COLOURING SEPARATED MILK TO PREVENT ITS USE FOR
ADULTERATING WHOLE MILK
By D. R. KASHYAP, NOSHIR N. DASTUR and ZAL R. KOTHAVALLA, Imperial Dairy Department,
Bangalore
(Received for publication on 17 May 1943)
(With two text-figures)
MILK obtained from Indian cows and buffaloes
is rich in fat. The usual legal limits prescribed
for fat in most of the provinces are very low.
This provides a great scope for practising adul-
teration by the simple manipulation of fat content
and specific gravity. When separated milk is
added even the chemical tests may fail. Under
these circumstances a consumer is hardly able to
judge the quality of his milk supply.
It is, therefore, proposed that all the separated
milk to be consumed in urban centres should be
distinctly coloured, so that even when small
quantities of colouring matter are added to milk,
its presence can be detected visually. For this the
colour chosen must naturally be attractive, and
it is thought that a light pink colour will best
serve this purpose. Similar devices have been
employed in other countries in the past to
encourage
milk
drinking
habits among
school children.
The following study was carried out to find a
suitable dye and to examine its stability under
trade conditions.
Selection of dyes. Observations were made with
(i) Edicol erythrosine, (ii) eosine, (iii) congo red,
(iv) cochineal extract and (v) beetroot extract.
All these colours are soluble in water.
The cochineal extract used in the present experi-
ments was one made by Messrs J. N. Nichols &
Co. Ltd., Manchester.
The beetroot extract was obtained by pulping
raw beetroots without any addition of water.
The extract was filtered and preserved in cold
storage.
Safranine was also found to impart the desired
colour to milk, but it is known to be poisonous
and hence no further trials were carried out.
Concentration of dyes. The minimum concen-
tration of dyes to be used for colouring separated
milk is shown in Table I. Such concentrations
are sufficient to permit visual detection of mixtures
of as little as 5 per cent coloured separated milk
with whole milk.
TABLE I
Concentration of dyes
Dye
Edicol erythrosine . .
Eosine
.
.
.
.
Congo red
.
.
.
Cochineal extract . .
Beetroot extract . .
Minimum concentration
A
In ordinary light
0.012 per cent
(gm./100 ml.)
0.003 per cent
(gm./100 ml.)
0.006 per cent
(gm./100 ml.)
0.3 (ml./100ml.)
1.2 (ml./100 ml.)
B
In artificial light
0.003 per cent
(gm./100 ml.)
0.0008 per cent
(gm./100 ml.)
0.0015 per cent
(gm./100 ml.)
0.04 (ml./100ml.)
0.60 (ml./100ml.)
Physical properties of coloured separated milk.
The effects of various conditions on the coloured
separated milk, which are likely to be encountered
under marketing conditions, were examined.
(a) Taste of coloured separated milk. Samples of
separated milk were prepared for each dye, using
the concentration mentioned above in column A.
A control uncoloured sample was also kept for
comparison. Judging for taste and flavour was
carried out independently by several persons at
intervals. The average results are shown in
Table II. The use of the first four dyes listed
above seems to mask the raw, normal flavour of
milk and thus improve its taste. Beetroot extract
on the other hand imparts a foreign flavour, pos-
sibly due to the large concentration in which it
was used.
(b) Effect of exposure to sunlight. Samples of
coloured separated milk were kept in direct sun-
light, together with the control for six hours. It
was found that there was no change in the quality
of treated samples as compared to the control.
All the coloured samples retained their original
colour. This was judged by comparing the colour
with a similar lot which was kept in the dark.
37