PRODUCTION OF MILK OP LOW BACTERIAL CONTENT. 



57 



The ratio of growth of bacteria in Table 28 shows an interesting 

 point. The ratios were determined as previously explained in this 

 publication (p. 46). It will be noted that there was a higher ratio 

 of growth in milk produced under dirty conditions in unsterilized 

 utensils than in samples of milk produced under clean conditions in 

 sterilized utensils. This seemed to be true when milk was held at 

 15.5° C. (60° F.) for 12 and 24 hours. At 21.1° C. (70° F.) the 

 statement holds true only for the first 12 hours. From that and 

 other observations it seems evident that the bacteria which are intro- 

 duced from unsterilized utensils grow faster at temperatures near 

 15.5° C. (60° F.) than those in a low-count milk produced in steril- 

 ized utensils. 



The results obtained by holding milk at 15.5° C. (60° F.) and 21.1° 

 C. (70° F.)' for various periods of time, show the advantage of the 

 lower temperature and further give data on the bacterial increase 

 which will take place at those temperatures when both low and high 

 count milk are held for varying periods of time. 



The effect of temperature on the growth of bacteria in milk during 

 storage and transportation is a matter of very great' importance. It 

 is evident from the previous results that if a low-count milk is de- 

 sired it must be cooled and held at 10° C. (50° F.) or lower on the 

 farm, unless it is delivered immediately after each milking. There- 

 fore, for the production, in a broad sense of the term, of milk of low 

 bacterial content a fourth factor, proper refrigeration, must be added 

 t'o the three factors previously discussed. 



Table 28. — Ratio of grcivth of bacteria in milk ivhen held at 15.5° C. (00° F.) 



and 21.1° C. (70° F.). 



MILK PRODUCED UNDER CLEAN CONDITIONS IN STERILIZED UTENSILS. 



Sample No. 



Eresh. 



Held at 15.5° C (60 



° F.) for— 



Held at 21.1° C (70 



° F.) for— 



12 hours. 



24 hours. 



48 hours. 



12 hours. 



24 hours. 



48 hours. 



1.. ..;.... 



2 





1.27 

 1.05 

 

 

 



1.07 

 1.16 

 2.43 

 



2.81 

 1.50 

 13.07 

 



1.66 

 

 1.04 



26.6 



29.4 



32.3 



17.4 



7.4 



6.4 



43.3 



40 



4.1 



67.2 



11.1 



578.5 



19.3 



217.5 



29.4 



66.3 



7, 333. 3 

 8,684 2 

 22, 352. 9 



4.5 



12.1 

 8 



9.3 

 1.3 

 4.6 

 1.2 

 9.7 

 4.5 



17.7 

 3.8 



41.4 

 1.3 



27.1 

 1.5 

 7.2 



2, 277. 7 

 13, 789. 4 

 13, 941. 1 

 4,000 



419.6 



1, 037. 9 



283.3 



2,685.7 



964.2 



27, 8lS. 1 



3,000 



4,071.4 



1, 322. 5 



4,100 



1, 578. 9 



5,227.2 



716, 666. 6 

 452,631.5 



3 



1,417,647 



4, 



5 ; 



36, 607. 1 



7. 215. 1 

 7, 166. 6 

 6, 428. 5 



3. 589. 2 

 38,181.8 



4,147 



119, 642. 8 



6 



229, 113. 9 



7 



45, 000 

 115, 714. 2 



8 



9 



532, 142. 8 



10 



116,363.6 



11 



282, 352. 9 



12 , 



13. 



5, 838. 7 

 38, 333. 3 

 4, 368. 4 



448,387 



14 



533,333.3 

 1, 700, 000 



15 



16 















1.69 



74.76 



14, 634. 3 



9.7 



5,407.3 



885,307.3 









