June 15,1914 
Flavor of Cheddar Cheese 
169 
the other groups of cheese organisms, so that a subinoculation into tubes 
of litmus milk containing dextrose and peptone resulted in the growth 
of the lactic bacilli alone. The culture was then purified by plating. 
The plate cultures of the cheese dilutions were made in casein agar 
(Ayers, 1911), to which 1 per cent of dextrose was added; they were 
incubated at 37 0 C. for two days and then kept at room temperature for 
four days. In order to obtain the percentage of the various cheese 
organisms which develop upon the casein-dextrose-agar plates, a portion 
containing 10 colonies was circumscribed, and the inclosed colonies were 
fished off into litmus milk. When growth appeared in the milk cultures 
a microscopic examination was made. Those cultures from a single 
plate which caused the same changes in litmus milk and were of the 
same morphology were considered of the same variety. Representatives 
of every variety were studied in detail and referred to their respective 
places, according to the classification given below. • 
This method of studying only 10 colonies from the plate cultures at 
one analysis and then reducing this number for more detailed study to a 
single representative of those cultures which are similar in their mor¬ 
phology and their action on litmus milk was intended to give a broad view 
of the flora of cheese rather than a detailed one. A more intensive study 
of the cheeses selected for analysis would necessarily reduce the number 
which could be examined. Inasmuch as the flora of normal Cheddar 
cheese will differ greatly in a detailed study, the methods used, which 
allow the examination of a large number of cheeses and give a rough 
picture of the cheese flora, were considered the best adapted to increase 
our knowledge in its present stage. 
FERMENTATION TESTS FOR THE CLASSIFICATION OF CHEESE 
ORGANISMS 
The cultural characteristics, morphology, and the few biochemical 
reactions which are ordinarily considered in classification of bacteria 
were found to be inadequate traits for distinguishing one variety of 
cheese organism from another of the same group. Therefore the system 
of classification based upon the fermentation of various test substances 
which has been used by Gordon (1905) and other English investigators 
and by Winslow (1912) and his colleagues for the classification of the 
Coccaceae and which was also used by Rogers and Davis (1912) for classi¬ 
fying the lactic-acid bacteria of the Bacterium lactis acidi type was 
adopted, with modifications suited to the problem in hand, for the clas¬ 
sification of cheese organisms. 
A sugar-free broth was made of 10 grams of compressed yeast, 10 
grams of peptone, and 5 grams of dibasic potassium acid phosphate per 
liter of water. To this mixture was added 1 per cent of the test substance. 
At first inoculations were made into dextrose, lactose, galactose, sucrose, 
salicin, mannit, glycerin, inulin, starch, and raffinose broths with all the 
