June 15,1914 
Ripening of Cheddar Cheese 
205 
bination with the cheese colloids; consequently the concentration of 
acid or alcohol in such water may be very large, thereby affording an 
opportunity for ester formation by mass action. On the other hand, it 
must not be assumed that the alcohols or acids are “free” in such a com¬ 
plex system, but may also be in combination with the colloids of the 
cheese mass. If this last alternative is permissible—and the writers 
believe it to be true, especially for the acids—then there is some reason, 
at least, for the assumption that ester formation is not the result of mere 
contact of acid and alcohol, but occurs through the intervention of some 
agent which shifts the point of equilibrium in the system toward ester 
stability. 
To determine whether inherent milk enzyms acting in curing cheese 
could produce esters, alcohols, or volatile acids, a cheese was made 
from chloroformed milk and kept in an atmosphere of chloroform for 5 
months. To determine the volatile bodies, 800 grams of the cheese were 
submitted to steam distillation, after acidifying with H 2 S0 4 . The entire 
analytical process was conducted as has been described. The results 
were negative, there being neither acids nor esters. This shows that 
inherent milk enzyms are not the cause of the production of volatile fatty 
acids and esters in curing cheese. From this experiment it is apparent 
that the inherent lipase in milk is either retarded in its action by chloro¬ 
form or else is very slow in its action. 
AMMONIA PRODUCTION IN MILK* 
The origin of ammonia in ripening cheese had been ascribed by Bab¬ 
cock and Russell (1897, p. 161) and Babcock, Russell, Vivian, and Hastings 
(1899, p. 157) to the action of galactase. In further work on this prob¬ 
lem Van Slyke and Hart (1903) showed that in chloroformed cheese, where 
galactase and pepsin would be the only proteolytic agents present, no 
ammonia was formed. To throw further light on this problem, cultures 
of a few of the organisms known to be active in Cheddar cheese were 
examined for ammonia production. Milk was the medium used for these 
determinations. A part of this medium, in the case of the coccus group, 
was distilled directly with MgO. In the case of Bacterium casei , the 
medium was first treated with tannic acid and salt solution according to 
the standard methods for separation of the tannin precipitate, and the 
ammonia determined in the filtrate by distillation with MgO. In Table 
XIV are recorded the results. 
