262
Fluorescence in Ghee, and Detection of its Adulteration
Mukherji [1940] suggested that adulteration of
ghee up to 10 per cent was detectable; but Narasim-
hamurthy and Suryanarayanamurthy [1940] found
conflicting fluorescence colours for ghee and were
of opinion that the method offered no hope.
It was thought profitable to make a rather more
extended study than the previous workers and take
into account a few at least of the numerous factors
that complicate any examination of a physiological
product like ghee. The practical aim was to see if
it was possible to detect easily the adulteration of
ghee with foreign fats. For this reason, the test
was kept qualitative only.
A Hanovia,∩-shaped mercury are was used as
the source of light, and a uviol filter used to cut off
all but ultra-violet light. The samples were examined
in thin tubes of non-fluorescent glass in a dark room.
Observations were made at room temperature
(23º-26ºC.). The results are arranged to facilitate
discussion.
TABLE I
Milk and milk products
Sample
Buffalo or cow
milk
Butter . .
Buttermilk .
Curd . .
Colour by day light
White
White solid, colo-
urless liquid
White granular
Thick white semi-
solid
Colour by ultra
violet light
Bright yellow
Yellow when solid,
greenish yellow
on melting
Dull yellow
Dull yellow
The yellow colour of these products could be
expected to be present in ghee, if at all, in very
minute quantities only and therefore, would not
interfere, to any appreciable extent, with the
fluorescence colour of ghee.
TABLE II
Adulterants of ghee commonly used
Sample
Crude cocoanut oil
Crude groundnut
oil
Groundnut hard-
ened oil
Cocoanut harden-
ed oil
Cotton seed hard-
ened oil
Colour by day light
Pale yellow
Pale greenish yel-
low
Colourless semi-
solid and liquid
do.
Colourless waxy
solid, melting to
colourless liquid
Colour by ultra-
violet light
Fairly dark blue
Bright purple
Very bright purple
in both semi-
solid and liquid
states do.
Pale blue when
solid;
bright
purple on melting
All these fluoresce various shades of blue and t
is an encouraging feature from the point of vi
of the analyst.
Some workers, e.g. Musher and Willoughby [19
state that the method of expression or extract
of an oil has some effect on its fluorescence.
see if this was the case, a deeper study was ma
with groundnut oil which was easily available. T
results show that the difference is only one of deg
and, as such, has no bearing on the qualitati
detection of adulteration.
TABLE III
A study of groundnut oil
Sample
Cold drawn pro-
cessed oil
Heated and drawn
oil
Refined and blea-
ched oil
Unrefined hydro-
genated oil
Finished, deodo-
rized, hardened
oil
Colour by day light
Pale yellowish
green
Light yellow .
Very pale yellow .
Colourless both in
the solid and
molten state
Colourless
solid
and liquid
Colour by ultra
violet light
Bright purple
Pale bluish violet
Dark sky blue
Pale lilac when
solid; dark violet
on melting
Light blue when
solid; dark blue
on melting
In Table IV are recorded the fluorescen
colours of some factors that might possibly ent
into the fluorescence colour shown by ghee.
Lustig and Botstiber, and Niethammer as quote
by Radley and Grant [1938] record a pale yello
colour for butyric acid and a deeper purple fa
oleic, probably because purer samples were use
The free acids could therefore be expected to giv
a blue colour taken together. The free acids extracte
from a rancid sample of ghee (amounting to 4.5 p
cent expressed as oleic acid) by neutralizatio
removal of the soap and subsequent liberation
the acids, gave on examination a beautiful purpl
colour.
Carotene gives an intense yellow colour; an
chlorophyll extracted from leaves by the metho
of Willstatter and Stoll [1928] a ruby-red colour
The latter however would be an insignificant const
tuent of ghee if at all. Annatto does not fluoresce
but the dirty red colour it imparts to ghee is easil
removed with animal charcoal. Lactochrome solu
tion was obtained by Würsters' modified method
[Radley, 1933] from whey; it is an important con
tituent of fresh ghee, but is easily destroyed on storage
It has been suggested that the unsaponifiabl
matter from ghee and from oils might fluoresc
differently. The results, however, were uniforml
disappointing. The unsaponifiable matter wa