30 Report of the Bacteriologist op the 



INTRODUCTORY.— FLAVOR IN MILK AND ITS PRODUCTS. 



In milk, and more especially in butter and cheese produced 

 •from it, flavor is the quality most noticed by the consumer. In 

 milk the volatile compounds which impress themselves upon our 

 senses are ordinarily spoken of as odors, while in butter and 

 cheese they are usually included under flavor; although in the 

 case of the expert, at least, they are determined in both cases by 

 the sense of s^mell. In this discussion of flavor we will not at- 

 tempt to distinguish between the impressions received through 

 the ordinary act of smelling, as practised by the cheese judge, 

 and the sensations received by tasting, in the case of the con- 

 sumer. To be sure, in the latter act the sensations of acidity, 

 bitterness and sweetness derived from the tongue are added to 

 those received from the volatile compounds floating up to the 

 olfactory membrane above. 



SENSE OF SMELL NOT AN EXACT STANDARD. 



Because the amount of this volatile matter is so slight we are 

 without any exact standard of measurement, and in an attempt 

 at careful work upon the subject recourse has been had to the 

 sense of smell of a trained individual in order to judge the results 

 obtained. When the work has to do with a very pronounced 

 flavor of any kind this method gives satisfactory results; but 

 when the presence of faint and complex odors is involved, as is 

 the case with ripening cheese, the opinions of equally skilled and 

 impartial judges often differ considerably. 



In the past little work has been done upon this subject, except 

 upon butter flavors, but there has grown up considerable infor- 

 mation based upon isolated and more or less questionable obser- 

 vation. 



TWO GE'NERAL CLASSES OP FLAVORS. 



On the basis of their origin these flavors may be divided into 

 two general classes — one directly connected' with the growth of 

 plant life in the milk, the other due to compounds taken up while 

 in the cow or absorbed after the milk is drawn. 



