Journal of Agricultural Research 
Vol. II, No. 3 
188 
active in the ripening changes. The by-products of this group of organ¬ 
isms are entirely different from those of the Bacterium lactis acidi group. 
Instead of a large quantity of lactic acid, with small quantities of other 
acids, as formed by the latter group, the streptococci produce no lactic 
acid, but produce large amounts of acetic acid, with smaller percentages 
of propionic, butyric, and caproic acids (Hart, Hastings, Flint, and 
Evans, 1914). The streptococci were also shown to produce small 
amounts of ammonia, a by-product not found in B . lactis acidi cultures. 
It is therefore to be expected that the large numbers of streptococci 
present in Cheddar cheese have a decided influence upon flavor develop¬ 
ment. The influence of individual cultures of this group in the ripening of 
pasteurized-milk cheese will be discussed later. 
Bacteria of the Micrococcus group were isolated from normal Cheddar 
cheese in percentages as high as 40. It does not appear that this 
group of organisms is of primal importance in the production of Cheddar 
flavor, however, for they have been found commonly in pasteurized-milk 
cheese in numbers comparable with those found in the raw-milk cheese 
with well-developed flavor. When added to the cheese in large per¬ 
centages of the starter, a bitterness is always produced within a few 
weeks. 
EXPERIMENTS IN THE PRODUCTION OF DESIRABLE FLAVORS IN 
PASTEURIZED-MILK CHEESE 
The study of the bacterial content of normal Cheddar cheese has 
demonstrated the fact that the flora is varied and is made up of several 
varieties of all four groups of cheese organisms. Therefore, in the 
attempt to prepare starters which might develop Cheddar flavors in 
the pasteurized-milk cheese it appeared reasonable to mix pure cultures 
together for the cheese inoculation, choosing the varieties most fre¬ 
quently found in Cheddar cheese with the well-developed flavor. Many 
experimental cheeses have been made with the use of such starters, 
the mixtures being made up of from two to nine pure cultures in various 
combinations and varying percentages, in order to determine which of 
the varieties in addition to Bacterium lactis acidi might improve the acid 
flavor of the pasteurized-milk cheese. 
The difficulties in preparing a starter which will reinstate in pasteurized 
milk a flora which will simulate raw milk well ripened for cheese making 
are apparent, even though the relative percentages of each group and 
variety were better known. 
Out of 20 experimental cheeses which were inoculated with Bacterium 
lactis acidi , a or b, together with one of the other varieties of this group 
or some variety of the coccus groups or with some mixture of these 
pure cultures, there was usually obtained a better flavor in the young 
cheese than in the control cheese inoculated with a pure culture of B . 
lactis acidi , a or b, alone. But by the time the cheese was well ripened a 
