184 
Journal of Agricultural Research 
Vol. II, No. 3 
pure cultures was used as a starter. Usually every type which was 
added to the cheese was isolated in considerable percentages in some 
one or more of the analyses. Thus, it has been shown that the flora 
of pasteurized-milk cheese consists almost entirely of the organisms 
which are introduced in the starter, with a small percentage of micro¬ 
cocci and steadily increasing numbers of Bacterium casei. 
RELATION OF THE VARIOUS TYPES OF CHEESE ORGANISMS TO FLAVOR 
PRODUCTION 
Since it has been shown that in pasteurized-milk cheese the bacterial 
content is practically limited to the varieties which are added during the 
making, together with small percentages of micrococci, and a development 
of the Bacterium casei group similar to that in a raw-milk cheese, although 
it is usually more or less retarded, it is possible to gain some knowledge of 
the influence of the different varieties in pure culture upon flavor pro¬ 
duction. 
A normal raw^-milk cheese of the Cheddar type will, after a few days’ 
ripening, begin to develop a delicate flavor which is characteristic of this 
type of cheese. This' flavor becomes intensified as the cheese matures, 
and after ripening for a number of weeks, depending upon the tempera¬ 
ture at which the cheese is kept, it acquires a pungent taste which also 
intensifies with continued ripening. 
A pasteurized-milk cheese made with a commercial starter will never 
develop the Cheddar flavor which characterizes a young raw-milk cheese 
of this type, but it does develop an acid flavor which is pleasant to the 
taste of many people. If the cheese is kept for several months, the acid 
flavor disappears and the biting taste common to well-matured raw-milk 
cheese becomes the characteristic flavor. 
THE RdLE OF BACTERIUM CASEI IN FLAVOR PRODUCTION 
The floras of the two types of cheese, which differ essentially during 
the first few weeks of ripening, become more and more alike as the cheese 
matures. As shown in Table XV, Bacterium casei develops in pasteurized- 
milk cheese in as large numbers as in raw-milk cheese. It is reasonable, 
therefore, to ascribe to this group of organisms the development of the 
pungent flavor common to the two types of well-matured cheese. 
In Table XV are given the numbers of Bacterium casei in a raw-milk 
and in a pasteurized-milk cheese made the same day from the same lot 
of milk. Until the forty-second day the raw-milk cheese contains about 
10 times as many of the B . casei as the pasteurized-milk cheese, but after 
the forty-second day the cheeses contain about equal numbers of these 
organisms. 
Cheeses Nos. 307 C and 307 illustrate the Bacterium casei content found 
in 12 similar cheeses—6 of the raw milk and 6 of the pasteurized milk— 
