8 
BULLETIN 782, IT. S. DEPARTMENT OF AGRICULTURE. 
The results of the 14-day incubation are similarly shown in this 
table. It will be noticed that the alkaline change in 46 of the 68 
cultures was due entirely to the formation of alkaline carbonates and 
in the other 22 to the presence of carbonates and ammonia. In 
almost every case the reduction in acidity was due largely to carbon- 
ates and at the same time there was a considerable increase in the 
amount of ammonia over that produced after 7 days' incubation. 
Culture 107 after 14 days' incubation showed a smaller reduction of 
acidity than after the 7-day period, indicating that there was a sec- 
ondary acid fermentation. 
After 30 days' incubation the reduction in acidity in 24 cultures 
was due entirely to formation of carbonates or bicarbonates, there 
being no increase in ammonia over that contained in the control 
tube of skimmed milk. In 37 cultures the alkaline change was due 
to the combined action of carbonates and ammonia. It will be 
seen, however, that in most cases the greater part of the change was 
due to the alkaline carbonates. In general there was an increase 
in the quantity of ammonia, found after 30 days, over that present 
at the end of the 7 and 14 day incubations. Cultures 107 and 137 
after 30 days' incubation were found to be more acid than the con- 
trol cultures. Both these cultures showed an alkaline change after 
7 and 14 days' incubation. In cultures 10, 12, 49, 113, 123, and 143 
an excess of ammonia was found over that necessary to produce the 
alkaline change, which showed that there must have been a secondary 
acid fermentation. This is further substantiated by the fact that 
these cultures showed a smaller change in alkalinity compared with 
the control after the 30-day incubation than they did at the end of 
the 7 or 14 day incubation. 
The results of the work shown in Table 2 are summarized in 
Table 3. 
Table 3. — Cultures grouped according to reaction and cause of ullcali production in 
skim milk. 
Incubation 
30° C 
Reduction of acidity 
due to— 
Increase of 
acidity 
over control. 
Ammonia 
and alkaline 
carbonate. 
Alkaline 
carbonate. 
Days. 
7 
14 
30 
Number of 
cultures. 
10 
22 
137 
Number of 
cultures. 
58 
46 
24 
Number of 
cultures. 


2 
Seven ammonia and no alkaline carbonate. 
This summary needs no discussion since it simply presents clara 
which have already been discussed. These results lead to the belief 
