DAIRY FARMING DAIRYING. 477 



able to ferment the more complex substances are likely to produce a bitter 

 taste. 



" Starters composed of both B. lactis acidi. b. and Streptococcus, b. when 

 added to pasteurized milk, improve the quality of the cheese. It does not 

 seem unreasonable to hope that starters may be obtained that will give the 

 characteristic Cheddar flavor to the cheese prepared from pasteurized milk." 



A biblioj;rai)hy of cited literature is appended. 



Relation of the action of certain bacteria to the ripening of cheese of the 

 Cheddar type, E. B. Hart, E. G. Hastings, E. M. Flint, and Alice C. Evans 

 (U. S. Dcpt. Agr., Jour. Agr. Research, 2 {WW, No. 3, pp. 193-216).— This work 

 was in cooperation with the Wisconsin Station. The authors summarize the 

 results as follows: 



" Rei)resent;itives of the coccus groups of organisms isolated from Cheddar 

 cheese when grown in milk produced large quantities of the volatile acids, 

 particularly acetic acid. These acids were produced from citric acid or lactose 

 or protein, as the medium was practically free from fat. These organisms did 

 not produce formic acid. As they are present at times in very large numbers 

 in cheese, they, no doubt, produce much of the volatile fatty acids which arise 

 during the ripening process. One of the strains of Streptococcus, b, was found 

 to produce comparatively large quantities of alcohols aud esters — bodies which 

 contribute in a large degree to the flavor of cheese. 



"A dilute solution of acetic acid and alcohol formed esters by mere contact, 

 without bacterial action. In cheese, however, the dilution is probably too 

 great for this manner of ester formation. Lactic acid was generally not formed 

 by the coccus groups. The representatives of the Bacterium casci group ex- 

 amined gave results different from those obtained from the coccus forms. 

 They pi'oduced no formic acid, but did form some propionic and much acetic 

 acid. These organisms produced a large quantity of lactic acid, both active and 

 racemic, and decomposed the citric acid of the media. Cheese made from 

 chloroformed fresh milk did not yield any volatile fatty acids, showing that 

 inherent milk enzyms are not capable of producing these bodies in any appre- 

 ciable quantity. Representatives of both the coccus and B. cnsei groups were 

 able to produce ammonia from milk. Whey and fresh curds contained active 

 lactic acid. Cheese one day old contained a mixture of active and racemic 

 lactic acids. 



" The cause of the disappearance of active lactic acid and the appearance 

 of racemic acid may be due to enzymic action, combined with the action of those 

 bacteria which can produce both kinds of acid. Some representatives of the 

 B. casei group produced levo lactic acid and others dextro lactic acid from 

 milk. A mixture of these two varieties produced racemic lactic acid. A mix- 

 ture of B. lactis acidi and a levo-producing member of the B. casei group gave 

 racemic and active lactic acid. The active acid was probably the result of the 

 longer continued activity of B. casci. Racemic lactic acid found in curing cheese 

 may therefore be produced in a small degree by euzym action, but more prob- 

 ably by the combined action of B. lactis acidi and the organisms of the B. casei 

 group." 



A bibliography of cited literature is appended. 



The action of Bacillus bulgaricus in suppressing' gassy fermentations in 

 cheese making, C. F. Doane (CentU. Balct. [etc.], 2. Aht., 40 {19U), No. 9-10, 

 p. 163). — " It was found that pure cultures of B. hulgaricus could be used with 

 perfect results in suppressing the undesirable fermentations, principally gas, 

 which have worried Swiss cheese makers in the past. There seems to be a 

 difference in the efficiency of different strains of B. hulgaricus for this purpose 

 without respect to their activity in forming acid. One per cent of a whey 



