172
Colouring Vanaspati with Ratanjot
for eight months did not suffer deterioration in the colour giving property and can thus be taken as
fairly stable under ordinary storage conditions. On the other hand, if the dye is heated to a very
high temperature it does not give any red colour to fats but will still give the characteristic blue
colour with alkali which is now taken as a specific test for indicating the presence of ratanjot.
Colouring vanaspati. The concentrate obtained by extraction with other is not directly used
for colouring vanaspati as it is found that all of it is not soluble in fats. One hundred grams of vanas-
pati require nearly 0.25 gm. of this concentrate to give an almost saturated solution of colour in fat.
To extract all the colour, the mixture is repeatedly heated to about 60ºC. with constant stirring.
This is then filtered and the deep red vanaspati used for colouring any further quantities of vanaspati
to the required intensity is obtained. On an average vanaspati of the kind ordinarily offered in the
market requires 5.5 gm. of the concentrated coloured vanaspati of the type, described above, to colour
1000 gm. of it to one red unit, as measured in Lovibond Tintometer using 1 cm. cell, the colour com-
parison being carried out at 50ºC. This gives a concentration of 0.0096 per cent. Under practical
trade conditions a colour intensity of seven red units is suggested as most suitable. A high intensity
of colour can easily be given, but for the purpose in view this is not necessary, as the presence of
vanaspati so coloured can fairly easily be detected as has been described later.
Stability of coloured vanaspati to light. Investigations were carried out with different brands of
vanaspaties available in the market, and they were coloured to three different intensities, viz. five,
six and seven red units. For the sake of brevity, however, results obtained with only one popular
brand of vanaspati, made from the groundnut oil, and coloured to seven red units, have been dealt
with below.
The vanaspati in question was kept in glass bottles stoppered with corks and exposed to ordinary
daylight in the laboratory. The changes in colour, peroxide values and acidity were recorded at
intervals. Peroxide values were determined by the method described by Dastur and Lea [1940]
and expressed as ml. of N/500 thiosulphate per gm. of fat. Acidity was estimated by the method
described in the Handbook of the A.O.A.C. [1945] and expressed as percentage of oleic acid. The
results are given in Table I.
TABLE I
Effect of diffused sunlight on coloured vanaspati
Time
interval
in days
0
7
14
28
42
56
70
86
100
132
157
Description of the samples
Vanaspati (A) . . .
coloured (B) . . .
A . . . . .
B . . . . .
A . . . . .
B . . . . .
A . . . . .
B . . . . .
A . . . . .
B . . . . .
A . . . . .
B . . . . .
A . . . . .
B . . . . .
A . . . . .
B . . . . .
A . . . . .
B . . . . .
A . . . . .
B . . . . .
A . . . . .
B . . . . .
Colour reading
Red
0.3
7.1
0.2
6.9
0.2
6.9
0.2
6.9
0.2
6.7
0.2
6.5
0.2
6.5
0.2
5.9
0.1
5.7
0.0
4.8
0.0
4.4
Yellow
1.0
1.3
1.0
1.4
1.0
1.3
0.6
1.5
0.4
1.3
0.5
1.5
0.8
1.6
0.7
1.7
0.5
1.7
0.4
1.6
0.3
1.5
Neutral
0.2
0.2
0.1
0.1
0.1
0.1
0.2
0.1
0.1
0.1
0.2
0.1
0.2
0.1
0.2
0.1
0.1
0.1
0.1
0.1
0.1
0.1
Decrease
in red
colour
(per cent)
..
..
2.8
2.8
2.8
5.6
8.4
8.4
16.9
19.7
32.4
38.0
Acid value
(percentage
of oleic
acid)
0.06
0.08
000
0.08
Peroxide
value
0.47
0.47
25.78
14.89