EXPERIMENT STATION BULLETINS. 215 



It is evident from Sample I to Sample U that there is no difference in the 

 length of time between the change in the Pasteurized sample and its 

 control, although the measure of acidity differs very markedly in sam- 

 ples I, J and K. From this the conclusion was drawn that the Pasteur- 

 izing apparatus used was not sufficiently accurate. There were too 

 many entrances for foreign bacteria by way of the rod, the slit in the 

 cover and the pouring into bottles. This resulted in the author's design- 

 ing another Pasteurizing apparatus based upon the shotgun can and 

 described elsewhere. The samples from N to Z were prepared in the 

 latter apparatus. 



The last half of samples furnished interesting data. The reaction of 

 both the bottle of the Pasteurized milk and that of the un-Pasteurized 

 was taken from the duplicate samples of each immediately upon their 

 receipt in the laboratory. The indicator used was phenol-phthalein. It 

 will appear from a study of this phase of the work, that although the time 

 after milking was about the same, the acidity varied considerably, and 

 that, as has been stated by several writers, the reaction began to change 

 from the amphoteric directly after milking. This was not the primary 

 purpose of this work, however; we wanted a mark from which to meas- 

 ure the change in the milk, consequently the determination of the 

 reaction at this stage provided us with a starting point. 



The bottles were watched closely in the laboratory and as soon as the 

 thickening of the milk was noticed, the time was noted from the hour of 

 receipt. This was thought a fairer test of the keeping qualities than 

 the placing of the bottles in a refrigerator, although the temperature of 

 the latter could be kept more constant. Inasmuch as the keeping quali- 

 ties are determined in hours, a tabulated statement will perhaps give 

 us a better notion of the comparative values of the Pasteurized and 

 un-Pasteurized milk. The temperature of the room varied from 45° F. 

 to 70° F. 



Samples N P O Q R S T U V W X Y Z 



Pasteurized 140 100 90 96 79 96 88 — 90 72 60 79 74 



Un-Pasteurized .110 96 82 72 55 72 64 48 48 H6 48 48 50 



It must be borne in mind that the variability of the change among 

 the different lots is due to the rise and fall of temperature during the 

 work, and that each lot consisting of Pasteurized and un-Pasteurized 

 bottles were treated identicallv the same and were under exactly the 

 same conditions. Although the relation of temperature differs between 

 the different lots, it does not affect the relation of the bottles of the 

 same lot, consequently the above table offers no direct bearing upon 

 the work when read from right to left, but its significance comes from 

 reading up and down. 



When the milk either Pasteurized or un-Pasteurized became the 

 least thickened, the acidity was tested and recorded in each bottle of 

 every lot. Again by this act we gain some idea of the progress of the 

 change as in the number of hours and likewise the kind of change, 

 whether acid or alkaline. At the same time, Uffelmann's test for lactic 

 acid was applied. 



