792 EXPERIMENT STATION RECORD. 



testing underwent the same kind of fermentation; and when the milk 

 was tested later there was a noticeable change in this respect. Men- 

 tion is also made of the variations in the bacteria found at the same 

 creamery at different times. 



The main part of the article is devoted to the results of experiments 

 with 08 species of bacteria. These were all distinctly dairy bacteria, 

 some being collected directly from cream at creameries, others from 

 milk, others from the dust which fell from the cow during milking, 

 etc. All of the general types of milk bacteria were included in the 

 list. The experiments were with pasteurized cream. In each series of 

 experiments one lot of the cream was ripened with the bacteria in ques- 

 tion and another lot was left without any starter. No technical descrip- 

 tions are given of the different species, but brief statements are given 

 regarding the origin of each species and its effect upon the cream and 

 the butter. The results are classified and discussed at considerable 

 length. 



"The majority of the species tested may be regarded as indifferent in their effect 

 upon the butter. About half of them, when used to ripen the cream, as will be seen 

 in the experiments described below, produced butter that had neither flavor nor 

 aroma nor acid, and the butter was practically indistinguishable from the control 

 butter. These species are the largest in number and are present in the greatest 

 variety around barns and dairies. . . . 



"A considerable portion of the species found are positively favorable in their 

 influence upon the butter. Of the 68 species tested. 20 produced butter that has 

 been described in our notes as good flavored. . . . 



" Of the 20 above mentioned, 9 were lactic organisms. On the other hand, 11 were 

 among the class which would be described as alkaline species, by which it is meant 

 that they either produced an alkaline reaction in the milk or produced no change in 

 its reaction. They are at all events distinctly not acid forms. Seven amo"ng them 

 liquefy gelatin and are, therefore, among what are called the putrefactive bac- 

 teria. . . . 



"A smaller number of species produced injurious effects upon the butter; 18 spe- 

 cies among the 68 tested have been described as producing butter that was bad, or 

 poor, or strong flavored, or disagreeable; various adjectives beiug used to indicate 

 the different effects. Sometimes the poor flavor was a putrefactive taste: in other 

 eases it was a bitter taste; in others, again, a strong sour taste; while in still others 

 the effect was of a peculiar indescribable character. In many of these 18 species 

 the unpleasant flavor was very slight, and probably insufficient to materially injure 

 the butter. . . . 



"Of the 18 species described as producing injurious effects upon the flavor of the 

 butter, 9 belonged to the acid-producing class, while 9 belonged to the class develop- 

 ing alkaline reaction. 



"From these facts it appears to me a safe and perfectly legitimate inference that 

 flavor is a matter entirely distinct from acid. It will be noticed that among the 

 acid-producing species there are some that develop good flavor, while others develop 

 a decidedly unpleasant flavor; and it will be noticed that among the species pro- 

 ducing good llavors in the butter, while many of them are acid producers, a large 

 number, 11 out of 20, are among those that develop no acid. . . . 



"While, therefore, the lactic bacteria maybe regarded as commonly producing 

 the butter flavor in practical butter making, they do not do this simply because they 

 produce acid, and we must recognize that other types of bacteria probably assist in 

 producing the desired flavor. It is important to note in this connection that of the 

 30 species described as indifferent in their actiou. none were acid organisms. 



