FLAT SOURS 



PART I 



An Interesting Thern^ophile Encountered in Canned String Beans 

 Technical Bulletin No. 59 



ZAE NORTHRUP WYANT 



The organism described in this paper was encountered in all cans examined 

 (quart Mason jars) of one pack of string beans which were under-processed 

 in the hot water bath (23^2 hours only) when canned by the cold pack method. 

 At this particular time a studj^ was being made of flat sours. Just previously 

 an effort had been made to obtain from a nearby source canned goods affected 

 in this way in order that more exact information could be obtained with re- 

 gard to the methods employed in preparing and processing food. The canned 

 string beans studied were home growm and all directions for picking, pre- 

 paring and processing by the cold pack method were followed with the ex- 

 ception of those for the length of time the cans were to be heated. The 

 cans were stored in a cool place in the basement. 



All of the cans of string beans sometime later were observed by the house- 

 wife to contain a greater or less amount of white sediment. There was no 

 evidence of a swell or leak. One of the cans was opened and prepared for a 

 meal, but the odor which had seemed normal at first became intensely disa- 

 greeable on heating, so that the beans were not eaten. An unopened can of 

 the spoiled beans containing a large amount of white sediment was obtained 

 for bacteriological analysis. Although the cover was not bulged, when 

 opened there was evidence of considerable gas pressure. This effect was 

 probably exaggerated as heat was employed in sterilizing the cover, alcohol 

 being poured over it and burned off. The string beans were decidedly sour, 

 having a pH value of 4.4. 



The beans at first had a decidedly putrefactive odor. Some of the liquor 

 when poured out into a beaker had this same odor; on standing, however, the 

 bad odor became less prominent and finally disappeared altogether or became 

 almost supplanted by an odor resembling that of pineapples. Several per- 

 sons described the odor as being "fruity." Bacteriological studies were 

 made of the liquor and sediment as follows : 



Microscopic examination of the sediment showed a large number of bac- 

 teria, some having about the same morphology as B. botulinus, others were 

 rods smaller and thinner. All proved to be Gram negative. (Gram nega- 

 tive rods, largely, were also found by Barlow in spoiled corn incubated at 

 high temperatures). However, this observation did not eliminate the pos- 

 sibility of the presence of B. botulinus. 



To determine what different types of bacteria were present, three dilution 

 plates were made in string bean agar plus brom th5Tiiol blue, and incubated 



