JOURNAL OF AGRICULTURAL RESEARCH 
DEPARTMENT OF AGRICULTURE 
Vol. II Washington, D, C., Junk 15, 1914 No. 3 
BACTERIA CONCERNED IN THE PRODUCTION OF THE 
CHARACTERISTIC FLAVOR IN CHEESE OF THE 
CHEDDAR TYPE 1 
By Alice C. Bvans, Bacteriologist , Dairy Division , Bureau of Animal Industry , 
B. G. Hastings, Bacteriologist , Wisconsin Agricultural Experiment Station , and 
B. B. HarT, Chemist , Wisconsin Agricultural Experiment Station 
In a previous publication (Hastings, Evans, and Hart, 1912) 2 a sum¬ 
mary of the knowledge concerning the bacteriology of Cheddar cheese 
was presented together with the results that were obtained by the authors 
in an effort to extend the knowledge concerning the flora of this type of 
cheese. It was shown, as had previously been demonstrated by numerous 
investigators, that Bacterium lactis acidi is an important factor in the 
making and ripening of Cheddar cheese. The lactic acid formed aids in 
the curdling of the milk by the rennet, and the acid formed in the curd 
assists in the expulsion of whey therefrom. The combination of the acid 
with the paracasein so changes the nature of the curd that the pieces 
readily coalesce or “mat.” The lactic acid also activates the pepsin 
of the rennet extract, enabling it to act on the paracasein, with the 
formation of soluble products. The acid reaction of the cheese is main¬ 
tained during the ripening period and thereafter, thus inhibiting the 
development of putrefactive bacteria which otherwise would soon destroy 
the commercial value of the cheese. 
It was further shown that lactic bacilli 3 occur in all Cheddar cheese in 
numbers approximating those of the ordinary lactic bacteria, B. lactis 
acidi , and that coccus forms are also of constant occurrence. 
At the beginning of the ripening period the ratio between Bacterium 
lactis acidi and lactic bacilli can, in a general way, be expressed as 99 to 1. 
This ratio gradually changes as the ripening progresses until in cheese 3 
to 6 months old the ratio is reversed. It is apparent that the larger part 
of the growth of the B. casei group must take place after the fermentation 
1 Work of Department of Agriculture in cooperation with Wisconsin Agricultural Experiment Station. 
* Bibliographic citations in parentheses refer to "Literature cited/' pp. 191-192. 
1 This group of lactic-acid-forming organisms appears in the literature under various names, the most 
common being "lactic bacilli/’ “ Bacterium bulgaricum” or " Bacillus bulgaricus,’ ’ and Bacterium casei.” 
The name "Bacterium casei” will be used in this article. 
(167) 
Journal of Agricultural Research, 
Dept, of Agriculture, Washington, D. C. 
Vol. II, No. 3 
June 15, 1914 
A—6 
