300 Effect of Heating Milk of Indian Cows and Buffaloes
state form only about 1.5=1.9 per cent of the
volume of milk taken. These materials are rich
in proteins, fat and minerals. On account, how-
ever, of the high moisture percentage, which is
mostly due to the retention of milk in the matrix
of the substances, any variation in the composi-
tion of these substances which may occur after
first boil and continued simmering, is likely to be
considerably masked and the data obtained thus
show that the average composition in both the
cases is very nearly the same.
(xi) Composition of milk of Indian animals. At
present very limited published data exist on this
subject. Hence a comparison of the results
amongst themselves and also with those collected
by foreign workers will be interesting. Such a
comparison must, however, be treated with cau-
tion on account of the limited data available here.
The high percentage of fat in Indian breeds of
cattle is too well-known to need any repetition.
The protein percentage of cow and buffalo milk
are within the limits of foreign figures, but the
average for buffalo (3.60 per cent) is slightly higher
than that for the cow (3.36 per cent).
The lactose content of buffalo's milk is distinctly
higher than that of the cow. The average for
buffalo's milk is 5.1 per cent which is considerably
higher than the figures given in the literature
(average 4.75 per cent). Davies [1940] has suggest-
ed a close relationship between the lactose and
chlorine content of milk, which is expressed by the
formula :
Lactose (per cent) + 13.5 × Cl (per cent)=6.26.
If calculations are made for the figures for raw
milk given in this paper, it is found that the average
ratio for cow's milk comes to 5.78 for buffalo,
5.98 and for mixed 5.88. On heating, these
average figures are decreased to 5.65, 5.86 and
5.82 respectively. Hence, it is seen that Davies'
formula needs considerable revision before it can be
made applicable to Indian conditions.
Recently Raffaelli [1940] has shown that the ratio
of lactose to ash in the milk of Italian cows varies
from 5.95 to 7.20 with an average of 6.57 and for
buffalo's milk, 5.60 to 9.20, averaging 6.86. This
ratio (anhydrous lactose : ash) for Indian animals
as obtained from the averages in the present studies
works out to 6.07 for cows and 6.77 for buffaloes.
Allen [1931-1932] has reviewed the existing lite-
rature on the mineral constituents of milk. The
average ash content of milk of foreign breeds
of animals is 0.73 per cent. The data reported
here show that the ash content of Indian breeds is
just on the border-line or even less than this
average. It will be worth investigating if this is
due to inherited characteristics or deficiency in the
food. The animals employed for this experiment
can hardly, however, be expected to suffer from
any such deficiencies.
Cow's milk seem to contain lower percentages
of both Ca (average 0.127 per cent) and P (average
0.092 per cent) than buffalo's, which on an average
contains 0.163 per cent Ca and 0.101 per cent P.
The latter figures closely approach the concentra-
tion of these elements in the milk of foreign breeds
of cows.
The figures reported in the literature for citric
acid content of milk vary within very wide limits,
from 0.070 to 0.400 per cent, with an average of
0.180 per cent [Allen, 1931-32]. From the data
given here it will be seen that the citric acid content
of Indian animals is fairly high and the figures for
cow's milk (average 0.225 per cent) are consider-
ably higher than those for buffalo's milk (average
0.193 per cent).
In India where heating of milk to high tempera-
tures is so commonly practised, these figures are of
special interest in view of the fact that citrates are
known to stabilize milk towards heat and the addi-
tion of soluble calcium salts renders milk less
stable to heat [Allen, 1932].
SUMMARY
(1) When milk is heated to first boil in a closed
vessel (practice commonly followed in Indian
houses), there is a decrease in its volume up to 6.0
per cent. This change in volume completely masks
the change in composition, but when correction is
made for the loss of moisture, milk is found to lose
about 5 per cent of its important constituents.
(2) When milk is allowed to simmer for 10
minutes after boiling, the effects are similar to those
obtained with the first boil but the loss of moisture
and other constituents with the former is higher.
(3) Pasteurization (Holding method) causes
very little change in the chemical composition of
original milk.
(4) Skin and residue obtained from boiled milk
samples contain on an average 49.3 per cent fat,
28.1 per cent protein and 4.4 per cent ash. The
last is rich in Ca and P.
(5) Analysis of samples of mixed milk from
Indian breeds reveals that lactose content of
buffalo milk is noticeably higher.
(6) Both for the cow and buffalo milks the lac-
tose chloride relationship, usually found to hold
good in other countries, is not applicable to Indian
conditions.
(7) Ash content of Indian milk, as compared with
figures published for foreign breeds, is not very
high. Both Ca and P figures for Indian cow are
much on the lower side of the average of those pub-
lished for foreign cows.
(8) Milk of Indian animals is rich in citric acid,
that from the buffalo being noticeably lower in this
respect than from the cow.