the cause of 

 the infection, and (2) to determine some methods of prevention 

 practical for the housewife. With these purposes in view the fol- 

 lowing experiments were carried out, the ordinary short process 

 method of bread-making being used. 



Experiment i. The aim of this experiment was to determine 

 the cause and source of the infection. 



Method. A flour considered as sound was first proved to con- 

 tain no rope-producing bacilli. This was done by making a loaf 

 of bread and incubating it at the same degree of moisture and tem- 

 perature as a corresponding loaf to which some infected flour had 

 been added. The fact that under exactly the same conditions the 

 latter loaf developed ropiness while the former did not was taken as 

 evidence that the former flour was sound. This sound flour was 

 then used in all control work, and when inoculations were made it 

 was used as the medium. 



Portions of the suspected flour were tested by mixing it with 

 sound flour and making breads. These breads were incubated at 

 various temperatures and under various conditions of moisture. 

 The suspected flour was also mixed with water and boiled for 20 

 minutes, after which it was used to inoculate sterile bread sticks 

 according to Watkins' method. 



Hanging drop studies were next made from some infected 

 bread. Gelatin-plate, gelatin-stab, and agar-streak cultures were 

 made from the same material. Capsule stains were subsequently 

 tried. Tables i and 2 show the results of this experiment. 



A study of the hanging drop showed a considerable number of 

 short, sluggishly-motile rod-shaped bacilli, and some cocci. On 

 staining, the bacillus showed the presence of a capsule. Inoculated 

 bread sticks developed ropiness. 



