ioo MILK AND DAIRY PRODUCTS PART 



heated to 80 C. or not, in the section dealing with the chemical 

 examination of butter (p. 141). 



D. PROOFS OF MILK ADULTERATION. 



The most important and at the same time the most difficult 

 use of milk analysis is in proving the adulteration of milk. It 

 is naturally of the greatest importance that such a valuable 

 and at the same time easily-damaged food as milk should be 

 delivered to the consumer in a pure and unadulterated form. 

 Not only because the abstraction of cream and the adulteration 

 with water dimmish the food value of the milk, but because 

 there is great danger in the latter case of the germs of infec- 

 tious and contagious diseases being introduced into the milk, 

 and so disseminated. 



In order to be able to judge if a milk has been adulterated 

 or not, it must first of all be made quite clear of what normal, 

 unadulterated milk is composed. Here, however, grave difficul- 

 ties present themselves at once, for it is very hard to say within 

 what limits the composition of the milk shall be held to lie. 

 As was noticed in the Introduction, the constituents of milk, 

 and particularly the fat, may vary considerably in quantity in 

 the case of an individual cow, or in the single milkings of 

 various animals. It is therefore essential not to make the 

 limits of normal milk too narrow, otherwise there is the danger 

 of a milk of abnormal composition, although proved to be un- 

 adulterated, being regarded as having undergone falsification. 

 In work of this kind, it is better to occasionally allow a guilty 

 person to escape than to punish the innocent. 



It has, however, been necessary for the control of the milk 

 trade to fix certain limits for the composition of milk, and these 

 limits refer to the specific gravity of milk, the amount of dry 

 matter, and the percentage of fat, and they vary in different 

 districts. 1 In general, ordinary mixed milk may be taken as 

 varying as follows : 



Specific gravity 1-029 1 '034 



Fat 2'5 4 '5 per cent. 



Total solids (dry matter) 10'3 14'7 



Solids, not fat ". 7'8 10'2 



Percentage amount of fat in the total 



solids 19-9-32-1 



Specific gravity of the total solids ... 1*3 1'4 



1 See A. Reinsch, Die gesetzliche Regelung des Milchverkehrs in Deutschland, 

 Hamburg, 1903. 



