52
TITRATABLE ACIDITY OF COW AND BUFFALO MILK
[Vol. XXV, Part I
acid respectively for the first milking, 0.33 and 0.38 per cent for second milking,
0.28 and 0.33 per cent for third milking and at the tenth milking the acidity
was 0.22 and 0.25 per cent acid respectively (Table III). The pH values were in
harmony with the trend in the titratable acidity (Table III). Average acidity of
buffalo colostrum is somewhat higher than that of cow colostrum.
While the acidity of milk continued to decline for a period of 15 to 20 days
following parturition, the change was most apparent in the first three milkings
(Table III and IV). On the seventh day the average acidity of cow and buffalo
milk was 0.21 and 0.19 per cent respectively, on the fourteenth day it was 0.21
and 0.18 per cent. No significant change in either the titratable acidity or the
pH was observed from twenty-first to thirty-fifth days in cow and buffalo milk
(Table IV).
Coefficients of variation ranging from 6 to 12 per cent for the first ten milkings
following parturition reflect the variability in acidity for individual cows and
buffaloes. All cows and buffaloes within the two groups, however, showed the
same general trend, namely a high initial acidity followed by a progressive decline
during the early part of the lactation period (Table III and Table IV).
Observations made at weekly intervals on two groups of 15 buffaloes and 10
cows for a complete lactation showed that the acidity of milk has a tendency
to decline throughout the entire lactation of the dairy cows and buffaloes (Fig. 1).
The most significant drop, however, occurred between the first and second months
of lactation. The average acidity of cow and buffalo milk for the first month
of the lactation was 0.26 and 0.28 per cent respectively and by the second month
it had declined to 0.18 and 0.17 per cent, a difference of 0.08 and 0.11 per cent
respectively. From the second to the seventh month of lactation, the average
acidity of milk remained quite constant. Following this a small decline was
registered from 0.158 and 0.153 per cent for cow and buffalo milk respectively
for the seventh month to 0.146 and 0.142 per cent for the tenth month. These
data substantiate the findings of Houston [1931] and Caulfield and Riddell [1936]
who observed a similar trend in the acidity of milk from groups of Shorthorn,
Ayrshire, Holstein, Guernsey and Jersey cows.
The stage of lactation has a significant influence on the variability in acidity
of milk from an individual buffalo or cow. It was observed that almost all cows
and buffaloes whose milk showed an acidity of 0.22 and 0.20 per cent or more had
been fresh for 14 days or less at the time the determinations were made (Tables II,
III and IV), while extremely low values were usually associated with cows and
buffaloes near the end of their lactations.
Although there is a general tendency in the acidity of milk to decline as the
lactation advances, individual cows and buffaloes will show considerable variation
in this respect. Data obtained on a group of 15 buffaloes and 10 cows in advanced
stages of lactation showed that the average acidity of milk had declined in
buffalo milk from 0.135 per cent, approximately one month before the end of the
lactation, to 0.08 per cent on the last day of the lactation; and in cow milk
from 0.140 to 0.09 per cent. However, the milk from some of the cows and