1. FLAVOR TESTS
A study of the odor and flavor of an oil, isolate,
or synthetic is essential in judging quality and aids in the detection of adulteration.
Comparison should always be made with an oil of good quality and of known purity.
Organoleptic tests are unquestionably the most sensitive and satisfactory method
for detecting slight spoilage in oils such as the citrus oils, and in detecting
burned, pyroligneous "by-notes" resulting from improper distillation.
Procedure Water Flavor Test:
Place J oz.
of alcohol in an 8 oz. glass. Add 1 drop of oil and then 7 oz. of cold water,
the water being added slowly with vigorous stirring. This should yield a clear
or opalescent mixture, which does not separate oily droplets on the surface. The
odor and flavor of these two water flavor tests should be carefully studied and
evaluated.
In the case of dill oils, it is well to add 3
drops of glacial acetic acid to approximate more accurately the conditions under
which this oil is usually employed. In the case of peppermint oils, it is best
to add hot water; the flavor tests should be of uniform temperature and tasted
while still warm.
Procedure Sugar Syrup Test:
An acidified
sugar syrup is prepared by adding 1 dram of 85% syrupy phosphoric acid and 7 drams
of 50% citric acid to 1 gal. of simple syrup (U.S. P. quality: approximately 65%
wt./wt.). Dilute 2 oz. of this prepared syrup with 2 oz. of cold water. Add 1 to
3 drops of a 10% alcoholic solution of the oil and mix thoroughly. The odor and
flavor of these two sugar syrup tests should be carefully studied and evaluated.
These syrup tests are best prepared in widemouthed,
screw-top bottles which permit of thorough mixing of the alcoholic solution and
the syrup by vigorous shaking.
Such syrup flavor tests are especially valuable
in evaluating citrus oils citrus concentrates, and oils and synthetics which duplicate
the flavor of highly acidic fruits.
In the case of sweetening agents (such as vanillin,
coumarin, and heliotropin), it is well to dispense with the acidic medium and to
use instead mixture of equal parts of simple syrup and water.
It should be remembered that comparison with a
product of good quality is essential.
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127 The procedure given is essentially
the official method of "The United States Pharmacopoeia," Thirteenth
Revision, 647 (Hanus Method).
128 The weight of the oil used
is best determined by weighing by difference. A small bottle containing a few cc.
of the oil and also a medicine dropper is accurately weighed; then about 8 or 9
drops of the oil are introduced into the Erlenmeyer flask, and the bottle with
the residual oil and medicine dropper is again accurately weighed: the difference
represents the weight of sample used.*. Small "petit cups" of glass may
also be used; these cups (containing the requisite amount of oil, accurately
weighed) are dropped into the Erlenmeyer flasks and' ate not removed during the
determination.
129 In the case of castor oil,
allow the mixture to stand for 60 min.
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