Aug. i, 1921 
A Souring of Beef Caused by Bacillus megatherium 693 
Table II .—Comparison of fermentation reactions 
Organism. 
Dextrose. 
Dactose. 
Saccharose. 
Mannite. 
Xylose. 
Levulose. 
B. megatherium . 
Acid.. . 
Negative. 
Slight 
Negative. 
Negative. 
Acid. 
acid. 
1510-B.. 
. ..do. 
Acid . . 
do 
do 
Do. 
Organism. 
Galactose. 
Inulin. 
Arabinosc. 
Dulcitc. 
Maltose. 
Salacin. 
B. megatherium . 
Acid. .. 
Negative. 
Negative. 
Negative. 
Acid... 
Acid. 
1510-B.. 
Npcrnti vo 
CHEMICAL EXAMINATION OF SOUR BEEF 
To determine the identity of the acid produced by organism 1510-B 
in the process of souring beef, the following preparations were tnade: 
About 125 gm. of sterile raw meat pieces were inoculated with organ¬ 
ism 1510-B and incubated for eight days. A corresponding container 
of sterile raw beef, uninoculated, was likewise treated as a control. At 
the end of eight days both specimens were removed from the incubator. 
The inoculated specimen had acquired an intensely sour odor, character¬ 
istic of that previously produced by the organism in meat, while the con¬ 
trol specimen was apparently unchanged. 
As a control on the purity of the culture which had produced the 
souring, bouillon cultures were inoculated with fluids from the sour speci¬ 
men. These cultures were plated, and eight representative colonies 
were “picked off’’ from the plates, each of which colonies subsequently 
developed, on agar slants, growths which invariably were true to type 
in morphology, cultural characteristics, and the ability to reproduce 
sour beef. 
It was therefore concluded that this specimen was rendered sour by a 
pure culture of organism 1510-B. 
This specimen and the uninoculated control specimen were then sub¬ 
mitted to J. F. Couch, pharmacological chemist of the Pathological 
Division, Bureau of Animal Industry, for an identification of the acid 
produced in the meat by the organism 1510-B. 
The report of his technic is as follows: 
Both samples were cooled in a refrigerator and were then extracted with cold ether. 
Upon evaporation of the ether extracts the rcsidne from the normal beef deposited 
a small quantity of fatty matter which was neutral in reaction and had the odor of 
beef tallow. The residue obtained from the inoculated beef, however, was acid to 
litmus and carried the offensive putrefaction odor of the sour-beef specimen. From 
this small residue some evidence of propionic acid was obtained. The sour-beef 
specimen was, therefore, extracted with 300 milliliters of 2 per cent sulphuric-acid 
solution by digestion at a moderate temperature. The aqueous solution was filtered 
by suction, and the clear fdtrate, which had the characteristic putrefaction odor, was 
