Chapter VIII 

 The Grading of Milk 



THIS chapter deals with the more important methods of judging 

 of the cleanness and freshness of milk and its suitability for the 

 making of good dairy products. 



EXAMINATION FOR TASTE AND SMELL 



As the senses of taste and smell are our best aids in avoiding 

 putrid or harmful food, every careful examination of milk should 

 include tasting and smelling. Unfortunately the test is of a 

 decidedly subjective nature, as the senses in question are soon 

 dulled. Further, considering that the temperature of the milk 

 varies considerably on arrival, and that the smell and taste are 

 most pronounced when the milk is warm from the cow, it is 

 evident that milk can only be graded very roughly by this method, 

 and that the detailed classification in fifteen grades according to 

 the taste and smell alone, as was previously carried out by the 

 Danish milk grading associations, was futile. 



ESTIMATION OF DIRT 



Milk which contains visible amounts of pus, blood, manure, etc., 

 must of course be regarded with suspicion from the outset. It 

 may justly be demanded that milk retailed in towns shall show 

 no sediment when 1 litre is allowed to stand at rest for two hours 

 in a vessel of colourless glass. It is advantageous to use vessels 

 tapering to the bottom, so that the sediment may readily be 

 collected for examination after the milk has carefully been decanted 

 off. As only the heaviest particles will separate, it is more usual 

 nowadays to filter a definite quantity through a^ disc of cotton 

 wool, which will become more or less dirty according to the state 

 of the milk. The discs may be dried and kept, so that a " dirt 

 scale" may be prepared for future reference and comparison 1 , 

 and the dirtiest discs may perhaps produce some moral effect if 

 sent to the suppliers responsible for them. As it is impossible to 

 take an average sample of dirt from a large quantity of milk, it 



1 See, for example, Hoyberg's Scale in " Maanedsskriftet for Sund- 

 hedspleje," 1910, p. 49. 



