38
Colouring Separated Milk
TABLE II
Effects of dyes on the flavour and taste of separated milk
Particulars of sample
Control sample . . . . . . . .
Coloured with Edicol erythrosine . . . . . .
Coloured with eosine
.
.
.
.
.
.
.
Coloured with congo red
.
.
.
.
.
.
Coloured with cochineal extract . . . . .
Coloured with beetroot extract. . . . . .
Average score
0
hour
+ +
+ + +
+ + +
+ + +
+ + +
+
2
hours
+ +
+ + +
+ + +
+ + +
+ + +
+
4
hours
+ +
+ + +
+ + +
+ + +
+ + +
+
6
hours
+ +
+ + +
+ + +
+ + +
+ + +
+
7
hours
+ +
+ + +
+ + +
+ + +
+ + +
+
(c) Effect of storage at room temperature. Sam-
ples of separated milk coloured with eosine, congo
red, beetroot extract and cochineal extract were
not found to fade or give any precipitate when
stored till they curdled.
Edicol erythrosine showed a noticeable tendency
to precipitate out, after standing over four hours.
(d) Effect of storage under refrigeration. Sam-
ples of separated milk coloured with eosine,
congo red and cochineal extract preserved their
freshness and colour when stored for 24 hours at
45°F.
The sample coloured with Edicol erythrosine
gave a precipitate, as also the one coloured with
beetroot extract. In the latter case the colour
of the precipitate was dirty white.
(e) Effect of boiling. When first brought to
a boil the samples coloured with eosine and Edic°
erythrosine showed no change.
In the case of congo red, the colour became more
intense, whereas that of cochineal extract faded
slightly and that of beetroot extract faded
markedly.
(f) Use of coloured milk for making curd. There
was no difference in the appearance and flavour
of curd obtained from the control sample and those
from the coloured samples.
(g) Effect of storing coloured milk in different
containers. Coloured and uncoloured samples were
stored simultaneously in containers made of differ-
ent material and tested for flavour at intervals
of two hours over a period of eight hours by
different judges independently. The average score
is shown in Table III.
TABLE III
Effect of storing milk in different types of containers
Containers used
Glass bottles . .
Tinned steel cans .
Aluminium cans .
Kallaied brass cans .
Dye used
Edicol erythrosine
Control
+ +
+ +
+ +
+ +
Coloured
+ + +
+ + +
+ + +
+ + +
Eosine
Control
+ +
+ +
+ +
+ +
Coloured
+ + +
+ + +
+ + +
+ + +
Congo red
Control
+ +
+ +
+ +
+ +
Coloured
+ +
+ +
+ +
+ +
Cochineal extract
Control
+ +
+ +
+ +
+ +
Coloured
+ +
+ +
+ +
+ +
Beetroot extract
Control
+ +
+ +
+ +
+ +
Coloured
+
+
+
+
Detection of adulteration of genuine milk with
coloured separated milk. When separated milk
coloured with various dyes, in the concentrations
indicated in column A, Table I, was mixed with
cow or buffalo milk, adulteration could be easily
detected by sight to the extent of five per cent and
more. With lower concentrations of the dye the
indication was not so definite.
The sensitivity of the test can, however, be
greatly increased by examining the sample in
artificial light. For this purpose, the device shown
in Fig. 1 is used. It consists of a wooden box
with two holes. The sides of these holes are
covered with rubber washer. Under each of the
holes there is an electric bulb (40W). On one
hole a control sample of milk contained in a glass
vessel is placed, while over the other one is placed
a sample that is suspected to contain coloured