4 BULLETIN 240, U. S. DEPARTMENT OF AGRICULTURE. 



Table 1. — Bacterial reductions during the process of pasteurization in bottles. 



Sample No. 



Raw milk. 



After pas- 

 teurization 



in the 

 bottle for 

 30 minutes 

 at 145° F. 



Percentage 

 reduction. 



Sample No. 



After pas- 

 teurization 



Raw milk. k^U^L. 

 ! Dottle for 



30 minutes 



at 145° F. 



Percentage 

 reduction. 



2 



Bacteria 



per c. c. 

 58,000 

 63, 000 



5,100,000 

 580,000 



5,900,000 

 99,000 



7, 400, 000 

 191,000 

 14, 100, 000 

 24,700 

 75,000 

 126,000 



4,100,000 

 76,000 



8, 100, 000 

 18, 900 

 24,000 

 28,300 



Bacteria 

 per c. c. 

 1,630 

 1,070 



11,800 

 8,000 



15,600 



980 



7,100 



7,600 



14,200 

 5,780 



28,000 

 1,720 

 2,410 

 3,550 

 1,660 

 710 



10, 900 



23,300 



97.18 i 

 98.30 

 99.76 j 

 98.62 

 99.74 

 99.01 

 99. 90 

 96.02 

 99.89 

 75.59 

 62.66 

 98.63 

 99.94 

 95.32 

 . 99. 98 

 96.24 

 50.41 

 17.67 



20 



Bacteria \ Bacteria 

 per c. c. per c. c. 

 80, 000 2. 010 



97.48 



3 



21 



160,000 



151,000 



81,000 



24, 900 



94,000 



305,000 



235,000 



176,000 



29.500 

 12; 500 



9,800 

 570 



2,200 

 55,800 



7,600 

 11,400 



8,350 



5,500 



1,500 

 11,400 



3,520 

 18,400 



9,300 



81.56 



4 



22 



91.72 



5 



23 



24 



87.90 



6 



97.71 



7 



25 



97.66 



8 



26 



81.70 



9 



27 



96.76 



10 



28 



93.52 



11 



29 



97,000 

 230.000 



91.39 



12 



30 



97.61 



13 



31 124,000 



32 : 450,000 



33 3, 950, 000 



34 985,000 



35 



98.79 



14 



97.46 



15 



99.91 



16 



98.13 



17 



95.10 





Average . 



' 





19 



1,570,493 



9,863 



90.86 







As may be seen from the table, the bacterial reductions were high 

 as a rule, but there were exceptions. The average total count of the 

 samples of raw milk was 1,570,493 and after pasteurization 9,863 bac- 

 teria per cubic centimeter. It is interesting to note that the percent- 

 age reductions averaged 90.86 per cent and ranged from 17.67 per 

 cent to 99.98 per cent. When the latter reduction was obtained the 

 raw milk contained 8,100,000 bacteria per cubic centimeter ; when the 

 minimum reduction was obtained the raw milk contained 28,300 bac- 

 teria per cubic centimeter. These results further substantiate the con- 

 clusion expressed in Bulletin 161, page 58 (3) ,that percentage bacterial 

 reduction has no special meaning, since it is influenced by the number 

 and kinds of bacteria in the milk when pasteurized. Considering 

 the results as a whole, it is evident that low counts may be obtained 

 by pasteurization in bottles. 



While carrying on these experiments the following points were 

 noted which are worthy of attention : 



TEMPERATURE OF THE MILK DURING HEATING. 



In the process of pasteurization it was found that the temperature 

 of the milk in different parts of the bottle was quite different during 

 the time the milk was being heated. Several experiments were made, 

 heating water in sealed bottles to determine the differences in the top, 

 middle, and bottom of the bottles. Three thermometers were inserted 

 through a rubber stopper into a bottle so that the stems were at the 

 top, middle, and bottom of the bottle, respectively. The bottles were 

 then submerged in hot water at a temperature of from 145° to 146° 

 F. and the temperatures of the water in the bottles were recorded. 



