STATUS OF PASTEURIZATION OF MILK. 5 



F. In the United States an electric process has been investigated by 

 Anderson and Finkelstein (1). Their conclusion as to the cause of 

 the destruction of the bacteria is as follows : 



The destruction of bacteria in the " " process is apparently due to 



the heat produced by the electric current rather than to the electric current 



itself. The " " process furnishes a method for producing a very 



sudden high temperature for a brief period of time. 



It seems evident from a review of the literature that in the use of 

 electricity, as it has been applied, sufficient heat is generated by elec- 

 tricity, or a combination of steam and electricity, to raise the milk 

 to the pasteurizing temperature. Since the temperatures reached 

 are in themselves destructive to most nonspore-forming bacteria, 

 the problem of determining whether the effect of electricity is due 

 to heat or direct electric action is a difficult one. 



The use of ultra-violet rays for the destruction of bacteria in milk 

 has not proved to be of value as a commercial process. Experiments 

 with these rays carried on by Ayers and Johnston (5) showed that 

 while the rays cause great destruction of bacteria in milk, when ex- 

 posed under suitable conditions, the process in its present state of 

 development can not replace that of pasteurization on a commercial 

 scale. It is difficult to obtain the proper exposure of milk to the 

 rays on a scale sufficient to permit of practical operation and im- 

 practicable to secure suitable bacteria reductions without seriously 

 injuring the flavor of the milk. 



EXTENT OF PASTEURIZATION IN THE UNITED STATES. 



Pasteurization when first practiced by milk dealers in this country 

 was carried on more or less secretly, and, except as a means of pre- 

 serving the milk, was regarded by them as a process of no value. As 

 the practice became more general the subject of pasteurization was 

 studied, and its value as a means of destroying disease-producing 

 bacteria was recognized. In consequence of the recognition of the 

 merits of the process there has been during the last 20 years a rapid 

 increase in the quantity of milk pasteurized. Jordan (23) , in a paper 

 published in 1913. stated that 10 years previously only about 5 per 

 cent of the milk supply of Xew York City was pasteurized ; figures 

 from other sources show that about 40 per cent in 1912, 88 per cent 

 in 1914, and 98 per cent in 1921 was pasteurized. In Boston very 

 little milk was pasteurized in 1902, but in 1915 80 per cent, while at 

 present about 90 per cent is so treated. In many of the smaller cities 

 there have been corresponding increases in the quantity of milk 

 pasteurized during the last few years. 



The general tendency in this country to-day is toward the pasteuri- 

 zation of all milk for direct consumption, with the exception of 



