ADULTERATION WITH STARCH. 71 



1 :8 to 1 :8.5 (Droop-Richmond). Further, in normal 

 milk the ratio of casein to fat should never be greater 

 than I :i.74 and never less than i :1.3s.* (L. Van Slyke.) 

 Unfortunately it must be admitted that these normal 

 numbers as given will not cover every case without ex- 

 ception. The composition of cow's milk (other kinds of 

 milk need not be considered here) is influenced by so 

 many factors such as climate, breed, feeding, keeping, 

 duration of lactation, etc., so that universal normals can- 

 not be established absolutely. 



A never failing proof still remains, namely, the "stall 

 test." In cases of extreme importance a number of sam- 

 ples of milk may be obtained directly from the animals in 

 the stalls. An analysis of these samples furnish data with 

 which results of tests of suspected milk may be compared. 

 Since the fat content and consequently the specific grav- 

 ity is subject to considerable variation in different sam- 

 ples, much more reliance is put upon the determination 

 of the other constituents, viz., albuminoids, a.sli, .sugar. 



II. ADULTERATION WITH STARCH, DEXTRIN', ETC. 



Sometimes it is found that skimmed milk is treated 

 with starch in the attempt to restore the original white 

 color. The detection of this adulterant by chemical means 

 is a simple matter. 



By acidifying with acetic acid and boiling, the milk is 

 freed from albuminoids. The filtrate obtained is treated 

 with a few drops of a dilute solution of iodine. In the 

 presence of starch the well known blue color appears. 

 This test, however, is no longer to be considered as proof 

 positive of starch. There is in milk and milk products 

 another substance giving a similar reaction. This sub- 

 stance is considered by Herz as an amyloid on account 

 of its similarity to the amyloid discovered by Virchow 



♦Results of 25,931 analyses. 



