FIXED OILS AND FATTY SUBSTANCES Flashcards
value or number of physical and chemical
property. Correctness of these values determines the
quality of substances judged
CONSTANT
CONSTANTS INCLUDE:
❖ specific gravity
❖ melting point
❖ congealing point
❖ refractive index
❖ optical activity
❖ acid value, saponification value, ester value, iodine value,
acetyl value, hydroxyl value, unsaponifiable matter,
water and sediment
The purity of fixed oils, fats, waxes, resins, etc. can not be
ascertained by the usual methods based on
gravimetric
or volumetric processes
The determination of these constants are made in conjunction
with the study of ______
tests for the substance analyzed and for the presence of
adulterants serve as a basis of the purity and quality of such
substances
color, odor, taste and special identity
compounds consisting of fatty acids combined with
glycerol via ester linkages
FATS
Fats – compounds consisting of
fatty acids combined with
glycerol via ester linkages
an ESTER derived from
glycerol and three fatty acids
TRIGLYCERIDES
are mixture of glyceryl esters
of high molecular weight fatty acids like palmitic (16),
stearic (18) and oleic( 18) acids.
Fixed oils and fats
Contain relatively high quantities of liquid
glycerides (glyceryl oleate)
FIXED OILS
Fixed oils contain relatively high quantities of
liquid
glycerides (glyceryl oleate)
contain large amounts of solid glycerides (glyceryl
stearate).
FATS
Fats contain large amounts of
solid glycerides (glyceryl
stearate)
HAVE DOUBLE BONDS
OILS
are esters of high molecular weight
monohydric alcohols and high molecular weight fatty acids.
WAXES
Waxes are
esters of high molecular weight
monohydric alcohols and high molecular weight fatty acids.
Sources include both plants (soybean, carnauba) and animals
(spermaceti, Ambergris
WAXES
are natural or induced solid or semi-solid
exudates from plants characterized by being insoluble in
water, soluble in alcohol and ether, crystallizable and softening or
melting at a moderate heat.
RESINS
are substances containing benzoic or cinnamic
acids or esters of these
BALSAMS
The fats and oils to be employed in the
determination of their chemical constants
should undergo preliminary treatment if they
are ______ due to separation of stearin.
turbid
oils should be made clear by ______
their container on a water bath at 50°C until
the turbidity disappears
heating
ACID value -also called
Acid Number or Acidity
Index
Defined as the number of milligrams of potassium
hydroxide required to neutralize the free acids in one
gram of oil, fat, wax, resin, balsam or other similar
substances of complex composition.
ACID VALUE
It may be expressed as the number of milliliters of
0.1-N sodium hydroxide required to neutralize the free
acids in 10 grams of sample
ACID VALUE
are due to hydrolysis of the esters that
compose them
FREE ACIDS
The hydrolysis is caused by
BACTERIAL OR CATALYTIC ACTION
If a substance has a high acid value, it does not
indicate _____ but _____
during their preparation, purification or storage.
rancidity
hydrolytic decomposition
Saponification Value
❖ Also known as the
Saponification Number or
Koettsdorfer Number
Defined as the number of mg of potassium hydroxide
required to neutralize the free acids and saponify
the esters in 1 gram of fat, fatty oil, wax, resin, balsam or
other substances of similar composition.
SAPONIFICATION VALUE
Determination of this constant helps in the detection of
the presence of glycerides of fatty acids which contain
less than 16 or more than 18 carbon atoms
SAPONIFICATION VALUE
saponification value is ______proportional to the
average of the molecular weights of the fatty acids
found in the sample
inversely
High SV, samples contain ______
low MW fatty acids
HCl cannot be substituted with ____because
K2 SO4 which would be the product of the
neutralization will not dissolve in the alcoholic
solution and interfere with the observation of the
endpoint
H2 SO4
______ is more advantageous than the
aqueous solution because the alcohol acts as a
solvent for the oil and the products of
saponification which are insoluble in water.
Alcoholic KOH
is performed to eliminate errors from all
sources like those produced by absorption of CO2 by the
alkali or by the alkalinity of the glass vessels.
BLANK TEST
Defined as the number of mg of potassium hydroxide
required to saponify the esters in 1 gram of fatty oil, fat,
wax, balsam, resin or other similar substances
ESTER VALUE/ NUMBER
Substances, which do not contain free acids, have_____
ester and saponification values.
equal
Substances containing free acids have their ester values
equal to the
difference between the acid value and
saponification value.
The ester value is important in the analysis of ____,
which serves to indicate the presence of adulterants like
_____
beeswax
paraffin
The determination of ester value of waxes is made in
conjunction with the determination of the
ACID VALUE
Adulterant would abnormally increase the ____ values and lowers the _____ value
acid
ester
These are substances that are not saponified by alkali
hydroxides but are soluble in ordinary fat solvents
unsaponifiable matter
After the saponification of oils and fats a small amount of
residue is left consisting of ______ if the oils or fats
are of vegetable origin and _____ if they are of
animal origin.
phytosterol
cholesterol
Determination of this constant will indicate the presence
of unsaponifiable adulterants such as petroleum oil added
to linseed oil.
Unsaponifiable Matter
Defined as the number of grams of iodine absorbed
under specified condition by 100 grams of oil, fat,
wax or other substance.
Iodine Value
This value is a quantitative measure of the proportion of
unsaturated fatty acids present both free and
combined
iodine value
Linseed, cod iodine value
> 120
Cottonseed,
sesame iodine value
100-120
Olive, almond iodine value
<100
In conjunction with the saponification value of a fat or oil, iodine
value also serves as a means of detecting
adulteration
Method I
Hanus method – Iodobromide, CHCl3
Method II
Wijs method – Iodochloride, CCl4
is used to prevent other side reaction
from taking place in which iodine monochloride is
consumed.
iodine flask
Defined as the number of milligrams of potassium hydroxide
equivalent to the hydroxyl content of one gram of the
substance.
hydroxyl value
hydroxyl value constant gives an indication of the identity and purity of
fatty substances possessing ______
alcoholic hydroxyl groups
An abnormally low hydroxyl value is indicative of
_____ with higher molecular weight
alcohols or with non-alcoholic fatty substances
adulteration
It is expressed as the number of mg of potassium
hydroxide required to neutralize the acetic acid
obtained by the saponification of 1 gram of acetylated
fatty acids.
acetyl value
The Acetyl Value corresponds closely to the ______ of fatty alcohol and the two constants have much
the same significance with respect to identity and purity
of substances
hydroxyl
value
Acetyl Value of Fatty Acids
❖ The acetyl value is determined by acetylating ____ e.g hydroxystearic acid or hydrogenated castor
oil and determining the saponification value of the
product ACETYLATED SAMPLE
hydroxy
fatty acids
From the saponification value of acetylated fatty acid and
acid value of the original fatty acid, ____ is
determined
acetyl value
defined as the reactive oxygen contents expressed
in terms of milliequivalents (meq) of free iodine per kg of fat
peroxide value (POV)
a measure of the aldehyde levels in an oil or fat,
in particular those that are unsaturated (and principally the 2–alkenals)
anisidine value (AnV)
Combined PV and Anisidine value (2PV
+ AV)
Total oxidation Value (TotOx)
Congealing point
Solidification Temperature of FA
mEq of iodine
0.127
mEq in mg of KOH
56.11
