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CHEMISTRYCHEMISTRY
OFOF
OILS AND FATSOILS AND FATS
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DefinitionDefinition
A group of substances that in generalA group of substances that in general
are soluble in organic solvents, but areare soluble in organic solvents, but are
not soluble in water are called lipids.not soluble in water are called lipids.
Oils & Fats are one class of lipid.Oils & Fats are one class of lipid.
They can be used for edible as well asThey can be used for edible as well as
non-edible purposes.non-edible purposes.
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Roles of Food LipidsRoles of Food Lipids
Energy Source
Source of essential fatty acids
Carrier of Fat Soluble Vitamins
Main Flavor Source of Foods
Regulates Hormone and Cell StructureHelp to Develop Nervous System
Build adipose tissues which cause ThermalInsulation of Body
Mouth Feeling
Texture of Foods
Emulsifying Agents
Mold Releasing and Anti-spattering Agent
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Source of Food LipidsSource of Food LipidsPlant source seeds, grains, fruits, brans etc.Animal source milk, egg, tallow, lard, microbial
etc.
Marine source fish and other animals.World Supply
Vegetable oil 68%
Animal fat 28%
Marine oil - 4%
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1. Fatty acids
2. Neutral fats and oils or triglycerides
3. Monoglycerides and diglycerides
4. Waxes
5. Phospholipids
6. Sterols
Types of Lipids
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Composition of fats and oilsComposition of fats and oils
Fatty acid esters of glycerol i.e.
triglycerides
Triglycerides which is liquid at room
temperature are termed as oils and those
solids are termed as fats
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Triglycerides
O
H2C OH
HC OH
H2C OH
HO C R
HO C R
HO C R
O
O
O
H2C O C RO
O
H2C O C R
HC O C R+
+ 3 H2O
Glycerol 3 Fatty Acids
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Saturated and Unsaturated Fatty AcidsSaturated and Unsaturated Fatty Acids
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Cis 9 - Octadecenoic Acid (oleic)
Trans 9 - Octadecenoic Acid (elaidic acid)
O
CH3(CH2)7 C C (CH2)7 C OH
HH
910
O
CH3(CH2)7 C C (CH2)7 C OH
H
H
Cis And Trans Fatty Acids
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Polyunsaturated Fatty Acids
Linoleic acid: Cis, cis, 9, 12 - Octadecadienoic acidLinolenic acid: Cis, cis, cis 9, 12, 15 - Octadecatrienoic
acid
Arachidonic acid: Cis, cis, cis, cis 5, 8, 11, 14 -Eicosatetraenoic acid
Linoleic Acid
Linolenic Acid
Arachidonic Acid
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Fatty AcidsMelting Points and Solubility in Water
Solubility in H O
Fatty Acid Chain Length
2
Melting Point
zx
x
x
x
x
x
x
x
MeltingPoin
t
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Effects of Double Bonds on the Melting Points
M.P.
