March, 1950]
C.
S.
DHARAMARAJAN
AND
OTHERS
37
freezing point of individual and herd cow milk samples lies within the range
of —0.546° C. to — 0.549°C. There is no marked difference in the freezing point of
milk of different breeds of animals, and the freezing point of the great majority of
samples falls in the range —0.531°C. to —0.560°C., only about 4 per cent of the sam-
ples examined lie outside this range. In the case of buffaloes the average freezing
point varies from—0.549°C. to —0.557°C. The higher limit for freezing point is
noticed only in the case of milk from Dharwar buffaloes, while milk from Murrah
buffaloes gives an average value very similar to that observed with cow milk. The
higher freezing point noted in the case of Dharwar buffalo milk may be a breed
characteristic. Aschaffenburg and Veinaglou [1942-44] also found that Guernesy
cow milk gave greater freezing point depression than Shorthorn cow milk, and
the difference was sometimes as high as 0.007°C. Buffalo milk samples tend to show a
wider scattering than cow milk. On an average only 81 per cent of the samples
have freezing point falling within the range of —0.531°C. to —0.560°C. About 8 to
20 per cent of the samples show freezing point ranging from —0.561°C. to —0.580°C.
The average freezing point of —0.548°C. found for cow milk agrees very closely
with the average of —0.544°C. obtained by Elsdon and Stubbs [1934] from an
analysis of 1,000 samples of milk from individual animals. Macdonald [1947] found
bulked milk samples also to give the same average. Aschaffenburg and Veinaglou
[1942-44] on the other hand gave a higher average figure of 0.548°C. from an
analysis of 3831 samples. The extreme range for freezing point is given by Elsdon
and Stubbs [1934] as —0.529°C. to —0.563°C. Bauer [1933] gives the minimum
and maximum freezing points as —0.526°C. and —0.570°C. respectively. The
average freezing point of buffalo milk comes to —0.552°C. which is slightly higher
than that found for cow milk. The average depression in the freezing point of cow
and buffalo milk might be taken as 0.550°C. For legal purposes it is suggested
that the minimum freezing point depression to be allowed should not be less than
—0.530°C. By observing this limit less than three per cent of genuine milk samples
are likely to be excluded, and hence it may be taken as a reasonable working limit.
Wide fluctuations were noted from day to day in the freezing point of milk
obtained from individual animals as well as in herd milk.
Lactose in milk
The average lactose content in cow milk was found to be 4.92 per cent. Certain
difference has been observed in the lactose content of milk from different breeds
of cows. Sahiwal cows' milk was richest in lactose, while Gir and Tharparkar
cows' milk contained the least. The range of variation in the average lactose con-
tent was from 4.82 to 5.01 per cent. Davies [1939] in reviewing all the published
data for Western breeds of animals gives the average lactose content of milk as 4.78
per cent. Indian cows' milk, therefore, seems distinctly richer in lactose than the
milk from Western breeds. The average lactose content in the milk of the same
breed of animals shows some fluctuations. Thus, the average lactose content in the
milk of three Sindhi cows examined varied from 4.85 to 5.06 per cent. The lactose
content of cow's milk as will be seen from Tables II and V, lies within the range
4.0-15.50.
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