a 
c) 
PRODUCTION OF MILK OF LOW BACTERIAL CONTENT. 54 
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 
ia? ©. (60° F:) tor 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 unsterilizea 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 farther 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 
to the three factors previously discussed. 
TABLE 28.—Ratio of grewth of bacteria in milk when held at 15.5° C. (60°. F.) 
Gnd Ql C= (70-28...) 
MILK PRODUCED UNDER CLEAN CONDITIONS IN STERILIZED UTENSILS. 
Ges Held at 15.5° C. (60° F.) for— Held at 21.1° C. (70° F.) for— 
Sample No. ao 
12 hours.}| 24 hours. 48 hours. | 12hours.} 24 hours. 48 hours. 
fier ha sie, mxke Ge. 1 1.27 26.6 7, 333.3 4.5 2,277.7 716, 666.6 
Ds as ere ear ie, aaa 1 1.05 29.4 8, 684 2 1291") 2 13,7894 452, 631.5 
Gi. 1, SNe ape ae 1 0 32.3 22, 352.9 8 13, 941.1] 1,417,647 
7 SS Se cage Nee ee 1 0 se eal ene ei 9.3 4; 000). \: || eae ee 
ae ple RRM carl cre gh 1 0 7.4 36, 607.1 1.3 419.6 119, 642.8 
Oo, Sigs, eel el ae 1 1.07 76:4 7,215.1 4.6 1,037.9 229, 113.9 
TEE hey SI eae, a i oe re 1 1.16 43.3 7,166.6 Je 52, 283.3 45, 000 
OAS as uneadoe aaa eee 1 2.43 40 6, 428.5 OS 2, 685. 7 115, 714.2 
O Meat een eae or se we Fe 1 0 4.1 3, 589. 2 4.5 964. 2 532, 142.8 
Ds SSSee ea Ee een 1 2.81 67.2 38, 181.8 WGC 27, 818.1 116, 363.6 
ibe seed Gat 8 see 1 1.50 11.1 4,147 3.8 3, 000 282, 352.9 
LID cas ai eer Ts aha gee 1] 13.07 By tea | ese te eae 41.4 AO TEAS eae eae cers ae 
(ee ee eee 1 0 19.3 5, 838.7 1.3 1, 322.5 448, 387 
eee oe Se Rates Searels may ie] 1.66 217.5 38, 333. 3 27.1 4,100 533, 333.3 
Os Bre cee Da eee eee 1 0 29.4 4,368.4 1.5 1,578.9 | 1,700, 000 
LU cecs Seta eee 1 1.04 GOSS ss en eee Ula? PSII a7 eee a eee 
AS oreo is pn Sea + 1.69 74.76 14, 634.3 | 9:7 | 5,407.3 885, 307.3 