# Double bonds
x
x
xx
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DIFFERENT TYPES OF GLYCERIDES
Monoglyceride ( - monostearin) Diglyceride (, ' - distearin)
H2C OHHC OH
H2C O
O
C (CH2)16 CH3
H2C O
HC OH
H2C O
O
C (CH2)16 CH3
C (CH2)16 CH3
O
Triglyceride ( - palmityl distearin)
H2C O
HC O
H2C O
O
C (CH2)16 CH3
C (CH2)16 CH3
O
O
C (CH2)14 CH3
( C18 )
(C16 )
(C18 )
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Fatty Acids (%) of Fats and Oils
4 3 - -
6 3 - -
-
-
-8 2 6 -
10 3 6 - --
-12 3 44 -
14 10 18 1
16 26 11
-
4 12
16:1 7 1 -
18:0 15 6 3 2
18:1 29 7 18 24
18:2 2 2 53 54
Fatty Acids Butter Coconut Cottonseed Soybean
18:3 2 - - 8
C
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Phospholipid
Lecithin (phosphatidyl choline)
O
O
H2C O C RO
R C O CH
H2 C O P O CH2 CH2 N
+
CH3
CH3
CH3
O_
Phosphatidic Acid Choline
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Other phospholipids are :
Phophatidyl ethanol amine
Phosphatidyl serine
Phosphatidyl inositol
Cardiolipin
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Esters of Fatty acid and Long chain alcohol
WAXES
OC30H61 O C C15H31
O
C16H33 O C C15H31
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Sterols
Plant sterols or PHYTOSTEROLS
Animal Sterols or CHOLESTEROLS
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Phytosterol
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Cholesterol
HO
H3C
H3
C
H3C CH 3
CH 3
1
234
56 78
910
11
12
1314
15
1617
18
2122
19
20
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Characteristic Components PresentCharacteristic Components Present
on Some Special Oilon Some Special Oil
Lignans in sesame oil;
Oryzanol in rice bran oil;
Gossypol in cottonseed oil;Cholesterol in butter as well as in animal fat;
Hydroxy fatty acid in Castor oil;
Cyclic acid in Sal fat;
Trans fatty acid in Vanaspati
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Non-lipid component present in
Oils & FatsFat soluble vitamins
Pigments
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Some important parameters to
Characterize Fats and Oils
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1. Acid Value
2. Saponification Value
3. Iodine Value
4. Peroxide Value
5. Gas Chromatographic Analysis for Fatty Acidcomposition
6. Liquid Chromatography for triglyceride composition
Analytical Methods
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Acid Value
Number of mgs of KOH required to neutralize the Free
Fatty Acid present in 1 g of oil/fat.
Fatty acid generate due to hydrolytic rancidity
Triglyceride Fatty acids
RCOOH + KOH ROO- K+ + H2O
AV = (56.1 x N x V)/ wt. of sample
Moisture/
Lipase
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Saponification Value
Saponification - Hydrolysis of ester (triglyceride) under
alkaline condition. It gives the idea about the average
molecular weight of fatty acid present in particular oil/fat.
O
C R
O
O
C R
C R
O
H2C O
HC O
H2C O
KOH
H
H
H
H2C O
HC O
H2C O
R C O-K
++ 3 + 3
Heat
Definition : mgs of KOH required to saponify 1 g of fat
SP# =56.1(B -S) x N of HCl
Gram of Sample
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Iodine Value
gms of iodine absorbed by 100 g of oil.
Iodine number indicates the amount of
unsaturation in fats and oils.
Iodine Value = (ml of Na2S2O3 volume for blank -
ml of Na2S2O3 volume for sample) N ofNa2S2O3 0.127g/meq 100
Weight of Sample (g)
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Peroxide Value
It indicates about the amount of primary oxidationproducts present in Oil/Fat.
Peroxide Value = ml of Na2S2O3 Normality 1000
Grams of Oil
Unit : (mill equivalent /kg)
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GC Analysis for Fatty Acids
1. Extract fat.
2. Saponify (hydrolysis under basic condition).
3. Prepare methyl ester (by BF3-methanol/CH3ONa).
4. Inject methyl ester in GC
5. Determine peak areas of fatty acids.
(Fatty acids are identified by relative retention time)
6. Compare with response curve of standard.
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Chromatogram of Fatty Acids Methyl
Esters
14
18:1
18:2 2018:3
22
21:1 2416
18
Time
Resp
onse
GC condition: 10% DEGS Column (from supelco)
Column temperature 200C.
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TAG Composition
Triglyceride composition (e.g. S3, S2U, SU2 or
U3) of oil/fat can be determined by HighPerformance Liquid Chromatography (HPLC)
In this chromatography, oil samples can beinjected directly.
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Soxhlet Method
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Fat Soluble Vitamins
Vitamin A
CH2OH
CH3 CH3
CH3
CH3H3C
12
34
5
67
8
9
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Vitamin D2
Vitamin E
HO
CH 2
HH
H3C
H3C CH 3
CH 3
CH 3
O
R1
R2
HO
R3
CH3(CH2CH2CH2CH2)2CH2CH2CH2CH(CH3)2
CH3
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Pigments
-Carotene and Chlorophyll (green)
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Chlorophyll