IV ]
P. GAJ RAJ SINGH, et al
239
month of lactation is found to be 0.12 per cent expressed as lactic acid but there is a slight gradual
increase in titratable acidity as the lactation advances; this is more pronounced in certain cases
while it is not so evident in other cases. Probably this increase in titratable acidity is not due to
true acidity but due to other factors like casein and phosphates which also combine with alkali as
suggested by Rogers et al. [1921].
TABLE II
Acidity of milk and phosphate test
Phosphate Numbers
0—15
.
.
.
.
15—25
.
.
.
.
25—35
.
.
.
.
35—45
.
.
.
.
45—55
.
.
.
.
55—65
.
.
.
.
65—75
.
.
.
.
75—85
.
.
.
.
Total . .
Acidity in milk (percentage of lactic acid)
0.10
..
5
13
1
5
6
10
..
40
0.11
..
17
50
11
6
20
17
..
121
0.12
5
26
68
21
15
29
8
1
173
0.13
33
42
55
21
4
13
4
..
172
0.14
7
49
73
18
11
14
8
..
180
0.15
18
38
49
9
10
14
8
..
146
0.16
5
44
21
13
13
12
4
..
112
0.17
14
25
6
5
4
4
..
..
58
0.18
9
16
11
9
2
7
..
..
54
0.19
9
6
33
4
2
1
1
..
56
Total
100
268
379
112
72
120
60
1
1112
Alcohol test
The test has been ordinarily used for assessing the hygienic quality of milk, although the relia-
bility of the same has been questioned by Sommer and Binny [1923]. The concentration of the
alcohol used is also not very definite, various concentrations ranging from 68 to 75 per cent by volume
being used by different workers. From Table III it is quite clear that positive alcohol test for the
same concentration of alcohol is distributed over a wide range of acidity of milk. This naturally
indicates that factors other than acidity come into play in making an alcohol test positive. But the
general tendency, as is evident from Table III, is that as acidity increases, greater percentages of
samples give a positive alcohol test with the same concentration of alcohol and this is found to be
statistically significant. Explanations for any disagreement with this general finding, have to be
sought in other factors like concentration of mineral salts, rennet forming organisms, etc., as suggested
by Sommer and Binny [1923]. Another point of interest evident from Table III is the unusually
high number of fresh milk samples that gave a positive alcohol test with 60 per cent alcohol.
Composite cow milk that was examined side by side very seldom gave a positive alcohol test below 70
per cent while composite buffalo milk in every case gave positive alcohol test almost always below
65 per cent. Therefore, it is clear that the present concentrations of alcohol generally used in the-
case of cow's milk are too strong for buffalo milk. Taking the average acidity of fresh buffalo milk
as 0.13 per cent and considering Table III, it is seen that about 42 per cent of the samples gave posi-
tive alcohol test with 60 per cent alcohol. Perhaps this peculiar behaviour has to be attributed to
some difference in salt balance in the case of buffalo milk as distinct from cow's milk. As the acidity
increases most of the samples give positive alcohol test with 60 per cent alcohol. Acidities like 0.16
and 0.17 per cent are sometimes observed in fresh buffalo milk and in such cases 70 and 85 per cent
respectively give positive alcohol test with 60 per cent alcohol. Whatever be the reasons for this,
it is quite clear that in the case of the alcohol test for buffalo milk, the concentration of alcohol has
to be reduced to 60 per cent. Even at 0.13 per cent acidity there are samples which do not give a
positive alcohol test even with 80 per cent alcohol, but the number of such sample is very few. This
also may be attributed to some change in salt balance.