BACTERIOLOGY OF CHEESE 429 
Bacteriology of Cheddar Cheese. Harding and Prucha (1908) studied 
more than 300 pure cultures of bacteria from cheddar cheese by means 
of the group number on the classification card of the Society of Amer- 
ican Bacteriologists. These finally reduced to 33 groups. ‘Ten of these 
groups disappeared at once; 9 others were found in but single cheeses; 
the remaining 14 groups were indicated as the most important members 
of the cheese flora. Bacterium lactzs acids included 4 of these 14 groups 
and was the only species always found and it practically included over 
99 per cent of the total bacterial content. 
Hastings, Evans and Hart (1912) conducted a similar study. They 
state that the Bacterxum lactis acid? groups is an important one and 
sum up the role of these organisms as follows: 
1. They favor the curdling process. 
2. They favor the expulsion of the whey. 
3. They permit of the fusing of the curd particles. 
4, They activate the pepsin in the rennin extract. 
5. They have a protective action against the putrefactive bacteria. 
They state thatthe development of B. lactis acidi is followed by the 
Bacillus bulgaricus group. 
These same authors in a later paper (Evans, Hastings and Hart, 
1914) found the following four groups and assumed that they must 
function in the ripening process: 
1. Bacteriwm lactis acid. 
2. B. caset. 
3. Streptococcus. 
4, Micrococcus. 
When the Bacterium lactis acidi group was used alone as starters, 
in pasteurized milk cheese, no cheddar flavor was obtained. Com- 
binations of the Streptococcus and JB. lactzs acidi groups when added 
to pasteurized milk improved the character of the cheese. Hart, 
Hastings, Flint and Evans (1914) isolated coccus forms of bacteria 
from cheddar cheese and cultured them in sterile milk. Large amounts 
of volatile acids were found on analysis of the culture. These acids 
were produced from either citric acid lactose or protein because the 
milk contained no fat. One strain of streptococcus formed large 
amounts of alcohols and esters which contribute to the flavor of the 
cheese. Suzuki, Hastings and Hart (1910) isolated and identified vola- 
tile acids during the ripening of cheddar cheese. Aleohol was formed 
probably from lactose fermentation. The agencies operative in the 
production of volatile acids and esters are not defined. 
Harding and Prucha (1908) analyzed different cheeses and demon- 
