210 STATE BOARD OF AGRICULTURE. 



METHODS EMPLOYED. 



Before discussing the above heads, it may be advantageous to review 

 the methods employed in the process of Pasteurization. 



What Constitutes Pasteurization. — Two factors are mainly concerned in 

 Pasteurization, temperature and time. Inasmuch as both are variable, 

 owing to the opinions of different workers, it was necessary to fix upon a 

 definite degree of temperature and period of time. To do this intelligently 

 it is well to bear in mind the principal objects of Pasteurization. Per- 

 haps most vital so far as bacteria are concerned is to have the heating 

 sufficiently high to kill or reduce the virulence of the disease-producing 

 (pathogenic) bacteria. The most important object from the dairyman's 

 view is to keep the milk below a temperature which will produce a 

 cooked flavor or change the composition of the milk. The temperature 

 was placed at 68° C. [155° P.]. The thermal death-points of the patho- 

 genic bacteria which may gain access to the milk probably fall below 

 this, and the change in the composition of the milk and the cooked flavor 

 do not appear in any noticeable degree below 75° C. [ 167° F. ]. The 

 period of time is twenty minutes, a sufficiently long time to attain the 

 objects above. 



Apparatus Used. — It is a little unfortunate that necessity compelled us 

 to change or modify the apparatus in the midst of our work. Owing to 

 the unsatisfactory results obtained from the first used, we were forced 

 into the modification. 



The first used was a shotgun can 8 in. in diameter and 2 ft. deep, with a 

 stirrer inserted through a slit in the cover. The objections to this were, 

 the constant exposure of the stirring rod and its interrupted contact with 

 the milk, the exposure of the thermometer used in determining the tem- 

 perature of the milk, and the slit in the cover itself, as well as the crude 

 means of getting the milk into the bottles by a siphoning process. 



The modification used overcame to a large extent these objections. The 

 truncated conical cover of the shotgun can was made solid with a single 

 perforation which contained a closely-fitting tube, the top of which over- 

 lapped a raised portion on the upper side of the cover. The handle was 

 fitted to the upper portion of the cover and to the lower portion of the 

 cover corresponding with the handle above was a cap into which fitted 

 the rod, resting on a pivot in the bottom of the can and carrying the fans 

 used in stirring. The cover overlapped the can by two inches and was 

 made to fit smoothly. So arranged, the cover of the can could be revolved 

 by the handle and in turning the cover, the rod bearing the fans inside 

 revolved. The tube passing through the cover down into the milk was 

 used for the reception of the thermometer in taking the temperature of 

 the milk. Since they all revolved with the cover the tube did not inter- 

 fere with the fans. In this way, neither the stirrer nor thermometer 

 furnished a source of contamination and there was no opening in the 

 cover to allow bacteria to enter. At the bottom of the can was a brass 

 stop-cock, having a cap screwed over it while Pasteurizing and when 

 ready for drawing off, a mouth-piece screwed on in place of the cap. This 

 mouth-piece was conical in shape that it might fit into the mouth of the 

 bottle and at the base of the cone was a three-inch circular flange to 

 arrest any falling dust. 



