388 CITY MILK SUPPLY 



milk merchant must judge of the food value and also of the sanitary character 

 of the commodity in which he deals. The high-grade product must get a better 

 price than at present. The low-grade product must bring less. In separating 

 milk into grades and classes the commission has endeavored to make its classi- 

 fication as simple as possible and at the same time to distinguish between milks 

 which are essentially different in sanitary character. 



In general two great classes of milk are recognized, namely, raw milk and 

 pasteurized milk. Under these general classes there are different grades, as indi- 

 cated in the report of the committee on classification. 



PASTEURIZATION 



While the process of pasteurization is a matter which has attracted a great 

 deal of attention in recent years, the commission has not entered into any discus- 

 sion of its merits or demerits, but has given it recognition in its classification as 

 a process necessary for the treatment of milk which is not otherwise protected 

 against infection. 



The commission thinks that pasteurization is necessary for all milk at all 

 times, excepting grade A, raw milk. The majority of the commissioners voted 

 in favor of the pasteurization of all milk, including grade A, raw milk. Since 

 this was not unanimous the commission recommends that the pasteurization of 

 grade A, raw milk, be optional. 



The process of pasteurization should be under official supervision. The super- 

 vision should consist of a personal inspection by the milk inspector; the inspec- 

 tions shall be as frequent as possible. Automatic temperature regulators and 

 recording thermometers should be required and the efficiency of the process fre- 

 quently determined by laboratory testing. 



The destruction of the chemical constituents of milk by heat occurs at higher 

 temperatures than those necessary for the destruction of the bacteria of infectious 

 diseases transmissible by milk. (See Fig. 41, p. 279.) 



The commission passed a resolution regarding the temperature of pasteuriza- 

 tion as follows: 



That pasteurization of milk should be between the limits of 140F. and 155F. 

 At HOT. the minimum exposure should be 20 min. For every degree above 

 140F. the time may be reduced by 1 min. In no case should the exposure be for 

 less than 5 min. 



In order to allow a margin of safety under commercial conditions the com- 

 mission recommends that the minimum temperature during the period of holding 

 should be made 145F. and the holding time 30 min. Pasteurization in bulk 

 when properly carried out has proven satisfactory, but pasteurization in the final 

 container is preferable. 



It is the sense of the commission that pasteurization in the final container 

 should be encouraged. 



LABELING AND DATING OF MILK 



The commission voted that all milk should be labeled and marked with the 

 grade in which it is to be sold. In dating milk uniform methods should be 

 adopted for all grades of both raw milk and pasteurized milk, both using the day 

 of the week or both using the day of the month. All milk should be dated uni- 



