DEVELOPMENT OF CITY MILK SUPPLY PROBLEMS 43 



small expense for laboratory equipment. 39 Among its limita- 

 tions the fact that it is not readily applicable to milk of low 

 germ content nor to pasteurized milk are the most important. 



As acid formation is the most prominent objectionable 

 feature in milk of poor keeping quality it has been suggested 

 as a measure of keeping quality. Studies of acid develop- 

 ment in milk show that at the temperatures to which milk 

 is ordinarily exposed during delivery and in the household, 

 changes in acidity occur at first so slowly as to appear of 

 little significance but that later acidity increases very 

 rapidly. 40 As a result milk at the time of delivery may be 

 so little changed as to show on titration a normal acidity and 

 yet be sour before the lapse of twenty-four hours. 



A simple and on the whole fairly satisfactory test of keep- 

 ing quality may be made by holding a sample of milk at a 

 definite temperature for a definite time and then examining 

 for acid and flavors. This test has the merit of not requiring 

 apparatus more complicated than a good ice chest and facili- 

 ties for the titration of acidity. It is a test which is within 

 the financial possibilities of any municipality which has suf- 

 ficient funds to provide an inspector to collect and observe 

 milk samples. 



THE PROBLEM OF INSPECTION 



Attention has already been drawn to the fact that a city 

 can learn little about the actual. condition of its milk supply 

 until it provides some form of inspection, but much of the 

 value of such information depends upon the form of in- 

 spection provided. 



Until about 1900 city milk inspection consisted almost ex- 

 clusively of the collection and examination of samples within 

 the municipality. At succeeding periods attention was 

 focused upon skimming and watering as affecting the food 



39 R. S. Reed and J. D. Brew, Counting Bacteria by Means of the Mi- 

 croscope, Tech. Bui. 49, N. Y. Agr. Exp. Sta., 1916. 



40 E. G. Hastings and A. C. Evans, A Comparison of the Acid Test and 

 the Rennet Test for Determining the Condition of Milk for the Cheddar 

 Type of Cheese, Circ. 210, U. S. D. A., Bureau of A. I., 1913. 



