206 
Journal of Agricultural Research 
Vol. II, No. 3 
Table; XIV .—Quantity of ammonia produced in 300 c. c. of milk by different organisms 
Organism. 
Quantity 
of NHj 
found. 
Quantity 
of NH 3 in 
control. 
Quantity of 
NH3 formed 
by organ¬ 
isms. 
Streptococcus b 2 . 
Grams. 
O. 0220 
. 0200 
.O45O 
.0520 
. 0690 
.0427 
.0382 
.0367 
•0453 
Grams. 
0. 023 
.023 
.023 
.023 
.023 
. 026 
. 026 
, 026 
. 026 
Grams. 
Streptococcus b 3 . 
O. 0220 
. 0290 
. 0460 
. 0167 
. 0122 
. 0107 
.OI93 
Micrococcus. 
Bacterium caseij. 
Bacterium casei 2 . 
No large quantity of ammonia was formed by any of the organisms 
examined. The difference in the amount of ammonia produced by 
Streptococcus b 2 and Streptococcus b 3 —two strains of the same variety— 
may be due to the fact that Streptococcus b 3 grew for more than twice as 
long a time as did the other. It is clear from Table XIV that some of the 
biological agencies active in the cheese are capable of forming both acids 
and ammonia. 
KINDS OF LACTIC ACID IN CHEESE 1 
In considering lactic acid and its changes in cheese, it will be remem¬ 
bered that lactose disappears from the cheese mass after a very few days 
of curing; subsequently the lactic acid increases up to the five weeks' stage. 
At later periods the lactic-acid content fluctuates, probably the result of 
production and decomposition by active organisms.. Thus, there seems 
to be a source of lactic acid other than lactose. A solution of alanin, one 
of the amino acids arising from casein proteolysis and very closely related 
to lactic acid, was inoculated with a piece of old cheese, in order to ascer¬ 
tain whether alanin could be a source of lactic acid (Suzuki, Hastings, 
and Hart, 1910). The results were negative, but it is possible that either 
the nature of the solution or the age of the cheese was responsible for 
this result. Additional work on this point is necessary. 
It is known that cheese contains lactic acid, which usually is racemic 
in variety. It has been shown in the preceding article that Cheddar 
cheese 4 or 5 days old contains both racemic and active lactic acid, the 
latter being present in much greater amount than the former. The 
active form gradually decreases until it disappears, while the racemic 
acid increases and remains. It was found by Salkowski (1909, p. 237) 
that the transformation of dextro lactic acid into racemic acid on pro- 
1 The work reported in the remainder of this paper was completed before the classification of cheese 
organisms referred toon page 195 and treated in detail in the preceding article entitled “ Bacteria concerned 
In the production ot the characteristic flavor of cheese of the Cheddar type" was adopted; consequently 
that classification is ignored in the following pages. 
