RELATION OF THE ACTION OF CERTAIN BACTERIA 
TO THE RIPENING OF CHEESE OF THE CHEDDAR 
TYPE 1 
By E. B. Hart, Chemist , Wisconsin Agricultural Experiment Station; E. G. Hastings, 
Bacteriologist, Wisconsin Agricultural Experiment Station; E. M. Flint, Chemist , 
Dairy Division, Bureau of Animal Industry; and Alice C. Evans, Bacteriologist , 
Dairy Division, Bureau of Animal Industry 
INTRODUCTION 
The ripening of Cheddar as well as other varieties of cheese has been 
studied by a large number of investigators. The decomposition of the 
protein and the nitrogenous substances thereby produced have been 
quite thoroughly studied in Europe and America. These studies have 
involved both hard and soft cheeses. The nature of the nonnitrogenous 
substances formed during fermentation in cheese, such as fatty acids* 
alcohol, esters, and aldehydes, has received less attention, but there can 
be no doubt that they contribute to the aroma and also to the taste of 
the product. In their relation to flavor they are equally, if not more, 
important than the nitrogenous substances. 
According to present views, the factors involved in the curing of 
Cheddar cheese are the pepsin contained in the rennet; the activating 
lactic acid formed from lactose fermentation; galactase, the proteolytic 
enzym of milk; other inherent enzyms of milk; and certain biological 
agents other than those simply concerned in the first lactose fermentation. 
Investigations at the Wisconsin Agricultural Experiment Station and 
the New York (Geneva) Agricultural Experiment Station have shown 
that the inherent enzyms of milk and rennet fail to produce the typical 
Cheddar cheese flavor. This has led to a more extensive investigation 
of the biological factors of Cheddar cheese ripening. 
In an earlier publication from the Wisconsin station (Suzuki, Hastings, 
and Hart, 1910) 2 both volatile acids and esters were separated and iden¬ 
tified from curing Cheddar cheese, but no data concerning the factors 
operative in their origin were presented. In a later publication (Hast¬ 
ings, Evans, and Hart, 1912) work was reported that showed the pres¬ 
ence and persistence in this type of cheese of three groups of organisms, 
the Bacterium lactis acidi group, the B. casei group, 3 and possibly a group 
of coccus forms. 
1 Work of the Department of Agriculture in cooperation with Wisconsin Agricultural Experiment 
Station. 
* Bibliographic citations in parentheses refer to “ Literature cited/* p. 214-216. 
* The organisms of the Bacterium casei group appear in the literature under a number of names, the most 
common being “lactic bacilli/* “ Bacterium bulgaricus ” or "Bacterium bulgaricum /* "Bacterium casei" 
and the "youghurt bacillus.** The name “ Bacterium casei" will be used in this article. 
Journal of Agricultural Research, 
Dept, of Agriculture, Washington, D. C. 
(193) 
Vol. II, No., 
June is, 1914 
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