ASEPTIC MILK. 61 
COMPARISON OF ORDINARY AND ASEPTIC MILK KEPT AT Boe 
1. During the first 12 hours there was practically no in- 
crease of bacteria. Sometimes the numbers increased slightly, 
sometimes they remained constant, and in some cases they 
decreased in both the ordinary milk and the aseptic samples. 
2. ‘The effect of aseptic milking upon the numbers of bac- 
teria found at later stages was even more striking than in milk 
retained at 70°. ‘The ordinary milk, with an average of 3,116, 
at 12 hours showed 6,049, at 24 hours 22,170, and at 36 hours 
101,000. ‘The aseptic sample, having 242 at the start, showed 
at 12 hours only 363, at 24 hours 5,991, and at 36 hours 2,802. 
In other words, for 36 hours there was practically no increase 
of bacteria in the aseptic milk kept at 50°, although there was 
a decided increase in the ordinary milk during this time. 
3. The average increase of bacteria at this temperature in 
36 hours was ten-fold in the aseptic milk and thirty-fold in the 
non-aseptic milk. These results agree quite closely with those 
of milk preserved at 70° for 12 hours. In other words, milk 
kept at 50° is at the end of 36 hours in much the same condi- 
tion as is milk kept at 70° for 12 hours. 
4. Aseptic milking has a very striking effect upon the time 
of curdling. Ordinary milk kept at 50° curdled on an average 
in 226 hours, the aseptic milk in 4oo hours. In one case the 
aseptic milk did not curdle for 1,300 hours, or 54 days. 
GENERAL EFFECT OF A TEMPERATURE OF 50°. 
1. The most striking results shown by these experiments 
is the effect of a temperature of 50° in checking bacteria growth. 
In 36 hours at 50° the average increase of bacteria is 10 and 
30-fold in the aseptic and ordinary milk respectively; at 70° 
the increase is 200,000 and 100,000 fold. ‘The significance of 
this fact in relation to the keeping quality of milk is very evi- 
dent. In some experiments there was practically no growth of 
bacteria for 36 hours after the milk was drawn, if preserved at 
(2) 
50°. 
2. ‘The effect of the lower temperature upon curdling was 
equally striking, making it possible to keep milk without curd- 
ling for from 79 hours to 40oo hours and in one case for 1,300 
hours. 
