24 
BULLETIN 202, U. S. DEPARTMENT OF AGRICULTURE. 
Table 19. — Acidity and bacterial count of samples of pasteurized market milk which 
gave negative alcohol tests with 75 per cent, 68 per cent, and 44 per cent alcohol. 
Sam- 
ple 
Acid- 
ity. 
Bacteria 
per cubic 
Sam- 
ple 
No. 
Acid- 
ity- 
Bacteria 
per cubic 
Sam- 
ple 
Acid- 
ity. 
Bacteria 
per cubic 
No. 
centimeter. 
centimeter. 
No. 
centimeter.' 
1 
1.85 
1,200 
20 
1.75 
15,000 
39 
1.85 
104,000 
2 
1.77 
1,200 
21 
1.70 
16,000 
40 
2.05 
110,000 
3 
1.66 
1,900 
22 
1.65 
16,000 
41 
1.65 
114,000 
4 
1.75 
3,000 
23 
2.05 
16,000 
42 
1.76 
120,000 
5 
1.66 
4,000 
24 
- 1.69 
17,500 
43 
1.80 
133,000 
6 
1.80 
5,000 
25 
1.78 
21,000 
44 
1.75 
194,000 
7 
1.85 
7,000 
26 
1.66 
21,000 
46 
1.73 
264,000 
8 
1.85 
7,600 
27 
1.80 
24,000 
47 
1.70 
284,000 
9 
1.80 
8,000 
28 
1.83 
32,000 
48 
1.90 
340,000 
10 
1.80 
9,000 
29 
1.67 
37,000 
49 
1.76 
446,000 
11 
1.71 
9,000 
30 
1.96 
41,000 
50 
1.85 
720,000 
12 
1.75 
11,000 
31 
1.75 
52,000 
51 
1.65 
740, 000 
13 
1.85 
11,000 
32 
1.90 
59,000 
52 
1.75 
940,000 
14 
1.70 
11,000 
33 
1.85 
62,000 
53 
1.74 
1,280,000 
15 
1.65 
12,000 
34 
1.85 
64,000 
54 
1.60 
1,660,000 
16 
1.85 
13,000 
35 
1.70 
65,000 
55 
1.97 
2, 460, 000 
17 
1.75 
14,000 
36 
1.75 
68,000 
56 
1.60 
3,100,000 
18 
1.75 
15,000 
37 
1.80 
71,000 
57 
2.00 
3,600,000 
19 
1.80 
15,000 
38 
1.70 
74,000 
In the early stages of the growth of acid-forming bacteria in milk, 
when the numbers are low, there is a period in which a rapid increase 
in numbers takes place without any increase in acidity which can be 
detected by ordinary chemical methods, or it may occur with only a 
slight increase in acidity; consequently if the alcohol test were made 
during that period there would be a high bacterial count and yet not 
high acidity enough to cause a positive alcohol test. The same is 
true of the action of the rennet-forming bacteria in their growth and 
action, as we have shown earlier in this paper when dealing with the 
relation of acidity, and also the effect of rennet on the alcohol test. 
Besides these facts there are other groups of bacteria which may 
develop in milk and yet have no influence on the alcohol test, as, for 
example, the alkah-forming group of bacteria. We have tried cul- 
tures of this group of organisms and found that they did not produce 
a positive alcohol test. There are other groups of bacteria in the 
flora of milk, such as the inert group, which also would probably 
develop without influencing the alcohol test in any way. When we 
consider all these facts it is not strange that there is no definite 
relation between the bacterial flora of milk and the bacterial count. 
When the 68 per cent alcohol test is positive with a sample of 
market milk, it is evidence that there is some change in the milk from 
normal. In some cases it may be due to an increased acidity and in 
consequence a change in the casein of the milk, due to bacterial 
action. In other cases it may be due to a pure rennet fermentation 
or there may be a combination of an acid-and-rennet fermentation. 
In such cases the bacterial count would undoubtedly be high. How- 
ever, there still remains to be explained the reason for a positive 
alcohol test in samples of market milk with a low bacterial count and 
low acidity. 
