PRESENT STATUS OE PASTEURIZATION OF MILK. 9 



In the best pasteurized milk, when held at about 40° F., there is only 

 a slight bacteria] increase during the first 24 hours. In many cases 

 the pasteurization and delivery may be so arranged that the con- 

 sumer gets the milk before much, if any, change has taken place in 

 the bacterial content. The tops of the bottles should have overlap- 

 ping caps to protect them from dust, dirt, or other contamination, 

 and the cap should be marked " Pasteurized " and show the date and 

 the temperature at which the milk was treated. For the benefit of 

 the consumer this information should be printed on the cap, as it is 

 only right for him to know whether he is using raw or pasteurized 

 milk, and if pasteurized, the temperature may be of importance to 

 him. Some people object to pasteurized milk, especially for infant 

 feeding, while others desire it. It has been the experience of numer- 

 ous milk dealers that the labeling of their product has greatly 

 increased their trade. 



COST OF PASTEURIZING MILK. 



The cost of pasteurizing milk is a matter of considerable impor- 

 tance. It has been found by Bowen (loc. cit.) that the average cost 

 of pasteurizing 1 gallon of milk is a little more than three-tenths of 

 a cent ($0.00313). He obtained this information from a series of 

 tests in five establishments which were considered to represent the 

 average city milk plant. The pasteurizing equipment in each con- 

 sisted of a heater, a holding tank, a regenerator, and a cooler. The 

 cost of the operation was based on the pasteurizing cycle, starting 

 with the initial temperature of the raw milk and raising it to the 

 pasteurizing temperature, then cooling to the initial temperature 

 of the raw milk. He based the costs on daity interest at 6 per cent 

 per annum on capital invested in pasteurizing equipment, and depre- 

 ciation and repairs per day at 25 per cent per annum, interest per 

 day at 6 per cent per annum on capital invested in mechanical equip- 

 ment for pasteurizing, and depreciation and repairs per day at 10 

 per cent per annum. Other costs figured were labor, coal at $4 a ton. 

 cooling water at 50 cents a thousand cubic feet, and refrigeration 

 at $1 a ton. 



BACTERIA WHICH SURVIVE PASTEURIZATION. 



Earlier in this paper it is stated that about 99 per cent of the 

 bacteria in milk are destroyed by pasteurization ; consequently about 

 1 per cent of the bacteria remain alive in the milk, and that just what 

 kinds are left depends entirely on the temperature to which the milk 

 is heated. From studies of the bacteria which survive pasteuriza- 

 tion (9) it is possible to show graphically the hypothetical relations 

 of the bacterial groups in raw milk and in milk pasteurized by the 

 holder process at various temperatures under laboratory conditions. 



